Device For Venting Oil Pumps

Abstract

The invention relates to pump control apparatus of the type used for supplying fuel oil at a constant pressure to the nozzle of an oil burner unit. The control apparatus comprises a valve assembly for performing pressure regulating, cut-off and venting function. The venting function is performed when the pump is started by a venting valve interposed between the supply and return pipes. The venting valve is controlled so as to close before the predetermined operating pressure is reached at which time a cut-off valve opens to allow pressurized fluid to be delivered by the valve assembly.

Parent Case Text

This application is a continuation of Ser. No. 842,243, filed July 16, 1969, and now abandoned.

Description

The invention relates to a device for venting oil-pumps comprising a valve arrangement incorporating, in particular, a cut-off valve and a pressure-regulating valve, which arrangement only opens a connection between the pump pressure-pipe and the supply pipe leading to the consumer unit when a prescribed opening pressure is reached, and returns surplus oil to the sump by way of a return pipe.

The primary function of the valve arrangement is to supply oil at a constant pressure to the consumer unit, e.g. the nozzle of a heating system, but when the pressure drops, to interrupt the supply suddently. The cut-off and pressure-regulating operations can be carried out by two separate valves, these however being contained in a single valve body.

In the case of pumps that have to draw oil from a sump situated at a low level, i.e. in the case of the so-called two-line system, care must be taken that the air which collects in the pump is removed as rapidly as possible, since otherwise the suction capacity of the pump is insufficient. It is therefore known to provide between the pump pressure side and the return pipe a throttle passage the resistance of which to air is considerably less than it is to oil. This however involves difficulties in so rating the passage that, on the one hand, the air, upon starting up, is discharged through it as rapidly as possible and, on the other hand, excessive losses of oil due to the leakage through this by-pass are prevented during operation.

The object of the invention is to provide a device for venting oil-pumps which enables rapid and complete venting to be carried out immediately after starting up while causing practically no losses of oil due to leakage.

According to the invention, this object is achieved by means of a venting valve interposed between the pressure-pipe and the return pipe, which valve is so controlled that it closes before the opening pressure is reached.

In this arrangement, the medium delivered by the pump can at first flow only through the venting valve into the return pipe, since the pressure-regulating valve and the cut-off valve are still closed. The path passing through the venting valve can of course also exercise a certain throttling effect on the oil. The less the amount of air delivered, the more the pump pressure increases. This causes the venting valve to close with varying rapidity. When this closing position is reached or after a further rise in pressure, the cut-off valve opens, so that normal operation commences. During this period of normal operation, no oil can be lost through the by-pass path because of the venting valve being closed.

Expediently, the venting valve is actuated by a control piston which is loaded on one side by a rated spring and on the other by the pump pressure. In this way the closing pressure of the venting valve can be very accurately fixed in a simple manner.

In a preferred construction, the control piston of the venting valve has an annular groove in its periphery and there are two openings at the same level in the wall of the cylinder surrounding the piston, which openings communicate with the pressure pipe and return pipe respectively. Since the control piston and closure member constitute only one element, a very simple construction results.

In a further aspect of the invention, the control piston can also control a check valve fitted between the branch leading to the venting valve and the cut-off and pressure-regulating valve, in such manner that, when the pressure rises, it only opens when the venting valve has closed. If the control piston additionally carries out this checking function, this ensures that, under all circumstances, the normal delivery operation can only start when the venting valve is closed. A cut-off valve arranged in tandem can only respond if the check valve is open.

For the purpose of forming a very simple check valve, a circumferential surface of the control piston can be adapted to cover a throughflow orifice, and the stroke as far as the point at which this orifice is uncovered can then be greater than the stroke as far as the point at which the orifices in the venting valve are covered.

The venting valve of the invention can also be combined with other parts of the construction for the purpose of effecting further simplification. Thus, the control piston can be combined with the valve piston of the pressure-regulating valve contained in the return pipe, i.e. can be coupled in some way thereto or even firmly connected thereto, and the rated spring can at the same time constitute the spring for regulating the pressure-regulating valve.

In another alternative form, the control piston can be combined with the closure member of the cut-off valve contained in the delivery pipe, and the rated spring can at the same time constitute the spring for closing the cut-off valve.

In the last-mentioned arrangement, it is also of advantage if the closure member and the control piston are axially displaceable relatively to each other, and, on the circumferential surfaces facing each other, form the check valve. Here, in addition, the pressure-regulating valve can be controlled in dependence upon the pressure-drop at a restrictor contained in the pressure pipe, and the check valve, in its open position, can constitute the restrictor. In this way, the venting valve, the check valve and restrictor are combined in a surprisingly simple manner.

A simple and very reliable construction is one in which an abutment, the rated spring, the control piston, the closure member -- surrounded by a pressure-regulating valve annular piston connected to it and loaded by a differential pressure spring -- and the fixed seat of the cut-off valve are arranged one after the other in a cylinder bore, the venting valve orifices being provided in the wall of the bore in the zone of the control piston, the mouth of the pressure pipe being between the control piston and the annular piston, and the mouth of the return pipe being in the zone of the opposite end edge of the piston, while a passage, containing the check valve and restrictor and surrounding the annular piston is provided in the closure member.

