US3568481A

US3568481A - Safety key and lock

Info

Publication number: US3568481A
Authority: US
Inventors: Oliver C Halfyard
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-02-21
Filing date: 1969-06-02
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09

Abstract

THE DISCLOSURE DESCRIBES A KEY FOR USE IN A CYLINDERTYPE LOCK WHEREIN THE KEY HAS INDEPENDENT MEANS FOR ACTUATING A TUMBLER PIN TO ITS UNLOCKED POSITION INCLUDING A HIDDEN PUSH ROD WHICH IS MANUALLY OR AUTOMATICALLY MOVED AXIALLY FROM WITHIN THE BASE OF THE KEY TO ACCOMPLISH THE FINAL DISENGAGEMENT OF THE CYLINDER. IN ONE EMBODIMENT THE AUXILIARY PIN-ACTUATING MEANS IS ACTUATED BY MANUAL MOVEMENT THROUGH A CAMMED SLOT WITHIN THE HANDLE OF THE KEY OR A PRESSURE ACTUATED LEVER MOVES THE PUSH ROD INTO ENGAGEMENT WITH A LOCKING PIN OF THE TUMBLER. IN ANOTHER EMBODIMENT THE INNER TIP OF KEY PROVIDES THE MEANS FOR ENGAGING AND ROTATING THE LOCKING LUG AND A SEPARATE CIRCUMFERENTIALLY SPACED TUMBLER IS PROVIDED IN THE LOCK CYLINDER FOR ACTUATION BY THE SIDE OF THE KEY OR FOR REGISTRY WITH AN APERTURE THROUGH THE SIDE OF THE KEY FOR POSITIONING TO UNLOCK POSITION. KEY AND LOCK COMBINATIONS INCLUDING ALL OF THE FOREGOING IMPROVEMENTS ARE DESCRIBED.

Description

March 9, 1971 o. c. HALFYARD 3,568,481

SAFETY KEY AND LOCK Original Filed Feb. 21, 1968 3 Sheets-Sheet 1 OLIVE/i a HALFMRD QM (W I NVENTOR.

March 9, 1971 O. n. HALFYARD 3,563,431

SAFETY KEY AND LOCK Original Filed Feb. 21, 1968 3 Sheets-Sheet 2 x xi P I I I /02 l /0 40 I INVENTOR.

A58 OL/VER C HALFM/PD March 9, 1971 o. c. HALF-YARD 3,563,481

' SAFETY'KEY AND LOCK Original Filed Feb. 21, 1968 5 Sheets-Sheet 5 E 1:I 9 m 1294 tI- /8 20 302 E 304 0 280290 22/ I INVENTOR.

286 OLIVER c. HALFYARD 300/ 282 74 2.92 29/ y ME 7 EHL /E.

United States Patent 3,568,481 SAFETY KEY AND LOCK Oliver C. Halfyard, 432 Belmont Ave., Chicago, Ill. 60657 Original application Feb. 21, 1968, Ser. N0. 707,189, now *Patent No. 3,486,355, dated Dec. 30, 1969. Divided and this application June 2, 1969, Ser. No. 847,763 Int. Cl. E05]: 15/14 U.S. Cl. 70-421 1 Claim ABSTRACT OF THE DISCLOSURE The disclosure describes a key for use in a cylindertype lock wherein the key has independent means for actuating a tumbler pin to its unlocked position including a hidden push rod which is manually or automatically moved axially from within the base of the key to accomplish the final disengagement of the cylinder. In one embodiment the auxiliary pin-actuating means is actuated by manual movement through a cammed slot within the handle of the key or a pressure actuated lever moves the push rod into engagement with a locking pin of the tumbler. In another embodiment the inner tip of key provides the means for engaging and rotating the locking lug and a separate circumferentially spaced tumbler is provided in the lock cylinder for actuation by the side of the key or for registry with an aperture through the side of the key for positioning to unlock position. Key and lock combinations including all of the foregoing improvements are described.

This is a division of application Ser. No. 707,189 filed Feb. 21, 1968 now U.S. Pat. No. 3,486,355 issued Dec. 30, 1969.

BACKGROUND OF THE INVENTION A wide variety of key and lock combinations are known and used in the art. The keys are designed with a camming edge which frees the lock cylinder for rotation, generally clock-wise, whereby the locking pawl is moved through an eccentric or cam from an extended (locked) position to a recessed (unlocked) position. A number of types of spring-loaded tumblers or pins are used to hold the cylinder in its locked position until a key is inserted. The cams on the edge of the key cause the various pins to be oriented axially so that their ends or shear points clear the circumference of the cylinder.

