GB2377256A

GB2377256A - The coupling of a drive shaft to the rotor of a progressive cavity pump

Info

Publication number: GB2377256A
Application number: GB0208157A
Authority: GB
Inventors: Jean-Pierre Marjelle
Original assignee: PCM Pompes
Current assignee: PCM Pompes
Priority date: 2001-04-13
Filing date: 2002-04-09
Publication date: 2003-01-08
Also published as: GB0208157D0; DE10216006A1; FR2823537A1

Abstract

A pumping system comprising: a Moineau pump with a helical rotor 2 inside a helical cavity of an outer stator; drive means; and means 35 for transmitting to the rotor the rotary movement of a drive shaft 14 of the drive means accompanying the rotary movement of the axis of the rotor about the axis of the stator cavity; said transmission means 35 comprise: two housings respectively fixed to the ends of the rotor 2 and the drive shaft 14 respectively; a rigid elongate element 36 fixed, with a degree of freedom of rotation about respective transverse axes, to two pivots 41 respectively housed in the two housings; the pivots 41 being retained in the housings with a freedom of rotary deflection about respective axes extending parallel to the elongate element 16 and transversely with respect to the pivots 41.

Description

r PUMPING SYSTEM COMPRISING A PROGRESSIVE CAVITY PUMP

This invention relates to progressive cavity pumps or Moineau pumps.

The invention relates more particularly to improvements to a conventional arrangement of a pumping system of this kind, which is shown in Fig. 1 of the accompanying drawings, said pumping system comprlslng: a progressive cavity pump 1 comprising a helical rotor 2 inside a helical cavity 4 of an outer stator 3; drive means 5 to drive the rotor 2, said drive means having an output shaft 6 substantially coaxial with the axis 7 of the stator cavity 4; an intermediate shaft or connecting rod 8 which is coupled at one of its ends by a cardan joint 9 to the end of the rotor 2 and which, at its other end, is moved in rotation by the output shaft 6 of the drive means 5 through the agency of a connecting shaft 14 and a cardan joint 10.

Also, a casing 11 protects the intermediate shaft or connecting rod 8 and is connected sealingly to the stator 2 of the pump 1, said casing having a lateral opening 12 forming the inlet (arrow 13) of the product which is to be delivered by the pump 1.

The connecting shaft 14 is externally smooth and co-

operates with a sealing means 15, for example of the gland type, which is held axially by an intermediate casing (or flange) 16 providing the structural connection between the end of the casing 11 of the intermediate shaft or connecting rod 8 and the casing of the drive means 5.

The cardan joints 9 and 10 are of a type designed more specifically for application to Moineau pumps and are described particularly in document FR-A-2 442 367, to which reference may now be made for more detailed information. A brief description is given

below. Referring to Fig. 2, the following description

relates more particularly to the fixing of the connecting rod 8 on the end of the connecting shaft 14, it being understood that the fixing of the connecting rod on the rotor is of the same type.

Said fixing is ensured: - axially, by means of a screw 18 extending through a smooth-walled bore 19, the centre of the base 20 of the pot, said screw being screwed in a hole 21 tapped along the axis of the facing end 22 of the shaft 14; - and, angularly, by co-operation of two cylindrical studs 23 force-fitted in the base 20 with complementary apertures 24 formed in the end 22.

The axes of the two studs 23 or holes 24 are parallel and symmetrical to one another with respect to the common central axis of the pot 17, screw 18 and end 22. The diameter of these studs and holes must be sufficient for said studs to be able to transmit the torques between the shaft 14 and the connecting rod 8.

Between the head of the screw 18 and the base of the pot 17 against which it is applied there is interposed a washer 25 of sufficient diameter to prevent any possibility of axial disengagement of the studs 23 from their housings.

The universal or cardan joint lO comprises a transverse pivot 26 mounted in the open end of the pot 17 and engaged in a collar 27 fixed to the corresponding end of the connecting rod 8.

