Brake actuator for bicycles and the like

A coaster brake for a bicycle has a brake operating lever consisting of a yoke and integral arm coupled to the pedal crankshaft of the bicycle by a self-acting unidirectional friction clutch, formed by a coil spring embracing the crankshaft. In order to facilitate its insertion into the crankshaft housing, the lever has no dimension greater than the internal diameter of the housing. The spring has two portions, one on either side of the yoke, the wire forming the part of each portion nearer the yoke being of greater cross section than the part further from the yoke. The lever moves a brake actuating rod or cable actuating a wheel brake which may be of several different types.

FIELD OF THE INVENTION 
This invention relates to brake actuating means for pedal-propelled 
vehicles such as bicycles. Although the invention is also applicable to 
pedal-propelled vehicles having more than two wheels, e.g. tricycles, it 
will for convenience hereinafter be explained and described in relation to 
bicycles, which are by far the most common form of such vehicles, without 
thereby implying any limitation of the scope of the invention to bicycles. 
REVIEW OF THE PRIOR ART 
Bicycle brakes are generally of two types, those that are hand operated and 
those that are foot operated. The most usual foot operated type is 
generally known as a "coaster" or back-pedalling brake. The braking 
mechanism of the conventional type of coaster brake is contained in the 
hub of the rear wheel of the bicycle and the operating force is 
transmitted by the same chain that is used for propelling the bicycle. The 
means of operating such a coaster brake is by back-pedalling, the reverse 
torque from the pedals being carried to the rear wheel via a tension force 
in the lower strand of the chain. The braking mechanism for a hand 
operated brake may be either a caliper arrangement which presses on the 
opposite flat sides of the rim of the wheel, a drum and shoe brake housed 
in the hub of the wheel, or a disc brake. Other and less satisfactory 
braking mechanisms have been used in the past for hand operated brakes, 
such as the simple "spoon" device that presses on the outside of the tire 
and the "stirrup" device that presses on the inside surface of the rim. 
Both hand brakes and coaster brakes have disadvantages. The main 
disadvantage of the hand brake is the manual force required to apply it. 
This reduces the sensitivity of the hand for steering the bicycle, 
especially when one hand is removed from the handle bars. 
The main disadvantage of the conventional coaster brake is that it becomes 
inoperative if the main drive chain accidentally breaks or slips off 
either the pedal or rear wheel sprocket, whilst it cannot be applied to 
bicycles equipped with derailleur or similar change-speed gears in which 
the lower strand of the driving chain cannot be used to transmit any 
tension force. 
It has several times been proposed, in order to overcome the problem, to 
associate a one way clutch mechanism with the pedal crankshaft, by means 
of which the back-pedalling effort may be applied to a lever and thence to 
a brake mechanism which may be of any of the types customarily operated by 
a hand brake lever. 
One group of such proposals makes use of a ratchet and pawl mechanism to 
provide the one way clutch, but such mechanisms require modification of 
the pedal crankshaft since either the ratchet or the pawl must be securely 
fixed to the shaft or incorpoated in it, and will necessarily involve a 
significant degree of lost motion before full engagement or disengagement 
is achieved. Moreover, according to the relative angular positions of the 
ratchet and pawl or pawls, the brake will only be applicable at certain 
predetermined angular positions of the crankshaft. Certain mechanisms of 
this type can also lock themselves on, which is at best inconvenient and 
at worst extremely dangerous. 
These problems can be overcome by using a one way clutch of the spring 
type, as shown in U.S. Pat. No. 1,488,714 issued Apr. 1, 1924, Italian 
Pat. No. 300,578 issued Sept. 13, 1932, Italian Pat. No. 456,997 issued 
Apr. 29, 1950 and U.S. Pat. No. 2,940,563 issued June 14, 1960. However, 
it is significant that although there is currently a well identified 
market for a coaster type brake for the popular five and ten speed 
bicycles equipped with derailleur type gears, none of the above inventions 
appears to have met with acceptance. 
