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Publication numberUS3692198 A
Publication typeGrant
Publication dateSep 19, 1972
Filing dateDec 28, 1970
Priority dateDec 28, 1970
Publication numberUS 3692198 A, US 3692198A, US-A-3692198, US3692198 A, US3692198A
InventorsLake Edward E
Original AssigneeClark Equipment Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Hydraulic lift truck with small number of fluid lines
US 3692198 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Lake Y HYDRAULIC LIFT TRUCK WITH SMALL NUMBER OF FLUID LINES Edward 'E; Lake, Battle Creek, Mich.

Assignee: Clark Equipment Company Filed: Dec. 28, 1970 Appl. No.: 101,547


us. Cl ..214/6s3 Int. Cl. ..B66f 9/18 Field of Search ..2l4/653 References Cited I UNITED STATES PATENTS 3,184,088 5/1965 Berge ..2l4/653 51 Sept. 19, 1972 Primary Examiner-Gerald M. Forlenza Assistant ExaminerGeorge F. Abraham Attorney-Paul H. Gallagher ABSTRACT A lift truck of the type including a vehicle component having a mast, and a clamp on the mast having clamp arms for gripping a load and moving it laterally as well as lifting it, including as few as three fluid lines to the clamp, for individually moving the arms laterally in clamping and releasing directions, and shifting both together laterally in each direction, and three manually operable control valves for effecting those movements.

7 Claims, 10 Drawing Figures PATENTEDsEP 1 e um 3.692.198

saw 1 or 4 EDWARD E. LAKE ATTORNEY PATENTEB 19 I973 3.692.198

SHEET 2 BF 4 I o -Z a N g FIG. 2



FIG. 6

FIG. 7


saw u or 4 FIG. 8


INVENTOR EDWARD E. LAKE ATTORNEY FIELD OF THE INVENTION v The'invention lies in the field of hydraulic lift trucks. Such a lift truck as is known, includes a mast, and a lifting component such as a clamp, fork, etc. The lifting component, as a clamp, has side clamp arms engaging the load in lateral direction, and operative for moving it laterally, and of course lifting it. The clamp, arms preferably aremovable individually, and in order to effectively move them in the necessary direction for handling the load, it has been necessary heretofore to have a large number-of fluid lines, most usually-six. Those lines necessarily go over the mast in order to accommodate the lifting movements of the clamp means, and because of the necessity of a relatively large number of such fluid lines, the difficulties encountered are' great; those difficulties increase as the number of lines increase.

OBJECTS OF THE INVENTION A broad object of the invention is to produce a hydraulic lift truck of the type incorporating a vehicle and a lifting component which includes clamping means for clamping the load to be lifted or handled, and a mast mounting the lifting component and providing the means for vertically moving the, lifting component, and in which the hydraulic lines leading to the lifting component or clamp means are necessarily positioned over the mast, and wherein such number of fluid lines are reduced to a minimum substantially less than has been possible heretofore.

A more specific object is to provide alift truck of the character referred to in which the fluid lines can be reduced in number from the usual six as has been necessary heretofore, to four, for example, and even three. I

Still another object is to provide a hydraulic lift truck of the character referred to above which includes a novel valve arrangement and control thereof whereby to enable full and effective operation of the clamp means through the relatively few hydraulic lines as referred to, such as four, or three.


FIG. 1 is a perspective view of a lift truck of a kind to which the present invention is particularly adaptable and including clamp means to which the hydraulic lines and control means of the invention are applied;

FIG. 2 is a diagram of the hydraulic circuit of the invention and a diagrammatic representation of the clamp means;

FIG. 3 is a fragmentary schematic view representing certain main components of the lift truck and the arrangement therein of certain fluid lines;

FIG. 4 is a view similar to FIG. 3 but showing a different arrangement of the same fluid lines; I

FIG. 5 is a diagram of the hydraulic system showing certain elements in active condition in a first step of an operation;

FIG. 6 is a diagram similar to FIG. 3 but showing other elements thereof in active condition;

FIG. 7 is a view similar to.FIGS. 3 and 4 but showing different elements in active condition;

FIG. 8 is a view similar to FIGS. 3-5 but showing still different elements in active condition;

FIG. 9 is a view similar to FIGS. 3-6 and showing additional elements in active position; and

FIG. 10 is a view similar to FIGS. 3-7 with still other elements in active position.

