GB2289092A

GB2289092A - The starting and stopping of hydraulic reciprocating machines

Info

Publication number: GB2289092A
Application number: GB9508935A
Authority: GB
Inventors: Alexander William Rowe
Original assignee: Vector Hydraulics Inc Switzerland
Current assignee: Vector Hydraulics Inc Switzerland
Priority date: 1994-05-03
Filing date: 1995-05-02
Publication date: 1995-11-08
Also published as: GB9508935D0; CA2148394A1

Abstract

A method of starting and stopping the operation of a hydraulic reciprocating machine such as a rock drill, uses a start/stop valve (64). The reciprocating machine is of the type which includes a piston (12), a fluid supply chamber (16) and a piston return chamber (18). The valve (64) is connected to the chambers (16, 18) and is supplied with pressure fluid (67). To start the machine a handle (82) is rotated so that a valve member (74) can move to the right and allow fluid to flow to the fluid supply chamber (16) to move the piston (12) towards the return chamber (18). Continued rotation of the handle (82) causes a second valve member (78) to move further to the right and let fluid flow through ports (86) in the first member (74) to the return chamber (18) to start the reciprocation cycle of the piston (12). Stopping reciprocation of the piston (12) is achieved by terminating the supply of hydraulic fluid to the machine and returning the valve to the position shown, thereby venting the return chamber (18) to atmosphere via ports (92). <IMAGE>

Description

THE STARTING AND STOPPING OF HYDRAULIC RECIPROCATING MACHINES This invention relates to a method of starting a hydraulic reciprocating machine such as a rock drill of the type disclosed In American Patent No.

5,222,452 and to a drill start/stop valve for carrying out the method.

Drills of the above type generally include three pressure chambers which in this specification will be referred to as the supply chamber, the return chamber and the drive chamber, and a linearly acting piston which is diametrically stepped and reciprocal in all three of the chambers.

The diametrical dimension of the steps in the piston obviously determine the reactive force imposed on the piston by hydraulic fluid acting on that step in the drill chamber in which the step is located. In the supply chamber the piston is weakly hydraulically biased towards the return chamber in the drive stroke direction of the piston. The bias on the piston in the return chamber is more firmly in the reverse direction towards the supply chamber and the piston bias in the drive chamber is overwhelmingly in the first direction of piston travel towards the return chamber.

During normal cyclic operation of the drill hydraulic fluid at supply pressure is continuously fed to the supply and return chambers and to and from the drive chamber by poppet valves. The operitive positions ni tne valves are primarily depeplent on the position of the dtlll piston during the piston cycle.

A problem with these drills Is that when the hydraulic fluid supply to the drill is terminated the piston and drive chamber valves are stopped at any arbitrary position of the piston cycle which, In the worst case, Can prevent restarting of the drill or may cause the driX not to be started posluvely enough to maintain the piston C-.

A method of starting and stopping a hydraulic reciprocating machine of the type which includes a piston, a fluld supply chamber and a piston rOm chamber accordIng to the invention includes the steps of supplying hyaraullc fluid at supply pressure to the fluid supply chamber to move the piston towards the return chamber and then only to the return clamber to start the reciprocation cycle of the machine piston and stopping reciprocation of the piston by terminating the supply of hydraulic fluid to the machine.

Conveniently the method includes the step of venting the return chamber prior to starting the machine In one form of the invention the method includes the step of venting the return chamber to atmosphere on terminating the supply of hydraulic fluid to the machine to stop the reciprocation of its piston.

In another form of the invention the method includes the step of venting the return chamber to the fluid supply chamber on terminating the supply of hydraulic fluid to the running machine to stop the reciprocation of its piston.

Further according to the invention the machine includes a piston drive chamber and the method includes the step, during or prior to starting, of filling the piston drive chamber with hydraulic fluid at a relatively lower pressure than the supply pressure prior to supplying hydraulic fluid at supply pressure to the return chamber.