The majority of bicycles that are equipped with derailleur or similar 
change speed gears are manufactured with pedal crankshaft housings about 
one and a half inches in external diameter and two and a half inches long 
although housings of smaller diameter are quite common. A brake actuator 
which will be acceptable to bicycle manufacturers must be very simple and 
robust, have minimum drag when the brake is "off," involve no major 
alteration to the crankshaft housing and have a similar, if not identical, 
pedal crankshaft. In addition, it must be able to withstand "panic" 
stopping conditions without failure, such as might occur with a two 
hundred pound individual stamping on one of the pedals in the 
back-pedalling mode. Whilst an advantage of the coaster type of brake is 
the very large braking effort which can be developed by the user, it also 
raises the problem that the stresses developed in the actuator mechanism 
and applied to the brake mechanism, if not otherwise prevented, can also 
be very large if the user's entire weight is applied to one of the pedals 
in an attempt to obtain extra braking effort. 
In the patents referred to above, proposals have been made to place the 
clutch mechanism either between the crank housing and one of the pedal 
cranks (as in Italian Pat. No. 456,997), or within the pedal crank arm (as 
in U.S. Pat. No. 1,488,714). In either case, the space available is very 
limited, and a non-standard crankshaft and/or crank arm is required. 
Moreover, the mechanism is subject to the accumulation of dirt and may be 
exposed to mechanical damage. Location within the crank housing itself (as 
in Italian Pat. No. 300,578) would thus be preferable were it not for the 
fact that in many cases the space between the crankshaft and the housing 
is extremely limited, thus making it difficult or impossible to house or 
assemble the structure shown in the Italian patent without cutting or 
slotting the housing to such an extent as to severely weaken it. The 
crankshaft housing is an integral part of the bicycle frame, and in order 
to obtain acceptance of a brake mechanism, it is desirable that no 
redesign of this component should be required, as would be the case for 
example in the structures of U.S. Pat. No. 2,940,563. Moreover, it should 
be possible to fabricate, assemble and maintan the brake mechanism without 
the use of esoteric or laborious techniques. 
SUMMARY OF THE INVENTION 
Objectives of the present invention are to provide a coaster type brake in 
which the brake actuating force is derived by a clutch connection from the 
pedal crankshaft, which can be constructed to withstand panic braking 
forces, which can be housed within most conventional types of pedal 
crankshaft housings, even those providing quite restricted clearance 
around the crankshaft, which is simple and inexpensive to manufacture and 
assemble, and which causes minimal drag during normal operation of the 
bicycle. 
The invention improves upon a device for operating a brake of a pedal 
operated vehicle which device comprises a brake operating lever projecting 
through an opening in a pedal crankshaft housing of the vehicle, the lever 
being connected to a friction coupling which concentrically surrounds a 
pedal crankshaft within the housing, the coupling comprising two spring 
coils lightly embracing the crankshaft, the sense of winding of each 
spring coil, proceeding from a free end to a constrained end connected to 
the lever, being the same as that direction of rotation of the crankshaft 
producing forward movement of the vehicle, and the two spring coils being 
wound from a common length of wire which is looped at said constrained 
ends, the loop engaging the lever. 
According to a first feature of the invention, the lever comprises an arm 
and a yoke encircling part of the circumference of the crankshaft, and is 
so dimensioned that in its plane of operation it has no dimension greater 
than the internal diameter of the pedal crankshaft housing but when the 
yoke engages the crankshaft, the arm of the lever projects through the 
opening in the housing beyond its outer surface. 
According to a further feature of the invention, the spring coils are of a 
diameter such as just not to embrace the crankshaft, and at one end a 
further spring coil lightly embracing the crankshaft, the turns of which 
coil are of wire having a smaller cross section than that forming the 
turns of the first coils, overlaps and is attached to the diametrically 
outward side of the free end of each first coil so as to draw the latter 
in contact with the crank shaft housing when the second coil is placed 
under tension. 
By these means, it is possible with the great majority of conventional 
crankshaft housings to assemble, without significant weakening of the 
housing, a clutch connection strong enough to withstand even panic 
breaking conditions, said clutch offering minimum drag on the pedal 
crankshaft during normal forward pedalling of the bicycle. 
