US2188672A - Grab bucket - Google Patents

Description

Jan. 30, 1940. H. s. ATKINSON GRAB BUCKET Filed June 6, 1938 5 Sheets-Sheet 1 w an Z m .7 Q J Q m H Q Q NM a; I [I INVENTOR BYE 2 ATTORNEYS 1940' H. s. ATKINSON 2,188,672

GRAB BUCKET Filed June 6, 1938 3 Sheets-Sheet 2 m m u N N 5 &

ml vIIIIIIIII/I/ /IyVENZOR I I ATTORNEA Jan. 30, 1940.

H. S. ATKINSON GRAB BUCKET Filed June 6, 1938 3 Sheets-Sheet 3 lNVEN OR ATTOR Jhiwl' Patented Jan. 30, 1940 GRAB BUCKET Herbert S. Atkinson, East Orange, N. J., assignor to The Hayward Company, New York, N. Y., a corporationof New York Application June 6, 1938, Serial No. 212,006

11 Claims.

This application is a continuation in part of my prior application filed May 15, 1936, Serial No. 79,945. The invention relates to excavating, lifting or conveying apparatus and will be herein referred to as grab bucket apparatus, as a comprehensive term. The object is the practical operation of such grab bucket mechanism by means of hydraulic pressure generated in a pump carried by the bucket itself under control from a remote operators station on a crane, or otherwise. Hydraulic grab buckets of such self-contained type offer many advantages in respect to capacity and power which have not heretofore been realized, because of the difliculties, among other things, in providing the proper reliable and continuous response to the remote control. By this invention the response is made as prompt and efiective as in any mechanically controlled bucket and the advantages of the hydraulic type are thereby extended to the various uses to which it is adapted. 1

The invention is illustrated in its form a present preferred and somewhat schematically in the accompanying drawings, wherein Fig. l is and elevation of the bucket with parts in sec tion;

Fig. 2 is a side elevation of Fig. 1, also with parts in section;

Fig. 3 is an enlarged longitudinal section of the automatic lock valve;

Fig. 4 is a section of Fig. 3;

Fig. 5 a section of the pressure reactor;

Fig. 6 a section of the pump;

Fig. 7 is an elevation partly in section of a modified form using a non-reversing motor, and

Fig.8 an elevation partly in section at right angles to Fig. 7.

Referring first to Figs. 1 and 2 the bucket comprises a hydraulic cylinder I secured to or forming part of the head frame 2 and provided with a suspension eye 3, or equivalent means of at tachment to a crane, boom, or other support, as will be understood. The bucket jaws 4, or equivalent grab members, are shown, in this'case, as link-connected to the head frame 2 in a usual way and operated by the piston rod 5 of the cyl inder. I: Raising the piston as by admission of pressure fluid to the low end of the power cylinder closes the jaw members together, or upon an object, and they remain closed so long as the pressure-is maintained. On release of the pressure, or withdrawal from the cylinder of the pressure fluid, the'jaws are opened and they may open .by their own gravity, forcing the pressure fluid out of the cylinder.

The pressure fluid is desirably oil. A sufiicient supply of it is contained in a reservoir 6 mounted on the head frame at one side of the upper part of the hydraulic cylinder, where it projects'above the head frame. Oil from the lower part of the reservoir is pumped to the lower end of the cylinder by a pump I driven by an electric pump motor 3, both of which are secured to the under side of the head frame at one side of the lower partof the hydraulic cylinder. A gear-type pump is preferred because of its lower cost but other types would be suitable.

