EP0047247A1

EP0047247A1 - Emergency brake

Info

Publication number: EP0047247A1
Application number: EP19800902190
Authority: EP
Inventors: Harvey C. Jacobs
Original assignee: MARK INDUSTRIES; Mark Industries Inc
Current assignee: MARK INDUSTRIES; Mark Industries Inc
Priority date: 1980-03-10
Filing date: 1980-03-10
Publication date: 1982-03-17
Also published as: WO1981002614A1

Abstract

Un frein de secours (10) possede un cylindre conique tronque, mobile, arme par un ressort, (48) dont la surface externe conique (49) est normalement poussee contre une surface interne complementaire (36A) d'un tambour de frein (36) pour effectuer une action de freinage. Le frein est libere par application d'un fluide hydraulique sous pression sur une bague annulaire (52) formee entre la surface interne du cylindre (48) et un piston fixe (40) monte dans celui-ci. La force exercee par le fluide hydraulique depasse la poussee des ressorts (50) sur le cylindre (48) contre le tambour de frein (36) et deplace le cylindre (48) en l'eloignant de la surface interne du tambour de frein (36A), liberant ainsi le frein.An emergency brake (10) has a truncated, movable, spring-loaded conical cylinder (48), the conical external surface (49) of which is normally pushed against a complementary internal surface (36A) of a brake drum (36 ) to perform a braking action. The brake is released by applying a pressurized hydraulic fluid to an annular ring (52) formed between the internal surface of the cylinder (48) and a fixed piston (40) mounted therein. The force exerted by the hydraulic fluid exceeds the thrust of the springs (50) on the cylinder (48) against the brake drum (36) and moves the cylinder (48) away from the internal surface of the brake drum (36A ), thereby releasing the brake.

Description

Emergency Brake

Technical Field

This invention relates to emergency brakes of the type which are actuated by a failure of hydraulic power in order to apply a braking force to a rotating member such as the wheel of a vehicle.

Background Art

Emergency brakes of various types have long been used, particularly with respect to vehicles. Such brakes, conventionally, have utilized the manual actuation of the brake to apply a braking action in conjunction with at least a portion of the existing brake system of the vehicle. Such emergency brakes suffer from various deficiencies, such as a lack of braking if the component of the braking system which is common between the emergency brake and the conventional brake is inoperative for whatever reason. Furthermore, such brakes normally must be released by manual actuation, and, often, are left unreleased in operation.

Disclosure of Invention

According to the present invention, an emergency brake utilizes a rotatable drive shaft extending from a fixed axle, and a hollow brake drum, having an inner face, and which is connected to the rotatable shaft. A piston is fixed to the axle within the brake drum, and a movable cylinder of a generally frustoconical configuration and having an outer face which is generally complementary to the configuration of a portion of the brake drum inner face, is disposed between the piston and brake drum so as to be in contact with the piston and immediately adjacent the brake drum complementary inner face portion. Means are provided for normally urging the cylinder outer face against the brake drum complementary inner face, and means are provided for selectively initiating movement of the cylinder relative to the piston so as to move the cylinder outer face away from the brake drum complementary inner face.

Brief Description of Drawing The invention may be more readily understood by referring to the accompanying drawing, which is a side elevation, partially in section, of an emergency brake according to the present invention.

Best Mode for Carrying Out the Invention

Referring now to the drawing, there is shown an emergency brake assembly 10 fitted on an axle 12 of a vehicle (not shown), the axle 12 being disposed within an axle tube 14. A hydraulic motor 16 is mounted on the end of the axle 12 by any conventional means so as to be fixed thereto. The hydraulic motor 16 has an output shaft 18 and a pair of hydraulic fluid couplings 20. Application of hydraulic fluid under pressure to these couplings 20 initiates and controls the direction of rotation of the output shaft 18. A drive hub 22 is mounted on the output shaft 18 and is keyed thereto by means of a key 24 disposed in a slot 26 formed in the hub 22. The key 24 also engages a slot (not shown) in the output shaft 18, and so causes the hub 22 to rotate in unison with the output shaft 18.

The hub 22 is held on the output shaft 18 by means of a nut 28 which is threaded onto a threaded portion 30 of the output shaft 18. The nut 28 is fixed in position by means of a cotter pin 32, in conventional fashion.

