United States Patent (12) (1o) Patent No.: US 8,091,445 B1 Stevens et al. (45) Date of Patent: Jan. 10, 2012 (54) OFFSET COMPOUND GEAR INLINE 1,966,874 A * 7/1934 Thompson ...................... 74/332 TWO-SPEED DRIVE 1,975,300 A * 10/1934 Thompson ...................... 74/332 2,998,729 A * 9/1961 Warsaw .......................... 74/7 R 3,053,326 A 9/1962 Derschmidt (75) Inventors: Mark A. Stevens, Broadview Heights, 5,178,028 A 1/1993 Bossler, Jr. OH (US); Robert E. Handschuh, North 6,612,195 132 9/2003 Gmirya et al. Olmsted, OH (US); David G. Lewicki, 6,641,365 132 11/2003 Karem 7,044,877 132 5/2006 Ai Avon, OH (US) 2007/0205321 Al 9/2007 Waide (73) Assignee: The United States of America as OTHER PUBLICATIONS represented by the Administrator of Mark A. Stevens, Robert F. Handschuh, David G. Lewicki; Concepts National Aeronautics and Space for Variable/Multi-Speed Rotorcraft Drive System; American Heli- Administration, Washington, DC (US) copter Society 64th Annual Forum; Montreal, Canada; Apr. 29-May 1, 2008. (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 * cited by examiner U.S.C. 154(b) by 455 days. Primary Examiner Dirk Wright (21) Appl. No.: 12/431,456 (74) Attorney, Agent, or Firm Howard M Cohn; Robert H. Earp, III (22) Filed: Apr. 28, 2009 (57) ABSTRACT (51) Int. Cl. A two-speed transmission having an input shaft and an output F1 6H 3104 (2006.01) shaft, the transmission being capable of transitioning (52) U.S. Cl . ......................................................... 74/332 between fixed ratios, the high-range ratio being direct 1:1 and (58) Field of Classification Search ........................ None the low-range ratio being about 2:1. The transmission is a See application file for complete search history. simple lightweight, yet robust, configuration utilizing only two gear meshes, being comprised of an input gear, a cluster (56) References Cited gear, and an output gear. The transmission is controlled with a clutch and a sprag and with the input and output shafts U.S. PATENT DOCUMENTS turning in the same direction. 1,872,338 A * 8/1932 Plexico ........................... 74/332 1,912,936 A * 6/1933 Fawick ........................... 74/332 21 Claims, 5 Drawing Sheets 12 21 1 30 U.S. Patent Jan. 10, 2012 Sheet 1 of 5 US 8,091,445 B1 m co NP C r O co N U.S. Patent Jan. 10, 2012 Sheet 2 of 5 US 8,091,445 B1 n N .Q M N .D N N O F N Q N W to LL U.S. Patent Jan. 10, 2012 Sheet 3 of 5 US 8,091,445 B1 co T- 0 m N W CL LL C Ir- U.S. Patent Jan. 10, 2012 Sheet 4 of 5 US 8,091,445 B1 a Cs ":t LO 00 NO W^/ .Jy.J L w Wr D 00 Z) 0 i UL U.S. Patent Jan. 10, 2012 Sheet 5 of 5 US 8,091,445 B1 cNo cNp d' d' O N O e-^ d' N N mt cTo N r NT Y Wt co W Of D N 0 CV) M C7 O M Cp u- Y 0) VI- M T M a M T M CTa M ^CD d j C'7 \04 M O T- M ^ M US 8,091,445 B1 1 2 OFFSET COMPOUND GEAR INLINE ing speed of the output shaft from a first speed ratio to a TWO-SPEED DRIVE second speed ratio. The shift between the first rotating speed ratio and the second rotating speed ratio is smoothly accom- STATEMENT REGARDING FEDERALLY plished by the combination of two sets of planetary gear SPONSORED RESEARCH OR DEVELOPMENT 5 clusters and two electric motors. The electric motors being are to smooth the mechanical shift between the first speed The invention described herein was made by an employee ratio and the second speed ratio. However, Ai does not dis- of the United States Government and may be manufactured close a transmission with a high-range ratio (1:1) and low- and used by or for the Government for Government purposes range reduction ratio, such as for example 50% (2:1), which without the payment of any royalties thereon or therefore. to changes from one to the other through a speed change mecha- nism including gears, a clutch and a sprag. TECHNICAL FIELD U. S. Pat. No. 6,641,365 to Karem disclosed for example "A variable speed helicopter tilt rotor system and method for The invention relates to transmissions, and more particu- operating such a system are provided which allow the heli- larly to a device(s) and configurations which provide a 15 copter rotor to be operated at an optimal angular velocity in simple, lightweight two-speed drive which can be used either revolutions per minute (RPM) minimizing the power required as an overall transmission or as a supplemental add-on input to turn the rotor thereby resulting in helicopter performance transmission (e.g., over-drive/under-drive) to extend the efficiency improvements, reduction in noise, and improve- capability of an existing transmission. ments in rotor, helicopter