US2450354A - Control lever - Google Patents

Description

G. QUAYLE CONTROL LEVER Sept.- 28, 1948.

Original Filed Jul 25, 1940 4 Sheets-Sheet 1 INVENTOR Q BY ATT'ORNEY Sep L' ZS, 1948. I

G. QUAYLE CONTROL LEVER Original Filed July 25, 1940 4 Sheets-Sheet 2 g5 INVENTOR y 5% ATTORNEY Sept. 28,1948. G. QUAYLE 2,450,354

CONTROL LEVER 7 m l w ATTORNEY herein to be described and hydraulic lifting mechanism and means-whereby the said lifting mechanism is controlled, so that v lar feature of the lIlVBIltlOn; ing thevalve mechanism are so arrangedthat Patented Sept. 28, 1948 George Quayle, Philadelphia, 2a., assignor to The Yale: &-Towne Manufacturingfiompany;Stamford, (301111., a corporal;

- 4..Claims.

Y 1 This application is a division; of my application Serial No. 347,466; filed July 25,1940, now Patent No. 2,309,138, January 26,1943.- My;-invention claimed relates to a it is particularly adaptedfor use in an industrial truck of the type described in my earlier application.

For convenience in describing my ,inventionand in emphasizing its value, I shall refer to the construction of an industrial lift truckin which my invention is particularly useful, and shall describe the manner in which my hydraulic mechanism is mounted so that the lifting ram thereof transmits lifting movement to alifting platforrrr mounted for lifting movement relatively to the liftinghead of an industrial lift truck.

I A feature of my invention resides in an exceedingly simple control mechani smfor the valves; of

the hydraulic mechanism; whereby the operation thereof may be readily controlled. .As a particuthe means foroperatwhen the valves are moved to allow the lowering of. the ram of the hydraulic mechanism, and the lifting platform to which it imparts lifting movement, the said means may be operated at the con clusion of .the lowering movement 3 so that: the valveswill. be restored for the. lifting operation without any further operation by the. operator.

s By a slightlygdifierentuoperation of the said means, the valves may be returned to what I term a free handle position, and which Ifishall later describe more in detail. The control features thus outlined are exceedingly important in speeding up the operation of anindustrial lift truck.

My invention contemplates further a very unusual arrangement of the valvesforcontrolling the hydraulic mechanism whereby the pedal operation of one of the valves of the mechanism, will effect theoperation of .thelother of the valves, it being further contemplated that the pedaloperation will also control the speed of lowering in a very simple manner. As a feature of my valve mechanism, I have devised a releaseyalve arranged to unseat substantially before fluid f iows past its seat, thereby slowingdown erosion of the valve seat.

I have attempted to set forth generally the more important features of my invention, buta readin of the. specification which follows will, indicate that there are aflco nsiderable number of addlonal i atu st at a e of gr at impqr enqee form valuable portions of my contribution to the Original. application July 2 347,466. .Diyided and this .942, St t a v NO- 44 ion 'of. Connecticut 5, 11940,; Serialv ,No. a plica i n Mar 2,

( CL Jul-e533 -art. ;;-'--'Ihese additional features, together with e those a ready discussed; will of coursebeset forth in th e elaims hereinafter, it being further-understood', moreover,-- that I claims should be granted me of-a scope to prevent the utilizationof my con- --tribution to the art in specific. forms other than those which -I show and describe inthis application.

*For a-description-of-myinventioml shall refer to the drawings wherein Fig. l is aplanviewlooking; downwardly on atruck utilizingmy inven- 1 t-ion;=with certain-parts cut-away tobetter expose othersfthe partsw Fig. -2 is aside viewofthe g. 1'; with some ofthepartscut-away to better illustratethe operation of others of the --parts.--= Fig. 3 is a viewtaken along-lines 3-3 of Figs. 2 andl0.

-Eig. 4 is aperspectiveview of ojertain-of the-parts shown in=-Fig 3.: Figs. 5 and 6 are sections taken substantially along lines 5-5 and i6 of Fig. 3; :Fig-l is a view of certain of the parts of Fig. 6 in another position. Figs. 8

v and 9 are-sections along lines 88-.and 9-9 re- ---spectively-of- Fig 6. -Fig10 is a viewalong lines views of parts OfFlg; 10 in other operating posiytions.

particularly adapte :maining figures as well as to Figs. land 2.--The -truck comprises-what Ichoose tocall a--lifting -;head;-l0;--relatively to which is pivotally secured 'zwhat I; terma lifting platform I I, thelifting platform' H having a front vertical standard I2 against which operates the thrust pin l3 of a hy- "draulic ram forming part ofmyfhydraulic; lifting assembly] 4.

