CA1066203A - Brake actuator for bicycles and the like - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
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 crank-shaft. In order to facilitate its insertion into the crank-shaft 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.

Description

` ~066Z~3 FIl;'.Il~_OF THE_INVE:N'IION
This invention relates to brake ac-tuatlny 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 con-venience hereinafter be explained and described in relation to bicycles, which are by far the most common form of such vehicles, without thereby implying any limltation oE the scope of the invention to bicycles.

10 ~e -~
Bicycle brakes are generally of two types, those ~hat 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 conven-tional t~pe of coaster brake is contained in the hub o~ the rear wheel of the bicycle and the operatin~ 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-pedallingJ
the reverse torque from the pedals being carried to the rear wheel via a tension force in the lower s-trand of the chain. T~e braking mech3nism fox a hand operated hrake 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 braXe. 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 hrakes and coaster brakes have disadvantages.
The main disadvantclye of the hand brake is the manual force

-2-: , -- ~06621~3 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 disadvanta~e of the conventional coaster brake is that it becomes inoperative iE 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 o the driving chain cannot be used to txansmit 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 ~ lever and thence to a brake mechanism which may be of any o~ the types customarily operated by a hand brake lever.
One group o such proposals makes use of a ratche-t and pawl mechanism to provide the one way clutchJ but such mechanisms re~uire modification of the pedal crankshaft since either the ratchet or the pawl must be securely fixed to the shaft or incorporated in it, and will necessarily involve a significant degree of lost motion beore full engagement or disengagement is achieved. Moreover, according ~o the relative angular positions of the ratchet and pawl or pawls~ the brake will only be applicable at certain predetermined angular posi-tions of the crankshaft. Certain mechanisms of this type can also lock themselves on, whi.ch is at best inconvenien-t and at worst extremely dangexous.
rr~ese problems can be overcome by using a one way clutch of the spxing type, as shown in U.S. Paten-t ~o. 1,488,714 ~.~6GZ~33 issued April 1, 192~ Italian Pa~ent No. 300J 57~ issued Septe~ber 13, 1932; Itallan Pa-tent No. 456, 997 issued April 29, 1950 and united S-tates Patent Wo. 2,940,563 issued June 14, 1960. ~o~ever, 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 de-railleur type gears~ none of the above inven-tions appears to have met with acceptance.
The great 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. A brake actuator which will be acceptable to bicycle manufacturers -must be very simple and robust, have minimum drag when the brake is "oEE", involve no major alteration to the crankshaEt housing and have a similar~ lF not identical, pedal crankshaEt.
In addition, it must be able to withstand "panic" stopping conditions without failure, such as might occur with a two hundred pound individual starnping on one of the pedals in ~he 20~ 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 enkire 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 mec~anism either between the , crank housing and one of -the pedal cranks (as in Italian Patent No. 456,9g7), or within the pedal crank arm (as in U.S. Patent . .. , . ' ' ' ' ,,~' , ~066Z1~3 No. 1,488,714). In elther case, the space available is very limited, and a non-standard crankshaft and/or crank arm is requi.red. Moreover, the mechanism is subject to the accumu~
lation of dirt and may be exposed to mechanical damage.
Location with.in the crank housing itself (as in Italian Patent No. 300,578) would thus be preferable were i~ 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 ~ithout cutting or slotting the housing to such an extent as to severely weaken it. The crankshaft housing is an in-tegral part of the bicycle frame, and in order to obtain acceptance of a brake mechanism, it is desirable that no re-desi~n of this component should be required, as would be the case for example in the structures of U.S. Patent No. 2~940,563.
SUMMARY OF THE I~VENTION
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 crankshaet ~ housings, even those providing quite restricted clearance ; around the crankshaftJ which is simple and inexpensive to manu-facture and assemble, and which causes minimal drag during normal operation of the bicycle.
The invention improves upon a device for operating a hrake of a pedal operated vehicle which device comprises a brake operating lever projecting throuyh an opening in a pedal crankshaft housing of the vehicle, the lever being connected to a friction coupling ~hich concentrically surrounds a pedal ' 62~93 crankshaft withi.n the houslng, the coupli.ng comprising two spring coils lightly embracing the cr~lcshaft, the sense of winding oE each spring coil, proceeding from a free end to a constrained end connected to the l~ver, being the same as that direction of rotation o:E the crankshaft producing forward ; movement of the vehicle, and the two springs being wound from a common length of wire which is looped at said con~tained ends, the loop engaging the lever. -According to a first feature of the invention, each spring coil has a firs-t por-tion comprising those turns nearest .
to the lever, and a second portion compr.ising those turns further from the lever, the turns in the second portion being of wire having a smaller cross-sec-tion than that forming the .
turns of the first portion, the crankshaft being normally ~ -embraced only by turns of said second portion.
According to a second feature of the invention, the lever comprises an arm and a yoke engaging a-t least part of the cixcumference of the crankshaft, and is so dimensioned ~ that in its plane of operation it has no dimension greater :. 20 than the internal diameter of the pedal crankshaft housing but :: when the yoke engages the crankshaft, an arm of the lever projects through khe opening in the housing beyond its outer surface.
By these means, it is possible ~ith the great ; majority of conventional crankshaft housin~ to assembleJ with-out significant weakening of the housin~J a clutch connection : strong enough to withstand even panic brak~ng conditionsJ said clutch offering minimum drag on the pedal crankshaft during - nonnal forward pedalling of the bi.cycle.
According to a further feature oE the i.nventi.on, the '- .

