Patent Description:
Scroll pumps are a known type of pump used in various different industries (e.g. in semi-conductor fabrication). Scroll pumps operate by using the relative motion of two intermeshed "scrolls" to pump fluid.

In scroll pumps, it tends to be desirable to maintain a seal at points of contact between the two scrolls to prevent undesired fluid leakage into certain areas of the scroll pump. It also tends to be desirable to improve the durability of the components of the scroll pump.

<CIT> relates to a scroll pump having a base seal disposed on the base surface of one or both scroll members, between adjacent turns of the corresponding scroll blade.

<CIT> relates to a scroll pump having thin steel plates between the end plate and the tip ends of two intermeshing scrolls. Each thin steel plate is provided with a conformable layer made from a material that is softer than the first and second tip ends to reduce the gap between the tip ends and the opposite scroll end plate. A leakage passage is provided in at least one of the thin steel plates to interconnect a central compression chamber formed by the spiral wraps and the outer circumferential chambers.

According to a first aspect of the invention, there is provided a scroll pump according to claim <NUM>.

The first and/or second pads may be formed from a polymer material.

The first and/or second scrolls may be formed from a metallic material.

The first and/or second pads may be formed from a polytetrafluoroethylene material.

The first and/or second scrolls may be formed from aluminium.

The scroll pump may further comprise a channel seal located between the first and second scrolls.

The second pad may be formed from the same material as the first pad.

The first and/or second pads may be formed from the same material as the channel seal.

The first and/or second pads may be integrally formed with the channel seal.

The first and second scrolls may each comprise a central aperture. The second pad may be adjacent to the central apertures.

The scroll pump may further comprise a drive shaft coupled to the second scroll and configured to cause the second scroll to orbit relative to the first scroll.

The drive shaft may extend through the central apertures.

The pad may comprise a plurality of lobes.

According to a second aspect of the invention, there is provided use of the scroll pump of the first aspect to pump fluid.

<FIG> is a schematic illustration (not to scale) showing a scroll pump <NUM> according to an embodiment.

The scroll pump <NUM> comprises a shell <NUM>, a fixed scroll <NUM>, an orbiting scroll <NUM>, a drive shaft <NUM>, an actuator <NUM>, a plurality of bearings <NUM>, a biasing apparatus <NUM>, and a pad <NUM>.

In this embodiment, the shell <NUM> and the fixed scroll <NUM> together form an overall housing of the scroll pump <NUM> within which the rest of the components of the scroll pump <NUM> are located. However, it will be appreciated that, in other embodiments, the fixed scroll <NUM> may not form part of the overall housing of the scroll pump <NUM> and instead may be located entirely within the overall housing.

The orbiting scroll <NUM> is located within the overall housing of the scroll pump <NUM> and intermeshed with the fixed scroll <NUM>. The orbiting scroll <NUM> is configured to orbit relative to the fixed scroll <NUM> to pump fluid from an inlet (not shown) of the scroll pump <NUM> to an outlet (not shown) of the scroll pump <NUM>. The physical mechanism by which fluid is pumped by the orbiting of the orbiting scroll <NUM> relative to the fixed scroll <NUM> is well known and will not be described herein.

The fixed scroll <NUM> comprises a first base <NUM>, a first spiral wall <NUM>, and an outer wall <NUM>. The orbiting scroll <NUM> comprises a second base <NUM> and a second spiral wall <NUM>.

The first spiral wall <NUM> extends perpendicularly from the first base <NUM> towards the second base <NUM>. The outer wall <NUM> extends perpendicularly from the first base <NUM> towards the second base <NUM>. The outer wall <NUM> is located radially outwards of the first spiral wall <NUM> and defines an outer periphery of the fixed scroll <NUM>. Thus, the outer wall <NUM> extends around the first spiral wall <NUM>. The second spiral wall <NUM> extends perpendicularly from the second base <NUM> towards the first base <NUM>. The second base <NUM> comprises a peripheral portion <NUM> which is located radially outwards of the second spiral wall <NUM> and which defines an outer periphery of the orbiting scroll <NUM>. In this embodiment, the first base <NUM>, first spiral wall <NUM>, outer wall <NUM> are integrally formed with each other. Also, in this embodiment, the second base <NUM> and second spiral wall <NUM> are integrally formed with each other.

