JPS5843617B2 - Naikakusyu Drum Brake - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inwardly expanding shoe drum brake, and more particularly, the shoes are actuatable by both fluid pressure and a gearing device, and when the brake is installed on a vehicle, the brake is operated by fluid pressure. The present invention relates to an inwardly expanding shoe drum brake that can be operated as a service brake through a mechanical device and as a parking brake through a mechanical device.

Expanding shoe drum brakes, which can be actuated by both fluid pressure and mechanical devices, are typically constructed in a leading, trailing shoe type, and are used for both service and parking brakes.

In such brakes, the same braking resistance force is induced for forward and reverse movement of the vehicle to which they are installed.

This is a basic requirement for parking brake action, and it is a relatively simple matter to arrange the mechanical actuator so that the fluid pressure and mechanical braking action do not interfere with each other. .

2- Leading shoe brakes provide a greater braking force in one direction of rotation than leading and trailing shoes of the same size and shape, so an extremely high degree of braking is required for forward movement of the vehicle. In such cases, the brakes of the vehicle in front are preferred.

However, when such a two-trailing shoe brake operates as a parking brake, the difference in braking force in the forward rotation direction and the reverse rotation direction is significant, reducing the effectiveness of the brake as a parking brake. When parking a vehicle on a slope, a situation may occur where the braking force is insufficient.

Therefore, in an internally expanding shoe drum brake of the type described above, when the brake is actuated by fluid pressure it acts as a two-leading shoe brake in at least one direction of rotation of the drum, and when actuated by a mechanical device at least one shoe is the leading shoe. It would be desirable to provide a brake that acts as a brake.

It is thus one object of the present invention to provide an inwardly expanding shoe drum brake having these characteristics.

According to the present invention, a brake shoe support member, first and second brake shoes provided on the brake support member, and first and second brake shoes provided between a pair of proximal end portions of the brake shoes, respectively. two hydraulically actuated brake shoe expansion devices, the first shoe expansion device having a thrust member acting on the proximal end of the first brake shoe, and the second shoe expansion device having a thrust member acting on the proximal end of the first brake shoe; A thrust member acting on the proximal end of each brake shoe is provided, and a fixed contact member is provided at the end opposite to the end acted upon by one of the thrust members of each brake shoe. In shoe drum brakes equipped with
A lever is pivotally attached to the second brake shoe near its center, and the lever is provided with arms projecting toward both ends of the brake shoe, one arm of the lever and the first brake shoe. A mechanically actuated expander is provided which operates between one end of the first pre-gok shoe under the action of a thrust member of a fluid pressure actuated shoe expander, the contact member for the other arm of the lever being A protrusion is provided on the brake shoe support member to restrict inward movement of the lever arm, and the other arm of the lever is provided with an outwardly protruding protrusion that engages with the second shoe. An inwardly expanding shoe drum brake is provided, wherein inward movement of an end of the second shoe adjacent to the second fluid pressure operated shoe expansion device with respect to the lever is restricted. .

The mechanically actuated shoe expander has a first hydraulically actuated shoe expander pivotally mounted on the first brake shoe and near the end of the brake shoe that is acted upon by the thrust member of the first hydraulically actuated shoe expander. a second lever; a thrust link projecting between the second lever and one arm of the two-arm lever; and a thrust link that acts on the second lever and connects the two-arm lever via the thrust link. Preferably, it has a tensioning device adapted to apply a thrust force.

Adjustment devices can be provided between the first brake shoe and the second hydraulic shoe expansion device as well as between the two-armed lever and the fixed contact member for the arm.

The fluid pressure actuated shoe expander may be of the single-end type, with the contact member for the expander end being acted upon by the wheel cylinder thrust member being provided on the closed end of the wheel cylinder. ing.

Alternatively, the hydraulically operated shoe expansion device can be a two-ended wheel cylinder, the piston of which is provided with a contact device to restrict inward movement of the piston relative to the wheel cylinder.

Referring to Figures 1-6 of the accompanying drawings, a brake shoe support member in the form of a back plate 10 is provided with first and second single-ended wheel cylinders 11 and 12 near each diametrical end thereof. and the open ends of the cylinders face in opposite directions.

the above-mentioned cylinders have substantially the same configuration;
Each has a sliding piston within it.

A wheel cylinder 11 is shown in cross section, the piston of which is designated by 13.

Each of the pistons defines therewith a thrust member 14 which projects into the open end of the wheel cylinder.

A flexible seal boot 15 prevents water and foreign matter from entering between the piston and cylinder holes.

A groove is provided on the circumference of each piston to accommodate a backing ring.

Here, the backing ring of the wheel cylinder 11 is designated by the symbol 1.
7.

The inner small diameter end portion 18 of the piston cooperates with the closed end of the wheel cylinder to limit inward movement of the piston.

A helical compression spring 16 surrounding the piston end portion 18 draws the piston away from the closed end of the wheel cylinder.

