Abstract:
Spool for receiving a wound skein product includes a rotationally symmetrical spool body, with two axial ends provided with flange discs ( 16, 18 ), the spool being divided into two parts ( 10, 12 ) by a substantially radial dividing surface, these parts having front surfaces ( 36, 38 ) running adjacent and parallel to the dividing surface ( 14 ), the front surfaces having locking projections ( 48, 50 ) on at least one surface and, on the other surface at least, detent recesses ( 40, 42 ) which interact with the locking projections of the other spool part ( 10, 12 ), respectively, interlocking therewith in the form of a bayonet catch by mutual rotation of spool parts ( 10, 12 ), and the front surfaces ( 36, 38 ) are contrived such that the dividing line appearing around the spool circumference is wave-shaped.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a spool for receiving a wound skein product comprising a rotationally symmetrical spool body with two axial ends provided with flange discs, said spool being divided into two parts by a substantially radial dividing surface, these parts having front surfaces running adjacent and parallel to the dividing surface, said front surfaces having locking projections on at least one surface and, on the other surface at least, detent recesses which interact with the locking projections of the other spool part respectively, interlocking therewith in the form of a bayonet catch by mutual rotation of the spool parts. 
   A spool of this type is disclosed in EP 404 043 A1, for example. DE 197 00 185 illustrates a similar solution. 
   In the case of these prior art spools, the spool parts taper conically towards the dividing surface. The advantage of the divisibility of the spools in connection with this conical tapering of the spool parts is that, once the skein product has been unwound, the spools can be taken apart and, thanks to their conical shape, stacked, so that they require little space during transport and storage. 
   But whilst the divisibility of the spools is associated with considerable advantages, it presents disadvantages in certain places. As, for example, when spools are used to wind very fine skein materials such as thin wires without insulation. These fine skein materials can slip into the gap between the two spool parts and become so firmly lodged that when the material is unwound, they remain in the gap and snap apart. This can hinder the process of unwinding the skein material and further necessitates additional work, as it is essential to remove any remaining skein material before reusing the spool. 
   Furthermore, experience has shown that it is impossible to press the two spool parts, which are usually made of plastic, so tightly together as to eliminate virtually any gap between them. This is true even where suitable sloping surfaces are provided in the bayonet connection used to join up the spool parts, or where thread-type structures are used to press the parts together (DE 40 01 250 A1). 
   SUMMARY OF THE INVENTION 
   The invention is therefore based on the task of providing a spool of the aforementioned type, where the gap between the spool parts is designed such that even very fine skein materials cannot slip into the gap. 
   This task is solved in that the spool of the above type is characterised in that the front surfaces are contrived such that the dividing line appearing around the spool circumference is wave-shaped. 
   As the skein material is always wound onto the spools of the type in question here in the circumferential direction, it cannot follow the wave-shaped path of the dividing line between the spool halves, and cannot therefore slip into the gap in any position. 
   Experience has shown that even a relatively flat wave shape such as a sinus line, for example, is sufficient to achieve the desired result. Experience has also shown that the spool parts of a spool with a wave-shaped dividing line can still be connected with connecting means based on the principle of a bayonet catch in spite of plausible initial reservations with respect to the possibility of the wave shape hindering the mutual rotation of the spool parts during connection. During the connection process, the two spool parts should initially be brought together with two wave peaks positioned opposite each other, and then rotated until the wave peaks engage with the wave troughs. The locking projections and detent recesses must naturally be disposed according to the wave structure. They must be disposed obliquely in relation to each other, in a manner corresponding to the axial distance between the wave peaks and troughs. 
   In practice, it is advisable to execute two absolutely identical spool halves so that they can both be injection-moulded as a plastic part using a single tool. In one preferred embodiment, each spool half therefore has both locking projections and detent recesses, which match up in pairs, respectively. Purely to connect the two spool halves, however, it would be sufficient to provide locking projections on one spool half and detent recesses on the other. The invention therefore also includes this type of embodiment. 
   Aligned with the detent recesses it is preferable to provide spring-loaded tongues which, in the connected position, engage behind the locking projections and prevent the bayonet connection from untwisting. Hence the bayonet connection can only be released when the spring-loaded tongues are pressed out of the locking position. 
