CA2188178C - Trailing arm suspension with lever arm - Google Patents
Trailing arm suspension with lever arm Download PDFInfo
- Publication number
- CA2188178C CA2188178C CA002188178A CA2188178A CA2188178C CA 2188178 C CA2188178 C CA 2188178C CA 002188178 A CA002188178 A CA 002188178A CA 2188178 A CA2188178 A CA 2188178A CA 2188178 C CA2188178 C CA 2188178C
- Authority
- CA
- Canada
- Prior art keywords
- arm
- frame
- suspension
- trailing
- trailing arm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000000725 suspension Substances 0.000 title claims abstract description 31
- 230000035939 shock Effects 0.000 claims description 18
- 239000006096 absorbing agent Substances 0.000 claims description 17
- 230000006835 compression Effects 0.000 claims 6
- 238000007906 compression Methods 0.000 claims 6
- 230000007423 decrease Effects 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 230000036316 preload Effects 0.000 description 2
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D61/00—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern
- B62D61/12—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern with variable number of ground engaging wheels, e.g. with some wheels arranged higher than others, or with retractable wheels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G11/00—Resilient suspensions characterised by arrangement, location or kind of springs
- B60G11/32—Resilient suspensions characterised by arrangement, location or kind of springs having springs of different kinds
- B60G11/48—Resilient suspensions characterised by arrangement, location or kind of springs having springs of different kinds not including leaf springs
- B60G11/56—Resilient suspensions characterised by arrangement, location or kind of springs having springs of different kinds not including leaf springs having helical, spiral or coil springs, and also fluid springs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G9/00—Resilient suspensions of a rigid axle or axle housing for two or more wheels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G9/00—Resilient suspensions of a rigid axle or axle housing for two or more wheels
- B60G9/003—Resilient suspensions of a rigid axle or axle housing for two or more wheels the axle being rigidly connected to a trailing guiding device
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2202/00—Indexing codes relating to the type of spring, damper or actuator
- B60G2202/10—Type of spring
- B60G2202/12—Wound spring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2204/00—Indexing codes related to suspensions per se or to auxiliary parts
- B60G2204/40—Auxiliary suspension parts; Adjustment of suspensions
- B60G2204/47—Means for retracting the suspension
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2500/00—Indexing codes relating to the regulated action or device
- B60G2500/20—Spring action or springs
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Vehicle Body Suspensions (AREA)
- Gear-Shifting Mechanisms (AREA)
Abstract
A retractable suspension (10) com-prises a trailing arm (22) pivotally mounted to a vehicle frame (12), an air spring (30) mounted between the trailing arm and the frame, and a lifting device (32) mounted between the trailing arm and the frame.
The lifting device (32) comprises a strut (60) pivotally mounted between the frame (12) and a lever arm (64) that is fixedly mounted to the trailing arm (22). The strut (60) applies a force to the lever arm (64) that imparts a moment to the trailing arm (22) to urge the trailing arm and attached wheels (14) to a retracted position. The force of the air spring (30) can be adjusted to counter the upward movement of the wheels (14).
The lifting device (32) comprises a strut (60) pivotally mounted between the frame (12) and a lever arm (64) that is fixedly mounted to the trailing arm (22). The strut (60) applies a force to the lever arm (64) that imparts a moment to the trailing arm (22) to urge the trailing arm and attached wheels (14) to a retracted position. The force of the air spring (30) can be adjusted to counter the upward movement of the wheels (14).
Description
2 ~ 1 8 8 ~ ~ ~ PCrlUS94/04228 TRAILING ARM SUSPENSION VVITH LEVER ARM
BD.4... ~ of the Invention Field Or the Invention This invention relates to vehicle ~ , and more particularly, to trailing arm ~ c : .~ ~ with axle lifts.
5 r~ . of Related Art Several types of vehicles, including semi-trailer truck vehicles and the like, have multiple sets of axle/wheel ~ ;F c arranged to ~d~luat~ support relatively heavy loads. To adjust the load support provided by these ~ ;F c, it is known to employ ~ systems utilizing trailing arms pivotally mounted to the 10 vehicle frame in c~mhinqtirm with adjustably ~ ~d air springs and the like.
When the vehicle is carrying a relatively light load, it is desirable to relieve the load Ll~u~.lulLillg 1~ between the vehicle in one or more of the axle/wheel ~cc~mhliF~ c, and also to disengage the axle/wheel assembly from ground contact to reduce tire wear. To relieve load support when an air ~ system 15 is employed, air pressure can be reduced. To achieve d~ c, .- ' of the tires from the road surface, devices commonly referred to as axle lift ",~ can be employed. Prior lift ~..r- 1- "' - -~c utilized stressed ~ spr~:ngs acting direF ,Iy between a vehicle frame and the axle. When the downward load forces exerted on the axle by the ~ system were relieved, such as through deflation of air 20 springs, lifting forces exerted by the m~rhqr;~l springs pulled the axle upwardly to a raised position. These lift ", 1,~ "~ required a sufficient spring stress to support the axle and the various ~ in a raised position and sl~hctzlntiqlly increased the spring stress when the axle was lowered, which Ul~ al,l~ imparted pre-load forces on the ~ l system, reducing the actual maximum vehicle 25 payload carried by the ~ system.
Improved axle lift ~r- 1,,..1:~,,l~ were later developed that overcame the problem of cl-bst~ntiql payload reduction. These Illc~llau.~ generally comprised a lever arm or cam pivotally mounted to the vehicle frame, with the lever being comnected to the axle/wheel a~ssembly by a flexible member such as a strap or a 30 chain and to a c~ d or ten~sioned spring mounted to the axle. T~e lever armor cam formed a moment arm with respect to the lever arm pivotal ~nnn~octinn to the frame. The moment arm was nlinimi7~d as the air spring wa~s pl~,.. ~Uh,.,~ to move the axle/wheel assembly to the road engaging position. By ~ L the moment WO 95/28312 ~ 18 ~ 1~ 8 PCI'NS9410 1228 arm when the axle/wheel assemblies are in the road engaging position, the preload forces were minimi7P-I Examples of these types of axle lift ~ are found in U.S. Patent No. 3,771,812, issued November 13, 1973 to Pierce et al. and U.S. Patent No. 4,634,141, issued January 6, 1987 to Hagan et al.
A~e lift ,.. l._,. .~ can also be used with trailers that are adapted for both highway and railroad use. The wheel gear upon which the trailers ride obviously depends upon whether or not the trailer is to be used in normal highway service or on a railroad track. In the former, co~ Liu-lal ~ ~ C~ ;a~ 5 rubber tires are required, and in the latter, a rail wheel set, sometimes known as a rail 10 bogie, must be used. Such ", l ~ are not only ~,Lla~,La'Ol_ to lift an axlerelative to a trailer, but are ~ ~ t~ r to lift a trailer relative to the ground to permit S.~ of a rail bogie.
Designs for an ~ lr, retractable ~ are disclosed in U.S.
Patent No. 5,058,916, issued October 22, 1991 to llicks, and U.S. Patent No.
5,058,917, issued October 22, 1991 to Richardson. Both patents disclose a ~ a~lal/lc trailing arm ~u~r that is also P . ~. ,.1 -1.1P to lift the vehicle frarne to provide for the insertion of a ~ , rail bogie to the vehicle frame without the need for an additional lifting l~.P.'._l. . ., or device. Both structures are relatively complex and have a ~..P. ~ l locking . P~ .. that locks the trailing arm of the '~ ;O~l to 20 the vehicle frame when the ~ is in the raised position. The Culll~ ~Ly of these designs renders their rnq~-.fqrtllring and operating costs relatively high.
The prior axle lift l, ' -~ - and Ic~la~La~l~ c~ . - -",~ ~qticfq~t-~rily performed their function. U-fvlLullat~:~, their ~aL~ra~Lvly F~ r"..- -. P was at the cost of undesirable ~ vl~ and increased ~ - ;.,l ~ ._. ,- ~ The prior a~de lift 25 , P - l l - l ;- - also required two pivotal ~ " ,~ one for tbe trailing arm and one for the lever arm. The second pivotal ~ .P~l;.." increased the ~v~ ily of the lift axle by requiring separate ~ r~ ;u..~ between the spring and lever arm and the lever arm and trailing arm. It is desirable to have a lift l"r- 1IAII ~II that reduces the ~;UllI~ Ail~ and ..,-;.,~ .- .- of the prior lift ... l,~. "~ without 30 sacrificing p~.ru.lllal.~ or durability.
