US3494491A

US3494491A - Materials handling vehicle

Info

Publication number: US3494491A
Application number: US677609A
Authority: US
Inventors: Toyotaro Sumida
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1966-10-29
Filing date: 1967-10-24
Publication date: 1970-02-10
Anticipated expiration: 1987-02-10
Also published as: GB1200097A; US3494259A; FR1558351A

Description

Feb. 10,1970 TOVYCTARO SUMIDA 3,494,491

MATERIALS HANDLING VEHICLE I Filed Oct. 24, 196' 4 Sheets-Sheet 1 II VVENTO R. To 10 Take sumo 77W amt M .FebQlO, 1970 TOYOTARO SUh A IDA v 3,494,491

MATERIALS HANDLING VEHICLE Filed Oct. 24. 19 1 4 Sheets-Sheet z INVENTOR, T0101"; 5 (mm/9 10; 1970 -1 '0YOTARO SUMI DA 3,494,491

MATERIALS HANDLING VEHICLE Filed Oct. 24, 1967 4'Sheeps-Sheet 3 FIG.5

FIG.7

INVENTOR. T010TnRa SUM/0n Y Mr W United States Patent Office 3,494,491 Patented Feb. 10, 1970 3,494,491 MATERIALS HANDLING VEHICLE Toyotaro Sumida, Tokyo, Japan, assignor to Mitsubishi Jukogyo Kabushiki Kaisha, Tokyo, Japan Filed Oct. 24, 1967, Ser. No. 677,609 Claims priority, application Japan, Oct. 29, 1966, 41/ '7 1,222 Int. Cl. 360p 1/.02; 366d 3/08; B66c 5/02 US. Cl. 214-394 9 Claims ABSTRACT OF THE DISCLOSURE A materials handling vehicle is comprised of a support frame arranged to afford the operator a clear unobstructed view in the operation of the vehicle particularly in lifting and transporting material. In a preferred arrangement, the support frame is formed of two spaced inverted U-shaped end frames connected by upper and lower side members. The construction of the frame permits movement of the vehicle over materials to be lifted and also provides a vertically extending open space within the frame for lifting the materials. A lifting member is located within the open space and is movable not only upwardly and downwardly, but also laterally. Lifting means such as hydraulic piston cylinders are located on the upright members of the end frames for the vertical movement of the lifting member. Additionally, the lifting member is secured to vertical guide rails located on one side of the frame and means are provided for laterally displacing the guide rails and, in turn, laterally positioning the lifting member which is secured to the rails. A cab for the operator is located at one end of the vehicle and contains not only the means for driving the vehicle but also control means for regulating the vertical movement of the lifting member. With the control means an equal flow of hydraulic fluid is provided to the various hydraulic piston cylinders for assuring simultaneous raising and lowering of the lifting member though the load may be unevenly distributed.

SUMMARY OF THE INVENTION The present invention is directed to improvements in materials handling vehicles and, more particularly, to providing a vehicle construction which provides the optimum unobstructed view for the operator and improved means for lifting materials to be transported.

In conventional materials handling vehicles, the vehicle is positioned over the materials to be transported, then the materials are lifted, moved to a predetermined place, and then lowered and released. To perform these operations, the vehicle is generally provided with a vertically extending open space within its frame. However, in known vehicles of this type the following drawbacks have been noted: 7

(1) to provide the required open space for handling various materials the side and cross frames of the vehicle have been unsubstantial and the ends of the side frame have had the tendency to move relative to one another when the vehicle is turning;

(2) the location of the hydraulic motor for lifting the materials and of the cross support members has often made it difficult for the driver to obtain an unobstructed view of the lifting operation.

(3) the means used for laterally positioning the lifting member has provided further obstacles in the path of the drivers vision; and

(4) the mechanically or hydraulically driven lifting apparatus often has been inadequate and has required excessive down time for repairs.

A primary object of the invention is to provide a materials handling vehicle in which any limitations on the field of vision of the operator are maintained to a minimum.

Another primary object of the invention is to produce a control arrangement for the lifting means whereby the lifting frame may be maintained in a plane parallel to the surface on which the vehicle is positioned in spite of any uneven distribution of load on the lifting frame.

