US3188917A

US3188917A - Telescoping lift ram

Info

Publication number: US3188917A
Application number: US216162A
Authority: US
Inventors: George F Quayle
Original assignee: Yale and Towne Inc
Current assignee: Yale and Towne Inc
Priority date: 1962-08-10
Filing date: 1962-08-10
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15
Also published as: GB972929A

Description

Filed Aug 10, 1962 INVENTOR. Geo/ ee F Owne- 4 rme/vsy 3,188,917 TELESCOPING LIFT PAM George F. Quayle, Philadelphia, Pa., assignor, by mesne assignments, to Yale & Towne, Inc., New York, N.Y., a company of Ohio Filed Aug. 10, 1962, Ser. No. 216,162 7 Claims. (Cl. 91-168) This invention relates to a hydraulic lift ram of the telescopic type. More particularly, my invention relates to the control and construction of a telescopic lift ram adapted for operation in an industrial truck.

In a ram of the class described, utilizing at least two telescoping ram pistons, one of the ram pistons will have a larger area exposed to the fluid pressure than does the other piston, and will extend first. Since the piston of larger area operates to lift the load, the load will move at a relatively slow speed during the first part of the lifting movement. If the fluid pressure is applied at a uniform rate, the smaller ram piston will extend late-r, and naturally at a faster speed. Thus, the conventional telescoping ram will move the load slowly in lower positions and faster in higher positions. That is objectionable in a lift truck, because the fast-er movements of the load thus take place when the load is relatively unstable due to its high position. Just the opposite type of operation is desirable. Further, since many lifting operations do not require lifting to high positions, there is considerable loss of efficiency in the operation of the conventional truck because the low lifting takes place at slow speed. On the contrary, the slow lifting speed should take effect when the load is in higher and less stable positions, but in conventional trucks, this is not possible.

I have now conceived by my invention a novel telescopic ram to which fluid may be applied at a uniform rate, but that will have a relatively fast lifting speed through its lower range of movement. This increases the efficiency of the lift truck when operating in the low lifting range, while increasing the stability of the truck.

As a feature of my invention, I control the larger of the telescoping ram pistons through fluid pressure that opposes lifting movement of that piston. That control will cause the smaller piston to extend first, while lifting pressure is applied in a usual way to lower surfaces on both pistons.

' The novel concept of my invention actually is quite simple, and I am able to use a ram construction that is more or less standard. Thus, the larger of the two pistons in my ram may have a head that is slightly wider than the cylindrical body portion of the piston. As will be appreciated, the piston head then has an upper surface forming the lower end of a circular space between the piston and outer ram cylinder, and a lower surface against which the lifting fluid pressure acts. In my invention, I equip the ram cylinder with a valve controlled passage through which fluid will flow relatively to the circular space between the larger piston and cylinder.

l lormally, the valve will be closed, locking the fluid relatively to the upper surface of the piston head so that the larger piston cannot lift. When the smaller piston moves 7 to fully extended position relatively to the large piston,

the particular valve will be automatically actuated to release the fluid pressure that locks the larger piston. The lifting pressure will then be effective to extend that piston to continue the lifting movement at a relatively low speed, the faster lifting having already been effected by the smaller piston.

As a further feature, I equip my ram with a valve that will automatically lock the lifting .iluid relatively to the smaller piston, so that the particular piston cannot retract. I prefer to arrange that valve on the head of the larger piston, in such a way as to be actuated to release position when the larger piston fully retracts. Thus, once the smaller piston extends, even partially, it will not retract until the larger piston again reaches fully retracted posi tion.

I have thus outlined rather broadly the more important features of my invention in order that the detailed de scription thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important, therefore, that the claims be regarded as ineluding such equivalent constructions as do not depart from the spirit and scope of my invention, in order to prevent the appropriation of my invention by those skilled in the art.

Referring to the drawings:

FIG. 1 is a vertical section showing the construction of my novel ram and the controls thereof.

PEG. 2 illustrates my ram with the larger piston starting its extending movement, the smaller piston having been fully extended.