A start/stop valve for a hydraulic reciprocating machine of the type which includes a piston, a fluid supply chamber and a piston return chamber according to the invention includes a housing having an inlet port for hydraulic fluid at supply pressure; first and second supply fluid outlet ports which are connected, in use, respectively to the machine fluid supply chamber and the return chamber, a valve arrangement in the housing, an actuator on the outside of the housing for moving the valve arrangement between a first position in which the first outlet port is open to the inlet port to supply hydraulic fluid at supply pressure to the machine's supply chamber and the second outlet port is closed and a second position in which both outlet ports are open to supply fluid at supply pressure to both machine chambers from the inlet port to start reciprocation of the machine piston.

Further according to the invention the machine has a piston drive chamber and the valve includes a third outlet port, which in use, is connected to the machine piston drive chamber with the valve arrangement being adapted to close the port in its second position of movement in the valve housing and to open the port to supply hydraulic fluid to the machine drive chamber only momentarily when the valve arrangement is moved between its first and second positions on starting the machine.

Still further according to the invention the valve includes means for venting the return chamber prior to starting the machine.

Yet further according to the invention the valve includes means for relieving excessive pressure which may be generated in the return chamber during the stopping of the drill.

In one form of the invention the valve is a rotary valve. In another form the valve arrangement is linearly movable in the housing between its first and second positions.

A hydraulic rock drill according to the invention includes the start/stop valve as described above.

Two embodiments of the invention is now described by way of example only with reference to the drawings in which: FIGURE 1 is a sectioned side elevation of a rock drill.

FIGURE 2 is a sectioned side elevation of the start valve of the invention shown schematically connected to the drill of Figure 1, FIGURES 3 and 4 are sectioned side elevations of the Figure 2 start valve illustrating the valve members in different positions of operation, and FIGURES 5 to 7 are sectioned side elevations of a second embodiment of the start valve of the invention.

The drill of Figure 1 is substantially identical to that described in American Patent No. 5,222,452 with the differences between the two being explained below.

The drill is shown in the drawing to include a housing 10, a piston 12, and a valve arrangement indicated generally at 14.

The housing 10 includes a supply chamber 16, a return chamber 18, a drive chamber 20, an inlet port 22 into the supply chamber, a fluid passage 24 extending between the inlet port 22 and a fluid passage 26 which extends from the passage 24 towards the drive chamber, an annular exhaust port 28 in the drive chamber and a fluid passage 30 connecting the exhaust port 28 to atmosphere on the outside of the housing.

The piston 12 includes four portions 32, 34, 36 and 38 which are downwardly stepped in diametrical measurement from the portion 32 to the portion 38 as shown in the drawing. The stepped portions of the piston provide lands or hydraulically exposed piston areas 40, 42 and 44 on the piston. The piston portion 38 includes a fluid passage 46 which extends from the outer surface of the piston adjacent the land 44 to the free end of the piston as shown in the drawing.

The valve arrangement 14 includes an exhaust valve member 48, an inlet valve 50 and a pick-up member 52 for the inlet valve 50.

The valve arrangement 14 is associated with a housing insert 51 which is fixed to the housing wall in any suitable manner The purpose of the insert is for ease of assembly and maintenance of the drill but need not necessarily be a separate component and could equally well be integral with the remainder of the housing.

The exhaust valve member 48 is annular with its inner surface radially spaced from the outer surface of the piston portion 36. The outer surface of the valve member is stepped into a complemental step in the chamber 20, as shown in the drawing, to provide a hydraulically exposed land on the exhaust member which is permanently in communication with the fluid supply passage 26. The forward end of the exhaust valve, at its limit of travel to the right in the drawing, seats on the insert 51 against a reduced diameter portion of the insert to close the exhaust port 28. The rear face of the exhaust valve, on the left in the drawing, carries radially extending fluid passage grooves.

The inlet valve is slidable on the portion 36 of the piston on a seal bearing, as shown in the drawing and includes a radially disposed head which seats on the rear face of the insert 51, to close the chamber 20 to fluid at supply pressure in the chamber 16, and a boss which is spaced from the inner surface of the insert.

The pick-up member 52 is slidable on the piston portions 36 and 38 on seal bearings as shown in the drawing. The pick-up member includes an annular groove which defines a chamber 54 in the member which, throughout the cyclic operation of the drill, is open to atmosphere through the passage 46 in the piston. The front face of the pick-up member carries fluid passage grooves similar to those in the rear face of the exhaust valve.

