Synchronized conical screw compressor or pump

Abstract

A conical screw compressor or pump comprising: an inner element configured to rotate around a first axis; and an outer element configured to rotate around a second axis; wherein an outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation; the first axis and the second axis are each stationary and the first axis is inclined relative to the second axis; and the inner element and the outer element are configured to be, in operation, synchronously rotated, thereby to reduce or eliminate force exerted by the inner element on the outer element or vice versa.

Claims

1. A conical screw compressor or pump comprising: an inner element configured to rotate around a first axis; and an outer element configured to rotate around a second axis; wherein an outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation; the first axis and the second axis are each stationary and the first axis is inclined relative to the second axis; and a) a gear arrangement configured to synchronise rotation of the inner element around the first, stationary axis and the rotation of the outer element around the second, stationary axis, thereby to reduce or eliminate force exerted by the inner element on the outer element or vice versa.

2. A conical screw compressor or pump according to claim 1, wherein the grooves and teeth comprise helical grooves and helical teeth.

3. A conical screw compressor or pump according to claim 1, wherein on rotation the grooves and teeth create lines of sealing which form at least one substantially closed chamber between consecutive sealing lines.

4. A conical screw compressor or pump according to claim 1, wherein the gear arrangement comprises a plurality of gears, wherein at least one of the plurality of gears is configured to be driven.

5. A conical screw compressor or pump according to claim 1, wherein the gear arrangement comprises a first gear and a second gear arranged to cooperate and arranged such that, in operation, driving the gear arrangement causes the first gear to rotate the inner element and causes the second gear to rotate the outer element.

6. A conical screw compressor or pump according to claim 5 wherein the first gear and the second gear have the same gear ratio as a ratio of a number of teeth of the inner element to a number of teeth of the outer element.

7. A conical screw compressor or pump according to claim 1, further comprising at least one driver that provides an external driving force to at least one of the inner element or outer element.

8. A conical screw compressor or pump according to claim 1 wherein: a) at least part of the outer surface of the inner element is formed from a material that is harder than a material from which at least part of the inner surface of the outer element is formed; or b) at least part of the inner surface of the outer element is formed from a material that is harder than a material from which at least part of the outer surface of the inner element is formed.

9. A conical screw compressor or pump according to claim 1 wherein at least part of the surface of at least one of the inner element and the outer element is formed from at least one of: a non-metallic material, a plastic material, a resiliently deformable material.

10. A conical screw compressor or pump according to claim 1 wherein substantially all of at least one of the inner element and the outer element is formed from at least one of: a non-metallic material, a plastic material, a resiliently deformable material.

11. A conical screw compressor or pump according to claim 1 wherein at least one of the inner element and the outer element comprises a main body and an outer layer, wherein the outer layer is formed of a softer material than the main body.

12. A conical screw compressor or pump according to claim 11, wherein the outer layer comprises at least one of a non-metallic material, a plastic material, a resiliently deformable material.

13. A conical screw compressor or pump according to claim 1, wherein each groove comprises a helical groove, and the pitch of each helical groove varies substantially continuously along the axis of the inner element or the axis of the outer element, the pitch angle of each helical groove being substantially constant along the axis of the inner element or the axis of the outer element.

14. A conical screw compressor or pump according to claim 1, wherein each groove comprises a helical groove, and each helical groove has a substantially constant pitch along the axis of the inner element or the axis of the outer element, the pitch angle of each helical groove varying substantially continuously along the axis of the inner element or the axis of the outer element.

15. A conical screw compressor or pump according to claim 1, wherein the inner element and the outer element are configured to, in operation, roll relative to each other in accordance with a pitch cone of the inner element and a pitch cone of the outer element.

16. A conical screw compressor or pump according to claim 1, wherein the first axis intersects the second axis.

17. A conical screw compressor or pump according to claim 1, wherein the first axis is inclined to the second axis at an angle between 0.01 and 45.

