Retainer clip for brake pad support pins

Abstract: A safety device for support pins for pads of vehicle brake calipers, particularly for disk brakes, in which at least one support pin (38) is supported removably by a caliper element (30) which is intended to hold the pads, and which has means (1) which can be associated removably with the support pin (38) to prevent the support pin (38) from slipping out of the caliper element (30) comprises, for each support pin (38), a respective clip (4) with an eye (7) which can be mounted astride the support pin (38) so as to extend around it, the pin support (38) having abutment means for preventing relative axial sliding of the clip (4) on the support pin (38) in at least one direction, so as to oppose slipping of the support pin (38) out of the caliper element (30).

Description: The present invention relates in general to brakes and, more particularly, to disk brakes, particularly but not exclusively for vehicles. More specifically, the invention relates to a safety device for brake-pad support pins or bolts, as defined in the preamble of claim 1. Safety devices of this type are known for example from GB-A-1 443 544 and GB-A-1 359 989. In disk brakes, particularly of the type fitted in vehicles, the pads which bear linings of friction material are supported within a so-called caliper body with the ability to move away from and towards the disk surface or braking band when they are acted on by hydraulic or pneumatic cylinder-piston units so as to be able to perform the braking action when required. Pins or bolts are used for supporting the pads in the caliper body and extend through the caliper body and through through-holes provided in the pads, their ends engaging in seats provided for the purpose in the caliper body. These support pins are supported by the caliper body so as to be removable axially since they have to be removed to enable the pads to be replaced when they are worn. However, the pins must be prevented from slipping out of the caliper body accidentally when the vehicle is in motion since this would result in the correct operative positioning of the pads no longer being ensured. According to a known solution, the pins supporting the pads are prevented from slipping out of the caliper body by means of safety split pins mounted substantially in the vicinity of one end of each support pin, each split pin having a first limb which can be fitted in a through-hole formed for the purpose in the support pin, transverse the axis thereof. The other limb of each split pin has a portion which is shaped to form an arc with a radius substantially corresponding to that of the support pin and which grips the support pin, when the split pin is mounted, to prevent the first limb from undesirably slipping out of the through-hole in the support pin. Moreover, the caliper body has recesses which leave the support pins exposed in the region of the transverse through-holes formed therein and the split pins are housed in these recesses. The split pins thus come into abutment with the walls of the recesses, preventing the support pins from slipping out. Clearly, once the split pins are fitted in the respective support pins, they are also fixed for rotation with the support pins about the axes thereof. When the vehicle is in motion and, in particular, each time braking takes place, vibrations are produced and are propagated to the pins supporting the pads. These support pins, which are housed substantially loosely in the caliper body, vibrate and tend to rotate about their own axes, also causing the respective split pins to rotate. To prevent the rotation of the support pins causing the split pins to strike against portions of the caliper body, for example, against the edges of the recesses housing the split pins, the eyes of the split pins are bent so as to lie in a plane perpendicular to the plane in which their two limbs lie. When the split pins are fitted, their eyes thus lie substantially on an outer surface of the caliper body in the vicinity of the edges of the respective recesses. This solution, which is advantageous from many points of view, could have disadvantages since the rotations of the support pin about its own axis are transmitted to the split pins, causing them to knock or at least rub against the caliper body. In time, the split pins could deteriorate or break. Any breakage of the split pins is an event which could have disastrous consequences and is absolutely to be avoided. In view of the prior art described, the object of the present invention is therefore to provide a safety device for brake-pad support pins which does not have the above-mentioned disadvantages. According to the present invention, this object has been achieved by means of a safety device for support pins for pads of vehicle brake calipers, particularly for disk brakes, according to claim 1. The characteristics and the advantages of the present invention will become clear from the following detailed description of a possible practical embodiment thereof, provided purely by way of non-limiting example and illustrated in the appended drawings, in which: Figure 1 is an elevational view of an element for preventing a support pin from slipping out which, by analogy with the prior art, will be referred to as a "safety pin", forming part of a safety device according to a possible embodiment of the present invention, Figure 2 is a section through the safety pin taken in the plane II-II of Figure 1, Figure 3 is a plan view of a vehicle disk-brake caliper, Figure 4 is an elevational view of a detail of the caliper, showing the stages of the fitting of the safety pin, and Figure 5 is a section taken in the plane V-V of Figure 4. With reference to the drawings, Figures 1 and 2 show, in an elevational view, and in a section taken in the plane II-II of Figure 1, respectively, a safety pin 1 forming part of a safety device according to a possible embodiment of the present invention. The safety pin 1 is constituted by a metal wire suitably bent in the manner clearly visible in the drawings and described in greater detail below. The metal