The first spiral wall <NUM> and second spiral wall <NUM> are intermeshed with each other such that an end surface of the first spiral wall <NUM> is in contact with an opposing surface of the second base <NUM>, and an end surface of the second spiral wall <NUM> is in contact with an opposing surface of the first base <NUM>. In this way, the first base <NUM>, first spiral wall <NUM>, second base <NUM> and second spiral wall <NUM> together define a space between the fixed and orbiting scrolls <NUM>, <NUM> which is used by the scroll pump <NUM> during operation to pump fluid. The first and second spiral walls <NUM>, <NUM> each define a respective spiral shaped channel between the turns of the spiral wall.

The drive shaft <NUM> is coupled to the orbiting scroll <NUM> and configured to rotate to drive the orbiting of the orbiting scroll <NUM>. The drive shaft <NUM> is located within the overall housing of the scroll pump <NUM>. In this embodiment, the drive shaft <NUM> is coupled to the orbiting scroll <NUM> and shell <NUM> via a plurality of bearings <NUM> which facilitate rotation of the drive shaft <NUM>.

The actuator <NUM> (e.g. a motor) is coupled to the drive shaft <NUM> and configured to actuate the drive shaft <NUM> to cause the drive shaft <NUM> to rotate to drive the orbiting of the orbiting scroll <NUM>. The actuator <NUM> is located within the overall housing of the scroll pump <NUM>.

The biasing apparatus <NUM> is configured to bias the fixed and orbiting scrolls <NUM>, <NUM> against each other. More specifically, the biasing apparatus <NUM> is configured to bias the orbiting scroll <NUM> towards the fixed scroll <NUM> such that the orbiting scroll <NUM> is axially loaded against the fixed scroll <NUM>. In more detail, the biasing is such that the end surface of the first spiral wall <NUM> is pressed against the opposing surface of the second base <NUM>, and the end surface of the second spiral wall <NUM> is pressed against the opposing surface of the first base <NUM>. Thus, part of the axial load on the fixed and orbiting scrolls <NUM>, <NUM> is supported by the end surfaces of the first and second spiral walls <NUM>, <NUM>. The axial loading caused by the biasing apparatus <NUM> maintains a seal between the end surfaces of the first and second spiral walls <NUM>, <NUM> and the respective opposing surfaces of the first and second bases <NUM>, <NUM>. This tends to act to prevent undesired leakage of fluid between different radial portions of the space between the fixed and orbiting scrolls <NUM>, <NUM>. In this embodiment, the biasing apparatus <NUM> comprises one or more springs which are configured to exert a force on the orbiting scroll <NUM> via the drive shaft <NUM> to bias the orbiting scroll <NUM> towards the fixed scroll <NUM>.

The pad <NUM> is located radially outwards of the first and second spiral walls <NUM>, <NUM>. More specifically, the pad <NUM> is located between the outer wall <NUM> of the fixed scroll <NUM> and the base <NUM> of the orbiting scroll <NUM>. More specifically, the pad <NUM> is located between the outer wall <NUM> and the peripheral portion <NUM> of the second base <NUM> such that the pad <NUM> is in contact with both the outer wall <NUM> and the peripheral portion <NUM>. In other words, the pad <NUM> is sandwiched between the outer wall <NUM> and the peripheral portion <NUM> of the second base <NUM>. In this way, the pad <NUM> is located such that part of the axial load on the fixed and orbiting scrolls <NUM>, <NUM> is supported by the pad <NUM>. Thus, the peripheral portion <NUM> is biased against the outer wall <NUM> via the pad <NUM>. The pad <NUM> is formed from a different material to the fixed and orbiting scrolls <NUM>, <NUM>.

In this embodiment, the pad <NUM> is an annular ring of material embedded in the outer wall <NUM> of the fixed scroll <NUM>. The pad <NUM> is formed from a material with high wear resistance when slid against the material or materials from which the fixed and orbit scrolls <NUM>, <NUM> are made. For example, the pad <NUM> may be able to withstand a contact load of 10N to 1000N at a sliding speed of <NUM>/s to <NUM>/s for a service life of <NUM> to <NUM> years. For example, the first pad <NUM> may be formed from a polymer material (e.g. a polytetrafluoroethylene material, optionally comprising carbon and/or glass to improve wear resistance) and the fixed and orbiting scrolls <NUM>, <NUM> may be formed from a metallic material (e.g. a light-weight metallic material such as aluminium, magnesium or titanium). Aluminium may be particularly desirable as it is a relatively low cost light-weight material.

