EP1211356A1

EP1211356A1 - Grab bucket

Info

Publication number: EP1211356A1
Application number: EP01309894A
Authority: EP
Inventors: Kiyoshi Nakajima
Original assignee: Tobu Jukogyo Co Ltd
Current assignee: Tobu Jukogyo Co Ltd
Priority date: 2000-11-24
Filing date: 2001-11-23
Publication date: 2002-06-05
Also published as: JP2002160890A; JP3385379B2

Abstract

A grab bucket having a grab (1) formed of shells (2) opposed to each other, a lower frame (3) for pivotably supporting the shells, an upper frame (5) placed above the lower frame and connected with the shells through the suspending arms (4), an intermediate movable frame (7) placed between the upper and lower frames and connected with the lower frame through a hydraulic cylinder (6) with a piston (6b), and a wire rope (8) for suspending and closing the grab is provided with a by-pass passage (25) for connecting the upper end portion of the hydraulic cylinder with the cylinder body of the hydraulic cylinder. Through the by-pass passage, an oil in an upper chamber defined above the piston (6b) flows into a lower chamber defined below the piston, thereby to accelerate the movement of the piston in the hydraulic cylinder. Thus, the scrap or other objective materials grabbed by the grab bucket of the invention can be efficiently thrown off by vibration and the action of inertia of the objective materials only by fully opening the grab.