The invention will now be described in more detail by reference to embodiments illustrated in the drawings, in which:

FIG. 1 is a schematic illustration of a pump system for an oil-heated installation,

FIG. 2 is a longitudinal section through a valve combination incorporating the venting valve of the invention, and

FIG. 3 shows, in longitudinal section and schematically, a second form of construction of the venting device of the invention, in another valve combination.

Referring to FIG. 1, an oil-pump 1 draws oil through a suction pipe 2 from a sump 3 and passes it to a pressure pipe 4. The pressure pipe leads, by way of a check valve 5, to a branch point 6, from which run, on the one hand, a delivery pipe, monitored by a cut-off valve 7 and leading to a nozzle 9 of an oil-fired system, and on the other hand, a return pipe 11, monitored by a regulating valve 10 and running back to the sump 3. A venting pipe 13, monitored by a venting valve 12, connects a point 14 in the pressure pipe 4 and in front of the check valve 5, with a point 15 in the return pipe 11 and behind the pressure-regulating valve 10.

Between the check valve 5 and the venting valve 12 there is a mechanical coupling 16 which ensures that the check valve 5 only opens when the venting valve 12 is closed. Both valves are controlled by the pump pressure as indicated by the impulse line 17. When there is no pump pressure, the venting valve 12 is open. It closes as soon as the pump pressure has reached a prescribed level. The check valve 5 then opens. The cut-off valve 7 and the pressure-regulating valve 10 are each controlled by their inlet pressure in the present embodiment, as indicated by the impulse lines 18 and 19. These two valves can only come into operation if the check valve 5 is opened, i.e. if a prescribed minimum pressure has been reached at which the venting valve 12 has closed.

Consequently, when the pump starts up, the total delivery quantity is first returned by way of the venting valve 12 to the sump and any air contained in the pump or in the suction pipe is thus removed. Here, the greater the quantity of oil delivered through the venting pipe 13, the greater becomes the resistance to flow and the further the venting valve 12 closes, until finally the closing pressure for this valve 12 is reached, whereupon the pump pressure rises again until the opening pressure for the valve 5 is reached. The system then operates in the normal manner.

The check valve 5 can be dispensed with if the response pressure of the cut-off valve 7 is somewhat higher than the closing pressure of the venting valve 12. Also, the cut-off valve 7 and the pressure-regulating valve 10 can be controlled in any manner, e.g. not only in dependence upon pressure, but also in dependence upon the quantity of oil delivered by the pump.

In the embodiment shown in FIG. 2, a housing 21 contains a cylindrical bore 22 in which a control piston 23 is displaceable. On the one side, this piston is acted upon by the pressure of a rated spring 24, which is supported against an adjustable abutment 25, and at tee other side the piston is acted upon by the pressure of the oil flowing from the pump by way of a bore 26 into a chamber 27. The control piston contains an annular groove 28, which, in the non-operative position, connects the mouth 29 of a bore 30 with the mouth 31 of a bore 32, which are both associated with the venting pipe. This connection is interrupted as soon as the pressure chamber 27 exceeds a prescribed value and thereby pushes the control piston 23 a corresponding distance to the right, overcoming the force of the rated spring 24.

By means of a hollow cylindrical extension 33, the control piston 23 surrounds a cylindrical closure member 34, which co-operates with an O-ring seal 35 and a fixed stop 36 in an insert fitted in the end-face, and so forms the cut-off valve. A hollow locking-pin 38 retains the O-ring and extends into a hole 39 in the closure member, which hole is closed by a ball 40. The hollow cylindrical extension 33 is closed by a base-plate 41. Consequently, the spring 24 acts as a closing spring for the cut-off valve when the pressure pump in the chamber 27 falls below a prescribed value.

The closure member 34 contains a longitudinal bore 42 and two transverse bores 43 and 44. The mouths of the transverse bore 44 form, together with the extension 33, the cut-off valve 5. As soon as the end-edge 46 of the extension 33 reaches the mouth 45, an aperture is formed through which the chamber 27 is connected to a chamber 47 by way of the bores 44, 42 and 43. Because of the aperture, a lower pressure obtains in this chamber 47 than in the chamber 27.

This differential pressure acts upon an annular piston 48, which surrounds the closure member 34 and, by its edge 49, overrides the mouth 50 of a bore 51 associated with the return pipe 11. This annular piston is also loaded by a differential pressure spring 55. In operation, the piston therefore occupies a position which is determined by the pressure-drop at the aperture 45, 46 and the force of the spring 55. The closure member 34 follows the annular piston 48, since it is pressed by a spring 56 incorporating a stop 52 against a resilient disc 53, which is fitted in the annular piston 48. In the illustrated non-operating position, the annular piston 48 forms a backing member for an O-ring 54, against which the extension 33 of the control piston 23 is pressed by the force of the rated spring 24, so that additional blocking is achieved at this point.

