EP0411564A2 - Pump for liquids - Google Patents

Abstract

The invention refers to a pump in which a diaphragm (8) is reciprocated to cause cycles of high and low pressure in a chamber (9), and two conduits (10,11) communicating between the chamber and the exteriors, contain oppositely directed one way valve elements (12,13). Because the forward directions of those valve elements may offer even very low resistance to such effects as gravity (Fig.3), an entire reservoir could empty inadvertently through the pump. The invention proposes that a single body (27) be shaped to contain the one-way elements (12,13), to fit in the lower pump body (24), to assist in clamping the diaphragm (8), and to present to the chamber (9) one or other of the conduits, preferably that destined as the inlet conduit (10A), with an orifice (27C) which will act as a valve seat. A portion (6) of the diaphragm is contrived as a valve flap, and can close that conduit which is presented with the orifice (27C). Return bias (5) of the pump acts on the diaphragm (8) such as to close the orifice under quiescent or switched off conditions of the pump.

Description

• The present invention relates to a pump for liquids having a pumping chamber, a reciprocable wall in the chamber to periodically alter tha volume thereof, inlet and outlet conduits communicating with the chamber, and appropriately directed unidirectional valves (such as check valves, duck-bill valves) controlling the flow direction in the conduits. Such pumps are known, e.g from EP-A-286 404 and FR-A-2262711. It is sometimes necessary to make sure that no liquid can pass between the condiuits through the chamber when the pump is not operative. This is because the pump may have long-term, semi-permanent connections between a liquid source or reservoir and, either a utilisation device requiring pumped liquid, or simply an open pipe or tube for attachment to such a device. Liquid pressure or gravity can then cause prejudicial leaking while the pump is at rest. It is therefore required to provide a kind of leak-proofing valve, preferably integrated with the pump and using parts of the pump. Accordingly, the invention provides that the reciprocable wall is quiescently biased in one direction towards, and in contact with, another member of the chamber (which is known in itself); and characterised in that the other member is the mouth of one of the conduits where it joins the chamber, and the contact is a substantially sealing one. The sealing action is derived from a spring, so does not absorb power and can be effective during long unenergised periods of the pump. Also the spring is not an extra, being already a component of the prior art pumps. Little or no extra space is taken up by the change in geometry of the chamber and the moving wall, e.g. diaphragm can be virtually unchanged, except that a valve seat closure or sealing member is now involved. Also the sealed mouth of the conduit must be provided as, or be made suitable to act as, a valve seat. So leaks are prevented by an auxiliary mechanical, normally-closed, valve which is provided with minimum extra parts and changes in flow geometry. An embodiment is described below with reference to the drawings in which:
• Fig. 1 shows a diametrical cross-section on a known pump;
• Fig. 2 schematically demonstrates normal use of such a pump;
• Fig. 3 likewise shows abnormal use leading to leaks on switch-off; and
• Fig. 4 shows the inventive pump.
Referring to Fig. 1, a known pump 1 has a solenoid 2 energised by intermittent pulses, e.g. by applying rectified ac mains to terminal 3, so that a reciprocating armature 4 rises intermittently against a bias spring 5; then the armature returns each time towards the rest position shown, whereof a shock-absorbing, resilient extension 6 lies against an abutment 7. However, during reciprocation, the armature never reaches the rest position on its downward stroke. The resilient extension 6 is part of a flexible rubber diaphragm 8, which provides one wall of an annular pumping chamber 9, surrounding the extension 6. The magnetic circuit may be two cylindrical pieces M1, M2, interposed between the coil former 2A and the armature guide 4A; and a third piece M3 external to the coil and forming part of the housing. The magnetic circuit and solenoid and coil former 2A may be retained by a widened eg. snap-­fitting portion 17A of the armature guide 17B, these being integral with an upper pump chamber housing part 17. In the pump housing there are also formed, or held, an inlet conduit 10 and an outlet conduit 11 leading to respective valve chambers 10A, 11A, in which are located the well-known, non-return duck-beak (duck-bill) valves 12, 13, and which valve chambers communicate at 14, 15 with pumping chamber 9. The abutment 7 of this known pump forms part of a single, moulded body (e.g. of glass loaded nylon), which forms part of the seating for the diaphragm, holds both valves 12, 13, forms the chamber 10A of the inlet valve 12, and forms the surrounding cylindrical wall 7B of the pumping chamber. The bottom part 16 of pump housing conforms with the single, moulded body, such that when it is held by fastener 18 to upper housing part 17 (which is integral with valve guide 4A and a lid part 4B), the valves, the diaphragm and the single body are all clamped firmly in the position for proper operation. It would be advantageous if these manufacturing assets, which give repeatability, simplicity and economy in parts, could be retained in a sealed