GB2187508A - Pneumatic actuator - Google Patents

Abstract

The actuator has two working chambers 1, 2 with diaphragms 5, 6 operated by vacuum applied to pipes 4. The lost motion connection between element 8, attached to diaphragm 5, and control member 20 attached to diaphragm 6 enables the output member (e.g. hook 27) to be moved, either a distance C1 by the evacuation of chamber 1, or a distance C2 by actuating chamber 2. Spring 28 returns the actuator to the illustrated start position in either case. Distances C1, C2 may be adjusted by setting screw 13 and nut 21, respectively to appropriate positions. <IMAGE>

Description

SPECIFICATION Pneumatic actuator for controlling displacement of a control member in a given axial direction The present invention relates to a pneumatic actuator for controlling displacement of a control member in a given axial direction, and enabling two different displacements independent of each other.

Pneumatic actuators of the aforementioned type are usually controlled by a vacuum produced by- an appropriate source, in particular, the vacuum inside the manifold of an internal combustion engine, and are usually employed for controlling various components and devices on motor vehicles.

Known actuators of the aforementioned type usually comprise a body in which is formed a first chamber communicating with the said source and one wall of which is defined by a first deformable diaphragm moving substantially in the same axial directon as the control member on the actuator. The said first deformable diaphragm moves in the said direction from a first limit position, wherein it contacts an arresting surface on the body, to a second limit position, wherein an element integral with the said diaphragm contacts a first stop, the position of which is adjustable in the said direction.The actuator also comprises a second chamber communicating with the said source, and one wall of which is defined by a second deformable diaphragm integral with the said control member and also designed to move, in the said direction, from a first limit position, wherein it contacts an arresting surface on the said body, to a second limit position, wherein a surface of the said control member contacts the said element integral with the said first diaphragm.

A first displacement of the control member is achieved by connecting the said two chambers on the actuator to the said vacuum source. In like manner, the said first diaphragm moves into the said second limit position, and the said second diaphragm is arrested against the element integral with the first. For controlling displacement of the control member otherwise than as described above, only the second chamber is connected to the vacuum source, in such a manner that the first diaphragm moves into the first limit position, and the second diaphragm into the second limit position, against the element integral with the said first diaphragm.

Actuators of the aforementioned type, however, do not provide for two different, independently adjustable displacements of the control member. Whereas one displacement may be appropriately adjusted by varying the position of the said stop, the other depends on the geometry of the device itself, which cannot be varied.

The aim of the present invention is to provide a pneumatic actuator of the aforementioned type, but designed to overcome the aforementioned drawback, i.e. an actuator enabling two different, independently adjustable strokes of the control member.

With this aim in view, according to the present invention, there is provided a pneumatic actuator for controlling displacement of a control member in a given axial direction, between a starting position and two different end positions; said actuator being controlled by a vacuum produced by an appropriate source, in particular, the vacuum inside the manifold of an internal combustion engine; characterised by the fact that it comprises a body in which are formed a first chamber communicating with the said source, and one wall of which is defined by a first deformable diaphragm moving substantially in the said direction from a first limit position, wherein it contacts an arresting surface on the said body, to a second limit position, wherein an element integral with the said first diaphragm contacts a first stop the position of which may be adjusted in the said direction; and a second chamber communicating with the said source, and one wall of which is defined by a second deformable diaphragm integral with the said control member and also moving substantially in the said direction from a first limit position to a second limit position wherein a surface of the said control member contacts a second stop; the relative position of the said surface of the said control member being adjustable in the said direction in relation to the said second stop, and the said element inte gral with the said first diaphragm being provided with a first shoulder cooperating with a second shoulder on the said control member, for moving the said second diaphragm from the relative first limit position to the relative second limit position, subsequent to displacement of the said first diaphragm from the relative first limit position to the relative second limit position.

The present invention will be described, by way of example, with reference to the attached drawing, which shows an axial section of a pneumatic actuator according to the teachings of the present invention.

The actuator according to the present invention substantially comprises a first and second chamber, 1 and 2, formed inside a body 3 on the actuator itself. Via a pipe 4, each of the said chambers 1 and 2 communicates with a vacuum source, e.g. the exhaust manifold of an internal combustion engine, so as to produce a given vacuum inside each chamber.

The actuator also comprises two substantially coaxial diaphragms, 5 and 6, defining one wall of chambers 1 and 2 respectively, as shown clearly in the attached drawing. The edges of diaphragm 5 are gripped between parts 3a and 3b of the said body 3, whereas those of diaphragm 6 are gripped between parts 3b and 3c. Diaphragm 5 presents a pair of plates 7 and an integral element 8 having a rod 9 and an end head 10. Diaphragm 5 is designed to move substantially from a first limit position, wherein one of plates 7 contacts surface 11 of body 3, to a second limit position, wherein the centre portion of element 8 is arrested against the end of a stop 12 substantially presenting a threaded shank screwed into a corresponding threaded hole on the body, and which may be adjusted externally of the actuator by means of head 13.

