Disc brake system

An improved disc brake system of the general type including a brake frame having a pair of spaced apart rails, a pair of brake linings slidably carried on the brake frame rails, a circular rotor rotatably carried on the wheel assembly of a vehicle and having smooth planar inboard and outboard contact faces, a caliper assembly slidably mounted on the rails of the brake frame, and, a brake pedal operatively associated with the caliper assembly, the caliper assembly having a piston which when actuated by depressing the brake pedal first forces one brake lining against the inboard contact face of the rotor and then causes the caliper assembly to slide along the brake frame rails to force the other brake lining against the outboard contact face of the rotor. The improved disc brake system minimizes the amount of heat generated when the brake linings frictionally contact the rotor and markedly increases the operational life of the rotor and brake linings.

This invention relates to disc brake systems for vehicles. 
More particularly, the invention relates to a disc brake system of the 
general type including a brake frame having a pair of spaced apart rails, 
a pair of brake linings slidably carried on the brake frame rails, a 
circular rotor rotatably carried on the wheel assembly of a vehicle and 
having smooth planar inboard and outboard contact faces, a caliper 
assembly slidably mounted on the rails of the brake frame, and, a brake 
pedal operatively associated with the caliper assembly, the caliper 
assembly having a piston which when actuated by depressing the brake pedal 
first forces one brake lining against the inboard contact face of the 
rotor and then causes the caliper assembly to slide along the brake frame 
rails to force the other brake lining against the outboard contact face of 
the rotor. 
In another respect, the invention pertains to a disc brake system of the 
type described which, when the brake pedal is depressed to force the brake 
linings against the rotor and is then released, minimizes the likelihood 
that the caliper assembly piston will jam in position and continue to 
force the brake linings against the rotor when the brake pedal is 
released. 
In a further respect, the invention relates to a truck disc brake system 
which does not require the use of metal cinder brake pads and which, in 
comparison to conventional truck disc brake systems, markedly increases 
the operational life of the brake system rotor and brake linings. 
In still another respect, the invention pertains to a disc brake system of 
the type described which, after the brake pedal is depressed to actuate 
the piston and force the brake linings against the rotor and is then 
released, facilitates the movement of the brake linings away from contact 
with the rotor. 
The air disc brake system described in B. F. Goodrich promotional circular 
ESD-79-HB-1 entitled "Power Screw Air Disk Brakes" is designed to meet 
braking requirements for air-brake Class 6, 7 and 8 vehicles. B. F. 
Goodrich power screw air disc brakes may be used for 10,500 pound to 
23,000 pound tractor or trailer axles. B. F. Goodrich air disc brakes 
include a brake frame having a pair of spaced apart rails, a pair of brake 
linings slidably carried on the brake frame rails, a circular rotor 
rotatably carried on the wheel assembly of a truck and having smooth 
planar inboard and outboard contact faces, and, a caliper assembly 
slidably mounted on the rails of the brake frame. The caliper assembly 
includes a piston which is actuated and extended by depressing the truck 
brake pedal. When the piston is actuated it forces one brake lining 
against the inboard contact face of the rotor and then causes the caliper 
assembly to slide along the brake frame rails to force the other brake 
lining against the outboard contact face of the rotor. The brake linings 
each include a backing portion and a pad portion. The pad portion contacts 
one of the rotor faces when the brake pedal is depressed and the caliper 
piston is displaced to force the linings against the rotor. When the brake 
pedal is released the piston retracts, permitting the brake linings to 
move away from the rotor. The pad portion of each lining is comprised of a 
metal cinder material. The rotor is fabricated from steel. The caliper 
assembly also includes a fitting for injecting grease into the assembly to 
lubricate the piston and includes a pressure relief fitting which permits 
grease to escape from within the caliper assembly when an excessive amount 
of grease is injected into the assembly. 
The B. F. Goodrich disc brakes described above have encountered serious 
operational problems. The metal to metal frictional contact between the 
rotor and metal pad portions of the brake linings generates an enormous 
amount of heat which wears out the pad portions in 3,000 to 10,000 miles 
of driving and causes the rotor to crack and warp. Consequently, when worn 
brake linings are replaced the rotor must be machined. Another problem 
associated with the brakes is that after the brake pedal has been 
depressed to actuate and extend the caliper to force the brake linings 
against the rotor, the piston jams in the extended position and does not 
retract after the brake pedal is released. When the caliper assembly 
piston jams in the extended position, the pad portions of the brake 
linings continue to contact the rotor, generating additional heat and 
incurring additional wear. Finally, another drawback of the B. F. Goodrich 
disc brake system is that when the brake pedal is released and the caliper 
piston retracts, the brake linings tend to tilt in the caliper assembly 
such that the pad portions are not parallel to the rotor faces, and, such 
that an edge of each pad portion leans against and contacts the rotor, 
causing uneven wear of the pad portions of the brake linings. 
