GB1563172A

GB1563172A - Pumping units particularly of centrifugal type

Info

Publication number: GB1563172A
Application number: GB106/78A
Authority: GB
Original assignee: Le Materiel Telephonique Thomson CSF
Current assignee: Thales SA
Priority date: 1977-01-04
Filing date: 1978-01-03
Publication date: 1980-03-19
Also published as: CH622895A5; ES465680A1; DE2800325A1; DK1878A; FR2376309B1; FR2376309A1; CA1072398A; IT7819005A0; SE7800034L; BE862633A; DK146663B; SE438531B; DK146663C; IT1158420B; DE2800325C2

Abstract

The device is situated at the intersection of four channels serving the intake area (2), delivery (3) area and the two shells (4 and 4'). It includes two valves (8, 9) mounted freely on a shaft (20) integral with a rotating member (10) and with a control button external to the pump body. The valves whose position depends on the pressure applied counter to a spring (23) provide the alternation in the flow coming from the active shell, in transit to the delivery side. The position of the rotating element controls the intake-delivery link and performs the function of flow rate regulator by common adjustment on the two pumps. The device is applicable to twin pumps, especially acceleration pumps for central heating. <IMAGE>

Description

(54) PUMPING UNITS, PARTICULARLY OF CENTRIFUGAL TYPE (71) We, LE MATERIEL TELEPHONIQUE, a French body corporate, of 46 quai Alphonse Le Gallo, 92103 B oulogne-Billancourt, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to pumping units and is particularly, but not exclusively, applicable to liquid pumping units consisting of multiple centrifugal pumps incorporated in a common pump body. The invention is concerned with devices for controlling the passage of the liquid between ducts inside the pumping unit and the adjustment of the flow-rate produced by the pumping unit.Developments of the invention are concerned, inter alia, with the mounting of these passage and flow-rate control devices in a pumping unit, such as a central-heating booster pump.

In order to reduce the dimensions and cost of pump installations, especially those relating to industrial or domestic heating, it is advantageous to produce a pumping unit constituted by the incorporation of several pumps in a common pump body. The pumps can be mass-produced. They may or may not have the same shape and operating characteristics. Above all, manufacturers produce modules grouping two, three or even more similar pumps in modular form.

The grouping of two identical pump elements in a common pump body constitutes a privileged configuration amongst pumping units. It is known as a twin pump. In the manufacture of pumps for industrial or domestic central heating, such pumping units are commonly known as twin booster pumps.

The twin pump or booster is advantageous since it ensures high dependability of the heating system in which it is installed, since the failure of a single pump is always possible. Replacing a pump by a new pump is in itself an easy operation, but requires the heating to be turned off and the circuit to be drained. These supplementary operations seriously disturb the operation of the installation, especially during cold spells. The choice of a twin pump protects the installation against this disadvantage.

The centrifugal pumps are chosen to be identical. Their operating characteristics and in particular the power of each are selected so as to satisfy the requirements of the installation. The twin pump is intended for alternate operation, i.e. the two pumps are operated alternately. In the event of failure of one of the pumps, the other automatically takes over. In general, in order to avoid unequal wear of the pumps, both pumps are operated on a 50 /O service basis.

The work loads are thus balanced in time.

Naturally, if one pump fails the situation does not disturb the installation in any way.

The situation can be re-established under satisfactory conditions. It is merely necessary to replace the defective pump by a new pump, without draining the installation. Finally, the use of a twin pump considerably reduces the risk of failure of the installation, since it is very rare for both pumps to fail at the same time. This is a conventional solution used more and more frequently. It is adopted for most new installations.

For the manufacturer, the production of these pumping units raises two kinds of problems. Firstly, it is necessary to provide a part alternating the flow in the channels feeding the pumps in a virtually automatic manner. Secondly, it is advantageous to provide a part for varying the flow-rate of either pump element in order to adjust this flow-rate to the installation served by the pumping unit. The flow-rate is adjusted in service by an adjustable shutter, known as a variator, located in a duct known as the discharge duct between the outlet and inlet. At first sight, this conventional arrangement would lead to providing on the pump body as many variators on as many discharge ducts as there are pump elements.

According to the present invention there is provided a pumping unit comprising an inlet duct, an outlet duct, two pumps connected in parallel between said inlet and outlet ducts, a first valve which is angularly movable about an axis to provide communication between said inlet and outlet ducts via one or the other alone of said pumps or via both pumps together, and a second valve which is angularly movable about said axis to adjust the output of the pumping unit by operating between said outlet and inlet ducts.

