Abstract: A cutter type knife comprises a hollow handle, a housing in said handle adapted to receive a removable blade fixed in position relative to said handle and projecting at least partly from one end of said handle. A blade cover is slidably disposed within said handle to be movable axially between a first position in which it is retracted into said handle and a second position in which it is adapted to surround or cover the part of said blade projecting from said handle. Means are provided for moving said blade cover between said first and second positions consisting of a trigger pivoted to said handle and a transmission mechanism is adapted to convert rotation of said trigger into axial displacement of said blade cover within said handle, whereby when said trigger is depressed said blade cover is moved to said first position.

Abstract: A cutter type knife having a handle with a blade disposed to slide axially within the handle. Elements are provided for manually deploying the blade and automatically retracting the blade when a manual operating element is released. The manual operating element is a member adapted to be at least partially retracted into the handle. An additional part is adapted to convert movement of the aforementioned member into axial movement of the blade within the handle. In this way, retracting the aforementioned member deploys the blade. Also provide is a latch or lever for initially impeding retraction of the aforementioned member, whereby an initially greater force is required in order to begin retracting the member and thus deploy the blade.