TECHNICAL FIELD DIAPHRAGM PUMP SYSTEM
The present invention relates to a pump system that incorporates a diaphragm pump particularly, but not exclusively, to supply liquid paint to a paint spraying system
ANTECEDENTS OF THE TECHNIQUE
Diaphragm pumps are well known and generally comprise a pumping chamber linked in part by a diaphragm capable of moving with the diaphragm being moved by the application of fluid under pressure to reduce the volume of the pumping chamber and thereby expel the fluid usually liquid from the pump chamber. Diaphragm pumps are usually built as double effect pumps because there are two pump chambers each having an associated diaphragm with the two diaphragms being physically interconnected in such a way that when one is moving to reduce the size of its pumping chamber to expel the fluid from the pumping chamber the opposite diaphragm is moving in a direction to increase the volume of the pumping chamber and draw fluid from a source of fluid into the pumping chamber It should be understood however that in its simplest aspect the present invention could be applied to a pump of a the effect (single diaphragm) although in practice it is much more likely to be applied with double-acting diaphragm pumps and in this way through the rest of this application reference will be made to double effect pumps instead of single effect pumps
Conventionally the fluid that is pumped by a diaphragm pump is a liquid and also conventionally the presumed fluid applied to the diaphragms that causes them to perform their pumping strokes is compressed air. Commonly the diaphragm pumps exhibit a pressure ratio of 1 1 because they are applies air at 1 bar of pressure to the pump to impel the pump producing a pressure in the liquid in the outlet line of the pump that is also 1 bar. It is known to provide diaphragm pumps with an increasing pressure ratio in which example, an air pressure of 1 bar that impels the pump produces an outlet pressure of 3 bar in the liquid outlet line of the pump. However, although these diaphragm pumps are significantly larger and more expensive to produce than they are the pumps having a ratio of 1 1 their use is not excluded in the systems according to the present invention for convenience hereinafter in this desc npcion it is assumed that the pump has a ratio of 1 1 In the industna of paint spraying it is conventional to provide a spray painting workshop with a pressure source nominally rated at 6 bar In practice the air pressure is unlikely to be lower of 5 bar but can be as high as 6 bar It is further recognized that in many applications it would be desirable to supply liquid for example paint from the diaphragm pump to a paint spray system at a nominal pressure of at least 10 bar and is an object of the invention. present invention provides a pump system incorporating a diaphragm pump in which this objective can be achieved in a simple and convenient manner being understood that the invention has a broader application than simply achieving a nominal paint pressure of 10 bar in a spray paint system powered with air at 5 bar nominally
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention there is provided a pump system incorporating a diaphragm pump and in association therewith a pressure intensifier which receives the presumed fluid driven from a source by the intensifier raising the pressure of the fluid driven beyond its supply pressure and feeding the fluid driven at said increased pressure to said diaphragm pump to generate the pumping strokes of the pump which produces an output pumping pressure in excess pressure of the supplied fluid supply Conveniently the pressure intensifier is at least a 2-fold intensifier (preferably a 2-fold intensifier) and conveniently the pump has an inlet-to-outlet pressure ratio of 1 1 per which the pressure in the line of exit of the pump is twice (preferably 2 5 times) the supply pressure of the fluid driven towards the pressure intensifier. Desirably the pressure intensifier is incorporated in the diaphragm pump Conveniently the pump diaphragm is a double-acting diaphragm pump and the pressure intensifier is incorporated in the spool valve that controls the supply of fluid driven to the diaphragms of the double-acting diaphragm pump. Preferably the diaphragm pump has a pressure ratio from entry to exit 1 1
BRIEF DESCRIPTION OF THE DRAWINGS
An example of the invention will now be described with reference to the accompanying drawings in which Figure 1 is a schematic cross-sectional view of a double-acting diaphragm pump. Figures 2 and 3 are schematic representations of part of the pump Figure 1 showing how the pump works Figures 4 and 5 are schematic cross-sectional views of alternative constructions of the pressure intensifier to be used in combination with the diaphragm pump of Figures 1 2 and 3