   In the broadest sense, the locking projections can be described as mushroom-shaped in that they have a vertically projecting stem portion and a head that overhangs radially in relation to the stem portion. Accordingly, the detent recesses have an enlarged entry area adjoined in the circumferential direction by a narrower locking portion, behind whose lateral edges the respective heads of the locking projections engage. 
   A spool according to the invention can be manufactured from injection-moulded plastic in particular, and this process offers the opportunity to mould the spring-loaded tongues directly onto the edge of the detent recesses. 
   To release the spring-loaded tongues it is preferable to provide sliding pressure elements, which, when moved sufficiently, press the spring-loaded tongues out of their engaged position with the locking projections. Depending on the number of locking projections and detent recesses, these pressure elements can be executed as individual parts or may be mounted on a ring which can be rotated around the rear-facing front surface of the spool parts. 
   Rear face means the face of each front surface positioned furthest from the locking projections. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred example embodiments of the invention are described in more detail below with reference to the attached drawings. 
       FIG. 1  is a view of a spool with two spool parts, according to the invention; 
       FIG. 2  is a cross-sectional view showing the connection between the two spool parts; 
       FIG. 3  is a view from the outside of one of the spool parts onto the rear face of the connecting area; 
       FIG. 4  shows an exploded view of the connection; 
       FIG. 5  is the same as  FIG. 4 , but shows the individual parts in another position. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a spool according to the invention with a first spool part  10  and a second spool part  12 , which are coaxially connected to each other. Departing from a central dividing surface  14 , where the two spool parts  10 ,  12  meet up, both spool parts widen conically outwards in a truncated-cone shape to radially projecting flange discs  16 ,  18  at the outer ends. It is apparent that dividing surface  14  is executed such that a wave-shaped line is visible running around the circumference of the spool as the outer dividing gap. 
   In the vicinity of dividing surface  14 , both spool parts  10 ,  12  have front surfaces provided at least as circular ring-shaped surfaces. These front surfaces need not feature the wave shape of  FIG. 1  across their entire surfaces. Rather, it is sufficient if the outer portion of the two front faces closest to the circumference is wave-shaped so that a wave-shaped gap appears around the circumference. 
     FIG. 2  is a cross-sectional view showing the two inner ends of two connected spool parts  10 ,  12 . The lighter hatching shows the two spool parts  10 ,  12 , whilst the darker hatching denotes two rings which are connected on the inside of the cone to the rear face of the two front surfaces of the spool parts, where they can be rotated. The rings are denoted by  20 ,  22 . The function of the two rings  20 ,  22  will be described in more detail below in connection with  FIGS. 4 and 5 . 
     FIG. 3  shows a view into the conical hollow space inside one of spool parts  10 ,  12 . The reader should assume that the part in question is spool part  10 . The rotatable ring  20  can be seen in  FIG. 3 . This ring  20  has openings  24 ,  26 ,  28 , distributed at an equal distance around the circumference of the ring at an angle of 120°. Aligned with these openings there are recessed grips  30 ,  32 ,  34  to accommodate a finger in order to rotate the ring  20  in relation to spool part  10 . The distribution of openings  24 ,  26 ,  28  and recessed grips  30 ,  32 ,  34  coincides with the distribution of the connecting means for connecting two spool parts  10 ,  12 . Reference will additionally be made to  FIGS. 4 and 5  in order to explain these connecting means. 
   The connecting means basically comprise, as usual per se, detent recesses in front surfaces  36 ,  38 , in which the locking projections on the other front surface engage, and in which these locking projections can be locked in place by rotating, like a bayonet lock. In  FIGS. 4 and 5 , the detent recesses are designated on spool part  10  as  40 , and on spool part  12  as  42 . In one preferred embodiment three detent recesses are distributed around the circumference at an angle of 120°. The locking projections are distributed likewise. 
   The detent recesses  40 ,  42  may be described in the broadest sense as keyhole-shaped. They have an enlarged entry area running in the circumferential direction into a narrow, essentially strip-shaped locking section. The entry area is designated in  FIG. 4  as  44 , the narrower locking section as  46 . The locking section is limited on both sides by parts of the front surface executed as sloping surfaces, as will be described in more detail below. 
