System and method for valve clearance adjustment

Abstract

A device (260) for adjusting the valve clearance in a machine comprising a sealable housing (310) and a valve actuator (210, 230) configured to operate a valve, the device comprising: a body (261) comprising a first portion (261A) and a second portion (261B); characterised in that the device further comprises: a valve actuator engaging surface (262) located at the first portion (261A) and configured to engage a portion of the valve actuator (210, 230) in use; an actuation means (263) located at the second portion (261B); wherein the body (261) is configured to be located through a sealed aperture (313) in the housing in use such that the first portion (261A) is located within the sealed housing (310) and the second portion(261B) is located outside of the sealed housing (310); wherein the device (260) is configured such that in use actuation of the actuation means (263) moves the valve actuator engaging surface (262) and in turn moves the valve actuator (210, 230) such that the valve clearance is adjusted.

Description

[0001] SYSTEM AND METHOD FOR VALVE CLEARANCE ADJUSTMENT

[0002] FIELD

[0003] The present invention relates to a system and method for valve clearance adjustment.

[0004] BACKGROUND

[0005] Poppet valves are a commonly used type of valve in, for example, internal combustion engines. Typically, poppet valves are used to control the timing and quantity of gas or vapour flow into a compression chamber. Poppet valves comprise a longitudinal stem portion which can be pushed by a rocker arm to open the valve. The valve may return to the closed position by a spring, or by another cam or active closure arrangement. The rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake / exhaust valve. As the name suggests, the rocker arm typically rocks near a centre portion of the rocker arm, with the pushrod pushing one side of the rocker arm up such that the other side of the rocker arm is pushed down onto the valve stem, thereby opening the valve. In this connection, the pushrod is typically pushed by a camshaft.

[0006] So-called valve clearance must be adjusted to maintain good performance and to avoid damage to the valve train. Valve clearance is a small gap between the rocker arm and the top of the valve stem. It is generally recommended to adjust the valve clearance after a certain period of service or if irregularities are noted, such as noise from the rocker arm. The main purpose of valve clearance is to provide a small gap such that expansion of components of the valve train such as the valve stem or pushrod, can be accommodated for so that the valve sits as intended in use and operates correctly at the working temperature. There are different ways to measure valve clearance which are not important here and which are well known in the art.

[0007] Valve clearance is typically adjusted by an adjustment bolt where the push rod connects to the rocker arm. When this adjustment bolt is adjusted, the effective length of the push rod is adjusted, which in turn moves the position of the rocker arm, thereby adjusting the valve clearance. Therefore, to adjust the valve clearance, the housing within which the valve, rocker arm, push rod etc. is located is opened to make the adjustment bolt accessible. Opening of the housing breaks the seal formed in the housing and lubricant contained therein must be drained to access the adjustment bolt. After the adjustment has been made, the lubricant must be replaced and the housing must be resealed. This process can lead to poor sealing in the housing. Additionally, lubricant in the housing needs to be replaced after the adjustment. Furthermore, the process is time consuming and requires training of personnel to perform the adjustment.

[0008] Patent document US1599260A discloses, in an internal combustion engine, the combination with a valve stem and an actuating arm for the same, of means for automatically adjusting said actuating arm and securing a substantially constant operating relation thereof to said stem, said means comprising a bearing mounted on the engine cylinder, an eccentric fulcrum journalled in said bearing and a rod connected with said fulcrum so as to turn it upon the movement of said bearing by the expansion and contraction of said cylinder. Patent document CN104948249A discloses a valve clearance adjusting mechanism, and belongs to the technical field of engines. A worm is driven by a drive motor, and the middle of the worm is meshed with a worm wheel. The upper end of a push rod is movably connected with an adjusting screw, the adjusting screw is in threaded connection with a longitudinal hole in the tail of a swing arm, and the lower end of the push rod makes contact with the surface of a camshaft through a tappet. One end of a swing arm shaft is fixedly connected with the worm wheel and a worm wheel shaft, the other end of the swing arm shaft is fixedly connected with worm wheel shaft outer edges and a worm wheel shaft, the middle of the swing arm shaft is movably connected with a transverse hole in the middle of the swing arm, the circle centers of the worm wheel, the two worm wheel shafts and the worm wheel shaft outer edges are located on the same axis, the axis is parallel to the longitudinal axis of the swing arm shaft, and the eccentric distance is formed between the two axes. The worm wheel shaft I and a worm wheel shaft sleeve are movably connected, and the worm wheel shaft and a worm wheel shaft sleeve are movably connected. The valve clearance adjusting mechanism can conduct automatic adjustment and allow valve clearances of an engine under various working conditions to be in an optimal state, the valve clearance adjusting mechanism can be applied to a valve mechanism composed of the camshaft, the swing arm and a valve, the original engine structure is slightly changed, and the economical efficiency and dynamic property of the engine can be effectively improved

