Guide pin and bearing for a disc brake

A guide pin (24) attached to a caliper (21) and located in a bore (28) of an anchor bracket or carrier member (22) in a disc brake (10). The carrier member (22) and caliper (21) move with respect to each other in response to a force developed by a piston for urging friction pads (18,20) into engagement with a rotor (12) to effect a brake application. The guide pin (24) is characterized by a head (36) having a shaft (38) extending therefrom into a bearing (62,64) which is located between the shaft (38) and housing surrounding the bore (28). The bearing (62,64) has dissimilar resistances to stiffness in a radial plane than in a tangential plane such that vibratory forces are attenuated and dynamic forces generated during a brake application are absorbed to maintain alignment between the friction pads (18,20) and rotor (12).

This invention relates to means for resiliently restraining a guide pin of 
a disc brake differently in a radial direction than in an arcuate 
direction to accommodate for different levels of stresses created by 
vibration and dynamic loads. 
BACKGROUND OF THE INVENTION 
In disc brakes, such as illustrated in U.S. Pat. Nos. 4,446,948, 5,526,904, 
5,562,187 and 5,785,156 wherein guide pins are provided to accommodate 
sliding motion between a carrier member and a caliper the elimination of 
noise caused by rattling of components is a concern. 
One way of reducing noise is through rubber bushings as disclosed in U.S. 
Pat. No. 4,446,948 which insulate guide pins. In addition, compensation 
for manufacturing tolerances can be achieved by tightly align one guide 
pin in a first bore while allowing a second guide pin to be loosely 
retained in a second bore as disclosed in U.S. Pat. No. 5,526,904. In this 
arrangement a resilient guide bushing which surrounds a portion of the 
second guide pin to sustain a desired alignment between friction pads and 
a rotor. 
Further, noise caused by rattling of the components in a disc brake have 
been greatly reduced through the use of resilient projection extending 
from the guide pins to retain the components in engagement as disclosed in 
U.S. Pat. No. 5,562,187. Unfortunately, such pins are costly to produce 
and as a result have not yet been endorsed by the industry. 
While the resilient bushings and special guide pins disclosed in the prior 
art function in a satisfactory manner, it has been observed that radial 
forces developed when a disc brake is subjected to vibration such as 
experienced in travel on rough roads are different that tangential forces 
caused by dynamic loading during a brake application. 
In the present invention, guide pins retained in a carrier member are 
aligned within bores in caliper by relatively low cost and easy to 
manufacture bearing means having dissimilar resistance's to stiffness in a 
radial plane than in a tangential plane. The bearing means is designed to 
attenuate vibratory forces and resultant noise while allowing tangential 
forces created by dynamic forces generated during a brake application to 
be absorbed such that the friction pads and rotor are maintained in a 
desired alignment. 
SUMMARY OF THE INVENTION 
A primary object of the present invention is to provide a bearing for a 
guide pin wherein different levels of stiffness are provided to resist 
radial and tangential forces. 
According to this invention, a disc brake has first and second guide pins 
attached to caliper and located in a bore of an anchor bracket or carrier 
member. The carrier member and caliper move with respect to each other in 
response to forces developed by a piston to urge friction pads into 
engagement with a rotor to effect a brake application. Each guide pin is 
characterized by a head having a shaft which extends into a corresponding 
bore in the anchor bracket or carrier member. A plurality of bearing means 
are located between each shaft and housing surrounding such bore. Each 
bearing means has a cross-sectional profile that provides a different 
stiffness in a radial plane than in a tangential plane such that different 
levels of vibrations or movements can be modified to assure that the 
friction pads and rotor remain in a desired alignment. 
An advantage of a brake system using this invention resides in an easy to 
select bearing configuration which has a different level of stiffness in a 
radial plane than in a tangential plane to compensation in manufacturing 
tolerances between guide pins secured to a carrier and bores in a caliper 
while at the same time attenuating vibrations of components which could 
produce noise.

