US3927781A

US3927781A - Excavator

Info

Publication number: US3927781A
Application number: US384299A
Authority: US
Inventors: Nobuya Okabe
Original assignee: Hitachi Construction Machinery Co Ltd
Current assignee: Hitachi Construction Machinery Co Ltd
Priority date: 1972-08-28
Filing date: 1973-07-31
Publication date: 1975-12-23
Anticipated expiration: 1992-12-23
Also published as: DE2342399B2; JPS4939905A; JPS5233883B2; DE2342399C3; DE2342399A1

Abstract

A levelling hydraulic cylinder is connected between the underside of a boom and the intermediate portion of an arm in addition to a hydraulic cylinder for operating the arm. A fluid chamber on the piston rod push-out side of the levelling cylinder is maintained in communication through a tube with fluid chambers on the piston rod push-out side of a pair of hydraulic cylinders for operating the boom while a fluid chamber on the piston rod pull-in side of the levelling cylinder is maintained in communication through another tube with fluid chambers on the piston rod pull-in side of the pair of hydraulic cylinders for operating the boom. A bucket supported at the forward end of the arm can be thrust horizontally forwardly to dig out soil as the arm is oscillated when a piston rod sliding into and out of the hydraulic cylinder for operating the arm.

Description

[ Dec. 23, 1975 EXCAVATOR [75] Inventor: Nobuya Okabe, Ibaraki, Japan [73] Assignee: Hitachi Construction Machinery Co., Ltd., Japan [22] Filed: July 31, 1973 [2]] Appl. No.: 384,299

[30] Foreign Application Priority Data Aug. 28, 1972 Japan 47-85352 [52] US. Cl. 214/763; 214/771; 214/778 [51] Int. Cl. B66F 9/00 [58] Field of Search 214/138 R, 761, 762, 763, 214/764, 778, 771

[56] References Cited UNITED STATES PATENTS 3,220,581 1 1/1965 Pedersen et al. 214/764 3,230,717 l/1966 214/771 3,339,763 9/1967 214/762 3,465,903 9/1969 Wilson 214/138 R 3,586,182 6/1971 Schwing 214/138 R I- I 8c |||||||l I l 1 8b Primary Examiner-Robert J. Spar Assistant Examiner-Lawrence J. Oresky Attorney, Agent, or Firm-Craig & Antonelli [57] ABSTRACT A levelling hydraulic cylinder is connected between 1 the underside of a boom and the intermediate portion of an arm in addition to a hydraulic cylinder for operating the arm. A fluid chamber on the piston rod pushout side of the levelling cylinder is maintained in communication through a tube with fluid chambers on the piston rod push-out side of a pair of hydraulic cylinders for operating the boom while a fluid chamber on the piston rod pull-in side of the levelling cylinder is maintained in communication through another tube with fluid chambers on the piston rod pull-in side of the pair of hydraulic cylinders for operating the boom. A bucket supported at the forward end of the arm can be thrust horizontally forwardly to dig out soil as the arm is oscillated when a piston rod sliding into and out of the hydraulic cylinder for operating the arm.

13 Claims, Drawing Figures m" 3 "30 I7 '1 15 A 23 My. ---29 'JF- g l I 34 1 19 I61 26 111!- L 27 "1,, I V 28 11 I 2| U.S. Patient Dec.23, 1975 Sheet10f3 3,927,781

FIG. I

PRIOR ART US. Patent Dec. 23, 1975 FIG. 3

Sheet 2 of 3 US. Patent Dec. 23, 1975 Sheet 3 of3 3,927,781

FIG. 4

PRIOR ART FIG. 5

EXCAVATOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an excavator of the type which is provided with a bucket for digging out soil supported at one end of an arm in turn is supported by a boom connected to an excavator proper so that the bucket can be pushed out horizontally forwardly by means of the boom and the arm to dig out soil.