[0009] Patent document US2772667A discloses a valve control for machines comprising a valve, a push rod, a rocking lever for transmitting the control motion from said push rod to said valve, means for supporting said rocking lever including an eccentric member, a lever connected with said eccentric member, a piston member connected with said lever, a rigidly arranged cylinder for said piston member, said piston member performing a forward and backward movement in said cylinder, a pressure means having a pressure medium, duct means from said pressure means to one side of said piston member for urging said piston member and said eccentric member by said pressure medium in the direction of compensation of play occurring in the direction of movement of said rocking lever, and means located on the other side of said piston for constantly urging said piston in the direction from the other side toward said one side.

[0010] Patent document US5018487A discloses a valve moving mechanism for a four-cycle engine of a vehicle which is operatively connected to a crank shaft of the engine and is adapted to move intake and exhaust valves. A cam shaft of the valve moving mechanism is operatively connected to the crank shaft and cam means including first, second and third cams is mounted upon the cam shaft, the second and third cams having outer profiles different from that of the first cam disposed between the second and third cams. Rocker arm means are mounted so as to be rotatable upon the rocker shaft which is rotatably mounted and includes first, second and third rocker arms driven in engagement with the first, second and third cams, respectively. The rocker arm means is operatively connected to the intake and exhaust valves, the first, second and third rocker arms having supporting bases mounted upon the rocker shaft. Bush means are mounted upon the rocker shaft so as to be selectively in engagement with the first, second and third rocker arms and has an axis eccentric with respect to the axis of the rocker shaft.

[0011] Patent document US4643141A discloses a mechanism for varying the lift, timing and duration of a valve member associated with an internal combustion engine comprising an elongated rocker arm having a first pivot end and a second end forming a valve member actuating free end, a pair of eccentric members forming a first eccentric member and a second eccentric member collectively defining a pivot axis within a circular opening for the rocker arm, the first eccentric member comprising a shaft having cylindrical end portions journaled for rotation about a shaft axis and an eccentric cylindrical portion located within the opening of the rocker arm, and the second eccentric member comprising a tubular sleeve rotatably supported on the surface of the shaft and concentric with a second eccentric axis spaced from the shaft axis, the second eccentric member rotating relative to the first eccentric member to provide a pivot axis for the rocker arm which is formed by the collective angular position of the first and second eccentric members.

[0012] Patent document US1967918A discloses a stem, an oscillatable rocker arm coacting therewith, an oil feed pipe having oil therein under pressure and on which the rocker arm is mounted for oscillation, one end of said arm approximating the stem, the opposite end of the arm having a bearing, an eccentric disposed in the bearing and having gear teeth, a push rod having a pin upon which the eccentric is mounted for rotation, the eccentric having its axis displaced radially relative to the axis of the bearing, the rocker arm being formed to provide a chamber intersecting said bearing, a rack disposed in said chamber and constituting a piston, the rack engaging the teeth on the eccentric, said chamber at its inner end having communication with the oil feed pipe, a check valve in the inner end of the chamber permitting the inflow of liquid into the chamber but preventing the outflow thereof, and a spring urging the rack outward.