Referring in detail to the accompanying drawings, at-

tention is directed first to FIG. .1 which shows a lift truck in its entirety at 10 which may be of the type disclosed in U. S. Pat. No. 3,184,088, to Berge, assigned to the assignee of this invention. It will be understood that the specific kind of lift truck, other than the particular features described in this disclosure, may be as desired. Such a lift truck may includea vehicle 12 and a lifting component 14, the lift truck including a body 15 and a mast 16 on which the lifting component 14 is mounted and which rides in vertical directions in lifting and lowering movements. The lifting component 14 in-' corporates clamp means 18 which includes a pair of clamp arms 20 individually identified as 20R and 20L (for right and left), which engage a load 23 to be lifted or handled. The lifting component 14 includes a carriage 21 directly mounted to the mast l6 and movable vertically thereon in the usual mannerby hydraulic means. The range'of vertical movementofthe lifting component on the'mast is determined by the desired extent of lifting of the load, and whatever that height is, the fluidjlines leading to the clamp means 18 must accommodat e it and to accommodate the greatest and the least extension, either by the provision of slack in the fluid lines or reeling them out or in, according to the vertical movements of the clamp means.

In such vertical movements of, the clamping component, the fluid lines which are disposed over the mast and lead to the clamping component, are worked to a very great extent, either by moving them to provide or take up slack, or in moving them over sheaves, and this results in relatively rapid deterioration of the lines. The greater the number of the lines, the greater will be the total deterioration, and the lesser the number of lines of course the lesser will be that deterioration, and it is directly in connection with this phenomenon that the present invention has particular significance. The present invention includes an effective number of fluid lines leading over the mast to the clamping means as low as three, and in come cases it may be desirable to have four, both in sharp contrast to the usual number, six, utilized heretofore for the same kind of operation.

Mounted in the carriage 24 are piston-cylinder units or jacks 24, 25 (see FIGS. 1 and 2) having cylinders 26, 27 and pistons 28, 29, respectively. The cylinders are fixedly mounted in the carriage against displacement in all directions and particularly transversely, and the pistons thereof respectively engage the clamp arms 20. Upon extension of the pistons, the clamp arms are spread and upon contraction thereof the clamp arms are drawn together, respectively clamping or releasing, depending upon whether they engage the load at outside surfaces or inside surfaces. The particular manner in which the load is engaged is not of the essence of the invention, this manner of engaging the load being known heretofore.

Attention is directed next to FIG. 2 showing the hydraulic system for operating the clamp means 18, the latter being also shown in this figure. The hydraulic mechanism includes a pump 30 drawing fluid from a reservoir or sump 32 and pumping it through a common line 34 and branches 35, '36, 37 leading to manually operated, oppositely acting control valves 38, 39, 40. Returning from the valves, are branches 41, 42, 43 of a common'return line 44 returning to the reservoir 32 and the pump.

Thecontrol valves 38, 39, 40 are of known kind having means for stopping the flow of fluid in a neutral position, or enabling flow of fluid therethrough in op posite directions respectively in opposite positions of the valves. Thesevalves-(FIG. 2) are shown in neutral position in which all flow of fluid ischecked, although in FIGS. -10, respective ones of the valves arein dif-' ferent positions indicating flow of the fluid in corresponding directions, in respective ones of the steps of the control operations.

