Pump gearbox

Abstract

A gearbox for a pump is described, the gearbox including a ring gear, a sun gear, and one or more planet gears disposed between the ring gear and the sun gear, the planet gears arranged to move along a continuous path around the sun gear, and the ring gear, sun gear, and planet gears arranged such that the radius of the path changes as the planet gears move along the path.

Description

[Technical Field]

[0001] The present disclosure relates to a gearbox, particularly a gearbox suitable for use in a pump (e.g., a radial hydraulic pump). The present disclosure also relates to a pump including the gearbox, a system including the gearbox and / or pump, and a method of operating the gearbox and / or pump. [Background technology]

[0002] A radial hydraulic pump (such as a radial piston pump) has one or more pistons extending radially from a drive shaft. Each piston is connected at one end to the drive shaft and at the other end to an external tappet, also known as a stroke ring, that surrounds the drive shaft. The pistons are mounted so that as the distance between the external tappet and the drive shaft increases, the volume within the piston increases (and therefore the pressure within the piston decreases). In such pumps, either the drive shaft or the external tappet is eccentric, so that as the drive shaft rotates, the drive shaft and the tappet work together to continuously change the volume of each piston. The change in piston volume causes a change in pressure within the piston, which can be used to drive fluid flow.

[0003] Such a pump is illustrated in FIG. 1, which shows a conventional radial hydraulic pump 100 with a drive shaft 102, an external tappet 104, and first and second pistons 106, 108. The drive shaft is fixed for rotation about an axis of rotation 110. An inner end 112 of the first piston 106 is fixed to the drive shaft, and an outer end 114 of the first piston is fixed to the external tappet. Because the axis of rotation of the drive shaft does not coincide with the center of the drive shaft, rotation of the drive shaft causes the distance between the inner and outer ends of the first piston to vary throughout a cycle, with one rotation of the drive shaft corresponding to one cycle between the maximum and minimum distances between these two ends and the first piston. Similarly, the extension of the second piston 108 also varies throughout a cycle (the second piston is located opposite the first piston, and its extension coincides with that of the first piston). The extension and compression of the piston causes a change in pressure within the piston, causing the piston to draw in and expel fluid at points in the cycle corresponding to extension and compression, respectively.

[0004] The pistons can be positioned to draw fluid from an interior region of the pump. For example, pistons 106, 108 can draw fluid from their inner ends, with the interior region of the pump connected to a fluid supply. This configuration is called "inner feed." Alternatively, the pistons can be connected to a fluid supply closer to the external tappet 104, with the outer ends of the pistons positioned to draw fluid from this reservoir.

[0005] The connections between the pistons and the fluid source may be valved to allow fluid to flow through the connections in only one direction. An internally fed pump may have two valved openings at the inner end of each piston. For example, the inner end 112 of the first piston 106 may have a valved opening that allows fluid to enter the first piston but not exit it, and the outer end 114 of the first piston may have a valved opening that allows fluid to exit the first piston but not enter it. When the piston is expanding, fluid enters through the first opening. When the piston is compressing, the valve at the first opening does not allow fluid to exit, so fluid can only exit through the second opening. Summary of the Invention

[0006] According to one aspect of the present disclosure, a gearbox for a pump is described, the gearbox comprising a ring gear, a sun gear, and one or more planet gears disposed between the ring gear and the sun gear, the planet gears arranged to move along a continuous path around the sun gear, the ring gear, the sun gear, and the planet gears arranged such that the radius of the path changes as the planet gears move along the path.

[0007] The change in radius of the planet gear path may be used to drive a pump.

[0008] Preferably, at least two of the ring gear, sun gear and at least one planet gear have a non-circular profile (and / or a non-circular pitch circumference and / or a non-constant pitch diameter).

[0009] The sun gear may have a non-circular pitch circumference and / or a non-circular profile, and the ring gear may also have a non-circular pitch circumference and / or a non-circular profile. The diameter, circumference, and / or profile of the ring gear may depend on the diameter, circumference, and / or profile of the sun gear. For example, the diameter of the ring gear may be equal to the sum of the diameter of the sun gear and twice the diameter of the planet gears. This has the advantage that the ring gear and planet gears, and the planet gears and sun gears, can mesh without placing significant strain on the gears.

[0010] The gearbox may comprise a plurality of planet gears. The gearbox may comprise a pair of planet gears. Preferably, the pair of planet gears are arranged symmetrically with respect to the center of the path and / or the center of rotation of the gearbox. Preferably, the gearbox comprises multiple pairs of planet gears.

[0011] The gearbox may comprise at least two planet gears, at least four planet gears, at least eight planet gears, and / or at least ten planet gears.

[0012] The gearbox may comprise a number of planet gears less than or equal to (and / or equal to) the degree of rotational symmetry of the gearbox. The gearbox may comprise a number of planet gears that is less than or equal to the degree of rotational symmetry of the sun gear and ring gear combination. If the gearbox comprises a number of planet gears less than or equal to the degree of rotational symmetry of the sun gear and ring gear combination, each planet gear may be arranged to follow a path of uniformly varying width as it orbits the sun gear. Each planet gear may be arranged to follow a path whose width remains constant throughout the planet gear's orbit, allowing each planet gear to remain in mesh with the sun gear and ring gear without experiencing significant compression at any point in its orbit.

[0013] The planet gears can be evenly spaced along the path.

[0014] The gearbox may include a carrier, and the planet gears may be attached to the carrier.

[0015] The width of the path along which the planet gears move between the sun gear and the ring gear may be substantially constant. The sun gear and ring gear may be arranged such that the radial distance between the sun gear and the ring gear at the contact point of each planet gear remains constant as the planet gears move along the path.

[0016] Each planet gear may have a circular profile. Each planet gear may have a similar shape. The ring gear and sun gear may each have a non-circular profile.

[0017] One or more (e.g., each) of the sun gear, ring gear, and planet gears may include a plurality of teeth. Preferably, the teeth of each gear are approximately equally spaced. Preferably, the teeth are regularly spaced around the contour of the corresponding gear.

[0018] The gearbox includes at least one piston, the piston being arranged such that the amount of compression of the piston varies as the planet gear moves along the path, preferably such that the amount of radial compression of the piston varies as the planet gear moves along the path. This radial compression may be used to cause a pressure change in the piston as the planet gear moves along the path, and this change may be used to drive a pump. A first end of the piston may be associated with (e.g., connected to) the planet gear. The first end of the piston may be connected to a carrier.

[0019] The gearbox may include a plurality of pistons, each piston having a first end associated with a different planet gear.

