Drum brake wear adjustor with eccentric roller and pawl assembly

The present invention relates to a cam-operated, self-adjusting brakeshoe adjustor that is utilized in heavy duty air braking vehicles that employ single and/or multiple-web brakeshoes. The brakeshoe adjustor includes a roller assembly, a cylindrical roller sleeve, and a pawl assembly. The roller assembly comprises a fixed eccentric roller(s) and spindle arrangement for slidable engagement with a cylindrical roller sleeve(s) which in turn is actuated by the rotation of the cam shaft. At least one portion of the spindle is provided with a ratchet for constant engagement with a mateable pawl. The rotation of the roller sleeve(s) about the eccentric roller(s) is limited by the arcuate distance of a slot contained about the edge of the roller sleeve within which a pin, radially extending from the roller, is engaged. In one embodiment, the pawl assembly comprises (i) at least one bracket sleeve for slidable engagement with a corresponding web end of the brakeshoe and having an opening for slidably receiving one of the extensions of the spindle therethrough; and (ii) at least one pawl secured to the side of the bracket sleeve for engagement with the ratchet about the spindle to permit rotation of the spindle in one direction only, the effect of which will be to restrain the combined spindle and eccentric roller(s) from turning in the direction of actuation of the cam shaft.

BACKGROUND OF THE INVENTION 
The present invention relates to a brake adjustment mechanism for adjusting 
a vehicle brake for wear, and more particularly to an automatic brakeshoe 
adjustor assembly to accommodate wear of brake linings on cam actuated air 
brakes of the type commonly employed on large heavy duty vehicles, such as 
trucks and truck trailers. 
The air brakes that are used on heavy duty vehicles generally include an 
air brake chamber to which air is supplied when the vehicle is subjected 
to braking. When pressurized air is admitted to the brake chamber, a 
braking force is transmitted to a cam shaft via the action of a push rod 
and brake lever. Once the cam shaft is rotated, the cam at the end 
thereof, commonly an S-cam, simultaneously rotates against a roller 
engaged at both ends of the brakeshoe webs. This actuation on the 
respective rollers causes the brakeshoes to be spread apart forcing the 
brakeshoe lining against the brake drum, thereby causing the wheels of the 
vehicle to stop. 
The brakeshoes generally employed on these types of vehicles can be of two 
types: a double web and/or a single web brakeshoe. The double web 
brakeshoe is used for brakes having a greater surface area which generally 
require a wider shoe and brake lining, and therefore necessitate a greater 
support in the form of a double web. This form of the brakeshoe is 
utilized on wheels of trailers and truck vehicles whose loads are 
substantial. The roller assemblies engaged at the ends of these webs for 
actuation by the cam shaft are generally made up of a hollow roller 
embodying a concentric pin axially extending from the roller along the 
roller's rotational axis, such as those set forth on pages 1-2 to 1-14, 
1-18 to 1-30, and 1-52 to 1-54 of the Euclid Brake Parts Manual. The 
rollers are disposed between the ends of the double webs by having the 
pins engaged in semi-circular or circular openings positioned at the ends 
of the webs as illustrated in the parts drawings of the Euclid Brake Parts 
Manual. 
The single web brakeshoe supports a lesser braking surface area for the 
brake lining and is generally used on the front of the truck where 
substantial weight loads are not a factor. Accordingly, these brakeshoes 
use a single web for supporting the shoe and corresponding brake lining. 
The type of roller assembly employed for actuation by the cam shaft 
usually consists of a pair of rollers on either side of an end portion of 
the single web and connected to each other by a pin concentrically fixed 
to each of the rollers. The exposed portion of the pin between the rollers 
is engaged in a semi-circular or circular opening in the end portion of 
the web, as illustrated on pages 1-2 and 1-16 of the Euclid Brake Parts 
Manual. 
The foregoing braking systems used on heavy duty vehicles typically include 
some form of mechanism that will compensate for and progressively take up 
the slack that is generated by wear of the brake linings. An adjustment is 
needed because the clearance that normally exists between the brake drum 
and brakeshoe lining will eventually increase beyond a preset limit due to 
the wear of the brakeshoe lining. When these brakeshoe linings wear, the 
push rod of the air brake chamber has to be extended or pushed further to 
rotate the cam shaft against the brakeshoes to compensate for the 
increased clearance. The Department of Transportation imposes strict 
requirements for the clearance limits depending on the size and 
configuration of the braking system employed. 