In the actual bucketthe pipe connections of the hydraulic system, between the reservoir, power cylinder and pump are compactly housed in the head frame so as to be least liable to injury, but in the drawings, for purpose of description, they are shown spaced apart. When the jaw-mechanism is to be closed, the course of the oil is as follows: From the bottom of the reservoir 6 by pipe 9 and check valve Hi to the pump I. The pump forces the oil by pipe I! to the lock valve l2 and through the latter by line l3 to the lower end of the hydraulic cylinder and at the same time by line H to the pressure reactor l5. I

This'device, sho'wn'in larger scale in Fig. 5, is a cylinder secured to the underside of the head frame and containing a free piston I 6 heavily loaded by a coil spring H and provided with a blow-ofl and pet cock l8 connected at a point above'the piston stroke.

iii

The lock valve l2, separately shown in Figs. 3

and 4 is mounted inan aperture in the head frame'on the opposite side of the hydraulic cylinder from the oil reservoir 6, and comprises a piston-type slide valve l9 working in a valvecasing which is so ported that the pressure fluid has access to it on all sides, that is to say, the valve is balanced and" thus the heavy pressures which it handles exert no tendency to bind it against the wall of its casing or interfere with the free and quick movement required of it. This valve member must have a specially close fit in its casing to avoid leakage and on this. account, and notwithstanding its pressure balance, it requires-considerably more'power foritsoperation than can be practically obtained from solenoids or magnets as employed in usual forms ofelectro-magnetic valves. According to this invention it is operated by a rotary motor 26, througha winch-form chain connection 2.! with its armature shaft. This motor is specially wound to produce a high torque andto be capable of sustaining a stalling over-load indefinitely without injury, which capacity is herein referred to de-energized the spring 22 is strong enough to snap the valve instantly back to its closed position. Proper response action requires that this valve have a short stroke and liberal portway so as to be quick in its change from full open to full closed position. It is pointed out that due to the mounting of the power cylinder directly on the head frame the whole liquid part of the system is rigid and devoid of packing glands which, under the conditions of'use of this type of apparatus, are practically impossible to keep tight against leakage.

In the form of the invention shown by Figs. 1 and 2, the pump motor 8 is of the reversible type, and the bucket jaws are closed by driving the pump in one direction, to force fluid into the cylinder and opened by driving it in the opposite direction to withdraw the fluid. The circuit of the lock valve is connected with that of the pump motor so that it is open whenever the motor is driving the pump in either direction but closes instantly when it stops.

In the reversed drive, to open the jaws, the pump withdraws the pressure fluid from the power cylinder through the same pipe connections by which it entered, but by virtue of the check valve H! the fluid is returned to the reservoir by the check-valved by-pass 22, which opens into the top of the reservoir, or above the liquid level therein. This method of return is a factor of great importance in preserving a constant response relation between the hydraulic and electric sides of the system, because it afiords an opportunity for air to escape from the oil and avoids foaming under long-sustained bucket operation with its frequent flowreversals. By causing-the oil toflovv always in one direction through the reservoir and by the use of screening over the outlet, air entrainment is avoided.

'The reservoir is vented to atmosphere at its top by a vent 25.

The electrical connections 23 to the pump motor and electric lock valve extend in the form of a flexible cable to the controller 24 (Fig. 1), which will be understood to be located at the operators station on the crane or elsewhere, and connected to a source of current supply. It will be understood from Fig. 2 that-two of the four circuit wires 23 lead to the field coil and two to the armature of the pump motor and that the lock-valve motor is in parallel across the latter so that, in this form, the lock-valve opens instantly on the starting of the pump and closes instantly on its cessation.

In the hydraulic system used in Figs. '7 and 8, the pump motor, here marked 25 is uni-directional in operation and the pipe system and lockvalve are organized somewhat differently as followszThe pump 1 delivers pressure fluid through a check valve 2! to the pipe line It to the power cylinder. The balanced valve I 2, which is the same as above described, is connected in a separate return branch pipe line 28 leading from the power cylinder direct to the top of the reservoir, and is closed when the pump operates. When the bucket jaws are closed together or upon an object, the pressure fluid is thus positively confined as before in the cylinder, by the check valve 21 in the delivery line and by the Q '7 electro-magnetic valve i2 in the return line.

When the jaws are to be opened, the lock valve the reservoir being in one direction, as before For the control of this bucket, thelock valve motor 20 has its separate circuit, in'dependent of the pump motor circuit, direct to the controller 29 at the operators station. Though separately Y shown, both circuits may be included in a single cable as will be understood.

