Servo-motors are increasingly being used as drives in the control of machinery component movement. There are servo-motor applications where it is desirable to stop movement of the machinery component being driven including but not limited to parking or emergency stop situations but also in the event of disruption of power to the servo-motor.

Typically, servo-motors were purchased from manufacturers either with or without an integral braking component.

However, a need has arisen for a brake to be added as a module separately to servo-motors. In particular, this would allow servo-motor users to purchase a standard servo-motor for all applications (assumedly at a lower per unit price due to quantity discounts) and then to add a brake module to the servo-motor only in applications where braking is needed or desired. In a preferred aspect, it would be desirable that such add on servo-motor brakes have performance characteristics which exceed those of integral servo-motor and brake units and which minimize the overall product size.

A major obstacle to satisfying this need is that the servo-motor industry has not adopted a standard configuration. In particular, the drive shafts of servo-motors are of different radial sizes. Also, although typically including a pilot on the output face, the sizes and shapes of pilot faces differ between manufacturers of servo-motors. Additionally, although typically the output face includes four bores which may be threaded and which were located at the corners of a square larger than the pilot and for receipt of screws extending from the apparatus component to be driven, such bores were of different

diameters and were located at different radial spacings from the drive shaft. To reduce inventory requirements and to take advantage of mass production, it is desirable that brakes intended to be modules for attachment to servo-motors should have universal application to all servo-motors of whatever manufacturer and should be easily and readily modifiable to that of the particular servo-motor to which it is desired to be attached.

SUMMARY The present invention solves this need and other problems in the field of rotation control by providing, in the preferred form, a plurality of slots extending radially inwardly from the outer surface of an annular disc of a housing portion, with each of the slots adapted to receive a screw for attachment to a drive such as a servo-motor, and with an axially extending recess formed in the face of the annular disc for receiving the pilot of the servo-motor. In most preferred aspects of the present invention, alignment of the servo-motor with the housing portion is obtained by receipt of the drive shaft of the servo-motor in an axial bore of the input of the rotational control apparatus, with an expandable coupling being utilized in the most preferred form to allow the axial bore to be of a standard size but connected to different sizes and shapes of drive shafts.

In another aspect of the present invention, a wedge shaped annular friction facing is moved between an engaged position and a disengaged position, with the input and output being rotatably independent in the disengaged position and being rotatably related for rotation together when first and second surfaces of the annular friction facing interface with an interface surface of the input and the friction surface of the output, respectively, with the interface and friction surfaces extending in opposite, nonparallel angles to the rotational axis of the input.

It is thus an object of the present invention to provide a novel rotational control apparatus.

It is further an object of the present invention to provide such a novel rotational control apparatus having special application for servo-motors.

It is further an object of the present invention to provide such a novel rotational control apparatus which can be easily added as a module to drives of differing configurations.

It is further an object of the present invention to provide such a novel rotational control apparatus which can be readily modified to that of the particular drive to which it is secured.

It is further an object of the present invention to provide such a novel rotational control apparatus which maximizes performance characteristics while minimizing size.

It is further an object of the present invention to provide such a novel rotational control apparatus having fewer number of parts which can be easily fabricated.

It is further an object of the present invention to provide such a novel rotational control apparatus having low inertia.

These and further objects and advantages of the present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings.

DESCRIPTION OF THE DRAWINGS The illustrative embodiment may best be described by reference to the accompanying drawings where: Figure 1 shows an end view of a rotational control apparatus in the most preferred form of a brake having special application to servo-motors.

Figure 2 shows a cross sectional view of the rotational control apparatus of Figure 1 according to section line 2-2 of Figure 1, with a servo-motor and apparatus component to be driven thereby being shown partially and in phantom.

All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following description has been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following description has been read and understood.

Where used in the various figures of the drawings, the same numerals designate the same or similar parts.

Furthermore, when the terms"first","second","inside", "outside","outer","inner","end","side","axial", "radial", and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the illustrative embodiment.

DESCRIPTION A rotational control apparatus according to the preferred embodiment of the present invention is shown in the drawings as a spring engaged fluid released brake and is generally designated 10. Brake 10 is shown in its most preferred form for rotationally controlling an input 12.

Input 12 generally includes a first axial portion 14 and a second axial portion 16. Portion 14 has an outer surface 18 of generally circular cross sections and an internal, axially extending bore 20 for receipt of a shaft 21 of a power source 96 in a nonrotatable manner. In the most preferred form, brake 10 is utilized with an electric servo-motor 96, with shaft 21 being part of servo-motor 96.

