Abstract: A twin-shaft pump comprising: a pumping chamber; two rotatable shafts each mounted on bearings is disclosed. Each of the two rotatable shafts comprises at least one rotor element, the rotor elements being within the pumping chamber and the two rotatable shafts extending beyond the pumping chamber to a support member. The support member comprises mounting means for mounting the bearings at a predetermined distance from each other, the predetermined distance defining a distance between the two shafts. A thermal break between the pumping chamber and the support member is provided for impeding thermal conductivity between the pumping chamber and the support member, such that the pumping chamber and support member can be maintained at different temperatures. The support member and the rotor elements are formed of different materials, a coefficient of thermal expansion of a material forming the support member being higher than a coefficient of thermal expansion of a material forming the rotor elements.

Abstract: A vacuum system non-return valve has a baffle for extending across a flow path The baffle has an aperture, a perimeter of the aperture having a valve seat. The valve also has a valve member having a protrusion extending from a surface configured to mate with the valve seat, the protrusion extending through the aperture; wherein the protrusion includes a retaining portion extending outwardly from the protrusion and configured such that the retaining portion cannot pass through the aperture. The valve member and aperture are configured such that the valve member obscures the aperture and seals with the valve seat to impede a flow of fluid from an outlet end to an inlet end in a closed position and is displaceable in use to move away from the valve seat and allow a fluid flow from the inlet end to the outlet end in an open position.

Abstract: A rotor for a multi-stage vacuum pump, a multi-stage vacuum pump and a method. The rotor comprises: a plurality of rotary vanes, the plurality of rotary vanes being axially displaced and coaxially aligned; a pair of end shafts, each end shaft extending from opposing axial ends of the plurality of rotary vanes; and an inter-vane shaft extending between adjacent rotary vanes of the plurality of rotary vanes, the inter-vane shaft having a diameter which is greater than that of the end shafts. In this way, the inter-vane shaft provided between each rotary vane may have an increased diameter, which improves the stiffness of the shaft and changes the modal frequency of the rotor. Such a change in the modal frequency is typically sufficient to improve its operation.

Abstract: A pump cooling system may include a cooling body configured to be fitted to a pump housing to receive heat from the pump housing via a heat conducting path between the cooling body and pump housing. The cooling body may have a passage through which, in use, a cooling fluid is passed to conduct heat away from the cooling body. The pump cooling system includes a cooling control mechanism configured to provide a gap in the heat conducting path at pump operating temperatures below a predefined temperature so heat conduction from the pump housing to the cooling body is interrupted.

Abstract: A pump cooling system may include a cooling body configured to be fitted to a pump housing to receive heat from the pump housing via a heat conducting path between the cooling body and pump housing. The cooling body may have a passage through which, in use, a cooling fluid is passed to conduct heat away from the cooling body. The pump cooling system includes a cooling control mechanism configured to provide a gap in the heat conducting path at pump operating temperatures below a predefined temperature so heat conduction from the pump housing to the cooling body is interrupted.

Abstract: A twin-shaft pump comprising: a pumping chamber; two rotatable shafts each mounted on bearings is disclosed. Each of the two rotatable shafts comprises at least one rotor element, the rotor elements being within the pumping chamber and the two rotatable shafts extending beyond the pumping chamber to a support member. The support member comprises mounting means for mounting the bearings at a predetermined distance from each other, the predetermined distance defining a distance between the two shafts. A thermal break between the pumping chamber and the support member is provided for impeding thermal conductivity between the pumping chamber and the support member, such that the pumping chamber and support member can be maintained at different temperatures. The support member and the rotor elements are formed of different materials, a coefficient of thermal expansion of a material forming the support member being higher than a coefficient of thermal expansion of a material forming the rotor elements.

Abstract: A rotor for a multi-stage vacuum pump, a multi-stage vacuum pump and a method. The rotor comprises: a plurality of rotary vanes, the plurality of rotary vanes being axially displaced and coaxially aligned; a pair of end shafts, each end shaft extending from opposing axial ends of the plurality of rotary vanes; and an inter-vane shaft extending between adjacent rotary vanes of the plurality of rotary vanes, the inter-vane shaft having a diameter which is greater than that of the end shafts. In this way, the inter-vane shaft provided between each rotary vane may have an increased diameter, which improves the stiffness of the shaft and changes the modal frequency of the rotor. Such a change in the modal frequency is typically sufficient to improve its operation.

Abstract: A multi-stage vacuum pump having an interstage coupling unit vacuum pump may include a first inter-stage coupling part defining a first portion of a void for receiving a common rotor shared by adjacent stages of the multi-stage vacuum pump; and a second inter-stage coupling part separable from the first inter-stage coupling part, the second inter-stage coupling part defining a second portion of the void for receiving the common rotor shared by adjacent stages of the multi-stage vacuum pump. In this way, a coupling is provided which enables an assembled rotor and assembled stages of the vacuum pump to be fixed together, since the assembled rotor can be received within the separable parts of the coupling which, in turn, can be fitted to the assembled adjacent stages. This enables the mechanical integrity of the rotor and adjacent stages to be preserved while still facilitating assembly of the multi-stage vacuum pump.

Abstract: A screw pump includes a stator having a fluid inlet and a fluid outlet, the stator housing first and second externally threaded, tapered rotors mounted on respective shafts and adapted for counter-rotation within the stator to compress fluid passing from the fluid inlet to the fluid outlet, wherein the threads have a pitch that increases towards the fluid outlet.