Another object of the invention is to supply equal quantities of hydraulic fluid to each of the lifting devices in the vehicle.

Still another object of the invention is to afford means for moving the material to be lifted laterally as well as vertically.

Therefore, the present invention is directed to a materials handling vehicle having a frame structure providing an open space for receiving and handling the materials to be transported. Preferably, the support frame comprises a pair of spaced end frames of inverted U- shaped configuration formed of a pair of spaced upright members secured at their upper ends by an integrally attached cross member. Side members secured to the end frames provide additional rigidity without encroaching on the open space within the frame or obstructing the view of the operators. A lifting member is located within the open space in the frame and is adapted to extend generally parallel with the surface on which the vehicle is positioned. The lifting member is arranged to be moved laterally as well as upwardly and downwardly within the open space. Lifting means are mounted on the upright members of the end frames for raising and lowering the lifting member. In addition, control means are provided for the lifting means to assure that the lifting member is maintained in a position substantially parallel to the surface on which the vehicle is positioned during lifting, regardless of any uneven distribution of load upon the lifting member.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of a somewhat schematic arrangement showing a conventional type of materials handling vehicle used in the prior art;

FIG. 2 is a perspective view of a materials handling vehicle embodying the present invention;

FIG. 3 is a rear view of the vehicle shown in FIG. 2 with a container shown in phantom arranged to be lifted by the vehicle;

FIG. 4 is a partial perspective view of the vehicle illustrating a device for laterally positioning a lifting member;

FIG. 5 is a partial sectional top view of the lower portion of the vehicle shown in FIG. 2;

FIG. 6 is a schematic arrangement showing a control apparatus for the lifting devices on the vehicle shown in FIG. 2;

FIG. 7 shows another arrangement of the wheels for the vehicle;

FIG. 8 is a partial sectional top view showing another arrangement of the means for laterally displacing the lifting member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 an arrangement is shown of a conventional materials handling vehicle, as known in the art, comprising a pair of side frames a, b and a cross frame at one end. In transporting material, as the vehicle turns the rear ends d of the side "frames w, b have a tendency to move either apart or toward one another since there is no means for adequately spacing them and the side frames are not sufficiently rigid to assure that they will remain in proper spaced parallel relationship. The hydraulic lifting cylinders e and located at either end of the vehicle and the gate or cross frame members g and h form obstructions in the line of sight of the operator of the vehicle as he sits in its cab i. Additionally, the cross frame c is another obstruction which makes it diflicult for the operator to seethe materials being handled within the open space in the vehicle. Where a motor unit or other apparatus iS provided for laterally positioning the lifting frame j, this also obstructs the vision of the operator.

In the materials handling vehicle 1, shown in FIGS. 2 to 6, a vertically extending open space is formed within the frame construction of the vehicle. The vehicle frame is comprised of two spaced

end frames

2 and 3 having a generally inverted U-shaped configuration. The

end frames

2 and 3 are interconnected by longitudinally extending lower beams 4 and upper beams 5. The lower and upper beams do not encroach on the vertical open space within the frame. The

end frames

2 and 3 are formed of

upright members

19 and 20 and cross members 19a and 200, respectively. Since the end frame is formed of an integral construction, it is sufliciently rigid to withstand the various forces exerted on it in lifting and in the movement of the vehicle. Moreover, since there are no cross members below the

upper members

19a, 20a, there is no obstruction in the open space within the frame for the vertical movement of materials to be transported.

Extending upwardly from the lower beams 4, outwardly from the uprights 20 of the end frame 3, are a pair of vertical support members 6 and knee brace members 7 which support a horizontally arranged plate 8. A cab 9 for the operator of the vehicle is located on the plate 8 as well as a motor 10 and differential gear 11 for driving the vehicle. A cantilever support member 12 extends from the plate toward the end frame 3 and support the differential gear 11. It will be noted that there is no cross member of the vehicle disposed in the path of the differenial gear. With this arrangement the operator has an unobstructed view from his cab into the open space within the frame of the vehicle wherein the materials liftingly device is located. The operator is able to view the entire lifting frame 13 as well as the books 14 which are located at its corners.

