Patent Abstract:
A removable core cylinder lock, comprising a casing, a lock core with a rotatable key plug in a cylindrical bore and a retainer adapted to releasably retain the lock core in an inserted position in the casing. The casing has two lugs extending radially inwards and being separated transversely from each other, whereas the lock core has two corresponding recesses on both sides of a central, rear portion, whereby the lock core can be fully inserted into the casing. The two lugs are provided with holes accommodating fasteners for fastening the casing to an object.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/SE00/00130 which has an International filing date of Jan. 21, 2000, which designated the United States of America and was published in English. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a removable core cylinder lock, comprising a cylinder lock casing having a casing wall defining an axially extending cavity with an insertion opening, a removable cylinder lock core which has an outer contour corresponding to the inner contour of said cavity and which is axially insertable into the cavity through the insertion opening. The lock core has an upper, substantially massive part with a row of holes for accommodating locking tumblers, and a lower part defining a cylindrical bore extending therethrough. A cylindrical, rotatable key plug is located in the cylindrical bore and has a longitudinal key slot for receiving a key co-operating with the locking tumblers, a retainer adapted to releasably retain the lock core in an inserted position in the cavity in the lock casing, and mutually fitting parts in the rear, axially inner portions of the casing and the lock core, including projections at the rear end portion of the casing and corresponding recesses at the rear end portion of the lock core. 
     2. Description of Related Prior Art 
     Such locks are previously known from commercial embodiments offered on the market by the Best Lock Company. In these embodiments, the projection at the rear end portion of the casing comprises a pair of relatively narrow pins on a rotatable locking member, whereas the corresponding recess comprises a corresponding pair of axial bores in the key plug. 
     However, in such a lock, including a casing and a lock core, it is quite possible to replace a lock core of a first kind by a lock core of a second kind provided that the replacing lock core has the same or a narrower outer contour and similar axial bores in the key plug. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the present invention is to further develop such a lock so as to prevent such replacement of the lock core, or at least make such replacement more difficult. 
     According to the present invention, this object is achieved in that the projections of the casing comprise two lugs extending radially inwards from the casing wall on each side of a central vertical plane of the casing, in that the corresponding recesses comprise two recesses located in the massive part on both sides of a central rear portion containing the row of holes, the two recesses being dimensioned to accommodate two lugs, so as to permit full insertion of the lock core into the casing, and in that the two lugs are each provided with means for fastening the casing to an object. 
     With such a structure, a similar lock core with exactly the same outer contour and the same length cannot be inserted into the casing unless it is provided with the same kind of recesses at its rear portion. It is a very difficult matter to measure the dimension of the lugs at the innermost end of the casing and to make a corresponding recess in the lock core. 
     The two lugs are separated transversely from each other so as to leave a central passage therebetween. The central rear portion of the removable core fits into this central passage. 
     Also, the lugs at the rear portion of the casing are used to provide means for fastening the casing to an object, such as a door or the like. Thus, the fastening means are concealed behind the lock core itself, and it will be difficult to reach the fastening means from the outside by drilling or similar operations. 
     The lugs and the recesses should have a substantially supplementary configuration. Preferably, each lug is defined by a concave cylindrically curved surface, whereas the lug has a corresponding convex cylindrically curved surface. 
     Accordingly, the structural features of the casing and the lock core will enable easy insertion of a correctly designed lock core into the casing, whereas a similar lock core, having the same outer contour, the same length but no corresponding recess of the specific kind and dimensions, cannot be inserted into the casing. Moreover, it is difficult to provide such a recess in the similar lock core by straight forward machining operations. Therefore, the removable core cylinder lock according to the invention has a high degree of security against unauthorized manipulation of the lock by replacement of the lock core with a less secure lock core of another kind. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 shows in a perspective view a door lock assembly with two lock casings and a removable lock core to be inserted into one of the casings; 
     FIG. 2 shows, in perspective view, the lock core of FIG. 1 (without key plug and retainer member); 
     FIG. 3 shows, likewise in perspective view, a retainer member and a key plug (taken out from the lock core in FIG.  1 ); 
     FIG. 4 shows the lock core of FIG. 1 as seen from the rear end (indicated by the line IV—IV in FIG.  1 ); 
     FIG. 5 shows the two casings in FIG. 1 in a perspective view from the front (from the right hand side); 
     FIG. 6 shows the lock core in FIG. 1 in perspective view from the rear; and 
     FIG. 7 is a cross-section through the casing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 there is shown a door lock assembly with two lock casings, viz. a rear casing  10   r  to be mounted at the inside of a door (not shown), and a front casing  10  to be mounted at the front side of the door, and a removable lock core  20  which is insertable into the casing  10 . A lock core of the same kind as the lock core  20  can be inserted into the rear casing  10   r . Alternatively, a door knob or like mechanism can be mounted in the casing  10   r  at the inside of the door. On both the rear and front sides, a rotary member  11   r  and  11 , respectively, is mounted so as to transfer a rotary movement from the door knob and a key plug of the lock core  20 , respectively, to a door lock mechanism (not shown) disposed between the casings  10   r  and  10 . 
     The lock core  20  shown in FIGS. 1,  2  and  6  has the general cross-sectional configuration of the digit “8” and fits with a certain play in a corresponding cavity  12  in the casing  10 . The core  20  has an upper, substantially massive part  21  and a lower part  22  with an interior cylindrical bore  23  for accommodating a rotatable key plug  30  (FIG.  3 ). In the rear part of the lock core  20 , there is a slot  25  approximately in the region between the upper and lower parts  21 ,  22  of the core. The slot is open at the rear end (compare FIG. 2) and extends along the core  20  somewhat longer than half the length thereof. 
