Note: Descriptions are shown in the official language in which they were submitted.
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This is a division of Canadian Application Serial No.
346,262, filed February 22, 1980.
The present invention relates to a new and improved
caliper brake having a new and improved automatic adjusting
mechanism wherein the brake clearance can be precisely increased
or decreased manually from a point exterior of the brake while
the brake is in operative position on the vehicle on which it
is installed.
A nun~er of designs o~ rotary cam actuators for caliper
brakes have been provided by the prior art and which suffer from
a number of adjustment and maintenance difficulties. In the
type of actuator with which we are concerned, the brake lining
is squeezed against the rotating disc by a threaded post that
in turn is engaged by a threaded nut that in turn is axially
driven by a rotary cam mechanism. In some of these mechanisms,
the rotary drive structure for the cam is in sliding contact
with portions o~ the nut, and when corrosion occurs o.r dirt
enters the structure, the nut may bind to the rotary drive struc-
ture so that it may drive the nut in both dlrections over the
threaded post thereby preventing proper clea.rance adjustment.
In other types of these stru~tures, the connection be-
tween the nut and the rotary drive structure is such that the
post is held stationary while the nut is adjusted both manually
and automatically to control brake clearance. In some of these
the nut cannot be backed off manually to increase clearance in
the brake without removing it~from the vehicle in which it is
installed.
In some other types of these brake mechanisms, it is
possible to retract the post to such an extent that the nut be-
comes jammed onto the threads of the post with such severity
that the automatic adjusting portion of the brake slips without ~ :
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making an automatic adjustment o~ the brake. Where such struc-
tures are actuated by air pressure, or other mechanism wherein
the actuating lever movement is not proportional to the brake
applying movement, the lack of adjustment is not sensed by the
driver, and unequal brake applications can occur.
In still other types of these structures, haxd to seal
passages lead through the housing to the adjustment mechanism
and/or the threaded nut extends externally of the housing where
corrosion can freeze the nut if rubber diaphragm type covers
become damaged or do not sea] for any reason.
According to the present in~ention there is provided a
self-adjusting brake mechanism, the mechanism comprising trans-
latable rod means for effect:ng frictional engagement between
friction element means provicled thereon and a rotor element of
the brake mechanism, the rod means having a first position rela-
tive to the rotor elementi rotary actuating means for causing
translation of the rod means from the first position in a brake
applying direction; and rod eldjustment means for indexing the
rod means in the brake applying direction to maintain a clear-
ance within predetermined lim1ts between the friction element
means and the rotor element, the rod adjustment means including
a rotatable annular nut circumscribing and threadably engaging
the rod means whereby rotation of the annular nut indexes the
rod means in the brake applying direction; clutch means for
transmitting rotary motion from the rotary actuating means to
the annular nut; and lost mot:ion means cooperating with the
clutch means whereby the rod means are indexed in the brake
applying direction after a predetermined rotation of ~he rotary
actuating means.
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In the preferred automatic adjuster disclosed herein
the adjuster cannot be manual:Ly adjusted to a point making
the automatic adjusting mechanism become inoperative.
Further features and advantages will be apparent to
those skilled in the art to which the invention relatesO
In the drawings,
Figure 1 is a longitudinal cross-sectional view through ~ :
a rotary cam actuated disc brake incorporating principles of
the present invention.
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Figure 2 is an exploded view of portions of the auto-
matic adjusting mechanism shown in Figure 1.
Figure 3 is an elevational view of the embodiment
shown in Figures 1 and 2 and showing an air pressure actuator
for the brake.
Figure 4 is a cross-sectional view taken approximately
on the line 4-4 of Figure 1.
Figure 5 is a fragmentary cross-sectional view taken
approximately along the line 5-5 of Figure 1, and showing a lost
motion connection in the automatic adjusting mechanism.
Figure 6 is a fragmentary enlarged view of another em-
bodiment of lost motion connection.
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Figure 7 is a fragmentary lon~itudinal sectional view
similar to Figure 1 r but showing another embodiment of brake
structure.
Figure 8 is a fragmentary enlarged sectional view
taken approximately on the line ~-8 of ~igure 7.
The reference numeral 11 indicates generally a cam
actuated disc brake constructed in accordance with a first em-
bodiment of the invention. The brake 11 includes a caliper
housing 12 that is supported adjacent a rotor 13. The caliper
12 is supported so that it may slide in an axial direction rela-
tive to the associated rotor 13 but is held against rotation
relative to the rotor.