A wheel spacer 34 and an outwardly tapering hollow brake drum 36 are mounted on the hub 22. Wheel mounting bolt holes 38 extend through the wheel spacer 34 and brake drum 36 into the hub 18. The portions of the wheel mounting bolt holes 38 in the hub 18 are preferably threaded so that wheel mounting bolts (not shown) may engage the hub 22 and hold a wheel (not shown) and the wheel spacer 34 and brake drum 36 fixed in position with respect to the hub 22.

A piston 40 is disposed within the brake drum 36 and is held fixed in position with respect to the hydraulic motor 16 by means of a backing plate 42 and mounting bolts 44. As seen in the drawing, the mounting bolts 44, only two of which are shown in the drawing, are of the conventional cap screw type and extend through the piston 40 and hydraulic motor 16 so as to engage threaded recesses 46 in the backing plate 42, thereby holding the piston 40 and backing plate 42 tightly against opposite sides of the hydraulic motor 16.

A frustoconicial cylinder 48, having ah outer face 49, is disposed within the brake drum 36 between a complementary inner surface portion 36A thereof and the fixed piston 40. A plurality of loading springs 50, only one of which is shown in the drawing, are disposed between the backing plate 42 and the cylinder 48. The cylinder 48 and backing plate 42 have opposing faces 48A, 42A, respectively, into which recesses 48B, 42B are formed so as to hold the loading springs 50 in position. As will be apparent from the drawing, the loading springs 50 urge the cylinder tapered outer face 49 agains the inner face 36A of the brake drum 36, thereby providing a braking action against the rotation of the hub 22. Release of the braking action just described is accomplished by the application of hydraulic brake fluid under pressure to an annular ring 52 formed at the interface between the inner surface of the cylinder 48 and the outer surface of the piston 40. Hydraulic brake fluid under pressure is applied to the annular ring 52 through a hydraulic brake fluid passage 54, formed in the fixed piston 40, by means of a hydraulic brake fluid hose 56 and a hydraulic brake fluid fitting 58. A fluid seal for the annular ring 52 is provided by a pair of O-rings 60 and backup rings 62 disposed to either side of the annular ring 52. Upon application to the annular ring 52 of hydraulic brake fluid under appropriate pressure, the ring 52 expands laterally by the sliding of the cylinder 48 linearly along the piston 40 toward the backing plate 42, and thereby away from the inner face 36A of the brake drum, so as to release the emergency brake. Obviously, the hydraulic fluid pressure applied must be sufficient to overcome the spring loading provided by the loading springs 50 in order to release the brake. As will be apparent from the foregoing description, when hydraulic fluid under pressure is not applied to the hydraulic brake fluid hose 56 at a pressure in excess of that required to overcome the urging of the loading springs 50, the brake will remain applied. In most instances, this automatic application of the brake until there is a selective application of hydraulic fluid above a pre-selected pressure to the hose 56, is desirable as a safety feature for the vehicle. In other words, when the vehicle is not energized so as to provide a source for the pressurized hydraulic fluid, the emergency brake is on. However, in certain instances, it will be desirable to release the hydraulic brake without the application of hydraulic fluid under pressure. For example, if it is desired to tow the vehicle, or roll the vehicle a short distance, it would not ordinarily be desirable to energize the power supply for the hydraulic fluid pressure. In order to enable the emergency brake to be released under such circumstances, the emergency brake of the present invention includes a plurality of studs 64, only one of which is shown in the drawing, and locking nuts 66. The studs 64 threadably engage recesses 48C formed around the face 48A of the piston 48 and extend through, but do not threadably engage, the backing plate 42. The locking nuts 66 are threaded on the studs 64 externally of the backing plate 42. By rotation of the locking nuts 66 in the appropriate direction, the studs 64 are withdrawn further from the brake assembly 10 so as to pull the piston 48 toward the backing plate 42 against the urging of the loading springs 50. When the locking nuts 66 have been rotated a sufficient number of turns to cause the piston 48 to clear the inner face 36A of the brake drum 36, the brake is released manually without respect to the application of hydraulic fluid.

