AU613263B2 - Tool for brake pad installation - Google Patents

Description

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613263 TRALIA COMMONWEALTH OF AUS FORM PATENTS ACT 1952 COMPLETE S PE C I FI CAT ION FOR OFFICE USE: Class Int.Class Application Number: Lodged: o,..omplete Specification Lodged: Accepted: o Published: o o* Priority: °'"Rlated Art: 00 fi o Name of Applicant: TULLIO MASTROIANNI 0 t 'Address of Applicant: S tual Inventor °Atstual Inventor: 89 WILLIAM STREET BROOKVALE N.S.W. 2100, AUSTRALIA TULLIO MASTROIANNI -h- 3 Address for Service: -SffEr-STN-WATERS--55-e-i-a-enc-e-St ee-t-Sydn-ey S11 Scakam Scroo v\c, lol o*-Gmplete Specification for the Invention entitled: "TOOL FOR BRAKE PAD INSTALLATION" The following statement is a full descriptijn of this invention, including the best method of performing it known to me/w:- (Complete of PJ3541 dated 6th April, 1989) 1 S013069 1 4/02/90

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The present invention relates to a tool for brake pad installation and in particular to a tool for manually depressing the actuating piston in a hydraulic disc brake calliper assembly.

The invention has been developed primarily for use with single piston floating calliper disc brake assemblies, and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this ±0 particular application. The device is also applicable to multiple and opposed piston callipers.

When replacing worn friction brake pads in hydraulic disc brake assemblies, it is necessary to retract or depress the actuating piston into the calliper body to allow the fresh replacement brake pads to be inserted.

The amount by which the calliper piston must be retracted corresponds to the total amount by which the brake pads have worn.

SIn practice, due to the pressure characteristics in the hydraulic system, considerable focce must be applied to displace the hydraulic fluid and depress the calliper piston.

SIn the past, this force has usually been applied by means of a G-clamp which is manually positioned over the calliper such that the moveable jaw engages the piston crown and the fixed jaw engages the calliper body behind the piston. The G-clamp is then manually screwed inwardly to depress the piston.

2 However, this known method has several inherent disadvantages. Firstly, the external surface of the calliper body directly behind the piston is usually not flat, but has a convexly contoured portion protruding outwardly so the fixed jaw of the G-clamp engages the calliper body in a condition of relatively unstable equilibrium. It is therefore necessary for the operator to hold the G-clamp in position with one hand while turning the adjusting screw with the other. This l0 operation is particularly awkward and time consuming if the calliper assembly per se must also be manually supported during the operation because of the tendency for the G-clamp to slip out of position.

Furthermore, because the positioning of the G-clamp is partly dependent upon the external shape of the calliper body, in practice, the adjusting screw of the G-clamp is usually not coaxial with or parallel to the piston axis. This can give rise to a twisting force couple acting on the piston and tending to wedge and lock the piston within its bore necessitating repositioning of the G-clamp. Worse still, this can cause mechanical damage such as scoring to the piston surface which may produce leakage in the hydraulic circuit, diminishing performance of the braking system.

The problem is further exacerbated if the piston is completely withdrawn from the calliper unit, for example, after disassembly of the calliper unit for maintenance or repair. In this case, initial alignment of the piston is 3 difficult and the piston is easily misaligned with respect to the bore, often causing damage to the rubber piston seals, the bore or the piston itself. This damage may not be detected immediately, but may go unnoticed until the leaking brake cylinder impairs proper functioning of the braking system which may be potentially hazardous to human life.

It is therefore an object of the present invention to provide a tool which overcomes or substantially i0 ameliorates at least some of the abovementioned problems disadvantages of the prior art.

Accordingly, the invention consists in a tool for depressing an actuating piston in a hydraulic disc brake calliper assembly having a generally U-shaped calliper body and a selectively operable actuating piston engageable with a brake disc, said tool comprising a plunger portion adapted for engagement with said piston, an elongate generally planar abutment plate adapted for engagement with said calliper body and selectively manually operable actuating means to displace the plunger portion and the abutment plate away from one another to cause the piston to be retracted into the calliper body, said abutment plate tapering transversely such that the effective longitudinal extent of one elongate edge is greater than the effective longitudinal extent of the other elongate edge to accommodate callipers of different size.

