GB1603064A

GB1603064A - Brake for vehicles

Info

Publication number: GB1603064A
Application number: GB1200678A
Authority: GB
Original assignee: Bridgestone Cycle Co Ltd
Current assignee: Bridgestone Cycle Co Ltd
Priority date: 1978-03-28
Filing date: 1978-03-28
Publication date: 1981-11-18

Description

(54) BRAKE FOR VEHICLES (71) We. BRIDGESTONE CYCLE CO. LTD.. of No. 5-14, 3-Chome. Nihonbashi, Chuo-Ku. Tokvo. Japan, a company organized according to the laws of Japan, do herebv declare the invention for which we pray that a patent may he granted to us. and the device by which it is to be performed. to be particularly described in and by the following statement: The present invention relates to a brake for vehicles. particularlv suitable for light vehicles such as bicvcles.

Various brakes for vehicles have been proposed such as drum brakes. contracting band brakes, disc brakes and the like. The expanding drum brake comprises brake shoes adapted to be urged against an inside of a drum. so that the drum is subjected to forces on the side and hence required to have a thick wall having high strength to support such forces acting on the side. As a result. the drum becomes unavoidably heavv and therefore the brake itself becomes large. In general. furthermore. such an expanding drum brake is not good at dissipating heat caused by the braking action and often cannot be used for a long period of time.

Prior art contracting band brakes comprise a lining covering substantially all over the drum. so that they are also not good at dissipating heat.

Prior art disc brakes inherentlv do not have a construction adapted to cause "self- energizing" action (servo effect). The selfenergizing action used herein means the effect that a fictional force between a brake shoe and a rotating drum tends to force the brake shoe against the drum to increase the braking function. As the disc brake does not have such a self-energizing action, a great operating force for braking is required to obtain enough braking force. In order to decrease the operating force. a brake disc must he of large diameter which would make the brake large.

According to the present invention there is provided a brake for a vehicle, comprising a brake drum rotatable with a wheel of the vehicle. an inner pin fixable to a vehicle body and extending within the brake drum, an inner shoe pivotally supported by the inner pin within the brake drum, an arm integral with the inner shoe and extending outwardly beyond the brake drum. an outer pin extending from an end of the arm. an outer shoe pivotally supported by the outer pin to be brought into contact with an outer peripherv of the brake drum. spring means for urging the inner shoe and the outer shoe away from the brake drum, and actuating means comprising a wire connected at one end thereof to the inner shoe or to means operably associated therewith and movable within an outer adaptor to cause the inner shoe and the outer shoe to be urged against the brake drum.

Embodiments of the present invention will now be described by way example and with reference to the accompanying drawings in which: Figure 1 is a partially cutaway front elevation of a first embodiment of a brake in an unactuated condition: Figure 2 is a front elevation similar to Figure 1 showing the brake in a position intermediate an operating and the unactuated position: Figure 3 is a front elevation similar to Figure 1 showing a brake in an operating or braking position: Figure 4 is a sectional view taken along the lines IV-IV Figure 3: Figure 5 is a partially cutawav front elevation of a second embodiment of a brake according to the invention: Figure 6 is a sectional view taken along the line VI-VI in Figure 5: Figure 7 is a partiallv cutawav front elevation of a third embodiment of a brake according to the invention; and Figure 8 is a part of the brake viewed in a direction of an arrow VIII in Figure 7.

Referring to Figures 1-4, the brake for vehicles comprises an axle 1 and a hub 2 for a wheel, which is coaxial with the axle 1 and provided with a brake drum 3 fixed to the hub 2 by means of screws (not shown) as shown in Figure 4.

A cover plate 4 having an enlarged portion 4a and an arm 4b extending toward one side thereof is fixed to the axle 1 with the enlarged portion 4a by means of a nut 5 (Figure 4). The end of the arm 4b is fixed to a vehicle body (not shown) by means of a bolt 6. A pin 7 extends from the cover plate 4 within the brake drum 3 and serves to rotatable pivot a lower end of a brake shoe 8 in the form of an arc within the brake drum 3. An arm 9 integral with the brake shoe 8 extends over the brake drum 3 and is provided at its end with a pin 10 which pivotally supports a lower end of a shoe 11 adapted to be in contact with the outer peripherv of the brake drum 3. The shoes 8 and 11 comprise respective linings 8a and Ila. A spring 12 extends between a projection 4c of the cover plate 4 and the upper end of the shoe 8 and serves to force the shoe 8 away from the inner surface of the drum 3. A spring 13 is provided l cìwccl1 the arm 9 and shoe 11 to force the shoe 11 away from the outer surface of the drum.

