GB2197416A

GB2197416A - Clutch/brake rotational control apparatus

Info

Publication number: GB2197416A
Application number: GB08721101A
Authority: GB
Inventors: Leonid Dayen; Charles D Raines
Original assignee: Horton Manufacturing Co Inc
Current assignee: Horton Manufacturing Co Inc
Priority date: 1986-09-12
Filing date: 1987-09-08
Publication date: 1988-05-18
Anticipated expiration: 2007-09-08
Also published as: AU592888B2; NL8702143A; AU7775787A; FR2603964A1; SE8703412D0; FR2603964B1; JPS63106166A; IT1218683B; AU627318B2; DE3730621A1; NL193389B; SE9101800D0; NL193389C; GB2197416B; JP2927429B2; SE8703412L; DE3730621C2; BR8704578A; SE9101800L; IT8767778A0

Description

SPECIFICATION Rotational control apparatus The present invention relates generally to rotational control apparatus, particularly to apparatus for controlling rotation of an output, and specifically in the preferred form to combination clutch-brakes.

It is often desired to control an output at different conditions such as by a clutch-brake.

However, prior clutch-brakes suffered from deficiencies in ease of manufacture, assembly, installation, and maintenance and in their ability to be utilized with differing industrial standard interconnections. Thus, a need has arisen for a clutch-brake having an improved housing utilizing modular, interchangeable, easily and inexpensively cast components which may be machined for varying industrial interconnections and which allow ease of apparatus installation and maintenance.

The invention provides apparatus for providing rotational control of an output, including an interface disc having first and second interface surfaces, a housing, a first interface member formed on an input for interfacing with the first interface surface of the interface disc, a second interface member formed on the housing for interfacing with the second interface surface of the interface disc, said housing comprising, a cylindrical body portion; a first housing end having a generally circular shape; a second housing end: with the cylindrical body portion including an axially extending annular member having a free annular end, with the second interface member being integral with and extending radially inwardly of the axially extending annular member; a mounting flange extending radially outwardly of the axially extending annular member slightly offset from the second interface member; means for removably securing the first housing end to the free annular end of the axially extending annular member; and means accessible outside of the axially extending annular member of the cylindrical body portion for removably securing the second housing end to the mounting flange of the cylindrical body portion.

The invention also provides an interface disc for an output having first and second interface surfaces, comprising a first, flat ring portion including the first interface surface, a first face opposite to the first interface surface, and a radially inward axially extending opening; an interface element including a second ring portion and means for connecting the second ring portion for rotation with the output, with the second ring portion including the second interface surface and a second face opposite the second interface surface; cirumferentially spaced webs upstanding from the second face of the interface element, with the webs having free ends; and means for securing the first, flat ring portion to the interface element with the first face abutting with the free ends of the webs and spaced from the second face of the interface element forming spaced cutouts for heat venting.

By way of example, embodiments of the invention will be now be described with reference to the accompanying drawings where: Figure 1 shows a cross sectional view of apparatus according to the present invention.

Figure 2 shows an exploded, perspective view of the housing of the apparatus of Fig. 1 illustrating the modular interchangeability thereof.

Figure 3 shows a cross sectional view of an alternate embodiment of apparatus according to the present invention.

Figure 4 shows an exploded, perspective view of the apparatus of Fig. 3.

Apparatus for providing rotational control of an output according to the present invention is shown in the drawings and is generally designated A. In the most preferred embodiments of the present invention, apparatus A is a clutch-brake and is an improvement of the type shown and described in U.S. Patent No.

4,534,454. For purpose of explanation, the same numerals designate the same or similar parts in the present figures and the figures of U.S. Patent No. 4,534,454. The description of the common numerals and the clutch-brake A may be found herein and in U.S. Patent No.

4,434,454, which is hereby incorporated herein by reference.

Referring to the drawings in detail, the clutch-brake A includes the driven rotatable output shaft 10. Further provided is the interface disc shown in its preferred form as friction disc 28. In the preferred embodiment of Figs. 1 and 2, mounted by means of bolts 29 on the first face of friction disc 28 is the first interface surface shown as friction lining ring 32. In the preferred embodiment of Figs 3 and 4, friction disc 28 includes a flat ring portion 23b and a friction interface element 25. Friction interface element 25 includes a flat ring portion 25a having circumferentially spaced, radially extending webs 27 upstanding from the face opposite to the interface surface thereof. Axially extending openings 95 of the type shown and described in U.S. Patent No.

