The invention relates to a pottery holding assem bly intended for use on a pottery wheel head, comprising a lower disc with a plurality of settable wheel head engage ment members, and an upper disc which in a concentric and rotatable manner is attached to and positioned on top of the lower disc, wherein the lower disc has a top surface that faces the upper disc and at which a number of spiral shaped guides are provided, whereas the upper disc is provided with a corresponding number of radial slots fully traversing a width of the disc between an upper and lower surface of the upper disc and opening at an outer rim of the upper disc, and slide members slidably housed in said slots which each carry a lower guide member protruding downwardly therefrom and engaging a respective one of the spiral shaped guides of the lower disc, and wherein each slide member further sup ports an upwardly extending pottery engagement member defin ing a pottery engaging surface intended for engaging a pot tery item held by the holding assembly.

Examples of such a pottery holding assembly are known from documents US 4,222,577 and US 4,585,240. In these known pottery holding assemblies the pottery engaging sur faces of the pottery engagement members depending on the relative rotation between the lower and upper disc move ra dially inwards and outwards together with the slide members, and always assume similar radial positions. This makes these pottery holding assemblies particularly fit for holding reg ularly shaped (for example circular) pottery.

It is an object of the present invention to pro vide an improved pottery holding assembly of the above- mentioned type.

Thus, in accordance with the present invention the pottery holding assembly is characterized in that the pot tery engagement member comprises an engagement head with a circumference which defines the pottery engaging surface, which head is rotatable relative to the remaining part of the pottery engagement member around an axis of rotation and wherein the circumference comprises circumference sections with different radial distances to the axis of rotation.

Thus, in such an embodiment the circumference of the engagement head defines the pottery engaging surface and by rotating the head different sections of the circumference (which assume different radial positions with respect to the upper disc) can be brought into engagement with the pottery item to be held. As a result the pottery engagement member is adjustable relative to the slide member such that, with out the need for a movement of the slide member along the respective radial slot, the pottery engaging surface can be defined at different radial positions relative to the upper disc .

In effect this means that the pottery engaging surfaces of different pottery engagement members may assume different radial positions, which allows to also effectively hold irregularly shaped pottery at a desired position on the upper disc (and thus on the pottery wheel head) . For example it is possible to position a pottery item at the desired lo cation on the upper disc when the slide members with pottery engagement members are sufficiently spaced apart, whereupon the upper disc is rotated with respect to the lower disc to move the slide members with pottery engagement members radi ally inwards until at least one pottery engaging surface of one pottery engagement member engages the pottery item. Next the remaining pottery engagement members are adjusted (with out changing the radial position of the respective slide members) such that their pottery engaging surfaces also will engage the pottery item.

The pottery holding assembly can operate both in a standard manner with regularly shaped pottery items (only radially moving the slide members) and in a novel manner with irregularly shaped pottery (both radially moving the slide members and subsequently adjusting at least one of the pottery engaging members) .

The circumference of the engagement head may have many different shapes (of which, in general, a common fea ture is that such shapes are not a circle with the axis of rotation as centre; if this would be the case, a rotation of the engagement head would not lead to a radial displacement of the position where the circumference engages the pottery item) . In one specific embodiment the circumference at least in part defines a spiral shape around the axis of rotation.

Also the manner in which the engagement head can rotate, may be accomplished in many different ways. In one embodiment the engagement head and remaining part of the pottery engagement member are provided with cooperating re cess and projection which are profiled such that the projec tion can be removably received in the recess in a plurality of different rotational positions. Thus, for adjusting the rotational position of the engagement head, the recess and projection firstly are disengaged, next the required rota tional position of the engagement head is set and finally the recess and projection again are engaged for maintaining the engagement head in the chosen rotational position.

In a specific embodiment the remaining part of the pottery engagement member comprises a bar with polygonal cross section wherein the recess is defined in the engage ment head and likewise has a polygonal shape. As an alterna tive (which however is fully equivalent) the engaging head may be provided with such a bar, whereas the remaining part of the pottery engagement member is provided with the re cess.

In one embodiment the bar has a square cross sec tion and the recess has a similar square shape or a star- shape with a number of points which is at least four or an integer multiple of four, and preferably with eight points. However, it is noted that many other shapes of the cross section of the bar and shapes of the recess are con ceivable which allow to position the bar in many different rotational positions in the recess. Thus also, for example, triangular or hexagonal cross sections of the bar are con ceivable, with appropriate shapes of the recess.

In another embodiment it is conceivable the bar is removably attached to the slide member. This allows to re place the bar by a different bar, for example a bar with a different length for optimizing the height where a pottery item is engaged by a respective engagement head. This fur ther increases the versatility of the pottery holding assem bly.

In such an embodiment it further is possible that the slide member is provided with a plurality of recesses for removably receiving the bar at different locations. Such a plurality of recesses (which will have different radial positions) already allows to change the radial position of a respective engagement head (and, thus, of its engaging sur face) without the need to change the radial position of the slide member. This further increases the versatility of the assembly .

