US3476016A - Apparatus for producing coordinated,simultaneous actuation of multiple rams - Google Patents

Description

NOV. 4. 1969 mxo ET AL 3,476,016 APPARATUS FOR PRODUCING COORDINATED, SIMULTANEOUS ACTUATION OF MULTIPLE RAMS Filed Oct. 20. 1967 Hg. 2 INVENTOR- MAX. FREY DONALD M. FALLST TOM E. DIXON HLLys 7pm, *WW

United States Patent U.S. Cl. 91-411 1 Claim ABSTRACT OF THE DISCLOSURE Load pusher apparatus with two rams for actuating a pusher member in the apparatus, the rams being arranged for coordinated, simultaneous actuation. A first conduit is provided connected to the head end of one ram, a transfer conduit interconnects the rod end of the one ram and the head end of the other ram, and a third conduit connects to the rod end of the other ram. With fluid supplied the one ram through the first conduit to actuate the ram, captive fluid in the one rams rod end transfers to the head end of the other ram causing the other ram to be actuated. The two rams are connected to the pusher member in such a manner that the rams on actuation move opposite pusher sides an equal amount, thus to prevent skewing. The apparatus further includes, in the piston of each ram, a fluid passage opening onto opposite sides of the piston, and a valve inhibiting fluid flow through the passage from the rod end to the head end of the ram While permitting flow in the reverse direction. In this way exhausting or replenishing of the captive fluid is permitted, whereby the volume of the captive fluid remains substantially constant.

The present invention relates to the operation of fluidoperated rams, and more particularly to apparatus for producing coordinated, simultaneous actuation of at least a pair of such rams. The preferred embodiment of the invention described herein has to do with a load pusher attachment for a lift truck, where two rams are utilized to cause equal movements in opposite sides of a pusher member in the attachment, with reduction of any tendencies of the pusher to skew in the attachment.

A common form of load pusher apparatus includes a frame, a pusher member mounted for movement toward and away from the front of the frame, and a pair of fluid-operated rams which are operated simultaneously to move the pusher member. For such equipment to function properly, obviously the rams must extend and contract evenly in order to avoid undesirable skewing of the pusher member and binding of various other parts of the equipment. However, in known means for actuating rams in such equipment, ram coordination has often been poor.

A general object of the present invention, therefore, is to provide, in an organization including at least a pair of fluid-operated rams, novel apparatus for producing coordinated, simultaneous actuation of such rams.

More particularly, an object of the invention is to provide such apparatus which includes means controlling fluid flow to and from the rams whereby the rams, during their simultaneous operation, extend and contract evenly.

To accomplish these objects, the apparatus contemplated herein includes a first conduit for carrying fluid to and from the head end of one of the rams, a transfer conduit connecting the rod end of the one ram to the ICC head end of the other ram for accommodating fluid transfer between the rams, and a third conduit for carrying fluid to and from the rod end of the other ram. The pistons of the rams are so sized that the effective piston area exposed to the rod end of the first-mentioned ram is substantially equal to the effective piston area exposed to the head end of the second-mentioned ram. With such a construction, fluid in the rod end of the first-mentioned ram, in the transfer conduit, and in the head end of the second-mentioned ram constitutes a captive fluid acted upon by, and acting on, the pistons of the rams, to produce simultaneous like movement of the pistons.

A further and related object of the invention is to provide novel means for automatically maintaining the volume of such captive fluid constant, regardless of any specific gravity change resulting from a change in temperature, or other factor such as leakage, which could alter the original volume of the captive fluid. Such a provision is important in insuring proper coordination of the rams. Thus the invention features, in the piston of each ram, a novel organization of a fluid passage opening onto opposite sides of the piston, and valve means inhibiting fluid flow through the passage in one direction while accommodating such flow in the reverse direction, with the flow direction being such as to bring about replenishing or exhausting of captive fluid, as needed.

Yet another object of the invention is to provide apparatus of the type so far described which is relatively simple in construction and reliable in operation.

These and other objects and advantages attained by the invention will become more fully apparent as the description which follows is read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified top plan view illustrating load pusher apparatus as contemplated by the invention, with a pair of hydraulic rams operable to extend a pusher member in the apparatus when actuated;

FIG. 2 is a schematic diagram illustrating the rams and other hydraulic components in the hydraulic circuit for the rams.

Turning now to the drawings, and referring first to FIG. 1, indicated generally at 10 is load pusher apparatus of the type adapted for attachment to the front of a lift truck. The pusher includes aframe 12 and apusher member 14 which is movable toward and away from the front of the frame. The pusher member may have a substantially rectangular outline, viewing it from the front, and is disposed in an upright position, with the front substantially perpendicular.