Between the said head 13 and body 3, provision is conveniently made for a helical spring 17 for preventing head 13 from being unscrewed accidentally. Provision is also made for a sealing ring 18 for ensuring efficient sealing of chamber 1. Diaphragm 6 presents a pair of plates 19, and an integral control member 20, axial displacement of which is controlled by the actuator. The said control member is conveniently tubular in shape, and presents a threaded end portion on to which is screwed a threaded ring nut 21, the axial position of which may be adjusted in relation to the said control member, and the surface 22 of which is designed to arrest against a stop surface 23 of body 3.

As shown cleariy in the attached drawing, the said stop member presents an inner hole 24 into which is inserted the head 10 of element 8; and the said control member presents an annular projection 25 projecting towards hole 24 and acting as a shoulder for head 10.

Hole 24 is conveniently closed by a plug 26; and a connecting element, e.g. hook 27, is designed to connect the control member on the actuator to the device being controlled by the same.

Diaphragm 6 is designed to move from a first limit position, as shown in the drawing and wherein the shoulder of annular projection 25 contacts head 10 of element 8, to a second limit position, wherein the active surface 22 of ring nut 21 contacts stop surface 23 of body 3.

Between diaphragm 6 and a supporting surface 28 of body 3, there is inserted a helical spring 29 for normally securing diaphragm 6 in the said first limit position.

The actuator as described above operates as follows. A first stroke of control member 20, indicated by Cl in the drawing, may be set by adjusting the end of stop 12 in relation to the top surface of element 8, by simply turning the stop by means of head 13.

A second stroke of control member 20, indicated by C2 in the drawing, may be set fully independently of the said firsi stroke, by adjusting ring nut 21 so as to set surface 22 to a given distance from stop surface 23 of body 3.

For performing the said first stroke C1, the actuator is activated by simply connecting first chamber 1 to the vacuum source, which causes diaphragm 5 to move from the said first limit position shown in the drawing to the said second limit position, which is reached when surface 30 of element 8 is arrested against the end of stop 12. Displacement of the said diaphragm 5, via element 8, causes control member 20 to be displaced in the same direction. Upon the vacuum in chamber I being released, the actuator is returned to the position shown in the drawing by virtue of helical spring 29, which controls downward displacement of both control member 20, and also diaphragm 5 via the connection of head 10 and annular projection 25.

For control member 20 to perform stroke C2, chamber 2 is connected to the vacuum source, so as to cause diaphragm 6 to move upwards against the force exerted by spring 29. During such displacement, control member 20 has no effect on element 8, which remains in its initial position. The limit position of control member 20 is reached, in this second case, when surface 22 of ring nut 21 comes to rest against stop surface 23 of body 3.

It follows, therefore, that the actuator according to the present invention provides for two different, fully independent strokes (Cl, C2) of control member 20, which strokes may also be adjusted fully independently.

The actuator according to the present invention also presents a highly straightforward, compact structure, and is therefore both reliable and cheap to produce.

To those skilled in the art it will be clear that changes may be made to the form and arrangement of the component parts of the actuator as described and illustrated herein without, however, departing from the scope of the present invention.

Claims (7)

1. A pneumatic actuator for controlling displacement of a control member in a given axial direction, between a starting position and two different end positions; said actuator being controlled by a vacuum produced by an appropriate source, in particular, the vacuum inside the manifold of an internal combustion engine; characterised by the fact that it comprises a body in which are formed a first chamber communicating with the said source, and one wall of which is defined by a first deformable diaphragm moving substantially in the said direction from a first limit position, wherein it contacts an arresting surface on the said body, to a second limit position, wherein an element integral with the said first diaphragm contacts a first stop the position of which may be adjusted in the said direction; and a second chamber communicating with the said source, and one wall of which is defined by a second deformable diaphragm integral with the said control member and also moving substantially in the said direction from a first limit position to a second limit position wherein a surface of the said control member contacts a second stop; the relative position of the said surface of the said control member being adjustable in the said direction in relation to the said second stop, and the said element integral with the said first diaphragm being provided with a first shoulder cooperating with a second shoulder on the said control member, for moving the said second diaphragm from the relative first limit position to the relative second limit position, subsequent to displcement of the said first diaphragm from thc relative first limit position to the relative second limit position.

2. An actuator as claimed in Claim 1, characterised by the fact that the said control member presents a threaded ring nut screwed on to the member itself; the said ring nut presenting a surface designed to rest against a surface of the said body, for the purpose of arresting displacement of the said control member subsequent to displacement of the said first diaphragm from the relative said first limit position to the relative said second limit position.

3. An actuator as claimed in Claim 1 or 2, characterised by the fact that the said element integral with the said first diaphragm comprises a rod having a head inserted inside an axial hole on the said control member and cooperating with an annular projection on the member itself.

4. An actuator as claimed in one of the foregoing Claims, characterised by the fact that it comprises a spring inserted between the said second diaphragm and a shoulder on the said body, and designed normally to retain the said diaphragm in the said first position.

5. An actuator as claimed in one of the foregoing Claims, characterised by the fact that the said first stop consists of a threaded rod screwed inside a hole on the said body.

6. An actuator as claimed in one of the foregoing Claims, characterised by the fact that the said body comprises at least three parts; the said first diaphragm being gripped between a first and second of the said parts, and the said second diaphragm being gripped between the second and third.

7. A pneumatic actuator for controlling displacement of a control member in a given ax ial direction, substantially as described and illustrated herein with reference to the attached drawing.