| 摘要 |
993,882. Reciprocating pumps. SUNDSTRAND INTERNATIONAL CORPORATION S.A. Feb. 12, 1962 [May 31, 1961], No. 5239/62. Heading F1A. A swash plate pump has a swash plate assembly 23 pivotable, by a hand-operated control rod 35 and link 34, about the neutral position to provide for reversal of flow. A spring mechanism 58 acting on the rod 35 biases the swash plate 28 towards its neutral position so as to counter the inertia effect of the reciprocating pistons 22. The swash plate 28 pivots about an axis 30 and the centres 25a of the piston ball ends 25 lie on a plane 31. The axis 30 is offset from this plane so as to produce a larger moment arm 55a than the moment arm 55b, thereby balancing the smaller mean pressure loading on the upper half of the swash plate. Owing to the compressibility effects of the liquid being pumped, the distribution of the piston loads, due to the liquid pressure, on the swash plate is as shown by graph G in Fig. 5. Alternatively the valve timing may be arranged so that on the inlet stroke the piston communicates with the delivery valve before reaching the end of its stroke, and vice versa on the delivery stroke. This produces a pressure gradient instead of the sharp cut off at the end of the delivery stroke shown in Fig. 5, to give a more equal pressure distribution above and below the axis 30. This method is used when the pump is connected to a motor which may tend to drive the pump during braking, in order to balance the pressure distribution (see Figs. 6-9, not shown). |
