Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02721166 2010-11-10
SPECIFICATIONS
FIELD OF THE INVENTION
The present invention is in the field of disc (or disk) brakes for vehicles
whereby a
rotating disc (rotor) attached to a wheel, rotates through a very narrow gap
between
opposing disc brake pads held in a powerful hydraulic caliper. During braking,
the brake
pads move through the small gap to squeeze the rotor with enormous force,
slowing the
vehicle. Each disc brake pad comprises a steel backing plate (plate) with a
brake friction
pad on one side. During braking, enormous shearing forces are generated
between the pad
and plate which is resisted by the adhesive and various mechanical means. The
friction
pad wears away with each application of the brakes.
BACKGROUND OF THE INVENTION
The present invention is for an improved disc brake pad.
In the present invention the backing plate and the friction pad are mass
produced
separately with interlocking, mating features, and then adhesively assembled
to create a
disc brake pad.
The thick, stiff, steel backing plates are continuously stamped in the
required shape
from coiled steel stock. During or after this stamping, discrete protuberances
are formed
on one face of the plate for engagement-mating with the friction pad to
provide resistance
to shear forces under braking.
Friction pads are punched-formed-molded-slit-cut from friction material and
discrete
recesses formed in one face for engagement-mating with the plate. They are
then cured
hard. The plate and pad are then mated with an adhesive therebetween.
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Using the present method of manufacture enable the use of many smaller
friction pads
on a plate which offers advantages such as lower cost and better cooling
which, in turn,
extends the life of the disc brake pad, which, in turn, lowers vehicular
operating cost.
SUMMARY OF THE INVENTION
A method of making brake pads comprising the steps of making plates and pads
with
complimentary engagement features and then bonding them together with
adhesive.
In the plate of the present invention, a discrete pattern of discrete
protuberances is
provided one face of said plate. Protuberances may include such shapes as
pins, hooks,
burrs, bristles, knurls, ridges, rings and the like. Preferably the discrete
protrusions form a
discrete pattern. Preferable the discrete pattern of discrete protuberances is
repeated at
different locations on the plate.
Friction mixture is formed into pads such as disc-like pads. Discrete recesses
are also
formed in the same discrete patten as the discrete protuberances on the plate.
The pads are
then cured (made hard) ready to be mated and adhesively bonded to the plate.
Pads may
be of any shape or size but preferably thick, disc-like pucks.
Preferably the protrusions on the plate are short so as to maximize the life
of the pad
before wear exposes their tips for unwanted contact with the rotor.
The protrusions may also be added to the plate as weldments, by, for example,
stud
welding techniques or by attaching an appropriately shaped material such as
spheres,
beads, wire, meshes, metal wools, or bristles, to the plate. Separately formed
sheet metal
having the necessary protuberances may also be attached to the plate by, for
example,
spot welding.
In one embodiment, pads may be cut from a large, pre-made plate of brake
friction
material using a laser, mill, or waterjet to cut the final contours.
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In another embodiment, if the lining is made into plate for cookie-cutting the
pads
therefrom, the plate can be formed in layers of different friction
compositions such as
gradients of hardness. For example the thermal conductivity may be increased
by having
a more metallic composition near the plate and less near the rotor face. In
this way the
thinning pad can offer driver safety through better management of the
different stages of
pad wear.
The present invention also contemplates the use of pads made from different
lining
compounds such as those of different hardnesses or having canceling NHV
characteristics
to be used at the leading and trailing edges of the brake pad (relative to
rotor contact.
In all cases, the pad and plate have complimentary mating features. The
features
should be fully contained within the perimeter of the pad so that the adhesive
forms a
surrounding seal that will prevent the ingress of water which could
disadvantageously
lead to interfacial rusting and then, almost certainly, to delamination.
The engagement of pads-to-plate may be such that an assembly force may
preferentially be required. The recess walls may, for example, be lightly
engaged by the
plate's protuberances. The recess can be made slightly deeper than necessary
to
accommodate the sheared of puck material in the resulting pocket at the top of
each post.
The adhesive applied to the pad and/or plate may be of a heat curing formula
whereby
the adhesive may be pre-applied as liquid and then dried. After assembly
heating cures
the adhesive. The adhesive necessarily forms a thin layer between pad and
plate and thus
can serve a secondary valuable function - that of a noise, harshness,
vibration (NHV)
dampening medium. The adhesive layer may be increased in thickness to improve
its
NHV dampening by incorporating particles such as glass beads to prevent too-
intimate
face-to-face contact between the plate and pad.