When the pump is switched on, the entire quantity of oil delivered flows through the bore 30, the annular gap 28 and the bore 32. When the pump pressure in the chamber 27 rises, the control piston 23 moves to the right, while the same pump pressure however holds the annular piston 48 and thus the closure member 34 in the at-rest position. After a short movement of the control piston, the venting line 32 is interrupted, and after further movement of the control piston the end-edge 46 uncovers the mouth 45. Oil then flows into the chamber 47, so that pressure builds up there. Consequently, the annular piston 48 and thus the closure member 34 move to the right. First the cut-off valve 34 is opened and then the pressure-regulating valve 49, 50. The annular piston 48 and closure member 34 remain in a position in which the force of the spring 55 balances the pressure drop at the aperture 45, 46. When the pressure in the chamber 47 rises, the annular piston 48 moves to the right, so that, on the one hand, the mouth 50 of the return bore is further uncovered and, on the other hand, the aperture, 45 and 46, is closed somewhat. When the pressure in the chamber 47 drops, this double regulation takes place in the reverse direction. If considerable fluctuations in pressure occur in the chamber 27, the control piston 23 can also participate in the act of regulation by way of the aperture 45, 46. If, when the pump is switched off, the pressure in the chamber 27 drops considerably, the control piston 23 even causes the cut-off valve to close.

In the construction seen in FIG. 3, a hollow cylindrical housing 60 contains a piston 61, which is divided into three cylindrical portions 64, 65 and 66 by two annular grooves 62 and 63. On the one side the piston 61 is acted upon by the pressure from a rated spring 67, the bias of which can be varied by means of a set-screw 68, and on the other side, by the pressure of the oil in the chamber 69 which is delivered from the pump through a bore 70. A further bore 71 runs from the chamber 69 to the delivery pipe 8 and return pipe 11, and a bore 72 in the piston-section 66 runs to the annular groove 63. The cut-out valve is not illustrated. The return pipe 11 contains a bore 73, the annular chamber 62 and a bore 74. The edge 75 of the piston-section 64 co-operates with the mouth 76 of the bore 74 to form a pressure-regulating valve.

Also provided is a bore 77, the mouth 78 of which co-operates with the end-edge 79 of the piston-section 66 to form a venting valve.

The arrangement disclosed in FIG. 3, is illustrated in the operating position in which the piston 61 is pushed so far upwards that the venting valve 78, 79 is closed and the pressure-regulating valve 75, 76 is opened. In the at-rest position however, the venting valve is opened and the pressure-regulating valve closed. Here, the rated spring 67 acts as a counter-spring for the venting valve and as a regulating spring for the pressure-regulating valve.

Claims

We claim:

1. Pump control apparatus comprising a housing having a cylindrical bore, a control piston valve slidably disposed in said bore, means biasing said piston valve in one direction, fluid inlet means in said housing for admitting pressurized fluid to bias said valve in the opposite direction, fluid outlet means in said housing having fluid communication with said fluid inlet means for discharging pressurized fluid from said housing, vent outlet means in said housing, vent passage means in said valve, said valve having a first position providing fluid communication between said housing vent outlet means and said valve vent passage means when the pressure of said pressurized fluid is below a predetermined pressure, said valve having a second position for blocking fluid communication between said housing vent outlet means and said valve vent passage means when the pressure of said pressurized fluid is greater than a predetermined pressure, said vent passage means including an annular groove in said valve, said vent outlet means being two orifices in said housing on diametrically opposite sides thereof, and a pressure pipe having fluid communication with the other of said orifices, cut-off and pressure regulating valve means in parallel flow branches in said housing, and check valve means on the upstream side of said cut-out and pressure regulating valve means controlled by said control piston valve.

2. Pump control apparatus according to claim 1 wherein said control piston valve has a bore, said check valve means including a cylindrical portion slidably disposed in said bore, a transverse bore in said cylindrical portion, said transverse bore being in fluid communication with said inlet means when said control piston valve is in said second position.

3. Pump control apparatus according to claim 1 wherein said means for biasing said valve in said one direction are resilient means, said control piston valve has a central bore, cylindrically shaped cut-off valve means slidably disposed in said bore for controlling the egress of fluid through said fluid outlet means, said resilient means effectively biasing said cut-off valve means in a closing direction.

4. Pump control apparatus according to claim 3 wherein said control piston valve and said cut-off valve means are axially movable relative to each other, and check valve means being formed between the mutually engaging circumferential surfaces of said control piston valve and said cut-off valve means.

5. Pump control apparatus according to claim 4 wherein said check valve means includes fluid passages, pressure regulating valve means controlled in accordance with the pressure of fluid in said check valve fluid passages.

6. Pump control apparatus according to claim 5 including a differential pressure spring biasing said pressure regulating valve means in a valve opening direction to reduce the pressure of fluid egressing from said fluid outlet means.