wire of which the safety pin 1 is made is preferably a wire made of steel, particularly stainless steel and even more preferably AISI 302 steel. The wire has a circular cross-section of substantially uniform diameter throughout its length. The diameter of the steel wire is, for example, approximately 1.2 mm. The safety pin 1 comprises a substantially straight central portion 2 of predominant length L1 relative to the overall length of the safety pin. The central portion 2 has, at its two ends, two wide bends 3, with a radius of curvature, for example, of about 8 mm, which connect the central portion 2 to two lobes 4 which act as clips. The length L1 of the central portion is, for example, about 88-89 mm, although this value is given purely by way of example and may vary from one case to another according to the distance between the elements (for example, the interaxial spacing between the brake-pad support pins, as will become clear from the following) on which the safety pin is to be mounted. Each clip 4 comprises a first limb 5 and a second limb 6 coplanar with the central portion 2 and perpendicular thereto, the first and second limbs 5, 6 being of substantially equal length and significantly shorter than the central portion, and being spaced apart by a portion D1 preferably of about 14 mm. The wire constituting the safety pin is bent, between the two limbs 5 and 6, to form a substantially "Ω"-shaped, re-entrant loop 7 or eye which has a narrower entry portion 8 with an aperture D2 and then widens out into a circular portion 9 of inside diameter D3, where D3>D2. For example, the aperture D2 may be about 3 mm and the inside diameter D3 of the circular portion 9 about 4.6 mm; naturally, as already stated for the length L1, the values of D2 and D3 may vary from one case to another according to the dimensions of the elements on which the safety pin is to be mounted. The end of the second limb 6 of each clip 4 is bent and extends towards the first limb 5 so as to form a respective appendage 10 which can be gripped manually or by means of a tool and which is inclined slightly towards the eye 7 so as to prevent the end of the metal wire from projecting dangerously. The clip-like behaviour of the lobes 4 is made possible by the resilient behaviour of the metal wire which forms the safety pin 1 and, in particular, by the ability of the circular portions 9 to bend under stress and to become wider, and of the limbs 6 to bend and/or to be inclined, under stress, towards the respective adjacent limbs 5, so as to bring about a temporary widening of the apertures D2 of the narrower portions 8 and then to return resiliently to the rest position when the stress is removed. The stress may be a stress applied directly to the narrower portions 8 by forcing the safety pin 1 astride the elements (pins, bolts, or the like) which are to be prevented from slipping out, as will be described below; in this case, the circular portions 9 bend and widen and the limbs 6 are inclined towards the respective limbs 5. Otherwise, the stress may be a stress applied to the ends of the limbs 6, for example, by pulling on the gripping appendages 10, as occurs when the safety pin is to be removed from the elements, for example, to allow them to slip out; in this case, the limbs 6 bend and are inclined towards the respective limbs 5 and the circular portions 9 in turn bend, bringing about a temporary widening of the narrower portions 8. Clearly, the flexibility characteristics of the clips 4 depend on a combination of factors, amongst which are the particular material of which the wire forming the safety pin is made, the diameter of the wire, the radius of curvature of the circular portions 9 and of the eyes of the clips 4, etc. More specifically, once the material to be used and the minimum desired "extraction load" (that is, the tensile force to be exerted on the safety pin in order to disconnect the clips 4 from the elements on which they are mounted) has been established, the principal dimensions of the clips 4 will consequently be determined. The values provided by way of example are suitable for ensuring a minimum extraction load of about 20 N. With reference now to Figures 3, 4 and 5, Figure 3 shows a vehicle disk-brake caliper in plan. The caliper comprises a caliper body, generally indicated 30, which, in the embodiment shown, is formed by two juxtaposed half-bodies 31 and 32 fixed together by screws 33, but which could also be constituted by a single element. The caliper body extends astride a portion of a braking band of a disk, schematically indicated 34. Seats 100 are formed in the caliper body 30 for housing two respective pads 35 of friction material disposed on either side of the disk 34. Each pad 35 is formed, in known manner, by a plate 36 supporting a lining 37 of friction material facing towards the braking band of the disk 34. The pads are rendered captive and positioned in the correct operative positions in the respective seats by support means which will be described below. Cylinder-piston pairs operated, for example, hydraulically, are formed in the two half-bodies 31 and 32, in known manner, in order to urge the pads 35 towards the two sides of the braking band of the disk 34 so that the linings 37 of friction material come into abutment with the braking band. In Figure 3, four cylinder-piston pairs, that is, two for each half-body 31, 32, are shown very schematically and indicated 50. The means for supporting the pads 35 comprise a pair of pins or bolts 38 which are arranged transversely relative to the caliper body and the opposed ends 39, 40 of which are housed by being fitted substantially loosely in respective seats provided in the caliper body 30. In particular, on the side formed by the half-body 31, the seats for the ends of the support pins 38 are two blind holes or through-holes with stop abutments for the support pins, and on the side formed by the half-body 32, two through-holes 46 are formed in a shoulder 45 of the half-body 32. The support pins 38 extend through through-holes 41 provided for the purpose in the plates 36 of the pads 35, thus supporting