4,078,637, whnich is hereby incorporated by reference, are formed in the flat ring portion 25a intermediate webs 27. Webs 27 include axially extending shoulders 27a for receipt of the radially inward axially extending opening of flat ring portion 23b. Bolts 29 threadably received in webs 27 extend through and secure friction lining ring 32 and the flat ring portion 23b to friction interface element 25 with the face opposite to the interface surface of ring portion 23b abutting with the free ends of webs 27 and spaced from the face of ring portion 25a to form spaced cutouts 23a for heat venting.

Disc 28 terminates radially inwardlykin the hollow hub 34 formed with splines 36 slidably engaged with splines 38 of shaft 10. Formed on the hub 24 is the annular recess 40 forming the shoulder 42. Mounted in the recess 40 and against the shoulder 42 is the inner race 44 of bearing 46.

The numeral 48 designates an annular piston which includes the axially disposed annular flange portion 50. The outer race 54 of bearing 46 is mounted on the inner surface of piston flange portion 50 and against the shoulder 56 thereby rotatably mounting shaft 10 and a portion of hub 34 within piston 48.

Clutch-brake A includes a housing 150 of an improved construction including modular, interchangeable components 82 or 156, 152, and 154. Specifically, housing 150 includes a cylindrical body portion 152 having a first, generally axially extending annular member 1 58 which intersects with a second, generally radially extending annular member 160. Member 158 includes a first, free annular end 164 and a second, free annular end 168. In the most preferred form, annular recess 186 is provided in the radially inward diameter of annular member 150 and adjacent end 168 for allowing ease of assembly.

Member 160 includes an integral, annular body portion 72 located radially inwardly of annular member 158 and extending toward its second end 168. Annular body portion 72 includes a backing portion 68 for mounting thereon the second, fixed interface member shown as friction lining ring 79 opposite friction disc 28. Friction lining ring 79 in the preferred form shown in Figs. 3 and 4 is formed of two, half-moon pieces to allow radial removal without removing friction interface element 25. Lining 79 is secured by bolts 81 to backing portion 68.

Member 160 further includes an annular, radially extending mounting flange 170 having circuferentially spaced, axially extending apertures 172. Flange 170 is generally located such that body portion 72 is slightly offset from flange 170.

Body portion 152 further includes in its most preferred form, integral, axially extending, circumferentially spaced fins 176 extending from annular member 158 from flange 170 to a point slightly axially spaced inwardly of end 168. Axially extending, circumferentially spaced mounting shoulders 178 are further provided in the preferred embodiments extending from annular member 158 from flange 170 to end 168 and circumferentially spaced from fins 176. One of the shoulders 178 in the preferred embodiment includes a port enlargement 180 including axially spaced, radially extending air ports 24 and 182.

Housing end 154 is generally planar and circular in configuration having a diameter larger than annular member 158 of cylindrical body portion 152. End 154 includes axially extending, integral projection 23 having radially intermediate axially extending surface 188 and radially outward axially extending surface 190 in its most preferred form. Surface 190 has a diameter generally equal to recess 186 and for receipt therein. End 1 54 is removably secured to cylindrical body portion 152 in its most preferred form by bolts 200 extending through circumferentially spaced, axially extending apertures 202 formed in end 154 and threadably received in mounting shoulders 178 of cylindrical body portion 152. In the most preferred form, apertures 202 include counter sunk entries for receipt of the heads of bolts 200.Suitable fluid sealing provisions 192 such as an O-ring is provided in the preferred embodiment between surface 190 of projection 23 of end 154 and cylindrical body portion 152.

In the preferred form of Figs. 1 and 2, annular flange portion 50 of piston 48 has formed on the outer surface thereof adjacent to its first end the annular groove 58 in which is positioned the O-ring 60 which makes sliding and sealing contact with surface 188 of projection 23. An annular portion 52 extends radially outwardly from annular flange potion 50. The second, free end of annular portion 52 of piston 48 has formed therein the groove 62 in which is positioned the O-ring 64 which makes sliding and sealing contact with the radially inward surface of annular member 158 of housing 150.