18. A conical screw compressor or pump according to claim 1, wherein the outer element has a number of grooves that is one greater than a number of grooves of the inner element.

19. A conical screw compressor or pump according to claim 1, wherein the outer element has at least one groove, and each groove has a wrap angle that exceeds 360.

20. A conical screw compressor or pump according to claim 1 further comprising a housing in which the inner element and the outer element are positioned.

21. A conical screw compressor or pump according to claim 1, wherein the length of at least one of the inner element and the outer element is between 10 mm and 10 m.

22. A method of operating a conical screw compressor or pump, wherein the conical screw compressor or pump comprises: an inner element configured to rotate around a first axis; and an outer element configured to rotate around a second axis, wherein an outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation; the first axis and the second axis are each stationary and the first axis is inclined relative to the second axis; the conical screw compressor or pump further comprises a gear arrangement configured to synchronise rotation of the inner element around the first, stationary axis and the rotation of the outer element around the second, stationary axis; and the method comprises: synchronously rotating the inner element and the outer element using the gear arrangement.

23. A conical screw compressor or pump comprising: an inner element configured to rotate around a first axis; and an outer element configured to rotate around a second axis; wherein an outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation; the first axis and the second axis are each stationary and the first axis is inclined relative to the second axis; and a first motor connected to the inner element and configured to rotate the inner element; a second motor connected to the outer element and configured to rotate the outer element; and a controller, wherein the controller controls a speed of rotation of the first motor and a speed of rotation of the second motor to synchronise rotation of the inner element around the first, stationary axis and the outer element around the second, stationary axis.

24. A conical screw compressor or pump according to claim 23 wherein the inner element and outer element are configured to be synchronously driven by the first motor and second motor respectively.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

(1) Embodiments of the invention are now described, by way of non-limiting example, and are illustrated in the following figures, in which:

(2) FIG. 1 is a schematic longitudinal sectional view of a compressor according to an embodiment;

(3) FIG. 2 is a schematic front view of the compressor of FIG. 1;

(4) FIGS. 3 and 3A are schematic longitudinal sectional views of a compressor according to further embodiments;

(5) FIG. 4 is a cross-section of the screw elements of an embodiment;

(6) FIG. 5 is a cross-section of the screw elements of another embodiment;

(7) FIG. 6a is a schematic longitudinal section view of a compressor according to a further embodiment;

(8) FIGS. 6b and 6c are enlarged views of the top and bottom end of FIG. 6a respectively;

(9) FIG. 7 is a schematic longitudinal section view of a compressor according to another embodiment;

(10) FIGS. 8a and 8b are schematic views of a cover of the compressor of FIG. 7.

(11) In a first embodiment, illustrated in FIG. 1, a conical screw compressor 20 comprises an inner element 1 and an outer element 2. The outer surface 4 of the inner element 1 is substantially in the shape of a truncated first cone. The outer surface 4 of the inner element 1 comprises a plurality of helical teeth.

(12) The inner surface 3 of the outer element 2 is substantially in the shape of a truncated second cone. The inner surface 3 of the outer element 2 comprises a plurality of helical teeth, one more than the number of helical teeth of the inner element 1. Each helical tooth on the inner element 1 and on the outer element 2 follows a helix of constant pitch (decreasing pitch angle from the wide end to the narrow end of the cone).

(13) The shape of the inner element 1 and outer element 2 may be determined, for example as part of a design or manufacturing process, using a method disclosed in PCT Application PCT/GB2013/051497, which is hereby incorporated by reference.

(14) The inner element 1 and the outer element 2 are arranged inside a housing 6 of the compressor 20. Both the inner element 1 and the outer element 2 can revolve inside the housing 6.

(15) The inner element 1 is coupled to a first gear 8 (which may be called a pinion) which has external teeth. The outer element 2 is coupled to a second gear 9 which has internal teeth. The internal teeth of the second gear 9 mesh with the external teeth of the first gear 8. The gear ratio of the first gear 8 to the second gear 9 equals the ratio of the number of teeth of the inner element 1 to the number of teeth of the outer element 2.

