US2569126A - Pulldown cylinder assembly for mast slides - Google Patents

Description

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Sept. 25, 1951 Sept. 25, 1951 f n .`c.. bANlELs I 2,569,126

PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES vFiled oct. 2o, 1949 s sheets-sheet 2 INVENTOR. 5E C. DAN/ELS Arfogwfr Sept. 25, 19,51

L. C. DANIELS PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES Filed Oct. 20, 1949 INVENToR, 5 c. DAM/L5 BY v ff ig Patented Sept. 25,1951

PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES Lee C. Daniels, Cleveland, Ohio. assignor to Towmotor Corporation, Cleveland, Ohio, a corporation of Ohio Application October 20, 1949, Serial No. 122,476

1 This invention relates broadlyto lift trucks, and more specifically to improvements in the mechanism employed to effect the retraction of the mast slide.

In detail, the invention pertains to lift trucks of the type that are provided with a mast having an extensible slide thereon, a ram for,the elevation thereof, and a carriage on the slide mounted for limited reciprocative movement relative thereto. In such structure it is customary to interlink the ram with the slide to assure the descent thereof during the retraction of the ram and to provide a lost-motion connection in the linkage to facilitate the action of the free lift mechanism for the carriage during the initial elevation of the ram. An objectionable characteristic of the lost-motion mechanism resides in the freedom of the slide to Vdrop under the influence of gravity lwhenever the tensive strain on the pulldown linkage is relaxed, as occurs in stacking, dock loading, and similar operations when the carriage is brought to rest during the descent of the slide, but before the pulldown links have traversed the escapement plate of the lost-motion mechanism. i I

The present invention eliminates the foregoing objection through the provision of a piston cylin der assembly disposed between the top of the slide and the cross-head on thefree end of the` ram, the assembly being designed to pull the slide down during thedescent of the ram and snub the free movement thereof whenthe tension on the piston rod is released.

Further objects of the invention reside in the provision of a slide-retracting mechanism'which may be assembled within the hydraulic ram, a structure which will cushion the shock upon the slide when the movement of the ram is reversed, a device to retard the sudden descent of the slide when the load is removed from the carriage While in an elevated position, and an assembly which is eincient of operation, durable of structure, and economic of manufacture.

Other objects and advantages, more or less ancillary to the foregoing, and the manner in which all the various objects are realized will appear in the following description, which, considered in connection with the accompanying drawings, sets forth the preferred embodiment of the invention. Y

In the drawings:

Fig. 1 is a vertical sectional view of a fragmentary portion of a lift truck mast embodying the improved slide-retracting mechanism, Vthe slide being illustrated in its lowered position;

6 Claims. (Cl. 187-9) Fig. 2 is a front elevational view of the mast illustrating the position of the parts thereof during the ascent of the ram;

Fig. 3 is a similar elevational view illustrating the position of the parts of the assembly during the descent of the slide;

Fig. 4 is a similar elevational view showing the carriage `in an elevated position (resting on a platform with the load released therefrom) and the mast slide in a partially retracted position; and

Fig, 5 is atransverse sectional view of the upper portion of the ram and associatedV parts of the assembly, the section being taken on a plane indicated by the line 5-5 in Fig. 1.

Referring first to Fig. 4. the lift truck chosen herein for the purpose of illustration comprises a motor propelled vehicle I0 having a mast II on the forward end thereof, an extensible slide I2 mounted thereon, a load-carrying platform I3 associated with'the slide, and a hydraulic ram I4 for raising and lowering the slide. The loadcarrying platform is mounted on a carriage I5 which is organized for limited reciprocative movement along the slide during the initial movement of the ram. The ram is constructed with a cross-head I6 on the free end thereof, a pair of sheaves I1 carried thereby with chains I8 roved thereover, which are anchored at one end to the mast and at the other end, to the carriage. The side rails of the slide are united at their upper ends by a cross member I9 which is disposed for engagement with the cross-head during the ele-KV vation of the ram, but spaced therefrom when the slide and ram are in their lowered position (Fig. l). With this construction the initial movement of the ram will elevate the sheaves and pull the carriage upwardly until the cross-head engages the cross member I9; thereafter the chains willi merely roll over the sheaves during the remainingv elevation of the ram. When the ram is retracted the slide will normally descend therewith underthe influence of gravity, the weight thereof being; borne by the head of the ram until the slide is; brought to rest by engagement of the cross mem-- ber I9 with the upper ends of the mast.' Frequently, however, when the engaging surfaces ofi the mast and slide are worn or improperly lubricated, the slide will cock during the descent of:

is machined for snug sliding movement Withinv The ring 24 is disposed-for" abutting engagement with the cross-head I6, the lowery the nut 22.

face thereof being bored for theireeption of a tube 25 constituting a supporting Ame'rnjber for the lower end of a hydraulic shock absorber 26.