In the preferred form of Figs. 3 and 4, annular piston 40 is generally Z-shaped and includes a second, axially disposed annular flange portion 51 and annular portion 52 extending radially between the ends of portions 50 and 51. The radially outer surface of portion 51 is complementary to and for sliding receipt within cylindrical body portion 1 52 and includes suitable sealing provisions therebetween such as O-ring 64 received within groove 62 formed in the radially outer surface of portion 51. The radially inner surface of portion 51 is complementary to and for sliding receipt on surface 188 of projection 23 and includes suitable sealing provisions therebetween such as O-ring 60 received within groove 58 formed in surface 188 of projection 23.

The radially outer surface of portion 50 is complementary to and for sliding receipt within radially inward, axially extending surface 198 of body portion 72 and includes suitable provisions therebetween such as O-ring 196 received within groove 194 formed in surface 198 of body portion 72.

It will be seen that piston 48, bearing 46, hub 34 and friction disc 28 thereof are all slidable on shaft 10. It will be further seen that the void defined by piston 48, cylindrical body portion 152, and end 154 forms a cylinder C to which there is communication by air port 24. It will be further seen that the void defined by piston 48, cylindrical body portion 152, and body portion 72 forms a cylinder C' to which there is communication by air port 182.For rotatably relating piston 48 to housing 150, an antirotation pin 204 shown in its preferred form as a spring pin is secured through the first end of annular flange portion 50 and is slidably received in an aperture 206 formed in end 154 in the preferred form of Figs. 1 and 2 and is secured in end 154 and is slidably received in an aperture 206 formed in the free end of annular flange portion 51 of piston 48 in the preferred form of Figs. 3 and 4. It can then be appreciated that the particular arrangement of pin 204 and its interrelationship to piston 48 and housing end 154 are advantageous in regard to formation of the apertures for receiving pin 204 without wall break through.

In the preferred form of Figs. 1 and 2, clutch-brake A includes first and second, Lshaped bushings 208 which are oppositely directed with the free ends of the first legs being contiguous and with the first legs of the first and second L-shaped bushings being received an output shaft 10. Bushings 208 are prevented from axially moving on shaft 10 by a shoulder 210 formed on shaft 10 and by a retaining ring 212 secured on shaft 10. In the most preferred form, bushings 208 are formed of Oilite Bronze. The second legs of bushings 208 capture an annular shoulder 19 formed in circular opening 18 of end 154 for axially securing bushings 208 in end 154.

In the preferred form of Figs. 3 and 4, mounted on shaft 10 are the inner races 12 of bearings 14 and 14a with the outer races 16 mounted in the circular opening 18 of housing end 154. in the preferred form of Figs. 3 and 4, opening 18 is formed by projection 23 which is of a two step form. Races 12 and 16 of bearings 14 and 14a are retained by a shoulder 210 formed on shaft 10, by retaining rings 211 secured in opening 18 of housing end 154, and by retaining ring 212 secured on shaft 10.

In the preferred form of Figs. 1 and 2, member 158 includes a first cylindrical portion 162 having the first, free annular end 164 and having a second end integrally attached to a first end of a second cylindrical portion 166 having the second, free annular end 168. The radially inward diameter of cylindrical portion 162 is generally equal to the radially outward diameter of cylindrical portion 166. Annular recess 184 is provided in the radially inward diameter of cylindrical portion 162 adjacent end 164 for allowing ease of assembly. Body portion 152 further includes in the preferred form of Figs. 1 and 2, integral, axially extending, circumferentially spaced, heat dissipating fins 174 extending from cylindrical portion 162 from flange 170 to a point slightly axially spaced inwardly of end 164.

The inner race 96 of bearing 94 is mounted in recess 98 formed on hub 100 of friction disc 102 having friction face 104. Hub 100 is keyed to the live input shaft of a motor or other source of power by means of keyway 110. Thus, as the power source shaft rotates so does disc 102.

