WO2008063193A1

WO2008063193A1 - Coaxial helical brake with rotary actuation

Info

Publication number: WO2008063193A1
Application number: PCT/US2006/061222
Authority: WO
Inventors: Lester J. Erlston; Michael D. Miles
Original assignee: Erlston Lester J; Miles Michael D
Priority date: 2006-11-22
Filing date: 2006-11-22
Publication date: 2008-05-29

Abstract

Multiple coaxial helically actuated disc brake including multiple pressure plate rotationally actuated and helically guided by support structure to axially engage a brake pad earner and rotor Pressure plate, brake pad earner and rotor are coaxial with the rotating member upon which the coaxial disc brake acts A low friction device, mateπal or element is applied between pressure plate and adjacent pad earner stator Multiple rotary actuators are mounted on the support structure and coupled to rotate the pressure plate through a dπve arranged to remain coupled throughout a range of axial movement of the pressure plate that permits the entire stack of rotors and stators to be engaged Dual-motor actuators provide fail-safe redundancy.

Description

COAXIAL HELICAL BRAKE WITH ROTARY ACTUATION

FIELD OF THE INVENTION

This invention relates to disc brakes and more particularly to coaxially helically acting disc brakes.

BACKGROUND OF THE INVENTION

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. Patent 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-rnetal 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.hlm>. The following excerpt explains some of the reasons: The parking brake (a.k.a. emergency brake) system controls the rear brakes through a series of steel cables that are connected to either a hand lever or a foot pedal. The idea is that the system is fully mechanical and completely bypasses the hydraulic system so that the vehicle can be brought to a stop even if there is a total brake failure. On drum brakes, the cable pulls on a lever mounted in the rear brake and is directly connected to the brake shoes. This has the effect of bypassing the wheel cylinder and controlling the brakes directly.

Dis[c] brakes on the rear wheels add additional complication for parking brake systems. There are two main designs for adding a mechanical parking brake to rear dis[c] brakes. The first type uses the existing rear wheel caliper and adds a lever attached to a mechanical corkscrew device inside the caliper piston. When the parking brake cable pulls on the lever, this corkscrew device pushes the piston against the pads, thereby bypassing the hydraulic system, to stop the vehicle. This type of system is primarily used with single piston floating calipers; i C the caliper is of the four (or multiple) piston fixed type then that type of system, can't be used. The other system uses a complete mechanical drum brake unit mounted inside the rear rotor. 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. Patent 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. Patent No. 4,809,824 to Fargier et al., Method and Device for Actuating a Braking Mechanism By a Rotating Electric Motor.

PCT Application No. PCT/US2005/03781 (WO 2005/076986), included herein, discloses a helically-operated disc brake useful for automobiles and trucks, which can incorporate a parking brake. This brake, when constructed with one or only a few brake pad/carrier discs, can be actuated by a simple linear actuator applying a short tangential actuation stroke, as shown and described in connection with FIG. 9. A large stack of brake pad/carrier discs and rotors, however, require a longer range of motion, and further this range of motion can shift as the stack wears. U.S. Pat. No. 4,596,316 describes a multi-disk structure for aircraft brakes in which rotary drive motors actuate the brake. This structure, however, is very complicated, requiring decoupling of axial and rotary motion of the ram member, and has never achieved acceptance. Accordingly, a better way is needed to actuate a helically- operated disc brake in which the pressure plate moves both axially and rotationally.

SUMMARY OF THE INVENTION

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 semicircular 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.