[0020] The second end of each piston is connected to a further part of the gearbox, and as the planet gear moves along the path the first end of that piston moves relative to the second end of the piston, preferably as the planet gear moves along the path the first end of the piston moves towards and / or away from the second end of the piston.

[0021] The second end of the piston may be connected to a further planet gear, preferably an opposing planet gear located at opposite points along the path of the planet gear (e.g., the planet gear and the opposing planet gear are spaced 180° apart along the path as each gear moves along the path).

[0022] The second end of the piston may be connected to one or more of the sun gear, the ring gear, the carrier, and a point near and / or at the center of the path and / or the center of rotation of the gearbox.

[0023] One or more of the pistons (eg, each piston) may be mounted on a carrier.

[0024] The ring gear may be arranged to remain stationary (e.g., relative to a housing portion of the gearbox) as the planet gears move along the path, and the sun gear may be arranged to remain stationary (e.g., relative to a housing portion of the gearbox) as the planet gears move along the path.

[0025] One or more (eg, each) of the sun gear and ring gear may be arranged to rotate (eg, relative to a housing portion of the gearbox) as the planet gears move along the path.

[0026] The gearbox may include a motor that drives the motion (e.g., rotation) of one or more of the sun gear, ring gear, one or more planet gears, and a carrier associated with the one or more planet gears.

[0027] The sun gear includes one or more root minimum points, and the radius of the sun gear at the root minimum points is less than the average radius of the sun gear. For example, the radial distance from the center of the sun gear to the root of the gear tooth may be less than the average value of the radial distance between the center of the sun gear and the root of the sun gear at the root minimum points.

[0028] The sun gear has one or more crest points, and the radius of the sun gear at the crest points is greater than the average radius of the sun gear. For example, the radial distance from the center of the sun gear to the root of the gear tooth at the crest points may be greater than the average radial distance between the center of the sun gear and the root of the sun gear.

[0029] The ring gear may have one or more root minimum points, and the radius of the ring gear at the root minimum points (e.g., the distance from the ring gear to the center of rotation of the ring gear and / or gearbox) is less than the average radius of the ring gear. For example, the radial distance from the center of the ring gear to the root of the gear teeth may be less at the root minimum points than the average value of the radial distance between the center of the ring gear and the root of the ring gear teeth.

[0030] The ring gear may have one or more crest points, and the radius of the ring gear at the crest point (e.g., the distance from the ring gear to the center of rotation of the ring gear and / or gearbox) is greater than the average radius of the ring gear. For example, the radial distance from the center of the sun gear to the root of the gear teeth may be greater at the crest point than the average value of the radial distance between the center of the sun gear and the root of the sun gear teeth.

[0031] The ring gear may be rotationally symmetric. Alternatively and / or additionally, the sun gear may also be rotationally symmetric. Preferably, both the sun gear and the ring gear are rotationally symmetric. This allows the planet gears to be arranged such that the radial distance between the sun gear and the ring gear at their respective contact points remains constant as the planet gears move along their paths.

[0032] The sun gear may have an equal number of minimum root values ​​and maximum crest values, and / or the ring gear may have an equal number of minimum root values ​​and maximum crest values.

[0033] The number of minimum valley values ​​of the ring gear may be the same as the number of minimum valley values ​​of the sun gear, and / or the number of maximum crest values ​​of the ring gear may be the same as the number of maximum crest values ​​of the sun gear.

[0034] The number of minimum valley values ​​of the ring gear may be greater than the number of minimum valley values ​​of the sun gear, and / or the number of maximum crest values ​​of the ring gear may be greater than the number of maximum crest values ​​of the sun gear.

[0035] The amplitude of the minimum valley value of the sun gear (e.g., the distance between the average radius of the sun gear and the radius of the sun gear at the minimum valley value) may be equal to the amplitude of the maximum crest value of the sun gear (e.g., the distance between the average radius of the sun gear and the radius of the sun gear at the maximum crest value).

[0036] Similarly, the amplitude of the minimum valley value of the ring gear (e.g., the distance between the mean radius of the ring gear and the radius of the ring gear at the minimum valley value) may be equal to the amplitude of the maximum crest value of the ring gear (e.g., the distance between the mean radius of the sun gear and the radius of the ring gear at the maximum crest value).

[0037] Preferably, the change in amplitude of the sun gear's minimum root point (eg, from the sun gear's average radius) is equal to the change in amplitude of the sun gear's maximum crest point.

[0038] Preferably, the change in amplitude of the minimum root point of the ring gear is equal to the change in amplitude of the maximum crest point of the ring gear.

[0039] Preferably, the change in amplitude of the minimum root point of the sun gear is equal to the change in amplitude of the maximum crest point of the ring gear.

[0040] Preferably, the change in amplitude of the maximum crest point of the sun gear is equal to the change in amplitude of the minimum trough point of the ring gear.

[0041] The sun gear may have a wave profile and / or the ring gear may have a wave profile.

[0042] The sun gear may have a profile comprising a sine wave superimposed on an ellipse, preferably a sine wave superimposed on a circle, and / or the ring gear may have a profile comprising a sine wave superimposed on an ellipse, preferably a sine wave superimposed on a circle.

[0043] The profile of the sun gear and / or ring gear (preferably the profile of the sun gear and ring gear respectively) is defined by the following formula:

number

[0044] The ring gear may have a different minimum number of valleys and / or a different maximum number of peaks than the sun gear. Preferably, the ring gear has a greater minimum number of valleys and / or a greater maximum number of peaks than the sun gear, and / or f_ring is greater than f_sun.

[0045] The amplitude of the minimum and / or maximum crest values ​​of the sun gear may be substantially equal to the amplitude of the minimum and / or maximum crest values ​​of the ring gear, and / or a_ring may be equal to a_sun. When a_ring is equal to a_sun, the gears can be configured such that the radial distance between the sun gear and the ring gear at the contact point of each planet gear remains constant as each planet gear moves along its path.

[0046] The ring gear and / or sun gear may have one or more waves. A wave is a sinusoidal portion (e.g., one cycle) around the circumference of the gear and / or a wave that includes minimum valleys and maximum peaks. Preferably, the ring gear and / or sun gear have an integer number of waves. The ring gear may have a greater number of waves than the sun gear.

[0047] The diameters and wave numbers of the sun and ring gears may be linked by the following formula:

number

[0048] The sun gear may have eight waves (e.g., f_sun=8). The ring gear may have ten waves (e.g., f_ring=10).

[0049] The diameter (e.g., pitch diameter) of the sun gear may be 100 mm or more, 200 mm or more, and / or 500 mm or more, and the diameter (e.g., pitch diameter) of the sun gear may be 1000 mm or less, 800 mm or less, and / or 500 mm or less.

