Bicycle wheel rim brake

A bicycle wheel rim brake having an actuating element which can be rotated against spring force is actuated via of a traction cable in such a way that a sliding member supporting a brake lining is displaced in a straight line at right angles to the rim. The axis of rotation of the actuating element coincides with the axis of displacement of the sliding member or lies parallel thereto. A control surface which is inclined relative to this axis of rotation is connected to the sliding member. The sliding member, the brake lining, and the actuating element are supported by a bearing housing which is retained by a bayonet catch in a recess in the wheel fork in such a way that the maintaining of the rim brake is extremely simple.

The invention relates to a two-wheel rim brake, particularly for bicycles. 
BACKGROUND OF THE INVENTION 
A two-wheel rim brake of the type to which the invention relates is the 
subJect matter of an earlier European Patent Application No. 82 110 473.4. 
In this rim brake the effective brake parts, that is, the sliding members 
with the brake linings and their actuating elements, can be retained 
directly on the frame or tube sections of the wheel fork lying immediately 
opposite the rim. The effective brake parts, which are of similar 
construction on either side of the rim, form compact units which can be of 
extremely space-saving construction. Because of the way the effective 
brake parts are assembled, they function in an extremely stable manner 
which leads to a sensitive and highly effective actuation of the brake in 
any weather conditions. 
The object of the invention is to develop the known two-wheel rim brake 
further so as to provide a particularly simple fitting of the brake on the 
bicycle wheel fork. 
SUMMARY OF THE INVENTION 
The stated object is achieved according to the invention in that the 
bearing housing is retained in the recess in the wheel fork by means of a 
bayonet catch. 
The construction according to the invention also makes use of the 
space-saving compact construction in which the principal effective brake 
parts, that is, the sliding members with the brake linings and their 
actuating elements located in the immediate proximity of the appertaining 
sliding member, are combined to form one assembly. Such an assembly can be 
inserted directly into a recess provided for such purpose on the wheel 
fork or the relevant tubular section of the wheel fork. The cooperating 
elements of the bayonet catch are provided on the one hand in the recess 
in the wheel fork and on the other hand on the bearing housing and they 
interengage in such a way that, when the assembly is mounted, the bearing 
housing is inserted in the recess in the wheel fork and by appropriate 
rotation can be brought into its fitting position in which the bearing 
housing is immovably received in the recess in the wheel fork and is 
retained there reliably. Such fixing by means of a bayonet catch also 
permits rapid removal of the assembly from the wheel fork if necessary for 
maintenance or repair work.

DETAILED DESCRIPTION 
The effective brake parts comprise an assembly 1 having a bearing housing 
2, a threaded socket 3 which is arranged therein so as to be partially 
rotatable, a threaded spindle 4 which engages in the threaded socket 3, a 
sliding member 5 which is mounted on one axial end of the threaded spindle 
4 and is received in a recess 6 in the bearing housing 2, and a brake 
lining 7 which is supported by a brake lining carrier 8 and is mounted by 
means of the latter on the end 5a of the sliding member facing one wheel 
rim of a cycle. The spindle 4, the sliding member 5 and the brake lining 
carrier 8 with the brake lining 7 can be connected one behind the other in 
the axial direction with the aid of a centrally arranged screw 9 and 
optionally by a serration (between the threaded spindle 4 and the sliding 
member 5) so as to be fixed against rotation and sliding. The sliding 
member 5 generally has a cross-section which deviates from a circular area 
and in the illustrated embodiment (FIG. 2) is approximately a pointed 
ellipse, and the cross-section of the recess 6 is adapted to that of the 
sliding member 5 so that the sliding member 5 can only be slid within the 
recess 6 but cannot be turned. 
In practice the threaded spindle 4 also forms a part of the sliding member 
5, namely, the part which is axially opposed to the brake lining 7. The 
treaded spindle 4 engages with its external thread in the internal thread 
of a central threaded bore 10 in the threaded socket 3. Therefore, if the 
threaded socket 3 is turned the threaded spindle 4 is forcibly displaced 
in the direction of the axis of displacement VA and thus the appertaining 
sliding member 5 with the brake lining carrier 8 which it supports and the 
brake lining 7 are forcibly displaced. 