Accordingly, it would be highly desirable to provide improved B. F. 
Goodrich air disc brakes which would markedly increase the operational 
life of the rotor and brake linings, would minimize the likelihood of the 
caliper piston jamming in extended position, and would insure that the 
brake linings do not tilt in the caliper assembly and lean against the 
rotor. 
Therefore, it is a principal object of the invention to provide improved 
disc brakes for a vehicle. 
Another object of the invention is to provide improved vehicle disc brakes 
of the general type including a brake frame having a pair of spaced apart 
rails, a pair of brake linings slidably carried on the brake frame rails, 
a circular rotor rotatably carried on the wheel assembly of a vehicle and 
having smooth planar inboard and outboard contact faces, and, a caliper 
assembly slidably mounted on the rails of the brake frame and having a 
piston actuated by depressing the brake pedal of a vehicle, the piston 
when actuated first forcing one brake lining against the inboard contact 
face of the rotor and then causing the caliper assembly to slide along the 
brake frame rails to force the other brake lining against the outboard 
contact face of the rotor. 
A further object of the instant invention is to provide improved disc 
brakes of the general type described which minimize the amount of heat 
generated when the brake lining frictionally contacts the rotor and which 
markedly increases the operational life of the rotor and brake linings. 
Still another object of the invention is to provide improved vehicle disc 
brakes of the general type described which minimize the likelihood that 
the caliper assembly piston will, when the brake pedal of a vehicle is 
depressed, jam in extended position and continue to force the brake 
linings against the rotor when the brake pedal is released.

Briefly, in accordance with my invention, I provide an improved disc brake 
system for a vehicle. The system includes a wheel assembly connected to 
the vehicle; a circular rotor rotatably carried on the wheel assembly of 
the truck and having a pair of opposed circular faces; a brake frame 
fixedly attached to the vehicle; a support bracket connected to and 
carried on the frame and including a pair of spaced apart rails; inboard 
and outboard brake linings each including a backing portion and a pad 
portion attached to the backing portion, the brake linings spanning the 
distance between and being slidably carried on the rails of the support 
bracket, the backing portion of each pad including an upper edge; and, a 
caliper assembly slidably carried on the rails of the support bracket. The 
caliper assembly includes first and second spaced apart generally opposed 
walls, a portion of the rotor being positioned between said opposed walls 
at all times during operation of the brake assembly, the brake linings 
being carried on the rails in position between the walls of the caliper 
assembly so that the pad portions are opposed to the rotor faces and the 
backing portions are opposed to the walls of the caliper assembly; a 
piston housing aperture formed in the caliper assembly and through the 
first wall of the caliper assembly; a piston movably carried in the 
housing; means for moving the piston between at least three operative 
positions, a first operative position with the pad portions of the brake 
linings spaced away from the rotor faces, a second intermediate operative 
position with the piston displaced against the backing portion of the 
inboard brake lining to force the pad portion thereof against one of the 
rotor faces, and a third operative position with the piston displaced 
against the backing portion of the inboard brake lining to force the pad 
portion thereof against one of the rotor faces and to force the second 
wall of the caliper assembly against the backing portion of the outboard 
lining to press the outboard lining against the rotor, the caliper 
assembly sliding along the rails of the support member to move the second 
wall toward the rotor when the piston is moved from the second operative 
position to the third operative position; first and second apertures 
formed through the caliper assembly and the first wall thereof; first and 
second bolt means extending through each of the first and second apertures 
and each having an end connected to the backing portion of the inboard 
brake lining; and, means contacting each of the bolt means and, when the 
pad portion of the inboard brake lining contacts the rotor, exerting a 
force on the bolt means, the force acting in a direction away from the 
rotor. The force acting in a direction away from the rotor facilitates 
displacement of each bolt means through its respective aperture in said 
direction, facilitates the sliding displacement of the inboard brake 
lining along the rails of the support bracket away from the rotor, and, 
facilitates the displacement of the piston from the third to the second 
operative position. 
