Integrated instrument assembly for compressors

An integrated instrument assembly for compressors, having a pressure switch and a pressure reducer connected to each other by a pneumatic circuit, is connectable to a compressor having a compressed-air tank communicating with the pneumatic circuit; the pressure switch and pressure reducer being supported on a supporting member having the pneumatic circuit.

DETAILED DESCRIPTION OF THE INVENTION Number 1 in FIG. 1 indicates as a whole a compressor comprising a compressed-air tank 2 , a motor 3 , and a pump assembly 4 . Compressor 1 is fitted with an instrument assembly 5 connected to pump assembly 4 by a conduit 6 and to tank 2 by a conduit 7 , and which comprises two taps 8 and 9 ( FIGS. 1 and 5 ) for feeding compressed air to respective user devices (not shown). As shown more clearly in FIGS. 2 to 5 , assembly 5 comprises a pressure switch 10 ; a pressure reducer 11 ; a pressure gauge 12 showing the air pressure in tank 2 ; a pressure gauge 13 connected downstream from pressure reducer 11 and showing the pressure of the air supplied by taps 8 and 9 ; and a thermal safety device 14 connected by cables, not shown, to motor 3 and to pressure switch 10 . In an alternative embodiment not shown, safety device 14 is integrated in pressure switch 10 . Safety device 14 may comprise a relay or resistor (known and not shown), and provides for sensing the temperature of motor 3 and disabling pressure switch 10 when the temperature of motor 3 exceeds a given threshold value. Components 10 to 14 of assembly 5 are all mounted on a supporting plate 15 forming part of assembly 5 and having an internal pneumatic circuit 16 communicating with pressure switch 10 , pressure reducer 11 , and pressure gauges 12 and 13 . Circuit 16 comprises an inlet 17 connected to pump assembly 4 by conduit 6 ; an exhaust conduit 18 connected to pressure switch 10 ; an inlet/outlet 19 connected to tank 2 by conduit 7 ; and two outlets 20 and 21 ( FIGS. 4 and 5 ) connectable to respective user devices (not shown) by respective taps 8 and 9 . Circuit 16 comprises an initial portion 22 communicating with inlet 17 and exhaust conduit 18 ; an intermediate portion 23 communicating with inlet/outlet 19 ; and an end portion 24 communicating with outlets 20 and 21 . Assembly 5 comprises a check valve 25 located along circuit 16 , between initial portion 22 and intermediate portion 23 ; and a known safety valve 26 located along intermediate portion 23 , and for connecting intermediate portion 23 with the outside when the pressure exceeds a given maximum value. Pressure reducer 11 comprises a piston 27 activated by a spring 28 ; and a truncated-cone-shaped on-off member 29 , which is moved by a spring 30 between a rest position ( FIGS. 4 and 5 ), in which no air is supplied by taps 8 and 9 , and member 29 closes an opening 31 between intermediate portion 23 and end portion 24 , and a work position (not shown), in which air is supplied by taps 8 and 9 , and member 29 is lowered by piston 27 to connect intermediate portion 23 and end portion 24 . In actual use, compressed air is fed by pump assembly 4 into tank 2 , and valve 25 is open to connect initial portion 22 and portion 23 until a given maximum pressure is reached; at which point, pressure switch 10 cuts off electric power supply to motor 3 powering pump assembly 4 , and a control device inside pressure switch 10 opens a known valve (not shown) to expel the air in portion 22 along exhaust conduit 18 , while valve 25 closes to prevent the compressed air from escaping from tank 2 . When compressed air is required by the user devices (not shown) tap 8 and/or 9 is/are opened, portion 24 is connected to the outside, thus lowering piston 27 , which intercepts one end of member 29 , which moves down in opposition to spring 30 to connect portions 23 and 24 and so release the compressed air stored in tank 2 . Using plate 15 to support components 10 - 14 , 25 , 26 , 8 , 9 is particularly advantageous by permitting fast assembly of the instruments as a whole, and by providing a compact, integrated instrument assembly. Moreover, supporting plate 15 is formed, e.g. cast, in one piece, and forming circuit 16 inside supporting plate 15 itself provides for improved strength, sealing and reliability of assembly 5 as compared with known assembly solutions in which the various component parts are connected by fittings. Clearly, changes may be made to the instrument assembly as described and illustrated herein without, however, departing from the scope of the present invention.