GB2510028A

GB2510028A - Screw conveyor coupling with relief groove

Info

Publication number: GB2510028A
Application number: GB1320125.6A
Authority: GB
Inventors: Peter James Wood
Original assignee: SHANDWOOD ENG Ltd
Current assignee: SHANDWOOD ENG Ltd
Priority date: 2012-11-14
Filing date: 2013-11-14
Publication date: 2014-07-23
Anticipated expiration: 2033-11-14
Also published as: GB2510028B; GB201320125D0; GB201220499D0

Abstract

A screw conveyor 10 comprises a body 12, a shaft 14 mounted within the body 12, a helical screw 16 disposed around the shaft, the shaft 14 having first and second ends, the first end having a projection 44 with a polygonal cross-section extending coaxially from the shaft 14 and the second end having a corresponding cooperative polygonal socket 14a within which a relief groove 400 is provided for receiving debris. Debris can collect in relief groove 400 instead of fouling the space between mating surfaces of the projection 44 and socket 14a. The projection 44 and socket 14a may be of hexagonal cross section and chamfered or bevelled fillets 44a may be provided between adjacent edges of the shaft 44. The projection 44 may be provided on an intermediate section 41 having two polygonal projections 44 joined coaxially and separated by a central section (42 fig. 3) of circular cross-section. The socket 14a may include a removable cover 14d. The projection 44 and socket 14a may provide couplings between abutting shafts 14. The screw conveyor 10 may be used for handling oilfield drilling cuttings.

Description

Screw Conveyor

Field of the Invention

The present invention relates to screw conveyors, especially those used in the

handling of oilfield drilling cuttings.

Background to the Invention

Screw conveyors or auger conveyors are used in a variety of applications. They generally comprise a rotating helical screw blade disposed within a trough or a tube.

The helical screw blade is disposed around a central shaft. A ribbon conveyor is another form of screw conveyor which also comprises a helical screw with a short shaft at either end of the helical screw to enable bearing support or joining sections together rather than a central shaft running along the length of the helical screw.

Bulk material, such as liquid or granular material, can be moved along the tube or trough by the action of the rotating screw blade, thereby transporting it between two different points.

Screw conveyors are used in oilfield drilling operations. Such drilling operations produce a large amount of debris from the drilling operation which must be transported from the drilling point Often, several separate screw conveyor units will be linked together to form a continuous pathway for the drilling debris. For example, an individual conveyor unit may be around 3-4m in length, whereas an application may require up to, or in excess of, 40m. The pathway may be horizontal, inclined or vertical, or a combination of these. The conjoined screw conveyor will usually have a driving torque applied at one end, with the torque being transmitted through the various joined units.

Prior art solutions have circular, square or rectangular cross-section shafts. For example, U.S. Patent No. 3,104,757 (A. L. Dougherty et al.) discloses a screw conveyor coupling having a stud shaft connector received within a circular socket of the shaft, the distal end thereof being provided with a square cross-section projection. Individual shaft lengths are joined by way of inserting the projection into a bushing of another socket and using a cross-bolt to fasten the projection into the socket The female shaft (i.e. the shaft having the socket) may have a slot cut to aid assembly and this is known to weaken the shaft, so much so, in fact, that the employment of such slot on the shaft directly connected to the drive motor, is not recommended.

In this arrangement there are several disadvantages. First, the drive torque is transmitted through the cross-bolts, which may lead to undesirable wear and misalignment of the shafts. This wear and misalignment can lead to unwanted vibration within a conveyor assembly, and "wagging" of the drive during operation, often up to around 10mm per 30m unit. Further, poor surface finish and sealing of the joints can lead to corrosion which can cause difficulty during assembly, maintenance and disassembly.

The mating of a square cross-section projection within a circular shaped socket can be disadvantageous on several levels. Firstly, the overall cross-sectional size of a square cross-section projection (i.e. the length of each square side) within a circular receiving socket is limited by the separation of the diametrically opposed corners of the square. A reduced cross-sectional size of the square cross-section projection necessarily results in a reduction in the torque that may be transmitted within a given internal socket diameter.

