AU604145B2 - Axle lift mechanism - Google Patents

Description

TO:

The Commissioner of Patents A' TICN ACCEPTED AND AMENDMENTS

IF

1 AUSlTRtALI A Form PATENTS ACT 1952 COMPLETE SPECIFICAO'ON4 1 FOR OFFICE USE Short Title: Int. Cl: pljqation Number: o Lodged: o o 00 0 ~00 o 0 ,qqrpiplete Specification-Lodged: 00 0 Accepted: G:00 Lapsed: 0 0 ItPublished: Priority: 0 00 0 00* 00 0 1Rdated Art: T his docu en t contai us th 7aendments made under ISection 49 and is correct for printina 0 00 of Aplcat TO BE COMPLETED BY APPLICANT Address of Applicant, -2 8-50--EA-N-P-A-RK-BOE)iVARa.

-SANTLA-GINI-CA,

-GA-r-1RN--A--9 0-406, AcS, ijdoi~srtc e V vd(t Actual Inventor: LYLE HAGAN and WILLIAM C. PIERCE Address for Service: Complete Specification for GRIFFITH HACK CO., 601 ST. KILDA ROAD, MELBOURNE, VIC. 3004,

AUSTRALIA.

the invention entitled: "AXLE LIFT MECHANISM" The iollowing statement Is a full description of this invention, j-,cluding the best method of performing it known to me:- PF/CPIF/2/80 GRIFFITH HACK CO PA' ENT AND TRADE MARK ATTORNEYS MELBOURNE SYDNEY PERTH AJFW:E:P9538 AXLE LIFT MECHANISM Description Technical Field The invention relates to axle lift mechanisms for load-carrying vehicles and, more particularly, to lift mechanisms for automatically raising an- axle/wheel assembly so as to disengage the wheels from a ground surface.

t B".tkground Art Several types of vehicles, including semi-trailer truck vehicles and the like, have multiple sets of axle/wheel assemblies arranged in tandem so as to adequately support relatively heavy loads. To adjust the load support provided by these tandem assemblies, it 15 is known to employ suspension systems utilizing adjustably pressurized air springs and the like.

c''C When the vehicle is carrying a relatively light load, it is desirable to relieve the load transmitting relationship between the vehicle and one or more of the tandem axle/wheel assemblies, and also to disengage the axle/wheel assembly from ground contact so as to reduce tire wear. To relieve load support when an air suspension system is employed, air pressure can be reduced.

To achieve disengagement of the tires from the ground surface, devices commonly referred to as axle lift mechanisms can be employed. Prior lift mechanisms utilized stressed mechanical springs acting directly between a vehicle frame and the axle. When the downward ,l load forces exerted on the axle by the suspension system were relieved, such as through deflation of air springs, lifting forces exerted by the mechanical springs pulled I the axle upwardly to a raised position.

The foregoing type of lift mechanism has several i disadvantages. For example, with the axle in a raised position, sufficient spring stress must be maintained to I support the axle and various components of the suspen- -2sion system. Correspondingly, the substantially increased spring stress when the axle is in the lowered position comprises preload forces on the suspension system, thereby reducing the actual maximum vehicle .payload carried by the suspension system.

Improved axle lift mechanisms were later developed which overcame the problem of substantial payload reduction. An example of one such axle lift mechanism is depicted in Figure I and generally corresponds to the mechanism disclosed in the commonly assigned U.S. Patent v0 00 a to Pierce et al, 3,771,812, issued November 13, 1973.

ooo Referring to Figure 1, a lift mechanism 10 is used 0 00 o o with a vehicle having a wheel 11 mounted to an axle 12. The axle 12 is connected to a trailing arm 14 Q..0o through a conventional U-bolt 16 and nuts 18. The 9 15 o 15 trailing arm 14 is pivotably mounted through pivot connection 20 to a bracket 22 rigidly secured to the vehicle frame 24. The opposing end of the trailing arm S00 14 is secured to a conventional air spring 26 having a o0 0 rolling lobe configuration mounted to the vehicle frame 24 through bracket 28.