In the controller, the contacts will be underl stood to be so organized that when the handle,

is thrown in one direction it causes the pump tobe driven and the lock-valve to be closed thereby closing the jaws and, when moved a certain distance in the opposite direction, stops the curand then, when moved to a further stop, opens the lock-valve. This lets the jaws swingopen by their gravity. The detail of the controller contacts is not shown because such apparatus is well understood in the electrical art. In both of the illustrated forms of the inven tion, on each closing of the jaw mechanism, the pump delivers somewhat more oil than actually enters the power cylinder. The excess passes into or toward the reactor cylinder above described and more or less compresses the heavy spring therein. At some point in its compression the pressure in the oil may become increased r 3.

to such degree as to open a spring-loaded by-pass 30 (Fig. 6) built into the pump structure, and discharge any further delivery of oil through this by-pass back to the suction side of the pump.

The spring acting on the by-pass valve serves as a resilient means for limiting the pressure which the pump can develop in the powercylinder. It is set so that it yields only'after the piston of the pressure reactor l5 has been some what displaced against its spring and the latter, supplemented to some slight extent by the air confined in the cylinder above the piston, has

been put under compression. When the pressure fluid has been locked in the power cylinder, as above described, the reaction of this spring thereon continues and sustains the pressure and keeps the jaws closed when the pump has stopped. The function of the pressure reactor can be performed by other analogous mechanism but, as here shown, is made as a cylinder of such capacity as to provide a continuing pressure for an in-' definite time notwithstanding the possibility of leakage at the piston rod packing, which may develop with wear. At the same time the pres sure reactor serves as a cushion which levels off 1 the presure surges incident to the abrupt stoping and reversals of the oil flow, thus eleminating injurious vibration and reducing the wear as motely controlled through flexible leads, the im- 7 provement which comprises the combination withsuch system of a pressure reactor subject to the rent to the pump motor, to hold the jaws closed 20 pressure developed by the pump and reacting to close the bucket when the pump stops.

2. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cyiinder are all incorporated in the bucket structure and re- 1 all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which comprises the combination with such system of a spring-loaded by-pass forthe pumped fluid, a pressure reactor for keeping the bucket closed and locking means for maintaining the pressure on said reactor when the motor stops. Y

4. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which comprises in such system, a pressure reactor and an electro-magnetic lockvalve of the kind consisting of a piston-type, pressure-balanced valve member provided with a high-torque rotary motor energized coincidently with the pump motor to open said valve.

5. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which comprises the combination in such system of a pressure reactor subject to displacement by the pumped fluid and an electromagnetically controlled lock-valve for locking the pressure on said reactor.

6. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which comprises the combination in such system of a lock-valve to prevent return flow from the cylinder toward the reservoir and a pressure reactor comprising alcylinder containing a spring-pressed piston connected to the circuit between the cylinder and said Valve.

'7. In a hydraulically operated grab bucket of the kind in which the hydraulic. system including reservoir, electric pump and power cylinderare all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which consists in said reservoir having separate inlet and outlet pipes, the outlet pipe extending from the bottom and theinlet entering at" a point remote from the outlet and a lock-valve connected for preventing fluid flow from the cylinder to or through said inlet.

8. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which consists in said reservoir having separate inlet and outlet pipes, the outlet pipe extending from the bottom and the inlet entering from a point remote from the outlet, a

lock-valve connected to prevent fluid flow from the cylinder through said inlet and a pressure reactor cylinder connected to the system on the cylinder side of said lock-valve.

9. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which comprises the mounting of said power cylinder rigidly on the bucket head frame with its piston connected to the jaw mechanism, the pipe connections'between said cylinder and pump thus constituting a rigid system and including an electro-magnetic lock-valve to confine the cylinder pressure and a pressure reactor acting to close the bucket.

10. In a hydraulically operated grab bucket of the kind in which the hydraulic system including ,cally operated lock-valve between the cylinder and said inletpipe.

11. In a hydraulically operated grab bucket of the kind in which the hydraulic system including reservoir, electric pump and power cylinder are all incorporated in the bucket structure and remotely controlled through flexible leads, the improvement which consists in said pump being non-reversing and having a check-valved connection to the power cylinder and said reservoir having a return connection from the'cylinder HERBERT S. ATKINSON.

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