US3220580A

US3220580A - Material handling apparatus

Info

Publication number: US3220580A
Application number: US346021A
Authority: US
Inventors: Elton B Long
Original assignee: JI Case Co
Current assignee: Case LLC
Priority date: 1964-02-19
Filing date: 1964-02-19
Publication date: 1965-11-30
Anticipated expiration: 1982-11-30

Description

Nov. 30, 1965 E. B. LONG 3,220580 MATERIA HANDLING APPARATUS Filed Feb. 19, 1984 z sheets-sheet 1 Nov. 30, 1965 E. B. LoNG MATERIA HANDLING' APPARATUS 3 Sheets-Sheet 2 Filed Feb. 19, 1964 IN VEN TOR. ELTo/Y a/Y.

Nov. 30, 1965 E. B. LONG MATERIA HANDLING APPARATUS 3 Sheets-Sheet 5 Filed Feb. 19, 1964 United States Patent O 3,220,580 MATERIA LENG APPARATUS Elton B. Long, lurlington, Iowa, assignor to J. I. Case Company, Racine, Wis., a corporation of Wisconsin Filed Feb. 19, 1964, Ser. No. 346,021 9 Claims. (Cl. 214-140) This application is a continuation-in-part of Long application Serial No. 257,538, filed February ll, 1963, now abandoned, and assigned to the assignee of the present invention.

This invention relates to material handling equipment and, particularly, to a loader assembly secured to a prime mover such as a tractor that includes a pivotally mounted bucket disposed across the front end of the tractor. Such an assembly is generally referred to as a front end loader, in which the bucket position thereof is usually loaded by moving the bucket into a pile of material, after which the lift arms may be raised and the tractor driven to a new location. At this point, the bucket is swung about the front end of the lift arms into a dumping position to discharge the contents, after which the tractor is driven back for another load.

Earth moving equipment, such as tractor mounted front end loaders, to which the present invention is directed, have been on the market for some time. A typical loader assembly includes a pair of lift arms that are pivotally mounted on a main frame fixedly securedto the tractor. The inner ends of the lift arms are located adjacent the tractor operator and the outer ends of the lift arms, when in the lowered position, are disposed adjacent the ground between the tractor radiator and the front Wheels. The `bucket extends across the front of the tractor and is pivotally connected to the lower ends of the lift arms. The bucket is moved between the digging, lifting and loading positions by a hydraulically operated linkage mechanism that is controlled by the operator through a valve arrangement located adjacent the tractor seat.

Up until recently, loaders have been essentially manually Controlled devices, which is to say that the positioning of the bucket through its various positions depended entirely upon the control of the operator. Thus, the operator was depended upon to move and maintain the bucket level during movement thereof between the loaded and dumping positions and to see to it that the bucket has been returned to the digging position before the tractor moves in to receive another load. The placing of this burden on the operator substantially reduced the speed at which he could operate and thus the amount of material that he could move in any given period. Furthermore, this also required a great deal of skill on the part of the operator in order to prevent spilling of material from the 'bucket during the lifting operation. The tendency to spill was due to the characteristic arcuate movement of the lift arms and bucket, during the raising movement in which the bucket is tilted more and more backwardly toward the tractor wherein the material is spilled over the rear edge, causing damage to the tractor and danger to the operator. Attempts have been made to correct this diculty by introducing the principle of the well known parallel motion linkage, or variations thereof, in combination with the lift arms so that the bucket is held substantially in fixed ang'ular relation to the ground throughout the raising movement. This, while it effectively avoided spilling over the back edge of the bucket, induced spilling of the load over the front edge or lip of the bucket, particularly at the beginning of the lifting movement which, although not particularly dangerous, was inefiicient and undesira'ble.

Another factor limiting the speed at which the loader can be operated is the one which requires that the opera- ICC tor take the time to accurately reposition the bucket to take on a subsequent load after the preceding one has been dumped. This has usually been accomplished by the operator lining up a ,bucket position indicator located within full view of the operator. Thus, it can be appreciated that if an apparatus was found which Would automatically level the bucket during the lifting operation and then return the 'bucket to the digging position after the bucket has 'been dumped, then the operator would be almost completely free to concentrate on Operating the tractor at its maximum speed and obtain capacity leading.

In accordance with the present invention, there is provided a loader mechanism which incorporates a novel yet highly efficient hydraulically operated self-leveling mechanism that will hold the bucket in substantially fixed relation to the lift arms during the initial lifting movement; but which will change this relation and maintain the bucket approximately level, or at least in approxirnately fixed angular relation to the ground during the remaining part of the upward movement, in spite of the swinging or arcuate upward movement of the lift arm. In this way, spilling of the load over the lip of the 'bucket during the first foot or two of lifting movement is greatly reduced, while spilling over the back edge is virtually eliminated during the rest of the upward movement. The mechanism includes a 'simple "slave cylinder that is linked hydraulically to the cylinders used for adjusting the position of the bucket. The slave cylinder is connected to the lift arms and goes into action as the lift cylinder is actuated to level the bucket and prevent the spilling of material over the end walls of the bucket.

The novel loader assem'bly further includes a hydraulic control system that acts to automatically return the bucket to the digging position after the bucket has been dumped. This is accomplished by vautomatically supplying fluid under pressure to the bucket positioning cylinders to reposition the bucket to the digging position during the downward movement of the lift arms.