For further optimising the manner in which a pot tery item is held by the pottery holding assembly, the pot tery engaging surface in one embodiment comprises a com pressible cushioning material. The compressibility of such cushioning material also allows a certain radial setting of the pottery engaging surface.

In yet another embodiment the pottery holding as sembly further comprises an angular subdivision aid slidable around the upper disc and provided with a marking allowing an angular subdivision to be made with respect to a pottery item. Using such an aid a pottery item in a very precise manner may be subdivided in a required number of sections (with each a specific angular extent) . The marking on the aid comprises, for example, marking points with a specific spacing, depending on the number of sections to be defined. The aid may, for example, be guided around the upper disc along a circular guide channel provided therein or along the outer rim of the upper disc for assuming consecutive marking positions .

In such an embodiment it is conceivable that said subdivision aid also comprises a vertical extending height subdivision aid allowing a height subdivision to be made with respect to a pottery item. Such a height subdivision aid may comprise a plate-like member provided with a height scale which in a removable manner may be attachable to the angular subdivision aid.

When the pottery holding assembly further compris es extension pieces which in a removable manner are attacha ble to the outer circumference of the upper disc for enlarg ing the effective diameter thereof, the assembly can be used with pottery items with an enlarged diameter range. In such an event, special slide members may be used which still en gage the spiral shaped guides of the lower disc (which has not been enlarged) but which are extended outwardly beyond the outer rim of the upper disc (in its original diameter) .

In such an embodiment it is of advantage when the number of extension pieces is equal to the number of slots in the upper disc wherein each extension piece is dimen sioned as to extend between two adjacent slots. As a result additional slots in line with the slots in the upper disc may be defined between adjacent extension pieces which may be used for guiding respective (extended) parts of the slide members .

In a specific embodiment the pottery holding as sembly according to the present invention comprises three slots positioned at angular intervals of 120°. This means that also three pottery engagement heads are present, which number is very effective in properly holding a pottery item. Hereinafter the invention will be elucidated while referring to the drawings, in which:

Figure 1 in a schematical manner, in perspective and in a partly taken apart position illustrates an embodi ment of the pottery holding assembly;

Figure 2 shows the constitutive parts of a combi nation of slide member and pottery engagement member in a perspective view;

Figure 3 shows a cross section according to III- III in figure 2;

Figure 4 shows a view according to IV in figure 2;

Figure 5 illustrates the use of extension pieces and of an angular subdivision aid, and

Figure 6 shows a combination of angular subdivi sion aid and height subdivision aid.

Firstly referring to figure 1 an exemplary embodi ment of a pottery holding assembly according to the inven tion is illustrated in a partly taken apart position. The pottery holding assembly is intended for use on a pottery wheel head (of which only a rotation axis 1 has been indi cated schematically by a broken line) .

The assembly comprises a lower disc 2 with a plu rality of settable wheel head engagement members 3. With the aid of such engagement members 3 the assembly can be remova bly attached to the pottery wheel head (for example through engagement with an outer rim of the wheel head) . Further the assembly comprises an upper disc 4 which in a concentric and rotatable manner will be attached to and positioned on top of the lower disc 3, for example using a bolt member 5 pene trating the lower disc 2 in an upward direction and engaging a central threaded hole 6 in the upper disc 4. Generally the bolt member 5 will be concentric with the rotation axis 1, and thus this generally also will apply for the upper and lower discs. The lower disc 2 has a top surface 7 that faces the upper disc 4 and at which a number (here three) of spi ral shaped guides 8 are provided. Depending on the embodi ment these guides may comprise elevated structures on top of the top surface 7 (such as ridges) or may comprise recessed structures in said top surface 7 (such as channels) . Gener ally these guides 8 start at the outer rim 9 of the lower disc with a radial part that has a length of at least the width of the radial part of said guides and from there spi rally extend inward.

The upper disc 4 is provided with a corresponding number (here three) of radial slots 10 fully traversing a width of the upper disc 4 between an upper and lower surface of the upper disc and opening at an outer rim 11 of the up per disc. Slide members 12 are slidably housed in said slots 10 for a movement therein (for example the slots have a cross section corresponding to a cross section of the slide members) . These slide members 12 each carry a lower guide member 13 protruding downwardly therefrom below the lower surface of the upper disc. These guide members 13 are in tended to engage a respective one of the spiral shaped guides 8 of the lower disc 2. For example, when said spiral shaped guides 8 comprise channel-like recesses, the lower guide members 13 will comprise guide pins projecting into said recesses.

When the lower and upper discs 2 and 4 are assem bled, the guide members 13 of the slide members 12 will co operate with the spiral shaped guides 8 in such a manner that a relative rotation between said discs urges the lower guide members 13 along the spiral shaped guides 8 and thus moves the slide members 12 radially along the radial slots 10.