The differential gear 11 is mounted on a shaft 15 and drives sprocket wheels 16 at the outer ends of the shaft which in turn transmit the driving motion through chains 17 downwardly to driving wheels 18 located at the lower end of the frame. Other wheels 18a for the vehicle are secured to the lower beam 4 and are located between the end frames 2, 3. The driving mechanism just described does not form an essential part of the present invention, accordingly, further detailed explanation of its construction is not set forth.

Each end of the vehicle has a pair of double acting

hydraulic piston cylinders

21, 21' and 22, 22, a separate cylinder is positioned on each of the uprights 19, of the end frames 2, 3. As shown in FIG. 2, the cylinders 21, 21' have vertically

movable pistons

23, 23 provided with wheels 24, 24' on the upper ends of the piston arms. Chains 25, 25' are secured to the hydraulic cylinders and extend over the wheels 24, 24'.

Within the vertically extending open space in the frame, a lifting member or open frame body 13 is positioned substantially parallel to the surface on which the vehicle rests. At each of its ends, the lifting member 13 is atlclCllCd to the

chains

25, 25 extending downwardly from the cross member 1901 of the end frame. The support or lifting chains 25, 25' extend vertically upward from the lifting member and pass over wheels 32, 32' located on the cross member 19a, of the end frame and then passes downwardly around another

wheel

33, 33 mounted on the uprights 19, 19' of the end frame 2. From the wheels 33, 33', which are located below the

wheels

24, 24 in their lowermost position in the

hydraulic cylinders

21, 21, the chains pass upwardly over the wheel 24, 24' and then, as mentioned previously, are secured to the body of the

hydraulic cylinder

21, 21. A similar lifting chain arrangement (not shown) is provided for the opposite end of the lifting member 13. With this chain and wheel arrangement, the lifting member 13 is designed to move vertically at the rate of 2 to 1 compared with the movement of the piston within the hydraulic cylinder.

In the hydraulic system, a hydraulic fluid equalizer is provided, as will be explained subsequently, to assure an equal feed of hydraulic fluid to each of the hydraulic cylinders on the vehicle. Due to the manner in which the hydraulic fluid is fed through to each of the cylinders, the lifting member 13 will be moved upwardly and downwardly in a plane substantially parallel to the plane in which the vehicle is positioned.

As can be seen in FIGS. 2 and 5, a pair of spaced support brackets 27 extend laterally outward from one of the longitudinally extending members 26 of the lifting member or frame 13. Near the outer end of each bracket a grooved wheel 28 is positioned. Mounted on the vehicle frame are a pair of vertically extending guide rails 29 with which the grooved wheels are engaged.

As shown in FIG. 4, a double-acting piston 34 having a piston rod 35 is connected through an arm 37 to the shaft 36 on which the laterally movable guide rail 29 is mounted. By displacement of the piston arm, the shaft 36 is rotated and the end of the rail in cont-act with the grooved wheel 28 can be moved laterally either outwardly from or inwardly toward the frame of the vehicle.

At each corner of the lifting member 13, a box member 30 is provided with a hook 14 depending downwardly from the lifting member. In FIG. 3, a container 31 is shown in phantom and the hooks 14 are designed to engage a recess component (not shown) provided in the top corners of the container 31. The construction of the hook for such a use is well known and further description is not considered essential to the disclosure of the present invention.

When the lifting member 13 and any load attached to it are raised or lowered, the member is lifted by the chains 25, 25' and is guided in its vertical path with a low fictional resistance by the rollers or grooved wheels 28 and the vertical guide rails 29 provided on one side of the lifting member.

In its normal position within the vehicle, the lifting member 13 is symmetrically arranged with respect to the sides of the vehicle, as shown in full line in FIG. 5. If, in a lifting operation, the vehicle 1 is symmetrically arranged with respect to the container 31 to be lifted, then the lifting member 13 is lowered on the lifting chains until its hooks 14 engage the recessed components on the container. However, if the vehicle is not symmetrically arranged with respect to the container 31, as is often the case, then the position of the lifting member 13 can be adjusted in the horizontal plane by means of controls located in the cab 9 of the vehicle. By means of these controls, the vertical guide rails 29 can be displaced laterally so that the hooks are properly positioned over the container. An example is shown in FIG. 5 where the right hand guide rail is moved outwardly (see the dashed lines), and the lefthand guide rail is moved inwardly whereby the lifting frame assumes an oblique position with respect to the sides of the vehicle.

