Production of releasably secured sleeve elements

Abstract

A conical thread structure α 1 , α 2 , t is provided to simplify the removal of threads in plastics sleeve elements 1,2,3,4 and to decrease production cost. The radial distance of the thread elements 50,60,51,61 of said thread structure and of the corresponding form tools, which elements being adjacent in translational z or −z direction, are dimensioned such that, when removed E0,E1,E2 of F0,F1 from the mold each thread element “snaps out” only once and does not snap into a second time.

1 . Process for production of sleeve elements ( 1 , 2 ) made of plastics material, which elements are easily removable from their mold ( 21 , 12 ) and releasable secured (by screwing)—particularly connecting the rear shaft ( 2 ) and the front gripping sleeve ( 1 ) or of the rear head piece or cap ( 3 ) and the front shaft ( 4 ) of a writing instrument—, wherein 
 (a) a series of thread webs, thread segments or thread points ( 1 , 1   a ′,  1   a ″, 1   a *) periodical in axial direction (z, 100 ), is provided on a slightly conical thread basis of one of said sleeves ( 1 );  
 (b) a series of webs or segments ( 1   a ,  1   a ′,  1 ″) periodical in axial direction (z, 100 ), is provided on a slightly counter-conical basic surface of the other one ( 2 ) of said sleeves ( 2 ).  
 
     
     
         2 . Process according to    claim 1   , wherein the angle of inclination (α 2 ) of one or both of said conical and counter-conical basic surface is adapted to the radial height (t) of said segments, webs or points ( 1   a,   1   a ′, 1   a ″, 1   a *) such that when removed (E 1 ,E 2 ) from the injection mold ( 12 , 21 ) with substantially translational removal movement, none of them snaps into a tool contour again, a slight plastic or ductile deformation not being regarded as “snapping into”.  
     
     
         3 . Process according to one of the aforementioned claims, wherein the removal from the mold ( 20 , 21 ) in direction of the axis (z) is effected by elastic (radial) deformation of said thread elements (webs, segments, points).  
     
     
         4 . Process according to    claim 1    or    2   , wherein the removal from the mold ( 21 , 21 ) in direction of the axis (z, 100 ) is effected by plastic or ductile radial 
 deformation with slight modification of said thread elements (webs, segments or points).  
 
     
     
         5 . Process according to one of the aforementioned claims, wherein the removal of said thread elements from the mold is effected in only axial direction (z, 100 ), particularly without or without substantial radial follower motion or screw motion.  
     
     
         6 . Process according to one of the aforementioned claims, wherein said thread webs, segments or points (thread elements) have rounded (R) edges.  
     
     
         7 . Form tool for carrying out the process according to one of the aforementioned claims, having 
 (a) a negative contour ( 12   a , 21   a ) of a thread structure (webs, segments, naps or points) of a female or male thread ( 1   a , 2   a ) of a sleeve ( 1 , 2 );    (b) a projection (X 1 ) in the form tool ( 12 , 21 ) for forming a recess ( 50 , 60 ,I 1 ) in the thread structure ( 1   a , 2   a ) of the sleeve, said projection radially not protruding or protruding only slightly with respect to 
 the next form tool recess (X 4 ) adjacent at least at a distance (σ) of the thread pitch contrary to the removing direction (z, 100 ); or  
 the next but one form tool recess (X 4 ) adjacent in axial direction (z, 100 ) for the molding of the next but one (the next one after the next) or the following elevation ( 51   b , 61   b ,I 4 ) respectively of the thread structure ( 1   a , 2   a ) of the sleeve; or  
   (c) a first projection (X 1 ;X 4 ) in the form tool ( 12 , 21 ) for forming a first recess ( 50 , 60 ,I 1  ;A 4 ) in the thread structure of the sleeve ( 1   a , 2   a ), said first projection (X 1 ;X 4 ) having a radially smaller dimension with respect to a second projection (X 3 ;X 2 ) in the same form tool ( 12 , 21 ), said second projection (X 3 ;X 2 ) being adjacent in a direction opposite to the direction of removal for forming a second recess ( 50   a , 60   a ,I 3 ;A 2 ) adjacent to the first recess ( 50 , 60 ,I 1 ;A 4 ) in the same thread structure of the sleeve ( 1   a , 2   a ).    
     
     
         8 . Form tool according to    claim 7   , wherein a connecting line of all form tool projections constitutes a (straight) line which is inclined or slant (α 2 ) with respect to said axis ( 100 ) or said removal direction (z) of said form tool ( 12 , 21 ) or said sleeve ( 1 , 2 ).  
     
     
         9 . Form tool according to    claim 8    or    7   , wherein a connecting line of all form tool recesses constitutes a second line which is inclined (α 2 )—particularly by the same angle (α 2 ) as the aforementioned first line—with regard to said axis ( 100 ) or said removal direction (z) of said form tool ( 21 , 12 ) or said sleeve member ( 1 , 2 ).  
     
     
         10 . Form tool according to one of the    claims 7    to    9   , wherein the second form tool recess (X 4 ) located prior to a form tool projection (X 1 )—viewed in mold removal direction (z)—substantially has the same radial dimension as said form tool projection (X 1 ), so that 
 (a) said form tool ( 21 ) is—viewed in direction (z) of the removal movement (F 1 ) of the external sleeve —slightly conically reduced in the thread molding section ( 21   a ) for the molding of a conical (inner) thread ( 2   a ); or  
 (b) the thread molding section ( 1   a ) of said form tool ( 12 ) has a slightly conical expansion—viewed in direction (z) of the removal movement (E 2 ) of said sleeve element ( 1 ) with outer thread—for the molding of a conical (outer) thread ( 12   a ).  
 
     
     
         11 . Sleeve element with conical quick-connecting thread section ( 1   a , 2   a ) for a writing instrument, such as a ball-point pen, pencil with retractable point or ink writer, produced according to one of the aforementioned process claims or with an apparatus according to one of the aforementioned apparatus claims, wherein said sleeve element ( 2 , 4 ,HI,HA) is provided with several, particularly more than two, bayonet-type thread elements (webs, segments or points) being circumferentially spaced with respect to each other and—in axial direction (z, 100 )—located one after the other, but on continuously offset radial levels on a conical basic surface.  
     
     
         12 . Sleeve element with conical quick-connecting thread section ( 1   a , 2   a ) on a conical thread basic surface produced according to one of the aforementioned process claims or with an apparatus according to one of the aforementioned apparatus claims, wherein said sleeve element ( 2 , 4 ,HI,HA) is provided with a helical or spiral—continuous—thread web ( 1   a , 2   a ) being radially dimensioned such that—viewed in section—a first thread web height (I 4 ,A 1 ) has substantially the same radial dimension as the next but one (the next one after the next) thread root (I 1 ,A 4 ) in removal direction (+z,−z, FIG. 8).