FR2480379A1 - DRUM BRAKE DEVICE HAVING INTERNAL JAWERS - Google Patents

Abstract

THE INVENTION RELATES TO A DRUM BRAKING DEVICE WITH INTERNAL JAWS WHICH INCLUDES A DRUM AND TWO JAWS INSIDE THE DRUM. ACCORDING TO THE INVENTION, AN ANCHOR 15 IS PLACED BETWEEN TWO FIRST ADJACENT ENDS OF THE JAWS 11 AND 12 AND A FIRST BRAKING ACTION DEVICE 19 IS PLACED BETWEEN THE TWO SECOND ADJACENT ENDS OF THE JAWS TO PLACE THEM AGAINST THE INTERNAL FACE OF THE DRUM WHEN IT IS TAKEN INTO ACTION. A SECOND BRAKE ACTION DEVICE 40 AND 44 IS PROVIDED TO FORCE THE SHOES TO SERVE AS UNIFORM BRAKE SHOES. THE SHOES SERVE AS A UNIFORM BRAKE WHEN THE SECOND DEVICE IS OPERATING, WHILE THEY ARE SERVED AS A PRIMARY-SECONDARY SHOE BRAKE WHEN THE FIRST DEVICE IS OPERATING. THE INVENTION APPLIES IN PARTICULAR TO THE AUTOMOTIVE INDUSTRY.

Description

The present invention relates to a braking device of the type

  internal jaw drum for a rotating object, such as a wheel of a vehicle, which can serve both as a primary-secondary jaw brake and a uniform-jaw brake.

  Drum brakes with two jaws are typically

  of two different types, one of which is the primary-secondary jaw type and the other is the type

  uniform o both jaws are applied evenly.

  When a drum brake is used on a vehicle, particularly on its rear wheels, the primary-secondary jaw brake is better suited to a service brake usually operating by depressing a brake pedal, in terms of braking force distribution, while the uniform brake is better suited to a parking brake operated by a brake lever to

  hand, because of its extra braking force.

  Like traditional drum type brakes

  jaws primary-secondary o is incorporated a mechanism

  Parking brake me still work as primary-secondary jaw brakes, they tend to offer insufficient braking power for parking. So, the brakes may have to be bigger or be used with another brake for

  complete braking power for parking.

  The subject of the present invention is a drum brake device with a parking brake mechanism which produces an appropriate power of

  braking for parking, without degrading

  braking force when in use or in service.

  It is another object of the present invention to provide a relatively simple construction drum brake device which provides adequate braking power for parking without degrading the performance for the parking brake.

  braking in use or in service.

  The present invention relates to an internal jaw drum type braking device having a braking drum and two jaws which are placed inside the drum so as to engage it in a controllable manner. An anchor is mounted to a stationary plate

  of support and is placed between two first ends

  respective jaws of the brake so as to allow these first ends to slide in the essentially radial direction. A first brake actuator is located between the two adjacent second ends of the respective jaws and is mounted on the stationary bearing plate so as to slide in the direction of actuation of the jaws. A second brake actuator is mounted on the jaws and includes a lever pivotally mounted on the first jaw and a spacer which is connected at one end to the first jaw and the lever and at its second end to the second jaw The jaws engage the drum like those of a primary-secondary jaw brake when the first actuator operated to separate the jaws. When the second actuator operates, the jaws engage the drum like those of a uniform brake where the lever pivots relative to the

  first jaw to separate the two jaws.

  The invention will be better understood, and other purposes,

  characteristics, details and advantages of it appear

  more clearly in the explanatory description

  which will be followed with reference to the accompanying drawings given by way of example only illustrating an embodiment of the invention, and in which - Figure 1 is a schematic sectional view of a preferred embodiment of a drum braking device according to the invention; FIG. 2 is a schematic sectional view taken along line 2-2 of FIG. 1; and - Figure 3 is a schematic sectional view taken along line 3-3 of Figure 1; Referring now to Figure 1, it can be seen. a drum braking device for vehicles, comprising a drum 10 and two jaws 11, 12.

  jaws has a curved outer surface corres-

  laying on the inner face of the drum 10 with respective lining 13 and 14 on the outer face. These jaws 11, 12 are placed inside the drum 10 so that the gaskets 13, 14 are turned towards the

inner face of the drum 10.

