10,791. Sinclair, G. W., and Blackwell & Co., R. W. May 10. Pump stroke, varying.-Relates to variable-stroke pumps of the type in which the variation in stroke is obtained by means of two eccentrics superimposed, and consists in combining with a crank shaft having eccentric portions thereon an internal shaft fitted with pinions adapted to gear with additional eccentrics mounted on the aforesaid eccentric portions, in such a manner that, when relative rotation between the two shafts is set up, preferably by differential gearing between the two shafts, relative displacement of the superimposed eccentrics is obtained which alters the effective stroke of the plunger or the like reciprocated by such eccentrics. Fig. 3 shows a crank shaft having three sets of crank webs a, a ; b, b ; c, c ; placed eccentrically so that the centre of each is at a distance of one fourth of the stroke of the plungers from the centre of the shaft. Mounted upon the crescent-shaped portions d connecting these webs are eccentrics e, placed relatively to the centre of the crank webs at a distance of one fourth of the stroke of the plunger and capable of rotation about the portions d by pinions j mounted upon a shaft g passing down the centre of the main shaft and by annular teeth formed within the eccentrics. Figs. 4, 5, 6, and 7 show the differential gearing connecting the two shafts, the action being as follows :-When the clutch y is held in engagement with the clutch v, the spur-wheel t is held fixed and the spur-wheels u, s and worm gears p, o, l, all of which are mounted upon and rotate with the discs m, n attached to the main shaft, are caused to rotate about their axes, the worm-wheel h, which is fixed to the shaft g and engages with the last of these, being thereby caused to rotate relatively to the main shaft so that the stroke of the pumps is altered. When, on the other hand, the clutch y engages with the clutch x, the pinion q becomes fixed and the shaft g now rotates in the opposite direction, as the spur-wheel u has now come out of action. When the clutch y is out of engagement with both of the clutches v, x, the spur-wheel h and disc m rotate together, so that there is no relative motion of the shafts. As an alternative arrangement, the worm-wheel h can be formed as part of the disc m and the worm-wheel l may be carried on a bracket or disc secured to the internal shaft g.