Summan of Invention The invention relates to an axle lift ",P~ "~ that can be used to extend and/or reuact a vehicle ~ The axle lift ~- P l _, ~", according to the invention is simpler in ~ul~LIu~iiv.. and requires less 1l~ t ~ P than the prior axle 35 lift ~ .P. l,_..;~."~ The invention fixes a lever arm directly to the trailing arm, thus WO 95/28312 218 8 ~ 7 8 PCT/US94/04228 utilizing the pivotal c~-nn~ction of the trailing arm with the vehicle for leverage. The invention thus eliminates any need for a separate pivotal ( .,. .~ ., between the lever arm and the vehicle.
A r ~ for a vehicle according to the invention comprises a frame S to which is pivotally mounted a pair of trailing arms that swing about an axis in generally vertical IIIU.~ relative to the frame. An axle is mounted to and between the trailing arms and has wheels mounted to each end of the axle. A
collapsible spring is disposed between the trailing arms and the frame for ' 3 the swinging Illu._lll.lll of the trailing arms. A lever arm is fixedly mounted to at least one of the trailing arms in such a malmer that it extends upwardly from the trailing arm. A ~u-~-~ spring has one end that is pivotally mounted to the frame and another end that is pivotally mounted to the lever arm above the axis about which the trailing arm pivots. The ~,Ulll~ iUII spring exerts a force on the lever arm that tends to urge the trailing arm to a retracted position.
Preferably, the collapsible spring is an air spring of the type commonly used m heavy duty ~ :u ~, and the ~,Ulll~ i ' spring is a coil spring. A
hydrau]ic cylinder can be disposed axially within the CUIII~ ' spring and commected to the frame and the lever arm to dampen the swinging movement of the trailing arm.
The lever arm is preferably mounted to the trailing arm between first and second ends of the trailing arm. The lever arm t.,llllill...~ ~ with a terminal end that is positioned above the trailing arm. The CUIII,UI. ' - spring is pivotallymounted between the frame and the terminal end of the lever arm and the collapsible spring is mounted between the trailing arm and the frame near the second 25 end of the trailing arm. The frame typically has opposed frame rails connected by a cross member and the Culll~l~ ' spring is pivotally mounted to the cross member.Preferably, as the trailing arm pivots about the axis toward the retracted position, the ~Ulll~ iUll spring, through the lever, imparts a moment to the trailing arm about the axis. The lever arm is positioned sû that a momerlt arm 30 associated with the moment increases as the wheel is moved toward the retracted position.
In another aspect of the invention, the ~ J~ comprises a frame to which is pivotally mounted a pair of trailing arms so that they pivot about an axis.
An axle is moumted to and between the trailing arms for carrying wheels. A
35 c- l'ops;~ spring is disposed between the trailing arms and the frame and cushions WO 95/28312 ~ 7 8 PCT/IJS94104228 the swinging movement of the trailing arms. A lever arm is fixedly mounted to atleast one of the trailing arms and extends upwardly from the trailing arm. A shock absorber ha~c one end mounted to the frame and another end pivotally mounted to the lever arm above the axis about which the trailing arm pivots. The shock absorber 5 damperls the pivotal movement of the trailing arm.
Brief r. ofthe Drawin~s The invention will now be described with reference to the drawings wherein:
F~G. 1 is a plan view of a trailing arm ~ according to the 10 invention mounted to a trailer-frame with the trailer omitted for clarity;
F~G. 2 is an elf vqtin~l view taken along line 2-2 of FIG. 1 with the ..- .,. illustrated in a nommal highway mode;
FIG. 3 is an f le~aliulldl view taken along line 3-3 of FIG. 2;
FIG. 4 is an f~ aliullal view taken along line 4-4 of F~G. 2;
FIG. S is an f ll,~aliullal view similar to FIG. 2 with the '~
illustrated in a retracted mode;
FIG. 6 is an elevational view similar to FIG. 2 with the ~IlCrf ncinn illustrated in an extended mode;
nG. 7 is an fl- ~JI;....~l view of a trailer mounted on a rail bogie, and having a tri-axle wheel set ill~Vl~UlaliUg a ~ in accv-dall~c with the invention in the retracted position; and F~G. 8 is an cL.~a~iùllàl view ' "~ sirnilar to FIG. 2, of an altemative ellll,o lill.~lll of a trailing arm ~ according to the invention.
D . sf the Pr~ferred F ' .
Referring now to the drawings in general and FIGS. 1 and 2 in particular, there is illustrated a retractable, trailing arm ~ ;n-~ system 10 corlstructed ~--hstq~ltiqlly in a~vldall~c with the principles of the invention. ~he -- n~ 10 is mounted beneath a frame having opposing frame rails 12 and supports ground engaging wheels 14. F~G. 2 illustrates a nommal highway mode of operation where the wheels 14 are in contact with a surface, such as a road surface 16. The ~..~I. . -: ,.. 10 is further adapted to be retractable whereby the wheels 14 can be lifted off the road surface 16 as illustrated in F~G. S in a retracted mode.
Further, the ~ q~ .- -..~ 10 is ~ hlr whereby the frame 12 may be lifted relative to the road surface 16 as sho~n in FIG. 6 with the ~ .c~... in an extended mode.
WO 95/28312 21 8 ~ ~ 7 ~ PCT/US94N4228 -5~
Although the ~ l 10 supports a single axle having two pair of ~ c~l6. 6 ~-6 wheels 14, it will be ~ ,od that the preferred construction utilizes a typical tandem axle ~ , or a tridem axle ---r ' In any event, a principal function of the retractable susr 10 is to lift the wheels 14 off the5 road surface when the wheels are not needed, such as when the load of the vehicle does not warrant the extra support. A~ or 2~/litinn~lly~ the ~ 10 can lift the frame with respect to the road surface 16 for the mounting of a rail bogie 20 (F~G. 7) to permit the utilization of the vehicle on a railway in addition to use on a highway. FIG. 7 illustrates a t~vpical c~ r;c~ of a tridem trailer 18 having a10 ---r 10 in the retracted position, and mounted on a rail bogie 20 for railroad use. It will be ~ that the rail bogie 2Q and d- ~ for securing the trailer to the rail bogie, form no part of this invention, and, in fact, are not necessary for practicing the invention.
The ~ 10 has identical parts that are o~ dl with respect 15 to a ~ centerline of the vehicle. For simplicity, only one side of the .. 10 will be described in detail with it being ~ od that the ~F~ ;
applies equally to the other side of the ~ 10.
Referring more closely to FIGS. 1 and 2, it can be seen that the . - 10 comprises a trailing arm æ, also cnmrtimF~c known as a control arm, which has a front end 24 and a rear end 26. The front end 24 is pivotally mounted to a frame bracket assembly 28. A first spring or biasing device, such as arl air spring 30, is disposed adjacent the rear end 26 of the trailing arm 22 and cushions theupward and downward lll~._..l~..l~ of the frame 12 with respect to the wheels 14. The force of the air spring 30 is adjustable by adding or ~LdLIaLllg ~ d air from the air spring 30. The air spring 30 can be adjusted to lift the frame with respect to the road surface 16. Although the first biasing device is shown as an air spring 30, it is ~ t~ t~r d that any suitable type of spring can be used. A lifting device 32 serves to retract the trailing arm æ and thus the ~ .- -., 10 relative to the frame 12.
Referring to FIGS. 2 and 3, the frame bracket assembly 28 comprises a frame bracket 34 that is mounted to the frame rail 12 and to which the front end 24 of the trailing arm æ is pivotally mounted. The frame bracket 34 has a pair of spaced arms 36 depending from the frame 12. Each arm 36 haa an opening (not shown) for ~---,----n~ a bushed ~ 40 between the trailing arm æ and the frame bracket 34 in a manner commonly known in the art. The bushed WO 95/28312 ~ PCT/US94/04228 ) 40 defines a pivot axis 41, ~ oriented with respect to the frame, and about which the trailing arm æ pivots.
