EP1020255A2

EP1020255A2 - Tool for use in replacing the pads of disk brakes

Info

Publication number: EP1020255A2
Application number: EP99830812A
Authority: EP
Inventors: Menicalli Mauro
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-01-08
Filing date: 1999-12-30
Publication date: 2000-07-19
Also published as: ITFI990004A1; ITFI990004A0; IT1309993B1; EP1020255A3

Abstract

The tool comprises a pair of tapered spreader elements (11, 13) which are integral, respectively, with the piston (15) and with the cylinder (17) of an air jack (19); guide means (11B, 13B) keep the elements (11, 13) facing each other in the same angular position with respect to each other.

Description

The caliper of a disk brake generally comprises two friction pads which are located on opposite sides so that they almost touch the faces of a brake disk and are easily replaceable by extraction and insertion radially with respect to the brake disk. The caliper can be fixed or floating, in other words free to move orthogonally to the faces of the disk; in the first case, each pad is provided with a corresponding hydraulic operating cylinder and piston unit to press it against the disk during braking, while in the second case a single cylinder and piston unit is sufficient to operate both pads simultaneously. Additionally, the caliper of a brake can be provided with a manual operating system using a linkage provided with cables and return levers, in addition to the hydraulic braking. In this case, the caliper is of the floating type and comprises a known wear take-up device by means of which the configuration of said linkage is not affected by the wear of the pads. When the pads are replaced, this device has to be reset to zero by rotating the operating piston of the pads through several revolutions about its axis.
The pads become thinner as a result of wear, and have to be replaced periodically. This operation can be carried out without removing the brake caliper from the vehicle, provided that the operating piston or pistons of the pads are moved back into their housings; otherwise the space available is not sufficient for the insertion of the new pads between the corresponding pistons and the disk.
The present invention relates to a tool for use in replacing the pads of disk brakes of motor vehicles, for moving the operating piston or pistons of the pads back into their housings without removal of the relevant caliper. The tools generally used for this task are provided with at least one tapered spreader which can be inserted between the front face of the piston to be made to move back and the disk of the brake, and a manual system of the lever or screw type, for operating said spreader element. These known tools are generally rather impractical since they require the use of both hands of the operator who is frequently in an awkward working position and who needs at least one hand free to offer up the new pads and insert them into their housings. Furthermore, these tools are poorly adaptable to vehicles of different types, possibly produced by different manufacturers, especially when the tools are used with brakes provided with the wear take-up system for manual brake operation.
The tool according to the invention comprises a pair of tapered spreader elements which can be inserted from opposite sides of the disk against the front surfaces of the operating pistons of the pads. One of these spreader elements is integral with the piston and the other is integral with the cylinder of an air jack, and guide means are provided to keep the elements facing each other in the same angular position with respect to each other.
Preferably, the cylinder of the jack is provided, at the point where the rod emerges, with a low-friction bush to facilitate the sliding of the rod even when there is a force out of alignment with the rod, said bush possibly being, for example, of the ball-bearing type for axial sliding. The bush may conveniently be inserted in a sleeve fitted to said end of the cylinder, and the spreader element integral with the cylinder is actually fixed to said sleeve.
Said guide means may comprise a channel formed in the element integral with the cylinder, and a bar fixed at one end to the spreader element which is integral with the rod, the bar being extended parallel to the axis of the rod and inserted slidably into said channel.
In a preferred embodiment, the tool comprises a two-way valve and a discharge valve, for the operation of the jack and for the discharge of the pressure within it respectively, so that the distance between the tapered elements can be adapted to the type of brake to be repaired without the need to overcome any pressure which may be present in the jack.
In a possible embodiment, in order to make the tool compact, the cylinder of the jack acts as a handle and the said valves are integral with the cylinder, and are provided with operating buttons or levers located within reach of the fingers of the hand which holds the tool, so that the tool can be operated by one hand only.