Preferably, the second valve is locked to a common shaft providing the axis of angular movement.

According to one practical form, the first valve comprises two valve members for cooperation with respective ones of the pumps, the valve members being associated with a common return spring placed over the common shaft.

According to one development of the invention, the second valve is mechanically locked to a control knob outside of the pumping unit.

According to a further development, the second valve is mechanically locked to the control knob by moulding the shaft in the knob.

The first and second valves may constitute a single unit fitted in a variablerate twin centrifugal pump.

For a better understanding of the invention and to show how it may be put into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 illustrates in section a twin centrifugal pumping unit; and Figure 2 illustrates the pumping unit of Figure 1 in a section at right angles to Figure 1.

The vertical section illustrated in Figure 1 shows the structure of a pump body 1 in the region of the valve assembly. The section is parallel to a front surface of the pumping unit in a plane containing centre-line A'A common to inlet and outlet orifices 5 and 6.

An inlet chamber 2 is at the bottom, and an outlet chamber 3 is at the top. The general structure is symmetrical with respect to centre-line AA' through the pump inlet orifice 5 and outlet orifice 6. Each of these orifices is common to both pumps located symmetrically, the section showing a right volute 4 and a left volute 4' which are parts of the two respective pumps (not shown in detail).

The compact shape of the pump body 1 is apparent, in particular the increasing width of the outlet chamber 3 below a throat 11 of the outlet orifice 6. The internal wall of the pump body possesses parts which protrude inwards close to outlets 13 and 13' respectively of the pump volutes 4 and 4'.

One of these protruding parts is terminated at the top by an edge 12 constituting a flat surface practically perpendicular to the top internal wall 14. It is terminated at the bottom by the volute 4. By forming the outlets 13 and 13' towards the outlet orifice 6, the right and left volutes 4 and 4' provide a central body 16 whose internal wall 15 has a substantially circular section contour centred about 0 and possessing a top orifice 17 and a bottom orifice 18.

Provision is made in the twin pump body 1 for mounting a cylindrical control shaft 20 centred at 0 and coaxial with the body 16.

Two valve members 8 and 9 of a first valve are mounted on this shaft 20. These are similar slightly curved parts, as shown by the vertical section in Figure 1. The curvature ensures that the underside of each valve member correctly matches the edge of each volute outlet, such as edges 19 and 12, against which it bears when in the closed position.

Ducts 42 and 42' provide comunication from the inlet chamber 2 to the two volutes 4 and 4' respectively.

Figure 2 shows in a vertical section perpendicular to the section of Figure 1 a side view showing inter alia the shape of the valve member 9. The shape of this valve member is the same as that of the orifice constituting the outlet of volute 4' in the outlet chamber 3. Naturally, the surface of the valve member exceeds that of the orifice to be shut off ensuring a proper seal. As illustrated by both Figures 1 and 2, the top surface of each valve is engaged by a return spring 21, whose coiled part is placed freely over the shaft 20. The valve members 8 and 9 also rotate freely about the shaft 20. As seen in Figure 2, each valve member is carried by a pair of arms 22 mounted substantially without friction on the shaft 20 by means of two sleeves such as sleeve 24. A free end 23 of spring 21 bears on the upper surface of valve member 9. It can slide on this surface, guided by a rib 25 on the valve surface. The free ends, such as end 23, and naturally in the same manner the corresponding free end of the spring in the case of valve 8, are bowed, as may be seen in the section drawing of Figure 1. The arms 26 and sleeves 24' of valve member 8 shown by dashed lines in Figure 2 alternate with arms 22 and sleeves 24 of valve member 9. When assembled, the arms are slid onto shaft 20 such they they can rotate freely substantially without friction. The spring 21 can rotate freely also.

In addition, a further valve member 10 is mounted in the body 16 locked to the control shaft 20 with which it can rotate about an axis of rotation BB' perpendicular at point 0 to axis A'A (see Figure 1). The valve member 10 is locked to shaft 20 by means of a rigid mechanical attachment during assembly. This attachment can be obtained by pinning or any other method. In addition, the common shaft 20 is also locked to a control knob 31 whose handle 32 is external to the pump body 1. This attachment can be provided by moulding the control shaft 20 into the knob 31 when the latter is made of moulded plastics material. The assembly of the knob and valve members locked to the control shaft 20 as illustrated in Figure 2 includes two washers 33 and 34 placed on shaft 20 at either side of a split lock-ring 35 inserted in groove 36 of shaft 20, holding the washers in position.Finally, a perfect seal to the right of control knob 31 is provided with the front surface of the pump body 1 by an O-ring 37.