  An anchor 15 is disposed between the upper ends

  jaws 11, 12 to form sliding engagements therewith, as will be described hereinafter, and is attached to a stationary bearing plate 16 by pins 17, 18. A wheel cylinder 19 of the hydraulic type symmetrical is disposed between these lower ends of the jaws 11, 12 to force the ends outward, and is slidably mounted on the plate

  support 16 as will be described below.

  The upper ends of the jaws 11, 12 are biased toward the narrowing 15 by a coil spring whose ends are attached to these ends of the jaws. The lower ends of the jaws 11, 12 are also biased towards the cylinder 19 by a U-shaped return spring 21, the ends of which are fixed to the jaws near their lower ends, and whose center is held by a means 22 fastened around the lug. 15. The jaws 11, 12 are forced outwards against the spring 21 while the cylinder 19 is actuated, and they are forced inwards by the return force of the spring 21 when the setting

action of the cylinder stops.

  The cylinder 19 comprises a body 23, two pistons 24, slidably disposed in the body and a pressure chamber 26 in the body, defined by the ends of the pistons and the inside of the body. The pistons 24, 25 abut against the lower ends of the jaws 11, 12 respectively, by their outer ends, and they have annular shoulders 27, 28 respectively at their outer ends to engage the outer ends of the body when the pistons return to their rest position. The pistons 24, 25 also have dust chambers 24a, 25a respectively at their outer ends, and protruding ribs 29,3orespective at their inner ends, contacting each other when the pistons return to their position. rest, and they - have more joints or annular caps 31, 32, respectively at their inner ends. The pressure chamber 26 communicates with a brake master cylinder 33, which operates when the brake pedal 34 is depressed in the cab of the vehicle, by a line 35. The pistons 24, 25 move according to the -ression on the fluid due to the chamber 26, supplied by the master cylinder 33 and the line 35, and they force the lower ends of the jaws 11, 12 outwards

  while the pedal 34 is depressed.

  One end of a lever 40 pivots on the jaw 12 by a pin 41 at a position between its upper end and its center, preferably near its upper end. A cable 42 is attached to the end

  free of the lever 40 and is guided by a guide 42a.

  The cable 42 extends out of the support plate 16 through an orifice 42b and is connected in turn to a lever of

  handbrake 43 in the cab of the vehicle.

  One end of a spacer 44 engages the lever 40 at an intermediate position, preferably closer to the pivoting end, and the jaw 12 at a position near its upper end, by engagement 45, and the other end thereof. the spacer 44 engages the other jaw 11 in a similar position near its upper end. Anti-rattling devices 46, 47 are attached to the jaws 11, 12 respectively, at their center, to retain the jaws on the support plate,

in the usual way.

  Figure 2 shows a sliding engagement between

  the ends of the jaws 11, 12 and the anchor 15.

  The anchor 15 includes an outer plate 50 and a spacing member 51 sandwiched between the plate 50 and the bearing plate 16 so that radial grooves 52a, 52b are formed at the ends of the anchor 15. plate 50 and the member 51 are fixed together to the support plate 16 by lesbmochesl7, 18. The spacing member 51 is slightly thicker than the section of the jaw which fits in the grooves 52a, 52b, as well as the ends of the jaws 11, 12 are formed in the grooves 52a, 52b, to form sliding engagements with the anchor 15, the jaws can move freely

  outward and away from the anchor 15.

  Figure 3 shows a mechanism for the cylinder

  wheel 19 to slide in the directionc3es put into action.

  The mechanism comprises an extension 60 of the body 23 of the cylinder having a head 61, and the bearing plate 16 having an orifice 62 which extends in the direction of the movement of the pistons 24, 25. The extension 60 is inserted in the orifice 62 so that the body 23 of the cylinder can slide in the direction of movement of the pistons 24, 25. A stop plate 63 is provided between the head 61 and the support plate 16 to prevent the body 23 of the cylinder from fall

out of the support plate 16.

  This drum braking device operates as follows: when the pedal 34 is depressed for service braking, the pistons 24, 25 move outwards according to the pressure of the fluid in the chamber 26, coming from the master cylinder 33, forcing the lower ends of the jaws 11, 12 outwards. As a result, the jaws 11, 12 press the gaskets 13, 14 against the inner face of the drum 10, thereby reducing the speed of rotation thereof by the bending force exerted on it. Thus, the jaw 12 serves as the primary jaw and the secondary jaw jaw as the drum 10 rotates in the direction of the arrow A in Fig. 1 and the vehicle moves forward. Similarly, the jaw 12 serves as a secondary jaw and the jaw 11 serves as a primary jaw when the vehicle is in reverse and the drum 10 is rotating in the opposite direction. Therefore, the braking device operates as a drum brake of the type primary-secondary jaws reducing the speed of the drum 10 regularly when the

  cylinder 19 operates by depressing the pedal 34.