The cap or end wall of the lower end ,of the when the ram is brought to rest when the tension on the flexible connections is relaxed.

43. I n a 'lift truck embodying a mast having 'a' slide thereon, and a hydraulic cylinder having 4a hollow` piston `therein disposed for abutting shock absorber is formed withan eye r21 forthe reception of a wrist pin 28 which is seated aligned cross bores adjacent the free end of the tube 25. The shock absorber is of conventional form, embodying a piston 29 which is formed with restricted openings 30 therein to ypermit the ow of fluid from one side of the piston to the other. The cross-head I6 is bored for the rec'eption of the end portion of the shocl; absorber cylinder, and the outer end of the piston rod 3| is provided with an eye 32 having a wrist pin 33 therein which is supported in lugs 34afxed to and depending from the lower face of the slide cross member. The free ends of the lugs 34 are notched (Fig. 4) to clear the shock absorber cylinder cap 35 when the slide is in its fully retracted position.

In operation, when the motive fluid is introduced into the ram cylinder 20, the piston 23 will be distended and thus cause the elevation of the carriage I5 until the cross-head engages the lugs 34; whereupon theslide will be elevated as shown in Fig.- 2. During the descent of the ram, the piston .rod 3| will pull-the slide downwardlynntil the movement thereof is arrested by the engagement of the cross member I9 with the end of vthe mast 26. As the shock absorber piston rod is distendedv during the descent of the slide, the oil will flow through the restricted openings 30 in the piston, and thus cushion the shock imposed uponthe cross member.

When the'carriage is brought to rest before the load-carrying platform reaches its lowermost position, as occurs in .stacking operations (Fig. 4), the tension on the chains I8 and shock absorber piston rod 3l will be relaxed; and the weight of the slide will be imposed ,upon the extended piston rod and effect the reversal of flow of the fluid through the opening 30 in the-piston, thus snubbing the sudden descent of the slide.

Although the foregoing description is necessarily ofva detailed character, in order that the invention may be completely set forth, it is to be understood that the specic terminology is engagement with the slide for the elevation thereof, mechanism for retracting said slide and snubbing the descent thereof comprising a tube amxed within the free end of the hollow piston, a hydraulic shock absorber cylinder supported in the lower end of said tube, a piston in said shock absorber cylinder`.connected to said slide, and a cap on said shock absorber cylinder engaged with said vpiston during the initial descent of said hollow piston.

. 4. Mechanism for the retraction of a poweractuated mast slide in a lift truck comprising a hydraulic piston cylinderassembly constituting a slide pulldown member and a shock absorber, one of the parts of said assembly being attached to said slide, and the other part'of said assembly being attached to the power-actuating mechanism for the slide, whereby said slide will be pulled downwardly during the initial movement of the power actuating mechanism for the slide and subsequent movement thereof will be retarded.

5. In a lift truck embodying a mast, a slide mounted for reciprocative movement therein, a hydraulicram piston for elevating the slide, and a cross-.head on the free end of the piston, mechanism to pull vthe `slide downwardly comprising a member aiiixed to'and depending from the cross-head, a hydraulic shock absorber cylinder connected thereto, a second member afxed to and depending from the slide, and a hydraulic shock absorber piston connected to the last-named member.

6. In a lift vtruck embodying a mast, a slide frame thereon and a hydraulic ram plunger arranged 'for abutting engagement with the slide frame, mechanism for retracting the slide frame comprising a hydraulic cylinder, a cap on the bottom thereof pivotally connected to said plunger, -a cap-on the top of said cylinder, a piston-in said cylinder engageable with the cap on the top of the cylinder, a piston rod on said piston protruding v,through the cap on the top of .the cylinder, said piston rod being pivotally connected 'to said slide frame, said cylinder being mounted so thatA the piston will be disposed adjacent the vcap on the bottom of the cylinder when the ram plunger is in its lowered position and will engage the cap on-the top of the cylinder during the descent of the ram plunger.

LEE C. DANIELS.

REFERENCESV CITED The Ufollowing references 'are of record'in the flle of this patent:

UNITED STATES PATENTS Number 2 ,419 ,9.38

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