BRAKE PAD RETENTION SPRING, IN PARTICULAR FOR SPOT-TYPE DISC BRAKES FOR AUTOMOTIVE VEHICLES

Abstract: The invention is directed to a brake pad retention spring, in particular for spot-type disc brakes for automotive vehicles, including a fastening section (10) for securing it to a pad backing plate (4) and spring arms (16, 18, 30) for engagement into a brake member, wherein two spring arms (16, 18) extend substantially in the circumferential direction and a third spring arm (30) extends substantially in the radial direction. In order to permit radial pad replacement also with thin pads with the housing in its mounted position, the invention provides for the spring arm (30) to have a bent section (32) extending substantially parallel to the backing plate and having an adjacent end section (34) extending substantially radially.

Description: This invention relates to a brake pad retention spring, in particular for spot-type disc brakes for automotive vehicles, according to the preamble of patent claim 1. A retention spring of the type referred to above is known from the Brake Handbook of ALFRED TEVES GMBH, Bartsch-Verlag, Ottobrunn, 8th new edition, page 201. This known retention spring serves to hold the brake pad against a brake member, particularly the brake piston, without clearance. The known spring has, however, certain disadvantages in respect of assembly and function. In this connection, particularly its large overall length is to be mentioned which, in the case of a radial pad replacement, permits the inboard brake pad which is pro­ vided with such a retention spring, to be assembled with the caliper in its mounted position, provided that the thickness of the outboard brake pad is greater than the length of the spring. Since the known spring is required to be up to about 25 mm long to fulfill its function, even sliding calipers allow such assembly only in some cases. Further, the use of the known retention spring often requires components such as brake carrier members, for example, which obstruct radial pad assembly, to be recessed or relocated inwardly by such high an amount that the direction of force lines may be adversely affected and additional bending moments may develop. It is, therefore, an object of this invention to pro­ vide a retention spring of the type identified in the preamble of patent claim 1 which, also with the brake pads conventionally thin, affords a simple way of changing the brake pads radially while the housing is in its mounted position. This object is accomplished according to the invention by the features characterizing patent claim 1. The solution of the invention provides a pad retention spring which avoids the above-mentioned drawbacks. The configuration of the radially extending spring arm as disclosed in the invention enables it to produce the same spring force as known springs having arms about twice its length. This permits a substantial reduction of the overall length so that also brake pads of a thick­ ness of only about 11 mm can be fitted radially without the holding function being impaired. In this arrangement, a force component is applied causing the brake pad to be biased into abutment with the brake caliper and there­ by excluding the tendency to rattle, with the clearances developing as a result of tolerances of the individual components being eliminated. The two spring arms ex­ tending in the circumferential direction have substantial­ ly the function to hold the pad against the appropriate component, particularly against the piston, whereas the radial spring arm applies the spring force necessary to keep the pad biased in abutment with the caliper or the brake carrier. In this arrangement, the forces have to be coordinated such as to produce a low bias, enabling the brake pad to be displaced parallel to the plane of the backing plate with ease. In accordance with an advantageous embodiment of the invention, the middle portion of the bent, in particular S-shaped, section extends substantially in the circum­ ferential direction. In this embodiment, the bent section is suitably arranged in the region of the one spring arm extending in the circumferential direction or at the fastening section adjacent to that spring arm, which enables the S-shaped section to be of a broad construction without requiring additional space. In accordance with another advantageous embodiment, the spring arms extending in the circumferential direction are arranged at an angle relative to the tangential plane which is substantially in the range of between 5° and 15°. By virtue of this configuration, they support the radially acting spring arm since they invariably tend to force the brake pad downwards in the direction of force of the bent spring arm without thereby impairing the resilience by an increased resistance, because the frictional resistance is adjusted as a result of the inclined position. In the known retention spring, already a minor off-center condition involves the risk of a spring arm becoming bent and folding outwardly. Bending the spring arm back may cause it to break eventually. Therefore, an advantageous em­ bodiment of the invention provides for bending of the end portions of the spring arms towards the backing plate. This makes it more difficult for the spring arms to become bent and jammed at the piston. In addition, this arrangement facilitates the insertion of the retention spring. Since the bearing spots of the known retention spring are undefined in the region of the spring arms, poor seating in the piston may result and consequently an inaccurate definition of spring excursion and spring force (wide scatter). In accordance with an advantageous embodiment of the invention, therefore, the