Furthermore, the process of assembling individual shaft lengths is also more difficult with a square cross-section projection. This is because the mating faces of the projection must be offered up to the socket in perfect alignment to permit their entry into any matching slot within the socket. This presents acute problems in already challenging field assembly situations. Alignment problems are exacerbated if any debris is present on the respective square mating surfaces. Unless all mating surfaces are free of debris -which is often not ftc case in field assembly situations the process of connecting adjoining individual shaft lengths maybe disrupted.

Summary of the Invention

According to a first aspect of the present invention there is provided a screw conveyor comprising a body, a shaft mounted within the body, a helical screw disposed at least around part of the shaft, wherein the shaft has a first end and a second end, the first end having a non-circular projection extending coaxially from the shaft, and the second end having a corresponding cooperative non-circular socket; and wherein a relief groove is provided within the socket for receiving debris.

The profile of the projection and socket are such that the drive is transmitted through the mating surfaces and not the retaining bolts.

The non-circular socket and projection may attach to corresponding non-circular projections and sockets of further screw conveyors according to the present invention such that a screw conveyor assembly comprising a plurality of such screw conveyors maybe constructed.

The non-circular projection and non-circular socket may have any suitable cross-section, for example: triangular, square, quadrilateral) pentagonal) hexagonal) heptagonal) octagonal, or some higher order polygon. Preferably, the cross-section has six or more sides. Most preferaNy, the polygon has an even number of sides.

Optionally, adjacent faces of the non-circular projection may not meet at a sharp angle. Instead, adjacent faces maybe separated by a chamfered or bevelled corner.

The socket may comprise a removable cover. The removable cover may comprise at least one of the sides of the polygon. The cover may be mechanically attachable to the socket to complete the internal polygonal shape substantially matching that of the non-circular projection.

A relief groove maybe located internally with the socket at the junction of two of its adjacent surfaces. Preferably, the relief groove is orientated at the lowest point within the socket The relief groove may be located at a position which is diametrically opposed to the removable cover. It will be appreciated that the chamfered or bevelled corners will permit small pieces of debris to travel downwards into the relief groove.

The non-circular projection may comprise an intermediate section. The intermediate section may comprise a member having two non-circular projections joined coaxially. The first end of the shaft may include a corresponding cooperative non-circular socket for receiving one of the intermediate section's two non-circular projections.

The intermediate section may have a central circular cross-section section located between the two non-circular projections.

The intermediate section may be used to join two adjacent shafts of two adjacent screw conveyors together.

The non-circular projection may comprise a bearing section or drive section. The bearing section or drive section may include a circular cross-section shaft portion joined coaxially to a non-circular cross section projection. The bearing shaft may be seated with the non-circular projection located within the corresponding and cooperative non-circular socket and the circular cross-section shaft portion located within a suitable bearing allowing rotation of the shaft The drive shaft may be seated with the non-circular projection located within the corresponding and cooperative non-circular socket and the circular cross-section shaft portion located within a suitable bearing allowing rotation of the shaft.

S

The screw conveyor may be provided with a suitable driving means. Suitable driving means may include an electric motor, an internal combustion engine, or any other suitable method of imparting a driving torque to the shaft of the screw conveyor.

According to a second aspect of the present invention there is provided a screw conveyor assemlMy comprising at least two conjoined screw conveyors according to the first aspect.

According to a third aspect of the present invention there is provided a method of forming a screw conveyor assembly including the step of joining a shaft of a first screw conveyor to the shaft of a second screw conveyor by providing a non-circular socket on the shaft of the first or second screw conveyor, providing a corresponding non-circular projection on the other shaft, and seating the non-circular projection in the non-circular socket The non-circular projection and non-circular socket may have any suitable cross-section, for example: triangular, square, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, or some higher order polygon.

The non-circular projection may comprise an intermediate section. The intermediate section may comprise a member having two non-circular projections joined coaxially. The first end of the shaft may include a corresponding cooperative non-circukr socket for receiving one of the intermediate section's two non-circular projections.

The intermediate section may have a centra' circular cross-section section located between the two non-circular projections.

Each end of the screw shaft may have a shaft slot formed at the non-circular socket This assists each screw shaft to be removed or replaced independently of any other shaft in the assembly. The slot may also be provided on a shaft adjacent to the drive motor and, due to the inherent strength of the non-circular join.

