Abstract:
Apparatus and method for a secure multi-level key system. A multi-level key system utilizes ribs of known width upon the higher level keys to properly displace obstruction pins corresponding to selected locking pins of the lock housing. A two-part cylinder pin is utilized in order that a higher level key may equalize the spring-biased locking pin with a shallower groove than is necessary for a subordinate key to equalize the same locking pin. The obstruction pins sense the presence or absence of the ribs associated with the high order keys. Subordinate keys, lacking ribs, depend on the additional displacement of the cylinder pin to properly position the obstruction pins to unlock the lock. Creation of a higher order key requires a two-step process of reducing the depth of the groove corresponding to a given cylinder pin of the lock as well as building up the ribs required to offset the obstruction pins associated with the same cylinder pin of the lock.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the invention is that of locks having multiple levels of keys such that some keys may open more locks than other keys. 
     2. Prior Art 
     It has been a problem with some multiple level key systems that higher level keys may be produced from lower level keys by removing lateral profile ribs on the lower level or subordinate keys. This technique works in installations where the higher level keys are distinguished by means of diminishing numbers of profile ribs compared with lower level keys. In order to prevent a key with a filed-away rib from being used as a higher level key, a profile lock in accordance with German Pat. No. 15 53 529 may be used. This lock consists of one or more laterally scanning locking pins which are positioned in bores of the rotary cylinder and are positioned with their outer edges corresponding to the perimeter of the rotary cylinder only when the key profile currently inserted in the lock has the predetermined size. If this profile width is reduced or completely lacking, then the locking pins are displaced a lesser amount and an obstruction of the lock occurs whereby after beginning to rotate the cylinder core, the spring-biased housing pin corresponding to that pair of scanning pins will drop into the bore occupied by one of the scanning pins which has been left partially opened due to the imperfect position of the scanning pins. 
     There has been a need for a simple though more secure means of safeguarding against unauthorized production of high level keys from subordinate keys. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention comprises a lock consisting of a housing and a rotary cylinder adapted for the receipt of flat keys. Within the cylinder, additional blocking pins are associated with one or more of the cylinder pins and are located at an angle with respect to the spring-loaded housing pin associated with each cylinder pin. The obstructing or blocking pins sense the profile size of the key which has been inserted and for a given predetermined profile size are urged outwards so that their outer ends correspond to the perimeter of the cylinder. 
     An improper key will have a reduced profile and the obstructing pins will not be urged far enough outward from the center of the cylinder so as to have their ends reach the perimeter of the cylinder. As a result, after the cylinder begins to rotate in the case of an improper profile, the spring-loaded housing pin may drop into the bore of an obstruction pin and block further rotation of the cylinder. 
     The proper higher order keys at the scanning or sensing location near the obstructing pins have a flat groove as well as an associated rib which provides the proper width. The rib or ribs are adapted to push against or push back the obstructing pins to the perimeter of the cylinder. When the obstructing elements are contacted by the spring-biased locking pin, the ribs of the key hold the obstructing pins against the outer perimeter of the cylinder thereby blocking the housing pin from entering the bore in the cylinder. 
     A subordinate key is provided at the proper scanning point with a deeply cut groove without having the necessary ribs. However, the cylinder pin has a diameter which is wide enough to drive the front surface of each of the blocking pins in the cylinder to the outer edge of the cylinder thereby holding the spring loaded locking pin out of the cylinder which is then free to rotate. 
     Because the lower level keys must allow the cylinder pin to rise higher in the cylinder bore than does a higher level key, a two part cylinder pin is utilized. One unlocking point of the cylinder pin corresponds to the displacement due to inserting the higher level key into the lock. A second unlocking point of the cylinder pin corresponds to the displacement of the lower level key. 
     Thus, a person attempting to make a higher level key must not only adjust the key to displace the cylinder pin properly, but the key must have the correct cross-section so that the obstruction pins are properly displaced in the cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged partial section of a typical cylinder showing the obstruction pins and the two part cylinder pin of the present invention. 
     FIG. 1a is a section taken along line Ia--Ia showing a key properly displacing a cylinder pin. 
     FIG. 2 is an enlarged partial section of a typical cylinder showing a subordinate key in section having displaced the two part cylinder pin so that the cylinder may rotate and having displaced the obstruction pins so that the cylinder will not be blocked. 
     FIG. 2a is an enlarged partial section taken along the line IIa--IIa showing a side view of a subordinate key having properly displaced the two part cylinder pin. 
     FIG. 3 is an enlarged partial section with an altered key shown in section having properly displaced the cylinder pin but improperly displaced the obstructing pins. 
     FIG. 3a is an enlarged partial section taken along the line IIIa--IIIa showing a side view of a subordinate key which has been altered to displace the cylinder pin an amount corresponding to the displacement produced by a higher level key. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the principles of the present invention find a particular utility in a multi-level cylinder lock, it will be understood that the combination of obstruction pins and two-part cylinder pins of the present invention may be utilized in other combinations. By way of exemplary disclosure of the best mode of practicing the invention, there is shown generally in FIG. 1 a cylinder 1 rotatably mounted within a lock housing 2. The cylinder 1 has a key slot 3 wherein a key 4 may be inserted. The cylinder 1 has a pair of obstruction borings 5 and 6 in which are slidably mounted a pair of obstruction pins 7 and 8. The cylinder 1 also has a cylinder boring 9 wherein is mounted a cylinder pin 10. The boring 9 is generally perpendicular to the borings 5 and 6. 
