1. * GB780088 (A)
Description: GB780088 (A) ? 1957-07-31
Improvements relating to assemblies of friction blocks and shoes
Description of GB780088 (A)
PATENT SPECIFICATION
Inventor: DEREK CAMPBELL JOHNSTON 780,088 Date of filing Complete
Specification (under Section 3 (3) of the Patents
Act, 1949): Jan. 23, 1956.
Application Date: Jan. 21, 1955.
Application Date: June 22, 1955.
No. 1936/55.
No. 18094155.
----a- Complete Specification Published: July 31, 1957.
Index at acceptance:-Classes 80(2), C1C3; and 103(1), ElA1Al.
International Classification:-FO6d.
COMPLETE SPECIFICATION
Improvements relating to Assemblies of Friction Blocks and Shoes We,
FERODO LIMITED, a British Company, of Asbestos House, 77/79 Fountain
Street, Manchester 2, do hereby declare the invention, for which I
pray that a patent maybe granted to me, and the method by which it is
to be performed, to be particularly described in and by the following
statement:-
This invention relates to friction linings suitable for use in clutch
or brake assemblies.
Such a friction lining is normally secured to a shoe or similar
support by nuts and bolts or rivets. The bolts or rivets pass
shank-first from the working face of the lining through holes made in
the lining, these holes being internally stepped to form shoulders
against which the bolt or rivet heads abut. There must be enough depth
of material between the bolt or rivet heads and the non-working or
rear face to withstand the stresses to which the lining is exposed; if
the material here, i.e.
around the shank of the bolt or rivet, is too thin, it may break away
from the body of the lining, and then the lining can move past the

2. bolt or rivet and become detached from the shoe or the like. Now the
lining wears down in use, and when the tops of the bolt heads are
reached it must be replaced. The total axial length of the bolt head
and that part of the shank which lies in the lining is often as much
as half the total thickness of the lining, so that in fact no more
than half the material of the lining has been used when it must be
replaced.
According to this invention the lining is secured to a shoe or similar
support by bolts or other fastening devices passing through holes in
one or more thin keeper strips housed in a shallow groove or grooves
in the rear face of the lining and bonded to the lining, the lining
being recessed to give access to the bolts or the like. Each keeper
strip is thinner than the amount of friction material required beneath
a bolt head in the usual construction.
Preferably the, strip has countersunk holes to receive the heads of
countersunk bolts, so that the depth of the friction material which
can be worn away before the heads of the bolts are reached and the
lining must be replaced is [Prim l substantially increased.
Preferably the strip extends from side to side of the lining. A very
small lining may be held by one such strip, but in general two or more
strips are needed. Each strip may be of rectangular cross-section with
a countersunk hole close to each end for the reception of a standard
bolt with a countersunk head.
A further important feature of the invention makes it easier than
hitherto to replace the lining in many instances. In some clutch and
brake assemblies the distance between the working face of a new
friction lining and its cooperating surface, when the assembly is in
the free or disengaged position, is too small to allow a bolt to be
introduced into a hole in the lining. It has hitherto been necessary
to dismantle such an assembly to enable this operation to be
performed. It is now possible, since the heads of the bolts bear on
metal keeper strips, to make recesses in the sides of the lining so as
to give access, both from the side and front of the lining, to holes
close to each end of the strip, i.e. each side of the lining. The
recess at each side of the block extends through the whole thickness
so that the head of each bolt can be reached from the working face of
the block. The recess need extend inwards only so far as is required
to leave the head of the bolt clear. The recesses may be made by
cutting away parts of the block.
In certain clutch and brake assemblies, such as brakes on winches,
access to one side of the lining is so obstructed that it has not
hitherto been possible without dismantling part of the assembly to
insert a bolt on that side when the distance between the co-operating
friction surfaces in the free or disengaged position is small.

3. According to a further feature of this invention not only are the
sides of the lining recessed but also one or both ends of the keeper
strip are recessed, the recesses in the strip leading into the holes
through which bolts pass and being large enough to allow the shanks of
the bolts to pass through them. This feature renders the dismantling
of part of the apparatus unnecessary; all that is now necessary is to
A _,' insert the bolt through the hole in the shoe and screw a nut
loosely over it so that the bolt has sufficient axial movement for the
bolt head to clear the keeper strip; then the lining is slid over the
shoe until the shank of the bolt lies in the recess in the strip and
the nut is screwed up tightly to urge the bolt down on to the strip.
The preferred constructions according to the invention will now be
described with reference to the accompanying drawings, in which:Figure
1 is a perspective view of the rear face ofthe lining; Figure 2 is a
perspective view of the front or working face ofthe same lining;
Figure 3 shows part of Figure 2 on a larger scale; Figure 4 is a view
similar to Figure 3 of another part of the same lining; Figure 5 is a
section through part of a winch; and Figure 6 is a cross-section
through part of a modified construction.
The lining shown in Figures 1 and 2 consists of an essentially
rectangular block of friction material 1 in which three shallow
grooves extend from side to side across the non-working or rear face.
A thin metal strip 3 is housed in each of these grooves, the exposed
face of each strip being flush with the rear face of the lining. These
strips are bonded firmly in position by any appropriate technique
commonly employed in bonding metal to friction blocks.
At each side the material of the lining is cut away over the end of
the keeper strip as shown at 9. Each keeper strip is made with a
countersunk hole 5 in that part exposed when the recess is made. The
lining can then be secured to a shoe by bolts with countersunk heads
one of which is shown at 6 in Figure 3 in the process of being
inserted.
It will be seen that the block 1, except for the grooves and recesses,
is a normal brake liner, and the support may, and usually will, be a
normal brake shoe. The invention enables the liner to be put in
position from either side of the shoe without moving the shoe
otherwise than through the distance normally allowed for adjustment,
since an appropriate tool can be passed into the recesses from the
side to hold the bolts whilst the nuts are being tightened.
Alternatively, the liner can be put in position from either the top or
the bottom of the shoe.
In any case the operation of changing the liner is simplified. As the
heads of the bolts are flush with the strips, the liner can be allowed
to wear down until the strips are almost reached.