(16) FIG. 2 shows an end view (cross-sectional view) of first gear 8 inside second gear 9.

(17) The first gear 8 is coupled with the shaft of an electric motor 14 (the electric motor 14 is not shown in FIG. 1). The shaft of the electric motor 14 lies along the axis of the inner element 1, which is the same axis as the axis of the first gear 8.

(18) The shaft of the electric motor 14 drives the inner element 1. The shaft of the electric motor 14 drives the first gear 8 which is coupled with the inner element 1. The first gear 8 in turn drives the second gear 9 which is coupled with the outer element 2. When the gears 8, 9 start revolving around their axes, they start rotating the inner element 1 and outer element 2 of the compressor 20.

(19) The inner element 1 rotates around its longitudinal axis, which may be referred to a first axis 10a, and the outer element 2 rotates around its longitudinal axis, which may be referred to as a second axis 10b. The first axis and second axis are inclined to each other (not parallel), with an angle between the axes. In the embodiment of FIG. 1, the first axis intersects the second axis, with an angle between the axes of 1.

(20) On rotation of the elements, the helical teeth of the inner element 1 mate with the helical teeth of the outer element 2, forming lines of contact between the inner element 1 and outer element 2. The lines of contact form substantially closed helical chambers 5 between the inner element 1 and the outer element 2.

(21) On revolution, a compressible fluid (for example, a gaseous fluid) is sucked through the inlet port 11 into a chamber 5 between the inner element 1 and the outer element 2. In the present embodiment, the inlet port 11 is placed adjacent to the end of the outer element 2 at the large end of the cone. In alternative embodiments, the inlet port 11 may be placed at any position near the large end of the cone, for example at any position that facilitates ease of use.

(22) Since the inner element 1 and the outer element 2 each have a conical shape and the grooves are helical, as the inner element 1 and the outer element 2 revolve, the chamber 5 moves along the longitudinal axis of the compressor 20, and decreases in volume. The decrease in volume of the chamber 5 results in compression of the compressible fluid. The compressible fluid increases in pressure.

(23) When the chamber 5 reaches the narrow end of the compressor 20, the compressed fluid is discharged through the outlet port 12. A high pressure seal is used at the outlet 12. In the present embodiment, the high-pressure seal is a metal face seal. In other embodiments, any suitable high-pressure seal may be used. It may be necessary for the high-pressure seal to be able to deal with high speed revolution on one side (for example, 1500 rpm) and high pressure.

(24) During operation of the conical screw compressor 20 of FIG. 1, each of the axis of rotation of the inner element 1 and the axis of rotation of the outer element 2 remains in a fixed, stationary position as the elements rotate around their respective axes. Neither of the elements 1, 2 performs eccentric motion.

(25) The inner element and the outer element are each driven by the motor rather than by the other element. Therefore, force exerted by the inner element on the outer element or vice versa is reduced or eliminated.

(26) Accurate positioning of the axes is achieved through accurate design and manufacturing of the housing 6 of the compressor 20. The shafts are positioned in part of the housing 6 which comprises covers that sit on both sides of the cone.

(27) In the embodiment of FIG. 1, the length of the compressor 20 is 189 mm and the perpendicular dimensions of the compressor are 95 mm by 95 mm. The tolerance on the elements is 10 micrometres.

(28) In the embodiment of FIG. 1, the outer element 2 is made of alloy steel and the inner element 1 is made of brass. In the embodiment of FIG. 1, brass is used for one element and alloy steel for the other because brass is softer than alloy steel. If any manufacturing inaccuracies are present, the brass may deform or wear in preference to the alloy steel, resulting in an improved fit between the inner element 1 and the outer element 2.