= Thi s -hydraulie--lifting assembly is actuated through means of a pivoting lever l5'by vertical winging movement of the steering handle I6 connectedto the leverby averticalstrut'll. The -;st eering handle; l6 oper ates the lifting mechanism and also steers the-front steering wheels l8 f'the; truck, aswill be'understoodby those-skilled ada ffied for-liftin movement relatively to the platform I I whereby the rearend of the platform is elevated at the same time that; the front' end carrying the vertical standard I2 is-elevated. Beferringnow-inore particularly to- Fig; '10, I

shallfirst 'descriloejhe' lifting head IU of my truck.

his lifting head has" mounted for rotation relat1ve1y thereto' the wheel supportingforks 20, in

which are mounted the front wheels I8 already described. The forks 20 form part of what I term a steering head 2 I, which is rotatable relatively to the lifting head through means of the roller bearings 22 and the sleeve bearing 23. Pinned to the steering head 2| as at 24, and forming part of the steering head 2|, is a collar 25, relatively to which is supported the lower main casting "a of the steering and lifting handle I6 through means of the pin 21. A rod 28 extending from the steering handle casting Ilia is pivoted at 29 to the collar 25 and forms part of the spring balancing mechanism for that handle, a construction which is not new in this application and need not be described therefore.

Formed as part of the handle casting IBa and movable integrally therewith is a pin 3|, relatively to which is secured the strut I'I terminating in a ball 33 resting in a ball socket of the actuating pivoted lever I5, already described. The main portion of this lever I5 is substantially triangular in form, as can best be seen in Fig. 1, and has formed as part thereof a sleeve 34 whereby it is secured for rotation about a shaft 35 carried in bearings 36 formed in each of the two up wardly extending standards 31 of the lifting head ID, as is probably best seen in Figs. 2, 3 and 10.

As is probably best seen in Figs. 2, 3 and 10, the lifting head has a downwardly and somewhat rearwardly extending portion 42 at each side thereof, within which are formed bearings for the mounting of a shaft 43. Right and left hand front lifting links 44 are adapted for mounting at the right hand and left hand ends of the shaft 43 just inwardly of the lifting head portions 42 for rotation on the said shaft. Each of these links has a bearing portion 45 (Fig. 5) whereby it is secured about a shaft 46 supported at each side of the lifting platform I I at points near the front end of that platform, as is quite apparent from Figs. 2 and 10.

Referrin now again to Fig. 5, each of the links 44 is shown as bifurcated at one end, forming bearings 41 for a pin 48, whereby each of the links 44 is pivotally secured to a threaded-rod connector 49. Each of the rod connectors 49 is threaded for the entry of a rod 5I which is secured thereto in adjusted threaded relation by a locking nut 50. As is best seen in Fig. 2, each rod 5I extends to the rear of the truck where it is secured to a second rod connector 52 in the same manner as it is secured to connectors 49. Each of the rod connectors 52 is in turn secured through a shaft 53 relatively to forks 54 forming the bifurcated ends of rear wheel supporting links 55. The links 55 in turn are pivoted at Ila to the platform frame II and support the rear load wheels I9.

It is now obvious that should the front vertical standard I2 of lifting platform II be moved vertically relatively to the lifting head I0, through the functioning of linkage and operating means not yet described, the shaft 46 on which are mounted the links 44 through their bearings 45, will cause the links 44 to rotate clockwise in Fig. 2 relatively to shaft 43 of the lifting head. This will cause the rods 5| to move to the right, thereby swinging the rear links 55 downwardly relatively to the lifting platform I I, effecting the movement of the lifting platform in a vertical direction to the position shown in dash and dot lines in Fig. 2.

For imparting lifting movement to the lifting platform I I as just outlined, I utilize the hydraulic liftin assembly of my invention, indicated generally by reference numeral I4. This hydraulic assembly includes a hydraulic ram having the rounded pin I 3 for imparting lifting thrust to the vertical standard I2 of the lifting platform as already discussed. Referring now to Figs. 3 and 10, my hydraulic lifting assembly I4 has a main base portion 51 from which extend ears 56 whereby the base portion, and therefore the entire hydraulic assembly, is secured for pivotal movement relatively to the shaft 43 already described is supported by the extensions 42 of the lifting head I 0. The base 51 extends upwardly and to each side to form a relatively large reservoir chamber 58 defined by an outer wall 59.

