EP0100627B1

EP0100627B1 - Helical gear pump

Info

Publication number: EP0100627B1
Application number: EP83304217A
Authority: EP
Inventors: Stanley Ashbourne Eaton Payne
Original assignee: Mono Pumps Ltd
Current assignee: NOV Process and Flow Technologies UK Ltd
Priority date: 1982-07-20
Filing date: 1983-07-20
Publication date: 1987-05-20
Also published as: GB8319576D0; ZW16083A1; NZ204931A; AU554747B2; BR8303901A; EP0100627A1; GB2124305B; MW3283A1; ES8405901A1; ES524252A0; GB2124305A; DE3371674D1; JPS5974385A; AU1692783A

Description

This invention relates to a helical gear pump.
There are several different types of helical gear pumps. Each of these types includes an inner member, usually a rotor, and an outer member, which is usually in the form of a stator. The rotor has an external helical gear form with n starts. The stator has a complementary internal helical gear form with n ± 1 starts. One of said members, usually the stator, is of resilient material.
In use, when rotary power is applied to the rotor, it rotates and orbits within the stator and, in engaging sealingly with the inner surface of the stator, causing pumping to take place by positive displacement of the rotor in the stator.
Such pumps are capable of delivering against high delivery pressures, and are suitable for borehole pumps. They require good sealing and hence adequate initial interference between inner and outer members, so that interference and hence sealing will not be lost completely when the resilient member deforms under pump delivery pressure. However, such adequate initial interference may result in a high starting torque being required. Such a high starting torque may be a drawback when the pump is to be hand- operated.
An example of such a pump is shown in AU-A-111901, in which the pump comprises a casing, an inlet to the casing, an outlet to the casing, a helical rotor mounted for rotation within said casing about its longitudinal axis, a stator of resilient material mounted within said casing and around said rotor, an end portion of the outer wall of the stator adjacent the end of the stator nearer said inlet being connected sealingly to the casing, the remainder of the outer wall of the stator being spaced from the casing so as to be unconstrained against radial movement. This sort of pump, of the so-called "self-compensating" type, has the pressure of the column of water in a rising main connected to the upper end of the casing acting on the exterior of the stator. If the pump is stopped, this pressure will cause a large interference between the stator and the rotor, so that a high starting torque will be required. Such pumps have therefore been unsuitable for manual operation.
Mention should also be made of US-A-3982858 in which a single rotor is associated with two stators, the stators being of the moulded-in type in which the outer surfaces of the stators are sealingly connected along their length to the casing. Because the clearance between the stators and the rotor must be small for successful operation of the pump, there is a high interference over a considerable length, this also giving rise to a high starting torque requirement, making it unsuitable for use as a hand pump, capable of pumping from a deep well or bore hole.
Starting from the concept of AU-A-111901, the present invention is characterised in that the inlet to the casing is connected to a foot valve, in that at least two stators of resilient material are mounted within said casing, that said rotor is a single helical rotor of constant helical cross-section, said single rotor being associated with both stators such that the stators are operatively in series, in that an end portion of the outer wall of each of said stators is connected sealingly to said casing, in each instance adjacent to the end of the respective stator nearer said inlet of the casing, in that at least the stator nearer the inlet of the casing has the remainder of its inner wall spaced from said casing so as to be unconstrained against radial inward movement and in that the stator remote from the inlet of the casing has a radial interference with respect to the rotor within a predetermined tolerance to enable the starting torque requirement to be sufficiently small for the rotation of the rotor from standstill to be effected manually.
Because of the provision of the foot valve, the pressure at the upper end of the lower stator is substantially equal to the pressure at the lower end thereof, when the pump is at a standstill. This has the effect of causing the pressure on the outside of the self-compensating lower stator to be substantially equal to the pressure on the inside thereof which means that the starting torque required to overcome the interference between the lower stator and its rotor is negligible and one therefore only has to overcome the radial interference of the upper stator or stators.
Both of the stators may have the remainder of their outer walls spaced from the casing so as to be unconstrained against radial inward movement along portions of their length, so that they are both of the self-compensating type but, alternatively, the upper stator may be of the moulded-in type.
The helical gear pump may be mounted in a borehole installation comprising a rising main with the pump at the lower end of the rising main which extends from a lower level upwardly to an upper level above the mouth of the borehole, a shaft inside the rising main being connected to and extending upwardly from the rotor to a level above the upper end of the rising main, the shaft having means above the outlet of the rising main to cause rotation and orbiting of the rotor within the stators, and to cause water to be pumped from the borehole for delivery out of the outlet opening.
The means to cause rotation may comprise manually-operable means which includes an arm operatively connected to the shaft, the arm having handle whereby the shaft may be rotated about its axis relative to the rising main. The manually-operable means may include a pedestal mounted over and connected to the upper end of the rising main, the upper end of the pedestal supporting a bearing for the arm and having a clutch device to permit rotation of the arm in one direction only, about the rotational axis of the rotor.
The pedestal may have a water outlet below the level of the bearing, and a sealing gland below the bearing but above the water outlet, the shaft being adapted to pass sealingly through the sealing gland. The water outlet may be in the form of a spout directed downwardly from the pedestal. An upwardly directed baffle may be provided at the inner end of the spout.
The arm may be provided with gripping means for co-operating with the shaft, the gripping means including two bushes in a transverse bore intersected by a longitudinal bore to accommodate the shaft, and the two bushes in use being urged together by a bolt passing through them to grip the shaft where it intersects the transverse bore.
Instead of manually-operable means, the means for causing rotation may be provided by a windmill-operated rotary drive having its output operatively connected to the shaft.
The invention will now be described by way of example with reference to the accompanying diagrammatic drawings.
In the drawings,