PREFERRED MODE OF CARRYING OUT THE INVENTION
Referring to the drawings, Figures 1 2 and 3 illustrate a known form of the diaphragm pump in which a generally metallic center body 1 1 has an axial bore pitch 12 and is adjusted at its opposite ends respectively with first end plates and second 13 14 The face of the body 1 1 exposed to the end plate 13 is concave and the face of the end plate 13 exposed to the body 11 is also concave The concavities of the end plate 13 and the body 1 1 define an inner chamber that is divided into a conducting chamber 15 and a pumping chamber 16 by a flexible metal diaphragm 17 having its periphery trapped between peripheral regions of the end plate 13 and the body 1 The arrangement at the opposite end The axial body 1 1 is similar in that an internal chamber is divided into a conducting chamber 15a and a pumping chamber 16a by means of a diaphragm 17a A connecting rod 18 is slidably received It is placed inside the bore 12 of the body and connected at its opposite axial ends respectively to the diaphragms 17 17a. At each end the connecting rod 18 passes through the respective diaphragm and diaphragm control washers 19 21 of different diameter are clamped against the opposite faces. The diaphragm pump illustrated in Figure 1 is designed to be impelled by compressed air and to pump a liquid paint. The references to pumped air and pumped liquid will be maintained. through the remainder of this application but it will be understood that there may be applications in which different fluids are pumped into the liquid paint and fluids other than compressed air are used to propel the pump. Each end plate 14 includes a liquid inlet passage. 23 communicating with its respective pumping chamber 16 16a through a check valve 24 conveniently In the form of a unidirectional ball valve, similarly, each end plate 13 14 includes a liquid outlet passage 25 communicating with the respective chamber 16 16a through a check valve 26 conveniently also in the form of a unidirectional ball valve The liquid inlet passage of the end plate 14 has an open connection 27 by means of which the inlet passage is connected to a supply of the liquid to be pumped during use. The inlet passage of the plate The end portion 14 of the respective check valve is coupled to the inlet passage 23 of the common end plate of the check valve 24 by a transverse passage 28 extending axially within the body 11. The outlet passage of the liquid 25 of the end plate 23 has an open connection 29 for connection to the arrangement that will be supplied with the pumped liquid for example a pi spraying system The connecting 29 is below the check valve 26 of the end plate 13 and a transverse passage 31 parallel to the passage 28 extends within the armpit-shaped body 11 to interconnect the liquid exit passage of the end plate 14. run under its check valve with the passage 25 of the end plate 13 under the check valve 26. Therefore, the liquid enters the double effect diaphragm pump through connector 27 to be pumped either from chamber 16 or chamber 16a and irrespective of which the chamber is performing a pumping stroke the pumped liquid flows from the pump through of the connector 29 Intermediate at its ends the rod 18 forms part of a spool valve 32 which controls the admission of the compressed air to the pump 15 15a of the pump The spool valve 32 forms part of a valve arrangement of change of the pump and operates in combination with a change valve 33 the housing of which is part of or is secured to body 11 The change or transfer valve 33 has a first operating position (as shown in Figure 2) for which is driven by the application of compressed air to one end of the valve and a second operating position (as shown in Figure 3) for which it is driven by a reverse spring. valve 34 A compressed air inlet port 35 of spool valve 32 is supplied with compressed air from a standardized main source (indicated in B in Figures 2 and 3) associated with the liquid pumping system. For purposes of this example, it can be assumed that the pressure in the standardized supply line B is 5 bar. An air inlet 36 under pressure 36 of the valve is supplied with compressed air from a standard source through the intermediary of a pressure intensifier 37 (Figure 4) The pressure intensifier 37 is a 2-fold intensifier and so the pressure in a supply line A of the intensifier 37 to the input input 36 is 12 5 bar Figure 2 illustrates the double-effect diaphragm pump at the right-hand end of its travel in which the diaphragm 17a has moved towards the end plate 14 in such a way that the camera 16a has experienced a pumping movement Since this point is reached in the path of the