As is typical with sliding caliper type disc brakes,
the caliper 12 has a first leg 14 disposed adjacent to one of
the braking surfaces of the rotor 13 and to which a brake pad 15
is affixed in any suitable manner. A second leg 16 of the
caliper 12 is disposed adjacent the opposite ro-tox braking sur-
face. An actuating mechanism, indicated generally by the re-
ference numeral 17 and an automatic adjusting mechanism, indi-
cated generally by the reference numeral 18, are associated with
the caliper leg 16.These mechanisms act upon a brake pad 19 that
is disposed in opposition to the brake pad 15 and which cooper-
ates with the adjacent braking surface of the rotor 13.
The caliper leg 16 is formed with an elongated bore 21
in which a non-rotatable cam element 22 and a rotary cam element
23 are supported. The non-rotatable cam element 22 has a heli-
cal cam surface 29 formed on its rearward most face (Figure 2).
The cam element 22 is supported within the bore ~1 for axial
movement but is held against rotativn. This is accomplished by
means of a staking pin 25-(Figures 2 and 4) that is held in
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place at the base of a tapped opening 26 of the caliper leg 16.
The pin 25 has a key portion 27 that extends into an elongated
groove 28 formed in the cam member 22.
The cam element 23 also has a helical cam surface 29
(Figure 2) that is complementary in shape to the cam surface 24
and which is juxtaposed to it. A suitable antifriction bearing
31 is interposed between the cam surfaces 29 and 24 so as to
limit the amount of friction between these surfaces.
The face 32 of the cam element 23 opposite its cam sur-
face 29 is engaged with an antifriction bearing 33 which, inturn, bears against a closure plug 34 that is affixed across the
open end of the bore 21 by means of machine screws 35.
The closure plug 34 is formed with an axially extending
bore 36 in which a sleeve bearing 37 and seal 38 are supported.
An actuating shaft 39 extends through the bore 36 and is rotat-
ably supported by the bearing 37. An actuating lever 41 is non-
rotatably affixed to the act~lating shaft 39 by a s~line and
machine screw 42. The actuating lever 41 is pivotably connected
to a rod 43 of an actuating air motor 44 (Figure 3) that is fixed
by means of a bracket 45 relative to the caliper assembly 12.
The actuating motor 44 effects rotation of the actuating shaft
39 via the lever 41, as will hecome apparent.
The actuating shaft 39 has a generally hollow cylin-
drical section 46 that extends into the bore 21 and which ex-
tends radially inwardly of the cam element 23. A spline connec-
tion 47 rotatably connects the actuator shaft portion 46 with the
cam element 23 to effect simultaneous rotation of these compo-
nents.
; The automatic adjustlng mechanism 18 includes an annu-
lar nut 48 having a shoulder 49 for abutment with a corresponding
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shoulder 51 fonmed on the cam element 22. Internal threads 52
of the nut 48 are engaged with threads of a longitudinall~ ex-
tending male threaded member or rod 53. The male threaded mem-
ber 53 has a reduced diameter end carrying a collar 54 that is
engaged with a load distributor 55 which bears against the
brake pad 19. A suitable boot or dust seal 56 encircles the
collar 54 and is held in place relative to the open end of the
caliper bore 21 by means of a retaining ring 57 that is position-
ed against the inner end of the bore 21 to seal the internal
portions of the brake actuating mechanism 17 and automatic ad-
justing mechanism 18. A helically wound compression spring 58
is positioned between the seal retaining ring 57 and a hat
shaped combination bearing plate and dirt seal or washer 59,
the radially outer portlon of which bears against the cam 22 to
effect brake retraction, as will become apparent. The spring
58 can also be termed a return spring.
The nut 48 has an axially extending projection 60 that
is slotted, as at 61, to receive one or more tangs 62 of a clutch
plate 63~ There lS a predetermined clearance of approximately
five degrees of rotation between the tangs 62 and sides of the -
slots 61 which clearance establishes the normal running clearance
of the brake 11, as will become apparent.