Referring to FIGS. 2 and 4, an axle bracket 42 is mounted near the rear end 26 of trailing arm æ. The axle bracket 42 comprises opposing side plates 44 that are mounted to the trailing arm æ by a pair of bushed ~ 46 and 48 in a manner well known in the art. An upper portion of the axle bracket 42 comprises a saddle seat to which an axle 52 is rigidly secured as by welding. An air spring support 54 is mounted to the axle 52 and has a platform 56 that supports a piston 57 for the air spring 30. A plate 58, typically welded to the frame rail 12, supports the upper portion of the air spring 30.
Refernng now to ~[GS. 1-4, the lifting device 32 comprises a lever arm 64 and a second spring or biasing device, such as a biased strut 60. The strut 60 is pivotally connected at one end to a cross member 62 disposed between the frame rails 12 and pivotally connected at the other end to the lever arm 64, which is fixedly connected to the trailing arm æ as h~ aft~" described. The strut 60 applies a force on the lever arm 64 to rotate the trailing arm æ about the pivot axis 41 of the bushed ~ ... 40. The strut 60 preferably comprises a hydraulic or pneumatic cylinder 66, such as a shock albsorber, disposed axially within a coil spring 68. The coil spring 68 is ~u. p-~ v~l~ retained between opposing end caps 69, one of which 20 is fixed to the casing of the shock absorber 66 and the other of which is fixed to the shaft of the shock absorber 66. The spring 68, being under ~;UIII~ exerts a force along a ~ axis 61 of the strut 60. The axial placement of the shock absorber 66 within the spring restrains the spring 68 from bowing outwardly during CUIll~l~ The shock absorber 66 also performs its usual function of ~l-",l,~ ,;"~
25 the l.IU.. of the trailing arm æ during operation of the vehicle. Although the second biasing device is illustrated as a strut 60, it is ~ t- d that the secondbiasing device can include any suitable spring.
The preferred ~IllI,o-lill..,lll is illustrated with the coil spring 68 coaxially disposed about the shock absorber 66. However, it is to be lln~l~t~Qd that 30 the coil spring 68 need not be mounted coaxially with the shock absorber 66. It is important only that there be a biasing device mounted directly between the lever arm and the frame. If the biasing device is a coil spring, then a retainer or guide must be used in ~..,.,l.;. ~;.... with the coil spring to retain the spring in axial alignment. The shock absorber or similar dampener would then be mounted in a COIIY~ OII~aI
WO 95/28312 218 ~ ~ 7 PCT/US94104228 manner directly between the frame and the trailing arm to dampen the IIIU.~ ofthe trailing arm with respect to the frame.
One end of the strut 60 is pivotally mounted to the cross member 62 by a bracket 70 having opposing arms 72 with aligned apertures (not shown). The strut 5 60 has a w~l~,O~ull~6 aperture (not shown) that is placed between the bracket arms 72 so that it is in alignment with the bracket arm apertures and a fastener 76 extends through the aligned apertures of the shock absorber and the bracket anns. The fastener 76 can be any suitable fastener such as a pin, bolt and nut, etc. The other end of the strut 60 is mounted to the lever arm 64 in a similar manner. The lever arm 64 carries a mounting bracket 80 at an upper end thereof to which the strut 60 is pivotally mounted. The bracket 80 can be yoke-shaped such that the end of the strut 60 is received between the arms of the bracket 80 with aligned apertures of the arms and the strut 60 receiving a fastener 85. (See F~G. 3.) In the preferred c IllI,~ ll llL, the lever arm 64 is welded to the trailing arm 22 between the front and rear ends 24, 26 and extends from the trailing arm æ
upwardly, inwardly and forwardly relative to the vehicle. The strut 60 attaches to a terminal end 65 of the lever arm 64. The ternninal end 65 of the lever arm 64 lies at a point roughly in the same plane in which the axis 41 of the bushed ~ ;o~ 40 hes, (the hrailing arm pivot axis), which plane is preferably normal to a lnn~itll~in~l 20 axis 23 of the trailing arm æ. The terminal end 65 also lies upwardly far enough so that in the normal highway mode as shown in FIG. 2 the lever arm 64 is nearly p~ di~ula~ to a ll~n~ih-~lin~l axis 61 of the strut 60. Further, the terminal end 65 is disposed inwardly at a point where the 1...,~;1, 1;"~1 axis 61 of the strut 60 vill lie in a plane parallel to a vertical plane extending through the frame rail 12. (See F~G.
25 1.) However, it is ~ t~ t ~ and within the scope of the invention for the trailing arm æ and the strut 60 to be in alignment to obviate the need for the angular ... of the lever am 64. For example, the trailing arm æ could have an inward curve to position the hrailing arm 22 under the strut 60 or the strut 60 could be moved above the trailing arm æ depending on the geometry of the vehicle 30 ~ Also, if there is sufficient space, the trailing arm 22 and lever arm 64 can be positioned directly below the frame rail 12.
The lever arm 64 can be positioned in any suitable location on the h ailing arm 22, preferably at a position where a moment arm behween the line offorce for the strut 60, axis 61, and the pivot axis 41 of the bushed ~ .. 40 35 increases as the wheels 14 are retracted and decreases as the wheels 14 are extended.
WO 95/28312 2 1 8 ~ 3 PCI'/US9.~/04228 The moment arm is denoted as M, when the ~ . 10 is in the highway mode (FIG. 2), M2 when the ~ is in the retracted mode (FIG. 5), and M3 when the ~ 10 is in the extended mode (FIG. 6). In the preferred ~mho~iim.on~
the ratio of M3 to M2 is ~ u~ at~ 3 so that the moment in the retracted mode 5 is greater than in tbe extended mode to ensure that the wheels will be raised even though the force of spring 68 is less in the retracted mode than in the extended mode because the spring 68 is less ~u...,u-~,...._~.
Referring to FIG. 8, the lever arm 64 can be comnected to the frame by a shock absorber 71 instead of a strut 60. With the shock absorber 71, the lever arm 64 serves as a mounting bracket for the shock absorber 71, which functions in its traditional manner as a dampener for the loads imparted to the, ~l,. -:, from the contact of the wheel 14 with the road surface 16. The following d~ Lic~-- of theoperation of the ~ . 10 is equally applicable whether or not the strut 60 or the shock absorber 71 is used.
Referring now to FIG. 2 for operation of the ~ ., the strut 60 exerts a force that is applied to the lever arm 64 along the l."L~ axis 61 of the strut 60. This force results ~n a moment being applied to the trailing arm æ about the axis 41 of the bushed ~""f' ~ 40 that tends to rotate the trailing arm 22 ~uullh-~lu~kvv~c as viewed in F~GS. 2, 5 and 6 about the bushed ~ i.. 40 and upward toward the frame rail 12. Thus, the strut 60 is always urging the wheel 14 upwardly. The force of the strut 60 is ~uu..'.,.l,al~cd by the force of the air spring 30, which, when lu~ ~iL~d, acts on the end of the trailing arm 22, resulting in a moment opposite the moment associated with moment arm M,. In addition, the weight of axle assembly 52 and wheels 14 which is typically about 1700 Ibs., creates a moment about the bushed c ~ " 40 that is opposite the moment associated with moment arm M,.
Thus, for the wheel 14 to be raised, the strut 60 must generate sufficient force so that the moment associated with moment arm M, is greater than the combined opposite moment created by the air spring 30 and the weight of part of the ~ , 10 CO---u-i~ the axle assembly 52 and wheels 14. A~-iV~ f~
the force of the air spring 30 can be adjusted and even reduced to zero by exhausting the air from the air spring 30. Therefore, the strut 60 need only to create a moment associated with moment arm M, great enough to overcome the moment created by the weight of part of the ~ ) 10 .l. l~ the axle assembly 52 and wheels 14 to fully retract the wheel 14 if the air spring 30 is exhausted of air.
2~8~17~
9, The air spring 30 is typically u~ .ul~d to ~IJlwulllàt~ 90 psig in the normal highway mode shown in FIG. 2. Also, in the highway mode, the strut 60 of the preferred ~, l,s),l;" .1 exerts a force of alJ~Jlu~ ullal~l~ 3,000 Ibs. such that the lerlgth of the moment arm M~ is alJ~lu~dulalely 10 inches in generally steady shte 5 where the combined force of the air spring 30 and the trailing arm weight roughly equal and counterbalance the force of the strut 60.