The present disclosure may also allow the intermediate bearing shaft to be replaced quickly and independently of the other shafts. This may mean that sealed roller bearings can be used in place of friction bearings -operators are wary of downtime required to replace sealed roller bearings on prior art equipment Use of sealed roller bearings mitigates the need to lubricate the conveyor daily as is required with

prior art conveyors.

Accurately fitting projections and sockets, along with a shaft socket cover, mitigate the ingress of debris into the shaft joints. Along with the surface treatment of the materials, and the application of suitable lubricants during assembly, this means that the conveyors can be readily dismantled after use. With the prior art this operation is very difficult and often leads to the shafts being torch cut.

Brief Description of the DrawinRs

Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: Fig. 1 is a perspective view of a screw conveyer according to the present invention; Fig. 2 is an exploded perspective view of the screw conveyer of Fig. 1 configured in a single conveyer arrangement; Fig. 3 is a perspective view of an intermediate shaft section of the screw conveyor of Fig. 1; Fig. 4 is an exploded perspective view of the screw conveyer of Fig. 1 configured in a multi-conveyer arrangement; Figs. S to 15 detail a sequence of interconnection of two screw conveyors to form a screw conveyor assembly; and Fig. 16 is a schematic cross-sectional view of a hexagonal projection located within a socket with the socket cover removed.

Referring to the drawings and initially to Fig. 1, a screw conveyor 10 according to the present invention is shown. The screw conveyor 10 comprises a body 12, a central shaft 14 mounted longitudinally within the body 12, with a helical screw 16 disposed around the shaft 14. An electric motor 18 is attached to a first end ba of the screw conveyor 10. The electric motor 18 is of a known type, and drives the shaft 14 in a known manner via a bearing assembly 19. An electric motor drive shaft 21 connects the electric motor 18 to the shaft 14. The electric motor shaft 21 comprises a circular cross-section shaft portion 21a joined coaxially to a non-circular cross section projection (see Fig. 3].

The body 12 comprises an elongate trough 20, with vertical parallel side walls 22 and a semi-circular cross sectional bottom 24. Connection flanges 26 are provided at first and second ends of the trough 20.

The body 12 is closed off at its first end ba with a motor end trough plate 28. The motor end trough plate 28 attaches to the connection flange 26 via nut and bolt arrangements 30. A gasket 32 is placed between the motor end trough plate 28 and the connection flange 26. The motor end trough plate 28 has a lower stand 33 which projects perpendicularly from the trough plate 28 to provide a means to mount the screw conveyor 10 on a suitable substrate. The motor end trough plate 28 has a central drive shaft aperture 29 allowing the electric motor drive shaft 21 to pass through it and freely rotate within it The helical screw 16 and semi-circular cross-sectional bottom 24 are dimensioned complementary, such that there is a close but sliding fit between the two, consequently allowing both the screw 16 to rotate freely within the trough 20 and mitigating the possibility of material being transported by the screw 16 fouling the screw 16.

A hanger bracket 34 is located at the second end lOb of the screw conveyor 10, the end located distally from the first end ba and electric motor 18. The hanger bracket 34 spans the two side walls 22 of the trough 20. The hanger bracket 34 comprises two connection flanges 36 which attach to the two side walls 22 at the end of the trough 20 and a central web 38. A hanger bearing 40 attaches to the central web 30, projecting into the trough 20, for receiving the non-driven end of the shaft 14.

A support foot 39 is attached to the connection flange 26 and comprises a generally triangular section 39a which projects downwardly and a perpendicularly projecting support section 39b for enabling mounting on a suitable substrate, similar to the lower stand 33.

In the currently described embodiment, the shaft 14 and helical screw 16 are welded together, although it will be understood by the skilled addressee that any suitable mode of joining the two parts may be used, such as casting, forging mechanical interconnection, etc. The shaft 14 is provided at its first and second end with a shaft socket 14a. The shaft socket 14a is substantially coaxial with the shaft 14 and is provided with a socket slot 14b along one edge. The shaft socket 14a is therefore semi-cylindrical thong most of its length, with a substantially C-shaped cross-section. Cross bolt apertures 14c are provided through the shaft 14 adjacent the shaft socket 14a and socket slot 14b.