In another embodiment the helical device, which may include track rollers in helical tracks, balls or rollers in helical races and screw thread features, is located at a smaller radius than the tangential actuation radius. In typical aircraft brake applications space and weight constraints dictate that maximum axial compactness of the brake mechanism is desirable. To accommodate rotary actuators of a size having the required torque, and to position such rotary actuators to apply tangential force at the maximum practical diameter of the pressure plate, it is preferable to locate the coaxial helical device at a smaller radial distance from the brake axis than the radius of the actuator gear interface with the driven gear mounted on the pressure plate. This arrangement permits radial space outward of the helical device to mount the rotary actuators and their related gear trains in order to transmit the drive to the pressure plate while enabling optimized axial compactness of the brake mechanism. A further embodiment of the invention employs a pinion fixedly mounted on the shaft of an electric motor or electric gear-motor that engages a driven gear or gear segment fixedly mounted on the pressure plate. Because the pressure plate moves axially away from the pinion, the driven gear or gear segment must be sufficiently wide so that it usefully engages the pinion over the full axial travel of the pressure plate. Alternatively, and equally functional, the pinion can be sufficiently wide in order to usefully engage a narrower driven gear or gear segment fixedly mounted on the pressure plate. In both cases the teeth of the pinion slide against the teeth of the driven gear or gear segment as the pressure plate moves axially away from the pinion. The gear teeth can be parallel or angled to the axis. In another embodiment of the invention, the pinion and driven gear or gear segment are captured within a guide device, which may be integral with or affixed to either the pinion or the driven gear or gear segment, so that they are fixed in axial relation to each other. In order to allow the pressure plate to move axially away from the fixed rotary motor either the pinion must be slidably located on the motor drive shaft, by means of splines or similar sliding device, with the driven gear or gear. segment fixed to the pressure plate. Alternatively, the pinion must be fixed to the motor drive shaft and the driven gear or gear segment slidably located on the pressure plate by means of splines, shafts, pins or other means of achieving an axial sliding function.

To improve the redundancy and fail-safe functionality of the electric gear motor actuators each actuator may be fitted with two electric motors. Where a worm and roller wheel is employed in the gear-motor actuator electric motors may drive both ends of the worm. Where spur, helical or bevel gears are employed in the gear- motor actuator the two electric motors may have a common output shaft to drive the gear or gear train. The two motors may be separately driven via electrical drive circuitry so that if one motor or its drive circuit fails the other motor can drive the actuator.

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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of an embodiment of a coaxial helical brake according to the invention.

FIG. 2 is a cross-sectional view of the coaxial helical brake of FIG. 1. FIG. 3 is a perspective exploded view of another embodiment of a coaxial helical brake according to the invention.

FIG. 4 is a cross-sectional view of the coaxial helical brake of FIG. 3. FIG. 5 is a perspective exploded view of yet another embodiment of a coaxial helical brake according to the invention. FIG. 6 is a cross-sectional view of the coaxial helical brake of FIG. 5.

FIG. 7 is a perspective exploded view of yet another embodiment of a coaxial helical brake according to the invention.

FTG. 8 is a cross-sectional view of the coaxial helical brake of FIG. 7. FIG. 9 is a perspective view of the assembled coaxial helical brake of FIG. 1 showing a brake actuator.

FIG. 10 is a cross-sectional view of yet another embodiment of a coaxial helical brake according to the invention for use with axles using ball bearings for axle bearings. FIG. 11 is a top plan view of a brake pad carrier according to an embodiment of the invention showing segmented brake pad material.

FIG. 12 is a top plan view of a segmented brake pad carrier according to another embodiment of the invention.

FIG. 13 is a perspective exploded view of a coaxial disc brake according to another embodiment of the invention showing the segmented brake pad carrier of

FIG. 12.

FIG. 14 is a perspective view of an aircraft-type multiple rotor and stator brake application according an embodiment of the invention.

FIG. 15 is a detailed perspective cut-away view of the brake application of FTG. 14.

FIG. 16 is a detailed perspective view of the brake application of FIG. 14 showing the Pressure Plate in phantom line.

FIG. 17 is a half cross-sectional view of the brake application of FIG. 14 with the tire removed. FIG. 18 is a perspective cut-away view of the brake application of FIG. 14 showing the Pressure Plate and the Stack of Rotors and Stators partially cut away.

FIG. 19 is a cross-sectional view of the brake application of FIG. 14 showing a rotary actuator.

FIG. 20 is a front cross-sectional elevation of the brake application of FIG. FIGS. 21 — 23 are perspective views of an alternative embodiment of the aircraft brake.

FIGS. 24a and 24b are partial cross-sectional views of a brake similar to that of FIGS. 21 — 23, but with multiple rotors, shown in released and applied positions respectively.

FIG. 25 is a partial cross-sectional view of an alternative embodiment to the embodiment illustrated in FIGS. 24a and 24b.

FIG. 26 is a perspective view of another embodiment of the foregoing structures with dual-motor rotary drive actuators. Elements in FIGS. 21 - 26 common to the embodiment of FIGS . 14 - 20 have the same reference number plus 100.