:''- ''" ' '" ' ' ', " ' , ," ~ '" ' , - ~06GZ03 travel of the lever is limited by the si.ze oE the openlng in the crankhousing so as to limit the strain which can be applied to the b.rake and b.rake linkage, thus preventing darnage to these parts under panic braking conditions.
Further features o~ the invention w.ill become appa-rent from the following description of pre:Eerred embodiments of the invention with reference -to the accompanying drawings.
SHORT D~SCRIPTIO~ OF THB DR~WI~GS
In the d.rawings:
Figure 1 is a vertical section through the crank-shaft housing o~ a bicycle, longitudinally of the housing and transversely of the bicycle, showing a first embodiment of brake operator according to the invention, Figure 2 i~ a section on the line 2-2 in Figure 1, Figure 3 is a section corresponding to Figure 2, but with certain parts omitted for clarity and illustrating a modiEication of the embodiment of Figures 1 and 2, Figure 4 is a section corresponding to that Oe Fi~ure

3, illustrating a further modification, Figures 5 and 6 each show fragmantary views of connections between the brake opera-tor and a brake cable and a brake rod respectively, Figure 7 is a front (relative to the direction o~
travel o the bicycle) elevation of the spring coil assembly seen in Figures 1 and 2.
Figure 8 is an end elevation of the spring coil.
assembly.
Fiyures 9-12 are diagramma~ic elevations of bicycles illustrating the application Oe the invention -to different types of rear wheel hrake mechanism, -7- ;
. - . ~ , .

Figure 13 is a section corresponding to that oF
Figure 3, il:Lustra-ting a modified embodiment of the invention suitahle for application when the clearance between the crank-shaft and the crankshaft hou~in~ is particularly limited, and Figure 14 is a fragmentary plan view showing parts of the brake actuator of Figure 13 assembled on the bicycle crankshaft.
DESCRIPT ON O~ THE PREFERRE _ ~ ODIME~TS
Referring first to the embodiment of Figures 1 and 2, the brake operator is accommodated between the pedal crankshaft 1 and the crankshaft housing 5 oE a bicycle, the crankshaft being -journalled within the housing by means of conventional ba]l race assemblies 14. All of these components may be oE entirely conventional construction except th~t crankshafts of a waisted proEile having a central portion of reauced 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 crankshat housiny is the presence of a slot 8, des-cribed 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 assemhly comprising spring coils 3 ~oined 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 ~ousing through the slot 8 and helping to retain the loop 15 in the groove 16.
The construction of the spring coil assembly is best 6S;2al3 understood by reFerence to Figures 7 and 8. The inner portions oE the two coils 3 and -the loop 15 are formed of a continuous length o:E square section steel wire. A square section is selected to provide maximum tensile strength in minimum bulk, but rectangular configurations o-ther than square are possible if space re~uirements 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 o~ 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 ~ire 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 in the inner portions is slightly larger so that they are normally just clear o the surface 2. The construction of the coil assembly i9 discussed further b~low in relation to the operation o the invention.
The lever comprising the yoke 24a and the a~n 4a is dimensioned so that, as shown in chain-dotted lines in Figure 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 ~a drops tbrough _9_ , - , ' ,:
.
. .
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~66;~03 slot 8 and the loop 15 enga~es the ~roove 16~ whereaFter the cranksl-aft 1 is passed through the sprincJ coils and the ball race assemblies 14 are assembled. Washers 7 may be provided to prevent any con-tact 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 uti-lized, the lever configuration may be as shown in Figure 3, the yoke ~4h 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 sho~n in chain-dotted lines in Figure 3.
In Figure 4) the yoke 24c is shown to include an integral strap so as to surround the crankshaf-t. 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 ~hich can be attached to the projecting portion of the axm 4c after the latter is assembled into the crankshaft housing. As shown, the ex-tension 4d is connected to the arm 4c by a dovetail -joint and a lockin~ pin 11J but ot~er forms of connection could of course be utilized.
- Figure 5 illustrate~ a typical form of connection between a lever arm such as 4a and a brake operatin~ cable C
ter~inating in a nipple ~T. The lever is formed ~ith 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 in-to its hore.
Figure 6 illustra~es a typical eorm oF connection bet~"een a lever arm such as 4h and a brake operatln~ rod R

