Abstract:
A lock and key combination includes profile shapes extending along the lateral faces of the key which extend at an angle relative to the key spine to make acquisition of replacement key copies more difficult.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a lock and key combination, and more specifically to improvements in the profile shape of the lateral faces of the key. 
     2. Description of the Related Art 
     It has become virtually impossible to control the acquisition of replacement key copies in lock and key systems since key blanks are available from sources other than the manufacture of the original lock and key systems. Provided suitable key blanks are available, duplicate key copies can be produced on conventional key cutting machines. 
     In a conventional key cutting machine, the key spine is used as a reference edge for exact fabrication of the notch depths. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to make the acquisition of replacement key copies more difficult and thereby provide a more secure lock and key system. 
     This and other objects are inventively achieved in a key and cylinder core having a profile shape proceeding at an angle greater than zero degrees relative to the key spine. This differs from the standard practice of providing the lateral profile shapes of a key parallel to the key spine. As used herein, the term &#34;profile shape&#34; refers to the generally longitudinally extending ridges and grooves formed in the lateral sides of a key and along the lateral inside surfaces of a cylinder core which inhibit the entry of other than a fitting key. 
     In a preferred embodiment of the invention, the profile shape of the key extends at an angle of between 5 and 10 degrees, inclusive, relative to the spine of the key. The angled profile substantially decreases the possibility of uncontrolled acquisition of duplicate keys. This is particularly true for individual fabrication of keys where no appropriate key blanks exist, since the angle of the profile to the key spine provides an additional degree of freedom to be taken into consideration in considering the possible key shapes, or &#34;codes&#34;, which will open a lock. 
     In the present invention there is also the additional possibility of providing &#34;chicanes&#34; in the lock cylinder for interacting with the key spine so as to provide an additional type of key coding. Such chicanes can include undercut portions or projections extending into the keyway or key channel which interact with cut-out protions of the key spine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross section of a lock cylinder and a key according to the principles of the present invention; 
     FIG. 2 is an enlarged side view of a key of the invention; 
     FIG. 3 is a plan view of a lock cylinder core including openings formed above the keyway; 
     FIG. 4 is an enlarged side view of a second embodiment of a key of the present invention; 
     FIG. 5 is an enlarged cross section through the lock cylinder of FIG. 1, showing tumbler pins and elements or projections; and 
     FIG. 6 is a side view of the key for use in the lock of FIG. 5 having a recess for the elements or projections. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a key 15 extending into a cylinder core 14 within a cylinder housing 13 of a lock. The key 15 includes a profile shape 1, in the form of grooves and ridges on the lateral portions of the key 15. As can be seen in FIG. 2,the profile shaping 1 lies at an angle α relative to a spine 16 of the key. Within the cylinder core 14 are a plurality of ridges and grooves (not shown) extending along the length of a keyway, or key channel, 9 and forming a corresponding profile for cooperative engagement with the profile shape 1 of the key 15. The corresponding profile of the cylinder core 14 lies at an angle substantially the same as the angle α of the key profile 1. 
     As with other keys, the key 15 is introduced into the keyway, or key channel, 9 in the cylinder core 14. However, the key 15 undergoes a somewhat upwardly slanting motion during insertion into the core 14. Depending upon the extent of the angle α, however, the slanting motion is hardly noticed by a user of the present key. The profile shape 1 guides the key 15 into place so that notches in the key 15 can interact with standard key sensing devices, such as tumblers 17 indicated schematically in FIG. 1. Only if the angle α of the key profile 1 matches that of the cylinder core 14, are the notches properly aligned with the tumblers 17 to open the lock, depending of course on whether the notches are cut the respective appropriate depths. 
     The slightly slanting motion of the key 15 as it enters the keyway 9 enables further protective measures to be provided, such measures being referred to as &#34;chicanes&#34;. The key spine 16 is tracked or cut in regions 4 in a suitable way and interacts with elements or projections 6, 7 and 8 in the cylinder core 14. The elements or projections 6, 7 and 8 are undercut and act as a detent during introduction of the key 15 into the keyway 9. Only a key 15 whose spine 16 is shaped to match to the particular arrangement of elements or projections 6, 7 and 8 can be completely introduced into the keyway 9. 
     To avoid having a universally ground key spine 16 which would enable complete introduction of a duplicate key and potential operation of the lock, assuming the duplicate key otherwise corresponds to the original, countersunk openings 12 are provided in the cylinder core 14 as shown in FIG. 3. One portion of the countersunk openings 12 is filled out by the elements or projections 6, 7 and 8 in accordance with the coding or cut out shape 4 of the key 15, while remaining portions of the counter sunk openings 12 remain free so that pins 17, shown in FIG. 5, can drop into the countersunk openings 12 upon rotation of the cylinder core 14 in the cylinder housing 13. Further rotation of the cylinder core 14, and opening of the lock, is thereby prevented. It is, of course, possible to fashion the countersunk openings so that the cylinder core 14 can be rotated back to its original position even though the pins 17 are engaged in the openings 12, such as by sloping the countersunk openings in a direction of rotation of the cylinder core 14. 
     In further embodiments of the invention, the angle of the profile shape on the lateral portions of the key can change along the length of the key. For example, in FIG. 4 is shown a profile shape 2 which extends arcuately with a radius R along the length of a key 15. 
     Not only can the profile shape be angled upwardly, as shown in FIG. 2, but it is also possible to angle the profile shape downwardly. Either of these two possibilities include the further possibility of an arcuately, or otherwise non-linear, profile shape. 
     Referring now to the illustrated cylinder core 14 of FIG. 5 and the fitting key 15 of FIG. 6, the profile shapes of both the key 15 and the core 14 lie on the same angle. Similarly, the faces of the elements or projections 6, 7 and 8 and the cut region 4 of the key 15 are at this same angle. The elements or projections 6, 7 and 8 extend into the cut region 4 when the key 15 is inserted into the core 14. If the cut region 4 is of the wrong shape for the elements 6, 7 and 8, either the lower portions of the corresponding tumbler pins 17 will extend into the countersunk openings and prevent unlocking of the lock, or the elements 6, 7 and 8 will prevent complete insertion of the key 15 into the key channel. 
     In conclusion, it is expedient to provide the profile shaping of the present invention beginning at the tip of the key to avoid sharp edges along the key spine 16. 
     Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.