[0013] Patent document WO2022152581 A1 discloses a roller shifter for a valvetrain which can comprise a shift bar assembly, a shift roller assembly, and a roller axle. The shift bar assembly can comprise a first and second limiter, a first and second spring, and a shift bar. The shift roller assembly can be mounted to slide on the shift bar in between the first spring and the second spring. The shift roller assembly can comprise a shift roller mount comprising a bushing connected to a roller coupling and a roller assembly comprising a shift roller. Roller axle can join the shift roller and the roller coupling. A valvetrain can further comprise a cam assembly configured to rotate around an axis. The cam assembly can comprise a rocker arm cam and a shift cam. The shift roller can be configured with the shift bar to selectively engage against or disengage from the shift cam.

[0014] Patent document GB782351A discloses an engine assembly having adjustable inlet valve gear coupled to the accelerator lever for varying the extent of opening of each inlet valve the arrangement being such that the adjustment of said inlet valve gear can be effected at will at any engine speed to control the supply of combustible mixture to the engine whereby the power of the engine is primarily controlled by adjustment of the inlet valve gear as distinct from adjustment of the carburettor throttle valve.

[0015] The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

[0016] The object is achieved through features, which are specified in the description below and in the claims that follow.

[0017] SUMMARY

[0018] According to a first aspect of the invention, there is provided a device for adjusting the valve clearance in a machine comprising a sealable housing and a valve actuator configured to operate a valve, the device comprising: a body comprising a first portion and a second portion; characterised in that the device further comprises: a valve actuator engaging surface located at the first portion and configured to engage a portion of the valve actuator in use; an actuation means located at the second portion; wherein the body is configured to be located through a sealed aperture in the housing in use such that the first portion is located within the sealed housing and the second portion is located outside of the sealed housing; wherein the device is configured such that in use actuation of the actuation means moves the valve actuator engaging surface and in turn moves the valve actuator such that the valve clearance is adjusted.

[0019] The body may be a rotatable shaft.

[0020] The body may be a screw configured to be received in a corresponding screw thread in the machine.

[0021] The body may comprise a first central axis around which the body is rotatable around in use. The valve actuator engaging surface may comprise a substantially cylindrical member comprising a second central axis, wherein the first and second central axes are eccentric.

[0022] The valve actuator engaging surface may comprise an arcuate outer surface configured to engage the valve actuator in use. The arcuate outer surface may comprise at least a first portion of a first radius and a second portion of a second radius, wherein the first and second radii are different.

[0023] The arcuate outer surface may comprise a plurality of portions of different radii.

[0024] The actuation means may be configured to allow manual rotation of the body.

[0025] The actuation means may be a socket configured to receive a key registered with the socket or a head portion configured to be turned by a user in use or a screw head configured to be engaged by a screwdriver.

[0026] The body may comprise a wedge configured such that translation of the body in the longitudinal direction causes translation of the wedge to move the valve actuator such that the valve clearance is adjusted.

[0027] The body may be translatable in use in a longitudinal direction of the body.

[0028] The second portion of the body may further comprise a position indicator.

[0029] According to a second aspect of the invention, there is provided a valve clearance adjustment system, comprising: the device according to the first aspect of the invention; a poppet valve comprising a valve stem; a sealable housing; and a valve actuator; wherein the valve actuator comprises a pivot point configured to allow the valve actuator to rotate and wherein the valve actuator is registered with the valve actuator engaging surface and is configured to operate the poppet valve by pressing of the valve actuator on the valve stem; and wherein the valve actuator and valve actuator engaging surface are configured such that in use actuation of the actuation means moves the valve actuator engaging surface and in turn the valve actuator such that the valve clearance is adjusted.

[0030] The valve actuator may comprise a push rod and a rocker arm. The valve actuator may further comprise a valve adjustment bolt. The pivot point may be a substantially circular central profile.

[0031] The valve actuator may be registered at the pivot point with the valve actuator engaging surface, such that in use the valve actuator can rotate around the pivot point and be moved by the valve actuator engaging surface at the pivot point to adjust the valve clearance.