Fig. 2 shows the screw conveyor 10 of Fig. 1 modified to be a "single" screw conveyor i.e. it transports bulk material or the like only along its length and is not attached to further screw conveyors.

The hanger bracket 34 and bearing 40 are removed and the second end lOb is provided with an end plate 60. End plate 60 is a largely identical to motor end trough plate 28 and is attached to the body 12 via the connection flange 26 with a gasket 62 located between them. A bearing assembly 64 of a known type is used.

The end plate 60 has a central aperture 66. A bearing shaft 68 passes through the central aperture 66. The bearing shaft 68 comprises a circular cross-section shaft portion 68b joined coaxially to a non-circular cross section projection 68a.

An intermediate shaft section 41 is shown in Fig. 3. The intermediate shaft section 41 allows attachment between individual shaft/screw assemblies of adjacent screw conveyors 10.

The intermediate shaft section 41 comprises a central cylindrical section 42. The central cylindrical section 42 is located in use within the hanger bearing 40 and is surrounded by the inner race of the hanger bearing 40 (see Fig. 4). Two non-circular projections 44 extend from each face of the central cylindrical section 42 (only one visible in Fig. 3). The non-circular projections 44 are substantially hexagonal in cross-section, forming a substantially hexagonal prism, although it will be noted that fillets 44a have been machined between the adjacent edges that are parallel to a general axis of the shaft section 40. Although this technically results in a non-uniform dodecagonal prismatic shape, it will be appreciated that this is still substantially hexagonal. It will be appreciated that other non-circular cross-sections such as, but not limited to, triangular, square, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, or some higher order polygon are possible. The applicants have found that a polygon with an even number of six or more sides is provides surprising advantages insofar as it facilitates ease of assembly by providing natural lead-in faces; and because it provides superior strength and torque transfer. By contrast, a square cross-section protrusion is weaker, and much more difficult to align prior to assembly. Whilst a circular projection can be easily aligned, its bolt holes -used to connect it to the socket -will then be more difficult to align and will usually require to be rotated with respect to each other before the connection can be finalised. All torque in a circular projection is transferred via its connecting bolts which is undesirable.

The shaft socket 14a has a corresponding internal profile, such that a secure interference fit is formed when the substantially hexagonal projection 44 is seated within it As can be more clearly seen in Fig. 6, the internal profile of the shaft socket 14a includes a relief groove 400 for receiving small pieces of debris. The relief groove 400 is located at the lowermost part of a natural V-shape at the junction of the two lowermost faces within the socket 14a. Debris can collect within the relief groove instead of fouling the space between the mating the surfaces of the projection 44 and the socket 14a. The aforementioned fillets 44a -which may be truncated flat surfaces, or chamfered or bevelled regions as shown in Fig. 16 -allow debris to pass downwards into the relief groove.

A first bore 46 is provided approximately halfway along the length of the hexagonal projection 44. The first bore 46 is located within a bore recess 47, the bore recess 47 being formed by a flat surface formed on the outer surface of the hexagonal projection 44 between two adjacent faces of the generally hexagonal prismatic shape, and the flat surface being in a plane generally parallel to a plane of the fillet 44a formed between said adjacent faces.

A second bore 48 is provided towards the distal end of the hexagonal projection 44 from the central cylindrical section 42. The second bore 48 is formed between two opposite faces of the generally hexagonal prismatic shape. Thus, the first bore 48 and second bore 48 are perpendicular to one another.

It will be understood by the skilled addressee that the description for the above hexagonal projection 44 of the intermediate section 41 is substantially the same as that for the non-circular cross section projection 68a of the bearing shaft 68 and the non-circular cross section projection 21± of the drive shaft 21.

A method of joining two or more screw conveyors to form a screw conveyor assembly 300 is depicted in Figs. S to 15.

A first screw conveyor 10, as described above, is depicted in Fig. 5. This is the drive end section of the assembly 300 as it is provided, as described above, with an ekctric motor 18. A second screw conveyor 100 is positioned adjacent the first screw conveyor 10. This is an intermediate section of the assembly 200 as it is not provided with an electric motor 18) although aside from the &ectric motor 18 and a motor end trough p'ate 28 it is substantially identical to the first screw conveyor 10.

A further intermediate third screw conveyor 200 is shown) with the method of joining it to the second screw conveyor 100 being largely similar to that as described below for joining the second screw conveyor 100 to the first screw conveyor 10.