According to a further feature of the invention, the resultant thrust on 
the lever during brake operation, applied by the spring coils and a brake 
operator actuated by the lever is sustained through a thrust bearing: this 
enables a more compact assembly to be utilized, and facilitates assembly. 
Further features of the invention will become apparent from the following 
description of preferred embodiments of the invention with reference to 
the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to the embodiment of FIGS. 1 and 2, the brake operator is 
accommodated between the pedal crankshaft 1 and the crankshaft housing 5 
of a bicycle, the crankshaft being journalled within the housing by means 
of conventional ball race assemblies 14. All of these components may be of 
entirely conventional construction except that crankshafts of a waisted 
profile having a central portion of reduced diameter are not suitable: the 
central portion of the shaft between the races should have a cylindrical 
outer surface 2 of uniform diameter. The only non-standard feature of the 
crankshaft housing is the presence of a slot 8, described further below, 
in the bottom of the housing. 
The major components of the brake operator are a lever comprising a yoke 
24a and a lever arm 4a, and a spring coil assembly comprising spring coils 
3 joined to one another by a connecting loop 15 which engages a 
complementary groove 16 formed in one arm of the yoke 24a. The lever arm 
4a projects through the slot 8, and an apertured sheet metal shield 6 
placed over the arm serves the dual purpose of preventing dirt from 
entering the housing through the slot 8 and helping to retain the loop 15 
in the groove 16. 
The construction of the spring coil assembly is best understood by 
references to FIGS. 7 and 8. The inner portions of the two coils 3 and the 
loop 15 are formed of a continuous length of square section steel wire. A 
square section is selected to provide maximum tensile strength in minimum 
bulk, but rectangular configurations other than square are possible if 
space requirements dictate a deeper but narrower coil. The outer portions 
3a of the two coils are formed of wire of smaller cross section than the 
inner portions. In the embodiment shown, the cross sectional dimensions of 
the wire forming the outer portions are half those of the wire forming the 
inner portions. This enables a substantially larger number of turns to be 
accommodated in an assembly of the same width than would be possible if 
wire of the same section as that used for the inner turns was used 
throughout. The inside diameter of the turns in the outer portions is such 
that they lightly embrace the surface 2 of the crankshaft: the inside 
diameter of the turns on the inner portions is slightly larger so that 
they are normally just clear of the surface 2. The combination of the coil 
assembly is discussed further below in relation to the operation of the 
invention. 
The lever comprising the yoke 24a and the arm 4a is dimensioned so that, as 
shown in chain-dotted lines in FIG. 2, it has no dimension exceeding the 
internal diameter of the crankshaft housing 5 and can thus be inserted 
into the housing until the arm 4a drops into the slot 8 without any 
necessity for the slot to be enlarged to accommodate oblique entry of the 
arm. Before the lever is so inserted, the shield 6 is placed over the arm 
4a, the latter extending through loop 15 of the spring assembly. The three 
parts are then inserted into housing 5 and manipulated so that arm 4a 
drops through slot 8 and the loop 15 engages the groove 16, whereafter the 
crankshaft 1 is passed through the spring coils and the ball race 
assemblies 14 are assembled. Washers 7 may be provided to prevent any 
contact between the coils and the balls, or ball cages, if used, of the 
ball race assemblies. 
In order to enable a longer lever arm to be utilized, the lever 
configuration may be as shown in FIG. 3, the yoke 24b being offset 
relative to the arm 4b. This arrangement permits a longer lever arm to be 
used without increasing the maximum dimension of the lever beyond the 
internal diameter of the crankshaft housing 5, as shown in chain-dotted 
lines in FIG. 3. 
In FIG. 4, the yoke 24c is shown to include an integral strap so as to 
surround the crankshaft. In this case, the length of the lever arm 4c that 
can be accommodated within the crankshaft housing internal diameter is 
very limited, so a separate lever arm extension 4d of any required length 
is provided which can be attached to the projecting portion of the arm 4c 
after the latter is assembled into the crankshaft housing. As shown, the 
extension 4d is connected to the arm 4c by a dovetail joint and a locking 
pin 11, but other forms of connection could of course be utilized. 
