WO2011110904A1

WO2011110904A1 - Adjustment mechanism for a foot plate assembly

Info

Publication number: WO2011110904A1
Application number: PCT/IB2010/055924
Authority: WO
Inventors: Philip Towle
Original assignee: Philip Towle
Priority date: 2010-03-11
Filing date: 2010-12-17
Publication date: 2011-09-15

Abstract

An adjustment mechanism (16) for a foot plate assembly (2) comprising: a foot plate (4) mounted on a foot plate support (6); at least one adjustment channel (10); engagement means (12), a first half (12a) of which is associated with the foot plate support (6) and a second half (12b) of which is associated with the adjustment channel (10); a releasable locking means (30) moveable between: i) a locked position in which the first and second halves of the engagement means (12a, 12b) are engaged, such that the foot plate support (6) is fixed in position relative to the adjustment channel (10); and ii) an open position in which the two halves of the engagement means (12a, 12b) can be moved relative to one another to adjust the position of the foot plate (4) relative to the adjustment channel (10); and a biasing means (26) arranged to bias the first half of the engagement means (12a) when the locking means (30) is in the open position.

Description

Title of Invention: ADJUSTMENT MECHANISM FOR A FOOT

PLATE ASSEMBLY

Description

[1] The present invention relates to an adjustment mechanism for a foot plate assembly, particularly, but not exclusively, to an adjustment mechanism for a foot plate assembly in a rowing boat. The term 'rowing boat', as used herein, refers to any craft which is manually powered using oars or paddles and includes rowing boats, sculling boats and any other craft in which a user requires to secure their feet. It is envisaged that the present invention could also be used in any situation where a foot plate is used to secure a user's feet, for example, on a stationary rowing machine.

[2] Participants in rowing activity need to be able to securely locate their feet within the boat in order to provide a working platform to provide input effort to the rowing stroke and thereby propel the boat. Typically a pair of shoes is screwed into a plate, known as a footplate; the footplate is attached to a frame known as a stretcher. In order to accommodate participants of different sizes, boats are fitted with an adjustable mechanism where the stretcher may be moved to different positions in the boat.

Commonly the mechanism consists of a toothed slide channel attached to the boat, a T- bolt which is able to slide within the channel, and a thumbscrew to clamp the assembly in position. The teeth in the slide channel engage matching teeth in the end fittings in the stretcher, allowing the assembly to lock in place when the thumbscrews are tightened.

[3] For the participant to adjust the foot plate to the correct position the stretcher

assembly needs to be released by unscrewing the thumbscrews locating the assembly. The assembly is then lifted and moved longitudinally within the boat to a new position where the assembly is re-tightened.

[4] Known issues with this type of arrangement include participants having difficulty with unscrewing the thumbscrews when in the boat, difficulty in lifting and sliding the mechanism, and the inability to slide the assembly with the feet in place in the boat. Consequently this leads to poorly adjusted boats; it is also common for younger athletes to force the adjustment leading to damage to the equipment.

[5] The present invention sets out to overcome the problems of the prior art, or at least to provide an alternative adjustment mechanism for a foot plate assembly.

[6] According to a first aspect of the present invention there is provided an adjustment mechanism for a foot plate assembly comprising: a foot plate mounted on a foot plate support; at least one adjustment channel; engagement means, a first half of which is as- sociated with the foot plate support and a second half of which is associated with the adjustment channel; a releasable locking means moveable between: i) a locked position in which the first and second halves of the engagement means are engaged, such that the foot plate support is fixed in position relative to the adjustment channel; and ii) an open position in which the two halves of the engagement means can be moved relative to one another to adjust the position of the foot plate relative to the adjustment channel; and a biasing means arranged to bias the first half of the engagement means when the locking means is in the open position.

[7] In an embodiment of the invention the biasing means is arranged to bias the first and second halves of the engagement means apart when the locking means is in the open position.

[8] The adjustment mechanism offers a number of advantages over the prior art systems.

