AU700945B2 - Improved roller skate - Google Patents

Description

IMPROVED ROLLER

SKATE

AND UNDERCARRIAGE

ARRANGEMENT

The present invention relates to an improved roller skate and an undercarriage arrangement.

Roller skates have traditionally comprised a boot having two pairs of wheels mounted underneath the boot. The wheels were mounted as a forward pair and a rear pair. Both wheels of the forward pair were mounted on a common axis and both wheels of the rear pair were also mounted along a common axis. Such roller skates enjoyed wide popularity in the late 1970's and early 1980's.

Subsequent developments of roller skates led to the production of in-line skates. In-line skates include a boot having a generally inverted U-shaped channel mounted underneath the boot. A plurality of wheels, usually three or four, were longitudinally spaced and mounted for rotation within the channel. This resulted in a skate having a single line of wheels mounted underneath the skate. Such in-line skates have skating characteristics more similar to ice skating than traditional roller skates. In-line skates have now achieved wide popularity.

~In one aspect, the present invention provides an undercarriage arrangement for a roller skate, skateboard or similar apparatus including mounting means fixed to a platform, the mounting means including a downwardly extending portion, a first wheel assembly including a first wheel rotatable about an axle, a second wheel assembly including a second wheel rotatable about an axle, said first and second wheel assemblies being mounted on opposite sides of the mounting means, wherein "the first and second wheel assemblies are arranged such that tilting the platform away from horizontal whilst said wheels are in contact with a surface causes one of 25 the first and second wheel assemblies to move relatively towards the platform and o the other of the first and second wheel assemblies to move relatively away from the platform, the movement of the first and second wheel assemblies being along a path that is substantially parallel to the downwardly extending portion of the mounting means.

Preferably, the first and second wheel assemblies are arranged such that the first and second wheels move towards the platform and away from the platform GNNB#20629.SPC 23 November 1998 -3along a path that is substantially parallel to the downwardly extending portion of the mounting means.

Preferably, the first wheel assembly includes a channel member having an inner side and an outer side connected by a cross web, the axle extending between the inner and outer sides, and the inner side being mounted to one side of the downwardly extending portion such that the first wheel assembly can move towards and away from the platform. In one embodiment, the inner side is slidably mounted to the downwardly extending portion, for example, by use of a dove tail connection between the inner side and the downwardly extending portion, or by use of a mounting arrangement including a groove and complementary projection.

Preferably, the second wheel assembly includes a second channel member having an inner side and an outer side connected by a cross web with the axle extending between the inner and outer sides of the second channel member, and the inner side being mounted to one side of the downwardly extending portion such that 15 the second wheel assembly can move towards and away from the platform.

In an especially preferred embodiment, the undercarriage arrangement further comprises a rotating gear mounted to the downwardly extending portion of the mounting assembly. The respective inner sides of the first and second channels further include linear gears or rack gears that cooperate with the rotating gear. This 20 is basically a rack and pinion arrangement. In use of the apparatus, when a user *"*inclines the platform, for example, by making a turn, the wheel assembly on the inside of the turn is forced upwardly by the weight of the user. As the inside wheel assembly moves upwardly, the linear gear on the inner side of the channel interacts with the rotating gear to thereby cause the rotating gear to rotate. The rotating gear then interacts with the linear gear on the inner side of the channel of the other wheel assembly and, as a result, the rotating gear positively drives the other wheel assembly downwardly. This thereby maintains both wheel assemblies in contact with the ground. The arrangement also ensures that the first and second wheels are maintained substantially parallel to each other at all times.

Alternative arrangements may also be used. For example, a series of GWN:NB.#20629.SPC 23 November 1998 -4interconnected linkages may be used to ensure that respective wheel assemblies move towards and away from the boot. Chains and sprockets may also be used. Other arrangements that cause one wheel assembly to move away from the platform when the other wheel assembly moves towards the platform also fall within the scope of the present invention, including hydraulic and pneumatic means.

The undercarriage arrangement may further comprise a biasing means mounted in juxtaposition to the first and second wheel assemblies such that said biasing means is compressed by movement of one of the wheel assemblies towards the platform. When the user's weight is lifted off the arrangement, for example, when doing a cross over during turning when the invention is in the form of a skate, the biasing means decompresses and forces the wheel assemblies back to a neutral position where both wheel assemblies are positioned a similar distance from the platform. The biasing means may comprise a compression block, such as a rubber block, or a spring arrangement such as a linear spring, a torsional spring S 15 arrangement, or any other spring arrangement known to be suitable by the person skilled in the art.