Each slide member 12 further supports an upwardly extending pottery engagement member 14 defining a pottery engaging surface 15 (for example made of a compressible cushioning material such as rubber) intended for engaging a pottery item (not illustrated) held by the holding assembly in a substantially centred position on top of the upper disc

4.

As will appear from the below description, each pottery engagement member 14 is adjustable relative to the slide member 12 such that, without the need for a movement of the slide member 12 along the respective radial slot 10 (thus without a rotation of the upper disc 4 relative to the lower disc 2), the pottery engaging surface 15 can be de fined at different radial positions relative to the upper disc 4 by rotating a respective part, as will be discussed below. This means that the radial position where a pottery engagement member 14 engages a pottery item with its pottery engagement surface 15 can be individually set for each sepa rate pottery engagement member 14, thus allowing to also se curely hold more irregularly shaped pottery items compared to the state of the art in which such radial position only can be changed for all pottery engagement members 14 simul taneously (by rotating the upper disc 4 relative to the low er disc 2 ) .

Some details of a pottery engagement member in a preferred embodiment thereof are illustrated in figures 2-4. In figure 2 a slide member 12 is illustrated which can sup port a pottery engagement member 14 which, in the illustrat ed embodiment, firstly comprises a bar 16 (for example made of stainless steel) having a polygonal (here square, see figure 3) cross section. The slide member 12 is provided with a plurality (here five) recesses 17 for releasably re ceiving one end of the bar 16. The pottery engagement member 14 secondly comprises an engagement head 18 with a circum ference which defines the pottery engaging surface 15. At its lower side (see figure 4) the engagement head 18 is pro vided with a polygonal recess 20. The recess 20 and (at least the upper end of) the bar 16 are profiled such that said upper end of the bar 16 can be removably received in the recess 20 in a plurality of different rotational posi tions. As stated before, the bar 16 in the illustrated em bodiment has a square cross section and the recess thus may have a similar square shape or, for example, a star-shape with a number of points which is at least four or an integer multiple of four, and preferably with eight points as illus trated in figure 4. This means that the bar 16 can be re ceived in the recess 20 in eight different angular posi tions. Thus one might say that engagement head 18 is rotata ble relative to the remaining part (here the bar 16) of the pottery engagement member 14 around an axis of rotation 21.

The circumference of the head 18 defining the pot tery engaging surface 15 comprises circumference sections with different radial distances to the axis of rotation 21, and in the illustrated embodiment said circumference at least in part defines a spiral shape around the axis of ro tation 21 (best illustrated in figure 4) .

Thus, in addition to a relative rotation between the upper and lower discs 4 and 2, a rotation of the head 18 offers an extra possibility to change the radial position where the pottery engagement member 14 (with its engaging surface 15) will engage a pottery item. A further adjustment is possible by placing the bar 16 in a different one of the recesses 17 in the slide member 12.

While in the illustrated embodiment the head 18 is stepwise rotatable relative to the bar 16, also an embodi ment with stepless rotation may be conceived. Further such a rotation instead (or additionally) may be accomplished at the junction between the bar 16 and slide member 12.

Referring to figure 5 (which shows a top plan view of the upper disc 4) extension pieces 22 are illustrated which in a removable manner are attachable to the outer cir cumference or rim 11 of the upper disc 4 for enlarging the effective diameter thereof. For example, the extension piec- es 22 may comprise projections 23 which snap in openings 24 of the upper disc.

Each extension piece 22 is dimensioned as to ex tend between two adjacent slots or, more precisely, to ex tend between outer prolongations 10' of the slots. As a re sult a properly shaped (for example longer) slide member 13, while engaging a spiral shaped guide 8 of the lower disc 2 with its lower guide member 13, also in part may be posi tioned in such a prolongation 10', such that a larger pot tery item may be held.

In figure 5 also an angular subdivision aid 25 is shown which can be placed in a position to be slidable around the upper disc 4. This aid 25 is provided with a marking 26 (only illustrated schematically) that corresponds with a second marking 31, consisting of one or more polygo nal line figures provided on the top surface of the upper disc 4, allowing an angular subdivision to be made with re spect to a pottery item. In one embodiment the angular sub division aid 26 may carry a guide rim 27 on a bottom surface (see figure 6) which may cooperate with the outer rim 11 of the upper disc 4 and/or with a seam 28 between said outer rim 11 and an inner edge of the extension pieces 22.

As shown in figure 6, this subdivision aid 26 also may comprise a vertical extending height subdivision aid 29 with respective marking 30 allowing a height subdivision to be made with respect to a pottery item. Such a height subdi vision aid 29 may exist of a strip which in a detachable manner (for example by a snap connection) may be connected to the angular subdivision aid 26.

The invention is not limited to the embodiments described before which may be varied widely within the scope of the invention as defined by the appending claims.