A large number of combinations of cam heights, different numbers of cams and cross-sectional configurations of keys, e.g., flat, curved or fluted, are used to insure that only one type of key can be used in a given design of lock. However, skillfully designed locks of this type can be opened by the unscrupulous using thin bladed instruments of special design. It is also relatively easy to make copies of keys by tracing or wax impressions since the cross-sectional configurations, lengths and number of cams on existing keys fall into a number of known patterns for which blanks are available. Such key duplication is, of course, sometimes a necessity.

In order to make the opening of a lock more diflicult, as in safe-deposit boxes, a double lock system is used requiring the simultaneous use of a master key and the key of the lock box lessee. Such systems are clumsy for ordinary household and business use. There is a need for a key which is not readily copied and which requires something more than its mere insertion into the lock cylinder to accomplish the unlocking process. The instant invention is directed to the provision of a key which operates stepwise to unlock the cylinder and the functions of which are not readily determined by casual inspection.

,568A3l Patented Mar. 9, 1971 s lit,

SUMMARY OF THE INVENTION The present invention concerns primarily a key adapted to be used in a cylinder-type lock which is provided with at least one independently movable cam surface along its cammed edge whereby after insertion of the key or during its insertion a separate unlocking action takes place. The key of this invention has an individual movable cam surface which may be in the form of a push rod that is either moved upwardly from the edge of the key by the operator to disengage the last in the series of locking pins in the cylinder or is automatically so moved by the thrust of the key into the cylinder. The movable cam is preferably in the form of a small diameter rigid wire operating within a bore hole which extends upwardly through the body of the key with one end movable into operative engagement with a particular locking pin in the lock and with the other end extending into the region of the handle of the key where it is accessible for movement either manually or automatically.

Manual operation of the movable cam is accomplished in accordance with this invention by providing a guide slot for the extended end of same in the handle region along which it can be moved to thrust the cam end in a lifting atcion against the bottom of at least one locking pin. Manual operation is also facilitated by providing a lever sheath on the handle end of the key, the pivotal end of which engages the extended end of the movable cam. A spring-loaded lever Which engages the extended end of the movable cam at the handle of the key at one of its ends and is engaged at its opposite end by the face of the lock provides the lifting or thrust action for the movable cam of this invention in another embodiment so that the latter functions as the key is placed in the lock. The movable cam is further provided with a recess along the top edge of the key so that in its retracted position it does not interfere with the insertion of the key in the lock and is substantially hidden. In addition, a modified locking lug is provided in this invention which is engaged and rotated by the inner tip end of the key, independent of the lock cylinder. Also a separate circumferentially spaced tumbler is provided in the lock cylinder for actuation by the side channel or rib or for registry with an aperture through the side of the key and thereby positioned to an unlocked position in synchronism with the normal tumblers of the cylinder. Also a key and lock combination including all of these improvements is contemplated. By these means, additional safety features are incorporated in the key and lock combination of this invention.

DESCRIPTION OF THE DRAWINGS Exemplary embodiments of this invention are shown in the drawings wherein:

FIG. 1 is a partial cross-sectional view of a lock with a side plan view of the key of this invention in position for insertion into the lock;

FIG. 1A is a partial cross-sectional view taken along the lines 1A-1A of FIG. 1;

FIG. 2 is a partial cross-sectional view of the lock and with the key of FIGS. 1 and 1A inserted and the lock in unlocked position;

FIG. 3 is a side plan view of another form of key of this invention;

FIG. 4 is a top plan view of the embodiment shown in FIG. 3;

FIG. 5 is a partial cross-sectional view of a lock with the key of FIGS. 3 and 4 inserted and the lock in unlocked position;

FIG. 6 is a side plan view of another form of key of this invention;

FIG. 7 is a top plan view of the embodiment shown in FIG. 6;

FIG. 8 is a cross-sectional view taken along the lines 88 of FIG. 6;

FIG. 9 is a partial cross-sectional view of the lock with the key of FIGS. 6, 7 and 8 inserted and the lock in unlocked position;

FIG. 10 is a side plan view of a lock with a modified locking lug and the key of this invention in position for insertion into the lock;

FIG. 11 is an end view of the lock shown in FIG. 10 showing the modified locking lug;

FIG. 12 is a partial cross-sectional view, along lines 12-12 of FIG. 11 of the lock with the key inserted and ready to turn to unlocked position;

