996,377. Change-speed control; clutch control; positive clutches; electromagnetic brakes. S. SMITH & SONS (ENGLAND) Ltd. Aug. 25, 1961 [Aug. 31, 1960; Jan. 11, 1961], Nos. 30026/60 and 1209/61. Headings F2C, F2D, F2E, F2K and F2L. In a motor vehicle change speed transmission of the type comprising a main clutch, a change speed gear and a friction synchronized positive isolating or tail clutch between the engine and propeller shaft, the tail clutch is interconnected with the gear changing mechanism so that the clutch is disengaged prior to ratio shift and remains disengaged until the new ratio is established. The isolating or tail clutch may, as shown, be between the change speed gear and propeller shaft or may, Fig. 21 (not shown), be between the main clutch and change speed gear. As shown an automatic control for a four speed and reverse gear is responsive to output speed and throttle pedal position. The control, Fig. 18, energizes an electric motor 5 which drives cams that position the selector rods 78, 88, 98 of the gear, operate the positive clutch and close the throttle during ratio shift. The control also provides engine speed responsive engagement of the main clutch during starting. Clutches.-The main clutch, Fig. 13 (not shown) is a magnetic particle clutch of the type having a stationary winding. The positive isolating or tail clutch, Fig. 1, comprises circumferentially toothed driving and driven members 9, 12 and an internally toothed axially slidable clutch ring 22 connected through pins 19 to an operating sleeve 21, which is biased to the left for clutch engagement by a spring 36 acting through a clutch operating rod 34 on the sleeve 21. Rightward movement of the rod 34 initially disengages the clutch ring 22 from the member 9 and thereafter a split spring ring 27 engages a V-groove 23 in the pin 19 so that on further rightward movement a coned friction clutch ring 25 is moved out of engagement with a coned disc 32 fast with the driving member 9. The clutch ring 25 is carried by the pins 19. On release of the rod 34 initial movement of the operating sleeve 21 under the action, of springs 14, 36 moves the clutch ring 25 into engagement with the disc 32 whereupon relative rotation between the ring 25 and disc 32 rotates the ring 25 relative to the pins 19 so that conical surfaces 24, Fig. 4, on pins engage complementary balk surfaces 37 or 38 on the ring 25 and prevent further axial movement of the sleeve 21 and clutch ring 22 until the driving and driven members 9, 12 are synchronized. The downshift balk ring surfaces 37 is deeper than the upshift surface 38. Brakes.-An electromagnetic brake for the output shaft 42 of the electric motor 5 comprises a friction faced disc 41 fast with the shaft 42 which disc is clampled between a fixed back plate 43 and a presser plate 44 by a spring 45 and is released on energization of an electromagnet 46. The winding of the electromagnet is in series with the winding of the electric motor. Cam selector mechanism.-The electric motor 5, the output of which is braked at 40 when the motor is stopped, drives a first cam-shaft 6 carrying a throttle closing cam 54 and a clutch actuating cam 55. A second cam-shaft 7 carries three double selector cams 70, 71; 80, 81; 90, 91 and is driven from the first camshaft 6. The shaft 7 rotates through a little less than a right angle for each complete revolution of the shaft 6. The cams 54, 55 are so shaped that on initial rotation of the shaft 6 the cam 54 acts through a lever 64, rod 67 and spring-loaded lost motion coupling on the throttle linkage to close the throttle. Simultaneously a projection 62 on the lever 64 opens a switch 63 to de-energize the main clutch. Thereafter the cam 55 moves its follower 59 and rod 34 right to disengage the positive tail clutch. A pin 61 fast with the rod 34 engages a slot 68 in the lever 64 and maintains the latter in the throttle closed position, after the cams have completed their rotation, until the positive clutch re-engages whereupon the lever 64 reopens the throttle and closes the switch 63. Each cam 70, 71 of each double selector cam is engaged by a cam follower 73, 72 carried by a bellcrank lever 74 which is thus positively positioned. The outer ends of the bellcrank levers engage the selector rods 78, 88, 98. Spring-loaded lost motion couplings 79, 89 in the selector rods 78, 88 provide lost motion when reverse and first ratios are being engaged. The cam-shaft 7 drives through one-to-one gearing a switch shaft 102. Electric control circuit.