In the preferred embodiment of Figs. 1 and 2, housing end 156 is generally planar and circular in configuration having a diameter larger than cylindrical body portion 152. End 156 includes integral, axially extending shoulder 214 having a diameter generally equal to recess 184 and for receipt therein. End 156 is removably secured to housing body 150 in its most preferred form by studs 216 extending through apertures 172 and threadably received in end 156. A jam nut 218 may be provided threadably received on stud 216 and abutting with end 156. Further, a lock washer and nut 220 may be provided threadably received on stud 216 and abutting with flange 170.

In the preferred embodiment of Figs. 3 and 4, axially extending fingers 80 of housing end 82 shown in its preferred form as stationary input housing define openings 84 for air cooling and the fingers 80 terminate at their outer edge in the ring like and radially disposed outer end wall 86. The inner diameter of fingers 80 is greater than the outer diameter of axially extending annular member 158. The inner edge of fingers 80 includes an annular recess 184 provided in the inner diameter of fingers 80 of a size and shape complementary to and for slidable receipt on an axially extending shoulder 185 integrally formed on mounting flange 170 of free end 164 of cylindrical body portion 152. Stationary input housing 82 is removably secured to body portion 152 in its most preferred form by bolts 216 extending through apertures 172 and threadably received in the inner edge of fingers 80.Disc 102 of Figs. 3 and 4 is equipped with the spaced cooling fins 106, Extending inwardly and axially of end 82 or 156 is the annular flange 88 which has formed on the inner surface thereof the annular recess 90 in which is mounted the outer race 92 of bearing 94. It can then be appreciated that friction discs 28 and 102 are not directly interconnected together, but are only interconnected together through their separate interconnection to housing 1 50. Therefor, no vibration is transferred between the power source shaft received in hub 100 of friction disc 102 and output shaft 10 due to off center mounting of clutch-brake A. Vibration may cause noise and premature component wear.

Thus, rubbing coating of splines 36 and/or 38 or other techniques to compensate for vibration are not necessary, reducing the cost of manufacture of clutch-brake A.

Housing end 82 or 156 includes provisions for mounting housing 150 and clutch-brake A to the motor or other source of power such as by a female C-face 222 and by cap screws received in circumferentially spaced, axially ex tending apertures 224. End 15lib includes provisions for mounting housing 150 and clutchbrake A to the output apparatus such as a gear reducer such as by a male C-face 226 and by circumferentially spaced, axially extending, apertures 123 for receipt of bolts extending from the gear reducer. Shaft 10 may also be keyed to a sheave, a sprocket, a coupling or the like for actuation thereof.

It will be seen that with no air pressure in cylinder C and upon introducing fluid pressure into cylinder C' by a source (not shown) connected to port 182, piston 48 moves towards end 154 whereby disc 28 is made to contact lining 79 and through hub 34 brake shaft 10.

With no air pressure in cylinder C' and upon introducing fluid pressure into cylinder C by a source (not shown) connected to inlet 24, piston 48 moves away from end 154 whereby disc 28 is separated from lining 79 and as a result there is no braking of shaft 10, and friction lining 32 contacts face 104 of live friction disc 102 whereby shaft 10 is clutched in.

A first difference between clutch-brake A disclosed herein and clutch-brake A disclosed in U.S. Patent 4,534,454 is that no springs are utilized in the present construction in moving piston 48 whereas springs are utilized for moving the piston in the construction described in U.S. Patent 4,534,454. Separate fluid cylinders C and C' as in the present apparatus allow more torque capacity in the engagement of the clutch or brake in clutchbrake A. Further, faster actuation of the clutch in clutch-brake A of the present invention is possible because it is not necessary to compress springs as in U.S. Patent 4,534,454.

However, it should also be appreciated that clutch-brake A of the present invention obtains many of the advantages gained by clutch-brake A of the U.S. Patent 4,534,454 including prevention of simultaneous clutching and braking of output shaft 10.

A further major difference between clutchbrake A of the present invention and U.S. Patent 4,534,454 is the housing construction. It should then be noted that housing 150 of the present apparatus is of a modular, interchangeable component type. Specically, housing ends of different types and constructions may be utilized and interchanged with a common body portion 152. For example, as shown in Fig. 2, housing ends 154M and 156M may be utilized with a body portion 152 for interconnection between a power source and output apparatus utilizing metric standard interconnections. Similarly, housing ends 154N and 156N may be utilized with some body portion 152 for interconnection betwen a power source and output apparatus utilizing NEMA (inch) standard interconnections.It can then further be appreciated that it is even possible to mismatch housing ends 154 and 156 between metric and NEMA standards.