O**e The air spring 26 includes a piston element directly mounted to the trailing arm 14 and extending inwardly into the rolling lobe. When the air spring 26 *R is inflated, load from the vehicle is transmitted through the vehicle frame 24 to the trailing arm 14.

The force exerted by the air pressure in air spring 26 pivots the trailing arm 14 through the pivot connection so that wheel 11 engages the ground surface.

The axle lift mechanism 10 includes a lover arm 34 mounted to the vehicle frame 24 through a conventional pivot connection 36. One end of a coil spring 38 is connected to the lever arm 34 above the pivot connection 36 as shown in Figure 1, with an opposing end of spring 38 secured to vehicle frame 24 in a manner so as to be adjustably tensionerS. For example, the adjustable connection between apring 38 and frame 24 can include a frame bracket 44 securing a screw eye 40 having a -3threadably engaged nut 42. Adjusting the axial oosition of nut 42 on screw eye 40 correspondingly adjusts the tension of spring 38.

The lift mechanism alpo includes an axle lifting link chain 46 having an upper end secured to lever arm 34 through clevis 48 and bolt 50. A lower end of the lifting link chain 46 is secured to the axle 12 through an apertured lug 52 mounted to axle-attaching hardware to axle 12 and secured to the link chain 46 with bolt 54.

10 o o. When the vehicle is carrying a relatively light 0 0a o° load, it is desirable to disengage the wheel 11 from a 0o o 0 ground surface. Accordingly, air pressure in the air °o °o spring 26 is decreased and the load forces normally o' exerted on the trailing arm 14 by vehicle frame 24 are "o 15 correspondingly relieved. With the load forces on trailing arm 14 relieved, the tension of coil spring 38 rotates lever arm 34 in a counterclockwise direction.

o Correspondingly, link chain 46 lifts the wheel 11 and o o axle 12 to an appropriately raised position as shown in dotted line format in Figure 1. In the raised position, o °the top of the piston element 30 of air spring 26 bears against a bumper or stop 32 and provides a limitation to upward movement.

The aforedescribed axle lift mechanism 10 is somewhat advantageous over previously designed lifting mechanisms in that the lever-type mechanical "lifting advantage" is decreased as the lever arm 34 pivots in a clockwise direction as viewed in Figure 1 and axle 12 moves to a lowered position. Accordingly, although the coil spring 38 is increasingly stressed as lever arm 34 rotates clockwise, lifting forces on axle 12 are not substantially increased, because of the decrease in mechanical lever-type advantage. The flexibility of the lifting link chain 46 is advantageous over rigid links between lever arm 34 and axle 12 in that alignment problems do not result in severe defects in operation.

In addition, a rigid linking structure is subject to 4 pormanentU deformation~ if it -sustains a sharp blow or the Another type of known' axle lifting mechanis~m is depicted as lift mechanism 60 shown in Figure 2. Lif t 60 is used with a trailing arm 62 pivotably mounted at one end to a bracket 66 through pivot connection 64. Bracket 66 is rigidly secured to a support frame 68 of a load-carrying vehicle. Although not shown in Figure 2, the trailing arm 62 can also be connected to a vehicle axle and releasably coupled in a load supporting relationship to vehicle frame 68 through an 000 air suspension system in a manner similar to trailing 0 00 arm 14 depicted in Figure 1.

0. The lift mechanism 60 includes a lever arm 70 having 00090 its lower end coupled to the vehicle frame 68 through a pivot connection 72. A rigid forged bar 74 is pivotably coupled at one end to a top portion of the lever arm in an overcenter arrangement through pivot connection An opposing end of forged bar 74 is received through an aperture of a spring cup 76 and secured thereto with nut 78, washer 80 and bushing 82.