DETAILED DESCRIPTION

FIGS. 1 and 2 show an embodiment of a coaxial helical brake utilizing a single pressure plate 11 and a single brake pad carrier 13. With the brake helically rotating in a direction opposite of rotor rotation, this configuration is suitable for use on vehicles that do not require a parking brake like, for example, motorcycles and bicycles. 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 FIGS. 1 and 2, a support element 10 is fitted with brackets (not shown) to mount it to the vehicle or item to be braked (not shown). A pressure plate 11 has a boss 21 affixed to or integral with its rear surface. An annular brake pad 12 is affixed to the front surface of a brake pad carrier 13. The brake pad may also comprise individual segments of friction material. The pressure plate 11 is fitted with a circular flange 22, which locates and centers the brake pad carrier 13. A rotor 14 is affixed to the rotatable hub or wheel of the vehicle or item to be braked (not shown).

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 FIG. 13) between the pressure plate 11 and the brake pad carrier 13. The slip plate 27 can be made of a graphite-based material or can be made of a material impregnated with graphite or some other low-friction material. Minimizing friction can also be achieved by applying a coating, finish or surface treatment to either or both the engagement surfaces of the pressure plate 11 and the brake pad carrier 13. An example of such a coating is the Diamond-Like Carbon (DLC) coating manufactured by Bekaert Advanced Coating Technologies of Amherst, NY.

An actuation mechanism 15 (shown in FIG. 9) is mounted on the support element 10 in such a fashion so as to provide the most useful rotational actuation to the pressure plate 11. A brake adjuster assembly may be of any appropriate conventional. 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 towards the brake pad carrier 13, pushing the brake pad 12 into contact with the rotor 14. 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 FIG. 9. 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. 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.

FIGS. 3 and 4 show another embodiment of a coaxial helical brake utilizing inner and outer concentrically arranged pressure plates. The outer pressure plate 11 has a helical rotation opposite of the rotor rotation and the inner pressure plate 29 has a helical rotation in the same direction as rotor rotation forming a safety or parking brake. The inner pressure plate 29, which can be mechanically actuated for safety reasons, can engage the same brake pad carrier 13 as the outer pressure plate 11 or engage a separate dedicated parking brake pad carrier 32. This configuration of concentrically arranged pressure plates is suited to most wheeled vehicles including motorcars, aircraft and railway vehicles, that require additional safety or parking brakes. Referring to FIGS. 3 and 4, a support element 10 is fitted with brackets (not shown) to mount it to the vehicle (not shown). An outer pressure plate 11 has a boss 21 affixed to or integral with its rear surface. An annular outer brake pad 12 is affixed to the front surface of an outer brake pad carrier 13. The outer brake pad may also comprise individual segments of friction material. The outer pressure plate

11 is fitted with a circular flange 22. which locates and centers the outer brake pad carrier 13. A rotor 14 is affixed to the rotatable hub or wheel of the vehicle to be braked (not shown).

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 I L 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 FIG. 9) is mounted on the support element 10 in such a fashion so as to provide the most useful rotational actuation to the outer pressure plate 11. 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 outer pressure plate 11 to rotate on the support element 10 and move towards the outer brake pad carrier 13, pushing the outer brake pad 12 into contact with the rotor 14. 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 outer 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 ceriterline, as shown in FIG. 9. 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. 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 stipport 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. FIGS. 5 and 6 show yet another embodiment of a coaxial helical brake that utilizes multiple rotors and brake pads. This configuration is suited for use in large vehicles and high-speed aircraft. In order to increase braking torque in these heavy- duty applications, the embodiment includes a stack of alternating rotors 14 and stators 54 with the rotors being keyed to a rotate with the vehicle's wheels and with the stators 54 keyed to a splined torque tube 50 and not rotating with the vehicle's wheels. The torque tube 50 has a cylindrical shape and is typically made of steel and is affixed to or integral with the support element 10 but can be affixed to the vehicle itself or some other fixed point. The pressure plate 11 pushes the brake pad carrier 13 toward the stack of rotors 14 and stators 54 forcing them into contact with each other to create the braking action. As in the previous embodiment, a parking brake pressure plate, with or without a separate brake pad carrier can be incorporated into this embodiment.

