Brake shoe assembly with sealing liner

The present invention relates to a brake shoe assembly with a sealing liner having a brake shoe (11) which includes a brake shoe table (13). A sealing liner (45) formed from an adhesive material is applied to the convex surface (31) of the brake shoe table (13). A friction brake liner (50) is positioned over the sealing liner and convex surface (31) of the brake shoe table (13) and is secured to the brake shoe table (13) by fasteners (61). The sealing liner forms a moisture barrier between the friction brake liner (50) and the brake shoe table (13) to retard the passage of moisture therethrough to prevent rust and corrosion of the brake shoe (11).

FIELD OF THE INVENTION 
The present invention relates in general to brake shoes. More particularly, 
the present invention relates to a brake shoe assembly having a sealing 
liner applied between the brake shoe table and the frictional brake liner 
applied thereto for sealing the brake shoe table against moisture to 
prevent corrosion. 
BACKGROUND OF THE INVENTION 
The brake assemblies of large industrial utility vehicles such as dump 
trucks, tractor and trailer rigs, and the like are subjected to extreme 
forces during braking operations. Accordingly, brake assemblies and the 
components therefor are specially designed to withstand the high heat and 
stresses created during braking. A problem that remains, however, is 
rusting and corrosion of the brake shoe. Such corrosion usually is due to 
the collection of moisture on the brake shoe, including on the brake shoe 
table, and the presence of moisture can lead to premature failure of the 
brake shoe, necessitating its removal and replacement. 
Brake shoes typically are unprotected from below the vehicle. As a result, 
spray from the road surface tends to be directed toward and collected on 
brake shoes, causing the brake shoes to rust. This problem is especially 
prevalent near the sea shore where salt is present on the roads and in 
areas of abundant rain and snow falls. The problem is further compounded 
by salt and other corrosive elements often applied to roads in areas of 
heavy snow falls to melt snow and ice. 
Additionally, frictional brake liners for brake shoe assemblies were 
formerly made of asbestos, which provided a relatively high degree of 
flexibility to the brake liners. The flexibility of the liners enabled the 
brake liners to bend and tightly conform to the curvature of the brake 
shoe table to create a tight sealing contact between the brake liners and 
the brake shoe table. The tight fit between the brake liner and the table 
of the brake shoe avoided the presence of gaps being formed between the 
brake liner and the brake shoe table and therefore avoided moisture being 
collected between the brake liner and the brake shoe table. However, due 
to health and safety concerns, the use of asbestos for such applications 
is now avoided. 
The frictional brake liners that are now being used typically are formed 
from high strength substantially rigid materials, which do not have the 
flexibility of the old asbestos brake liners. As a result of being stiff, 
the newer conventional brake liners do not always accurately mate with the 
brake shoe tables as well as did the old asbestos brake liners. 
Accordingly, gaps or cracks are often formed between the brake liners and 
the brake shoe tables, which enables moisture to accumulate between the 
liner and the table of the brake shoe. 
To correct these gaps and provide a tighter sealing fit between the brake 
liners and brake shoe tables, most brake manufacturers typically rework or 
"coin" the tables of their brake shoes after manufacture to achieve a 
radius that better fits the radius of the brake liner. Such a process 
increases the cost of the brake shoes and does not completely eliminate 
the gaps or cracks between the brake liners and the brake shoe tables. As 
a result, moisture is still able to reach the brake shoe table of some 
brake shoes. 
Further, the methods of attachment of the brake liners to the brake shoes 
have contributed to the contact of moisture with the brake shoe tables. In 
the past, rivets or bolts have been used to attach the brake liners to the 
brake shoe table. Such fasteners require holes to be drilled through the 
brake liner and through the brake shoe table. These fastener holes enable 
the passage of moisture through the brake liner and brake shoe. 
Recently, heat induced epoxies have been utilized to attach the brake liner 
to the brake shoe table. The epoxies are applied to the brake shoe table 
as a molten adhesive, filling any gaps between the brake shoe table and 
the brake liner. The epoxies are then allowed to cool and set, forming a 
rigid non-fluid attachment between the brake liner and the brake shoe 
table. However, once these adhesives dry, they form a hard, solid layer 
which tends to crack and break over time under high heat and stress, thus 
forming gaps and cracks between the brake liner and the brake shoe table. 