[0050] The diameter of the planet gears may be 50 mm or more, 100 mm or more, and / or 200 mm or more, or 500 mm or less, 400 mm or less, and / or 300 mm or less.

[0051] The pump may comprise a radial pump and / or a radial hydraulic pump, and may be configured to pump fluid through a piston and / or in a radial direction of the gearbox (e.g., perpendicular to the rotational axis of the gearbox) and / or in the direction of the rotational axis of the gearbox (e.g., the rotational axis of the sun gear and / or ring gear).

[0052] The pump is arranged on an axis such that one or more (preferably each) of the sun gear, ring gear, and carrier rotate about the axis.

[0053] According to another aspect of the present disclosure, there is provided a (e.g., computer-implemented) method of operating the gearbox and / or pump of any embodiment of the first aspect. The method may comprise driving one or more of a sun gear, a ring gear, and a planet gear. The method may comprise driving the gears in response to a predetermined pumping force.

[0054] According to another aspect of the present disclosure, there is provided a method of manufacturing the gearbox and / or pump of the first aspect.

[0055] According to another aspect of the present disclosure, there is provided a parts kit for a gearbox according to any of the preceding claims, the parts kit comprising a ring gear, a sun gear and one or more planet gears.

[0056] According to another aspect of the present disclosure, a computer program product (and / or machine-readable medium) is described comprising instructions that, when executed, cause a processor to control a gearbox and / or a pump according to any of the preceding claims.

[0057] Features of one aspect of the present disclosure may be applied to other aspects of the invention in any appropriate combination, in particular method aspects may be applied to apparatus aspects and vice versa.

[0058] Additionally, functionality implemented in hardware may also be implemented in software and vice versa, and references herein to software and hardware functionality shall be construed accordingly.

[0059] Apparatus features described herein may also be provided as method features, and vice versa. Means-function combination features herein may be represented by corresponding structures, such as a suitably programmed processor and associated memory.

[0060] It should also be understood that specific combinations of the various features described and defined in any aspect of the disclosure may be implemented and / or provided and / or used independently.

[0061] The present disclosure also provides computer programs and computer program products comprising software code adapted to perform any of the methods described herein (including some or all of their constituent steps) when executed on a data processing apparatus.

[0062] The present disclosure also provides a computer program and a computer program product comprising software code which, when executed on a data processing device, provides any of the features of the devices described herein.

[0063] The present disclosure also provides computer programs and computer program products with an operating system that supports the computer programs for performing any of the methods described herein and / or embodying any of the apparatus features described herein.

[0064] The present disclosure also provides a computer-readable medium having stored thereon the aforementioned computer program.

[0065] The present disclosure also provides signals carrying the aforementioned computer programs, and methods for transmitting such signals.

[0066] The present disclosure extends to methods and / or apparatus substantially as herein described with reference to the accompanying drawings.

[0067] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0068] [Figure 1] FIG. 1 shows a radial piston pump according to the prior art. [Figure 2] FIG. 2 shows a system including a pump. [Figure 3] Figure 3 shows the Planet Gear gearbox. [Figure 4A] FIG. 4A shows a planet gear box according to the present disclosure. [Figure 4B] FIG. 4B shows a planet gear box according to the present disclosure. [Figure 5A] FIG. 5A shows an exemplary gear. [Figure 5B] FIG. 5B shows an exemplary gear. [Figure 6] FIG. 6 shows a further embodiment of a planet gear gearbox according to the present disclosure. [Figure 7] FIG. 7 shows another embodiment of a planet gear gearbox according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0069] Referring to Figure 2, a system contemplated by the present invention is shown. Figure 2 shows a fluid source 252, such as a water source. The fluid source is connected to a pump 254 at a fluid inlet 262. The pump draws fluid from the fluid source through the fluid inlet and then expels the fluid through a fluid outlet. The fluid outlet is connected to a fluid output. Typically, one-way valves are connected to the pump inlet and outlet to prevent fluid from flowing in the opposite direction through the system, for example, from the fluid output to the pump or from the pump back to the fluid source.

[0070] The present disclosure relates to a gearbox suitable for use in a pump, particularly a radial hydraulic pump. More particularly, the present disclosure relates to a planet gear gearbox usable in a pump.

[0071] Referring to FIG. 3, a conventional planet gear gearbox 300 is shown, comprising a sun gear 310, a first planet gear 320, a second planet gear 325, and a ring gear 330. Each gear has a series of teeth and grooves that mesh with one another. More specifically, each planet gear meshes with both the sun gear and the ring gear, so that as the planet gear moves, it rolls without slipping relative to the sun gear and the ring gear. Typically, the planet gears are supported by a carrier (not shown in FIG. 3). Therefore, movement of the planet gears causes movement (e.g., rotation) of the carrier, which can be used to power other components.

[0072] The planet gear gearbox can be operated by driving one or more of the sun gear 310, ring gear 330, carrier (not shown), and planet gears 320, 325. For example, a motor may be attached to one of these components and used to move that component. In operation, driving the sun gear about its central axis causes the planet gears to orbit around the sun gear 310. If the ring gear 330 is fixed (e.g., fixed relative to the gearbox housing), the meshing contact between the ring gear and planet gears causes the planet gears to rotate about their respective axes (and thus the carrier to move). Similarly, for example, the ring gear may be fixed and the planet gears driven. Such movement of the planet gears causes movement of the sun gear.

[0073] A conventional planet gear gearbox includes a circular sun gear 310, circular planet gears 320, 325, and a circular ring gear 330. As shown in Figures 4a and 4b, this disclosure considers a planet gear gearbox 400 with a non-circular ring gear 402 and a non-circular sun gear 404.

[0074] The planet gear gearbox 400 of the present disclosure further includes one or more planet gears 406, 408 disposed between the ring gear 402 and the sun gear 404 and arranged for movement along a path around the sun gear. Typically, the ring gear, sun gear, and planet gears each include a series of teeth and grooves that intermesh (as discussed above) to facilitate such movement.

[0075] The planet gears 406, 408 are arranged to move along a continuous (e.g., non-circular) path defined by the ring gear 402 and the sun gear 404. Thus, as the planet gears move along their path, the distance between the planet gears and the axis of rotation 410 of the sun gear (and planet gear reducer) changes. This may be thought of as the radius of the planet gear's path changing as the planet gears move along their path.

[0076] The sun gear 404 has one or more valleys (or minimum valley values) and one or more crests (or maximum crest values), where the crest radius is greater than the valley radius, and these valleys and / or crests cause the aforementioned changes in the path radius of the planet gears 406, 408 as they move around the sun gear.