pump of the invention. Referring to Fig. 2, a normal use of such a pump 1 may be, as indicated by directional arrows, to have inlet conduit 10 connected to a water source such as reservoir 19 and outlet 11 connected through a long, flexible pipe 20 to apparatus such as a steam iron 21. For instance, the pump avoids the irritating task of repeatedly filling a reservoir on the iron itself, typically at the front below the handle. In the normal use, these items are located on an ironing board 22, but sometimes (e.g. to avoid dropping the iron, or accidentally coming into contact with it while distracted, telephoning, etc), a user, houseperson, etc., will place the instrument on the floor 23, as shown in Fig. 3, below the level of the reservoir 19 and table or ironing board 22. Then, even with the pump de-energised or disconnected from power, the water will flow by gravity through pipe 20 into the iron 21, or other instrument, and overflow. If no instrument is connected, water can leak out of the end of tubing 20. The leaking is caused by gravitational forces being sufficient to surpass a threshold value, i.e. overcome a threshold resistance, and thus to open the inlet valve 12, see Fig. 1. Water then passes through the valve cavity mouth 14, the annular pumping chamber 9, out of the outlet valve 13, to conduit 11, and thence to the ground 23. Accordingly, only the small threshold resistance to the opening distortion of the one-way valves opposes, but is soon overcome by, gravitational effects tending to open them. The threshold resistance can be increased, but this undesirably increases resulting pumping force and power requirements, i.e. energy costs and heating may become intolerable, likewise the ratings of components. Accordingly, the invention is applied to the pump embodiment of Fig. 4, in which the same or nearly analogous parts are unreferenced, or have the same reference numbers. Down to the arrows 24, the pump resembles pump 1 of Fig. 1, except for a member 27, which provides abutment for the resilient extension 6 of the armature 4. As before, extension 6 is part of a similar rubber diaphragm 8 and may be snap mounted onto a knob-like projection 4B. The member 27 replaces the composite part 7 of Fig. 1, and likewise provides valve chambers 10A, 11A, pressure surfaces 28, 29 angled so as to clamp flanges of the valves 12, 13 and hold these in position in their chambers, and the cylindrical wall 27B of the pumping chamber 9. Also it seats the bottom of the rim 8A of the diaphragm. The lower housing 26 is shaped to allow inlet valve chamber 10A to be vertical, and in line with the reciprocating stroke of armature 4, and to allow outlet valve chamber 11A to be about 60 degrees to the vertical, with a bend 30 from a short outlet portion communicating with the pumping chamber (9) and parallel to the axis. Thus, the valves and their chambers are no longer symmetrical, and the positioning of the chamber 10A collinear with the armature stroke achieves the inventive object of sealing, with the co-operation of spring 5 and armature projection 6. The sealing takes place with the pump de-energised, because the mouth 27C of member 27 is formed as a valve seat, without sharp edges or irregularities, to seat the resilient armature extension 6, preferably provided by the diaphragm. Whenever the pump 25 is operating, armature 4 and projection 6 reciprocate towards seat 27C, but do not reach it to abut and close it. On switch-off, however, spring 5 urges armature extension 6 into contact with seat 27C, thus obstructing liquid passage. Therefore gravity, or liquid pressure at the inlet conduit 10, can only urge liquid as far as the firmly obturated seat 27C, and it does not enter the pumping chamber 9, far less exit to conduit 11. The obturated seat could instead be the mouth, if formed suitably, of the outlet valve chamber 11A; presently preferred is blocking the inlet conduit mouth, however, partly because no liquid can then enter the chamber when the gravitation, or other pressures, may cause it to. The invention is not restricted, therefore, to blocking the inlet valve chamber 10A. This conduit is preferably tapering as shown, large enough towards one end so that the duck-bill valve 12 can be contained, but tapering at the other end so that the valve seat can be of small diameter. Of course, the invention is not limited to blocking passage to any specific utilisation device, such as a smoothing iron, nor to countering only the forces of gravity. The invention is not limited to the seat being aligned, with the armature stroke and the spring 5, but such alignment is greatly preferred for a better sealing action. The invention thus provides a pump (25) having a pumping chamber (9), a moving wall (8, 6) thereof being reciprocable against bias (5), inlet and outlet valve chambers (10A, 11A) communicable with the pumping chamber when the pump is operable, one-way valves (12, 13) in the chambers; characterised in that one of the valve chambers presents a seating (27C) to a part (6) of the moving wall, moved by the bias towards said seating whereby, only on non-energization of the pump, the part is moved under the action of the bias, to obturate said valve seating; or indeed any one of the appended claims. A normally closed valve is thus formed in the pump housing, which valve uses many pump parts, and plays no role except when the pump is not operated. The part (6) is preferably in line with the bias and the armature stroke, and central to the diaphragm.

