BACKGROUND OF THE INVENTION Disc brakes wherein two support members, which are spaced apart from each other and slidably guide first and second friction pads on first and guide pins during a brake application are known in the prior art. The ., following U. S. Patents 4,958,703; 5,749,445; 5,810,112; 5,819,884 5,934,416 may be considered to be typical of such disc brakes. In these disc brakes, the first and second guide pins are correspondingly retained in first and second bores in a support member that is fixed to the frame of a vehicle. The first and second guide pins move in the first and second bores as the thickness of the first and second friction pads decrease during the engagement with a rotor and as a result the bearing engagement surface correspondingly decreases. Under some circumstances as the bearing surface decreases, the resistance to a moment caused by the engagement of the friction pads with the rotor may cause twisting of the caliper such that the wear surface of the friction pads is not entirely uniform. This non- uniform wear may result in a need to replace the friction pad before its projected usefulness life is achieved.

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a disc brake wherein the effect of a caliper twisting moment caused on engagement of friction pads with a rotor is essentially reduced or eliminated

while the cumulative bearing length of engagement between the first and second guide pins and a support member remain substantially constant with changes in thickness of the first and second friction pads caused by wear engagement with a rotor.

In more particular detail, the disc brake has a support member secured to a vehicle with a first guide pin located in a first bore and a second guide pin located in a second bore. The first and second bores are complimentary and define first and second bearing surfaces for aligning a caliper over a rotor associated with a wheel of the vehicle. The caliper is a uniform housing with an actuation section located on a first side of the rotor and connected by a bridge to an arm located on a second side of the rotor.

The actuation section has a bore therein for retaining a piston to define an actuation chamber. A first friction member is connected to the piston and a second friction member connected to the arm. To effect a brake application pressurized fluid is presented to the actuation chamber which acts on the piston and actuation section to develop a force for moving the first and second friction members into engagement with the rotor to effect a brake application. The caliper is characterized by a first ear that extends from the actuation section and a second ear that extends from the arm. The first guide pin engages the first ear and is located in the first bore while the second guide pin engages the second ear and is located in the second bore.

The engagement of the first and second pins with the first and second pins resists caliper twisting moments caused by off-set forces between friction members on engagement with the rotor to retain the corresponding engagement surfaces of the first and second friction members in a parallel planes with the rotor. With changes in the thickness of the first and second friction member caused by wear engagement with the rotor, the arm moves toward the support member and correspondingly the second pin moves into the second bore to increase its bearing length while the actuation section moves away from the support member and correspondingly the first pin moves out of the first bore to decrease its bearing length. The increase in

the bearing length of the second pin and the decrease in the bearing length of the first pin are cumulative and as a result a substantially constant bearing length of engagement is maintained between the first and second guide pins and the support members with changes in thickness of the first and second friction pads caused by wear engagement with the rotor.

An advantage of the disc brake results in a uniform wear of a thickness of a friction member on engagement with a rotor.

An object of this invention is to provide a disc brake with a guide pins whereby a cumulative bearing length remains constant with a decrease in a thickness of friction pads caused by wear.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a prior art disc brake; Figure 2 is a sectional view of Figure 1 taken along lines 2-2 illustrating an initial relationship between first and second guide pins, friction pads, a support member and a rotor of the disc brake; Figure 3 is a sectional view illustrating the relationship of the components shown in of Figure 2 after wear has reduced the thickness of the friction pads causing a proportionally reduction in the bearing support for the first and second guide pins; Figure 4 is a schematic illustration of a disc brake made according to the principals of the present invention illustrating an initial relationship between a first guide pin (36,236,336) located by a first ear in a first bore a support member and a second guide pin located by a second ear in a second bore in the support member wherein the first and second bores are located on opposite sides of support member to oppose twisting moments developed during a brake application ; Figure 5 is a sectional view showing the relationship of the components illustrated in Figure 4 with a decrease in the thickness of the friction members whereby a constant commutative bearing length is maintained between the first and second guide pins and the support member;