[0077] The ring gear 402 typically has similar maxima and minima (e.g., peaks and valleys) and is typically positioned such that during normal rotation of the planet gears 406, 408, the peaks of the sun gear 404 coincide with the valleys of the ring gear, thereby defining a path of substantially constant width between the sun and ring gears. Thus, as the planet gears move around the sun gear, they pass through the peaks and valleys, causing the radius of the path to change.

[0078] The maximum / peak of the sun gear 404 is considered to be the point on the sun gear that is farthest from the axis of rotation of the sun gear (or the axis of rotation of the planet gear gearbox), and the minimum / valley of the sun gear is considered to be the point on the sun gear that is closest to the axis of rotation of the sun gear.

[0079] Conversely, the maximum / peak of the ring gear 402 is considered to be the point of the ring gear closest to the axis of rotation 410 of the sun gear 404 (or the axis of rotation of the planet gear gearbox), and the minimum / valley of the ring gear is considered to be the point of the ring gear furthest from the axis of rotation of the sun gear.

[0080] Typically, each planet gear 406, 408 is sized to fit between a crest on the sun gear 404 and a valley on the ring gear 402, or between a valley on the sun gear and a crest on the ring gear.

[0081] The above-described change in the path radius of the planet gears 406, 408 can be utilized to realize a radial pump. Specifically, the pump consists of a planet gear reducer 400 and one or more pistons, each connected to (or more generally associated with) one of the planet gears 406, 408 of the planet gear box machine. Driving any gear of the planet gear box causes relative motion between the planet gear and the sun gear 402, and the change in the path radius of the planet gear changes the volume (e.g., compression and / or decompression) of the piston, which in turn changes the pressure of the piston.

[0082] As used herein, the term "piston" refers to any part that generates a force in response to compression and / or expansion, allowing the piston to exert a pumping force. Thus, a piston typically comprises a piston head that is arranged to move to change the volume within the piston (thereby exerting a pumping force), but the piston may also be comprised of a solid material, such as a spring or rubber part, that uses the compression and expansion of the material to exert a pumping force.

[0083] Each piston is associated at a first end with (e.g., connected to) one of the planet gears 406, 408. To create the aforementioned pressure changes, a second end of each piston may be connected to one or more of another planet gear, a sun gear, and / or other external components that move relative to the planet gear as it moves along the path.

[0084] 4a and 4b, in some embodiments, the piston is connected to a first planet gear 406 and a second planet gear 408, which are typically arranged symmetrically about a sun gear (e.g., the axis of rotation of the sun gear). Planet gears arranged symmetrically about a sun gear include planet gears arranged on opposite sides of the sun gear and / or at opposite points in the path.

[0085] The embodiment of Figures 4a and 4b shows a ring gear 402 and a sun gear 404 with a regular arrangement of peaks and valleys and multiple ring gears. More generally, it will be understood that the sun gear and / or ring gear may have any number of peaks and valleys (e.g., a single peak and valley), and the planet gear box 400 may have any number of planet gears (e.g., a single planet gear). Furthermore, while the embodiment shown in Figures 4a and 4b includes a rotationally symmetric sun gear and a rotationally symmetric ring gear, it will be understood that the change in radius can be achieved with an asymmetric sun gear and / or ring gear (e.g., a sun gear with a single short valley and a single long peak). However, rotationally symmetric gears are typically used because they make it easier to periodically change the radius of the planet gear path, thereby achieving a consistent pumping force.

[0086] 4a and 4b, this embodiment comprises a first planet gear 406 and a second planet gear 408 arranged to move along a (regularly) oscillating (e.g., sinusoidal) path, with each gear moving through a series of peaks and valleys or a series of maximum and minimum radius points. As the gears move along this path, the radial distance between the planet gears and the sun gear's rotational axis 410 changes, and so does the radial distance between the planet gears. In this regard, a pair of planet gears will typically be arranged to simultaneously pass through a pair of peaks and / or a pair of valleys, thereby ensuring a change in the radial distance between the planet gears.

[0087] This movement causes a volume change in a piston connected to one or more planet gears (e.g., via a carrier connected to the planet gears). As previously mentioned, this volume change causes a corresponding pressure change, which can be used to apply a pumping force to a fluid.

[0088] Typically, the planet gear gearbox 400 includes multiple planet gears 406, 408 and / or multiple planet gear pairs, each typically symmetrically positioned about the axis of rotation 410 of the sun gear 404.

[0089] Typically, the planet gears 406, 408 are evenly spaced along the path defined by the sun gear and planet gear 402, which provides constant pressure and constant pumping power. Typically, each planet gear is similar to the others, which provides constant pressure and constant pumping power.

[0090] Typically, one or more (and / or each) of the planet gears 406, 408 is associated with a piston, a first end of the piston arranged to move with the associated planet gear and cause compression or extension of the piston, and a second end of the piston is typically connected to one or more of another planet gear (e.g., the other planet gear of a pair of planet gears) or the sun gear 404.

[0091] The second ends of the pistons may be connected to components of the sun gear 404 and / or planet gears that are configured to rotate relative to the sun gear and / or planet gear, thereby avoiding collisions between the various pistons. In particular, the connections between the second ends of the pistons and the sun gear and / or planet gears may be configured to rotate in radial alignment with the planet gears associated with the pistons (the axial distance between the second ends of the pistons and the planet gears varies). By attaching each piston to a pair of planet gears, it is possible to arrange multiple pistons while maintaining a constant circumferential distance between each piston (because all planet gears, and therefore all pistons, rotate at the same speed). This allows for the use of a compound piston carrier with multiple pistons attached, which rotates with the planet gears and is configured to allow only radial movement of the pistons.

[0092] To provide a pump, the first and / or second end of each piston is connected to a fluid source (e.g., fluid source 252 in FIG. 2 ), and pressure changes within the pistons pump the fluid. The connection between the pistons and the fluid source can be a direct connection, where the pistons draw fluid from the fluid source and then expel it, or an indirect connection, where pressure changes within the pistons are used to expel fluid from the fluid source (e.g., perpendicular to the direction of the pistons). For example, the second end of the pistons can be connected to a sun gear, and pressure changes within the pistons can be used to drive the working fluid along an axis coincident with the axis of rotation of the sun gear.

[0093] Parametric Contours Typically, both the ring gear 402 and the sun gear 404 have a non-circular (e.g., parametric) profile. Specifically, the ring gear and the sun gear each have a profile that is a sine wave superimposed on an ellipse (e.g., a circle).