Figure 1 shows a part-axial section through a borehole pump installation in accordance with the invention;
Figure 2 shows a part-axial section of a stator-rotor combination mounted according to the invention;
Figure 3 shows a part-axial section through an alternative stator-rotor combination according to the invention;
Figure 4 shows a part-axial section through the upper end of a borehole hand pump installation according to the invention; and
Figure 5 shows a part-sectional plan at V-V in Figure 4.

Referring to Figure 1 of the drawings, there is shown a borehole, generally indicated by reference numeral 10. It has a borehole casing 12 within which a rising main 14 is centrally located by stabilizers 16 arranged at axially spaced intervals within the casing 12. A helical gear pump 18, according to the invention, is mounted at the lower end of the rising main 14. A foot valve and strainer 20 is provided below the pump 18. The pump 18 has a shaft 22 located centrally within the rising main 14 by bobbin bearings 24. Rotary power is applied to the shaft 22 by means of manually-operable means in the form of a hand pump arm 26 of a hand pump head, generally indicated by reference numeral 27. The hand pump arm 26 is rotatably mounted on pedestal 28 which is mounted by means of a base member 30 over the borehole 10. The pedestal 28 has a delivery or outlet pipe 32 which is provided with a baffle 34 on the inside of the pedestal so as to prevent the introduction of foreign matter into the pedestal 28 from outside, via the outlet pipe 32. The base member 30 is mounted on a concrete block 36 cast into the soil 38 around the mouth of the borehole 10.
Referring to Figure 2 of the drawings, the pump 18 comprises a cylindrical casing 40 connected to the lower end of the rising means 14 (not shown). Within the casing 40, stators 42.1 and 42.2 are mounted sealingly in tandem around the rotor 44. The ring 45 is arranged at the suction end of the stator 42.2. The rotor 44 is connected to the lower end of the shaft 22.
The stator 42.1 is moulded into casing 42.11 which is attached to the casing 40. The stator 42.2 is moulded into ring 45 which is attached to the casing. A clearance space 48 is provided around the upper end of the stator 42.2.
The rotor 44 will be arranged to have conventional radial interference with the stator 42.1, and little radial interference with the stator 42.2. The stators 42.1 and 42.2 are also arranged in timed relationship with each other relative to the rotor 44 and are held in position in the casing 40. Under no load, the radial interference between the rotor 44 and the inner surface of the stator 42.2 will be less than the radial interference between the rotor 44 and the inner surface of the stator 42.1.
The shaft 22 is sufficiently flexible to take up the eccentricity of the rotor orbiting within the stator. It is therefore not necessary to have flexible connectors, such as universal joints and so on, in line with shaft 22. The shaft 22 is made up of a number of sections joined end-to-end.
In use, there will be such interference between the rotor 44 and the inner surface of the stators 42.1 and 42.2 at start-up as can be tolerated. The interference provided by the stator 42.1 will be within a predetermined tolerance for start-up purposes, so that the starting torque will not be excessive.
Referring to Figure 3 of the drawings, the arrangement is similar to that shown in Figure 2. The upper stator 42.3 is also sealingly mounted in similar fashion to the stator 42.2 within the casing 40. Rotor 44 and stator 42.2 of Figure 3 operate in the same way as described for the stator 42.2 and the rotor 44 of Figure 2. The stators 42.2 and 42.3 of Figure 3 are also arranged in timed relationship relative to each other and relative to the rotor 44, and are held in position in the casing 40.
The delivery pressure at the outlet from the stator 42.3 will act on the outside of the stator in the clearance space 48 and will balance to some degree the internal pressure inside the stator 42.3. Thus, sealing interference between the stator 42.3 and the rotor 44 will be substantially maintained so that delivery can take place even under a high head.