In addition to the lines referred to above, are the following fluid lines: a line 45 leads from the valve 38 to a cross line 46 which in turn connects with a line 47 leading from the valve 39, both connecting with a line 48 which includes a pilot check valve 49 and leads to a cross line 50 communicating with the rod sides of the cylinder-pistons or jacks 24, 25. I

Leading from the valve 38 is another line 52 communicating with a line 54 which includes a first pilot check valve 56, a second pilot check valve 58 and a shuttle valve 60. The line 54 continues beyond the valve 56 and communicates with the control valve 40. Also communicating with control valve 40 is another line 62 communicating with the line 54. The control valve 39 has a line 64 also communicating with the line 54.

Leading from the line 54 outwardly beyond the check valve 56 is an outer line 66 leading to the base end of the jack 24. Additionally another outer line 68 leads from the lines 54, 62, at a point outwardly beyond the check valve 58, to thebase end of the other jack 25. The line 54 includes a portion 54a between the outer lines 66, 68 which may be referred to as a by-pass line.

Additional lines in the circuit include a pilot line 70 leading from the line 45 to the check valve 56, and a pilot line 72 leading from the line 47 to the check valve 58; an additional pilot line 74 leads from the shuttle valve 60 to the check valve 49.

The check valves 56 and 58 prevent opening of the check valve 49 when side shiftingv the two clamp arms together. A pilot check valve 76 is placed in a line 78 connected between the pilot line 74 and the line 48, and communicates with an element 32a of the reservoir 32 to relieve any pressure trapped between the shuttle valve 60 and the check valve 49.

The clamp means 18 is arranged for the arms thereof to be individually moved inwardly or outwardly, or together shifted to the-left or to the right. The clamp arms may be moved inwardly for gripping the load, and moved outwardly for releasing the load. When the clamp arms are shifted to the left or right, they are effective for shifting the load itself in corresponding directions. It is desired that the clamp arms be individually moved in or out, and it is found not necessary that they be moved inwardly or outwardly together in a single movement, although these movements may be accomplished if it should be so desired by conjoint movements of the corresponding individual control valves. The control valve 39 is utilized for moving the clamp arm L individually, the control valve 38 for moving the clamp arm 20R individually, while the con trol valve 40 is utilized for shifting both together.

Assuming as a first step, it is desired to move the left clamp arm 20L inwardly by contracting the jack 25. To do so the control valve 39 is shifted to the position shown in FIG. 5 (to the left from FlG. 2) wherein the oil is forced from the pump 30 through the line 34 and branch line 36; through the valve 39 and then out through the line 47. The oil under pressure from the line 47 then flows through the line 48, the check valve 49 and into the cross line 50 and the rod ends of the jacks. The pressure in the line 47, which is also developed in the line 46, is transmitted through the pilot lines 70, 72 to the checkvalves 56, 58, opening those valves. The oil in the base end of the jack 25 returns through the line 68 and line 54, through the check valve 58 which isthen open, and then the line 64 inv return to the control valve 39. The circuit is thus completed through the branch line 42 communicating with the return line 44 to the reservoir 32 and the pump 30.

In this same step, the jack 24 is constrained against movement because the oil in the base end thereof is obstructed from returning; the return would be through the line 66, and in one direction (downwardly) through the line 54 (the check valve 56 being open) and line 52 but the latter is obstructed because the valve 38 is in neutral position; the other path of return of the oil from the base of the jack 24 is from the line 66 through the line 54 (upwardly) and then to' the valve 40, but at this end also it is closed. Hence only the jack 25 can be actuated.

