US3192717A - Hydraulically operated reciprocating apparatus - Google Patents

Description

N. LEE 3,192,717

HYDRAULICALLY OPERATED RECIPROCATING APPARATUS July 6, 1965 2 Sheets-Sheet 1 Filed June 18, 1963 fivmewroe flormal: lee $4, 42 Arm/ens);

July 6, 1965 N. LEE. 3,192,717

HYDRAULICALLY OPERATED RECIPROCATING APPARATUS Filed June 18, 1963 2 Sheets-Sheet -2 United States Patent HYDRAULICALLY OPERATED RECIPROCA'HNG APPARATUS Norman Lee, Coventry, England, assignor to Keelavite Hydraulics Limited, Coventry, England, a company of Great Britain Filed June 18, 1963, Ser. No. 283,776 Claims priority, application Great Britain, June 19, 1962, 23,584/ 62 5 Claims. (Cl. 60-51) This invention relates to hydraulically-operated reciprocating apparatus of the kind comprising a double-acting working piston disposed within a working cylinder between which and the working piston relative reciprocation is caused by variations, produced by control valve apparatus, in the relationship between the working liquid pressures in two chambers, the liquid pressures in which act respectively on the two oppositely directed faces of the working piston.

The two chambers, to the pressures in which the opposed faces of the double-acting working piston are exposed, will herein for convenience be referred to as the working chambers while it will be assumed for convenience that the working piston reciprocates within the working. cylinder although it will be understood that the working piston may be stationary and the working cylinder be arranged to reciprocate, or in some cases both the working piston and the working cylinder might reciprocate.

In one form of hydraulically operated reciprocating apparatus of the kind referred to as previously proposed, the control valve apparatus comprises a hydraulicallyoperated piston valve of the shuttle type arranged to connect the two working chambers alternately to the delivery passage of a pump constituting the source of working liquid pressure and to connect that one of the two working chambers which at any moment is not connected to .the pump delivery, to a relief passage, the movement of the valve at the end of each stroke of the Working piston being effected by liquid under pressure delivered through a port which is opened by the working piston towards the end of its stroke so as to come into communication with that working chamber which is at the moment under working liquid pressure.

It is an object of the present invention to provide a form of hydraulically operated reciprocating apparatus of the general kind referred to having certain advantages over the previously proposed apparatus mentioned above, particularly when applied to percussive tools such as rock drills and the like.

Hydraulically-operated reciprocating apparatus according to the present invention comprises a double-acting working piston disposed within a working cylinder with which it forms working chambers of different effective cross-sectional area, to the liquid pressures in which work- 'to connect the working chamber of larger cross-sectional area alternately to the source of working liquid pressure and to a relief passage.

Thus, charging and discharging of the accumulator will take place with movement of the working piston respectively against the fluid pressure in the working chamber of smaller cross-sectional area and under the influence of that pressure.

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Usually the source of working liquid pressure will be a pump arranged to be constantly driven and, accord ng to a further feature of the invention, a further hydraulic accumulator (preferably also of the gas-loaded type) is provided in direct communication with the pump delivery passage at a point between the pump and the control valve apparatus adjacent to the apparatus. This further accumulator thus enables the rate of pump delivery to be maintained approximately constant at the mean rate of delivery required to operate the working piston. Alternatively a pressure relief valve may be provided between the pump delivery passage and the control valve apparatus at a point adjacent to the control valve apparatus to enable fluid delivered by the pump is excess of consumption of working fluid by the working piston and cylinder assembly to be returned to the reservoir via the relief passage.

In one preferred arrangement according to the invention applicable to reciprocating apparatus for operation of or as a percussive tool, both working chambers are of annular form, the inner circumferential wall of the annular working chamber of larger effective cross-sectional area being constituted by a piston rod, which can thus act on a percussive tool, and which is of smaller diameter than the piston rod or the equivalent forming the inner circumferential wall of the annular working chamber of smaller cross-sectional area.