Referring now more particularly to FIG. 1 of the drawing, I indicate my novel telescoping ram generally by the numeral Ill, that ram having a rather usual arrangement including an outer ram cylinder 11, a relatively large ram piston 12 that slides in cylinder 11, and a smaller ram piston 13 that slides in piston 12. The ram cylinder 11 has a lower end member 14, and an upper closure 15 that encircles the relatively large ram piston 12. An extension 1-6 at one side of the lower end member 14 is formed with a passage 17 through which lifting fluid pressure will be applied to the pistons l2, 13 in the cylinder, as will be understood. Merely for the purposes of disclosure, I show a fluid pump 18 adapted to draw fluid from a reservoir l9 and to apply the lifting pressure through passage 17, and a valve 20 that will be operated to discharge the pressure.

As will be seen, the larger ram piston 12 has a cylindrical body portion 21 that is somewhat smaller than the inner diameter of cylinder 11, thus leaving a circular space 2 between that piston and the cylinder. The body portion 21 is equipped with a slightly wider piston head 23 that slides on cylinder ii, and that presents an upper surface 24 forming the lower end of circular space 22 The piston head 23 has a lower surface 25 against which the lifting fluid pressure will act, and an opening 26 through which the lifting pressure will act simultaneously against a surface 27 on the smaller ram piston 13, as I shall later describe. The details of the smaller piston 13 are not important to an understanding of my invention, and it is merely necessary to know that the movements of piston 13 are controlled by fluid pressure acting within the larger piston 12.

In my invention, I form the upper closure 15 on ram cylinder 11 with a passage 30 that leads from the circular space 22 to a spring pressed check valve diagrammatically shown at 31. In its normal spring pressed position, shown in FIG. 1, the check valve 31 is closed and prevents a discharge of fluid from the circular space 22 in ram 14 but can yield to allow fluid to move toward the space 22. Further, I indicate at 32 a cam member having two alternate positions allowing check valve 31 to close, as in FIG. 1, or holding valve 31 open, as in FIG. 2. On the upper end of the smaller ram piston 13, I show a part 33 that moves in opposed directions past cam member 32,

, open position away from its seat 38. g

After the smaller piston 13 is elevated relatively to j while coacting with member 32 to place in its alternate positions. To understand the particular operation, it will first be necessary to consider the action of check valve 31.

Since in its normal FIG. 1 position, check valve 31' has startedto move from the circular space 22 through valve 31 and back to the passage 17 ion the ram cylinder. That movement of fluid fromthe space 22 has allowed a the larger ram 12 to start its extending movement due to with an inverted sealing ring that will prevent'flow in a downward direction from space 22.

When'check valve 3.1'is held open, as in FIG. 2, the

fluid cam discharge from circular space 22 through valve 31, and through a line 36 connecting valve 31 to the passage 17 at the lower end of the outer cylinder 11;

That discharge can take place against the lifting pressure applied by the pump 18 because the area of the uppersurface 24 on piston head 23 is small, as compared to the lower surface'25 against which the fluid pressure acts to extend the piston 12. Thus, with valve 31 in the FIG. 2 position, the fluid pressure naturally will'be eifective'to extend the larger ram 12. a I

Whether or not the check valve 31 is held in open position, it will be appreciated that the fluid pressure in the line 36 always can move through that valve in a direction to replenish the fluid in the circular space 22, should that be necessary.

The part 33 on the upper end of small piston. 13 is so arranged as to place the check valve 31 in open position when piston 13 becomes fully extended relativelyto the larger piston 12. FIG. 2 illustrates the operation of the ram just after that happens, fluid having started to discharge from the circular space 22 through valve 31, as

will be understood, enabling the lifting fluid pressure to start the extending movement of the larger piston 12.

That piston naturally carries with it the previously extended small piston 13. a

I now call attention to' the fact that I equip the piston head 23 of the larger piston with a valve'me rnber 37..

