US 3133655 A
Description (OCR text may contain errors)
May 19, 1964 H. GARDNER LIFT TRUCK 5 Sheets-Sheet l Filed Sept. 8, 1961 @n I mm J mw nw @N mp2 T No wv u me 2 mw on vm o n uw N N INVENTOR Hal Gardner H. GARDNER May 19, 1964 LIFT TRUCK 3 Sheets-Sheet 2 Filed Sept. 8, 1961 INVENTOR. Gardner Ho l BY H. GARDNER May 19, 1964 LIFT TRUCK 3 Sheets-Sheet 3 Filed Sept. 8. 1961 dr 'Il l mvENToR y Hol Gardner UnitedStates Patent O "ice 3,133,655 LIFT TRUCK Hal Gardner, Box 96, Rte. 2, Richins Ave., Gridley, Calif. Filed Sept. 8, 1961, Ser. No. 136,766 Claims. (Cl. 214-652) This invention relates to lift trucks. More particularly, it relates to fork lift trucks and to improvements by reason of which the stability of the truck during movement of a load is significantly increased. In other specific aspects it relates to novel clamp means for maintaining the load on the forks of the truck.
In the accompanying drawings:
FIG. 1 shows in side elevation a fork lift truck embodying the present invention.
FIG. 2 shows in end elevation the fork lift truck of FIG. l.
FIG. 3 in side elevation shows the front portion of the fork lift truck of FIG. 1 wherein the forks are tilted at the ground level.
FIG. 4 shows in side elevation a portion of the lift truck shown in FIG. 3 wherein the forks have been raised above ground level and rotated 90 with respect to the ground;
FIG. 5 is a side sectional view including parts of the forks and its lifting and turning mechanism of FIG. 4 and taken along the line 5 5.
FIG. 6 is an end sectional view of the fork turning mechanism shown in FIG. 5 and taken along the line 6 6. v
FIG.- 7 is a side view partially broken away of the hydraulic rams associated with both the boX clamp and the fork turning mechanism shown in FIG. 1.
The stability of a fork lift truck, when attempting to raise a relatively heavy load on the forks, is a significant problem because the forks are at one end of the truck. In previously used designs the forks are supported by a mast at a point remote from the center of gravity of the truck. The weight of the load to be lifted has been strictly limited so as not to upset the entire truck.
The present invention provides a truck construction that greatly increases the stability of the truck and allows the lifting of greater weights by the forks without danger of upsetting the truck. This is accomplished in the present invention by two main innovations comprising generally (l) the relative position of the mast on the truck frame which supports the load carrying forks, and (2) the shape of the main frame itself.
Thus the present invention provides a lift truck comprising a generally horizontal frame having forward and rear wheels rotatably mounted thereon. A generally vertical mast is Vfixed to the frame rearwardly of the forward wheels.` The load carrier is positioned in front of the forward wheels. The truck includes means for supporting and linking the load carrier with the mast and means for tilting the load carrier with respect to the ground independently of the mast. AThere is also providedmeans for raising and lowering the load carrier wth respect tothe mast.
As a result of employing a fixed mast and positioning it behind the forward wheels'l and close to the center of gravity of the truck, great stability is achieved even when 3,133,655 Patented May 19., 1964 the load on the forks is moved to the upper part of the mast.
As in prior trucks, the load carrier with its forks is forward of the front wheels and is thereby capable of being used in the same manner as in prior vehicles.
The forks are tilted independently of the main mast as will be more fully described hereinafter. As a result, the mast may be rigidly connected to the frame. Because the tilting of the fork does not depend upon the mast being tilted as in prior vehicles, the present truck is capable of having its forks tilted at greater angles than previously possible in trucks where tilting was accomplished by movement of the mast.
As alluded to above, stability is also enhanced by employing a frame having a configuration wherein it is bent downwardly in the central part and is thereby closer to the ground between the forward and rear wheels than in the vicinity of the forward and rear wheels. The lower central portion of the frame provides a lower center of vgravity for the entire truck and thereby contributes to the overall superior stability.