Common forms of brake adjustors generally employed include slack adjustors, 
which are usually positioned between the push rod and the cam shaft. Other 
forms include self adjusting brake adjustors that operate more directly at 
or near the brakeshoe(s) to compensate for wear. The present invention 
falls within this latter class of brake adjustors, and typical disclosures 
may be found in U.S. Pat. Nos. 1,875,064 and 1,875,065, both issued to 
Lyman (1932); U.S. Pat. No. 2,522,903 issued to Shively (1950); and U.S. 
Pat. No. 4,586,589 issued to Idesawa (1986). Unfortunately, the mechanisms 
disclosed therein contain a multitudinous number of parts, require 
extensive assembly and disassembly when the brakes are subjected to 
routine maintenance, and require extensive and frequent maintenance 
themselves by the replacement of worn, misaligned or failed parts which 
can lead to a costly and time consuming practice. These factors render the 
foregoing devices impractical for extensive and reliable use. 
What is needed then is a self adjusting brakeshoe adjustor that consists of 
a minimum number of parts, is relatively inexpensive to manufacture, and 
which is dependable and reliable in its construction. It is also desirable 
that such a device be easily incorporated into existing braking 
configurations, installed or removed without disassembly, one that 
requires minimal maintenance, and optimally, one which can operate with or 
without the existence of an automatic slack adjustor. 
The foregoing desirable characteristics of a self adjusting brake adjustor 
are accomplished by the invention herein which is described below. 
SUMMARY OF THE INVENTION 
The present invention provides a brakeshoe adjustor that is self adjusting 
and actuated by a cam shaft usually found in a vehicle air braking system. 
The brakeshoe adjustor according to the invention is preferably utilized 
in heavy duty air braking vehicles that employ single and/or multiple-web 
brakeshoes, the latter usually being double web brakeshoes. In both 
arrangements, the adjustor is deployed intermediate to the end of each 
brakeshoe web and a cam of a cam shaft for simultaneous actuation by the 
cam shaft. 
For the double web brakeshoe, the brakeshoe adjustor includes a roller 
assembly, a cylindrical roller sleeve, and a pawl assembly. The roller 
assembly comprises a fixed eccentric roller and spindle arrangement for 
engagement with the cylindrical roller sleeve. The eccentric roller 
fixedly embodies a spindle eccentrically extended on both ends thereof for 
engagement with the end portions of each web of the brakeshoe. At least 
one portion of the spindle is provided with ratchet means for constant 
engagement with a mateable pawl. The ratchet means can be in the form of 
ratchet teeth disposed on the surface of the spindle extension or an 
annular ratchet wheel having ratchet teeth disposed about the wheel and 
concentrically mounted and secured to the spindle for engagement with the 
mateable pawl. 
As noted above, a cylindrical roller sleeve is provided which is slidably 
mounted onto the eccentric roller. Means are also provided for limiting 
the rotation of the sleeve about the eccentric roller by a predetermined 
amount when the sleeve is actuated by the cam shaft. The roller sleeve 
preferably include at least one arcuate slot within one or both ends 
thereof for receiving a corresponding number of pins extending from one or 
both proximate ends of the eccentric roller to permit a corresponding 
arcuate rotation of the roller sleeve about the roller when the sleeve is 
actuated by the cam of a cam shaft, preferably an S-cam. The rotation of 
the roller sleeve about the eccentric roller is therefore limited by the 
protrusion of the pin extending from the roller into the arcuate slot of 
the roller sleeve. Multiple arcuate slots in each circumferential end of 
the roller sleeve, along with a corresponding number of pins extending 
from the eccentric roller, can also be provided to ensure the secure 
limited rotation of the roller sleeve about the eccentric roller, and also 
for fixedly securing the spindle within the roller if the spindle and 
roller are manufactured from separate components. 
The brakeshoe adjustor further comprises a pawl assembly which in one 
embodiment may include (i) at least one bracket sleeve for slidable 
engagement with a corresponding web end of the brakeshoe and having an 
opening for slidably receiving one extension of the spindle therethrough; 
and (ii) at least one pawl secured to the side of the bracket sleeve for 
engagement with the ratchet means about the spindle extension to permit 
rotation of the spindle in one direction only, which will generally be to 
restrain the combined spindle and eccentric roller from turning in the 
direction of actuation of the cam shaft. 
Another embodiment for the pawl assembly includes more than one bracket 
sleeve with the multi-webbed or double-webbed brakeshoe, one for mounting 
onto each web end to engage both the respective extensions of the spindle 
from the eccentric roller. Ratchet means are then provided about both 
spindle extensions, such as ratchet teeth about the ends thereof or 
annular ratchet wheels concentrically mounted onto the spindle extensions, 
for engagement with the respective pawl(s) secured to the side of each 
bracket sleeve. 
