GB1590861A - Hydraulic actuators - Google Patents

Description

(54) HYDRAULIC ACTUATORS (71) We, AUTOMOTIVE PRODUCTS LIM ITED, a British Company of Tachbrook Road, Leamington Spa, Warwickshire, CV3 1 3ER, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to hand operable actuators for hydraulic brake systems of the type utilised in motor cycle hydraulic systems and is a development of the matter disclosed in our Patent No.

1,536,353.

Accordingly there is provided a hand operable hydraulic actuator as claimed in Claim 1 of the Complete Specification of the above number in which the master cylinder piston comprises two parts, a central part fixed to the piston operating rod and an annular floating part slidably fitted on the rod and having a fluid passageway therebetween, and operation of the hand lever moves the central part so as to close the passageway and then moves the piston to displace hydraulic fluid, wherein the floating part comprises a flat annular washer which is sealed against the bore by an annular ring seal located on the high pressure side of the flat washer. Annular ring seals of this type is as a 'Baldwin' seal.

Also there is provided a second improvement which depends from Claim 2 of the Complete Specification of the above number, in which the support is formed with a bracket having an abutment surface for fitting against the handlebar, and the master cylinder bore is orientated so that its logitudinal axis is at an acute angle to the abutment surface.

Preferably the annular washer provides the location and bearing surface for the axial movement of the central part of the piston in the larger diameter portion of the bore.

The invention will now be described by way of example and with reference to the following drawings in which: Fig. 1 is a sectional view of an actuator for a hydraulic brake system; Fig. 2 is a detail drawing of the pistons and seals used in Fig. 1; and Fig. 3 is a cross-section on the line Ill-Ill in Fig. 2.

With reference to Fig. 1, Fig. 2 and Fig. 3, the actuator for the hydraulic brake system is a hand operable pull-type brake actuator for mounting on the handlebars (not shown) of a motor cycle.

The master cylinder 11, fluid reservoir 12, and bracket 13 are all formed as a single integral unit, either as an aluminium diecasting, or a plastics moulding from, for example glass-fibre filled nylon 66.

The bracket 13 provides an abutment surface 14 for mounting the brake actuator onto the handlebars (not shown) of a motor cycle, and it also provides the support for a lever 15 which pivots about a pivot pin 16 mounted on the bracket 13. The lever 15 is arranged so that in its brakes-off position it lies substantially parallel to the handlebars, and the brakes are then applied by moving the lever 15 about the pin 16, such that the lever moves towards the handlebars (in the direction of arrow X).

The master cylinder 11 is formed in the integral unit and has a stepped blind bore 17, the mouth 18 of the bore 17 being towards the pivot pin 16. The longitudinal axis of the bore 17 is at an acute angle to the abutment surface 14 whilst still lying in substantially the same plane as the handlebars. A piston head 19 is sealingly slidable within the bore 17 in the direction of the mouth 18 and is connected through an axial rod 21 to the lever 15. The axial rod 21 sealingly passes through an annular end cap 22 which closes the mouth 18 of the bore 17 and the end portion 23 of the rod 21 is pivotally connected to one end portion of a link member 24, the other end of which is connected by a pivot pin 25 to the lever 15. The pivot pin 25 is positioned so that when the brakes are applied the pivot pin 25 moves away from the mouth 18 of the bore 17.

A torsion type spring 26 acts between an abutment 27 provided on the bracket 13 and the pivot pin 25 so as to return the lever 15 to its brakes-off position. The lever 15 will return until it abuts against surface 28 provided on the side of the master cylinder II.

The piston head 19 is slidable within the stepped bore 17. The piston head 19 as shown in Fig. 2 comprises two parts, a central part 29 fixedly connected to the rod 21 and a floating part 30 in the form of an annular washer. The stepped bore 17 consists of a smaller diameter end portion 31 adjacent the blind end of the bore and a larger diameter portion 32 which constitutes the major portion of the bore 17 and extends from the smaller diameter end portion 31 to the mouth 18. A shoulder 33 is formed between the two different diameter portions of the bore.

The central part 29 is substantially an annular cup and is firmly attached to a smaller diameter end portion 34 of the rod 21, and is non sealingly slidable in the smaller diameter end portion 31 of the bore 17. The - mouth of the cup faces towards the mouth 18 of the bore and holds an annular rubber seal 35 which lies a little proud of the walls of the cup and also grips that portion of the rod 21 which it surrounds. The seal 35 also abuts a shoulder 36 on the rod 21 formed between the smaller diameter end portion 34 and the rest of the rod 21.

