Pump system using a vacuum chamber and mechanical pump combinations

A pump arrangement having a mechanical pump in series with a vacuum compartment on an inlet side of the mechanical pump. The vacuum compartment has a suction line flow connected to the supply of liquid to be pumped and draws that liquid by vacuum to the inlet of the mechanical pump. The mechanical pump includes an outlet for delivering the liquid to be pumped.

BACKGROUND OF THE INVENTION 
The invention relates to a pump arrangement for transporting a liquid from 
a first location by means of a pump positioned at a second location which 
may be at a higher level than the first location. The invention also 
relates to a method for such pumping. 
A commonly occurring problem is to pump liquid from a lower level to a 
higher level in a situation in which the liquid to be pumped is not easily 
accessible to permit a pump of the required lifting capacity to be 
positioned with its inlet located near the level from which the liquid is 
to be drawn. In situations like that, an immersible pump is normally used, 
but such a solution is not always satisfactory. 
An object of the invention is to provide a simple and efficient pump 
arrangement which offers a good solution to the problem, and a simple and 
efficient method for pumping operations of the kind indicated. 
These and other objects of the invention are achieved with a pump 
arrangement and a method as defined in the claims. 
The invention is described in greater detail below with reference to the 
annexed drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1, numeral 11 designates a hermetically sealed vacuum compartment 
which is kept under negative pressure through a conduit 12 connected to a 
suction pump or other suitable vacuum source. The vacuum compartment 11 
houses a pump 13 the inlet 14 of which is always in communication with the 
interior of the vacuum compartment at a level A and the outlet 15 of which 
is in communication with the surrounding space by way of an outlet conduit 
16. 
The pump 13 is a pressure pump, that is, a pump that pressurizes the pumped 
fluid to the degree required for lifting the liquid to the desired level 
which is designated by B in FIG. 1. Basically, any pressure pump may be 
used, such as a positive-displacement pump (piston pump) or a centrifugal 
pump. 
Connected to the vacuum compartment 11 is also one end of a suction conduit 
17. The other end of the conduit 17, which may be a pipe or a hose capable 
of resisting the occurring negative pressure without collapsing, is 
intended during the pumping operation to be immersed in the liquid to be 
pumped; the level of that liquid is indicated at C in FIG. 1. 
In this case, level A is presumed to be higher than level C and lower than 
level B but this vertical relationship is not necessary in all cases. For 
example, level B may well be lower than level A. 
In operation of the pump arrangement, liquid is lifted through the suction 
conduit 17 to the interior of the vacuum compartment 11 under the 
influence of the negative pressure in that compartment. When the liquid in 
the vacuum compartment reaches the inlet level A, the pump 13 carries the 
inflowing liquid away through the outlet conduit 16. 
The vacuum compartment 11 may be provided with a level control or level 
monitoring device (not shown) which ensures that the liquid level in the 
vacuum compartment never drops below the pump inlet level A. However, as 
will become apparent from the following description, such a device can be 
dispensed with if the pump is of the inflow-controlled type and provided 
with a valve which prevents backflow through the pump. 
As long as the liquid is being pumped out of the vacuum compartment 11 and 
flows into the compartment at the same rates, no air has to be pumped out 
of the vacuum compartment to maintain the required negative pressure, 
provided of course that no air leaks into the compartment. 
Obviously, the pump has to operate against the negative pressure, but this 
does not mean any loss of energy, because basically no energy is consumed 
for maintaining the negative pressure and the energy consumption which is 
caused by the pump having to operate against the negative pressure is 
balanced by the gain of energy resulting from the pump lifting from level 
A instead of lifting from level C. 
In FIG. 2, the main components of the pump arrangement have the same 
reference numerals as in FIG. 1 with the addition of the digit 1 as a 
prefix. 
In this case, pump 113 is an inflow-controlled pump of the type known from 
EP-A-0 374 115, that is, its discharge flow rate is determined, within the 
limits set by the capacity of the pump, by the rate of inflow. 
Accordingly, the pump is a positive-displacement pump having a piston 118 
operating in a pump chamber 119 into which the inflow takes place by way 
of an inlet valve 120, which is a one-way valve and provided in an inlet 
gap extending around the pump chamber. 
The pump piston 118 is driven positively at least in the displacement 
direction (upwardly) by a suitable drive which is symbolised by a 
crankshaft 121 in the figure but which needs not necessarily comprise such 
an element. 
The pump piston 118 is arranged such that it does not produce any suction 
in the pump chamber 119 during its downward movement, so that the pump 
chamber is expanded and filled solely by the inflow in the manner 
described in the just-mentioned publication. 
Adjacent the pump outlet 115, a one way valve 122 is provided which 
prevents backflow through the pump. 
At the pump inlet 114 a water seal 123 is provided, and at the bottom of 
this water seal there is a liquid compartment, herein termed accumulating 
compartment, which is limited upwardly by a vertically movable wall 125 
supported by a soft compression spring 126. The accumulating compartment 
124 serves during those phases of the pump cycle in which the inlet valve 
120 is closed to allow liquid to continue to flow through the pump inlet 
114 essentially as during the open phases. The accumulating compartment is 
then expanded while compressing the spring 126. Upon opening of the inlet 
valve 120, the energy stored in the spring is utilised to feed the 
accumulated liquid volume into the pump chamber 119 together with the 
continuous, substantially constant inflow from the pump inlet 114. 
The supply of the accumulated volume speeds up the filling of the pump 
chamber 119 without affecting the inflow from the pump inlet, because the 
gap-like inlet passage opened by the inlet valve 120 is large enough for 
the inflow into the pump chamber to take place without any appreciable 
pressure drop. 
As is apparent from FIG. 2, the side of the movable wall 125 of the 
accumulating compartment which faces away from the pump inlet 114, and the 
side of the pump piston 118 facing away from the pump chamber 119 are 
subjected to the negative pressure existing inside the vacuum compartment 
111. This negative pressure is communicated by way of branches of the 
vacuum conduit 112. Accordingly, the positioning of the pump in the vacuum 
compartment 111 has no consequence to the pump apart from the fact that 
the pump piston has to operate against the negative pressure during the 
pumping operation.