Turning now to the drawings, which depict the presently preferred 
embodiment of the invention for the purpose of illustrating the practice 
thereof and not by way of limitation of the scope of the invention and in 
which like reference characters refer to corresponding elements throughout 
the several views, FIGS. 1 to 3 illustrate a conventional B. F. Goodrich 
power screw air disc brake unit including air chamber 11, caliper piston 
drive arm 12, caliper assembly 13, torque plate 14, and rotor 15. Rotor 15 
includes circular planar inboard contact face 16 and outboard contact face 
17 generally parallel and opposed to inboard contact face 16. Caliper 
assembly 13 includes piston housing member 18, outboard wall 19, and 
inboard wall 20 spaced away from and opposed and generally parallel to 
outboard wall 19. Ceiling 21 of assembly 13 spans the distance between and 
interconnects walls 19, 20. U-shaped grooves 20, 23 formed in caliper 
assembly 13 slidably engage rail 25 of U-shaped frame member 26. Member 26 
is fixedly secured to torque plate 14 by bolts 28 thereof. U-shaped 
grooves (not visible) identical to grooves 20, 23 are formed in the side 
of assembly 13 opposite the side having grooves 20, 23. The U-shaped 
grooves (not visible) on the opposite side of assembly 13 slidably engage 
rail 30 of support member 26. Brake lining 31 includes elongate backing 
portion 32 and metal cinder pad portion 33 fixedly attached to backing 
portion 32. Brake lining 35 includes backing portion 36 and metal cinder 
pad portion 37 fixedly secured to backing portion 36. U-shaped grooves 38, 
39 formed in the near ends of linings 31, 35 slidably engage rail 25. 
Similar U-shaped grooves formed in the far ends of linings 31, 35 slidably 
engage rail 30 of support member 26. Grease is injected into piston 
housing member 18 through fitting 40. Pressure relief valve 41 permits 
grease to escape from housing 18 when excess grease is injected through 
fitting 40. 
FIGS. 3A to 3C illustrate the general mode of operation of the disc brake 
unit of FIGS. 1 and 2. In FIG. 3A the vehicle is moving and rotor 15 is 
turning on a wheel assembly of the vehicle without the brake unit being 
utilized. Piston 44 is in retracted position and pad portions 33, 37 of 
brake linings 31, 35 are spaced away from opposed faces 16, 17 of rotor 
15. When the vehicle brake pedal is depressed, piston 44 begins to extend 
in the direction of arrow A as shown in FIG. 3B and presses pad portion 33 
of lining 31 against rotor face 16. After pad portion 33 contacts rotor 
15, piston 44 continues to extend in the direction indicated by arrow A in 
FIG. 3B. This continued movement of piston 44 in the direction of arrow A 
after lining 31 contacts rotor 15 causes caliper assembly 13 to be 
displaced in the direction of arrows B in FIG. 3C such that outboard face 
19 of assembly 13 contacts backing portion 36 of lining 35 and forces pad 
portion 37 thereof against rotor face 17. The combined pressure of pads 
33, 37 against rotor 15 stops the rotation of the rotor. When the vehicle 
brake pedal is released, piston 44 retracts in the direction of arrows B 
and piston 44, caliper 13 and brake linings 31, 35 reassume the position 
shown in FIG. 3A. Air chamber 11, lever arm 12 and other system components 
control the displacement of piston 44 in directions A and B when the 
vehicle brake pedal is depressed and released. 
In utilizing the B. F. Goodrich disc brake system shown in FIGS. 1 to 3, 
the trucking industry has found that piston 44 tends to become jammed in 
the extended position illustrated in FIG. 3C and will not, when the 
vehicle brake pedal is released, retract to its original position of FIG. 
3A. The jamming of piston 44 in the extended position of FIG. 3C is 
believed to result when pressure relief valve 41 becomes plugged so that 
excess grease injected into housing 18 through fitting 40 under pressure 
cannot escape through valve 41. Once valve 41 becomes plugged, grease 
accumulates in housing 18 under increasing pressure. This pressure acts 
against piston 44 and maintains the piston in the extended position of 
FIG. 3C. 
In the disc brake system of the invention, illustrated in FIGS. 4 to 10, 
fitting 40 is removed from piston housing 18 and bolt 50 inserted to seal 
the opening 51 into which fitting 40 is normally threaded. Pressure relief 
valve 41 is also removed from housing 18 and is replaced with an orifice 
52 which vents the interior of housing 18 to the atmosphere. Caliper 
assembly 13 is taken apart and housing 18 and piston 40 are packed with 
grease. Caliper 13 is then reassembled. Caliper assembly 13 is 
periodically torn down, taken apart, cleaned, and repacked with fresh 
grease. Any excess grease inside housing 18 readily escapes through 
orifice 52. The utilization of bolt 51 and orifice 52 prevents a build up 
of pressure within piston housing 18. The pressure inside housing 18 is, 
of course, generally always equal to atmospheric pressure. 
