Abstract:
A stator ( 1 ) and sleeve ( 5 ) are secured to one another by means of nonpositive engagement in the form of a bayonet mount ( 30 ). The apparatus is employed in particular in electric motors.

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on an apparatus with a stator and a sleeve. 
     From British Patent Disclosure GB 2303744 A1 or GB 1401234 A1, it is already known for a stator to be secured in a housing by means of a heat fit or shrink fit. However, this method is complicated since the housing has to be heated, and during use the combination of stator and housing can come loose again during heating of the housing. 
     French Patent Disclosure FR 2726700 A1 already shows how a bayonet mount is used to secure a brush holder housing to a stator. However, this brush holder housing does not surround the stator. 
     From U.S. Pat. No. 4,992,686, it is also known for a stator to be secured in the axial direction in a housing by means of a bayonet mount. However, the bayonet mount is not formed here by the outer housing and stator but rather by an additional element and the housing. This additional element is forced into the housing and rotated therein and thereby secures the stator in the housing. 
     SUMMARY OF THE INVENTION 
     The apparatus of the invention with a stator and a sleeve has the advantage over the prior art that a sleeve can be secured to a stator in a simple way. 
     One advantageous embodiment of a bayonet mount is that the bayonet mount is formed by nonpositive engagement. 
     For the magnetic properties of the stator, it is advantageous if the stator comprises at least one lamination packet. 
     It can be equally advantageous for the magnetic properties of the sleeve if the sleeve comprises at least one lamination packet. 
     An advantageous use of the sleeve is that it form a magnetic short-circuit element. 
     It is also advantageous if the stator has an at least partly present plastic sheath, which can also form a bayonet mount with the sleeve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One exemplary embodiment of the invention is shown in simplified form in the drawing and described in further detail in the ensuing description. 
     Shown are 
     FIG. 1, an apparatus according to the invention, with a stator and a sleeve; 
     FIG. 2, a stator pole tooth; 
     FIGS. 3 a  and  3   b,  a detail of the apparatus of FIG. 1 with a stator and a sleeve, in the open and closed state of a bayonet mount. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an apparatus having a stator  1  embodied according to the invention and a sleeve  5  embodied according to the invention, of the kind used for instance in an electric motor. 
     The apparatus with the stator  1  and sleeve  5  has a center axis  7 . Stator pole teeth  11 , for instance six of them, are distributed, uniformly for example, about the center axis  7 . The stator  1  can comprise a solid material or can for instance comprise a lamination packet that is formed of at least one lamination. 
     In this exemplary embodiment, each stator pole tooth  11  forms one lamination packet; that is, there are six separate lamination packets, which are connected as individual stator pole teeth  11  to one another in a non-magnetically conductive fashion. 
     The stator  1  has a plastic sheath  15 , which for instance is at least partially present and which in this exemplary embodiment carries and holds together the individual stator pole teeth  11 . If the stator  1 , which has magnetically conductively connected stator teeth  11 , comprises a lamination packet or a solid material, then nevertheless a plastic sheath may be present, for instance to protect the stator  1  against corrosion or to form a waterproof inner conduit  18 . The sleeve  5  can likewise comprise solid material or at least one lamination packet. If the sleeve  5  comprises a soft magnetic material, it can also act as a magnetic short-circuit element. A rotor (not shown) is for instance disposed around the center axis  7  and together with the stator  1 , among other elements, forms an electric motor. Such a rotor is shown for instance in GB 2303744 A1. 
     FIG. 2 shows a stator pole tooth  11 . The stator pole tooth  11  has a pole foot  45 , a pole head  47 , and a pole tooth axis  21 , which passes through the center axis  7 . An inner radius  22 , forming a inner face  49  of the pole foot  45  of the stator pole tooth  11 , this foot being embodied in curved fashion, likewise passes through the center axis  7 . An outer radius  26  on the pole head  47 , also embodied in curved fashion, of the stator pole tooth  11  extends from an offset axis  24  that extends parallel to the center axis  7 . The offset axis  24  is offset from the center axis  7  by a spacing a, for instance along a line  51  extending perpendicular to the pole tooth axis  21  and in the plane of the drawing. On each pole head  47  of the stator pole teeth  11 , this creates curved outer faces  43 , which are offset from the inner face  49  of the pole foot and to which the sleeve  5  can be joined with play in a rotated position. If the sleeve  5  is then rotated relative to the stator pole teeth  11 , then as a consequence of positive engagement, the sleeve  5  becomes wedged at the stator pole teeth  11 , which has the effect of a bayonet mount  30 , thereby compensating for slight production variations. 
     FIG. 3 a  shows a stator  1  with a sleeve  5  in a position of the bayonet mount  30  in the open state, and FIG. 3 b  shows it in a position of the bayonet mount  30  in the closed state. 
     The sleeve  5  has at least one shoulder  37 , for instance on its inner face  33 . There are repeated shoulders  37 , spaced apart uniformly in the direction of revolution on the inner face  33  of the sleeve  5  and corresponding in number to the number of stator pole teeth, for instance. The inner face  33  of the sleeve  5  is embodied in the vicinity of each shoulder  37  in such a way that the spacing from the center axis  7  suffices for the sleeve  5  in this position to be thrust over the stator  1  with its stator pole teeth  11 . In a direction of revolution that is opposite from what is shown here as a clockwise closing direction  35 , the inner face  33  is embodied such that its spacing from the center axis  7  decreases, so that when the sleeve  5  is rotated in the closing direction  35 , the sleeve  5  wedges with at least one stator pole tooth  11 , or with the plastic sheath that extends as far as the pole head  47 , and enters into nonpositive engagement, thereby forming a bayonet mount  30 . 
     It is not necessary that every stator pole tooth  11  come into contact with the sleeve  5  to form a bayonet mount  30 . 
     The plastic sheath  15  can also be embodied in such a way that it forms the bayonet mount  30  with the sleeve  5 , and/or it can also be shaped as a coil body, for instance, for a coil  40 .