To move the clamp arm 20L in the opposite direction, or outwardly, the valve 39 is moved to the opposite position, shown in FIG. 6, and in such position the oil leaves the pump 30 through the line 34 and branch 36 and then flows to the valve '39 and the line 64. The oil in line 64 progresses through the line 54 the jack 25. The oil is relieved from the rod end of this jack, and enabling the jack to be'extended, through the cross line 50 and then the line 48; the oil continues through the check valve 49 in reverse direction, this check valve being opened by the pressure through the pilot line 74 which is produced by the shuttle valve being moved to its position shown in FIG. 6; the oil then continues in return direction through the line 47 and through the valve 39 and then through the branch line 42 and return line 44 to the reservoir and the pump. At the same time the jack 24 is prevented from moving the right clamp ann inwardly, because of the obstruction to relief of oil from the base end of that jack, the relief movement otherwise being through the line 66, line 54 which is closed at valve 40, that valve being in its neutral position. The other path of the return of the oil from the jack 24 would be through line 66, then line 54 (down) to check valve 56 which is closed, since no pressure has been developed in the with FIGS. 5 and 6, whereby it will be seen that the clamp arm R is moved in the direction stated.

FIG. 8 is a correlative of FIG. 6 and shows the position of the control valve 38 for moving the right hand clamp arm 20R outwardly, and is an opposite situation relative to FIG. 7.

The arrangement is also adaptable to shifting the clamping means together in either direction, i.e., while holding the load, shifting it to the left, or to the right. FIGS. 9 and 10 show the arrangement of the circuit for accomplishing these movements, the control valve 40 being used for this purpose, as stated above. To shift the clamp means to the right, for example, the valve 40 is shifted to the position represented in FIG. 9, i.e., to the right from its neutral position of FIG. 2; in such position of the valve, the oil is pumped from the pump through the line 34 and branch line 37 and through the valve to the line 54, the oil then going through the line 66 to the base end of the jack 24. The piston in that jack is forced to the right, and the oil is forced out of the rod end of that jack and into the rod end of the other jack and thus forcing the piston in the latter jack to the right. The oil returns from the base end of the jack 25 through the line 68 and line 62 through the valve 40 and in return through the branch line 41 and line 44 to the reservoir 32 and pump 30. I

To shift the clamp means in the opposite direction, i.e., to the left, the valve 40 is shifted to the opposite position, relative to that of FIG. 9, as represented in FIG. 10. The diagram of FIG. 10 shows the direction of oil flow, and upon consideration thereof as compared with the direction of flow in FIG. 9, the operation now referred to will be understood.

Summarizing the actions of the fluid lines and valve means, the check valves 56, 58, 49 are open 'when either of the control valves 38, 39 is actuated, and the shuttle valve 60 controls the flow from the actuated control valve through the corresponding check valve 56, 58; for example when the control valve 39 is actuated to the position shown in FIG. 6, the shuttle valve is forced to upper position enabling flow through check valves 58, 49, but preventing flow through the check valve 56; when the control valve 38 is actuated to the position shown in FIG. 8, the shuttle valve is forced to lower position enabling flow through check valves 56, 49, but preventing flow through check valve 58; when only the control valve 40 is actuated, in either direction, all the check valves are closed, and the circuit is through that control valve, the outer lines and the jacks. In the operations represented in FIGS. 5, 7, 9, 10 the shuttle valve does not enter into the control functions and it assumes a random position or the position it happens to be in at that time.

The apparatus of the invention is effective in the utilization of three hydraulic lines namely 48, 66, 68, leading to the clamp means, these lines necessarily extending over the mast as represented in FIG. 1, and these three lines will accomplish all of the necessary clamping and releasing movements of the clamp means for clamping a load and moving it in the usual fashion. Thus these three lines take the place of six lines heretofore utilized and found necessary. Because of the fact that the line 48 extends over the mast, and is subjected to the movements and actions leading to deterioration of any line in such situation, it may be desired that the check valve means 49 be mounted on the clamp means itself, asindicated in FIG. 4, rather than on the vehicle body as represented in FIG. 3, because if the pressure line 48 should break because of the deteriorating effect in running over the sheaves, the check valve would prevent dropping of the load, because of the small likelihood of breaking of the section of the line between the check valve and the jacks. In such case there would be four lines to the clamping means, namely 48, 66, 68 and the pilot line 74; however it may be desired, and it is practical to do so, to put the check valve 49 on the vehicle body, (FIG. 3), and in that case the pilot line-74 would not extend to the clamp means,

' and only the three lines 48, 66, 68 would do so, but in this case care would have to be taken that the line 48 be replaced sufficiently often to prevent its breaking.