An adjusting screw or bolt 14 whose end is in opposition to the edge of the cover plate 4 is threadedly engaged in a projection 9a formed integrally with the arm 9. The adjusting screw 14 is rotated and fixed by a lock nut 15 in its adjusted position whereby the clearance between the lining 8a and the inner surface of the drum 3 can be adjusted.

In the embodiment illustrated in Figures 1-4, an actuating means for the brake is constructed by securing the end of an inner wire 16 to the shoe X bv means of a screw or bolt 17 and fixing an outer adaptor 18 to the shoe 11 bv means of a nut 19.

Figures 5 and 6 illustrate another embodiment of the invention. wherein an actuating means for the brake is provided with a toggle joint. In this case, the shoe 8 is formed integrallv with an arm 8b projecting outwardly over the drum 3. and the shoe 11 is provided with a projection 1 Ib extending over the arm 8b. The projection lib is provided at its end with a pin 20 which pivotally supports a lever 22 having an extending piece 21 integral therewith. An adjusting screw or bolt 23 is threadedly engaged in the end of the arm 8b. which is in opposition to the extending piece 21 and adapted to be fixed in position by a lock nut 24. Accordingly. the clearance between the drum 3 and the lining 1 lea is adjustable to a suitable value by adjusting the adjusting screw 23. The end of the inner wire 16 is fixed to the end of the lever 22 by means of a screw 25. A bracket 26 together with the cover plate 4 is fixed to the vehicle body (not shown) by means of the bolt 6. The outer adaptor 18 is fixed to the bracket 26 by means of the lock nut 19.

Referring to Figures 7 and 8 illustrating another embodiment of the invention using another toggle joint, an arm 8b integral with the shoe 8 extends outwardly beyond the drum 3 and is provided at its extreme end with a pin 20 which pivotally supports a lever 22 having at its upper end an extending piece 22a into which is screwed an adjusting screw or bolt 23 whose end is in opposition to the upper end of the shoe 11. The adjusting screw 23 is fixed by the lock nut 24. The clearance between the lining ila and the drum 3 is therefore adjustable by means of the adjusting screw 23 adapted to be fixed in adjusted position by the lock nut 24. The inner wire 16 is fixed to the lower end of the lever 22 by means of the screw 25.

The bracket 26 together with the cover plate 4 is fixed to the vehicle body (not shown) by means of the bolt 6. The outer adaptor 18 is fixed to the bracket 26 by means of the lock nut 19.

The brake system constructed as above described operates as follows.

Referring to Figure 1, assuming that the drum 3 is rotated in a normal direction of an arrow D. when an operating force is applied to the inner wire 16, the shoe 8 is pivotally moved about the pin 7 in a direction of an arrow E from the position shown in Figure 1 to that shown in Figure 2 and the arm 9 integral with the shoe 8 is moved in a direction of an arrow F in Figure 2 simultaneously. As a result, the shoe 11 and the lining I la fixed thereto are also moved in the direction of the arrow F, and are simultaneously rotated about the pin 1() in a direction of an arrow G by the operating force acting upon the inner wire 16 from the condition in Figure 2 to that of Figure 3. As the pin 7 pivotally supporting the shoe 8 is not on a line T (Figure 2) which is a tangent to the inner surface of the drum 3 at the center of the lining 8a, the rotation of the drum 3 in the direction of the arrow D tends to urge the shoe 8 and lining 8a toward the inner surface of the drum. which tendency is referred to as "servo" effect or *'selfenergizing" action. Accordingly. the lining 8a is subjected to the braking action resulting from the self-energizing action in addition to the wire operating force. Similarly, the lining 11 a fixed to the shoe 11 pivotally supported by the pin 10 is also subjected to the braking action resulting from a selfenergizing action. With the arrangement shown in Figures l to 4. a resultant force of the braking force acting upon the lining 11a resulting from the wire operating force and the self-energizing effect of the lining lia acts on the pin 10 in the direction of the arrow F. As the pin 10 is provided in the arm 9 integral with the shoe 8. the resultant braking force of the lining ila urges the lining Xa in the direction of the arrow E against the inside of the drum 3. Thus when the operating force is applied to the inner wire 16, the linings 8a and lia are subjected to the braking forces resulting from the wire operating force and the self-energizing action (servo effect). and as described the lining Xa is subjected to the further braking force resulting from the resultant braking force of the lining 11 a in the same manner as the operating force to increase the braking force acting upon the lining 8a. In this manner. a slight operating force is sufficient to provide an enough braking force because of the braking forces acting upon the pair of linings Xa and 1 lea in opposition to each other and embracing the drum 3 therebetween bv the operating force and further brakin,g force acting upon the lining 8a resulting from the braliing force of the lining Ila acting as if it were an operating force.

