Patent Application
20070170018
The invention relates to disc brake systems and, more particularly, relates to a disc brake system having a brake pad retained in place within the system using a spring clip-type spring clip.
Disc brake systems are used in a wide variety of applications such as bicycles, snowmobiles, golf carts, and automobiles. The typical disc brake system includes 1) a power source, such as a hydraulic master cylinder, and 2) a mechanical disc brake assembly that is actuated by the power source to apply the brake. The disc brake assembly includes a disc that rotates with the wheel, one or more brake pads, and one or more calipers each of which includes at least one piston that is selectively forced towards the disc by the power source to press the brake pad into frictional contact with the disc, thereby applying the braking force.
Within traditional braking environments, brake calipers are actuated to slow or stop a vehicle of some sort. However, when brake system pressure is released, a brake caliper piston pulls back into a brake caliper housing. Friction between the brake pad and brake disc can be reduced when the brake system pressure is released on the brake caliper piston. When this happens, the brake pad is generally free to run with very close proximity to the disc. However, because the brake pads are in such close proximity to the brake disc, these two parts can touch. Disadvantageously, this free running drag can cause losses in speed and generate excess heat by and into the disc. Unfortunately, this condition can deteriorate the condition of the brakes and/or braking system and rendering the same altogether ineffective.
Pad holders are used for installing brake pads of a disc brake assembly. Attempts have been made to address drag and rattling problems and to hold pads tightly against associated pistons. For instance, using pad holders formed from any of a variety of structures such as retainer clips, bolts, and/or fastening lugs are disclosed, for example, in U.S. Pat. No. 5,529,150, GB Patent No. 2,017,236, and GB Patent No. 2,056,601. These pad holders are typically of a relatively complex design, making them rather expensive to fabricate. They also tend to be relatively difficult to remove and install, usually requiring special tools and often requiring partial or complete removal of the caliper and/or disc from the assembly before the pad can be removed from the remainder of the assembly. Many are less than fully effective at holding the pad tight against the associated piston, thereby giving rise to drag and rattling problems.
A spring clip type spring clip is described in U.S. Pat. No. 6,003,639 to James Buckley et al., the disclosure of which is incorporated by reference herein. This spring clip overcomes some of the drawbacks listed above. However, it has several other drawbacks. For example, this type of spring clip must be used with a relatively wide caliper because it requires space in the piston bore for the spring clip to pass. Another drawback of this spring clip is that it is used with a piston having a post. This makes the piston relatively costly to produce. Furthermore, this spring clip is external to the piston, exposing it to dirt, grease, and wear. Lastly, there is only one point of engagement between the spring clip and the piston, increasing the risk of detachment.
In view of the foregoing, it would be desirable to provide a brake assembly that provides at least one of the following advantages when compared to previous brake assemblies: a decreased risk of detachment of the piston and back plate, less expensive to manufacture, that improves fuel economy, that reduces wear on brake pads, improves cooling of the pad, and lowers the virtual inertia of the wheel.
The invention, which is defined by the claims set out at the end of this disclosure, is intended to solve at least some of the problems noted above.
A disc brake assembly is provided that includes a disc, a caliper, and a piston having a rear end slidably mounted in a bore in the caliper, a front end that faces the disc, and an inner axial surface. A brake pad is disposed between the piston and the disc. The brake pad has 1) a back plate having front and rear surfaces and 2) a friction pad mounted on the front surface of the back plate. The assembly also has an improved spring clip for holding the brake pad in the brake assembly. The spring clip is configured to be connectable to the rear surface of the back plate and engageable with the inner axial surface of the piston. The spring clip holds the rear surface of the pad tightly against the front surface of the piston or pistons of the caliper to prevent brake drag and brake rattle. The pad can be removed from the brake assembly, without using any special tools, simply by imposing sufficient downward vertical retraction forces on the pad to deflect the spring clip and to remove the pad from the spring clip to which it is attached.
Also provided is a disc brake assembly including a disc, a caliper, and a piston having a rear end slidably mounted in a bore in the caliper, a front end that faces the disc, and an inner axial surface. A brake pad is disposed between the piston and the disc. The brake pad includes 1) a back plate having front and rear surfaces, the back plate including a structure situated on the rear surface of the back plate and 2) a friction pad mounted on the front surface of the back plate. The assembly also includes a spring clip that is configured to be connectable to the structure situated on the rear surface of the back plate and the piston.