Preferably, the actuating means comprises a threaded 4

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shaft connected with said plunger portion aw engaging a complementary threaded hole extending througt said abutment plate such that selective rotation of the shaft effects a corresponding axial displacement of the plunger towards or away from the abutment plate.

Preferably the abutment plate is generally "dovetailed" in shape, having a shorter longitudinal edge and tidering uniformly to a longer parallel longitudinal edge. This feature provides the advantage that the I3 orientation of the abutment plate can be reversed to accommodate larger calliper assemblies.

The actuating means preferably includes a handle in the form of a generally cylindrical knurled knob connected with the adjustment shaft.

Preferably also, the handle includes a protruding head portion comprising a plurality of flat faces and engageable with a complementary sozket sp ,ner to permit the application of increased torque to the adjustment shaft if require.

S 20 Preferably also, a number of interchangeable plunger portions are provided for use with pistons of different i size and configuration such as pistons of the screw-retracting type.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing which is a partly sectioned cutaway perspective view showing a tool according to the invention in position on a typical hydraulic disc brake 5 calliper assembly.

Referring to the drawing, a single cylinder free floating hydraulic disc brake calliper assembly 1 includes a generally U-shaped calliper body 2 defining a longitudinally extending centrally spaced throat region 3. The calliper 1 further includes a hydraulically operable actuating piston 4 axially slidable within a hydraulic cylinder 5 formed in the calliper body 2. The body 2 includes a back plate 6 opposing the piston 4 and ±0 having a generally U-shaped cutout opening 7 which is generally aligned with piston 4 and cylinder 5. The back plate 6 and piston 4 respectively support mutually opposed fixed and moveable friction brake pads (not shown) in the conventional manner.

In use, actuation of the piston 4 urges the moveable piston brake pad into sliding frictonal engagement with the brake disc (not shown) rotating in rhroat region 3 intermediate piston 4 and back plate 6. Further displacement of the piston causes a reaction force which draws the free floating calliper assembly 1 transversely across the brake disc until the fixed brake pad associated with back plate 6 is also urged into sliding frictional engagement with the brake disc. Further pressure increase in the hydraulic cylinder tends to displace the piston giving rise to a clamping force between the brake pads and the brake disc to effect frictional braking of the vehicle in a manner well kno 1 to those skilled in the art.

6 With use, the brake pads become t .essively worn and must be periodically replaced. In order to accommodate the increased width of the fresh replacement pads, the calliper piston 4 must be depressed into the calliper body by a corresponding total amount, which may be typically of the order of 10mm to Accordingly, the tool 10 includes a threaded adjustment shaft 11 which extends through a complementary threaded hole 12 in elongate abutment plate 13 co JoPD terminate in a plunger portion 14 adapted for engagement o 0o with recessed piston crown 0 0 Q o The elongate abutment plate 13 is generally dovetailed in shape and is adapted to span the cutout o I opening 7 and engage the surface of calliper back plate 6 adjacent the cutout opening. In this way, the adjustment shaft 11 extends through threaded hole 12, through opening 7 to terminate at its remote end in handle means in the form of a knurled cylindrical knob. The handle 16 includes a protruding hexagonal head portion 17 engageable with a complementary socket spanner (not shown) to permit the application of increased torque to the adjustment shaft if require. The handle may also include an elongate extension lever 18 to provide additional leverage.

Turning now to describe the operation of the tool to replace brake pads, the worn pads are first removed to expose piston 4 and back plate 6. The adjustment shaft 11 of tool 10 is then screwed outwardly by handle 16 7 until the distance between plunger 14 and abutment plate 13 is reduced sufficiently to enable the tool to be located in the operative position in throat region 3 intermediate piston 4 and back plate 6 as shown in the drawing.

Adjustment shaft 11 is then screwed progressively inwardly by means of handle 16 to displace the plunger and abutment plate away from one another until the plunger 14 engages recessed piston crown 15 and the outer O-k0 surfaces of abutment plate 13 engage the calliper back plate 6. Further rotation of the adjustment shaft will o displace the hydraulic fluid in the cylinder and cause o0 0C the piston to be progressively depressed into the calliper body as the resultant force is reacted against ooao the back plate 6. The tool is then removed and fresh repacement brake pads fitted. It will be appreciated -0o that the tool can also be used with the brake pad CO associated with the piston still in position in the 01 4 calliper. In this case, the plunger portion bears directly against the brake pad to depress the piston.