For a caliper provided with a wear take-up system for the manual operation of the brake, the tool may comprise a rotatable disk, pivoted on one spreader element, for example the one integral with the rod of the jack, and capable of being coupled frontally to channels of the face of the operating piston to be made to move back into its housing, in a preliminary operation before the insertion of the new pad into its housing. This disk is preferably removable for occasions when the tool is used with calipers not having manual operation. The disk has a peripheral toothing for the insertion of a spanner capable of rotating the disk and with it said piston about its axis, thus resetting the wear take-up system. Preferably, the face of the disk designed to come into contact with the brake piston is covered with a layer of rubber or other resilient material which can engage with the channeled face of the piston, in such a way as to adapt itself to the configuration of this face even in the case of brakes of different types. Alternatively, this face may have means of keying with the brake piston, in order to provide more certain rotation of the piston when the disk is rotated. These keying means may also be adaptable to different types of piston in use in motor vehicles.
The invention will be more clearly understood from the description and the attached drawing, which shows a non-restrictive example of the invention. In the drawing,
Fig. 1 shows a view of the tool, cut along an axial plane;
Fig. 2 shows a partial view of the tool in the direction of the arrows ll-ll in Fig. 1;
Fig. 3 shows a side view of an operating spanner for the tool in Fig. 1;
Figs. 4 and 5 show, respectively, a front view and a sectional view, through V-V in Fig. 4, of another embodiment of the element shown in Fig. 2;
Figs. 6 and 7 show, respectively, a front and side view of a keying means;
Figs. 8, 9 and 10 show, respectively, a plan, front and side view of another keying means.
Fig. 1 shows a disk brake of a motor vehicle, comprising a caliper 1 which, by means of friction pads 3, 5 (shown in broken lines), interacts with a disk 7 which is integral with the wheel of a motor vehicle. The pads 3, 5 are housed in corresponding recesses 1A, 1 B of the caliper, and a small cylinder, formed in the caliper itself, opens into the recess 1A and is provided with a piston 9 to directly move the pad 3 and to indirectly move the pad 5 (the caliper being free to move along the axis of the piston 9), to grip the disk 7 from opposite sides by means of the pads 3, 5 when the brake control is operated.
In the part shown by a solid line in Fig. 1, the brake is shown in the course of maintenance, with the pads removed because they are worn. As a result of the wear, the pads become thinner, forcing the piston 9 to emerge further from the corresponding cylinder as the wear increases. The piston, projecting in this way with the face 9A flush with the base 3A of the worn pad which is removed, impedes the insertion of the new pads, whose thickness is greater than that of the worn pads which have been detached. The piston must therefore be made to move back into its cylinder by means of a force applied to its face 9A. However, if the caliper is not detached from the vehicle, the piston cannot be reached by the operator's hands, owing to the narrowness of the passages between the caliper 1 and the disk 7.
The tool according to the invention comprises a pair of tapered spreader elements 11, 13 (Fig. 1) which can be inserted between the disk 7 and the front surface 9A of the piston, from opposite sides of the disk. Said spreader elements 11, 13 have extensions 11 A and 13A which are sufficiently thin to be inserted from opposite sides of the disk into the passages between the disk 7 and the caliper 1 and are of sufficient length to reach the front surface of the operating piston or pistons of the pads for brakes of different types used in commercially available motor vehicles.
The elements 11, 13 are integral, respectively, with the piston 15 and the cylinder 17 of an air jack 19. In particular, the element 11 is fixed by a screw 21 to the rod 23 of the piston 15 of the jack, while the element 13 is fixed by screws 25 to a face of a sleeve 27 fitted by means of threading at one end of the cylinder 17. A ball-bearing bush 29 for axial sliding, within which the rod 23 of the jack 19 can slide with minimum friction, is inserted into the sleeve 27. Thus the piston 15 of the jack is enabled to slide even in the presence of loads which are concentrated at the end of said spreader elements 11, 13, and which are therefore considerably out of alignment with the piston. A straight bar 11B, extending parallel to the axis of the jack, is fixed at one end in a hole of the element 11, at the opposite end from the extension 11A. This bar is housed in a channel 13B of the other spreader element 13, in such a way that, during the travel of the piston 15 and the rod 23 of the jack 19, the spreader elements 11, 13 remain facing each other, with no possibility of rotation with respect to each other about the axis of the jack.