The pusher member is mounted on the frame for movement toward and away from the latter through a pair offoldable arm assemblies 16, 18.Arm assembly 16 is disposed aboveassembly 18, and includes an inner arm part 16a pivotally connected at 20 to anouter arm part 16b. The inner end of part 16a is anchored to an elongatedupright tube 22 which is journalled on an uprightelongated pin 24 suitably mounted onframe 12. The outer end ofpart 16b is slidably mounted onpusher member 14, adjacent the right side thereof in FIG. 1, through an elongatedupright pin 26 suitably secured to the outer end of the arm part, which pin is slidably received in a pair of opposed, vertically-spaced channel pieces, such aschannel piece 28, mounted on the pusher member.

Arm assembly 18 is similar in construction toassembly 16 with inner andouter arm parts 18a, 18b, respectively, mounted in a similar manner onframe 12 andmember 14, respectively. Thus, part 18a has its inner end anchored to a tube 27 which is journaled on apin 29 mounted on the frame, and its outer end pivoted topart 18b through apin 31. The outer end ofpart 18b is slidably mounted onpusher member 14 in a manner substantially the same as that shown for the outer end ofarm part 16b.

The outer arm parts of the arm assemblies are pivotally connected together through a suitable pivot pin 30.Part 16b, in addition, is connected toframe 14 through alink 32 having one end pivoted at 34 to arm part 1612 and the other end pivoted at 36 to the pusher member.Link 32 preventsmember 14 from shifting laterally relative to the frame.

Details of a similar pusher member mounting are described in a copending application of Donald M. Faust entitled Folding Arm Assembly for a Load Pusher, filed July 17, 1967, Ser. No. 653,695.

A pair ofhydraulic rams 38, 40 are provided for shifting the pusher member toward and away from the front of the frame. Ram 38 has its cylinder 38a pivotally connected toframe 12 through an upright pivot pin 42 suitably mounted on a pair of vertically-spaced,parallel plates 44, 46 that form part of the frame. The rod 38b of the ram is pivoted at 48 to acrank 50 which is suitably anchored to previously-mentionedtube 22. Similarly,ram 40 has its cylinder pivoted toplates 44, 46 of the frame through a pin 52. Its rod is pivoted at 54 to acrank 56 which is anchored to tube 27.

On extension of the rams the arm assemblies unfold with shifting of the pusher member forwardly away from the frame. Contraction of the rams causes the reverse operation.

Turning now to FIG. 2, and further considering the rams,ram 38 includes inside its cylinder apiston 58 joined to the inner end of its rod. The piston includesopposite sides 58a, 5812 which face toward what are referred to herein as head and rod ends, respectively, of the ram. The surface areas ofsides 58a, 58b constitute opposing effective piston areas ofpiston 58.Side 58a has a greater area than that ofside 58b, due to the lack of any piston rod projecting from the side.

Provided inpiston 58 is abore 60 which extends downwardly part way into the piston from side 5812. The base ofbore 60 communicates with analigned bore 62 of somewhat reduced diameter which opens ontoside 58a. Bores 60, 62 are referred to herein collectively as means defining a fluid passage opening onto opposite sides of the piston.

Seated at the base ofbore 60, and closing off the upper end ofbore 62 is a ball, or valve means, 64 having a diameter somewhat smaller than the diameter ofbore 60. The ball is urged against the base ofbore 60 by means of a biasingspring 66 the lower end of which acts against aring 68 seated on the ball, and the upper end of which seats against aplug 70 screwed into the upper end ofbore 60.Plug 70 is provided with an axial bore 70a which opens onto the upper side of the piston and also opens to the interior ofbore 60.Spring 66 is so chosen that with fluid at normal operating pressures acting onside 58a of the piston, and hence on the base ofball 64, the ball remains seated in the position shown.

The head and rod ends of the cylinder ofram 38 are provided withports 72, 74, respectively, for admitting hydraulic fluid to and exhausting it from the ram. The rod end ofram 38 is also provided with ableeder screw 78 which is screwed into a suitable bore provided in the cylinder.

Ram 40 is similar in construction toram 38, and includes in its cylinder apiston 80 joined to the inner end of the rod of the ram. Piston 80 includesopposite sides 80a, 80b facing the head and rod ends, respectively, of the ram. The surface areas ofsides 80a, 80b constitute opposing effective piston areas ofpiston 80. The piston is so sized that the elTective piston area of side 80a is substantially the same as effective piston area of side 80a is substantially the same as the effective piston area of previously-mentionedside 58b, and less than the area ofpiston side 58a.