An important feature of the present invention is the utilization of the frustoconical cylinder to provide a tapered outer face for engagement with the complementary inner face portion of the brake drum. The angle of taper of the outer face, and therefore of the brake drum, are preferably selected with respect to the particular application of the brake of the present invention to provide maximum efficiency. For example, if, as is the case with many hydraulic motors, hydraulic fluid of a pressure of about 17.5 kilograms per square centimeter is utilized, then the angle of taper is selected with respect to such pressure and the braking force required, rather than providing a separate source of supply for the braking hydraulic fluid pressure. Such an embodiment, for a heavy vehicle which required significant braking force, would preferably utilize a relatively small angle of taper, such as 10° to 15°, and consequently, the number of loading springs required and the energy stored by the industrial spring will be such as to enable the available hydraulic pressure to release the brake. Alternatively, for applications in which hydraulic fluid under high pressure is readily available, the angle of taper can be increased, and greater numbers of springs and/or springs of greater capacities utilized to take advantage of the higher hydraulic fluid pressure available.

In another application of the brake of the present invention, the brake is used as a "dead man" brake, with the brake release pressure being generated by the equipment operator by hand or foot operated hydraulic master cylinder arrangements, so that the brake is released only so long as the operator generates the required hydraulic pressure in the separate release system.

While the invention has been described in particular with respect to vehicles of the type which utilize individual hydraulic motors to individually drive the wheels of a vehicle, as will be apparent from the foregoing description, the emergency brake of the present invention has much broader applications. Thus, the brake can be used in wheeled vehicles in which the drive source is not located at the end of the axle, but rather is a single drive source driving shafts disposed within hollow axles, as, for example, in conventional automobiles. In such embodiments, the driven member would correspond to the output shaft 18 of the drawing. Nor is the emergency brake limited to wheeled vehicles. Thus, all that is required for its adaptation for a particular use is a fixed member for attachment of the piston, cylinder and backing plate and a rotary member for attachment of the brake drum. Therefore, the present invention is not limited to utilization with hydraulic motors, or wheeled vehicles, and its scope is to be interpreted in accordance with the following claims.

Claims

Claims 1. An emergency brake comprising: a rotatable drive shaft extending outwardly from a fixed axle; a hollow brake drum having an outwardly tapering inner face; means for connecting the brake drum to the rotatable shaft; a piston fixed in position with respect to the axle and disposed within the brake drum; a movable frustoconical cylinder with an outer face, said cylinder outer face and a portion of said drum inner face having configurations which are generally complementary, said cylinder being disposed between the piston and brake drum complementary inner face portion so as to be in contact with the piston and immediately adjacent the brake drum complementary inner face portion; means for normally urging the cylinder outer face against the brake drum complementary inner face portion; and means for selectively initiating movement of the cylinder relative to the piston so as to move the cylinder outer face away from the brake drum complementary inner face portion.

2. An emergency brake according to claim 1, and in which the means for normally urging the cylinder outer face adjacent the brake drum includes a plurality of loading springs, each having a first end and a second end, means for fixing said spring first ends in position with respect to said cylinder, and means for engaging said cylinder by said spring second ends.

3. An emergency brake according to claim 2, and in which the means for fixing said spring first ends includes a backing plate fixed in position with respect to the piston so as to be disposed in a plane perpendicular to the direction of motion of the cylinder and means on said backing plate for engaging said spring first ends.

4. An emergency brake according to claims 1, 2 or 3 and in which the cylinder has an interior surface which forms an interface with the piston, the cylinder being slidable along the piston along the interface and in which the means for selectively initiating movement of the cylinder relative to the piston includes an annular ring formed in a portion of the interface, and means for selectively applying hydraulic fluid to the annular ring at a pressure which is of a magnitude sufficient to overcome said means for normally urging the cylinder outer face against the brake drum complementary face.

5. An emergency brake according to claim 4, and including a hydraulic motor fixed to the ends of the axle, and means for selectively applying hydraulic fluid to said motor to actuate it, said rotatable shaft extending outwardly from said hydraulic motor and being rotated thereby, said piston being disposed around said hydraulic motor so as to be fixed thereto.

6. An emergency brake according to claim 5, and in which the means for connecting the brake drum to the rotatable shaft includes a drive hub, means for mounting said drive hub on the rotatable shaft so that the drive hub rotates in unison with the shaft, and means for attaching the brake drum to the drive hub so that the brake drum is fixed thereto.

7. An emergency brake according to claim 6, and in which hydraulic fluid is applied to the hydraulic motor and to the annular ring from the same source.

8. An emergency brake according to claim 6, and in which the hydraulic fluid is applied to the annular ring from a first fluid source and hydraulic fluid is applied to the hydraulic motor from a second hydraulic fluid source, said second source being independent of said first source.