[1]2 1 9 9 0 , 0 7 2 Ullited States Patent Office Patented June 27, 1961 2,900,072 MATERLA L ILANDLING MEICHANISM Kenneth H. Mindrum, Baffle Creek, Tdieh., assignor to Clark Equipment Company, a corporation of Mich. 5 igan FU . ed June 8, 1956, Ser. I No. 590,211 3 Claims. (CI. 214-IL40) T'his invention relates to materials handling, engaging and loading eq@uipment, particularly to such equipment 10 when 'mounted on a mobile vebicle such as a tractbr (>r the like and to novel and improved confr6l mechanism therefor. Conventionall y, such devices ha @e embodied a boom or mast pivotally mountedat one end to the forward 6nd 15 of the tractor and supporting a fork, shovel or other load en,@a,-Ing means pivotally mounted ori its oiher end and operating means in the forni of hydraulic rams or similarly operating mechanical means for independently raising and lowering the mast about its @pivotal connection 20 and tilting the load engaging means are also commonly provided. Successful operation of such devi= in loadin.- or other handling operations has been, however, largely dependent on the ability of the operator to move his tractor toward or away from the load in order to re@ich 25 or release the load. Under some circumstances, as when workin@ on rough terrain, this constitutes a real problem. Moreover, in raising and lowering the loaded fork, it is impgrtant to be able to maintain the angle of the fork either at parallel, i.e. 180 degrees with respect to the hori- 30 zontal or inclined,a few degrees therefrom to prevent premature dislodgin,a or dumping of the load. It is thus an important object of the present invention to provide a liff mechanism for a tractor or other vehicle by means of which its loading fork or other lo,ad engaging 35 means may be elevated and outwardly extended @and ro. tated to various positions of tilt. Another object of the invention is to provide such a lift mechanism with means whereby the load engaging means may be rotated to a given angle of tilt relative to 40 horiz6ntal and maintained in said angular relation during the raising and lowering or extension and retraciion Of the IDad supporting mast. Still another object of the invention is to provide -a lift mechanism for atractor or the like embodying an exten- 45 sible mast or boom pivotally connectable at one end to the tractor and supporting a loading fork or other engaging means at its outer end pivotally mounted thereon whereby the operator may, without moving his tractor, reach out with the load engaging means, retract and 50 raise and lower the same in addition to maintaining a given angle to which the load enaaging means has beeit . tilted during said raising, lowering, retractin.- and reaching out with the load engaging means. A further object is to provide in combination with such 55 a pivotally mounted extensible mast and load engaging means, a pair of cylinders, one being a slave cylinder and the otber a tilt cylinder, which are interconnected with each other and individually mounted between the vehicle and a fixed por-tion of the mast and between the 60 movable portion of the mast and said load engaging means in a manner such that change in pressure in one is accompanied by an opposite change of p@ressure in the other cylinder whereby in the raising, lowering, pivoting and extending of the mast the an,-ular relation of the load 65 engaging means to the horizontal will remain constant or substantially so. Still another object is to provide means whereby the pressure in the tilt cylinder, which is mounted between the extensible por-tion of the mast and the load engagirig 70 means, may be varied independently of and without effecting a simultaneous change in @the slave cylinder so as 2 to tilt the load engaging means to a new angle when desir@d. Still another ;object is to provide compensating means for ,iutomatically redistributing fluid on opposite sides of the plunger in the slave cylinder when the plunger is actuated by the raising or lowering of the mast and the load engaging means has been pieviously so tilted about its pivot -,is to move the pl-ung&r in the iilt cylinder to a p!osition where the tilt cylinder will not respond to demand for inore fluid by the slave cylinder. M@ny other objects and advantages of the invention will become apparent from the description of a preferred erilbodiment: of the invention which follows. It is furtiier to' be understood that many changes and modificati'ons of the embodiment of the invention as hereinafter d6scribed -may be had without dep-arting from the spirit of the invention as defined in the appended claims. Now referrin.