SELECTIVELY CONTROLLED DUAL DELIVERY PUMP, PARTICULARLY FOR MOTOR VEHICLE APPLICATION

Abstract: A pump is disclosed wherein, in order to provide switch­ ing ability between two different delivery outlets, a stator ca­ sing (16) bounds two superimposed manifold chambers (19, 20), each chamber being in communication with the pump im­ peller housing (15) through a respective tangential conduit. The chambers are sealed from each other by an elastic mem­ brane (23) operative to selectively cut off valve seats (24, 25) in each manifold chamber for rotation of the pump impeller in either directions.

Description: This invention relates to a selectively controlled dual delivery pump, particularly for motor vehicle application. As is known, modern motor vehicles, and especially motor cars, are equipped with windshield and rear window washers, while a similar system is gaining increasing acceptance for the headlights. In general, each washing system is supplied by an individual pump which may, however, draw from a common reservoir. This involves significant installation costs, which are sometimes unjustified by the motor vehicle class. For example, rear window washers are indeed required on so-called two-volume cars, to which class belong most.of compact cars. In order to lower costs, it has been proposed to use a dual delivery pump, wherein selective delivery to either of two different systems, such as the windshield washer and rear window washer, is controlled by the direction of rotation of the pump impeller; the two directions of rotation being obtained by switching the polarity of an impeller drive motor. A dual delivery, selectively controlled pump of this type is disclosed, as an example, in DE-A-3 023 897. That pump makes use, for selectively switching between two delivery lines, of a changeover shutter rotatively driven by the impeller hub, whereto it is connected via a friction clutch. Depending on the impeller direction of rotation, the shutter is moved to engage by. contact with the inlet port of either delivery manifold to cover said port. This prior arrangement, which has been acknowledged in the pre-characterising clause of Claim 1 has several disadvantages, and primarily a poor seal at the shutter, which results in the liquid seeping past it into the cut off manifold to the detriment of the enabled one, and a significant power loss due to dissipation by the friction clutch between the shutter and impeller hub, which brings about a further load loss in useful delivery. Other prior approaches are based on the principle of utilizing the pressure differential which is established at the inlet end of a pair of tangential manifolds selectively positioned the one in the pressure section of the stator and the other in the suction section thereof on changing the impeller direction of rotation. Such manifolds are cut off by one-way valves, the shutter whereof is urged into sealing engagement with its respective valve seat by the action of a spring which is calibrated to the maximum pressure differential value. Even the latter approach shows several draw-backs, and especially a great load loss, which brings about a significant reduction in the useful delivery rate owing to the throttling down introduced by the valves and the preload acting on the valve shutters. US-A-2 916 997 discloses a similar pump in which, instead of valve means, vanes are provided which control the fluid flow depending on the direction of rotation of the impeller. The turbulence induced by the vanes lowers the pump efficiency and cannot prevent loss. FR-A-1 142 593. discloses a selectively controlled dual delivery pump of the type as defined in the pre-characterizing clause of claim 1. From Figure 5 of this prior art reference it may be seen that the wall means provided between the collecting compartments and the impeller chamber project into the impeller chamber thereby limiting the diameter of the impeller in relation to the diameter of the impeller chamber. Moreover, the membrane 11 arranged between the valve seats and separating the collecting chamber into two collecting compartments, is arranged in a plane substantially parallel to the axis of rotation of the impeller so that, in operation, the fluid caused by the impeller to flow along a circular path within the impeller chamber impinges transversely against the membrane and is caused there to deviate by an angle of almost 180° thereby undergoing a pressure loss. This invention is essentially directed to obviate such problems. In particular an important object of the invention is to provide a dual delivery pump which can be selectively controlled by reversal of the impeller direction of rotation and incorporating delivery manifold changeover members adapted to ensure, on the one side, complete absence of seepage into the cut off manifold, and on the other side, full use of the pump head for the useful delivery thanks to substantial elimination of leakage, load losses, and/or power losses. A further important object of the invention is to provide a dual delivery pump as specified, which has a simplified construction, it including in particular no shutter components which are liable to jamming, thereby the pump can be reliable in operation and relatively inexpensive to manufacture and install. The invention providing the solution of the problem inherent in the achievement of the aforesaid object is defined by amended Claim 1. The manifold compartments preferable have a circular profile defining the plane of the membrane. Formed at the center of each manifold compartment is a circular lip defining a valve seat wherewith a thickened center portion of the membrane is arranged to cooperate in contact engagement. The elastic membrane is preferably formed from an elastomer material, and comprises a peripheral lip of O-ring configuration to provide a seal between the manifold chambers. The advantages of the invention will be more readily understood from the following detailed description, with reference to the accompanying drawings, given herein by way of example and not of limitation, and where: Figure 1 is an axial sectional view taken through this pump; Figure 2 is an enlarged scale, axial section view of the membrane separating the pump manifold chambers; and Figure 3 is a sectional view taken along the line III-III of Figure 1. In the drawings, the reference numeral 10 designates the body of a pump, which comprises a cylindrical shell of a polymeric material, wherein a housing is formed for accommodating a small electric motor 11; the housing being closed by a cover 12. Keyed to the output shaft 13 of the motor 11 is a pump impeller 14 of the centrifugal type which is mounted for rotation within a respective impeller chamber 15 in a pump casing 16. A fitting 17 admits the liquid into the chamber 15 through an axial port 18 which surrounds the impeller hub. Bounded by the pump casing 16 is a collecting chamber divided by a membrane 23 into two superimposed collecting compartments 19, 20 of circular configuration, each compartment being communicated with the impeller chamber 15 by a respective tangential conduit 21, 22. The axial dimension of the impeller is substantially twice the axial dimension of conventional single delivery pump impellers and the tangential conduits open, the one at the level of the lower half 15a of the chamber 15, and the other at the level of the upper half 15b thereof, respectively. Furthermore, said conduits are positioned symmetrically to an axis led through the centers of the collecting chamber and impeller, as shown best in Figure 3. Thus, with the impeller rotating in one direction, one conduit will be located at the pressure side and the other at the suction side, and vice versa on reversing the direction of rotation. The collecting compartments 19, 20 are sealed from each other by the membrane 23, preferably made of an elastomeric material, whose profile is detailedly shown in Figure 2. It comprises a peripheral lip 23a configured as an O-ring and adapted to be clamped, for retention as well as to provide a seal, in a respective annular seat 16c of the pump casing which includes, as shown in Figure 1, a base 16a on which a cover 16b is superposed. The center portion of the membrane has a thickened portion 23b adapted to sealingly contact corresponding annular raised lips 24 and 25 provided at the center of each collection compartment 19, respectively 20. Said annular lips form shut-off valve seats for corresponding delivery manifold ducts 26, 27 which are selectively activated according to the impeller direction of rotation. In fact, for one direction of rotation, e.g. counterclockwise as viewed in-Figure 3, the conduit 22 will be under positive pressure and the conduit 21 under negative pressure. The pressure differential which correspondingly establishes itself in the manifold chambers 19 and 20, will act on the faces of the membrane 23 causing it to move in the direction of the positive pressure gradient and engage with its center portion 23b of the respective valve seat, in the example shown, the seat 24 of the negative pressure chamber 19. Thus the membrane will shut off its respective manifold duct 26, and all of the useful delivery volume from the pump will be discharged to the enabled manifold duct 27. Upon reversal of the impeller direction of rotation, as by switching the power supply polarity to the motor 11, the pressure differential acting on the membrane faces is correspondingly reversed to result in the manifold duct 27 being shut off and the manifold duct 26 being enabled. It should be noted that, owing to the substantial extension of the membrane 23 and the absolute value of the pressure differential, in the 0.6 to 0.9 atm range, the portion 23b of the membrane is caused to adhere close against the valve seats 24 or 25, thus ensuring a perfect seal with total absence of seepage into the shut-off manifold, which improves the useful delivery rate.