     In this rear portion of the lock core  20 , there is an adjoining chamber  26  (FIG.  4 ), in which there is journalled a retainer member  40  (FIG.  3 ). The latter is movable in the chamber  26  between a releasing position (as shown in FIG. 1) and a locking position. In the locking position, it engages with a locking projection  13  (FIGS. 1 and 5) inside the cavity  12  of the casing  10  so that it is retained in the casing and also holds the lock core  20  and the key plug  30  in inserted positions inside the cavity  12 . 
     As is known in the art, the key plug  30  has a longitudinal key slot  31  (FIG. 4) with a front opening  32  (FIG. 3) and a row of six holes  33 . The holes  33  are located in line with a row of six corresponding holes  34  in the lock core  20 , when the key plug is oriented in its releasing position (as shown in FIGS.  2  and  3 ). In each pair of corresponding holes  33 ,  34 , there are upper and lower tumbler pins  36 ,  37 , which are biased downwards by helical springs  38  (FIG.  2 ). The tumbler pins cooperate with the upper edge of a key inserted into the key slot  31 . 
     The door lock assembly described so far is of the general kind described in WO 96/36782 (WINLOC AG) and the Swedish patent application filed concurrently by the same applicant (WINLOC AG). 
     In accordance with the present invention, the casing  10  and the lock core  20  have mutually fitting projections and recesses which ensure that the lock core  20  cannot be replaced by another lock core having the same contour and length unless it is provided with exactly the same recesses. 
     As appears from FIGS. 5 and 7, the casing  10  is provided, at its rear end portion, with two lugs  14 ,  15 , which are formed in one piece with the casing  10  and extend radially inwards from the upper cylindrical wall surface  12   a  of the cavity  12 . Each lug  14 ,  15  is approximately triangular with a beveled or rounded edge  14   b ,  15   b  between two substantially planar, mutually perpendicular surface portions  14   a ,  14   c  and  15   a ,  15   c , respectively. In the axial direction, the lugs  14 ,  15  extend from a rear end wall  17  (FIGS. 1 and 7) along a length corresponding approximately to 0.1-0.4 of the total length of the casing  10 . The end wall  17  has a lower circular opening  18 , in which the rotary member  11  is mounted (see also FIGS.  1  and  5 ). 
     In a cross-sectional view (FIG.  7 ), the length of the sides  14   a ,  14   c ,  15   a ,  15   c  of the lugs  14 ,  15  is about 0.2-0.4 times the diameter of the cylindrical upper portion  12   a  of the cavity, and the distance between the parallel side surfaces  14   c ,  15   c  of the lugs is therefore at least 0.2 times the last mentioned diameter. Accordingly, the lugs  14 ,  15  define a central passage  16  between the side surfaces  14   c ,  15   c.    
     In each lug  14 ,  15  there is an axial hole  14   h ,  15   h  near the cavity wall  12   a . These holes  14   h ,  15   h  serve to provide screw fasteners for fastening the casings  10 ,  10   r  to each other (or to some other part of the door or the like). A fastening screw  1  with a head  1   a  can be inserted from either side, i.e. from the inside of the door, as indicated in FIG. 1, or from the outside of the door (not shown), or one screw from each side, as shown in FIG.  5 . The screws can engage with internal threads in the holes  14   h ,  15   h  (as shown) or with corresponding nuts (not shown). In order to make room for the screw head  1   a , an extra recess  12   b  is formed in the cavity wall  12   a  adjacent to the respective hole  14   h ,  15   h.    
     In the preferred embodiment of the invention, the lock core  20  is provided with two recesses  27 ,  28  at the rear end portion, as appears from FIGS. 1,  2 ,  4  and  6 . The recesses  27 ,  28  are concavely curved with a curvature corresponding to the two lugs  14 ,  15 , so as to leave a central rear portion  29  in which two of the holes  34  are located. This rear portion  29  has a length which corresponds to the axial dimension of the lugs  14 ,  15 . Thus, the rear portion  29  can be fitted snugly into the central passage  16  of the casing  10  when the lock core  20  is inserted therein. On the other hand, any other lock core, without such recesses, cannot be inserted into the casing  10 . 
     Of course, the exact geometrical configuration of the lugs  14 ,  15  and the corresponding recesses  27 ,  28  can be modified by those skilled in the art. 
     As illustrated in FIGS. 1,  4  and  5 , there is a further way to prevent insertion of the lock core  20  into the casing  10 , unless the lock core  20  is designed in a specific manner. The rotary member  11 , which is basically cylindrical and journalled for rotation in the rear opening  18  of the casing  10 , is provided with an axially extending rod  2 , which is located eccentrically and is rather wide, in the specific example 3.7 to 4.5 mm. As appears from FIG. 4, the rod  2  is cylindrical (but could have any other suitable cross-sectional shape) and projects into a corresponding, somewhat wider hole  35  (4-5 mm) in the key plug  30 . The hole  35  extends from the rear end surface of the key plug  30  along about half the length of the latter. 
     The width of the rod  2  and the corresponding hole  35  is such that the interior walls of the hole  35  are located very close to the key slot  31  and the outer circumferential surface of the key plug  30 . In this way, it will be practically impossible to make such a hole in an existing lock core and key plug unit not originally designed to cooperate with the wide rod  2 . 
     In order to secure a good transfer of the rotary movement from the key plug  30  to the rotary member  11 , the latter is also provided with a short axial lug  3  which has a rectangular cross-section and fits into a corresponding groove at the rear end surface of the key plug  30 .

Technology Classification (CPC): 4