transmission and engine life." 20 US Patent Application No. 2007/0205321 to Waide dis- BACKGROUND closes for example gearboxes providing first and second power-balanced paths in which a speed changer is configured In several recent studies and on-going developments for to operate with only one path. Most preferably, the gearbox advanced rotorcraft, the need for variable or multi-speed includes a friction clutch and a sprag clutch arranged such capable rotors has been raised. A speed change of up to 50% 25 that, together with a lay-shaft and spur-gear differential, gear has been proposed for future rotorcraft to improve overall shifting can be done while transmitting power. The speed vehicle performance. Accomplishing rotor speed changes changing gearbox of the '321 application has first and second during operation requires both a rotor that can perform effec- independently and concurrently operational drive paths for tively over the operational speed-load range, and a propulsion transmission of torque. However, Waide does not disclose a system that can enable these speed changes. 30 transmission with a high-range ratio (1:1) and low-range Rotorcraft propulsion is a critical element of the overall reduction ratio, such as for example 50% (2:1), which rotorcraft. Unlike fixed wing aircraft, the rotor propulsion changes from one to the other and directs the torque through system provides lift and control as well as forward thrust. As an output shaft which is in the same drive path as the input a result, the rotorcraft engine-gearbox system must be highly shaft. reliable and efficient. In addition, the gearbox system must be 35 kept at minimum weight. Presently, the propulsion system SUMMARY OF THE INVENTION accounts for up to 25% of empty vehicle weight. The drive system accounts for up to 72% of the total propulsion system With the present invention, a transmission, preferably for a weight. Future rotorcraft trends call for more versatile, effi- rotorcraft is provided where the rotation of the rotor blades cient, and powerful aircraft, all of which challenge state-of- 40 can be at 50% or less while maintaining engine speed at the the-art propulsion system technologies. Variable speed rotors optimal efficiency/performance speed. A portion of the over- have been identified as having a large impact on many critical all 50% reduction can come from extending the engine speed rotorcraft issues. operability range beyond present 15% decrease with the bal- Currently, rotor speed can only be varied a small percent- ance provided by the transmission of the present invention. At age by adjusting the speed of the engine. The variation in rotor 45 the present time, the reduction in rotor speed of about 15% is speed is generally limited by engine efficiency and stall mar- presently accomplished by changing the engine speed. How- gin, permitting speed changes limited to approximately 15% ever, with the transmission of the present invention, the entire when used in current tilt-rotor applications. 50% decrease in rotational speed can be realized without There is a need for a transmission with a high-range ratio requiring any additional reduction in the speed of the engine. (1:1) for hover mode operation and low-range reduction ratio, 5o Future overall propulsion system (engine, driveline, and such as for example 50% (2:1), through a speed change rotor) studies will determine what portion the transmission mechanism, for cruise mode operation. A transmission of this device should provide for overall optimal performance. This type could be incorporated as an element within the overall invention uniquely provides both a high-speed 1:1 range and propulsion system resulting in overall ratios of 50:1 to 100:1 a low-speed 2:1 range (50% speed reduction) with minimal in the aircraft. 55 robust parts. The low range ratio being dependent upon the It is commonly recognized that variable speed propulsion gearing contained within can be varied, as required, to meet is required for the design of future advanced rotorcraft. specific requirements. Reductions in rotor speed are required to limit the advancing According to the present invention, there is disclosed a rotor tip speed and reduce rotor noise. transmission having a gear arrangement for transmitting 60 torque from an input shaft to an output shaft. The input shaft RELATED PATENTS rotates about a first rotational axis and has a first gear coupled thereto. An elongated, hollow, cylindrical shaft rotates about The following patents are incorporated by reference in a second rotational axis that is