(29) In the embodiment of FIG. 1, oil is used to lubricate the motion of the elements 1, 2 and to reduce the temperature in the compressor in operation. The good fit between the inner element 1 and outer element 2 may allow less oil to be used than may be required in a compressor of an alternative design, for example one in which one element drives the other.

(30) An alternative embodiment of a conical screw compressor is illustrated in FIG. 3. The embodiment of FIG. 3 offers an alternative implementation of the synchronisation of the conical screw elements 1, 2 to the embodiment of FIG. 1. In the embodiment of FIG. 3, only gears with external teeth are used in the synchronisation of the conical screw elements 1, 2.

(31) The inner element 1 and outer element 2 of the embodiment of FIG. 3 are arranged and operated in a similar way to the inner element 1 and outer element 2 of the embodiment of FIG. 1.

(32) In the embodiment FIG. 1, the motor 14 shares a common axis with the inner element 1, and is connected to inner element 1 by a shaft. By contrast, in the embodiment of FIG. 3, neither element is connected directly to the motor 14 by a shaft. Both elements are synchronized and driven simultaneously by the motion of gears 13, 16 and 17. In the embodiment of FIG. 3, the gears have external teeth meshing with each other and driven by a motor shaft 18. Gear 16 is driven by shaft 18 and drives outer element 2. Gear 17 is driven by motor shaft 18 and drives gear 13, which drives inner element 1.

(33) In alternative embodiments, any suitable gear mechanism may be used to drive the inner element 1 and the outer element 2 synchronously.

(34) In the embodiment of FIG. 3, the inner element 1 and the outer element 2 are synchronised in such a way that the rotational speed ratio of the inner element 1 and the outer element 2 equals the ratio of teeth of the screw surfaces of those elements. In the embodiment of FIG. 3, inner element 1 and the outer element 2 are installed with the bearings 15 inside the compressor housing 6.

(35) In the embodiment of FIG. 3, motor 14 is an alternating current motor. In alternative embodiments, motor 14 is a direct current motor, a hydraulic motor, an internal combustion engine, or any suitable means of driving the rotation of the inner element 1 and outer element 2. In other embodiments, a driving means that does not comprise a motor may be used to drive the rotation of the inner element 1 and outer element 2.

(36) In some embodiments, as shown in FIG. 3A, a first motor 14a is used to rotate the inner element 1 and a second motor 14b is used to rotate the outer element 2. The first motor may be connected directly to the inner element 1, for example by a shaft, or connected indirectly to the inner element 1, for example using gears. The second motor may be connected directly to the outer element 2, for example by a shaft, or connected indirectly to the outer element 2, for example using gears. The first motor and second motor may be controlled by a controller 33 such that the rotation of the inner element 1 is synchronised with the rotation of the outer element 2.

(37) Although particular arrangements of helical grooves are illustrated in FIG. 1 and FIG. 3, in alternative embodiments, any appropriate number or arrangement of grooves may be used. FIG. 4 shows a cross section of an inner element 1 having three helical grooves and an outer element 2 having four helical grooves. FIG. 4 also shows chambers 5 between the inner element 1 and outer element 2. FIG. 5 shows an alternative design of an inner element 1 and outer element 2. In different embodiments, different numbers of helical grooves may be used.

(38) In the embodiment of FIG. 1, the helical grooves have constant pitch (variable pitch angle). In other embodiments, the helical grooves have varying pitch, for example continuously varying pitch. In some embodiments the helical grooves have a varying pitch such that the pitch angle remains constant along the length of the inner or the outer element 1, 2.

(39) In the above embodiments, each helical groove extends along the entire length of the inner or outer element 1, 2. In alternative embodiments, each helical groove may extend along at least part of the length of the inner or outer element 1, 2.

(40) The compressor 20 of FIG. 1 was produced as a prototype of 189 mm in length. In alternative embodiments, the compressor 20 may be produced to a wide range of dimensions. For example, the length of the compressor may be in a range from 10 mm to 5 m. Smaller compressors 20, for example from 10 mm to 100 mm may be used for certain applications, for example for use in air conditioners. Larger compressors, for example from 0.5 to 2 m or greater, may be used, for example, in oil and gas applications.