In any case, according to a further feature of the invention, means may be provided by which when the reciprocating apparatus is not in operation, escape of working liquid at a low volumetric rate flow can take place from the accumlator which communicates with the working chamber of smaller cross-sectional area, as by forming the associated non-return valve so as to permit leakage past or through it at a low volumetric rate. Thus, this accumulator can discharge or substantially discharge itself automatically when the apparatus is out of operation for any substantial period, thus avoiding risk of danger should some part of the apparatus be dismantled, for example while substantial quantities of working liquid under pressure are stored within the accumulator.

Conveniently the control valve apparatus is in the form of a hydraulically-operated shuttle type control valve, and one form of apparatus according to the invention embodying such a valve is illustrated diagrammatically by way of example in the accompanyig drawings, in which FIGURE 1 is a diagrammatic drawing, mainly in crosssection of the complete apparatus with the control valve in one of its limiting positions,

FIGURE 2 is a cross-sectional view showing the control valve in its other limiting position,

FIGURE 3 is a fragmentary view of an alternative arrangement of the fluid delivery and relief passages, and

FIGURE 4 is an enlarged cross-sectional view of valve means incorporated in the apparatus.

In the construction shown in FIGURES 1 and 2 the apparatus comprises a Working cylinder 1 in which is arranged to reciprocate a working piston comprising two lands 2 separated by an annular recess 3, a cylindrical projection 4 extending from one face of the working piston and through a gland 5 in the adjacent end of the cylinder 1, and a second projection 6 in the form of a piston rod projecting from the other face of the working piston through a gland 7 in the other end of the cylinder 1 so that a working chamber 8 of smaller cross-sectional area is formed at one end of the working cylinder 1 and a working chamber 9 of larger cross-sectional area is formed at the other end of the working cylinder 1.

Communicating freely through a passage 19 with the working chamber 3 is the liquid chamber 11 of a hydraulic accumulator 11a of the gas loaded type, the piston of which is indicated at 12. The working chamber 9 communicates through a combined inlet and outlet passage 13 with a port 14 in a control valve cylinder 15 containing a shuttle type hydraulically-operated control valve comprising two lands 16 and 17 separated by an annular recess 18. Also formed in the control valve cylinder 15 is an inlet port 19 and two relief ports 20, 20a.

A continuously driven pump 21 is provided for the delivery of working liquid to the apparatus, this pump being arranged to draw Working liquid from a reservoir 22 and deliver it to a delivery passage 23. The delivery passage 23 is connected through a non-return valve/24 to the liquid chamber 11 of the accumulator 11a and is directly connected to the inlet port 19 while the relief ports 29, 23a are connected to the reservoir 22 by a relief passage 25. A pressure relief valve 21a is provided adjacent the pump to prevent damage in the event of a blockage occurring. The lengths of the passages 23 and 25 are long compared to the other passages and accordingly are indicated by broken lines.

Also communicating with the delivery passage 23 is the liquid chamber 26 of an accumulator 26a, also of the gas-loaded type situated between the pump 21, and the inlet port 19.

It will be seen that actuating liquid chambers 27, 28 a are formed respectively at the ends of the control valve cylinder 15, and these chambers communicate respectively with ports 29 and 36 formed in the working cylinder 1, which is also provided with a port 31 communicating,

through a relief passage 32, and the passage 25 with the reservoir 22.

Formed respectively in the ends of the control valve are cylindrical bores 33, 34 into which extend pistons 35, 36 secured to the ends of the control valve cylinder, these pistons and cylinders constituting holding piston and cylini cler assemblies. The cylinder 34 communicates through a passage 37 with the recess 18 while the cylinder 33 communicates with a port 38 in the circumference of the control valve.