In one embodiment, the structure situated on the rear surface of the back plate comprises a finger having a valley and the spring clip includes free ends and a loop disposed between the free ends. The loop is configured to be connectable to the valley of the finger.
In another embodiment, the structure situated on the rear surface of the back plate comprises a post and the spring clip includes a loop that is configured to be connectable to the post.
A method of using the assemblies is also provided. In it, a spring clip is compressed. The compressed spring clip is aligned with a groove on an inner axial surface of a piston of a brake assembly. The compression force on the spring clip is released such that the spring clip fits into the groove of the piston. A brake pad is secured to the spring clip. The securing step comprises connecting a structure on the brake pad to the spring clip.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.
Many aspects of this invention will be better appreciated and understood in conjunction with the following drawings and description, each of which form integral components of this provisional patent application, in which like reference numerals generally represent like elements, and in which:
The disc brake assemblies described herein can be used on disc brake assemblies that are mounted on wheels. The disc brake assemblies described herein can be used on motorcycles, bicycles, snowmobiles, ATVs, automobiles, buses, and trucks, ATVs, golf carts, go-karts, and the like. The disc brake assemblies described herein can be used on a dual piston caliper, a single piston caliper, on a caliper having a back plate actuated by two pistons, as is described in U.S. Pat. No. 6,318,514, and on a caliper having a back plate actuated by more than two pistons. The disc brake assemblies will be described herein with respect to dual piston application for convenience sake only. The invention is not limited to this application. The disc brake assemblies described herein can include a fixed caliper or a floating caliper.
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The brake pad 12 is securely clamped to the piston 14 by the spring clip 32, which is configured to permit the brake pad 12 to be installed in the assembly 10 and removed from the assembly 10 without using any special tools and without disassembling the brake system in any way. Towards these ends, the spring clip 32 takes the form of a wire form 32. Referring additionally to
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The piston engaging sections 76 and 78 of the spring clip 32 are curved with a radius of curvature that generally matches the radius of curvature of the piston 14. However, the maximum undeflected distance between the section 78 on one side of the spring clip 32 and section 78 on the other side of the spring clip 32 is greater than the diameter of the inner axial surface 30 of the piston 14 so that the wire form 32 must deflect radially when the wire form 32 is inserted. This combination of radial and axial deflection minimizes or even eliminates movement of the brake pad 12 relative to the piston 14 both axially and radially, thereby preventing drag and rattle as well as unintended pad removal.
The brake pad 12 is installed simply by compressing the spring clip 32 by pushing the piston engaging sections 78 together. The spring clip 32 is placed inside the piston cavity. The piston engaging sections 76 are then inserted into the groove on the inner axial surface of the piston near the top of the piston. The piston engaging section 78 is aligned with the groove, and pressure on the piston engaging section 78 is released such that the spring clip 32 springs into the groove, and spring clip 32 is held therein.
The brake pad 12 is inserted from the bottom of the caliper, moved upwardly, and tilted so that the free end of the finger 64 aligns with the loop. As the pad is pushed into position, the finger 64 slips under the loop, displaces the loop slightly, and then allows the loop to fall into the valley of the finger 64. This produces a spring force that holds the pad tightly to the piston.
The brake pad 12 is removed from the piston and spring clip 32 by pulling the pad downwardly with a removal force that overcomes a retention force imposed on the brake pad 12 by the spring clip 32. The brake pad 12 is tilted as it is being pulled downwardly such that the spring clip 32 does not hit the piston.
A second embodiment of the disc brake assembly 110 is shown in
Each caliper 118 includes a bore 122 that slidably receives a rear axial end 20 of the piston 114. A front axial end 24 of the piston 114 faces the disc 116. The brake pad 112 is disposed between the piston 114 and the disc 116.
The back plate 144 has a relatively flat rear surface 148, a relatively flat front surface 150, and left, right, upper, and lower side edges 152, 154, 156, and 158, respectively. The friction pad 146 is glued or otherwise affixed to the front surface 150 of the back plate 144. The back plate 144 has a tab 160 extending upwardly from the upper edge 156 of the back plate 144. The tab 160 includes an opening 162 that receives a pin 96 (
The back plate 144 includes a post 80 with a plate engaging portion 82 that is embedded in the back plate 144 via an interference fitting. The post 80 has a cap 84 provided on a free end 86 of the post 80 and a groove 88 partially defined by the cap 84. The groove 88 is further defined by a side 90 of an annular flange 92. The opposite side 94 of the annular flange 92 rests on the rear surface 148 of the back plate 144.