In addition to affording the correct positioning of the lifting member over a container to be transported, as shown in FIG. 5, the means for laterally moving the lifting member may also be employed when the container is in a lifted position for placement on another container or for proper placement in a new location. Further, the

control means for operating the piston cylinder 34, which moves the vertical guide rails, can be employed to lock the position of the lifting member 13 so that it does not move during the transporting operation.

During the lifting operation, the pistons within the hydraulic cylinders are uniformly set in motion using a hydraulic fluid quantity equalizer. If the center of gravity of the container 31 or other materials to be lifted are displaced closer to one end of the vehicle, then to the other, then the pistons on one end would be subjected to more load than those at the other end. Even in such a case, however, the hydraulic fluid is fed equally to each of the cylinders by means of a divider valve arrangement so that all four pistons have the same relative motion. Moreover, the hydraulic fluid quantity equalizer apparatus contains means whereby a single hydraulic cylinder can be operated by the driver of the vehicle.

In FIG. 6, the arrangement of the hydraulic fluid quantity equalizer apparatus is illustrated. A container 38 forms a reservoir of hydraulic fluid for the operation of the lifting member 13. From the reservoir 38, the hydraulic fluid is taken into the equalizer apparatus by means of two pair of strainers 39 and oil pumps 40. The number of pumps employed is dependent upon the hydraulic fluid quantity required for the apparatus and the capacity of the pumps.

Branch pipes

40a, 40a extend from each of the pumps 40 and combine in a

single delivery pipe

40b, 40b which extends to a flow divider valve 41, 41'. The hydraulic fluid leaves the

flow divider valve

41, 41 through two outlets and the quantity of hydraulic fluid is equal at each outlet. Accordingly, even if a difference in pressure exists within the discharge passages from the outlets, the quantity of hydraulic fluid fed from the valve is equal. Downstream of each of the

flow divider valves

41, 41 is four way valve 42, 42'. These four way valves 42, 42' control the movement of the piston in the two cylinders 21, 21' at one end of the vehicle while the other valve 42 controls the movement of the piston in the

other cylinders

22, 22 at the opposite end of the vehicle. The four way valves 42, 42' normally are controlled by the operator from the vehicle cab.

A conduit 43 is connected to the lefthand outlet of the valve 41 and extends to the four way valve 42 and similarly, a conduit 46 extends from the righthand outlet of the valve 41 to the four way valve 42. From the other or righthand outlet of the flow divider valve 41, a conduit 45 extends to the conduit 46 and similarly from the lefthand outlet of the flow divider valve 41 another conduit 44 extends into connection with the conduit 43. Accordingly, due to the arrangements of the

flow divider valves

41, 41, the quantity of hydraulic fluid flowing through the

passages

43 and 45 from one of the valves is equal to that flowing through the

conduits

44, 46 from the other valve, regardless of any difference in pressure in these conduits. Because of this conduit arrangement, the quantity of hydraulic fluid entering each of the

fourway valves

42, 42 isequal.

The four way valves 42, 42' have three positions for controlling the pistons in the hydraulic cylinders. When the piston is to remain stationary, the hydraulic fluid flowing from the divider valves 41, 41' through the

passageways

43, 46 to the four

way valves

42, 42 is bypassed through the

lines

43a, 46a to the reservoir 38. With the flow bypassed, there is no passage of hydraulic fluid into the cylinders and the position of the piston remains unchanged. If the

pistons

23, 23 or 24, 24' are to be moved upwardly the hydraulic fluid from the four way valves 42, 42' is fed into the

lines

42a, 42a and passes upwardly through another

flow divider valve

47, 47 into the cyliinders. At the same time, the hydraulic fluid on the opposite side of the piston floWs out through the upper end of the cylinder passes through the conduit 48 and returns into the four way valve.

If the pistons in the cylinders are to be moved downwardly, then the hydraulic fluid passes through the conduits 42b, 42'!) into the passageways 48, 48' and thence into the upper ends of the cylinders, and the oil or hydraulic fluid contained at the opposite side of the piston is forced out through the lines 47a, 47b and returns to the four way valve in a manner to be described subsequently.