These and other advantages will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of a tractor with a loader mechanism mounted on the |front end thereof;

FIGURE 2 is a right side elevation of the loader mechanism with parts broken away and the bucket and associated control therefor illustrated in the digging and lifting positions and the hydraulic system shown in diagrammatic form;

FIGURE 3 is a left-side elevation of the loader mechanism similar to FIGURE 2;

FIGURE 4 is a view showing the positions taken by the bucket and bucket positioning mechanism when the lift arms have just been raised ofi the ground;

FIGURE 5 is a view similar to FIGURE 4 showing the lift arm, *bucket and associated bucket linkage in the partially raised position;

FIGURE 6 is a view similar to FIGURE 5 showing in solid lines the lift arms and bucket in the fully raised position and in dotted lines the positions of the various components after the 'bucket has been dumped; and

FIGURE 7 is a schematic diagram showing the hydraulic control system for the loader.

The same reference numbers have been given to the same or similar parts wherever they appear in the drawings and specification, and in the case of FIGURE 3, the components corresponding to those shown in FIG- URE 2 have been given the same number with a prime added thereto.

Referring first to FIGURE 1, there is shown a tractor 12 on which has been mounted at the front end thereof a loader mechanism indicated by the letter L. The loader mechanism includes a main frame structure 10 that is attached to the tractor 1-2- by suitable fastening means. The frame serves as the main support member and is generally U-shaped in the plan view in that it extends parallel to'the sides of the tractor forward of the operator and includes an inverted U-shaped section across the front thereof. The frame 10 includes uprights or stanchions 14, 16 spaced on opposite sides of the tractor 12, which stanchions are connected to the transversely extending inverted U-shaped support 17 by forwardly extending braces 15,

The various details of the loader construction can be best seen by referring to FIGURES 2 and 3. As shown in these figures, the loader structure consists of aV pair of lift arms or booms 18, 18' located on opposite sides of the tractor. The lift arms 18, 18' are pivotally connected to stanchions 14, 16, respectively, by pivot pins 22, 22'. Connected to the lower ends of the lift arms 18, 18' by means of pivot pins 24, 24', respectively, is the bucket 26. The lower` end of lift arm 18 is located between brackets 42, 44 secured to bucket 26 and the pin 24 extencls therethrough. The pin 24' extends through the lower end of lift arm 18' and bucket brackets 42', 44'.

The lift arms 18, 18' are pivoted about pins 22,` 22' by the operation of hydraulic cylinders 34, 34' through the extension or retraction of piston rods 32, 32' extendingl outwardly from cylinders 34, 34', respectively. The inner or lower ends of cylinders 34, 34' are connected to stanchions 14, 16, respectively, by pins 36, 36'. The outer ends of rods 32, 32' are disposed between and connected to pairs of downwardly extending re-enforcing plates 28', 28' that are secured to an intermediate portion of the lift arms 18, 18', respectively. Thus, it can be seen that when fiuid pressure is applied to the left-hand end of cylinders 34, 34' (FIGURE 2), the lift arms 18, 18' are moved in a counterclockwise direction about pivot pins 22, 22' to raise the bucket 26. Conversely, when fiuid is supplied to the opposite ends'of cylinders 34, 34', the lift arms 18, 18' are moved in a' clockwise direction to lower the bucket 26.

The positioning of the bucket relative to pivot pins 24, 24' to move the bucket' between the digging, loading, and unloading positions is accomplished by the hydraulically operated bucket poistioning mechanism shown in various positions in FIGURES 2 through 6. The hydraulically operated bucket positioning mechanisms connected to each of the lift arms and at their opposite end to the bucket 26 are identical and thus only the one disposed between lift arm 18 and brackets 42,` 44 will be described in detail. The bucket positioning mechanism connected between lift' arm 18' and oppositely disposed brackets 42', 44' is illustrated in FIGURE 3, and the corresponding parts are appropriately numbered.

The bucket positioning mechanism consists of a link 38 that is secured between the upper portion of the brackets 42,` 44 by a pin 40. The opposite end of the link 38 is connected by pin 46between a pair of levers 48.' The levers 48 are in turn connectedat their opposite ends. to an intermediate portion of the lift arm 18 by pin 50. It can thus be seen that pivotal movement of the lever 48' about pin 50 will pivot bucket 26 in the same direction'about the end of lift arm 18. To eifectuate movement of the linkage mechanism and through it bucket26, la fluid cylinder 54 is pinned to an intermediate portion of levers 48 by a pivotal connection 52' which comprises a trunnion type support for the cylinder 54. The cylinder 54 has a piston rod 56 that extends forwardly along lift arm 18 and is pivotally connected at its end thereof to a lug or stop 60 by means of pin 58. Thus, introduction of pressure fiuid into one end of the cylinder 54 and corresponding withdrawal of fiuid from the other end will result in axial movement of cylinder 54 which will cause pivotal movement of levers 48 and corresponding pivotal movement of bucket 26. It is, of course, understood that the two bucket positioning mechanisms operate simultaneously to bring about the desired result.