The valve -means 24 as shown in detail in FIGURE 4 is formed so as to act during normal operation virtually as a non-return valve but to allow for a small rate of leakage past the valve from the accumulator 110 such that while during operation the valve means act effectively as a non-return valve, during periods when'the apparatus is out of operation the accumulator 11a can unload itself. Thus the valve means 24 comprises a casing 39 the opposite ends of which are connected respectively to the accumulator 11 and to the passage 23, the end of this casing which is connected to the passage 23 being formed to provide a conical seating for a ball valve 41 acted ,upon by a light spring 42, the seating having formed in it a narrow and shallow groove as indicated at 43.

Thus, while the valve means 24 permits relatively unrestricted fiow from the passage 23 into the accumulator 11 and acts efiectively as a non-return valve during operation of the apparatus when, it will be understood, the piston 2 is moving back and forth in the cylinder 1, it will, during long periods of idleness of the apparatus, permit a slow rate of leakage from the accumulator 11 into the passage 23 so that the accumulator 11 can unload itself.

The operation of the apparatus is as follows.

Assuming the parts to occupy the position shown in FIGURE 1, namely that which they occupy at the extreme end of the movement of the working piston to the left, it will be seen that the delivery passage 23 of the pump 21 is connected through the port 19, the recess 18, the port 14- and the passage 13 to the working chamber 9 of larger cross-sectional area, while the working chamber 8 will be at its maximum volume and the pressure in the liquid chamber 11 of the accumulator 11a will be approximately that in the delivery passage 23 of the pump 21 so that the accumulator piston 12 will occupy the position appropriate to that pressure.

Since the working chamber 9 is of larger cross-sectional area than the working chamber 8, the working piston will now be moved by working liquid pressure to the right and, since the non-return valve 24 prevents flow of more than a very small quantity of liquid from the chamber 11 into .the passage 23, this movement will compress liquid into the liquid chamber 11 of the accumulator 11a so that, when the working piston reaches the end of its stroke to the right, the accumulator 11a will be charged at a pressure substantially above that in the delivery passage 23 of the pump 21. The pressure to which the accumulator 11a is thus charged can be varied and determined by varying the mass of gas in the gas chamber of the accumulator 11a, and it will be understood that the capacity and characteristics of the accumulator 11a, the dimensions and relationship between the cross-sectional areas of the chambers 8 and 9, the designed stroke of the working piston, and the pressure at which the pump 21 delivers liquid, will be determined appropriately according to requirements. The arrangement in any case is such vthat with the control valve in the position shown in the working chamber 9, the actuating liquid chamber 27 becomes subject to working liquid pressure and the actuating liquid chamber 28 is opened to relief. The control valve is thus moved into its righthand position as shown in FIGURE 2 in which it will be seen that the recess 18 communicates with the relief port 20a so that the 'working chamber 9 is brought into communication with this port. The working piston is therefore free to move to the left under the action of the pressure in the working chamber 8, this pressure being derived from the accumulator 11a. The working piston therefore moves rapidly to the left until the righthand land 2 uncovers the port 30, at which time the ports 29 and 31 are in communication, so that the control valve is moved again to the left into the position shown in FIGURE 1, by liquid pressure from the working chamber 8, and the cycle begins afresh.

It will be seen that when the control valve is in the lefthand position shown in FIGURE 1 the holding cylinder 34 is in communication through the recess 18 with the port 19 and is therefore under working liquid pressure which holds the control valve in this position until the actuating liquid chamber 27 is brought by movement of the working piston, into communication with the working chamber 9, whereupon, owing to the cross-sectional area of the end of the control valve being substantially greater than that of the holding cylinder 34, the control valve is moved to the right against the action of the pressure in the cylinder 34. Similarly when the control valve occupies its righthand position as shown in FIGURE 2, the port 38 is in communication with the port 19 and the holding cylinder 33 is thus under working liquid pressure. It will be seen that whichever of the two holding cylinders 33 or 34 is not at the moment in communication with the port 19 is in communication either with the relief port 20a or the relief port 20.

In an alternative arrangement shown in FIGURE 3 the hydraulic accumulator 26a and pressure relief valve 21a are replaced by a single pressure relief valve 26b between the delivery passage 23 and the relief passage 25, at the end of the delivery passage adjacent the control valve apparatus.