FIG. 13 is an exploded perspective view of the modified locking lug shown in FIGS. 10, 11 and 12;

FIG. 14 is a fragmentary cross-sectional view, along the lines 14-14 of FIG. 11 to show the details of the positioning detent;

FIG. 15 is an end view of a lock showing another modification including an angular side tumbler (parts shown in dotted lines) protruding into the lock cylinder for engagement by the side of the key;

FIG. 16 is a plan side view of the lock of FIG. 15 with a portion of the key blade ready for insertion therein;

FIG. 17 is a cross-sectional view along lines 1717 of FIG. 15 with a portion of the key blade shown as it first engages the side tumbler on being inserted into the cylinder;

FIG. 18 is a cross-sectional view of one form of cylinder, side tumbler and key of this invention with an aperture in the key to allow the tumbler to assume the unlocked position with the key in place; and

FIG. 19 is a fragmentary side view of the key shown in FIG. 18.

THE PREFERRED EMBODIMENT Referring to the drawings, particularly FIGS. 1 and 1A there is shown a key 10 having a blade portion 12 and handle 14 with the aperture 16 for attachment in a key ring. The key 10 may be constructed of any desired metal or metal alloy such as brass which is strong and machinable. The blade 12 has one or

more flutes

18 and 20 along one side and a corresponding groove (not shown) on the opposite side, in the manner known in this art, so that the blade 12, when viewed from the end 22, is circuitous in cross-section and adapted to fit a certain design of slot in a lock cylinder face.

The end 22 of the blade 12 has an upper beveled edge 24 and a series of cams 26 with intervening valleys 28 adapted to slide under and receive the spring-biased pins or tumblers of a lock. A lower head 30 may be provided on the bottom of the blade to impart additional circuitous configuration to the blade. This bead is also carried around the lobes of the handle as indicated at 32. A pair of shoulders 34 and 36 having at least one square face 38 are provided on the top and bottom edges to limit the inward movement of the key into the slot in a lock cylinder.

The bottom lobe of the handle 14 has an arcuate slot 36 therethrough. A movable cam means 40 in the form of an elongated steel rod having a curved end 42 at the handle end with a bent end 44 (FIG. 1A) extending through the slot 36 is provided in accordance with this invention. The cam means, in the embodiment shown in FIG. 1, has a straight shank 46 extending through the recesses 48 in the

flutes

18 and 20 and carries at its upper end the cam tip or surface 50 formed by bending the end at about 90 to the shank 46. The shank 46 extends through a guide bore 52 in the top part of the blade 12 in a sliding fit relationship. A recess 54 is provided in the top surface of the blade 12 to receive the cam end 50 so that it is flush with or recessed in the top surface in its retracted position. The tip 44 in the slot 36 also rides in a sliding fit relationship and has affixed thereto one or more finger knobs 60 and 62 on either side which serve to retain the tip 44 within the slot and act as a protuberance enabling a person operating the key to grasp same between the fingers or push against either side knob and move the cam means 46 from its retracted position shown in FIG. 1 to the extended position shown in FIG. 2. This action, the limits of which are controlled by the length of the slot 36 and its arcuate guiding shape raises the cam surface 50 from the recess 54 to a raised position above the top edge of the blade 12.

The key 10 is adapted to be used with any form of cylinder tumbler lock, one type of which is illustrated in FIG. I having a cylindrical housing and the face plate 72, the inner block 74 which carries the cylinder lock 76 in a bore therebetween and provided with an outer flange 78 with a key slot 80. The block 74 has a series of in line radial bores 82 serving as housings for the springs 84 carrying at their ends the pins or tumblers each having a separable tip 92 which is carried within a series of bores 94 in the cylinder lock 76. The bores 94 register with the corresponding bores 82 in one position of the cylinder 76 and allow the tumblers 90 to extend therein under the biasing of the springs 84 to prevent rotation of the cylinder 76. The cylinder 76 has an opening 96 to receive the key and each tip 92 is prevented from further entry into the opening 96 by means of a shoulder (not shown) in the bores 94 or a shoulder (not shown) on the outer periphery of each tip. The ends are chamfered, as at 98, to provide a camming surface for the end 24 of the key 10. Each tumbler 90 is separable from its corresponding tip 92 at the shear line 100 when the cams 26 or recesses 28 of the key bring same into alignment with the juncture line 102 of the cylinder lock 76 as shown in FIG. 2.