For effecting control of the lift cylinders 34, 34' and bucket cylinders 54, 54', a conventional or other suitable type of hydraulic system is employed, and is conventionally illustrated as follows. A reservoir 62 contains a supply of hydraulic fiuid which is pressurized and transmitted by means of a pump 64 to a valve 66. A control lever 68 when actuated in one direction admits fiuid to conduit 70 while allowing fiuid in conduit 72 to return through an exhaust conduit 74 to reservoir 62. The conduit '70 leads to conduit 76, which in turn leads to the upper end of cylinders 54, 54'. The conduit 72 communicates with conduit 78, which communicates with the lower end of cylinders 54, 54'. The above described manipulation of control 68 will therefore cause upward movement of cylinders 54, 54' and tilting of bucket 26, for example, for the full line position of FIGURE 2 to the dotted or rolled-back position thereof. This, of course, is the break-out action of the device, and it will be noted that the larger capacity ends of the cylinders 54, 54.-' -those not encumbered by their corresponding piston rods are used in the break-out operation. Since this operation is the one which requires the greatest development of force on the part of cylin-ders 54, 54', it is a decided advantage that the larger ends of these cylinders are utilized in this break-out operation.

The manipulation of handle 68 in the opposite direction directs pressure fiuid through

conduits

72 and 78 into the lower end of cylinders 54, 54', where it` works on the limited area of pistons 80, 88' to cause downward movement of cylinders 54, 54'. The downward movement of cylinders 54, 54' causes tilting of levers 48, 48', and bucket 26 in a clockwise direction and ultimately into the dotted position shown in FIGURE 6.

The valve 66 has another control lever 82 which when actuated in one direction will direct pressure fiuid into conduit 84 which leads to the lower end of abovementioned lift cylinders 34, 34'. Such action will also exhaust fiuid from a conduit 86 which leads from the right end of cylinders 34, 34'. The pressure fluid will cause outward movement of the piston rods 32, 32', and swinging of lift arms 18, 18' in a counterclockwise direcv tion about pivotal connections 22, 22', as hereinbefor'e suggested.

In the usual operation of a device of this kind, bucket 26 is placed approximately in the full line position indicated in FIGURE 2, and the tractor is maneuvered into a position to force the bucket into a pile of material to be handled. Next, lever 68. is actuated in the proper direction to cause bucket 26 to be tilted or rolled back to the dotted position in FIGURE 2. It, will be noted that, in this position, which represents the extreme rearward position of the bucket, the. upper rim 88 is tilted forwardly to some extent, which is undesirable since appreciable quantities of the load may spill if the tractor is driven any distance with the bucket in this position. Accordingly, control 82 is actuated to raise lift arms 18, 18' to some desired position for traveling to the point of discharge. Such a position is shown in FIGURE 4 in which the lift arms have been raised appreciably until rim 88 has become essentially level. It is to be noted that links 38, 38' are still in close proximity to stops 60, 60', if not actually in contact therewith. In other words, bucket 26 has changed its relation to lift arms 18, 18', if at all, only a very small amount in moving from the dotted position in FIGURE 2 to the full line position in FIGURE 4.

Turning now' to FIGURE 5, it will be noted that the lift arms have been raised substantially from the FIGURE 4 position. Rim 88, however, is still level and this has been brought about by changing the relation between bucket 26 and lift arms 18, 18' substantially from that shown in FIGURES 2 and 4. This is brought about by the manipulation of cylinders 54, 54' to the right to swing lever 48 in a clockwise direction. It is to be noted that links 38, 38' are now a substantial distance from stops 60, 60'.

In FIGURE 6, lift arms 18, 18' have been swung still further upwardly to approximately its maximum upward position. However, rim 88 is still level by virtue of further movement to the right of cylinders 54, 54', in the manner just described. FIGURE 6 also shows the dumping position of bucket 26, this being brought about by manipulation of control 68 and movement of cylinders 54, 54' to the right a maximum amount, as indicated in dotted lines in FIGURE 6.

As will be apparent, in order to maintain the described control of bucket 26, rather precise actuation of cylinders 54, 54' is required and, while this might be accomplished through control 68 by a highly skilled operator, in the present instance it is accomplished automatically Without any attention on the part of the operator.

As discussed above, suitable provision must be made to change the position of the bucket relative to the lift arms, when the lift arms are being rased, to prevent the material contained in the bucket from spilling back over the operator. After the bucket has been loaded and moved to an upright position by the operator, the normal tendency is for the bucket to dip toward the operator during the upward movement of the lift arms. This is due to the fact that the lift arms and the bucket move in an arcuate path due to their pivotal movement about pvot pins 22, 22'.

In order to prevent the bucket from tipping out of the level position, provision must be made to move the bucket forward about pivot pins 24, 24' an amount necessary to compensate for the backward tilting movement of the bucket during raising of the lift arms. To this end, the tilting and attendant spilling is prevented by providing a novel hydraulic self-leveling mechanism which directs fiuid under pressure to the hydraulic bucket positioning cylinders to move the bucket forward a predetermined incremental amount, relative to the end of the lift arms, to compensate for the rearward bucket movement brought about by the arcuate travel of the lift arms.

The novel system in question includes a hydraulic slave cylinder 96 that has one end thereof connected to the lower portion of stanchion 14 by a pin 1430. Extending outwardly of the cylinder 96 is a piston rod 94 and attached piston 98 that is connected between a pair of rearwardly extending brackets 90 secured to the lift arm 18 by a pin 92. The opposite ends of the cylinder 96 are connected through suitable

hydraulic lines

74, 76 to opposite ends of the cylinders 54, 54'. In particular, the head end of the cylinder 96 communicates with the head end of the cylinders 54, 54' through conduit 76 and the rod ends of the

cylinders

96, 54, 54' are interconnected through conduit 78.