A transport bracket 180 is provided on the second screw conveyor 100 which spans the connection flange 126 at its first end bOa to assist in transportation and movement of the second screw conveyor 100. The transport bracket 180 comprises an elongate bar 182 which spans the connection flange 126 and a shaft support 184 projecting into the body 112 of the second screw conveyor 100. Tn Fig. 5, and in transportation and movement of the second screw conveyor 100, the shaft support 184 supports the central shaft 114 of the conveyor 100, maintaining it substantially horizontal within the body 112. A hanger bracket 134 is provided at the distal or second end lOOb of the conveyor 100.

The transport bracket 180 is removed and the shaft 114 and helical screw 116 assembly are removed from the body 112. A gasket 132 is placed over the first end bOa connection flange 126 and the two conveyors 10, 100 are brought together such that corresponding connection flanges 26, 126 are adjacent with the gasket 132 sandwiched between them. Nut and bolt arrangements 130 are used to mechanically fasten the connection flanges 26, 126 together. The support foot 39 is also sandwiched between the two connection flanges 26) 126 with the nut and bolt arrangements 130.

In this stage of assembly (Fig. 9), the intermediate section 41 projects through the hanger bearing 40 and into the body 112 of the second screw conveyor 100. The non-circular projection 44 is then coated with an anti-seize compound C (Fig 10).

The shaft 114 and helical screw 116 assembly are reintroduced into the body 112, the shaft socket 114a receiving the non-circular projection 44 via the socket slot 114b. An interference fit is formed between the shaft socket 114a and the non-circular projection 44, and therefore between the shaft 14 and helical screw 16 assembly of the first screw conveyor 10 and the shaft 114 and helical screw 116 assembly of the second screw conveyor 100. It will be noted that per Fig. 11 especially, the shaft 214 and heilcal screw 216 assembly of the third screw conveyor need not be removed before installation as the introduction of the shaft 114 and helical screw 116 assembly will allow interconnection of the two adjacent shaft/screw assemblies.

Cross bolts 190 are inserted through the cross bolt apertures 114c and through the first bore 46 and second bore 48. A shaft slot cover 114d is then fitted over the shaft slot 114b. The shape of the shaft slot cover 114d is complementary to that of the shaft slot 114c. This allows for additional torque to be transmitted through the shaft 114. Nuts 192 are then attached to the cross bofts 190, which secures the shaft slot cover 114d into the space of the shaft slot 114c creating a substantially cylindrical shaft end and providing a further mechanical fastening of the shaft 114 and helical screw 116 assembly to the intermediate shaft section 41 to enhance the interference fit already formed. It will be understood by the skilled addressee that this is a similar manner in which the intermediate section 41 is already seated within the shaft socket 14a of the shaft 14 of the first screw conveyor 10. The connections are largely symmetrical about the central cylindrical section 42.

It will be understood by the skilled addressee that the description for the method of attaching the non-circular projection 44 of the intermediate section 41 to the shaft/screw assemblies is substantially the same as that for connection of shaft/screw assemblies to the non-circular cross section projection 68a of the bearing shaft 68 and the non-circular cross section projection 21b of the drive shaft 21 and further elaboration is unnecessary.

The hanger bracket 40 is then mechanically fastened to the body 112 of the second screw conveyor 100 via nut and bolt assemblies 195. A cover 194 is then fitted over the top of the second screw conveyor 100. A corresponding cover 94 is also fitted over the first screw conveyor 10. Further, the cover 94 is less than the full longitudinal dimension of the body 12 such that an inlet flange 96 may be joined to the top of the body 12 allowing access of bulk material to the screw conveyor assembly formed.

In use, the electric motor 18 will drive the shaft 14 and helical screw 16 assembly of the first screw conveyor 10 and torque will be transmitted through the intermediate section 41 to the shaft 114 and helical screw 116 assembly of the second screw conveyor 100. The exterior non-circular profile of the non-circular projections 44 and the corresponding inner profile of the shaft sockets 14a, 114a to produce a fit which allows transmission of driving torque. The driving torque is primarily transmitted through the mating faces of the various non-circular projections and sockets and not through the nut and bolt assemblies. The nut and bolt assemblies are intended to mitigate unwanted longitudinal movement of projections within sockets and not for the transmission of torque.

prior art conveyors.