2. Description of the Prior Art In the excavator of the type described, it has hitherto been customary to mount an arm 1 at the foward end of a boom 2 for pivotal movement, and a bucket 3 is supported at the forward end of the arm 1 for pivotal movement as shown in FIG. 1. The operation of digging out soil and dumping the soil into a truck performed by a conventional excavator is such that the bucket 3 initially disposed near an excavator proper 4 in a position designated I is pushed out horizontally forwardly from position I to a position designated II. When the bucket 3 is in this position, the front end of the bucket 3 is moved upwardly and the rear end thereof is moved downwardly so that the bucket 3 moves to a position designated III to scoop up soil. When the bucket 3 is disposed in this position, the boom 2 is moved to an upright position so that the bucket 3 is moved to a position designated IV. When the bucket 3 is in this position, the rear end of the bucket 3 is moved upwardly and the front end thereof is moved downwardly so that the soil in the bucket is dumped into the truck for transportation. The movements of the bucket 3, arm 1 and boom 2 are controlled by hydraulic cylinders 5., 6 and 7 respectively connected to these parts as shown in FIG. 1.

Of all the movements of the parts described above, the horizontal forward movement of the bucket 3 for scooping up soil and dumping the soil in the bucket into the truck can be performed adequately only if the boom 2, arm 1 and bucket 3 are simultaneously operated so that each of them moves a proper distance in a proper direction. This makes it necessary for the operator to operate the plurality of hydraulic cylinders 5, 6 and 7 at a time when the bucket 3 is to be pushed out horizontally forwardly as aforementioned. Thus, conventional excavators have the disadvantage of their operators having to be highly skilled in the art of operating their machines. An added disadvantage is that even skilled operators get greatly tired when they operate their machines to push out the bucket 3 horizontally forwardly.

SUMMARY OF THE INVENTION This invention obviates the aforementioned disadvantages of conventional excavators of the bucket type in which the bucket is pushed out horizontally forwardly. Accordingly, the invention has as its object the provision of an excavator of the bucket type which can be operated with greater ease and which permits an excavating operation to be performed with a higher degree of efficiency.

According to the invention, there is provided an excavator of the bucket type comprising an excavator proper including a movable body, a rotary body and a swivel body, a boom pivotally supported at a forward end portion of the swivel body of the excavator proper for movement between a lying position and an upright position, a pair of hydraulic cylinders for moving the boom between the lying position and upright position, an arm pivotally supported through a pin at a forward end of the boom for oscillating motion, a hydraulic cylinder for operating the arm and causing the same to move in oscillating motion, a bucket pivotally supported at a forward end of the arm, a hydraulic cylinder for operating the bucket pivotally connected through a pair of rigid links to a forward end portion of the arm for moving the bucket horizontally forwardly away from the excavator proper in oscillating motion, and a levelling hydraulic cylinder connected at one end to the boom at its underside and at the other end to the arm at its substantially intermediate portion, said levelling hydraulic cylinder having a fluid chamber on its piston rod push-out side maintained in communication through a tube with a fluid chamber on the piston rod push-out side of each hydraulic cylinder for operating the boom and another fluid chamber on its piston rod pull-in side maintained in communication through another tube with a fluid chamber on the piston rod pullin side of each hydraulic cylinder for operating the boom whereby the bucket can be pushed out horizontally forwardly as the arm is moved in oscillating motion by the action of the hydraulic cylinder for operating the arm.

One of the features of the invention is that the bucket can be pushed out horizontally forwardly merely by manipulating the hydraulic cylinder for operating the arm.

Other and additional objects and features of the invention will become evident from the description set forth hereinafter when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a conventional excavator of the bucket type in which the bucket is pushed out horizontally forwardly;

FIG. 2 is a schematic view of the excavator of the bucket type comprising one embodiment of the invention;

FIG. 3 is a view in explanation of the operation of excavator according to the invention;

FIG. 4 shows the relation between the digging force and the reaction at work when soil digging is carried out by the conventional excavator shown in FIG. 1; and

FIG. 5 shows the relation between the digging force and the reaction at work when soil digging is carried out by the excavator according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT The excavator according to the invention will now be described with reference to the preferred embodiment shown in the drawings.

In FIG. 2, 8 generally designates an excavator proper according to the invention including a movable body 8a having a caterpillar, a rotary body 8b mounted on the movable body 8a, and a swivel body mounted on the rotary body 8b. The swivel body 8c is provided with an operators cab 8d.

A boom 9 is pivotally connected to the swivel body 8c for movement in one vertical plane between a lying position and an upright position by the action of a pair of hydraulic cylinders 10, 10 for operating the boom 9. The hydraulic cylinders 10, 10 are each disposed on one of opposite sides of the boom 9 and connected at its base to the swivel body 80 through a pin 11.