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Further, the features on the plate and pad could be reversed such that the
plate has
recesses and the pad has protuberances. For example, the plate may have
circular
depressions and the pad raised plateaus that engage the depressions.
In yet another embodiment, a combination of recesses and protuberances may be
formed on each component.
In this way the myriad range of vehicular plate designs can all be fitted from
a range of
`stock' pads in contrast to the slow, messy, and expensive current batch
manufacturing
process.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1, 2 and 3 shows the Prior Art; a backing plate with a bonded on, one-
piece lining
and showing other features sometimes present;
Figures 4, 5, and 6 shows the same plate design but with separate plate and
pads
mechanically engaged and adhesively bonded; the pattern of protrusions and
recesses are shown to have a radial symmetry such that assembly is not
dependent
on a pad's radial orientation or position;
Figure 7 shows detail of the plate and two pads where a pattern of recesses on
a first face
of the lining line up to mate with a like pattern of post-style protrusions on
the
first face of the plate;
Figure 8 shows variations of protrusions which may be the preferred hooks on
the upper
portion of the plate and ridges or burrs, pins, dimples, ridges, or knurl, and
the
matching engagement recesses;
Figure 9 shows the second face of the plate and the punch marks left from the
extrusion
of pin-like protrusions on the opposite first face where the lining will be
attached;
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Figure 10 shows another variation on the upper portion of the plate where a
grid of wire
mesh is welded to the first face of the plate and a matching grid of recesses
on the
lining allow their engagement; on the lower portion is shown knurls (pyramid
shaped) raised features formed in the preferred circular pattern for easy
assembly
of the matching pads (not shown) thereon;
Figure 11 shows other multiple pad shapes;
Figure 12 shows a one-piece pad based on the present invention and where
multiple
groups of engagements are provided;
Figure 13 shows another embodiment where a single, larger recess in the lining
encloses
multiple protrusions, such as the preferred raised hook or burr shown, and how
this arrangement is repeated in different locations on the lining and plate;
Figure 14 shows the same embodiment in a side view;
Figure 15 shows an extruded rod of compacted friction material and multiples
of
individual pad sliced therefrom;
Figure 16 shows multiple pads that are cookie-cut from a sheet of compacted
friction
material.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, Figures 1-3 depict a Prior Art disc brake pad 100.
Fig I is
the front view of the second face 2b of friction lining 2 which is the face
that contacts the
disc brake rotor. Fig 2 is a side view of the same embodiment showing the
first and
second faces, 2a and 2b respectively of lining 2 and, first and second faces
Ia and lb
respectively of the brake pad backing plate 1. Fig 3 is a back view of brake
pad 100
CA 02721166 2010-11-10
where is shown the second face lb of the plate 1 that contacts the caliper
piston and/or
anvil.
In the Prior Art the first face 2a of the one-piece lining 2 is bonded during
molding to
the first face la of the backing plate 1. Features such as holes 3 in the face
la of plate 1
are filled with lining material 2c during the molding process and serves to
help anchor the
lining to the plate. This particular Prior Art brake pad has an auxiliary
feature in the form
of a locator pin 5 protruding from the second face lb of plate 1, although
this is not
present on all designs of disc brake pads, its inclusion here is for reference
and show how
pin 5 has been formed by punch-extrusion from the second face lb of plate 1.
The pin-
shaped punch has left a cavity 4 in the surface of the second face that has a
shape and
volume very similar to the shape and volume of pin 5. Having no purpose on the
first face
Cavity 4 is covered over by lining 2. Its function may be to locate certain
pieces such as
anti-rattle clips when the brake pad is installed in a caliper.
Other features known to exist on Prior Art plates 1 include raised hooks,
weldments,
ridges and the like. However these are all designed for embedment in the
flowable friction
material during the molding operation previously described.
Prior Art brake pads linings 2 may also include features such as grooves 41
and
chamfers 31 to manage harshness, noise, and vibration (HNV) and for thermal
and dust
control.
In summary the Prior Art disc brake pad comprises a steel backing plate which
may
have certain raised or recessed features such as hooks, pins and holes 3 on
its first face l a,
and, a lining 2 which is pressure- and temperature molded from flowable
friction material
onto the first face la of plate 1 and into or about any such features which
become
embedded or filled 2c by it.
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In the disc brake pad of the present invention, the plate 1 and pad 2 are
produced
separately and the first face la of plate 1 and first face 2a of pad 2 are
provided with a
complimentary pattern of features that can interdigitate, interlock, engage,
mate or plug
together. An adhesive 60 (shown only in Fig 5) is provided on either or both
first faces I a,
2a, including in and on their respective interlocking features (not shown).