Accurately fitting projections and sockets, along with the shaft socket cover, mitigate the ingress of debris into the shaft joints. Along with the surface treatment of the materials, and the application of suitable lubricants during assembly, this means that the conveyors can be readily dismantled after use. With the prior art this operation is very difficult and often leads to the shafts being torch cut.

The surfaces of the shaft socket cover 14d which engages with the shaft socket 14a (see Figs. 3 and 16) may include an elastomeric material. This forms a compression seat when the shaft socket cover lAd is attached to the shaft socket 14a, thus preventing the ingress of debris.

It will be further appreciated by the skilled addressee that further screw conveyors maybe added to form screw conveyor assemblies of appropriate dimensions for the required application.

Modifications and improvements may be made to the present invention without departing from its scope. Again, it will be appreciated by the skilled addressee that other non-circular cross-sections, such as triangular, square, quadrilateral, pentagonal, heptagonal, octagonal, or some higher order polygon may be used in place of the substantially hexagonal projection hereinbefore described.

Claims

CLAIMS1. A screw conveyor comprising a body, a shaft mounted within the body, a helical screw disposed at least around part of the shaft, wherein the shaft has a first end and a second end, the first end having a polygonal projection extending coaxially from the shaft, and the second end having a corresponding cooperative polygonal socket; and wherein a relief groove is provided within the socket for receiving debris.
2. A screw conveyor according to claim 1 wherein the polygonal projection and polygonal socket have a cross-section chosen from the group comprising: hexagonal, octagonal, or some higher order polygon with an even number of sides.
3. A screw conveyor according to claim 1 or 2, wherein adjacent faces of the polygonal projection are separated by a chamfered or bevelled edge.
4. A screw conveyor according to any preceding claim, wherein the cooperative polygonal socket comprises a removable cover.
5. A screw conveyor according to claim 4, wherein the internal surface of the removable cover comprises at least one of the sides of the polygon.
6. A screw conveyor according to any preceding claim, wherein the relief groove is located internally within the cooperative polygonal socket.
7. A screw conveyor according to claim 6, wherein the relief groove is located at the lowermost position within the cooperative polygonal socket proximate the junction of two faces of the polygon.
B. A screw conveyor according to any preceding claim wherein the polygonal projection comprises an intermediate section.
9. A screw conveyor according to claim B wherein the intermediate section comprises a member having two polygonal projections joined coaxially.
10. A screw conveyor according to claim 9 wherein the first end of the shaft includes a corresponding cooperative polygonal socket for receiving one of the intermediate section's two polygonal projections.
11. A screw conveyor according to any of claims 9 or 10 wherein the intermediate section has a central circular cross-section section located between the two polygonal projections.
12. A screw conveyor according to any preceding claim wherein the polygonal projection comprises a bearing section or drive section.
13. A screw conveyor according to claim 12 wherein the bearing section or drive section may include a circular cross-section shaft portion joined coaxially to a polygonal cross section projection.
14. A screw conveyor according to claim 13 wherein the bearing section or drive section is seated within polygonal projection located within the corresponding and cooperative polygonal socket and the circular cross-section shaft portion is located within a suitable bearing allowing rotation of the shaft.
15. A screw conveyor according to claim 14 wherein the drive shaft is seated with the polygonal projection Thcated within the corresponding and cooperative polygonal socket and the circular cross-section shaft portion located within a suitable bearing allowing rotation of the shaft
16. A screw conveyor assemNy comprising at least two conjoined screw conveyors according to any preceding claim.
17. A for a screw conveyor screw conveyor comprising a shaft, a helical screw disposed at least around part of the shaft, wherein the shaft has a first end and a second end, the first end having a polygonal projection extending coaxially from the shaft, and the second end having a corresponding cooperative polygonal socket; and wherein a relief groove is provided within the socket for receiving debris.
18. A method of forming a screw conveyor assembly including the step of joining the respective shafts of two or more screw conveyors according to claims 1 to 15.
19. The method of claim 18 wherein the non-circular projection and non-circular socket have a cross-section chosen from the group comprising: hexagonal, octagonal, or some higher order polygon with an even number of sides.