Briefiy, it will be seen that when the lift arrn 18 is rased, it carries with it the rod 94, which displaces fiuid from the rod end of the cylinder 96 through conduit 78 to the rod end of cylinders 54, 54' to effectuate downward movement of the cylinders 54, 54' and clockwise movement of levers 48 (FIGURE 2). This clock- Wise movement of levers 48 will tend to tilt the bucket forwardly an amount calculated to compensate for the tendency of the arcuate action of the lift arms to move the bucket rearwardly and thus retain the bucket in the horizontal position.

Briefiy, swingng motion of lift arms 18, 18' will eventually cause movement of piston 98 and a pumping action in cylinder 96. However, in the position of the parts shown in FIGURE 2, such motion will be insignificant or very slight, whereas as the lift arms swing upwardly and piston rod 94 becomes more nearly tangent to the -arc described by the lever arm represented by the distance between

pivotal connections

22 and 92, the motion will become greater until in the position of the lift arm shown in FIGURE 5 it is quite substantial. Since all of the several cylinders and conduits are normally entirely full of fiuid, the motions of piston 98 will be reflected in similar motions of cylinders 54, 54' and, therefore, without any manipulation of control 68, the upward swinging of lift arm 18, through cylinder 96 will cause movement of cylinders 54, 54' and shifting of the relation of bucket 26 to the lift arms. As Will be apparent, upward swinging of lift arm 18 will cause development of pressure in the upper end of cylinder 96 which will be transmitted through conduit 78 to the lower end of cylinders 54, 54'. This will cause a certain amount of downward movement of cylinders 54, 54', and relative tilting of bucket 26 in a clockwise direction. However, owing to the fact that lift arm 18 under these conditions is swinging in a counterclockwise direction, the result will generally be to maintain bucket 26 in a level position, and the dimensions of cylinder 96 and cylinders 54, 54' are readily chosen so that these relations will be obtained. The dimensions of cylinder 96 are chosen to supply suflicient fiuid to actuate both cylinders 54, 54' the necessary amount to maintain the bucket in the required position. However, it is undesirable to maintain bucket 26 in the dotted position of FIGURE 2, relative to the lift arms throughout the lifting movement, and it is for this reason that cylinder 96 is so placed as to be in a substantially dead center relation to pvot 22 when lift arm 18 is lowered. The initial movement of lift arm 18 from the FIGURE 2 to the FIGURE 4 position, causes little, if any, pumping action in cylinder 96. Therefore, bucket 26 is not shifted in relation to lift arms 18, 18' to any appreciable extent, at least, in its movement from the FIGURE 2 to the FIGURE 4 position. However, after leaving the FIGURE 4 position, the pumping action of cylinder 96 will have increased to 'such an extent as to supply sufiicient fluid to cylinders 54, 54' to maintain bucket 26 substantially in a level position throughout the rest of the upward movement, even to the extreme position shown in FIGURE 6.

From this latter position, the bucket may be readily dumped by a simple manipulation of control 68, which will feed the necessary fluid into conduit 78 to cause movement of cylinders 54, 54' into the dotted position of FIGURE 6, which will cause dumping of the bucket.

It can 'be -appreciated that since this 'novel hydraulically operated self-leveling system operates independently of the operator, he is left free to perform his other duties, such as moving the tnactor to and from the pile being moved, and to perform any other functions that may be required during the lifting action of the bucket.

After the bucket has been raised to its uppermost position and dumped (FIGURE 6), it must be subsequently moved to the position shown in FIGURE 2 to handle the next load. Prior to the instant invention, it has been the oper'ator's job to take the time and effort to reposition the bucket, and even then it was necessary to provide him with some sort of indioating means due to the lack of clear visibility.

In accordance with the instant invention, there is provided a novel hydraulic system that functions to automatically return the bucket to the digging position from the dumped position as the lift anns are being lowered. The details of this arrangement can best be seen by referring to FIGURES 3 and 7 which show the appanatus and hydraulic circuitry provided for accornplishing this function.

Referng first to FIGURE 7, it is seen that there is illustrated in schematic form a conventional mech-anism for lifting and dumping the cylinders and the novel selfleveling mechanism referred to above. In addition, there is provided a return-to-dig slave cylinder 101 which is interrelated to the bucket positioning or dump cylinders 54, 54' in 'a manner to be hereinafter described, but which in essence functions to position the cylinders 54, 54' to return the bucket 26 to the digging position when the lift arms are lowered.

The cylinder 101 is positioned on the opposite side of the frame 10 from cylinder 96 and is interconnected between 'stanchon 16 and lift arm 18'. As illustrated, the cylinder 101 includes a piston rod 102 that is connected by pin 103 to a pair of brackets 105 secured to lift arm 18'. The cylinder housing is connected to stanchion 16 by pivot pin 107. When the lift arm 18' is raised, the piston rod 102 connected to piston 104 located in cylinder 101' is moved upward, 'as shown in FIGURE 3, and to the right in FIGURE 7. The piston end of cylinder 101 is connected through a first branch of conduit 106 and anti-cavitation check valve 108 to the reservoir 62 and through a second branch of conduit 106 and check valve 110 to conduit 76 leading to the piston end of bucket positionng cylinders 54, 54'. The rod end of cylinder 101 is directly connected to reservoir 62, which thus makes cylinder 101 a single acting cylinder. The anticavitation check valve 108 permits the flow of fiuid from reservoir 62 into the piston end of cylinder 101 during the outward or suckiing movement of piston 104 and prevents the backflow of fiuid in conduit 106 from returning to reservoir 62 during the pressure stroke of piston 104. Similarly, the check valve 110 permits fluid to fiow into conduit 76 during the pressure stroke of piston 104 and prevents the backflow of fiuid in conduit 106 from conduit 76 during the sucking stroke of piston 104.