     The obstruction pin 7 has a smaller diameter sensing shaft 7a and a large diameter body portion 7b. The sensing shaft 7a has a sensing surface 7c. The body member 7b has an external spherical surface 7d. The obstruction pin 8 has a corresponding set of members and surface. A sensing member 8a is connected to a body member 8b. The sensing member 8a has a sensing surface 8c and the body member 8b has an external spherical surface 8d. 
     The cylinder pin 10 has a reduced diameter key sensing pin 10a having a tapered sensing surface 10b which directly bears against a slot 11 of the key 4. The proper higher level key 4 has a pair of ribs 12 and 13 which are disposed generally perpendicular to the plane of the key 4 and have a width which is wide enough such that the sensing surfaces 7c and 8c of the obstruction pins 7 and 8 are pushed away from the cylinder pin 10 and toward the outer edges of the borings 5 and 6. 
     A spring-biased locking pin 15 is located in a boring 16 of the locking housing 2. The boring 16 is parallel to and lines up with the cylinder pin boring 9 when cylinder 1 is aligned properly for the key 4 to be inserted therein. The cylinder 1 has a peripheral surface 19 which lies adjacent to a corresponding surface 19a in the housing 2. The borings 5 and 6 have a pair of depressions 20 and 21 located at the ends of the borings 5 and 6 near the peripheral surface 19 of the cylinder 1. Associated with the cylinder pin 10 is a second partial cylinder pin 22. The pin 22 has a flat upper surface 24 and a hemispherical lower surface 26. The surface 26 intersects a flat surface 28 of the locking pin 15. The flat surface 24 of the partial cylinder pin 22 intersects a hemispherical surface 30 of the cylinder pin 10. Both the hemispherical surface 30 and the hemispherical surface 26 have a radius of curvature corresponding to the radius of curvature of the external peripheral 19 of the cylinder 1. 
     FIG. 1 discloses the condition of the lock when a high order key 4 has been inserted into the slot 3. The ribs 12 and 13 of the key 4 have driven the obstruction pins 7 and 8 toward the outer peripheral 19 of the cylinder 1 so that the external surfaces 7d and 8d correspond at least in part to the peripheral surface 19 of the cylinder 1. Further, the key 3 has caused the cylinder pin 10 to be offset by a groove 32 which is the innermost point of the groove 11 displacing the tapered surface 10b of the member 10a a predetermined amount such that the surface 30 of the cylinder 10 now is aligned with the external peripheral surface 19 of the cylinder 1. In this condition, the second cylinder pin 22 has been driven into the boring 16 and in turn has depressed the spring-biased locking pin 15 further in the boring 16. The two-part cylinder pin 10 and 22 has been properly displaced so as to equalize the unlocking pin 15 hence, if other cylinder pins have properly equalized other locking pins in the lock, the cylinder 1 may now be rotated. 
     When the cylinder 1 is rotated in either direction an amount corresponding to approximately 90° the external surfaces 7d or 8d of the obstruction pins 7 or 8 will be in contact with the flat surface 24 of the cylinder pin 22. The spring-biased locking pin 15, because of the spring-bias which has not been shown, will attempt to drive the cylinder pin 22 into the boring 5 or 6, depending on which way the cylinder pin 1 has been rotated. However, because of the ribs 12 or 13, bearing against the sensing surface 7c and 8c of the obstruction pins 7 and 8, the pins 7 and 8 will not be allowed to move thereby blocking the cylinder pin 22 and the locking pin 15 from entering the boring 5 or 6. As a result, the cylinder may be rotated fully and the lock opened. 
     FIG. 1a discloses the relationship between the cylinder pin 10 and the higher level key 4. The notch 32 has caused the pin 10 to be displaced a predetermined amount such that the surface 30 of the pin 10 is aligned with the external peripheral surface 19 of the cylinder 1. The rib 13 against which the sensing surface 8c of the sensing member 8a bears is also shown. 
     FIG. 2 discloses the same lock housing 2 and cylinder 1 as was disclosed in FIG. 1. However, in FIG. 2, a key 4a has been inserted into the slot 3. The key 4a is a subordinate key and is designed to open fewer locks than the key 4 of FIG. 1. When the key 4a is inserted into the key channel 3, it does not contain the ribs 12 and 13 that were found on the high order key 4. The ribs 12 and 13 have been eliminated from the key 4a by providing a deep notch 14 having a point 36 into which the tapered surface 10b of the cylinder pin 10 slides. Thus, as may be seen from FIG. 2, the cylinder pin 10 under the action of the spring-biased locking pin 15 rises higher into the cylinder bore 9 when the subordinate key 4a has been inserted into the key channel 3 than when the higher order key 4 has been inserted into the key channel 3. In order that the subordinate key 4a may unlock the cylinder 1, the second cylinder pin 22 is utilized. The presence of the second cylinder pin 22 between the primary cylinder pin 10 and the spring-biased locking pin 15 is to provide a second displacement corresponding to the surface 26 of the cylinder pin 22 which is aligned with the external peripheral 19 of the cylinder 1, at which the cylinder 1 may be unlocked and rotated. 
