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1. WO2018070881 - A PNEUMATIC OR HYDRAULIC MECHANISM

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[ EN ]

WHAT WE CLAIM IS:

1. A pneumatic or hydraulic mechanism comprising :

a housing defining a piston chamber and having a fluid inlet port;

a piston slidable in the piston chamber, the piston partitioning the piston chamber into a front chamber and a rear chamber, the piston having one or more passages for fluid communication between the rear chamber and the front chamber, the one or more passages being sealed by a sealing mechanism;

the sealing mechanism having a sealing state in which the sealing mechanism substantially inhibits fluid communication between the rear chamber and the front chamber, and a non-sealing state in which the sealing mechanism allows fluid

communication between the rear chamber and the front chamber;

the piston being slidable between a first position and a second position;

wherein, when the piston is positioned in the first position, the sealing mechanism is in the sealing state;

upon supply of a fluid to the inlet port, the fluid urges the piston to its second position and then causes the sealing mechanism to change to the non-sealing state until the pressure in the rear chamber and the front chamber equalises, allowing the sealing mechanism to return to the sealing state;

upon removal of fluid from the rear chamber, the fluid in the front chamber urges the piston to return to its first position.

2. The mechanism of claim 1, wherein the sealing mechanism comprises a sealing member.

3. The mechanism of claim 2, wherein the sealing member is an expandable sealing member that is arranged to expand to be in the sealing state.

4. The mechanism of claim 1, wherein the piston chamber has a first portion having a first diameter corresponding to the first position of the piston and a second portion having a second diameter corresponding to the second position of the piston, the second diameter being larger than the first diameter.

5. The mechanism of claim 1, wherein the piston chamber has a first portion corresponding to the first position of the piston and a second portion corresponding to the second position of the piston, the second portion having a plurality of channels.

6. The mechanism of any one of the preceding claims, wherein the one or more passageways comprises one or more bores.

7. The mechanism of any one of the preceding claims, wherein the expandable sealing member is an annular member.

8. The mechanism of any one of the preceding claims, further comprising one or more additional seals between the piston and the piston chamber.

9. The mechanism of any one of the preceding claims, further comprising one or more exhaust ports.

10. The mechanism of any one of the preceding claims, wherein the mechanism further comprises a piston rod.