Furthermore, it should be appreciated that since body portion 1 52 is identical for either metric or NEMA type interconnections, it is then only necessary to manufacture and keep on inventory a single type of body portion 152 rather than separate housing constructions for each type of industry interconnections such as metric or NEMA standards.

Similarly, the remaining components are of identical constructions such as piston 48, friction disc 28, bearings 46 and 94, friction linings 79 and 32 and the like or may be machined from a common casting to either a metric, NEMA, or other industry standard such as shaft 10 and hub 100, and housing ends.

Therefore, machining from a common casting greatly reduces the number of casting molds and the capital expenditures required to manufacture clutch-brake A for interconnection with other components of varying industrial standard. Further, it is then only necessary to manufacture and keep in inventory a significantly reduced number of components while having clutch-brakes A which fit both metric and NEMA industry standard.

It should be further noted that the preferred construction of cylindrical body portion 152 is further advantageous. First, body portion 152 is adaptable for easy casting. Further, the provision of fins 176 allows for the dissipation of heat from clutch-brake A without requiring cores during casting. Furthermore, fins 176 structurally reinforce mounting flange 170 and annular member 160.

Further, in the preferred embodiment of Figs. 1 and 2, mounting flange 170 lies between the mold interface and divides the draft angles of cylindrical body portion 152. Further, the provision of fins 174 allows for the dissipation of heat from clutch-brake A without requiring cooling air apertures requiring window cores during casting. Furthermore, fins 174 structurally reinforce mounting flange 170.

Similarly, stationary input housing 82 of Figs. 3 and 4 is further advantageous. First, stationary input housing 82 is adaptable for easy casting. Specifically, openings 84 of stationary input housing 82 are formed by fingers 80 and thus do not require window cores during casting. Further, the interface interaction locations which are the major source of heat generation are positioned axially within stationary input housing 82 to allow rapid heat dissipation as the result of the axial openings in interface element 25 and friction disc 103, cutouts 23a, openings 84 and fins 106.

Additionally, housing 150 and clutch-brake A are particularly advantageous when it is necessary to disassemble clutch-brake A for installation and maintenance, such as when the C-face is larger than the bore circle of apertures 224. Specifically, clutch-brake A can be separated into two major components, a first component including housing end 82 or 156 and friction disc 102 and a second component including body portion 152, housing end 154, friction disc 28, and piston 48 held together by the interconnection of body por tion 152 and housing end 154 by bolts 200.

Housing end 82 or 156 may then be interconnected to the power source by bolts extending through apertures 224 and body portion 152 may be interconnected to housing end 82 or 156 by bolts 216, with housing end 154 being interconnected to the output apparatus utilizing bolts received in apertures 123 either before or after the interconnection of body portion 152 to housing end 82 or 156.

Furthermore, due to the preferred construction of housing end 82 and body portion 152 of Figs. 3 and 4 easy access is allowed to friction lining ring 79 due to the offset nature of mounting flange 170 from body portion 72 to allow radial removal from between backing portion 68 and friction interface member 25 without dismantling friction interface member 25 from the second component including body portion 152, housing end 154, and piston 48. Thus, clutch-brake A is advantageous in the ease of maintenance and specifically the replacement of friction lining rings 32 and 79 and particularly does not require reaching radially inward of a closed housing for lining replacement.

It should be additionally noted that the preferred construction of friction disc 28 of Figs.

3 and 4 is further advantageous. Specifically, friction disc 28 is adaptable for easy casting without requiring casting cores. Specifically, one piece friction disc 28 of the type of U.S.

Patent 4,534,454 required spaced cutouts 23a be formed by using cores located between the cavities which formed the flat ring portions of the friction disc 28, greatly increasing the cost of the molds as well as the casting. The two piece construction of friction disc 28 and specifically the construction of friction interface element 25 eliminates the requirement for casting cores for disc heat ventilation as webs 27 which space ring portion 23b and 25a to allow for heat ventilation are formed on and upstand from the rear face of flat ring portion 25a. Flat ring portion 23b need not be cast and may be simply cut or stamped from sheet material, greatly reducing the cost of manufacture.