The opposite or rod ends of bucket positioning cylinders 54, 54' are in communication with conduit 72 connected to which there is an inline relief valve 114. Other relief valves, not shown, are also provided wherever necessary to relieve Iany undesirable build-up of pressure occurring during the openation of the loader. The relief valve 114 provides for an escape of fiuid from the

conduits

72, 78 leading fromthe rod ends of bucket positioning cylinders 54, 54' to permit movement of cylinders 54, 54' to the left when they are subjected to fluid under pressure through conduit 106 and check valve 110. The cylinder 101 is designed to provide fiuid under pressure to cylinders 54, 54' which, when combined with the fiuid forced out of cylinder 96 by the inward movement of piston rod 94, will move cylinders 54, 54' the distance necessary to return the bucket to the digging position. The fiuid forced out of the rod ends of cylinders 54, 54' minus the fluid that flows into the rod end of cylinder 96 will force open relief valve 114 and return to reservoir 62.

The aforementioned hydraulic system functions to automatically return the bucket to the flat level position at the ground line when the lift arms are (lowered. Briefly stated, during the raising of lift arms 18, 18', the piston rod 102,:is moved outwardly of thecylinder 101, which results in oil being sucked through the anti-cavitation check valve 108. When the lift arms reach the full lift position, the piston side of piston 101 is full of oil. Also, at the same time, piston rod 94 moves outwardly and the piston side of cylinder 96 is filled with fiuid. The bucket is then dumped by iactuation of the dump control valve 'and the valve controlling the operation of lift cylinders 34, 34' is. positioned to return the lift arms to` their lowered position. As the lift arms lower, the piston rod 102 moves into cylinder 101 which forces the oil trapped in the'piston end of cylinder 101 out. through conduit 106, past check valve 110, into conduit 76 and the piston end of cylinders 54, 54', and inward moveme'nt of piston rod 94 forces fiuid out of cylinder 96 into conduit 76. The introduction of this fiuid into the cylinders 54, 54' builds up the pressure therein to move the cylinders 54, 54' to the left, as shown in FIGURE 7, an amount suficient to retum the bucket to the diggi'ng position when the lift arms have reached ground level. During this portion of the cycle, the oil in the rod end of the bucket positioning cylinders 54, 54' is pressurized to a point whereit reaches an inline relief pressure that opens reIiefvalVe 114 to return the excess oil in

conduits

72, 78 to the reservoir. After the lift arms reach the ground line, the bucket has been returned to the digging position since the total volume of oil that has been pumped out of the cylinders 101 and` 96' equals'the correct volume needed for thecylin'- ders 54, 54' to move them the correct amount of stroke required to reposition the bucket to a digging attitude.

While the return-to-dig hydraulic system has been disclosed in conjunction with a hydraulic self-leveling arrangement, it is, of course, obvious that if desired such arrangement` could be -used with loaders that have mechanical self-leveling, or no self-leveling system of any kind, since the return-to-dig arrangement can operate completely independent therefrom. In this situation, the cylinder 101 would 'be designed so that it pumped into conduit 76 that 'amount of fiuid necessary to move the bucket positioning cylinders the distance necessary to move the bucket to the digging position when the lift arms are lowered.

The method of operation of the entire system illustrated in the drawings can best be seen by referring to FIGURE 7 and is summan'zed as follows:

The Operating sequence will be set forth beginning with the bucket in the digging position and will be carried through the loading, lifting, self-leveling, dumping and return-to-dig stages.

After the bucket is loaded, the control valve 66 is operated to move the bucket positoni-ng cylinders 54, 54-' and bucket to the position shown in dotted lines in FIG- URE 2. Fluid is then directed 'through conduit 84 to the piston ends of lift cylinders 34, 34' to raise the lift arms 18, 18' to move the bucket -to the dumping position. During this upward movement of the lift arms, lthe piston rod 94 of cylinder 96 is moved outwardly to pump fiuid through conduit 74 to the rod end of cylinders 54, 54' to -move the bucket clockwise (IFIGURE 2) to compensate for the arcuate movement of the lift arms and thus maintain the bucket level and prevent spilling. The fiuid forced out of the piston ends of the cylinders 54, 54' is I simultaneously returned to the piston end of self-leveling cylinder end 96 through conduit 76. Also, during the raising of the lift arms, the piston rod '102 is moved out of cylinder 101, which draws fiuid from the reservoir 62 through conduit 106 past check valve 108 into the piston end of cylinder 101.

When the lift arms have reached their maximum raised positions and the tractor is properly positioned, the bucket is dumped by introducing fiuid to the rod end of cylinders '54, 54'. When the dumping has been completed, -the lift arms are again lowered by suitable operation of lift cylinders 34, 34'. When this occurs, the. piston rod 102 is moved 'to the left (or down by lift arm 18'), which forces fiuid from the piston end of cylinder 101 past check. valve 1'10 -into the piston ends of cylinders 54, 54'. At the same time, the piston rod 94 of self-levelng cylinder 96 is moved in the same direction as rod 1102 which forced fiuid. out of cylinder 96 into conduit 76. The amount of fiuid forced into the piston ends of cylinders 54, 54' is calculated to be sufiicient to move the cylinders and associated linkages the :distance necessary to move the bucket to the return-to-dig position when the lift arms reach ground level.