(41) The elimination or reduction of force exerted by the inner element 1 on the outer element 2 (or vice versa) by driving the elements synchronously may have a particular impact in the case of a large compressor.

(42) A small compressor may not have large torque compared to the properties of the materials used to fabricate the compressor. However, in a large compressor (for example, a 1 metre long compressor) the elements have a large mass. Therefore there is a large torque. The area of contact between the inner element 1 and outer element 2 is only a line so there is a small contact area. If one element drives the other, the resulting hysteresis and wear may be large. If one element drives the other, a larger compressor may experience greater wear than would be experienced by a small compressor. Therefore, synchronisation of the elements may lead to a greater reduction in wear for a large compressor than would be seen in a small compressor.

(43) In further embodiments, an outer layer, for example a coating layer, is applied to at least part of the outer surface 4 of the inner element 1 and/or to at least part of the inner surface 3 of the outer element 2. Such a coating may reduce friction forces and/or increase corrosion resistance. In one embodiment, the coating material is Teflon. In other embodiments, the coating material is any friction-reducing material. In further embodiments, the coating material is any corrosion-resistant material. In some embodiments, one or both elements comprises a main body 37 with an outer layer 39 covering part or all of the surface of the main body. In some embodiments, the main body is a solid material, for example a metal, and the outer layer is a softer material, for example a plastic.

(44) In the embodiment of FIG. 1, one element is formed from alloy steel and the other element from brass. In an alternative embodiment, each of inner element 1 and outer element 2 is fabricated from an industrial plastic, Polyamide-6 (which is sold by BASF under the trade name Ultramid). Elements made from plastic material, such as Polyamide-6, may be suitable for use with corrosive gases. Plastic may deform and restore its shape as it comes in and out of contact, which may achieve a tighter contact between the elements when the elements are made of plastic than if the elements were made of a harder material, for example a metallic material.

(45) In the embodiment of FIG. 1, oil is used for lubrication. In other embodiments, oil may also be used for cooling. In embodiments in which the surface of one or more of the elements is made of a softer material, for example a plastic material, the use of oil for lubrication may be reduced or eliminated.

(46) Synchronously driving the inner element 1 and outer element 2 using the motor 14 may reduce wear on the element, and allow for more accurate tolerances and a better fit between the elements. If the fit between the elements is improved, less oil may be required to be used.

(47) In some embodiments, positioning the axes of the elements accurately reduces wear on the elements. In some embodiments, positioning the axes accurately may allow the clearance between the elements to be precisely set. In one such embodiment, the compressor 20 is designed to compress a gaseous fluid which comprises small solid particles, for example dust or sand. The clearance between the elements may be precisely set to take into account the size of the particles. Precisely setting the clearance may increase the lifetime of the compressor.

(48) A conical screw compressor of a further embodiment is illustrated in FIGS. 6a, 6b and 6c (where FIGS. 6b and 6c are detailed views of parts of FIG. 6a).

(49) The conical screw compressor 20 of FIG. 6a comprises an inner element 1 and an outer element 2 having helical teeth and grooves similar to those described with reference to FIG. 1. The inner element 1 is a solid element (although it is represented as unshaded in FIGS. 6a to 6c).

(50) The inner element 1 is coupled to a shaft 21 which is driven by a motor 14 (not shown in FIG. 6a). In operation, the motor 14 (via shaft 21) drives the inner element 1 to rotate around its longitudinal axis (first axis 22). The rotation of inner element 1 drives a rotation of the outer element 2 around the outer element's own longitudinal axis (second axis 23), which is inclined relative to the longitudinal axis 22 of inner element 2.

