Can closures

Abstract

 A method of closing a can includes the following stages;
locating a closure member (l4) within a cylindrical wall portion (l2) of the can (ll) with a resilient sealing element (l7,23ʹ) disposed between the periphery (l9) of the closure member (l4) and the cylindrical wall (l2), so that the closure member (l4) is slidable axially of the cylindrical wall portion (l2);
adjusting the position of the closure member (l4) axially of the cylindrical wall portion (l2) to give the required internal axial dimension;
and rolling a groove (l5) in the cylindrical wall (l2) of the can (ll) to abut one side of the closure member (l4) while simultaneously rolling the end of the can (ll) over to abut the other side of the closure member (l4), the sealing element (l7,23ʹ) being compressed during the rolling process. This method may be used to produce the casing (l0) for a servo actuator.

Description

[0001] The present invention relates to can closures and in particular to a method of securing a closure member in a can of generally cylindrical formation.

[0002] Devices such as servo actuators include casings which are closed at both ends to define a fluid tight chamber. Such casings are often made from cans having a base and cylindrical wall with a closure member secured at the open end. Such closure members are typically secured in abutting relationship against the end of the cylindrical wall, or are abutted against a shoulder on the internal surface of the cylindrical wall. In such devices, it is often necessary to accurately control the internal axial dimension of the casing. In view of the tolerance variations in the axial dimension of the can, which may for example be made by a spinning or drawing technique, where the closure member is to be secured against the end of the can, the can would typically be made oversize and trimmed down accurately to give the required internal axial dimension. Alternatively, where the closure member is to abut an internal shoulder of the cylindrical wall, this shoulder would typically be within the required axial dimension and shims interposed between the shoulder and the closure member, to make up the difference in the axial dimension. In both cases, additional manufacturing steps and/or materials are required to effect the necessary adjustment in the internal axial dimension of the casing.

[0003] According to one aspect of the present invention, a method of closing a can is characterised in that; a closure member is located within a cylindrical wall portion of the can with a resilient sealing element disposed between the periphery of the closure member and the cylindrical wall of the can, so that the closure member is slidable axially of the cylindrical wall portion; the position of the closure member is adjusted axially of the cylindrical wall portion to give the required internal axial dimension; and a groove is rolled in the cylindrical wall of the can to abut one side of the closure member while the end of the can is simultaneously rolled over to abut the other side of the closure member, the sealing element being compressed during the rolling process.

[0004] In this specification the term "can" is intended to cover any casing or container with a generally cylindrical wall. Such cans will normally have one end closed by a wall formed integrally of the cylindrical wall. However, both ends of the cylindrical wall may, for example, be closed by separate closure means in the manner described above. Alternatively, the cylindrical wall may be closed at one end by some other formation or may form part of some other formation.

[0005] The invention is now described, by way of example only, with reference to the accompanying drawings, in which;

Figure l shows in section a partial view of the casing for a servo actuator formed in accordance with the present invention; and

Figure 2 shows in section a partial view of a modified construction of the casing shown in Figure l.

[0006] The servo actuator illustrated in Figure l comprises a casing l0 formed from a can ll having a cylindrical wall l2 and end wall l3. A closure member l4 is positioned in the open end of can ll and is located in position between an inwardly directed annular groove l5 in the cylindrical wall l2 and an inwardly directed flange formation l6 at the end of the cylindrical wall l2.

[0007] A resilient sealing ring l7 is located in an annular groove l8 in the periphery l9 of the closure member l4 and is compressed between the closure member l4 and the cylindrical wall l2, to provide a fluid tight joint.

[0008] A piston 20 is slidingly located within the casing l0 and is urged towards the closure member l4 by spring means 2l. An elastomeric diaphragm 22 is connected between the piston 20 and casing l0, a formation 23 on the outer periphery of diaphragm 22 being clamped between the junction of the cylindrical wall l2 and closure member l4 and a retaining plate 24 which is rivetted to the closure member l4. The diaphragm 22 thereby divides the casing l0 into two fluid tight chambers 26 and 27.

[0009] When in use chamber 26 of the solenoid actuator would be connected to a source of vacuum and chamber 27 would be selectively connected to vacuum or atmosphere. When chamber 27 is connected to vacuum, the pressure differential across the piston 20 and diaphragm 22 will be zero and the spring means 2l will force the piston towards the closure member l4. However, when chamber 27 is connected to atmosphere, a pressure differential will be established across the piston 2l and diaphragm 22 and this will act against spring means 2l to urge the piston 20 away from closure member l4. This movement of piston 20 may be used to control a plunger to actuate valve means.

