the slot 35 travels in an arcuate path pressing the spring 36 against the second electrical contact 33 to lie in a position 36a this serves to close a low voltage circuit provided through wires not shown in fig8 but see wires 13 in fig2 connected to the electrical outlet 11 to activate the suction source 1 1a a brass rim 37 may be mounted on the switch activating pin 48 to reduce wear fig9 11 and 12 show a receptacle 4 with the door 26 open fig1 is a cross sectional view taken through fig1 the shows the inner space 38 of the transfer chamber 17 also shown is the ramp 25 the portion of the ramp 25 adjacent to the vacuum suction inlet 16a preferably has a concave curvature relative to the suction inlet 16a in fig1 a hose coupling 40 is positioned against the front face of the front plate 22 of a receptacle 4 with the door 26 in an open position a hose 41 is connected outwardly from the coupling 40 in fig1 16 17 and 18 the coupling 40 is shown in greater detail the coupling 40 has a coupling plate 42 and gasket 43 that lies over the suction inlet portion 16a of the opening 16 in the face plate 22 of the receptacle 4 an opening 44 in the coupling plate 42 transforms from a generally rectangular form at the coupling plate 42 to a circular opening 46 at the hose coupling end the top edge of the coupling plate 42 preferably carries a small bevelled flange 47 that engages the inner side of the door 26 on the receptacle along the closure plate portion 27 the lower.