(51) The inner element 1 is substantially fixed in a longitudinal position along its axis of rotation 22. The outer element 2 is substantially fixed in a longitudinal position along its axis of rotation 23. The axes 22, 23 are also in fixed positions. A relative longitudinal positioning of the outer element 2 and the inner element 1 is substantially maintained because the inner element 1 and outer element 2 are held in a relative fixed position so that the inner surface 3 of the outer element 2 and outer surface 4 of element 1 form a tight fit and gas is maintained in the closed chambers 5 between the inner element 1 and outer element 2.

(52) Inner element 1 and outer element 2 are relatively longitudinally positioned by a bearing, for example an axial bearing, 28. The bearing 28 is in contact with a substantially end-facing surface 34 of the inner element 1.

(53) In the embodiment of FIG. 6a, the top end of the housing 6 comprises a recess 35 having an inner surface 36 aligned with the top of inner element 1. An end-facing surface 34 of inner element 1 faces the inner surface 36 of the outer element 2. The axial bearing 28 is disposed between the recess inner surface 36 of the housing 6 and the end-facing surface of the inner element 1.

(54) In some embodiments, the top end of inner element 1 is stepped, and an end-facing step surface 34 faces the inner surface 36 of the housing 6.

(55) In some embodiments, the top end of outer element 2 comprises a recess having an inner surface aligned with the top of inner element 1. The axial bearing 28 is disposed between the recess inner surface of the outer element 2 and an end-facing surface of the inner element 1, for example an end-facing step surface of the inner element 1.

(56) Although in the present embodiment the axial bearing 28 is in contact with end-facing step surface 34, in other embodiments, the axial bearing 28 may be in contact with any substantially end-facing surface of the inner element 1 and any suitably facing surface of the outer element 2.

(57) In further embodiments, the axial bearing may be in contact with any substantially end-facing surface of the inner element 1 and any suitably facing surface of the housing 6.

(58) The inner element 1 is fixed in the housing 6 by a bearing, for example a radial bearing, 26 between the shaft 21 and the housing 6. In the embodiment of FIG. 6, the shaft 21 comprises a step having a surface 27 facing part of the housing 6 which covers the bottom end of the compressor. This cover part of housing 6 has a corresponding notch 29 such that, longitudinally, the radial bearing 26 is disposed between the step surface 27 and the notch 29.

(59) The inner element 1 is fixed in the housing 6 by bearing 26 in such a manner that the motion of the inner element 1 is limited to rotation around its longitudinal axis 22. The arrangement of the bearing 26 between the inner element 1 and the housing 6 may ensure that the inner element 1 cannot move along its axis 22 relative to the outer element 2, and therefore may limit the possibility of gas leakage through gaps between inner element 1 and outer element 2.

(60) The outer element 2 comprises a corresponding flange 40 which extends substantially perpendicularly to the outer element's longitudinal axis 23. The flange 40 faces the housing inner surface 38.

(61) Bearing 24 is disposed between the outer element 2 and the housing 6 in the radial direction.

(62) Bearing 24 is disposed between the housing inner surface 38 and a surface of flange 40 in the longitudinal direction, thereby fixing the longitudinal position of the outer element 2 relative to the housing 6. Bearing 24 is a radial bearing which limits the relative movement of outer element 2 and housing 6 to a rotation of the outer element 2 around its longitudinal axis 23.

(63) In other elements, bearing 24 may be longitudinally disposed between any inner surface of the housing and any suitable surface of outer element 2.

(64) A high-pressure seal 60 is disposed between the end of the outer element 2 and the housing 6.

(65) A further bearing, for example a further radial bearing, 25 is placed between the outer element 2 and the housing 6 proximate to the bottom end of the outer element 2. The longitudinal position of bearing 25 is determined by a lip in the housing 6 having a surface perpendicular to the longitudinal axis 23 and a corresponding, facing, lip in the outer element 2.

(66) The outer element 2 is fixed in the static housing 6 by the two bearings 24, 25 in such a manner that the motion of the outer element 2 is limited to rotation around its longitudinal axis 23.