The abutment plate 13 includes a locating protrusion 20 extending vertically downwardly from the lower edge thereof to abut bridge portion 21 of the calliper body and locate plate 13 vertically with respect to the back plate. The locating protrusion also engages the surface of back plate 6 directly below cutout opening 7 to provide stability of the plate 13 over the opening and an increased area of surface contact to prevent unstable 8 T~ L_,c rocking of the abutment plate on the back plate 6.

For larger calliper assemblies, where the opening 7 extends further than the extent of the shorter longitudinal edge of the abutment plate, the plate 13 can i be inverted so that the longer longitudinal edge which fully spans the opening 7 is lowermost relative to the back plate to provide a more stable operating configuration.

The tool can also be used when assembling a brake calliper unit for example, following maintenance or repair when the piston would be completely removed from the calliper. In this case, the initial alignment of the piston relative to the cylinder bore is critical if damage to the rubber seal or the piston is to be avoided. The tool of the present invention is particularly suitable for this application, because it provides a uniform, steady force, coaxial with the piston Sand bore, thereby eliminating or minimising any twisting force couple tending to wedge and lock the piston within the bore. This represents a substantial improvement over the prior art.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

For example, the tool may be adapted for use with multiple cylinder or multiple piston callipers. In addition, the plunger may be in the form of a keyed head 9 ;-II to rotatingly engage calliper pistons of the screw-retraction type.

Furthermore, the abutment plate need not be dovetail in shape, but could be semi-circular, semi-ovaloidal, trapezoidal or triangular for example.

It will also be appreciated that the manually operable means need not be a threaded shaft, but could comprise any other form of mechanical linkage arrangement such as a "pliers" mechanism or a four bar link mechanism.

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Claims (10)

1. 2. A tool according to claim 1 wherein said actuating means comprises a threaded shaft connected with said plunger portion and engaging a complementary threaded hole extending through said abutment plate such that selective rotation of the shaft effects a corresponding axial displacement of the Dlunger towards or away from 2 the abutment plate.
2. 3. A tool according to claim 1 or claim 2 wherein the abutment plate defines a trapezium and said elongate edges are generally parallel.
3. 4. A tool according to claim 1 or claim 2 wherein said abutment plate defines a dovetail configuration, 11 A tool according to claim 1 or claim 2 wherein said abutment plate defines a segment of a circle.
4. 6. A tool according to'claim 1 or claim 2 wherein said abutment plate is semi-ovaloidal in configuration.
5. 7. A tool according to claim 1 or claim 2 wherein said abutment plate is triangular.
6. 8. A tool according to any one of claims 2 to 7 wherein the end of said shaft remote from said plunger terminates in handle means.
7. 9. A tool according to claim 8 wherein said handle means comprises a generally cylindrical knurled knob. A tool according to claim 8 or claim 9 wherein said handle means includes an outwardly protruding head portion comprising a plurality of flat "aces adapted for engagement with a complementary spanner.
8. 11. A tool according to any one of the preceding claims wherein said plunger is electively releasable. S 12. A tool according to claim 11 further adapted to receive any one of a plurality of selectively interchangeable plungers of different configurations. |I 13. A tool according to any one of claims 8 tC 12 wherein said handle is adapted to receive an elongate extension lever to facilitate the application of torque.
9. 14. A tool according to any one of the preceding claims wherein said abutment plate includes a centrally disposed locating protrusion extending outwardly from one of said elongate edges to engage a bridge portion of the calliper body and thereby provide positive location for the abutment plate. 12 A tool according to any one of the preceding claims wherein said plunger comprises a keyed head to rotatingly engage a calliper piston of the screw retraction type.
10. 16. A tool for depressing an actuating piston in a hydraulic disc brake cElliper assembly having a generally U-shaped calliper body and a selectively operable actuating piston, said tool being substantially as hereinbefore described with reference to the accompanying drawings. DATED this 14th day of February, 1990 TULLIO MASTROIANNI Attorney: LEON K. ALLEN Fellow Institute of Patent Attorneys of Australia 13 L 49780/90 A A W