To raise the wheels 14 or retract the c ~ 10, air is exhausted from the air springs 30 so that the moment associated with moment arm M, will overcome the combined force in the air springs 30 and the weight of the ~
system 10 and axle assembly 52 and wheels 14. The l.. l.~ - f d forces will start rotating the trailing arm æ about the pivot axis 41 of the bushed c~ 40 and raise the wheels 14. Preferably, the air will be c~ t~ly exhausted. As the trailing arm æ rotates, the force of the strut 60 decreases, but the moment arm defined between the line of force of the strut 60 and the pivot axis 41 increases until the ---r 10 is in the fully retracted mode.
When the ~ ~- system 10 is in the fully retracted mode, the strut 60 will typically exert a~ylU~illlat~ l~ 2,000 Ibs. of force and the moment arm M2 is ~Jlu~luaL~l~ 12 inches. The resulting moment is sufficient to overcome the opposing moment of the air bags 30, if any, and the weight of the ~ system 1û and axle assembly 52 and wheels 14. However, the strut 60 exerts less force as it is expanded. Thus, the moment arm must increase as the spring 68 expands so thatthe moment does not fall below that needed to keep the s~l~r retracted. The decrease in the force of the springs is more than countered by the increase in the moment arm, resulting in a moment that is greater when the wheels are in the retracted position than in any other position. Thus, the lever arm 64 ~ for the reduction in the force of the strut 60 as the spring 68 expands from a culll~ d state (FIG. 2~ highway mode) to a less ;u~ f d state (FlG. 5~ retracted mode).
The geometry of the lever arm 64 further reduces the size of the spring 68 required in the strut 60 to retract the wheels 14 and securely retain the wheels 14 in the 30 retracted position without the need for a separate locking device.
If the vehicle frame 12 needs to be raised such as, for example, if a rail bogie 20 (EiIG. 7) is to be installed under the vehicle frame, force must be applied to the trailing arm æ against the moment arm M~. This is ?.~ rd by IJIC~ UliLIllg the air spring 30 a sufficient amount to raise the frame with respect to the wheels 14 35 to the extended position as illustrated in FIG. 6. Preferably, each air spring 30 will WO 95/28312 ~ 17 8 PCT/US91/0~228 be ~ li~d to ~,U,UIU~ ill~t~ly 120 psig to move the frame to the raised position.
In the raised position, the spring 68 of the strut 60 is almost fully Cuu~,ul~ and exerts a,UIUlU~ 4,400 Ibs of force. The mûment arm ~4, on the ûther hand, is alJ,UlU~ ly 4 inches. It will be apparent that because of the position of the lever 5 arm 64, the change in length of the moment arm is not linearly ,u-uluu- liu~lal to the change in force of the strut 60. Thus, the ~ u~ air spring 30 is sufficient to overcome the moment, even with the increased force of the strut 6Q
After the frame rails 12 are raised by ~l~, ...lliLillg the air springs 30 to overcome the force of the strut 60, a rail bogie 20 can be positioned beneath the 10 frar~e rails 12 and the frame lowered thereon by exhausting u~ ui ~d air from the air springs 30 until the frame contacts the rail bogie 20. The rail bogie 20 is secured to the frame in a manner commonly known in the art.
Whereas the invention has been described with reference to a ~UUIyl~ spring between the frame 12 and the lever arm 64, it is also within the 15 scope of the invention to substitute a fluid cylinder or other tgpe of force applying element for the ~;UIII~UI~, spring 68. The fluid cylinder can be ,ul~ li~d at the same time that the air is exhausted from the air spring 30 to raise the trailing arms 22 to the retracted position illustrated in FIG. 5. The fluid cylinder can be dC~Li~L.,~ tû act as a shock absorber at times when the trailing arm is in the rûad 20 ~ngaging position.
Anûther form of a force applying element is an air spring which can be selectively activated to raise the trailing arm to the retracted position. Thus, an air spring can be used in lieu of the ~:UIII~ ' spring 68.
While particular ~ " ~` of the invention have been shown, it will 25 be ln-lPrcft)o.1 of course, that the invention is not limited theretû since ,..,~.liri.~i,",~
may be made by those skilled in the art, particularly in light of the foregoing teachings. ~Pq~rmq~ variation and ",~ are possible within the scope of the foregoing disclosure without departing from the spirit of the invention.
BD.4... ~ of the Invention Field Or the Invention This invention relates to vehicle ~ , and more particularly, to trailing arm ~ c : .~ ~ with axle lifts.
5 r~ . of Related Art Several types of vehicles, including semi-trailer truck vehicles and the like, have multiple sets of axle/wheel ~ ;F c arranged to ~d~luat~ support relatively heavy loads. To adjust the load support provided by these ~ ;F c, it is known to employ ~ systems utilizing trailing arms pivotally mounted to the 10 vehicle frame in c~mhinqtirm with adjustably ~ ~d air springs and the like.
When the vehicle is carrying a relatively light load, it is desirable to relieve the load Ll~u~.lulLillg 1~ between the vehicle in one or more of the axle/wheel ~cc~mhliF~ c, and also to disengage the axle/wheel assembly from ground contact to reduce tire wear. To relieve load support when an air ~ system 15 is employed, air pressure can be reduced. To achieve d~ c, .- ' of the tires from the road surface, devices commonly referred to as axle lift ",~ can be employed. Prior lift ~..r- 1- "' - -~c utilized stressed ~ spr~:ngs acting direF ,Iy between a vehicle frame and the axle. When the downward load forces exerted on the axle by the ~ system were relieved, such as through deflation of air 20 springs, lifting forces exerted by the m~rhqr;~l springs pulled the axle upwardly to a raised position. These lift ", 1,~ "~ required a sufficient spring stress to support the axle and the various ~ in a raised position and sl~hctzlntiqlly increased the spring stress when the axle was lowered, which Ul~ al,l~ imparted pre-load forces on the ~ l system, reducing the actual maximum vehicle 25 payload carried by the ~ system.
Improved axle lift ~r- 1,,..1:~,,l~ were later developed that overcame the problem of cl-bst~ntiql payload reduction. These Illc~llau.~ generally comprised a lever arm or cam pivotally mounted to the vehicle frame, with the lever being comnected to the axle/wheel a~ssembly by a flexible member such as a strap or a 30 chain and to a c~ d or ten~sioned spring mounted to the axle. T~e lever armor cam formed a moment arm with respect to the lever arm pivotal ~nnn~octinn to the frame. The moment arm was nlinimi7~d as the air spring wa~s pl~,.. ~Uh,.,~ to move the axle/wheel assembly to the road engaging position. By ~ L the moment WO 95/28312 ~ 18 ~ 1~ 8 PCI'NS9410 1228 arm when the axle/wheel assemblies are in the road engaging position, the preload forces were minimi7P-I Examples of these types of axle lift ~ are found in U.S. Patent No. 3,771,812, issued November 13, 1973 to Pierce et al. and U.S. Patent No. 4,634,141, issued January 6, 1987 to Hagan et al.
A~e lift ,.. l._,. .~ can also be used with trailers that are adapted for both highway and railroad use. The wheel gear upon which the trailers ride obviously depends upon whether or not the trailer is to be used in normal highway service or on a railroad track. In the former, co~ Liu-lal ~ ~ C~ ;a~ 5 rubber tires are required, and in the latter, a rail wheel set, sometimes known as a rail 10 bogie, must be used. Such ", l ~ are not only ~,Lla~,La'Ol_ to lift an axlerelative to a trailer, but are ~ ~ t~ r to lift a trailer relative to the ground to permit S.~ of a rail bogie.
Designs for an ~ lr, retractable ~ are disclosed in U.S.
Patent No. 5,058,916, issued October 22, 1991 to llicks, and U.S. Patent No.
5,058,917, issued October 22, 1991 to Richardson. Both patents disclose a ~ a~lal/lc trailing arm ~u~r that is also P . ~. ,.1 -1.1P to lift the vehicle frarne to provide for the insertion of a ~ , rail bogie to the vehicle frame without the need for an additional lifting l~.P.'._l. . ., or device. Both structures are relatively complex and have a ~..P. ~ l locking . P~ .. that locks the trailing arm of the '~ ;O~l to 20 the vehicle frame when the ~ is in the raised position. The Culll~ ~Ly of these designs renders their rnq~-.fqrtllring and operating costs relatively high.