In the path of flow of the hydraulic fluid from the four way valve 42 to the lower ends of the

cylinders

21, 21, it passes through the flow divider valve 47 which separates the fluid into two halves for passage through the lines 47a, 47b to the

cylinders

21, 21.

Accordingly, an equal amount of hydraulic fluid is delivered to each of the cylinders 21, 21'. A similar flow divider valve 47 is provided for the fluid passing from the four way valve 42 to the cylinders 22, 22' and the hydraulic fluid delivered to each of these cylinders is equal. Due to the arrangement of the hydraulic fluid equalizer apparatus passing first through the

flow divider valves

41, 41 and then through the

flow divider valves

47, 47 an equal quantity of fluid is fed into each of the four cylinders and the pistons can therefore be moved upwardly within the cylinders at the same speed.

Though

flow divider valves

47, 47 are provided in the path of flow of the hydraulic fluid from the four way valves to the lower ends of the

cylinder

21, 21, 22, 22 there is no such divider valve in the path of the hydraulic fluid to the upper ends of the cylinders. Accordingly, the flow through the cylinders has to be controlled to assure proper operation. For controlling the flow of the fluid through the cylinders when the piston is being moved downwardly, the hydraulic fluid instead of flowing through the flow divider valves 47, 47' is blocked by the

check valves

49, 49 and passes through the bypass conduits 50, '50 and flow limiting valves 51, 51' and then through the conduits 52, 52' into the four way valves. In normal operation, the flow limiting valves 51 are closed by means of springs to prevent any passage of hydraulic fluid through them. If, however, the hydraulic fluid pressure is applied to the upper sides of the

pistons

23, 23" then this pressure plus a pressure due to the weight of the piston exerts a pressure in the conduits 50, 50' which is sufliciently high to overcome the spring action within the flow limiting valve 51, 51'. As a result, a small piston within the valve is shifted and the hydraulic fluid is fed to the four way valve through the conduit 52. The position of the small piston within the flow limiting valves 51, 51' is designed so that the passage of hydraulic fluid may be regulated whereby the quantity of the fluid flowing through the

valve

51, 51 is dependent on the cross sectional area of the valve opening and in this way, the four pistons may be moved at the same speed regardless of the load which is being supported. Therefore, the pistons within the cylinders may be moved upwardly or downwardly in a uniform fashion by employing the flow divider valves 47, 47' or the flow limiting valves 51, 51' depending on the direction of travel.

There may be instances where less than the full number of four cylinders are to be used and in such a case the circuit illustrated in FIG. 6 operates in the following manner. For purpose of explanation it will be assumed that cylinder 21 is the only one to be used. The operator sets the four way valve 42 in the desired position and also actuates one of a series of buttons (not shown) for the flow limiting valve 51. Four of these buttons are provided in the cab of the vehicle and are connected to the four flow limiting valves respectively. An electric current is supplied to each of the valves when its corresponding button is actuated and solenoid is operated which withdraws the small piston which limits the flow through the valve. In this way, the hydraulic fluid passage in the bypass about the flow divider valve 47 is opened.

Since only the cylinder 21 is to be used, the flow of hydraulic fluid is opened between the lower end of the cylinder and the four way valve 42. Further, the passage or conduit 48 extending from the upper end of the cylinder 21 to the four way valve is also opened for passage of the hydraulic fluid therethrough. However, the cylinder 21 which receives hydraulic fluid from the same four way valve is subjected to resistance to flow in its return passage by means of the divider valve 47, the flow limiting valve 51 and the check valve 49. Because of this arrangement the hydraulic fluid which is discharged from the four way valve only enters the cylinder 21 and directs the piston in the desired direction.

It is to be understood that the present invention is not limited to the various embodiments illustrated and various modifications may be possible within the scope of the invention.

Other possible modifications employing the basic arrangement of the invention, as disclosed above, are to arrange the end frames directly over the wheels of the vehicle as is shown in FIG. 7. In such an arrangement, the support member '6 and knee brace member 7, for the cab, as shown in FIG. 2, are eliminated, and the cab 9 is supported directly from the end frame 3 and the driving wheels 18 are aligned below the end frame.