When the locking means is in its open position the biasing means overcomes the downward pressure exerted by the mass of the foot plate and causes a positive separation between the two halves of the engagement means. This enables a user to smoothly slide the foot plate support to its desired position without the cooperating members of the engagement means catching. In the prior art systems the weight of the foot plate caused the teeth of the engagement means to remain engaged even when the locking means was released. This resulted in difficulty for the user in adjusting the position of the foot plate as the teeth of the engagement means tended to 'catch' as the foot plate was moved.

[9] The separation of the two halves of the engagement means also makes it much easier for a user to adjust the position of the foot plate with their feet still in the shoes. This ensures a much more accurate positioning of the foot plate. In the prior art systems it was not generally possible to move the foot plate with the feet in position, with the result that the foot plate was often incorrectly positioned.

[10] A further advantage of the present invention is that it can be retro-fitted into existing systems. While it is intended that the adjustment mechanism will be incorporated into new rowing boats it is appreciated that there are a vast number of rowing boats already in existence which are fitted with prior art adjustment mechanisms. The present system can be used with existing adjustment channels already provided on boats, and the foot plate supports, or stretchers, can be easily adapted to incorporate the present invention.

[11] In an embodiment of the invention the biasing means is a spring. In an embodiment of the invention the spring is a flat spring. In an embodiment of the invention the spring is coil spring.

[12] In an embodiment of the invention the spring is an elongate flat spring with end

portions which contact the base of the adjustment channel and are responsible for exerting the biasing force, and a central portion which is not in contact with the base of the adjustment channel, the arrangement being such that when one of the end portions extends beyond the end of the adjustment channel the biasing force is decreased or removed and the two halves of the engagement means come together to prevent the foot plate support from further movement. This is a useful feature in preventing the foot plate support from disengaging from the adjustment channel, which can be an awkward problem. If the foot plate support is moved out of its intended range then the leading edge of the spring will 'drop' out of the adjustment channel and the central portion of the spring will contact the base of the adjustment channel. This causes the foot plate support to move towards the adjustment channel and enables the two halves of the engagement means to come together to prevent further movement of the foot plate support.

[13] In an embodiment of the invention the biasing means is arranged to bias the first half of the engagement means into an indexing engagement with the second half of the engagement means, wherein the biasing force is sufficient to provide an indexing engagement but may be easily overcome to enable the first and second halves of the engagement means to move relative to one another in a controlled manner.

[14] The term 'indexing engagement' refers to an engagement in which the first half of the engagement means locates with a corresponding feature of the second half of the engagement means to provide a user with an indication that it is in the correct position, i.e. one in which it can be locked. The biasing force necessary to achieve the 'indexing engagement' will typically be fairly low such that it can be easily overcome to enable the user to adjust the footplate to a new position in a controlled manner. The benefit of the 'indexing engagement' is that it provides positive feedback to the user as the footplate is moved.

[15] In an embodiment of the invention the releasable locking means is a lever operated mechanism. In an embodiment of the invention the lever operated mechanism is an over-centre lever arrangement. This offers a number of advantages over the prior art thumbscrew, which could be difficult for users to operate, especially with cold hands. The lever enables adjustment to be made using finger pressure only and adjustment can easily be made in the boat with feet in position. It was quite common for users to carry their own tools in the boat for the purposes of adjusting the thumbscrews, but this is not necessary to operate the lever. The lever also offers a visual indication that the mechanism is locked as it is easy to see when the lever is in its closed position, unlike the thumbscrew. The lever offers a positive locking and avoids the danger of overtightening.

[16] In an embodiment of the invention the releasable locking means is connected to the biasing means by a threaded pin and nut, which can be used to adjust the locking mechanism. By tightening the nut a user can adjust the force applied by the locking means when it is in the locked position.

[17] In an embodiment of the invention the threaded pin is provided with an anti-rotation feature. In an embodiment of the invention the threaded pin passes through an aperture in the biasing means, the shape of the aperture being selected to prohibit rotation of the threaded pin. For example, the aperture in the biasing means may be square and at least a portion of the body of the threaded pin may have a square profile. If the size of the square profile on the pin closely corresponds to the size of the aperture then this will prevent rotation of the pin. It will be readily appreciated that other shapes of aperture and pin may be utilised in order to achieve the same result, for example triangular, pentagonal or hexagonal.