the pads 35 and ensuring their correct operative positioning. A cross-shaped spring 42 comprises a spring portion 420 which extends longitudinally relative to the caliper body 30 and a spring portion 421 arranged transversely relative to the spring portion 420 and operatively connected, for example riveted, thereto. The spring portion 421 urges the pads 35 away from the disk 34, that is, towards the respective cylinder-piston units 50 so that, when the braking action is not exerted, the pads are invariably removed from the braking band. The two ends 44 of the cross-shaped spring 42, on the other hand, extend beneath the two support pins 38. Two recesses 47 formed in the shoulder 45 of the half-body 32 on the side facing inwardly, that is, towards the pads 35, in the region of the through-holes 46, are open on the side facing towards the pads 35. The two recesses 47 can house the two lobes 4 or clips of the safety pin 1 described above after the safety pin 1 has been mounted astride the two support pins 38. The central portion 2 of the safety pin 1 extends between the two support pins 38, remaining slightly above the shoulder 45 of the half-body 32. It can be seen that, although in the embodiment shown the two recesses 47 are open towards the pads 35, these recesses could also be formed as open-topped grooves, closed at the bottom and at the sides, and wide enough to allow the clips of the safety pin to be inserted. With reference now to Figures 4 and 5, the support pins 38 have respective peripheral grooves 48 in the vicinity of their ends 40. In one possible embodiment, the safety pins are of a size such that the inside diameter D3 of the circular portion 9 of the eye 7 is slightly smaller than the diameter of the support pins 38 in the respective grooves 48 so that, once the clips 4 have been mounted astride the support pins 38 in the region of their grooves 48, there is slight interference between the eyes 7 and the support pins. In an alternative embodiment, the safety pins are of a size such that the inside diameter D3 of the circular portion 9 of the eye 7 is between the diameter of the support pins 38 in the groove 48 and the diameter of the support pins beside the groove 48, that is, of the remaining portions of the support pins, so that the clips 4 are mounted astride the grooves 48 of the support pins 38 with slight clearance. The aperture D2 of the narrower portion 8, on the other hand, is smaller than the diameter of the support pins 38 in the groove 48 to an extent sufficient to ensure that the clips 4 of the safety pin do not slip off the support pins 38 spontaneously once they have been mounted thereon. The values given above by way of example for the most important dimensions of the safety pin are suitable for use with support pins having a maximum diameter of at least approximately 6 mm and a diameter in the grooves 48 of approximately 4.7 - 4.8 mm, and relate to a situation in which the safety pins are required to be mounted astride the support pins with slight interference. It will, however, be clear to an expert in the art that the dimensions of the safety pins may be modified to adapt them to support pins of different diameters. In order to mount the safety pin, it suffices to proceed as shown schematically in Figure 4, by positioning the safety pin so that the eyes 7 are disposed adjacent the grooves 48 of the support pins and then to push the safety pin onto the support pins 38 so that the apertures D2 of the narrower portions 8 are widened sufficiently, owing to bending of the circular portions 9 of the eyes 7, for the support pins to pass through the narrower portions 8 and to snap into the respective circular portions 9 of the eyes 7. The clips 4 are thus mounted astride the support pins 38. When the safety pin is mounted on, that is, astride the support pins 38, the support pins 38 are prevented from slipping out of their seats in the caliper body and the support of the pads 35 is thus ensured. However, since the eyes 7 of the safety pin extend around the support pins 38 with slight interference, or alternatively with slight clearance, the rotation of the support pins 38 which is brought about as a result of vibrations generated when the vehicle is in motion and particularly during braking does not unavoidably result in rotation of the safety pin 1 which, in contrast with previously known solutions, is not fixed relative to the support pins but restrains them from slipping out purely axially. The fact that the support pins can rotate without the safety pin rotating means that the safety pin is not subjected to repeated knocking against the caliper body or other parts of the brake and is therefore not subject to breakages over time. This is also due to the fact that the safety pin extends astride and is mounted on both of the support pins. In order to remove the safety pin, for example, when the pads 35 need to be replaced, it suffices to exert a pull on the gripping appendages 10 of the safety pin until the eyes 7 of the safety pin snap out of grooves 48 of the respective support pins 38, and possibly at the same time to push the limbs 6 towards the limbs 5 so as to bend the circular portions 9, consequently widening the apertures D2 of the narrower portions 8 of the eyes 7. In the foregoing description, a so-called fixed caliper is referred to purely by way of example. Clearly the present invention may also be applied to calipers of other kinds, for example, to so-called floating calipers, in which at least one bolt or pin is nevertheless used for supporting the pads; these may either be calipers of the type having a support for housing the pads which is separate from but operatively connected to an actual caliper body, or of the type which does not have such a separate support. Similarly, the invention also applies when the number of pins supporting the pads is other than two, possibly even when there is only one support pin. Naturally, variants and or additions may be applied to the embodiment described and illustrated above without thereby departing from the scope of protection defined in the appended claims.

