Two wheel rim brake with rotatable actuating element

The invention relates to a rim brake for a bicycle or the like and in which the brake lining can be moved via a pivotally mounted actuating member and a support member which carries the brake lining and is movable at right angles to the rim. The actuating member is rotatable about an axis which may coincide with the axis of displacement of the support member and is connected to the support member via a threaded control such that rotation of the actuating member in one direction imparts axial movement of the support member in a direction to apply the brake lining to the rim.

BACKGROUND OF THE INVENTION 
The invention relates to a two wheel rim brake, especially for bicycles, in 
which each brake lining can be moved inwards by means of a pivotally 
mounted actuating member which can be actuated by a cable and a sliding 
member which carries the brake lining and can be moved in a straight line 
at right angles to the rim so that the brake lining rests on the rim and 
can move back outwards by spring action. 
Rim brakes are known using brake levers pivotable about a common axis 
running in the longitudinal direction of the bicycle. The stability of 
such rim brakes and their braking effect when wet leave much to be 
desired. 
A known two wheel rim brake is disclosed in German Auslegeschrift No. 26 55 
699 in which brake linings carried by sliding members can be moved in a 
straight line and can be actuated by angle levers which are pivotable 
about an axis which runs at right angles to the axis of displacement of 
the sliding member. These rim brakes do have a greater stability than the 
constructions referred to above, but they have the disadvantage that they 
require a relatively large amount of space (in the direction at right 
angles to the rim). 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a two wheel rim brake which is 
distinguished by a stable and space-saving construction, sensitive 
actuation which is easy and effective in all weathers, and a design which 
is simple to manufacture and assemble. 
This object is achieved in that the actuating member is pivotable about an 
axis which coincides with the axis of displacement of the sliding member, 
or is parallel thereto, and is connected to the sliding member by means of 
a control surface which is inclined relative to such axis. 
In the construction according to the invention the effective brake parts, 
especially the sliding members with the brake linings and the actuating 
levers, are held directly on the bicycle frame or forked tube sections 
immediately opposite the rim. The actuating lever is thus located in the 
immediate proximity of the sliding member, which results in an extremely 
compact construction, in particular at right angles to the rim. The rim 
brake according to the invention is distinguished by extraordinary 
stability and by particularly sensitive actuation of the brake which is 
highly effective in all weathers.

DETAILED DESCRIPTION 
In the first embodiment illustrated in FIGS. 1-3, a bearing housing 1 is 
mounted on a tube frame section R opposite the wheel rim F. The tube 
section R can be either an arm of the fork for the front wheel or a 
corresponding frame tube section in which the rear wheel of a bicycle is 
located. Only the left-hand half of the rim brake is illustrated, but it 
should be understood that a corresponding brake half is provided on the 
right-hand side of the rim F. 
The bearing housing 1 contains an upper and a lower housing section 2 and 
3, respectively, which are connected to each other by means of screws 19. 
The bearing housing 1 is fixed by means of screws 20 to a plate 32 which 
is welded to the tube section R. 
On the end face 4 facing the rim F, the bearing housing 1 has a recess 5 in 
which a sliding member 6 can be moved in a straight line along an axis of 
displacement VA at right angles to the rim. That end face 7 of the sliding 
member 6 facing towards the rim F bears a brake lining 8 which is firmly, 
but removably, connected to the sliding member 6 in known manner. 
The sliding member 6 is constructed in two parts. A first part 6a bears the 
brake lining 8 and is capable of sliding movement in the direction of the 
axis of displacement VA inside the recess 5 in the bearing housing 1, but 
is mounted so that it is not rotatable. For this purpose the first part 6a 
of the sliding member 6 has a cross-section which is not circular, and is 
preferably square. The cross-section of the recess 5 is adapted to that of 
the part 6a of the sliding member. 
The second part of the sliding member 6 is formed by a threaded spindle 10 
with a relatively large pitch. This is axially connected directly onto the 
end face 9 of the first part 6a of the sliding member facing away from the 
rim F and is connected to this part 6a by means of a serration and a screw 
33 so as to be fixed against rotation and displacement. The external 
thread of the threaded spindle 10 engages with the internal thread of a 
threaded bush 11, the outer periphery of which is essentially cylindrical 
and rotatably mounted in a cylindrical internal bore 1a in the bearing 
housing 1. 