[18] In an embodiment of the invention the engagement means comprises a toothed arrangement. In an embodiment of the invention the adjustment channel comprises an external toothed arrangement which is configured to engage with a complementary feature on the foot plate support.

[19] In an embodiment of the invention the adjustment channel comprises an internal toothed arrangement which is configured to engage with a complementary feature on the foot plate support.

[20] In an embodiment of the invention the adjustment mechanism comprises three adjustment channels and three engagement means, such that the foot plate support engages at three locations, each engagement means having its own releasable locking means and biasing means.

[21] The invention described above relates to the longitudinal positioning of the foot plate within the rowing boat. However, it has been appreciated by the present inventor that it may also be desirable to alter the vertical position of the foot plate to suit different users. In an embodiment of the invention the foot plate is adjustably mounted on the foot plate support.

[22] In an embodiment of the invention the foot plate support comprises: at least one foot plate adjustment channel; foot plate engagement means, a first half of which is associated with the foot plate and a second half of which is associated with the foot plate adjustment channel; a releasable locking means moveable between: i) a locked position in which the first and second halves of the foot plate engagement means are engaged, such that the foot plate is fixed in position on the foot plate adjustment channel; and ii) an open position in which the two halves of the foot plate engagement means can be spaced apart such that the foot plate may be moved along the foot plate adjustment channel to adjust its position relative to the foot plate support; and a biasing means arranged to bias the first and second halves of the foot plate engagement means apart when the locking means is in the open position.

[23] In an embodiment of the invention the foot plate comprises: at least one foot plate adjustment channel; foot plate engagement means, a first half of which is associated with the foot plate support and a second half of which is associated with the foot plate adjustment channel; a releasable locking means moveable between: i) a locked position in which the first and second halves of the foot plate engagement means are engaged, such that the foot plate is fixed in position on the foot plate support; and ii) an open position in which the two halves of the foot plate engagement means can be moved relative to one another; and a biasing means arranged to bias the first half of the engagement means into an indexing engagement with the second half of the engagement means, wherein the biasing force is sufficient to provide an indexing engagement but may be easily overcome to enable the first and second halves of the engagement means to move relative to one another in a controlled manner.

[24] These embodiments of the invention enable the vertical position of the foot plate to be altered to suit the user. Although the term 'vertical' is used, in practice the adjustment takes place over an inclined plane of approximately 45 ⁰ to the horizontal; the precise angle depending on the installation and adjustability of the footplate support. The advantages offered by the biasing means are the same as those described above in relation to the longitudinal adjustment mechanism in terms of the smooth adjustment and improved operation.

[25] According to a second aspect of the present invention there is provided a releasable locking mechanism for use in an adjustment mechanism comprising: a locking member moveable between a locked position and an open position; and a biasing means associated with the locking member, wherein, in use, in the locked position the locking member acts against the biasing means and forces the first and second halves of the engagement means into engagement such that the foot plate support is fixed in position relative to the adjustment channel, and in the open position the biasing means acts on the first half of the engagement means such that the two halves of the engagement means can be moved relative to one another to adjust the position of the foot plate relative to the adjustment channel

[26] As discussed above, it is envisaged that existing rowing boats could be retro-fitted to implement the present invention. In this case the adjustment channel is already provided on the rowing boat and only the locking member and biasing means are supplied to enable a use to adapt a prior art system.

[27] According to a third aspect of the present invention there is provided an adjustment mechanism for a foot plate comprising: a foot plate; a foot plate support with at least one adjustment channel; engagement means, a first half of which is associated with the foot plate and a second half of which is associated with the adjustment channel; a releasable locking means moveable between: i) a locked position in which the first and second halves of the engagement means are engaged, such that the foot plate is fixed in position relative to the adjustment channel; and ii) an open position in which the two halves of the engagement means can be moved relative to one another to adjust the position of the foot plate relative to the adjustment channel; and

[28] a biasing means arranged to bias the first half of the engagement means when the locking means is in the open position.