Another novel aspect included in the present lift truck lies in the clamp associated with the load carrier and its forks. The clamp serves to engage a load to be moved so that the load is gripped between the clamp and the forks and maintains the load in proper position on the forks.
More specifically, the clamp provided by the present invention is associated with the load carrier, the load carrier including a head having fork members. In a specific embodiment the clamp unit comprises at least one set of three telescoping vertical spacers. Each set of spacers includes a middle spacer and first and second end spacers. The second end spacer has a plurality of stops spaced along its length, and the middle spacer has a manually `operable lock member for cooperable enaggement with the stops of the second end spacer whereby the combined length of the middle and second end spacers may be adjustably fixed.
A hydraulic ram is connected between the first end spacer and the middle spacer for selectively adjusting the combined length of the middle and first end spacers. One ofthe spacers is attached to the head of the load carrier and the other end spacer has clamping means opposed to the fork members to grip a load therebetween.
The clamping means noted in the previous paragraph comprises at least one arm generally parallel to the fork members and has a depending cylinder therefrom. A spring mounted Vrod is positioned partially interiorly of the cylinder and has a load contacting disc on the downward end of the rod.
In operation the manually operable lock member between the middle spacer and the second end spacer is released and the spacers positioned for the particular size and shape of the load to be moved. The load is then picked up by the fork and the hydraulic ram actuated to bring the disc of the clamping means in contact with the 3 type of ram is also used in respect to the load carrier turning mechanism to be described hereinafter. The ram includes a cylinder having a piston therein defining a rst side and a second side in the cylinder. This piston has a hole therethrough establishing uid communication between the rst side and the second side of the cylinder.
A tubular piston rod is connected at the hole in the piston at the second side of the cylinder so that piston actuating fluid may pass through the tube and the hole to the first side of the cylinder to drive the piston toward the second side of the cylinder. There is a iuid inlet port in the second side of the cylinder for the entrance of piston actuating fluid to return the piston to the first side of the cylinder.
The principal advantage of such a construction as applied to lift trucks lies in the freedom from entanglement of fluid conduits such as hoses when the forks are lifted on the mast and rotated by a fork rotating mechanism as will be described more fully hereinafter.
The foregoing ram construction permits uid hoses all to be fixed to the lower end of the ram when the ram is positioned vertically. When the ram is rotated along with the load carrier, the hoses do not become entangled as would be the case if the hose were attached to the upper end of the ram.
With reference to the drawings, FIG. l in particular, the entire lift truck may be more easily understood by considering it as being composed of three major units comprising a main frame with power supply and main mast A, a load carrier supporting, rotating, and tilting mechanism B, and load carrier and clamp mechanism C.
Part A serves as a mobile base and source of power for the entire truck upon which part B rides up and down and is supported thereby. Part B causes part C to rotate about a generally horizontal axis and to tilt with respect to the ground. Part C also rides up and down with part B of course, when part B is moved with respect to part A. The load to be moved is picked up with part C.
More specifically, part A includes a generally horizontal main frame having front wheels 11 and 11 and rear wheel 12. Frame 10 is stinken in the central portion 13 so that it is lower between the wheels 11, 11' and 12 then it is in the vicinity of the wheels 11, 11' and 12. As previously noted, this gives the entire truck a greater stability owing to a lower center of gravity.
Mounted on the major portion of the frame is a power supply plant shown generally at 14 with its usual attendant components and controls. These form no part of the present invention and will not be described in detail. It is sufficient to state that the power plant, controls, and the like are similar to those well known in the art.
It should be noted however, that the various moving parts of the truck are operated by fluid actuated rams driven by fluid under pressure from a variable pump to valves (not shown) supplied from storage tank 15. Storage tank 15 contains suitable fluid to maintain the necessary volume of the pump (not shown) driven from power plant 14. Since there are a plurality of rams and it is desirable to be permitted to operate more than one ram simultaneously, it is preferred to employ a constant pressure variable volume pump.