Referring to FIGS. 5 and 6, a support element 10 is fitted with brackets (not shown) to mount it to the vehicle (not shown). A pressure plate 11 has a boss 21 affixed to or integral with its rear surface. An annular brake pad 12 is affixed to the front surface of a brake pad carrier 13. The pressure plate 1 1 is fitted with a circular flange 22, which locates and centers the brake pad carrier 13.

A spliiied 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 lube 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 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 FIG. 9. 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. FIGS. 7 and 8 show yet another embodiment of a coaxial helical brake utilizing contra-rotating concentrically arranged pressure plates that engage a single brake pad carrier and brake pad. The helical rotation of the outer pressure plate 11 rotates opposite the rotor rotation when the vehicle travels forward. The helical rotation of the inner pressure plate 29 rotates opposite the rotor rotation when the vehicle travels in reverse. This configuration is suited to a brake-by- wire actuation system that can selectively actuate the outer pressure plate 11 when the vehicle is traveling forwards or actuate the inner pressure plate 29 when the vehicle travels in reverse. A parking brake pressure plate, with or without a dedicated brake pad carrier, can be incorporated into this embodiment. Referring to FIGS. 7 and 8, a support element 10 is fitted with brackets (not shown) to mount it to the vehicle (not shown). An outer pressure plate 11 has a boss 21 affixed to or integral with its rear surface. An annular brake pad 12 is affixed to the front surface of brake pad carrier 13. The brake pad may also comprise individual segments of friction material. The outer pressure plate 11 is fitted with a circular flange 22 that locates and centers the brake pad carrier 13. A rotor 14 is affixed to the rotatable hub or wheel of the vehicle to be braked (not shown).

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 FIG. 9) is mounted on the support element 10 in such a fashion so as to provide the most useful rotational actuation to the outer pressure plate 11. A brake adjuster assembly may be of any appropriate conventional type. When the vehicle is traveling forward and the brake is applied, an actuation system (not shown) selects the outer actuator 15, which includes but is not limited to mechanical, hydraulic, pneumatic, spring, electric or magnetic systems, causing the outer pressure plate 11 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. The outer 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 outer actuator 15 can be mounted in such a manner so as to provide the most useful rotational actuation to the outer pressure plate 11. The most favorable location and direction of the outer actuator 15 would be acting tangentially at the largest radius practical from the axle/brake assembly centerline, as shown in FIG. 9. 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.

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 W

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. FIG. 10 is a cross-sectional view of yet another embodiment of a coaxial helical brake that eliminates axial or sideways loading on axle bearings. This configuration is especially suited for applications where conventional ball bearings rather than tapered bearings are used for axle bearings, as is the case with most karts. In order to eliminate axial loading from being transmitted to the axle bearings, all axial loading must be transmitted to the support element 10 which itself transmits such axial loading to the frame of the vehicle.

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 1 1 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 FIG. 10, pressure plate 11 has a boss 21 affixed to or integral with its rear surface. An annular outer brake pad 12 is affixed to the front surface of the brake pad carrier 13. The pressure plate 1 1 is fitted with a circular flange 22, which locates and centers the brake pad carrier 13. A floating rotor 14 is located by means of splines 14a to the driven shaft 10b. A second brake pad 12a is fixedly mounted to the support element 10 inboard of the floating rotor 14.

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 scries 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 1 1 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 11₅ and a return spring 20 is affixed to both the pressure plate 11 and the support element 10.

An actuation mechanism 15 (shown in FIG. 9) is mounted on the support element 10 in such a fashion so as to provide the most useful rotational actuation to the pressure plate 11. 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 towards the brake pad carrier 13, pushing the brake pad 12 into contact with the rotor 14. The actuator 15 can include a multiplicity of actuators and the acLuator(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 FIQ. 9. 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.

FIG. 11 shows a top plan view of a single brake pad carrier 13 with segmented brake pad material 72. The brake pad material 12 is segmented into pieces 72 for easier manufacturing of the brake pad material and easier installation and maintenance of the brake pad material. FIG. 12 shows a top plan view of a segmented brake pad carrier 70. Here, the brake pad carrier 13 is segmented into three brake pad carrier segments 70 for easier installation and removal from the support element 10.