[29] As discussed above, in addition to there being a need to alter the longitudinal

position of the foot plate in a rowing boat the present inventor has also appreciated that it would be desirable to be able to alter the vertical positioning of the foot plate. This is rendered possible by providing an adjustment mechanism to enable adjustment of the foot plate relative to the foot plate support or stretcher. The basic construction of the adjustment mechanism is the same as for the mechanism for adjusting longitudinal position described above and the benefits and additional advantageous features described above also apply to this aspect of the invention.

[30] An embodiment of the present invention will now be described, solely by way of example, with reference to the accompanying drawings, in which:

[31] Fig. 1 shows a perspective view of a foot plate assembly incorporating an adjustment mechanism according to the present invention;

[32] Fig. 2 shows a perspective view of an adjustment mechanism with the locking means in its open position;

[33] Fig. 3 shows an exploded view of the adjustment mechanism of Fig. 2;

[34] Fig. 4 shows a perspective view of the adjustment mechanism with the locking

means in its locked position;

[35] Fig. 5 shows an exploded perspective view of an alternative embodiment of an adjustment mechanism with the locking means in its open position; and

[36] Fig. 6 shows an exploded sectional view of the mechanism of Fig. 5.

[37] Referring firstly to Fig. 1, this shows a perspective view of a foot plate assembly 2 of the type which would be used in a rowing boat (not shown). The basic construction of the foot plate assembly 2 is well known and comprises a foot plate 4, mounted on a foot plate support 6. The foot plate support 6 is commonly referred to as a 'stretcher' and it may take the form of a frame which attaches the foot plate 4 to the boat. A pair of shoes 8 are screwed into the foot plate 4. Alternatively, the foot plate 4 may be provided with securing means for securing a user's feet to the foot plate 4.

[38] As discussed above, most rowing boats need to be capable of accommodating users of different sizes. In order to do this the foot plate support 6 is adjustably attached to the rowing boat, such that the position of the foot plate 6 can be altered to suit the size of the user. As shown in Fig. 1, three adjustment channels 10a, 10b, 10c are provided and the foot plate support 6 engages with each of the adjustment channels 10 in a sliding relationship, to permit the position of the foot plate 4 to be adjusted to suit the requirement of the user. Although not shown in Fig. 1, the adjustment channels 10 are attached to the boat by means of screws.

[39] As will be described in more detail with reference to Figs. 2-4, the foot plate

assembly 2 is provided with engagement means 12 for engaging the foot plate support 6 on the adjustment channels 10 when the foot plate 4 is located in the desired position. The engagement means 12 comprises a first half 12a, which is provided on the foot plate support 6, and a second half 12b, which is provided on the corresponding adjustment channel 10. The two halves of the engagement means 12a, 12b are provided with complementary mating features such that they lock together and prevent unwanted movement of the foot plate 4 during use. The foot plate assembly 2 is also provided with a locking lever 14, which is moveable from a locked position (as seen in Fig. 4), in which the two halves of the engagement means 12a, 12b are forced together, to an open position (as seen in Fig. 2), in which the two halves of the engagement means 12a, 12b may be separated for adjustment of the position of the footplate 4.

[40] Referring now to Figs. 2-4, these show a single adjustment mechanism 16 for a foot plate assembly 2. As will be readily appreciated from the foregoing description, the foot plate assembly 2 shown in Fig. 1 will be provided with three of the adjustment mechanisms 16, corresponding to each of the adjustment channels 10a, 10b, 10c. It will also be appreciated that a foot plate assembly 2 may have greater or fewer than three adjustment mechanisms 16, depending on the construction of the foot plate assembly 2.

[41] Referring firstly to Fig. 3, this shows an exploded view of the adjustment mechanism 16 and serves to aid understanding of the construction and operation of the mechanism shown in Figs. 2 and 4.

[42] The adjustment mechanism 16 comprises an adjustment channel 10 which, in use, is attached to a rowing boat. The adjustment channel 10 is a generally u-shaped elongate channel with a plurality of externally facing teeth members 18 running along its length on both sides of the u-shaped opening. The teeth members 18 form the second half of the engagement means 12b referred to above in respect of Fig. 1. The teeth members 18 extend part way across the opening of the adjustment channel 10, such that the width of the opening is narrower than the internal width of the channel 10. The construction of the adjustment channel 10 is known from the prior art, and it is envisaged that the present invention could be retro-fitted into existing rowing boats using the adjustment channels which are present.

