This invention relates to disc brakes and more particularly to coaxially helically acting disc brakes.
A screw action disc brake is described in U.S. Pat. No. 6,112,862 (“the '862 patent”). The disc brake described in the '862 patent provided advantages over a conventional caliper disc brake but has a significant drawback. The disc brake of the '862 patent tends to seize or “lock-up” when the brake is applied while the vehicle to which it is mounted is traveling in reverse.
The '862 patent disclosed at column 1, lines 62-65, that the “direction of the screw-threads must be such that when the collar is rotated on the cradle in the opposite direction to that of the forward turning hub it moves towards the brake disc.” The reason that the collar in the '862 patent, to which the brake pad is affixed, must rotate on its support element towards the disc in the opposite direction of the forward turning hub is that when the brake is applied, the brake pad works against the rotation of the disc and so cannot tighten against the disc. In fact, the brake pad will tend to be spun away from the disc when the brake is released.
However, when the vehicle is driven in reverse in the '862 patent, the collar, when the brake is applied, rotates towards the disc in the same directional rotation as the disc. Because of the helical motion of the collar and the friction generated between the brake pad and disc, the pad tends to tighten against the disc until the brake locks up and seizes. Furthermore, the '862 patent does not disclose a means to disengage the brake.
The brakes disclosed in U.S. Pat. Nos. 4,596,316 and 4,567,967, utilize ball screws to move a pressure plate axially toward a brake pad but specifically decouple and isolate the helical motion from the axial movement. In these brakes, the pressure plate does not rotate helically during the braking action. Such decoupling of the helical motion from the pressure plate would address the “lock-up in reverse” issue discussed above in the '862 patent, but would negate the advantages that the helical motion offers, namely, the propensity for the brake pad to be “spun” away from the rotor/disc when the brake is released, or, if the helical angle is reversed, create a self-energizing braking action.
Bicycle coaster brakes also utilize helical motion. The bicycle coaster brake typically operates by way of two shoes (or in some designs a conical shoe with a split along its axis) that sit along the radius of the axle inside the hub, or by way of a stack of alternating rotors and stators located within the hub. When the axle is reversed (when the rider backpedals), a helical piece on the axle, called a driver, is engaged moving a cone into the shoes that expands the shoes outward to contact the hub shell. Or, in the case of rotors and stators, the rotors and stators are forced to contact each other. In most coaster brakes, the braking power is supplied by metal-to-metal contact. Numerous U.S. patents for coaster brakes disclose such helical actuation.
Another aspect of braking technology is the combination disc and parking brake. The reasons for having a separate parking brake integral with a disc brake are explained in “A short Course on Brakes,” by Charles Ofria found at <http://www.familycar.com/brakes.htm>. The following excerpt explains some of the reasons:
The brake shoes on this system are connected to a lever that is pulled by the parking brake cable to activate the brakes. The brake “drum” is actually the inside part of the rear brake rotor.
Such parking drum brakes mounted within disc brake rotors are disclosed in U.S. Pat. Nos. 6,484,852; 5,715,916; 5,529,149; 5,180,037; 4,995,481; 4,854,423; 4,313,528; 3,850,266; and 3,447,646. With respect to concentric “brakes within brakes,” see U.S. Pat. No. 4,809,824 to Fargier et al., Method and Device for Actuating a Braking Mechanism By a Rotating Electric Motor.
Accordingly, a better form of disc brake is needed preferably incorporating a parking brake.
One aspect of an embodiment of the present invention relates to a brake that solves the “braking in reverse” lock-up issue described above by dividing the abovementioned collar into two separate elements. One element is a pressure plate that rotates in a helical motion on a support element. Another element is a brake pad carrier that can be coupled to and disengaged from the pressure plate.
In this embodiment, the pressure plate, like the collar, rotates in a helical motion (which couples rotational motion to axial motion) on the support element. The function of the pressure plate is to push the brake pad, which can be fixedly mounted on the brake pad carrier, into contact with a rotor. The helical motion of the pressure plate generates increased braking torque due to its inherent wedge-like or camming properties. The helical motion may be achieved in a number of ways including but not limited to screw threads, bearing balls or rollers in races, pins or track rollers in grooves, or by a combination of radially-arranged linear actuators.