As the pair of linings 8a and lia are substantiallv in opposition to each other on both sides of the wall of the drum 3. the thickness of the wall of the drum 3 can be thinner than that of the prior art having linings urging a drum on one side thereof or inside as an expanding drum brake. Therefore. it is possible according to the present invention to decrease the weight of the brake drum and hence all the weight of the brake system.

The part of the drum 3 is embraced by a pair of linings 8a and I I a, so that the surface areas of the drum covered by the linings are relatively small and therefore exposed areas of the drum are relatively large which serve to cool the drum effectivelv. Accordingly.

the brake can be used for a long period of time because of the effective cooling of the drum.

Referring to Figures 5 and 6, when an operating force is applied to the inner wire 16. the lever 22 is rotated about the pin 20 and then the extending piece 21 strikes the adjusting bolt 23 to urge the arm 8b integral with the shoe 8 and lining 8a against the inner surface of the drum 3. On the other hand, the reaction force of the lining 8a urged against the drum 3 acts upon the extending piece 21 to force the shoe 11 and the lining 1 la against the outer surface of the drum 3 about the pivot pin '().

Referring to Figures 7 and 8. when an operating force is applied to the inner wire 16. the lever 22 is pulled to urge the arm 8b integral with the shoe 8 and lining Xa against the inner surface of the drum 3. As a reaction of this braking action, the extending piece 22a integral with the lever 22 is rotated about the pin 20, with the result that the adjusting bolt 23 forces the shoe 11 and lining 11a against the outer surface of the drum 3.

As can be seen from the above description, the braking force can be considerably increased by incorporating a toggle joint utilizing a cam or lever in the brake system for helping the direct operating force by a wire. Accordingly, the brake with such a toggle joint performs a sufficient braking operation only by a slight wire operating force. Therefore, the brake according to the invention provides sufficient brake forces to ensure the safe and positive operation for light vehicles, particularly lady's and child's bicylces whose riders are weak in grasping power.

When an adjusting bolt is provided in the lever connected to the inner wire. the space between the drum and lining can be adjusted within wide ranges in the event that the lining is worn.

WHAT WE CLAIM IS: 1. A brake for a vehicle. comprising a brake drum rotatable with a wheel of the vehicle, an inner pin fixable to a vehicle body and extending within the brake drum, an inner shoe pivotally supported by the inner pin within the brake drum, an arm integral with the inner shoe and extending outwardly beyond the brake drum, an outer pin extending from an end of the arm, an outer shoe pivotally supported by the outer pin to be brought into contact with an outer periphery of the brake drum, spring means for urging the inner shoe and the outer shoe away from the brake drum, and actuating means comprising a wire connected at one end thereof to the inner shoe or to means operably associated therewith and movable within an outer adaptor to cause the inner shoe and the outer shoe to be urged against the brake drum.

2. A brake as claimed in claim 1. where- in the arm is provided with an adjusting screw threadedly engaged therewith and having an end bearable against a member fixable to the vehicle body to enable a clearance between the inner shoe and the brake drum to be adjusted.