In this embodiment, during operation of the scroll pump <NUM> in which the orbiting scroll <NUM> orbits relative to the fixed scroll <NUM>, the end surfaces of the first and second spiral walls <NUM>, <NUM> slide against the respective opposing surfaces of the first and second bases <NUM>, <NUM>. This in combination with the above-mentioned axial loading means that the end surfaces tend to experience significant frictional forces during operation of the scroll pump <NUM>. The presence of the pad <NUM>, which supports at least part of the axial load, tends to mean that a smaller proportion of the axial load is supported by the end surfaces of the first and second spiral walls <NUM>, <NUM>. This, in turn, tends to reduce the frictional forces on the end surfaces of the first and second spiral walls <NUM>, <NUM>, which tends to reduce wear on the spiral walls <NUM>, <NUM>.

<FIG> is a schematic illustration (not to scale) showing a cross-sectional view of part of a scroll pump <NUM> according to another embodiment.

The scroll pump <NUM> comprises a shell <NUM>, a fixed scroll <NUM>, an orbiting scroll <NUM>, a drive shaft <NUM>, an actuator (not shown), a plurality of bearings (not shown), a biasing apparatus (not shown), a first pad <NUM>, a second pad <NUM>, a first channel seal <NUM>, and a second channel seal <NUM>.

The fixed scroll <NUM> comprises a first base <NUM>, a first spiral wall <NUM>, an outer wall <NUM> and an inner wall <NUM>. The orbiting scroll <NUM> comprises a second base <NUM> and a second spiral wall <NUM>. In this embodiment, the fixed and orbiting scrolls <NUM>, <NUM> each have a central aperture.

The first spiral wall <NUM> extends perpendicularly from the first base <NUM> towards the second base <NUM>. The outer wall <NUM> extends perpendicularly from the first base <NUM> towards the second base <NUM>. The outer wall <NUM> is located radially outwards of the first spiral wall <NUM> and defines an outer periphery of the fixed scroll <NUM>. Thus, the outer wall <NUM> extends around the first spiral wall <NUM>. The second spiral wall <NUM> extends perpendicularly from the second base <NUM> towards the first base <NUM>. The inner wall <NUM> extends perpendicularly from the first base <NUM> towards the second base <NUM>. The inner wall <NUM> is located radially inwards of the first spiral wall <NUM> between the central aperture and the first spiral wall <NUM>. The inner wall <NUM> is adjacent to the central aperture of the fixed scroll <NUM>.

The second base <NUM> comprises a peripheral portion <NUM> which is located radially outwards of the second spiral wall <NUM> and which defines an outer periphery of the orbiting scroll <NUM>. The second base <NUM> also comprises a radially inner portion <NUM> which is located radially inwards of the second spiral wall <NUM> between the central aperture of the orbiting scroll <NUM> and the second spiral wall <NUM>. The radially inner portion <NUM> is adjacent to the central aperture. In this embodiment, the first base <NUM>, first spiral wall <NUM>, outer wall <NUM> are integrally formed with each other. Also, in this embodiment, the second base <NUM> and second spiral wall <NUM> are integrally formed with each other.

The first and second channel seals <NUM>, <NUM> are seals located in the channel between the fixed and orbiting scrolls <NUM>, <NUM>. The first channel seal <NUM> is adjacent to the second base <NUM> and fully extends across the width of the channel defined by the second spiral wall <NUM>. The first channel seal <NUM> is located between the first spiral wall <NUM> and the second base <NUM>. The second channel seal <NUM> is adjacent to the first base <NUM> and fully extends across the width of channel defined by the first spiral wall <NUM>. The second channel seal <NUM> is located between the second spiral wall <NUM> and the first base <NUM>.