Abutments formed within the chamber 58 of the base 51 are bored and threaded as at 60 and 6|, there being secured relatively to the threads at 60 a sleeve-like member 62 forming the cylinder of the hydraulic pump of the hydraulic mechanism. Secured relatively to the threads 6|, there is a sleeve-like member 63 forming the cylinder for a hydraulic ram 64, the ram being of any type well known in the art, and carryin a series of piston rings '55, as Will be readily appreciated by those skilled in the art.

A pair of cover plates 66 and 51 are secured to the upper peripheral edge of the wall 59, whereby to completely enclose the reservoir 58, as best seen in Figs. 3 and 10. The cover plates 68 and I3! allow for the extension of the cylinders 62 and I33 therethrough, suitable sealing means being provided for sealing the openings through which the cylinders protrude, all as will be understood by those skilled in the art.

Mounted within the cylinder 62 is a pump rod 68, to the upper end of which is pinned an actuating collar 69 carrying a cap 10 which in turn has a skirt 'II surrounding the upper end of the cylinder 62. The lower end of the pump rod 68 carries a piston and a suitable leather or other type sealing washer I2, whereby reciprocation of the rod 68 will cause a pumping action within the cylinder, all as will appear clearly later.

A pair of telescoping compression springs I3 surround the pump rod 68 and lie between a washer 13a and the collar 69 whereby to urge pump rod 58 upwardly so as to bring the cap I0 against the pump actuatin roller 4|. The springs serve to press the cap against the roller 4|, thereby pressing the roller 4I and the actuating lever I5 in a counter clockwise direction, as viewed in Fig. 10, and thereby bringing the ball socket of the actuating lever I5 against the ball end 33 of the strut I'I so as to take up any lost motion between the several parts, all as will be quite apparent.

The ram 64 carries at the upper end thereof the rounded pin I3, which has already been described, and'which operates in a cooperating depression I4 formed Within a block I5 that is secured as by welding or in any other manner, to parallel beams 15. The beams 16 have mounted between them and on each end thereof a roller 1! as best seen in Fig. 4, the rollers 11 in turn bearing against a plate I8 which is welded or otherwise secured to form an integral part of the forward vertical standard I2 of the lifting platform. This construction has certain advantages that are emphasized in my earlier application and which need not here be discussed.

There is of course a suitable stufing box between the end of the hydraulic ram 64 and the cylinder 83 in which it is mounted, all as is well understood by those skilled in the art. For protecting the hydraulic ram, I employ a skirt I9 secured to the end of the ram through a cap 80,

I also secured. by linkage to Thus, welded or otherwise secured to vertical standard I2 are spaced stantially H-shaped lever- 83,

' The opposite end is closed by a threaded ily with. the. said skirtburrounding the outer .wall

. of the cylinder 93. As the hydraullcram moves vertically from Fig. ofcourse obviousthat the skirt-'19 will maintain the end ofthe ram covered at all times,

3. tolift the platform, it is thereby protecting it against picking up and carrying abrasive material into the cylinder. 63. The skirt 1! of cap 19 of. the pump rod. 68 has a like function.

, There was described earlier. the linkage where-. by the .lower end. of the platform ll. ismount- .ed relatively to the. lifting head .be well to .indicate that.

It. It will now the. upper end of the verticalstandard l2 of the lifting platform is plates 8|, between which land 10).. A sub.- .best shown in Fig. 1, islequipped with a sleeve portion .84 at one is supported a shaft 82 (Figs.

' end thereof whereby it is secured about. the

the H-shaped lever shaft 82. At its otherend,

83 has formed thereon a sleeve portion 85 where- .by it is secured relatively ,inbearings, 86a at the upperend 31 of the liftto a shaft 85 carried It is the function of the lever 83 ing head" 19.

of the vertical standard to guide the upper end .l2 in its movement relatively to the lifting head, just as the lower links M uide the lower end of the. standard and the platform I I in their elevating movement.