[43] The remainder of the adjustment mechanism 16 is provided on the foot plate support 6 and comprises an engagement member 12a, which is provided with teeth 22 which are arranged to engage with the teeth members 18 of the adjustment channel 10. The engagement member 12a is attached to fittings 24 of the foot plate support 6 (only a portion of which is shown in Figs. 2-4).

[44] The adjustment mechanism 16 further comprises a biasing member 26 and a locking lever 14. The biasing means 26 is in the form of a flat spring. The term 'flat spring' refers to the fact that the spring 26 is formed from a flat strip of resilient metal which is formed into a spring shape to provide a biasing force to the assembly 2. The flat spring 26 comprises generally circular end portions 27 and a raised middle section 28. The end portions 27 of the spring 26 are shaped to allow the spring 26 to run along the inner lower face of the adjustment channel 10. In normal use the middle section 28 does not contact the inner lower face of the of the adjustment channel 10. The middle section 28 of the spring 26 is wider than the u-shaped opening in the channel 10, such that it provides a running interface and the spring 26 can only be removed from the ends of the channel 10.

[45] A threaded bolt 32 passes through an aperture 35 in the spring 26 and through corresponding apertures in the engagement member 20, washer 34 and bush 36. The bush 36 comprises an internal thread which engages with the thread of the bolt 32 to hold the parts together. The bush 36 can be used to adjust the mechanism as appropriate. The aperture 35 in the spring 26 is square and the threaded bolt 32 is provided with a corresponding square-shaped feature 33, which engages with the aperture 35 and prevents unwanted rotation of the threaded bolt 32. This anti-rotation feature makes it possible to adjust the locking mechanism by loosening or tightening the bush 36.

[46] Turning now to Figs. 2 and 4. Fig. 2 shows the adjustment mechanism 16 with the locking lever 14 in the open position. The locking lever 14 is an over-centre lever and it sits in washer 34. In the open position the biasing force of the spring 26 acts on the engagement member 12a and pushes it away from the adjustment channel 10. The biasing force is sufficient to overcome the weight of the foot plate assembly 2 and hold the engagement member 12a in a disengaged position, in which the teeth 22 are separated from the teeth 18 of the adjustment channel. In the open position the foot plate support 6 may slide freely along the adjustment channel 10 to the desired position. This operation may be conducted while a user has their feet in the shoes attached to the foot plate 4, which is hugely beneficial in terms of achieving the correct positioning.

[47] Once the user has moved the foot plate support 6 to the desired position the locking lever 14 is moved from the open position to the closed position, as shown in Fig. 4. In moving from the open position to the closed position the lever 14 pivots in an over- centre manner (indicated by arrow A in Fig. 2) and in doing so it exerts a downward force on the engagement member 12a. The force exerted by the locking lever 14 is sufficient to overcome the biasing force of the spring 26 and to force the teeth 22 of the engagement means 12a into locking engagement with the teeth 18 of the adjustment channel 10. The force applied by the locking lever 14 can be adjusted by tightening or loosening the bush 36 as appropriate. When the lever 14 is in its closed position the foot plate 4 is locked in position and cannot move unless the lever 14 is opened. The locking mechanism is a simple and may be operated while a user has their feet in position in the boat. There is no need for any additional tools and the adjustment can be made using finger pressure only. A further advantage is that the locking lever 14 provides a clear visual indication of locking status.

[48] As noted, in normal use of the adjustment mechanism 16 the spring 26 runs on its end portions 27. However, if the foot plate support 6 is moved beyond its intended range of motion then one of the end portions 27 will drop out of the adjustment channel 10. When this happens the middle section 28 comes into contact with the inner lower face of the adjustment channel 10, which in turn causes the teeth 22 of the engagement member 12a to move into engagement with the teeth 18 of the adjustment channel 10. This prevents further movement of the foot plate support 6 and stops the assembly 2 from accidentally coming apart.