The first spiral wall <NUM> and second spiral wall <NUM> are intermeshed with each other such that an end surface of the first spiral wall <NUM> is in contact with an opposing surface of the first channel seal <NUM>, and an end surface of the second spiral wall <NUM> is in contact with an opposing surface of the second channel seal <NUM>. In this way, the first channel seal <NUM>, first spiral wall <NUM>, second channel seal <NUM> and second spiral wall <NUM> together define a space between the fixed and orbiting scrolls <NUM>, <NUM> which is used by the scroll pump <NUM> during operation to pump fluid.

The drive shaft <NUM> is coupled to the orbiting scroll <NUM> and configured to rotate to drive the orbiting of the orbiting scroll <NUM>. The drive shaft <NUM> is located within the overall housing of the scroll pump <NUM>. In this embodiment, the drive shaft <NUM> is coupled to the orbiting scroll <NUM> and shell <NUM> via the plurality of bearings which facilitate rotation of the drive shaft <NUM>. In this embodiment, the drive shaft <NUM> extends through the central apertures of the fixed and orbiting scrolls <NUM>, <NUM>. This configuration tends to enable placement of the bearings in the pump's exhaust, which tends to keep bearing grease and contamination away from the pump's inlet.

The actuator (e.g. a motor) is coupled to the drive shaft <NUM> and configured to actuate the drive shaft <NUM> to cause the drive shaft <NUM> to rotate to drive the orbiting of the orbiting scroll <NUM>. The actuator is located within the overall housing of the scroll pump <NUM>.

The biasing apparatus is configured to bias the fixed and orbiting scrolls <NUM>, <NUM> against each other. More specifically, the biasing apparatus is configured to bias the orbiting scroll <NUM> towards the fixed scroll <NUM> such that the orbiting scroll <NUM> is axially loaded against the fixed scroll <NUM>. In more detail, the biasing is such that the end surface of the first spiral wall <NUM> is pressed against the opposing surface of the first channel seal <NUM>, and the end surface of the second spiral wall <NUM> is pressed against the opposing surface of the second channel seal <NUM>. Thus, part of the axial load on the fixed and orbiting scrolls <NUM>, <NUM> is supported by the end surfaces of the first and second spiral walls <NUM>, <NUM>. The axial loading caused by the biasing apparatus maintains a seal between the end surfaces of the first and second spiral walls <NUM>, <NUM> and the respective opposing surfaces of the first and second bases <NUM>, <NUM>. This tends to act to prevent undesired leakage of fluid between different radial portions of the space between the fixed and orbiting scrolls <NUM>, <NUM>. In this embodiment, the biasing apparatus comprises one or more springs which are configured to exert a force on the orbiting scroll <NUM> via the drive shaft <NUM> to bias the orbiting scroll <NUM> towards the fixed scroll <NUM>.

The first pad <NUM> is located radially outwards of the first and second spiral walls <NUM>, <NUM>. More specifically, the first pad <NUM> is located between the outer wall <NUM> of the fixed scroll <NUM> and the base <NUM> of the orbiting scroll <NUM>. More specifically, the first pad <NUM> is located between the outer wall <NUM> and the peripheral portion <NUM> of the second base <NUM> such that the first pad <NUM> is in contact with both the outer wall <NUM> and the peripheral portion <NUM>. In other words, the first pad <NUM> is sandwiched between the outer wall <NUM> and the peripheral portion <NUM> of the second base <NUM>. In this way, the first pad <NUM> is located such that part of the axial load on the fixed and orbiting scrolls <NUM>, <NUM> is supported by the first pad <NUM>. Thus, the peripheral portion <NUM> is biased against the outer wall <NUM> via the first pad <NUM>. The first pad <NUM> is formed from a different material to the fixed and orbiting scrolls <NUM>, <NUM>.

In this embodiment, the first pad <NUM> is integrally formed with the first channel seal <NUM>. Also, the first pad <NUM> is the same thickness as the first channel seal <NUM>. In other words, the first pad <NUM> may be said to be an extension of the first channel seal <NUM>. In this embodiment, the first pad <NUM> is formed from a material with high wear resistance when slid against the material or materials from which the fixed and orbit scrolls <NUM>, <NUM> are made. For example, the first pad <NUM> may be able to withstand a contact load of 10N to 1000N at a sliding speed of <NUM>/s to <NUM>/s for a service life of <NUM> to <NUM> years. For example, the first pad <NUM> may be formed from a polymer material (e.g. a polytetrafluoroethylene material, optionally comprising carbon and/or glass to improve wear resistance) and the fixed and orbiting scrolls <NUM>, <NUM> may be formed from a metallic material (e.g. a light-weight metallic material such as aluminium, magnesium or titanium). Aluminium may be particularly desirable as it is a relatively low cost light-weight material.

