Patent GB-482577-A (GB)
Title: Improvements in or relating to transmission mechanism
IPC: F16H61/02
Filed: 1936-08-26
Abstract: 482,577. Variable speed gearing. BARNES, W. B. Aug. 26, 1936, No. 23431. [Class 80 (ii)] An epicyclic overdrive gearmechanism for automobiles comprises planets 15 mounted on a carrier 18 on the driving shaft 2, a sun gear 19 freely mounted on the shaft 2 and normally held from rotating by a brake device 26, and an annulus 12 freely mounted but engageable with a member 9 secured to the driven shaft 5 by centrifugal dogs 21. For normal direct drive the dogs 21 which are carried in radial slots 20 in the driven member 9 engage under pressure of springs 23 with recesses 22 in the driving planet carrier 18. As the speed of the driven member 9 and driven shaft 5 increases the dogs 21 move outwards under centrifugal force and tend to disengage from the recesses 22 and to engage with recesses 25 in an extension 13 of the annulus 12. The actual change is effected on releasing the aceclerator pedal with a consequent slowing up of the annulus 12 until its speed approaches that of the member 9, when the dogs 21 will move into the recesses 25 in the annulus extension 13. The driving shaft is then accelerated and the planet carrier drives the annulus at an increased speed, the sun gear 19 being held from rotation. A one-way clutch 11 is provided between the shaft 2 and the member 9 so that the drive is always transmitted even when the dogs 21 are disengaged from the recesses 22 in the carrier 18 and before they engage with the annulus. The sun gear 19 is normally held stationary by a radially movable dog 31 which slides in a, guide in a substantially fixed ring 32, which ring has however a small amount of circumferential movement against springs 41, and engages in notches 30 in a ring 26 secured to the sun gear, under pressure of a spring-pressed plunger 46. If the dog 31 is moved outwardly out of the notch 30, the sun gear is released and the overdrive through the planetary gearing does not take place, the carrier driving the member 9 direct through the one-way clutch 11. This release of the sun gear is effected by decelerating the driving shaft and so producing a coasting load on the sun gear which produces movement of the ring 32 against the springs 41. This movement releases the dog 31 by means of a cam slope 43 on the dog engaging a fixed pin 44, the ring and sun gear rotating freely when the driving shaft is again accelerated and the oneway clutch 11 taking up the direct drive. The acceleration of the driving shaft to ensure the release of the sun gear must be relatively sudden so that the notch 30 in the ring 26 will pass over the dog 31, which is provided with a cam-shaped end 50a for this purpose. The continued rotation of the ring 26 and sun gear prevents the re-engagement of the dog 31. If the driving shaft is only accelerated gradually the dog will re-engage in the notch 30 and the overdrive will be resumed. A return to the overdrive from direct drive is accomplished by a deceleration of the driving shaft, which slows down the sun gear and ring 26 until the dog 31 engages in a notch 30 to hold it stationary on again accelerating. A frictionally actuated baulk ring 32<1> with a notch 322 may be secured to the ring 32 with a limited amount of movement to be moved frictionally by the ring 26 to prevent re-engagement of the dog 31 whilst the ring 26 is rotating, and a similarly actuated baulk ring 57 may be provided for controlling the engagement of the centrifugal dogs 21 with the annulus 12.