Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A BRAKE APPLICi~aTION MECHANISM FOR A DISC BRAKE CALIPER
Technica_L Field
This invention relates to a brake application mecha-
nism for a disc brake caliper, the caliper comprising a
housing to be <~rranged astraddle of a vehicle brake disc, a
cover attached to the housing, two thrust sleeves, which
are connected t.o a brake pad holder provided with a brake
pad for braking engagement with the brake disc and which
are axially movable in the housing at a distance from each
other, a cross bar connecting the two thrust sleeves, and a
lever for tran;~mitting a brake force from a brake cylinder,
attached to th<s caliper, to the cross bar.
A disc brake caliper as defined above is primarily
intended for a road vehicle but may quite as well be used
for a rail vehicle.
Background of the invention
Prior de:~igns for disc brake calipers of this kind
are known.
The mounting of the different parts of a brake appli-
cation mechanism for such a disc brake caliper can be
rather complic<~ted, also against the background that more
parts than those mentioned above are involved in the
design.
It is accordingly an object of the present invention
to facilitate the mounting of a brake application mechanism
as defined.
In view of its complexity and the tolerances invol-
ved, a brake mechanism as defined has normally to be manu-
factured by a :brake specialist, whereas the housing and
certain other :parts of the disc brake caliper may well be
manufactured for example by the vehicle manufacturer, such
as a truck manufacturer. For different reasons this may
provide an economic advantage for this manufacturer. Also,
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the transport costs are decreased. A drawback, however, may
be the difficu=Lty to deliver and to mount the different
parts of the mechanism.
A further object of the invention is accordingly to
facilitate the delivery of a brake application mechanism
from a special_i_st manufacturer for mounting in a housing of
a brake caliper manufactured by somebody else.
The Invention
The above objects are according to the invention
l0 fulfilled in that the brake application mechanism including
the thrust sleeves, the cross bar and the lever is a self-
sustained unit for insertion in the housing.
In this way the different parts of the brake applica
tion mechanism can not only be manufactured by a specialist
manufacturer but also mounted as a self-sustained unit.
This unit may be delivered to the vehicle manufacturer,
where it is easily mounted by workers without specialist
skill in the caliper housing provided in situ.
In a practical case the cover and the cross bar can
be resiliently connected by means of screws extending
through holes :in the cross bar and attached to the cover, a
compression spring being arranged between the head of each
screw and a spring sleeve bearing against the cross bar. By
this design the cover and the rest of the mechanism are
held together as a unit even in the absence of the housing,
which accordingly may be manufactured separately, but a
return force for the cross bar and accordingly for the
thrust sleeves is obtained.
Brief Description of the Drawings
The invention will be described in further detail be-
low reference being made to the accompanying drawings, in
which
Fig 1 is a section of a disc brake caliper according
to the invention (along the lines I-I in Fig 2),
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Fig 2 is a section of the caliper along the line III
II in Fig l,
Fig 3 is a plan view of a lever in the caliper accor-
ding to the invention,
Fig 4 is a side view of the above lever,
Fig 5 is a plan view (in two levels) of a sub assem-
bly of the caliper according to the invention, including
the lever shown in Figs 3 and 4,
Fig 6 is an enlargement of the central part of Fig 2
for more clearly illustrating the adjuster part of the ca
liper,
Fig 7 is a plan view, partly in section, of an adjus-
ter housing with its contents,
Fig 8 is a sectional side view corresponding to Fig 1
but to a larger scale and showing a modified embodiment,
and
Fig 9 is a section corresponding to Fig 6 of the mo-
dified embodiment of Fig 8.
Detailed Description of Preferred Embodiments
A disc brake caliper, preferably for use in heavy
road vehicles, is shown in Figs 1 and 2. As is well known
in the art., a caliper of this kind is to be mounted in a
vehicle underfx-ame astraddle of a brake disc (not shown) on
a rotating axle of the vehicle.
The main components of the disc brake caliper are a
housing 1 and a cover 2, which are attached to each other
by means of scx-ews 3. Attached to the cover 2 is a brake
cylinder 4, nox-mally a pneumatic brake cylinder, for deli-
vering a brake force to the caliper. The brake cylinder 4
is only indicated in Fig 1 with dash dotted lines.
In a way to be described the brake force from the
brake cylinder 4 is transmitted to a brake pad 5 engaging
the brake disc (not shown). The reaction force at braking
is taken up by a similar brake pad (not shown) attached to
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the housing 1 at the other side of the brake disc (not
shown), as is well known in the art.