As an alternative to the bracket sleeve, the pawl assembly can include a 
pawl mounted directly to the side of the web end of the brakeshoe for 
respective engagement with the ratchet means about the spindle 
extension(s). Constant engagement of the pawl with the ratchet means is 
required and is maintained by the constant engagement of the cam with the 
roller sleeve, which in turn holds the spindle extensions to the web ends 
of the brakeshoe by appropriately shaped openings about the web ends for 
receiving the spindle extensions therein. Constant engagement of the pawl 
with the ratchet means may also be obtained by the use of a spring clip 
disposed about the spindle extensions and secured to the web end. At least 
one pawl can be positioned on the side of both webs for engagement with 
the respective ratchet means provided about both spindle extensions. 
The bracket sleeve is used to permit incorporation of the brakeshoe 
adjustor herein onto existing double webbed brakeshoes without any 
modification to the brakeshoe web, e.g., in the situation where a pawl or 
plurality of pawls are mounted directly to the web itself. As already 
noted, constant engagement of the pawl with one of the ratchet teeth of 
the ratchet means is required for the successful operation of the 
brakeshoe adjustor according to the invention herein. 
For the single web brakeshoe configuration, the brakeshoe adjustor 
comprises a roller assembly, a cylindrical roller sleeve, and a pawl 
assembly. The roller assembly comprises a pair of eccentric rollers 
axially separated by and fixedly secured to a spindle for engagement of 
the spindle with the end portion of the brakeshoe web at a point between 
the eccentric rollers. The spindle is provided with ratchet means disposed 
about at least one portion thereof, and may be positioned about a point 
between the eccentric rollers or about one or both ends of the spindle if 
the spindle is extended beyond the eccentric rollers, for engagement with 
a corresponding number of pawls to restrain the rollers and spindle from 
turning in the direction of actuation of the cam shaft. 
A pair of cylindrical roller sleeves are provided for slidably receiving 
each of the corresponding eccentric rollers therein. Means are also 
provided for limiting the rotation of the sleeve about the eccentric 
roller by a predetermined amount when one or both sleeves is actuated by 
the cam shaft. This is preferably accomplished by providing at least one 
arcuate slot about an end of at least one of the sleeves, preferably both, 
to receive a corresponding number of pins extending from a proximate end 
of the respective eccentric roller to permit corresponding arcuate 
rotation of the sleeve about its respective roller when one or both roller 
sleeves are tangentially engaged and actuated by the cam of the cam shaft. 
While it is desirable to have both roller sleeves provided with at least 
one arcuate slot about one or both ends thereof, only one roller sleeve 
need have the arcuate slot and pin combination about an end thereof for 
the operation of the brakeshoe adjustor according to the invention herein. 
In this case, the roller sleeve that is without the slot can be held into 
place on its respective eccentric roller by any conventional means known 
in the art, for example, by the employment of a cotter pin, snap ring, 
etc. 
In one embodiment for the single web brakeshoe, the pawl assembly comprises 
(i) a bracket sleeve for slidable engagement with the end portion of the 
single web and having at least one opening for slidably receiving the 
spindle therethrough and beyond at least one of the eccentric rollers; and 
ii) at least one pawl secured to one or both sides of the bracket sleeve 
for engagement with a ratchet means disposed about the spindle portion 
extended beyond one or both rollers, as in the double web configuration, 
to permit rotation of the roller sleeves about their respective eccentric 
rollers in one direction only, which will generally be to restrain the 
spindle and eccentric rollers, which are in fixed engagement with respect 
to each other, from turning in the direction of actuation of the cam 
shaft. The ratchet means may be in the form of ratchet teeth provided 
about one or both spindle extensions, or annular ratchet wheels fixedly 
mounted onto the spindle extension(s), for engagement with the respective 
pawl(s) secured to one or both sides of the bracket sleeve. 
As an alternative to the bracket sleeve, the pawl assembly can include at 
least one pawl mounted directly to one or both sides of the web end of the 
brakeshoe for respective engagement with the ratchet means disposed about 
one or both of the spindle extensions. Constant engagement of the pawl 
with the ratchet means of the spindle may be maintained by the constant 
engagement of the cam with the roller sleeve, which in turn holds the 
spindle to the web end of the brakeshoe at a point between the eccentric 
rollers, or by the use of a spring clip disposed about the spindle and 
secured to the web end. 