- t6,the drawings: FIGURE I is a side elevational view of -a trartor having a material loading, lifting or handling mechanism a@eording to the present invention mounted on the, forward end thereof; FIGURE 2 is a plan of the embodiment of my invention as shown in FIGURE 1; FIGURE 3 is a view taken along lines 3-3 in FIGURE 1 looking in the direction indicated by the arrows; FIGURE 4 is a view somewliat diagrammatic of the lo@ding or lifting mechanism separa@ted from the tractor and showing the hydraulic piping and cylinders to, effect the various required motions; and FIGURE 5 is an enlarged f-r-agmentary and diagrammatic showing of the two interconnected slave cylinders and the operating means and pressure relief means employed in conjunction therewith. Referring to said several views wherein like parts are identified by like reference numerals and first to FIGURE 1, a materials lo-ading, lifting or handling device is illustrated as comprising an extensible mast 11 pivotally connected :as dt 12 to a mobile vebiele such as tractor 13 h@ving a pair of front wheels 14 and a pair of rear wheels 15 steeringly operated by means and suitable linkage, not shown. Extensible mast 11 is thus illustrated as wheel or tractor-bdrne, and it is to be understood that in keeping with the spirit, of the in@vention extensible mast 11 might be pivotally mounted to any other suitable vehicle. As seen bya com@parison of FIGURES 1 2 and 3 with each other, the ex@tensible mast 11 comprises a main frame 16 comprising a pair of parallel, spaced U-channelled members 17 and 18 joined by reinforcing cross pieces 19 and provided with triangular ear scgtions 20 welded to the inner ends thi@reof which are pivotally connected to portions 21 of the tractor by means of shaft 12 passing through aligned openings provided in said por-tions 21 and sections 20. Collars 23 or other suitable means are pinned to the outer ends o-f said shaft 12 to prevent its lateral discement and pivotally secure said main frame 16 to the body of the tractor 13. I A secondary frame 24 is provided comprising a pair of parallel spaced U-channelled members 25 and 26 which telesco pically fit within U-channelled members 1'7 and 18, @respi@ctively, of the main frame 16 so as to be slidably adjustable longitudinally thereof. Said U-channelled members 2@ and 26 are also joined by reinforcing members 27 to.give strength and rigidity to the structure. Rigidly mounted on the forward or outer ends of the telescopic chan@nel members 25 and 26 are a pair of angled portions 28 between which is pivotally connected, by pin means 29 a load engaging means, such las :a fork, shovel or the like, indicated generally at 30. A pair of hydraulic cylinder assemblies 31 are located on opposite sides of the tractor 13 having their plunger stem 32 pivotally connected by pin means 33 to the op-
[2]3 posite ends of a bracket 34 or the like, welded or otherwise secured to the mai-n frame 16. Such cylinder assemblies are actuatable to elevate and lower the mast 1,1 and thereby load engagin- means 30 about its pivotal connection 1:2 with tractor 13. The fluid cylinders of assemblies 31 are pivotally connected to the sides 21 of the tractor in any convenient manner and in FIGURE 1 of the drawi.ng are shown as connected by pivot means 36 to a housing assembly 37 which is bolted or riveted to the sides 21 of the tractor. Preferably, the cylinders are thus pivotally connected int,-rmediate their ends rather than at the extreme outer ends of the cylinders to increase the controllable range through which the mast 11 may be swung about its pivotal connection 12 in raising and lowering the load engaging means 30. One of the features of the invention is the adjustability of the secondaryframe 24 of the extensible mast 11 relative to its supporting main frame 16 which permits the operator to rea-ch out with and retract the loading fork 30 without having to move the tractor. This is conveniently and smoothly accomplished by a pair of hydraul@ic fluid operated reach cylinders 38 v@,hich are located between and alongside of the channel members 17 and 18. Such are pivotally connected at 39 to a suitable boss or the like provided at the inner end of the channelled members 17 and 18 of the mast's main frame 16 and have a stem 40 of their plungers - pivotally connected, as at 41, @to the forward brace iar reinforcing members 27 of said secondary frame 24. As illustrated by dotted lines in FIGURE 1, through suitable actuation of the plunger in reach cylinders 38, it is possible for the operator to conveniently and smodthly extend angled supportin-, arms 28 on the ends of the