This embodiment creates the helical motion of the pressure plate in relation to the support element by a series of equidistantly spaced helical grooves with semi-circular profiles formed into the pressure plate's inner radial surface which, in effect, forms the outer ring of a helical ball bearing arrangement. Matching grooves are similarly formed into the outer radial surface of the support element which, in effect, forms the inner ring of a helical ball bearing arrangement. When the pressure plate is mounted on the support element, the aligned grooves on the pressure plate and support element form circularly shaped helical races. A series of ball bearings, suitably caged, can be inserted into each race.
In another embodiment, the inner and outer rings having aligned helical grooves are separate elements from the pressure plate and support element and can be combined to form a complete helical ball bearing unit that is inserted between the support element and the pressure plate.
The major components of the embodiments comprise a support element, a pressure plate, a brake pad carrier, a brake pad, and a rotor, all of which are coaxial with each other, and a means of actuating the brake.
Within the various embodiments, the brake pad, which can be formed as a continuous annular ring of friction material or can comprise individual segments of friction material attached to or integral with a backing plate, is fixedly mounted on the brake pad carrier. The brake pad carrier is mounted on either the pressure plate or the support element in such a fashion that the brake pad carrier is coaxial with the pressure plate. The helical advance of the pressure plate maintains the face of the brake pad parallel to the rotor surface. This allows for equal loading or distribution of force between the brake pad and the rotor surface.
Also, the face of the pressure plate is fitted with features, such as, but not limited to, lugs or teeth, which engage features on the back of the brake pad carrier and couple the pressure plate and brake pad carrier together so that they rotate as one when the brake is actuated. The engagement features are designed to allow a small amount of rotational movement or slack sufficient to enable the pressure plate to rotate away from the brake pad carrier in order to unseize or disengage the brake. A return spring between the pressure plate and the support element, together with a friction minimizing element or features placed between the pressure-plate and the brake pad carrier, can be incorporated to assist and encourage such disengagement.
When the brake is applied, the actuator, which includes but is not limited to mechanical, hydraulic, pneumatic, spring, electric or magnetic systems, causes the pressure plate to rotate on the support element and move towards the brake pad carrier, pushing the brake pad into contact with the rotor. The actuator can include a multiplicity of actuators and the actuator(s) can be mounted on the support element, the vehicle, or some other fixed point. The actuator is mounted in such a manner so as to provide the most useful rotational actuation to the pressure plate. The most favorable location and direction of the actuator would be acting tangentially at the largest radius practical from the axle/brake assembly centerline. A return spring and wear adjustment mechanism may be incorporated into the means of actuation or mounted directly to the relevant components, the vehicle, or some other fixed point.
More advantages of the invention are that minimal clearance is needed between the pressure plate, brake pad carrier/brake pad, and the rotor, and that only a few degrees of rotation of the pressure plate on the support element is required to engage the brake. The amount of rotational movement is governed by the helix angle and lead of the thread or thread equivalent; for example a 5:1 lead ratio means that 5 mm of rotation (at the radius of the thread) results in 1 mm of axial movement. Given minimum friction, a mechanical advantage of 5:1, due to the leverage effect, would be generated.
In another embodiment of the invention, concentric arrangement of the brake elements enables multiple concentric pressure plates and brake pad carriers to be incorporated into the design of a particular brake depending upon the desired function and performance characteristics. Each pressure plate in a concentric arrangement can have a specific helical angle to determine its rate of axial motion and direction of rotation. Each pressure plate can have its own actuator or multiple actuators, or a single or multiple actuators can actuate all pressure plates simultaneously. Multiple actuators can be used to provide increased actuation force and/or redundancy. The outermost concentric pressure plate will generate the most braking torque, with each inner concentric pressure plate generating less torque. An inner pressure plate is suited to parking brake or emergency brake use.