FIG. 5 illustrates a typical form of connection. between a lever arm such 
as 4a and a brake operating cable C terminating in a nipple N. The lever 
is formed with a clevis, one arm of which is provided with a slot S so 
that the cable may be introduced into the fork of the clevis when the 
nipple is introduced into its bore. 
FIG. 6 illustrates a typical form of connection between a lever arm such as 
4b and a brake operating rod R using a shackle K. This form of connection 
requires a greater projection of the lever arm from the crankshaft housing 
to provide the necessary clearance for the shackle. 
FIGS. 9-12 illustrate different ways in which the brake actuator can be 
applied to a bicycle. In FIG. 9, the lever arm 4a of a lever as shown in 
FIG. 2 is attached to a cable 17 which passes through a flexible sheath 18 
to a conventional caliper brake 19. Because of the direction of approach 
of the brake cable, the type of brake normally used on ladies' bicycles 
with hand operated rear brakes is appropriate, although it should be noted 
that it is an advantage of the present invention that the same brake 
assemblies can be used for bicycles both with and without cross-bars. 
In FIG. 10, a caliper brake 20 is operated by a direct tension linkage 
which may be either a cable, or a rod 21 attached to the lever arm 4b of a 
lever as shown in FIG. 3 (or the extension 4d of a lever as shown in FIG. 
4). In FIG. 11, a drum brake 22 of known type is applied to the rear wheel 
hub of the bicycle, and braking force is transmitted to a braking arm of 
the drum brake from the lever arm 4b (or 4d) by rods 23 and 30 and a 
step-out lever 25. 
In FIG. 12, a brake disc 26 is applied to the rear wheel hub of the 
bicycle, and a brake caliper 27 is actuated by a cable 28 connected to the 
lever arm 4a and passing through a flexible sheath 29. 
Considering now the operation of the embodiments so far described, normal 
forward pedalling of the bicycle will result in the crankshaft 1 rotating 
in an anticlockwise direction as seen in FIG. 2. The light engagement 
between the spring coil portion 3a and the surface 2 of the crankshaft 
will generate a reaction in the coils, which are restrained against 
rotation by the lever, tending to unwind the coils and thus reduce their 
engagement with the crankshaft and the resultant drag on the crankshaft. 
Since the portions 3a are in any event of fairly light gage wire, this 
drag will be slight in the first place. Upon back-pedalling, the drag of 
the coils will be transmitted to the brake rod or cable, and the resulting 
reaction will tend to wind up the coils, thus tightening their embrace of 
the crankshaft 2 and producing a positive feedback effect. As the force 
applied to the brake rod or cable increases, the inner portions of the 
coils 3 will also embrace the crankshaft, yet further enhancing the 
braking effort available. The tension in the wire forming the coils when 
these are in frictional engagement with the crankshaft will fall 
exponentially according to the distance from the loop 15 and thus the 
maximum tensions developed in the turns of the outer portions of the coils 
will always be small compared with the maximum tension developed in the 
inner coils. This enables the outer coils to be of greatly reduced cross 
section with the dual benefits of reducing the width of the coil for a 
given number of turns and reducing the drag on the crankshaft during 
normal forward pedalling. At the same time, the section of the wire used 
for the inner portions of the coils can be made large enough to withstand 
the tensions generated under panic braking conditions. With components of 
typical dimensions, and assuming worst-case conditions, the sum of the 
tensile loads sustained by both spring coils at their ends adjacent the 
loop 15 could be of the order of 5000 lbs. Such a load can be sustained if 
the wire is of quite ordinary spring steel, 0.110 inches square and heat 
treated to provide sufficient ultimate tensile strength. Only a small 
fraction of this load will be transmitted to the coil portions 3a, the 
actual proportion depending on the coefficient of static friction between 
the coil assembly and the crankshaft. Even if the coefficient of static 
friction is as low as 0.075, which is most improbable, and there are three 
turns in each inner portion of the coils, less than a quarter of the 
maximum tension will be applied to the coil portions 3a, and if the 
coefficient of static friction is a more probable 0.150, less than one 
sixteenth of the maximum tension will be applied to the coil portions 3a. 
