Abstract: A pivot device for supporting a working device is disclosed. The pivot device has a load-bearing structure, an arm and a control rod. A first end of the arm is pivotably mounted in the load-bearing structure. The working device is pivotably connected to the second end of the arm. A first end of the control rod is hinged to the pivotable working device. A hinged quadrangle acts as a pivot point for the second end of the control rod. The quadrangle encompasses the load-bearing structure as a chassis, the arm acting as a driven element, as well as two coupling elements which close the quadrangle. The control rod is hinged, by its second end, to one of the two coupling elements. When the arm pivots, the pivot point of the second end of the control rod remains on the same side of the arm, so that the control rod does not cross the arm during pivoting.

Abstract: The device includes a chuck designed to be secured to a working tool and which has a front cavity for receiving an end of a drilling rod and a gripping device for fastening the end of the rod in this cavity. The gripping device is actuated by pneumatic or hydraulic pistons, sliding in a cylindrical chamber closed at the rear by a plug. In order to avoid rapid wear of this plug, a spring is arranged between the said plug and the adjacent face of the piston, the spring being strong enough to keep the piston away from the plug.

Abstract: A machine for opening tapholes has a conical guide and support head which is slidably mounted on a mount and which includes at least one hook equipped with two mutally opposite catching slots. The catching slots allow the hook to occupy two catching positions. In the first catching position, the head is secured to a sliding frame displacable by use of a sliding carriage. In the second catching position, the head is secured to the front end of the mount.