[0032] According to a third aspect of the invention, there is provided a method arranging a valve clearance adjustment system comprising the steps of: providing a valve clearance adjustment system according to the second aspect of the invention; arranging the poppet valve stem such that the poppet valve stem can be moved by the valve actuator in use; arranging the valve actuator such that the valve actuator can rotate about the pivot point; aligning or engaging the valve actuator engaging surface with the valve actuator such that in use the valve actuator engaging surface can cause movement of the valve actuator to adjust the valve clearance.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The prior art and embodiments of the invention will now be described with reference to the following drawings, in which:

[0035] Fig. 1 shows a prior art poppet valve arrangement; and

[0036] Fig. 2 shows a valve clearance adjustment system.

[0037] For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

[0038] DETAILED DESCRIPTION

[0039] Figure 1 shows a prior art poppet valve arrangement 100 comprising a push rod 110, a valve adjustment bolt 120, a rocker arm 130 and a poppet valve 140 comprising a valve stem 141 . The push rod 110 is actuated by a camshaft 150 such that the pushrod 110 moves up and down to cause rotation of the rocker arm 130 and therefore opening and closing of the valve 140. It will be understood that the rocker arm 130 is arranged to rotate such that as the push rod 110 pushes the rocker arm 130 upwards on a first side 131 of the rocker arm 130, a downwards motion results on a second side 132 from the rocker arm 130 which is applied to the valve stem 141 , thereby pushing the valve 140 to an open position. The rocker arm 130 is arranged to rotate on a cylindrical shaft 160 and in some prior art examples there may be a wear bearing located between the cylindrical shaft 160 and the rocker arm 130.

[0040] Figure 2 shows an exploded view of a valve clearance adjustment system 200 to be assembled with a compressor 300. The valve clearance adjustment system 200 comprises a push rod 210, a valve adjustment bolt 220 and a rocker arm 230 configured to operate a poppet valve (not shown) comprising a valve stem. Together the push rod 210 and rocker arm 230 together form a valve actuator since they together allow actuation of the valve. The valve adjustment bolt 220 is optional and provides another method of adjusting the valve clearance in addition to the presently described invention. It will therefore be understood that in some examples (such as the example shown herein) this additional known method may also be incorporated, however in other examples this may be excluded. The push rod 210 is actuated by a camshaft such that the push rod 210 moves up and down to cause rotation of the rocker arm 230 and therefore opening and closing of the valve. The rocker arm 230 is arranged to rotate such that as the push rod 210 pushes the rocker arm 230 upwards on a first side 231 of the rocker arm 230, a downwards motion results on a second side 232 from the rocker arm 230 which is applied to the valve stem, thereby pushing the valve to an open position. The valve clearance adjustment system 200 further comprises a valve clearance adjustment device 260. The rocker arm 230 is arranged to rotate on a portion of the valve clearance adjustment device 260 as will now be explained. The valve clearance adjustment device 260 comprises an elongate body

[0041] 261 comprising a first portion 261 A and a second portion 261 B. In some examples the first portion 261 A and the second portion 261 B may be unitarily formed and / or non-detachable from each other. In other examples the first portion 261 A and the second portion 261 B may be detachable from each other. It will become apparent that the exact size of the first portion 261 A and second portion 261 B or the proportion of the elongate body 261 comprising the first portion 261 A relative to the second portion 261 B is not important. In this regard, the first portion 261 A may for example span a half of the elongate body 261 , with the second portion 261 B spanning the other half of the elongate body 261 . In another example, the first portion 261 A may span a quarter of the elongate body 261 , with the second portion 261 B spanning three quarters of the elongate body 261 . In yet another example, the first portion 261 A may span three quarters of the elongate body 261 , with the second portion 261 B spanning a quarter of the elongate body 261.

[0042] Still referring to Figure 2, it can be seen that the elongate body 261 comprises a rocker arm engaging surface 262 located in the first portion 261 A. The rocker arm engaging surface 262 is configured to engage the rocker arm 230 in use, as will be explained later.

[0043] Furthermore, the elongate body 261 comprises a socket 263 configured to receive a key registered with the socket 263 in use. The socket 263 is arranged on an end of the elongate body 261 such that the socket 263 can be turned by a user in use to turn the elongate body 261 to adjust the valve clearance, as will be explained later.