Piston rods

12, 12 each received in one of the pair of hydraulic cylinders 10, are connected to the boom 9 through a pin 13. 7

An arm 15 is pivotally connected through a pin 14 to a forward end of the boom 9 for movement in one vertical plane, like the boom 9, by the action of a hydraulic cylinder 16 for operating the arm 15. The hydraulic cylinder 16 is connected at its base through a pin 17 to a bracket 18 projecting downwardly from the underside of a forward end portion of the boom 9. The hydraulic cylinder 16 receives therein a piston rod 19 connected at its forward end to a forward end portion of the arm 15 through a pin 20.

A bucket 21 is connected through a pin 22 to the forward end of the arm 15 and moves in what is referred to as a wrist motion by the action of a hydraulic cylinder 23 for operating the bucket 21. The hydraulic cylinder 23, which is connected at its base through a pin 24 to the forward end portion of the boom 9, receives therein a piston rod 25 connected at its forward end through a pin 26 to one end of each of rigid links 27 28. The

rigid links

27, 28 are connected at the other end to the forward end of the piston rod 19 received the hydraulic cylinder 16 respectively.

A levelling hydraulic cylinder 29 operatively associated with the hydraulic cylinder 16 for operating the arm 15 is connected between the boom 9 and the arm 15 and disposed nearer to them than the hydraulic cylinder 16, so that the levelling hydraulic cylinder 29 can move into the arm 15. More specifically, the levelling hydraulic cylinder 29 is .connected at its base through a pin 30 to the bracket 18 projecting downwardly from the underside of the forward end portion of the boom 9 and receives therein a piston rod 31 connected through a pin 32 to the underside of the substantially intermediate portion of the arm 15.

The levelling hydraulic cylinder 29 has a fluid chamber on the piston rod push-out side thereof which is maintained through a tube 33 in communication with fluid chambers on the piston rod push-out side of the hydraulic cylinders 10, 10, and another fluid chamber on the piston rod pull-in side thereof which is maintained through another tube 34 in communication with fluid chambers on the piston rod pull-in side of the hydraulic cylinders'10, 10.

The connections between the levelling hydraulic cylinder 29 and the hydraulic cylinders 10, 10 perform an important function in pushing out the bucket 21 horizontally outwardly. More specifically, when the arm 15 is pivoted in the direction of an arrow A in FIG. 2 by the action of the hydraulic cylinder 16, the piston rod 31 is forced to slide out of the levelling hydraulic cylinder 29. This results in the fluid under pressure in the fluid chamber on the piston rod pull-in side of the levelling hydraulic cylinder 29 being forced to flow out of the fluid chamber and moving through tube 34 into the fluid chambers on the piston rod pull-in side of the hydraulic cylinders 10, 10. This in turn results in the fluid under pressure in the fluid chambers on the piston rod push-out side of the hydraulic cylinders 10, 10 returning through tube 33 to the fluid chamber on the piston rod push-out side of the levelling hydraulic cylinder 29. This causes the boom 9 to move to the lying position.

If the arm 15 is pivoted in a direction opposite to the direction of the arrow A, the boom 9 can be moved to the upright position. The hydraulic cylinders 10, 10 and 29 are constructed such that they are equal to each other in the diameter of their piston and piston rod or in the pressure receiving area ratio in order to prevent the occurrence of a vacuum due to the oversupply or the lack of fluid when the aforementioned operation is performed.

The position in which the base of the hydraulic cylinder 23 is connected to the boom 9 through pin 24 is selected such that a quadrilateral is formed by the

pins

14, 20, 26 and 24 in the plane of FIG. 2, so that a toothed portion 21a of the bucket 21 can be maintained at a predetermined angle with respect to the horizontal when the arm 15 is oscillated and the boom 9 is moved between the lying and upright positions. The hydraulic cylinders l0, l6 and 23 can be actuated independently of one another by manipulating control levers provided in the operators cab 8d.

