in the direction of arrow 24 and releases the actuating element 23 due to gravity the valve 20 tilts into a position in which the compressed air flow is set free from the supply component 2 to the handpiece 10 there is thus effected an automatic release of the compressed air flow when the dentist takes the handpiece 10 into his hand the compressed air may hereby serve for a turbine drive as spray air or for the blowing out of tooth cavities each of the handpieces shown in fig1 may each respectively have a valve 20 associated therewith the valve 20 may hereby be also a valve unit which encompasses a plurality of individual valves and which are supported so as to be commonly pivotable through the provision of a plurality of valves for example there may be concurrently released the drive air for the turbine and the spray air fig3 illustrates the construction of a valve which is utilizable in connection with fig2 the valve possesses a housing 25 which has an internal cylinder chamber 26 within which a sphere 27 is movable to and fro in the direction of two headed arrow 28 in the one end position thereof the sphere 27 closes off a valve seat 29 which forms the mouth of the outlet conduit 30 in the valve.