In the embodiment illustrated, the truck has a front wheel drive in which the front wheels are powered by means of chains 16 and 16 which are in turn driven through a shaft and gear train (not shown) variable in speed in relation to the r.p.m. of the motor in power plant 14. The truck is clutch steered (not shown). Rear wheel 12 is mounted on a bracket and axle assembly 1'? that is freely rotatable throughout 360 with respect to frame 10.
Mast 18 is Xed to frame 1t) at slotted cross member 19 and ismade rigid with a plurality of suitable braces such as brace 20. As previously mentioned, this posi- 4 tion of the mast is a radical departure from previous designs and results in the unusual stability of the fork lift truck during its operation.
Mast 13 includes a telescoping mast channel member 21. Mast channel member 21 telescopes up and down inside mast 18. Such telescoping movement serves to raise and lower part B attached thereto which in turn moves part C.
Part B is a mechanism for rotating, tilting, and supporting part C and includes an outer frame structure 22. Frame structure 22 has flanges (not shown) suitably adapted to mesh with and slide up and down interior grooves 23 of mast 18.
Outer frame structure 22 is elevated for up and down movement by means of chain 24 linked to bracket 25 on frame structure 22 and at its other end linked to bracket 26 on mast 18. Up and down movement of frame strueture 22 with respect to mast 18 is accomplished by up and down movement of channel member 21. Channel member 21 is telescoped in and out of mast 18 by the operation of hydraulic ram 27. Chain 24 is fed over sprocket wheel 2S on channel member 21. As channel member 21 is raised by ram 27, chain 24 pulls frame structure 22 upwardly, and when ram 27 moves channel member 21 downwardly, the reverse downward positioning of frame structure 22 occurs.
Part B, with reference to FIGS. 5 and 6 in particular, includes cylinder or drum 29 which is rotatably mounted interiorly of frame structure 22 on a plurality of bearings 30. Drum 29 is maintained in position by means of a bolt 31 attached to an angle iron 32 Welded to frame structure 22.
Cylinder or drum 29 is rotated on its bearings 30 by means of chains 33 and 33'. Chains 33 and 33 are moved by ram 34. The rotational aspect of part B and the corresponding rotation in turn caused part C forms no part of the present invention and a detailed description of the parts is not required. Any of the rotational mechanisms known in the art may be used for this purpose.
It should be noted however, that the mechanism employed must, in accordance with this invention, be modified to include a generally horizontal elongated member such as cylinder or drum 29 since its function is, in addition to causing rotation of the load carrying part C, to support part C with respect to mast 18. Since mast 1% is behind the front Wheels 11 and 11 and the load carrying part C is in front of the truck, a relatively long member is required.
Also, ram 34 is of the special type previously noted which eliminates the necessity for hose connections at its upper end. The specific construction will be described more fully in relation to the ram of part C which is identical to ram 34.
Load carrying part C contains a head comprising a pair of braces 35 and 35 with forks 36 and 36 mounted thereon.
Brace 35 forms part of a pivot joint by being inserted through a tubular portion 37 of apron 38. The pivot joint is used during tilting which will be described hereinafter. Apron 3S is in turn mounted across part of the forward open end of drum 29.
Lateral shifting of load carrier part C is accomplished by laterally sliding brace 33"' back and forth through tubular portion 37. The actuating force for the motion is provided by ram 7i) anchored at one of its ends to the left side of apron 38 as viewed in FIG. 2 and at its other end to the rear of fork 36.
Two sets of telescoping vertical spacers shown generallyat 39 and 40 support an upper clamping means shown generally at 41 in oposed relation to forks 36 and 36. Each set of spacers 39 and 40 is substantially identical and only set 39 will be described in detail.