Figure 6 is a second embodiment of the disc brake of the present invention wherein a first bore is located in the support member and a second bore is located in the caliper ; Figure 7 is a sectional view showing the relationship of the first and second guide pins in the first and second bores of the disc brake illustrated in Figure 6 after wear has reduced the thickness of the friction pads and wherein a constant commutative bearing length between the first and second guide pins and the support is maintained with a decrease in a thickness of friction member caused by wear engagement with a rotor; and Figure 8 is another embodiment of the disc brake of the present invention showing the relationship of the components wherein a first guide pin is secured to the caliper and a second guide pin is secured to the support member and correspondingly engage first and second ears of the support member and caliper to resist twisting moments created on engagement of friction pads with a rotor.

DETAILEDDESCRIPTION The disc brake 10 shown in Figures 1 and 2 is of a type known in the prior art, see U. S. Patent 5,810,122, wherein an anchor or support member 12 which is fixed to the housing 14, in a manner as disclosed in U. S. Patent 5,988,761, for use in a brake system of a vehicle. Disc brake 10 has an integral caliper 16 that includes an actuation section 18 that is connected by a bridge 22 to an arm 20. The actuation section 18 has a bore 24 therein for retention of a piston 26 to define an actuation chamber 28. A first friction member 30 is connected to piston 26 while a second friction member 32 is connected to arm 20. The first 30 and second 32 friction members are respectively located adjacent a first face 34a and a second face 34b of a rotor 34 which is connected to rotate with an axle of the vehicle. A first guide pin 36 is connected to ear 38 which extends from the actuation section 18 and is mounted to slide in a first bore 40 in the support member 12. A second guide pin 42 is connected to ear 44 which extends from the actuation section 18 and is mounted to slide in a second bore 46 in

the support member 12. The first 40 and second 46 bores are parallel to each other and designed to respectively hold the first guide pin 36 and the second guide pin 42 in a perpendicular relationship with respect to the rotor 34 such that the first friction member 30 and the second friction member 32 are held in corresponding planes respectively parallel with faces 34a and 34b on rotor 34. When an operator desires to effect a brake application, pressurized fluid is supplied to an actuation chamber 28 of bore 24. The pressurized fluid acts on piston 26 and the bottom 24a of bore 24, to develop a force which moves the first friction member 30 into engagement with face 34a and the second friction member 32 into engagement with face 34b of rotor, see Figure 2, to retard the rotation of rotor 34 and effect a brake application.

In this disc brake 10, the bearing support for the first guide pin 36 and second guide pin 42 is defined by an initial length"I, and and carries torque forces developed during a brake application from the caliper 16 into the support member 12. The cumulative bearing support"L"is defined by plus 12 and initially 11 and 12 have equal length. During a brake application, a leading edge of each friction members 30 and 32, as defined by the rotation of rotor 34, first engage the rotor 34 and as a result introduce a rotational moment or force into caliper 16 which is part of the torque forces experienced during a brake application.

Disc brake 10 functions in an adequate manner, however, after a period of time, the thickness of the first 30 and second 32 friction members are reduced through wear, see the illustration in Figure 3. When this situation occurs, the bearing support for the first 36 and second 42 guide pins is correspondingly reduced by the decrease in thickness of the friction pads results in bearing lengths of 11-x1 and 12-x2 to provide an on-going overall bearing support of L= (11-x1) + (12-x2) where: x, is the wear of the first friction member and x2 is the wear of the second friction member.

This decrease in bearing length results in an increase in a strength requirement for the first 36 and second 42 guide pins as they now must be

capable of carrying additional torque forces into the support member 12.

Further, as the thickness of the first 30 and second 32 friction members decrease, additional forces make it harder for the first 36 and second 42 guide pins to hold the first 30 and second 32 friction members in corresponding planes which are parallel with faces 34a and 34b of rotor. If the first 30 and second 32 friction members are not in parallel planes, a result a leading edge on the first 30 and second 32 friction members may wear at a faster rate than a trailing edge which may require replacement of the first 30 and second 32 friction members at an earlier time than with uniform wear.