secondary framo 24 which carry the fork 30 or other loading device, to a position B beyond A (indicated in full lines) or retract it to a position C as determined by the range of reciprocal movement of the plungers in their respective cylinders 38. It will be noted also that the secondary frame 24 and main frame 16 are so constructed that the secondary frame, in its ful@ly retracted position, indicated by C is withdrawn well beyond the outer end of the main fram@ 16, th, ,ifo,cin.,@ portions 27 of said frame Z4 passing beneath the reinforcing portions 19 and supporting brackets 34 and 42 of the main ftame 16, thus further contributing to the strength and rigidity of the construction. If desired, the m-ain frame 16 and its channeled members 17 and 18 could be of a length sucb as to enclose the channelled members of the secondary frame even to their fully extended position at B. Ti@lting of the load engaging means is accomplished by a tilt cylinder 43 having a plunger stem 44 pivotally connected, as at 45, tb the upper end of the fork 30 at a location spaced above its pivotal connl-ction 29 with arms 28. As shown in FIGURES 1 and 2, the cylinder 43 is pivotally mounted at its one end to one of the reinforcing cross pieces 27 of the secondary frame 24 by pin means 46. Such cylinder is located on the underside of the seco-ndary frame @and so does not interfere with the extension and retraction of said secondary frame within the main or pivotally connected frame portion 16 of the mast 11. A servo or slave cylinder 47 is also shown pivotally connected at one end by pivot rneans 48 to the forward end of -the tractor beneath the mast 11, such having a plun,@er reciprocally mounted therein with its stem 49 pivotally connected @at 50 to a short arm 50A rigidly secured to shaft,12 (see FIGURE 3). Stem 49 thus moves with the rotation of the mast 11 about its pivot center 12. The servo cylinder 47 is in hydraulic circuit with tilt cylinder 43 -for a purpose which will hereinafter be made clear. Referring now to FIGURE 4, wherein the various mechanisms described are somewhat diagrammatically illustrated for ease of understanding, the hydraulic controls and their operation as are required for the tilting, r-ai@ing and lowering and reaching out and retracting of the fork 30 in the use of the device will now be explained. 2,990,072 4 Preferably, for greater control and smootbness of operation the reacli cylinders 38, the elevating cylinders 31, as well as tilt cylinder 43, are of the double action type. That is to say, for example in the case of the reach cyli-nders 38, a first set of conduit lines 51 connect one end of the cylinders 38 wit-h the operator's control valve 51A while a secon@d set of conduits 52 connect the opposite end of the cylinders with such valve control 51A. 'fhus, by suitable actuation of the valve 51A pressurized fluid may 10 be supplied from the pum@p 53 via conduit 54 to either line 51 or 52 for exerting pressure on either side of the pltinger 40A. For exan-,ple, if the valve control 51A is actuated to supply fl@id throu.-h line 5@l the effect will be to build up a pressure on the upper side of -plungers 40A to 15 force the seconidary frame 24 and fork carried thereby toward -the pivotal connection 12. Conversely actuation of control valve 51A toforce fluid through lines 52 will have the opposite effect, namely to further extend the mast 11. Thus, a very positive smooth and accurate control of the 20 reaching action may be had. In a similar manner, conduit 55 connects control valve 56 to pump 53 so that ffuid can be selectively supplied via lines 57 to the upper side of plungers 32A in the elevating cylinders 31 or by lines 58 to connect valve 25 56 to the lower side of said plungers 32A. Thus, by suitable operation of control valve 56, oil may be purnped from the supply source through line 57 to lower the mast 11 and fork 30 about pivot:12; Ene 58 under that condition acting as a return far the oil being driven out 30 of cylinder 31. Conversely, valve 56 may be operated to di-rect ftuid through line 58 to the underside of plunger 32A forcing the plungers upwardly to elevate the mast 11 and fork 30. In this circumstance, line 57 functions as @a return line for releasing the excess fluid on the top 35 side of the cylinder as it is moved to extended position. A third manually controlled slide valve 59 communicates via line 60 to pump 53 and the supply source. Such valve is connected to the left end of servo cylinder 47 by way of conduit 62, pressure relief valve 63 and 40 conduit @64, and also by way of conduit 68, pressure relief valve 69 and conduit 