Patent Publication Number: US-6910825-B2

Title: Cap for a writing drawing or painting instrument

Description:
This patent is the U.S. National Phase of International Application No. PCT/DE02/02445, which was filed on Jul. 4, 2002. 

   The present invention relates to a cap for a writing, drawing or painting implement with a cap sheath and a clamping ring. 
   Many writing implements with removable caps, especially fountain pens, possess a screw-on cap which, while ensuring a secure connection between the housing of the writing implement and the cap, is nevertheless inconvenient and therefore cannot be used quickly. 
   DE-U 1 802 121 discloses a cap with a clamping ring disposed on the housing of the writing implement that provides a snap connection. There is, however, a risk that the snap connection might give way and that the housing might slip out of the cap or that the cap might slip out of the housing. 
   The invention is therefore based on the problem of improving the generic cap in such a way that a secure connection is provided between the housing of a writing, drawing or painting implement and the cap, while at the same time ensuring ease of operation. 
   In accordance with the invention, this problem is solved by having the clamping ring disposed separately in the cap sheath and designing the inner peripheral surface of the cap sheath and the outer and inner peripheral surfaces of the clamping ring such that, by placing the cap on the housing of a writing, drawing or painting implement and then executing a relative axial twist between the cap and the housing, a firm axial fit between the cap and the housing results. 
   In particular, it can be provided for the inner peripheral surface of the clamping ring to be designed such that, by placing the cap on the housing, a friction fit or positive fit results between the clamping ring and the housing. 
   In addition, it can be provided for the inner peripheral surface of the cap sheath and the outer peripheral surface of the clamping ring to be designed such that, by placing the cap on the housing of the writing, drawing or painting implement and then executing a relative axial twist between the cap and the housing, a friction fit results between the cap sheath and the clamping ring. 
   A particular embodiment of the invention is characterised by the fact that at least one wedge-shaped surface rising radially in the circumferential direction is disposed on the outer peripheral surface of the clamping ring and that a corresponding number of matching wedge-shaped surfaces are disposed on the inner peripheral surface of the cap sheath. 
   It is advantageous for the slopes of the wedge-shaped surfaces facing each other after the clamping ring has been inserted into the cap sheath to be identical. 
   Finally, it can be provided for the cap to be designed such that it can be placed on the housing and creates a seal in the process. 
   The invention is based on the surprising finding that the use of a clamping ring which develops its function by twisting the cap makes it possible to create a secure connection in a simple manner. The cap can be placed on in the usual manner and locked in place with a simple twist (&lt;120°). The use of a separate clamping ring means that it is not necessary to search radially for the correct position, as is the case with a bayonet catch. 
   Furthermore, during the production of the cap, no spindle removal is needed, which would be necessary with a thread for a screw connection. 

   
     Further features and advantages of the invention will become apparent from the claims and the following description, in which one working embodiment is explained in detail with reference to the schematic drawings. There, 
       FIG. 1  shows a longitudinal section view of a cap sheath of a cap in accordance with a particular embodiment of the invention; 
       FIG. 2  shows a section view along the line II—II in  FIG. 1 ; 
       FIG. 3  shows a view of the side wall of a housing for a writing implement; 
       FIG. 4  shows a perspective view of a clamping ring for the cap; 
       FIG. 5  shows a view of the clamping ring in the direction of arrow A in  FIG. 4 ; 
       FIG. 6  shows a view of the clamping ring in the direction of arrow B in  FIG. 4 ; 
       FIG. 7  shows a section view along the line VII—VII in  FIG. 6 ; 
       FIG. 8  shows a longitudinal section view of the housing of  FIG. 3  with the cap attached; 
       FIG. 9  shows a further longitudinal section view of the housing of  FIG. 3  with the cap attached; and 
       FIG. 10  shows a section view along the line X—X in FIG.  8 . 
   

   The cap sheath  10  shown in  FIG. 1  has an open end  12  and a closed end (not shown). Beginning at the open end  12 , the cap sheath has a first portion  14  with an internal diameter d 1 , a second portion with three wedge-shaped surfaces rising radially in the circumferential direction, only two of which, namely  18  and  20 , are visible, a third portion  23  with an internal diameter d 2 , where d 2 &lt;d 1 , a fourth portion  24  with an internal diameter d 3 , where d 3 &lt;d 2 , and a fifth portion  26  with an internal diameter d 4 , where d 4 &lt;d 3 . This creates inwardly projecting shoulders  28  and  30 . Shoulder  30  serves as a stop face for a clamping ring (not shown). 
   As  FIG. 2  shows, the wedge-shaped surfaces  18 ,  20  and  22  each extend through 120°. 
   The housing  32  of a writing implement shown in  FIG. 3 , e.g. a fountain pen, has a housing tip  34  with two cylindrical portions  36  and  38  with different external diameters, which are connected to one another via a frustoconical portion  40  and the shoulder  39 . 
     FIG. 4  shows a perspective view of a clamping ring  42 . It can be clearly seen that, in its longitudinal direction, the clamping ring  42  has wedge-shaped surfaces  44 ,  46  and  48  on the outer peripheral surface  3  rising radially over a portion in the circumferential direction, which are shaped in accordance with the wedge-shaped surfaces  18 ,  20  and  22 . Between the wedge-shaped surfaces  44 ,  46  and  48  in each case, there is a gap  50 ,  52  or  54 . 
   The clamping ring  42  can be subdivided into three portions  56 ,  58  and  60 . The wedge-shaped surfaces  44 ,  46 ,  48  are disposed in portion  56 . Three shoulders  62 ,  64  and  66  (see also  FIG. 6 ) extending in the circumferential direction merely over a partial portion are provided in portion  58 . The third portion  60  has a constant external diameter, which is less than the effective external diameter of portions  56  and  58 . 
     FIG. 5  shows a view of the clamping ring  42  in the direction of the arrow A. Each gap  50 ,  52  and  54  extends over an angular range of 10°. 
     FIG. 7  shows a section view along the line VII—VII of FIG.  6 . 
     FIG. 8  shows a longitudinal section view of the housing  32  of  FIG. 3  with the cap  68  attached. The section corresponds to the section of FIG.  7 . The cap  68  comprises the cap sheath  10  and the clamping ring  42 , which is separate from the cap sheath. The clamping ring  42  is in friction fit with the housing  32 . In addition, it can be seen that the shoulder  39  of the housing  32  abuts a shoulder  70  on the inside of the clamping ring  42 . The clamping ring  42 , for its part, has a portion  60  which abuts the shoulder  30  (see  FIG. 1 ) of the cap sheath  10 . 
     FIG. 9  shows a further longitudinal section view of the housing  32  of  FIG. 3  with the cap  68  attached. Whereas the section shown in  FIG. 8  runs through the shoulder  64 , this section passes through one of the gaps  50 ,  52  and  54 . 
     FIG. 10  shows a section view along the line X—X of FIG.  8 . The three wedge-shaped surfaces  18 ,  20  and  22  of the clamping ring  42  and the corresponding wedge-shaped surfaces  44 ,  46  and  48  of the cap sheath  10  can be seen clearly. When the clamping ring  42  is twisted relative to the cap sheath  10 , its internal diameter is reduced accordingly. This leads to the cap  68  being clamped and thus also being firmly seated axially on the housing  32 . The twisting imparted to the clamping ring  42  is caused by the friction fit with the housing  32 . The cap  68  can be placed on in the usual fashion and locked in place with only a slight twist (&lt;120°). 
   The features of the invention disclosed in the above description and in the claims can be essential, both alone and in any combination, for carrying out the invention in its various embodiments.