Referring now to Figures 4 and 5 of the drawings, there are shown details of manually-operable means in the form of a hand pump head 27, which includes the pedestal 28 rotatably supporting the arm 26 via anti-friction bearing 60. The arm 26 has a ratchet device 62 to prevent it from being turned in the wrong direction. The teeth for the ratchet device 62 and bearing 60 are mounted in a plug 64 which is located in the upper end of the pedestal 28. The shaft 22 passes. through seals 66 which engage sealingly with the shaft 22 along its outer surface. The shaft 22 is locked in relation to the arm 26 by gripping means which includes bushes 68 and 70 urged together by a bolt 72 passing with clearance through them. The bushes have faces 68.1 and 70.1 urged into gripping relationship with the shaft 22 by means of the bolt 72. The bushes are located axially in a bore 74 which is intersected by the shaft 22. If desired, the ends of the bore 72 are closed off by plugs 76 and 78 to prevent tampering with the locking arrangement on the shaft 22. The bolt 72 is provided with a socket head 72.1, further to discourage tampering if the cover 76 should be removed. In Figure 4 the plug 78 is shown removed.
In a preferred configuration of the helical gear pump, the stator has three starts and the rotor has two starts.
The lower ends of the casing is conveniently threaded to engage with a foot valve or a foot valve and strainer 20.
In use, the direction of rotation of the rotor is arranged to take place in such a direction that water will be pumped upwardly. The upper ends of the stators 42.2 will be subjected to partial delivery pressure. The upper ends of the stators 42.1 and 42.3 will, on the other hand, be subjected to full delivery pressure. This is the pressure which is applied to the clearance spaces 48. During start-up, the interference between the rotor and the stators 42.2 and 42.3 can be minimal. As pressure builds up, however, a tendency for the stators to expand under internal pressure can be cancelled or counteracted or compensated for by the external pressure around the outside of the stators, in the clearance spaces mentioned. It is thus possible to start with minimal interference between the rotor and the stators, yet without the danger of losing necessary sealing interference, as pressure builds up inside the stators.
Because of the compensating effect which the delivery pressure has on the outer surfaces of the stators 42.2 and 42.3, they may for brevity be referred to as compensating stators.
The hand pump embodiment shown in the drawings, shows the handle connected directly to the pump shaft without an intermediate gear ratio. It is possible to have the pump shaft driven via a step-down or step-up drive to drive it slower or faster than the handle. Such a drive may be provided by chain and sprockets, V-belts and pulleys, or a gear drive with toothed gearwheels. The pump shaft may also be driven by a rotary windmill-driven shaft directly or via a step-up or step-down drive.
A pump according to the invention, having the stator nearer the inlet as a compensating stator, also has advantages in pumping hot liquids or in pumping cold liquids which later become hot. In order to allow for temperature, the moulded-to metal stator 42.1 must have greater initial clearance at low temperature.
This would result in poor performance in the cold condition, if used alone, because of excessive clearance. The addition of a compensating stator 42.2 ensures adequate performance in the cold condition. As temperature rises, so the stator 42.1 expands, thereby taking up the greater initial clearance and providing required interference and hence good sealing at the final operating temperature.
The Applicants have found that helical gear pumps having stators arranged in series in accordance with the invention, have low starting torques in practice yet have adequate deliveries even at high heads and at low speeds, without excessive torque requirements. Thus, such pumps are very suitable for use as hand pumps on boreholes.
The Applicants have found that in order to pump at high heads an increase in length of a compensating stator will lead to an unacceptably high load torque and low delivery rate. They have found that this drawback can be overcome by mounting an equivalent length of compensating stators in series around a rotor. Such a pump does not have an unacceptably high load torque, and yet has an adequate delivery rate.
In other words, a pump having a series mounting of compensating stators has an increased efficiency over a pump having a single compensating stator of a length equivalent to the series- mounted compensating stators.