In another variation, the vertical guide rail 29 may be replaced by a movable channel member C secured to the side of the vehicle as shown in FIG. 8-. Instead of a grooved roller, a roller A is fixed on the outer end of a laterally extending arm B of the lifting member 13 and rolls within the vertically arranged channel C.

In view of the foregoing, it will be appreciated that the present invention as compared with the conventional apparatus shown in FIG. 1 has the following advantages.

(1) As the integral end frame members are connected to each other by means of both upper and lower beams, the vehicle body is strong in construction; and because of this construction, any deformation or relative movement of its side members at the rear of the vehicle is limited to a point where it is not in any way a problem to the operation of a vehicle. This construction is particularly useful for the design of large sized materials handling vehicles.

(2) The position of the lifting cylinders on the upright members of the frame provide an unobstructed path of view for the operator in handling materials.

(3) Since the hydraulic fluid quantity equalizer apparatus moves the pistons equally, the location of the lifting member is maintained in a plane parallel with the surface in which the vehicle is positioned and smooth operation is achieved during the transportation of the materials.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A materials handling vehicle comprising a support frame having a pair of opposite ends and being open at least at one end and having an upwardly extending open space within said frame, said frame adapted for movement over the material to be lifted within the open space in the frame, a lifting member located in the open space within said frame and adapted to extend generally parallel to the surface on which the vehicle is positioned, said lifting member being arranged to be moved upwardly and downwardly in the open space within said frame, a plurality of separate lifting means positioned at spaced locations on said support frame and secured to said lifting member for raising and lowering said lifting member, each of said lifting means comprises a double-acting hydraulic piston cylinder having a piston arm extending therefrom, means for operating said lifting means comprising a container forming a reservoir for hydraulic fluid, conduit means extending between said container and said hydraulic piston cylinders, and valve means in said conduit means for feeding equal quantities of hydraulic fluid to each of said cylinders; said valve means comprising a pair of first flow divider valves arranged in parallel for receiving hydraulic fluid from said reservoir, a pair of four-way valves arranged in said conduit means to receive hydraulic flow from said flow divider valves, and said conduit means including a first conduit member extending between one of said flow divider valves and one of said four-way valves, a second conduit member extending between the other one of said flow divider valves and the other one of said four-way valves, a third conduit member extending between said one of said flow divider valves and said second conduit member, and a fourth conduit member extending between said other one of said flow divider valves and said first conduit member for assuring an equal quantity of hydraulic fluid flowing from said flow divider valves to said four-way valves, whereby said lifting member is raised and lowered in a position substantially parallel to the surface on which the vehicle is positioned regardless of any uneven dis tribution of the load on the lifting member.

2. A materials handling vehicle, as set forth in claim 1, wherein each of said four-way valves is in communication with a different pair of said double-acting hydraulic piston cylinders, said conduit means including a tubular assembly interconnecting said four-way valves and the first ends of said piston cylinders and tubular members interconnecting said four-way valves and the second ends of said piston cylinders, said four-way valves arranged for regulating the path of hydraulic fluid through one of said tubular assembly and tubular members for selectively positioning said piston in said piston cylinder.

3. A materials handling vehicle, as set forth in claim 2, wherein a second flow divider valve is disposed in said tubular assembly, said tubular assembly comprising a first tubular section extending between said four-way valve and said flow divider valve, and a pair of second tubular sections each extending from said flow divider valve to a different one of said first ends of said piston cylinders for providing an equal quantity of hydraulic fluid to each of said cylinders.

4. A materials handling vehicle, as set forth in claim 3, wherein a check valve is located in each of said second tubular sections between said flow divider valve and said first ends of said piston cylinders.

5. A materials handling vehicle, as set forth in claim 4, wherein a bypass line is connected to each of said second tubular members and to said first tubular section for bypassing the back flow of hydraulic fluid from the first ends of said cylinders about said flow divider valve.

6. A materials handling vehicle, as set forth in claim 5, wherein a flow limiting valve is located in each of said bypass lines for regulating the flow of hydraulic fluid therethrough.

7. A materials handling vehicle, as set forth in claim 1, wherein said conduit means includes a return flow member communicating between said four-way valves and said reservoir of hydraulic fluid.