The plate and
pad are then brought together and the adhesive is cured to permanently secure
the pad to
the plate resulting in a novel brake pad.
Figs 4, 5 and 6 show this inventive brake pad 10 in the same view
configurations as the
Prior Art described above but with multiple pads 2, in this case circular
ones. Recesses 20
are on first face 2a of pad 2, protuberances 21 are on first face l a of plate
1, and cavities
20 are on second face lb of plate 1. Punch-pin cavities 20 do not have any
operative
function but are remnants of the punch that created (one form of)
protuberances 21.
In Figs 4-6 all the protuberances are pin-or post-like structures shown punch-
extruded
from second face lb resulting in cavities 20 in second face lb. The four pads
2 are shown
to be cylindrical, such a shape being the simplest and cheapest to manufacture
in that they
can be sliced like bread from a continuously extruded rod of friction material
46. These
pads 2 can be made in a variety of diameters to enable a best-fit to a wide
range of plate 1
shapes and sizes. The first face of the uncured lining is pressed onto an
appropriate form,
such as a pattern of tapered pins, so as to create the shallow recesses 22.
After curing hard
the pads are then ready for further processing such as grinding to finished
size or
application of adhesive.
In Figs 4-6 dashed line 30 represents the pad outline of the Prior Art lining.
The pads 2
are nested together so as to be within the required area indicated by line 30.
As can be
appreciated the shape and number of pad 2 can be whatever is required in terms
of cost
and total area contacting the disc brake rotor (not shown).
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Fig 7 shows a pre-assembly view of the two first faces of plate and pad 1 a,
2a with
their respective protuberances 21 and recesses 22. The recesses are such that
the plate and
pad fully engage allowing the face surfaces to contact each other where
minimum
adhesive thickness is specified.
Fig 8 shows a preferred embodiment where a pattern of hook-like burrs 5 are
raised
directly from first face la of plate 1 and only in areas covered by the pad.
On the same
plate is shown another form of mating where the plate 1 has a recessed ring 25
and a
centered recess 26. They mate with raised groove shape 24 and plug shape 23
respectively on pad 2.
Fig 9 shows how the plate 1 may have the recesses 25a and 26a to mate with
raised
features on the pad (not shown).
Fig 10 shows how a weldments such as the a wire mesh 43 shown on plate 1 may
be
mated with a complimentary pattern of recesses 42 on pad 2. Also show in Fig
10 are
knurl protrusions 45 which are pyramid-shaped features often used to provide
grip on
surfaces (matching pad not shown);
Fig 11 shows different shapes of pads 2 that maximize coverage within line 30
that
represents the Prior Art pad area.
Fig 12 shows another embodiment where a single pad 2 has four separate areas
of
mating structures. Pad 2 is shown as being one piece but may be two or any
number.
Fig 13 shows another embodiment where recesses 50 in pad 2 are large enough to
enclose a multitude of burrs 5. The burrs are shown to have been formed in a
pattern as
would result from a plurality of parallel toothed blades used to raise the
burrs. The recess
would be filled with adhesive on assembly. Fig 14 shows the same embodiment in
side
view. With this embodiment multiple pads could each have one or more large
recess(es)
each recess encompassing a multitude of plate protrusion burrs 5.
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Fig 15 shows a rod-shaped circular extrude 46 from which multiple pads 2 are
sliced
while Fig 16 shows a molded plate or extrude 47 for cookie-cutting multiple
pads 2.
Fig 16 also shows the laminated form of pad where the final wearing layer 48
adjacent
the plate (not shown) contains a tell-tale material that, as the pad wears
down, is
eventually ablated or also worn away. Dispersed as an air-born powder some
will deposit
onto nearby wheel, body and suspension parts. The tell-tale material in layer
48 may
include those that fluoresce under ultra violet light, for example. This
fluorescent deposit
can be readily detected visually using ultraviolet light to provide a safety
to alert to the
vehicle owner to schedule a brake pad replacement. Beside fluorescent
materials, the tell-
tale material may also emit an odour, a sparkle, a colour, or a sound, or any
combination
thereof.
Some examples of minerals that fluoresce in colour under ultraviolet light
include the
red or orange fluorescence of calcite, the green fluorescence of willemite,
the yellow
fluorescence of esperite, and the orange fluorescence of wollastonite.
The present invention also includes an automatic, drive-by ultraviolet light
and
fluorescent detector for gas- and service stations.
The present invention should become mandated in the interest of everyones
safety.
It will be appreciated that any combination of the embodiments herein
described can
be used as may be required for safe, low-cost brake pad manufacture.
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