Furthermore, during maintenance of clutch brake A and specifically the replacement of friction lining rings 32 and 79, it should be noted that friction disc 28 of Figs. 3 and 4 is also of an advantageous construction. Specifically, flange 1 70 is located axially inward of end 164 and of friction lining 79 secured to annular body portion 72. Thus, after housing end 82 is removed by removing bolts 216, bolts 28 may be removed which secure friction lining ring 28 may be removed which se cure friction lining ring 32 and flat ring portion 23b to friction interface element 25. After removal of ring 32 and portion 23b, easy access is allowed to bolts 81 through openings 95 to allow removal of friction lining ring 79 and in particular it is not necessary to reach through ring portions 23b and 25a and cutouts 23a.

Further, the use of bushings 208 in housing end 154 in Figs. 1 and 2 is particularly advantageous over utilization of ball bearings. Specifically, bushing 208 are clearly less expensive than ball bearings. Further, the fabrication of end 154 and its assembly with bushings 208 and output shaft 10 is easier and less expensive. Furthermore, the axial length required for bushings 208 is considerably shorter than for ball bearings allowing clutch-brake A to be axially shorter and friction disc 28 to be axially closer to the output apparatus than when roller bearings are utilized. Thus, although roller bearings are more capable of receiving overhand and radial loads, the construction of clutch-brake A and the direct interconnection of housing end 154 to the output apparatus allows use of bushings 208 which reduces the overall cost of clutch-brake 10.

Although housing 150 in the preferred form of the present invention in Figs. 1 and 2 does not include cooling air apertures and is believed to be advantageous, such cooling air apartures or other cooling provisions may be provided in addition to and/or instead of fins 174 and 176 such as provided in Figs. 3 and 4.

Further, although securement of housing ends 82 or 156 and housing end 154 to body portion 1 52 is shown in the preferred embodiment including bolts 200 and bolts 216 and associated structure, other forms of securement may be apparent to one skilled in the art.

Although shown as formed of one piece, friction lining ring 32 may be formed in a manner as friction lining ring 79 of Figs. 3 and 4 to allow interchangability and component inventory and manufacture reduction.

Although air pressure on both sides of piston 48 is utilized to activate clutch-brake A in the preferred form, other forms and types of activation may be utilized.

Claims

1. Apparatus for providing rotational control of an output, including an interface disc having first and second interface surfaces, a housing, a first interface member formed on an input for interfacing with the first interface surface of the interface disc, a second interface member formed on the housing for interfacing with the second interface surface of the interface disc, said housing comprising, a cylindrical body portion; a first housing end having a generally circular shape; a second housing end; with the cylindrical body portion including an axially extending annular member having a free annular end, with the second interface member being integral with and extending radially inwardly of the axially extending annular member; a mounting flange extending radially outwardly of the axially extending annular member slightly offset from the second interface member; means for removably securing the first housing end to the free annular end of the axially extending annular member; and means accessible outside of the axially extending annular member of the cylindrical body portion for removably securing the second housing end to the mounting flange of the cylindrical body portion.

2. Apparatus as claimed in claim 1 wherein the interface disc comprises: a first, flat ring portion including the first interface surface, a first face opposite to the first interface surface, and a radially inward axially extending opening; an interface element including a second ring portion and means for connecting the second ring portion for rotation with the output, with the second ring portion including the second interface surface and a second face opposite the second interface surface; circumferentially spaced webs upstanding from the second face of the interface element, with the webs having free ends; and means for securing the first, flat ring portion to the interface element with the first face abutting with the free ends of the webs and spaced from the second face of the interface element forming spaced cutouts for heat venting.

3. Apparatus as claimed in claim 2 and further comprising at least a first axially extending opening formed in the second ring portion of the interface element and located intermediate the circumferentially spaced webs for access to the second interface member.

4. Apparatus as claimed in claim 2 and further comprising axially extending shoulders formed on the free ends of the webs for receipt of the radially inward axially extending opening of the first, flat ring portion to aid in positioning of the first, flat ring portion relative to the interface element.

