When a start SW 3 is pressed, a one-shot multivibrator circuit 15 turns on and releases a pulse. The pulse is transmitted to a self-hold circuit 16 which in turn stays in self-hold mode and releases an H level output continuously until it is reset. This cause a transistor 17 to turn on and actuate a ram downward movement relay R1. When the ram arrives at the lower limit of its movement, a lower LS 4 is opened causing a self-hold circuit 21 to produce an H level signal in accordance with an output of a one-shot multivibrator 18. The H level signal from the self-hold circuit 21 is delayed by a delay circuit 22 and turns on a transistor 23. As the result, a ram upward movement relay R2 is actuated. Because of the function of the one-shot multivibrator circuit 15, the ram will not restart when the start SW 3 is continuously depressed. The delay circuit 22 contributes to the longer operational life of a directional valve switching mechanism. Also, a combination of another delay circuit 19 and a logical product circuit 24 is provided for preventing any fault action derived from chattering of the lower LS 4.

An apparatus for punching a plurality of predetermined spaced mounting holes in a building roof panel support member includes an elongated housing having an oil sump therewithin, a hydraulic pump together with an electric motor for actuation thereof mounted on the housing, guide structure which can be opened and closed for temporarily mounting the housing upon a roof panel support member, an adjustable gauge pin mounted on the housing near one end thereof, the gauge pin being supported on a mount which is adjustable along both the length and the width of the housing, and a hydraulic punch adjustably mounted near the other end of the housing from the gauge pin for punching holes in the support member. The method of punching holes in a roof panel support member as disclosed herein is also part of this invention.

A method and apparatus for removing spot welds from a sheet metal structure is shown. A fluid powered hand punch has a handpiece and an L-shaped extension forming a punch die. An elongated rod extends from a fluid piston within the handpiece to a punch bit, allowing the punch to be conveniently positioned over spot welds in diverse structures. An extension of the handpiece body guides and stabilizes the rod. Spot welds are removed by positioning the punch bit over the weld and entirely punching it out. A tapered punch bit engaging the metal along a partial perimeter of its front face is also shown.

A hydraulic puncher comprises a cylindrical casing, a pump unit including a pump and fixedly held in the casing, a cylinder chamber defined by the cylindrical inner face and the inner end face of the pump unit, a piston reciprocatingly and slidably provided in the cylinder chamber and an oil reservoir which is formed adjacent to the pump unit in the casing and from which the pump sucks operating oil filled within the cylindrical casing.

An apparatus for punching a plurality of predetermined spaced mounting holes in a building roof panel support member includes an elongated housing having an oil sump therewithin, a hydraulic pump together with an electric motor for actuation thereof mounted on the housing, guide structure which can be opened and closed for temporarily mounting the housing upon a roof panel support member, an adjustable gauge pin mounted on the housing near one end thereof, the gauge pin being supported on a mount which is adjustable along both the length and the width of the housing, and a hydraulic punch adjustably mounted near the other end of the housing from the gauge pin for punching holes in the support member. The method of punching holes in a roof panel support member as disclosed herein is also part of this invention.