Patent GB-191200676-A (GB)
Title: Improvements in Variable Speed Power Transmission.
Inventor: PLETTS JOHN ST VINCENT
IPC: F16H33/02
Filed: 1912-01-09
Granted: 1913-02-10
Abstract: 676. Pletts, J. St. V. Jan. 9. Automatic speed or power control; governors, applications of.-Relates to power-transmission gear, applicable to motor-cars &c., in which the drive is so transmitted through springs that the gear automatically varies with the load. In the form shown in Figs. 1 and 5, a disk d is connected by a spring p to the engine shaft e. links r being pivoted to the disk and to clutch blocks c sliding radially in a fly-wheel f secured to the shaft e. A drum o secured to a shaft w<1> has ratchet teeth t engaged by pawls t<1> on a fixed frame b to prevent the drum from rotating backwards. The shaft w<1> may be connected to the shaft w either directly by a clutch i or for reverse drive by toothed wheels h, h<1>, chainwheels k, k<2>, and a chain k<1>. The shaft w is connected to one end of a spring s, the other end of which is connected to the wheel axles through the usual bevel and differential gearing. A spindle s<1> is also connected to the wheel axles, and may turn loosely in the end of the shaft w, or, if the spring is not strong enough to transmit a drive in the reverse direction, the spindle may have a notch, Fig. 4, engaged by the end of a catch a pivoted on the shaft w and connected to the spring s at the other end. In the forward direction the spindle is free, but if the drive is reversed the spindle and shaft are connected together. If there is a heavy load, as when starting or in ascending a hill, the engine is slowed down so that the centrifugallyoperated clutch blocks c are disengaged from the drum o. The engine, being thus freed, speeds up and re-engages the clutch, so that the engine is connected to, and winds up, the spring s. This again throws the load on the engine and disengages the clutch, this cycle continuing while the load is too great for the engine to drive continuously. The pawls t prevent the spring from unwinding, and power is supplied from the spring to the wheel axles, the speed depending upon the load. The arrangement of the parts of the clutch is such that engagement is sudden, but, if desired, the action may be gradual. In the form shown in Figs. 2 and 6, the engine shaft e carries an arm, on which turn bevel-pinions g gearing with a pinion g<1> on a loose fly-wheel f and with a pinion g<2> on the driven shaft w. A centrifugal claw clutch, Fig. 6, connects the fly-wheel f to a clutch casing o connected by a flat spiral spring s to the shaft w, backward turning being prevented by a roller ratchet t<1>. With the arrangement of gearing shown, the clutch is engaged at a lower engine speed when the car is stationary than when the car is running. In the form shown in Fig. 3, the engine shaft e carries the fly-wheel f, the inner part c of an electromagnetic induction clutch, and a gear-wheel g. The outer clutch part o is retained by a friction ratchet t and is connected by the coiled spring s to an epicyclic casing q, which carries, fixed on spindles w<1>, planet pinions g<1>, g<2> gearing respectively with the wheel g and a wheel g<3> on the driven shaft w. The clutch windings are connected to a slip-ring m, engaged by a brush n, and to a slip-ring m<1> engaging a squared part of the shaft e and moved by a governor y at the required speed against a brush n<1>. When the engine is running slowly, the shaft w is driven slowly through the epicyclic gearing, the casing being held stationary by the pawl t. When the clutch is energized by increase of engine speed, the casing is rotated forwards through the spring s, and the speed of the shaft w increases. To allow the engine to run freely, a lever l<1> connected to the pawl t is depressed, releasing the casing q and at the same time operating a lever l<2>, which moves the ring m<1> out of position to engage the brush n<1>. A cord z attached to the lever l<2> may be used for adjusting the speed at which the clutch is excited. To obtain a reverse speed with this device, the gear-wheel g<3> may be locked, and the casing q clutched to the shaft w, the lever l<1> being depressed.