. ~ . . ... .

i62~3 using a shackle K. This forln oF connection requires a greater projection o~ the lever arm from the crank~haFt housing to provide the necessary clearance for the shackle.
F;.gures 9-12 illustrate different ways in ~7hich the brake actuator can be applied to a bicycle. In Figure 9, the lever arm 4a oE a lever as shown in Figure 2 is attached to a cable 17 which passes through a flexible sheath 18 to a con-ventional 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 appra~
priate, although it should be noted that it is an advantage of the presen-t invention that the same brake assemblies can be .
used for bi.cycles both with and without cross-bars.
In Figure 10, a caliper brake 20 is operated by a direct tension linkage which may be either a cableJ or a rod 21 attached to the lever arm 4b of a lever as shown in Figure 3 (or the extension 4d of a lever as shown in Figure~4). In Figure 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 ~raking arm of the drum brake from the lever arm 4b (or 4d) by rods 23 and 30 and a step-out lever 25. , In Figure 12, a brake disc 26 is applied to the . .
rear wheel hub o~ the bicycle, and a brake cal.iper 27 is - actuated by a cable 28 connected to the lever arm 4a and passing through a flexible sheath 29.
Considering no~7 the operation of -the emhod.iments so .
far described, norrnal forward ped111inc3 of the bicycle will result in the crankshaFt 1. rotat.in.g in an anticlockwlse :~
direction as seen in Figure 2. The light engagement between 30 the spring coil portion 3a and the surface 2 oE the crankshaft .
~, . . , . , . . :.' , Z~3 will generate a reaction in the coils, which are restrained against rota-tion by the lever, tending to unwind the coils and thus reduce their engagemen-t with the crankshaft and the resultant dra~ on the crankshaft. Since the portions 3a are in any event oE 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 cableJ and the resulting reaction will tend to wind up the coils, thus tightening their embrace of the crankshaft 2 and producing a positive feedback ef-fect. 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 brak-ing effort a~ailable. The tension in -the wire forming the coils when these are in frictional engagement with the crank-shaft will fall exponentially according to the distance rom 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 hraking conditions. With components of typical dimensions, and assuming worst-case conditionsl the sum of the tensile loads sustained hy both spring coils at their ends ajacent the loop lS could be o~ the order oE 5000 lbs. Such a load can be sustained if the wire is of quite 3n ordinar~ spring steel, 0.110 inches s~uare and heat treated '' ' ' ' '' ' ' '' ~ - ., . , ~662(1 3 to provide sufEicien~ ultimate tensile strength. Only a small raction oE this load will be transmitted to the coil portions 3a, the actual proportion depending on the coef~icient of static fric-tion between the coil assembly and the crankshaft.
Even if ~he coefficient oE static friction is as low as 0.~75 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, it is preferred that the wire forming the portions 3a be butt welded to the wire forming *he remainder of the coils prior to coil winding and heat treatment~ but other forms of connection could be used, provided that they will sustain the necessary loads and be sufficiently reliable. Although the portions 3a have been shown as having a square sectionJ a round section could be employed prov.ided the space available permits the cross-sectional area to be maintained. Moreover, although springsteel has been mentioned as a material for the sprin~ coils, only a very small degree of resilience in the latter .i9 in ~act required. The tensile strength of the metal employed is more important than its yield strength since a small degree o*
plastic yielding can be sustained without failure of the clutch.
The yoke 24a, b or c should of course be suEiciently strong to sustain the loads applied to it by the coil assembly~
but conventional bicycle brake e~uipment may not be stron~
enough to ~,~ithstand the forces ~hich could be applied through the lever arm under panic braking conditions. However, such -13~