[0094] Such a contour can be defined by the following parametric equation:

number

[0095] These Cartesian coordinate systems can be represented as polar coordinate systems as well.

number

[0096] It turns out that this polar equation (and the associated Cartesian equation) can also be written as

number

[0097] The diameter of the sun gear 404 is smaller than the diameter of the ring gear 402, and the planet gears 406, 408 are sized to fit between these diameters.

[0098] a is the wave amplitude, which defines the amplitude of the gear's maxima and minima (e.g., peaks and valleys). In other words, a defines the gear's profile variation from the mean diameter P. The value of a will vary depending on the available space in the PlanetGear gearbox 400 and / or pump, and / or the required pump power / volume.

[0099] f is the frequency of the wave, which defines the number of maxima and minima (e.g., peaks and valleys) in the gear. In this respect, one period of a sine wave (from one maximum to the next) is considered one wave, and there are f waves in each gear.

[0100] The ring and sun gears typically have profiles that include both a constant radial term and a variable (e.g., sinusoidal) radial term. This results in a non-circular gear profile, and the use of a sinusoidal radial term results in a regular (but non-circular) gear profile. Typically, the gear profiles are each rotationally symmetric, and such rotational symmetry can be achieved by using integer values ​​for the wave frequency (f).

[0101] Gears typically have multiple teeth that allow adjacent gears to mesh with each other. Because of these teeth, each gear is usually not perfectly circular. In this respect, gears can be thought of as consisting of a friction wheel with teeth. The gear's pitch circle coincides with the circumference of the friction wheel, and the pitch circle is the reference circle used to determine the gear tooth pitch. Specifically, the circular pitch of a gear, or the distance from the centerline of one tooth to the centerline of the next tooth, can be calculated by dividing the circumference of the pitch circle by the number of teeth on that gear.

[0102] Thus, the term pitch diameter is used to indicate that a gear is comprised of a series of teeth arranged around a typically circular gear. When a gear is referred to as non-circular herein, it means that the gear is non-circular due to factors other than the teeth. Because the disclosure herein is applicable to non-circular gears generally, the detailed description will refer to gears having a non-constant pitch diameter (e.g., where the gear profile is a sinusoid superimposed on a circular profile), but it should be understood that more generally, the disclosure relates to providing gears having non-circular pitch circumferences.

[0103] As used herein, the "profile" of a gear refers to the shape of the gear excluding the teeth. For example, Figures 4a and 4b show a ring gear 402 and a sun gear 404, each with a non-circular profile, and a pair of planet gears 406 and 408 with a circular profile. In practice, each gear typically has multiple teeth; for example, the planet gears are shaped similarly to planet gears 320 and 325 of the conventional planet gear gearbox shown in Figure 3. These planet gears can be considered to have a set of teeth arranged along a circular profile. Similarly, the ring gear and sun gear can also be considered to have a set of teeth arranged along a non-circular profile.

[0104] The above variables are shown in Figures 5a and 5b.

[0105] Referring to Figure 5a, an embodiment of a conventional gear is shown having a circular profile. The gear has a pitch diameter P and further includes a series of teeth arranged around the pitch diameter. Such a gear may be used, for example, for planet gears 406, 408 in planet gear gearbox 400 of Figures 4a and 4b. While the gear is not strictly circular due to the teeth, it can be considered to have a circular profile because the teeth are arranged around the circular profile.

[0106] Referring to Figure 5b, an embodiment of a ring gear and sun gear according to the present disclosure is shown. The ring gear has 12 waves (e.g., f_ring = 12) and the sun gear has 6 waves (f_sun = 6). The ring gear and sun gear each have a non-circular profile, and the embodiment of Figure 5b shows a sun gear with a profile consisting of a sine wave superimposed on a circle, with the sun gear having a series of maximum points with a radius equal to P / 2 + a_sun and a series of minimum points with a radius equal to P / 2 - a_sun. Typically, the sun gear and ring gear each have a series of teeth arranged along the non-circular profile.

[0107] In the embodiment of Figure 5b, a_(sun,minima) = a_(sun,maxima). It will be appreciated that gears may be set with different values ​​of a_(sun,minma) and a_(sun,maxima).

[0108] As previously mentioned, the ring gear and sun gear each typically further include a series of teeth arranged around the circumference of the gear, which are not shown in the figures.

[0109] In the illustrated example, the ring gear 402 is defined with f_ring=10 and the sun gear 404 is defined with f_sun=8. It will be appreciated that various combinations of wave frequencies may be applied.

[0110] To avoid damage to the planet gears 406, 408 as they move along the path defined by the ring gear 402 and sun gear 404, the planet gear gearbox 400 is typically arranged so that the width of this path is substantially constant during use. Values ​​for achieving such a path of substantially constant width are given below. In some embodiments, the sun gear, ring gear, and / or planet gears may be flexible to reduce potential damage caused by (small) variations in the path width.

[0111] As described above, when the sun gear 404 is driven (e.g., by a motor associated with the sun gear), the planet gears 406, 408 are urged to orbit around the sun gear by the meshing of their respective gear teeth. As the planet gears rotate, they are urged toward the maximum and minimum points (e.g., peaks and valleys) of the parabolas defining the sun gear and ring gear 402. Figure 4a shows the planet gears at the maximum points of the parabolas defining the sun gear and ring gear, respectively. At this point, the distance between the planet gears is at a maximum. Therefore, the piston fixed between the planet gears will be at its point of maximum extension, or maximum volume, at this point in the cycle.

[0112] Figure 4b shows the planet gears 406, 408 positioned at the minimum points of the parabolas defining the sun gear 404 and ring gear 402, respectively. At this point, the distance between the planet gears is minimum. Therefore, the piston fixed between the planet gears will have its point of maximum compression, and therefore minimum volume, at this point in the cycle.

[0113] As shown in FIG. 1, in a conventional radial hydraulic pump, each piston experiences one maximum and one minimum extension value per drive ring cycle. Therefore, to operate the pump at high speeds, the drive ring must rotate at high speeds. This means that converting external rotational force, such as from a large turbine, into pumping action requires large, additional gearing to increase the rotational speed of the drive ring relative to the drive turbine. This additional gearing reduces the efficiency of the overall system. The planet gear gearbox 400 of the present disclosure can be used to provide a radial hydraulic pump in which each piston experiences multiple extension cycles per drive ring cycle. This allows for efficient conversion of external rotational force into pumping action. For example, FIGS. 4a and 4b illustrate a gearbox embodiment in which pistons connected to first planet gear 406 and second planet gear 408 are driven through multiple maximum and minimum values ​​per revolution of the sun gear 404.