The clutch plate 63 is received between a pair of
clutch plates 64 and 65 which, in turn, have a tanged connection
to the hollow cylindrical section 46 of the actuating shaft por-
~ tion 39. The tanged connection comprises tangs 66 formed on the
: clutch plates 64 and 65 (Figure 5) and slots 67 formed in the
; hollow cylindrical section 46. A snap ring 68 bears against the
clutch plate 64 and is affixed wlthin a groove in the hollow
cylindrical section 46. A large compression spring 69 bears
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against the clutch plate 65 and a shoulder 71 fonmed at the base
of the hollow cylindrical section 46. The spring 69 presets
the pressure existing between the clutch plates 64 and 65 and
the clutch plate 63 and determines the torque at which this
clutch will slip, as will become apparent.
It will be seen that forward rotation of the actuating
shaft 39 will produce an advancing rotation of the nut 48 through
the clutch plate 63, except during the five degrees of lost
motion clearance between the tangs 62 and the sides of the
slots 61 in the nut. In order that this five degrees of lost
motion will occur at the start of each actuation, means are pro-
vided for preventing the nut from being rotated backwardly when
the actuating shaft 39 is rotated backwardly. In the embodiment
shown in Figures 1-5, this is accomplished by a spring brake 72
that encircles the nut 48 and which has a projection 73 fixed
relative to the nonrot~ting cam element 22. The spring brake 72
acts as a one way brake so that the nut 4~ may be rotated in the
for~ard direction, but not in the reverse direction. During ini-
tial reverse rotation, the reactive forces produced by the brake
lining of the rotor 13 hold the shoulder 49 of the nut in engage-
ment with the shoulder 51 of the actuating cam element 22 to
prevent rotation of the nut. Thereafter, the nut ~8 moves out of
engagement with the shoulder 51 and rotation of the nut 48 is
prevented by the spring brake. During this time, the shoulder 49
of the nut moves away from the shoulder Sl while the forward face
of the nut 4g moves into engagement with the washer 59 which
thereafter positively retracts the nut and push rod 53 to leave
running clearance in the brake. In the embodiments shown in
Figures 1-5, there is a clearance of 0O015 inch between the
shoulders 49 and 51 at this time. Throughout this deactuating
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movement of the shaft 39, the clutch discs 64 and 65 axe rotated
clockwise as seen in Figure 5 to move the tang ~2 of the clutch
disc 63 into engagement with the trailing side edges o~ the
slot 61. During the next actuation, therefore, the tangs 62 will
move the full five degrees of counter clockwise rotation as seen
in Figure 5 before they engage the leading side edges of the
slot 61. The clearance between the shoulders 49 and 51 previous-
ly referred to prevents binding between the nut and the cam por-
tion 22 during automatic adjustment.
One of the problems which occur with prior art slack
adjuster constructions is that they do not allow access to the
threaded rod 53 after the brake is installed. In the construc-
tion so far described, the nonrotating cam member 22 is posi-
tioned adjacent the nut 48~ and the rotating portion 23 of the
cam is positioned outwardly of the nonrotating portion 22 of the
cam. With this construction, the xotating portion 23 can be
driven by an axially extending shaft projecting through the outer
wall of the actuator away from the brake rotor and the actuating
and adjusting mechanism is positioned between the closure plug
34 and the inner seal structure of the brake. This seal struc-
ture includes the hat shaped washer 59. It is a feature of the
present invention that the outer periphery of the washer 59 is
always held into sliding engagement with the nonrotating cam
element 22 while the center portion of the washer 59 has a
sliding nonrotational close fit with the actuating rod 53. It
will now be seen that the washer 59, therefore, provides a metal
sliding seal which protects the inner workings of the brake
while also providing a ~riction clutch for preventing rotation of
the push rod 53 by the nut 48. In some prior art designs, it is
necessary to non-rotatably hold ~he push rod 53 by sliding struc-
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ture located in the space adjacent the rotor 13 where the slid-
ing structure is bathed in water and dirt.
According to a further feature Of the present inven-
tion r the running clearance of the brake can be adjusted while
the brake is in position over the rotor by rotating the push rod
53 relative to the nut 48. This is accomplished by a torque
transmitting surface 74, which in the present instance is a
screwdriver slot, fixed in the end of the actuating rod 53.
Access to the screwdriver slot 54 is had through a passageway 75
that extends through the center of the actuating shaft 39 and
the outer end of which is closed off by machine screw 42.