As indicated above, both clamp arms 20 can be actuated simultaneously, by simultaneously actuating the control levers which move the valves 38, 39, for gripping or releasing, although this would not be a normal or routine operation.

I claim 1. A hydraulic lift truck comprising a hydraulic motor, a fluid line system, clamp means including laterally movable clamp arms, a hydraulic jack operatively connected with each clamp arm for'moving it laterally, a common fluid line communicating with the jacks, an outer line communicating with each jack individually, three manual control valves each having a neutral position and including a first and a second associated individually with the jacks, and a third associated with both jacks, the first controlvalve being operative for establishing a circuit through the common line and a first associated outer line and the associated jack, the second control valve being operative for establishing a circuit through the common line and a second associated outer. line and the associated jack, a single check valve in the common line, and a single check valve between eaeh outer line and the respective first and second control valve and a shuttle valve between the check valves in the outer lines, all said check valves normally blocking flow in direction toward the control valves, each of the first and second control valves being operative for opening the check valves and being operative for doing so upon establishing a circuit through the associated jack, and the check valves being closed when the first and second valves are in neutral position whereby to shut off the three lines mentioned from the first and second control valves, and the third control valve when actuated being operative for establishing a circuit through the outer lines and both jacks, said shuttle valve being operative for opening the check valve in the common line to enable flow of fluid through the common line to the actuated one of the first and second control which is being actuated valves.

2. A hydraulic lift truck according to claim 1 wherein the fluid lines include a by-pass line interconnecting the outer lines in by-passing relation to the jacks, and said by-pass line includes the check valves shutting off the outer lines from the first and second control valves.

3. A hydraulic lift truck according to claim 2 wherein the fluid lines include a pilot pressure line from each of the first and second control valves for opening the checkvalves in the by-pass line.

4. A hydraulic lift truck according to claim 3 wherein the lines leading from the first and second control valves for opening the check valves also interconnect with the common line to the jacks.

5. A hydraulic lift truck according to claim 2 wherein the fluid lines include 'a line leading from each the first and second control valve to the by-pass line and connected thereto at points between the check valves in the by-pass line and the check valves being arranged for normally passing fluid from the associated control valves outwardly into the corresponding outer lines.

6. A hydraulic lift truck according to claim 5 wherein

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3831795 *Jul 12, 1972Aug 27, 1974Toyoda Automatic Loom WorksSide shift clamp device
US4161256 *Oct 4, 1977Jul 17, 1979Cascade CorporationFluid power system having multiple, separately controllable double-acting fluid motors and reduced number of fluid conduits
US4215622 *Sep 22, 1978Aug 5, 1980Clark Equipment CompanyHydraulic control system
US4286692 *Sep 22, 1978Sep 1, 1981Clark Equipment CompanyHydraulic control system for operating multiple remote devices with a minimum number of connecting conduits
US4467894 *Jan 15, 1982Aug 28, 1984Anderson, Clayton & Co.Fluid power system
CN102107837A *Dec 21, 2010Jun 29, 2011斗山英维高株式会社Hydraulic device for driving fork of forklift
DE2937814A1 *Sep 19, 1979Apr 3, 1980Clark Equipment CoHydraulisches system
EP0489255A1 *Oct 25, 1991Jun 10, 1992Caterpillar Industrial Inc.Fluid operated fork positioning control system
WO2015172763A1 *May 14, 2015Nov 19, 2015Kaup Gmbh & Co KgAdd-on device to be attached to a lifting vehicle, and method for actuating said add-on device
U.S. Classification414/621
International ClassificationB66F9/18
Cooperative ClassificationB66F9/183
European ClassificationB66F9/18D