CA2343047A1

CA2343047A1 - Hydraulic impact machine actuator

Info

Publication number: CA2343047A1
Application number: CA 2343047
Authority: CA
Inventors: Alexander Rowe; Warren Kay; James Bawden
Original assignee: Individual
Current assignee: Vector Hydraulics Inc South Africa
Priority date: 2000-03-30
Filing date: 2001-03-30
Publication date: 2001-09-30
Anticipated expiration: 2021-03-30
Also published as: CA2343047C

Abstract

An actuator for a hydraulically operable impact machine which includes a machine body, a piston drive chamber in the body, a stepped piston which is reciprocal in the body and drive chamber, a sleeve which surrounds a step in the piston to define, on the inside of the sleeve, between the sleeve and a portion of the piston, a piston return chamber with a forward end of the sleeve and a seat in the body defining an exhaust valve which opens to the outside of the body with the rear end of the sleeve and a seat in the body defining an inlet valve for feeding hydraulic fluid under pressure from the drive chamber into the return chamber, and a seal bearing, in which the piston is reciprocable, between the drive and return chambers characterised in that the actuator includes a pusher which is reciprocally located in the body for movement between a first position in which it is engaged with the sleeve to close the return chamber inlet valve and open the exhaust valve and a second position in which it is held clear of the valve sleeve by fluid pressure in the drive chamber and means biasing the pusher to its first position of operation when the machine drive chamber is vented to atmosphere.

Claims

1. An actuator for a hydraulically operable impact machine which includes a machine body, a piston drive chamber in the body, a stepped piston which is reciprocal in the body and drive chamber, a sleeve which surrounds a step in the piston to define, on the inside of the sleeve, between the sleeve and a portion of the piston, a piston return chamber with a forward end of the sleeve and a seat in the body defining an exhaust valve which opens to the outside of the body with the rear end of the sleeve and a seat in the body defining an inlet valve for feeding hydraulic fluid under pressure from the drive chamber into the return chamber, and a seal bearing, in which the piston is reciprocable, between the drive and return chambers characterised in that the actuator includes a pusher which is reciprocally located in the body for movement between a first position in which it is engaged with the sleeve to close the return chamber inlet valve and open the exhaust valve and a second position in which it is held clear of the valve sleeve by fluid pressure in the drive chamber and means biasing the pusher to its first position of operation when the machine drive chamber is vented to atmosphere.

2. An actuator as claimed in claim 1 wherein the pusher is a cylindrical body which surrounds the exhaust valve end of the sleeve with a portion of its length from one end slidably located in a circular groove in an end wall of the machine body with the biasing means being a spring which acts on a formation at the opposite end of the pusher body to bias the pusher to its first position of operation.

3. An actuator as claimed in claim 2 wherein the pusher groove has a blind end in the machine body end wall and the machine body includes a passage which extends between the blind end of the pusher groove and the outside of the machine body.

4. An actuator as claimed in claim 2 wherein the formation on the pusher body is an outwardly directed flange on the end of the pusher body and the spring is a coil spring which surrounds the pusher body to bear on the machine body adjacent the pusher groove and the formation

5. An actuator as claimed in claim 1 wherein the piston includes a fluid passage which extends over a portion of the length of the piston with its one end open to hydraulic fluid in the drive chamber during reciprocation of the piston and its other end open, across the piston seal bearing, into the return chamber only during the final portion of the piston drive stroke and the initial portion of its return stroke.

6. An actuator as claimed in claim 5 wherein the piston fluid passage is a flute in the surface of the piston.

7. An actuator for a hydraulically operable impact machine which includes a machine body, a piston drive chamber in the body, a stepped piston which is reciprocal in the body and drive chamber, a sleeve which surrounds a step in the piston to define, on the inside of the sleeve, between the sleeve and a portion of the piston, a piston return chamber with a forward end of the sleeve and a seat in the body defining an exhaust valve which opens to the outside of the body with the rear end of the sleeve and a seat in the body defining an inlet valve for feeding hydraulic fluid under pressure from the drive chamber into the return chamber, and a seal bearing, in which the piston is reciprocable, between the drive and return chambers characterised in that the machine includes a fluid passage in the piston which extends over a portion of the length of the piston with its one end open to hydraulic fluid in the drive chamber during reciprocation of the piston and its other end open, across the piston seal bearing, into the return chamber only during the final portion of the piston drive stroke and the initial portion of its return stroke.

8. An actuator as claimed in claim 7 wherein the piston fluid passage is a flute in the surface of the piston.

9. A method of starting a hydraulically operable impact machine actuator which includes a machine body, a piston drive chamber in the body, a stepped piston which is reciprocal in the body and drive chamber, a sleeve which surrounds a step in the piston to define, on the inside of the sleeve, between the sleeve and a portion of the piston, a piston return chamber with a forward end of the sleeve and a seat in the body defining an exhaust valve which opens to the outside of the body with the rear end of the sleeve and a seat in the body defining an inlet valve for feeding hydraulic fluid under pressure from the drive chamber into the return chamber, and a seal bearing, in which the piston is reciprocable, between the drive and return chambers including the steps of venting the drive and return chambers to atmosphere, applying force to the sleeve to close the return chamber inlet valve to isolate the drive and return chambers from each other and to open the return chamber exhaust valve, charging the drive chamber with hydraulic fluid at supply pressure to cause the piston to be moved in its drive stroke direction towards the open return chamber exhaust valve, charging the return chamber with hydraulic fluid prior to the opening of the inlet valve at supply pressure when a formation on the piston reaches an exhaust flow restriction formation on the inner surface of the sleeve, and decelerating the piston and reversing its direction of motion into its return stroke direction at a rate of acceleration which is adequate for starting of the cyclic action of the actuator.

10. An actuator starting method as claimed in claim 9 including the step of applying the closing force to the sleeve prior to charging the drive chamber with hydraulic fluid at supply pressure by moving a pusher member against the sleeve by means of biasing means and moving the pusher member clear of the sleeve against the bias of its biasing means by means of hydraulic fluid at pressure on charging of the drive chamber.

11. An actuator starting method as claimed in claim 9 including the step of charging the return chamber with hydraulic fluid at supply pressure prior to the opening of the return chamber inlet valve through a fluid passage in the piston which is open at one end to the drive chamber and open at its other end to the return chamber across the piston seal bearing.