In operation, fluid under pressure is supplied to a fluid chamber on the piston rod push-out side of the hydraulic cylinder 16 for operating the arm 15 when the bucket 21 is disposed in a position designated V in which it is near the excavator proper 8 as shown in FIG. 2. This results in the piston rod 19 sliding out of the cylinder 16 and causing the arm 15 to pivot in the direction of the arrow A about the pin 14 at the forward end of the boom 9. As a result, the piston rod 31 is forced to slide out of the levelling hydraulic cylinder 29, and the fluid under pressure in the fluid chamber on the piston rod pull-in side of the levelling hydraulic cylinder 29 flows into the fluid chamber on the piston rod pull-in side of each hydraulic cylinder 10 through tube 34 to operate the boom 9. This results in the piston rod 12 sliding into the respective hydraulic cylinder 10, so that the boom 9 moves into the lying position. Thus, the bucket 21 is pushed out horizontally forwardly away from the excavator proper 8 into a position designated VI in FIG. 3 while its toothed portion 21a is maintained in the horizontal position by the quadrilateral formed by the

pins

24, 20, 26 and 24. By moving the bucket 21 from this position into a position designated VII in which the front end of the bucket is disposed at a higher level than its rear end, soil can be dug out by the bucket 21 and held therein.

When it is desired to move the bucket 21 toward the excavator proper 8, the operator has only to cause the piston rod 19 to slide into the hydraulic cylinder 16 for operating the arm 15 by supplying fluid under pressure to a fluid chamber on the piston rod pull-in side of the hydraulic cylinder 16.

By merely manipulating the hydraulic cylinder 16 alone, it is possible to push out the bucket 21 horizontally forwardly away from the excavator proper 8 to dig out soil. Also, by moving horizontally forwardly the bucket 21 containing therein the scooped soil from a dash-and-dot line position designated VIII to a dashand-dot line position designated IX in FIG. 3, it is possible to move the bucket 21 to a position in which the contents of the bucket 21 can be dumped into a truck.

When it is desired to move the boom 9 to the upright position by causing the

piston rods

12, 12 to slide out of the hydraulic cylinders 10, 10 as the bucket 21 is pushed out horizontally outwardly away from the excavator proper 8 to a maximum as shown in FIG. 3, fluid under pressure is caused to act on the fluid chambers on the piston rod push-out side of the hydraulic cylinders l0, 10. The fluid under pressure caused to act on the fluid chambers on the piston rod push-out side of the hydraulic cylinders 10, 10 in this way may act on the fluid chamber on the piston rod push-out side of the hydraulic cylinder 29 through tube 33. This causes no trouble because the hydraulic cylinder 16 for operating the arm 15 is locked at this time.

The excavator according to the invention is constructed such that the force with which the bucket is 'rushed out horizontally forwardly away from the excavator proper in digging out soil is greater than the force with which the bucket of a conventional excavator is pushed out in the same direction, so that soil digging can be carried out with a higher degree of efficiency. Generally, a reaction to the force with which digging is carried out is produced at the toothed portion of the bucket when the bucket is pushed out horizontally forwardly and its front end is raised to a higher level than its rear end when an earth digging operation is performed. If a reaction F1 to the force with which earth digging is carried out is produced at the toothed portion of the bucket 3 of a conventional excavator as shown in FIG. 4, the reaction F1 and a force P produced by the hydraulic cylinder 6 for operating the arm will balance as follows.

P I= F1 m (1) where l is the distance between the point at the forward end of the boom 2 at which the arm 1 is pivotally supported at its base and the hydraulic cylinder 6 for operating the arm 1, and m is the distance between the point at the forward end portion of the boom 2 at which the arm 1 is pivotally supported at its base and the point at which the reaction F1 is produced. From formula (1), the reaction F1 can be rewritten as follows:

7 F1 l/m P (2) If a reaction F2 to the force with which earth digging is carried out is produced at the toothed portion 21a of the bucket 21 of the excavator according to the invention as shown in FIG. 5, the reaction F2 and a force Q exerted by thelevelling hydraulic cylinder 29 in operation will balance as follows:

Pl'+Q-n'-F2'm' (3) where l is the distance between the point 14 at the forward end portion of the boom 9 at which the arm 15 is pivotally supported at its base and the hydraulic cylinder. 16, n is the distance between the pivot 14 and the levelling hydraulic cylinder 29, and m is the distance between the pivot 14 and the point at which the reaction F2 is produced. From formula (3), the reaction F2 can be rewritten as follows:

Thus, the reaction F2 is greater than the reaction F1 in the prior art by (n'/m') Q.

