Patents Assigned to David Thomson Allan
  • Scabbler bit floor surfacing machine
    Patent number: 4225187
    Abstract: A scabbler machine for breaking concrete etc. having a number of scabbling bits made up of a shank for connection to the reciprocal piston of the scabbler machine and a head provided with tungsten carbide, or like, cutting members. To ensure complete scabbling of the surface to be treated the head of the scabbling bits have portions which overlie portions of other bits so that the bits overlap one another in the direction of movement of the scabbler machine over the surface to be treated.
    Type: Grant
    Filed: August 4, 1978
    Date of Patent: September 30, 1980
    Assignees: David Thomson Allan, John MacDonald & Co. (Pneumatic Tools) Ltd.
    Inventor: David T. Allan
  • Fluid operated undercutter
    Patent number: 4186810
    Abstract: An undercutter comprising a slotted tubular body in which is mounted an extendable and retractable cutting head for undercutting a bore into which the tubular body is positioned and rotated. The cutting head includes a fluid-operated reciprocally movable piston, the reciprocating rate of which is determined by an annular liner positioned between the outer wall of the piston body and the inner wall of the piston cavity.
    Type: Grant
    Filed: July 5, 1977
    Date of Patent: February 5, 1980
    Assignees: John MacDonald & Company (Pneumatic Tools) Limited, David Thomson Allan
    Inventor: David T. Allan
  • Fluid operated wall groove cutter
    Patent number: 4140347
    Abstract: A hand-held groove cutter, particularly for cutting grooves in concrete structures, comprises a movable carriage having wheels for rolling over the concrete structure, and a fluid-operated percussion hammer mounted on the carrier. The hammer includes a piston and a cylinder which is mounted for sliding movement in a housing, and a tool which is connected to the piston. An adjustment arrangement is operative for moving the cylinder relative to the housing to thereby adjust the stroke of the piston and the depth of stroke of the tool.
    Type: Grant
    Filed: January 19, 1977
    Date of Patent: February 20, 1979
    Assignees: John MacDonald & Co. (Pneumatic Tools) Ltd., David Thomson Allan
    Inventor: David T. Allan