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(11) | EP 1 013 943 A1 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Limit switch device for fluid actuators |
(57) A cylinder 1 has an outer housing 2 defining a pressure chamber and an inner piston
3 which is slidably movable through the pressure chamber. An electrical signal is
provided from within the pressure chamber depending on the axial position of the piston
3 within the chamber. The piston 3 carries a contacting device which completes a circuit
and provides a control signal. The control signal is generated at a pre-determined
position before the piston 3 reaches the end of the stroke. The travel of the piston
3 is not restricted when the circuit is completed. A full bore side contact device
is provided by an auxiliary plunger (31) which is slidably movable against the biassing
of a spring 32 when the contact is made with a contact is made with a contact pin
30. |
Introduction
Statements of Invention
an outer housing with a pressure chamber;
an inner piston which is movable through the pressure chamber;
a sensing device located within the pressure chamber to sense the position of the piston; and
a contacting device carried by the piston which contacts the sensing device when the
piston is at a predetermined position in the housing to provide a control signal,
characterised in that the contacting device is movable relative to the piston to allow
the travel of the piston to continue within the pressure chamber on engagement of
the contacting device with the sensing device.
Brief Description of Drawings
Fig. 1A is a longitudinal cross sectional view of a cylinder according to the invention with a piston in a mid position;
Fig. 1B is transverse cross sectional view of the cylinder of Fig. 1A;
Fig. 1C is a diagram illustrating the circuit formed by the cylinder of Fig. 1A;
Figs 2A to 2C are views similar to Figs 1A to 1C with the piston in an annular closing position;
Figs 3A to 3C are views similar to Figs 1A to 1C with the piston in an annular closed position;
Figs 4A to 4C are views similar to Figs 1A to 1C in a full bore closing position; and
Figs 5A to 5V are views similar to Figs 1A to 1C in a full bore closed position.
Detailed Description
an outer housing (2) with a pressure chamber;
an inner piston (3) which is movable through the pressure chamber;
a sensing device (15, 30) located within the pressure chamber to sense the position of the piston (3); and
a contacting device (16, 18, 31, 33) carried by the piston (3) which contacts the
sensing device (15, 30) when the piston (3) is at a predetermined position in the
housing (2) to provide a control signal,
characterised in that the contacting device (16, 18, 31, 33) is movable relative to
the piston (3) to allow the travel of the piston (3) to continue within the pressure
chamber on engagement of the contacting device (16, 18, 31, 33) with the sensing device
(15, 30).
Amended claims in accordance with Rule 86(2) EPC.
1. A cylinder (1) having:
an outer housing (2) with a pressure chamber;
an inner piston (3) which is movable through the pressure chamber;
a sensing device (15, 30) located within the pressure chamber to sense the position of the piston (3); and
a contacting device (16, 18, 31, 33) carried by the piston (3) which contacts the sensing device (15, 30) when the piston (3) is at a predetermined position in the housing (2) to provide a control signal,
the contacting device (16, 18, 31, 33) being movable relative to the piston (3) to
allow the travel of the piston (3) to continue within the pressure chamber on engagement
of the contacting device (16, 18, 31, 33)with the sensing device (15, 30);
characterised in that:-
the contacting device (16, 18, 31, 33) is a secondary plunger (31) mounted within the piston (3) for movement between a retracted position and an extended position.
2. A cylinder as claimed in claim 1 wherein the contacting device (16, 18, 31, 33) is biassed (19, 32) between the retracted position and the extended position.
3. A cylinder as claimed in claim 2 wherein the contacting device (16, 18, 31, 33) is spring biassed from the retracted to the extended position.
4. A hydraulic cylinder as claimed in any preceding claim wherein the sensing device (15, 30) includes a contact pin (15, 30) which extent into the pressure chamber for engagement with the contacting device (16, 18, 31, 33).
5. A cylinder as claimed in claim 4 wherein the contacting device (16, 18, 31, 33) includes a flange or washer (16, 33) for contacting the contact pin (15, 30) of the sensing device.
6. A cylinder as claimed in claim 5 wherein the flange or washer (16) extends outwardly of a sleeve (18) which is slidably movable relative to the piston (3) when the flange or washer (16) engages a contact pin (15).
7. A cylinder as claimed in any preceding claim wherein the cylinder has a full bore side sensing device (30) with an associated full bore side contacting device (31, 33) and an annular side sensing device (15) with an associated annular contacting device (16, 18).
8. A cylinder as claimed in claim 7 wherein the full bore contacting device comprises a secondary plunger (31) mounted within the piston (3) for movement between a retracted and an extended position and a flange or washer (33) mounted to the secondary plunger (31) for engagement with a full bore contact pin (30) extending into the pressure chamber.
9. A cylinder as claimed in claim 7 or 8 wherein the annular side contacting device comprises a sleeve (18) mounted to the piston (3) for movement between a retracted and an extended position and a flange or washer (16) mounted to the sleeve (18) for engagement by an annular contact pin (15) extending into the pressure chamber.