During assembly, the pump body 1 is then wide open at the rear. After installation of the valve mechanism the opening is blanked by a plate 38 assembled on a flat gasket 39.

Once fully assembled, the pumping unit is completely watertight. With regard to its operation, the valve assembly described performs two functions: the first consists in automatically controlling the pumvolute outlets to the outlet chamber 3. If the righthand pump only is operating, the circulating liquid passes through the pump volute 4 in the direction of arrows F, and F2 shown in Figure 1. The pressure of the liquid at outlet 13 pushes against the underside of the valve member 8. The force of the return spring on this valve member 8 is designed to be slightly less than that produced by the pressure of the fluid. Valve member 8, pushed by the greater force produced by the fluid, pivots towards the centre-line A'A, thereby opening the passage to the outlet chamber 3.This situation is illustrated in Figure 1, where outlet 13 of volute 4 is open, whilst outlet 13' of volute 4' is held closed by the return spring 21 against which no clockwise pressure operates, since the left-hand pump is not operating. This prevents the circulating liquid from flowing back through the left and pump which is not operating.

The second function consists in enabling the user to adjust a pump flow irrespective of which pump is operating. It is seen that the valve member 10 can occupy any possible position with respect to orifice 18 terminated by internal edges 40 and 41 of the inlet chamber 2. When the valve member 10 leaves this orifice 18 open, communication is provided from the outlet chamber 3 to the inlet chamber 2. If the valve member 10 leaves the orifice 18 partially open, partial communication is established between the outlet chamber 3 and inlet chamber 2. Finally, this communication can be completely cut-off between the outlet and inlet chambers 3 and 2 when the valve member 10 is in the position shown in Figure 1, completely closing orifice 18. Control knob 31 thus provides full flow adjustment.It is to be noted that the valve member 10 does not operate on the ducts 42 and 42', but acts as a by-pass valve to allow liquid to flow from the outlet chamber 3 to the inlet chamber 2 without passing through the pumps.

It is apparent that the location of the variator device (valve member 10) is privileged in that the adjustment is identical and simultaneous for both pumps because of its symmetry. This configuration also has the advantage of simplifying the construction of the twin pump body 1, since formerly the use of a flow variator necessitated the provision in a multiple pump body of as many discharge ducts as pumps. The illustrated and described embodiment avoids the necessity of providing any such specially provided discharge duct, thereby simplifying pump body construction.

Finally, placing the valve members 8, 9 and 10 and the control knob 31 on a single common shaft 20 results in a single assembly for the two functions and considerably simplifies the twin pump body 1.

Such simplification results in appreciable cost savings and an advantageous decrease of physical dimensions.

It should be mentioned that a twin pump in accordance with that described can also operate correctly, though perhaps less advantageously, when both pumps are running. In this case, the two valve members 8 and 9 are half-open with no particular disadvantage, since the circulating liquid cannot flow back through one of the pumps.

Simultaneous operation is possible as in the case of previously known twin pumps, but this mode of operation offers little advantage which would lead to its wider use.

The real advantage of multiple pumps, and in particular twin pumps, is that of alternate operation.

WHAT WE CLAIMS IS: 1. A pumping unit comprising an inlet duct, an outlet duct, two pumps connected in parallel between said inlet and outlet ducts, a first valve which is angularly movable about an axis to provide communication between said inlet and outlet ducts via one or the other alone of said pumps or via both pumps together and a second valve which is angularly movable about said axis to adjust the output of the pumping unit by operating between said outlet and inlet ducts.

2. A pumping unit according to claim 1, wherein said pumps are centrifugal pumps.

3. A pumping unit according to claim 1 or

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Claims

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at point 0 to axis A'A (see Figure 1). The valve member 10 is locked to shaft 20 by means of a rigid mechanical attachment during assembly. This attachment can be obtained by pinning or any other method. In addition, the common shaft 20 is also locked to a control knob 31 whose handle 32 is external to the pump body 1. This attachment can be provided by moulding the control shaft 20 into the knob 31 when the latter is made of moulded plastics material. The assembly of the knob and valve members locked to the control shaft 20 as illustrated in Figure 2 includes two washers 33 and 34 placed on shaft 20 at either side of a split lock-ring 35 inserted in groove 36 of shaft 20, holding the washers in position.Finally, a perfect seal to the right of control knob 31 is provided with the front surface of the pump body 1 by an O-ring 37.

During assembly, the pump body 1 is then wide open at the rear. After installation of the valve mechanism the opening is blanked by a plate 38 assembled on a flat gasket 39.