Referring now to Figs. 3, 5 and 6, I shall describe the various passages formed within the base 51 of'the hydraulic mechanism, and the valvespositioned relatively to those passages whereby the operation and 'draulic mechanism will be understood. A longitudinally extending main valve bore 81, 88 is formed in the control of my hybase 51 inclined somewhat relatively to the horizontal, as best shown in Fig.

i 6; This main valve bore includes a bore 81 and a-further-bore 88, the two bores being coaxial.

- The valve'bore 81, 88 is closed at one end through the screw threaded cap 89 holding in place the gasket 90, all as is best seen in Figs. 3 and 6. plug I95.

Mounted within the bore 81 is a valve 9| having a series of holes 92 drilled therethrough, as

- is best illustrated in section in Fig. 9. This valve is formed to cooperate hand end of the bore 81. A plug 94 is mounted with a seat 93 at the left within the bore 98, and itself has abore 95 therethrough forming a valve passage for cooperation with a valve 96. The

valve 96 is seated relatively to a valve seat 91 formed on the plug 94, and is held against this seat by a spring. 98, as is readseen.- A spring 99 lies'betweenthe plug 94 and the valve 95 to maintain the valve 9| normally against its seat 93.

a A passage I89 leads through base 51 into the valve bore 81- from the reservoirchamber 58, while a bore iill leads to the valve bore 88 from the pump cylinder 92, as can be seen by reference to Figs. 3, 5 and 6, the bore i9! communicating with the cylinder 82 through the bore-'- I92. "Through bores M9 and lil i, communication is established between the ram cylinder 63 and the extreme left hand end of the main valve bore which is to the left of the valve-96. Thus, it may be said that in Fig. 6 the right end of valve bore 81, 88 communicates with the reservoir, the central portion communicates with the pump, and the left end communicates with the ram.

*Theoperation of the several valves and pasthe lifting head 19..

usages so .-far-.- described will. nowebe-sexplained.

Upon-upward movement of the-pumprod Hand 4 its piston,-pressure againstithe end ofthe valve 7 9| will naturally be relieved; whereby to .move it away from its seat at 93 so-v that fluid will flow from the passage 190 through the holes 920i the stem ofvalve 9i and through, the passages llll,

. 192 into the pump- At the beg-inning of the downward -pumping stroke, the valve 91 ,wilLbe-come seated at 93, and all ofthe pump pressure will .b-eointrod-uced againstthe endof-thevalve 96.

This will unseat valve 98 relatively to its seat at 91 and against the resistance of spring 98, wherei by to force the fluid through the passages l M and .183 into the ram-.cylinder,-whereby to move the ram 64 verticallyto lift the platform. Through a ,series of strokes,.the,ram will bemoved to its completely elevated position.

scam surface Hi1. :aoperating shaft. 186 is.

If .now it isdesired to lower the lead, utilization is made of a camoperating shaft l Elli -and its Itwill be noted that the-cam mounted within a transverse bore 198 formed in. the base 51, as'best illustrated in Figs. 5, and 6,-the shaft extending ou'twardly of the. base 51 through a .suitable There will be described later :the mechanisms which are-mountedon the shaft .196 for operating that shaft and for controlling its movement. Suflic-e it to say at this time that when .theshaft. I06 isrotated in a counterclock- .wisedirec-tion toposition F, as seenin Fig. 6, its

surface I91 will move the valve'flloii its seat at 93, so as to establish low pressure communication passages I90, lfll, 192.

betweenthe pump and the reservoinBB. through Thereafter, up and down movement of the pump will have no effect whatsoever on the pumping mechanism, since it will be impossible to generate sufli-cient pressure tomove .thevalve 96 offits seat at 91, as is necessary when ,the position F it is desired to admitfiuid under pressure to, the

hydraulic. ram. .In this position of the parts,

This. rotation of rod ,end of the valve 9| against the right hand end of the valve 99, moving that valve off its seat at 91'. Communication will thenbe established between the ram and the reservoir 53 throughr't'he valve passage 95, the open valve seat 93, and the bores of valve 9| whereby to effect the lowering of the load platform.

Those skilled in the art will fully appreciate that the initia1 withdrawal of ,theyalve96 from its seat at 91, especially with a heavy load on the ram, will cause, an extremely swift movement of a. small quantity of fluid past the valve seat 91.