The coaxial helical brake may be actuated by applying a tangential force to the pressure plate via a rotary actuator which creates a torque sufficient to rotate the pressure plate in relation to the support element. Such rotational actuation may be achieved by electric, hydraulic, pneumatic or mechanical means. Electric rotary actuators comprise electric motors such as, but not limited to, conventional electric motors, pancake motors, ring motors and stepper motors. Hydraulic and pneumatic rotary actuators comprise hydraulic or pneumatic motors respectively.
The rotary actuator may be mounted eccentrically or concentrically to the axis of the brake, and may be perpendicular or skewed to the axis of the brake. The rotary actuator may include gears, linkages, shafts and other mechanical means to effect the power conversion to drive the pressure plate. The rotary drive may be geared directly to the pressure plate by means of a corresponding gear on the pressure plate, by means of a cam which engages a corresponding feature on the pressure plate, or by means of a gear train including, but not limited to, spur gears or spur gear segments, helical gears, bevel gears, spiral bevel gears, worm gears, harmonic drives, sprockets operating in conjunction with chains or toothed belts, and other means of power transmission.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.
With the brake helically rotating in the same direction of rotor rotation this configuration is suitable for use as a safety brake or an emergency brake in such applications including elevators, cranes, lawnmowers and chain saws. When the helical rotation is in the same direction as rotor rotation, the brake will lock up or seize after a specific event or action triggers its actuation.
Referring to
A series of equidistantly spaced helical grooves 16 with semicircular profiles is formed into the pressure plate boss's inner surface 23, and a matching series of grooves 17 is formed into the outer surface 24 of the support element 10. When the pressure plate 11 is mounted on the support element 10 the aligned grooves 16 and 17 form circular races 18. A caged series of bearing balls 19 is inserted into each race 18.
A series of lugs 25 is located on the face of the pressure plate 11 and a similar series of lugs 26 is located on the back surface of the brake pad carrier 13. The lugs 25 and 26 are designed to engage when the pressure plate 11 is rotated towards the brake pad carrier 13 so that the brake pad carrier 13 rotates with the pressure plate 11. A small amount of rotational movement allows the pressure plate 11 to disengage and rotate away from the pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 27 or similar friction-minimizing technique is located on the face of the pressure plate 11, and a return spring 20 is affixed to both the pressure plate 11 and the support element 10.
Other friction minimizing techniques include interposing a low-friction slip plate 27 (see
An actuation mechanism 15 (shown in
A further embodiment of the invention is dependant upon the use of anti-lock braking (ABS) technology. As in the emergency brake described above, this embodiment has the helical rotation of the pressure plate 11 in the same direction as the rotor rotation. Due to the helical motion of the pressure plate 11 and the friction created between the brake pad 12 and the rotor 14, the brake pad 12 tends to tighten against the rotor 14, generating a self-energizing braking action that will ultimately lock up or seize the brake. Incorporating an electronic ABS system into this embodiment will prevent such lock-up and provide a powerful braking system. As shown below in other embodiments, a separate parking brake pressure plate, with or without a separate dedicated brake pad carrier, can be incorporated into this embodiment.
Referring to
A series of equidistantly spaced helical grooves 16 with semicircular profiles is formed into the outer pressure plate boss's inner surface 23, and a matching series of grooves 17 is formed into the outer surface 24 of the support element 10. When the outer pressure plate 11 is mounted on the support element 10 the aligned grooves 16 and 17 form circular races 18. A caged series of bearing balls 19 is inserted into each race 18.
A series of lugs 25 is located on the face of the outer pressure plate 11 and a similar series of lugs 26 is located on the back surface of the outer brake pad carrier 13. The lugs 25 and 26 are designed to engage when the outer pressure plate 11 is rotated towards the outer brake pad carrier 13 so that the outer brake pad carrier 13 rotates with the outer pressure plate 11. A small amount of rotational movement allows the outer pressure plate 11 to disengage and rotate away from the outer pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 27 or similar friction-minimizing device is located on the face of the outer pressure plate 11, and a return spring 20 is affixed to both the outer pressure plate 11 and the support element 10.