The piston is guided for reciprocal movement in the housing In seal bearings 58 and the exhaust valve member 48 is similarly guided in seal bearings in the insert 51 which are spaced from each other in the axial direction of the piston on either side of the step in the outer surface of the valve member.

The supply chamber 16 of the Figure 1 drill typically includes a pressure accumulator which conventionally is in the form of a gas pressurised diaphragm (not shown in the drawing). This accumulator substantially maintains the supply pressure in the supply chamber 16 irrespective of abrupt changes in fluid flow caused by the piston operation and valve actions in the drill.

Although only the body of the rock drill is shown in the drawing it does in practise include a front end which carries a conventional chuck and rotor for the drill steel 56.

As mentioned above the drill of Figure 1 is substantially identical to the drill described with reference to Figure 1 of American Patent No. 5,222,452 with the only differences between the two drills being that in the previous drill the fluid passage 24 is connected from the supply inlet 22 to the return chamber while the inlet 60 of the present drill is a separate inlet and the earlier drill does not include a fluid passage 62 which is in communication with the exhaust port 28 in the drive chamber 20.

The start valve, in the first embodiment of the invention, is shown in Figure 2 to include a housing 64 having two chambers 65 and 66, a supply fluid inlet port 67 which is adapted for connecting to a high pressure hydraulic fluid hose and fluid outlet ports 68, 70 and 72. As is shown in the composite drawing the outlet port 68 is connected in use to the inlet port 22 of the Figure 1 drill, the port 70 is connected to the return chamber 18 through the fluid inlet passage 60 and the port 72 of the valve is connected to the drive chamber 20 of the drill through the fluid passage 62 and the exhaust port 28.The start valve further includes a composite valve arrangement which consists of a hollow stepped body 74, a headed valve member 78 which carries a stem 80 and an operating handle 82 which is located on a stud which is threadedly engaged with a threaded aperture in the wall of the housing 64. The free end of the handle stud is, for convenience of assembly, separate from and bears up against the free end of the valve stem 80. The valve housing 64 is divided into its two chambers 65 and 66 by a throat 84 in which the reduced diameter portion 85 of the sleeve 74 is sealingly freely slidable.

The valve member body 74 includes one or more inlet ports 86 which pass through its wall to permit hydraulic fluid flow between the chamber 65 and the interior of the valve member body. The free end of the reduced diameter portion 85 of the body 74 is open. A spring 87 in the chamber 65 biases the valve body 74 to the right of the chamber 65.

The valve member 78 carries a bore 88 which passes through its stem 80 and which is in axial register with a bore 90 which passes through the threaded handle stud to atmosphere. The bore 88 is open into the housing chamber 66 through a port 92.

In the Figure 2 position of the composite valve member components all three of the outlet ports from the housing 64 are closed to supply fluid connected to the port 67 by the closed head of the valve member body 74 and the valve member 78. Prior to starting the drill of Figure 1 by means of the valve, the handle 82 is rotated to move the valve member 78 and the valve body 74, by the pressure of the supply fluid acting on it, to the right from the closed isolation position shown in Figure 2 to the starting position shown in Figure 3. In this position of the valve, fluid at supply pressure flows through the valve inlet port 67 and from the port 68 to the fluid supply chamber 16 of the drill through the drill inlet port 22.

Fluid flow from the port 22 through the passages 24 and 26 bias the drill exhaust valve member 48 to the left in the drawing in which position the exhaust port 28 is open to the drive chamber 20 as shown in Figure 1. In moving to the Figure 3 start position fluid at supply pressure also flows from the valve port 72 to the fluid passage 62 and into the annular exhaust port and the drive chamber while the exhaust port is open through the fluid exhaust passage 30 so that the fluid in the drive chamber 20 is at a substantially lower pressure than the fluid supply pressure in the chamber 16.The valve body 74 is, in this stage of operation of the valve, biased by fluid pressure in the valve chamber 65, and the bias of the spring 87, tightly onto the valve member 78 to prevent fluid flow from the open end of the body 74 into the chamber 66 and so through the port 70 to the drill return chamber 18. The port 92 in the valve member 78 is now open to atmosphere and the return chamber pressure is relatively low with the consequence that fluid at supply pressure in the supply chamber 16 biases the piston to the right in the drawing.

