Patent GB-255226-A (GB)
Title: Improvements in and relating to power transmissions embodying ratchet or other intermittently operating devices
IPC: F16H29/08
Filed: 1925-01-17
Abstract: 255,226. Prendergast, R. S., Prendergast, C. S., and Sonsthagen, A. Jan. 17, 1925. Variable-speed gearing.-In a power-transmission system having a rotary member driven by frictional or positive ratchets or other intermittently-operated devices actuated by rotary or reciprocating driving-members, speed fluctuations in the driven member are eliminated by an epicyclic train, the timing or amplitude (or both) of the impulses transmitted to two elements of the train being so determined by links interposed between the driving-members and the ratchets &c., that these elements maintain a substantially constant effort on the third element. The motion transmitted to the second element may be a pure oscillation, or an oscillation superimposed on a rotation in the same direction as that of the first element, or in the opposite direction thereto. Adjustable shock-absorbing springs and slides or other variable-throw devices may be embodied in the link-work. In a variable-speed ratchet gear, Figs. 1 and 4, a four-throw crankshaft 4 drives ratchets 15a by connecting-rods 5, floating links 6, and rods 15, each bevel-gear element 16b, 17<b> of a differential train being driven by a pair of ratchet-wheels mounted respectively on sleeves 16, 17. The sleeves bear on the driven shaft 3, which carries on one or more radial arms 18<a> a pinion or pinions 18b, the phase and amplitude of movement of the ratchets being such that the irregular motions of the wheels 16<b>, 17<b> are neutralized, and the shaft 3 is smoothly driven. The floating links 6 are pivoted to arms 6a, angularly adjustable about a common rod 7, which is carried in a frame comprising terminal arms 8 connected by a bar 10. The frame is rotated about the shaft 4 to vary the inclination of the links 6, and hence the travel of the rods 15, by a hand-actuated worm 12 and wheel 11, the hand-wheel shaft driving also a speed-ratio indicator (not shown). The gear-train may be of the sun-and-planet type, the internally-toothed ring forming the final driven element. Fig. 6 shows a modified variable-throw arrangement, comprising blocks 19 slidable radially in guides 19<a> on the ratchet elements 15<a> by lifting-links 19<b>, actuated from a manually-operated shaft 20. Fig. 8 shows a further modification, wherein the lifting-links 19<b> &c. adjust blocks 24 in slotted levers 21a, which are oscillated about pivots 22 by the connecting-rods 5, the ratchet-rods 15 being pivoted to lugs 27 of the blocks 24. The ratchets may be driven by links directly from the pistons of an internal-combustion or other reciprocating engine. Specification 217,527 is referred to. One of the Provisional Specifications mentions the application of the invention to variable-speed gearing comprising driving and driven members operably connected by one or more intermediate members, the speed of which is controlled by variable-throw ratchet mechanism. The other Provisional Specification describes an epicyclic form of such variable-speed gearing, wherein a clutch is provided for direct drive, the ratchets being either of the toothed or roller type, or comprising friction wedges with or without interposed expansible rings. It is also stated therein that the oscillation of the second element of the correcting-train may be controlled by springs, and that the variable-throw mechanism may be driven from countershafts geared or coupled to a member of the primary epicyclic train, for instance by a further epicyclic train having one member uniformly driven, and so proportioned that the top speed of the primary member corresponds with the bottom speed or state of rest of the countershaft.