The undercarriage arrangement may include a further wheel mounted to the platform either forward or aft of the first and second wheel assemblies. More preferably, the arrangement further includes third and fourth wheels mounted either 20 forward or aft of the first and second wheels. This results in the apparatus having the first and second wheels mounted at or towards either the front or rear of the *9 platform, and the third and fourth wheels located at or towards either at the rear or front, respectively, of the platform.

Preferably, the first and third wheels are arranged in substantial alignment 25 along a line generally parallel to the centre line of the boot and the second and fourth wheels are arranged in substantial alignment along a line generally parallel to the centre line of the platform. In this configuration, when used on a roller skate, the skate comprises a quad in-line skate and may be considered analogous to a double-track in-line skate.

The third and fourth wheels are most preferably arranged in third and fourth GWN:NB'#20629.SPC 23 November 1998 wheel assemblies, respectively, with the third wheel assembly including the third wheel rotatable about an axle and the fourth wheel assembly including the fourth wheel rotatable about an axle. The third and fourth wheel assemblies are preferably mounted to a downwardly extending portion of a mounting means. The mounting means may comprise the mounting means to which the first and second wheel assemblies are mounted. Alternatively, the mounting means to which the third and fourth wheel assemblies are mounted may comprise a separate mounting means.

The third wheel assembly may include a channel having an inner side and an outer side connected by a cross web with the axle extending between the inner and outer sides. The fourth wheel assembly may also include a channel having an inner side and an outer side connected by a cross web with the axle extending between the inner and outer sides. In this embodiment, the third and fourth wheel assemblies are preferably mounted to the downwardly extending portion of the mounting means by a similar rotating gear and linear gear arrangement as described for the first and 15 second wheel assemblies.

f As mentioned above, the first and second wheel assemblies may comprise a ":front set of wheels and the third and fourth wheel assemblies may comprise a rear set of wheels. The front set of wheels may operate independently of the rear set of wheels. Alternatively, the front set of wheels may be linked to the rear set of 20 wheels such that operation of the front set of wheels and the rear set of wheels are Do linked. This may be achieved by use of a linking bracket or even by inserting one *6 or more further wheel assemblies between the front and rear set of wheels.

""0Alternatively, the first and third wheels may be mounted within a common 5600 0* channel and the second and fourth wheels may be mounted within a common o• channel. In this embodiment, elongated channels are required. A single rotating gear and a linear gear (rack and pinion) arrangement may be used to mount the two channels or a plurality of rotating gears and linear gears arrangements may be used.

In embodiments where the first and second wheel assemblies comprise a front set of wheels and the third and fourth wheel assemblies comprise a rear set of wheels, a spacer element may be positioned between the front and rear sets of GWN NB:#20629.SPC 23 November 1998 -6wheels. Alternatively, provision may be made for one or more further wheels to be mounted between the front and rear sets of wheels to give a skate with five or six wheels.

The mounting means may be permanently fixed to the platform or, more preferably, may be releasably fixed to the platform by, for example, bolts, nuts, screws or even a quick release mechanism.

The undercarriage arrangemerit may form part of a rollerskate. The platform may comprise the sole of the boot (with the mounting means being directly connected to the sole of the boot). Alternatively, the platform may be connected to the boot.

The invention may also extend to other apparatus to which the underfoot arrangement of the invention could suitably be fitted, including skateboards.

A preferred embodiment of the present invention will now be described with reference to the drawings, which show the undercarriage apparatus of the invention as part of a roller skate.

Brief Description of the Drawings o• Figure 1 is a front elevation view of a roller skate in its neutral position, that :i is, when travelling in a straight line alignment either in a clockwise or anticlockwise direction.

20 Figure 2 is a front elevation view of the roller skate when travelling in a clockwise direction and in a curved path alignment.

Figure 3 is a front elevation view of the roller skate when travelling in an o So S.o S o• 55 GWN:NB:#20629.SPC 23 November 1998 -7anticlockwise direction and in a curved path alignment.

Figure 4 is a side elevation view of the roller skate in its neutral position, that is, when travelling in a straight line alignment either in a clockwise or anticlockwise direction.

Detailed Description of the Preferred Embodiment An exemplary embodiment of the invention is disclosed herein; however it is to be understood that it is not limiting, but merely illustrative of the present invention.