Provided in piston are a pair of aligned bores 82, 84, which correspond to previously-describedbores 60, 62, respectively, inpiston 58. Seated in the base ofbore 82 is aball 86 closing off the upper end ofbore 84 and corresponding toball 64 inbore 60.Ball 86 is biased by aspring 88 corresponding tospring 66, which is held in place between aring 89 and aplug 91 that correspond to ring 68 and plug 70, respectively.

Ports 90, 92 are provided for admitting and exhausting fluid to the head and rod ends, respectively, of the cylinder ofram 40. A bleeder screw 96, which is similar to previously-mentionedscrew 78, is provided, which is screwed into a suitable bore in the head end of the rams cylinder.

The cylinders of the rams are so constructed thatpistons 58, 80 are permitted substantially the same amount of travel therein between opposite ends of the cylinders.

Considering further details of the hydraulic circuit provided forrams 38, 40, a main control valve is shown at 102 connected withram 38 through aconduit 104 leading toport 72 in the ram. Aconduit 106 connectsport 74 of theram 38 to port ofram 40, and aconduit 108 connectsport 92 tovalve 102.Conduits 104, 106, 108 are referred to herein, respectively, as first, transfer, and third conduits.

Valve 102 is also connected to a source of hydraulic fluid including apump 110 and areservoir 112. The pump has its intake and connected to the reservoir through aconduit 114 and its discharge end connected to the valve through aconduit 116.Reservoir 112 is connected directly to the valve by aconduit 118.

The valve spool ofvalve 102 is represented in the drawing as an elongated rectangle divided into three squares. The valve spool is adjustable to any one of three positions, and the symbols in each of the various squares indicates how flow takes place through the valve for each of such positions. Thus, with the valve spool in the position illustrated,conduits 104, 108 are closed off where they join with the valve andconduits 116, 118 are connected together through the valve. With the valve spool shifted to the right in the figure, fluid flow takes place as indicated by the arrows in the left square of the valve spool. More particularly, hydraulic fluid is pumped intoconduit 104 and exhausted fromconduit 108. With the valve spool shifted to the left in the figure, flow takes place as indicated by the arrows in the right square. In this position of the valve spool fluid is pumped intoconduit 108 and exhausted fromconduit 104. Also shown for the valve are springs represented at 105, 107 which bias the valve spool to the neutral position indicated, and manual means 109, 111 which are actuatable to shift the valve spool.

Further describing the apparatus shown in FIG. 2, it includes means for charging, or filling, the rams with bydraulic fluid. Such means includes a normally closed chargingvalve 120, a'pair ofconduits 122, 124 connecting valve toconduit 104, and aconduit 125 connecting the valve toconduit 106. A spring-biasedcheck valve 126 is connected toconduit 104 byconduit 124, and toconduit 108 by aconduit 128.Valve 126 operates as a pressure relief valve betweenconduits 104, 108.

Explaining the operation of the pusher apparatus, to fill the rams initially with hydraulic fluid, bleeder screws 78, 96 are adjusted to open the bores that receive them,valve 102 is adjusted to admit fluid under pressure toconduit 104, and chargingvalve 120 is opened. Under such circumstances, fluid under pressure is introduced into the rams throughports 72, 74, 90.

With bleeder screws 78, 96 open, the space insideram 38 which is bounded bypiston side 58b is vented to the atmosphere, and similarly, the space withinram 40 bounded by side 80a ofpiston 80 is vented to the atmosphere. With venting, fluid introduced into the spaces is permitted to completely fill the spaces and flush out any air. In this connection, in an actual installation, the two rams are usually disposed horizontally (as shown in FIG. 1), and bleeder screws 78, 96 are located to produce optimum venting, i.e., on the sides of the rams which are on top in the particular installation.

With fluid under pressure introduced intoports 72, 74, '90piston 80 moves to the rod end ofram 40 with the space inside of the ram bounded by side 80a entirely filling with fluid. Also, despite the fact that hydraulic fluid is supplied simultaneously to both ends ofram 38, since the surface area of piston side 58w exceeds that ofside 58b,piston 58 moves toward the rod end ofram 38. The space inside ofram 38 bounded byside 58 fills with bydraulic fluid. All air is purged fromconduit 106 and the spaces in the rams vented bybleeder screws 78, 96,

With the pistons thus shifted to the rod ends of the rams, bleeder screws 78, 96 are readjusted to close the bores that hold them, and chargingvalve 120 is closed. Withvalve 120 now closed, it will be noted that there is captive fluid in the head end ofram 40 and also intransfer conduit 106. Such captive fluid transfers back and forth between the head end ofram 40 and rod end ofram 38 as the rams are contracted and extended with operation ofvalve 102.