While a particular embodiment has been disclosed, many changes and substitutions of equivalents can be made without departing from the scope of the invention. It is, of course, intended to cover by the appended claims all such modifications that fall within the true spirit and scope of the invention.

I claim:

1. A' front end loader for a'tractor lincluding a frame adapted to be secured to said tractor, a pair of transversely spaced lift arms pivotally mounted at one end thereof to said frame, a bucket pivotally mounted to the opposite ends of said lift arms, hydraulic means disposed between the frame and one of said lift arms for raising and lowering said lift arms, a bucket positioning'means dis'- posed between at least one of said lift arms and said bucket and including la double acting hydraulic cylinder for moving 'the bucket between the digging and dumping positions, a first slave' cylinder assembly 'interconnected between said frame and one of said lift arms, means for supplying fluid to one side of said first slave cylinder during the raising of said lift arms, means for directing fluid 'from said one side of said first slave cylinder to one side 'of said bucket cylinder during the lowering movement of said lift arms, a second double acting slave cylinder assembly interconnected between said frame and the other of said lift arms, means for directing fluid from one side of said second slave cylinder to the other side of said bucket positioning cylinders to maintain the bucket level during raising of said lift arms and means for directing fluid from the other side of said second slave cylinder to sa-id one side of said bucket cylinder during lowering of said 'lift arms, 'the bucket cylinder and slave cylinders being so designed that the fluid 'supplied from said slave cylinders to said bucket cylinder during lowering movement of the lift arms will effect movement of 1the bucket positioning means to return the bucket to the digging position when the lift arms return to ground level.

2. A front end loader for a tractor including a main frame, a pair of transversely spaced klift arms pivotally mounted at one end thereof to said frame, a bucket pivotally mounted to the opposite ends of said lift ar'ms, hydraulic means disposed between the frame and each of said lift -arms for raising and lowering said lift arms, a bucket positioning means disposed between each of said lift -arms and said bucket including a double acting hydraulic cylinder for moving the bucket between the digging and dumping positions, a first slave cylinder assembly interconnected between said frame and one of said lift arms, a reservoir, means for directing fluid from said reservoir to one side of said first slave cylinder during the raising of said lift arms, a check valve in said last mentioned means for preventing the flow of fluid from said first slave cylinder to said reservoir during lowering of said lift arms, conduit means interconnecting said one side of said -first slave cylinder and one side of both of said bucket cylinders during the lower-ing of said lift arms, a check valve in said last conduit means for preventing fluid from fiowing to said one side of said first slave cylinder from said bucket cylinders during lifting of said lift arms, a second double acting slave cylinder assembly interconnected between said frame and the other of said lift arms, means for directing fluid from one side of 'said second slave cylinder to the other side of said bucket positioning cylinders to maintain the 'bucket level during raising of said lift arms and means for directing fluid from the other side of said second slave cylinder to said one side of said bucket cylinders during lowering of said lift arms, the bucket cylinders and slave cylinders being so designed that the fluid flow from said slave cylinders to said bucket cylinders during lowering movement of 'the 'lift arms will efiect movement of the bucket positioning means to return the bucket to the digging position when the lift arms return to ground level, and valve means for relieving the fluid from said one side of said bucket cylinders during said lowering movement.

3. A front end loader for a tractor including a frame adapted to be secured to the tractor, a pair of transversely spaced lift arms pivotally mounted at one end thereof to said frame, a bucket pivotally mounted to the opposite ends of said lift arms, lifting means disposed between the frame and each of said lift arms for raising and lowering said lift arms, a bucket positioning means disposed between each of said lift arms and said bucket including a lever linkage assembly and a double acting hydraulic cylinder including a piston end and a rod end for moving the bucket between the digging and dumping positions upon actuation of said cylinder, a first slave cylinder assembly including a cylinder element connected to said frame and a piston rod connected to one of said lift arms, a reservoir, means for directing fluid from said reservoir to the piston side of said first slave cylinder during the raising of said lift arms, a check valve in said last-mentioned means for preventing the return of fluid from the piston side of said first slave cylinder to said reservoir during lowering of said lift arms, conduit means interconnecting the piston side of said first slave cylinder and the piston end of each of said bucket cylinders during the lowering of said lift arms, a check valve in said conduit means for preventing fluid from fiowing to the piston side of said first slave cylinder from the piston end of said bucket cylinders during lifting of said lift arms, a second double acting slave cylinder assembly including a cylinder element connected to said frame and a piston rod secured to the other of said lift arms, means for directing fluid from the rod side of said second slave cylinder to the rod end of said bucket positioning cylinders to maintain the bucket level during raising of said lift arms and means for directing fluid from the piston side of said second slave cylinder to the piston end of said bucket cylinders during lowering of said lift arms, the bucket cylinders and slave cylinders being so designed that the fluid flow from said slave cylinders to said bucket cylinders during lowering movement of the lift arms and associated piston rods will effect movement of the bucket positioning means to return the bucket to the digging position when the lift arms return to ground level,, and relief valve means for venting the rod ends of the bucket positioning cylinders during the lowering movement of said lift arms.