[49] Referring now to Figs. 5 and 6, these show an alternative embodiment of a vertical adjustment mechanism. Although the drawings illustrate a mechanism for the vertical adjustment of a foot plate, it will be appreciated that the mechanism could also be used to facilitate the longitudinal adjustment of the foot plate, as described with reference to the mechanism of Figs. 1-4.

[50] In a prior art design, a footplate is drilled with a series of holes which locate over a threaded bolt protruding from the footplate support, or stretcher, and held in place with a suitable thumbscrew. Known issues with this arrangement include the difficulty in adjusting footplate height due to the need to completely unscrew and remove the thumbscrew and footplate from engagement with the stretcher in order to move to a new position through the selection of a different hole in the footplate. These result in mislaid components, are very time consuming, and lead to a reluctance by athletes to make adjustment when required to achieve the optimum position in the boat.

[51] The embodiment of the design shown in Figs. 5 and 6 incorporates a footplate

support or stretcher (40) with one or more threaded screws (42) which pass through a corresponding channel (44) in the footplate (41), and through corresponding apertures in an engagement member (46), washer (48), bush (50), and through a coil spring (52). The bush (50) can be used to adjust the mechanism as appropriate. The channel (44) in the footplate (41) is provided with a plurality of recessed teeth (45), the function of which will be described in more detail below.

[52] The figures show the exploded view of the mechanism, and showing a locking lever (54), in the open position. In the open position the biasing force of the spring (52) acts on the engagement member (46) and pushes it away from the washer (48) and locking lever (54). The biasing force is sufficient to provide an indexing function such that the engagement member engages with one of the recessed teeth (45) in the channel (44) in the footplate (41). In the open position the biasing force can be fairly easily overcome so that the footplate (41) may be adjusted to a new position in a controlled manner by sliding it such that it moves relative to the screw (42) and engagement member (46).

[53] Once the user has moved the footplate (41) to the desired position the locking lever (54) is moved from the open position to the closed position. In the locked position the lever (54) pivots in an over-centre manner and provides sufficient force to overcome the biasing force of the spring (52) and to clamp the engagement member (46) into locking engagement with the corresponding recessed toothed feature in the footplate (41).

[54] Advantages of this design include the ability of the user to adjust their feet in a

vertical direction along the plane of the footplate without removing the fastener and footplate from the stretcher. Although the term 'vertical' is used to describe the adjustment plane, in practice the adjustment takes place over an inclined plane of approximately 45° to the horizontal; the precise angle depending on the installation and adjustability of stretcher angle.

[55] The invention has been described with reference to an adjustment mechanism for adjusting the longitudinal position of a foot plate 4 in a rowing boat. However, it is also envisaged that the adjustment mechanism could be used for providing means for adjusting the position of the foot plate relative to the foot plate support, or stretcher. In this case the adjustment channel is provided on the foot plate support and the foot plate is provided with an engagement member, a releasable locking member and a biasing means. The operation and advantages of this embodiment are generally as described with reference to Figs. 1-6.

Claims

[Claim 1] 1. An adjustment mechanism for a foot plate assembly comprising:

a foot plate mounted on a foot plate support;

at least one adjustment channel;

engagement means, a first half of which is associated with the foot plate support and a second half of which is associated with the adjustment channel;

a releasable locking means moveable between: i) a locked position in which the first and second halves of the engagement means are engaged, such that the foot plate support is fixed in position relative to the adjustment channel; and ii) an open position in which the two halves of the engagement means can be moved relative to one another to adjust the position of the foot plate relative to the adjustment channel; and

a biasing means arranged to bias the first half of the engagement means when the locking means is in the open position.

2. An adjustment assembly according to claim 1, wherein the biasing means is arranged to bias the first and second halves of the engagement means apart when the locking means is in the open position.

3. An adjustment assembly according to claim 1, wherein the biasing means is arranged to bias the first half of the engagement means into an indexing engagement with the second half of the engagement means, wherein the biasing force is sufficient to provide an indexing engagement but may be easily overcome to enable the first and second halves of the engagement means to move relative to one another in a controlled manner.