The various embodiments of disc brake 100, 200,300 of the present invention essentially eliminates problems relating to twisting and a reduction in the bearing surface between guide pins and a support member in a disc brake 10 caused by engagement of friction members with a rotor. Disc brake 100 as illustrated in Figures 4 and 5, is essentially identical in structure to the disc brake 10 of Figure 1 with the exception of the caliper 116. Disc brake 200 as illustrated in Figures 6 and 7 and is essentially identical in function to disc brake 100 Figure 4 with the exception of the alignment bores. Disc brake 300 as illustrated in Figure 8 is functionally similar to the disc brake 200 of Figure 6.

In the details of the invention, only when a difference in structure occurs will a new number be used to identify such structure, otherwise the same number is used to identify the component and describe its operation with respect to the disc brakes in the various embodiments of the invention.

In particular detail, the disc brake 100, as shown in Figures 4 and 5, has a support member 112 that is secured to a vehicle. The support member 112 has an integral first bore 40 that is parallel with a second bore 146 and corresponding closed ends 40a and 146a that are located on opposite sides of a peripheral surface of a rotor 34. Caliper 116 has an actuation section 18 with a first ear 38 that extends therefrom while arm 120 has a second ear 144 that extends therefrom. A first guide pin 36 is

connected to the first ear 38 and is located in the first bore 40 while a second guide pin 142 is connected to the second ear 144 and is located in a second bore 146 to align the caliper 116 over a rotor 34 on a vehicle. The bearing length for the first guide pin 36 that extends into the first bore 40 is I, and the bearing length for the second guide pin 142 is 12that extends into the second bore 146. The first bearing length 11 and the second bearing length 12 have an initial cumulative length of L (Linitia + 12)-As with disc brake 10, when pressurized fluid is presented to actuation chamber 28, the pressurized fluid acts to and moves piston 26 away from the bottom 24a of bore 24 and correspondingly moves the first friction member 30 into engagement with face 34a on rotor 34 and the second friction member 32 into engagement with face 34b on rotor 34 to retard the rotation of rotor 34 to effect a brake application. With the first ear 38 located on actuation section 118 and the second ear 144 located on arm 120, in a manner as illustrated, greater resistance is provided to prevent any movement caused by the rotational moment (twisting torque) developed during a brake application.

The disc brake 100, shown in Figure 4, will function in a consistent during an entire life of the friction members 30 and 32 even though guide pin 142 is shorter than guide pin 36 as the cumulative on-going bearing support Lon-going remains constant, see Figure 5. In disc brake 100 cumulative on-going bearing support L. n-going remains constant with a decrease in the thickness of the friction members 30 and 32 defined by x, and x2 caused by wear because a decrease in the bearing support length 11- x of pin 36 in bore 40 results in a corresponding increase in the bearing support length 12 + x of pin 142 in bore 146. Thus, the bearing support through which part of the braking torque is transmitted from caliper 116 into support member 112 remains constant for an entire life of the friction members 30 and 32 of disc brake 100.

In more particular detail, disc brake 200, as illustrated in Figures 6 and 7 while functionally similar to disc brake 100 of Figure 4 is