On its outer periphery the threaded bush 11 has a radially extending 
actuating member 12 accommodated in a guide slot 13 provided in the upper 
housing section 2. This guide slot 13 defines the possible pivotal 
movement of the actuating lever 12 in the direction of the two-headed 
arrow 12 a. The cable 16 of a Bowden wire 17 is clamped onto the outer end 
14 of the actuating lever 12 by means of a rotatably mounted screw 
connection 15. A helical spring 18, one end of which engages on the 
actuating lever 12 and the other end of which is secured to the bearing 
housing 1, is provided on the outer periphery of the bearing housing 1. 
When the rim brake is actuated the cable 16 is pulled in the direction of 
the arrow Z. In this way the actuating lever 12 is pivoted against the 
force of the helical spring 18. Consequently the threaded bush 11 
connected to the actuating member 12 is rotated in the bore 1a in the 
bearing housing 1. Since the guide slot 13 for the actuating lever 12 lies 
in a plane at right angles to the axis of displacement VA, during this 
rotary movement the threaded bush 11 cannot move axially inside the bore 
1a in the bearing housing 1. The threads of the threaded bush 11 and the 
threaded spindle 10 engage with each other and produce a control surface 
running at an angle to the pivot axis of the actuating lever 12. 
Consequently rotation of the threaded bush 11 results in rectilinear 
displacement of the threaded spindle 10 and thus also of the part 6a of 
the sliding member and the brake lining 8 borne thereon. Consequently the 
brake lining 8 comes to rest on the rim F. 
When the cable 16 is released the tensioned helical spring 18 turns the 
actuating lever 12 back in the clockwise direction (FIG. 2). The rotary 
movement of the threaded bush 11 thus results in an axial movement of the 
threaded spindle 10 and movement of the brake lining 8 away from the rim 
F. 
In the embodiment according to FIGS. 4 and 5, the brake lining 22 is borne 
by the first part 23a of a sliding member 23 which can move in a straight 
line at right angles to the rim. The first part 23a of the sliding member 
is arranged substantially in front of the end face 24 of the housing 
outside the bearing housing 21 and is provided in the ion of its outer 
periphery with axial guide lugs 25 which face away from the brake lining 
22 and are each guided in an axial guide groove 26 in the outer periphery 
of the bearing housing 21. Thus the first part 23a of the sliding member 
is not rotatable but is guided in the bearing housing 21 so as to be 
axially movable. 
The second part 23b of the sliding member 23 which is located inside the 
housing is connected to the first part 23a by a connecting pin 27 so that 
it is fixed against displacement but is rotatable. The second part 23b of 
the sliding member can also be constructed in this embodiment in the form 
of a threaded spindle which has an external thread with a large pitch. 
In contrast to the embodiment according to FIGS. 1-3, in the variant 
according to FIGS. 4 and 5 no separate threaded bush is provided in the 
bearing housing 21. The cylindrical inner wall 21a of the bearing housing 
21 has an internal thread which connects with the external thread of the 
part 23 of the sliding member. 
The part 23b of the sliding member constructed as a threaded spindle 
carries an actuating member 29 which projects radially outwards through a 
guide slot 30 provided in the bearing housing 21 and is connected at its 
outer end 29a to the Bowden cable 31. In this embodiment the guide slot 30 
has a helix which is adapted to the internal thread 28 and the part 23b of 
the sliding member. 
If the actuating lever 29 is moved by the cable 31 in the direction of the 
arrow Z then the part 23b of the sliding member rotates in the internal 
thread 28 of the bearing housing 21 and at the same time moves along the 
axis VA so that the brake lining 22 is pressed onto the rim. The return 
movement is produced by a spring (not shown) which can react for example 
between the small hole 29b in the actuating lever 29 and a convenient part 
of the housing 21. 
