The invention to which this application relates is a castor assembly of a type which can be provided for operation in a first mode in which the roller or wheel parts of the assembly are free to rotate about a first axis and the body of the assembly is free to rotate about a second axis, and a second mode in which one, but preferably both axes of rotation are locked so as to maintain the castor assembly in a fixed position.

The use of castor assemblies at the base of items of furniture such as tables, chairs, stands and the like is well known and castor assemblies are widely used as they allow the item to which they are fixed to be more easily moved acro ss a surface by pushing or pulling the same. The body of the castor assembly is typically rotatable about an axis which is substantially perpendicular to the support surface which the castor contacts and this allows the wheel or roller parts to rotate so as to be correctly aligned with respect to the intended direction of movement of the item to which they are attached across the support surface. The wheel or roller parts of the assembly are also typically rotatable with respect to the rest of the castor assembly about an axis substantially parallel with the surface so as to allow the item to be rolled acro ss the support surface. It is known to allow the rotation of the wheel or roller part to be selectively locked so as to prevent the movement of the item across the support surface. It is also known. However these locking systems are bulky in terms of the components which are required to be included in the assembly, which in turn means that the castor assembly is relatively bulky such that for certain potential uses where the aesthetic appearance is important, such as for an item of furniture, the known castor assembly is not usable. This has meant that the known castor double locking arrangement tends to have only been implemented in relatively large, industrial, castor assemblies which are unsuitable for use with items of furniture due to their size and/or appearance.

However, the ability to lock rotation about both axes is advantageous as it allows the castor assembly and the item to which the same is fitted to be less susceptible to "rocking" or relative movement between the castor assembly and the item to which it is fitted when the same is in use which can be problematic as the aim, when the castor assembly is in a non- movable mode of operation is that the castor assembly acts as a fixed part of the item such that it's presence does not affect the use of the item, such as for example when the item is a desk, the castor assembly does not affect the stability of the desk when in use. The problem of instability is typically due to the fitment tolerances between the stem of the castor assembly and the item to which it is fitted and the problem is sufficiently great that in many instances castor assemblies are not fitted to the item despite the other advantages which they provide.

The aim of the present invention is therefore to provide a castor assembly which can be moved between a first, rotatable, mode and a second, locked, mode of operation in which preferably first and second axes of rotation are locked, and to provide a means of achieving this which allows the same to be incorporated in an assembly suitable for use with an item of furniture.

In a first aspect of the invention there is provided a castor assembly, said assembly provided with at least one wheel or roller part and a body, and in a first mode of operation said wheel or roller part is rotatable about a first axis and the body is rotatable about a second axis substantially perpendicular to the first axis, and in a second mode of operation movement of the wheel or roller part and body about the respective axes is prevented

In one embodiment the change of modes is achieved by user actuation of an actuation member, typically a lever. Typically the actuation member acts on at least one component within the assembly.

Typically the component or components which are acted on by the movement of the actuation member includes, or includes in combination, two different engagement formation components which, in the second mode, are brought into engagement with respective further components of the first and second engagement formations to prevent movement about the first and second axes. In one embodiment the engagement formations are grooves or teeth.

In one embodiment, to prevent rotation of the wheel or roller part the first engagement formation component engages with the other component of the engagement formation provided on at least one of the wheel or roller parts of the assembly.

In one embodiment, to prevent rotation of the body, the second engagement formation component contacts with the other component of the second engagement formation located on the stem, in turn is attached to the item of furniture. Typically the second engagement formation components are in the form of a recess or cup with side walls into which the other component in the form of a substantially frustoconically shaped member is placed and contacts with the conically shaped member to prevent rotation. Typically the side walls of the recess and the outer surface of the sub stantially frustoconically shaped member have teeth and grooves which engage to lock and prevent rotation.

The provision of the recess or cup and the substantially frustoconically shaped component o f the second engagement formation ensures that the movement of the components together is guided such that the same engage in the required manner and that the required secure engagement of the stem wit the body can be achieved and maintained.