distinguished by a first guide pin 236 is located in bore 240 in support member 212 and a second guide pin 242 is located in a bore 246 in the arm 220. The support member 212 has a first bore 240 which receives a first pin 236 connected to a first ear 238 that extends from the actuation section 218 while a caliper 216 has a second bore 246 which is located in ear 244 on arm 220 for receiving a second guide pin 242 that extends from the support member 212. The first bore 240 and second guide pin 242 are parallel to each other and designed to respectively receive the first guide pin 236 and second bore 246 such that the first 30 and second 32 friction members, connected to piston 26 and arm 220, are maintained in corresponding planes parallel with faces 34a and 34b on rotor 34. The bearing support length 11 of the first guide pin 236 that extends into the first bore 240 and the support length 12 of the second guide pin 242 that extends into the second bore 246 define bearing surfaces that have an initial cumulative support length equal to Ljnjtjal (L = 11 + 12). As with disc brake 10, when pressurized fluid is presented to actuation chamber 28, pressurized fluid acts on and moves piston 26 away from the bottom 24a of bore 24 to correspondingly move the first friction member 30 into engagement with'face 34a on rotor 34 and the second friction member 32 into engagement with face 34b on rotor 34 to retard the rotation of rotor 34 and effect a brake application. With the first ear 238 located on actuation section 218 and the second ear 244 located on arm 220 in a manner as illustrated in Figure 6, resistance is provided to prevent any twisting movement caused by the rotational moment developed during a brake application.

Disc brake 200 functions in a consistent manner during an entire life of the friction members 30 and 32 (assuming equal wear) even though guide pin 242, as illustrated in Figure 7, is shorter than guide pin 36. The cumulative on-going bearing support length Lot gown remains constant because a decrease in the thickness of the friction members 30 and 32 caused by wear produces a decrease in the length of bearing support (1,-x,)

of 236 in bore 240 results in a corresponding increase in the length of bearing support (12 + x2) of pin 242 in bore 246. Thus, the cumulative bearing support length Longojng, through which part of the braking torque is transmitted from caliper 216 into support member 12, remains constant for the disc brake 200.

In more particular detail disc brake 300 which is illustrated in Figure 8 functions in a manner similar to disc brake 200 of Figure 6 to oppose rotative moments introduced through the engagement of friction members 30 and 32 with rotor 34 but is distinguished therefrom by a first guide pin 336 which is located in bore 340 in support member 312 and a second guide pin 342 which is located in a bore 346 in the arm 320 of caliper 316.

The support member 312 has a first bore 340 which receives a first pin 336 which is connected to a first ear 338 which extends from the actuation section 318 of a caliper 316. Support member 312 has a second bore 313 which receives a threaded end of a second pin 342 that extends through a second bore 346 located in an ear 344 on arm 320. The first bore 340 and second guide pin 342 are parallel to each other, such that the first bore 340 receives the first guide pin 336 while the second bore 346 receives the second guide pin 342 and correspondingly the first 30 and second 32 friction members connected to piston 26 and arm 320 are maintained in planes parallel with faces 34a and 34b on rotor 34. The bearing support length 11 of the first guide pin 336 that extends into the first bore 240 and the bearing support length 12 of the second guide pin 342 that extends into the second bore 246 define bearing surfaces which have an initial cumulative ength"L" (L = 11 + 12). When pressurized fluid is presented to actuation chamber 28, the pressurized fluid acts on and moves piston 26 away from the bottom 24a of bore 24 to correspondingly move the first friction member 30 into engagement with face 34a on rotor 34 and the second friction member 32 into engagement with face 34b on rotor 34 to retard the rotation of rotor 34 and effect a brake application. With the first ear 338 being located on actuation section 318 and the second pin 342

being held by ear 344 on arm 320 resistance is provided to prevent caliper rotational twisting developed during a brake application.

Disc brake 300 functions in a manner to resist rotational moments during an entire life of the friction members 30 and 32, however, the total bearing support L is equal to (11-xi + 12) as the total in this embodiment is reduced by an amount equal to a decrease in the thickness by an amount equal to x, caused by wear of the first friction member as the bearing support of guide pin 342 remains constant with respect to ear 344.

However, even with an overall decrease in the on-going bearing support length of disc brake 300 as compared with disc brake 100 shown in Figure 4 and disc brake 200 shown in Figure 6, the disc brake 300 shown in Figure 8 provides an improvement over the known disc brakes in the prior art as shown in Figure 1. Indeed, if the fixed pin and the sliding pin shown in Figure 8 were reversed, a resulting bearing length would be defined by L = 11 +x + 12 with wear of the friction members which would be greater than either disc brake 100 or disc brake 200.