(57) A double diaphragm pump comprises a pair of axially spaced apart pumping chambers
(1,2), each chamber has a pumping diaphragm (3,4) to divide each chamber into an inner
(5,6) and an outer compartment (7,8). The outer end of each pumping chamber is closed
by a cover (9,10) and the inner ends of both pumping chambers (1,2) are closed by
a central element (11). Connection cylinder (12) extend between the diaphragms (3,4)
and through the central element (11). The supply (13) of operating fluid to the outer
compartments (7,8) causes the diaphragms (3,4) to oscillate and vary the capacities
of the inner compartments (5,6). Each of the inner compartments (5,6) has an inlet
(14) and outlet port (15) leading to unidirectional valves (16,17) to allow fluid
to be drawn into one of the compartments (5,6) when the appropriate diaphragm (3,4)
moves outwardly and expelled from that compartment when the diaphragm moves inwardly.
The central element has a unitary partition wall (20) which extends between and closes
the inner ends of the inner compartments (5,6), said wall being substantially solid
over a major portion of its area apart from a sealed aperture (21) to allow the connection
cylinder (12) to pass through it and being enlarged at its outer periphery (22) to
carry the inlet and outlet ports (14,15) which are located respectively at the lower
and upper portions of the element (11).
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