In accordance with this invention a selected tumbler such as 90' is provided in the lock which is not actuated as the key is thrust into the cylinder, until the cam means 40 is moved into the upward position shown in FIG. 2. By this separate camming action the tumbler 90' is raised so that its end surface 104 is at the shear line 102 of the cylinder. Not until then can the key 10 be turned to rotate the cylinder 76 and actuate the latch mechanism (not shown) which is connected to the tumbler and allow the opening of the door, drawer or other device with which the lock is used. Referring to FIGS. 3, 4 and 5, another embodiment of this invention is shown wherein the key is fitted with the lever which is pivotally mounted on the pin 112 which extends through the handle 14 at any desired position between the top and bottom edges of the key, but preferably at a point which is substantially mid-way of the blade 12. The lever 110 has a pair of

flat side plates

116 and 118 which engage the pin 112 on either side of the handle 14 and are closely spaced therefrom. The side plates are connected to each other at the top by the transverse end 120 and at the bottom by the transverse arcuate wall 122. A spring 124 is provided, with one turn around the pin 112 as indicated at 126, to bias the lever 110 in a counter-clockwise direction about the pin 112. The spring 124 has a tab 128 which engages the end 120 of the lever 110 and the remaining end 130 passes through a hole 132 in the rear edge of the handle 14 and is crimped around the bead 32. This holds the spring 110 in place as illustrated.

The tip end 44 of the cam means 40 is guided by the slot 36 and is affixed to one or both of the

side plates

116 and 118. The transverse end 120 and the

sides

116 and 118 are shaped to form a flat-ended lobe 136 at the other end of the lever 110. As the key is inserted into the lock cylinder 76 (FIG. 5) the lobe 136 of the lever 110 strikes the face 78 of the cylinder, just as the cam surface 50 is below the tumbler 90' and rotates the lever clockwise against the spring 124, whereby the cam surface 50* of the cam means 40 is thrust upward to raise the tumbler 90' to unlocked position.

Referring to FIGS. 6, 7, 8 and 9, another embodiment of this invention is shown wherein the key 10 is fitted with a sheath lever 140 having

side walls

142 and 144 joined at a curved connecting wall 146 which encompasses the bottom portion of the handle 14. The lever 140 is pivotally mounted at its extended end 148 to the pin 150 which extends through the handle. A recess 152 is provided in the bottom edge of the handle to receive the spring 154, the bottom end of which extends into pressure contact with the inside of the wall 146 between the

side walls

142 and 144. The spring may be afiixed to the key at one end and to the Wall 146 at the other end or may be free at both ends as desired.

In this embodiment the cam means 40 is modified at its lower end to be aifixed to the other end of the sheath lever 140 as indicated by the loop 156 engaging the second pin 158 which is held by the

opposed walls

142 and 144. By making the cam means 40 of spring steel rod the pin and loop arrangement, to provide a pivot can be eliminated and the end of the cam means welded or soldered to the lever.

In operation the key is inserted in the lock as shown in FIG. 9 and finger pressure is applied at the lower wall 146 to actuate the cam means 40 to raise the tumbler 90. If desired, the lever 140 can be omitted and the cam means 40 provided with a finger knob, like 60 and 62, or a loop as at 156, for engagement with the users finger to thrust the cam means into the position shown in FIG. 9. The cam surface 50 at one end of the cam means and a knob 60-62 or the loop 156 at the other end prevent loss of the cam means from the key.

Although this invention has been described in relation to specific embodiments it is readily apparent that various modifications can be made within the scope and spirit of the invention. The cam means 40, for example, can have more than one cam surface 50 of the same or different heights to simultaneously or sequentially actuate two or more tumblers 90' in the series. The cam surface 50 can depend toward the handle 14 of the key instead of toward the blade 12. Normally the slot 36 is constructed of such a length that when the cam means 40 is in the retracted positions in the embodiments shown, as in FIG. 1, the tip 44 is at or near the one end of the slot 36; and when the cam means 40 is in its actuated or extended position (FIG. 2) the tip 44 abuts against the other end of the slot 36. This assures the proper in-line registry of the bottom 104 of the tumbler 90' with the juncture 102 so that the lock cylinder 76 can be rotated. The slot 36 can be made longer than the movement of the cam means 40 so that the proper positioning of the cam 50 and the tumbler 90' is a matter of feel by the user of the key.

Similarly in FIG. 3, the pivotal action of the lever 110 can be adjusted so that in addition to the thrust of the key into the lock cylinder as shown in FIG. 5, the lever 110 has to be manually moved an additional small distance clock-wise to bring the tumbler 90' into proper registry to free the lock cylinder. Also the lever action shown in FIG. 5 can be made to operate to the position of proper registry before the shoulder 38 abuts the face of the cylinder and to provide an over-riding or caminterfering safety lock, through only partial or excessive displacement of the tumbler 90 in any other position.