In order to avoid extending the spindle beyond either or both eccentric 
rollers of the roller assembly, the foregoing annular ratchet wheels of 
the ratchet means may be employed interior of the eccentric rollers for 
engagement with the respective pawl(s) secured to one or both sides of the 
single web or bracket sleeve, as the case may be. 
Inasmuch as there are two brakeshoes employed for each brake assembly on a 
given wheel, two brakeshoe adjustors according to the invention will be 
employed in the brake assembly, one at the end portion of each brakeshoe 
for simultaneous actuation by the cam shaft. 
In operation, the push rod of the braking system is depressed which causes 
the brake lever to rotate the cam shaft. The cam in turn simultaneously 
actuates both of the roller sleeves at each end of the brakeshoe web, 
which in turn forces the brakeshoes and their respective linings outward 
into contact with the brake drum. The arcuate slot in the roller sleeve 
accommodates the permissible critical distance that the sleeve must travel 
for the brakeshoe lining to make contact with the brake drum when the 
brakes are applied. 
As the lining of the brakeshoes wear, the roller sleeves will have to 
rotate a greater arcuate distance about the eccentric roller. Eventually, 
the sleeve will become engaged with the pin extending from the eccentric 
roller to cause a rotation of the rollers about their respective spindles. 
Once the spindles are rotated, the pawl will encounter the next ratchet 
tooth of the ratchet means and restrain the spindle and eccentric roller 
from moving in the direction of actuation of the cam shaft. In this 
manner, the distance that the push rod must be depressed will always stay 
within the limits of brake specifications as reflected by the arcuate 
length of the slot within the roller sleeve. Thus, the brakes will 
maintain their adjustment and be self adjusting to accommodate wear of the 
brakeshoe linings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following is a description of a preferred embodiment of the self 
adjusting brakeshoe adjustor according to the invention herein for use 
with a cam operated double web brakeshoe that is typically employed in the 
trailer and/or truck portion of a heavy duty vehicle. 
Referring to FIG. 1, a self adjusting brakeshoe adjustor 2 is shown in an 
exploded perspective view wherein a roller assembly is provided comprising 
a cylindrical eccentric roller 10 mounted onto a spindle 12 extended on 
both ends of the eccentric roller. A hollow cylindrical roller sleeve 16 
is also provided to slidably receive eccentric roller 10 therein for 
rotational engagement therewith. Roller sleeve 16 contains a slot 18 at 
one proximate end for engagement with a pin 20 inserted into (with a press 
fit, or by any other conventional means known in the art) and extending 
from the roller 10 to limit rotational movement of the roller sleeve 16 
relative to the roller 10 by the length of the arcuate slot 18. 
As shown in FIG. 1A, an additional pin 21 may optionally be inserted into 
eccentric roller 10, which is circumferentially equidistant from pin 20, 
for engagement with a corresponding slot 18A provided about the edge of 
sleeve 16. Any number of pins and corresponding sleeve slots may be 
employed to insure engagement of roller 10 with sleeve 16. 
Spindle 12 and eccentric roller 10 may be fabricated as a one piece 
construction, or as two separate units in which case the spindle 12 can be 
inserted into an off center opening of roller 10, and then fixed within 
roller 10 by means of pin 20 inserted through spindle 12 and into the 
roller. In the latter case, pin 20 will serve the dual function of 
maintaining spindle 12 and roller 10 in fixed engagement with respect to 
each other and limiting the rotational movement of roller 10 within the 
roller sleeve 16 by the arcuate distance of slot 18. In either case, care 
should be taken not to have pin 20 extend beyond the outside diameter of 
roller sleeve 16 to avoid impingement with the surface of S-cam 30 
(illustrated in FIG. 2). 
One portion of the spindle 12 is provided with a plurality of ratchet teeth 
14 about its surface for continuous engagement with a mateable pawl 26 
mounted to the side of a bracket 24. This is accomplished by the circular 
opening in bracket 24 adapted in size to slidably receive the ratcheted 
portion of spindle 12 therethrough. As illustrated in FIGS. 2, 3 and 9, 
bracket 24 is also sized and configured to slidably mount onto the web 
ends 41 and 43 of double web brakeshoes 39,40 for accommodating the 
disposition of the self adjusting brakeshoe adjustor between webs 43,44 
and 41,42 for engagement with S-cam 30. It is to be noted that double web 
brakeshoe 40 can accommodate a bracket 24 on each web end as illustrated 
in FIG. 4A. In this case a plurality of ratchet teeth 14 is provided to 
both ends of spindle 12 for engagement with pawl 26 secured to each 
bracket 24 which in turn is slidably mounted to the end of webs 43 and 44. 