In some instances it is possible for a mechanic to un-
knowingly back off the actuating rod 53 to such an extent that
it is jammed up against the actuating shaft 39. When this is
done, the bind between the actuating rod 53 and the shaft will be
such that the clutch plates 63, 64 and 65 slip without adjusting
the nut 48. This, of course, will defeat the self adjusting fea-
ture of the brake.
In the embodiment shown in Figures 1-5, this is pre-
vented by providing teeth on the abutting surfaces of the rod and
the surface which it abuts whi h prevent the rod from being ro-
tated into a jammed condition. In the embodiment shown, it is
accomplished by providing an annular ring 76 which surrounds the
passageway 75 and which has ridges or square teeth 77 on its
abutment surface. The end of the rod 53~has an abutment 78
pressed therein for engaging the square teeth, and its abutment
surface is provided with ratchet teeth 79~, the flat sides of
which will engage the flat side of the square teeth 77 to limit
the retraction of the rod 53 toward the annular ring 76. The
ratchet teeth 79, however, permit the rod 53 to be easily xotated
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in an advancing direction away ~rom the annular ring 76 by the
automatic adjusting mechanism.
Relining of the brakes is made simple by the present
invention. The machine screw 42 is removed from the passageway
75, and a screwdriver is inserted into the slot 74 to turn the
rod 53 counterclockwise as seen in Figures 4 and 5. This backs
the adjustment rod 53 out of the nut 48 to provide clearance
between the pads 15 and 19 and the rotor 13. New pads 15 and 19
are inserted, the brake assembly is put back on the vehicle and
the adjustment rod 53 is rotated clockwise until the brake pads
are brought adjacent the rotor 13. During rotation of the ad-
justment rod 53 by the screwdriver, its motion is opposed by
sliding friction between the washer 59 and the cla~lping action
of spring 58 on the non-rotatable cam member 22. This friction-
al engagement will hold the adjustment rod 53 in its adjusted
position, and the clutch plates 63, 64 and 65 are operative
thereafter to rotate the nut 4B relative to the adjuster rod 53.
The machine screw 42 is reinstalled to seal off the mechanism
from water and dirt.
The figures illustrate the brake 11 in a released posi-
tion. To actuate the brake, the piston rod 43 is extended so as
to rotate the lever 41 and shaft 39 in a counterclockwise direc
tion as seen in Figures 3-5. This effects rotation of the cam
element 23 relative to the cam element 22 to exert an axial force
on the cam element 22. The cam element 22 i9, therefore, shift-
ed to the left along with the nut 48 and threaded member 53 to
compress the spring 58. The brake pad l9 will then be brought in-
to engagement with the associated braking surface of the rotor 13
and effect a reactive force on the caliper 12 to slide it toward
the right as viewed in Figure 1. The brake pad 15 will, there-
fore, be brought into engagement with the opposing braking sur-
face of the rotor 13.
At the time the cam element 23 is rotated, the clutch
plates 64 and 65 will also effect rotation of the clutch plate
63. Assuming that insufficient lining wear has taken place to
require adjustment, the tangs 62 of the clutch plate 63 will
merely traverse the slots 61 and no rotation of the nut 48 will
result.
Assurning, however, that sufficient lining wear has
taken place so as to necessitate adjustment, the clutch plate 63
will take up the clearance in the slots 61 and will rotate the
nut 48 in an adjusting dlrection. This rotation is permitted by
slippage of the one way spring brake 72. The rotation o~ the nut
48 will cause extension of the screw threaded member 53 to take
up the clearance, the latter element being held against rotation
by the washer 59 and compression spring 58. Once the brake pads
15 and 19 engage the rotor braking surface with a predetermined
pressure, as set by the spring 69, continued rotation of the cam
23 in the actuating direction will cause the clutch plates 64
and 65 to slip relative to the clutch plate 63. Therefore, over
adjustment is prevented.
Assuming that adjustment has been made in the manner
-~ aforedescribed, ~the brake is released by rotating the cam element
23 in the opposlte direction. Thus, the cam suraces 29 and 24
permit the spring 58~to~return the cam element 22 to its at rest
position along with the nut 48 and threaded member 53. Any~ten-
dency for the nut 48 to rotate in an anti-adjusting direction
will, however, be prevented by the one-way spring brake 72. Thus,
the nut 48 will~be maintained in its newly adjusted position re-
30 lative to the threaded mernber 53. ~-
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The embodiment shown in Figure 6 corresponds generally
to the embodiment shown in Figures 1 through 5, except in the
arrangement of lost motion connection utilized. Those portions
of the embodiment shown in Figure 6 which correspond to similar
portions of the embodiment shown in Figures 1-5 are designated
by a like reference numeral characterized further in that a
suffix "a" is affixed thereto.