This embodiment utilises a hardware configuration as described in Figures 1 to 4 respectively wherein the roller skate comprises a main assembly structure wheel assembly units each of which incorporate an integrated linear gear arrangement As shown in Figure 4, the skate includes front and rear wheel sets. Both front and rear wheel sets are identical on each skate and for both pairs of skates and include a rotational gear assembly unit which interacts with the linear gears (4a) attached to or formed in the wheel assembly units a linear spring assembly unit which is common to both wheel assembly units (3) which realigns the wheel assemblies to a neutral position, a standard in-line wheel t and bearing assembly which can be purchased off the shelf, a specially designed recessed axle arrangement to support the in-line wheel assembly, a removable section or spacer linking both front and back main assembly structures on the same skate to facilitate the attachment of smaller sized skating shoes or boots and .555 a skating shoe or boot which is mounted on the main assembly structure (2 of per skate). It is to be noted that the front elevation view represented in Figures 1, 2 and 3 focuses on the front sets of wheels of each skate. The rear sets of wheels on the skate function in a similar manner. It is also to be noted that the front sets of wheels and its associated hardware attachments are assembled on the same skate one hundred and eighty degrees relative to that of the rear set of wheels and its associated hardware attachments. The hardware components for both the right hand skate and the left hand skate are identical with respect to their mechanical operation and limitations.

GWN:NB:#20629.SPC 28 June 1996 -8- The operation of the roller skate in accordance with the invention is as follows.

When travelling in a straight line the roller skate is in its neutral position and this is shown in Figures 1 and 4, that is, the operator's weight is equally distributed about the centre line of the front set of wheels, refer to Figure 1.

Wheel assembly unit comprises a channel (10) including an inner side (11) and an outer side (12) connected via a cross web Axle extends between inner side (11) and outer side (12) and is mounted to those sides. The wheel and bearing assembly rotate about axle The wheel assembly units and which are attached to and slide along the downwardly extending portion (Ib) are equally balanced about the rotational gear assembly unit and the linear spring assembly unit exerts an equal tension on both the wheel assembly units and respectively in this neutral position. If the operator's weight is not equally distributed about the centre line of the main 15 assembly unit the wheel assembly units and will be equally displaced in opposite directions about the rotational gear assembly unit and the roller skate S.will move either left or right depending on the weight distribution applied about the centre line of the chassis arrangement. Movement of the roller skate is achieved by displacing the body weight of the skater relative to the centre line of the skate or alternatively pushing off to gain momentum and speed.

The front set of wheels includes a mounting means (1 a) attached to the sole of the boot The mounting means may be attached to the boot by use of bolts, screws or the like, or a quick release mechanism may be used to attach the mounting means to the boot. The mounting means (la) includes a downwardly 25 extending portion (lb).

When travelling in a clockwise direction around a curved path as shown in Figure 2, the roller skate is in its biased position, that is, the operator's weight is unequally distributed about the centre line of the front set of wheels. When travelling in a curved path in a clockwise direction, the weight of the skater is concentrated on the right hand side (15) of the chassis arrangement. The wheel GWN:NB #20629.SPC 28 June 1996 -9assembly units and which are attached to and slide along the downwardly extending portion (lb) are equally displaced from the neutral position by the rotational gear assembly unit in opposite directions. Both wheel assembly units and incorporate an integrated linear gear or rack which is attached on or formed on the inner external surfaces and interact with the rotational gear assembly to provide angular displacement relative to the horizontal plane of the surface being travelled on. As the body weight of the operator is concentrated on the right hand side of the front set of wheels, the wheel assembly unit moves upwards as a consequence of the applied pressure. As the wheel assembly unit moves upwards the rotational gear assembly rotates in a clockwise direction thus forcing wheel assembly unit into a downwards motion. The angular displacement of the roller skate relative to the horizontal plane is attributed to this linear to rotational gear movement along the downwardly extending portion (lb) of the mounting means.