Claims: A selectively controlled dual delivery pump with two delivery manifold duct means (26, 27), particularly for motor vehicle application, wherein the pump includes an impeller (14) arranged in an impeller chamber (15) of a pump casing (16) in which a collecting chamber (19, 20) is provided in communication with the impeller chamber (15) and with said delivery manifold duct means (26, 27), said impeller being selectively driveable in opposite directions, shutter means (23) being provided in said collecting chamber (19, 20) for selective cooperation with valve seats (24, 25) provided therein in opposite positions to each other, said shutter means (23) being arranged between said valve seats and alternatively preventing the flow of liquid through one of said delivery manifold duct means (26, 27), said shutter means being constituted by an elastic membrane (23) arranged between said valve seats (24, 25) and separating said collecting chamber into two collecting compartments (19, 20), each of said collecting compartments (19, 20) communicating with said impeller chamber (15) through respective conduits (21, 22) opening in mutually opposite directions into said impeller chamber (15), whereby when the impeller (14) is rotated in one direction a pressure difference acting on said elastic membrane (23) is induced between said collecting compartments (19, 20) urging said membrane (23) in sealing engagement with one of said valve seats (24, 25), respectively, thereby shutting off one of said delivery manifold duct means (26, 27) and maintaining open the other of said delivery manifold duct means (26, 27), respectively, for liquid passage therethrough and vice versa when the impeller is rotated in the opposite direction, and whereby the collecting compartments (19, 20) are arranged laterally to the impeller chamber (15) and wall means (219, 220) are provided between the collecting compartments and the impeller chamber, characterized in that the membrane (23) lies in a plane substantially perpendicular to the axis of the impeller, in that one side of the wall means forms a smooth streamlined continuation of the circular inner surface of the impeller chamber, and in that said conduits (21, 22) pass through the wall means to open tangentially into said impeller chamber whereby one conduit (21) lies below and the other conduit (22) lies above said plane of the membrane and said conduits extend towards the central area of the membrane when viewed in a direction perpendicular to said plane. A pump according to claim 1, characterized in that said conduits (21, 22) extend symmetrically to the pump midplane. A pump according to claims 1-2, wherein said valve seats are in the form of a raised center annular lip (24, 25) provided on said delivery manifold duct means (26, 27) and cooperating with said membrane (23). A pump according to claims 1-3, wherein said membrane (23) comprises a peripheral lip (23a) of O-ring configuration adapted to cooperate for retention and to provide a seal with a groove in said pump casing (16), and a thickened center portion (23b) adapted to cooperate with said valve seats (24, 25) of said delivery manifold duct means (26, 27). A pump according to claims 1-4, wherein said collecting compartments (19, 20) have circular shape.

Inventors: BIANCO, CARLO
Applicants: MES S.A.
Application year: 1984
Main classification: B60S1
IPC codes: B60S1, F04D29, F04D13, F04D15