3. A brake as claimed in claim 1. or claim 2, wherein the actuating means comprises toggle means.

4. A brake as claimed in claim 3, wherein the toggle means comprises a further arm integral with the inner shoe and projecting outwardly of the drum. a projection extending from the outer shoe, and a lever having an extending piece pivotally supported at its one end by a pin provided on the projection of the outer shoe. the further arm being provided on the projection of the outer shoe. the further arm being provided with a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. resulting from the wire operating force and the self-energizing effect of the lining lia acts on the pin 10 in the direction of the arrow F. As the pin 10 is provided in the arm 9 integral with the shoe 8. the resultant braking force of the lining ila urges the lining Xa in the direction of the arrow E against the inside of the drum 3. Thus when the operating force is applied to the inner wire 16, the linings 8a and lia are subjected to the braking forces resulting from the wire operating force and the self-energizing action (servo effect). and as described the lining Xa is subjected to the further braking force resulting from the resultant braking force of the lining 11 a in the same manner as the operating force to increase the braking force acting upon the lining 8a. In this manner. a slight operating force is sufficient to provide an enough braking force because of the braking forces acting upon the pair of linings Xa and 1 lea in opposition to each other and embracing the drum 3 therebetween bv the operating force and further brakin,g force acting upon the lining 8a resulting from the braliing force of the lining Ila acting as if it were an operating force. As the pair of linings 8a and lia are substantiallv in opposition to each other on both sides of the wall of the drum 3. the thickness of the wall of the drum 3 can be thinner than that of the prior art having linings urging a drum on one side thereof or inside as an expanding drum brake. Therefore. it is possible according to the present invention to decrease the weight of the brake drum and hence all the weight of the brake system. The part of the drum 3 is embraced by a pair of linings 8a and I I a, so that the surface areas of the drum covered by the linings are relatively small and therefore exposed areas of the drum are relatively large which serve to cool the drum effectivelv. Accordingly. the brake can be used for a long period of time because of the effective cooling of the drum. Referring to Figures 5 and 6, when an operating force is applied to the inner wire 16. the lever 22 is rotated about the pin 20 and then the extending piece 21 strikes the adjusting bolt 23 to urge the arm 8b integral with the shoe 8 and lining 8a against the inner surface of the drum 3. On the other hand, the reaction force of the lining 8a urged against the drum 3 acts upon the extending piece 21 to force the shoe 11 and the lining 1 la against the outer surface of the drum 3 about the pivot pin '(). Referring to Figures 7 and 8. when an operating force is applied to the inner wire 16. the lever 22 is pulled to urge the arm 8b integral with the shoe 8 and lining Xa against the inner surface of the drum 3. As a reaction of this braking action, the extending piece 22a integral with the lever 22 is rotated about the pin 20, with the result that the adjusting bolt 23 forces the shoe 11 and lining 11a against the outer surface of the drum 3. As can be seen from the above description, the braking force can be considerably increased by incorporating a toggle joint utilizing a cam or lever in the brake system for helping the direct operating force by a wire. Accordingly, the brake with such a toggle joint performs a sufficient braking operation only by a slight wire operating force. Therefore, the brake according to the invention provides sufficient brake forces to ensure the safe and positive operation for light vehicles, particularly lady's and child's bicylces whose riders are weak in grasping power. When an adjusting bolt is provided in the lever connected to the inner wire. the space between the drum and lining can be adjusted within wide ranges in the event that the lining is worn. WHAT WE CLAIM IS:

1. A brake for a vehicle. comprising a brake drum rotatable with a wheel of the vehicle, an inner pin fixable to a vehicle body and extending within the brake drum, an inner shoe pivotally supported by the inner pin within the brake drum, an arm integral with the inner shoe and extending outwardly beyond the brake drum, an outer pin extending from an end of the arm, an outer shoe pivotally supported by the outer pin to be brought into contact with an outer periphery of the brake drum, spring means for urging the inner shoe and the outer shoe away from the brake drum, and actuating means comprising a wire connected at one end thereof to the inner shoe or to means operably associated therewith and movable within an outer adaptor to cause the inner shoe and the outer shoe to be urged against the brake drum.

further adjusting screw threadedly fitted therein. the further screw being bearable against the extending piece and the other end of the lever being connected to the wire, a clearance between the drum and the outer shoe being adjustable by adjusting the further adjusting screw.

5. A brake as claimed in claim 3, wherein the toggle means comprises a further arm integral with the inner shoe and projecting outwardly of the drum and provided at an end thereof with a pin. and a lever having an end pivotally supported bv the pin of the further arm and an extending piece provided with a further adjusting screw threadedly fitted therein, the further adjusting screw being bearable against the outer shoe. and the other end of the lever being connected to the wire. a clearance between the drum and the outer shoe being adjustable by adjusting the further adjusting screw.

6. A brake for vehicles substantially as herein described with reference to Figures l to 4 or Figures 5 and 6 or Figures 7 and 8 of the accompanying drawings.