As shown in FIGS. 4-6 and 8, apertures 60, 61 are formed through caliper 
assembly 13 and apertures 62, 63 are formed through backing portion 32 of 
lining 31. Bolt 64 slidably extends through apertures 60 and 62. Nut 66 is 
attached to the end of bolt 64 extending through aperture 62. Spring 65 is 
positioned between head 70 of bolt 64 and surface 71. A second bolt (not 
shown) identical to bolt 64 is slidably positioned in apertures 61, 63 and 
a nut identical to nut 66 is attached to the end of the second bolt 
extending through aperture 63 toward rotor 15. A spring identical to 
spring 65 is positioned between the head of the second bolt and surface 72 
of caliper assembly 13. When the brake pedal of a vehicle is depressed and 
piston 44 displaces lining 31 towards rotor 15, back portion 32 of lining 
31 pushes against nut 66 and the nut on the second bolt to slidably pull 
bolt 64 and the second bolt through apertures 60, 61 in the direction of 
arrow C in FIG. 5 and to compress spring 65 and the identical spring 
associated with the second bolt. When spring 65 and its partner spring 
associated with the second bolt are compressed they exert a force against 
head 70 and the head of the second bolt in the direction of arrow D in 
FIG. 5. This force assists in retracting piston 44 and in pulling brake 
lining 31 away from rotor 15 when the vehicle brake pedal is released. 
In FIGS. 8 and 9 hatched areas 82, 83, 84 represent portions of a 
conventional B. F. Goodrich caliper assembly which are not included in the 
disc brake of the invention, or, which are simply machined out of existing 
B. F. Goodrich caliper assemblies. In B. F. Goodrich disc brake units, 
linings 31, 35 are sized such that the top edges 80 of the linings can 
contact thatched areas 82, 83 causing the linings to tilt against rotor 15 
as the linings slide back and forth along rails 25, 30 of frame 26 during 
operation of the disc brake unit. Machining thatched areas 82, 83 from 
ceiling 21 of caliper assembly 13 provides sufficient clearance so that 
upper edges 80 of linings 31, 35 do not contact ceiling 21 as they slide 
along rails 25, 30. As is depicted in FIG. 10, when thatched areas 82, 83 
are machined from existing conventional B. F. Goodrich disc brake units, 
linings 31, 35 do not contact ceiling 21 and the pad portions of linings 
31, 35 generally remain parallel to the faces of rotor 15 as linings 31, 
35 move back and forth along rails 25, 30. When thatched portion 84 is 
machined from an existing conventional B. F. Goodrich air disc brake unit, 
thicker pad portions 33, 37 can be utilized on the brake linings. 
FIGS. 6 and 7 illustrate the presently preferred brake linings of the 
invention including a backing portion 32 having internally threaded 
apertures 90 formed therethrough to receive externally threaded bolts 91. 
Apertures 92 are formed through brake pad portion 33. Each aperture 92 is 
provided with countersunk aperture 93 sized to receive the head of a bolt 
91. Bolts 91 permit a worn pad 33 to be readily removed from backing 32 
and replaced with a new pad. 
The truck of FIG. 11 includes tractor 94 and trailer 95. Tractor 94 is 
provided with rear wheels 96 and front wheels 97. Trailer 95 is provided 
with rear wheels 98 and air control unit 99. Compressed air lines 100, 
101, 102 lead from control unit 99 to the disc brake units associated with 
wheels 96, 98. Control unit 99 is activated when the truck driver 
depresses the brake pedal. When unit 99 is activated, compressed air flows 
through lines 100,101,102 to the air disc brake units associated with 
wheels 96, 98 and causes the units to operate to brake the truck. The 
braking system of FIG. 11 is designed such that when the driver depresses 
the brake pedal of the vehicle, the disc brake units associated with 
wheels 98 engage and slow rotors 15 associated with wheels 98 just before 
the brake units associated with wheels 96 engage and slow the rotation of 
wheels 96. Braking wheels 98 prior to braking wheels 96 or other wheels 
forward of rear wheels 98 stabilizes the truck while it is stopping and 
tends to greatly minimize the likelihood the truck will jackknife or 
shimmy while it is being braked. 
Brake pads 33 are presently fabricated with three polymer resins 
impregnated with fiber glass, zinc and brass particles. 
Conventional B. F. Goodrich truck disc brakes includes "chatter" retainer 
spring clips (B. F. Goodrich Part No. 56-741, Service Kit No. 304-204 
shown on page 4, in "Illustrated Parts List with Service Kit Reference" of 
B. F. Goodrich Circular OH 186 entitled Air Disk Brake Parts Catalog for 
Truck, Tractors and Trailers) which bear against the caliper housing 13. 