The provision of the first and second engagement formations in the manner herein described also ensures that the required locking effect is achieved with a minimum of additional components being required to be fitted into the overall assembly. For example, as the actuating member acts directly on the means on which components for the first and second engagement formations are formed, no additional components are required. This is particularly the case as the rotational movement of the actuating member is translated into movement of the components in a wholly linear or linear plus rotational component.

In one embodiment, if there is no requirement to prevent rotation of the assembly with respect to the item of furniture the cup or conically shaped member can be removed from the castor assembly.

In one embodiment the movement of the first and second engagement formations to release and lock rotation in both axes is along the same, common axis, typically a substantially vertical axis. Alternatively the movement of the respective components of the first and second engagement formations is sub stantially linear along respective, substantially parallel axes. In one embodiment the movement of the actuation member is about a pivot axis and the movement of the component or components acted upon by the actuation member includes a pivotal component.

The components and movement of the same in accordance with the invention allow the castor assembly to be scalable without compromising the operation of the same and therefore allow the castor assembly to be formed to suit any use such as for use and fitment to items of furniture.

The movement of the assembly to the second mode of operation also allows the assembly to be fixed in position with the item and thereby reduce or prevent relative movement of the assembly and item as the castor assembly is effectively an integral part of the item of furniture. In one embodiment the receiving means on the item of furniture and at least that portion of the stem located in the receiving means are formed from machined parts, typically of metal or metal alloy, so as to reduce the relative movement and hence reduce the relative movement between the item of furniture and the castor assembly and improve the stability of the item of furniture when in the second mode of operation.

In one embodiment, a single component is acted upon by the actuation member and said component includes the first and second engagement formations thereon. In one embodiment the single component is formed by joining together two plates, a first plate having a first engagement formation component formed thereon and a second plate having a second engagement formation component thereon. In one embodiment the plate with the second engagement formation component thereon also has a first engagement formation component thereon. Typically the plates are joined together such that one is located adjacent and to one side of the assembly body from which depends the stem and the other plate is located adjacent to the opposing side of the assembly body ,said plates jointed together.

In an alternative embodiment there are provided first and second components which are acted upon by the actuating member, a first component to one side of the body which carries a first engagement formation thereon and a second component on the opposing side of the body which carries a second engagement formation thereon. In this embodiment the components are separate and guided in their movement between first and second modes by respective guide means, typically provided in the said body.

In a further aspect of the invention there is provided an item in furniture including one or more castor assemblies as herein described.

Typically, the item of furniture is a table or a desk.

Specific embodiments of the invention are now described with reference to the accompanying drawings; wherein

Figure 1 illustrates a table with castor assemblies in accordance with the invention in one embodiment;

Figure 2 is a perspective view of a castor assembly in accordance with the invention;

Figure 3 is an exploded diagram showing the parts of the castor assembly of Figure 2 in one embodiment; and Figure 4 is an exploded diagram showing the parts of the castor assembly of Figure 2 in a second embodiment.

Referring firstly to Figure 1 there is illustrated an item in the form of a table 2 which has a worktop 4 and legs 6. At the end of each of the legs there is provided a castor assembly 8 in accordance with the invention, and as shown in more detail in Figure 2. The assembly 8 includes a stem 10 which is received in the end of the leg 6 using machined engagement means to locate the castor assembly 8 with the leg 6 and this arrangement acts to reduce vibration. However, it is often found, certainly with conventional castor assemblies, that there is a degree of movement between the assembly and leg which transfers to the rest of the table and which can be annoying to the user of the table when in a stationary position. This problem is overcome, or at least reduced, by the current invention.

In a first mode of operation, the castor assembly, or at least components thereof, are rotatable about two axes 14, 1 6, which are sub stantially perpendicular. With regard to axis 14, the wheel or roller parts 1 8, 20 rotate with respect to the remainder of the assembly and this allows the item to be rolled along the surface with which the castors are in contact. With regard to axis 1 6, the body 24 is rotatable with respect to the stem 10 to allow the body and, in particular wheel or roller parts 1 8, 20 to be moved into the correct alignment to move the item in a particular direction.