[0114] To achieve an efficient and reliable planet gear gearbox arrangement, in some embodiments, several constraints are placed on the ratios and parameters that define the sun gear 404, ring gear 402, and planet gears 406 and 408. These constraints can be used to ensure that the planet gears remain in contact and mesh with the sun and ring gears throughout the entire orbit.

[0115] In some embodiments, these constraints relate to the values ​​of P, a, and f in the above equations, with particular values ​​being found to provide a particularly effective gearbox.

[0116] Typically, the sun gear 404 and ring gear 402 are shaped so that the planet gears 406, 408 contact both the sun gear and the ring gear at every point along their path around the sun gear. Such constraints require that at every point along the path of the planet gears around the sun gear, there must be a point where the sun gear profile is a maximum, e.g., at every crest on the sun gear, there must also be a corresponding minimum on the ring gear. Similarly, there must be a point where the sun gear profile is a minimum, e.g., at every valley on the sun gear, there must also be a corresponding maximum on the ring gear.

[0117] In some embodiments, to ensure this consistent contact, the sun gear and ring gear have a different number of local maxima and minima (e.g., peaks and valleys). In some embodiments, the sun gear and ring gear have a different number of local maxima and minima (e.g., peaks and valleys). In this case, the sun gear and / or ring gear can be arranged to rotate as the planet gears move along the path, so that the planet gears remain in contact with the sun gear and ring gear, even though the number of local maxima and minima is different.

[0118] Parametric Dimensions There are three primary curves that define the operation of the PlanetGear gearbox machine 400: the curve defined by the radius of the ring gear 402 (r_ring(t)), the curve defined by the radius of the sun gear 404 (r_sun(t)), and the curve defined by the radius of the path of the planet gears 406, 408 (r_planetpath(t)). The value of each curve is typically determined depending on the values ​​of one or more other curves. In this case, a value is selected for one of the curves (e.g., based on the desired size of the PlanetGear gearbox), and the values ​​of the other curves are determined based on the selected value. In particular, the value of a ring gear dimension can be determined based on the selected sun gear dimension (or vice versa).

[0119] In a preferred embodiment, the pitch diameters of the planet gears and the planet gear paths are determined depending on the pitch diameters of the ring gear and the sun gear, so that the pitch diameters of the planet gears may be selected such that the planet gears mesh with both the sun gear and the ring gear.

[0120] The pitch diameter of each planet gear 406, 408 can be determined using the following formula:

number

[0121] The pitch diameter of the paths of the planet gears 406, 408 can be determined using the following formula:

number

[0122] To calculate the constraints on the ring gear 402 and sun gear 404 that ensure a constant width of the path, equations for the angular motion of the parts can be derived.

[0123] First, consider the motion of the parts, with the ring fixed between the first and second positions. The sun gear rotates through an angle ω_s. As a result of this rotation, the planet gears rotate through an angle ω_P, and the carrier attached to the center of the planet gear rotates through an angle ω_c. The contact point between the planet gear and the sun gear, measured along the surface of the sun gear, moves a total of N_sω_s+N_sω_c, where N_s is the number of teeth on the sun gear. This is because the contact point moves due to both the rotation of the sun gear and the movement of the contact point with the planet gear due to the orbit of the planet gear.

[0124] The contact point between the planet gear and the sun gear, measured along the surface of the planet gear, moves a total of N_Pω_P-N_Pω_C, where N_P is the number of teeth on the planet gear, because the contact point with the sun gear changes as the planet gear rotates.

[0125] Since the distance of movement of the contact points of the sun gear and planet gears must be the same, the following equation can be derived:

number

[0126] Similarly, if we consider only the movement of the ring gear and planet gears while keeping the sun gear stationary, we can derive the following equation:

number

[0127] Rearranging the second equation, we can express N_Pω_P in terms of other variables. Substituting this into the first equation gives us:

number

[0128] This can be transformed into the following:

number

[0129] If the ring gear is considered fixed, the above equation further simplifies to:

number

[0130] Note that the number of gear teeth is directly proportional to the gear's pitch diameter, which is proportional to the length L of the orbital path.

[0131] As mentioned above, the profiles of the sun gear and ring gear are usually expressed by the following equations:

number

[0132] In order for the maximum and minimum values ​​of the ring gear 402 and sun gear 404 to coincide during rotation, the sun gear must rotate by ω_s=1 / f_s+1 / f_r as the planet gear moves from one maximum value of the ring gear to the next, e.g., as the planet gear (or equivalent carrier) moves 1 / f_r along its orbital path.

[0133] Substituting these two conditions into the equation for ω_c gives us:

number

[0134] This formula can be further transformed as follows:

number

[0135] As mentioned above, N is proportional to P (the pitch circle diameter, i.e., the orbital path length). Therefore, this equation can also be rewritten as:

number

[0136] For any choice of f for the ring and sun gears, the above formula can be used to determine their diameters so that the planet gears can travel in a constant width path. Using a constant width path ensures that the planet gears do not compress during the cycle and can mesh with the sun and ring gears at every point along their path.

[0137] By transforming the above equation, the following equation is obtained:

number

[0138] Thus, given a selected diameter of the sun gear 404 and a selected ratio of the wave frequencies of the ring gear and the sun gear 402, an appropriate diameter for the ring gear can be determined.

[0139] Next, regarding the length, the perimeter (or length of the parametric curve) l of each gear can be determined as follows:

number

[0140] Similarly, this length is determined as follows:

number

[0141] As can be seen from this formula, when f=0 (for example, there is no peak and the sun gear and ring gear are circular), the perimeter of each gear is simply the circumferential length

number

[0142] The parametric equation used to determine the length of each gear has three variables: pitch diameter P, wave frequency f, and wave amplitude a.

[0143] As discussed above, given the selected diameter of the sun gear 404 and the ratio of the selected wave frequencies of the ring gear and sun gear 402, it is possible to determine the appropriate diameter of the ring gear. It is noteworthy that this diameter is independent of the wave amplitude of either gear. Rather, this wave amplitude is independent of the relationship between the pitch diameter and the wave frequency. Therefore, the wave amplitude a can be adjusted independently. Increasing the value of a increases the change in radius as the planet gears 406, 408 move between the maximum and minimum values ​​of the ring gear 402 and sun gear 404. Therefore, increasing the value of a increases the pressure change that can be driven by the gearbox. However, increasing a also increases the resistance of the system. This tends to create a limit to the usable value of a (which depends, for example, on the materials used in the planet gearbox 400 and the mechanical properties associated with those materials).