The inside profile of said collar is doubly frusto-

conical with convergence towards the centre so that the contact between the collar and the pivot is provided solely at the constricted central zone of the collar, thus allowing angular deflections of the connecting rod not only about the axis of the pivot 26 but also about the straight line perpendicular to both said axis and that of the connecting rod and passing through the point of intersection of said two axes (straight line perpendicular to the plane of the paper in Fig. 2).

The pivot 26 is held in place by a ring 28 surrounding the open end of the pot and keyed thereon by means of a screwthreaded nipple 29.

A flexible and sealing-tight sleeve 30, the ends of which are sealingly clamped on respectively the connecting rod 8 and the pot 17 - at a groove 31 formed externally therein - enables the mechanism to be isolated from the products requiring to be pumped. To complete this sealing and at the same time perfect the relative centring between the end 22 and the pot 27, an annular rim 32 is provided at the base of the latter and projects axially beyond the base 20 and is adapted contiguously to surround the end 22 and a toric gasket 33 is interposed between said rim and said end. In practice, an annular chamfer 34 is provided on the periphery of the front surface of the end 22; the gasket 33 can then be housed in the annular cavity of triangular section delimited by said chamfer and by the re-entrant annular zone along which the rim 32 is connected to the base 20.

The cardan joint connection which has just been described briefly with respect to Fig. 2 and set out in document FR-A-2 442 367 is widely used in progressive cavity pumping systems where it gives satisfaction within the framework of the objectives assigned to it.

The main advantage of this connection is its ability to transmit much higher torques (about 1.5 times higher) than those that can be transmitted by a conventional cardan joint coupling, because of the relatively large dimensioning which can be given to

the central pivot which is thus mechanically very strong. Another important advantage lies in the structural simplicity of said connection which, with just a single axis, is capable of a double movement of rotation due to the biconical bore of the connecting rod head.

However, it is precisely in the biconical configuration of this bore that the limits to the use of this known arrangement are found. In actual fact, satisfactory operation results from a compromise between: the maximum inclination of the connecting rod with respect to the axis, which implies a clearance between said axis and the biconical bore which is all the greater with increasing maximum inclination of the biconical bore, and the clearance between the axis and the biconical bore which, if it is excessive, results in impacts in the transmission, and hence vibration and loud noise during operation. In practice, the value of the inclination of the connecting rod with respect to the horizontal does not exceed 2 , with already, for this value, a clearance which is considered considerable.

Conventionally, said inclination is chosen to be about 1 .

This small value of the inclination of the connecting rod to the horizontal results in a considerable length of the connecting rod; as can be seen in Fig. 1, the transmission between the connecting shaft 14 and the end of the rotor 2 is at least as long as, if not substantially longer than, the pump 1 itself.

The pumping system in its entirety is therefore very long and bulky and there is today an urgent demand by users for pumping systems which are less bulky while retaining the same pumping performance.

The object of the invention is to propose an improved technical solution which enables the disadvantage of the excessive length of the present systems to be eliminated and which thus satisfies the requirements of users, while being capable of transmitting identical torques and hence retaining the performances of current pumping systems.

To these ends, the invention proposes a pumping system comprising: a pump with progressive cavities, or Moineau pump, comprising a helical rotor inside a helical cavity of an outer stator, drive means to drive the rotor in rotation, said drive means having a drive shaft

substantially coaxial to the axis of the stator cavity, movement transmission means adapted to transmit to the rotor the rotary movement of the drive shaft of the drive means while accompanying the movement in rotation of the axis of the rotor about the axis of the stator cavity, said movement transmission means comprising a rigid elongate element whose ends are articulated by respective articulation means to the respective ends of the rotor and the drive shaft, said pumping system being arranged according to the invention is characterized in that the said articulation means comprise, at each end of the elongate element, a pivot which is housed in a housing provided with a transverse extent in the end respectively of the rotor and of the drive shaft, in that the elongate element is coupled to said pivot with a degree of freedom of rotation about an axis transversely of said element, and in that said pivot is retained in the respective housing with a degree of freedom of rotary deflection of a limited angular amplitude in a plane defined by the axis of said elongate element and its axis of rotation relative to the pivot, whereby the articulated connection between the elongate element and the pivot provides transmission of the torque while the articulated connection between the elongate element and its axis of

connection to the pivot provides transmission of the axial reaction force of the rotor.