The brake pad 5 is attached to a pad holder 6, which
in turn - via a heat shield 7 - is attached to two thrust
plates 81. Rotationally attached to these thrust plates 81
are thrust sleeves 8, which thus are axially and rotatio-
nally movable _Ln the housing 1. The two thrust sleeves 8
are provided w_Lth external threads, and a cross bar 9, ha-
ving two internally threaded bores 10 (Fig 5), is attached
l0 to these thrust, sleeves 8; the three parts 8 and 9 form a
brake force transmitting unit. The cross bar 9 is provided
with a praject_Lon 9' engaging a corresponding recess in the
housing 1 for t:he guiding of the cross bar 9.
Hold-off or return springs 11 are arranged between
the housing 1 or rather the cover 2 and the cross bar 9 in
the following way. The cross bar 9 is provided with bores
12 at its two ends. Screws 13 surrounded by the springs 11
pass freely through these holes 12. The screws 13 are atta-
ched in corresponding holes in the cover 2. Each spring 11
is arranged between the head of the screw 13 and the bottom
end of a spring sleeve 14 which bears against the shoulder
on the cross bar 9 with its other end. By the described
hold-off spring arrangement delivery of the mechanism as a
unit including the hold-off springs is possible, in spite
of the fact that the hold-off force acts between the cross
bar 9 and the housing 1. The arrangement will act to hold
the cover 2 and the rest of the mechanism together also in
the absence of the housing 1.
A protect=ive bellows 15 is arranged between each
3o thrust plate 8:L and the housing 1 for preventing contami-
nants to enter into the mechanism inside the housing 1.
Each bellows 15 is attached to the thrust plate 81 at the
manufacture of the mechanism, whereas the attachment
thereof to the housing 1 at the later mounting at the ve-
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hicle manufacturer can occur by means of a cup 16 pressed
in place by the thrust plate 81.
The brake force from the piston rod (not shown) of
the brake cylinder 4 is transmitted to the mechanism, espe-
5 cially the cro:~s bar 9, by means of a lever 17. The lever
17 consists in essence of an arm 18 extending out from what
could be called a curved wedge 19 having cylindrical sur-
faces in engagement with corresponding cylindrical surfaces
of the cross bar 9 and bearing tappets 20. Each of these
l0 bearing tappet: 20 rests by means of a bevel on the cover 2
and is connected thereto by means of a pin 21, so that it
can be regarded as a part of the cover 2.
As will appear below there are two bearing tappets
20, and an adjuster mechanism 28 is arranged between them.
An inner cylindrical surface 19' of the curved wedge
19 cooperates with the bearing tappets 20, whereas an outer
cylindrical surface 19" with larger radius than the inner
cylindrical surface 19' cooperates with the cross bar 9.
The centez-s for these two cylindrical surfaces 19' and 19"
are offset. in relation to each other, as appears especially
well in Fig 4, where the center for the outer cylindrical
surface 19" is higher than that of the inner cylindrical
surface 19'.
Inner needle bearings 22 with inner roller cages 23
are arranged between the inner cylindrical surface 19' and
the bearing tappets 20. In a similar manner outer needle
bearings 24 wil~h outer roller cages 25 are arranged between
the outer cylindrical surface 19" and the cross bar 9. Each
outer roller cage 25 is held in a hardened insert 25' held
in place by a pin 25" in the cross bar 9 (Figs 5 and 6).
The purpose of these needle bearings is to enable a high
efficiency for the engagement between the curved wedge 19
and the curved surfaces cooperating therewith.
Where the lever 17 moves from its position to the
right in Fig 1, drawn with full lines, to its position to
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the left in Fic~ 1, drawn with dashed lines, the curved
wedge 19 will be forced in between the bearing tappets 20
and the cross bar 9 and push the latter to the left in the
drawing, accomplishing a brake application via the thrust
sleeves 8. For axial guidance the lever 17 is provided with
an outer ridge 26 between the two inserts 25'. Further,
there are lower pins 27 in the inner cylindrical surface
19' and the outer cylindrical surface 19", respectively,
for circumferential guidance of the roller cages 23 and 25,
l0 respectively.
The adju:~ter function of the disc brake caliper
according to the invention will now be described. The ad-
juster mechani:~m 28 is arranged between the bearing tappets
20 and is most clearly shown in Figs 6 and 7. However, the
general arrangE:ment will first be described with reference
to Fig 2.
The adju:~ter mechanism 28 to be described is arranged
on a splined shaft 29, which extends through the adjuster
mechanism 28 and freely through the bearing tappets 20.
