Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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
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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
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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
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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,
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66Z633
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
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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
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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
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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
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~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
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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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