Valve member 37 acts as a check valve, allowing the lifting fluid pressure to flow upwardly throughthe opening 26 in the head, but coacting with valve seat'38 to prevent reverse flow. Valve 37. has an integral pin 39 adapted to coact with an inner surface 40 on the cylinder and memthe lifting pressure already acting against'its lower surface. Also, the movementof ram 12 has carried the valve member 37 away from the surface 40 on the lower end of the cylinder causing valve member 37 to lock the fluid pressure relatively to the smaller piston 13. Thus, the larger pistons 12 is extending at its relatively slow speed while smaller piston 13 is locked and cannot retract.

If we now assume that the lifting pressure isallowed to discharge through the passagel'l', as through operation of the valve-2t the larger piston 12 will retract at its relatively slow speed While piston 13 remains locked in its extended position relatively to piston 12. When the "larger piston 12 is fully retracted, valve member 37 will open due to its contact with the cylinder surface 40, so that smaller piston 13 will retract at its faster speed. It will be understood that the smaller piston 13 now has effected closing of the check valve 31, thus locking the largerpiston 12 in fullyretracted position preparatory to the next lifting operation.

I believe that the operation and advantages of my novel telescoping lift ram will now be understood. Thus, through the concept ofrelatively simple means, I am able to use telescoping pistons that will contribute relatively fast lifting of a' load to relatively low positions, being automatically effective to lift more slowly to higher positions. When used on a lift truck, my ram will enable thetruck to operate more efliciently, and with the stability I 'of 'the truck more easily controlled. -Moreover, I can her 14 so that when the larger piston 12 is fully retracted,

as in FIG. 1, valve member37 will be held by the larger piston 12, lifting movement of piston 12 will allow check valve 37 to seat, locking piston 13 relatively to piston 12. Small piston 12 cannot now retract until such time as the larger piston 12 maybe fully retracted, causing'valve member 37 to open.

, To review the operation of my novel ram, we may first assume that lifting fluid .pressure is applied throughpassage 17 while the ram is in, lowered position, with both

pistons

12, 13 fully retracted as in FIG. 1. That pressure will act simultaneously against the lower surfaces' of both

pistons

12, 13.. Because of its larger area, the" larger pis ton 12 naturally will tend to rise while piston13 doesnot move relatively topiston 12. However, the check valve 31 is in closed position, locking hydraulic. fluid -in the.

circular space 22 between the outer cylinderll and larger- Referring to FIG/2, the smaller piston 13 has been fully extended and has operated the cam member 32 to place the check valve 31 in open position. Hydraulicyfluidj pin 39 in;

achieve these things while using a ram construction that is standard in many respects. I believe, therefore, that the very considerable merits of my inventionwill'be fully appreciated by those skille'din the art.

I now claim:

1. In an industrial truck ofthe classdescribed,

a lift ram having a cylinder,

I a relatively large ram piston and a relatively small ram piston in telescopingr'elation in the ram cylinder and adapted for upward lifting movement relatively to the cylinder, I

said relatively large. rampiston having a lower end portion formed with an opening through which the small ram piston will be exposed to fluid pressure that may be applied below the large piston,

means for directing fluid pressure, to the pistons in the cylinder for extending said pistons,

' said ram cylinder and said large rain piston being constructed to form a circular space between that piston n and cylinder, with an uppersurface on the lower end portion of the large piston acting against the fluid in said circular space, i

fluid passage means communicating with an upper part of said circular space in the cylinder,

a check valve controlling said passage means and allowing' fluid to move to the circular space while normally in position retaining the fluid in said space whereby to hold the large ram piston in lowered position, v I i means through which the small rampiston'when lifting places said check Valve'in position allowing a discharge of fluid from the circular space in the cylinder soithat the large ram piston will liftdue to the lifting pressure acting against its end portion,

a further check valve controlling the opening in the lower end portion of the large rain piston and effec tive for retaining fluid pressure relatively to the small a piston when the large piston is relieved of lifting pressure, v I

' and an inner surface on the ram cylinder. actuating said 7 further check valve to. release the fluid pressure re1a-,

tively to the small ram piston when the large piston moves to lowered position.

