GB2089468A

GB2089468A - Clamping actuator diaphragm

Info

Publication number: GB2089468A
Application number: GB8137515A
Authority: GB
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1980-12-12
Filing date: 1981-12-11
Publication date: 1982-06-23

Abstract

In a fluid pressure diaphragm actuator, e.g. a brake actuator, the bead of the clamped diaphragm tapers inwardly to counteract inward tension in operation and restraining means are provided around the periphery to prevent outward flow of the bead between clamping flanges of the housing of the actuator. The restraining means may comprise wires 23 and 33, heel 47, ribs 67 or flanges 87, 88. <IMAGE>

Description

SPECIFICATION Fluid pressure operable actuators This invention relates to fluid pressure operable diaphragm actuators, especially fluid pressure operable actuators for braking systems.

Fluid pressure operable diaphragm actuators are well known, particularly for fluid pressure operable braking systems, such actuators including a housing with a circular diaphragm having a peripheral bead clamped by means of a clamping ring between flanges of respective parts of the housing. Diaphragms for such actuators have typically been provided hitherto with a circumferential bead which thickens outwardly such as to firmly retain the clamped diaphragm against inward tensions resulting from fluid pressure in operation of the actuator in which the diaphragm is installed.One problem which has been experienced with such diaphragms is that owing possibly to flow of the material of the bead of the diaphragm at local points, especially in the vicinity of the one or more openings in the clamping ring which clamps the two flanges on respective sides of the diaphragm, there is occasional leakage and partial failure of the actuator can result.

The present invention provides a solution which seeks to reduce the incidence of such failure.

According to the present invention there is provided a fluid pressure operable diaphragm actuator having a housing and a diaphragm which has a central portion an intermediate flexible portion and a peripheral bead for retention by clamping between flange parts of the housing, said bead having a thickness which increases radially outwardly but restraining means being provided which is distributed substantially entirely around the bead counteracting outward flow thereof under compression.

In order that the invention may be more clearly understood and readily carried into effect, the same will be further described by way of examples with reference to the accompanying drawings in which Fig, 1 illustrates a typical fluid pressure operable brake actuator, Fig. 2 illustrates in part and in cut-a-way view a diaphragm including a reinforcement in accordance with the invention, Fig. 3 illustrates an alternative manner of introducing a reinforcement for the bead of such a diaphragm, Fig. 4 illustrates a clamped diaphragm, the diaphragm being provided with an alternative means of restraining the bead of the diaphragm against outward flow, and, Figs. 5, 6, 7 and 8 illustrate alternative means in a fluid pressure operable actuator for restraining the outward flow of a diaphragm under clamping conditions.

Referring to Fig. 1, this shows a simple fluid pressure operable brake actuator such as may typically be used for the brakes of the trailer vehicle or the front or rear wheel brakes of a tractor vehicle provided with fluid pressure operable braking. The actuator consists of a first housing part 1, a second housing part 2, these parts being provided with outwardly turned flanges between which a bead 3 of a diaphragm having a central part 5 and a flexible part 4 is clamped by means of a clamping ring 6 with a single clamping bolt 7. The actuator is provided with an inlet boss 7 adapted for connection into the fluid pressure braking system to apply fluid pressure to the left-hand side of the diaphragm to deflect it against a push plate 8 mounted on the inward end of a push rod 9 the outer end of which is threaded for connection to a brake linkage.The region 10 to the right of the diaphragm is vented via an aperture 11 and a light return spring 12 is retained between the housing part 1 and the push plate 8 for returning the push rod to the position shown on the release of pressure. Mounting studs 13 are provided on the housing part 1 for mounting to the chassis of the vehicle.

As foreshadowed in the foregoing, it will be seen that the bead 3 of the diaphragm thickens outwardly from the flexible portion 4 for positive retention between the flanges of the housing against the inward operating tension inserted by the diaphragm. The effect of outward thickening is that if the diaphragm bead tends to flow outwardly under the effect of clamping forces and especially in the region of the clamping bolt 7 this flow is relatively unrestrained and can introduce leakage and at least partial failure of the actuator.

Referring to Fig. 2, in accordance with the invention, it is proposed that a diaphragm such as 21 which again has an outwardly thickening bead 22 and in addition to overall fabric reinforcement 25 is provided with a continuous annular reinforcement wire 23 moulded into the bead which restrains the bead against outward flow under clamping conditions in an actuator such as shown in Fig. 1. The clamping faces of the diaphragm are provided with annular upstands 24 which permit of good ceiling conditions by allowing for imperfections of the moulding or the flanges of the housing.

