GB2158515A

GB2158515A - Improvements to actuators

Info

Publication number: GB2158515A
Application number: GB08508330A
Authority: GB
Inventors: Brian P Neal
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1984-05-05
Filing date: 1985-03-29
Publication date: 1985-11-13
Also published as: GB8411573D0; GB2158515B; GB8508330D0

Abstract

A spring-operated actuator having a housing containing piston (1) movable by compressed air in a cylinder (2) against the force of a spring 4 retained in the housing by cover (5) and a circlip 8 in a groove 7 has a two part retaining clip 10 with portions which act between the ends of the circlip in the groove and against the face of the circlip for preventing the circlip working its way out of the groove during cycling of the actuator. <IMAGE>

Description

SPECIFICATION Improvements to Actuators This invention relates to actuators and relates especially but not exclusively to spring-brake actuators for vehicles.

Certain types of vehicle brake actuators, known as spring brake actuators comprise a piston in a cylinder which is urged by compressed air into a brake release position against the force of a heavy spring. A brake application is produced by a reduction of the air pressure supplied by a control valve to the piston. In one form of such actuator the heavy spring is housed in a generally cylindrical body retained in the end of the cylinder by an internal circlip. Removal of this circlip is extremely difficult and hazardous without mounting the assembly in a jig to constrain the action of the heavy spring. Nevertheless, unless strict dimensional tolerances are observed it has been found that in operation the circlip can tend to progressively work its way out of its retaining groove over a large but indeterminate number of operating cycles of the actuator.The invention therefore has an object of providing an effective but inexpensive addition to an actuator for preventing this happening.

According to the invention there is provided an actuator comprising a fluid pressure responsive member and a heavy spring contained under compression in a housing the force of the spring being contained by a closure member of said housing which is retained in position by an internal circlip in a groove and a retaining part having a first portion acting between ends of the circlip to prevent movement of the ends towards one another.

Preferably the retaining means also includes portions acting towards the face of the circlip to oppose twisting movement thereof away from the circlip groove.

In order that the invention may be clearly understood and readily carried into effect, the same will be further decribed by way of example with reference to the accompanying drawings of which: Fig. 1 illustrates in part-sectional view part of an actuator together with retaining means for an internal circlip, Fig. 2 illustrates at A and B front and side view of part of the retaining means of Fig. 1 and, Fig. 3 at A and B illustrates upward and front view of another part of the retaining means.

Referring to Fig. 1 an air pressure operable actuator has a pressure responsive member in the form of a piston 1 slideable in the bore 2 of a cylinder 3. The actuator operates by means of a sealingly slideable tubular rod (not shown) connected to the piston. The piston 1 is acted upon by a heavy coil spring indicated by reference 4 and this spring is retained in the end of the cylinder by means of a cup-shaped closure member 5 having an annular flange 6 held which it is retained in position against the action of the spring 4 by circlip 8 located in an internal groove 7 in the end of the cylinder 2.

The actuator is assembled by mounting the cylinder 3 and the closure member 5 in a suitable jig to enable the spring 4 to be so sufficiently compressed that the flange 6 rests on a shoulder 9 following which the circlip can be compressed and allowed to spring into position in the groove 7.

In order to retain the circlip 8 in the required position in the groove 7 a retaining means is additionally provided by the invention. The retaining means comprises a first pressed steel part 10 and a second pressed steel part 11 which cooperates with a welded-in stud 17 of part 10 and a nut 20 to retain the part 10 in position. The part 11 is shown in two views in Fig. 2 and the part 10 is shown in two views in Fig. 3 respectively. The retaining part 10 has an outwardly projecting portion comprising a tongue 13 profiled to match the base of the groove 7 and flanks 13 which with 10 in position are abutable by the ends of the circlip in the event of any tendency for these ends to move together.The part 10 also has two outwardly directed projections 14 in a displaced plane which rest against the outer flat face of the circlip 8 in a sense to resist a possible tendency for the circlip to twist out of the groove 7 during operating cycles of piston 1 and spring 4. A recess 15 is provided into which the countersunk head of a bolt providing stud 17 is welded and a flange 16 co-operates with the inner surface of a similar flange 18 of the further part 11. Corners of 11 are bent at right angles thereto to form supporting legs against the outer wall of the cylinder as shown.

The clamping nut 20 is provided on stud 17 to assemble the retaining means to the actuator. When screwed home nut 20 has its hexagon 21 arranged to break off at a thin neck 22 so that the nut 20 is not then readily removable. Preferably, the nut 20 is also provided with a suitable helical inter-thread locking element for preventing inadvertent loosening by vibration or movement after assembly.

1.An actuator comprising a fluid pressure responsive member and a heavy spring contained under compression in a housing the force of the spring being contained by a closure member of said housing which is retained in position by an internal circlip in a groove and a retaining part having a first portion acting between ends of the circlip to prevent movement of the ends towards one another.