FIG. 13 shows a perspective exploded view of a coaxial disc brake 100 according to another embodiment of the invention. In FIG. 13, brake pad carrier segments 70 are arranged in the support element 10 such that the segments 70 can be installed and removed from the disc brake 100 without the need to further disassemble the disc brake 100 or remove the rotating member (not shown) upon which the disc brake 100 acts. FIG. 13 also shows the previously described low-friction material 27 interposed between the pressure plate 11 and the brake pad carrier segments 72. The low-friction material 27, shown here mounted on the engagement surface of the pressure plate 11, allows for easier disengagement of the pressure plate 11 from the brake pad carrier segments 72 upon completion of braking. 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 FIGS. 5 and 6, that embodiment employs a radially outer support element 10 which supports a radially inner pressure plate 1 1 in siich a manner that the pressure plate 11 is rotatable in a helical motion relative to the support element 10. Light weight is an important design criterion for aircraft components. In order to reduce the weight of the brake, the radial dimension of the support element may be reduced by arranging the support element as the radially inner component and the pressure plate as the radially outer component. In this arrangement, the pressure plate is pressure plate is positioned radially outward of the support element so that the entire pressure plate, or a substantial portion of the pressure plate, is radially outward of the outer surface of the support element, as depicted in FIGS. 14-18. This structure reduces the size and weight of the support element which is advantageous to reducing the overall brake weight and size. e.g. for aircraft use.

Conversely, it maybe advantageous in certain application to locate the pressure plate radially within the support element in a similar fashion to pressure plate 29 shown in FIGS. 3 and 4. There, the pressure plate is positioned radially inward of the support element and the entire pressure plate, or a substantial portion of the pressure plate, is inside the inner surface of the support element.

FIG. 14 is a perspective view of an aircraft-type multiple rotor and stator brake application according an embodiment of the invention. A fixed torque tube 50 is affixed to an aircraft strut 66 that is structurally connected to the aircraft body (not shown). The support element 10 and a first end each of three actuators 15 are affixed to the non-rotating torque tube 50. The second end of each actuator 15 is connected to the radially outwardly positioned pressure plate 11 such that the actuators 15 apply a tangential force and motion to the pressure plate 11 when actuated. The pressure plate 11 is helically engaged to an outer surface of the non-rotating support element

10. The brake rotors 14 are keyed to the rotating wheel. While three actuators 15 are shown in FIG. 14, it is contemplated that one, two or more than three actuators could be implemented depending on the force requirements.

FIG. 15 is a detailed perspective cut-away view of the brake application of FIG. 14. The tire, a portion of the pressure plate and one of the three actuators are not shown so that the helical elements 28 on the outer surface of the support element and the stack of rotors 14 and stators 54 can be more clearly shown. The actuators 15 are arranged to apply a tangential force and thus motion to the pressure plate 11. The helical elements 28 on the outer surface of the support element 10 then cause the pressure plate 11 to move helicalfy against the stack of rotors 14 and stators 54.

FIG. 16 is a detailed perspective view of the brake application of FIG. 14 showing the pressure plate 11. The pressure plate 11 is positioned to be completely radially outward of the support element 10. This allows for a smaller support element than in other embodiments which results in smaller and lighter brake components. FIG. 17 is a half cross-sectional view of the brake application of FIG. 14 with the tire removed. The support element 10, the stators 14 and the back plate 52 are all affixed to the non-rotating torque tube 50 which is connected to the aircraft strut 66. The pressure plate 11 is helically engaged through the helical elements 28 with the support element 10 so that it also does not rotate except through the helical engagement during brake actuation. The rotors 14 are keyed to the rotating wheel. FIG. 18 is a perspective cut-away view of the brake application of FIG. 14 showing the pressure plate 11 and the stack of rotors 14 and stators 54 partially cut away. The spindle 61 is journalled on the torque tube 50 to allow rotation of the wheel and the rotors 14 keyed to the wheel. The torque tube 50 is affixed to the strut

66 with the support element 10 and the stators 54 affixed to the torque tube 50. The support element 10 supports the radially outwardly positioned pressure plate 11 with the helical elements 28 helically engaging the pressure plate 11.