Spacer set 39 is composed of first end spacer 42, middle spacer 43 and second end spacer 44. Second end spacer 44 contains a plurality of spaced holes 45 along its length. Middle spacer 43 contains a keyk 46 at its upper end. As a result, second end spacer 44 may be manually telescoped within middle spacer 43 to any desired point and locked in place by positioning key 46 through an appropriate hole 45. This permitsk adjustments to accommodate different size loads. Y
First end spacer 42 and middle spacer 43 are selectively telescoped with respect to each other to provide their desired combined height by means of hydraulic ram 47. The specific construction of ram 47 will be more fully described hereinafter.
Second end spacer 44 supports horizontal arms 48 and 49. Depending'from arms 48 and 49 are a plurality of pipes or cylinders of which cylinder 50 is typical. Rod 51 is mounted partially within cylinder 50 by spring 52 extending outwardly and downwardly from cylinder 50. At the end of rod 51 there is found a disc 53. (The remaining cylinders have similar rods, springs, and discs.) Thus, when spacer sets 39 and 40 are telescoped together to decrease their total length by the action of ram 47, disc 53 will contact the top of a load supported on forks 36 and 36 and serve to clamp the load in place. The degree of force exerted by disc 53 on the load may be visually estimated by observing the degree of compression of spring 52. An adjustment screw 52a. is suitably positioned to adjust the compression of each spring 52 and thereby equalize the pressure of all of the discs 53 on the load to be moved.
A plurality of brace elements 54 and 56 are suitably employed as required to lend structural rigidity to the spacers and clamping means.
Tilting of forks 36 and 36 is accomplished by means of hydraulic ram 65. Ram 65 is fixed to the interior side walls of cylinder or drum 29 by means of an ear 66 on ram 65 which forms a loose play connection with angle iron 66a. Piston connecting rod 67 of ram 65 is attached to bracket 68 on the underside of head brace 35. Piston connecting rod 67 clears apron 38 during operation by virtue of notch 69 in the top of apron 38.
In operation, when connecting rod 67 is withdrawnwithin ram 65, forks 36 and 36' are caused to tilt upwardly as shown in FIG. 1. When rod 67 is positioned outwardly from ram 65, forks 36 and 36 are caused to tilt downwardly as shown in FIG. 3. The up and down pivotal motion of forks 36 and 36 attached to brace 35 is permitted by virtue of the pivot joint formed by the insertion of brace 35 through tubular portion 37 previously mentioned.
Ram V47, which is substantially identical to ram 34 on part B, is shown most clearly in FIG. 7. There it will be seen that ram 47 includes a cylinder 57 and a piston 58 with a hole therethrough at 59. Connecting rod 60 is hollow and is connected to piston 58 at hole 59. As a result, pressure fluid may in turn ow through connecting rod 60 from point 61 and pass through the hole 59 in piston 58 to drive cylinder 57 upwardly. Since connecting rod 60 is attached to second end spacer 42 and cylinder 57 is connected to middle spacer 43 by bracket 63, such movement of cylinder 57 will cause middle spacer 43 to be lifted upwardly and the clamping action of disc 53 will be released.
Cylinder 57 may be returned to its vinitial position by the inlet of fluid through a port 64 to the interior of cylinder 57. This fluid pushes cylinder 57 downwardly and consequently causes second end'spacer 42 and middle spacer 43 to telescope together and apply clamping pressureto a load on forks 36 and 36' by means of disc 53.
It should be noted that the fluid enters ram 47 at the bottom of the ram for both strokes of the piston. lThis eliminates the necessity of a` hose attached to the top of the ram which might become entangled during rotation of load supporting part C as illustrated in FIG. 4.
6 l Pairs of hoses for ram operating fluid, linking storage tap 15-and each of the rams hereinbefore mentioned have been omitted for ease in viewing the drawings. v
Although the foregoing invention has been described in some `detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.