15 As the wheel assembly unit moves in an upwards direction the wheel assembly unit moves in a downwards direction thus pushing the operator or skater with a force equal to the combined body weight and applied pressure exerted by the operator whereby the operator gains momentum and speed. As the wheel assembly unit moves in a downwards motion the linear spring assembly unit 20 is compressed by the movement of the wheel assembly unit When the operator's skate is raised above the surface being travelled on, the linear spring assembly unit decompresses or discharges its stored energy thus realigning the wheel assembly unit through the rotational gear assembly to its neutral position and in preparation for the next downwards motion of the wheel assembly unit The linear spring assembly unit connects both wheel assembly units (2) and through a tee bar connection (5a) as shown in Figure 4. The entire skate assembly is depicted in Figure 4 and comprises assembly for the front section of the skate and assembly for the back section of the skate. The forces which are exerted on assembly may vary to those exerted on assembly since each assembly or functions independently relative to the other, and the wheel GWN:NB:#20629.SPC 28 June 1996 assembly units and and their associated attachments the in line wheel and bearing assembly will always operate parallel with respect to each other to maintain stability and traction relative to the surface being travelled on. The position of the rotating gear as shown in Figure 2 and 4 allows the operator to attain an angular displacement of fifty degrees relative to the horizontal plane of the surface being travelled on, although the angular displacement can be varied above or below this value. For example, the angular displacement may be decreased by repositioning the rotational gear assembly unit to a lower position on the main assembly unit The desired angular displacement of the roller skate is dependent on two factors, the positioning of the rotational gear assembly unit and the length of the linear gears attached to the wheel assembly units and respectively, the constraint being the proximity or clearance of the linear gear relative to the surface being travelled on.

Figure 3 shows the roller skate travelling in a curved path alignment and in 15 an anticlockwise direction.

oo When travelling in an anti-clockwise direction around a curved path the roller skate is in its biased position, that is, the operator's weight is unequally distributed about the centre line of the downwardly extending portion the weight being concentrated on the left hand side of the skate, The wheel assembly units and 20 which are attached to and slide along the downwardly extending portion lb are a. equally displaced about the rotational gear assembly unit in opposite directions.

Both wheel assembly units and incorporate an integrated linear gear which is attached on the inner external surfaces and interact with the rotational gear assembly to provide angular displacement relative to the horizontal plane of the surface being travelled on. As the body weight of the operator is concentrated on the left hand side (16) of the skate, the wheel assembly unit moves upwards as a consequence of the applied pressure, as the wheel assembly unit moves upwards the rotational gear assembly rotates in an anticlockwise direction thus forcing wheel assembly unit into a downwards motion. The angular displacement of the roller skate relative to the horizontal plane is attributed to this GWN:NB:#20629.SPC 28 June 1996 11 linear to rotational gear movement along the main assembly unit As the wheel assembly unit moves in an upwards direction the wheel assembly unit moves in a downwards direction thus pushing the operator or skater with a force equal to the combined body weight and applied pressure exerted by the operator to attain momentum and speed. As the wheel assembly unit (2) moves in a downwards motion the linear spring assembly unit is compressed by the movement of the wheel assembly unit When the operator's skate is raised above the surface being travelled on, the linear spring assembly unit decompresses or discharges its stored energy thus realigning the wheel assembly unit through the rotational gear assembly to its neutral position and in preparation for the next downwards motion of the wheel assembly unit The linear spring assembly unit connects both wheel assembly units and through a tee bar connection (5a) as shown in Figure 4. The entire skate assembly is depicted in Figure 4 and comprises assembly for the front section of the skate and assembly .i 15 for the back section of the skate. The forces which are exerted on assembly "A" oo may vary to those exerted on assembly since each assembly or functions independently relative to the other in the embodiment shown in the Figures. However, the skate may be constructed such that the front and rear assemblies have common movement. This may be achieved by connecting the front and rear assemblies with a bracket, or by inserting additional wheels between the front and rear assemblies, or by mounting the left hand side front and rear wheels in a single channel and the right hand side front and rear wheels in a single channel.

The wheel assembly units and and their associated attachments the in- 2 line wheel and bearing assembly will always operate parallel with respect to 25 each other to maintain stability and traction relative to the surface being travelled on.

The position of the rotational gear assembly unit as shown in Figure 3 and 4 allows the operator to attain an angular displacement of fifty degrees relative to the horizontal plane of the surface being travelled on. The angular displacement can be altered by repositioning the rotational gear assembly unit to a lower position on the main assembly unit The desired angular displacement of the roller skate is GWN:NB:#20629.SPC 28 June 1996 12dependent on two factors, the positioning of the rotational gear assembly unit and the length of the linear gears attached to the wheel assembly units and (3) respectively, the constraint being the proximity or clearance of the linear gear relative to the surface being travelled on.