4. The amount of wear that has taken place can be readily seen, so there
is little risk of metal coming into contact with the brake drum or
other element as a result of failer to appreciate the need for
replacement.
As the recesses 9 at the side are open, products of wear can easily
escape.
Even if the bond between a strip and a block should fail, the strip
will still restrain the movement of the block over the surface of the
shoe because the gap between the block and the brake drum or other
element is normally less 70 than the thickness of the strip.
Figure 5 shows part of a winch and its brake which present a special
problem. The winch comprises a rope drum 11 with an end flange 13, and
a brake 15 concentric with the drum 11 75 and presenting a cylindrical
brake surface or path 16. A part-cylindrical shoe 19 carries a number
of friction blocks, each as shown in Figures 1 and 2. The shoe 19 is
pivotally mounted in a stationary part of the winch, and 80 moves to
carry the blocks 1 into contact with the brake path 16, but cannot
move outwards sufficiently either to clear the flange 13 or to enable
the inner bolts 6 adjacent to the flange to be reached by hand from
the outer side of 85 the brake assembly without dismantling the
assembly.
For use in such a brake one end of each keeper strip 3 is recessed as
shown at 7 in Figure 4, so that in effect a key-hole slot is made.
Before 90 the lining is fitted in position the inner bolts 6 are
passed through the corresponding holes in the shoe, which can easily
be done in the space available when the lining is not present.
The lining is then slid over the shoe so that the 95 shank of each
bolt 6 passes radially through the corresponding recess 7. When the
lining is in position nuts 8 are screwed up on the bolts and the head
of each bolt drawn into the counterbore of the hole 5. Thereafter each
outer bolt 100 is inserted in the way illustrated by Figure 3.
If a lining must be changed, the outer bolts are first removed and the
inner bolts 6 are then slackened enough to allow the bolt heads to
move clear of the strip. Then the lining can be 105 slid outwards, the
inner bolts 6 remaining behind.
When the invention is applied to wide brake liners or other friction
blocks, say 12 inches or more across, two bolts, one close to each
edge, 110 may not be enough in each strip to secure the block firmly
to the support. In such a case it is necessary to provide one or more
additional bolts or other fastenings in the middle of the strip, and
in order to give access to these holes 115 are made from the face of
the block. This has the disadvantage that the bolts or the like cannot
all be loosened from the side, since the recesses in the block extend
only to the end bolts. Nevertheless, in comparison with the 120

5. constructions in use hitherto the block can wear down further before
it needs replacement, the amount of wear can still be more readily
seen and the products of wear can still escape more readily. 125 In
such wide blocks with additional bolts or the like, the need for
working from the front or working face of the block to loosen the
middle bolts or the like can be avoided by using the modified lining
shown in Figure 6. In this a 130 780,088 3. A friction lining,
suitable for use in a clutch or brake assembly, in which one or more
thin keeper strips of rectangular crosssection, adapted to be secured
to a shoe or similar support by bolts, extend from side to side of the
lining in shallow rectangular grooves in the rear face of the lining
and are bonded to the lining, each strip having a countersunk hole
close to each end for the reception of a standard bolt with a
countersunk head and the sides of the lining being recessed to give
access to the bolts.
4. A lining according to claim 1, substantially as described with
reference to Figures 1 to 4 of the accompanying drawings.
5. An assembly of a friction lining with a shoe or other support in
which a keeper strip is housed in a slot of corresponding shape in the
rear face of the lining and is bonded to the lining, and the sides of
the lining are recessed to give access to holes in the strip through
which fixing bolts or other fastening devices pass to secure the strip
to the support.
6. An assembly according to claim 5 in which not only the sides of the
lining but also one or both ends of the keeper strip are recessed, the
recesses in the strip leading into the holes through which bolts pass.
7. A winch in which a rope is wound around the winch drum on one side
of a flange which is rigid with the drum and a co-axial
partcylindrical brake is fixed to the other side of the flange, the
brake including a shoe fitted with friction linings according to claim
6, the strip being recessed adjacent to the flange.
For the Applicants:GILL, JENNINGS & EVERY, Chartered Patent Agents,
51/52, Chancery Lane, London, W.C.2.
boss 18 is secured to the inner face of the metal strip 3, i.e. the
face bonded to the liner, and a tapped hole is made through the boss
and strip to receive a bolt 14 passed through the support shown at 17.
The hole 20 in the block which receives the boss may be a recess
formed from from the non-working face or may (as shown) pass
completely through the block to the working face. This construction
presents the advantage that all the bolts can be loosened without
slacking the assembly away from the brake drum or other surface
frictionally engaged by the block, but it does necessitate replacement
of the block when this wears down to the top of the boss, and so
reduces the life of the block.

6. It will be clear that the number of keeper strips required varies from
one upwards in accordance with the size of the lining, and that if
both sides of the lining are accessible in the assembly the keeper
strips need not be recessed at all. Moreover, if there is enough space
between the co-operating surfaces to insert a bolt, the recesses in
the lining need not open into the sides of the lining but rather may
all be of the kind shown at 20 in Figure 6.
Finally, the keeper strips may be made of other material of adequate
rigidity and strength instead of metal.
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