rod 18 relative to the body 11 the spool valve 32 places the hole 35 in communication with an outlet opening 38 coupled to the hole that senses the pressure of the valve 33 air pressure of the main supply applied to the valve 33 of the body 38 of the body 11 impels the valve 33 against the spring 34 to a position in which the high supply A is connected through line 39 to the chamber 15 of the pump and at the same time the chamber 15a is connected through a line 41 and the valve to the atmosphere in such a way that the pressure inside the chamber 15a can be exhausted. Therefore, in compressed air at 12 5 bar, it is supplied through the the valve 33 to the chamber 15 that drives the piston 17 to the left carrying with it the rod 18 and the piston 17a The liquid inside the chamber 16 is ejected by this movement of the diaphragm 17 and flows from the chamber 16 through the check valve 26 and the pressure supply port 29 of the pump The check valve 24 at the inlet side of the chamber 16 remains firmly closed and in this way the left-hand end of the pump ( as shown in Figure 1) performs a pumping movement or stroke Simultaneously chamber 16a at the right-hand end of the pump is undergoing reduced pressure as the volume of chamber 16a increases and thus the check valve on the outlet side of the chamber 16a remains firmly closed but the check valve on the inlet side of the chamber 16a opens to allow fresh liquid to be drawn into the chamber 16a of the liquid supply 27 As the diaphragm 17 achieves its maximum displacement towards the left that is to say at the end of the pumping movement of the chamber 16 the spool valve 32 moving with the rod 18 achieves a position in which the onfiao pressure detector of the valve 33 is connected to an orifice 44 of the body 11 the position of the change valve 33 switches under the influence of the spring 34 to bring the line 39 into communication with the atmosphere through the valve 33 and places the line 41 in communication with the increased pressure of the air in A In this way the chamber 15a is now supplied with pressure and thus the diaphragm 17a performs a pumping movement while the diaphragm 17 is retracted by increasing the volume of the chamber 16 and allowing the liquid to be entrained from the inlet connector 27 through the passage 28 and the valve 24 towards the chamber 16 The liquid pumped from the chamber 16a by the movement of the diaphragm 17a flows through the check valve at the outlet of the chamber 16a and through the passage 31 towards the connector Pump outlet 29 The pump continues to reciprocate in the antenor manner under the control of the spool valve 32 and the change valve 33 as long as there is compressed air in A and B Com or the pump is a 1 1 pump and the air pressure applied to the diaphragms 17 17a is 12 5 bar then the liquid pumped from the connector 29 is nominally 12 5 bar (ignoring the common losses of operation) The intensifier The pressure of 2 5 times illustrated in Figure 4 is in a manner known to be commercially available and will be connected between the standard supply of air pressure of the system and the orifice 36 of the change valve 33. However, it is anticipated that an increase in pressure will occur. it fulfills the same function as the intensifier 37 can be mechanically incorporated in the exchange or transfer system consisting of the spool valve 32 and the change valve 33 thereby reducing to a minimum the count of system components and ensuring that the The pump incorporates the pressure intensifier and in such a way that it can be simply coupled to an existing arrangement of compressed air and liquid supply. The indicator shown in Figure 4 uses pistons of different diameters suitably sized to effect the intensification or increase of pressure to 2 5 1 It will be understood that although the pressure increase of approximately 2 1 is desired for the paint spray system previously described other applications may require other pressure increase relationships The experienced person will recognize that other relationships can be obtained using intensifiers based on the design of Figure 4 with the adjustment of their relative dimensions according to the required relationship Figure 5 shows an alternative design of intensifier arranged using pistons of equal diameter to obtain a pressure increase ratio of 2 1 which could be substituted for the design of Figure 4 in an appropriate application The construction and operation of the intensifiers of Figures 4 and 5 will be understood well by the person with experience Although the above-described pump has a pressure ratio of 1 to between the inlet air and the liquid outlet it will be understood that the invention can use pumps having other input to output ratios if desired