  On the other hand, when the parking brake lever 43 is moved to pull the cable 42 for parking braking, the lever 40 rotates clockwise, moving the spacer 44 and thus the upper end of the jaw 11, towards the face

  internal drum 10, pressing the lining 13 against it.

  At the same time, the lever 40 rotates about the pivot point formed by the engagement 45 and moves the upper end of the jaw 12 outwardly, squeezing the pad

  14 against the inside of the drum 10.

  The braking reaction force exerted on the jaw 11 is transmitted to the cylinder 19 in the form of a force pressing against the piston 24 in the body 23, provided that the drum 10 rotates in the direction of the arrow A. shoulder 27 of the piston 24 abutting against the left end of the body 23, forcing it to the right. When the right end of the body 23 has touched the shoulder 28 of the piston 25, the body 23 moves the lower end of the jaw 12 towards

  the outside squeezing the lining 14 against the inter- face

  Thus, the reaction force exerted on the jaw is transmitted to the lower end of the jaw 12 as an additional braking force on the jaw 12, and therefore the jaws 11, 12 serve both to primary jaws, and uniform action is produced in the braking device when the hand brake lever 43 is operated to turn the

  lever 40 in a clockwise direction, that is,

  That is, to the spacer 44. Therefore, the braking device serves as a drum brake of the uniform type, producing an additional braking force when the lever 40 is turned in the direction of the points of a watch. The resulting force on the jaw 12 is ultimately carried by the anchor 15. The jaws 11, 12 change function as the drum 10 rotates in the opposite direction. Thus, the lever 40 and the spacer 44 constitute a device for actuating the jaws of the brake to force these jaws 11, 12 to serve as

jaws of an even brake.

  Those skilled in the art will readily note that the shoulders 27, 28 serve to shift the body 23 of the cylinder into the elongate slot 62, while simultaneously retaining the piston seals 31, 32 in their respective "working zone" (the distance on which the joints move in the cylinder during a

  normal service braking) in the cylinder body.

  In this way, the cylinder 19 slides to transmit the braking force of the hand lever between the two jaws 11, 12 in opposition to the distance traveled by the piston seals 31, 32 sliding beyond their working area. As a result, the service life of

piston-is extended.

  Of course, the invention is not limited to the embodiment described and shown which has been given by way of example. In particular, it includes all the means constituting technical equivalents of the means described, as well as their combinations, if they are executed according to its spirit and implemented in

  the framework of protection as claimed.

Claims (4)

R E V E N D I C A T I 0 NS   Brake device of the internal jaw drum type, characterized in that it comprises: a) a drum (10), b) first and second jaws (117 12) placed inside said drum for engaging in a controlled manner, said drum; c) an anchor (15) mounted on a stationary bearing plate (16) and placed between two adjacent first ends of the respective jaws so as to allow said first ends of said jaws to slide therein in a substantially directional direction; radial, d) a first brake actuation device (19 placed between the two adjacent second ends of said respective jaws, said first device   actuator being mounted on said stationary plate   a second actuator mounted on said jaws, said second device comprising: 1) a lever (40) pivotally mounted on said first member; jaw; 2) a spacer (44) connected at a first end to said first jaw and to said lever and at its second end to said second jaw, whereby pivoting said lever relative to said first jaw forces said jaws to separate and engage said drum, and forces said first means of   put in action to slide in the direction tending to trans-   put the movement of one of said jaws to another.   2. Device according to claim 1, characterized in that the first aforementioned actuating device comprises a symmetrical hydraulic cylinder (19) having two pistons (24, 25) which separate axially under hydraulic pressure, each of said pistons having a annular shoulder (27, 28) for engaging the respective end of said hydraulic cylinder to bias said cylinder and said pistons in a direction   axial to one of said jaws to actuate it.   3. Device according to claim 1, characterized in that it further comprises a hand brake lever (43) and a cable (42) connected between said lever and the free end of the lever of the second actuating device aforementioned, so that said device operates in moving said lever.   4. Device according to claim 2, characterized in that it further comprises a pedal (34) and a hydraulic cylinder (33) actuated by said pedal to supply fluid to said hydraulic cylinder, and said hydraulic cylinder operates by pressing said pedal.