In a second mode of operation the desire is to provide the castor assembly in a locked form so that it effectively forms a fixed part of the leg and hence minimises relative movement between the castor assembly and the leg when the table is in position to be used. In order to achieve this second mode of operation, an actuation member 26 is moved downwardly and about a pivot axis on the body as indicated by arrow 28 in Figure 2. This pivotal movement causes the actuation member to act on an internal means formed of a plate or plates 30, which includes second engagement formations in the form of teeth provided within a cup or recess 32 and first engagement formations 34 in the form of teeth. The movement of the actuation member in direction 28 causes movement of the means 30 in a direction towards the item to which the assembly is fitted. This in turn causes the first engagement formations 34 to engage with teeth 36 formed in a circular path internally of at least one of the wheel or roller parts 18, 20 to prevent rotation of the same about axis 14. It also causes the cup 32 to move into engagement with a substantially frustoconically shaped component 38 which is located along axis 16 at the end of the stem 10. Both the component 38 and cup 32 are provided with engagement formations which, when engaged, prevent relative rotation and hence prevent rotation of the body 24 about the axis 1 6. Furthermore it is found that the engagement of the end of the stem via component 38 in the cup 32 rather than trying to lock the stem at a location along the length of the stem serves to minimise the movement of the respective stem and body in the plane perpendicular to the axis 16 and it is found that this in turn greatly reduces the tendency for relative movement between the item and the castor assembly when the same are in the second mode of operation and hence reduces the possibility of wobbling of the top when the item is a table or desk.

In this second mode of operation the castor assembly forms a unitary assembly and effectively acts as an integral, fixed, part o f the item to which is fitted. This therefore reduces or prevents relative movement between the item and the castor assembly. In order to move the castor assembly to the first, unlocked, mode of operation, the actuation member is moved in the reverse direction to arrow 28 and this releases the engagement formations from contact and hence allows rotational movement of the castor assembly once again.

In the assembly shown in Figure 3 which shows a first embodiment of the invention the respective parts are shown as are described above. In this embodiment the means 30 acted upon by the actuation member is formed of two plates joined together by pegs 31 received in apertures 33 to form the single means 30 lying to either side of the body 24 as shown. In this case one of the parts has first and second engagement formation components 34, 32 formed thereon and the other part has a first engagement formation component 34 formed thereon.

In an alternative embodiment shown in Figure 4 two separate, unattached, means 30, 30' are provided. One of the means 30 is provided on one side of the body 24 and the other means 30' is provided on the other side of the body 24. In this arrangement, the first means 30 includes first engagement formations 34 thereon so as to engage with the teeth 36 of one of the rollers or wheels 1 8 which lie adjacent thereto on that side of the body. The other of the components 30' does not have a first engagement formation component 34 but instead includes second engagement formation component 32 provided as a cup so as to engage with the conical teeth of the substantially frustoconically shaped component 38 on the stem. Thus, in this embodiment, one means 30 is provided to lock and prevent rotation of the castor wheel and the other means 30' is provided with teeth 32 to prevent rotation of the stem 10 about the axis 16.

In either embodiment, in order to ensure that the movement of the means 30, 30', is maintained in a defined path so as to ensure engagement of the respective portions, guide means are provided to allow the guided movement of the means 30 between first and second modes of operation. In the embodiment shown in Figure 4, the side walls 50, 50' of the respective components 30, 30', are received within guide means grooves 52 provided on the mounting pin 54 on either side of the body. These grooves prevent lateral movement of the components 30, 30' with respect to the mounting pin while allowing the required vertical or pivotal movement of the components 30, 30' between locked and unlocked positions.

Typically, both of the components 30, 30' are acted upon, at the same time, by the movement of the actuating member 26 so as to ensure that both of the components 30, 30', move between the unlocking and locking positions at the same time.

In a yet further embodiment of the invention, the component 30 can be provided as in the first embodiment described herein or as components 30,30' described in the second embodiment and in either case, rather than linear movement being achieved by the movement of the actuating member 26, the pivotal movement of the actuating member 26 is translated into pivotal movement of the component 30 or components 30, 30' with the pivotal movement being guided by the respective shaping of the external faces 56 of the component or components with regard to the body.