offset from the first rotational their entirety herein. axis. The hollow cylindrical shaft has a second gear at one end U.S. Pat. No. 7,044,877 to Ai discloses for example a two 65 thereof which meshes with the first gear and a third ring gear speed transmission having an input shaft and an output shaft. at an opposite end thereof. A fourth gear is mounted to one The two-speed transmission is capable of changing the rotat- end of a hollow drive shaft. The fourth gear and the hollow US 8,091,445 B1 3 4 drive shaft rotate about the first rotational axis. The fourth the present invention is added to an existing design engine- gear is meshed with the third gear of the hollow, cylindrical transmission driveline and used as a supplemental inline shaft. The hollow drive shaft has a cylindrical end portion at speed change device. an opposite end thereof. The output shaft rotates about the Yet further according to the present invention, the first first rotational axis and has a flange portion attached thereto. 5 input shaft of the transmission is connected to the output shaft A sprag clutch has an input side mounted to the cylindrical of a second gear arrangement for transmitting torque from a end portion of the hollow drive shaft and an output side second input shaft to the first input shaft. The second gear mounted to the flange portion of the output shaft. A multi- arrangement comprises a second input shaft rotating about plate clutch is attached to an end portion of input shaft and to the first rotational axis and having a first gear coupled thereto. Io the output shaft. Coupling structure is provided for coupling An elongated, hollow, cylindrical shaft rotating about the the input shaft with the output shaft whereby the transmission second rotational axis is offset from the first rotational axis. operates in first and second modes. The hollow cylindrical shaft having a second gear at one end Further according to the present invention, the first mode of thereof which engages the first gear and a third gear at an operation results in a rotating speed ratio R, of 1 to 1 between 15 opposite end thereof. A fourth gear is supported by a bearing the input shaft and the output shaft and the second mode of at the aft end of the input shaft of the transmission. operation results in the rotating speed reduction ratio range of Still further according to the present invention, the rela- 4.00>Rz>1.50 between the input shaft and the output shaft. tionship between the output speed and input for low speed Preferably, the second mode of operation results in the rotat- operation of the second gear arrangement is given by the 20 equation: ing speed reduction ratio range of 2 to 1 between the input shaft and the output shaft. Still further according to the present invention, coupling Output Speed—Input Speedx(N414/N430)x(N434/N418) structure for coupling the input shaft with the output shaft can where N14 is equal to the number of teeth on first gear cause the rotational speed of the output shaft to be the same as (414), the rotational speed of the input shaft is the multi-plate clutch. 25 N30 is equal to the number of teeth on the second gear Yet further according to the present invention, the clutch is (430), a multi-plate clutch having first spaced clutchplates driven by N34 is equal to the number on the third gear (434), an end portion of the input shaft and second spaced clutch and N1a is equal to the number of teeth on the fourth gear (418). plates which drive the output shaft and interspersed between So Yet further according to the present invention, the trans- the first spaced clutch plates. mission is a rotorcraft transmission of a light weight configu- Moreover, according to the present invention, a clutch ration with reduced parts. actuator means engages or disengages the first and second According to the present invention, there is disclosed a interspersed clutch plates whereby if the multi-plate clutch is method of transmitting torque from an input shaft to an output engaged the rotational speed of the output shaft is at a first 35 shaft of a transmission. The method includes the steps of speed which is the same as that of the input shaft and if the rotating the input shaft having a first gear coupled thereto clutch is disengaged the rotational speed of the output shaft is about a first rotational axis; rotating an elongated, hollow, at a speed that is different from that of the input shaft. cylindrical shaft about a second rotational axis that is offset Also, according to the present invention, the multi-plate from the first