FIG. 19 is a side cross-sectional view of an aircraft-type multiple rotor and stator brake application according an embodiment of the invention shown in FIG. 14 and described below. FIG. 20 is a front cross-sectional view of the embodiment shown in FIG. 19. In the embodiment illustrated in Figures 19 and 20 support element 10 has three equidistantly spaced track rollers 60 affixed to its outer surface. Pressure plate 11 has three equidistantly spaced helical guide tracks 61 machined or cast into its inner surface, the helical guide tracks being dimensioned to accept track rollers 60. A single rotary actuator 64, which can be either an electric or a hydraulic motor, and gear train 63 assembly is shown, although additional actuators and gear trains can be employed for fail-safe functionality, redundancy or for applying higher forces. Actuator 64 is mounted on the actuator mounting bracket 65 which is affixed to or integral with support element 1.0. Support element 10 is affixed to torque tube

50. A stack of rotor 14 and stator 54 discs are located on torque tube 50.

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 geax 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.

FIG. 21 shows pressure plate 111 rotatably mounted on support element 110 with rotary actuators, such as electric gear motors 164, affixed to support element 110. Friction material 112 is affixed to stator pad carriers 154. FIG. 22 depicts an inside view of pressure plate 111 with support element

110 removed. Pinions 163 engage driven gear segments 162 mounted inside the periphery of pressure plate 111. A series of track rollers 160 mounted on support element 110 run in helical tracks 161 on pressure plate 111. Splined torque tube 150 is mounted on support element 110. One or all of the gear motors 164 may employ an internal worm and roller wheel drive mechanism 175 coupling each motor to the drive gear 163. When the motor is powered in either direction it can rotate gear 163 to advance or retract the pressure plate. When the motor is de- energized, rotation of the pressure plate cannot back-drive the worm and roller wheel drive mechanism. TMs state can therefore serve as a parking brake which can automatically be engaged through appropriate controls when the brake is applied.

FIG. 23 shows inside views respectively of facing sides of support element 110 (with track rollers 160 and pinions 163) and pressure plate 111 (with helical tracks 161 and driven gear segment 162).

FIGS. 24a and 24b are cross section views of the brake in released and applied positions respectively. Pressure plate 111 is rotatably mounted on support element 110 by means of a series of radially spaced track rollers 160 affixed to support element 110 which run in a circumrerentially distributed series of helically shaped tracks 161 located in pressure plate 1 11. A rotary actuator 164 is mounted on support element 110. Actuator 164 has a drive shaft 168 on which is mounted pinion 163 that engages teeth of driven gear segment 162 affixed to pressure plate 11 1. The axial width, of gear segment 162 is sufficiently wider than the axial width of pinion 163 to permit the desired axial travel of the pressure plate 111.

Torque tube 150 is mounted on support element 110 and is fitted with a back plate 152. Stator pad carriers 154 are mounted in a splined fashion on torque tube 150 so as to allow them to move axially on torque tube 150. Friction material 112 is affixed to the faces of the stator pad carriers 154 which face the rotors 114 which are located in a splined fashion on splines 157 inside the wheel rim 156. Pressure plate 111 has a low friction element 127, such as Diamond-Like Carbon (DLC) coating on its surface facing innermost stator pad carrier 154. When the brake is applied, actuator 164 rotates drive shaft 168 and pinion

163 which rotates pressure plate 1 11 by means of engagement with gear segment 162. Since pressure plate 162 is rotatably mounted on support element 110 by means of a helical device comprising track rollers 160 running in helically shaped tracks 161, pressure plate 111 moves axially away from actuator 164 and pinion 163. The wide gear segment 162 enables a constant drive engagement between pinion 163 and driven gear segment 162 as pressure plate 111 moves axially away from actuator 164 towards the stack of stators 154 and rotors 1 14. Pressure plate 111 axially forces stators 154 and rotors 114 against back plate 152 to create braking friction. Low friction element 127 enables smooth disengagement or decoupling of the pressure plate 111 from the innermost stator pad carrier 154 by preventing the helically rotating pressure plate 111 from tightening and seizing against the stator pad carrier 154.

