Hydraulic guns for the installation of rivets and self-locking inserts are well-known and can be obtained from various manufacturers such as the Parker Manufacturing Company in Worcester, Massachusetts. The hydraulics guns are particularly useful in the installation of inserts in sheet metal where the inserts may be used in a number of applications such as mounting brackets to tubing, covers to electronic chassis, and covers to communication equipment. Where it is necessary to place hundreds of such inserts in place, the guns provide a quick and efficient means for installing the inserts.
The hydraulic guns generally are comprised of three parts: the adapter/mandrel assembly; the hydraulic housing; and the pump assembly. The adapter/mandrel assembly is provided with a shaft, i.e., mandrel, with a threaded end upon which an insert is threaded. The hydraulic housing covers, among other parts, a cylinder and a piston which is coupled to the mandrel. The pump assembly supplys the fluid under pressure to the hydraulic housing.
Briefly, the inserts are threaded in the mandrel and are inserted into an opening in a panel until the circular end flange of the insert abuts the panel surface. Generally, the "barrel" or anvil of the gun abuts the flange. Fluid under pressure is then caused to enter the cylinder, resulting in the withdrawal of the anvil. The walls of the insert buckle against the interior surface of the panel, locking the insert in place. The mandrel is unthreaded from the insert which is then ready for use.
When installing inserts of the so-called blind type, a problem can occur when the operator of the gun does not have visual contact with the insert. Most hydraulic guns are of the pump variety which requires the operator to continually pump a lever which actuates the hydraulic mechanisms, causing the mandrel to withdraw. Without visual contact the operator is unable to know except through "feel" whether the mandrel has withdrawn the appropriate distance or not. Too much pumping of the gun may damage the insert or create enough pressure within the cylinder of the gun to rupture the cylinder walls.
The assignee of the present invention has adapted a hydraulic gun of the type mentioned above so that the hydraulic mechanism can be made inoperative after the mandrel has moved a certain distance irrespective of the repeated pumping of the gun. While this is a highly advantageous feature, it has been found that different inserts require different depths and therefore varying predetermined distances of mandrel movement.
It is therefore a paramount object of the present invention to provide for an improved hydraulic gun which can be operated in a consistent manner and which minimizes insert or cylinder damage and can be used with various sizes of inserts.
It is another important object of the present invention to provide for an improved hydraulic gun that can be adjusted for different sizes of inserts.