With the features of the invention, connections are made which, on the one hand, can allow much greater inclinations of the elongate element to the horizontal and which, on the other hand, are so arranged that different components provide the torque transmission (flat surfaces of the elongate element and the pivot) and the transmission of the axial reaction force of the rotor (elongate element/pin/pin support). This distribution of the two types of force results in each component part being relieved of stress and enables their dimensions to be reduced.

It then becomes possible to operate the elongate element at an inclination which, in a typical example, may be as much as 5 , for a length of the elongate element of about 135 mm centre-to-centre, against about 675 mm in a prior-art arrangement for the transmission of the same torque.

In addition, each coupling can be made in a much more compact form, with an outside diameter substantially smaller than the prior-art couplings (for example typically a diameter of about 51 mm against 76 mm before).

Generally, the movement transmission means according to the invention are very compact and are therefore capable of giving users full satisfaction.

In a preferred embodiment, the elongate element is fixed to each pivot by a pin constituting the said axis of rotation of the elongate element with respect to the pivot and in that each pin extends through the respective pivot beyond the latter to be received in hollow impressions formed in opposite walls of the housing, at least one of said hollow impressions being oblong parallel to the extent of the elongate element to allow deflection of the corresponding end of the pin, and hence allow the said rotary deflection of limited angular amplitude of the said pivot with respect to the housing. Not only does this embodiment use parts which are simple to make and assemble, it also offers the advantage that in the inclined position of the elongate element the pin of each coupling bears on the side wall of the oblong hollow impression: thus the vertical component of the axial reaction force of the rotor is taken.

Advantageously, and simply, the said housings and said pivots are of complementary cylindrical shapes of revolution.

In a preferred embodiment, the movement transmission means comprise a cover in the form of a tubular sleeve whose ends sealingly surround the respective ends of the rotor and of the drive shaft.

Preferably, the tubular sleeve cover is made of a deformable material, particularly an elastomer, and its ends are clamped by respective collars sealingly on the respective ends of the rotor and the drive shaft. As a result of this arrangement, the constituent parts of the transmission (i. e. not only

the parts of the couplings, but also the elongate element, are isolated from the pumped product; the parts may be made from a conventional material, for example steel, without any risk of interaction with the pumped product.

Also, the transmission means are then in the form of a cylindrical smoothwalled element, the diameter of which is approximately that of the end of the rotor and that of the drive shaft of the drive means; the flow of the pumped product then encounters no obstacle between the casing inlet orifice and the actual pump.

Moreover, the inlet orifice in this case has a diameter which now represents a very considerable fraction of the length of the casing of the transmission means (for example typically about one-

third of said length). The inlet orifice can then be disposed in a centred position on the casing; it is now said inlet orifice, which opens out facing the transmission means, which acts as a technical inspection orifice for the said transmission means.

This results in a structural simplification of the casing which, in the prior-art systems, has a product inlet orifice towards its end situated on the drive means side and a technical inspection hatch towards its end situated on the pump rotor end side. The invention will be more readily understood from the following detailed description of certain

preferred embodiments given solely by way of example

purely for illustration. The description refers to

the accompanying drawings wherein: Fig. 3 is a top plan view in section of transmission means arranged according to the invention.

Fig. 4 is an end view in cross-section on the line IV-IV in Fig. 3.

Fig. 5 is an external side view of the transmission means shown in Fig. 3.

Fig. 6 is a top plan view similar to Fig. 3 showing part of a variant embodiment of the means shown in Fig. 3 and Fig. 7 is a diagrammatic side view in section showing the assembly of a pumping system including transmission means according to the invention.

Referring firstly to Figs. 3 to 6, the movement transmission means 35 according to the invention will now be described, said means comprising a rigid elongate element 36 connected, at its ends, to respective articulated coupling means 37 and 38, of which one, 37, is fixed to the end of the rotor 2 and of which the other, 38, is fixed to the end of the drive shaft 14.