The spring cup 76 and forged bar 74 are mounted within a tubular housing 84 shown in sectional configuration in Figure 2. A compression spring 86 is also linearly mounted within the housing 84. One end of spring 86 bears against spring cup 76, while the other end of spring 86 bears against a stationery lip 77 of housing 84. Tension forces exerted on spring cup 76 by spring 86 can be varied by adjusting the axial location of threaded nut 78 along bar 74.

Also coupled to lever arm 70 and forged bar 74 at the pivot connection 75 is a bar link 90. The bar link 90 is correspondingly connected to a clevis link 92 and lifting chain 98 comprising a series of links 94. The lifting chain 98 is connected at Its lower end to the trailing arra 62 through anchor 96.

The operation of the axle lift mechanism 60 is similar to the operation of the lift mechanism 10 previously described with respect to Figure 1. That is, with the air spring (not ishown) in a deflated state, the lift mechanism 60 will operate to lift the trailing arm 62 and interconnected axle and wheels. The lifting force is provided by forces exerted by the compression spring 86 bearing against spring cup 76. The forces exerted on spring cup 76 are translated throuao the forged bar 74 to rotate the lever arm 70 through pivot connection 72. Rotation of lever arm 70 correspondingly exerts lifting forces on trailing arm 62 through bar i1 g link 90, clevis link 92 and lifting chain 98.

0 In the raised position, the lever arm 70 and other 0 0 o Oo components of lift mechanism 60 will have the relative o o positions depicted in Figure 2. When the air spring is 0ooo o 0 adequately inflated, forces exerted thereby on the oo0 15 o 15 trailing arm 62 overcome the forces exerted by compression spring 86, and the trailing arm 62 moves to a lowered position, thereby rotating the lever arm 70. As l the lever arm 70 pivots in a clockwise direction as C viewed in Figure 2, the lever-type mechanical "lifting advantage" is decreased. That is, although the forces exerted by the compression spring 86 increase as lever arm 70 pivots, the lifting forces on trailing arm 62 will not substantially increase.

Although the previously described axle lift mechanism is advantageous over other devices, substantial frictional forces are generated during movement of the spring cup 76 relative to housing 84. Frictional forces are also generated in the regions surrounding the coupling of bar 74 to spring cup 76 and the spring cup 76 and compression spring 86 bearing surfaces, Furthermore, the spring 86 exhibits wear due to its close proximity with the tubular housing 84. This wear causes accelerated spring failure.

In addition to the foregoing, it has also been found that the lifting forces exerted on the trailing arm 62 relative to the distance of the axle away from a raised position are relatively nonuniform. That is, as the 6 trailing arm 62 and interconnected axle -move downward f:om.

the raised position, the rate of change of the lifting forces exerted by compression spring 86 through forged bar 74, links 90 and 92, and link chain 98 is a relatively variable and non-uniform rate. The lifting forces increase at a non-uniform rate until the lever arm 70 rotatez through an angle whereby the rate of lifting force increase resulting from contraction of compression spring 86 is oo oa overcome by the decreasing mechanical advantage resulting 00 0 0 from the decrease in lever arm distance between pivot 0 00 0 o connection 72 and the forged bar 74. Accordingly, during 0 travel of the trailing arm 62 away from an initie' raised S0o position, the lifting forces exerted on the trailing arm 62 o0 exhibit a non-uniform increase up to a maximum, from which o oa point further travel results in a relatively rapid and non-uniform rate of decrease in the lifting forces.

0 0 0 00 cooo0o Summary of the Invention 0 0 According to the present invention there is a o provided in an axle lift mechanism for use in a vehicle having a support frame, an axle movable between lowered and raised positions, and suspension means for selectively 0" engaging and disengaging the axle from a load transmitting relationship with the vehicle, wherein the lift mechanism comprises: lever means pivotably copled to the frame for rotation between first and second positions corresponding to the lowered and raised axle positions, respectively; 7- i rra -n~a i ~PSn4Prr~m biasing means for exerting forces relative to the frame and sufficient to rotate the lever means from the first position to the second position, and lift the axle from the lowered position to the raised position in response to load-transmitting disengagement of the axle; and linkage means for operatively coupling the biasing means to the lever means, and for operatively coupling the lever means to the axle; go 00 the improvement wherein the linkage means comprises 0 oo00 a flexible strap for translating the biasing forces to o oo oo 0 lifting forces exerted on the axle and formed by o° continuously winding a KEVLAR (Registered Trade Mark) or oo o o 00oo other suitable cable back and forth between its ends so as 09 0 0 oo0 to form a series of parallel cords therebetween, and encasing the cords between a pair of flexible plastic sheets or molded enclosure.