The floating washer 30 is located between the fixedly connected central part 29 and the mouth 18 of the bore 17 and is slidable within the larger diameter portion 32 of the bore and is urged against the shoulder 33 by a compression spring 37. The washer 30 is a slide fit upon the rod 21 which has diametrically opposed flats 38 on the rod 21 to provide two passageways 44 for the fluid. An annular seal 39 of the type known as a "Baldwin" seal is a loose fit on the rod 21 and seals the washer 30 against the wall of the bore 17 when the piston head moves towards the mouth 18 and the fluid in the actuator becomes pressurised. The annular seal 39 is held against the piston 30 by the compression spring 37. A loose fit washer 40 transmits the load in the spring 37 to the seal 39.The other end of the spring 37 is acting upon another seal 45, which seals the passage of the rod 21 through the end cap 22, so as to maintain the seal 45 in position. The end cap 22 is held in position by a circlip 41 and the entry of dust into the master cylinder 11 is prevented by a boot 42.

To apply the brakes, the lever 15 is pivoted about the pin 16, to move the lever in the direction of arrow X. This moves the pivot pin 25 away from the mouth of the bore 18 and hence moves the central part 29 of the piston head 19 from the blind end of the bore and into abutment with the washer 30, (as shown in Fig. 2) the seal 35 then seals against the back face of the washer 30 thus cutting off the passageways 44. Further movement of the central part 29 towards the mouth 18, causes the washer 30 to move away from the shoulder 33, and the annular seal 39 is forced, by hydraulic pressure acting on its inner periphery, against the walls of the bore 17. The piston 30 also now acts to locate the central part 29 in the larger diameter bore and as a bearing for the rod 21.Thus movement of piston head 19 towards the mouth of the bore 18 displaces hydraulic fluid from the master cylinder 11 via a port 43 into the hydaulic brake system. Brake fluid is fed from theyeservoir to the unpressurised side of the piston head.

When the brakes are released the spring 26 returns the lever 15 to its original position.

This moves the central part 29 back into the smaller diameter portion 31 of the bore 17.

The washer 30 and seal 39 are returned by the spring 37 so that the washer 30 rests against the shoulder 33. Further movement of central part 29 towards the blind end of the bore continues until either the end of the rod 21 abuts the end wall of the bore 17 or the lever 15 abuts the abutment 28. The brake system can now recuperate, the brake fluid flowing from the blind end of the bore around the non-sealable central part 29, and into the axial gap between the two parts 29 and 30.

Fluid then flows through the passageway 44 between the flat 38 and the inner peri phery of the washer 30, and along the flats to the pressurable side of the master cylinder.

WHAT WE CLAIM IS: 1. A hand operable hydraulic actuator as claimed in Claim 1 of the Complete Specification, Patent No. 1,536,353 and in which the master cylinder piston comprises two parts, a central part fixed to the piston operating rod and an annular floating part slidable fitted on the rod and having a fluid passageway therebetween, and operation of the hand lever moves the central part so as to close the passageway and then moves the piston to displace hydraulic fluid, wherein the floating part comprises a flat annular washer which is sealed against the bore by an annular ring seal located on the high pressure side of the flat washer.

2. A hand operable actuator as claimed in Claim 1, above, and in Claim 2 of the Complete Specification, Patent No. 1,536,353 wherein the support is formed with a bracket having an abutment surface for fitting against the handlebar, and the master cylinder bore is orientated so that its logitudinal axis is at an acute angle to the abutment surface.

3. A hand operable hydraulic actuator as claimed in Claims 1 or 2, wherein the annular washer provides a location and bearing surface for movement of the central part relative to the bore of the actuator.