4. A material handling device including a frame, a pair of lift arms pivotally mounted to the frame adjacent one end thereof, a transversely extending bucket pivotally mounted to the opposite ends of said lift arms, lifting means disposed between said frame and at least one of said lift arms to pivot same relative to said frame, bucket positioning means disposed between an intermediate portion of at least one of said lift arms and said bucket, said bucket positioning means comprising a hydraulically operated linkage mechanism including a lever assembly pivotally connected at one end thereof to an intermediate portion of said one lift arm, a link interconnecting the opposite end of said lever assembly to a portion of said bucket spaced from said one lift arm and a cylinder assembly secured to an intermediate section of said lever assembly, said cylinder assembly including a cylinder trunnion mounted to said lever assembly and a piston rod fixedly connected to said lift arm adjacent the bucket end thereof, whereby upon introduction of fluid to the large end of said cylinder the bucket will be moved into an upwardly extending position, a self-leveling slave cylinder assembly mounted between said frame and one of said lift arms adjacent the pivotal connection between said lselected lift arm and frame whereby said slave cylinder will be positioned in accordance with the movement of said aforementioned lift arm, and conduit means interconnecting said self-leveling cylinder and bucket positioning cylinder whereby fluid will be pumped to the rod end of the cylinder to maintain the bucket substantially level during upward movement of the lift arms.

5. A material handling device including a frame, a pair of lift arms pivotally mounted to the frame at one end of each of said arms, a transversely eXtending bucket pivotally mounted to the other end of each of said lift arms, lifting means disposed between said frame and at least one of said lift arms to pivot same relative to the frame, bucket positioning means disposed between an intermediate portion of at least one of said lift arms and said bucket and including a linkage mechanism controlled by a hydraulic cylinder, a bucket self-leveling cylinder assembly mounted between said frame and one of said lift arms adjacent the pivotal connection between said one lift arm and frame including a cylinder element and a rod element, means pivotally securing said cylinder and rod elements to the lift arm and frame, said last mentioned means being disposed in substantial alignment with the pivotal connection between said one lift arm and frame when the lift arms are in their lowermost position, and conduit means linterconnecting said self-leveling cylinder and bucket positioning cylinder whereby When the bucket is rolled back the lift arm may be raised sufficiently to level the bucket without appreciable effect on the bucket from the hydraulic self-leveling cylinder but upon further up- Ward movement of the lift arms the self-leveling cylinder will be .regulated to direct fluid to the hydraulic cylinder to maintain the bucket substantially level and thus prevent spilling thereof.

6. A material handling device including a frame, a pair of lift arms pivotally mounted to the frame adjacent one end thereof, a transversely extending bucket pivotally mounted to the opposite ends of said lift arms, a bucket stop member secured to said lift arms adjacent said op posite ends, hydraulically operated lifting means disposed between said frame and each of said lift arms to pivot them relative to said frame, bucket positioning means disposed between an intermediate portion of each of said lift arms and said bucket, said bucket positioning means including a hydraulically operated linkage mechanism including a lever assembly pivotally connected at one end thereof to an intermediate portion of its respective lift arms, a link interconnecting the opposite end of said lever assembly to a portion of said bucket spaced from said lift arm and a cylinder assembly secured to an intermediate section of said lever assembly, said cylinder assembly including a cylinder element trunnion mounted to said lever assembly' and a piston rod fixedly secured to said stop member, whereby upon introduction of fluid to the piston end of said cylinder the bucket will be moved upwardly relative to the ends of said lift arms and when fluid is directed to the rod end of the cylinder the bucket will be moved in the opposite direction, a self-leveling slave cylinder assembly pivotally mounted between said frame and one of said lift arms and including a piston rod secured to said one lift arm and a cylinder element secured to said frame, and conduit means interconnectinng said self-leveling cylinder and bucket positioning cylinders whereby when the lift arms are raised fluid will be supplied from the rod end of said slave cylinder to the rod end of said bucket positioning cylinders to automatically maintain the bucket level and prevent spilling therefrom 7. A front end loader for a tractor including a frame adapted to be secured to said tractor, a pair of transversely spaced lift arms pivotally mounted at one end thereof to said frame, a bucket pivotally mounted to the opposite ends of said lift arms, hydraulic means disposed between the frame and one of said lift arms for raising and lowering said lift arms, a bucket positioning means disposed between at least one of said lift arms and said bucket and including a hydraulic cylinder for moving the bucket between the digging and dumping positions, a slave cylinder assembly interconnected between said frame and one of said lift arms, means for supplying fluid to one side of said slave cylinder during the raising of the lift arms, means for directing fluid from said one side of said slave cylinder to saidl bucket positioning cylinder during the lowering movement of said lift arms, the bucket cylinder and slave cylinder being constructed and arranged so that the fluid supplied from said slave cylinder to said bucket cylinder during lowering movement of the lift arms will effect movement of the bucket positioning means to automatically return theV bucket to the digging position when the lift arms are returned to ground level.