[0044] The elongate body 261 further comprises a position indicator 264 in the form of a slot configured with markings (not shown) to indicate the exact rotation of the elongate body 261 is use. It will be easily understood that a myriad of alternative positional indicators may be utilised instead of a marked slot as in the present example.

[0045] The elongate body 261 further comprises a first circular locating feature 265 and a second circular locating feature 266. The first and second circular locating features 265, 266 are for locating the elongate body 261 in a position where it can be rotated.

[0046] Still referring to Figure 2, the assembly of the valve clearance adjustment system 200 inside the compressor 300 is now explained. The compressor 300 comprises a sealed housing 310 arranged to be substantially filled with lubricating fluid (not shown) such as but not limited to oil. The housing 310 has a head cover 311 and a side cover 312. The head cover 311 and side cover 312 are configured to seal against the housing 310 in use. The head cover 311 is primarily to allow access to the internal components of the valve assembly, thereby allowing access to the valve assembly such that the valve assembly inside the housing 310 can be maintained when required.

[0047] To assemble the valve clearance adjustment system 200 inside the compressor 300, the rocker arm 230 is assembled with the push rod 210 to form a valve actuator. The rocker arm engaging surface 262 is therefore a valve actuator engaging surface. The optional valve adjustment bolt 220 as is known in the prior art may be provided in some examples. The rocker arm 230 comprises a substantially circular internal profile 233 which is configured to allow both rotation of the rocker arm 230 about the circular internal profile 233 and adjustment of the valve clearance. It will be understood that in alternative examples the substantially circular internal profile 233 may be replaced by a noncircular shape such as a, or part of, an oval shape, as a non-limiting example. In some examples, the circular or substantially circular internal profile 233 may be provided by a bearing component. The rocker arm 230 is located inside the housing 310 in line with an aperture 313 in the housing 310. The elongate body 261 is then inserted through the aperture 313 until the first circular locating feature 265 is received in a corresponding circular blind hole 314 which ensures the lateral movement of the elongate body 261 into the housing 310 is arrested but that the elongate body 261 is still free to rotate when required. At the same time, the second circular locating feature 266 is received in the aperture 313. The rocker arm engaging surface 262 is located inside the substantially circular internal profile 233. The rocker arm engaging surface 262 in the presently described example has a circular profile with a central axis. The rocker arm engaging surface 262 is configured on the elongate body 261 such that the central axis of the circular profile of the rocker arm engaging surface 262 is eccentric with the central axis of the elongate body 261 . This provides an arrangement whereby as the elongate body 261 is rotated, for example by manual rotation of the socket 263, the eccentrically arranged rocker arm engaging surface 262 will move the rocker arm 230. Movement of the rocker arm 230 either upwards or downwards causes adjustment of the valve clearance. It is essential that the rocker arm engaging surface 262 is located on the first portion 261 A of the elongate body 261 and the first portion 261A is configured to be located inside of the housing 310 in use. In this connection, the elongate body 261 is configured to connect the rocker arm engaging surface 262 inside the housing 310 with the socket 263 outside of the housing 310, such that in use the valve clearance can be adjusted without opening the housing 310.

[0048] The first circular locating feature 265 and second circular locating feature 266 remain located in the circular blind hole 314 and aperture 313 while the elongate body 261 is rotated. In this connection, rotation of the elongate body 261 does not dislocate the elongate body 261 from the desired location. The rocker arm engaging surface 262 is rotated and due to the eccentricity of the rocker arm engaging surface 262 relative to the elongate body 261 , the rocker arm engaging surface 262 moves the rocker arm 230 to adjust the valve clearance.

[0049] In the presently described example shown in Figure 2, the rocker arm engaging surface 262 is substantially circular. It will be understood that in the presently described example an eccentric circular shape provides adjustment of the rocker arm 230. The rocker arm engaging surface 262 may be oval or another shape in some other examples and in such cases the rocker arm engaging surface 262 need not be eccentric relative to the elongate body 261 because as another non-circular shape located on the elongate body 261 is rotated, the shape may move the rocker arm 230 by exposing the circular internal profile 233 to a rotating non-circular shape. For example, an oval shape rotated inside the circular internal profile 233 would serve to lift and lower the rocker arm 230, without the oval being provided eccentrically on the elongate body 261 .

