Abstract: In apparatus for drilling a hole in the ground comprising tubing for shoring up the walls of the drilled hole and a drilling member comprising a pneumatic percussion hammer having an eccentric cutting edge, the drilling member extending in the tubing and having a working position in which the cutting edge extends below the lower end of the tubing and a removal position in which the cutting edge is within the tubing, the extension tube for supplying gas to the hammer is connected to the hammer by a helicoidal telescopic connection which is rotatable through 180.degree.

Abstract: There is described a pressure-responsive switch device particularly suitable for the detection of a pressure drop in a pneumatic tire on a vehicle wheel, wherein a contact carrying movable rod member is securely urged into a contact closing position by means of a conical compression spring to actuate a warning device whenever the internal pressure of the tire drops below a predetermined level. A permanent magnet may be mounted at the contact point of the switch to impart a quick motion thereto.