The disc brake system of the invention does not utilize these retainer 
clips. Removing the chatter springs permits housing 13 to slide more 
freely along rails 25, 30. 
The disc brake system of the invention typically extends the operational 
life of rotor 16 to from 750,000 to 1,000,000 miles of truck travel. The 
rotor in a conventional B. F. Goodrich disc brake system normally has an 
operational life of approximately 60,000 to 90,000 miles. 
The temperature generated at the interface of polymer 
resin-brass-zinc-fiber glass pads 33, 37 and rotor 16 when the disc brakes 
of the invention are utilized to stop a truck is in the range of 
200.degree. F. to 800.degree. F. When a truck is being braked on level 
ground the temperature generated when pads 33, 37 frictionally engage 
rotor 16 is usually in the range of 200.degree. F. to 250.degree. F. In 
contrast, when the conventional B. F. Goodrich disc brakes are utilized, 
temperatures in the range or 1000.degree. F. to 1800.degree. F. are 
generated when the metal cinder brake pads 33, 37 are forced against rotor 
16. 
The coefficient of friction for the polymer resin pads 33, 37 utilized in 
the disc brake system of the invention is 40 to 50. This means rotor 16 is 
effectively slowed as soon as pads 33, 37 contact rotor 16 during braking 
of a vehicle. The metal cinder pads 33, 37 utilized in a conventional B. 
F. Goodrich disc brake system must contact rotor 15 and frictionally 
generate a substantial amount of heat before they effectively engage and 
slow rotor 16. 
When, during the operation of a conventional B. F. Goodrich disc brake 
system and the system of the invention, a truck driver depresses the brake 
pedal, unit 11 is activated causing piston 100 (FIGS. 1 and 2) to be 
displaced and extended in the direction of arrow N to rotate arm 12 
clockwise in the direction of arrow M. When arm 12 is rotated in the 
direction of arrow M, piston 44 is displaced towards rotor 16 and brake 
linings 31, 35 are forced against rotor 16. In a conventional B. F. 
Goodrich truck disc brake system the thickness of the inboard and outboard 
pads 33, 37 is 0.75 inch, the thickness of the inboard backing 32 is 0.5 
inch, and the thickness of the outboard backing 36 is 0.25 inch. In the 
brake system of the invention the thickness of the inboard backing 32 is 
0.3125 to 0.375 inch, of the outboard backing 36 is 0.25 inch, of the 
inboard pad 33 is 1.125 inches, and, the thickness of the outboard pad is 
1.0625 inches. Accordingly, the overall thickness Q and P of brake linings 
31, 35 are greater in the disc brake system of the invention than in a 
conventional B. F. Goodrich brake system. The overall thickness Q of the 
inboard brake lining 31 in the system of the invention is 1.4375 inches; 
in a conventional B. F. Goodrich system thickness Q is 1.25 inches. The 
overall thickness P of the outboard brake lining 35 in the system of the 
invention is 1.3125 inches; in the conventional B. F. Goodrich system 
thickness P is 1.00 inches. This means linings 31 and 35 utilized in the 
invention take up a greater proportion of spaces S and R, respectively, in 
caliper 13 than do linings 31, 35 in a conventional B. F. Goodrich disc 
brake system. Consequently, when the disc brake system of the invention is 
utilized to slow a vehicle, pads 33, 37 contact rotor 16 more quickly than 
when they would in a conventional B. F. Goodrich brake system. In the 
system of the invention arm 100 (FIGS. 1 and 2) has to travel a shorter 
distance in the direction of arrow N to force pads 33, 37 against rotor 16 
than arm 100 has to travel to force pads 33, 37 against rotor 16 in a 
conventional B. F. Goodrich disc brake system. The use of thicker brake 
linings 31, 35 in the system of the invention also prevents pivot point 
101 from moving too far "past center" before pads 33, 37 contact rotor 16. 
Point 101 has moved past center when the angle W between arm 100 and line 
Z is less than ninety degrees. Line Z passes through pivot point 101 and 
through the center of circular knob 102. 
When conventional B. F. Goodrich disc brakes are modified to the brake 
system of the invention an area 84 (FIGS. 8 and 9) 0.20 inch thick is 
machined from face 19. Therefore, in the brake system of the invention, 
distance V (FIG. 10) between faces 19 and 20 is equal to 0.20 inch plus 
the distance V in a conventional B. F. Goodrich caliper 13.