Continued rotation of the handle 82 causes the valve member 78 to move from the Figure 3 start position to the Figure 4 running position at which the motion of the valve body 74 to the right in the drawing is arrested by the throat shoulder in the chamber 65, the step on the body 74 closes the port 72 and the valve member 78 separates from the open end of the valve member body 74. When the rear face of the valve member 78 bears up against the wall of the chamber 66, as shown in Figure 4, the vent port 92 into the valve member bore 88 is closed by the chamber wall. Fluid at supply pressure now flows through the valve body ports 86, from the open end of the body into the chamber 66 and from the port 70 through the fluid passage 60 in the drill into the drill return chamber 18. The flow of hydraulic fluid, which is now at supply pressure, into the return chamber imposes a high pressure on the land 40 of the piston to drive the piston in the direction of the arrow in the drawing on its return stroke to commence cyclic operation of the piston. The piston is driven more positively than is the case with the drill described in the American patent as the pressure accumulator in the supply chamber 16 is charged prior to the drill starting through the starting valve as shown in Figures 3 and 4.

With the fluid flow to the exhaust port 28 now cut off through the passage 62 by the closure of the port 72 of the start valve, fluid in the drive chamber 20 is forced from the chamber by the land 42 on the piston through the open exhaust port 30. The return stroke of the piston continues until the land 42 on the piston strikes the forward face of the exhaust valve member 48 to move the exhaust valve to the left in the drawing with the forward portion 32 of the piston then closing the exhaust port. The shock of the impact of the piston land 42 on the exhaust valve is transmitted through the valve to the inlet valve 50 to knock the inlet valve to the left in the drawing from its seat on the insert 51 to a position remote from the insert.As the inlet valve leaves its seat pressurized fluid from the supply chamber 16 enters the drive chamber 20 which is still fluid flooded at no pressure because of the initial fluid flooding through the port 72 in the valve and the passage 62 in the valve body. In practice, the outlet of the open exhaust port 30 is on the upper surface of the drill, and not in the position shown in Figure 1, to prevent fluid in the drive chamber 20 from draining under gravity from the chamber. Being fluid filled the small injection of fluid from the supply chamber into the drive chamber 20 rapidly builds up pressure in the drive chamber and against the land 42 of the piston to decelerate the piston and reverse its direction of travel into its drive stroke more efficiently than in the embodiment of the drill described in the American patent to ensure very positive starting of the drill.

In order to stop the drill, the handle 82 is rotated in the opposite direction.

Initially the motion of the valve member 78 from its running position in Figure 4 to that in Figure 3 opens the port 92 to exhaust fluid through the bores in the valve member stem and the handle stud, so venting the return chamber. As a consequence of this venting of the return chamber to atmosphere pressure spikes in the return chamber arising from the forward motion of the piston are minimised.

The second embodiment of the valve of the invention is shown in Figures 5, 6 and 7 in which like reference numbers are used as those in Figures 2 to 5 of the first embodiment. In this embodiment of the valve the throat 84 is stepped to provide a seat 94 and the reduced diameter portion 85 of the valve body 74 is complementally outwardly stepped to an increased diameter 96. The reduced diameter portion 85 of the valve body is smaller in diameter than the portion of the throat 84 in which it is located to permit free fluid flow between the valve chamber 66 and the port 73 when the port 73 is open.

The start-stop valve of this embodiment of the invention operates in much the same manner as that of the first embodiment save that while the valve body 74 is moved from the Figure 1 isolation position to the Figure 2 start position fluid at supply pressure is not fed from the now non-existent valve port 72 to the drill drive chamber, and in stopping the drill fluid is no longer exhausted through the previous embodiment handle passages 88 and 90.

During starting of the drill, between the valve body 74 positions of Figures 5 and 6, the port 73 is open to the valve chamber 66 and retained fluid is pumped through the valve from the drill return chamber 18 through the valve ports 70 and 73 to the drill drive chamber 20 to pre-charge the drive chamber. Should the retained fluid have drained from the drill return chamber 18 over a long period of non-use of the drill the drill is, as with the previous valve embodiment, merely false started to pre-charge the drive chamber during start-up of the drill.