Once fully assembled, the pumping unit is completely watertight. With regard to its operation, the valve assembly described performs two functions: the first consists in automatically controlling the pumvolute outlets to the outlet chamber 3. If the righthand pump only is operating, the circulating liquid passes through the pump volute 4 in the direction of arrows F, and F2 shown in Figure 1. The pressure of the liquid at outlet

13 pushes against the underside of the valve member 8. The force of the return spring on this valve member 8 is designed to be slightly less than that produced by the pressure of the fluid. Valve member 8, pushed by the greater force produced by the fluid, pivots towards the centre-line A'A, thereby opening the passage to the outlet chamber 3.This situation is illustrated in Figure 1, where outlet 13 of volute 4 is open, whilst outlet 13' of volute 4' is held closed by the return spring 21 against which no clockwise pressure operates, since the left-hand pump is not operating. This prevents the circulating liquid from flowing back through the left and pump which is not operating.

The second function consists in enabling the user to adjust a pump flow irrespective of which pump is operating. It is seen that the valve member 10 can occupy any possible position with respect to orifice 18 terminated by internal edges 40 and 41 of the inlet chamber 2. When the valve member 10 leaves this orifice 18 open, communication is provided from the outlet chamber 3 to the inlet chamber 2. If the valve member 10 leaves the orifice 18 partially open, partial communication is established between the outlet chamber 3 and inlet chamber 2. Finally, this communication can be completely cut-off between the outlet and inlet chambers 3 and 2 when the valve member 10 is in the position shown in Figure 1, completely closing orifice 18. Control knob 31 thus provides full flow adjustment.It is to be noted that the valve member 10 does not operate on the ducts 42 and 42', but acts as a by-pass valve to allow liquid to flow from the outlet chamber 3 to the inlet chamber 2 without passing through the pumps.

It is apparent that the location of the variator device (valve member 10) is privileged in that the adjustment is identical and simultaneous for both pumps because of its symmetry. This configuration also has the advantage of simplifying the construction of the twin pump body 1, since formerly the use of a flow variator necessitated the provision in a multiple pump body of as many discharge ducts as pumps. The illustrated and described embodiment avoids the necessity of providing any such specially provided discharge duct, thereby simplifying pump body construction.

Finally, placing the valve members 8, 9 and 10 and the control knob 31 on a single common shaft 20 results in a single assembly for the two functions and considerably simplifies the twin pump body 1.

Such simplification results in appreciable cost savings and an advantageous decrease of physical dimensions.

It should be mentioned that a twin pump in accordance with that described can also operate correctly, though perhaps less advantageously, when both pumps are running. In this case, the two valve members 8 and 9 are half-open with no particular disadvantage, since the circulating liquid cannot flow back through one of the pumps.

Simultaneous operation is possible as in the case of previously known twin pumps, but this mode of operation offers little advantage which would lead to its wider use.

The real advantage of multiple pumps, and in particular twin pumps, is that of alternate operation.

WHAT WE CLAIMS IS: 1. A pumping unit comprising an inlet duct, an outlet duct, two pumps connected in parallel between said inlet and outlet ducts, a first valve which is angularly movable about an axis to provide communication between said inlet and outlet ducts via one or the other alone of said pumps or via both pumps together and a second valve which is angularly movable about said axis to adjust the output of the pumping unit by operating between said outlet and inlet ducts.
2. A pumping unit according to claim 1, wherein said pumps are centrifugal pumps.
3. A pumping unit according to claim 1 or

2, wherein said pumps provide a twin pump.
4. A pumping unit according to claim 1, 2 or 3, wherein said axis is provided by a shaft about which said first valve is angularly movable.
5. A pumping unit according to claim 4, wherein said second valve is mechanically locked to said shaft.
6. A pumping unit according to claim 5, wherein a control knob accessible from the exterior of the pumping unit is connected to said shaft.
7. A pumping unit according to claim 6, wherein the control knob is moulded onto said shaft.
8. A pumping unit according to any one of the preceding claims, wherein said first valve comprises two valve members for cooperation with respective ones of said pumps.
9. A pumping unit according to claim 8, wherein said two valve members are associated with a common return spring.
10. A pumping unit according to any one of the preceding claims, wherein the second valve is operable to adjust a flow path between the outlet and inlet ducts, and also to close this flow path completely.
11. A pumping unit according to any one of the preceding claims, wherein the first and second valves are inserted into a body of the pumping unit via a hole which is closed by a plate and a gasket which are secured to said body.
12. A pumping unit substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.