   The locking projections may be described in the broadest sense as mushroom-shaped, as they have a narrow stem portion and a head which overhangs the stem portion laterally. The locking projections are designated as  48 ,  50  in  FIGS. 4 and 5 . Taking as an example one of the locking projections, designated in  FIG. 4  as  56 , it can be seen that locking projection  56  comprises a stem  52  which is narrower in the radial direction, and a head  54 , which overhangs in the radial direction. 
   When the two spool parts are joined, locking projections  48 ,  50 ,  56  are brought into the enlarged entry areas of detent recesses  40 ,  42 , and when the spool parts are then mutually rotated, heads  54  engage in the narrower locking sections  46 . The non-designated sloping surfaces on both sides of the narrower locking sections ensure that the two spool parts are tensioned tightly against each other. The sloping surfaces also serve to compensate for the axial difference in height between the wave peaks and troughs of the front surfaces. 
   As shown in  FIGS. 4 and 5  in the view of the top spool part  10 , a spring-loaded tongue  58  is provided adjacent to the entry area of detent recess  40 . When locking projections  50  as in  FIGS. 4 and 5  are pushed into the enlarged entry area of the detent recesses in the axial direction and the two spool parts  10 ,  12  are then mutually rotated, the spring-loaded tongue  58  is first pushed up through the head  54  of the locking projections so that the locking projection can enter into the narrower locking section  46 . When the locking projection reaches this section, the spring-loaded tongue  58  springs back or downwards in  FIG. 5  into the position shown in  FIG. 4 . In this position, the spring-loaded tongue engages in a recess  60  ( FIG. 5 ) on the rear face of locking projection  50 , so that the locking projection cannot be untwisted and the bayonet connection, once established, cannot be released. 
   To release the bayonet connection the spring-loaded tongue  58  has to be pressed upwards, as shown in  FIG. 5 , out of recess  60  on the rear face of locking projection  50 . 
   Various types of pressure elements may be provided for this purpose, disposed slidingly on the corresponding spool. According to the invention, rotatable rings  20 ,  22  are provided for this purpose. 
   Rings  20 ,  22  are rotatably attached to the rear or inner faces of front surfaces  36 ,  38 , which, like the two spool parts  10 ,  12 , are executed in identical fashion, so that the text below will refer to the ring  20  for the top spool part  10  shown in  FIGS. 4 and 5 . 
   On the underside of ring  20  shown at the top of  FIG. 5 , there is a pressure element  62 , which, once attached to spool part  10 , moves beneath spring-loaded tongue  58 . On the underside of spring-loaded tongue  58 , there is a sloping surface  64 . When ring  20  is rotated so that pressure element  62  moves from left to right beneath spring-loaded tongue  58  as shown at the top of  FIG. 5 , the spring-loaded tongue is lifted into the position shown in  FIG. 5 , and locking projection  50  can again be twisted in the opening direction of the bayonet connection. 
   Pressure elements  62  are provided with a projecting coupling part  66  in the direction of the other spool part. When the two spool parts are separated, i.e. when the locking projections are moved out of the narrower locking sections  46  and into the larger entry areas  44  of the locking projections, this coupling part  66  is carried by the locking projections of the other spool part. When the two spool parts  10 ,  12  are taken apart, rings  20 ,  22  are thus returned to a position corresponding to the locking position, in which, therefore, the spool parts cannot be taken apart. This position is maintained when the two spool parts  10 ,  12  are reassembled. 
   The present description and the following claims are based on the assumption that both front surfaces are provided with corresponding locking projections and detent recesses. Obviously, a connection can be achieved with locking projections on one surface and detent recesses in the other, even though, with this type of solution, the connection between the two spool parts may be less tight. 
   Hence the dual-surface arrangement of both locking elements—locking projections and detent recesses—as envisaged by the invention—is considered preferable. 
   There may be openings in the winding core surfaces of the two spool parts  10 , 12  to allow treatments for the windable product to filter through the latter from the inside of the spool parts, for example warm air to dry the windable product, or a gas or liquid for treating the windable product in some specific way.