70. Slide valve 59 is also connected to the right-hand end of ser-vo cylinder 47 by way of conduit 68, press@ure relief valve 69,, conduit 71, pressure relief valve 72, conduit 73, check valve 74 and 4LO 75. Finally, valve 59 is also connected to the =nd end of the cylinder 47 by conduit 62, pressure relief valve 63 and conduit 76. Conduits 77 and 78, respectively connect the left and right hand ends of cylinder 47 to the upper and lower ends of tilt cylinder 50 43. The operation of the hydraulic circuitry will be explained in detail hereinafter. Assuming, for the present, that control valve 59 is closed, a closed circuit will exist between cylinders 47 and 4-3, through conduits 77 and 78. As a result of the 5,5 intercircuitry between cylindets 47 and 43 the actuation of the piston of one cylinder in one direction serves to actuate the plunger of the other cylinder in an opposite direction so that the actions of the two cylinders when control valve 59 is closed are each subservient 60 to the other and in reverse directions. Tbus, for example, upward rotation of mast 11 about pivot 12 by actuation of lift cylinders 31, results in a counterclockwise rotation of arm 50A which actuates stem 49 and plunger 49A of cylinder 47 toward a col(5 lapsed position. The cylinder fluid displaced thereby flows through conduit 78 to cylinder 43, with actuating plunger 44A being moved therein toward its extended position which through the pivotal connection of the plunge@r stem 44 with engaging means 30 has the effect 70 of rotating the fork in a clockwise direction about axis 29 a proportionately similar amount. As previously pointed out, the fluid displaced by plunger 44A is returned to cylinder 47 via conduit 77. Lowering of the mast by actuation of lift cylinders 75 31 in the opposite direction reverses the above sequence,
[3]5 i.e., lever arm 50A is rotated @lockwise With the ma t 11 about pivot 12 to extend plunger 49A thereby displacing a,@olume of fluid to the upper end'of cylinder 43 throiigh conduit 77 returning to the right-hand end of cylinder 47 through- conduit 73. This action causes rotation of the engaging means 30 in a counterclockwise direction'about its pivot 29. The design of the interlocked slave and tilt cylinders 47 and 43 and the actuation of their respective plunger@ 49A and 44A plus their coniiection with the lever arni 50A and fork 30 is such that the fork tongs 30A will be maintained in a pre-set angular relation, such as parallel With respect to the horizontal during any and all rotational movement of the mast 11 between minimum and inaximum elevation limits. As will be apparent, since cylinder 43 is pivotally connected at its lower end to the extensible portion 24 of the mast 11, as previously described, energization of the ieach cylinders 38 to aetuate plungers 40A in either collapsed or extended direction does not alt.-r the pre-set angular relation of the fork tongs 30A since the latter ard effectively maintained in their pre-set position by the cooperation of the two cylinders 47 and 43. This will,be the case whether the reach cylinders 38 and lift cylinders 31 are separately or simultaneously operated. I In the condition of operation in which the angle of elevation of the mast is fixed (see, FIGURE 4), the slave piston 49A will be stationary due to the lack of rotational movement of the mast. If valve 59 is then opened, in adirerction to collapse the tfft cylinder 43, the fork or load engaging means 30 will rotate in a counterclockwise direction about its axis 29 at the given elevation of the mast as in this condition, the pump 53 supplies fluid through valve 59, conduits 62, 64 and 77 to the upper end of tilt cylinder 43. Since the slave piston 49A is incapable of movement due to the fixed angular position of the mast, the fork or load engaging means 30 will tilt independently about its axis 29. Oil on either side of the slave piston 49A is inoperative and the movement of the tilt pistbii '44 is downwardly or to the left as viewed in FIGURE 4 to discharge oil through conduit 78, 75, 73, and 72 for return to the tank or reservoir for the pump. In the reverse operating condition wherein valve 59 is moved to connect the left or lower end of the t"t cylinder to the pump and the right end thereof to the tank, pressurized oil is supplied via conduit 68, pressure relief valve 69, and conduits 71, 73, 75 and 78 to the lower end of the tilt cylinder 43. Oil re'@urns to the tank from the right-hand or piston rod end of cylinder 43 through conduits 77, 64, valve 63 and conduit 62. In this condition the slave cylinder is again inactive with the oil connectin.