Figure 6 shows a type of lost motion connection which
can be used to replace the clearance between the tangs 62 and
slots 61. In the embodiment shown in Figure 6, the tangs 62
will substantially fill the slots 6I and the five degrees of lost
motion is provided by clearance between the projection 73a of the
spring brake 72a and its retaining surfaces in the non-rotatable
cam element 22a.
Operation of the embodiment shown in Figure 6 will be
similar to that of the device shown in Figures l through 5 ex-
cept for the location where the lost motion takes place.
The embodiment shown in Figures 7 and 8 corresponds
generally to the embodiments previously described, but differs
principally in that the clamping spring for the clutch is posi-
tioned on the inner side of the clutch plates instead of the
outer side as occurred in the embodiments previously described.
Those portions of the embodiments shown in Figures 7 and 8 which
are similar to corresponding portions of the embodiments shown
in Figures 1-6 are designated by a like reference numeral charac-
terized further in that a suffix "b" is affixed thereto.
In the embodiment shown in Figures 7 and 8, the nut
48b is elongated and the clutch spring 69b is positioned between
the inner clutch plate 64b, and an annular spring retainer 81
that in turn is positioned against an outwardly facing shoulder
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82 in the nut 48b. In order that the spring 69b will be posi-
tioned between two surfaces which do not rotate relative to
each other, the clutch plates 64b and 65b are slidably coupled
to the nut 48b rather than to the actuating shaft 39b. The in-
ner periphery of the clutch plates 64b and 65b carry tangs 66b
that are received in the slot 61b of the nut 48b, while the
clutch plate 63b is supplied with tangs 82 on its outer peri-
phery that are received in slots 83 in the inner periphery of
the rotary cam member 23b. The actuating shaft member 39b also
carries teeth that engage the splined configuration 47b of the
cam member 23b. This construction has the advantage that it
permits the actuating shaft 39b to have a much shorter annular
driving projection 46b than was required in the previously des-
cribed embodiments.
The clutch discs 64b and 65b are held onto the nut 48b
by a snap ring 84 that is positioned outwardly of the clutch
plate 65b, and which is received in a groove 85 in the outer end
of the nut 48b. Also in the embodiment shown in Figures 7 and 8,
no collar 54 is used, and the rod 53b has its inner end enlarged
to act as the retainer for the dust seal 56b. Also, the sleeve
bearing 37 of the previous embodiment is replaced by two roller
bearings 86 which, as in the previous embodlment, support and
center not only the drive shaft 39b, but holdthe cam~member 23b
out of sliding engagement with the side walls of the bore Zlb by
reason of the tightly fitting spline 47b. Five degrees of lost
motion are provided between the tangs 32 of the clutch plate 63b
and the sidewalls of the grooves 83.
In all of the embodiments above described, the side
wall of the elongated bore 21 is enlarged slightly as at 87 over
the rotary portion of the cam actuator, so that it is held out of
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sliding engagement with the housing by the actuating shaft 39.
The spline 47 between the rotary cam 23, and the annular shaft
extension 46 is a tight sliding fit so that the rotary cam 23 is
held away from the side walls of the bore 87. On the other hand,
the axially driven cam 22 bears against the side walls of the
bore 21, and it in turn journals the nut ~8 to center the
threaded rod 53 relative to the actuating structure. It will
further be seen that the construction of the invention seals off
the frictional drive mechanisms between the sliding washer 59 and
the rotary seal 38 which surrounds the shaft 39, so that the
torque developed by the frictional devices does not appreciably
change during use. It will further be seen that the device can
nevertheless be manually adjusted while the actuator is install-
ed on the vehicle through a passageway through the actuating
shaft which is located in the outer end of the housing.
While the invention has been described in considerable
detail, the applicant does not wish to be limited to the parti-
cular embodiments shown and described, and it is intended to
cover hereby all novel adaptations, modifications, and arrange-
ments thereof, which come within the practice of those skilled inthe art to which the invention relates, and which come within
the scope of the following claims.
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