-An electric switch Figs. 15, 16 (not shown) comprises a disc fast with the shaft 102, one side of which is coated with conducting material and has a stepped non-conducting strip thereon, this is represented in Fig. 18 by two conducting portions 149, 150. The steps are arranged so that contacts 143 ... 147 are each on the non-conducting strip 151 during fourth, third, second, first and reverse ratios respectively. Contacts 142, 148 in permanent contact with the conducting strips 149, 150 respectively are connected through change up and change down relay coils 193, 192 to a battery terminal 203. The other side of the switch disc has inner and outer conducting parts each having a strpped non-conducting strip thereon, represented in Fig. 18 by conducting portions 163, 164; 165, 166. The non-conducting strips 167, 170 are arranged so that contacts 158, 161 engage portions 164, 166 during reverse and first ratio and engage portions 163, 165 during the other ratios. Contacts 143 ... 147 are connected to switches 181... 183 of an output speed responsive governor 180. The speeds at which the governor switches 181 . . . 183 change over are increased with throttle opening. Contacts 160, 159 are connected directly and through resistor 200 to the battery terminal 203 and contacts 157, 158, 162, 161 are respectively connected to a voltage regulator field winding terminal 205, dynamo field coil terminal 204, dynamo armature terminal 206 and main clutch winding 107. A manual forward D, neutral N, reverse R lever 223 closes switch 188 in neutral, switches 184, 186 in reverse and switches 185, 187 in forward. Switches 191, 190 are respectively closed when the throttle opening is between 5-8 degrees and 20-25 degrees where full throttle opening is 60 degrees. Operation.-With the vehicle stationary, first gear engaged, manual lever 223 in the neutral position, and throttle closed the control circuit is conditioned as shown in Fig. 18. Movement of lever 223 into forward drive position D closes switch 185 energizing main clutch winding 107 from dynamo armature terminal 206 for engine speed responsive clutch engagement. At an appropriate speed according to throttle position, governor switch 181 changes over to energize the change up relay coil 193 through the switch 191 which is now closed. The relay 193 changes over switch 195 whereupon the battery energizes the field winding 207 and armature 208 of motor 5 and also the release winding 46 of brake 40. The motor 5 then drives the cams which close the throttle, deenergize main clutch winding 107 by opening switch 63, disengage the clutch and move selector rods to second gear. When the ratio shift is completed the non-conducting strip 151 engages contact 145 to de-energize relay 193 and stop the motor 5. Re-engagement of the main and tail clutches and opening of the throttle is then effected as above described. Due to rotation of the switch disc the main clutch winding 107 is now energized direct from the battery terminal 203 and the dynamo field terminal 204 is connected directly to the voltage regulator field terminal 205. Further increases in vehicle speed change over switches 182, 183 for upshift to third and fourth ratios which upshifts are effected as above described. For 4-3 downshift switch 183 changes back to the position shown thereby energizing downshift relay 192 through contacts 144, 148. The relay 192 changes over switch 194 whereupon the battery energizes the motor field winding 207 in the opposite sense to that for upshift and energizes the motor armature 208 and brake release winding 46. The motor is thus driven in the reverse direct for downshift, until the non-conducting strip 151 engages contact 144. Further downshifts are effected in a similar manner. If during downshift the main clutch output shaft overruns the input shaft a switch 131 opens to provide reduced energization of the main clutch winding 107 through resistor 202. If, however, the throttle is opened sufficiently to close switch 190 part of the resistor 202 is bridged to provide reduced energization of lesser extent. if the vehicle slows down in third ratio with the throttle closed, the then open switch 191 prevents the normal change to second ratio. For reverse the lever 223 is moved to the reverse position to close switches 184, 186 and open switches 185, 187. The downshift relay 192 is then energized through contacts 157, 158. Modification.-In Fig. 21 (not shown) the gear shift is effected manually and the positive isolating clutch is operated by a solenoid under the control of a gear shift lever switch. Specifications 803,614 and 970,535 are referred to.