4. A hand operable hydraulic actuator as claimed in anyone of Claims 2 or 3, wherein

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. provided on the side of the master cylinder II. The piston head 19 is slidable within the stepped bore 17. The piston head 19 as shown in Fig. 2 comprises two parts, a central part 29 fixedly connected to the rod 21 and a floating part 30 in the form of an annular washer. The stepped bore 17 consists of a smaller diameter end portion 31 adjacent the blind end of the bore and a larger diameter portion 32 which constitutes the major portion of the bore 17 and extends from the smaller diameter end portion 31 to the mouth 18. A shoulder 33 is formed between the two different diameter portions of the bore. The central part 29 is substantially an annular cup and is firmly attached to a smaller diameter end portion 34 of the rod 21, and is non sealingly slidable in the smaller diameter end portion 31 of the bore 17. The - mouth of the cup faces towards the mouth 18 of the bore and holds an annular rubber seal 35 which lies a little proud of the walls of the cup and also grips that portion of the rod 21 which it surrounds. The seal 35 also abuts a shoulder 36 on the rod 21 formed between the smaller diameter end portion 34 and the rest of the rod 21. The floating washer 30 is located between the fixedly connected central part 29 and the mouth 18 of the bore 17 and is slidable within the larger diameter portion 32 of the bore and is urged against the shoulder 33 by a compression spring 37. The washer 30 is a slide fit upon the rod 21 which has diametrically opposed flats 38 on the rod 21 to provide two passageways 44 for the fluid. An annular seal 39 of the type known as a "Baldwin" seal is a loose fit on the rod 21 and seals the washer 30 against the wall of the bore 17 when the piston head moves towards the mouth 18 and the fluid in the actuator becomes pressurised. The annular seal 39 is held against the piston 30 by the compression spring 37. A loose fit washer 40 transmits the load in the spring 37 to the seal 39.The other end of the spring 37 is acting upon another seal 45, which seals the passage of the rod 21 through the end cap 22, so as to maintain the seal 45 in position. The end cap 22 is held in position by a circlip 41 and the entry of dust into the master cylinder 11 is prevented by a boot 42. To apply the brakes, the lever 15 is pivoted about the pin 16, to move the lever in the direction of arrow X. This moves the pivot pin 25 away from the mouth of the bore 18 and hence moves the central part 29 of the piston head 19 from the blind end of the bore and into abutment with the washer 30, (as shown in Fig. 2) the seal 35 then seals against the back face of the washer 30 thus cutting off the passageways 44. Further movement of the central part 29 towards the mouth 18, causes the washer 30 to move away from the shoulder 33, and the annular seal 39 is forced, by hydraulic pressure acting on its inner periphery, against the walls of the bore 17. The piston 30 also now acts to locate the central part 29 in the larger diameter bore and as a bearing for the rod 21.Thus movement of piston head 19 towards the mouth of the bore 18 displaces hydraulic fluid from the master cylinder 11 via a port 43 into the hydaulic brake system. Brake fluid is fed from theyeservoir to the unpressurised side of the piston head. When the brakes are released the spring 26 returns the lever 15 to its original position. This moves the central part 29 back into the smaller diameter portion 31 of the bore 17. The washer 30 and seal 39 are returned by the spring 37 so that the washer 30 rests against the shoulder 33. Further movement of central part 29 towards the blind end of the bore continues until either the end of the rod 21 abuts the end wall of the bore 17 or the lever 15 abuts the abutment 28. The brake system can now recuperate, the brake fluid flowing from the blind end of the bore around the non-sealable central part 29, and into the axial gap between the two parts 29 and 30. Fluid then flows through the passageway 44 between the flat 38 and the inner peri phery of the washer 30, and along the flats to the pressurable side of the master cylinder. WHAT WE CLAIM IS:

1. A hand operable hydraulic actuator as claimed in Claim 1 of the Complete Specification, Patent No. 1,536,353 and in which the master cylinder piston comprises two parts, a central part fixed to the piston operating rod and an annular floating part slidable fitted on the rod and having a fluid passageway therebetween, and operation of the hand lever moves the central part so as to close the passageway and then moves the piston to displace hydraulic fluid, wherein the floating part comprises a flat annular washer which is sealed against the bore by an annular ring seal located on the high pressure side of the flat washer.

2. A hand operable actuator as claimed in Claim 1, above, and in Claim 2 of the Complete Specification, Patent No. 1,536,353 wherein the support is formed with a bracket having an abutment surface for fitting against the handlebar, and the master cylinder bore is orientated so that its logitudinal axis is at an acute angle to the abutment surface.

3. A hand operable hydraulic actuator as claimed in Claims 1 or 2, wherein the annular washer provides a location and bearing surface for movement of the central part relative to the bore of the actuator.

4. A hand operable hydraulic actuator as claimed in anyone of Claims 2 or 3, wherein

the fluid path between the rod and the floating part is provided by opposing flats on the input rod.

5. A hand operable hydraulic actuator substantially as described herein and as shown in the accompanying drawings.