(67) The arrangement of the bearings 24, 25 between the outer element 2 and the housing 6 may ensure that the outer element 2 cannot move along its axis relative to the inner element 1 and may in limit the possibility of gas leakage through gaps between the inner element 1 and outer element 2.

(68) In other embodiments, the outer element 2 may be fixed in the housing 6 by any configuration of two or more bearings, which may be placed at any appropriate positions along the length of the outer element 2.

(69) The inner element 1 and outer element 2 each rotate around a respective fixed axis. Since the inner element 1 is fixed in the housing 6 by bearing 26, the inner element 1 may make no other motion than revolving around its axis 22. Therefore, a large proportion of the energy in the system may be used to compress gas. By avoiding other forms of motion such as an eccentric oscillatory motion of the inner element 1, the system may be made more efficient and energy wastage may be reduced.

(70) Fixing the inner element 1 inside the outer element 2 with axial bearing 28 may allow the relative position of the inner element 1 and the outer element 2 to be set accurately. As a result, tolerances may be reduced. By setting the relative position of the inner element 1 and outer element 2 accurately, the use of unnecessary force may be avoided and it may be possible to avoid unnecessary friction between the surfaces of the inner element 1 and the outer element 2.

(71) The inner element 1 is held by bearings on two sides, and the outer element 2 is held by bearings on two sides. Due to the elements being held by the bearings, the position of the inner element 1 and the position of the outer element 2 can be accurately set up relative to each other and relative to the housing. Such a configuration may be particularly effective when the inner element 1 and outer element 2 are manufactured from hard materials such as steel.

(72) A further embodiment is illustrated in FIG. 7.

(73) The embodiment of FIG. 7 comprises an inner element 1, outer element 2, and housing 6 similar to those of FIG. 6. The outer element 2 is fixed by two bearings 24, 25.

(74) The inner element is fixed by one bearing 26 on the bottom end. The top end of the inner element 1 is fixed by the surface of the outer element 2, in the lines of contact between the inner element 1 and the outer element 2.

(75) The inner element 1 in its position may push the surface of the outer element 2 along the lines of contact, and may thereby create better sealing between the elements, separate the closed chambers 5, and prevent the compressible fluid in the chambers from escaping. A configuration such as that in FIG. 7, in which the inner element 1 is held by one bearing 26, may be particularly effective when at least one of the inner element 1 and outer element 1 is made from a soft material such as a polymer.

(76) The compressor 20 further comprises a high-pressure seal 60 disposed between the end of the outer element 2 and the housing 6, and a connector for a pipe or other conduit at the discharge end of the compressor (not shown) for removing compressed fluid.

(77) In the embodiment of FIG. 7, the housing 6 comprises a cover 32 which covers the bottom end of the compressor. Cover 32 is illustrated in FIGS. 8a and 8b.

(78) Cover 32 is configured so as to hold the relatively inclined axes 22, 23 of the two elements in a fixed manner. The cover has two axes: a) a main axis which sits on the same longitudinal position as the second axis 23 of the outer element 2 and b) a place for mounting the bearing 26 for the inner element 1 having an offset resulting in the first axis 22 (the axis of the inner element 1) being inclined relative to the second axis. In FIGS. 8a and 8b, the offset resulting in the relative inclination is exaggerated for clarity.

(79) In a further embodiment, the housing 6 comprises a housing cover which covers the bottom end of the compressor. Attached to the housing cover is a bearing cover.

(80) The bearing cover comprises a plate covering the bottom end of radial bearing 26 and a cylindrical section surrounding radial bearing 26. Radial bearing 26 is located between the shaft 21 and an inner surface of the cylindrical section of the bearing cover.

(81) The housing cover and bearing cover are designed so as to hold the shaft 21 of the inner element 1 at an appropriate angle of inclination relative to the axis of the outer element 2. The housing cover and bearing cover may form a detachable unit.