The embodiment shown in FIGS. 69 can also be modified so that the tumbler 90' is cleared of the lock cylinder before the sheath lever 140' has reached the maximum rotation about the pivot 150. The cam 50 can be omitted from the tip and the cam means terminated in a truncated cylinder at the tip end. The key 10 may be suitably reinforced to overcome any weakness imparted 6 by the bore hole 52 for the cam means 40. Both the levers and can be constructed to house the entire handle 14 in a manner to further obscure the functioning of the key.

Referring to FIGS. 10-14, still anotherembodiment of this invention is shown wherein, in .10 the lock housing '70 has the conventional threads 200 and key-way 202 for attachment into a door assembly in the known manner, along with the key 14, already described. The internal parts of the lock 70 are, as shown in FIG. 1, for cooperation with the movable cam means 40 and the cam tip 50. In this embodiment the tip 22 formed by the intersecting beveled edges 24 and 24' of the key 14 are utilized to actuate the locking lug 204 which is mounted on the inner end of the lock housing 70. Normally the key of a lock does not engage the locking lug which is carried by the lock cylinder alone.

However, in accordance with this aspect of the invention, the locking lug 204 is mounted independent of the lock cylinder 76 by means of the yoke plate 206, which is afiixed to the back plate or wall 208 (FIG. 11) of the lock housing 70 by any suitable means such as the screws 210. The screws 210 pass through the apertures 212 (FIG. 13) of the plate 206 and into the body of the wall 208. The plate 206 has an otf-center circumferential arcuate edge 214 about which the locking lug 204 rotates with the underside 216 of the offset actuator end 218 in spaced or guiding relationship therewith. The radius of the edge 214 is larger than and its center is oif-set from the radius and center of the rotation of the lug so that in locked position (FIG. 11) the underside 216 of the lug end 218 is closely spaced or in sliding contact therewith as indicated at 220 in FIG. 12. In unlocked position, a where the locking lug 204 has been turned clock-wise or counter clock-wise depending on the lock design, a required number of degrees, generally about 15 to 45, in order that the latch mechanism (not shown) of the enclosure or door in which the lock is used is reciprocated, the underside 216 will be removed or radially spaced from the surface 214. This assures a sturdy rigid construction for the lock 70 in its locked position and also freedom of movement to the unlocked position.

The modified locking lug 204 has a fiat radial arm 222 formed integral with the rounded body 224 and may be provided with a central aperture 226 for the reception of the tip 22 of the key 14 as will be described, depending on the key design. The aperture 226 also permits inspection of the parts in their assembled condition by a locksmith and the proper assembly during manufacture. The aperture 226 can be omitted.

The locking lug is offset to provide a flat inner side 228 which is flush against the outer surface 230 of the plate 206, and rotates thereagainst. These opposed surfaces may be lubricated if desired. The radial arm 222 has a small aperture 232 therethrough and a pair of radially spaced apertures 236 in the rounded body 224. The plate 206 has an aperture 240 which aligns with the aperture 232 in the locked position of the locking lug 204. The inner end of the lock cylinder 76 (FIG. 12) has afiixed thereto a washer 242 having a pair of apertures 244 and a central key slot 246. The washer is held to both the locking lug 204 and the cylinder 76 by means of a pair of pins 246 which are press-fitted into the apertures 236 and the apertures 244. Instead of using pins for this construction screws may be used. A bore hole 250, larger than the outer circumferential distance across the pins 246 is provided in the plate 206, so that the pins can pass therethrough and also rotate within the bore hole as the lug 204 is turned.

The back plate or wall 208 of the lock housing 70 has a blind bore 252 (FIGS. 12 and 14) forming a retaining housing for the spring 254 (FIG. 13) which biases the detent 25,6. The detent 256 has a flanged base 258 which is in sliding relationship within the blind bore 252 and has a detent end 260 which extends through the bore 240 of the plate 206 and engages the inner open end of the aperture 232 in the arm 222 of the locking lug 204. The relationship of these parts can be reversed with the spring biased detent being carried by the locking lug.