The prior axle lift l, ' -~ - and Ic~la~La~l~ c~ . - -",~ ~qticfq~t-~rily performed their function. U-fvlLullat~:~, their ~aL~ra~Lvly F~ r"..- -. P was at the cost of undesirable ~ vl~ and increased ~ - ;.,l ~ ._. ,- ~ The prior a~de lift 25 , P - l l - l ;- - also required two pivotal ~ " ,~ one for tbe trailing arm and one for the lever arm. The second pivotal ~ .P~l;.." increased the ~v~ ily of the lift axle by requiring separate ~ r~ ;u..~ between the spring and lever arm and the lever arm and trailing arm. It is desirable to have a lift l"r- 1IAII ~II that reduces the ~;UllI~ Ail~ and ..,-;.,~ .- .- of the prior lift ... l,~. "~ without 30 sacrificing p~.ru.lllal.~ or durability.
Summan of Invention The invention relates to an axle lift ",P~ "~ that can be used to extend and/or reuact a vehicle ~ The axle lift ~- P l _, ~", according to the invention is simpler in ~ul~LIu~iiv.. and requires less 1l~ t ~ P than the prior axle 35 lift ~ .P. l,_..;~."~ The invention fixes a lever arm directly to the trailing arm, thus WO 95/28312 218 8 ~ 7 8 PCT/US94/04228 utilizing the pivotal c~-nn~ction of the trailing arm with the vehicle for leverage. The invention thus eliminates any need for a separate pivotal ( .,. .~ ., between the lever arm and the vehicle.
A r ~ for a vehicle according to the invention comprises a frame S to which is pivotally mounted a pair of trailing arms that swing about an axis in generally vertical IIIU.~ relative to the frame. An axle is mounted to and between the trailing arms and has wheels mounted to each end of the axle. A
collapsible spring is disposed between the trailing arms and the frame for ' 3 the swinging Illu._lll.lll of the trailing arms. A lever arm is fixedly mounted to at least one of the trailing arms in such a malmer that it extends upwardly from the trailing arm. A ~u-~-~ spring has one end that is pivotally mounted to the frame and another end that is pivotally mounted to the lever arm above the axis about which the trailing arm pivots. The ~,Ulll~ iUII spring exerts a force on the lever arm that tends to urge the trailing arm to a retracted position.
Preferably, the collapsible spring is an air spring of the type commonly used m heavy duty ~ :u ~, and the ~,Ulll~ i ' spring is a coil spring. A
hydrau]ic cylinder can be disposed axially within the CUIII~ ' spring and commected to the frame and the lever arm to dampen the swinging movement of the trailing arm.
The lever arm is preferably mounted to the trailing arm between first and second ends of the trailing arm. The lever arm t.,llllill...~ ~ with a terminal end that is positioned above the trailing arm. The CUIII,UI. ' - spring is pivotallymounted between the frame and the terminal end of the lever arm and the collapsible spring is mounted between the trailing arm and the frame near the second 25 end of the trailing arm. The frame typically has opposed frame rails connected by a cross member and the Culll~l~ ' spring is pivotally mounted to the cross member.Preferably, as the trailing arm pivots about the axis toward the retracted position, the ~Ulll~ iUll spring, through the lever, imparts a moment to the trailing arm about the axis. The lever arm is positioned sû that a momerlt arm 30 associated with the moment increases as the wheel is moved toward the retracted position.
In another aspect of the invention, the ~ J~ comprises a frame to which is pivotally mounted a pair of trailing arms so that they pivot about an axis.
An axle is moumted to and between the trailing arms for carrying wheels. A
35 c- l'ops;~ spring is disposed between the trailing arms and the frame and cushions WO 95/28312 ~ 7 8 PCT/IJS94104228 the swinging movement of the trailing arms. A lever arm is fixedly mounted to atleast one of the trailing arms and extends upwardly from the trailing arm. A shock absorber ha~c one end mounted to the frame and another end pivotally mounted to the lever arm above the axis about which the trailing arm pivots. The shock absorber 5 damperls the pivotal movement of the trailing arm.
Brief r. ofthe Drawin~s The invention will now be described with reference to the drawings wherein:
F~G. 1 is a plan view of a trailing arm ~ according to the 10 invention mounted to a trailer-frame with the trailer omitted for clarity;
F~G. 2 is an elf vqtin~l view taken along line 2-2 of FIG. 1 with the ..- .,. illustrated in a nommal highway mode;
FIG. 3 is an f le~aliulldl view taken along line 3-3 of FIG. 2;
FIG. 4 is an f~ aliullal view taken along line 4-4 of F~G. 2;
FIG. S is an f ll,~aliullal view similar to FIG. 2 with the '~
illustrated in a retracted mode;
FIG. 6 is an elevational view similar to FIG. 2 with the ~IlCrf ncinn illustrated in an extended mode;
nG. 7 is an fl- ~JI;....~l view of a trailer mounted on a rail bogie, and having a tri-axle wheel set ill~Vl~UlaliUg a ~ in accv-dall~c with the invention in the retracted position; and F~G. 8 is an cL.~a~iùllàl view ' "~ sirnilar to FIG. 2, of an altemative ellll,o lill.~lll of a trailing arm ~ according to the invention.
D . sf the Pr~ferred F ' .
Referring now to the drawings in general and FIGS. 1 and 2 in particular, there is illustrated a retractable, trailing arm ~ ;n-~ system 10 corlstructed ~--hstq~ltiqlly in a~vldall~c with the principles of the invention. ~he -- n~ 10 is mounted beneath a frame having opposing frame rails 12 and supports ground engaging wheels 14. F~G. 2 illustrates a nommal highway mode of operation where the wheels 14 are in contact with a surface, such as a road surface 16. The ~..~I. . -: ,.. 10 is further adapted to be retractable whereby the wheels 14 can be lifted off the road surface 16 as illustrated in F~G. S in a retracted mode.
Further, the ~ q~ .- -..~ 10 is ~ hlr whereby the frame 12 may be lifted relative to the road surface 16 as sho~n in FIG. 6 with the ~ .c~... in an extended mode.
WO 95/28312 21 8 ~ ~ 7 ~ PCT/US94N4228 -5~
Although the ~ l 10 supports a single axle having two pair of ~ c~l6. 6 ~-6 wheels 14, it will be ~ ,od that the preferred construction utilizes a typical tandem axle ~ , or a tridem axle ---r ' In any event, a principal function of the retractable susr 10 is to lift the wheels 14 off the5 road surface when the wheels are not needed, such as when the load of the vehicle does not warrant the extra support. A~ or 2~/litinn~lly~ the ~ 10 can lift the frame with respect to the road surface 16 for the mounting of a rail bogie 20 (F~G. 7) to permit the utilization of the vehicle on a railway in addition to use on a highway. FIG. 7 illustrates a t~vpical c~ r;c~ of a tridem trailer 18 having a10 ---r 10 in the retracted position, and mounted on a rail bogie 20 for railroad use. It will be ~ that the rail bogie 2Q and d- ~ for securing the trailer to the rail bogie, form no part of this invention, and, in fact, are not necessary for practicing the invention.
The ~ 10 has identical parts that are o~ dl with respect 15 to a ~ centerline of the vehicle. For simplicity, only one side of the .. 10 will be described in detail with it being ~ od that the ~F~ ;
applies equally to the other side of the ~ 10.
Referring more closely to FIGS. 1 and 2, it can be seen that the . - 10 comprises a trailing arm æ, also cnmrtimF~c known as a control arm, which has a front end 24 and a rear end 26. The front end 24 is pivotally mounted to a frame bracket assembly 28. A first spring or biasing device, such as arl air spring 30, is disposed adjacent the rear end 26 of the trailing arm 22 and cushions theupward and downward lll~._..l~..l~ of the frame 12 with respect to the wheels 14. The force of the air spring 30 is adjustable by adding or ~LdLIaLllg ~ d air from the air spring 30. The air spring 30 can be adjusted to lift the frame with respect to the road surface 16. Although the first biasing device is shown as an air spring 30, it is ~ t~ t~r d that any suitable type of spring can be used. A lifting device 32 serves to retract the trailing arm æ and thus the ~ .- -., 10 relative to the frame 12.