One of these coupling means, for example 38, will now be described, it being understood that the other is symmetrically identical.

:) The coupling means 38 comprise a body 39 fixed to the end of the drive shaft 14 (respectively the end of the rotor 2 in the case of the coupling means 37); the body 39 is either integral with the shaft 14 or added to said shaft and fixed thereto.

The body 39 has its end axially hollowed thus defining an axial housing 40 in which there is engaged a pivot 41 which is split 42 axially in its central zone. Preferably, because this is a simple arrangement, the housing 40 and the pivot 41 are of complementary cylindrical shapes of revolution. The pivot 41 has a diameter substantially equal to the distance between the walls of the housing 40 and is engaged in the housing with its axis perpendicular to the axis of the housing 40, so that the pivot 41 can turn in the housing 40.

The slot 42 is defined by two substantially parallel walls spaced apart by a distance equal to the thickness of the flattened end 43 of the elongate element 36, said flattened end 43 being engaged in said slot.

The pivot 41 and the end 43 are rotatably coupled relatively to one another by means of a pin 44 diametrically traversing the pivot 41 and approximately perpendicular to the walls of the housing 40.

The ends of the pin 44 project beyond the pivot 41 and co-operate with facing slots formed in the walls of the housing 40. In the example illustrated in Fig. 3, one end 45 of the pin 44 is rounded and is

close to a perforation 46 in the corresponding wall of the body 39 which has a diameter substantially less than that of the pin; this provides a possibility of access to the pin for its removal.

The other end 47 of the pin is engaged in an oblong aperture 48 formed in the corresponding wall of the body 39 which is axially elongate but which has a width substantially equal to the diameter of the pin. A support screw 49 is provided in the edge of the flattened part 43 of the elongate element 36 to fix it in rotation with the pin 44.

In these conditions, the elongate element 36 is adapted to perform a rotary movement about the axis of the pin 44, while the pivot 41 is capable of a certain angular deflection as a result of the freedom of movement of the end 47 of the pin 44 in the elongate aperture 48 with guidance of the pin 44 in said aperture 48.

In the variant embodiment shown in Fig. 6, the two sides of the axial housing 40 are made symmetrically, with two elongate apertures 46, 48 receiving the two respective projecting ends of the pin 44, which is thus guided bilaterally in the rotation of the pivot 41 about its axis.

This results in coupling means which have a particularly high performance, wherein the two orthogonal articulation axes are embodied by two separate parts, namely the pivot 41 and the pin 44.

Moreover, the torque is transmitted by the co-

operation of the surfaces of the flattened end 43 of the elongate element 36 and the facing surfaces of the slot 42 of the pivot 41; in other words, the relatively large surface area of the mutually contacting surfaces of the end 43 of the elongate element 36 and the pivot 41 enables torques of high value to be transmitted.

On the other hand, the axial reaction component of the rotor is taken solely by the pin which, as a result, may have a diameter much smaller than the axis 26 of the prior-art device which transmitted the two forces on its own.

The elongate element 36 may be in any form adapted to ensure its function; it may be a flat iron member, but it may also be a rod --round or square -

the ends of which are machined to be in the flattened form required for its co-operation with the pivot 41.

The elongate element 36, the pivots 41 and the pins 44 are metal, more particularly of steel.

Finally, it should be noted that the transverse bulk of the coupling means is reduced and corresponds approximately to the diameters of the ends of the rotor 2 and of the drive shaft 14 respectively.

Consequently, the transmission means assembly is inserted without any appreciable radial projection between the rotor 2 and the drive shaft 14.

Consequently, as will be seen in the side view in

Fig. 7, which shows the assembly of a pumping system equipped with movement transmission means arranged according to the invention, said movement transmission means do not obstruct the penetration of the product into the inlet orifice of the stator cavity of the Moineau pump.

It also follows that it is possible to isolate the mechanical components of the movement transmission means with respect to the product being pumped, by providing a protective tubular sleeve 50, advantageously made of a deformable material (for example an elastomer), which has its ends clamped in sealing-tight manner on the body 39 by hoops 51.