Portion 16 is in the form of a shaft for interrelation with a machine, robot, or other apparatus component 23 being controlled by servo-motor 96. In its most preferred form, input 12 further includes a radially extending interface 24

generally at the interconnection between portions 14 and 16.

Interface 24 terminates in an annular interface surface 26 extending at a nonparallel angle to the axis of input 12 and to the radial direction to the axis of input 12 and specifically extends radially outwardly to the axis when viewing Figure 2 from left to right. In the most preferred form, surface 26 extends at an angle in the order of 20° to 25° to the axis of input 12. Surface 26 is at a relatively short radial spacing from the axis of input 12 and in the most preferred form which is less than twice the radial spacing of surface 18 from the axis of input 12. In the most preferred form, portions 14 and 16 and interface 24 of input 12 are integrally formed as a single piece of material.

Brake 10 further includes an output shown as a housing 28 in its most preferred form, with input 12 being rotatable relative to and in the most preferred form within housing 28 about its axis. Housing 28 includes a servo-motor attachment housing portion 30 and an air-chamber housing portion 32. Housing portion 30 generally includes a radially oriented, annular disc 34 and a generally axially extending cylindrical member 36 extending from a first face 37 of disc 34. Disc 34 according to the teachings of the present invention includes an axial opening 38 extending through first face 37 and its second, opposite face 39 of disc 34 and having a size greater than shaft 21 of servo-motor 96 and in the most preferred form of a radial size greater than surface 18 of input 12. Disc 34 further includes a cylindrical recess 40 extending from second face 39 of disc 34 towards but spaced from first face 37. Recess 40 is generally concentric to opening 38 and is of a radial size greater than opening 38 and is of a radial size at least equal to or preferably slightly larger than the largest pilot 98 of servo-motor 96 available on the market.

The outer surface 42 of disc 34 is of a generally square shape. Apertures 44 extend through first and second faces 37 and 39 of disc 34 at a radial spacing greater than

cylindrical member 36 and cylindrical recess 40, with apertures 44 being counterbored from second face 39 towards but spaced from first face 37 in the most preferred form.

Four apertures 44 are provided in the form shown adjacent to but equally circumferentially offset of the corners of the square shape of outer surface 42 of disc 34. Disc 34 according to the preferred teachings of the present invention further includes slots 46 circumferentially spaced from apertures 44 extending radially inwardly from each of the corners of the square shape of outer surface 42 of disc 34. Slots 46 in the form shown have an inner radial extent generally equal to but slightly greater than the outer surface of cylindrical member 36. A radial tool channel 45 extends perpendicularly from one of the sides of the square shape of outer surface 42 and radially intersects with axial opening 38. Channel 45 extends from face 39 of disc 34 towards but spaced from face 37.

The inner and outer surfaces of cylindrical member 36 are circular in cross section in the most preferred form and are concentric with the axis of input 12 and axial opening 38. Cylindrical member 36 of housing portion 30 includes an annular shoulder 47 extending inwardly from its free axial end and its outer surface.

Housing portion 32 generally includes a radially oriented, annular collar 48 and an integral ring 50 extending generally axially from a first face 52 of collar 48. Collar 48 according to the teachings of the present invention includes an axial opening 54 extending through first face 52 and the opposite, second face 56 and having a size greater than axial portion 16 and in the most preferred form of a radial size generally equal to surface 18 of axial portion 14. A shoulder 58 extends into opening 54 generally coextensive with face 56 and of an axial length considerably shorter than the axial length of opening 54.

Input 12 is rotatably mounted to housing portion 32 by a bearing 60. Particularly, bearing 60 includes an inner race received on axial portion 16 and having an inner end

generally abutting with axial portion 14 and interface 24.

Bearing 60 further includes an outer race received in opening 54 and having an outer end abutting with shoulder 58. The outer surface of collar 48 is coextensive with the outer surface of ring 50 and in the most preferred form is generally square in shape of a size generally corresponding to outer surface 42 of housing portion 30. Collar 48 includes an annular piston chamber 62 having an axially extending inner surface 64 of a radial size greater than opening 54 and having an axially extending outer surface 66 of a radial size greater than surface 64.

Ring 50 includes a first axially extending inner surface 68 of a radial size and coextensive with surface 66.