A first and second brake shoe 19 and 21 of the known type, each consisting of an arcuate lined support rim 22 and a flat web 23 projecting inwardly from a concave surface of said rim, is located between the two wheel cylinders. The shoe web extends and has a convexly curved end.

The web end 24 of the first brake shoe 19 engages in a diametric groove in the thrust member 14 of the piston in the wheel cylinder 11, and the other end 25 of the shoe web provides a seal between itself and the wheel cylinder 12. An adjusting device 26 of the type described in GB 595,343 is inserted between the ends.

The adjustment device 26 is provided with a U-shaped member 27, the base of which engages the outer surface of the wheel cylinder, the dispensing member 28 of which is shown at 29 in FIG. As shown, a groove is provided, and a pin 31 is housed in the groove.

On the pin there is a pawl cam 3 with two axially spaced notched edges arranged between the dispensing member 28.
2 are provided.

The end 25 of the web of the brake shoe 19 is cut bare to accommodate the pin 31 and is located between the pawl cams 32.

A rib 33 provided on the base of the member 27 cooperates with the pawl cam, and the position of the shoe end relative to the wheel cylinder 12 is adjusted by rotation of the pawl cam.

The web 23 of said second brake shoe 21 is arranged at one end of said shoe and in a diametric groove 34 in the closed end of said first wheel cylinder 11 and at the other end of said second brake shoe 21 . It engages in a diametric groove of a thrust member 14 carried via a piston of a wheel cylinder 12 .

The curved levers 35 are pivotally mounted on the web of the second brake shoe 21 at a point near the center of both ends of the shoe, and the levers 35 each protrude toward one end of the brake shoe. two arms holding 3
6.37.

The block 38 is fixed to the back plate 10 in the vicinity of the wheel cylinder 12, and the end of the lever arm 3T adjacent to the end of the brake shoe 21 that engages the wheel cylinder thrust member 14 has an adjustment similar to the adjustment device 26 described above. It is supported by the block 38 via a device 39.

The pivot mechanism between the target lever 35 and the brake shoe 21 consists of a pin 41 (see FIG. 6) passing through the brake shoe web and a hole in the lever, a pin head 42 engaged with the surface of the lever 35, and a spring washer. 43.

The washer 43 is compressed between the shoe web surface and a washer 44 held on the pin 41 via a clip ring 45, and the clip ring 45 is held on the pin 41.
It has the effect of pressing the annular surface 46 of the lever 35 against the surface of the shoe web around the lever hole housing the lever 35.

A second bent lever 47 is pivotally mounted on the web 23 in the vicinity of the end of the brake shoe 19 engaging the thrust member 14 of the wheel cylinder 11; The difference is that a spring washer 48 is provided between the head 49 of the pivot pin 50 and the lever 47, as shown in FIG.
0 is in direct engagement with the shoe web 23.

The rigid column 53 has both ends marked with reference numeral 5 as shown in FIG.
4 and extends between two bars 35, 47 adjacent to and parallel to the axis of the wheel cylinder 11.

Levers 35 and 47 are arranged between the brake shoe web 23 and the back plate 10, the outer edges of which are indicated by dotted lines in FIG.

The arm 37 of the lever 35 has an outwardly projecting portion 55 (first
(see figure), and this part engages with the rim of the brake shoe 21.

Tension springs 56A, 57 extending between brake shoes 19 and 21 pull the shoes against the surrounding drum surface 58.
It acts to pull it away from the

By the action of the springs 56A and 57, the ends of the brake shoes 19 and 21 are pressed against the thrust member 14 and the closed end of the wheel cylinder 11, respectively, and the end 25 of the brake shoe 19 is pressed against the pin of the regulator 26. for,
The U-shaped member 27 of the regulator is connected to the wheel A. Towards the closed end of the cylinder 12, the rim of the brake shoe 21 is connected to the lever 3.
5 are respectively pressed against the outwardly projecting portions 55 of the levers 5, so that the levers are pressed towards the block 38.

Note that the position of block 38 is determined by adjustment device 39.

A cable 55A connected to the end of lever 47 remote from its pivot point passes across the backplate and through an opening 56 in the backplate.

The cable sheath 57A contacts the surface of the backplate around the opening 56 (see FIG. 3).

Although the cable 55A is shown in FIG. 1, it is omitted from FIG. 3 for clarity.

The cable 5 is connected between the lever 47 and the end of the sheath 57A.
The compression coil spring 58A surrounding the lever 47
is pressed outward, and its outward movement is limited via a stop member (not shown) on the back plate 10 or a stop member at the other end of the cable.

The above cable is connected to the parking brake lever.

When the brake is not operating, the first shoe 19
The location is as follows.