As an optional embodiment, an additional pawl 26A may be mounted to 
bracket 24 as shown in FIG. 3, to insure engagement with ratchet teeth 14. 
Securement of both ends of spindle 12 to the web of the brakeshoe by means 
of bracket 24 is important to insure and maintain continuous engagement of 
the pawl 26 with any one of ratchet teeth 14 on spindle 12 (FIGS. 2 and 
3). 
FIG. 2 illustrates the assembly of conventional double web brakeshoes 39 
and 40 in a heavy duty vehicle incorporating the self adjusting brakeshoe 
adjustors shown in FIG. 1. Double web brakeshoes 39 and 40 are operatively 
joined to each other at one end in a hinged arrangement by means of pins 
54 and 56 inserted through brake spider 50 for engagement with webs 41,42 
and 43,44 which engage the self adjusting brakeshoe adjustors at the 
opposite ends. Brakeshoe spring 58 insures continuous return of the 
brakeshoes to their original position after engagement with the brake 
drum. 
As shown in FIG. 2, two self adjusting brakeshoe adjustors, one for each 
end of the double web of each brakeshoe 39 and 40, are required to make up 
the entire double web brake assembly. The roller sleeves 16 of each self 
adjusting brakeshoe adjustor for brakeshoes 39 and 40 are brought to bear 
on S-cam 30 by means of brakeshoe spring 58 which insures continuous 
engagement of the S-cam with the roller sleeves. Upon actuation of the 
brake pedal by the driver of the heavy duty vehicle, rotational movement 
of S-cam 30 by cam shaft 32 exerts a force on the respective roller 
sleeves 16 to cause brakeshoes 39 and 40 to expand outwardly into contact 
with the brake drums (not shown), which in turn causes a braking of the 
vehicle. 
FIG. 4 shows an alternative embodiment for the engagement of pawl 26 with 
ratchet teeth 14 of spindle 12, which differs from the arrangement shown 
in FIG. 3 in that pawl 26 is fixed directly to the side of web 44 (as 
opposed to pawl 26 being fixed to bracket 24 in FIG. 3). As an optional 
embodiment, pawl 26B may be mounted to the lower or end portion of web 44 
as an added insurance for engagement with ratchet teeth 14. The self 
adjusting brakeshoe adjustor is held into place between and at the lower 
end of webs 43 and 44 by the engagement of roller sleeve 16 with the S-cam 
30. The advantage of this configuration is that the need for bracket 24 as 
an extra component of the self adjusting brakeshoe adjustor is obviated. 
The advantage of the configuration shown in FIG. 3 utilizing bracket 24 is 
that the self adjusting brakeshoe adjustor can be easily incorporated into 
existing brake assemblies without the need for redesigning the brakeshoe 
webs for incorporation of pawl 26. Bracket 24 also provides additional 
support for securing spindle 12 into place between webs 43 and 44. 
In accordance with another aspect of the invention, the bracketed 
configuration for brakeshoe web 43 illustrated in FIG. 3 can be duplicated 
for brakeshoe web 44 of FIG. 4. That is, an additional bracket, having a 
mirror image of bracket 24, with a corresponding pawl identical to pawl 
26, can be made a part of the self adjusting brakeshoe adjustor for 
engaging ratchet teeth 14 and for securing spindle 12 to web 44. The 
additional bracket and pawl assembly, which mounts onto web 44 in the same 
manner as bracket 24 mounts onto web 43, will provide added insurance for 
the proper functioning of the self adjusting brakeshoe adjustor. 
An alternative arrangement for the pawl assembly is illustrated in FIG. 8 
wherein an annular ratchet wheel 82 is provided for slidable engagement 
with spindle 12, the ratchet wheel being provided with a plurality of 
ratchet teeth 84 radially extending from substantially the wheel's inner 
circumference to its outer circumference on the side of the wheel facing 
the pawl. A key member 86, extending inwardly from the inner circumference 
of the annular wheel 82, is provided for engaging a corresponding key slot 
19 incorporated into the surface of spindle 12 such that when ratchet 
wheel 82 is slidably mounted onto spindle 12, the ratchet wheel is 
rotatably fixed in place and prevented from rotating about spindle 12. As 
will be seen in FIG. 9, one of the ratchet teeth 84 will engage pawl 27 
mounted to bracket 24 when the ratchet wheel is concentrically mounted 
onto spindle 12 and moved up against bracket 24. In order to maintain 
constant engagement of the ratchet wheel with pawl 27, a coil spring 88 is 
slidably mounted onto spindle 12, followed by a circular locking ring 89, 
for urging the ratchet wheel 82 against bracket 24. A slot 13 is provided 
about the circumferential surface of spindle 12 (see FIG. 8) for fixedly 
securing the locking ring 89 in place. Additional pawls, such as that 
shown by reference numeral 27A, may be added to bracket 24 to insure 
proper alignment of the ratchet wheel with pawls 27 and 27A. Any number of 
pawls may be added about bracket 24 (or about web end 44 in FIG. 10). 