Referring to FIGS. 2 and 3, the frame bracket assembly 28 comprises a frame bracket 34 that is mounted to the frame rail 12 and to which the front end 24 of the trailing arm æ is pivotally mounted. The frame bracket 34 has a pair of spaced arms 36 depending from the frame 12. Each arm 36 haa an opening (not shown) for ~---,----n~ a bushed ~ 40 between the trailing arm æ and the frame bracket 34 in a manner commonly known in the art. The bushed WO 95/28312 ~ PCT/US94/04228 ) 40 defines a pivot axis 41, ~ oriented with respect to the frame, and about which the trailing arm æ pivots.
Referring to FIGS. 2 and 4, an axle bracket 42 is mounted near the rear end 26 of trailing arm æ. The axle bracket 42 comprises opposing side plates 44 that are mounted to the trailing arm æ by a pair of bushed ~ 46 and 48 in a manner well known in the art. An upper portion of the axle bracket 42 comprises a saddle seat to which an axle 52 is rigidly secured as by welding. An air spring support 54 is mounted to the axle 52 and has a platform 56 that supports a piston 57 for the air spring 30. A plate 58, typically welded to the frame rail 12, supports the upper portion of the air spring 30.
Refernng now to ~[GS. 1-4, the lifting device 32 comprises a lever arm 64 and a second spring or biasing device, such as a biased strut 60. The strut 60 is pivotally connected at one end to a cross member 62 disposed between the frame rails 12 and pivotally connected at the other end to the lever arm 64, which is fixedly connected to the trailing arm æ as h~ aft~" described. The strut 60 applies a force on the lever arm 64 to rotate the trailing arm æ about the pivot axis 41 of the bushed ~ ... 40. The strut 60 preferably comprises a hydraulic or pneumatic cylinder 66, such as a shock albsorber, disposed axially within a coil spring 68. The coil spring 68 is ~u. p-~ v~l~ retained between opposing end caps 69, one of which 20 is fixed to the casing of the shock absorber 66 and the other of which is fixed to the shaft of the shock absorber 66. The spring 68, being under ~;UIII~ exerts a force along a ~ axis 61 of the strut 60. The axial placement of the shock absorber 66 within the spring restrains the spring 68 from bowing outwardly during CUIll~l~ The shock absorber 66 also performs its usual function of ~l-",l,~ ,;"~
25 the l.IU.. of the trailing arm æ during operation of the vehicle. Although the second biasing device is illustrated as a strut 60, it is ~ t- d that the secondbiasing device can include any suitable spring.
The preferred ~IllI,o-lill..,lll is illustrated with the coil spring 68 coaxially disposed about the shock absorber 66. However, it is to be lln~l~t~Qd that 30 the coil spring 68 need not be mounted coaxially with the shock absorber 66. It is important only that there be a biasing device mounted directly between the lever arm and the frame. If the biasing device is a coil spring, then a retainer or guide must be used in ~..,.,l.;. ~;.... with the coil spring to retain the spring in axial alignment. The shock absorber or similar dampener would then be mounted in a COIIY~ OII~aI
WO 95/28312 218 ~ ~ 7 PCT/US94104228 manner directly between the frame and the trailing arm to dampen the IIIU.~ ofthe trailing arm with respect to the frame.
One end of the strut 60 is pivotally mounted to the cross member 62 by a bracket 70 having opposing arms 72 with aligned apertures (not shown). The strut 5 60 has a w~l~,O~ull~6 aperture (not shown) that is placed between the bracket arms 72 so that it is in alignment with the bracket arm apertures and a fastener 76 extends through the aligned apertures of the shock absorber and the bracket anns. The fastener 76 can be any suitable fastener such as a pin, bolt and nut, etc. The other end of the strut 60 is mounted to the lever arm 64 in a similar manner. The lever arm 64 carries a mounting bracket 80 at an upper end thereof to which the strut 60 is pivotally mounted. The bracket 80 can be yoke-shaped such that the end of the strut 60 is received between the arms of the bracket 80 with aligned apertures of the arms and the strut 60 receiving a fastener 85. (See F~G. 3.) In the preferred c IllI,~ ll llL, the lever arm 64 is welded to the trailing arm 22 between the front and rear ends 24, 26 and extends from the trailing arm æ
upwardly, inwardly and forwardly relative to the vehicle. The strut 60 attaches to a terminal end 65 of the lever arm 64. The ternninal end 65 of the lever arm 64 lies at a point roughly in the same plane in which the axis 41 of the bushed ~ ;o~ 40 hes, (the hrailing arm pivot axis), which plane is preferably normal to a lnn~itll~in~l 20 axis 23 of the trailing arm æ. The terminal end 65 also lies upwardly far enough so that in the normal highway mode as shown in FIG. 2 the lever arm 64 is nearly p~ di~ula~ to a ll~n~ih-~lin~l axis 61 of the strut 60. Further, the terminal end 65 is disposed inwardly at a point where the 1...,~;1, 1;"~1 axis 61 of the strut 60 vill lie in a plane parallel to a vertical plane extending through the frame rail 12. (See F~G.
25 1.) However, it is ~ t~ t ~ and within the scope of the invention for the trailing arm æ and the strut 60 to be in alignment to obviate the need for the angular ... of the lever am 64. For example, the trailing arm æ could have an inward curve to position the hrailing arm 22 under the strut 60 or the strut 60 could be moved above the trailing arm æ depending on the geometry of the vehicle 30 ~ Also, if there is sufficient space, the trailing arm 22 and lever arm 64 can be positioned directly below the frame rail 12.
The lever arm 64 can be positioned in any suitable location on the h ailing arm 22, preferably at a position where a moment arm behween the line offorce for the strut 60, axis 61, and the pivot axis 41 of the bushed ~ .. 40 35 increases as the wheels 14 are retracted and decreases as the wheels 14 are extended.
WO 95/28312 2 1 8 ~ 3 PCI'/US9.~/04228 The moment arm is denoted as M, when the ~ . 10 is in the highway mode (FIG. 2), M2 when the ~ is in the retracted mode (FIG. 5), and M3 when the ~ 10 is in the extended mode (FIG. 6). In the preferred ~mho~iim.on~
the ratio of M3 to M2 is ~ u~ at~ 3 so that the moment in the retracted mode 5 is greater than in tbe extended mode to ensure that the wheels will be raised even though the force of spring 68 is less in the retracted mode than in the extended mode because the spring 68 is less ~u...,u-~,...._~.
Referring to FIG. 8, the lever arm 64 can be comnected to the frame by a shock absorber 71 instead of a strut 60. With the shock absorber 71, the lever arm 64 serves as a mounting bracket for the shock absorber 71, which functions in its traditional manner as a dampener for the loads imparted to the, ~l,. -:, from the contact of the wheel 14 with the road surface 16. The following d~ Lic~-- of theoperation of the ~ . 10 is equally applicable whether or not the strut 60 or the shock absorber 71 is used.
Referring now to FIG. 2 for operation of the ~ ., the strut 60 exerts a force that is applied to the lever arm 64 along the l."L~ axis 61 of the strut 60. This force results ~n a moment being applied to the trailing arm æ about the axis 41 of the bushed ~""f' ~ 40 that tends to rotate the trailing arm 22 ~uullh-~lu~kvv~c as viewed in F~GS. 2, 5 and 6 about the bushed ~ i.. 40 and upward toward the frame rail 12. Thus, the strut 60 is always urging the wheel 14 upwardly. The force of the strut 60 is ~uu..'.,.l,al~cd by the force of the air spring 30, which, when lu~ ~iL~d, acts on the end of the trailing arm 22, resulting in a moment opposite the moment associated with moment arm M,. In addition, the weight of axle assembly 52 and wheels 14 which is typically about 1700 Ibs., creates a moment about the bushed c ~ " 40 that is opposite the moment associated with moment arm M,.