DETAILED DESCRIPTION 
The disc brake 10 as best shown in FIGS. 1 and la includes a rotor 1 2 
having a pair of opposing friction faces 14,1 6 which rotate with an axle. 
A pair of friction pads 18 and 20 disposed adjacent friction faces 14,16 
are urged into braking engagement therewith in response to a force 
developed by hydraulic fluid acting on a piston retained in caliper 21 
during a brake application. 
The caliper 21 slides with respect to a anchor bracket or carrier 22 by 
means of first 24 and second 26 axial guide pins. The carrier 22 being 
fixed to a vehicle and the first 24 and second 26 axial guide pins are 
slidably fixed to arms 27 and 27' of caliper 21. The first guide pin 24 is 
located in a first bore 28 in boss 32 of carrier 22 while the second guide 
pin 26 is located in a second corresponding bore in boss 34 of carrier 22. 
In more particular detail, guide pins 24 and 26 are identical and as a 
result only guide pin 24 will be described in detail and where needed the 
same number is used for corresponding component with respect to guide pin 
26. 
Guide pin 24 has a head section 36 with a general cylindrical shaft 38 
extending therefrom. Head section 36 has identical first 40 and second 42 
flats or locking surfaces 40 and 42, see FIG. 2, one of which is 
designated to engage surface 44 on caliper 21. As illustrated in FIG. 1, 
locking surfaces 44,44' on caliper 21 is located in a plane substantially 
parallel to each other. A bolt 47 extends through opening 45 in arm 27 to 
secure guide pin 24 to caliper 21 and position guide pin 24 in a desired 
orientation with respect to carrier 22. In addition, it should be 
understood that opening 45 is designed to have a slightly larger diameter 
than bolt 47 to compensate for manufacturing tolerances between carrier 22 
and caliper 21. 
Shaft 38 on guide pin 24 has a first bearing groove 46 located adjacent end 
25, a seal groove 50 located adjacent shoulder 52 of head section 36 and a 
second bearing groove 48 located between seal groove 50 and the first 
bearing groove 46. A bellows 54 has a first bead 56 located in seal groove 
50 and a second bead 58 located in a groove 60 on carrier 22. When shaft 
38 is positioned in bore 28 bellows 54 prevents contamination from being 
communicated to bore 28. 
Guide pin 24 is aligned in bore 28 by first 62 and second 64 resilient 
bearings. Resilient bearings 62 and 64 are identical and only bearing 62 
is hereinafter described in detail in conjunction with FIG. 3. Bearing 62 
has a cylindrical body made of alternating first 66,66' and second 68,68' 
resilient segments. The first segment 66 is made of a first elastomeric 
material having a first coefficient of resiliency while the second segment 
68 is made of a second elastomeric material having a second coefficient of 
resiliency. The first segment 66 has a plurality of axial slots 
70,70'71,71' which extend along the entire length of the bearing 62 to 
provide a flow path for air from the bottom 29 of bore 28 to bellows 54. 
Since the material for the first segment 66 has a higher resiliency than 
the material for the second segment 68 a correspondingly greater 
resistance to radial movement of pin 24 is provided than with respect to 
tangential movement. 
In assembling the disc brake 10, guide pins 24 and 26 are initially located 
in corresponding bores 28 (only one of which is shown) in the anchor 
bracket or carrier member 22. Friction pads 18 and 20 are aligned with 
respect to friction faces 14 and 16 on rotor 12 and caliper 21 positioned 
on carrier 22. A first bolt 46 which extends through opening 45 in arm 32 
is secured to head 36 of guide pin 24. Thereafter, a second bolt 47' which 
extends through opening 45' is secured to head 36' of guide pin 26. 
Because openings 45,45' are slightly larger than bolts 47,47' any 
dimensional differences caused by manufacturing tolerances can be 
compensated for to assure that friction pads 18 and 20 are aligned with 
friction faces 14 and 16 while at the same time allowing caliper 21 to 
freely move with respect to carrier 22 by way of guide pins 24 and 26 
sliding without binding in bores 28 within carrier 22. Locking surfaces 40 
and 42 on head 36,36' of guide pins 24 and 26 assure that the first 
segment 66,66' on bearings 62 and 64 remain in a desired aligned position 
to provide greater resistance to movement is provided along a radial plane 
extending from the axis of rotor 12 than is provided along a tangential 
arc extending through the center of guide pins 24 and 26. 
FIG. 4 illustrates another embodiment of the invention wherein the shaft 
100 for a guide pin 124 has a rectangular shape and a cylindrical bearing 
162 is made of a single resilient material. The locking surface on head 36 
holds the rectangular shape such that the length along a tangential arc is 
greater than along a radial section to position a greater volume or 
thickness of material in a radial plane that in an arcuate plane. The 
greater thickness of resilient material in the radial plane provides a 
lower stiffness than the lessor thickness of material in the tangential 
plane such that vibratory forces are attenuated in a different manner than 
dynamic forces developed during braking. 
FIG. 9 illustrates another embodiment of the invention wherein a shaft for 
a guide pin 224 has a circular shape and a bearing member 262 has an oval 
cross-section with a central circular opening 261. Bearing member 262 is 
designed to be located in a corresponding oval bore in an anchor bracket 
or carrier member. In this embodiment, the bearing material is uniform 
resilient material, however the volume or thickness of material along a 
radial plane through the axial center of the guide pin 224 is greater than 
along a tangential arc. As with the bearing structure 162, bearing 262 
providing greater resistance to radial movement than to arcuate movement 
to attenuate vibrations while maintaining pin 224 in axial alignment with 
respect to rotor 12. 
FIGS. 5 and 6 illustrate a still further embodiment of the invention 
wherein guide pin 324 has a axial shaft 338 with first 366,366' and second 
368,368' segments of different resilient materials axially extending from 
adjacent a seal groove to the end thereof. A layer of material 367,367' 
and 369,369' having a low coefficient of friction is respectively placed 
on the top of the segments 366,366' and 368,368'. The layer is designed to 
provide for low resistance to movement of guide pins 324 in a bore of the 
carrier 322 such that movement of a caliper is substantially only 
controlled by the force developed by the reaction of pistons in the 
caliper to pressurized fluid. 
FIGS. 7 and 8 illustrate a still further guide pin 424 for use in a disc 
brake wherein a layer of resilient material 466 is sandwiched between 
first 444 and second 446 arcuate strips of that make up shaft 438. Shaft 
438 has an oval cross-section as best shown in FIG. 7 and is designed to 
be located in a circular bore 28 such greater stiffness is provided along 
a radial plane than in a tangential plane.