Claims: A safety device for support pins for pads of vehicle brake calipers, particularly for disk brakes, in which at least two support pins (38) are supported removably by a caliper element (30) which is intended to hold the pads, the device comprising, for each support pin (38), at least one respective clip (4) with an eye (7) which can be removably mounted astride the support pin (38) so as to extend around it and abutting abutment means provided in each support pin (38) for preventing relative axial sliding of the clip (4) on the support pin (38) in at least one direction so as to oppose slipping of the support pin (38) out of the caliper element (30), the clips (4) being constituted by bent portions of a single metal wire and being joined together by a respective intermediate portion (2) of the metal wire, the intermediate portion (2) extending between the support pins (38), characterized in that each of the clips (4) comprises a first limb (5) connected to the intermediate portion (2) of the metal wire and extending at an angle to the intermediate portion (2), a second limb (6) substantially parallel to the first limb (5), a loop which is disposed between the first and second limbs (5, 6), is re-entrant towards the intermediate portion (2), and forms the eye (7) which is open on the opposite side to the intermediate portion (2), the loop having a narrower entry portion (8) which communicates with a substantially circular portion (9). A device according to Claim 1, characterized in that the abutment means comprise a smaller-diameter portion (48) of the support pin axially adjacent a large-diameter portion of the support pin, and in that the clip (4) is mounted on the support pin (38) on the smaller-diameter portion (48) and can abut the adjacent, larger-diameter portion of the support pin. A device according to Claim 2, characterized in that the smaller-diameter portion (48) of the at least one support pin (38) is constituted by a peripheral groove in the support pin (38). A device according to any one of Claims 1, 2 and 3, characterized in that the clip (4) can cooperate with a wall of the caliper element (30) to prevent the respective support pin (38) from slipping out of the caliper (30). A device according to Claim 1, when it is dependent on Claim 2, characterized in that the circular portion (9) has an inside diameter (D3) substantially corresponding to or slightly smaller than the diameter of the smaller-diameter portion of the support pin so that the clip (4) is mounted astride the support pin (38) with interference, and the narrower portion (8) has an aperture (D2) which can be widened resiliently to allow the clip (4) to be mounted on and removed from the respective support pin (38). A device according to Claim 1, when it is dependent on Claim 2, characterized in that the circular portion (9) has an inside diameter (D3) between the diameter of the smaller-diameter portion (48) of the support pin and the diameter of the larger-diameter portion of the support pin so that the clip (4) is mounted astride the support pin (38) with clearance, and the narrower portion (8) has an aperture (D2) which is smaller than the diameter of the smaller-diameter portion of the support pin and which can be widened resiliently to allow the clip (4) to be mounted on and removed from the respective support pin (38). A device according to Claim 5 or Claim 6, characterized in that the second limb (6) of each clip (4) terminates in a gripping appendage (10) which can be acted on to widen the aperture (D2) of the narrower portion (8) resiliently. A vehicle brake caliper, particularly for a disk brake, comprising a caliper element (30) which is intended to hold pads of friction material and at least two pad-support pins (38) supported removably by the caliper element (30), characterized in that it comprises a safety device according to any one of the preceding claims for preventing the at least two support pin (38) from slipping out of the caliper element (30).

Inventors: GANDOLFI FAUSTO, PARAVISI MARCO, GANDOLFI, FAUSTO, PARAVISI, MARCO
Applicants: FRENI BREMBO SPA, FRENI BREMBO S.P.A.
Application year: 1999
Main classification: F16D55
IPC codes: F16D55, F16D65