[0010] The force exerted on the piston 20 by spring means 2l will depend on the spring rate and initial compression of spring means 2l. If consequently it is necessary to accurately control the force applied by the spring means 2l, it will be necessary to accurately control the internal axial dimension between the end wall l3 and the closure member l4 and take into account tolerance variations in the axial length of the can ll which occur during manufacture.

[0011] In order to achieve this, the can ll with plane cylindrical wall l2 and end wall l3 is produced using suitable techniques, for example spinning or drawing. After pre-assembly of the piston 20 and diaphragm 22 on the closure member l4, the closure member l4 is inserted into the open end of can ll with spring means positioned between the end wall l3 and piston 20. The closure member l4 is a close fit within the can ll, so that the sealing ring l7 engages the cylindrical wall l2, but the closure member l4 may be moved axially within the can ll. The closure member l4 is moved towards the end wall l3 until the required internal axial dimension is achieved. Alternatively, the closure member l4 could be advanced towards the end wall l3, until the spring means 2l exerted a predetermined load, thus also taking into account any tolerance variations in the spring means 2l.

[0012] Once the closure member l4 is accurately positioned in the can ll, the end of the cylindrical wall l2 is rolled over to form flange l6 and the annular groove l5 is formed simultaneously during the rolling process, thereby locating the closure member l4 in position. During this rolling process, the sealing ring l7 will also be further compressed between the closure member l4 and cylindrical wall l2, to provide a fluid tight joint.

[0013] In the modified construction illustrated in Figure 2, instead of sealing ring l7, the formation 23ʹ on the outer periphery of diaphragm 22 is located in an annular groove l8ʹ in the closure member l4. The formation 23ʹ is thus trapped and compressed between the closure member l4 and cylindrical wall l2 of can ll, to provide a fluid tight seal and to retain the outer periphery of the diaphragm 22 in position without the need for a separate retaining plate. The inner lip 30 which defines one wall of groove l8ʹ is of reduced diameter in order to provide a clearance between it and the wall l2 of the can, for the web portion of the diaphragm 22.

[0014] Various modifications may be made without departing from the invention. For example, while the invention has been described with reference to a servo actuator, the method may be used to provide a fluid tight closure for a can in any other application, particularly where provision must be made for axial adjustment of the closure member with respect to the can.

[0015] Also while it is preferred to provide an annular groove l8 in the closure member l4 in which to locate the sealing ring l7 or peripheral formation 23ʹ, this is not essential and a resilient sealing element may be disposed between the circumferential edge of the closure member l4 and the cylindrical wall l2 of can l0 in any suitable manner.

Claims

1. A method of closing a can characterised in that a closure member (l4) is located within a cylindrical wall portion (l2) of the can (ll) with a resilient sealing element (l7;23ʹ) disposed between the periphery (l9) of the closure member (l4) and the cylindrical wall (l2) of the can (ll), so that the closure member (l4) is slidable axially of the cylindrical wall portion (l2); the position of the closure member (l4) is adjusted axially of the cylindrical wall portion (l2) to give the required internal axial dimension; and a groove (l5) is rolled in the cylindrical wall (l2) of the can (ll) to abut one side of the closure member (l4) while the end of the can (ll) is simultaneously rolled over to abut the other side of the closure member (l4), the sealing element (l7;23ʹ) being compressed during the rolling process.

2. A method according to claim l characterised in that the sealing element (l7;23ʹ) is retained in a peripheral groove (l8;l8ʹ) in the closure member (l4).

3. A method according to claim l or 2 characterised in that the sealing element (l7) is in the form of a ring of resilient material.

4. A method according to any one of the preceding claims characterised in that the sealing element (23ʹ) is provided by a peripheral formation of an elastomeric diaphragm (22).

5. A method according to any one of the preceeding claims characterised in that spring means (2l) is located within the can (ll) and acts against the closure member (l4), the position of the closure member (l4) in the can (ll) being adjusted until the spring means (2l) exerts the pre-determined load on the closure member (l4), before the closure member (l4) is secured to the can (ll) by rolling.

6. A servo actuator comprising a casing (l0) formed from a can member (ll) and a closure member (l4), characterised in that the closure member (l4) is secured to the can member (ll) by the method claimed in any one of claims l to 5.

Drawing