This prevents product deposits from forming encrustations in the mechanism crannies. Also, it becomes possible to pump products (for example acids) which are not compatible with the metal components (for example of steel) of the movement transmission means.

The features described above enable the elongate element 36 to be inclined to a greater extent than can be carried out with the connecting rod 8 of the prior art systems (for example typically an

inclination of about 5 to the horizontal, as against approximately 1 before). This enables the movement transmission means 35 to be made in a much more compact form than hitherto (for example typically a length of about 135 mm centre-to-centre, as against approximately 675 mm in the prior art systems).

To give a better idea, a pumping system using the features of the invention is shown in Fig. 7 under

the same conditions as the prior-art system shown in Fig. 1 (the same numerical references are used to denote the same parts). It will be seen that the shortening of the movement transmission means particularly has the effect that the product inlet orifice 12 is now situated substantially in a central position on the casing 11 facing the movement transmission means 35. Taking into account its relatively considerable diameter in relation to the length of the movement transmission means 35, the inlet orifice 12 on its own can give access to all the components of the movement transmission means 35. In other words, the inspection hatch (52 in Fig. 1) which gave access to the cardan joint 9 situated on the rotor side can now be dispensed with and the structure of the casing 11 is simplified as a result.

Claims

C L A I M S

1. A pumping system comprising: a pump with progressive cavities, or Moineau pump (1), comprising a helical rotor (2) inside a helical cavity (4) of an outer stator (3), drive means (5) to drive the rotor (2) in rotation, said drive means having a drive shaft (14) substantially coaxial to the axis of the stator cavity, movement transmission means (35) adapted to transmit to the rotor (2) the rotary movement of the drive shaft (14) of the drive means while accompanying the movement in rotation of the axis of the rotor about the axis of the stator cavity, said movement transmission means (35) comprising a rigid elongate element (36) whose ends are articulated by respective articulation means to the respective ends of the rotor and the drive shaft, characterized in that the said articulation means comprise, at each end of the elongate element (36), a pivot (41) which is housed in a housing (40) provided with a transverse extent in the end respectively of the rotor and of the drive shaft, in that the elongate element is coupled to said pivot (41) with a degree of freedom of rotation about an axis transversely of said element,

and in that said pivot (41) is retained in the respective housing (40) with a degree of freedom of rotary deflection of a limited angular amplitude in a plane defined by the axis of said elongate element 36 and its axis of rotation relative to the pivot (41), whereby the articulated connection between the elongate element and the pivot provides transmission of the torque while the articulated connection between the elongate element and its axis of connection to the pivot provides transmission of the axial reaction force of the rotor.

2. A pumping system according to claim 1, characterized in that the elongate element (36) is fixed to each pivot (41) by a pin (44) constituting the said axis of rotation of the elongate element (36) with respect to the pivot and in that each pin (44) extends through the respective pivot (41) beyond the latter to be received in hollow impressions (46, 48) formed in opposite walls of the housing, at least one of said hollow impressions (48) being oblong parallel to the extent of the elongate element (36) to allow deflection of the corresponding end (47) of the pin (44), and hence allow the said rotary deflection of limited angular amplitude of the said pivot (41) with respect to the housing (40).

3. A pumping system according to claim 1 or 2, characterized in that the said housings (40) and the said pivots (41) are of complementary cylindrical shapes of revolution.

4. A pumping system according to any one of the preceding claims, characterized in that the movement transmission means (35) comprise a cover in the form of a tubular sleeve (50) whose ends sealingly surround the respective ends of the rotor (2) and of the drive shaft (14).

5. A pumping system according to claim 4, characterized in that the tubular sleeve cover (50) is made of a deformable material, particularly an elastomer, and in that its ends are clamped by respective collars (51) sealingly on the respective ends of the rotor (2) and the drive shaft (14) .

6. A pumping system according to claim 4 or 5, characterized in that the elongate element (36), the pivots (41) and the pins (44) are metal parts, more particularly of steel.

7. A pumping system substantially as hereinbefore described with reference to Figures 3 to 7 of the accompanying drawings.