As a result, moisture can still eventually pass to the brake shoe table 
through the cracks in the epoxy. 
Accordingly, it can be seen that it would be desirable to provide a brake 
shoe assembly having a means for sealing the brake shoe against contact 
with or the passage therethrough of moisture, to prevent the rusting and 
corrosion of the brake shoe. 
SUMMARY OF THE INVENTION 
Briefly described, the present invention comprises a sealed brake shoe 
assembly for an automobile such as a truck, dump truck, truck and trailer 
assembly, or other load carrying vehicle. The brake shoe assembly 
typically includes a web typically formed from one or more curved struts 
or runners, a curved brake shoe table mounted on the web, and a friction 
brake liner mounted on the brake shoe table for engagement with the rotary 
brake drum. The struts are formed from steel or a similar high strength 
metal and extend parallel to and are spaced from each other in an arcuate 
shape. Notches and holes are formed in one or both of the ends of the 
struts of the web of the brake shoe for engagement with anchor pins, 
roller pins, return springs, and other elements for securing and moving 
the brake shoes within the vehicle braking assembly. 
The brake shoe table usually is a substantially rectangularly shaped plate 
formed from the same high strength metal, such as steel, and the brake 
shoe web and is curved to correspond to the arcuate shape of the brake 
drum of the wheel of the vehicle. 
An adhesive sheet is applied to the convex surface of the brake shoe table, 
between the brake shoe table and the friction liner. The adhesive sheet 
typically is a thin film or layer of a high temperature adhesive, which 
remains substantially fluid and pliable without deteriorating even at the 
high temperatures generated during braking, and functions as sealing liner 
between the table and the friction liner. The adhesive sheet is 
substantially rectangularly shaped and sized to correspond to the size and 
shape of the brake shoe table to provide substantially complete coverage 
of the upper surface of the brake shoe table. 
The friction brake liner is mounted to the convex surface of the brake shoe 
table, substantially covering the convex surface of the brake shoe table, 
with the adhesive sheet positioned between the friction liner and the 
upper surface of the brake shoe table. The friction liner typically 
includes one or more brake pads formed from a high strength frictional 
material such as a steel wool or metal alloy material. The brake pads 
usually are substantially rectangularly shaped blocks and are curved about 
a radius corresponding approximately to the radius of the brake shoe 
table. 
Fasteners, such as rivets or bolts, are driven through the brake pads and 
through the adhesive sheet and the brake shoe table. The fasteners attach 
the brake pads to the brake shoe table with the adhesive sheet engaged 
therebetween. The adhesive sheet creates a moisture and vapor barrier 
between the brake pads and the upper surface of the brake shoe table to 
retard the passage of moisture therethrough and into contact with the 
brake shoe table in order to prevent rust and corrosion of the brake shoe. 
Thus, it is an object of this invention to provide a brake shoe that is 
substantially sealed against the accumulation of moisture between the 
friction liner and the brake shoe table to which the friction liner is 
mounted to prevent rust and corrosion of the brake shoe table. 
Another object of this invention is to provide a brake shoe assembly having 
a sealing liner applied to the brake shoe table and formed from a 
substantially fluid adhesive means that fills and seals any gaps between 
the friction liner and the brake shoe table to form a moisture barrier 
therebetween. 
Another object of this invention is to provide a brake shoe assembly having 
a sealing liner formed from an adhesive that is sufficiently fluid under 
extreme temperatures to fill and seal any gaps between the brake shoe 
table and the friction liner without requiring reworking of the brake shoe 
table to achieve a sealing engagement between the brake shoe table and the 
brake friction liner pads. 
Another object of this invention is to provide a brake shoe assembly with a 
sealing liner between the brake shoe table and the friction liner of the 
brake shoe assembly that is easy and economical to manufacture. 
Other objects, features, and advantages of the present invention will 
become apparent upon reading the following detailed description, when 
taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in greater detail to the drawings in which like numerals 
indicate like parts throughout the several views, FIG. 1 illustrates in 
exploded perspective the brake shoe assembly with sealing liner 10 for 
vehicles such as automobiles and trucks. As illustrated in FIG. 1, the 
brake shoe assembly with sealing liner 10 includes an arcuate shaped brake 
shoe 11 The brake shoe 11 includes a semicircular web 12 and a curved 
brake shoe table 13 mounted over the web in an overlapping relationship. 