To contract the rams,valve 102 is adjusted to supply fluid under pressure to conduct 108. Such fluid flows into the rod end ofram 40 causing contraction of the ram, and exhaust of fluid from the head end of the ram throughconduit 106 to the rod end ofram 38. Since the eifective piston area of piston 80a is substantially equal to that ofpiston side 58b, fluid exhausting fromram 40, on contraction thereof, produces simultaneous, like contraction ofram 38. And, on contraction ofram 38, fluid exhausts from the head end of the ram and flows to the reservoir throughconduit 104,valve 102 andconduit 118.

According to the invention, the bores and ball pro vided in each piston function to maintain the overall volume of the captive fluid substantially constant, despite the usual expansion and contraction of fluid that occurs with temperature changes. Explaining what takes place when a temperature increase causes the volume of the captive fluid to expand, on extension of the rams,piston 80 reaches the rod end ofram 40 beforepiston 58 reaches the rod end ofram 38. Withpiston 80 at the end of its travel, the pressure of captive fluid in the head end ofram 40 increases. When this pressure is sufliciently high (i.e., well above normal operating pressures),ball 86 shifts upwardly againstspring 88 and opens the top ofbore 84. This permits fluid to flow from side 80a toside 80b of the piston, withpiston 58 continuing toward the rod end ofram 38. Whenpiston 58 reaches the limit of its travel,valve 102 is adjusted to its neutral position and the pressure of fluid in the head end ofram 40 drops. Therefore, ball '86 again closes oif the top ofbore 84, with the overall volume of the captive fluid again the same as it was when the rams were initially filled with fluid.

In a somewhat similar manner, when leakage or a temperature drop contracts the volume of the captive fluid, on extension of the rams,piston 58 reaches the limit of its travel first. On this occuring, the pressure of fluid in head end ofram 38 increases, and when it becomes sufliciently high,ball 64 shifts upwardly againstspring 66 to open the top ofbore 62. Fluid then flows fromside 58a toside 58b ofpiston 58 causing piston to continue moving toward the rod end ofram 40. Whenpiston 80 reaches the limit of its travel,valve 102 is adjusted to its neutral position to reduce the pressure of fluid in the head end ofram 38.Ball 64 again closes offbore 62, and the overall volume of captive fluid is adjusted to that which initially existed.

During operation of the apparatus, and more particularly during extension of the rams, should the pressure of fluid inconduit 104 ever get too high,valve 126 opens to provide relief. This further ensures good coordination between the rams whereby skewing in the pusher parts is avoided.

Thus, the invention provides apparatus for automatically producing simultaneous, coordinated operation of a pair of rams. This results from the action of captive fluid transferring between the rod end of one ram and the head end of the other ram as the rams are actuated. With the apparatus herein employed to operate equipment such asload pusher 10, the rams always extend and contract equally during operation, and skewing ofpusher member 14, and resultant binding of other parts of the pusher are avoided.

It is claimed and desired to secure by Letters Patent:

1. A load pusher combination comprising a frame, and a pusher member movable relative to said frame,

a pair of fluid-operated rams for moving said pusher member, said rams being disposed with one adjacent one side and the other adjacent the other side of the pusher member, and being operatively interposed between the pusher member and frame,

each of said rams including a piston having means therein defining a passage opening onto opposite sides of the piston, and valve means inhibiting fluid flow through said passage from the rod end to the head end of the ram while accommodating flow in the reverse direction,

the effective piston area exposed to the rod end of one of the rams substantially equalling the effective piston area exposed to the head end of the other ram,

a source of fluid under pressure, and a pair of supply conduits operatively connecting said source to said rams, with one supply conduit connected to the head end of said one ram and the other supply conduit connected to the rod end of said other ram,

2. pressure relief valve operatively interposed between said supply conduits accommodating fluid flow from said one supply conduit to said other supply conduit while blocking flow in the reverse direction,

and a transfer conduit interconnecting the rod end of said one ram and the head end of said other ram.

References Cited UNITED STATES PATENTS 2,261,444 11/ 1941 Neubert 91 -401 2,462,580 2/ 1949 Watson 91411 3,318,199 5/1967 Parrett 91-411 PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 9l--415, 422, 451

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