rotational axis, the hollow cylindrical shaft clutch causes the rotational speed of the output shaft to be the 4o having a second gear at one end thereof which engages the same as the rotational speed of the input shaft whereby the first gear and a third gear at an opposite end thereof, rotating transmission operates in first mode (high speed range, 1:1 • fourth gear mounted to one end of a hollow drive shaft with ratio). • cylindrical end portion at an opposite end thereof about the Also, according to the present invention, the sprag clutch first rotational axis whereby the fourth gear engages the third causes the rotational speed of the output shaft to be less than 45 gear of the hollow, cylindrical shaft; rotating the output shaft the rotational speed of the input shaft whereby the transmis- with a flange portion attached thereto about the first rotational sion operates in second mode (low speed range, 2:1 ratio). axis; mounting an input side of a sprag clutch to the cylindri- According to the present invention, the first gear has exter- cal end portion of the hollow drive shaft and an output side of nal teeth adapted to mesh with the internal teeth of the second the sprag clutch to the flange portion of the output shaft; and gear and third gear has external teeth adapted to mesh with the 50 coupling the input shaft with the output shaft whereby the internal teeth of fourth gear. transmission (10) operates in first or second modes. Further according to the present invention, the relationship Further according to the present invention, there is dis- between the output rotational speed and the input rotational closed the steps of operating in the first mode of operation speed for the second mode of operation is given by the equa- resulting in a rotating speed ratio R, of 1 to 1 between the tion 55 input shaft and the output shaft; and operating in the second mode of operation resulting in the rotating speed ratio Rz of and the second mode of operation results in the rotating speed Output speed = Input speed x (N14) X (N14 reduction ratio range of 4.00>R2>1.50 between the input N30 N1s shaft and the output shaft. 60 Still further according to the present invention, means are where N14 is equal to the number of teeth on first gear, N30 is provided for attaching first spaced clutch plates of a multi- equal to the number of teeth on the second gear, N34 is equal plate clutch to an end portion of input shaft and attaching to the number of teeth on the third gear, and N, a is equal to the second spaced clutch plates to the output shaft whereby the number of teeth on the fourth gear. second clutch plates are interspersed between the first spaced Still further according to the present invention, the input 65 clutch plates; and engaging the first and second interspersed shaft is driven by a device from which it receives rotational clutch plates whereby the rotational speed of the output shaft power such as an engine or an intermediate drive coupling if is the same as that of the input shaft or disengaging the first US 8,091,445 B1 5 6 and second interspersed clutch plates whereby the rotational cross-hatched element from a neighboring un-shaded ele- speed of the output shaft is less than that of the input shaft. ment). It should be understood that it is not intended to limit Also according to the present invention, there is disclosed the disclosure due to shading or cross-hatching in the drawing a method of transferring torque from an input shaft to an figures. output shaft of a transmission including the steps of operating 5 FIG. 1 is an oblique cross sectional view of a two-speed, in the first mode of operation resulting in a rotating speed ratio mechanical-power-conveying transmission, according to the R, of 1 to 1 between the input shaft and the output shaft; and present invention. operating in the second mode of operation resulting in the FIG. 2A is an orthogonal cross sectional view of the two- rotating speed ratio RZ of 2 to 1 between the input shaft and speed, mechanical-power-conveying transmission, according the output shaft. 