(82) A compressible fluid is injected into the compressor through a nozzle.

(83) The bottom end of outer element 2 is covered by an outer element cover. The outer element cover is a broadly annular structure having a longitudinal extent such that bearing 25 may be placed radially between a radially outer surface of the outer element cover and a radially inner surface of the housing cover.

(84) At the top end of the compressor, the outer element 2 extends to form a tubular region which extends beyond the end of the inner element 1. To the flange 40 is affixed an endpiece. Radial bearing 24 is placed between the endpiece and a part of the housing 6.

(85) In the embodiments of FIGS. 6 and 7, each of the bearings comprises a ball bearing or plurality of ball bearings. In other embodiments, any suitable type of bearing may be used.

(86) In some embodiments, the compressor comprises means for adjusting the relative longitudinal position of the inner element 1 and outer element 2.

(87) By adjusting the relative longitudinal position of the inner element 1 and outer element 2, the fit between the inner surface 3 of the outer element 2 and the outer surface 4 of the inner element 1 may be made tighter or less tight. A clearance between the elements may be adjusted by adjusting the relative longitudinal position of the elements. It has been found that adjusting the relative longitudinal position of the elements may result in a significant change in the pressure achieved in the compressor 20 therefore a significant change in the heat generated by the compressor 20 in operation.

(88) In some embodiments, the relative longitudinal position of the inner element 1 and outer element 2 is adjusted by adjusting the longitudinal position of bearings 24, 25, 26 and 28.

(89) By adjusting the relative longitudinal position of the elements to achieve a tight fit, the chambers may be well sealed and a high pressure achieved. However, as the fit becomes tighter, the torque may increase due to mechanical losses. The temperature of the system increases due to pressure.

(90) Therefore, it is important to control precisely the relative longitudinal position of the outer element 2 and inner element 1 for a particular application, to balance the pressure that may be achieved and the heat that is generated.

(91) In further embodiments, the compressor may comprise any means for substantially fixing a longitudinal position of the inner element 1 along its axis of rotation 22 and for substantially fixing a longitudinal position of the outer element 3 along its axis of rotation 23, so as to substantially maintain a relative longitudinal positioning of the inner element and the outer element during rotation.

(92) In some embodiments, the means for substantially fixing a longitudinal position of the inner element 1 and of the outer element 2 comprises a gearing arrangement comprising at least one gear.

(93) For example, in one embodiment the inner element 1 is driven by a first gear 8. The first gear 8 is coupled to the shaft of a driving motor 14. The first gear 8 in turn drives a second gear 9 which is coupled with the outer element 9. The outer element 2 is fixed in a housing 6 by two bearings 24, 25, one at each end of the outer element 2. The compressor may further comprise an axial bearing 28 between the outer element 2 and inner element 1. Therefore, in this embodiment, the relative longitudinal position of the inner element 1 and outer element 2 is substantially maintained by a combination of gears and bearings.

(94) The first gear 8 and second gear 9 may be as described above with reference to FIG. 1. In another embodiment, the inner element 1 and outer element 2 may be driven by an arrangement of gears 13, 16, 17 as described above with reference to FIG. 3. In further embodiments, any suitable gear arrangement may be used.

(95) Elements of the different embodiments described herein may be combined in any appropriate manner. For example, an embodiment of a compressor may comprise one or more gears, for example as shown in FIG. 1 or 3, while also comprising one or more bearings, for example axial bearing 28 as shown in FIG. 6a or 7a. The housing 6 and covers 30, 31, 32 described with reference to FIG. 7a may be applied to the embodiment of FIG. 1 or FIG. 3.

(96) It will be understood that the conical screw compressor of the described embodiments can be operated as a pump.

(97) The conical screw compressor or pump of the above embodiments may be used for a variety of applications across many industries, for example in oil and gas offshore platforms, offshore carbon capture and storage, mining, submarines, ships and spacecraft.

(98) It will be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention.

(99) Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.