The pawl assembly utilizing the annular ratchet wheel configuration (as 
illustrated in FIGS. 8, 9 and 10) offers an economical advantage in that 
the pawl assembly takes up less space. It also permits the ratchet means 
to be utilized between web 43 (and/or 44) and roller sleeve 16, as is 
illustrated by ratchet wheel 82A engaged with pawl 27B and held in place 
by disc spring 94. 
The foregoing alternative arrangement for the pawl assembly can be modified 
as shown in FIG. 10 wherein the above-identified pawl(s) can be attached 
directly to each side of web 44 itself, thereby eliminating the need for 
the bracket configuration shown in FIG. 9. One configuration does not 
preclude the use of the other, and any of the pawl assemblies can be used 
in combination with each other, such as, for example, a combination of the 
arrangements shown in FIGS. 9 and 10. 
Next follows a description of a preferred embodiment of the self adjusting 
brakeshoe adjustor when used with a cam operated single web brakeshoe 
which is typically employed in the front axle portion of a heavy duty 
vehicle. 
Referring to FIG. 6, a single web brakeshoe assembly is illustrated showing 
the incorporation of a pair of corresponding self adjusting brakeshoe 
adjustors according to the invention herein. As shown in greater detail in 
FIG. 5, a spindle 12 is provided having a pair of eccentric rollers 72 and 
73 eccentrically and fixedly engaged therewith in a spaced apart 
relationship. Spindle 12 extends through and beyond roller 73, whereas the 
opposite end is inserted in and fixed within roller 72. A corresponding 
pair of hollow cylindrical roller sleeves 70 and 71 are provided and 
adapted to receive rollers 72 and 73, respectively, therein, for 
rotational engagement with their counterparts. As illustrated in FIG. 5, 
roller sleeve 71 contains a slot 71' at its outer edge for engagement with 
pin 20 fixedly secured in and extending from roller 73 to limit rotational 
movement of roller sleeve 71 relative to roller 73 by the length of the 
arcuate slot 71'. In similar fashion, roller sleeve 70 on the opposite 
side of web 66, contains a slot 70' at its outer edge for engagement with 
pin 20A secured in and extending from roller 72 to limit rotational 
movement of roller sleeve 70 relative to roller 72 by the length of the 
arcuate slot 70'. Pins 20A and 20 are press fitted into rollers 72 and 73, 
respectively, after roller sleeves 70 and 71 are mounted onto to their 
counterpart rollers. Arcuate slots 70' and 71' are equidistant to provide 
synchronous rotational movement of both roller sleeves about respective 
eccentric 
Spindle 12 and rollers 72 and 73 may be fabricated as a one piece 
construction, or as three separate units in which case the spindle 12 can 
be inserted through an off center (eccentric) opening of roller 73, and 
into an identical opening within (but not all the way through) roller 72. 
Spindle 12 is fixed within roller 72 by any conventional means (such as by 
a spline or key arrangement) and within roller 73 by means of extended pin 
20 which can be press-fit through roller 73 and into spindle 12 after the 
respective sleeves are mounted onto spindle 12. With this latter 
arrangement, pin 20 will serve the dual function of (i) maintaining 
spindle 12 and roller 73 in fixed engagement with respect to each other, 
and (ii) limiting the rotational movement of roller 73 within the roller 
sleeve 71 by the arcuate distance of slot 20. Pin 20A will likewise serve 
to restrict the rotational movement of roller sleeve 70 about roller 72 by 
the arcuate distance of slot 70'. 
The portion of spindle 12 extending beyond the roller assembly of rollers 
70 and 71 is provided with a plurality of ratchet teeth 76 about its 
surface for continuous engagement with a mateable pawl 68 mounted to the 
side of a bracket identical to the bracket 24 shown in FIGS. 1 and 3. As 
in FIGS. 1 and 3, this is accomplished by the circular opening in bracket 
24 which is sized to slidably receive the ratcheted portion of spindle 12 
therethrough. Bracket 24 is then slidably mounted onto single web 66 of 
brakeshoe 60, which includes brakeshoe lining 64 and brakeshoe lining 
support plate 62, for positioning the brakeshoe adjustor onto the end of 
web 66 for engagement with S-cam 30. Securement of spindle 12 to the web 
of the brakeshoe by means of bracket 24 insures the continuous engagement 
of pawl 68 with any one of ratchet teeth 76 on the extended end of spindle 
12, although when assembly of the brakeshoe is complete, the action of 
S-cam 30 on rollers 70 and 71 will serve to keep the adjustor assembly in 
place in the half moon opening 79 on the end of web 66. 