10 to the present invention. Further according to the present invention, there is dis- FIG. 2B is a schematic axial view of the gear relationships closed a method of transferring torque from an input shaft to in the two-speed, mechanical-power-conveying transmis- an output shaft of a transmission including the step of engag- sion, in according to the present invention. ing or disengaging the multi-plate clutch whereby when the FIG. 3A is an orthogonal cross sectional view of the present multi-plate clutch is engaged the rotational speed of the out- 15 invention showing the path of power flow during high-speed put shaft is at a first speed which is the same as that of the input output operation of the two-speed, mechanical-power-con- shaft and when the multi-plate clutch is disengaged the rota- veying transmission, according to the present invention. tional speed of the output shaft is at a speed that is less than FIG. 3B is an orthogonal cross sectional view of thepresent that of the input shaft. invention showing the path of power flow during low-speed Also according to the present invention, there is disclosed 20 output operation of the two-speed, mechanical-power-con- the steps of engaging or disengaging the clutch whereby when veying transmission, according to the present invention. the clutch is engaged the rotational speed of the output shaft FIG. 4 is an orthogonal cross sectional view of multiple is at a first speed which is the same as that of the input shaft stages of the two-speed, mechanical-power-conveying trans- and when the clutch is disengaged the rotational speed of the mission in series, according to the present invention. output shaft is at a speed that is less than that of the input shaft. 25 Still further according to the present invention, there is DETAILED DESCRIPTION OF THE INVENTION disclosed the steps of coupling the input shaft with the output shaft to cause the transmission to operate in the first mode Throughout the descriptions set forth herein, various fea- with the rotational speed of the output shaft the same as the tures of the invention may be described in the context of a rotational speed of the input shaft is with the multi-plate 30 single embodiment. The features, however, may also be pro- clutch. vided separately or in any suitable combination. Conversely, Still further according to the present invention, there is although the invention may be described herein in the context disclosed the steps of coupling the input shaft with the output of separate embodiments for clarity, the invention may also be shaft to cause the transmission to operate in the second mode implemented in a single embodiment. Furthermore, it should with the rotational speed of the output shaft less than the 35 be understood that the invention can be carried out or prac- rotational speed of the input shaft is with the sprag clutch ticed in various ways, and that the invention can be imple- where the output speed is governed by the overall ratio of the mented in embodiments other than the exemplary ones gear set comprised of the first, second, third and fourth gears. described hereinbelow. The descriptions, examples, methods Yet further according to the present invention, there is and materials presented in the description, as well as the disclosedthe step of connecting the input shaftto a device that 40 claims, should not be construed as limiting, but rather as transmits rotational power. illustrative. Further according to the present invention, there is dis- If any dimensions are set forth herein, they should be closed the step of serially connecting a plurality of gear construed in the context of providing some scale to the rela- arrangements and determining the overall output ratio of the tionship between the elements. For example, a given element two serially connected gear arrangements from the product of 45 may have an equal, lesser or greater dimension (such as the two in-series ratios, R1, Rz. diameter) than another element. Any dimensions that are important or critical will generally be identified as such. The BRIEF DESCRIPTION OF THE DRAWINGS term "at least" includes equal to or greater than. The term "up to" includes less than. Also, an open-ended range or ratio as Reference will be made in detail to embodiments of the 50 "at least 2:1" should be interpreted to include sub-ranges such disclosure, examples of which may be illustrated in the as at least 2:1, at least 5:1, and at least 10:1. accompanying drawing figures (FIGS). The figures are The present two-speed transmission invention 10 is intended to be illustrative, not limiting. Although the inven- referred to herein as a "transmission," "two-speed transmis- tion is generally described in the context of these embodi- sion," "compound gear transmission," or variations thereof, ments, it should be understood that it is not intended to limit 55 or as the inventors' preferred usage: "offset compound gear the invention to these particular embodiments. drive," or OCG. Certain elements in selected ones of the figures may be Referring to FIG. 