At the opposite end of the cylinder 17 to that carrying the sleeve 27, the jack 19 has an end 31 to which compressed air flows through a tube 33. The end 31 comprises a two-way (on-off) valve, not shown in the drawing, which can be operated by a handle 35 to feed compressed air to the jack, and a discharge valve 37 which can be operated by a button 39, to put the jack into communication with the environment, enabling the rod 23 to be pulled out or pushed in to place the spreader elements 11,13 at a convenient distance from each other. For use, the tool can be held in one hand by grasping the cylinder 17 of the jack, with the handle 35 and the button 39 remaining within reach of the fingers of this hand for the operation of the jack.
As mentioned above, in the case of maintenance of disk brakes provided with the known wear take-up device for manual operation of the brake, it is necessary not only to make the brake piston move back inward but also to rotate the piston through a number of revolutions about itself to return the wear take-up device to a configuration compatible with the axial dimension of the new, non-worn pad. For this purpose, the piston 9 has its face 9A channeled to permit the engagement of a screwdriver or other tool capable of rotating the piston about its own axis. This operation, however, normally requires the removal of the caliper from the vehicle. To overcome this disadvantage, the tool according to the invention comprises a disk 41 which has an axial pin 42 on which it is pivoted, rotatably about an axis X-X parallel to the axis of the jack, on the spreader element 11 which is integral with the rod 23 of the jack. The disk 41 is provided with peripheral teeth 43 which can be moved by means of a spanner 45 to make the disk rotate, in a preliminary operation. The surface 41A of the disk designed to come into contact with the brake piston is covered in a layer of rubber or other resilient material capable of engaging with the channeled face of the piston, thus adapting itself automatically to different configurations of the face of the piston, according to the type of brake which is to be worked on. The pin 42 is integral with the disk, and has a groove for an O-ring made from rubber or other similar material capable of providing a slight friction in the hole of the element 11, permitting rotation of the disk with respect to the element. Thus the disk 41 can remain temporarily joined to the element 11 during the manipulation of the tool, and can easily be separated from the element 11 when the tool is used for calipers without a manual operating system.
In another embodiment, the disk 141 (Figs. 4 and 5), which in other respects is identical to the disk 41 described above, has keying means comprising a channel 143 on its face 141A designed to come into contact with the face 9A of the piston 9. This channel is capable of receiving different types of frontal engagement members of the piston 9 according to the configuration of the latter. In the example shown in Figs. 4 and 5, the channel 143 slidably houses two blocks 145, 147, each of which carries a corresponding pin 149 projecting beyond the face 141A of the disk 141. In a cavity of each block there is inserted a resilient pad 151 capable of temporarily retaining the block by friction in the channel 143 of the disk 141. Thus, in order to rotate about its own axis a piston 9 which has two holes for a key on its outer face 9A, the spacing between the pins 149 is matched to the spacing between these holes by sliding the blocks 145, 147 in the channel 143, after which the projecting parts of the pins 149 can be inserted into the corresponding holes of the piston 9 and the latter can be rotated by acting with the spanner 45 on the outer toothing of the disk 141. For other types of piston 9, which have a key slot or a socket for a hexagonal key, it is possible to insert a key 245 (Figs. 6 and 7) into the channel 143 of the disk 141, said key 245 being provided with a resilient pad 251 to retain it temporarily in the channel 143, and having a linear projection 249 projecting beyond the face 141A of the disk 141 and capable of being inserted into a corresponding linear socket of the face 9A of a piston 9; alternatively, a tapered part 345 (Figs. 8, 9 and 10) (provided with a resilient pad 351) of a hexagonal key 349 projecting beyond said face 141A of the disk so that it can be inserted into said hexagonal socket of the piston 9.
Thus the tool according to the invention can be adapted to most of the brakes in use in motor vehicles.
It should be understood that the drawing shows only an example provided solely as a practical demonstration of the invention, and that this invention can be varied in its forms and arrangements without departure from the scope of the guiding principle of the invention. The presence of any reference numbers in the attached claims has the purpose of facilitating the reading of the claims with reference to the description, and does not limit the scope of the protection represented by the claims.

