Patent GB-190819376-A (GB)
Title: Improvements in Unloaders for Compound Fluid Compressors.
Inventor: LAKE WILLIAM EDWARD
Filed: 1908-09-15
Granted: 1909-09-15
Abstract: 19,376. Lake, W. E., [Ingersoll-Rand Co.]. Sept. 15. Compressing.-Compound fluid-compressors are unloaded and re-loaded at predetermined receiver pressures by effecting a variation in cylinder clearance, auxiliary receivers being connected to each cylinder through valves which are adapted to remain open or closed under the action of a regulating-device operated by the pressure existing in the main receiver. The unloading and loading may take place step by step, and may be applied to both the high-pressure and low-pressure cylinders, or to the low-pressure cylinder only. As applied to a compound compressor with inter-cooler 3, Fig. 1, the double-acting low-pressure and highpressure cylinders 1, 2 respectively are each provided with two auxiliary receivers 9, 10 at each end of the cylinder, the receivers communicating with the cylinders by valves 11, 12 in the cylinder ends. The spaces at the back of the valves 11, 12 are normally open respectively to the inter-cooler 3 and the final receiver (not shown) connected with the pipe 6. At a predetermined receiver pressure, however, the spaces at the back of the valves are opened to the atmosphere by regulating-devices, the valves are held open, the auxiliary receivers constitute an additional clearance space, and the compressor is wholly or partly unloaded. Each regulating-device comprises a slide valve 14, Figs. 4 and 5, enclosed in a casing 13 and provided with bridge ports 14<1>, 14", piston heads 15, 16, and an intervening space constantly open to receiver pressure by way of a pipe 28. The valve is actuated by compressed air admitted to act on one of the piston heads by way of ports 22, 23 controlled by an auxiliary slide valve 24. The valve 24 is provided with suitable ports adapted to co-act with the supply ports 22, 23 and an exhaust port 35, and is connected to a weighted plunger 30, the underside of which is always subjected to receiver pressure. With the main valve in the position shown, the space at the back of one of the valves 11 is open to the inter-cooler by way of the ports 20, 14', 19, and the space at the back of one of the valves 12 is open to the final receiver by way of port 21, the space between the piston heads, and the pipe 28. When a predetermined receiver pressure raises the plunger 30, and thereby moves the auxiliary valve 24, the main valve is moved so that the spaces at the back of the valves 11, 12 are open to ports 17, 18 leading to the atmosphere. Any number of auxiliary receivers may be employed, and one regulating-device may be provided for two or more pairs of valves 11, 12 instead of only one pair as described. The low-pressure cylinder only maybe unloaded. By varying the weights on different plungers 30, the compressor may be unloaded step by step and in such a manner that the loads on the forward and backward strokes are maintained substantially uniform, that is to say, an auxiliary valve at the front end of the high-pressure cylinder is opened simultaneously with one at the back end of the low-pressure cylinder, and so on.