As FIG. 1 illustrates, the web 12 typically includes a pair of arcuately 
shaped struts or runners 14 and 16, although it will be understood that a 
single strut can be used to form the web. Each strut 14 and 16 is formed 
from a high strength metal such as a high tensile strength steel. Each 
strut has a curved outer convex edge 17, a curved inner concave edge 18, 
substantially flat side surfaces 19, and first and second ends 21 and 22. 
Each strut is curved about a predefined radius as required to fit the 
desired braking assembly. Substantially semicircular notches 23 and 24 are 
formed at the first and second ends respectively of the struts 14 and 16 
for engaging the anchor pin and roller of a braking assembly and for 
rotatably securing the brake shoes to the anchor pins. 
As illustrated in FIG. 1, the brake shoe table 13 is mounted to the outer 
convex edges 17 of the struts 14 and 16 of the web 12 of the brake shoe 11 
as by welding. The brake shoe table is a generally rectangularly shaped 
plate formed from the same high tensile strength steel or similar high 
strength metal as the struts of the web. The brake shoe table is curved 
about a radius that corresponds approximately to the radius of the web 12 
of the brake shoe and to the inside surface of the brake drum. The brake 
shoe table includes a convex surface 31 that faces away from the web 12, a 
concave surface 32 that extends parallel and is attached to the convex 
outer edges 17 of the struts 14 and 16 of the web, and a series of side 
edges 33, 34, 36, and 37, at the periphery of the brake shoe table. As 
illustrated in FIG. 1, the brake shoe table is positioned over the convex 
outer edges 17 of the struts 14 and 16, with the struts 14 and 16 spaced 
apart from each other and with side edges 33 and 34 of the brake shoe 
table substantially overlapping the convex edges of the struts in a 
substantially T-shaped configuration. 
A plurality of fastener openings 38 are formed through the brake shoe table 
adjacent the side edges 33, 34, 36, and 37 of the brake shoe table for the 
insertion of fasteners therethrough. The fastener openings are generally 
cylindrically shaped bores arranged in groups 39, here illustrated as 
being groups of four fastener openings. It will, however, be understood 
that while groups of four fastener openings are illustrated herein, groups 
of greater or lesser numbers of fastener openings, i.e. two fastener 
openings, can be formed therethrough as desired. 
As FIGS. 1 and 2 illustrate, an adhesive sheet 45 is applied to the convex 
surface 31 of the brake shoe table 13. The adhesive sheet 45 typically is 
a thin film or layer having a thickness of approximately five milliliters 
(ml) and having a substantially rectangular shape and size approximately 
corresponding to the shape and size of the brake shoe table. The adhesive 
sheet is a high-temperature adhesive generally composed of an 
acrylic/polymer material or a urethane base adhesive material. The 
adhesive sheet is designed to function as a sealing liner or membrane to 
provide a relatively strong adhesive bond under both severe shear and pull 
conditions created during braking. The adhesive material of the adhesive 
sheet generally remains sufficiently fluid over a wide range of 
temperatures of approximately -50.degree. F. up to approximately 
800.degree. F. without deteriorating to enable the adhesive to flow or 
spread as pressure is applied. As illustrated in FIG. 3, the adhesive 
sheet 45 is a double-sided adhesive film or strip typically cut from a 
roll in a length approximately equal to the length of the brake shoe 
table, and has a pair of adhesive faces to which peelable backing layers 
47 and 48 are applied to protect the adhesive when not in use. A first one 
of the backing layers is peeled away to reveal one of the adhesive faces 
for application of the adhesive sheet to the brake shoe table. After the 
exposed surface of the adhesive sheet has been applied to the brake shoe 
table, the other peelable backing layer is removed and a friction liner 50 
(FIG. 1) is applied to the adhesive sheet and the brake shoe table. 
As shown in FIG. 1, a series of openings 46 are formed in the adhesive 
sheet aligned with the fastener openings 38 of the brake shoe table 13. 
The openings in the adhesive sheet are formed when the openings in the 
friction brake liner and the brake shoe table are properly aligned, and 
the fasteners are inserted through the brake shoe table, the friction 
brake liner and the adhesive sheet. This action results in the plastic 
flow of the material that is a composite of the adhesive sheet to surround 
and encase the fasteners. This provides an insulating barrier that helps 
to prevent galvanic action that may result from dissimilar metals in the 
brake shoe table and the fasteners. 
