(57) A hammer that is capable or receiving a tool bit (30) for acting on a workpiece,
and includes an air cushion hammering mechanism that comprises a cylinder (2), a piston
(6) that can be caused to reciprocate within the cylinder, and an impact member (12)
that is slidably located within the cylinder and can be caused to move in response
to reciprocation of the piston by means of an air cushion between the piston and the
impact member so that the impact member can strike the end of a bit (30) that is held
in the hammer. The hammer includes a web (22) of flexible impervious material that
extends from the impact member to prevent ingress of dust from the region of the bit
to the cylinder. A hammer is also provided which includes an arrangement for arresting
the impact member in its forward position, which comprises a resilient ring (52) that
is located within the cylinder and extends around the impact member, the impact member
(12) having an intermediate portion (100) of varying diameter so that, at a given
position of the impact member in the cylinder, the intermediate portion (100) of the
impact member touches the resilient ring (52) and a substantially closed chamber is
formed within the cylinder (2) that extends around the resilient ring (52), further
forward movement of the impact member reducing the volume of the chamber (70) and
causing the resilient ring (52) to constrict the impact member. A hammer is also provided
which includes a housing (1) and a tool holder (4) that can receive a tool bit (30)
for acting on a workpiece, in which the bit (30) is retained in the tool holder by
means of one or more locking elements (42) and the hammer includes one or more cushioning
elements (34, 36) located between the tool holder (4) and the housing (1) so that
impacts that are reflected by the workpiece back along the bit (30) are transmitted
to the housing via the tool holder (4) and the cushioning element(s) (34, 36).
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