1 there is shown in cross sectional view illustrated not-to-scale, for illustrative clarity. The cross-sec- the novel two-speed, mechanical-power-conveying transmis- tional views, if any, presented herein may be in the form of sion 10 comprising an input shaft 12 having a first gear 14 "slices", or "near-sighted" cross-sectional views, omitting 6o attached thereto, an output shaft 26, an elongated, hollow, certain background lines which would otherwise be visible in cylindrical shaft 16 having a second gear 30 possessing inter- a true cross-sectional view, for illustrative clarity. In some nal teeth at one end 16a of the cylindrical shaft, and a third cases, hidden lines may be drawn as dashed lines (this is gear 34 possessing external teeth at the other end 16b of the conventional), but in other cases they may be drawn as solid cylindrical hollow shaft, a fourth gear 18 integral with or lines. 65 attached to wheel 65 and supported on bearing 62 maintain- If shading or cross-hatching is used, it is not intended to be ing concentricity with gear 14 by means of the aft end of shaft of use in distinguishing one element from another (such as a 12, a multi-plate clutch 22, and a sprag clutch 28. The input US 8,091,445 B1 7 8 shaft (12) is rotationally driven by a device (13), such as an 14 attached thereto, aball or roller type bearing 17, the second engine, from which it receives rotational power. The elon- gear 3 0 and the third gear 34 that are part of, and integral with, gated cylindrical shaft 16 has a rotational axis 19 that is offset the offset hollow cylindrical shaft 16, and the fourth gear 18. from a shared main rotational axis 21 of the input shaft 12 and The solid line 27 defines the foreshortened, end view of the the output shaft 26. Input shaft 12 is supported on bearings 60 5 cylindrical surface plane of bearings 48, which provide sup- and 62. Output shaft 26 is supported on bearings 64 and 66. port to offset hollow shaft 16. The offset aspect of the hollow Bearings 60 and 66 serve as drive system main bearings. driveshaft 16 is evident in the location of its axis of rotation 19 Bearings 62 and 64 serve as intermediate bearings. Bearing in relation to the axis of rotation 21 that is shared by the input 62 maintains concentricity and permits relative differential shaft 12 and the output shaft 26. Axis of rotation 21 is the rotational speeds between gear 18 and shaft 12. Bearing 64 io central, or primary, machine axis on which the drive system serves as a pilot bearing between input shaft 12 and output input and output are centered, whereas axis of rotation 19 is a shaft 26 to maintain concentricity and permit relative differ- secondary axis of rotation on which some of the internal ential rotational motion between input shaft 12 and output components between the input and output rotate, primarily shaft 26 (i.e., differential rotational speeds). Bearings 60, 62, hollow shaft 16, second gear 30, and third gear 34. The dashed 64, and 66 share a common central axis 21. Shaft 16 is 15 oval 37a encompasses a first mesh plane 37 where the first supported on bearings 48 which are concentric with the axis gear 14 meshes withthe second gear 30, and the second dotted 19 and are offset from the central axis 21 of bearings 60, 62, oval 41a encompasses the second mesh plane 41 where the 64, and 66. The offset between the axis 19 and 21 is a direct third gear 34 meshes with the fourth gear 18. FIG. 2B in an function of the gear ratios. Bearings 60, 62, 64, and 66 are idealized view combining mesh plane 37 and mesh plane 41 represented as rolling element type bearings but may also be 20 into a single plane for presentation of the OCG Offset Com- of the fluid film type or magnetic type as warranted by overall pound Gear concept basis, whereas in the present invention transmission speed and power requirements, and bearings 48 the two mesh planes are separated axially. which are represented as fluid film type journals may also be A first bearing set 60 (see FIGS. 1 AND 2A) supports the of the rolling element type. input end 12a of the input shaft 12. A first single bearing 62 The first gear 14 having external teeth, is affixed to the 25 supports the fourth gear 18 in relation to the input shaft 12. A input shaft 12, and meshes with the second gear 30 having second single bearing 64 supports the output shaft 26 in internal teeth, on the forward end 16a of the elongated hollow relation to the input shaft 12. A second bearing set 66 supports shaft 16. At the aft end 16b of the elongated hollow shaft 16 is the output shaft 26. The