That is, the piston 13 in the first wheel cylinder 11 is fully retracted into the cylinder, and the retracted position of the shoe 19 is adjusted via the adjustment device 26 arranged between the shoe and the second wheel cylinder 12. It is possible to adjust the

The position of the second shoe 21 is such that at one end it is in contact with the closed end of the first wheel cylinder 11 and the fixed contact member 38 of said two-armed lever 35 pushes said shoe 21 through a projection 55 on said lever. Determined by holding it in a fixed position relative to the lever.

The regulator 39 is thus connected to the lever 35 and its contact member 38.
By moving the lever 35 and the second shoe 21 in unison, the position of the second shoe relative to the drum 58 is adjusted.

It should be noted that the piston in the second wheel cylinder 12 does not support the shoe 21 when it is in the retracted position, but follows the shoe outwardly as the shoe τ is adjusted.

When the brake shoe is actuated by fluid pressure, shoe 1
9 pivots around the pin of the adjustment device 26 and the shoe 21
pivot around shoe contact members at the closed end of the wheel cylinder 11, so that these shoes act as leading shoes for one direction of rotation of the drum and as trailing shoes for the opposite direction of rotation of the drum.

Cable 55 to which these shoes are connected to lever 47
When actuated by tension A, the strut 53 exerts an outward thrust force on the arm 36 adjacent the first wheel cylinder 11 of the lever 35, which thrust force is transmitted via the pivot pin 41 of the lever 35. It is transmitted to the second shoe 21.

At the same time, the lever 47 pivots counterclockwise, as viewed in FIG. As a result, the end of the brake shoe 19 adjacent to the first wheel cylinder 11 moves outward.

The first shoe 19 thus acts as a leading or trailing shoe depending on the direction in which the drum rotates or is intended to rotate, and the second shoe 21 acts as a leading or trailing shoe in its central area due to the thrust force exerted on the drum. It will act as a leading shoe in both rotational directions.

The thrust force applied to the shoe 21 here is twice as large as the thrust force applied to the first shoe due to the lever mechanism.

Thus, if the brake drum rotates in the direction of arrow A in FIG. 1 during forward movement of the vehicle, both shoes act as leading shoes for the service brake for forward movement of the vehicle, and as a parking brake for the vehicle. It acts as a leading shoe to prevent the forward movement of , and acts as a leading shoe and a trailing shoe, respectively, against backward movement.

As shown in FIG. 7 of the accompanying drawings, the first wheel cylinder has a double end in which the inward movement of both pistons 61, 62 is restricted by a piston flange 63 cooperating with the end face of the cylinder. It is also possible to use a type wheel cylinder 59.

When such a cylinder is provided, the brake operated by the fluid pressure is 2-2 in the direction of drum rotation in the direction of arrow A.
It operates as a leading shoe brake, and in the drum rotation direction opposite to arrow A, it operates as a leading and trailing shoe brake.

Also, in this case the mechanical actuation system is substantially the same as that shown in FIGS. 1-6, so that the brake can also be operated for parking purposes as described above.

[Brief explanation of drawings]

1 is a front elevational view of an internally expanded shoe drum brake showing some parts in cross section; FIG. 2 is a cut-away view taken along line 2--2 of FIG. 1; FIG. 3 is a view similar to that of FIG. 4 is a sectional view taken along line 3--3 of FIG. 1, FIG. 4 is a sectional view taken along line 4--4 of FIG. 1, and FIGS. 6-6
The cross-sectional view along FIG. 7 corresponds to a part of FIG. 1 shown in partial cross section, and shows the same exact view showing the corrected alignment. 10... Brake shoe support member, 19, 21
......First and second brake shoes, 11,1
2...First and second hydraulic brake shoe expansion devices, 14...Thrust member, 38.
...Fixed contact member, 35...Lever 3
6,37...Arm.

Claims (1)

[Claims] 1. A brake shoe support member, and first and second brake shoes provided on the brake shoe support member;
first and second hydraulically actuated brake shoe expansion devices respectively disposed between the pair of proximal end portions of the brake shoes, the first shoe expansion device being disposed between the pair of proximal end portions of the first brake shoe; a thrust member acting on the proximal end of the second brake shoe, the second shoe extension device including a thrust member acting on the proximal end of the second brake shoe;
A shoe drum brake in which a fixed contact member is provided at an end of each brake shoe opposite to the end that is acted upon by one of the thrust members, and the second brake shoe has a fixed contact member near its center. A lever is pivotally mounted, the lever having arms projecting toward opposite ends of the brake shoe, and one arm of the lever and a thrust member of the first fluid pressure operated shoe expansion device. A mechanically actuated expansion device is provided for operation between one end of the first brake shoe being actuated, and a contact member for the local arm of the lever is provided on the brake shoe support member to extend the brake shoe. Inward movement of the lever arm is restricted, and the other arm of the lever is provided with an outwardly projecting protrusion that engages the second shoe so as to prevent the second fluid from flowing in the second shoe. An inwardly expanding shoe drum brake, characterized in that inward movement of the end adjacent to the pressure-operated shoe expanding device with respect to the lever is restricted.