2. In an industrial truck of the class described, a lift ram for lifting a load, said ram including a cylinder, a relatively large ram piston and a relatively small ram piston in telescoping relation in the ram cylinder and adapted to extend upwardly relatively to the cylinder, said relatively large ram piston having a lower end portion formed with an opening through which the small ram piston will be exposed to fluid pressure that may be applied below the large piston, means for directing fluid pressure to the pistons in the cylinder for extending each piston for lifting the load, said ram cylinder and said large ram piston being constructed to form a circular space between that piston and cylinder, an upper surface on the lower end portion of the large piston being exposed to fluid in said circular space, passage means connected to an upper part of said circular space in the cylinder and through which fluid moves relatively to said space, a movable valve normally in position closing said passage means and retaining fluid in the circular space whereby to hold the large ram piston in retracted position, means through which the small ram piston when lifting the load moves said movable valve to allow a discharge of fluid through said passage means so that the fluid pressure acting against the end portion of the large ram piston thereafter will extend the large piston to lift the load, a check valve mounted on the lower end portion of the large ram pis ton and coacting with its opening for retaining the fluid pressure relatively to the small piston, and a part on the ram cylinder coacting with said check valve when the large ram piston moves to retracted position whereby to release the fluid pressure relatively to the small ram piston.

3. In an industrial truck of the class described, a lift ram for lifting a load comprising a cylinder having a Wall and a pair of telescoping pistons in the cylinder, one of said pistons being adapted for movement to a stop position relatively to the other piston and said other piston being adapted for movement thereafter to a stop position relatively to said cylinder whereby to lift a load a distance directly related to the extension of said telescopic ram, each of said pistons having a low and high pressure side, inlet means connected to one end of said cylinder for directing fluid pressure simultaneously against said high pressure ends of both pistons, passage means connected to and leading through the upper end of said cylinder wall and connected to the low pressure side of said larger piston, said passage means having a valve for preventing the flow of fluid therethrough so that the application of said fluid pressure simultaneously to both said pistons effects first the movement of said smaller piston relatively to said larger piston and said cylinder, means actuated by said smaller piston upon its reaching substantially its stop position for opening said valve to permit said fluid pressure to actuate the larger piston to complete the lifting of the load.

4. In an industrial truck of the type described in claim 3 wherein said inlet means for directing fluid simultaneously against the high pressure ends of both pistons comprises an aperture extending axially through the head portion of said larger piston and valve means operable within said aperture to control the flow of fluid therethrough and thereby subject the high pressure ends of both pistons to the same pressure simultaneously.

5. In an industrial truck of the class described, a telescopic lift ram for lifting a load comprising a cylinder and a pair of telescoping pistons in the cylinder, one of said pistons being adapted for movement to a stop position relatively to the other piston and said other piston being adapted for full movement thereafter to a stop position relatively to said cylinder whereby to lift a load a distance directly related to the extension of said telescopic ram, each of said pistons having a low and high pressure side, inlet means connected to one end of said cylinder for directing fluid pressure simultaneously against said high pressure ends of both pistons, the larger piston of said telescoping pistons and said cylinder having therebetween a fluid chamber at the low pressure side of said larger piston, passage means connecting said fluid chamber with said inlet means, a valve in said passage means for preventing flow of fluid from said chamber whereby to hold the larger piston against lifting movement relatively to said cylinder so that the application of said fluid pressure simultaneously to both said pistons eifects first the movement of said smaller piston relatively to said larger piston and said cylinder, means actuated by said smaller piston upon its reaching substantially its stop position relatively to said larger piston for opening said valve to permit said fluid pressure to actuate the larger piston to complete the lifting of the load.

6. In an industrial truck of the type described in claim 5 wherein said inlet means for directing fluid simultaneously against the high pressure ends of both pistons comprises an aperture extending axially through the head portion of said larger piston and valve means operable within said aperture to control the flow of fluid therethrough and thereby subject the high pressure ends of both pistons to the same pressure simultaneously.