Axially inward of and coextensive with surface portion 68 is a second, intermediate, inner, friction surface portion 70 which extends at a nonparallel angle to the axis of input 12 and in the most preferred form at an angle in the order of 10° to the axis of input 12. In the most preferred form, surface portion 70 extends radially inwardly to the axis of input 12 when viewing Figure 2 from left to right. Axially inward of and coextensive with surface portion 70 is a third, axially extending inner surface portion 72 of a radial size greater than surface portion 68 and generally equal to and for receipt in shoulder 47 of housing portion 30. Threaded bores 76 extend axially through ring 50 and collar 48 of housing portion 32 and at radial spacing and location corresponding to apertures 44 of housing portion 30. Housing portions 30 and 32 are retained in position by screws 78 extending through apertures 44 and threaded into bores 76. Housing portions 30 and 32 are retained in axial position relative to each other by the receipt of surface portion 70 and the free end of ring 50 of housing portion 32 in shoulder 47 of cylindrical member 36 of housing portion 30. Suitable provisions are provided in housing portion 32 for the introduction of fluid under pressure into piston chamber 62 in housing portion 32.

Brake 10 according to the preferred teachings of the present invention further includes an annular friction facing 82 of a generally wedge shape. In particular, friction facing 82 includes a first radially extending surface 84 of a radial size generally equal to but slightly less than and for receipt between surface 26 and surface portion 70. Friction facing 82 further includes an outer surface 86 extending from surface 84 and of a radial size and shape corresponding to and for frictionally engaging and interfacing with surface portion 70. Friction facing 82 also includes an inner surface including a first surface portion 88 extending from surface 84 and of a radial size and shape corresponding to and for frictionally engaging with surface 26. The inner surface of friction facing 82 also includes a second surface portion 90 extending axially inwardly from surface portion 88. Friction facing 82 further includes a second radially extending surface 92 extending between the inner ends of surface 86 and surface portion 90. Thus, surface 86 and surface portion 88 have increasing spacing with increasing radial spacing from surface 84 and have decreasing radial spacing with increasing spacing from surface 92.

Brake 10 according to the preferred teachings of the present invention further includes suitable provisions for moving friction facing 82 between an engaged position and a disengaged position. In the most preferred form, friction facing 82 is moved to an engaged position by being biased by a compression spring 94 extending axially between surface 92 of friction facing 82 and face 37 of housing portion 30 and positioned adjacent to the inner surface of cylindrical member 36.

In the most preferred form, friction facing 82 is moved to a disengaged position by an annular piston 100 slideably received in piston chamber 62. In the most preferred form, piston 100 has L-shaped radial cross sections including a piston body 102 having inner and outer surfaces corresponding to and for slideable receipt in surfaces 64

and 66. Suitable sealing provisions such as 0-rings as shown are provided between piston body 102 and chamber 62.

Piston 100 further includes an annular flange 104 extending axially from body 102, with annular flange 104 having an outer surface coextensive with and at the same radial spacing as the outer surface of body 102 and of a maximum radial size generally equal to and for slideable receipt in surface portion 68. Flange 104 has a radial size less than body 102 and less than and for receipt between surface 26 and surface portion 70. Flange 104 terminates in a free end for abutting with radially extending surface 84 of friction facing 82. Flange 104 allows body 102 to have greater cross sectional area in piston chamber 62 for force generation by the fluid pressure while minimizing the radial spacing between surface 26 and surface portion 70 and the radial extent of surface 84 and of friction facing 82. With the introduction of fluid into chamber 62, piston 100 axially slides relative to housing portion 32 under fluid pressure to move friction facing 82 from the engaged position to the disengaged position against the bias of spring 94. Axial movement of friction facing 82 by piston 100 is limited by the abutment of surface 92 with the free end of cylindrical member 36 of housing portion 30.

Now that the basic construction of brake 10 according to the preferred teachings of the present invention has been set forth, a preferred application and some of the advantages of brake 10 can be explained. In particular, shaft 21 of servo-motor 96 is axially extended into and secured in axial bore 20. In the most preferred form as shaft 21 can be any one of a variety of differing sizes and shapes and to allow bore 20 to be of a standard size for ease of manufacture of input 12, an expandable coupling 106 is utilized to secure shaft 21 in bore 20. In particular, coupling 106 includes first and second components which are axially movable relative to each other such as by the use of threadable interconnection to provide an outer axial surface for nonslideable receipt in bore 20 and an inner axial

surface for nonslideable receipt of input shaft 21 of whatever size and shape. In particular, shaft 21 is inserted on coupling 106 in turn inserted in bore 20, with coupling 106 in an unexpanded condition. Servo-motor 96 and brake 10 are moved relative to each other with pilot 98 received in recess 40 until face 39 of housing portion 30 abuts with the face of servo-motor 96 radially outwardly of pilot 98. At that time, a wrench or similar tool can be inserted through tool channel 45 for purposes of expanding coupling 106 into its expanded condition and thereby securing shaft 21 in axial bore 20.