This extremely swift movement of fluid will gradually wear away the valveseat under the. usual operating conditions. Therefore, I have arranged means whereby there is substantially ,no how of vfluid past the valve seat 91 until the valve 96 has been m-ovedjoff its seat a sufficient distance to present a relatively large opening. The flow of fluid is then in relativelylarge volume, and as will beunderstood by those skilled in the art, the speed of the flow of the ,fluid will be. considerably reduced.

A is best shown in ll'igs. 6, .Tland 8,.theva1ve plug 94 is counterbzored alt 94a to present a somewhat larger flow opening than the remainder of valve bore 95. The valve stem of valve 96 has a necked portion 96a which is normally opposite counterbore 94a and is defined at one end by a shouldered portion III] which, in the normal position of the parts in Fig. 6, fully closes the bore 95 within which the valve 96 is adapted to slide. Extending from this surface III] in valve 96 are gradually tapered grooves I I I, shown in section in Fig. 8, the grooves III being entirely eliminated at the shouldered surface I I0.

Because of this relation of the parts, it is readily seen that even if the valve 96 is moved off its seat 91 toward the position of Fig. 7, there still will be very little flow past the seat 9! because the surface III! of the valve maintains substantially closed the valve bore 95. It is only after the valve 96 has been moved for a considerable distance, and somewhat further than shown in Fig. '7, whereby to space it from its seat 97 an appreciable amount, that the surface H is moved sufficiently out of the main portion of the bore 95 and opposite the counterbore 94a to expose part of the grooves II I of the valve stem.

An appreciable amount of fluid may then begin its flow past the valve seat 91, and at a speed which is comparatively low, so that the worst possible wear condition no longer exists. In effect, the valve bore 95 is thus controlled by two valves, the more critical of which is relieved of wear by the particular arrangement. It is well to indicate that the grooves III act to control the platform lowering speed, that speed being increased as the valve 96 is moved to the left in Figs. 6 and 7 to expose the deeper portions of the grooves to the fluid.

Referring now once again especially to Figs. 3, 5, 11 and 12, the end of the valve control rod I06 has secured thereto a foot treadle II5 through its sleeve portion I I 6 and cotter pin IIEa, whereby the treadle will rotate the rod I I35 to control the valve mechanism, as previously described.

Rotating with the treadle H5 and its sleeve IIB are a pair of ears II'I carrying a pin IIS. Mounted on this pin IIB through bifurcated legs H9 is a cam piece I20. This cam piece I20 has secured thereto a rod I2I which slides at its upper end in holes I22 formed in the cover plates 56 and 51 of the reservoir 58. A spring I23 surrounds the rod IZI and bears between the lower cover plate 6? and the upper surface of the cam I 20, whereby through the pin H8, it tends to rotate the treadle in a clockwise direction, looking at Figs. 11 and 12, and to maintain the valve control rod I06 in its full line position of Fig. 6. In this position of the parts, lifting movement of the hydraulic mechanism will be effected by the pumping action of the steering handle I6.

Movable also integrally with the treadle H5 is the roller I25 which, in the normal position of the parts, that is, in the position of the valve stem in Figs. 5 and 10, lies within a depression or cam surface I26 formed on the cam piece I20. It will of course be appreciated that the relation of the roller and cam surface may easily be reversed and that other cooperating parts may be used. With the truck platform in any particular elevated position, should it be desired to obtain a free handle by the moving of the valve control rod I85 and its cam surface IIII to the position F in Fig. 6, as already described, the operator steps on the treadle H5 and moves that treadle from the position of Fig. 10 to the position of Fig. 11 against the resistance of spring I23, whereby to move the roller I25 out of the depression or cam surface I26 to the position of Fig. v11. In this position of the parts, the spring I25 will tend, of course, to rotate the roller I25 and the treadle I I5 back to the position of Fig. 10 but the surface I21 cooperating with the roller will prevent such movement.

If, in this position of the parts, it is now desired to rotate the valve control rod I06 to the position L in Fig. 6, whereby to release the load by the movement of the valve stem 96 off its seat as in Fig. 7, the operator will move the pedal I I 5 to the position of Fig. 12, thereby compressing the spring I23 even more than previously. Naturally, in this position of the parts, the ram and platform II will be lowered and the fluid will be moved back into the reservoir.