An actuation mechanism 15 (shown in
An inner pressure plate 29 has a boss 30 affixed to or integral with its rear surface. An annular inner brake pad 31 is affixed to the front surface of an inner brake pad carrier 32. The inner brake pad may also comprise individual segments of friction material. The inner pressure plate 29 is fitted with a circular flange 33, which locates and centers the inner brake pad carrier 32.
A series of equidistantly spaced helical grooves 34 with semicircular profiles is formed into the inner pressure plate boss's outer surface 35, and a matching series of grooves 36 is formed into the inner surface 37 of the support element 10. When the inner pressure plate 29 is mounted on the support element 10 the aligned grooves 34 and 36 form circular races 38. A caged series of bearing balls 39 is inserted into each race 38.
A series of lugs 40 is located on the face of the inner pressure plate 29 and a similar series of lugs 41 is located on the back surface of the inner brake pad carrier 32. The lugs 40 and 41 are designed to engage when the inner pressure plate 29 is rotated towards the inner brake pad carrier 32 so that the inner brake pad carrier 32 rotates with the inner pressure plate 29. A small amount of rotational movement allows the inner pressure plate 29 to disengage and rotate away from the inner pad carrier 32 when the brake is released. To assist such disengagement, a thrust race 42 or similar friction-minimizing device is located on the face of the inner pressure plate 29, and a return spring 43 is affixed to both the inner pressure plate 29 and the support element 10.
An inner brake actuation mechanism (not shown) is mounted on the support element in such a fashion so as to provide the most useful rotational actuation to the inner pressure plate. A brake adjuster assembly may be of any appropriate conventional type needing no detailed description for the purpose of this invention. When the inner brake is applied the inner brake actuator, which is preferably mechanical but also could be hydraulic, pneumatic, spring, electric or magnetic systems, causes the inner pressure plate 29 to rotate on the support element 10 and move towards the inner brake pad carrier 32, pushing the inner brake pad 31 into contact with the rotor 14 and in the same rotational direction as rotor 14. Because the helical rotation of the inner pressure plate is in the same direction as the rotor rotation, the inner brake pad 31 can cause the rotor 14 to seize or lock-up, thereby providing an effective parking or emergency brake. A return spring and wear adjustment mechanism may be incorporated into the means of inner actuation or mounted directly to the relevant components, the vehicle, or some other fixed point.
Referring to
A splined torque tube 50 is affixed, at its forward end 51, to the support element 10. A back plate 52 is affixed to the back end of the torque tube 50. A series of annular brake pad stators 54, each stator having appropriately placed tangs 55, which engage with the splines of the torque tube 50, is mounted on the torque tube 50. The inner section of the aircraft's wheel that surrounds the brake 56 is fitted with splines 57. A series of rotors 14, each rotor having appropriately placed tangs 58 which engage with the aforementioned wheel splines 57, is mounted on the wheel in such a manner that the rotors 14 and stators 54 alternate.
A series of equidistantly spaced helical grooves 16 with semicircular profiles is formed into the pressure plate boss's inner surface 23, and a matching series of grooves 17 is formed into the outer surface 24 of the support element 10. When the pressure plate 11 is mounted on the support element 10 the aligned grooves 16 and 17 form circular races 18. A caged series of bearing balls 19 is inserted into each race 18.
A series of lugs 25 is located on the face of the pressure plate 11 and a similar series of lugs 26 is located on the back surface of the brake pad carrier 13. The lugs 25 and 26 are designed to engage when the pressure plate 11 is rotated towards the brake pad carrier 13 so that the brake pad carrier 13 rotates with the pressure plate 11. A small amount of rotational movement allows the pressure plate 11 to disengage and rotate away from the pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 27 or similar friction-minimizing device is located on the face of the pressure plate 11, and a return spring 20 is affixed to both the pressure plate 11 and the support element 10.