In the event that the pressure becomes excessive in the return chamber during stopping of the drill the pressure pulse or spike will act on the stepped face of the valve body 74 in the bore 84 to cause the valve body to act as a spring and hydraulically loaded relief valve which is liffed by the excess pressure from its seat 96 to relieve the fluid pressure through the port 73, the drive chamber and the exhaust port 30 which is directed away from the drill operator. Fluid may similarly be exhausted from the drill during the commencement of the start-up of the drill if the drill chamber 18 is fluid filled as described above, by moving the valve body 74 towards the Figure 5 isolation position to vent the drill return chamber fluid through the valve ports 70 and 73 over the seat 94 to the drill drive chamber and exhaust port 30.

The invention is not limited to the precise details as herein described. For example the start valve need only be operable between the Figures 3 and 4 and 6 and 7 positions as the Figures 2 and 5 shut-off positions would in any event only be required in exceptional circumstances and the drive chamber may be fluid filled by false starting the drill.

Claims

1. A method of starting and stopping a hydraulic reciprocating machine of the type which includes a piston, a fluid supply chamber and a piston return chamber including the steps of supplying hydraulic fluid at supply pressure to the fluid supply chamber to move the piston towards the return chamber and then only to the return chamber to start the reciprocation cycle of the machine piston and stopping reciprocation of the piston by terminating the supply of hydraulic fluid to the machine.

2. A method as claimed in claim 1 including the step of venting the return chamber prior to starting the machine.

3. A method as claimed in either one of claims 1 or 2 including the step of venting the return chamber to atmosphere on terminating the supply of hydraulic fluid to the machine to stop the reciprocation of its piston.

4. A method as claimed in either one of claims 1 or 2 including the step of venting the return chamber to the fluid supply chamber on terminating the supply of hydraulic fluid to the running machine to stop the reciprocation of its piston.

5. A method as claimed in any one of the above claims in which the machine includes a piston drive chamber and the method includes the step, during or prior to starting, of filling the piston drive chamber with hydraulic fluid at a relatively lower pressure than the supply pressure prior to supplying hydraulic fluid at supply pressure to the return chamber

6.A start/stop valve for a hydraulic reciprocating machine of the type which includes a piston, a fluid supply chamber and a piston return chamber, with the valve including a housing having an inlet port for hydraulic fluid at supply pressure; first and second supply fluid outlet ports which are connected, in use, respectively to the machine fluid supply chamber and the return chamber, a valve arrangement in the housing, an actuator on the outside of the housing for moving the valve arrangement between a first position in which the first outlet port is open to the inlet port to supply hydraulic fluid at supply pressure to the machine's supply chamber and the second outlet port is closed and a second position in which both outlet ports are open to supply fluid at supply pressure to both machine chambers from the inlet port to start reciprocation of the machine piston.

7. A start/stop valve as claimed in claim 6 in which the reciprocating machine has a piston drive chamber and the valve includes a third outlet port, which in use, is connected to the machine piston drive chamber with the valve arrangement being adapted to close the port in its second position of movement in the valve housing and to open the port to supply hydraulic fluid to the machine drive chamber only momentarily when the valve arrangement is moved between its first and second positions on starting the machine.

8. A start/stop valve as claimed in either one of claims 6 or 7 in which the valve includes means for venting the machine return chamber prior to starting the machine.

9. A start/stop valve as claimed in either one of claims 6 or 7 in which the valve includes means for relieving excessive pressure which may be generated in the machine return chamber during the stopping of the machine.

10. A stop/start valve as claimed in any one of claims 6 to 9 in which the valve arrangement is rotary.

11. A start/stop valve as claimed in any one of claims 6 to 9 the valve arrangement is linearly movable in the housing between its first and second positions.

12. A hydraulic rock drill including the start/stop valve as claimed in any one of claims 6 to 11.

13. A method of starting and stopping a hydraulic reciprocating machine substantially as herein described with reference to the drawings.

14. Astart/stopvalvefora hydraulic reciprocating machine substantially as herein described with reference to the drawings.

15. A hydraulic rock drill substantially as herein described.