Claims

1. A helical gear pump for a bore hole comprising a casing (40), an inlet (20) to the casing, an outlet to the casing, a helical rotor (44) mounted for rotation within said casing about its longitudinal axis, a stator (42) of resilient material mounted within said casing and around said rotor, an end portion of the outer wall of the stator adjacent the end of the stator nearer said inlet (20) being connected sealingly to the casing, the remainder of the outer wall of the stator being spaced from the casing so as to be unconstrained against radial movement, characterised in that the inlet (20) to the casing is connected to a foot valve (20), in that at least two stators of resilient material are mounted within said casing, in that said rotor (44) is a single helical rotor of constant helical cross-section, said single rotor being associated with both stators such that the stators are operatively in series, in that an end portion of the outer wall of each of said stators (42) is connected sealingly to said casing (40), in each instance adjacent the end of the respective stator nearer said inlet of the casing, in that at least the stator (42.2) nearer the inlet (20) of the casing has the remainder of its outer wall spaced (at 48) from said casing (40) so as to be unconstrained against radial inward movement and in that the stator (42.1, 42.3) remote from the inlet (20) of the casing has a radial interference with respect to the rotor within a predetermined tolerance to enable the starting torque requirement to be sufficiently small for the rotation of the rotor from standstill to be effected manually.

2. A pump according to claim 1, characterised in that both of said stators (42.3, 42.2) have the remainder of their outer walls spaced (at 48) from said casing (40) so as to be unconstrained against radial inward movement along portions of their lengths.

3. A pump according to claim 1 or 2, characterised in that it is mounted in a bore hole pumping installation comprising a rising main (14) with the pump at the lower end of the rising main, which extends from a lower level upwardly to a level above the mouth of the bore hole, in that a shaft (22) inside the rising main is connected to, and extends upwardly from the rotor to a level above the upper end of the rising main, in that the shaft has, at a level above the outlet opening (32), means (26) to rotate the shaft whereby, in use, the rotor is caused to rotate and orbit within the stators to cause water to be pumped from the bore hole out to the outlet opening.

4. A pump according to claim 3, characterised in that the rotating means is provided by a manually operated device including an arm connected to the shaft, said arm having a handle (26.1) whereby the shaft may be rotated manually about its axis.

5. A pump as claimed in claim 4, characterised in that the manually operable means includes a pedestal (28) mounted over and connected to the upper end of the rising main (14), the upper end of the pedestal supporting a bearing (60) and in that a ratchet (62) is provided to permit rotation of the arm in one direction only about the rotational axis of the shaft.

6. A pump as claimed in claim 5, characterised in that the pedestal (28) has the water outlet (32) below the level of the bearing (60).

7. A pump as claimed in claim 6, characterised in that the pedestal (28) has a sealing gland (66) below the bearing (60), but above the water outlet (32), said shaft being adapted to pass sealingly through the sealing gland.

8. A pump as claimed in claim 6 or 7, characterised in that the water outlet is in the form of a spout directed downwardly from the pedestal and in that a baffle (34) extends upwardly at the inner end of the spout.