In the third embodiment shown in FIGS. 6 and 7, a sliding member 42 is 
movable in a straight line in a bearing housing 41 and the first part 42a 
of the sliding member facing the rim F bears a brake lining 43. This first 
part 42a of the sliding member is guided in a corresponding recess 44 in 
the housing so as to be slidably movable but not rotatable. The second 
part 42b of the sliding member is connected to the first part 42a so as to 
be fixed against displacement but rotatable relative thereto. The second 
part 42b of the sliding member is constructed as a cylindrical pin which 
is mounted in a cylindrical bore 41a in the bearing housing 41. The 
bearing housing 41 has a guide slot 45 through which an actuating lever 46 
which is connected to the second part 42b of the sliding member so as to 
be fixed against rotation extends radially outwards. The guide slot 45 
extends helically and with its radial longitudinal faces 45a, 45b forms 
the control surface for the actuating lever 46 and the sliding member 42. 
The actuating lever 46 is constructed as a pin and passed through a bore in 
the second part 42b of the sliding member. The outer end of the actuating 
lever 46 is connected to a Bowden cable 47. A retracting spring 48 ensures 
the return of the actuating lever 46 and the sliding member 42 to the 
starting position after release of the cable 47. 
A further preferred embodiment of the invention is illustrated in FIGS. 
8-13. These show a variant of the embodiment according to FIGS. 1 to 3. 
Insofar as the parts identical the same reference numerals are used as in 
FIGS. 1-3. Accordingly, only those features of the embodiment according to 
FIGS. 8-13 which differ from the arrangement according to FIGS. 1-3 are 
explained in detail. 
The threaded bush 11, which in the embodiment according to FIGS. 1-3 is 
constructed in one piece as a metal part, consists in the variant 
according to FIGS. 8-13 of an outer metal part 11a (which is preferably 
produced as an extrusion molded part made from steel or nonferrous metal) 
which forms actuating lever 12 and an injection molded inner threaded part 
11b made from plastics material. 
Whereas a metal thread with a very large pitch can only be mass produced at 
relatively high cost, an injection molded plastic thread can be produced 
very economically (the outer metal part is advantageously provided with 
one or more radial bores for injection of the plastics material). The 
injection molded plastic thread has very good antifriction properties 
(less friction than steel on steel) and does not require any lubrication, 
which means that the rim brake requires little maintenance. 
As can be seen in particular in FIG. 13, the outer metal part 11a of the 
threaded bush 11 has a polygonal internal cross-section (hexagonal) which 
serves to receive the plastic thread part 11b so as to be fixed against 
rotation. In order to secure the plastic thread part 11b in the axial 
direction, a collar 11c which projects radially inwards is provided on the 
outer part 11a. 
In contrast to the embodiment according to FIGS. 1-3, in the arrangement 
according to FIGS. 8-13 the actuating member 12 is also connected to a 
cylindrical intermediate member which is rotatably mounted on the bearing 
housing 51 and is constructed in the form of an outer cover plate 52 for 
the bearing housing. This cover plate 52 has a recess 52a in which the 
actuating member 12 fits. The cover plate 52 also has a forked carrier 52b 
on which the cable 16 engages. As can be seen in particular from FIG. 9, 
the cable 16 is passed over a part of the cylindrical periphery of the 
cover plate 52 and connected to the latter at such a point on the 
periphery (in the carrier 52b) that during the whole actuating movement 
the lever member remains constantly between its connection point to the 
carrier 52b and the axis of rotation, i.e., the axis of displacement VA. 
The constancy of the lever transmission thus provided during the whole 
actuating movement facilitates sensitive actuation of the brake requiring 
little force. The cover plate 52, which thus forms the intermediate member 
between the cable 16 and the actuating lever 12, at the same time 
constitutes an outer cover for the brake which prevents dirt from 
penetrating the brake unit. 
The construction of the bearing housing 51 in the embodiment according to 
FIGS. 8-13 differs from that of the first embodiment. It contains an 
insert 53 made from sheet steel which is covered with plastic 54. The 
plastic part facing the rim is advantageously constructed in the form of 
two half shells 54a, 54b. This construction of the bearing housing 51 as a 
composite part made from metal and plastic ensures the necessary strength 
and stability with very economic production. 
The inner periphery of the bearing housing 51 is provided with an annular 
groove 55 in which a radially projecting collar 11d of the metal outer 
part 11a of the threaded bush 11 is received. This ensures the necessary 
axial securing against displacement of the threaded bush 11 in the bearing 
housing 51. 