Description

This invention relates to a grab bucket for use in cargo work for handling bulk cargo of various materials, which is suspended from a crane or the like.
In general, a single-rope grab bucket operated by a crane or the like has been conventionally used for hauling bulk cargo such as a pile of wood chips, crushed ore, earth, sand, wastes, scrap, rubbish and other fragmentary materials.
There has been known the conventional single-rope grab bucket of this type having the structure shown in FIG. 7 and FIG. 8 by way of example. The illustrated grab bucket comprising a grab 1 formed of a pair of shells 2 hinged facing each other, a lower frame 3 having axes 2a for rotatably supporting the shells 2, an upper frame 5 placed over the lower frame 3 and connected with the lower frame 3 through the rear walls of the shells 2 and suspension arms 4, an intermediate movable frame 7 placed between the upper frame 5 and lower frame 3 and connected with the lower frame 3 through a hydraulic cylinder 6, a wire rope 8 run around sheaves which are mounted respectively on the intermediate movable frame 7 and upper frame 5 and elongate upward to lift and close the grab, and a hydraulic cylinder control means for controlling the operation of the hydraulic cylinder 6 by opening or dosing an oil passage in the hydraulic cylinder 6.
When opening the grab 1, the hydraulic cylinder control means is operated to set the hydraulic cylinder 6 free, so that the lower frame 3 is separated from the intermediate movable frame 7 and lowered by the weight of the lower frame including the shells. Consequently, the rotating axes 2a are brought down while suspending the rear walls of the shells 2 by the suspension arms 4, thereby to open the grab.
The closing operation of the grab 1 in the open state is effected by letting out the wire rope 8 in the descending direction while keeping the hydraulic cylinder 6 in its free state, to lowering the intermediate movable frame 7 to be placed close to the lower frame 3, tugging the wire rope 8 while keeping the hydraulic cylinder 6 in its inextensible state to pull up the intermediate movable frame 7 toward the upper frame 5, thus to cause both the shells 2 to be mutually closed.
However, in a case where adhesional materials such as high viscous powdered ore and clay soil, which are easily adhesive to the inside of the grab, are handled by using the aforementioned conventional single-rope grab bucket, the adhesional materials adhered to the grab are not easily released even by opening the grab. Accordingly, the conventional grab bucket entailed a disadvantage such that the subsequent grabbing work cannot but seize hold of the adhesional materials while allowing the adhesional materials adhered to the grab, consequently to decreasing the working efficiency.
This invention is made to eliminate the drawbacks suffered by the conventional grab bucket as described above and seeks to provide a grab bucket capable of successfully releasing materials grabbed even if the materials held inside are easily adhesive to the inside of the grab bucket.
To attain the object described above according to the present invention, there is provided a grab bucket comprising a pair of shells opposed to each other in their openable state for constituting a grab, a lower frame for pivotably supporting the shells, an upper frame placed above the lower frame and connected with the backs of the shells through suspending arms, an intermediate movable frame placed between the upper and lower frames and connected with the lower frame through a hydraulic cylinder, a wire rope for suspending and dosing the grab, which wire pope has the lower end fixed onto the intermediate movable frame and runs through sheaves mounted on the intermediate movable frame and the upper frame, and a by-pass passage for connecting the upper end portion of the hydraulic cylinder with the cylinder body of the hydraulic cylinder to accelerate a piston movable between the upper end portion and the cylinder body of the hydraulic cylinder.
It is desirable to place a control valve for regulating the flow of oil in the by-pass passage. The shells may preferably be formed so that their inner bottoms are inclined up inwardly when opening the grab. The shells may preferably have the inside made of stainless steel.
Other and further objects of this invention will become obvious upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.
One way of carrying out the invention is described in detail below with reference to drawings, which illustrate only one specific embodiment, in which:-
FIG. 1 is a front view showing one embodiment of a grab bucket according to the present invention.
FIG. 2 is a side view of FIG. 1.
FIG. 3 is a front view showing the grab bucket of FIG. 1, in its opening state.
FIG. 4 is a perspective view showing the state in which a wire rope runs sheaves in the grab bucket of the invention.
FIG. 5 is a longitudinal cross-sectional view showing a hydraulic cylinder in the grab bucket of the invention.
FIG. 6 is a schematic view showing an oil hydraulic circuit in the grab bucket of the invention.
FIG. 7 is a front view showing a conventional grab bucket.
FIG. 8 is a side view showing the conventional grab bucket of FIG. 7.
One preferred embodiment of the grab bucket according to the present invention will be described hereinafter with reference to FIGS. 1 through 6 of the accompanying drawings. In describing the embodiment of the present invention, the same parts as in the conventional grab bucket described above are not described for the sake of simplicity in description.
In the drawings, reference numeral 1 denotes a grab, 3 a lower frame, 4 suspending arms, 5 an upper frame, 6 a hydraulic cylinder, 7 an intermediate movable frame, and 8 a wire rope.
That is, similarly to the prior art grab bucket as described above, the grab bucket of this invention comprises a pair of shells 2 opposed to each other in their openable state for constituting the grab 1, the lower frame 3 for pivotably supporting the shells 2, which is rotatable around axial shafts 3a, the upper frame 6 placed above the lower frame 3 and connected with the backs of the shells 2 through suspending arms 4, the intermediate movable frame 7 placed between the upper and lower frames and connected with the lower frame 3 through the hydraulic cylinder 6, the wire rope 8 for suspending and closing the grab, which has the lower end fixed onto the intermediate movable frame 7 and runs through sheaves mounted on the intermediate movable frame 7 and the upper frame 5, and a control means for controlling the hydraulic cylinder 6 by opening or closing an oil passage leading to the interior of the hydraulic cylinder 6.