It should be appreciated that alignment between brake 10 and servo-motor 96 is obtained by the receipt of shaft 21 (and coupling 106 in the most preferred form) in bore 20.

In particular, it is not necessary that recess 40 be slideably received on pilot 98 with a close tolerance for alignment purposes. In fact, in the most preferred form, recess 40 is normally larger than pilot 98 of whatever size and shape of the particular servo-motor 96. Thus, recess 40 according to the preferred teachings of the present invention does not need to be machined or otherwise modified to match the particular size and shape of pilot 98 of any particular servo-motor 96, but rather recess 40 allows housing portion 30 to be of a universal, standard design independent of the particular servo-motor 96 to which brake 10 is to be applied.

After shaft 21 has been aligned with bore 20, screws 108 can be inserted into slots 46 and threaded into the threaded bores in the face of servo-motor 96 or secured by nuts in the case of plain bores. A wrench or similar tool can be inserted between face 37 of disc 34 and the free end of ring 50 for purposes of tightening screws 108. In this regard, screws 108 can be positioned in slots 46 at a radial position corresponding to the radial positions of the bores of servo-motor 96. In particular, the bores of servo-motor 96 could be at different radial spacings from shaft 21 according to the particular manufacturer of servo-motor 96.

Thus, slots 46 or disc 34 according to the preferred teachings of the present invention do not need to be machined or otherwise modified to match the particular locations of the bores of any particular servo-motor 96 but rather slots 46 allow housing portion 30 to be of a universal, standard design independent of the particular servo-motor 96 to which brake 10 is to be applied.

In the most preferred form of the present invention, face 56 of housing portion 32 includes a pilot 110 for receipt of component 23 and bores 112 for receipt of screws for securing component 23 to housing 28 of brake 10 according to the teachings of the present invention.

Although it would be advantageous for input 12 and housing portion 32 to be universal in all applications, it may be desirable to machine face 56 to include pilot 110 and threaded bores 112 to correspond to pilot 98 and the bores of the particular servo-motor 96 that brake 10 is being applied to. Similarly, it may be desirable to machine shaft portion 16 axially outward of bearing 60 to be of a size and shape corresponding to the size and shape of shaft 21 of the particular servo-motor 96 that brake 10 is being applied to. Thus, axial portion 16 and face 56 would present the same connection configuration with component 23 as servo-motor 96 would if brake 10 according to the teachings of the present invention were not provided.

According to the preferred teachings of the present invention, friction facing 82 provides an interface between input 12 and housing 28 with a wedge action. This wedge action creates a mechanical advantage in increasing the amount of torque which can be transferred through input 12, housing 28, and facing 82 versus the amount of biasing force produced by spring 94. Specifically, such a wedging action results in much greater force transfer than if linear surfaces were simply abutted together such as in conventional flat plate or conical type control apparatus.

Additionally, the wedging action produced by a wedge shaped friction facing 82 provides several advantages.

First, the force of spring 94 can be minimized while still providing the required torque transfer which in the most preferred form is of an amount sufficient to stall servo-motor 96. Also, the axial extent of brake 10 can be minimized according to the teachings of the present invention. But more importantly, the radial extent of brake 10 can be minimized and in the most preferred form generally corresponds to the radial extent of servo-motor 96.

Additionally, surface 26 can be positioned radially inward to minimize the radial extent of interface 24. This is very important in minimizing the distance of the mass of input 12 from the rotational axis and thus the inertia forces which are placed upon servo-motor 96. Furthermore, the integral fabrication of input 12 according to the most preferred form of the present invention plays an important factor in minimizing the total mass which is rotated by servo-motor 96 and thus in minimizing the inertia forces which are placed upon servo-motor 96. Since inertia forces are dependent upon the amount of mass being rotated and the distance of the mass from the rotation axis, brake 10 according to the preferred teachings of the present invention minimizes inertia forces which is important in start-up and stopping of servo-motor 96 in normal operation. In addition to reducing inertia forces, the integral fabrication of input 12 is simpler and less expensive and results in a stiffer component than if input 12 were fabricated from multiple pieces.

It should be appreciated that due to the wedging action provided by friction facing 82 according to the preferred teachings of the present invention, friction facing 82 will be subject to considerable wear in normal operation. Thus, according to the preferred teachings of the present invention, brake 10 is held in its disengaged position by the introduction of fluid pressure in chamber 62 in normal operation of servo-motor 96 and is moved to its engaged position only in static situations such as parking movable components or in emergency situations to minimize wear of friction facing 82.