' ' ' ` ''' ' ''' 1L~66;~3 Eorces can be limited by locating the forward end 8a o~ the slot 8 at a point such that it will act as a stop Eor the lever arm beEore the strain irnposed on the brake linkaye and brake reaches an excessive level. Should the stop 8a ever become operative under normal conditions~ this indicates an immediate need for hrake adjustment. The s-top also preven-ts excessive forces being applied to the outer end of the lever arm, a particularly valuable feature when a lever arm ex-tension 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 Figure 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 housinys about one and a half inches external diameter and two and a half inches long, with a crankshaft about 13/16 inch in maximum diambter. Although these dimensions are typical, both larger and smaller housings are used, and with housings of small~r internal diameter~ it may be found that the presence of the A groove 1~ in the yoke of the embodiments previously described will reduce the dimension Z (see Figure 3) to such an exten~
that the yoke is seriously weakened. In the ernbodiment of Figures 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 assernbly during braking will now tend to cause the yoke to rock away from -the crankshaEt, rather 3Q than heiny pulled ayainst i-t as in the previous. embodiments, ~OG6Z03 and this problem i5 overcome by forming side flanges 31 on the yoke 24e which support por-tions of the first turn of each coil 3, resulting in tension in the coils generating forces holding the yoXe 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 brak~ng foroes within a crankshaft housing having an outside diameter of only 1 3/8 inches, a wall thickne~s of about 3/32 inch and a crank-shaft diameter of 13/16 inch.
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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for operating a brake of a pedal operated vehicle which device comprises a friction coupling and a brake operating lever projecting through an opening in a pedal crankshaft housing of the vehicle to a connection with a brake linkage operating the brake, the lever being connected within the housing to the friction coupling which concentri-cally 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, proceed-ing 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 springs being wound from a common length of wire which is looped at said constrained ends, the loop engaging the lever, wherein each spring coil has a first portion comprising those turns nearest to the lever, and a second portion comprising those turns further from the lever, the turns in the second portion being of wire having a smaller cross-section than that forming the turns of the first portion, the crankshaft being normally embraced only by turns of said second portion.

2. A device according to claim 1, wherein the turns of the coil in at least the first portions of the coils are formed from wire of rectangular cross-section.

3. A device according to claim 1 or 2, wherein the lever is engageable with an end abutment bounding the opening in the pedal crankshaft housing, in response to application of a predetermined strain to the brake lever.

4. A device according to claim 1, wherein the lever comprises a yoke engaging at least 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 dia-meter of the pedal crankshaft housing but when the yoke engages the crankshaft an arm of the lever projects through the opening in the housing beyond its outer surface.

5. A device according to claim 4, wherein the loop connecting the spring coils engages a groove at that end of the yoke which is leading with respect to forward rotation of the crankshaft.

6. A device according to claim 4 or 5, wherein the yoke of the lever is offset in the leading direction relative to the lever arm.

7. A device according to claim 4, wherein a detachable extension is applied to the lever arm externally of the pedal crankshaft housing.

8. A device according to claim 7, wherein the ends of the yoke are connected by an integral strap surrounding the crankshaft.

9. A device according to claim 4, 7 or 8, wherein the loop connecting the spring coils passes around the lever arm, and wherein the portions of the coils nearest the loop overlie flanges extending from the yoke.

10. A pedal operated vehicle having a brake, a pedal crank and a pedal crank housing having an opening, and including a brake operating device in accordance with any of claims 1, 2 or 4.