The friction brake liner 50 generally includes a pair of brake pads 51 and 
52, although it will be understood by those skilled in the art that 
several smaller brake pads or a single brake pad of approximately double 
the size of one of the brake pads 51 or 52 could be utilized instead. Each 
brake pad 51 and 52 is a substantially rectangularly shaped block formed 
from a frictional material such as steel wool or a similar metal alloy 
material. Each brake pad includes a convex outer surface 53 for engaging a 
confronting surface of a rotary brake drum (not shown), and a concave 
inner surface 54 which faces and mates with the convex surface 31 of the 
brake shoe table 13 in a tight seated engagement with the adhesive sheet 
engaged therebetween. As illustrated in FIGS. 1 and 2, the brake pads are 
of a length and width slightly less than the length and width of the brake 
shoe table. 
A series of fastener openings 56 (FIG. 1) are formed through the brake 
pads. The fastener openings 56 of the brake pads 51 and 52 are generally 
cylindrically shaped bores arranged in groups 57 with the number of 
fastener openings of each group 57 corresponding to the number of fastener 
openings in each group 39 formed through the brake shoe table 13, and are 
aligned with the fastener openings 38 formed through the brake shoe table. 
As shown in FIG. 2, each of the fastener openings 56 includes a 
cylindrical recess 58 (shown in dashed lines) formed adjacent the upper 
surface of the brake pads and a cylindrical lower bore 59 (shown in dashed 
lines) of a substantially smaller diameter than recess 58 extending from 
the recess 58 through the lower surface of each brake pad. 
As illustrated in FIGS. 1 and 2, a series of fasteners 61 are inserted 
through each of the aligned fastener openings 56 and 38 of the brake pads 
and brake shoe table, respectively, to secure the brake pads 51 and 52 to 
the brake shoe table 13. The fasteners typically are rivets or bolts, 
although other conventional fastening means also can be used. Each 
fastener 61 includes a head portion 62 and a shank portion 63 depending 
from the head of each fastener. The fasteners are inserted into the 
fastener openings with the shank 63 of each fastener 61 extending through 
the cylindrical recesses 58 and lower bores 59 of the fastener openings of 
the brake pads and through the fastener openings of the brake shoe table. 
The fastener shanks 63 are secured at their opposite ends as by flattening 
the ends of the shank portions, if rivets are used, or by the use of a 
locking means such as a nut where bolts are employed. 
As illustrated in FIG. 2, the head portion 62 of each fastener is received 
within the cylindrical recesses 58 formed in the brake pads 51 and 52, 
seated within the recesses. Such a seating engagement of the fasteners 
within the recesses of the brake pads insures that the fasteners are not 
engaged by the confronting frictional surface of the brake drum with the 
engagement of the brake pads against the brake drum during braking. Thus, 
the fasteners securely mount the brake pads to the brake shoe table. 
To construct the brake shoe assembly with sealing liner 10 as illustrated 
in FIG. 1, one of the peelable backing layers 47 or 48 is removed from one 
side of the adhesive sheet to expose a first adhesive face thereof. The 
exposed adhesive face of the adhesive sheet is positioned over and engages 
the convex surface 31 of the brake shoe table. The adhesive sheet 45 is 
pressed tightly against the convex surface of the brake shoe table 13, 
urging any air bubbles from between the adhesive sheet and the brake shoe 
table and covering the convex surface 31 of the brake shoe table in 
substantially complete adhesive contact with an adhesive film 
approximately 5 ml. thick. Once the adhesive sheet has been applied to the 
brake shoe table, openings 46 are formed through the adhesive sheet 45, 
aligned with the fastener openings formed through the brake shoe table. 
Generally, fastener openings 38 are formed through the brake shoe table 
adjacent the side edges 33, 34, 36, and 37 of the brake shoe table as by 
drilling during the manufacture of the brake shoe prior to the application 
of the adhesive sheet to the brake shoe table. However, it is also 
possible to first apply the adhesive sheet and thereafter form the 
openings through the adhesive sheet at the same time the fastener openings 
are formed in the brake shoe table. 