The force exerted by the levelling hydraulic cylinder 29 may be either positive or negative. The force Q is positive when the working angle 0 of the reaction F2 produced at the toothed portion 21a of the bucket 21 is such that the reaction F2 acts from above on the surface of the toothed portion 21a; the force Q is negative when the working angle 0 of the reaction F2 produced at the toothed portion 210 of the bucket 21 is such that the reaction acts from below on the surface of the toothed portion 21a. If the working angle 0 of the reaction F2 is positive, the hydraulic cylinders 10, 10 for operating the boom 9 will be subjected to a force which will tend to cause the

piston rods

12, 12 to slide into the respective cylinders 10, 10. Thus, a pressure will be produced in the fluid chambers on the piston rod pushout side of the cylinders 10, 10 and transmitted through tube 33 to the levelling hydraulic cylinder 29 where a pressure will be produced in the fluid chamber on the piston rod push-out side thereof, thereby causing the piston rod 31 to slide out of the levelling hydraulic cylinder 29. When the working angle 0 of the reaction F2 is negative an operation reversed to the aforementioned operation will be performed.

When an earth digging operation is performed, the working angle 0 of the reaction F2 is positive in most cases and the excavator according to the invention exerts a greater digging force than a conventional excavator by (n'lm') Q. When the working angle 0 is negative, however, the digging force exerted by the excavator according to the invention is reduced as much. This offers an advantage in that the excavator proper is kept from slipping because at this time it is subjected to an upwardly oriented force and its ground gripping force is reduced in magnitude.

From the foregoing description, it will be appreciated that the invention is characterized by the provision, in addition to the hydraulic cylinder for operating the arm, of the levelling,hydraulic cylinder between the boom and the arm. Such levelling hydraulic cylinder being constructed such that its fluid chambers are maintained in communication with corresponding fluid chambers in the hydraulic cylinders for operating the boom, so that the bucket supported at the forward end of the arm can be pushed out horizontally outwardly away from the excavator proper merely by manipulating the hydraulic cylinder for operating the arm. By virtue of this feature, the invention offers many advantages. Operation of the excavator is facilitated, fatigue of the operator is greatly lessened and operation efficiency is greatly increased. The invention permits the bucket to be pushed out horizontally outwardly with a greater force in digging out soil, so that the ability of the excavator to dig out soil can be greatly enhanced. The embodiment shown and described herein has a link ratio such that the capacity of the excavator can be increased by 30 percent.

What I claim is:

1. An excavator of the bucket type comprising an excavator proper including movable body means, rotary body means and swivel body means, boom means pivotally supported at a forward end portion of said swivel body means of the excavator proper for movement between a lying position and an upright position, boom hydraulic cylinder means for moving the boom means, arm means pivotally supported at a forward end of said boom means for oscillating motion, arm hydraulic cylinder means for operating said arm means, bucket means pivotally supported at a forward end of said arm means, bucket hydraulic cylinder means for operating said bucket means pivotally connected through linking means to an end portion of said arm means for moving the bucket means horizontally forwardly away from the excavator proper in oscillating motion, and levelling hydraulic cylinder means connected at one end to the boom-means and at another end to the arm means, said levelling hydraulic cylinder means having a first fluid chamber on a piston rod push-out side thereof maintained in fluid communication with a fluid chamber on a piston rod push-out side of the boom hydraulic cylinder means for operating the boom means, said levelling hydraulic cylinder means also having a second fluid chamber on a piston rod pull-in side maintained in fluid communication with a 7 fluid chamber on a piston rod pull-in side of the boom hydraulic cylinder means for operating the boom means whereby the bucket means can be pushed out horizontally forwardly as the arm means is moved in oscillating motion by the action of the arm hydraulic cylinder means.

2. An excavator according to claim 1 wherein said levelling hydraulic cylinder means and said boom hydraulic cylinder means are constructed such that they are equal to each other in the diameter of their piston and piston rod or in the pressure receiving area ratio in order to prevent the occurrence of a vacuum due to the oversupply or the lack of fluid when the bucket means is pushed horizontally outwardly from the excavator proper.