portions of the spring arms abutting the piston are suitably profiled, in particular, bulged, and are conformed to the curvature of the piston such that only a point or line contact is established between the parts. This improves the slip during assembly (less resistance because the necessity of cutting in edges is obviated) and the seating in the piston while the spring force and the spring excursion can be clearly determined. In view of three defined bearing spots, low fluctuations result. This is of particular importance for the arms extending in the circumferential direction in order to maintain the angular range identi­ fied above. The claw-type spring may be secured to the backing plate by means of notched nails, rivets, screws, by caulking or spot-welding, or the like. An additional means to secure the brake pad in its position is not required. Even should a spring arm break, the pad will continue to be held captive by the remaining spring portions. Another solution of the invention (claim 9) allows to still further reduce the spring length in the axial direc­ tion. This achieves smaller space requirement in the as­ sembly. The two spring arms extending substantially in the circumferential direction assist the radially acting spring arm still more in pressing the brake pad onto the retaining arrangement and the housing, respectively. Owing thereto, radial pad replacement is possible while the housing is in its mounted position. An additional means to secure the brake pad in position is not re­ quired. Even should one of the spring arms break, the pad will continue to be held captive by the remaining spring portions. The special design of the spring likewise af­ fords very simple manufacture at reduced cost. According to an advantageous embodiment of this so­ lution, two legs of the arms forming the U-shaped or V-shaped bent section extend transversely, that means in the radial direction. By virtue of this, a particularly good resiliency of these spring arms in the circumferen­ tial direction is accomplished. In another embodiment in which the arms extending in the circumferential direction comprise end sections which extend substantially in the circumferential direction and which are arranged on the backing plate such that their ends abut on the brake pis­ ton above the centre line of said, a precisely defined bearing point on the brake piston will result, whereby the radially acting spring arm is still further assisted in pressing the brake pad onto the retaining arrangement and onto the brake housing, respectively. According to another favourable embodiment of this in­ vention, it is arranged for that the spring arm extendng substantially in the radial direction comprises an end section extending in the radial direction. Expediently, all sections of the spring arms are lo­ cated in planes which extend substantially vertically to the backing plate. This results in ease of manufacture and thus in rendering the spring less costly due to the straightforward winding and design of the spring arms. The waste of material can be kept very low. In a very favourable manner, noses are provided at the end sections of the spring arms extending in the circumferential direc­ tion, which noses show to the pad backing plate and which form projections in the circumferential direction by which the spring engages into corresponding grooves or the like designed at the brake member. Embodiments of the invention will now be described in the following with reference to the accompanying drawings, wherein: Fig. l is a view of the rear side of a brake pad provided with a retention spring; Fig. 2 is a sectional view of the retention spring of Fig. l, taken along the line A-A of that Figure, Fig. 3 is a sectional view of the retention spring of Fig. l, taken along the line B-B of that Figure, and Fig. 4 is a view of the rear side of a brake pad provided with a retention spring embodying a different configuration, Fig. 5 is a view of the rear side of a brake pad provided with a retention spring; Fig. 6 is a sectional view of the pad of Fig. 5, taken along the line A-A of that Figure, Fig. 7 is a plan view of the retention spring, Fig. 8 is a side view of the retention spring, and Fig. 9 is an inwardly straddling disc brake with an inner brake pad which is attached to the brake piston by means of a retention spring. Referring now to FIGS. 1 to 3 of the drawing, there is illustrated a brake pad 2 for a spot-type disc brake which has a metallic backing plate 4 with the actual friction lining 6 (shown in broken lines) affixed to its front side. A retention spring 8 is secured to the backing plate 4. The retention spring 8 has a substantially rectangular fastening section 10 whose lower corners are cut off. The fastening section 10 has two through holes 12, 14 serving to secure the retention spring 8 to the backing plate 4. For this purpose, notched nails, rivets, screws and the like are suitably used. Other fastening methods such as caulking or spot-welding or the like may also be applied. Extending from the sides of the fastening section 10 are two spring arms 16, 18 having their central axes ex­ tend through the center point M at an angle relative to the tangential plane which is essentially in the range of between 5° and 15° and amounts to 7°, for example. The spring arms 16,18 are bent in several places, forming a substantially U-shaped end section 20, 24 as becomes apparent particularly from the sectional view of FIG. 3 illustrating the spring arm 18. The extreme ends of these end sections 20, 24 extend towards the backing plate 4, forming another angle of about 30°. In the region of these angles, they are profiled as at 26, 28 to provide defined bearing spots. A third spring arm 30 has a bent, in this embodiment particulary an S-shaped section 32 continuing in a radially extending end section 34. The S-shaped section 32 begins adjacent to the fastening section 10 in the region of the spring arm 18. In the manufacture of the retention spring 8 in which the U-shaped end section 24 of the spring arm 18 is formed by bending over, the portion forming the S-shaped section 32 is thus in a plane extending substantially perpendicular to the plane of the fastening section 10. The middle portion 36 of the S-shaped section 32 extends substantially in the circumferential direction, approximately over the width of the fastening section 10. Similar to the end sections of the spring arms 16, 18, the end section 34 of the spring arm 30 is likewise bent in several places as becomes apparent from the sectional view of FIG. 2, with its end being substantially of U-shape and having its ex­ treme end extend in the direction of the backing plate and profiled as at 38. In the embodiment of FIG. 4, a retention spring 40 is provided which is substantially identical to the re­ tention spring 8 in respect of its fastening section 42 and the arms 44, 46 extending in the circumferential direction. By contrast with the retention spring 8, however, the bent portion 48 of the radially extending spring arm 50 is provided in the region of the fastening section 42, which results in a different spring excursion for this particular arm. Since, among other things, the retention springs of the invention are to permit a displacement of the brake pad, it may be useful to introduce suitable means to reduce the friction of that area of the pad backing plate which is held against the appropriate brake member by means of the spring. To this end, for example, a piece of sheet metal may be used which rests on the backing plate underneath the retention spring and is secured to the retention spring. The inwardly embracing disc brake illustrated in Fig. 9 comprises a brake carrier l02 rigidly mounted on the ve­ hicle as well as a brake housing l04 axially slidably sup­ ported on the brake carrier l02, the said brake housing embracing the inner edge of a brake disc l06 (indicated by a dash-dot line) and two brake pads l08, ll0 arranged on either side of the brake disc l06. The brake housing l4 is of substantially U-shaped configuration having two ra­ dially extending legs ll2, ll4 which are interconnected through a substantially axially extending bridge section ll6. In the inward leg ll2, an actuating device is ar­ ranged which comprises a piston l20 slidable in a cylinder bore ll8 and abutting with its open side on the backing plate l22 of the brake pad l08. The brake pad l08 is secured to the piston l20 by a retention spring l24. The brake pad l08 with retention spring l24 is illus­ trated in detail in Figs. 5 to 8, to which now reference is made. The retention spring l24 comprises a substanti­ ally rectangular fastening section l26 containing two through holes l28, l30, in order to secure the retenton spring l24 to the backing plate by means of rivets l32, l34. Other fastening methods such as caulking or spot-welding or the like may also be applied. Extending from the sides of the fastening section l26 are two spring arms l40, l42 being in particular integral­ ly designed with the fastening section l26. Said spring arms l40, l42 have U-shaped sections l44, l46, the open side of the U showing upwards. Succeeding the sections l44, l46 are end sections l48, l50 which extend in the circumferential direction and whose ends, in the mounted condition, are disposed above the horizontal centre line of the piston l20. Designed at the end sections l48, l50 are noses l52, l54 which are directed to the backing plate l22. The end sections likewise form projections l56, l58 which extend in the circumferential direction and which, in the mounted condition, engage into corresponding inden­ tations in the associated brake member, that is the brake piston l20 in the instant case. For this purpose, trans­ versely extending abutment surfaces l60, l62 are designed at the projections l56, l58, the said abutment surfaces taking support in the annular groove l84 of the piston l20 and thus draw the brake pad l08 axially to the piston. The spring arm l42, which is on the right side in the illustration, passes into a substantially radially ex­ tending spring arm l64 having an S-shaped section l66 whose mid-portion l68 extends substantially in the circum­ ferential direction and whose legs l70, l72 adjacent thereto extend substantially radially. Adjoining the leg l72 is a section l74 which extends in parallel to the mid-portion l68 up to roughly the middle thereof and which then passes into an end section l76 that is disposed on the centre line of the pad and extends radially. Said end section l76 forms an axially protruding nose l78 having abutment surfaces l80, l82 for the pad and for the inner piston wall, respectively. As becomes apparent from Fig. 9, the nose l78 of the end section l76 bears with the bearing surface l80 against the inner wall of the brake piston l20. Said nose l78 bears against the backing plate during the assembly only. In the operating condition, a play of 0.5 to l mm approxi­ mately will result. The noses l52, l54 of the spring arms l40, l42 engage into an annular groove l84 provided at the inner surface of the piston. As the noses are arranged above the centre line l86 of the piston, a force is ex­ erted by the piston inner wall onto the noses which aims at urging the retention spring l24 and hence the brake pad l08 towards the brake disc axis. The frictional resist­ ance in the direction of force of the spring arm l64 can be precluded thereby.

Claims: 1. A brake pad retention spring, in particular for spot-type disc brakes for automotive vehicles, including a fastening section for securing it to a pad backing plate and spring arms for engagement into a brake member, wherein two spring arms extend substantially in the circumferential direction in relation to the brake disc and a third spring arm extends substantially in the radial direction,characterized in that the spring arm (30) has a bent section (32) extending substantially parallel to the backing plate (4) and having an adjacent end section (34) extending substantially radially. 2. A retention spring as claimed in claim 1,characterized in that the middle portion (36) of the bent section (32) extends substantially in the circumferential direction. 3. A retention spring as claimed in claim 1 or claim 2,characterized in that the bent section (32) is arranged in the region of the one spring arm (18) ex­ tending in the circumferential direction. 4. A retention spring as claimed in claim 1 or claim 2,characterized in that the bent section is arranged at the fastening section adjacent to the one spring arm extending in the circumferential direction. 5. A retention spring as claimed in any one of the preceding claims,characterized in that the spring arms (16, 18) extending in the circumferential direction are arranged at an angle relative to the tangential plane which is substantially in the range of between 5° and 15°. 6. A retention spring as claimed in any one of the preceding claims,characterized in that the end portions of the spring arms (16, 18, 30) are bent towards the backing plate (4). 7. A retention spring as claimed in any one of the preceding claims,characterized in that the end portions of the spring arms (16, 18, 30) are profiled (26, 28, 38). 8. A retention spring as claimed in any one of the preceding claims,characterized in that the width of the bent, in particular S-shaped section (32) corresponds sub­ stantially to the width of the fastening section (10). 9. A brake pad retention spring, in particular for spot-type disc brakes for automotive vehicles, including a fastening section for securing it to a pad backing plate and spring arms for engagegement into a brake member, wherein two spring arms extend substantially in the cir­ cumferential direction (main direction of spring) in rela­ tion to the brake disc and a third spring arm extends sub­ stantially in the radial direction (main direction of spring), in particular according to any one of the preceding claims,characterized in that the spring arms (l40, l42) extending in the circumferential direction comprise U-shaped or V-shaped bent sections (l44, l46). l0. A retention spring as claimed in claim 9,characterized in that two legs of the spring arms forming the U-shaped or V-shaped bent section extend transversely to the circumferential direction. 11. A retention spring as claimed in claim 9 or l0,characterized in that the spring arms (l40, l42) extending in the circumferential direction have end sections (l48, l50) which extend substantially in the cir­ cumferential direction and which are arranged at the back­ ing plate (l22) such that their ends abut on the brake piston (l20) above said's centre line (l86). 12. A retention spring as claimed in any one of the claims 9 to ll,characterized in that the spring arm (l64) extending substantially in the radial direction has an end section (l76) extending in the radial direction. 13. A retention spring as claimed in any one of the claims 9 to l2,characterized in that all sections of the spring arms (l40, l42, l64) are disposed in planes which extend substantially vertically to the backing plate. 14. A retention spring as claimed in any one of the preceding claims,characterized in that the spring arms (l40, l42) extending substantially in the circumferential direc­ tion have noses (l52, l54) protruding in the axial direc­ tion. 15. A retention spring as claimed in any one of the preceding claims,characterized in that the substantially radially extending spring arm (l64) has a nose (l78) protruding in the axial direction.

Inventors: KLIMT, ULRICH, THIEL, RUDOLF, ZAVISKA, DALIBOR
Applicants: ALFRED TEVES GMBH
Application year: 1986
Main classification: F16D55
IPC codes: F16D65, F16D55