Either end the splined shaft 29 is provided with a bevel
gear 30 meshing with a corresponding bevel gear 31 on a
splined adjustrnent shaft 32 in engagement with internal
splines in each thrust sleeve 8. By turning the splined
shaft 29 by means of the adjuster mechanism 28 in a way to
be described below, the adjustment shafts 32 will be syn-
chronously turned for turning the thrust sleeves 8 in the
cross bar 9 and moving them forward in order to compensate
for wear of the the brake pad 5. '
As most clearly appears from Fig 7, the adjuster
mechanism 28 has an adjuster housing 33. This adjuster hou-
sing 33 is arranged between the two bearing tappets 20 and
also in a suit<~ble recess in the cover 2, as appears from
Fig 6. The adjuster housing is provided with a key groove
33' for a pin :34 (Fig 6) attached in the curved wedge 19
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and constituting a means for transferring motions to the
adjuster housing 33.
The adju~;ter housing 33 contains the following ele
ments to be further described: an adjustment spring 35, a
guiding sleeve 36, a one-way spring 37, a driving ring 38,
an adjuster hub 39 and a locking ring 40 in the end of the
adjuster housing 33 for keeping all the other parts to-
gether in the housing.
The adju:;tment spring or friction spring 35 has an
l0 outer diameter which is slightly larger than the inner dia-
meter of the housing 33 and is in friction engagement
therewith. At one end it is provided with a radial exten-
sion 35' engaging a corresponding recess 38' of the driving
ring 38. A control distance or A-measure for the adjuster
can be formed Either in that the groove 33' has a greater
circumferentia7_ dimension than the diameter of the pin 34
or that the recess 38' in the driving ring 38 has a greater
circumferential_ dimension than the adjustment spring exten-
sion 35'. A radial extension of the one-way spring or lock-
ing spring 37 is attached to the driving ring 38, and two
or three turns of this spring may be in firm engagement
with the driving ring for providing assistance to the force
transmission, whereas the remaining turns of the spring 37
may engage the adjuster hub 39 at mutual rotation in one
direction, the driving direction. The purpose of the gui-
ding sleeve 36 between the two springs 35 and 37 is to
guide them and thus to assist in obtaining an accurate
clutch function. The adjuster hub 39 is in splines engage-
ment with the :~plined shaft 29 (Fig 6).
During an application stroke, i a when the lever 17
is moved to the left in Fig 1 by the brake cylinder 4 and
the curved wedge 19 is pushing the cross bar 9 (and associ-
ated parts) to the left in Fig 1, the control distance or
A-measure defined in either of the two places mentioned
above will_ fir:~t be traversed. At the continued application
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stroke the adjustment spring 35 will be in engagement with
the housing 33 by means of friction forces and will turn
the thrust: sleeves 8 for slack decreasing, if the slack
between the brake pad and the brake disc is excessive in
relation to thE: set control distance, until a counter-force
and thus a torque is built up, when the brake pad engages
the brake disc.. The force transmission during adjustment
occurs by mean: of the one-way spring 35 drivingly acting
between the driving ring 38 and the adjuster hub 39. When
the brake pad is in engagement with the brake disc, the
torque is such that slip will occur between the housing 33
and the adjustment spring 35.
During the release stroke no torque is transmitted by
the one-way spring 37 between the driving ring 38 and the
adjuster hub 39. If the slack between the brake pads and
the brake disc was excessive and a portion of this exces-
sive slack has been taken up by a small rotation of the
thrust sleeve F3 in relation to the cross bar 9, this new
relative posit_~on will be maintained during the release
stroke .
A modified design for the adjuster mechanism is shown
in Figs 8 and 9. These figures are only provided with refe-
rence numerals for parts that are referred to below and/or
are different _Ln relation to the first embodiment, shown in
the previous f _Lgures .
In this embodiment according to Figs 8 and 9 the
movement from t:he curved wedge 19 to the adjuster housing
33 is not performed in the same way as in the previous em-
bodiment. Instead the lever 17 is provided with an arcuate
3o yoke 17' having an internal, cylindrical gear segment 17"
concentric: with the bearing tappets 20. The housing 33 is
provided with external gears, and a gear wheel 41 meshing
with the gear :segment 17" and with the adjuster housing 33
is rotatably journalled in the cover 2. For obtaining the
desired result with this modified embodiment the contents
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of the adjuster housing 33 can be the same as in the first
embodiment. but reversed.
By this design it is possible to obtain a higher ex-
change ratio and thus a faster takeup of excessive slack.