[0144] To maintain a constant connection between the ring gear 402 and the sun gear 404, the planet gear gearbox 400 is typically arranged so that the width of the locus of the planet gears 406, 408 is approximately constant. To achieve this, the ring gear and sun gear are typically arranged so that the radial distance between the ring gear and the sun gear is approximately constant. Thus, typically a_sun = a_ring.

[0145] Further constraints may apply due to the space available for the planet gears 406, 408, which must not exceed the space available within the ring gear 402 and sun gear 404. To ensure that sufficient space is available, the gearboxes are typically arranged as follows:

number

number

[0146] It will be appreciated that a fewer number of planet gears may be provided.

[0147] Given the input values ​​of the selected pitch diameter of the sun gear 404, the selected wave amplitude of the sun gear, and the selected wave frequency of the sun gear, the above equations can be used to determine the appropriate values ​​for the remaining components.

[0148] Example using the following input values: [Table 1]

[0149] The above formula can be satisfied using the following values: [Table 2]

[0150] In this example, f_ring=10, f_sun=8. Therefore, in order for the sun gear rotation to match the maximum value of the next ring gear, the sun gear 104 must rotate 2π / f_ring+2π / f_sun. With f_ring=10, f_sun=8, the sun gear rotation between the maximum values ​​is approximately 1.414 radians.

[0151] It will be understood that these values ​​are merely examples and that a variety of different values ​​can be selected to obtain the desired pumping power.

[0152] For example, Figure 6 shows a gearbox with ring and sun gears similar to those of Figures 4a and 4b (f_ring=10, f_sun=8). In the embodiment of Figure 5, the system consists of 18 planet gears.

[0153] Another embodiment of a gearbox according to the present disclosure is shown in FIG. 7, which shows a planet gear gearbox according to the present disclosure with values ​​f_ring=10 and f_sun=4.

[0154] Alternatives and fixes It will be understood that the invention has been described above by way of example only and modifications of detail may be made within the scope of the invention.

[0155] For example, a gearbox can have any number of planet gears, as long as they fit between the ring gear and the sun gear and do not touch each other. For example, a gearbox can have 1, 2, 4, or 8 planet gears.

[0156] In some embodiments, the gearbox includes a number of planet gears equal to or less than the order of rotational symmetry of the gearbox (e.g., the order of rotational symmetry of the sun gear 404 and ring gear 402 combination). For example, if the gearbox has rotational symmetry of order 2 (e.g., f_ring=10, f_sun=8), the gearbox can include one or two planet gears. If the system has rotational symmetry of order 4 (e.g., f_ring=16, f_sun=8), the gearbox can include one, two, three, or four planet gears. Such an embodiment ensures that all planet gears are positioned at points where the radial distance between the sun gear and the ring gear is equal to a constant value. This constant value is preferably the diameter of the planet gear.

[0157] Similarly, while the above example employs frequency values ​​f_ring=10 and f_sun=8, it will be appreciated that many other combinations of values ​​will also satisfy the above constraints. Similarly, while the sun and ring gears in the above example can be modeled with the parametric equations shown in Equation 1 and Equation 2, in other embodiments, these gears can be modeled with alternative parametric equations.

[0158] Similarly, although the detailed description has primarily discussed the use of circular planet gears, in alternative embodiments the planet gears may have non-circular profiles, for example the planet gears may have an elliptical profile, in which case either the sun gear or the ring gear may have a circular profile.

[0159] Generally, multiple gears have non-circular profiles, and more specifically, two of the ring gear 402, sun gear 404, and planet gears 406, 408 have non-circular profiles.

[0160] The piston can be connected to the center of the planet gear via a linkage. Similarly, the piston can be attached to a point other than the center of the planet gear. For example, if the planet gear is elliptical, the piston can be attached to the focus of the ellipse.

[0161] Although the detailed description has primarily discussed an embodiment in which the sun gear 404 is driven, the ring gear 402, planet gears 406, 408, and / or carrier can be driven instead of or in addition to driving the sun gear. Also, any one of the sun gear, ring gear, and carrier can be fixed, or none of the gears can be fixed.

[0162] Typically, the planet gear gearbox 400 and / or pump includes and / or is associated with a control unit that is arranged to drive one or more gears of the gearbox (e.g., the sun gear 402) according to a desired pumping power. In this regard, the pumping power is typically a function of the torque supplied to the gearbox and / or the speed of movement of the planet gears 406, 408.

[0163] Although the above example discloses a single carrier, in other embodiments there may be multiple carriers, each associated with a respective subset of planet gears.

[0164] The pistons may be integral with or separate from the carrier, and may be attached (directly or indirectly) to one or more of the planet gears, ring gear, carrier, or sun gear.

[0165] In some embodiments, the piston has one end connected to the center of the sun gear and the other end connected to the center of the planet gears, hi some embodiments, the piston has one end connected to the center of the sun gear and the other end connected to the carrier.

[0166] In some embodiments, each planet gear is associated with a corresponding piston, and in some embodiments, each planet gear is associated with a corresponding plurality (e.g., a pair) of pistons.

[0167] In some embodiments, each piston may have a single opening to the fluid reservoir, and in some embodiments, each piston may have a connection to each of the fluid reservoirs and a fluid outlet.

[0168] Pumps can be used in a variety of applications. For example, heat pumps use the compression and expansion of a working fluid at different times in the pump cycle to capture thermal energy from the surroundings at one point in the cycle and release it at another. This can be used to cool or heat a device, depending on the pump's configuration.

[0169] Pumps are also used to maintain pressure within a vessel. For example, a pump can be used to raise or lower the pressure in a chamber to a desired level. This has applications in devices such as scanning electron microscopes, where the pressure in the operating chamber must be kept low, and in simple devices such as bicycle tires.

[0170] Another use for pumps is to transport fluids. For example, pumps are used in plastics processing to transport molten plastic from melting furnaces. Pumps are also used to transport water in and out of ships and to move coolants in equipment such as automobile engines.

[0171] Hydraulics generally refers to the use of fluid power to perform work. However, the operating principles of hydraulic pumps also generally apply to pneumatic pumps, which use compressible gas as the working fluid. The PlanetGear gearbox 400 disclosed herein can be used in combination with hydraulic pumps, pneumatic pumps, or other types of pumps.

Claims

1. 1. A gearbox for a pump, the gearbox comprising: Ring gear and Sungia and one or more planet gears disposed between the ring gear and the sun gear, the planet gears arranged to move along a continuous path around the sun gear; The gearbox, wherein the ring gear, the sun gear, and the planet gears are arranged such that a radius of the path changes as the planet gears move along the path.

