| 摘要 |
<p>A pumping apparatus for pumping liquids such as slurrys comprises a pumping cylinder/piston (6, 8) driven by the piston/cylinder (16, 18) of an operating device, the supply of fluid under pressure either to an upper port (16a) of the cylinder (16), or the lower port (16b) of the cylinder, being controlled by valve mechanism (28). The valve mechanism is moved between two conditions, in which it supplies fluid under pressure to one or other of said ports, consequent upon the arrival of a member (20) connecting the two pistons (8, 18) at one or other of its extreme positions of movement. Alternatively, or in addition, the fluid pressure circuit powering the operating device includes a regenerative branch, through which fluid under pressure flows from the low pressure side of the operating device directly back to the high pressure line of the fluid circuit, upstream of the motor supplying fluid under pressure. In this manner, the apparatus can operate both at an initial high speed, under relatively low resistance to pumping, and at a later stage in a pumping operation, at a lower speed, at a relatively higher resistance to pumping, whilst utilising a power source which is smaller than would otherwise be required. In this manner, not only is a saving of energy obtained, but (because of a reduction of work done on the fluid) water cooling of the fluid circuit may be dispensed with. </p> |