     Because the subordinate key 4a does not have the ribs 12 and 13 as does the higher order key 4, an alternate means must be found to properly displace the obstruction pins 7 and 8. The housing pin 10 has a body portion 38 whose diameter corresponds to the width between the outside surfaces of the ribs 12 and 13 of the key 4. Thus, as the cylinder pin 10 rises in the boring 9 as indicated in FIG. 2, the sensing surfaces 7c and 8c of the obstruction pins 7 and 8 bear against the surface of the body member 38 of the cylinder pin 10. As a result, the external spherical surfaces 7d and 8d of the obstruction pin 7 and 8 once again correspond to the external peripheral surface 19 of the cylinder 1. When the cylinder pin consisting of the parts 10 and 22 has been properly displaced as indicated in FIG. 2 and the cylinder 1 is rotated either direction approximately 90°, the surfaces 7d and 8d will contact the surface 28 of the spring-biased locking pin 15 at a point corresponding to the external periphery 19 of the cylinder pin 1 thereby preventing the spring-biased pin 15 from dropping into the grooves 20 and 21 along with the borings 7 and 8. The lock may then be fully unlocked without interference from the locking pin 15. 
     FIG. 2a discloses the key 4a with the notch 14 with the high point 36 into which the tapered end 10b of the pin 10 slides. The additional displacement of the cylinder pin 10 to include the cylinder pin 22 so that the lower spherical surface 26 of the cylinder pin 2 coincides with the external peripheral surface 19 of the cylinder 1 is also shown. 
     FIG. 3 discloses a key 4a&#39;, a subordinate key which has been altered in an attempt to make it a higher order key, demonstrates why it is the present invention makes such a modification a practical impossibility. In order to create a higher order key such as the key 4 out of a subordinate key such as the key 4a both the depths of the groove in the key, such as the groove 14 of the key 4a, must be adjusted and further, the ribs 12 and 13 of the key 4 must be restored. With respect to FIG. 3a, the key 4a&#39; has had the groove 14 rebuilt to correspond to the groove 11 of the key 4 by the addition of a strip of material 40. The strip of material 40 has reduced the depth of the groove 14 to that of a groove 11a which corresponds to the groove 11 of the key 4. The groove 11a has a high point 32a corresponding to the point 32 of the key 4. Because of the added material 40, the cylinder pin 10 is displaced a lesser amount than is the case for the key 4a. In fact, as can be seen in FIGS. 3 and 3a, the cylinder pin 10, due to the addition of the material 40, has been displaced an amount corresponding to the amount that the key 4 would displace the cylinder pin 10. As a result, the surface 30 of the cylinder pin 10 is aligned with the external peripheral surface 19 of the cylinder 1. Assuming all of the other cylinder pins are properly aligned, the cylinder 1 would be free to turn. However, as can be seen with respect to FIG. 3, the sensing surfaces 7c and 8c bear not against the ribs 12 and 13 of the key 4, but bear against the surface of the cylinder 10a of the cylinder pin 10. Thus, the external spherical surfaces 7d and 8d of the obstruction pins 7 and 8 are not displaced so as to correspond to the external peripheral surface 19 of the cylinder 1. As a result, when the cylinder 1 is rotated in either direction the cylinder pin 22 and the spring-biased locking pin 15 will enter the depressions 20 or 21 at the ends 5a and 6a of the borings 5 or 6. When the spring-biased locking pin 15 enters the end 5a or 6a of the boring 5 or 6 it will thereby block any further rotation of the cylinder 1 even though the displacement of the cylinder pin 10 has been such to unlock the cylinder and permit partial rotation thereof. 
     Thus, in order to create a higher level key from a subordinate key not only is it necessary to reduce the depth of the groove such as the groove 14, of the subordinate key 4a, but it is also necessary to restore the ribs such as the ribs 12 and 13 of the key 4 in order to properly displace the obstruction pins 7 and 8. Both of these steps require an addition of material to the subordinate key 4a. This is much more difficult to carry out then is a removal of material from the key 4a as could be done with the prior art systems. Because of the two steps required to convert a subordinate key to higher order key utilizing the present invention, such conversion as a practical matter is almost impossible. 
     It should be noted that while the above enumerated FIGS. 1 through 3 disclose the invention utilized with respect to a selected cylinder pin, obstruction pins such as the pins 7 and 8 may be incorporated and utilized with one or more cylinder pins thereby requiring a key having a complex ridge structure. It should also be noted, that within any given level of key, the ordinary differentiation between one cylinder pin and another may be utilized to provide a large number of different keys at the same level. Finally, the cylinder bore 9 has been shown perpendicular to the obstruction bores 5,6. The invention is not limited to a perpendicular relationship. Instead, an arrangement where the cylinder bore intersects the obstruction bores at an acute angle could also be used. 
     Although various modifications might be suggested by those skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.