[0050] The shape of the rocker arm engaging surface 262 may be modified to adjust the rate at which the valve clearance is adjusted. For example, if the rocker arm engaging surface 262 is provided as an oval shape, the rocker arm 230 will be lifted different heights for the same amount of rotation as the oval rotates, depending on which part of the oval is exposed to the circular internal profile 233.

[0051] It will also be appreciated that in some examples the circular internal profile 233 may also be another non-circular shape. For example, in some other examples not shown in the Figures, the internal profile may be oval or another shape and the rocker arm engaging surface 262 may be oval or circular or another shape. It will be understood that when circular or non-circular rocker arm engaging surfaces 262 are used as described herein, there are a myriad of possible combinations of shapes of rocker arm engaging surfaces 262 registered with circular or non-circular internal profiles 233 such that rotation of the elongate body 261 causes movement upwards or downwards of the rocker arm 230.

[0052] By locating the first portion 261 A within the sealed housing 310 and the second portion 261 B out of the sealed housing 310, the valve clearance can be adjusted as above without opening the sealed housing 310. In some examples, the elongate body 261 is a rotatable shaft.

[0053] In some examples not shown, the elongate body 261 may be replaced by a screw configured to be received in a corresponding screw thread. In this connection, the screw thread may retain the screw and stop movement of the screw in a similar manner to the above-described circular blind hole 314 and aperture 313. In this example, the screw may be provided with an eccentrically arranged rocker arm engaging surface 262 such that as the screw is driven into or out of the screw thread, the rocker arm engaging surface 262 can move the rocker arm 230 upwards or downwards in the same manner as described above.

[0054] Alternatively, in some other examples not shown in the Figures, the elongate body 261 may be replaced by a wedge which may be configured to be moveable into / out of the housing 310 to adjust the position of the rocker arm 230.

[0055] As previously discussed, the housing 310 has a head cover 311 and a side cover 312. The head cover 311 and side cover 312 are configured to seal against the housing 310 in use. The side cover 312 is configured to cover the socket 263 and position indicator 264 and may be removed to provide access to the socket 263 and position indicator 264 when required. This protects the socket 263 and position indicator 264 from wear or from accidental adjustment but makes it easy to access the socket 263 and position indicator 264 when valve clearance adjustment is required. The side cover 312 also provides a secondary seal to the housing 310.

[0056] In this connection, a first seal 312A in the form of an o-ring is provided to seal the elongate body 261 in the aperture 313. This may be provided in the form of any known seal type suitable for sealing a static shaft, or a static shaft which may be rotated slightly and infrequently, i.e. whenever valve clearance adjustment is required. In this connection, if the first seal were to fail, the lubricating fluid inside the housing 310 would leak out to the outside of the housing 310. By providing a side cover 312, any leaking lubricating fluid will be caught within the side cover, as the side cover 312 is sealed against the outside of the housing 310 around the aperture 313. Furthermore, this allows the side cover 312 to be inspected for leaking lubricating fluid whenever the valve clearance is to be adjusted, or at regular intervals. It would be more difficult to catch and monitor leaked lubricating fluid if the lubricating fluid was allowed to leak from the housing 310 and run down the housing 310 or flow to another nonrestricted location. In this connection, the provision of the side cover 312 allows the seal integrity at the aperture 313 to be monitored.

[0057] The invention may find particular utility in the field of heat pumps. More particularly, in the field of high-temperature heat pumps. However, it will be understood that the invention may be applied in many different applications including many different types of machines.

