Abstract: A power tool (10) is provided having a plastic casing (12) and a scraper blade (14). The blade (14) is caused to reciprocate by an internal low power rotary motor (24) which drives a cylinder cam (28) having a sinusoidal cam track (34). A pair of studs (36) ride in the cam track (34), and drive the reciprocal movement of the blade (14). The tool (10) is substantially sealed against liquid ingress by means of an elastomeric membrane within the casing (12), and may be used as a marine growth remover, for defouling boats and the like.

Abstract: A number of cam-operated devices such as power tools (10) are described, the tools having a rotary drive device (24) for rotating a drive shaft (36) having a cylinder cam (42) mounted thereon. A pair of cam followers (54) are located within a cam track (44) provided on the cam member (42), such that rotation of the cam (42) causes axial movement of the cam followers (54), which may be attached to a drive shaft (48) and a tool bit (12). A range of shapes of cam track (44) are described, each of which is non-sinusoidal in shape. Various embodiments of the invention provide non-sinusoidal cam tracks having forward or rearward throw sections which are respectively steeper, shorter, or provide greater acceleration of the cam followers than sinusoidal cam tracks of equivalent wavelength and amplitude. Related piston and cylinder devices and reciprocal drive devices are also described.

Abstract: An apparatus (10) for use in boring is described, the apparatus including a rotatable drive shaft (12), a cam member (20) and followers (16) for converting rotational motion into reciprocal motion, and a shroud (24) having a cutting edge (26) driven by the cam member and followers. The shroud may be selectively engageable with the cam member and followers, allowing the drive shaft to be removed through the shroud. A fluid circulation arrangement (31), (13) allows air to be injected into loose drilling substrate, so assisting removal of drill cuttings from the boring apparatus. Also described is a drill string incorporating a similar arrangement, allowing the drill string to be reciprocated within a bore. The drill string may further include casing sections, which may have intumescent coatings to allow the sections to be fixed in a wellbore.