FIG. 25 depicts a further embodiment of the invention wherein actuator drive shaft 168 is supported by bearing 172 mounted in support bracket 173 affixed to or integral with support element 110. Drive shaft 168 is provided with splined section

170. Pinion 163 is provided with a correspondingly splined central hole so that it can slide axially on splined section 170 while transmitting drive to driven gear segment 162 fixedly mounted on pressure plate 111. Guide device 169 is affixed to or integral with gear segment 162 and captures both sides of pinion 163 so that pinion 163 moves along splined section 170 to remain axially aligned with gear segment 169 and moves axially with gear segment 169 as pressure plate 111 moves axial Iy away from actuator 164 when the brake is applied.

FIG. 26 shows dual-motor electric gear motor actuators 164, employing internal worm and roller wheel drive mechanisms 175 (see FIG. 21), mounted on support element 110 of a coaxial helical brake. Each gear motor actuator 164 is fitted with two electric motors 174 driving both ends of the worm gear.

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.

Claims

1. A coaxial disc brake comprising: a brake support structure mounted to a non-rotating structure associated with a rotating member; one or more rotors, each having a braking surface, coupled to the rotating member; one or more brake pad carriers coupled non-rotatably to the brake support structure and axially slidable to engage a braking surface against an adjacent braking surface of one of the rotors; brake pad material attached to the braking surface of each brake pad carrier; a pressure plate supported for axial and rotational movement by the brake support structure and positioned on a side of an adjacent one of the brake pad carrier opposite the rotor; the rotor, brake support structure, brake pad carrier, and pressure plate being arranged coaxial to the rotating member; and the brake support structure being arranged to helically guide the pressure plate during actuation to axially engage the pressure plate against the brake pad carrier thereby axially engaging the brake pad material against the braking surface of the rotor; and a rotary actuator mounted on the brake support structure, the actuator arranged to couple a rotational motion to the pressure plate while the pressure plate moves axially.

2. The disc brake of claim \, in which the rotary actuator includes two or more rotary actuators distributed circumferentially around the brake support structure and rotatably engaging the pressure plate.

3. The disc brake of claim 1 , in which the rotary actuator has a drive gear coupled to a driven gear mounted on the pressure plate coaxially to the rotating member, the drive gear and driven gear being arranged to remain coupled during rotation through a range of axial movement of the pressure plate and driven gear.

4. The disc brake of claim 1, in which the rotary actuator has a drive gear coupled to a gear segment mounted on the pressure plate coaxially to the rotating member, the drive gear and driven gear being arranged to remain coupled during rotation through a range of axial movement.

5. The disc brake of claim 3 or 4, in which the range of axial movement corresponds to a width of the drive gear or of the driven gear or gear segment.

6. The disc brake of claim 1, in which the rotary actuator has a drive gear coupled to a driven gear mounted on the pressure plate coaxially to the rotating member, the drive gear being coupled to a drive motor output shaft for axial movement to maintain axial alignment with the driven gear.

7. The disc brake of claims 3 or 4, in which support structure includes a helical structure coupling the pressure plate to the support structure for rotational and axial movement, the helical structure being coaxial with the support structure and the pressure plate.

8. The disc brake of claim 7 in which the driven gear or gear segment are positioned radially outward of the helical structure.

9. The disc brake of claims 3 or 4, in which driven gear or gear segment are positioned adjacent a periphery of the pressure plate.

10. The disc brake of claim 1. in which the rotary actuator has a drive gear coupled to a gear or gear segment mounted on the pressure plate coaxially to the rotating member, the rotary actuator including two drive motors coupled to the drive gear.

11. The disc brake of claim 10, in which the two drive motors are powered simultaneously during normal operation to advance or retract the pressure plate and are powered separately so that in case of failure of one of the two motors the other motor can advance or retract the pressure plate.

12. The disc brake of claim 1 , in which the rotor includes a plurality of rotors coaxially attached to the rotating member; the brake pad carrier is a stator and includes a plurality of stators supported coaxially in the brake support structure and arranged to have each stator between two of the rotors; and the rotary actuator is arranged to move the pressure plate axially during actuation to axially engage all of the stators with all of the rotors.

13. The disc brake of claim 1 , in which the rotary actuator has a drive gear coupled to a gear or gear segment mounted on the pressure plate coaxially to the rotating member, the rotary actuator including at least one drive motor coupled to the drive gear though a worm gear so that the drive motor cannot be back-driven by counter-rotation of the pressure plate.