What is claimed is:
1. A fork lift truck comprising a generally horizontal frame having forward and rear wheels rotatably mounted thereon, said frame being sunken between said wheels so as to be closer to the ground than in the vicinity of both `said forward and rear wheels, a generally vertical mast fixed to said frame between said forward Iand rear wheels, a load carrier including fork members in front of said forward wheels and opposed yclamp means for securing a load on said fork members, a generally horizontal elongated load carrier rotating unit supportably linking said load carrier with said mast, said load carrier being pivotally attached to said rotating unit for tilting said load carrier forks with respect to the ground, means for causing said load carrier to pivot, and lift means for raising and lowering said rotating unit on said mast.
2. A fork lift truck in accordance with claim 1 wherein said load carrier rotating unit is actuated by a hydraulically operated double acting ram having a cylinder, a double ended piston within said cylinder for up and down reciprocating movement and having a hole for fluid communication between the ends of the piston, a tubular connecting rod for said piston joined to one end of the piston at said hole so that piston actuating fluid may ow through said tubular connecting rod and through the hole in said piston to thereby drive the piston in one direction, and a fluid inlet port to said cylinder for the entrance of actuating fluid for said piston to cause a return stroke thereof. j
3. In a lift truck, a load carrier including a. head having fork members for engaging a load to be moved, and a clamp unit for maintaining the load in engaged position on the fork members comprising at least one set of three telescoping vertical spacers, each set of spacers including a middle spacer and iirst and second end spacers, said second end spacer having a plurality of stops spaced along its length, said middle spacer having a manually operable lock member for cooperable engagement with the stops of said second end spacer whereby the combined length of said middle and second end spacers may be adjustably xed, and a hydraulic ram connected between said rst end spacer and said middle spacer for selectively adjusting the combined length of the middle and rst end spacers, one end spacer of said set of spacers being attached to the head of said load carrier and the other end spacer of said set of spacers having load clamping means opposed to said fork members to grip Ia load therebetween.
4. A load carrier for a fork lift truck in accordance with claim 3 wherein the fluid actuated ram connected between the middle and lirst end spacers includes a cylinder, a piston within said cylinder creating a first side and a second side in said cylinder, a hole in said piston estabvlishing fluid communication between the rst side and the second side of said cylinder, a tubular piston rod connected at the hole in said piston at the second side of said cylinder so that piston actuating fluid may pass through said tube and hole to the iirst side of said cylinder to drive the piston toward the second side of the cylinder, a fluid inlet port in the second side of said cylinder for the entrance of piston actuating lluid to return the piston to the first side of said cylinder.
5. A fork lift truck comprising a generally horizontal frame having forward andrear wheels rotatably mounted thereon, a generally vertical mast fixed to said frame to the rear of said forward wheels, a load carrier including a head having fork members supported in front of said forward wheels, said load carrier having a clamp unit mounted on the head in opposed relation to said fork members to grip the load therebetween, said clamp unit including at least one outwardly extending arm generally parallel to said fork members, at least one downwardly positioned cylinder on said arm having a spring mounted rod depending interiorly therefrom, and a disc at the end of said rod for abutment with a clamped load, and means to urge said clamp unit toward said fork members; a generally horizontal elongated load carrier rotating unit directly supportably linking said load carrier with said mast, said load carrier being pivotally attached to said rotating unit for tilting said load carrier forks with respect to the ground, means for causing said load carrier to pivot, and lift means for lowering 'and raising said lift unit on said mast.
References Cited in the tile of this patent UNITED STATES PATENTS Towson Jan, 2, Sears Apr. 28, Puim Sept. 9, Wellman May 16, Weiss Apr. 22, Montanus Sept. 14, Woodward Feb. 7, Puirn Mar.y 25, Oury May 27, Thresher et al. Mar. 3, Shimmon Mar. 13,
FOREIGN PATENTS Germany Sept. 25,
(German application Kl81e)