In order to sustain the tensions applied, the wire forming the portions 3a 
may be butt welded to the wire forming the remainder of the coils prior to 
coil winding and heat treatment, but other forms of connection may be 
preferred, provided that they will sustain the necessary loads and be 
sufficiently reliable. Some advantageous methods of joining the wires are 
discussed below with reference to FIGS. 21-24. Although the portions 3a 
have been shown as having a square section, a round section could be 
employed provided the space available permits the cross sectional area to 
be maintained. Moreover, although spring steel has been mentioned as a 
material for the spring coils, only a very small degree of resilience in 
the latter is in fact required. The tensile strength of the metal employed 
is more important than its yield strength since a small degree of plastic 
yielding can be sustained without failure of the clutch. 
The yoke 24a, b or c should of course be sufficiently strong to sustain the 
loads applied to it by the coil assembly, but conventional bicycle brake 
equipment may not be strong enough to withstand the forces which could be 
applied through the lever arm under panic braking conditions. However, 
such forces can be limited by locating the forward end 8a of the slot 8 at 
a point such that it will act as a stop for the lever arm before the 
strain imposed on the brake linkage and brake reaches an excessive level. 
Should the stop 8a ever become operative under normal conditions, this 
indicates an immediate need for brake adjustment. The stop also prevents 
excessive forces being applied to the outer end of the lever arm, a 
particularly valuable feature when a lever arm extension 4d is being 
employed. 
With certain types of brake, the high forces which can readily be developed 
by the brake operator of the invention are an advantage, as when a disc 
brake as shown in FIG. 12 is to be operated. Such disc brakes often 
require higher operating forces than can readily be developed by 
conventional hand brake operating levers. 
The embodiments of the invention so far described are suitable for use with 
bicycles having crankshaft housings about one and a half inches external 
diameter and two and a half inches long, with a crankshaft about 13/16 
inch in maximum diameter. Although these dimensions are typical, both 
larger and smaller housings are used, and with housings of smaller 
internal diameter, it may be found that the presence of the groove 16 in 
the yoke of the embodiments previously described will reduce the dimension 
Z (see FIG. 3) to such an extent that the yoke is seriously weakened. In 
the embodiment of FIGS. 13 and 14, the loop 15a of the spring coil 
assembly is taken around the root of the lever arm 4e, The reaction to 
tension in the spring coil assembly during braking will now tend to cause 
the yoke to rock away from the crankshaft, rather than being pulled 
against it as in the previous embodiments, and this problem is overcome by 
forming side flanges 31 on the yoke 24e which support portions of the 
first turn of each coil 3, resulting in tension in the coils generating 
forces holding the yoke against the crankshaft surface 2. The shield 6b is 
formed with side flanges 32 which act to prevent the coils 3 from slipping 
sideways off the flanges 31. 
With this arrangement, it is possible to fit a brake actuator of adequate 
strength to withstand panic braking forces within a crankshaft housing 
having an outside diameter of only 13/8 inches, a wall thickness of about 
3/32 inch and a crankshaft diameter of 13/16 inch. 
The embodiment of FIGS. 15-17 represents a further approach to 
accommodating the brake mechanism within a housing of limited diameter, as 
well as facilitating assembly. The arrangements previously described 
necessitate installation of the yoke and spring in the crankshaft housing 
prior to installation of the crankshaft itself. This assembly procedure 
cannot be adopted where the crankshaft is forged in one piece with the 
pedal cranks, and also requires care to obtain and maintain the desired 
interrelationship of the various parts until they are locked in place by 
insertion of the crankshaft. The embodiment of FIGS. 15-17 permits the 
spring to be pre-assembled on the crankshaft before insertion of the 
latter and minimizes the free space required within the crankshaft housing 
to permit assembly, whilst maximizing the length of the operating lever 
arm obtainable relative to the overall yoke dimensions. In describing 
these embodiments, the same reference numerals will be used as in FIGS. 1 
and 2 except where parts are significantly modified, and only those 
features will be described which are necessary to the understanding of 
these differences. 