What I claim as my invention and desire to secure by Letters Patent is:

1. Hydraulically-operated reciprocating apparatus comprising a double-acting working piston disposed within a working cylinder with which it forms working chambers of different effective cross-sectional area to the liquid pressures in which working chambers the oppositely directed faces of the working piston are respectively subject a source of working liquid pressure, a hydraulic accumulator, preferably of the gas-loaded type, the liquid chamber of which is connected directly to the working chamber of smaller cross-sectional area and is connected to the source of working liquid pressure through valve means permitting relatively free flow from the source of liquid pressure into the accumulator while resisting to a substantial degree flow in the opposite direction, and control valve apparatus arranged to connect the Working chamber of larger cross-sectional area alternately to the source of working liquid pressure and to a relief passage.

2. Hydraulically operated reciprocating apparatus as claimed in claim 1 wherein the source of working liquid pressure is a pump, and means for constantly driving the pump, a pump delivery passage for delivery of said working liquid and wherein the apparatus includes a pressure relief valve between said delivery passage and said relief passage at a point adjacent to the control valve apparatus.

3. Hydraulically operated reciprocating apparatus as claimed in claim 1, in which said valve means permit escape of working liquid at a low volumetric rate of flow such that said accumulator can unload itself when the apparatus is out of operation.

4. Hydraulically operated reciprocating apparatus as claimed in claim 3, wherein said valve means includes a valve member associated with a seating and arranged to lift from its seating for flow from the source of working liquid pressure into the accumulator and to rest on its seating when flow in the opposite direction tends to occur, while restricted passage means are provided through which flow can take place from the accumulator past said valve towards the source of working liquid pressure.

5. Hydraulically operated reciprocating apparatus as claimed in claim 1, wherein the source of working liquid pressure is a pump, and means for constantly driving the pump, and wherein the apparatus includes a second hydraulic accumulator in unrestricted communication with the pump delivery passage at a point between the pump and the control valve apparatus adjacent said control valve apparatus.

References Cited by the Examiner UNITED STATES PATENTS 734,282 7/03 Pengilly 9l320 1,460,586 7/23 Howse -52 2,151,057 3/39 Suth 60--52 2,802,336 8/57 Ball 6051 JULIUS E. WEST, Primary Examiner.

EDGAR W. GEOGHEGAN, Examiner.

Claims (1)

1. HYDRAULICALLY-OPERATED RECIPROCATING APPARATUS COMPRISING A DOUBLE-ACTING WORKING PISTON DISPOSED WITHIN A WORKING CYLINDER WITH WHICH IT FORMS WORKING CHAMBERS OF DIFFERENT EFFECTIVE CROSS-SECTIONAL AREA TO THE LIQUID PRESSURES IN WHICH WORKING CHAMBERS THE OPPOSITELY DIRECTED FACES OF THE WORKING PISTON ARE RESPECTIVELY SUBJECT A SOURCE OF WORKING LIQUID PRESSURE, A HYDRAULIC ACCUMULATOR, PREFERABLY OF THE GAS-LOADED TYPE, THE LIQUID CHAMBER OF WHICH IS CONNECTED DIRECTLY TO THE WORKING CHAMBER OF SMALLER CROSS-SECTIONAL AREA AND IS CONNECTED TO THE SOURCE OF WORKING LIQUID PRESSURE THROUGH VALVE MEANS PERMITTING RELATIVELY FREE FLOW FROM THE SOURCE OF LIQUID PRESSURE INTO THE ACCUMULATOR WHILE RESISTING TO A SUBSTANTIAL DEGREE FLOW IN THE OPPOSITE DIRECTION, AND CONTROL VALVE APPARATUS ARRANGED TO CONNECT THE WORKING CHAMBER OF LARGER CROSS-SECTIONAL AREA ALTERNATELY TO THE SOURCE OF WORKING LIQUID PRESSURE AND TO A RELIEF PASSAGE.

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