4. An adjustment assembly according to any one of claims 1-3, wherein the biasing means is a spring.

5. An adjustment assembly according to claim 4, wherein the spring is a flat spring.

6. An adjustment assembly according to claim 2, wherein the biasing means is an elongate flat spring with end portions which are in contact with the base of the adjustment channel and are responsible for exerting the biasing force, and a central portion which is not in contact with the base of the adjustment channel, the arrangement being such that when one of the end portions extends beyond the end of the adjustment channel the biasing force is removed and the two halves of the en- gagement means come together to prevent the foot plate support from further movement.

7. An adjustment assembly according to claim 4, wherein the spring is coil spring.

8. An adjustment assembly according to any preceding claim, wherein the releasable locking means is a lever operated mechanism.

9. An adjustment assembly according to claim 8, wherein the lever operated mechanism is an over-centre lever arrangement.

10. An adjustment assembly according to any preceding claim, wherein the releasable locking means is connected to the biasing means by a threaded pin and nut, which can be used to adjust the locking mechanism.

11. An adjustment assembly according to claim 10, wherein the threaded pin is provided with an anti-rotation feature.

12. An adjustment assembly according to claim 11, wherein the threaded pin passes through an aperture in the biasing means, the shape of the aperture being selected to prohibit rotation of the threaded pin.

13. An adjustment assembly according to any preceding claim, wherein the engagement means comprises a toothed arrangement.

14. An adjustment assembly according to claim 13, wherein the adjustment channel comprises an external toothed arrangement which is configured to engage with a complementary feature on the foot plate support.

15. An adjustment assembly according to claim 13, wherein the adjustment channel comprises an internal toothed arrangement which is configured to engage with a complementary feature on the foot plate support.

16. An adjustment mechanism according to any preceding claim, wherein the adjustment mechanism comprises three adjustment channels and three engagement means, such that the foot plate support engages at three locations, each engagement means having its own releasable locking means and biasing means.

17. An adjustment mechanism according to any preceding claim, wherein the foot plate is adjustably mounted on the foot plate support.

18. An adjustment mechanism according to claim 17, wherein the foot plate support comprises:

at least one foot plate adjustment channel;

foot plate engagement means, a first half of which is associated with the foot plate and a second half of which is associated with the foot plate adjustment channel;

a releasable locking means moveable between: i) a locked position in which the first and second halves of the foot plate engagement means are engaged, such that the foot plate is fixed in position on the foot plate adjustment channel; and ii) an open position in which the two halves of the foot plate engagement means can be spaced apart such that the foot plate may be moved along the foot plate adjustment channel to adjust its position relative to the foot plate support; and a biasing means arranged to bias the first and second halves of the foot plate engagement means apart when the locking means is in the open position.

19. An adjustment mechanism according to claim 17, wherein the foot plate comprises:

at least one foot plate adjustment channel;

foot plate engagement means, a first half of which is associated with the foot plate support and a second half of which is associated with the foot plate adjustment channel;

a releasable locking means moveable between: i) a locked position in which the first and second halves of the foot plate engagement means are engaged, such that the foot plate is fixed in position on the foot plate support; and ii) an open position in which the two halves of the foot plate engagement means can be moved relative to one another; and a biasing means arranged to bias the first half of the engagement means into an indexing engagement with the second half of the engagement means, wherein the biasing force is sufficient to provide an indexing engagement but may be easily overcome to enable the first and second halves of the engagement means to move relative to one another in a controlled manner.

20. A releasable locking mechanism for use in an adjustment mechanism according to any one of claims 1 to 19 comprising:

a locking member moveable between a locked position and an open position; and

a biasing means associated with the locking member,

wherein, in use, in the locked position the locking member acts against the biasing means and forces the first and second halves of the engagement means into engagement such that the foot plate support is fixed in position relative to the adjustment channel, and in the open position the two halves of the engagement means can be moved relative to one another to adjust the position of the foot plate relative to the adjustment channel.

21. An adjustment mechanism for a foot plate comprising:

a foot plate;

a foot plate support with at least one adjustment channel;

engagement means, a first half of which is associated with the foot plate and a second half of which is associated with the adjustment channel;