The grab 1 is constituted by the shells 2 supported on the lower frame 3 rotatably around the axial shafts 3a. When the shells mesh together to assume their closed state, a grabbing space 9 for seizing hold of a pile of wood chips, crushed ore, earth, sand, wastes, scrap, rubbish and other fragmentary materials is formed therebetween.
Each shell 2 has an inner surface made of stainless steel and an inner bottom 10 which assumes its posture inclined slightly inward and perpendicularly to the surface of the earth when the grab is opened fully.
The lower end of the suspending arm 4 is rotatably joined to the back of each shell 2, and the upper end of the suspending arm 4 is rotatably joined to the upper frame 5, so that the shells 2 are suspended from the upper frame 5.
On the lower frame 3, there are mounted an oil tank 11 and a radio-signal receiver 12. In the accompanying drawings, reference numeral 13 denotes an oil port formed in the upper portion of the oil tank 11, and reference numeral 14 denotes a receiving antenna for the radio-signal receiver 12.
The radio-signal receiver 12 issues a command to open an oil hydraulic circuit for controlling the hydraulic cylinder 6 upon reception of a signal from the radio-signal receiver.
The intermediate movable frame 7 is formed so as to define a hollow space 15 thereinside. On its front lower right side and rear lower left side of the intermediate movable frame 7, there are fixed sheave cases 16 containing rotatable sheaves 17.
The hydraulic cylinder 6 is provided with a cylinder body 6a, a piston 6b reciprocatively contained within the cylinder body 6a, and a piston rod 6c connected with the piston 6b and retractably protruding upward from the cylinder body 6a.
The lower end of the cylinder body 6a is joined to the lower frame 3, and the leading end of the piston rod 6b is joined to the top portion of the intermediate movable frame 7 by using a bolt or other fixing means, so that the lower dame 3 is connected with the intermediate movable frame 7 through the hydraulic cylinder 6.
The piston 6b has passages 18 passing from the upper side through to the lower side thereof. Within each passage 18, a check valve 19 is disposed for regulating the flow of the oil passing from the upper side to the lower side of the piston 6b.
The piston rod 6c elongates upward from the piston 6b.
As shown in FIG. 6, the oil hydraulic circuit for controlling the operation of the hydraulic cylinder 6 includes a conduit pipe, which is connected at its one end with the upper part of the cylinder body 6a of the hydraulic cylinder 6 and at the other end thereof with the lower part of the cylinder body through a throttle valve 21 and a pilot check valve 22. With the lower part of the cylinder body 6a, there is connected a connecting pipe 23 leading to the oil tank 11.
The throttle valve 21 is interposed between the upper part of the cylinder body 6a and the pilot check valve 22, so as to regulate the flow of the oil flowing from the upper part to the lower part of the cylinder body 6a.
The pilot check valve 22 is opened and closed by means of an electromagnetic valve 24. When the pilot check valve 22 is dosed, the oil within the upper chamber defined above the piston 6b in the piston body 6a is prevented from flowing to restrain the hydraulic cylinder 6 from moving downward. When the pilot check valve 22 is open, the oil is allowed to flow into the lower chamber defined below the piston 6b in the hydraulic cylinder 6 through the conduit pipe 20, thus to bring the hydraulic cylinder 6 into its free state.
The hydraulic cylinder 6 is further provided with a by-pass passage 25 for accelerating the piston 6b. The by-pass passage 25 connects the upper portion of the cylinder body 6a with a portion apart from the upper portion at a prescribed distance through a by-pass conduit pipe 26.
The by-pass conduit pipe 26 includes a throttle valve 27 for regulating the flow of the oil passing therethrough.
The upper frame 5 is formed so as to allow the intermediate movable frame 7 to enter into the central portion thereof. The upper frame 5 is further provided on its front and rear sides with rotating sheaves 28.
The intermediate movable frame 7 is suspended from the upper frame 5 and vertically movable by operating the wire rope 8. That is, as shown in FIG. 4, the wire rope 8 has the lower ends connected with both sides of the intermediate movable frame 7 and run through the sheaves 28 on the upper frame 5 and the sheaves 17, and the upward elongated part of the wire rope is caught on a hook 29.
Next, the opening and closing operations of the grab 1 and the hydraulic cylinder 6 of the grab bucket of the invention will be described
Initially, the grab 1 assumes its closed state in which the upper and lower frames and intermediate movable frame are close to one another and is suspended from a crane or the like.
At this time, the pilot check valve 22 of the oil hydraulic circuit is closed to prevent the oil in the hydraulic cylinder 6 from flowing, thus to bring the hydraulic cylinder 6 to a deadlock.
To open the grab 1, a grab-opening command is first transmitted to the radio-signal receiver 12 to apply an operating current to an electromagnetic valve (solenoid valve) 24. Thereupon, the electromagnetic valve 24 is actuated to form a passage to the pilot check valve while the operating current flows.
As the result of actuating the electromagnetic valve 24, the pilot check valve 22 opens to allow the oil to flow the upper chamber to the lower chamber in the cylinder body 6a through the conduit pipe 20, thus to bring the hydraulic cylinder into its free state.
Consequently, the lower frame 3 is separated from the intermediate movable frame 7 and moves downward by its own weight, thus to lower the position of the axial shaft 3a while the rear of each shell 2 is suspended from the suspending arm 4, as the result of which the grab 1 is opened.