The second pad <NUM> is located radially inwards of the first and second spiral walls <NUM>, <NUM>. More specifically, the second pad <NUM> is located between the inner wall <NUM> of the fixed scroll <NUM> and the base <NUM> of the orbiting scroll <NUM>. More specifically, the second pad <NUM> is located between the inner wall <NUM> and the radially inner portion <NUM> of the second base <NUM> such that the second pad <NUM> is in contact with both the inner wall <NUM> and the radially inner portion <NUM>. In other words, the second pad <NUM> is sandwiched between the inner wall <NUM> and the radially inner portion <NUM>. The second pad <NUM> is located radially inwards of the first and second spiral walls <NUM>, <NUM> between the central apertures of the fixed and orbiting scrolls <NUM>, <NUM> and the first and second spiral walls <NUM>, <NUM>. The second pad <NUM> is adjacent to the central apertures.

In this way, the second pad <NUM> is located such that part of the axial load on the fixed and orbiting scrolls <NUM>, <NUM> is supported by the second pad <NUM>. Thus, the radially inner portion <NUM> is biased against the inner wall <NUM> via the second pad <NUM>. The second pad <NUM> is formed from a different material to the fixed and orbiting scrolls <NUM>, <NUM>.

In this embodiment, the second pad <NUM> is integrally formed with the first channel seal <NUM>. Also, the second pad <NUM> is the same thickness as the first channel seal <NUM>. In other words, the second pad <NUM> may be said to be an extension of the first channel seal <NUM>. In this embodiment, the second pad <NUM> is formed from the same material as the first pad <NUM>. In this embodiment, the second pad <NUM> is formed from a material with high wear resistance when slid against the material or materials from which the fixed and orbit scrolls <NUM>, <NUM> are made. For example, the second pad <NUM> may be able to withstand a contact load of 10N to 1000N at a sliding speed of <NUM>/s to <NUM>/s for a service life of <NUM> to <NUM> years. For example, the second pad <NUM> may be formed from a polymer material (e.g. a polytetrafluoroethylene material, optionally comprising carbon and/or glass to improve wear resistance) and the fixed and orbiting scrolls <NUM>, <NUM> may be formed from a metallic material (e.g. a light-weight metallic material such as aluminium, magnesium or titanium). Aluminium may be particularly desirable as it is a relatively low cost light-weight material.

In this embodiment, during operation of the scroll pump <NUM> in which the orbiting scroll <NUM> orbits relative to the fixed scroll <NUM>, the end surfaces of the first and second spiral walls <NUM>, <NUM> slide against the respective opposing surfaces of the first and second channel seals <NUM>, <NUM>. This in combination with the above-mentioned axial loading means that the end surfaces of the first and second spiral walls <NUM>, <NUM> and the respective opposing surfaces of the channel seals <NUM>, <NUM> tend to experience frictional forces during operation of the scroll pump <NUM>.

The presence of the first and second pads <NUM>, <NUM>, which support at least part of the axial load, tends to mean that a smaller proportion of the axial load is supported by the end surfaces of the first and second spiral walls <NUM>, <NUM> and the respective opposing surfaces of the channel seals <NUM>, <NUM>. This, in turn, tends to reduce the frictional forces on the end surfaces of the first and second spiral walls <NUM>, <NUM> and the respective opposing surfaces of the channel seals <NUM>, <NUM>.

The second pad <NUM> also provides an additional seal which tends to prevent undesired fluid flow in and out of the space between the fixed and orbiting scrolls. This tends to prevent a vacuum forming in other parts (e.g. the part of the housing containing the actuator) of the scroll pump <NUM> and also tends to prevent pumped fluid entering other parts (e.g. the part of the housing containing the actuator) of the scroll pump <NUM>.

<FIG> is a schematic illustration (not to scale) showing perspective views of the orbiting scroll <NUM> and the first channel seal <NUM>.