Claims

CLAIMS1 . A device (260) for adjusting the valve clearance in a machine comprising a sealable housing (310) and a valve actuator (210, 230) configured to operate a valve, the device comprising: a body (261 ) comprising a first portion (261 A) and a second portion (261 B); characterised in that the device further comprises: a valve actuator engaging surface (262) located at the first portion(261 A) and configured to engage a portion of the valve actuator (210, 230) in use; an actuation means (263) located at the second portion (261 B); wherein the body (261 ) is configured to be located through a sealed aperture (313) in the housing in use such that the first portion (261 A) is located within the sealed housing (310) and the second portion (261 B) is located outside of the sealed housing (310); wherein the device (260) is configured such that in use actuation of the actuation means (263) moves the valve actuator engaging surface (262) and in turn moves the valve actuator (210, 230) such that the valve clearance is adjusted.

2. The device (260) according to claim 1 , wherein the body (261 ) is a rotatable shaft.

3. The device (260) according to claim 1 or 2, wherein the body (261 ) is a screw configured to be received in a corresponding screw thread in the machine.

4. The device (260) according to any preceding claim, wherein the body comprises a first central axis around which the body is rotatable around in use and the valve actuator engaging surface (262) comprises a substantially cylindrical member comprising a second central axis, wherein the first and second central axes are eccentric.

5. The device (260) according to any preceding claim, wherein the valve actuator engaging surface (262) comprises an arcuate outer surface configured to engage the valve actuator (210, 230) in use, wherein the arcuate outer surface comprises at least a first portion of a first radius and a second portion of a second radius, wherein the first and second radii are different.

6. The device (260) according to claim 5, wherein the arcuate outer surface comprises a plurality of portions of different radii.

7. The device (260) according to any preceding claim, wherein the actuation means is configured to allow manual rotation of the body.

8. The device (260) according to any preceding claim, wherein the actuation means (263) is a socket configured to receive a key registered with the socket or a head portion configured to be turned by a user in use or a screw head configured to be engaged by a screwdriver.

9. The device (260) according to claim 1 , wherein the body (261 ) comprises a wedge configured such that translation of the body (261 ) in the longitudinal direction causes translation of the wedge to move the valve actuator (210, 230) such that the valve clearance is adjusted.

10. The device (260) according to any preceding claim, wherein the body (261 ) is translatable in use in a longitudinal direction of the body.11 .The device (260) according to any preceding claim, wherein the second portion (261 B) of the body (261) further comprises a position indicator.

12. A valve clearance adjustment system (200), comprising: the device (260) according to any of claims 1 to 11 ; a poppet valve comprising a valve stem; a sealable housing (310); and a valve actuator;wherein the valve actuator (210, 230) comprises a pivot point configured to allow the valve actuator (210, 230) to rotate and wherein the valve actuator (210, 230) is registered with the valve actuator engaging surface (262) and is configured to operate the poppet valve by pressing of the valve actuator (210, 230) on the valve stem; and wherein the valve actuator (210, 230) and valve actuator engaging surface (262) are configured such that in use actuation of the actuation means moves the valve actuator engaging surface (262) and in turn the valve actuator (210, 230) such that the valve clearance is adjusted.

13. The valve clearance adjustment system (200) of claim 12, wherein the valve actuator (210, 230) comprises a push rod (210) and a rocker arm (230).

14. The valve clearance adjustment system (200) of claim 13, wherein the valve actuator (210, 230) further comprises a valve adjustment bolt (220).

15. The valve clearance adjustment system (200) of claim 12, wherein the pivot point is a substantially circular central profile.

16. The valve clearance adjustment system (200) of any of claims 12 to 15, wherein the valve actuator (210, 230) is registered at the pivot point with the valve actuator engaging surface (262), such that in use the valve actuator (210, 230) can rotate around the pivot point and be moved by the valveactuator engaging surface (262) at the pivot point to adjust the valve clearance.

17. A method arranging a valve clearance adjustment system (200) comprising the steps of: providing a valve clearance adjustment system (200) according to any of claims 12 to 16; arranging the poppet valve stem such that the poppet valve stem can be moved by the valve actuator (210, 230) in use; arranging the valve actuator (210, 230) such that the valve actuator (210, 230) can rotate about the pivot point; aligning or engaging the valve actuator engaging surface (262) with the valve actuator (210, 230) such that in use the valve actuator engaging surface (262) can cause movement of the valve actuator (210, 230) to adjust the valve clearance.

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