The description of the roller skate the invention and its method of operation as described within this embodiment is not limiting. The method of operation of the invention can be applied to any other form of mechanical application where a similar movement is sought to accomplish a specific task in a manner described within this embodiment.

.o o GWN:NB:#20629.SPC 28 June 1996 13 The claims defining the invention are as follows: 1. An undercarriage arrangement for a roller skate, skateboard or similar apparatus including mounting means fixed to a platform, the mounting means including a downwardly extending portion, a first wheel assembly including a first wheel rotatable about an axle, a second wheel assembly including a second wheel rotatable about an axle, said first and second wheel assemblies being mounted on opposite sides of the mounting means, wherein the first and second wheel assemblies are arranged such that tilting the platform away from horizontal whilst said wheels are in contact with a surface causes one of the first and second wheel assemblies to move relatively towards the platform and the other of the first and second wheel assemblies to move relatively away from the platform, the movement of the first and second wheel assemblies being along a path that is substantially parallel to the downwardly extending portion of the mounting means.

2. An undercarriage arrangement as claimed in claim 1 wherein the first wheel assembly includes a channel member having an inner side and an outer side connected by a cross web, the axle extending between the inner and outer sides, and the inner side being mounted to one side of the downwardly extending portion such that the first wheel assembly can move towards and away from the platform and the second wheel assembly includes a second channel member having an inner side and 20 an outer side connected by a cross web with the axle extending between the inner and outer sides of the second channel member, and the inner side being mounted to one side of the downwardly extending portion such that the second wheel assembly can move towards and away from the platform.

3. An undercarriage arrangement as claimed in claim 2 wherein the first and second wheel assemblies are slidably mounted to respective sides of the :downwardly extending portion.

4. An undercarriage arrangement as claimed in claim 3 wherein the first and second wheel assemblies are mounted to respective sides of the downwardly extending portion by a dove-tail connection or a mounting arrangement including a groove and complementary projection.

GWN:NB:#20629 SPC 23 Novembff 1998

Claims (12)

14- An undercarriage arrangement as claimed in any one of claims 2 to 4 further including a rotating gear mounted to the downwardly extending portion of the mounting means and the respective inner side of the first and second channels include linear gears or rack gears that interact with said rotating gear wherein when one of said wheel assemblies moves towards the platform during use, wherein the linear gears or rack gears of that wheel assembly cause the rotary gear to rotate and said rotating gear thereby interacts with the linear gears or rack gears of the other wheel assembly to move the other wheel assembly away from the platform. 6. An undercarriage arrangement as claimed in any one of claims 1 to further comprising a biasing means mounted in juxtaposition to the first and second wheel assemblies such that said biasing means is compressed by movement of one of said wheel assemblies towards the platform, said spring arrangement effective to return said one of said wheel assemblies to a neutral position if weight is removed from the undercarriage arrangement. 7. An undercarriage arrangement as claimed in claim 6 wherein the biasing means comprises a compression block or a spring arrangement such as a *linear spring or a torsional spring. S8. An undercarriage arrangement as claimed in any one of the preceding claims including at least one further wheel mounted to the platform either forward 20 or aft of the first and second wheels. 9. An undercarriage arrangement as claimed in any one of claims 1 to 8 2 further including third and fourth wheels mounted either forward or aft of the first and second wheels. *o• 10. An undercarriage arrangement as claimed in claim 9 wherein the first and third wheels are arranged in substantial alignment along a line generally parallel to the centre line of the platform and the second and fourth wheels are arranged in substantial alignment along a line generally parallel to the centre line of the platform. 11. An undercarriage arrangement as claimed in claim 9 wherein the third and fourth wheels are arranged in third and fourth wheel assemblies, respectively, RGWN:NB#20629.SPC 23 November 1998 S GWNNB #20629.SPC 23 November 1998 with the third wheel assembly including the third wheel rotatable about an axle and the fourth wheel assembly including the fourth wheel rotatable about an axle. 12. An undercarriage arrangement as claimed in claim 11 wherein the third and fourth wheel assemblies are mounted to opposite sides of a downwardly extending portion of a mounting means connected to the platform. 13. An undercarriage arrangement as claimed in claim 12 wherein the mounting means to which the third and fourth wheel assemblies are mounted comprises the mounting means to which the first and second wheel assemblies are mounted. 14. An undercarriage arrangement as claimed in claim 12 wherein the third and fourth wheel assemblies are mounted to a separate mounting means. An undercarriage arrangement as claimed in any one of claims 12 to 14 wherein the third wheel assembly includes a channel having an inner side and an outer side connected by a cross web with the axle extending between the inner and outer sides and the fourth wheel assembly includes a channel having an inner side and an outer side connected by a cross web with the axle extending between the inner and outer sides with the inner sides of respective channels of the third and fourth wheel assemblies being mounted to respective sides of the downwardly extending portion such that the third and fourth wheel assemblies can move towards 20 and away from the platform.