2. 2. The gearbox of claim 1, comprising a piston associated with at least one planet gear such that an amount of compression of the piston varies as the planet gear moves along the path.

3. 3. The gearbox of claim 2, wherein the second end of the piston is associated with a further component of the gearbox such that the first end of the piston moves relative to the second end of the piston as the planet gear moves along the path.

4. 4. The method of claim 3, wherein the piston is positioned such that the first end of the piston moves toward and / or away from the second end of the piston as the planet gear moves along the path.

5. the second end of the piston the sun gear; The ring gear; Yet another Planet Gear, 5. A gearbox according to claim 3 or 4, connected to one or more of the carrier of the gearbox.

6. 6. A gearbox as claimed in any preceding claim, comprising a plurality of pistons, each piston being associated with a different planet gear.

7. 7. A gearbox according to claim 1, wherein at least two of the ring gear, the sun gear and the one or more planet gears have non-circular profiles.

8. 8. The gearbox of claim 7, wherein the sun gear and the ring gear each have a non-circular profile, and preferably the sun gear and the ring gear have the same non-circular profile.

9. the sun gear has a profile comprising a sine wave superimposed on an ellipse, preferably a sine wave superimposed on a circle, and / or A gearbox according to any preceding claim, wherein the ring gear comprises a profile comprising a sine wave superimposed on an ellipse, preferably a sine wave superimposed on a circle.

10. 10. A gearbox according to any one of claims 1 to 9, wherein the profile of the sun gear and / or the profile of the ring gear, preferably the pitch diameter of each of the sun gear and the ring gear, is defined by formula (1). [Equation 1] (In the formula, t is a parametric variable that takes values ​​from 0 to 2π; r is the radius of the gear at some value of t; P is the average diameter of the gear; a is the amplitude of the wave, f is the wave frequency.)

11. 11. A gearbox according to any preceding claim, wherein the ring gear has a different minimum number of valleys and / or a different maximum number of peaks than the sun gear.

12. The gearbox of claim 11 , wherein the ring gear has a greater minimum number of valleys and / or a greater maximum number of peaks than the sun gear.

13. 13. A gearbox according to any preceding claim, wherein the mean diameters and wave numbers of the sun gear and the ring gear are linked by equation (2). [Equation 2] (In the formula, P ｓｕｎ is the average diameter of the sun gear, P ｒｉｎｇ is the average diameter of the ring gear, f ｓｕｎ is the wave frequency of the sun gear, f ｒｉｎｇ is the wave frequency of the ring gear.)

14. A gearbox according to any preceding claim, comprising a plurality of planet gears, preferably comprising at least one pair of planet gears, and more preferably comprising multiple pairs of planet gears.

15. 15. A gearbox according to any preceding claim, comprising a number of planet gears equal to the order of rotational symmetry of the gearbox, preferably the order of rotational symmetry of the sun gear and ring gear combined.

16. 16. A gearbox according to any preceding claim, wherein the planet gears are arranged symmetrically about the centre of rotation of the gearbox.

17. the ring gear is rotationally symmetrical; and / or A gearbox according to any preceding claim, wherein the sun gear is rotationally symmetric.

18. A gearbox according to any preceding claim, wherein the width of the path is substantially constant.

19. 19. A gearbox according to any preceding claim, wherein the sun gear, ring gear and planet gears are arranged such that the radial distance between the sun gear and the ring gear at each contact point of the planet gears remains constant as the planet gears move along the path.

20. 20. A gearbox as claimed in any preceding claim, wherein one or more of the ring gear and sun gear are arranged to remain stationary as the planet gears move along the path.

21. 20. A gearbox according to any preceding claim, wherein each of the sun gear and ring gear is arranged to rotate as the planet gears move along the path.

22. the sun gear; The ring gear; one or more of said planet gears; a carrier associated with one or more of said planet gears; a motor for driving one or more of the movements of A gearbox according to any preceding claim, wherein the motor is preferably arranged to operate in response to a predetermined pumping force.

23. the sun gear has one or more minimum root points, the radius of the sun gear at the minimum root points being less than the average radius of the sun gear; and / or 23. A gearbox according to any preceding claim, wherein the sun gear comprises one or more crest points, the radius of the sun gear at the crest points being greater than the average radius of the sun gear.

24. the ring gear has one or more minimum valley points, the radius of the ring gear at the minimum valley points being less than the average radius of the ring gear; and / or 24. A gearbox according to any preceding claim, wherein the ring gear comprises one or more crest points, the radius of the ring gear at the crest points being greater than the average radius of the ring gear.

25. The change in amplitude of the minimum valley point of the sun gear is equal to the change in amplitude of the maximum crest point of the sun gear; and / or 25. A gearbox according to any preceding claim, wherein the change in amplitude of the minimum root point of the ring gear is equal to the change in amplitude of the maximum crest point of the ring gear.

26. the change in amplitude of the minimum root point of the sun gear is equal to the change in amplitude of the maximum crest point of the ring gear; and / or 26. The method of claim 25, wherein the change in amplitude of the peak point of the sun gear is equal to the change in amplitude of the valley point of the ring gear.

27. The diameter of the sun gear is 100 mm or more, 200 mm or more, and / or 500 mm or more, and / or 27. A gearbox according to any preceding claim, wherein the gearbox is no greater than 1000mm, no greater than 800mm, and / or no greater than 500mm.

28. The diameter of the planet gear is 50 mm or more, 100 mm or more, and / or 200 mm or more, and / or 28. A gearbox according to any preceding claim, wherein the gearbox is 500mm or less, 400mm or less, and / or 300mm or less.

29. 29. A gearbox as claimed in any preceding claim, wherein one or more, preferably all, of the sun gear, ring gear and planet gears may be provided with a plurality of teeth, preferably the plurality of teeth being regularly arranged around the contour of the gear.

30. 30. A gearbox according to any preceding claim, comprising at least two planet gears, at least four planet gears, at least eight planet gears, and / or at least ten planet gears.

31. A pump comprising a gearbox according to any one of claims 1 to 30.

32. 32. The pump of claim 31, which is a radial pump and / or a radial hydraulic pump.

33. 31. A method of operating a gearbox according to any preceding claim, comprising driving one or more of the sun gear, the ring gear and one or more of the planet gears.

34. 34. The method of claim 33, comprising driving the gear in response to a predetermined pump force.

35. A computer program product comprising instructions which, when executed by a computing device, cause said computing device to perform the method of claim 33 or 34.

36. 36. A method of manufacturing a gearbox and / or pump according to any preceding claim.

37. 37. A kit of parts for a gearbox according to any preceding claim, comprising: The ring gear; the sun gear; one or more planet gears.

Images