0 00 0 O 0 0 00 0 00 0o 0 Brief Description of the Drawings 0 The invention will now be described with respe~t to ad'0 the drawings in which: Figure 1 is a side elevational view in section of a prior art axle lift mechanism; Figure 2 is a side elevational view in section of another prior art axle lift mechanism; Figure 3 is a side elevational view in section of an axle lift mechanism in accordance with the invention; Figure 4 is a sectional view of the axle lift -8 -86

Y

mechanism showing the configuration of tfhe :;prinq Cup, taken along lines 4-4 of Figure 3; Figure 5 is a sectional view of the a:xl liCt mechanism showing the conifiguration of the clovi.

connection between the flexible strap and rod, taken along lines 5-5 of Figure 3; Figure 6 is a sectional view showing the relative configurations of the cam and flexible strap of the axle lift mechanism, taken along lines 6-6 of Figure 3; Figure 7 is an enlarged sectional view of the °o oa flexible strap, taken along lines 7-7 of Figure 3; and o 0 0 oo Figure 8 is a plan view of the flexible strap during o 00 formation.

00.0 0 00 000 °000 0 Detailed Description o00o 15 o0 15 The principles of the invention are disclosed, by way of example, in an axle lift mechanism 100 as depicted in Figure 3. Like the known axle lift mechana ao isms 10 and 60 previously described with respect to 00 o 00 Figures 1 and 2, respectively, lift mechanism 100 is adapted for use with load carrying vehicles, such as S"o semi-trailer truck vehicles and the like, for automatically lifting a vehicle axle to a raised position when the vehicle is not heavily loaded. The lift mechanism 100 is also adapted to allow the axle to move from a raised position to a lowered position when the axle is in a load transmitting relationship with the vehicle frame.

With like numbered elements corresponding to similar elements of the vehicles and lift mechanisms previously described with respect to Figures 1 and 2, the axle lift mechanism 100 is shown in Figure 3 in use on a vehicle having a trailing arm 62 pivotably mounted at one end to a vehicle frame bracket 66 through a pivot connection 64. Bracket 66 is, in turn, rigidly secured to a frame 68 of the vehicle. Although not shown in Figure 3 of the drawings, an axle movable between raised and lowered positions can be conventionally coupled to the trailing 9 arm 62 In a manner: ,,imilav of comparable to thal previously described with respect to Figure 1. Xn addi tion, a suspension system such as air spring 26 shown in Figure 1. can be mounted to the opposing end of arm 62 for selectively engaging or disengaging the axle from a load transmitting relationship with vehicle frame 68.

Rigidly mounted to the upper surface of trailing arw 62 in a spaced apart relationship from the pivot conne-' tion 64 is a conventional anchor 96. The lift mechanism 100 includes a flexible strap 102 having one end 104 flexibly coupled to the anchor 96 through anchor bolt 106 or other comparable connecting means.

0 0 The strap 102 extends upwardly from the anchor 96 00a0 and engages a cam 108 as depicted in Figure 3.

0 o i1 Referring to Figures 3 and 6, cam 18 is pivotably mounted to the vehicle frame 68 through a pivot connection 110 comprising a pivot tube 111 and rocker shaft o0 °0 0 oo 112 coupled to frame 68 and received through tube 110.

o 00 00 0 Bearings or similar means can be employed to provide 000 20 relatively frictioness movement of shaft 112 relative to 0 00 tube 111. The tube 111 extends between and is secured to a pair of end supports 120. Only one end support 120 being shown on Figure 3. With the tube 110 rotatably receiving the rocker shaft 112, the tube 110 and interconnected end supports 120 can freely rotate relative to shaft 112.