16. An undercarriage arrangement as claimed in claim 15 further including °0 a rotating gear mounted to the downwardly extending portion of the mounting assembly and the respective inner sides of the third and fourth channels include o* o. linear gears or rack gears that interact with said rotating gear wherein when one of 25 said wheel assemblies moves towards the platform during use, the linear gears or rack gears of that wheel assembly cause the rotating gear to rotate and said rotating gear thereby interacts with the linear gears or rack gears of the other wheel assembly to move the other wheel assembly away from the platform.

17. An undercarriage arrangement as claimed in claim 15 or claim 16 wherein the first and second wheel assemblies comprise a front set of wheels and the GWNNB:#20629 SPC 23 November 1998 GWN NB:#20629 SPC 23 November 1998 16- third and fourth wheel assemblies comprise a rear set of wheels and the front set of wheels operate independently of the rear set of wheels.

18. An undercarriage arrangement as claimed in claim 15 or claim 16 wherein the first and second wheel assemblies comprise a front set of wheels and the third and fourth wheel assemblies comprise a rear set of wheels and the front set of wheels are linked to the rear set of wheels such that operation of the front set of wheels and the rear set of wheels are linked.

19. An undercarriage arrangement as claimed in claim 15 or claim 16 wherein the first and third wheels are mounted within a common channel and the second and fourth wheels are mounted within a common channel. An undercarriage arrangement as claimed in claim 17 wherein a spacer element is positioned between the front and rear set of wheels.

21. An undercarriage arrangement as claimed in claim 17 wherein one or more further wheels may be mounted between the front and rear sets of wheels.

22. An undercarriage arrangement as claimed in any one of claims 2 to 4 wherein said wheel assemblies are interconnected by a series of linkages such that one of said wheel assemblies moves away from the platform when the other of said wheel assemblies moves towards the boot. to*

23. An undercarriage arrangement as claimed in any one of claims 2 to 4 oo" 20 wherein the wheel assemblies each include a sprocket and chain drive mechanism connected to a rotating gear mounted to the downwardly extending portion of the mounting means, said rotating gear and sprocket and chain drive mechanism of each wheel assembly effective to cause one of the wheel assemblies to move away from the platform when the other of the wheel assemblies moves towards the platform.

24. An undercarriage arrangement as claimed in any one of claims 1 to 23 *ooo further including boot attachment means for attachment to a boot. A roller skate comprising a boot having an undercarriage arrangement as claimed in any one of claims 1 to 23 mounted thereto.

26. A roller skate as claimed in claim 24 wherein the platform comprises a sole of the boot. RA WN:N:20629PC 2Nomb GWN:NB:820629.SPC 23 November 1998 17-

27. A roller skate substantially as hereinbefore described with reference to the accompanying drawings.

28. An undercarriage arrangement substantially as hereinbefore described with reference to the accompanying drawings. DATED: 23 November 1998 CARTER SMITH BEADLE Patent Attorneys for the Applicant: ALEXANDER VOSKRESENSKY t S C V e V GWN NB:#20629 SPC 23 November 1998 ABSTRACT A roller skate includes a set of front wheels and a set of rear wheels Each set of wheels is mounted to a skating boot by a mounting means The mounting means includes a downwardly extending portion Wheel assemblies are mounted to either side of the downwardly extending portion (1 The wheel assemblies include a wheel mounted on an axle extending between inner and outer walls (11,12) of a channel The inner wall (11) of the channel (10) is slidably mounted to the downwardly extending portion (1 A rack and pinion arrangement comprising a rotating gear that interacts with linear gears (4a) on the inner walls of channels (10) drives wheel assembly downwardly when wheel assembly moves upwardly, for example, when the skate is inclined during turning. The arrangement ensures that wheel assemblies always remain parallel to each other and that wheel assemblies are displaced equal distance about rotating gear 9 *e *e *e* *e *oe *e