Abstract: A rotor for a screw vacuum pump has a threaded body in which a central cavity is formed. A coolant is supplied to the cavity from a supply line provided in a shaft attached to the body. A coolant flow guide, which may be either separate from or at least partially integral with the shaft, is located within the cavity. The flow guide has an outer surface adjacent, preferably in contact with, the body to enable heat to the transferred from the rotor to the guide. The guide also has an inner surface defining a bore, and defines at least in part a plurality of axially extending slots radially spaced from and in fluid communication with the bore. In use, coolant flows into the cavity through the bore of the guide, and out from the cavity through the axially extending slots, extracting heat from the guide as it flows both into and out form the cavity. The discharged coolant is conveyed form the slots into a discharge line located within the shaft.

Abstract: A screw pump (10) comprises a stator (12) having a fluid inlet (18) and a fluid outlet (20), the stator housing first and second externally threaded, tapered rotors (26, 28) mounted on respective shafts and adapted for counter-rotation within the stator (12) to compress fluid passing from the fluid inlet to the fluid outlet, wherein the threads (30, 32) have a pitch that increases towards the fluid outlet (20).

Abstract: A method for controlling the temperature of a rotor of a vacuum pump comprising said rotor and a stator comprises the steps of flowing a rotor cooling fluid through a rotor cooling circuit to cool the rotor, flowing a stator cooling fluid through a stator cooling circuit to cool the stator, conveying the stator cooling fluid from the stator cooling circuit to a heat exchanger of the rotor cooling circuit to cool the rotor cooling fluid, returning the stator cooling fluid from the heat exchanger of the rotor cooling circuit to the stator cooling circuit, supplying a further coolant to a heat exchanger of the stator cooling circuit to cool the stator cooling fluid, and controlling the supply of further coolant to the heat exchanger of the stator cooling circuit to control the temperature of the stator cooling fluid.

Abstract: A scroll compressor which comprises a scroll assembly comprising two scroll walls, and a drive for causing a relative orbiting motion between the scroll walls for compressing fluid on two fluid flow paths between an inlet and an exhaust of the scroll assembly. A first fluid flow path is formed between a wall surfaces of the scroll walls and a second fluid flow path is formed between another facing wall surfaces of the scroll walls. A first ambient clearance A1 is selected between the first two facing surfaces, and a second ambient clearance A2 is selected between the second two facing surfaces, and where the first and the second ambient clearances are selected independently from each other. Independent selection permits each ambient clearance to be designed according to its own performance requirements, to take into account thermal expansion and manufacturing tolerances.

Abstract: A scroll compressor which comprises a scroll assembly comprising two scroll walls, and a drive for causing a relative orbiting motion between the scroll walls for compressing fluid on two fluid flow paths between an inlet and an exhaust of the scroll assembly. A first fluid flow path is formed between a wall surfaces of the scroll walls and a second fluid flow path is formed between another facing wall surfaces of the scroll walls. A first ambient clearance A1 is selected between the first two facing surfaces, and a second ambient clearance A2 is selected between the second two facing surfaces, and where the first and the second ambient clearances are selected independently from each other. Independent selection permits each ambient clearance to be designed according to its own performance requirements, to take into account thermal expansion and manufacturing tolerances.

Abstract: A vacuum pump having a screw mechanism and comprising two externally threaded rotors mounted on respective shafts in a pump body and adapted for counter-rotation therein with intermeshing of the rotor threads with close tolerances between the threads and internal surfaces of the pump body in order that gas may be pumped from a pump inlet to a pump outlet by action of the rotor threads, the root diameter of each rotor increases and the thread diameter of each rotor decreases in a direction from the pump inlet to the pump outlet, and wherein the pitch of the rotor threads decreases in a direction from the pump inlet to the pump outlet.

Abstract: A screw pump has two parallel shafts mounted in a pump body, each shaft thereon and each rotor has at least one helical vane or thread. When the helical vanes or threads inter mesh causing a fluid to be pumped from an inlet towards an outlet of the pump. The bearings associated with each shaft are being positioned in cavities within the first and second rotors which are sealed at their ends closest to the pump inlet. A thermal shield is provided between the bearing arrangements and the internal cavity surfaces.

Abstract: A vacuum pump includes a pump body in which is mounted two externally threaded rotors. The thread profile of each rotor is tapered in a substantially radial direction to facilitate the machining and fitting of the rotors with the required close tolerances.

Abstract: A vacuum pump having a screw mechanism and comprising two externally threaded rotors mounted on respective shafts in a pump body and adapted for counter-rotation therein with intermeshing of the rotor threads with close tolerances between the threads and internal surfaces of the pump body in order that gas may be pumped from a pump inlet to a pump outlet by action of the rotor threads, the root diameter of each rotor increases and the thread diameter of each rotor decreases in a direction from the pump inlet to the pump outlet, and wherein the pitch of the rotor threads decreases in a direction from the pump inlet to the pump outlet.

Abstract: A screw pump provided with a first shaft and spaced therefrom and parallel thereto a second shaft mounted in a pump body. A first rotor is mounted on the first shaft and a second rotor mounted on the second shaft. Each of the first and second rotors having formed on an outer surface thereof one or more one helical vanes or threads intermeshing together so that rotary movement of the shafts will cause a fluid to be pumped. A first bearing arrangement is associated with the first shaft and a second bearing arrangement is associated with the second shaft. A bearing carrier is provided for each bearing arrangement and mounted within the pump body so as to be independent from each other.

Abstract: A vacuum pump incorporating a screw mechanism section and comprising two externally threaded rotors mounted on respective shafts in a pump body. The externally threaded rotors are adapted for counter-rotation in a first chamber within the pump body with intermeshing of the rotor threads in order to pump gas from a pump inlet by action of the rotors. The root diameter of each rotor increases and the thread diameter of each rotor decreases in a direction from pump inlet and in which the gas is pumped. The two externally threaded rotors are positioned in the pump body by means of shaft bearings located inside cavities in the rotors. The cavities are sealed at the ends closest to the pump inlet.