FIG. 7 shows an alternative embodiment for bracket 24 and the brakeshoe 
adjustor assembly of FIG. 5 whereby pawls 68 and 69 are positioned on both 
sides of bracket 80 for corresponding engagement with ratchet teeth 76 and 
77, respectively, provided on both ends of spindle 12. In this 
configuration, spindle 12 is extended through and beyond each roller 72 
and 73 and fixedly secured therein either by conventional means or by pins 
20 and 20A in the same manner as described for the configuration 
illustrated in FIG. 5. Bracket extensions 80A and 80B are provided with 
appropriate openings for the insertion of spindle 12 therethrough. The 
arrangement of the remainder of brakeshoe adjustor components, roller 
sleeves 70 and 71, rollers 72 and 73, pins 20 and 20A, and arcuate slots 
70' and 71', are the same as shown in FIG. 5. 
FIG. 6 shows the self adjusting brakeshoe adjustors engaged with pawls 68 
and 68A which are mounted directly to the side of single webs 66 and 67, 
respectively. The advantage of this configuration is that the need for a 
bracket, such as those illustrated in FIGS. 4 and 6, is obviated. As with 
the brakeshoe adjustor used in the double web configurations of FIGS. 1-3, 
the use of a bracket allows the brakeshoe adjustor to be easily 
incorporated into existing brake assemblies without the need for 
redesigning the brakeshoe web for direct attachment of pawls 66 and 67. 
The bracket arrangement also provides additional support for securing 
spindle 12 into place at the end 79 of single webs 66 and 67. 
Securement of the assembled self adjusting brakeshoe adjustor onto the end 
of web 79 (FIG. 6) is accomplished by the engagement of the roller sleeves 
70,71 with S-cam 30 or by means of a wire clip (not shown) attached to 
bracket 24 and web 66 or 67, as the case may be. In the event no bracket 
is used, as with the configuration shown in FIG. 6, a spring clip (not 
shown) may be mounted onto the brakeshoe adjustor for engagement with the 
end of web 79. 
As shown in FIGS. 11 and 12, the ratchet wheel 82 of the ratchet means can 
also be used in conjunction with the brakeshoe adjustor for a single web 
brakeshoe. FIG. 11 illustrates a pawl 92 secured directly to the side of 
single web 66 for engaging ratchet wheel 82. The ratchet wheel is held 
engaged with pawl 92 by means of a circular disc spring 94 mounted onto 
spindle 12 such that the presence of the roller and roller sleeve 
combination will provide the requisite support for urging disc spring 94 
against annular ratchet wheel 82 to secure such engagement. 
The configuration illustrated in FIG. 12 is identical to that shown in FIG. 
11 with the exception that a U-shaped bracket 90 having pawl 92 secured to 
the side thereof is mounted onto single web 66. Bracket 90 is provided 
with the appropriate openings for having spindle 12 inserted therethrough. 
The ratchet wheel 82 is held engaged with pawl 92 in similar fashion by 
means of disc spring 94 mounted onto spindle 12 between bracket 90 and the 
roller and roller sleeve combination, 73 and 71. 
To insure proper functioning of the brakeshoe adjustor during operation, an 
annular ratchet wheel and pawl assembly, identical to a mirror image of 
that set forth in FIGS. 11 and 12, may be added on the other side of the 
single web (not shown), i.e., between the roller and roller sleeve 
combination, 73 and 71, and single web 66. 
The material used for the various components of the self adjusting 
brakeshoe adjustor is a metal whose structural integrity is capable of 
withstanding the force exerted by operation of the S-cam against the 
roller sleeve(s), and which will withstand the corrosive effects normally 
encountered during vehicle operation. The preferred metal is stainless 
steel, although other metals of a similar nature can be utilized. 