In the illustrated embodiment the bearing housing 2 has a first, inner 
housing section 2a and a second, outer housing section 2b. The sliding 
member 5 is axially slidable inside the first housing section and the 
threaded socket 3 is mounted inside the second housing section 2b so as to 
be rotatably and slidably movable. The threaded socket 3 has on its outer 
surface facing away from the rim or the brake lining 7 (on the left-hand 
side in FIG. 1) a collar 11 which engages over the second, outer section 
2b of the bearing housing 2 and is provided with an internal thread 11a 
which engages with a thread 2b' provided on the outer periphery of the 
second housing section 2b. While the central threaded bore 10 and the 
threaded spindle 4 of the sliding member 5 have a relatively large thread 
pitch, the pitch of the internal thread 11a of the collar and the 
corresponding external thread 2b' of the bearing housing are considerably 
smaller. 
A first annular groove 12 is constructed between the first, inner housing 
section 2a and the second, outer housing section 2b of the threaded socket 
collar 11 which is screwed thereon. A helical spring 13 is received in the 
annular groove 12 and has one end 13a fixed with the aid of a pin 14 on 
the first housing section 2a and the other end 13b fixed on the threaded 
socket collar 11. Mounted on the outer peripheral surface of the threaded 
socket collar 11 are on the one hand two fastening projections 15 and on 
the other hand two guide projections 16 which are offset from the 
fastening projections in the peripheral direction and are in the form of 
radially projecting tabs. A traction cable 17 shown in FIG. 6 is fixed 
with its end 17a on the fastening projections 15 and is guided around a 
part of the outer periphery of the collar 11 and held in position between 
the two guide projections 16 so that it cannot slip off. 
The threaded socket 3 can be completely closed on its outer surface 3a 
facing away from the brake lining 7 (as shown in FIG. 1) and can thus at 
the same time form a sort of cover for the brake assembly 1. 
The construction and arrangement of the threaded socket 3 with its outer 
collar 11 in this embodiment thus produce the actuating element by means 
of which the sliding member 5 is moved. Therefore, when the traction cable 
17 is pulled in the direction of the arrow 18, for example by a Bowden 
wire, the threaded socket 3 rotates against the force of the helical 
spring 13 (in the direction of the arrow 19 in FIG. 6) in such a way that 
the threaded socket 3 moves a short distance axially relative to the fixed 
bearing housing 2. However, since the internal thread of the central 
threaded bore 10 has a substantially greater pitch than the internal 
thread 11a of the threaded socket collar 11, with this rotary movement of 
the threaded socket 3 the threaded spindle 4 and with it the appertaining 
sliding member 5 with the brake lining carrier 8 and the brake lining are 
displaced in the axial direction (axis of displacement VA). The automatic 
locking between the threads 11a and 2b' has the advantageous effect for 
the user that braking only requires a relatively little force since the 
user only needs to apply a little more force than is necessary to overcome 
the force of the retracting spring (a significant proportion of the 
braking force when the brake is applied, however, is absorbed by the 
thread 11a or 2b' between the threaded socket 3 and the bearing housing 
2). 
The construction of the brake assembly 1 as described above principally 
provides advantages for production. The individual parts of this assembly 
1 can be made from any suitable material which is sufficiently stable; 
because of the favorable construction and the uniform transfer of force 
both the threaded socket 3 and the bearing housing 2 can be made from 
plastics material. 
It will be understood that a bicycle will include a similar brake assembly 
1 on both sides of the wheel rim. For this purpose a recess 21 (FIG. 3) is 
provided in the wheel fork of the bicycle or in each tubular section of 
the wheel fork opposite one another (aligned), and the bearing housing 2 
which supports the sliding member 5, the brake lining 7, and the actuating 
element (threaded socket 3), and thus finally the whole brake assembly 1 
are firmly retained in this recess. 