As can be seen in particular from FIG. 10, the whole assembly 56 consisting 
of the bearing housing 51 (with all the parts accommodated therein) and 
the cover plate 52 can be pushed in the direction of the arrow 57 (i.e., 
at right angles to the rim) into a housing fixture 58 mounted on the 
bicycle and can be retained in this fixture by means of a screw 59, the 
tip of which fits into a recess 60 on the periphery of the bearing housing 
51. For this purpose the housing fixture 58 is provided with an opening 61 
through which the part 6a of the sliding member bearing the brake lining 8 
passes and is secured against rotation. 
The housing fixture 58 can be fastened by means of screws 62, 63 on a plate 
64 which is welded to the tube section R. The housing fixture 58 also has 
a projection 65 in which a guide groove 66 for the cable 16 is provided. 
In this way the cable 16 is passed reliably along the periphery of the 
cover plate 52 and secured against lateral slipping. 
If a tube section of the bicycle is constructed in a form corresponding to 
the housing fixture 58, i.e., is provided with an opening suitable for 
insertion of the assembly 56, then a separate housing fixture 58 can be 
dispensed with. The brake according to the invention can therefore be 
mounted very easily and simply as a unit, for example in a front wheel 
fork of a bicycle provided with a corresponding recess. 
Although in the embodiments discribed the axis of displacement VA of the 
sliding member at the same time constitutes the pivot axis for the 
actuating lever, constructions are also possible within the scope of the 
invention in which these two axes are parallel to each other. 
As far as the thread pitch of the control surface is concerned, on the one 
hand this is chosen to be large enough for the desired rapidity of the 
braking movement to be ensured, but on the other hand only large enough 
for sensitive actuation of the brake to be possible without jamming. The 
screw thread can be constructed with a single or multiple thread. With a 
single thread it is generally advantageous to have a greater depth of 
thread with correspondingly stable flanks, whereas with a multiple screw 
thread a reduced depth of thread with less strong flanks is sufficient. 
The rim brake according to the invention can be mounted both on the arms of 
the front wheel fork of a bicycle and on the corresponding tube sections 
of the frame for the rear wheel. An especially preferred location for 
arrangement of the brake parts for the rear wheel is the U-shaped frame 
portion which is located immediately behind the pedal bearing and is 
formed like a fork around the rear wheel. This arrangement of the rear 
wheel brake parts permits the same arrangement and cable guiding for 
women's and men's bicycles. This mounting point is also particularly 
favored by the particularly stable construction of this part of the frame. 
FIG. 14 shows a fifth embodiment which is a further improvement of the 
embodiment of FIGS. 8-13. A bush 71 having an internal thread 71a 
accommodates a threaded spindle 10 and is provided with a collar 71b 
surrounding a bearing housing 72. Collar 71b has an internal thread 71c in 
engagement with an external thread 72a of the bearing housing 72. The 
pitch of the internal thread 71c of collar 71b is substantially less than 
the pitch of the thread 71a which engages the spindle 10. 
The threaded bush 71 is connected to the cable 16 (not shown) in the same 
manner as the cover plate 52 of embodiment FIGS. 8-13 is connected with 
the cable 16. The threaded bush 71, therefore, is the actuating member 
connected with the cable and effects the axial movement of the sliding 
member 6. 
A small axial movement of the threaded bush 71 relative to the stationary 
bearing housing 72 is effected when the threaded bush 71 is rotated by the 
cable. As the pitch of thread 71a, however, is much greater than the pitch 
of thread 71c, the threaded spindle 10 is axially moved by this rotation 
of the threaded bush 71 so that the brake lining 8 contacts the rim. A 
self-locking effect is obtained between threads 71c, 72a which has the 
advantage that the driver has to exert only a small force when braking 
(only a force has to be used sufficient to counteract the force of the 
spring, whereas the main part of the braking force is counteracted by the 
self-locking between threads 71c, 72a). 
A further advantage of the embodiment of FIG. 14 is the very simple 
construction. The threaded bush 71 can be produced in one piece from 
plastic material. The same observation applies to the bearing housing 72.