At this time, the hydraulic cylinder 6 is expanded to move the piston 6b upward in the cylinder body 6a. When the piston 6b reaches the point connected to the by-pass conduit pipe 26, i.e. the position depicted by the chain line in FIG. 5, the by-pass passage 25 is opened to permit the oil to flow from the upper chamber to the lower chamber in the cylinder body. Consequently, the amount of the oil flowing into the lower chamber of the cylinder body is increased to speed up the expansion of the hydraulic cylinder 6. Thus, the opening speed of the grab is accelerated from the open state indicated by the imaginary line (alternate long and short dash line) until the full-open state indicated by the solid line in FIG. 3.
As described above, since the expansion rate of the hydraulic cylinder 6 is increased to accelerate the opening speed of the grab, even the grabbed fragmentary materials sticking to the inner surfaces of the shells can be efficiently thrown off by the action of inertia. The acceleration of the opening speed can be controlled by regulating the throttle valve 27.
Then, the grab 1 is landed on an object to be grabbed as it is kept in its open state. Thereafter, the grab 1 in the open state is closed in such a manner that the wire rope 8 is let out downward while keeping the hydraulic cylinder 6 in the free state, thereby to lower the intermediate movable frame 7 toward the lower frame 3, and then, the wire rope 8 is pulled up to permit the lower frame 7 to approach the upper frame 5 while keeping the hydraulic cylinder 6 in its inextensible state. As a result, the axial shafts 3a are moved upward to close the shells 2.
At this time, the pilot check valve 22 is closed to prevent the oil in the upper chamber in the cylinder body 6a from flowing into the lower chamber, thus to restrain the hydraulic cylinder from expanding. On the other hand, the oil in the lower chamber in the cylinder body flows into the upper chamber of the cylinder body through the oil passage 18 formed in the piston 6b. Consequently, the hydraulic cylinder 6 is shortened, holding its cushion effect.
The throttle valve 27 in the by-pass passage 25 is controlled taking stickiness of the objective materials to be grabbed by the grab. Ordinarily, the hydraulic cylinder 6 may be used as usual in such a manner that the throttle valve 27 is closed to dose the by-pass passage 25.
In the embodiment described above, a wireless control system for controlling the electromagnetic valve is used, but a wired control system may be substituted in place of the wireless system.
As is apparent from the foregoing description, the grab bucket according to the present invention comprises the grab formed of the paired shells opposed to each other in their openable state, the lower frame for pivotably supporting the shells, the upper frame placed above the lower frame and connected with the shells through the suspending arms, the intermediate movable frame placed between the upper and lower frames and connected with the lower frame through the hydraulic cylinder, the wire rope for suspending and closing the grab, and the by-pass passage for connecting the upper end portion of the hydraulic cylinder with the cylinder body of the hydraulic cylinder to accelerate the piston movable between the upper end portion and the cylinder body of the hydraulic cylinder. The wire pope has the lower end fixed onto the intermediate movable frame and runs through sheaves mounted on the intermediate movable frame and the upper frame. According to the grab bucket of the present invention, the opening speed of the grab can be varied, so that the scrap or other objective materials grabbed by the grab bucket of the invention can be efficiently thrown off by vibration and the action of inertia of the objective materials only by fully opening the grab. Thus, according to the grab bucket of the invention, the work of grabbing a pile of wood chips, crushed ore, earth, sand, wastes, scrap, rubbish, and any other materials can effectively operated
Furthermore, since the grab bucket according to the invention is provided with the control valve for regulating the flow of oil in the by-pass passage, the opening speed of the grab can readily be controlled so as to throw off materials grabbed by the grab bucket, while controlling the impact caused when opening the grab with holding the cushion effect of the hydraulic cylinder. In a case of grabbing materials easy to release, the control valve may be dosed to restrain a shock from occurring when releasing the grabbed materials.
Besides, since the bottoms of the shells in the grab bucket according to the invention are inclined inward and upward, the materials grabbed by the grab of the invention can easily be thrown off when opening the grab. By providing the shells with the inner surfaces of stainless steel, the materials grabbed by the grab can more easily be thrown off

Claims

A grab bucket comprising a pair of shells (2) opposed to each other in their openable state for constituting a grab (1), a lower frame (3) for pivotably supporting said shells (2), an upper frame (5) placed above said lower frame (3) and connected with the backs of said shells (2) through suspending arms (4), an intermediate movable frame (7) placed between said upper and lower frames and connected with said lower frame through a hydraulic cylinder (6), and a wire rope (8) for suspending and closing said grab (1), said wire pope having a lower end fixed onto said intermediate movable frame (7) and running through sheaves mounted on said intermediate movable frame and said upper frame (5),
characterised by a by-pass passage (25) connecting an upper end portion of said hydraulic cylinder (6) with the cylinder body of said hydraulic cylinder operative to allow a piston (6b) movable between said upper end portion and said cylinder body of said hydraulic cylinder (6) to accelerate.
A grab bucket as claimed in claim 1, further comprising a throttle valve (27) disposed in said by-pass passage (25).
A grab bucket as claimed in claim 1 or claim 2, wherein each of said shells (2) has an inner bottom assuming its posture inclined slightly inward and upward.
A grab bucket as claimed in any of claims 1 to 3, wherein each of said shells (2) has an inner surface made of stainless steel.