The brake pad 112 is securely clamped to the piston 114 by the spring clip 132. The spring clip 132 is configured to permit the brake pad 112 to be installed in the assembly 10 and removed from the assembly 110 without using any special tools and without disassembling the brake system in any way. Towards these ends, the spring clip 132 is preferably formed from a single piece of spring wire or “wire form.” The wire form 132 includes a pair of free ends 170, and a U-shaped loop 172 disposed intermediate the free ends 170. The loop 172 is bent away from the back plate 144. Piston engaging portions 174 are disposed between the loop 172 and the free ends 170. Piston engaging portions 174 are configured to extend substantially in parallel with the rear surface 148 of the back plate 144.
Each of the piston engaging portions 174 includes two piston engaging sections 176 and 178 that are separated by a radially inward curve and that are received in the groove 128 of the piston 114. Piston engaging sections 176 are located closer to the loop 172, and piston engaging sections 178 are located closer to the free end 170 of the spring clip 132. The loop 172 is slipped over the cap 84 of the post 80 and fits into the groove 88 of the post 80 to hold the wire form 132 in place.
The piston engaging sections 176 and 178 are curved with a radius of curvature that generally matches the radius of curvature of the piston 114. However, the maximum undeflected distance between section 178 on one side of the spring clip 132 and section 178 on the other side of the spring clip 132 is greater than the diameter of the inner axial surface 130 of the piston 114 so that the wire form 132 must deflect radially when the wire form 132 is inserted. This combination of radial and axial deflection minimizes or even eliminates movement of the brake pad 112 relative to the piston 114 both axially and radially, thereby preventing drag and rattle as well as unintended pad removal.
The brake pad 112 is installed simply by compressing the spring clip 132 by pushing the piston engaging sections 176 together and piston engaging sections 178 together. The spring clip 132 is placed inside the piston cavity. The piston engaging sections 176 are then inserted into the groove 128 on the inner axial surface 130 of the piston 114 near the top of the piston 114. The piston engaging sections 178 are aligned with the groove 128 of the piston 114, and pressure on the piston engaging sections 178 is released such that the spring clip 132 springs into the groove 128, and spring clip 132 is held therein.
The brake pad 112 is inserted from the bottom of the caliper 118, moved upwardly, and tilted so that the 80 post aligns with the loop 172. As the brake pad 112 is pushed into position, the cap 84 of the post 80 slips under the loop 172, displaces the loop 172 slightly, and then allows the loop 172 to fall into the groove 88 of the post 80. This produces a spring force that holds the brake pad 112 tightly to the piston 114.
The brake pad 112 is removed from the piston 114 and spring clip 132 by pulling the brake pad 112 downwardly with a removal force that overcomes a retention force imposed on the brake pad 112 by the spring clip 132. The brake pad 112 is tilted as it is being pulled downwardly such that the spring clip 132 does not hit the piston 114.
In both embodiments of the disc brake assembly 10 and 110, the brake pad 12 and 112 retracts with the piston 14 and 114 away from the disc 16 and 116 when brake system hydraulic pressure is released. With the brake pad 12 and 112 retracting away from the disc 16 and 116, the chance of parasitic drag between disc 16 and 116 and pad 12 and 112 is reduced or eliminated. This advantageously increases the performance of the disc brake assembly 10 and 110, increases fuel economy, and increases brake pad 12 and 112 life due to lower running temperatures achieved because the brake pad 12 and 112 spends less time in contact with the disc 16 and 116 and air can cool the brake pad 12 and 112. This also lowers the virtual inertia of the wheel, making the wheel act lighter. In antilock brake systems, this feature provides the benefit of releasing the wheel sooner than without this. The disc brake assembly 10 and 110 described herein also lessens or eliminates the aforementioned known problems in the prior art. For example, the assemblies 10 and 110 cost less to manufacture than previous assemblies employing spring clip.
By this invention, a brake pad 12 and 112 is fixed to a piston 14 and 114 through the use of a spring or the like, which allows the brake pad 12 and 112 to retract with the piston 14 and 114 away from the disc 16 and 116 when the brake system pressure is released.
Many changes and modifications can be made in the invention without departing from the spirit thereof. The scope of some of these changes is discussed above. The scope of the remaining changes will be apparent from the appended claims.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/740,227, filed Nov. 28, 2005, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60740227 | Nov 2005 | US |