- the same to the relief valves 63 and 69 which open under predetermined extreme operating conditions to permit one-way flow throu-,h one of the overload lines 70 or 76 to the related ends of both of the cylinders 43 and 47. In another condition of operation, with valve 59 closed, the tilt piston 44A in its extreme extended position and the lift cylinders ener.aized to elevate the boom thereby also actuating the slave piston to theright in FIGURE 4 or toward its collapsed position, obviously the oil applied to the tilt cylinder will be inoperative because the latter resides in its extreme position. Movement of the slave piston to the right thereby causes relief valve 69 tO lift which connects the large volume or right hand end of the slave cylinder 47 with the small volume end thereof throu.-h conduits 75, 73, 71 and 70. Relief valve 72 is provided in conduit 71 so that the volume of fluid displaced from the ri.-ht end of the slave cylinder in excess of that volume receivable in the left end of the cylinder may be vented back to the tank. From this, it will be und,-rstood that even though the operator has actuated the tilt cylinder to an extreme extended position in which the fork or load engaging members are pointed substan2,990,072 @6 tially vertically dowiiwatd followed by energization 6f the lift cylinders to lower the boom, no dainage to the system will result because of the provision of the relief valves 69 and 72.: 5 In a reverse of the above situation, wherein the tilt cylinder or piston is actuated to:an extreme collapsed position so that the fork or loading engagin.- means 30 is pointed substantial-ly vertically upward, it is possible to again individually @ actuate the lift cylinders to lower or 10 raise the boom. Agaifi the oil in the tilt cylinder is inoperative as is the oil supplying the now closed valve 59. In this case, extended movement of the slave piston opens relief valve 63 permitting oil to flow through conduits 64 and 76 to the large or right hand end of the slave 15 cylinder, as viewed in FIGURE 4. Because the oil volume moved out of left hand end of the cylinder is less than that receivable in the right hand end thereof, check valve 74 is provided to open at a prddetermined low pressure in the latge or right hand end of the slave 20 cylinder to supply additional oil from the lank., In summary the hydraulic system of my invention may be considered to comprise a main hydraulic circuit defined by a first branch r-ircuit extending from valve 59 and including condui-t 62, pressure relief valve 63, conduit 64, 25 and conduit 77 for connecting the left and right hand ends, respectively, of slave cylinder 47 and the tilt cylint der 43; @a second branch circuit including a conduit 68 extending from valve 59, pressure relief valve 69, conduit 71, conduit 73, conduit 75, :and conduit 78, to provide 30 for connection of the right and left hand eids, Tespectively, of the slave cylinder 47 and the tilt cylinder 43. Further, the main hydraulic circuit includes a conduit 76 connecting pressure relief valve 63 with the aforedescribed second branch circuit, and a second conduit 70 which 35 connects pressure rehef valve 69 with the aforedesrribed first branch circuit. The hydraulic system is further defined by an auxiliary hydraulic r-ircuit connected between sump and the afore-described second branch circuit and includes the pressure Telief valve 72 connected between ?40 conduits 71 and 73; and,the low pressure check valve 74 connected by a T connection between conduit 73 and the conduit 75; fluid under pressure from a pressure source, such as pump means 53, is conducted by conduit 60 to valve 59 for distribution by actuation of the latter as al45 ready described. From the foregoing, it will be seen that a vertical fork control meehanism is provided by whigh the fork or load engaging means may be elevated and outwardly extended and rotated to various positions of tilt or control to mainr)o tain a preselected horizontal position irrespective of variatiols, in elevation retraction oT exteiisions thereof. NVI-iile I have herein sliown and desciibed my unique control mechanism in association with a particular type of load engaging means and a particular lift truck ap.55 paratus, nevertheless it will be recognized that various changes, modifications and substitutions of equivalents may be made therein without necessarily departing from the spirit and scope of the invention. As a consequence it is not my intention to be restricted to the particulars (o of the embodiment herein described and illustrated except as may appear in the following appended claims. I