Thus, for the wheel 14 to be raised, the strut 60 must generate sufficient force so that the moment associated with moment arm M, is greater than the combined opposite moment created by the air spring 30 and the weight of part of the ~ , 10 CO---u-i~ the axle assembly 52 and wheels 14. A~-iV~ f~
the force of the air spring 30 can be adjusted and even reduced to zero by exhausting the air from the air spring 30. Therefore, the strut 60 need only to create a moment associated with moment arm M, great enough to overcome the moment created by the weight of part of the ~ ) 10 .l. l~ the axle assembly 52 and wheels 14 to fully retract the wheel 14 if the air spring 30 is exhausted of air.
2~8~17~
9, The air spring 30 is typically u~ .ul~d to ~IJlwulllàt~ 90 psig in the normal highway mode shown in FIG. 2. Also, in the highway mode, the strut 60 of the preferred ~, l,s),l;" .1 exerts a force of alJ~Jlu~ ullal~l~ 3,000 Ibs. such that the lerlgth of the moment arm M~ is alJ~lu~dulalely 10 inches in generally steady shte 5 where the combined force of the air spring 30 and the trailing arm weight roughly equal and counterbalance the force of the strut 60.
To raise the wheels 14 or retract the c ~ 10, air is exhausted from the air springs 30 so that the moment associated with moment arm M, will overcome the combined force in the air springs 30 and the weight of the ~
system 10 and axle assembly 52 and wheels 14. The l.. l.~ - f d forces will start rotating the trailing arm æ about the pivot axis 41 of the bushed c~ 40 and raise the wheels 14. Preferably, the air will be c~ t~ly exhausted. As the trailing arm æ rotates, the force of the strut 60 decreases, but the moment arm defined between the line of force of the strut 60 and the pivot axis 41 increases until the ---r 10 is in the fully retracted mode.
When the ~ ~- system 10 is in the fully retracted mode, the strut 60 will typically exert a~ylU~illlat~ l~ 2,000 Ibs. of force and the moment arm M2 is ~Jlu~luaL~l~ 12 inches. The resulting moment is sufficient to overcome the opposing moment of the air bags 30, if any, and the weight of the ~ system 1û and axle assembly 52 and wheels 14. However, the strut 60 exerts less force as it is expanded. Thus, the moment arm must increase as the spring 68 expands so thatthe moment does not fall below that needed to keep the s~l~r retracted. The decrease in the force of the springs is more than countered by the increase in the moment arm, resulting in a moment that is greater when the wheels are in the retracted position than in any other position. Thus, the lever arm 64 ~ for the reduction in the force of the strut 60 as the spring 68 expands from a culll~ d state (FIG. 2~ highway mode) to a less ;u~ f d state (FlG. 5~ retracted mode).
The geometry of the lever arm 64 further reduces the size of the spring 68 required in the strut 60 to retract the wheels 14 and securely retain the wheels 14 in the 30 retracted position without the need for a separate locking device.
If the vehicle frame 12 needs to be raised such as, for example, if a rail bogie 20 (EiIG. 7) is to be installed under the vehicle frame, force must be applied to the trailing arm æ against the moment arm M~. This is ?.~ rd by IJIC~ UliLIllg the air spring 30 a sufficient amount to raise the frame with respect to the wheels 14 35 to the extended position as illustrated in FIG. 6. Preferably, each air spring 30 will WO 95/28312 ~ 17 8 PCT/US91/0~228 be ~ li~d to ~,U,UIU~ ill~t~ly 120 psig to move the frame to the raised position.
In the raised position, the spring 68 of the strut 60 is almost fully Cuu~,ul~ and exerts a,UIUlU~ 4,400 Ibs of force. The mûment arm ~4, on the ûther hand, is alJ,UlU~ ly 4 inches. It will be apparent that because of the position of the lever 5 arm 64, the change in length of the moment arm is not linearly ,u-uluu- liu~lal to the change in force of the strut 60. Thus, the ~ u~ air spring 30 is sufficient to overcome the moment, even with the increased force of the strut 6Q
After the frame rails 12 are raised by ~l~, ...lliLillg the air springs 30 to overcome the force of the strut 60, a rail bogie 20 can be positioned beneath the 10 frar~e rails 12 and the frame lowered thereon by exhausting u~ ui ~d air from the air springs 30 until the frame contacts the rail bogie 20. The rail bogie 20 is secured to the frame in a manner commonly known in the art.
Whereas the invention has been described with reference to a ~UUIyl~ spring between the frame 12 and the lever arm 64, it is also within the 15 scope of the invention to substitute a fluid cylinder or other tgpe of force applying element for the ~;UIII~UI~, spring 68. The fluid cylinder can be ,ul~ li~d at the same time that the air is exhausted from the air spring 30 to raise the trailing arms 22 to the retracted position illustrated in FIG. 5. The fluid cylinder can be dC~Li~L.,~ tû act as a shock absorber at times when the trailing arm is in the rûad 20 ~ngaging position.
Anûther form of a force applying element is an air spring which can be selectively activated to raise the trailing arm to the retracted position. Thus, an air spring can be used in lieu of the ~:UIII~ ' spring 68.
While particular ~ " ~` of the invention have been shown, it will 25 be ln-lPrcft)o.1 of course, that the invention is not limited theretû since ,..,~.liri.~i,",~
may be made by those skilled in the art, particularly in light of the foregoing teachings. ~Pq~rmq~ variation and ",~ are possible within the scope of the foregoing disclosure without departing from the spirit of the invention.
Claims (25)
1. In a suspension for a vehicle comprising a frame, the suspension including a pair of trailing arms pivotally mounted to the frame for vertical swinging movement relative thereto about a transverse axis between at least a retracted position and a road engaging position, an axle mounted to and between the trailing arms for carrying wheels for contact with a road surface, and a selectably variable force spring between the trailing arms and the frame for cushioning the swinging movement of the trailing arms in the road engaging position, the improvement comprising:
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm relative to the transverse axis that increases as the at least one trailing arm is moved toward the retracted position, and a compression spring mounted between the frame and the lever arm above the transverse trailing arm axis to bias the at least one trailing arm to the retracted position, whereby the force of the compression spring exerted on the lever arm tends to raise the at least one trailing arm to the retracted position when the force on the variable force spring is reduced.
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm relative to the transverse axis that increases as the at least one trailing arm is moved toward the retracted position, and a compression spring mounted between the frame and the lever arm above the transverse trailing arm axis to bias the at least one trailing arm to the retracted position, whereby the force of the compression spring exerted on the lever arm tends to raise the at least one trailing arm to the retracted position when the force on the variable force spring is reduced.
2. A suspension for a vehicle according to claim 1 wherein the variable force spring is an air spring.
3. A suspension for a vehicle according to claim 1 wherein the compression spring comprises a coil spring.
4. A suspension for a vehicle according to claim 3 and further comprising a dampening member mounted between the frame and the lever arm above the transverse trailing arm axis to dampen the swinging movement of the at least one trailing arm.
5. A suspension for a vehicle according to claim 4 wherein the dampening member is a shock absorber.
6. A suspension for a vehicle according to claim 4 wherein the dampening member is mounted coaxially with the spring.
7. A suspension for a vehicle according to claim 3 wherein the variable force spring is an air spring.
8. A suspension for a vehicle according to claim 1 and further comprising a dampening member mounted between the frame and the at least one trailing arm to dampen the swinging movement of the at least one trailing arm.
9. A suspension for a vehicle according to claim 1 wherein the at least one trailing arm has first and second ends and the lever arm is fixedly mounted to the at least one trailing arm between the first and second ends.
10. A suspension for a vehicle according to claim 9 wherein the lever arm has a terminal end which is disposed above the at least one trailing arm.
11. A suspension for a vehicle according to claim 10 wherein the compression spring is pivotally mounted at one end to the frame and at another end to the terminal end of the lever arm.
12. A suspension for a vehicle according to claim 11 wherein the variable force spring is mounted between the at least one trailing arm and the frame near the second end of the at least one trailing arm.
13. A suspension for a vehicle according to claim 12 wherein the frame further comprises opposed frame rails connected by a cross member and the compression spring is pivotally mounted at one end to the cross member.
14. A suspension for a vehicle according to claim 1 wherein the compression spring is pivotably mounted at one end to the frame and pivotably mounted at another end to the lever arm.