3. An excavator according to claim 1 wherein said linking means includes a pair of rigid links, and wherein said pair of rigid links are pivotally connected at one end through a pin to a forward end of a piston rod received in said bucket hydraulic cylinder means and another end of one of said pair of rigid links is pivotally connected through another pin to a forward end portion of said arm means while the other end of the other rigid link is pivotally connected to the bucket means.

4. An excavator according to claim 3 wherein said bucket hydraulic cylinder means is pivotally connected at its base through a pin to said boom means, so that said pin for pivotally connecting the base of bucket hydraulic cylinder means to said boom means, a pin for pivotally supporting the arm means at the forward end of the boom means, said pin for pivotally connecting one end of one of said pair of rigid links to the forward end of the piston rod received in said bucket cylinder means, and said pin for pivotally connecting the other end of said one of said pair of rigid links to the front end portion of said arm means form a quadrilateral whereby a toothed portion of said bucket means can be maintained at a predetermined angle with respect to the horizontal when the boom means is moved between the lying and upright positions and the arm means is moved in oscillating motion.

5. An excavator according to claim 4 wherein said boom hydraulic cylinder means, said arm hydraulic cylinder means, and said bucket hydraulic cylinder means can be operated independently of one another by manipulating control levers provided in an operators cab in said swivel body of said excavator proper.

6. An excavator according to claim 1, wherein the boom means is movable between a lying position and an upright position, and wherein the arm means is movable in oscillating motion.

7. An excavator according to claim 6, wherein the boom hydraulic cylinder means comprises a pair of hydraulic cylinders, and wherein the arm means is pivotally supported to the boom means through a pin.

8. An excavator according to claim 7, wherein the linking means comprises a pair of rigid links.

9. An excavator according to claim 1, wherein the levelling hydraulic cylinder means is connected at the underside of the boom means and at an intermediate portion of the arm means.

10. An excavator according to claim 9, wherein said first and second fluid chambers are in fluid communication with corresponding fluid chambers of a common boom hydraulic cylinder means.

11. An excavator according to claim 1, wherein the boom hydraulic cylinder means and the arm hydraulic cylinder means are arranged such that the bucket means is forced outwardly from the body means with an increased force in response to increased resistance forces experienced by the bucket means which forces tend to move the boom means toward a lying position.

12. An excavator according to claim 10, wherein said first and second fluid chambers are in fluid communication with corresponding fluid chambers of each boom hydraulic cylinder means.

13. An excavator according to claim 1, wherein the boom hydraulic cylinder means and the arm hydraulic cylinder means are arranged such that the bucket means experiences a reduced outward movement force in response to increased resistance forces experienced by the bucket means which forces tend to move the boom means toward an upright position.

Claims

1. An excavator of the bucket type comprising an excavator proper including movable body means, rotary body means and swivel body means, boom means pivotally supported at a forward end portion of said swivel body means of the excavator proper for movement between a lying position and an upright position, boom hydraulic cylinder means for moving the boom means, arm means pivotally supported at a forward end of said boom means for oscillating motion, arm hydraulic cylinder means for operating said arm means, bucket means pivotally supported at a forward end of said arm means, bucket hydraulic cylinder means for operating said bucket means pivotally connected through linking means to an end portion of said arm means for moving the bucket means horizontally forwardly away from the excavator proper in oscillating motion, and levelling hydraulic cylinder means connected at one end to the boom means and at another end to the arm means, said levelling hydraulic cylinder means having a first fluid chamber on a piston rod push-out side thereof maintained in fluid communication with a fluid chamber on a piston rod push-out side of the boom hydraulic cylinder means for operating the boom means, said levelling hydraulic cylinder means also having a second fluid chamber on a piston rod pull-in side maintained in fluid communication with a fluid chamber on a piston rod pull-in side of the boom hydraulic cylinder means for operating the boom means whereby the bucket means can be pushed out horizontally forwardly as the arm means is moved in oscillating motion by the action of the arm hydraulic cylinder means.

5. An excavator according to claim 4 wherein said boom hydraulic cylinder means, said arm hydraulic cylinder means, and said bucket hydraulic cylinder means can be operated independently of one another by manipulating control levers provided in an operator''s cab in said swivel body of said excavator proper.