hollow, cylindrical offset shaft 16 is a third gear 34, having external teeth, and which meshes with carried by bearings 48, which are of the fluid film journal/ a fourth gear 18, having internal teeth. The fourth gear 18 is 30 thrust type or rolling element bearing type based upon spe- attached to a hollow drive shaft 20 at a forward end 20a, by cific transmission requirements. means such as bolts 29 (see FIG. 2A). The opposite or distal Operational Dynamics end 20b of hollow drive shaft 20 has a cylindrical end portion During operation, if the multi-plate clutch 22 is engaged, 20c onto which is mounted the input side 28a of a sprag clutch then the rotational speed of the output shaft 26 is the same as 28. 35 that of the input shaft 12 and the power flows directly from the The output shaft 26 has an integral flange portion 43 that is input shaft 12 to the output shaft 26 through the multi-plate located between opposite ends 26a and 26b of the output shaft clutch 22 by means of torque transmitted via friction created 26. Flange portion 43 has an upstanding rim 43a with an inner by the clamping force provided by releasing clutch actuator surface 43b that receives the output side 28b of the sprag 51. If the clutch 22 is disengaged, then the rotational speed of clutch 28. The input shaft 12 has an end portion 12b that is 40 the output shaft 26 is less than that of the input shaft 12 and the large in diameter as compared to the remainder of the input power flows from the fourth gear 18 to the flange portion 43 shaft 12. of the output shaft 26 by way of the sprag clutch 28. The ratio A hollow cylinder 24, sized to accommodate the multi- of the input rotational speed and the output rotational speed plate clutch assembly 22, is attached or contiguous with the when the clutch 22 is disengaged is on the order of 2:1 as input shaft distal end portion 12b of input shaft 12. The clutch 45 described or some other ratio as required. assembly 22 has alternating stacked clutch plates 22a, 22b, The input/output speed ratio is a function of the effective 22c, 22d (22a-22d) (see FIG. 2) that are driven by, and rotate respective diameters of the first and second meshing gears 14 at the same speed as hollow cylinder 24 by means of spline or and 30, respectively, and the respective diameters of the third tooth engagement at the outer perimeter. The spaced stacked and fourth meshing gears 34 and 18, respectively, as should be plates 22a-22d engage by means of friction a set of inter- 5o readily evident to those who are skilled in the art of transmis- spersed stacked clutch plates 23a, 23b, 23c, 23d (23a-23d) sion of rotary mechanical power. The input/output ratio is which drive and rotate at the same speed as the output shaft 26 discussed in more detail hereinbelow. by means of spline or tooth engagement at the inner perim- The two-speed operation of the present transmission inven- eter. An annularly arranged clutch actuator 51, which is tion 10 becomes more evident upon contemplation of cross mounted to and rotates with the end portion 12b of input shaft 55 sectional views of FIGS. 3A and 3B. FIG. 3A illustrates 12, compresses or releases the clutch 22 to cause it to engage high-speed operation of the present transmission invention or disengage during operation, as described herein below. The 10, which takes place when the multi-plate clutch assembly configuration of the clutch actuator 51 is a mechanical spring 22 is engaged. The direction of flow of rotary mechanical arrangement (e.g., helical coil, Belleville, diaphragm spring) power is shown by means of the line 77 with arrowheads 77a. activated and hydraulically released (e.g., by an annular pis- 6o The direction of flow of mechanical rotary power is from ton). A mechanical fail safe feature is incorporated in the input shaft 12, hollow cylinder 24, to clutch assembly 22 and clutch release (disengagement) mechanism so that the clutch through output shaft 26, such that the output speed is the same will be engaged if there is a failure of the clutch release as the input speed (the output ratio is 1:1.) mechanism. FIG. 2B provides an axial schematic view of the FIG. 3B illustrates low-speed operation of the present rotating components of the present transmission invention 10. 65 transmission invention 10, which takes place when the multi- The elements shown are the input shaft 12 (which has the plate clutch assembly 22 is disengaged. Power enters at the output shaft 26 behind it and out of view), having the first gear input shaft 12 and is transferred by way of the first gear 14 to