As compared with FIGS. 1 and 2, the main difference resides in the yoke 24f 
and its engagement with the bight portion 15 of the spring which passes 
around the entire yoke so that the bight portion engages the rear end 33 
of the yoke. This means that when the brake is applied tension in the 
spring pulls the front end 34 of the yoke against the shield 6 which acts 
as a thrust bearing to transfer the load imposed on the yoke by the spring 
and the brake operator through the lever 4f to the crankshaft housing. The 
shield 6 should be of material such as bronze appropriate to perform this 
function as well as preventing dirt from entering the crankshaft housing. 
In order to maintain the bight portion 15 of the spring in contact with 
the yoke during forward pedalling of the bicycle, a tab 35 on the shield 
is bent up around the bight portion. This function may alternatively be 
performed by an extension 36 of the yoke as shown in FIG. 18. 
In assembling the embodiments of FIGS. 16-18, the shield 6 is placed over 
the arm of the lever 4f and the assembly placed in the crankshaft housing 
so that the lever projects through the opening 8 in the crankshaft housing 
5. The spring coil assembly is then positioned over the surface 2 of the 
crankshaft 1, which is inserted into the housing sufficiently 
eccentrically (see the broken lines in FIG. 16) for one half of the spring 
assembly to pass the yoke 24f. The crankshaft is then lowered so that the 
bight 15 of the spring assembly passes between the tab 35 and the end 33 
of the yoke, or between the end 33 of the yoke and the extension 36, 
whereafter the bearing assemblies 14 can be installed. With this 
arrangement, the minimum clearance between the crankshaft surface 2 and 
the interior of the housing need be little more than double the thickness 
of the wire forming the spring portions 3, whilst the yoke 24f may be made 
short, thus minimizing the overall dimensions of the lever 4f. The 
arrangement may also be used where the crankshaft 1 and pedal cranks are 
forged in one piece. 
FIGS. 19 and 20 show a stronger alternative to the yoke 24b shown in FIG. 
3. The yoke 24b in FIG. 3 is weakened by the presence of groove 16. In the 
embodiment of FIGS. 19 and 20, the weakness introduced into the yoke 24g 
is compensated for by providing lateral flanges 37 which underlie the 
bight 15 of the spring. 
FIGS. 21 to 24 illustrate two alternative methods of securing the spring 
portions 3a to the spring portions 3. In the arrangement of FIGS. 21 and 
22, the wire forming the spring portion 3a is formed with a hammer end 
which is received in a complementary slot in the upper surface of the end 
of the wire forming spring portion 3 and held in place simply by its own 
spring action. This is an arrangement that is suitable when a single piece 
crank is used as the portions 3 and 3a of the clutch coil may be 
separately assembled onto shaft 1 and then the hammer heads of portion 3a 
sprung into the complementary slots of portion 3. The hammer end may be 
replaced with a straight end and complementary slot 39 as shown in FIGS. 
23 and 24 with the fastening being done by brazing. The engagement of 
these fastening arrangements with the outer side of the wire 3 assists in 
drawing the latter into contact with the crankshaft during engagement of 
the brake, whilst the lapped nature of the joints makes them very strong. 
The bight 15 of the spring assembly may be received in a groove on the 
radially inner surface of the yoke without the reaction from the spring 
and the brake actuator being sustained by the crankshaft housing 5. Such 
an arrangement is shown in FIGS. 25 and 26 and has the advantage of 
permitting simplified fabrication of the yoke 24h. A part ciruclar groove 
is formed near the front end 34 of the yoke in its radially inner surface 
by simple application of a trepanning cutter so as to leave a round pillar 
40 which is engaged by the loop 15. The configuration causes the resultant 
of the reaction from the braking forces 41, 42 to be sustained by the 
crankshaft whilst greatly simplifying machining of the yoke. The groove is 
located so that the spring acts on the yoke at a point on the opposite 
side of the lever 4h from the direction of the braking force 42.