An actuation mechanism 15 is mounted on the support element in such a fashion so as to provide the most useful rotational actuation to the pressure plate. A brake adjuster assembly may be of any appropriate conventional type. When the brake is applied the actuator 15, which includes but is not limited to mechanical, hydraulic, pneumatic, spring, electric or magnetic systems, causes the pressure plate 11 to rotate on the support element 10 and move toward the stack of rotors 14 and stators 54 forcing them into contact with each other to create the braking action. The actuator 15 can include a multiplicity of actuators and the actuator(s) can be mounted on the support element 10, the vehicle, or some other fixed point. The actuator 15 can be mounted in such a manner so as to provide the most useful rotational actuation to the pressure plate 11. The most favorable location and direction of the actuator 15 would be acting tangentially at the largest radius practical from the axle/brake assembly centerline, as shown in
Referring to
A series of equidistantly spaced helical grooves 16 with semicircular profiles is formed into the outer pressure plate boss's inner surface 23, and a matching series of grooves 17 is formed into the outer surface 24 of the support element 10. When the outer pressure plate 11 is mounted on the support element 10 the aligned grooves 16 and 17 form circular races 18. A caged series of bearing balls 19 is inserted into each race 18.
A series of lugs 25 is located on the face of the outer pressure plate 11 and a corresponding series of lugs 26 is located on the back surface of the brake pad carrier 13. The lugs 25 and 26 are designed to engage when the outer pressure plate 11 is rotated toward the brake pad carrier 13 so that the brake pad carrier 13 rotates with the outer pressure plate 11. A small amount of rotational movement allows the outer pressure plate 11 to disengage and rotate away from the pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 27 or similar friction-minimizing device is located on the face of the outer pressure plate 11, and a return spring 20 is affixed to both the outer pressure plate 11 and the support element 10.
An outer actuation mechanism 15 (shown in
An inner pressure plate 29 has a boss 30 affixed to or integral with its rear surface. The brake pad 12 remains affixed to the front surface of the brake pad carrier 13. The inner pressure plate 29 is fitted with a circular flange 33 that locates and centers the brake pad carrier 13.
A series of equidistantly spaced helical grooves 34 with semicircular profiles is formed into the inner pressure plate boss's outer surface 35, and a matching series of grooves 36 is formed into the inner surface 37 of the support element 10. When the inner pressure plate 29 is mounted on the support element 10 the aligned grooves 34 and 36 form circular races 38. A caged series of bearing balls 39 is inserted into each race 38.
A series of lugs 40 is located on the face of the inner pressure plate 29 and a corresponding series of lugs 41 is located on the back surface of the brake pad carrier 13. The lugs 40 and 41 are designed to engage when the inner pressure plate 29 is rotated towards the brake pad carrier 13 so that the brake pad carrier 13 rotates with the inner pressure plate 29. A small amount of rotational movement allows the inner pressure plate 29 to disengage and rotate away from the pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 42 or similar friction-minimizing device is located on the face of the inner pressure plate 29, and a return spring 43 is affixed to both the inner pressure plate 29 and the support element 10.
An inner brake actuation mechanism (not shown) is mounted on the support element in such a fashion so as to provide the most useful rotational actuation to the inner pressure plate. A brake adjuster assembly may be of any appropriate conventional type. When the vehicle is traveling in reverse and the brake is applied, the actuation system selects the inner brake actuator, which includes but is not limited to mechanical, hydraulic, pneumatic, spring, electric or magnetic systems, causing the inner pressure plate 29 to rotate on the support element 10 and move towards the brake pad carrier 13, pushing the brake pad 12 into contact with the rotor 14 in the opposite rotational direction as rotor 14. Because the helical rotation of the inner pressure plate 29 is in the opposite direction as the rotor rotation when the vehicle is traveling in reverse, the brake pad 12 does not cause the rotor 14 to seize or lock-up. A return spring and wear adjustment mechanism may be incorporated into the means of inner actuation or mounted directly to the relevant components, the vehicle, or some other fixed point.