The bearing housing 2 has on the outer periphery of its first, inner 
section 2a a peripheral groove 22 and--in the illustrated embodiment--two 
diametrically opposed milled out areas 23 which extend to the base of the 
groove and which can essentially be flattened areas running approximately 
tangentially to the base 22a of the groove. A lug 24 the peripheral length 
of which is at most as great as the peripheral length of the appertaining 
milled out area 23 projects from the inner peripheral surface of the 
recess 21 in the wheel fork to engage in the peripheral groove 22 and is 
associated with each of the milled out areas 23. The lugs 24 are 
preferably projections which are directed radially inwards and are 
constructed in one piece on the inner periphery of a substantially 
cylindrical bush 25 which is fixed, for example by welding, in the recess 
21 in the wheel fork which is aligned at right angles to the rim 26 (see 
FIG. 4). The lugs 24 in the bush 25 together with the appertaining milled 
out areas and the peripheral groove 22 form a bayonet catch by means of 
which the bearing housing 2 is retained in the recess 21 in the wheel fork 
(see FIGS. 4 and 5). 
In order to bring the brake assembly 1 shown in FIGS. 1 and 2 into its 
assembled condition according to FIG. 4, the brake assembly 1 with its 
bearing housing 2 is arranged relative to the recess 21 in the wheel fork 
in the manner shown in FIGS. 1 and 3, that is to say, in particular that 
the milled out areas 23 are arranged in such a way that they lie opposite 
the appertaining lugs 24 like a cover, and as a result the bearing housing 
2 can be inserted into the recess 21 in the wheel fork or into the bush 25 
fixed therein until the annular peripheral groove 22 is located exactly 
opposite the lugs 24 which fit into it. For this purpose the front 
sections 23a of the milled out areas 23 in the direction of insertion 
(arrow 27 in FIG. 1) can be machined out further--as shown in FIG. 2--than 
the rear sections 23b in the direction of insertion so that--as is clearly 
shown in FIG. 2--these rear sections 23b of the milled out areas form 
contact surfaces 23b' which come to rest against the end faces 24a of the 
lugs 24 facing them and thus limit movement of the bearing housing 2 into 
the bush 25. When the bearing housing 2 reaches this position in the bush 
25 it is merely necessary for the bearing housing 2 to be turned in the 
direction of brake actuation (arrow 19 in FIG. 6) so that the milled out 
areas 23 are rotated in the peripheral direction relative to the lugs 24 
and the bayonet catch reaches its closed position and the bearing housing 
2 is in its fitting condition. The bearing housing 2 is turned by 
corresponding rotation of the whole brake assembly 1, and according to 
FIG. 5 this rotation can amount to approximately 90 degrees and be limited 
by a stop which in the illustrated embodiment is advantageously formed by 
the pin 14 which holds the helical spring 13 and passes through the 
peripheral groove 22 in the transverse direction (see FIG. 1). Any removal 
of the whole brake assembly 1 from the wheel fork (tubular section 20) 
which may be necessary for the purpose of maintenance or repair is carried 
out in the reverse manner by turning the bearing housing 2 against the 
direction of actuation (arrow 19 in FIG. 6) and thus bringing the milled 
out areas 23 and the extensions 24 into coincidence again; it is then 
sufficient simply to pull the bearing housing 2 out of the bush 25. 
When the brake is actuated by means of the traction cable 17 and thus when 
the threaded socket 23 is rotated the bearing housing 2 is always held in 
the closed position of the bayonet catch, and therefore reliable retention 
of the bearing housing 2 and with it the whole brake assembly 1 in the 
recess 21 in the wheel fork is ensured by simple means. However, the 
bearing housing 2 can also be additionally secured in its fixed position 
by means of an anchor or locking screw 28 inserted from the outer side of 
the wheel fork, as indicated in FIGS. 4 and 5, and this locking screw 28 
can engage in a corresponding bore 29 in the bearing housing 2. 
It has proved particularly advantageous to provide only two diametrically 
opposed milled out areas 23 and two correspondingly diametrically opposed 
lugs 24 to form the bayonet catch, but naturally more such milled out 
areas and lugs of matching arrangement and construction could be provided. 
In addition, the brake assembly with the bearing housing and the essential 
brake parts mounted therein do not necessarily have to be constructed in 
the manner shown in FIGS. 1 and 2, and variations thereof could be used 
such as those set out in particular in the various embodiments according 
to European Patent Application No. 82 110 473.4. In this connection it 
should be pointed out that the axis of displacement VA of the sliding 
member 5 in the illustrated embodiment coincides with the axis of rotation 
of the actuating element, but this axis of rotation of the actuating 
element can be displaced parallel to the axis of displacement of the 
sliding member.