| 摘要 |
955,264. Piston and stuffing-box packings. REGIE NATIONALE DES USINES RENAULT. Nov. 28, 1960 [Nov. 30, 1959], No. 40835/60. Headings F2B and F2T. In a pneumatic cylinder incorporating a double-packing sealing device for the piston and/or the stuffing-box, the two portions of the device are provided with a space between them communicating through a channel with the compressed air supplied to the cylinder and in which, during movement of the piston, the air pressure is allowed to rise to the value of that of the air supply so as to avoid jamming or sticking of the packing lips on the walls of the cylinder and/or on the piston rod. In Fig. 1, the space 3 between lipped packings 13, 14 communicates through an orifice 25 with a cylindrical bore 15 formed in the piston 5 and fitted at its ends with plugs 22, 23 provided with orifices 20, 21. A movable member 16 slidably fitted in the bore 15 is provided with a packing having beads 19 acting as dampers and as obturators for the orifices 20, 21. Alternatively, the member 16 is replaced by a plastic or steel ball. On the upward stroke of the piston, compressed air supplied through an inlet 26 displaces the member 16 to close the orifice 20 and enters the space 3 so that packing 14 becomes pressure balanced and packing 13 is made fluid tight against the cylinder wall. In Fig. 4, the underside of a piston 28 is under constant pressure and the piston rod stuffiing- box comprises packings 33, 34 formed therebetween with a radial orifice 35 connected through a pipe 36 to a line 37 through which compressed air is supplied to the upper chamber 39 of the cylinder. In another embodiment, a double acting cylinder is equipped with a piston similar to that of Fig. 1 but with packings having lugs as described in Specification 955,263, and with a stuffing-box sealing device similar to that of Fig. 4 but in which the pipe 36 incorporates a time-lag valve whereby compressed air is supplied between the packings for a very short time at the start of an operation. |