Claims

Tool for use in replacing the pads of disk brakes of motor vehicles, to make the operating pistons of the pads move back without removing the corresponding caliper, and comprising a pair of tapered spreader elements which can be inserted, each from an opposite side of the disk, between the disk and the front surfaces of the operating pistons, characterized in that said elements (11, 13) are integral, respectively, with the piston (15) and the cylinder (17) of an air jack (19), and in that guide means (11B, 13B) are provided to keep the elements (11, 13) facing each other in the same angular position with respect to each other.
Tool according to Claim 1, characterized in that the cylinder (17) of the jack is provided, at the point where the rod (23) emerges, with a low-friction bush (29) to facilitate the sliding of the rod even when there is a force which is out of alignment with the rod.
Tool according to Claim 2, characterized in that said bush (29) is of the ball-bearing type for axial sliding, is inserted in a sleeve (27) fitted to said end of the cylinder, and the spreader element (13) integral with the cylinder is actually fixed to said sleeve (27).
Tool according to any one of Claims 1 to 3, characterized in that said guide means comprise a channel (13B) formed in the element integral with the cylinder, and a bar (11B) fixed at one end to the spreader element (11) which is integral with the rod (23) of the jack, the bar (11B) being extended parallel to the axis of the rod and inserted slidably into said channel (13B).
Tool according to any one of the preceding claims, characterized in that it comprises a two-way valve and a discharge valve (37), for the operation of the jack and for the discharge of the pressure within it respectively.
Tool according to Claim 5, characterized in that said valves are integral with the cylinder (17) and are provided with operating buttons (39) or levers (35) located within reach of the fingers of the hand which holds the tool which is grasped by the cylinder (17).
Tool according to any of the preceding claims, characterized in that it comprises a rotatable disk (41), pivoted on one of the spreader elements (11, 13), and capable of being coupled frontally to the channeled surface of the piston (9) to be made to move back, in a caliper (1) of a disk brake provided with the wear take-up system for the manual operation of the brake, said disk (41) being provided with peripheral teeth (43) for the insertion of a spanner (45) capable of rotating the disk (41) and with it the piston (9) about its own axis.
Tool according to Claim 7, characterized in that the disk (41) is pivoted on the element (11) by means of a pin (42) provided with a groove for an O-ring (45) capable of generating a slight friction in the housing hole in the element (11) to make the disk easily removable.
Tool according to Claim 7 or 8, characterized in that the surface (41A) of the disk designed to come into contact with the brake piston (9) is covered with a layer of rubber or other resilient material capable of engaging with the channeled face (9A) of the piston.
Tool according to Claim 7 or 8, characterized in that the disk (141) has, on the face (141A) designed to come into contact with the outer face (9A) of the brake piston (9), means (143, 145, 147; 245, 345) of keying with corresponding means on said face (9A) of the piston.
Tool according to Claim 10, characterized in that said keying means comprise a channel (143) in the disk (141) into which blocks (145, 147), each carrying a pin (149) projecting beyond the face (141A) of the disk, are friction-fitted.
Tool according to Claim 10, characterized in that said keying means comprise a channel (143) in the disk (141) into which a key (245) having a linear projection (249) projecting beyond the face (141A) of the disk is friction-fitted, the projection (249) being capable of being inserted into a corresponding linear socket of the face (9A) of a brake piston (9).
Tool according to Claim 10, characterized in that said keying means comprise a channel (143) in the disk (141) into which a tapered part (345) of a hexagonal key (349) projecting beyond said face (141A) of the disk is friction-fitted, the key (349) being capable of being inserted into a corresponding hexagonal socket of a brake piston (9).