The operation of any of the illustrated self-adjusting brakeshoe adjustors 
according to the invention herein, is achieved by the normal functioning 
of the cam-operated brakes typically employed on heavy duty vehicles. As 
already noted hereinbefore, and as shown in FIG. 2, a pair of brakeshoe 
adjustors is required for the proper functioning of the brakeshoes 39 and 
40. Thus, when the vehicle's brake pedal is depressed by its operator, air 
under pressure is caused to be supplied to the air brake chamber (not 
shown), thereby transmitting a braking force to cam shaft 32 via the 
action of a push rod and brake lever (also not shown). 
By additionally referring to FIGS. 3 and 4, once cam shaft 32 (shown in 
FIG. 2) is rotated, the S-cam 30 at the end thereof simultaneously rotates 
against roller sleeves 16 of each brakeshoe adjustor engaged at the end of 
each brakeshoe webs 41, 42 and 43,44. The outside surface of the roller 
sleeves for both arrangements of the single and double web brakeshoe 
adjustors are preferably knurled as indicated by the numeral 17 in FIGS. 
1, 1A, 8 and 11. The actuation of S-cam 32 against roller sleeve 16 of 
each brakeshoe adjustor, causes roller sleeve 16 to rotate about roller 
10, and operates to expand brakeshoes 39 and 40 for making contact of the 
brake linings 46 and 48, supported by brakeshoe lining support plates 45 
and 47, respectively, with the brake drum (not shown), thereby causing the 
rotating wheels of the vehicle to come to a halt. The arcuate distance 
that roller sleeve 16 must travel, or the distance that the brakeshoes 39 
and 40 must expand outward about pins 54 and 56, represents the distance 
or "play" that the push rod must travel before brakeshoes 39 and 40 engage 
the brake drum. Once contact is made between the brake linings and brake 
drum, the rotation of S-cam 30 and roller sleeve 16 (and roller sleeves 70 
and 71 in the case of the single web arrangement) will cease. 
The distance that brakeshoes 39 and 40 must expand outward about pins 54 
and 56 will gradually increase due to the wear of the brake linings 46 and 
48 coming into repeated contact with the brake drum. This will cause 
roller sleeves 16 and 70 and 71 to rotate further in order to make the 
necessary contact of the brake lining of the brakeshoe with the brake 
drum. Eventually, roller sleeve 16 (and 70 and 71) will make contact with 
corresponding pins 20 and 20', thereby actuating the eccentric roller and 
spindle arrangement. Once eccentric roller 10 (and 72 and 73), and thus 
spindle 12, is rotated, the brakeshoe lining will expand outwardly until 
the brake lining makes contact with the brake drum. After the brake is 
released by the vehicle operator, the distance between the brake lining 
and brake drum will be maintained by the engagement of pawl 26 with 
ratchet 14 at the end of spindle 12 to prevent spindle 12 from rotating 
back to its original position before being advanced by its corresponding 
roller sleeve. Thus, each engagement with the next ratchet tooth by pawl 
26 will reflect a corresponding amount of wear experienced by the 
respective brake lining. 
Stated another way, the arcuate distance of slot 18 (FIGS. 3, 4, 9 and 10) 
and slots 70' and 71' (FIGS. 5, 7, 11 and 12) represents the maximum 
distance that S-cam 30, and roller sleeve 16 and roller sleeves 70 and 71, 
can travel before engaging pins 20 and 20' to advance the eccentric 
rotation of spindle 12 for maintaining the proper clearance of the brake 
lining with the brake drum. Automatic adjustment of the brakeshoe is 
thereby achieved in an efficient and economical manner with a minimum of 
moving parts. 
It will be readily seen that the ratchet and pawl assemblies represented in 
FIGS. 8 through 12 are another way of maintaining the rotational advance 
of spindle 12 for maintaining the proper clearance between the brake 
lining and brake drum. 
In order to maintain a proper or predetermined distance between the brake 
linings and brake drum (when the brakes are not applied), the eccentric 
distance between the axis of spindle 12 and the axis of roller 10 (and 
rollers 72 and 73 in the single web configurations) will represent the 
maximum distance that the brakeshoes can be outwardly expanded for 
adjustment before making contact with the brake drum. This distance must 
be at least as great as the thickness of the brake lining in order that 
the distance between the brake lining and the brake drum will always be 
maintained. Thus, the diameter of roller 10 (double web) and rollers 72 
and 73 (single web) in relation to the eccentric positioning of spindle 12 
will vary depending on the diameter size of brakeshoes 39 and 40 and 
corresponding brake linings 48 and 46. 
Since other modifications and changes varied to fit particular operating 
requirements and environments will be apparent to those skilled in the 
art, the invention is not considered limited to the example chosen for 
purposes of disclosure, and covers all changes and modifications which do 
not constitute departures from the true spirit and scope of this 
invention.