Claims (10)

1. A pump for liquids having a pumping chamber, a reciprocable wall in the chamber to periodically alter the volume thereof, inlet and outlet conduits communicating with the chamber, and appropriately directed unidirectional valves (such as check-valves, duck-bill valves) controlling the flow direction in the conduits, characterized in that the reciprocable wall (8,6) is quiescently biased in one direction towards, and in contact with, another member (27) of the chamber (which is known in itself) but that during reciprocation the bias on said wall is arranged not to attain contact by said wall with said other member; and also characterised in that the part of the other member (27) contacted includes the mouth (27c) of one of the conduits where it joins the chamber, wherein said contact is effective as a substantially sealing contact.

2. A pump according to Claim 1 characterized in that the sealing action is derived from a spring known from the state of the art, whereby to absorb only minor amounts of power and to be effective during long unenergised periods of the pump, preferably also from a resilience in the contacting portion (6) of the wall.

3. A pump according to Claim 2 in which the sealed conduit (10A) has an axis generally collinear with the direction of bias on said wall and with the stroke of its reciprocation.

4. A pump according to Claim 3 wherein the sealed conduit has an axis which corresponds with the general axis of the pump.

5. A pump according to any previous Claim, wherein the inlet conduit and chamber (10,10A) are axial to the pump, but the outlet conduit (11,11A) is angled to the pumping chamber (9), eg. with a bend (30) giving a transition from the pumping chamber which is parallel to the axis of the pump.

6. A pump according to any of Claims 3-5 characterized or modified in that the conduit and chamber quiescently obturated by said wall contact with said other member, are the outlet (not the inlet), eg. by appropriate locations of unidirectional flow inserts (12,13) in the outlet and inlet chambers.

7. A pump according to any of Claims 1-6 wherein a single lower housing member (26) shaped for annular attachment to the upper housing member (17), is also shaped to accommodate said outlet and inlet (10,11) and its valving inserts (12,13) in assymmetrical manner.

8. A pump according to Claim 7 characterized in that a further insert member (27) provides the following, ie. the obturated valve seat (27C), chambers (10A,11A) for said valving inserts, and also the lower wall and side wall (27B) of the pumping chamber (9).

9. A pump according to Claim 8 wherein the further insert member (27) also has an annular bead portion which seats the bottom of the rim (8A) of the pumping diaphragm, on a clamping together (attachment fastener 18) of said upper and lower housing members (17,26).

10. A pump according to Claim 8 or 9 wherein the further insert member (27) also has formed within it, the axial chamber (10A) which is not only in the quiescent obturated and closed off from the pumping chamber (9) by the bias on the reciprocable wall portion (27A), but also axially houses one of the unidirectional valving elements.

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