5. Apparatus as claimed in any preceding claim wherein the free annular end has a diameter and the apparatus further comprises an axially extending projection integrally formed on the first housing end having a radially outward axially extending surface with a diameter generally equal to and for receipt within the diameter of the free annular end of the axially extending annular member.

6. Apparatus as claimed in claim 5 and further comprising a piston; means for interconnecting the piston for axial movement with the interface disc and for rotation relative to the interface disc; and means for reciprocally mounting the piston within the housing comprising a radially inward axially extending surface formed on the axially extending projection of the first housing end; an axially extending surface formed on the second interface member of the cylindrical body portion; with the piston comprising an axially disposed annular flange portion; with the piston abutting with and for reciprocal movement within the axially extending annular member, with the piston being slideable on the radially inward axially extending surface formed on the axially extending projection of the first housing end, and with the axially disposed annular flange portion of the piston being slideable on the axially extending surface formed on the second interface member of the cylindrical body portion.

7. Apparatus as claimed in claim 6 and further comprising means for sealing between the radially outward axially extending surface formed on the axially extending projection of the first housing end and the free annular end of the axially extending annular member; means for sealing between the piston and the axially extending annular member; means for sealing between the piston and the radially inward axially extending surface formed on the axially extending projection of the first housing end; means for sealing between the axially disposed annular flange of the piston and the axially extending surface formed on the second interface member of the cylindrical body portion, with a first pressure cylinder defined by the piston, the axially extending projection of the first housing end, and the axially extending annular member, with a second pressure cylinder defined by the piston, the second interface member, and the axially extending annular member; means for introducing fluid pressure into the first pressure cylinder; and means for introducing fluid pressure into the second pressure cylinder.

8. Apparatus as claimed in any preceding claim and further comprising circumferentially spaced heat dissipating fins integrally formed with and extending axially from the axially extending annular member and integrally formed with and extending axially from the radially extending mounting flange.

9. Apparatus as claimed in any preceding claim wherein the means for removable securing the second housing end to the mounting flange comprises axially extending studies having a first end threadably received in the second housing end and having a second end secured to the radially extending mounting flange.

10. Apparatus as claimed in any preceding claim wherein the output and the first interface member are rotatably mounted with respect to the housing and independent of each other allowing the apparatus to be readily disassembled into first and second major components for apparatus installation, with the first major component including the first interface member and the second housing end and with the second major component including the output, the cylindrical body portion, and the first housing end.

11. Apparatus as claimed in any preceding claim and further comprising first and second L-shaped bushings having first and second legs, with the first legs having free ends, with the first and second L-shaped bushings being oppositely directed with the free ends of the first legs being contiguous, with the fist legs of the first and second L-shaped bushings being rotatably received on the output; an annular shoulder formed in a circular opening of the first housing end, with the annular shoulder being captured between the second legs of the first and second L-shaped bushings; and means for preventing axial movement of the first legs of the first and second L-shaped bushings on the output.

12. An interface disc for an output having first and second interface surfaces, comprising a first, flat ring portion including the first interface surface, a first face opposite to the first interface surface, and a radially inward axially extending opening; an interface element including a second ring portion and means for connecting the second ring portion for rotation with the output, with the second ring portion including the second interface surface and a second face opposite the second interface surface; circumferentially spaced webs upstanding from the second face of the interface element, with the webs having free ends; and means for securing the first, flat ring portion to the interface element with the first face abutting with the free ends of the webs and spaced from the second face of the interface element forming spaced cutouts for heat venting.

13. An interface disc as claimed in claim 12 and further comprising at least a first axially extending opening formed in the second ring portion of the interface element and located intermediate the circumferentially spaced webs.

14. An interface disc as claimed in claim 12 or claim 13 and further comprising axially extending shoulders formed on the free ends of the webs for receipt of the radially inward axially extending opening of the first, flat ring portion to aid in positioning of the first, flat ring portion relative to the interface element.

15. Apparatus for providing rotational control substantially as hereinbefore described with reference to the accompanying drawings.

16. An interface disc substantially as hereinbefore described with reference to the accompanying drawings.