The cam 108 also includes a curved wrapper 121 welded or otherwise secured to end supports 120 at their lower portion. At the rear portion of cam 108, the side supports 120 curve inwardly and are integrally secured to a tongue portion 114, extending upwardly along the rear of cam 108. With the cam 108 in the position shown in Figure 3, the flexible strap 102 extends along the tongue 114 and is received on an upper guide shaft 116 transversely mounted between the cam end supports 120.

The strap 102 is further threaded around a lower guideshaft 118 also transversely mounted to the end supports 120.

10 i The flexible strap 102 oxtends outwardly between t1he lower guide shaft 118 andicam wrapper 121 into a tubula housing 146 secured by suitable mounting means (not.

shown) to the vehicle frame 68. As shown in Figures 3 and 5, a terminating end 122 of the flexible atrap 102 is secured to a clevis 126 through a pin 124 securoe to the clevis 126 by means of retaining rings 125.

Extending outwardly from an opposing end of clevio 126 and rigidly welded or otherwise secured thereto in I1 substantially the same plane as strap 102 is a threado< 0o rod or bolt 128. Referring to Figures 3 and 4, the hoZt 0 0 o no 128 is received through an aperture 144 of a spring cup S130. A nut 132 threadably engaged on bolt 128 holds a bushing 134 in an abutting relationship against a 0000 000 surface of spring cup 130.

oO 0 15 o o0° The spring cup 130 has a substantially round configuration with a peripheral recess 138 and integral central portion 140, the aperture 144 extending through 0 00o "central portion 140. An annular inner rod housing 142 o o 0 is welded or otherwise secured to the central portion 140, and a portion of the threaded rod 128 axially Soo extends therethrough. A second nut 136 is threadably received (and rigidly attached) on the rod 128 to 0 prevent rotation of threaded rod 128 within housing 142, a 0 0 and prevents twisting of the strap 102 during adjustment of the coil spring 152 subsequently described herein.

The end of the tubular housing 146 adjacent spring cup 130 can be enclosed by an end cover 148 or similar means, with an opening 150 centrally positioned therein. Opening 150 allows for adjustment of nut 132 on threaded rod 128, so as to allow biasing of the position of rod 128 relative to spring cup 130 without any substantial disassembly oE lift mechanism 100.

Bearing against the spring cup 130 within recess 138 is one end of a tapered coil spring 152 as shown in Figure 3. The coil spring 152 extends longitudinally through the housing 146, with the threaded rod 128, clevis 126 and interconnected strap 102 located along 11 the axis of spring 152. The opposing end of spring 152 bears against an inner housing lip 153. The coil soring 152 tapers outwardly from the spring cup 130 to the housing lip 153. Mounted to the spring a n 130 intermediate the outer cylindrical surface of '3p 0 and the inner surface of tubular housing 146 is an annular wear plate 154. The wear plate 154 maintains a spaced relationship between the spring cup 130 and tubular housing 1Q6G Referring specifically to Figure 7, the flexible strap 102 can preferably include a set of spaced apart cords 156 formed from material such as that commercially Gold by DuPont Corporation under the trademark Kevlar, or other suitable cable and like articles. The cords 156 are encased in flexible polyurethane 158 or other 0o Q is material suitable for holding the cords 156 in place, by S0 o0 o0o means such as molding the cords 156 within the poly- 0 00 0 oo ue thane.

0o 0 first winding a single tKevlar or other suitable cable 0 0 o0 0 0continuously back and forth between a pair of sleevcs 160 to form the set of cords 156, Preferably, the flexible polyurethane 158 can then be molded with tho Kevlar or other suitable cords 156 embedded therebetween, Alternatively, the cords 156 can be encased within the polyurethane 158 by means of heat-sealing or similar adhesive treatments. During construction of the flexible strap 102, clamps 162 can be utilized at eac; end of the strap 102 adjacent the holding sleeves 166 as to ensurc the cordt! Lay in a single planar layer to reduce stress when the strap 102 is bent over a cam surface. It should also be noted that the spacing ot the cords 156 can vary. For example, the cords 156 shown in Figure 7 are spaced more closely together than are the cords 156 shown in Figure 8.

The operation of the axle lift mechanism 100 will now be described with respect to Figures 3-6, When the axle is in the raised position, elements of 12 2 4 flexible strap for translating the biasing forces to /21 a lift mechanism 10O will have the relative configurations shown in solid-line format in Figure 3. When the axle is in the lowered position, the trailing arm 62, anchor 96, cam 108 and clevis 1,26 will have the relative configurations shown in dotted-line format in Figure 3.

When the a;ile is in the lowe:ed position, and it is desired to lift the axle to the raised position, air pressure in the previously described air spring assembly can be decreased so as to relieve vehicle load from the trailing arm 62. When the vehicle load is relieved, the only forces exerted downwardly on the flexible strap 102 throuLh anchor 96 will be the weight of the trailing arm 62 and axle. Lifting forces will be exerted on the trailing arm 62 by compression spring 152 acting through strap 102. That is, spring 152, being in a loaded state, will exert forces on the spring cup 130 so as to 0 0 0 move the spring cup 130 toward the position adjacent end cover 148 as shown in Figure 3. In turn, spring cup 13Q will exert pulling forces on threaded rod 128 througih 0 2 the central portion 140 bearing against bushing 134.

With threaded rod .28 connected to flexible strap 102 through clevis 126, orrespoiiding forces are exerted -on the flexible strap 1,02. With the cam 1.08 pivotable through rocker shaft 112, and the flexible strap 102 wound around guide shafts 116 and 118, the cam 108 will be rotated in a counterclockwise direction as viewed in Figure 3. Rotation of cam 108 will exert lifting forces on trailing arm 62 through strap 102 and anchor 96, As the cam 108 rotat(,. towards the raised position, the length of flexible otrap 102 bearing against tongue 114 A 30 will increase, while the length of strap 102 bearing against wrapper 121 will decrease. The cam I08 therefore acts as a lever to translate linear forces exerted on flexible strap 102 through rod 128 to upward liftinq forces at the connection of flexible strap 102 to trailing arm 62. Accordingly, the trailing arm 62 and interconnected wheel/axle assembly (not shown) are lifted toward a raised position so that the wheels are 13 disengaged fromw a ground surface.

It should be noted that the threaded rod 128 maintains a substantially coaxial relationship to the spring cup 130 and spring 152. Furthermore, lines of force exerted through the portion of flexible strap 102 interconnecting rod 128 and cam 108 remain parallel to rod 128 during lifting of the axle. Accordingly, the vector sum of the forces exerte on spring cup 130 is coaxial with rod 128 and parallel to force lines through strap 102. By maintaining this relationship, frictional forces between the spring cup 130 and the tubular housing 146, and between spring cup 130, spring 152 and rod 128 are minimized relative to frictional forces exhibited in other types of lift mechanisms. In addition, the lift mechanism 100 provides a relatively unico oc form lifting force change rate on the axle throughout movement between the lowered and raised axle positions.

When it is desired to transmit vehicle load to the wheel/axle assembly, the previously described air spring assembly can be inflated so as to exert downward forces on the end of trailing arm 62 opposing the pivot connection 64. With the downwardly exerted forces exerted on trailing arm 62 sufficient to overcome the lifting forces exerted by the coil spring 152 through flexible strap 102, the cam 108 will rotate thv)ugh rocker shaft 112 in a clockwise direction as viewed in Figure 3. As the cam 108 rotates, the length of flexible strap 102 bearing against tongue 114 will decrease. Correspondinqly, however, an increasing portion of the flexible strap 102 between clevis 126 and lower quideshaft 118 will bear against the cam wrapper portion 121. With the cam 108 rotating in a clockwise direction, forces are exerted on threaded rod 128 through clevis 126 and flexible strap 102. These forces are correspondingly exerted on spring cup 130 through bushing 134 in a direction opposing forces exerted by tapered coil spring 152. Accordingly, clevis 126, threaded rod 128 and spring cup 130 will move to the right as viewed in 14 -i i- ~~rll ~.i~F Figure 3.

As the spring cup 130 moves toward the cam 108, the tapered coil spring 152 is increasingly loaded and exerts increasing forces against spring cup 130 opposing movement. As the cam 108 rotates, the lifting forces provided by the lever arm advantage of the cam 108 relative to the rod 128 connection decrease. However, with the tapered coil spring 152 beingj increasingly tensiored as the cam 108 rotates, the opposing forces exerted on rod 128 through spring cup 130 will correspondingly increase. Accordingly, the lifting forces exerted on trailing arm 62 as the cam 108 rotates either clockwise or from its raised position, or counterclockwise from a lowered position, change at a substantially uniform rate.

15 o o° By maintaining the forces acting through rod 128 o substantially coaxial relative to spring cup 130 and o 0 sprino 152, relative friction between cup 130, tapered S° coil spring 152 and tubular housing 146 is minimized.

0000 o. 0 Tapering of the coil spring 152, in addition to the 00 o 20 0 Oa arrangement of cam 108, flexible strap 102 and threaded rod 128, provides for a relatively higher and more uniform lifting force on trailing arm 62.

In addition, the flexible strap 102, constructed of Kevlar or other suitable material and providing linkage 25 between threaded rod 128 and trailing arm 62, has a relatively high tensile strength. Furthermore, the strap 102 has a relatively minimum tendency to stretch and provides good abrasion resistance. In addition, with the strap 102 constructed as described herein, manufacturing costs are relatively less expensive.

It will be apparent to those skilled in the pertinent arts that other embodiments of an axle lift mechanism in accordance with the invention can be designed. That is, the principles of an axle lift mechanism are not limited to the specific embodiment described herein. Modifications and other variations of the above-described illustrative embodiment of the 15 invention may be effected without departing from the spirit and scope of the novel concepts of the invention.

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Claims (4)

1. In an axle lift mechanism for use in a vehicle having a support frame, an axle movable between lowered and raised positions, and suspension means for selectively engaging and disengaging the axle from a load transmitting relationship with the vehicle, wherein the lift mechanism comprises: lever means pivotably coupled to the frame for rotation between first and second positions corresponding to the lowered and raised axle positions, respectively; on o0 0 0 10 biasing means for exerting forces relative to the oo° o frame and sufficient to rotate the lever means from the o o0 oOOo 0 first position to the second position, and lift the axle o oo from the lowered position to the raised position in ooo response to load-transmitting disengagement of the axle; o 0 oo and linkage means for operatively coupling the biasing means to the lever means, and for operatively coupling the o: lever means to the axle; ooo the improvement wherein the linkage means comprises :20 a flexible strap for translating the biasing forces to lifting forces exerted on the axle and formed by continuously winding a KEVLAR (Registered Trade Mark) or other suitable cable back and forth between its ends so as to form a series of parallel cords therebetween, and encasing the cords between a pair of flexible plastic sheets or molded enclosure.

2. An axle lift mechanism in accordance with Claim 1 wherein the plastic sheets are constructed of flexible polyurethane and are secured together with the cords therebetween,

3. An axle lift mechanism in accordance with Claim 2 wherein the plastic sheets are glued together.

4. An axle lift mechanism in accordance with Claim, 4 wherein the plastic sheets are molded together. 17 20283/88 An axle lift mechanism substantially as herein described with reference to and as illustrated in the accompanying drawings. DATED this 7th day of February, 1990. LEAR SIEGLER, INC. By Its Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 09 00 00 0 0 00 o 00 00 0 0 00 0 00 0000 0 0 00 00 00 0 0 00 0 0 I C 1 18 20283/88