The operator now has a choice of two actions. If he wishes to have a free handle so that-the truck may be hauled about, he may return the treadle slowly to the position of Fig. 11 where it is stopped by roller I25 striking surface I 21. In this position of pedal II5, the valve 9| will be maintained off its seat at 93 and free communication is had between the pump and reservoir to yield the free handle desired. On the other hand, if the operator wishes to place the valve mechanism in its initial position of Fig. 6 so that operation of the lifting handle will elevate the truck platform, he has only to release the treadle in the position of Fig. 12 to allow the full action of the spring I 23. The spring I23 will, in its then state of compression, rotate the treadle I I 5 rather swiftly towards the position of Fig. 11. The speed of movement is such that the surface IZ'I and cam piece I20 will merely be deflected upwardly by roller I25 and will be incapable of preventing the movement of the roller I25 back into the depression I25, as shown in full lines in Fig. 10. Therefore, the treadle will return to its initial position of Fig. 10, all as is quite apparent.

Also mounted for movement with the treadle H5 is a cam I28, the purpose of which will now be described. Referring also to Figs. 3, 5 and 10, it will be noted that the left hand front lifting link 44 has mounted thereon an adjustable screw bolt I29. It is the function of this bolt when the platform is in a fully elevated or other predetermined position, to strike the cam I28 so as to move the treadle from its position of Fig. 10 to the position of Fig. 11. The purpose of this action is to present a free handle immediately upon the elevation of the load platform to a predetermined position. This predetermined position may be varied, of course, by an adjustment of the bolt I29, all as is quite apparent.

It is thought that a further analysis and description of my invention is not necessary, especially since reference to the claims will further clarify the significance and value of various cooperating parts thereof.

I now claim:

1. In a combination of the class described, a control pedal, means mounting said pedal for movement into three controlling positions, a spring pressing said pedal into its first or normal position, said pedal being movable manually against said spring pressure to its second position, yielding detent means constructed and arranged for maintaining said pedal in said second position against the pressure of said spring tending to return it to its first position, said pedal being manually movable further against the pressure of said spring to its third position and being free of detent control in its third position, said pedal when released for free movement from said third position to said first position moving swiftly under the pressure of said spring to said first position, said pedal in said movement striking and overcoming said yielding detent means by the momentum of said swift movement, and said yielding detent means halting the return of said pedal at said second position when said pedal is returned slowly under manual control from said third position.

2. In a combination of the class described, a control pedal, means mounting said pedal for movement into three controlling positions, a spring pressing said pedal into its first or normal position, said pedal being movable manually against said spring pressure to its second position, yielding detent means constructed and arranged for yieldingly maintaining said pedal in said second position against the pressure of said spring tending to return it to its first position, said pedal being movable against the pressure of said spring to its third position beyond said yielding detent means and adapted to be held only manually in said third position, said pedal when released for free movement from said third posi tion to said first position moving swiftly under the pressure of said spring to said first position, said pedal in said movement striking and overcoming said yielding detent means by the momentum of said swift movement, and said detent means halting the return of said pedal at said second position when said pedal is returned slowly under manual control from said third position.

3. In a truck of the class described, a control pedal, means mounting said pedal for movement into three controlling positions, a spring pressed cam bearing against said pedal and yieldingly resisting its movement from a first or normal position, a roller on said pedal lying against a surface of said cam and further resisting the movement of said pedal from said first or normal position, said pedal when moved to a second position moving said cam against said spring pressure to withdraw said roller from said surface, whereupon a second surface of said cam through its spring will resist yieldingly the return of said roller from said second position into cooperation with said first surface, said pedal when moved even further to a third position against the resistance of the spring pressure and then released moving swiftly to said first or normal position by overcoming the yielding resistance of said second surface to the return of said treadle to said normal position, said econd surface halting said roller and pedal against return to said first position when said pedal is returned slowly as under manual control from said third position.

4. In a truck of the class described, a control pedal, means mounting said pedal for movement under manual pressure into three controlling positions, a spring pressing against said pedal and yieldingly resisting its movement from a first or normal position to a second position and then to a third position, a yielding detent, means whereby said yielding detent yieldingly resists the return of said pedal to said first position by said spring when said pedal has been moved from said first position to said second position, said pedal being movable to said third position by manual pressure against the resistance of the spring pressure, said pedal being free of detent control in said third position and when released from said manual pressure moving swiftly under said spring pressure to said first or normal position from said third position, said pedal in said swift movement overcoming the yielding resistance of said detent at said second position, and said yielding detent halting said pedal at said second position when said pedal is returned slowly as under manual control from said third position toward said second position.

GEORGE QUAYLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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