2. An actuator as claimed in claim 1, said part also having further portions acting towards the circlip face to oppose movement thereof away from the groove.

3. An actuator as claimed in claim 1 and claim 2 said retaining means comprising a sheet metal member whereof said first portion comprises a tongue in a plane displaced from said further portions.

4. An actuator as claimed in claim 1,2 or 3 said retaining means having a further part shaped to bear against an outer surface of the housing and clamping means co-operable therewith to clamp the first part in position.

5. An actuator as claimed in claim 4, said clamping means comprising a stud of the first part passing through the further part and provided with a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements to Actuators This invention relates to actuators and relates especially but not exclusively to spring-brake actuators for vehicles. Certain types of vehicle brake actuators, known as spring brake actuators comprise a piston in a cylinder which is urged by compressed air into a brake release position against the force of a heavy spring. A brake application is produced by a reduction of the air pressure supplied by a control valve to the piston. In one form of such actuator the heavy spring is housed in a generally cylindrical body retained in the end of the cylinder by an internal circlip. Removal of this circlip is extremely difficult and hazardous without mounting the assembly in a jig to constrain the action of the heavy spring. Nevertheless, unless strict dimensional tolerances are observed it has been found that in operation the circlip can tend to progressively work its way out of its retaining groove over a large but indeterminate number of operating cycles of the actuator.The invention therefore has an object of providing an effective but inexpensive addition to an actuator for preventing this happening. According to the invention there is provided an actuator comprising a fluid pressure responsive member and a heavy spring contained under compression in a housing the force of the spring being contained by a closure member of said housing which is retained in position by an internal circlip in a groove and a retaining part having a first portion acting between ends of the circlip to prevent movement of the ends towards one another. Preferably the retaining means also includes portions acting towards the face of the circlip to oppose twisting movement thereof away from the circlip groove. In order that the invention may be clearly understood and readily carried into effect, the same will be further decribed by way of example with reference to the accompanying drawings of which: Fig. 1 illustrates in part-sectional view part of an actuator together with retaining means for an internal circlip, Fig. 2 illustrates at A and B front and side view of part of the retaining means of Fig. 1 and, Fig. 3 at A and B illustrates upward and front view of another part of the retaining means. Referring to Fig. 1 an air pressure operable actuator has a pressure responsive member in the form of a piston 1 slideable in the bore 2 of a cylinder 3. The actuator operates by means of a sealingly slideable tubular rod (not shown) connected to the piston. The piston 1 is acted upon by a heavy coil spring indicated by reference 4 and this spring is retained in the end of the cylinder by means of a cup-shaped closure member 5 having an annular flange 6 held which it is retained in position against the action of the spring 4 by circlip 8 located in an internal groove 7 in the end of the cylinder 2. The actuator is assembled by mounting the cylinder 3 and the closure member 5 in a suitable jig to enable the spring 4 to be so sufficiently compressed that the flange 6 rests on a shoulder 9 following which the circlip can be compressed and allowed to spring into position in the groove 7. In order to retain the circlip 8 in the required position in the groove 7 a retaining means is additionally provided by the invention. The retaining means comprises a first pressed steel part 10 and a second pressed steel part 11 which cooperates with a welded-in stud 17 of part 10 and a nut 20 to retain the part 10 in position. The part 11 is shown in two views in Fig. 2 and the part 10 is shown in two views in Fig. 3 respectively. The retaining part 10 has an outwardly projecting portion comprising a tongue 13 profiled to match the base of the groove 7 and flanks 13 which with 10 in position are abutable by the ends of the circlip in the event of any tendency for these ends to move together.The part 10 also has two outwardly directed projections 14 in a displaced plane which rest against the outer flat face of the circlip 8 in a sense to resist a possible tendency for the circlip to twist out of the groove 7 during operating cycles of piston 1 and spring 4. A recess 15 is provided into which the countersunk head of a bolt providing stud 17 is welded and a flange 16 co-operates with the inner surface of a similar flange 18 of the further part 11. Corners of 11 are bent at right angles thereto to form supporting legs against the outer wall of the cylinder as shown. The clamping nut 20 is provided on stud 17 to assemble the retaining means to the actuator. When screwed home nut 20 has its hexagon 21 arranged to break off at a thin neck 22 so that the nut 20 is not then readily removable. Preferably, the nut 20 is also provided with a suitable helical inter-thread locking element for preventing inadvertent loosening by vibration or movement after assembly. CLAIMS

5. An actuator as claimed in claim 4, said clamping means comprising a stud of the first part passing through the further part and provided with a clamping nut.

6. An actuator as claimed in claim 1 when the clamping nut has a twist-off hexagon.

7. An actuator substantially as described herein with reference to Figs. 1,2 and 3 of the accompanying drawings.