15. A suspension for a vehicle according to claim 1 wherein the at least one trailing arm pivots between the retracted position and an extended position where the frame is raised relative to the surface by the variable force spring, and the ratio of the moment arm in the retracted position to the moment arm in the extended position is greater than one-to-one.
16. A suspension for a vehicle according to claim 15 wherein the ratio of the moment arm in the retracted position to the moment arm in the extended position is three-to-one.
17. In a suspension for a vehicle comprising a frame, the suspension including a pair of trailing arms pivotally mounted to the frame for vertical swinging movement relative thereto about an axis between at least a retracted position and a road engaging position, an axle rigidly mounted to and between the trailing arms for carrying wheels, and a spring between the trailing arms and the frame for cushioning the swinging movement of the trailing arms, the improvement comprising:
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm about the axis that increases as the at least one trailing arm is moved toward the retracted position; and a dampening member having one end mounted to the frame and another end mounted to the lever arm above the axis;
whereby the dampening force from the dampening member on the at least one trailing arm increases as the at least one trailing arm is retracted to variably dampen the swinging movement of the at least one trailing arm.
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm about the axis that increases as the at least one trailing arm is moved toward the retracted position; and a dampening member having one end mounted to the frame and another end mounted to the lever arm above the axis;
whereby the dampening force from the dampening member on the at least one trailing arm increases as the at least one trailing arm is retracted to variably dampen the swinging movement of the at least one trailing arm.
18. A suspension for a vehicle according to claim 17 wherein the dampening member is a shock absorber.
19. A suspension for a vehicle according to claim 17 wherein the spring is an air spring.
20. A suspension for a vehicle according to claim 17 wherein the at least one trailing arm has a first and second end and the lever arm is fixedly mounted to the at least one trailing arm between the first and second ends.
21. A suspension for a vehicle according to claim 20 wherein the lever arm has a terminal end, which is disposed above the at least one trailing arm.
22. A suspension for a vehicle according to claim 21 wherein the dampening member is pivotally mounted to the frame and the terminal end of the lever arm.
23. A suspension for a vehicle according to claim 22 wherein the spring is mounted between the at least one trailing arm and the frame near the second end of the at least one trailing arm.
24. A suspension for a vehicle according to claim 23 wherein the frame further comprises opposed frame rails connected by a cross member and the dampening member is pivotally mounted to the cross member.
25. In a suspension for a vehicle comprising a frame, the suspension including a pair of trailing arms pivotally mounted to the frame for vertical swinging movement relative thereto about a transverse axis between at least a retracted position and a road engaging position, an axle rigidly mounted to and between the trailing arms for carrying wheels for contact with a road surface, and at least one selectably variable force spring between the trailing arms and the frame for cushioning the swinging movement of the trailing arms in the road engaging position, the improvement comprising:
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm relative to the transverse axis that increases as the at least one trailing arm is moved to the retracted position; and a force generating member mounted between the frame and the lever arm above the transverse axis to urge the at least one trailing arm toward the retracted position when the force on the variable force spring is reduced;
whereby the at least one trailing arm is in the road engaging position when the variable force spring is at a predetermined force level and the at least one trailing arm will automatically move toward the retracted position when the force of the variable force spring is reduced from the predetermined force level.
a lever arm fixedly mounted to at least one trailing arm and extending upwardly therefrom, the lever arm being positioned to define a moment arm relative to the transverse axis that increases as the at least one trailing arm is moved to the retracted position; and a force generating member mounted between the frame and the lever arm above the transverse axis to urge the at least one trailing arm toward the retracted position when the force on the variable force spring is reduced;
whereby the at least one trailing arm is in the road engaging position when the variable force spring is at a predetermined force level and the at least one trailing arm will automatically move toward the retracted position when the force of the variable force spring is reduced from the predetermined force level.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US1994/004228 WO1995028312A2 (en) | 1994-04-18 | 1994-04-18 | Trailing arm suspension with lever arm |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2188178A1 CA2188178A1 (en) | 1995-10-26 |
| CA2188178C true CA2188178C (en) | 2001-03-20 |
Family
ID=22242472
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002188178A Expired - Fee Related CA2188178C (en) | 1994-04-18 | 1994-04-18 | Trailing arm suspension with lever arm |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0752948A1 (en) |
| JP (1) | JPH09512223A (en) |
| KR (1) | KR970702189A (en) |
| AU (1) | AU694117B2 (en) |
| CA (1) | CA2188178C (en) |
| DE (1) | DE752948T1 (en) |
| ES (1) | ES2115567T1 (en) |
| WO (1) | WO1995028312A2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2779095B1 (en) * | 1998-06-02 | 2000-07-21 | Exel Ind | SUSPENSION FOR AGRICULTURAL MACHINERY, SUCH AS A SPRAYER |
| AU2003900336A0 (en) * | 2003-01-28 | 2003-02-13 | Steerable Wheel Systems Pty Ltd | Steerable single wheel unit for trailers |
| US8182193B2 (en) | 2008-10-28 | 2012-05-22 | Max-Atlas | Trailer for transporting freight containers and method of use |
| US8641062B2 (en) | 2011-10-07 | 2014-02-04 | Hendrickson Usa, L.L.C. | Lift axle suspension systems incorporating compression coil springs |
| US10308088B2 (en) | 2017-08-30 | 2019-06-04 | Hendrickson Usa, L.L.C. | Mechanical down-stop for axle/suspension systems |
| CN112440641A (en) * | 2019-08-30 | 2021-03-05 | 郑州宇通客车股份有限公司 | Liftable axle type suspension driving system assembly and multi-axle electric vehicle |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3674249A (en) * | 1970-07-13 | 1972-07-04 | H & H Equipment Co | Pneumatic suspension axle return device |
| US3771812A (en) * | 1972-04-25 | 1973-11-13 | Lear Siegler Inc | Air suspension with improved axle lifting structure |
| US4293145A (en) * | 1978-02-28 | 1981-10-06 | Taylor Glenn E | Auxiliary lift axle wheel assembly |
| US4166639A (en) * | 1978-02-28 | 1979-09-04 | Taylor Glenn E | Lift axle wheel assembly |
| US4497507A (en) * | 1983-04-11 | 1985-02-05 | Granning Suspensions, Inc. | Vehicle axle suspension |
| US4634141A (en) * | 1984-07-03 | 1987-01-06 | Lear Siegler, Inc. | Axle lift mechanism |
| FR2579144B1 (en) * | 1985-03-22 | 1989-06-30 | Renault | SUSPENSION ELEMENT, PARTICULARLY FOR MOTOR VEHICLE |
| IT1211186B (en) * | 1987-07-07 | 1989-10-12 | Fiat Auto Spa | REAR SUSPENSION FOR VEHICLES |
| DE9307587U1 (en) * | 1993-05-13 | 1993-08-05 | Wache GmbH & Co. KG, 20539 Hamburg | Spring-loaded wheels or rollers |
| US5403031A (en) * | 1993-12-08 | 1995-04-04 | The Boler Company | Parallelogram lift axle suspension system with a control for axle caster adjustment |
-
1994
- 1994-04-18 AU AU67068/94A patent/AU694117B2/en not_active Ceased
- 1994-04-18 CA CA002188178A patent/CA2188178C/en not_active Expired - Fee Related
- 1994-04-18 EP EP94914820A patent/EP0752948A1/en not_active Withdrawn
- 1994-04-18 WO PCT/US1994/004228 patent/WO1995028312A2/en not_active Ceased
- 1994-04-18 KR KR1019960705844A patent/KR970702189A/en not_active Abandoned
- 1994-04-18 ES ES94914820T patent/ES2115567T1/en active Pending
- 1994-04-18 DE DE0752948T patent/DE752948T1/en active Pending
- 1994-04-18 JP JP7526928A patent/JPH09512223A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ES2115567T1 (en) | 1998-07-01 |
| AU694117B2 (en) | 1998-07-16 |
| CA2188178A1 (en) | 1995-10-26 |
| DE752948T1 (en) | 1998-05-14 |
| AU6706894A (en) | 1995-11-10 |
| WO1995028312A3 (en) | 1996-02-15 |
| EP0752948A1 (en) | 1997-01-15 |
| WO1995028312A2 (en) | 1995-10-26 |
| KR970702189A (en) | 1997-05-13 |
| JPH09512223A (en) | 1997-12-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |