JP2007522413A - Brake shoe holddown clip - Google Patents

Abstract

Brake shoe holddown clips 23, 24 are provided that are shaped to provide a non-linear spring action to resist movement of the brake shoes 11, 12 away from the back plate 13. The hold-down clip has a low spring constant to resist small movements of the brake shoe away from the back plate and a high spring constant that becomes functional in response to large movements of the brake shoe away from the back plate. The clip includes spring loops 33, 34, one end 35, 36 of the loop being designed to contact the brake shoe to provide a low spring constant, and a plurality of portions 37, 38 of the loop remote from the one end. Is designed to contact the brake shoes so that the loops become stiffer and provide a higher spring rate in response to large movements of the brake shoes 11, 12 away from the back plate 13.
[Selection] Figure 4

Description

  The present invention relates to a brake shoe holddown clip that presses a brake shoe against its associated drum brake backplate.

  Such hold-down clips are conventionally used between the head of the hold-down pin and the associated brake shoe web (the other end of the hold-down pin engages the drum brake backplate). To do).

  Such hold-down clips are well known and are shown, for example, in British Patent Nos. 2000561 and 2300302.

  Such hold-down clips generally function satisfactorily, but brakes that leave the backplate to handle both normal braking operations and extreme braking loads that can occur under certain dynamic conditions. Problems can arise when controlling the movement of the shoe.

  It is an object of the present invention to provide an improved form of hold-down clip that overcomes or at least partially alleviates the above problems.

  Thus, in accordance with the present invention, a brake shoe holddown clip is provided that is shaped to provide a non-linear spring action to resist brake shoe movement away from the backplate. The hold-down clip has a low spring constant to resist small movements of the brake shoes away from the back plate and a high spring constant that will function in response to large movements of the brake shoes away from the back plate It is.

  Such a non-linear spring constant provides the brake shoe with both a low spring constant designed to resist the movement of the brake shoe away from the backplate during normal operation of the brake and both hand brake and service brake functions simultaneously. It enables high spring constants to function when certain high dynamic loads occur, such as when driven or when rough braking is performed. This provides a more suitable level of control over the entire operating range of the brake shoe. In addition, because of the low spring constant that resists the movement of the brake shoe away from the back plate during normal operation of the brake, the friction between the brake shoe and the back plate is low, so that the friction force is applied when braking. The braking action wasted to overcome is reduced. A high spring constant results in a high frictional force and will only work when needed.

  This non-linear spring constant is achieved as a result of the shape of the hold-down clip.

  In one preferred configuration, the hold-down clip includes a spring loop, one end of the loop being designed to contact the brake shoe to provide a low spring constant, and a plurality of the loops remote from the one end. This portion is designed to contact the brake shoe such that the loop becomes stiffer and provides a higher spring rate in response to a large movement of the brake shoe away from the back plate.

  In one preferred configuration, the clip includes a central locking portion that engages the head of the associated holddown pin and two external spring loop portions that extend one from each end of the central locking portion; The loop portions extend toward and contact the associated brake shoe to normally hold the central securing portion in spaced relation to the brake shoe, and the spring portion is connected to the brake shoe. Is configured to deform when it tends to move away from its associated backplate.

  Conveniently, the free end of the spring loop normally contacts the brake shoe to provide a low spring constant for small movements of the brake shoe away from the back plate, and the elbow portion of each spring loop is a brake away from the back plate. The large movement of the shoe is configured to contact the brake shoe and stiffen each loop, thereby providing a high spring rate.

  Preferably, the holddown clip is configured to limit the possible movement of the brake shoe away from the backplate.

  This prevents the further movement of the brake shoe from the hold-down clip becoming substantially rigid and moving away from the back plate, or the two parts of the clip itself come into contact to make the clip substantially rigid and back. This can be accomplished by configuring the abutment on the clip to engage the shoe web so as to limit the movement of the brake shoe away from the plate.

  For example, a flange formed on the central fixed portion of the holddown clip can be configured to contact the brake shoe web to limit the movement of the brake shoe away from the back plate. Alternatively, in contact with the central fixed portion of the hold-down clip, or in contact with the upper sloped portion of each individual spring loop adjacent to the attachment of the loop to the central fixed portion, It is possible to construct a flange on the free end of the spring loop.

  The hold-down clip preferably includes a slot that receives the head of the associated hold-down pin, the slot having a contact area surrounding it, the contact area being conical, spherical , Or rectangular, each in contact with a conical, spherical, or rectangular cooperating portion of the associated hold-down pin head.

  Also, the central fixing portion included in the brake shoe holddown clip provided by the present invention extends to and contacts the head of the associated holddown pin and the associated brake shoe 2. Engaging the two outer spring portions to normally hold the central locking portion in a spaced relationship with the brake shoe and when the brake shoe tends to move away from its associated back plate The spring portion is configured to deform.

  An example of the present invention will now be described with reference to the accompanying drawings.

  Referring to FIGS. 1-3, a drum brake 10 having a pair of brake shoes 11, 12 mounted on a back plate 13 is shown. The brake shoe reacts with the fixed contact portion 14 that contacts the lower ends 11a, 12a, and a conventional wheel cylinder 15 mounted on the back plate 13 is disposed between the upper ends 11b, 12b of the brake shoe. Is done.

  When the brake is not being driven, conventional return springs 16 and 17 act between the brake shoes to retract the brake shoes. The self-adjusting strut 18 also acts between the brake shoes so as to automatically adjust the distance between the brake shoe and a drum (not shown) that cooperates with the brake shoe when the brake shoe is in its brake released position. Thus, the effectiveness of the brake is maintained when the brake shoe is consumed. A suitable form of self-adjusting strut is described in the Applicant's patent EP0538909.

  In addition to the brake hydraulically operated by the wheel cylinder 15, the hand brake lever 19 also rotates below the brake shoe 12 by the rotation shaft 20. As in the prior art, a handbrake operating cable (not shown) is attached to the lower end 19a of the lever 19, and the lever 19 is rotated in the direction of arrow B to engage the upper part 19b of the handbrake lever with the automatic adjustment strut 18. As a result, the struts are forcibly moved to the right as indicated by arrow C to bring the brake shoe 11 into contact with the brake drum associated therewith, and the reaction of the brake shoe 12 also engages the brake drum. It will be.

  The drum brake described so far has a conventional configuration.

  According to the present invention, the brake shoes 11 and 12 are pressed onto the back plate 13 by the hold-down pins 21 and 22, respectively, and the hold-down clips 23 and 24 are connected to the heads 21a and 22a of the respective hold-down pins. Between the brake shoe webs 25 and 26. This configuration can be most easily understood from FIG. 2, which also shows that each other end 21b, 22b of each holddown pin engages the underside of the backplate 13.

  As clearly shown in FIGS. 4-7, the clip 24 (identical to clip 23) has a central securing portion 30 having a slot 31, which is associated with an associated hold-down pin. It includes 22 heads 22a and includes a somewhat spherical pedestal portion 32 that cooperates with the somewhat spherical lower side of the head 22a. Extending from each end of the central fixed portion 30 is a spring loop portion 33, 34 that extends round toward the web portion 26 of the associated brake shoe 12 and extends to the web portion 26. Contact. In the hold-down clip configuration shown in FIGS. 4-7, during normal operation of the brake, the free ends 35, 36 of the spring loop contact their associated brake shoe webs (see FIGS. 2 and 4) and from the back plate The spring loops 33 and 34 operate at a low spring constant when resisting the movement of the brake shoe that leaves. Each spring loop 33, 34 also includes elbows 37, 38 so that each of the elbows 37, 38 (as shown in FIGS. 3 and 5) when a large displacement of the brake shoe away from the back plate occurs. It comes into contact with the associated brake shoe 12. The contact of the elbows 37 and 38 with the brake shoe causes the loops 33 and 34 to provide a high spring constant. This high spring constant causes certain high dynamic load conditions, such as when the brake shoe is driven to provide both handbrake and service brake functions simultaneously, or when rough braking is performed. This is especially effective when the brake shoe moves away from the back plate.

  Each spring loop is also provided with a flange 39, 40 at its free end, which is located in the center above them when large movements of the brake shoe move away from the back plate (see FIG. 4). It is configured to contact the lower parts 41, 42 of the fixed part 30, thereby providing a higher spring constant, at which time the clip is effectively rigid and further movement of the brake shoe away from the back plate Be blocked.

  A further advantage of the clip of the present invention is that the corners 23a, 24a of the clip (see FIG. 1) abut the underside of the shoe table 11a, 12a so that the clip protrudes beyond the associated shoe. Contact with rotating components (eg mounting studs for the associated wheel) is prevented.

  8, 9 and 11 show further details of an alternative form of holddown clip.

  In FIG. 8, the hold-down clip has a central securing portion 50 that also includes a curved, somewhat spherical pedestal 52 and a slot 51. The clip shown in FIG. 8 does not have the elbow portions 37 and 38 shown in the clip shown in FIGS. 4 to 7, but has substantially straight portions 57 and 58 respectively facing both ends of the loops 53 and 54 of the clip. is doing. This clip is the straight part of each loop as the brake shoe moves progressively away from the backplate under normal load conditions, with only the free end portions 55,56 of the loop contacting the associated brake shoe. It is possible to configure such that more of 57,58 is in contact with the brake shoe and the clip is more rigid. The movement of the brake shoe away from the back plate can be limited by a flange 59, 60 extending from the central fixed portion 50, which is applied when the brake shoe is biased far away from the back plate. It is designed to contact the brake shoe web to make the clip substantially rigid.

  In the clip configuration shown in FIG. 9, the central securing portion 70 has loops 73, 74 extending therefrom, the free ends of the loops being formed as bifurcated arms 75, 76, respectively, with each bifurcated arm having a flange 79, Each having 80, the flange eventually contacts the underside of the central fixed portion 70 and the clip becomes rigid, thus limiting the movement of the brake shoe away from the backplate. The clip shown in FIG. 9 is also used when the normal brake operating conditions only contact the associated brake shoe adjacent to the free ends of the arms 75, 76 and the brake shoe tends to move away from the back plate. It will be appreciated that the contact points are further moved away from their free ends, so that the stiffness of the spring loops 73, 74 is increased. The clip can also be designed to allow the flanges 79, 80 to contact each other to further increase the stiffness of the clip before the clip is effectively rigid.

  In the clip configuration shown in FIG. 10, the lengths of the spring loops 73 and 74 are variable (regardless of whether or not they are bifurcated as shown in FIG. 9), and the flanges 79 and 80 are positioned at positions 79a, 79b, 79c and It is possible to be positioned at the positions 80a, 80b, and 80c. When the flange is located at positions 79a and 80a, it will make a square contact with the lower side of the central fixed portion 70, whereas the flange is located at position 80b. If so, it will be appreciated that the flange will tend to contact the curved portion 70a of the central fixed portion 70. When in the outermost position 79c, 80c, the flange will not touch the rest of the clip at all, so a brake away from the back plate as described above with respect to the flanges 59, 60. It is conceivable to use another method for limiting the overall movement of the shoe. By selecting the position of the flanges 79, 80, it is possible to adjust the change in the overall spring constant of the clip to provide the desired characteristics.

  In a further alternative form of hold-down clip shown in FIG. 11, the clip has a central securing portion 90 having a slot 91 and a flange 92, the flange 92 being one of the central securing portions 90. It is bent downward from the edge of the. This flange is combined with a large upward bent flange 99,100 at the free ends of the loops 93,94 to provide a rigid stop to limit the movement of the associated brake shoe away from the back plate, in this case, The flange 92 contacts the associated brake shoe web and the flanges 99, 100 contact the underside of the central fixed portion 90.

  The clip configuration of FIGS. 8-11 may also include a limited elk configuration, such as indicated by reference numerals 37 and 38 in FIG.

  FIG. 12 shows a further form of hold-down clip. In this case, the central fixed portion 100 has a substantially rectangular slot 101 through which the conventional T-shaped head 22c of the hold-down pin 22 can be inserted. . The hold-down pin head 22c is then rotated 90 degrees with respect to the slot 101 to drop the T-shaped head into the rectangular recess 102. Regarding the loops 103 and 104, the elbows 107 and 108, and the flanges 109 and 110, the shape of the remaining part of the hold-down clip is the same as that of the clip 24.

  The hold-down clip configuration with non-linear spring characteristics described above provides a simple but effective solution to the problem of adapting the spring characteristics of the hold-down clip to changing brake operating conditions. It will be understood that. The low spring constant of the holddown clip is set to a level that provides the control required for brake shoe movement during normal operation of the brake, and a high spring constant may be added to the brake shoe from time to time. It will control a high level of dynamic force. The design of the clip that makes the clip substantially rigid after the brake shoe has moved a predetermined amount provides for tighter control of the brake shoe movement.

  The holddown clip arrangement described above is suitable for all types of drum brakes, whether hydraulically and / or mechanically or electrically actuated.

  The general double loop clip configuration described above, where the loop of the clip extends from both ends of the central fixed portion, can be used with the clip without a non-linear spring characteristic function. For example, in the configuration shown in FIG. 8, it is possible to configure the straight portions 57, 58 so that the entire surface is always in contact with the associated brake shoe, and in this case the entire movement of the brake shoe away from the back plate. A single spring constant is provided by loops 53 and 54 for. Similarly, in the configuration shown in FIGS. 9, 10, and 11, the linear portion 57 of FIG. 8 is also provided so that the entire brake contact is always in full contact to provide a single spring constant. , 58 can be designed for the part of the clip.

1 is a plan view of a drum brake using a holddown clip according to the present invention. FIG. FIG. 2 shows the AA cross section of FIG. 1 showing the holddown clip in its low spring constant position. FIG. 2 shows the AA cross section of FIG. 1 showing the holddown clip in its high spring constant position. The hold-down clip of FIG. 2 is enlarged and shown in its low spring constant position. The hold-down clip of FIG. 3 is enlarged and shown in its high spring constant position. It is a top view of the clip of FIG. It is a perspective view of the clip of FIG. Fig. 6 shows an alternative holddown clip embodying the present invention. Fig. 6 shows an alternative holddown clip embodying the present invention. Fig. 6 shows an alternative holddown clip embodying the present invention. Fig. 6 shows an alternative holddown clip embodying the present invention. Fig. 6 shows an alternative holddown clip embodying the present invention.

Claims (14)

  A brake shoe hold-down clip shaped to provide a non-linear spring action to resist movement of the brake shoe away from the back plate, resisting small movement of the brake shoe away from the back plate A brake shoe hold-down clip having a low spring constant for and a high spring constant that becomes functional in response to a large movement of the brake shoe away from the back plate.   Including a spring loop, wherein one end of the loop is designed to contact the brake shoe to provide a low spring constant, and a plurality of portions of the loop remote from the one end separate from the back plate The clip of claim 1, wherein the clip is designed to contact the brake shoe such that the loop becomes stiffer and provides a higher spring rate in response to a large movement of the brake shoe.   A central securing portion that engages the head of the associated holddown pin and two external spring loop portions that extend one from each end of the central securing portion, the loop portions comprising the central securing portion To contact the brake shoe, and the spring portion separates the brake shoe from its associated back plate so that the brake shoe is normally held in spaced relation to the associated brake shoe. The clip of claim 2, wherein the clip is configured to deform when it tends to move.   A central locking portion that engages the head of the associated holddown pin and two external spring portions, the two external spring portions being spaced from the associated brake shoe. Normally configured to extend toward and contact the brake shoe, and the spring portion is configured to deform when the brake shoe tends to move away from the associated back plate. Brake shoe holddown clip.   The free end of the spring provides a low spring constant for small movements of the brake shoe that normally contact the brake shoe and away from the back plate, and the elbow portion of each spring loop separates the back plate from the back plate. 5. A clip according to claim 3 or claim 4, wherein the clip is configured to contact the brake shoe to make each loop stiffer and provide a higher spring rate when large movements occur.   6. A clip according to any one of the preceding claims, configured to limit the possible movement of the brake shoe away from the back plate.   The abutment on the clip is configured to engage the shoe web so that the clip is substantially rigid and prevents further movement of the brake shoe away from the backplate. Clip as described in.   The clip of claim 7, wherein a flange formed in the central securing portion of the clip contacts the brake shoe web to limit movement of the brake shoe away from the back plate.   7. A clip according to claim 6, wherein the two parts of the clip are brought into contact with each other so that the clip is effectively rigid, thereby limiting movement of the brake shoe away from the back plate.   The spring loop is free to contact the central securing portion of the holddown clip or to contact the upper sloped portion of each individual spring loop adjacent to the attachment of the loop to the central securing portion. 10. A clip according to claim 9, wherein a flange is configured on the end.   Including a slot for receiving the head of an associated holddown pin, the slot having a contact area surrounding it, the contact area being conical, spherical or rectangular Each in contact with a conical, spherical, or rectangular cooperating portion of the associated hold-down pin head. The clip according to any one of claims 1 to 10.   The spring loop is configured to contact the underside of an associated brake shoe table to prevent the clip from rotating to a position that projects beyond the associated shoe. The clip according to any one of 10.   A drum brake, wherein the brake shoe is pressed against the back plate by the hold-down clip according to any one of claims 1 to 12.   Brake shoe holddown as shown in FIGS. 1-7, or 8, or 9, or 10, or 11, or 12, substantially constructed and arranged as described with respect to those figures. ·clip.

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