7. In an industrial truck of the class described, a telescopic lift ram for lifting a load comprising a cylinder and a pair of telescoping pistons in the cylinder, one of said pistons being adapted for movement to a stop position relatively to the other piston and said other piston being adapted for movement thereafter to a stop position relatively to said cylinder whereby to lift a load a distance directly related to the extension of said telescopic ram, each of said pistons having a low and high pressure side, inlet means connected to one end of said cylinder for directing fluid pressure simultaneously against the high pressure ends of both pistons, the larger piston of said telescoping pistons having a fluid chamber at the low pressure side thereof, passage means interconnecting said fluid chamber with said inlet means, a valve in said passage means for preventing flow of fluid from said chamber whereby to hold the larger piston against lifting movement relatively to said cylinder so that the application of said fluid pressure simultaneously to both said pistons effects first the movement of said smaller piston relatively to said larger piston and said cylinder, control means actuated by said smaller piston upon its reaching substantially its stop position for opening said valve to permit said fluid pressure to actuate the larger piston to complete the lifting of the load.

References (lited by the Examiner UNITED STATES PATENTS 165,472 7/75 Brinkerofl 91169 2,400,330 5/46 Allen 17318 2,513,192 6/50 McFarland 91167 FRED E. ENGELTHALER, Primary Examiner. SAMUEL LEVINE, Examiner.

Claims

1. IN AN INDUSTRIAL TRUCK OF THE CLASS DESCRIBED, A LIFT RAM HAVING A CYLINDER, A RELTIVELY LARGE RAM PISTON AND A RELTIVELY SMALL RAM PISTON IN TELESCOPING RELATION IN THE RAM CYLINDER AND ADAPTED FOR UPWARD LIFTING MOVEMENT RELATIVE TO THE CYLINDER, AND RELATIVELY LARGE RAM PISTON HAVING A LOWER END PORTION FORMED WITH AN OPENING THROUGH WHICH THE SMALL RAM PISTON WILL BE EXPOSED TO FLUID PRESSURE THAT MAY BE APPLIED BELOW THE LARGE PISTON, MEANS FOR DIRECTING FLUID PRESSURE TO THE PISTONS IN THE CYLINDER FOR EXTENDING SAID PISTONS, SAID RAM CYLINDER AND SAID LARGE RAM PISTON BEING CONSTRUCTED TO FORM A CIRCULAR SPACE BETWEEN THAT PISTON AND CYLINDER WITH AN UPPER SURFACE ON THE LOWER END PORTION OF THE LARGE PISTON ACTING AGAINST THE FLUID IN SAID CIRCULR SPACE, FLUID PASSAGE MEANS COMMUNICATING WITH AN UPPER PART OF SAID CIRCULAR SPACE IN THE CYLINDER, A CHECK VALVE CONTROLLING SAID PASSAGE MEANS AND ALLOWING FLUID TO MOVE TO THE CIRCULAR SPACE WHILE NORMALLY IN POSITION RETAINING THE FLUID IN SAID SPACE WHEREBY TO HOLD THE LARGE RAM PISTON IN LOWERED POSITION, MEANS THROUGH WHICH THE SMALL RAM PISTON WHEN LIFTING PLACES SAID CHECK VALVE IN POSITION ALLOWING A DISCHARGE OF FLUID FROM THE CIRCULAR SPACE IN THE CYLINDER SO THAT THE LARGE RAM PISTON WILL LIFT DUE TO THE LIFTING PRESSURE ACTING AGAINST ITS END PORTION, A FURTHER CHECK VALVE CONTROLLING THE OPENING IN THE LOWER END PORTION OF THE LARGE RAM PISTON AND EFFECTIVE FOR RETAINING FLUID PRESSURE RELATIVE TO THE SMALL PISTON WHEN THE LARGE PISTON IS RELIEVED TO LIFTING PRESSURE, AND AN INNER SURFACE OF THE RAM CYLINDER ACTUATING SAID FURTHER CHECK VALVE TO RELEASE THE FLUID PRESSURE RELATIVELY TO THE SMALL RAM PISTON WHEN THE LARGE PISTON MOVES TO LOWERED POSITION.