In this embodiment, the pressure plate 11 moves toward the support element 10 when the brake is applied as opposed to the previous embodiments where the pressure plate moved away from the support element. The brake pad carrier 13 and brake pad 12 are located outboard of the rotor 14 and the pressure plate 11 is constructed to extend over the brake pad carrier 13 and brake pad 12. The pressure plate 11 can then pull the brake pad carrier 13 and brake pad 12 toward the outer face of the rotor 14 as the pressure plate 11 moves toward the support element 10.
The rotor 14 may be of the floating type, located on the axle, shaft or hub by means of splines or pins. A second brake pad 12a is affixed to the support element 10 inboard of the floating rotor 14. When the brake is applied, the pressure plate forces the outer brake pad 12 into contact with the floating rotor 14 which in turn is forced into contact with the inner brake pad 12a creating the braking action.
This embodiment works equally well with multiple floating rotors and multiple floating intermediate brake pads similar to the above-described embodiment employing multiple rotors and stators.
Referring to
A series of equidistantly spaced helical grooves 16 with semicircular profiles is formed into the pressure plate boss's inner surface 23, and a matching series of grooves 17 is formed into the outer surface 24 of the support element 10. When the pressure plate is mounted on the support element, the aligned grooves 16 and 17 form circular races 18. A caged series of bearing balls 19 is inserted into each race.
A series of lugs 25 is located on the face of the pressure plate 11 and a similar series of lugs 26 is located on the back surface of the brake pad carrier 13. The lugs 25 and 26 are designed to engage when the pressure plate 11 is rotated toward the brake pad carrier 13 so that the brake pad carrier 13 rotates with the pressure plate 11. A small amount of rotational movement allows the pressure plate 11 to disengage and rotate away from the brake pad carrier 13 when the brake is released. To assist such disengagement, a thrust race 27 or similar friction-minimizing device is located on the face of the pressure plate 11, and a return spring 20 is affixed to both the pressure plate 11 and the support element 10.
An actuation mechanism 15 (shown in
A further embodiment of the invention relates to its application to aircraft-type brakes that comprise a stack of alternating rotors and stators, the rotors being keyed to rotate with the wheel and the stators being keyed to a splined torque tube which is affixed to the vehicle and does not rotate with the wheel. The brake stack can comprise a single rotor and a single stator or a multiplicity of rotors and stators.
As described in a preceding embodiment relating to multiple rotor and stator brakes and illustrated in
Conversely, it may be advantageous in certain application to locate the pressure plate radially within the support element in a similar fashion to pressure plate 29 shown in
At least one of the helical guide tracks 61 has its outer surface configured as a spur gear segment 62. Gear train 63 connects the actuator 64 with the spur gear segment 62. Spur gear segment 62 has sufficient axial width to permit pressure plate 11 to accommodate the maximum axial travel allowed by the helical guide tracks 61. When the shaft of the actuator 64 is rotated in a clockwise direction it causes, via the gear train 63, the pressure plate 11 to rotate in an anti-clockwise direction causing the track rollers 60 located within the helical track guides 61 to move the pressure plate 11 axially towards the stack of rotor 14 and stator 54 discs forcing them against each other to create friction and brake torque. The low friction interstitial element 27 disconnects the helical action from brake torque. Reversing the actuator shaft direction of rotation moves the pressure plate away from the disc stack.
Having described and illustrated the principles of the invention in the preferred embodiments thereof it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. We claim all modifications and variations coming within the spirit and scope of the invention. The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications and variations would come within the scope of this invention.
This application claims priority from U.S. provisional patent application 60/711,804, filed Aug. 26, 2005, and is a continuation-in-part of PCT application No. PCT/US2005/03781, filed Feb. 3, 2005, which claimed priority from U.S. provisional patent application Ser. No. 60/542,523, filed Feb. 5, 2004, all incorporated by reference herein.
Number | Date | Country | |
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60711804 | Aug 2005 | US | |
60542523 | Feb 2004 | US |
Number | Date | Country | |
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Parent | PCT/US05/03781 | Feb 2005 | US |
Child | 11461912 | Aug 2006 | US |