8. A front end loader for a tractor including a frame adapted to be secured to said tractor, a pair of lift arms located on opposite sides of the tractor and pivotally mounted at one end thereof to said frame, a bucket pivotally mounted to the opposite ends of said lift arms, hydraulic means disposed between the frame and one of said lift arms for raising and lowering the lift arms, a bucket positioning means disposed between at least one of said lift arms and said bucket and adapted to position said bucket relative to said lift arms, said bucket positioning means including a hydraulic cylinder for moving the bucket between the digging and dumping positions, a slave cylinder assembly interconnected between said frame and one of said lift arms adjacent the pivotal connection of said one lift arm and frame, a fluid filled reservoir, conduit means interconnecting said reservoir and slave cylinder, a check valve in said conduit means permitting fluid to flow from said reservoir to said slave cylinder during upward movement of said lift arms, and conduit means leading from said slave cylinder to said bucket cylinder whereby fluid is directed from said slave cylinder to said bucket positioning cylinder during the lowering movement of said lift arrns to actuate the bucket positioning means to automatically return the bucket to the digging position when the lift arms are returned to ground level.

9. A front end loader for a tractor including a frame, a pair of lift arms pivotally secured at one of their ends to said frame, lifting means disposed between said frame and said lift arms to pivot same relative to said frame, a bucket pivotally mounted to the opposite ends of said lift arms, a bucket positioning means disposed between each of said lift arms and said bucket and adapted to position the bucket relative to said lift arms, said bucket positioning means including a double acting hydraulic cylinder for moving the bucket between the digging and dumping positions, a slave cylinder assembly including a piston rod secured to one of said lift arms adjacent the pivotal connection between said lift arm and said frame, and a cylinder element secured to said frame member, a fluid filled reservoir, conduit means interconnecting the reservoir and piston end of said cylinder element, a check valve in said conduit means permitting fluid to flow from said reservoir to the piston end of said slave cylinder during upward movement of said lift arms, conduit means leading from said slave cylinder to one side of said bucket cylinders whereby fluid is directed from said slave cylinder to said bucket cylinders during the lowering movement of said lift arms to position said cylinders to automatically return the bucket to the digging position when the lift arms are returned to ground level, relief valve means for venting the other side of said bucket positioning cylinders during downward movement of said lift arms, and check valve means in said last mentioned conduit means for preventing the backflow of fluid into the piston end of said slave cylinder during upward movement of said lift arms.

References Cited by the Examiner UNITED STATES PATENTS 2,731,162 1/1956 Walstrom 214fl- 2,782,946 2/1957 Hough 214- 140 2,860,793 11/1958 Lapsley 214-140 2,881,931 4/1959 Mackie 214-140 2,990,072 6/ 1961 Mindrum 214--140 3, 140,001 7/ 1964 Stroder 214-140 HUGO O. SCHULZ, Primary Examiner.

Claims

1. A FRONT END LOADER FOR A TRACTOR INCLUDING A FRAME ADAPTED TO BE SECURED TO SAID TRACTOR, A PAIR OF TRANSVERSELY SPACED LIFT ARMS PIVOTALLY MOUNTED AT ONE END THEREOF TO SAID FRAME, A BUCKET PIVOTALLY MOUNTED TO THE OPPOSITE ENDS OF SAID LIFT ARMS, HYRAULIC MEANS DISPOSED BETEWEEN THE FRAME AND ONE OF SAID LIFT ARMS FOR RAISING AND LOWERING SAID LIFT ARMS, A BUCKET POSITIONINE MEANS DISPOSED BETWEEN AT LEAST ONE OF SAID LIFT ARMS AND SAID BUCKET AND INCLUDING A DOUBLE ACTING HYDRAULIC CYLINER FOR MOVING THE BUCKET BETWEEN THE DIGGING AND DUMPING POSITIONS, A FIRST SLAVE CYLINDER ASSEMBLY INTERCONNECTED POSITIONS, A FIRST SLAVE CYLINDER ASSEMBLY INTERCONNECTED SUPPLY FLUID TO ONE SIDE OF SAID FIRST SLAVE CYLINDER DURING THE RAISING OF SAID LIFT ARMS, MEANS FO DIRECTING FLUID FROM SAID ONE SIDE OF SAID FIRST SLAVE CYLINDER TO ONE SIDE OF SAID BUCKET CYLINDER DURING THE LOWERING MOVEMENT OF SAID LIFT ARMS, A SECOND DOUBLE ACTING SLAVE CYLINDER ASSEMBLY INTERCONNECTED BETWEEN SAID FRAME AND THE OTHER OF AID LIFT ARMS, MEANS FOR DIRECTING FLUID FROM ONE SIDE OF SAID SECOND SLVE CYLINDER TO THE OTHER SIDE OF SAID BUCKET POSITIONING CYLINDERS TO MAINTAIN THE BUCKET LEVEL DURING RAISING OF SAID LIFT ARMS AND MEANS FOR DIRECTING FLUID FROM THE OTHER SIDE OF SAID SECOND SLAVE CYLINDER TO SAID ONE SIDE OF SAID BUCKET CYLINDER DURING LOWERING OF SAID LIFT ARMS, THE BUCKET CYLINDER AND SLAVE CYLINDERS BEING SO DESIGNED THAT THE FLUID SUPPLIED FROM SAID SLAVE CYLINDERS TO SAID BUCKET CYLINDER DURING LOWERING MOVEMENT OF THE LIFT ARMS WILL EFFECT MOVEMENT OF THE BUCKET POSITIONING MEANS TO RETURN THE BUCKET TO THE DIGGING POSITION WHEN THE LIFT ARMS RETURN TO GROUND LEVEL.