Referring to Fig. 3, the diaphragm shown therein is substantially the same as the diaphragm of Fig. 2 to the extent that it is provided with a fabric reinforcement 35 upstands 34 but the outer periphery of the bead 32 is provided with a groove which extends continuously there around and prior to assembly of the diaphragm into an actuator such as shown in Fig. 1, an annular reinforcement ring 33 is slipped over the bead and on clamping of the diaphragm between the flanges of the actuator this bead comes under tension due to the tendency for outward flow thereby constraining the bead of the diaphragm into a uniform condition all around the flanges of the housing.

Referring to Fig. 4, this shows a part sectional view of a portion of an actuator with two housing parts 40 and 41 with flanges 42 and 43 respectively, between which a bead 44 of a diaphragm 45 is clamped by means of a clamping ring 46, the bead of the diaphragm 44 is constrained in this embodiment against outward movement under clamping conditions by virtue of the provision of a thickened heel 47 of the diaphragm material which acts inwardly of the flanges of the housing.

In Fig. 5 again the sectional view shown therein includes part of the first part 50 and a second part 51 of the housing of an actuator with respective flanges 52 and 53 between which a bead 54 of a diaphragm 55 is clamped by a clamping ring 56.

In this particular actuator, the flange 52 of the second part 51 of the actuator is provided on its clamping face with an annular upstand 57 which under clamping conditions impresses into the material of the bead and thereby restrains the bead against outward flow. As shown in Fig. 6 moreover, the flange 62 of one part and the flange 63 of the other part of the housing of such an actuator may each be provided with respective upstands 67 and 68 to further enhance the restraint exerted upon the bead of the diaphragm against outward flow under clamping conditions.

Referring to Fig. 7, yet another alternative arrangement for restraining the outward flow of the bead of such a diaphragm is provided by virtue of the outer edge of the flange 72 of the one part 71 of the actuator housing being extended in a direction such that under clamping conditions it passes at least partially around the outside edge of the bead of the diaphragm to thereby constrain the material of the bead of the diaphragm against outward flow under clamping conditions. Again, in Fig. 8 both the flange 82 of the part 81 and the flange 83 of the part 80 are provided with respective extensions 87 and 88 which under clamping conditions act to restrain the material of the bead of the diaphragm against outward flow.

Whilst in the arrangements of Fig. 5 and Fig. 6, the up-stands 57 or 67 and 78 respectively are continuous annular up-stands extending continuously around the respective flanges, these up-stands may be discontinuous if required whilst still providing for restraint of the outward flow of the material of the diaphragm under clamping conditions. Furthermore, although it is envisaged that the up-stands 57 or 67 and 68 respectively merely impress the clamp surfaces of the bead of the diaphragm, these up-stands may be made of a sharp configuration such as to actually impale the surface of the diaphragm under clamping conditions and thereby positively engage the bead of the diaphragm between the flanges of the housing. Again, the bead may alternatively be provided with moulded in grooves or apertures to receive such up-stands provided on the, or each, adjacent clamping part.

Claims

1. A fluid pressure operable diaphragm actuator having a housing and a diaphragm which has a central portion, an intermediate flexible portion and a peripheral bead for retention by clamping between flange parts of the housing, said bead having a thickness which increases radially outwardly but restraining means being provided which is distributed substantially entirely around the bead counteracting outward flow thereof under compression.

2. A fluid pressure operable diaphragm actuator as claimed in claim 1, said bead being provided with a moulded in reinforcement extending substantially continuously there around.

3. A fluid pressure operable diaphragm actuator as claimed in claim 1, said bead being provided with a continuous reinforcing band around the periphery thereof.

4. A fluid pressure operable diaphragm actuator as claimed in Claim 3, said reinforcing band being retained in a groove around said periphery.

5. A fluid pressure operable diaphragm actuator as claimed in Claim 1, said restraining means comprising a thickened portion of the diaphragm inward of the bead.

6. A fluid pressure operable diaphragm actuator as claimed in claim 1, the restraining means comprising one or more up-stands distributed around at least one of the flange parts to enter the respective face of the bead.

7. A fluid pressure operable diaphragm actuator as claimed in claim 1, the restraining means comprising distributed around the periphery of the bead an extension of at least one said bead.

8. A fluid pressure operable diaphragm actuator substantially as described herein with reference to Fig. 1 and Fig. 2 or Fig 3 or Fig. 4 or Fig. 5 or Fig. 6 or Fig. 7 or Fig. 8 of the accompanying drawings.