Once the fastener openings 38 and the openings 46 have been formed through 
the brake shoe table and adhesive sheet sealing liner as desired, the 
backing layer 47 or 48 (FIG. 3) covering the second adhesive face of the 
adhesive sheet is removed to expose the second adhesive face. The 
installer then positions the brake pads 51 and 52 (FIG. 1) of a friction 
brake liner 50 over the brake shoe table with the concave inner surfaces 
54 of the brake pads positioned in facing relationship with the convex 
surface 31 of the brake shoe table. The installer positions the brake pads 
such that the fastener openings 56 formed through the brake pads are 
aligned with the fastener openings 38 formed through the adhesive sheet 
and brake shoe table. Once the fastener openings 56 of the brake pads have 
been so aligned, the brake pads are urged against the adhesive sheet 45 
into tight adhesive contact with the adhesive sheet and into mating 
engagement with the convex surface 31 of the brake shoe table 13. 
As the brake pads are pressed against the convex surface of the brake shoe 
table, the adhesive material of the adhesive sheet 45 is urged toward the 
side edges of the brake shoe table. The adhesive material of the adhesive 
sheet flows and spreads to fill any gaps between the concave surfaces 54 
of the brake pads 51 and 52 and the convex surface 31 of the brake shoe 
table, due to any slight differences in the radius of curvature of each of 
these components. This spreading of the adhesive is further enhanced by 
the insertion of fasteners 61 through the aligned fastener openings 56 and 
38 of the brake pads and brake shoe table. As the fasteners 61 are 
secured, as shown in FIG. 2, adjacent the concave surface 32 of the brake 
shoe table, the concave inner surfaces 54 of the brake pads are pulled 
into tighter adhesive contact with the convex surface of the brake shoe 
table. 
The adhesive sheet 45 substantially covers the convex surface of the brake 
shoe table, filling any gaps between the concave inner surfaces 54 of the 
brake pads 51 and 52 and the convex surface 31 of the brake shoe table 13. 
The adhesive sheet thus functions as a sealing liner to create a moisture 
barrier between the brake pads and the brake shoe table. This moisture 
barrier retards the passage of moisture and corrosive elements such as 
salt and grime through the brake pads and into contact with the brake shoe 
table to prevent rust and corrosion of the brake shoe table. Thus, there 
usually is no necessity for coining or reworking the brake shoe table to 
achieve a tighter sealing fit between the friction brake liner and the 
brake shoe table. 
The ability of the adhesive material of the adhesive sheet to remain 
pliable and substantially fluid at the high temperatures created during 
braking of the vehicle enables the adhesive sheet to flow and move over 
the brake shoe table to fill and seal any gaps formed by the shifting of 
the brake pads on the brake shoe table during braking. Additionally, by 
remaining pliable, the adhesive material is kept from solidifying and 
cracking, as occurs with conventional epoxies, to retard the creation of 
gaps between the brake pads and the brake shoe table. Thus, the seal 
between the brake shoe table and the friction brake liner is maintained 
even under extreme temperatures and stress created during braking. The 
adhesive sheet also provides an additional adhesive bond between the brake 
pads and the brake shoe table to further secure the brake pads and brake 
shoe table together in tight adhesive contact sealed against the passage 
of moisture and vapors therethrough. By inhibiting rust and corrosion of 
the brake shoe table, the useful life of the brake shoe and the brake shoe 
assembly itself is extended, resulting in cost savings. 
It will also be understood that while the adhesive sheet typically is 
applied to the convex upper surface of the brake shoe table prior to 
attachment of the friction brake liner to the brake shoe table, it is also 
possible to apply an adhesive sheet to the concave surfaces of the brake 
pads of the friction brake liner before attaching the brake pads to the 
brake shoe table. 
In some instances, the brake shoe is manufactured by one manufacturer and 
sold to another company that mounts the brake liner to the brake shoe. It 
will thus often be the customer or installer who will apply friction brake 
liners. Accordingly, the brake shoes can be shipped to the customers with 
the adhesive sheets unattached or already applied to the brake shoe table, 
or the complete assembly can be formed by the manufacturer. 
While the foregoing invention has been described in the form of a preferred 
embodiment, it will be understood by those skilled in the art that 
numerous modifications, variations, and changes may be made thereto 
without departure from the spirit and scope of the invention as set forth 
in the following claims.