The channel seal <NUM> comprises a spiral gap <NUM> which matches the shape and size of the second spiral wall <NUM> such that the second spiral wall <NUM> is able to snugly fit through the spiral gap <NUM>. The channel seal <NUM> also comprises a central aperture which matches the shape and size of the central aperture of the orbiting scroll <NUM> so that the drive shaft <NUM> is able to extend through the channel seal <NUM>.

In this embodiment, the first pad <NUM> comprises a plurality of lobes <NUM> with cut-out portions therebetween. The cut-out portions between the lobes provide space for other parts of the scroll pump <NUM> to reside (e.g. space for a mechanism that prevents the orbiting scroll from rotating and/or space for screws that secure a cover over the orbiting scroll). This tends to enable the overall pump size to be reduced compared to a first pad <NUM> without lobes <NUM>.

Advantageously, in the above-described embodiments, the spiral walls tend to experience reduced wear during operation of the scroll pump. Thus, the scroll pump tends to have better overall durability.

Advantageously, the above-described scroll pumps tend to allow a pressure-velocity value of the scroll pump to be kept relatively low so that the walls and the seals of the scroll pump are not damaged.

Advantageously, in embodiments which include a channel seal, the channel seal tends to experience reduced wear during operation of the scroll pump. Thus, the channel seal tends to have better overall durability.

Advantageously, in embodiments in which a pad is integrally formed with a channel seal, the pad tends to be easily manufactured as it can be manufactured along with the channel seal rather than being manufactured separately. Also, making the channel seal and pads in one piece tends to enable the channel seal and pads to be easily manufactured with the same thickness. In this way, the end clearance between the scroll walls and the channel seals tends to be near zero, which tends to minimise leakage of the pumped fluid and maximise pump performance.

In the above embodiments, the biasing apparatus comprises one or more springs. However, in other embodiments, the biasing apparatus comprises a different type of device to provide biasing instead of or addition to the one or more springs.

In the above embodiments, the outer wall extends from the fixed scroll. However, in other embodiments, the outer wall extends from the orbiting scroll instead.

In the above embodiment of <FIG>, the scroll pump comprises a second pad and the scrolls comprise central apertures. However, in other embodiments, the scroll pump comprises a second pad without the presence of the central apertures. In some embodiments, the scroll pump comprises the central apertures without a second pad. In some embodiments, the second pad and the central apertures are all omitted.

Claim 1:
A scroll pump (<NUM>; <NUM>) comprising:
a first scroll (<NUM>; <NUM>) comprising a first spiral wall (<NUM>; <NUM>) and an inner wall (<NUM>) located radially inward from the first spiral wall (<NUM>; <NUM>);
a second scroll (<NUM>; <NUM>) comprising a base (<NUM>; <NUM>) and a second spiral wall (<NUM>; <NUM>) extending from the base (<NUM>; <NUM>), the second spiral wall (<NUM>; <NUM>) being intermeshed with the first spiral wall (<NUM>; <NUM>);
a first pad (<NUM>) formed from a different material to the first and second scrolls (<NUM>, <NUM>; <NUM>, <NUM>), the first pad (<NUM>) being located between the first and second scrolls (<NUM>, <NUM>; <NUM>, <NUM>) radially outwards of the first and second spiral walls (<NUM>, <NUM>; <NUM>, <NUM>);
a second pad (<NUM>) formed from a different material to the first and second scrolls (<NUM>, <NUM>; <NUM>, <NUM>), the second pad (<NUM>) being located between the first and second scrolls (<NUM>, <NUM>; <NUM>, <NUM>) radially inwards of the first and second spiral walls (<NUM>. <NUM> ; <NUM>, <NUM>) and axially between the inner wall (<NUM>) of the first scroll (<NUM>, <NUM>) and the base (<NUM>, <NUM>) of the second scroll (<NUM>, <NUM>), the inner wall (<NUM>) and second pad (<NUM>) preventing a fluid flow out of a space between the first scroll (<NUM>, <NUM>) and the second scroll (<NUM>, <NUM>) to a central aperture; and
a biasing apparatus (<NUM>) configured to bias the first and second scrolls (<NUM>, <NUM>; <NUM>, <NUM>) against each other via the first and second pads (<NUM>, <NUM>).