8. A materials handling vehicle comprising a support frame having a pair of opposite ends and being open at least at one end and having an upwardly extending open space within said frame, said frame adapted for movement over the material to be lifted within the open space in the frame, a lifting member located in the open space within said frame and adapted to extend generally paral- -lel to the surface on which the vehicle is positioned, said lifting member being arranged to be moved upwardly and downwardly in the open space within said frame, a plurality of separate lifting means positioned at spaced locations on said support frame and secured to said lifting member for raising anl lowering said lifting member, and means for operating said lifting means whereby said lifting member is raised and lowered in a position substantially parallel to the surface on which tse vehicle is positioned regardless of any uneven distribution of the load on the lifting member, a frame member being located at each of the opposite ends of said support frame, each frame member having an inverted U-shaped configuration and comprising a pair of spaced upright members connected at the upper ends thereof by an integral cross member, an upper linking member and a lower linking member located on each side of said support frame and secured to and extending between the upright members at the opposite ends of the'side of said support frame whereby the open space within said support frame extends at least longitudinally between said portal members at the opposite ends of said support frame and transversely between said upright members of said portal frame member, said lifting means comprising a double-acting hydraulic piston cylinder located on each of said upright members, and a piston arm positioned within said cylinder and adapted to move upwardly and downwardly therein, said lifting member comprising an open framework having a shape generally conforming to the shape of the open space within said support frame in the plane of said lifting member and having a width less than the width of said open space whereby said framework is movably displaceable laterally of said support frame, and each of said lifting means including a chain member attached to said lifting member and to one said piston cylinder, a first wheel positioned on said piston arm, a second wheel mounted on said upright member below the first wheel at its lowermost position on said piston arm in said piston cylinder, a third wheel mounted on said cross member, said chain member serially extending about said first, second and third wheels whereby as the piston arm is extended upwardly from the piston cylinder the lifting member is raised within said open space and when said piston arm is lowered the lifting member is lowered.

9. A materials handling vehicle comprising a support frame having a pair of opposite ends and being open at least at one end and having an upwardly extending open space within said frame, said frame adapted for move ment over the material to be lifted within the open space in the frame, a lifting member located in the open space within said frame and adapted to extend generally parallel to the surface on which the vehicle is positioned, said lifting member being arranged to be moved upwardly and downwardly in the open space within said frame, a plurality of separate lifting means positioned at spaced locations on said support frame and secured to said lifting member for raising and lowering said lifting member, and means for operating said lifting means whereby said lifting member is raised and lowered in a position substantially parallel to the surface on which the vehicle is positioned regardless of any uneven distribution of the load on the lifting member, a frame member being located at each of the opposite ends of said support frame, each frame member having an inverted U-shaped configuration and comprising a pair of spaced upright members connected at the upper ends thereof by an integral cross member, an upper linking member and a lower linking member located on each side of said support frame and secured to and extending between the upright members at the opposite ends of the side of said support frame where by the open space within said support frame extends at least longitudinally between said portal members at the opposite ends of said support frame and transversely between said upright members of said portal frame member, said lifting means comprising a double-acting hydraulic piston cylinder located on each of said upright members, and a piston arm positioned within said cylinder and adapted to move upwardly and downwardly therein, said lifting member comprising an open framework having a shape generally conforming to the shape of the open space within said support frame in the plane of said lifting member and having a width less than the width of said open space whereby said framework is movably displaceable laterally of said support frame, a pair of upright guide rails being located at spaced locations on one side of said support frame, a pair of spaced support brackets extending laterally outward from one side of said lifting member, a grooved roll being mounted on said bracket and extending into rolling engagement with one of said guide rails for guiding the lifting member in its upright path of travel, and means being mounted on said support frame for laterally displacing said guide rails whereby said lifting member interconnected to said guide rails by means of said groover rollers is also laterally displaceable relative to the position of said guide rails.

References Cited UNITED STATES PATENTS 2,240,564 5/1941 LeTourneau 214394 3,146,903 9/ 1964 Bjorklund 214394 3,344,940 10/1967 Burgess et al 214394 3,381,833 5/1968 Gordon 214392 ALBERT J. MAKAY, Primary Examiner- U.S. Cl. X.R.