As shown in FIG. 12, the top and bottom edges 262 and 264 of the slot 246 are beveled to receive the tip 22 and the beveled edges 24 of the key 14. The inner edges of the radial arm 222 are beveled, as at 266 and 268 (FIGS. 11 and 14) and the inner open end of the aperture 232 has a pocket 270 to receive the tip end of the detent 256. As an alternate construction the bore 232 can be made smaller than the diameter of the detent 260 or the pocket 270 alone can be used. The body 224 has a boss 272 on the inner side which rotates within the bore hole 250 of the lug 204. Also, the back or inner side of the plate 206 is off-set inwardly as at 274 to receive the washer 242 though is not concentric therewith.

In operation of the modified lock and key combination described in relation to FIGS. -14, as the key 14 is inserted the tip 22 passes into and is engaged by the key slot 246. The tumblers 90 are raised to the shear lines 100 so that the cylinder 76 can be rotated by the key. This causes the tip 22 to rotate the washer 242 and through the pins 246 carries or rotates the lug 204 in the direction of the key turn. The rotative pressure of 25 the key causes the detent 256 to ride out of the pocket 270 and the lug 204 is moved to actuate the latch and unlock the door. Upon removal of the key, in the locked position, not only do the modified tumblers 90' and the cam means 40 offer theft-proof design, but the added necessity of turning the washer 242 simultaneously to unlock the lock makes unauthorized entry highly improbable. Although the tip 22 of the key 14 is shown to be spaced radially from the edges of the slot, it is to be understood that the slot and key can be made so that these parts are flush or more closely spaced when the key 14 is in the position shown in FIG. 12. Other modifications are apparent. The washer 242 can be omitted and the boss 272 extended into the cylinder or adjacent the end thereof, so that the key tip 22 engages the lug 204 as directed. In this arrangement, the boss 272 would be enlarged and the inner open end of the bore 226 would be slotted as at 276 to receive the tip 22 in the same manner as described in relation to the Washer 242.

Referring to FIGS. to 19, still another embodiment of this invention is shown which can be used alone as a safety lock and key combination or used in combination with the embodiments shown in FIGS. 1-9, or the embodiments shown in FIGS. 10-14. It is also apparent that the safety key 14 and modified lock 70 of FIG. 1 can incorporate the modified lug and washer arrangement of FIGS. 10-14 along with the third safety feature to be described in relation to FIGS. 15-19. Also each of these embodiments can be used alone in a key-lock combination.

In FIGS. 15, 16, 17 and 18 the lock or lock housing 70 has the conventional cylinder lock 76 with inner key slot 96 and face plate or outer flange 78 with exposed key slot opening as previously described. The cylinder 76 is modified to include an angular radial bore 280 with a tumbler 282 having separable tip 284 and shear line 286 (FIG. 18) biased therein by the spring 288 operating within the radially aligned bore 290 in the body 74 of the lock 70. The tumbler 282 is larger in diameter than the separable tip 284 and the interengagement of the inner surface 292 of the tumbler maintains the rounded tip 294 at least part way across the slot (FIG. 15). A cover member 291 is attached or made integral with the body 74.

The key 14 has been modified to include a side cam surface 300 at the tip 22 between the grooves 18 and of the blade 12. The key 14' has an aperture 302 with a chamfered or beveled edge 304 therearound on one side of the key, i.e., on the side toward the tumbler 282. The chamfer 304 may surround the aperture 302 or be on the leading edge only, that is the edge nearest the tip 8 22. The aperture 302 can be a blind bore, however by drilling a hole through the blade 12 and chamfering both sides of the hole, the manner of operation of the modified key blade is more obscure. In either event the structure is such that as the key 14' is inserted into the slot the beveled tip 300 engages the rounded tip 294 of the tumbler (FIG. 17) and moves the tumbler to a locked position so that the cylinder 76 cannot at this time be turned. As the key 14 is moved to its fullest extent into the key slot 96, the rounded end of the top 294 registers with the aperture (or blind bore) 302 and the shear line 286 is brought in circumferential registry with the juncture line 102 between the cylinder 76 and the body 74 of the lock 70. The cylinder 76 can then be turned in the lock since the key is holding the other tumblers (not shown) in proper release position as previously described. The aperture 302 can be omitted and the cam tip 300 used alone to move the tumbler 104 to unlocked position, in which event the shear line 286 would not be in registry with the juncture 102 when the key 14 is not in the lock.

While this invention has been described fully and completely with special emphasis upon certain preferred embodiments, it is to be understood that within the scope of the appended claim this invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A key lock combination comprising:

a lock having a housing;

a lock cylinder rotatably mounted in said housing and having a longitudinal key slot therein, said lock cylinder having a series of tumblers to be engaged by the cammed edge of a key for movement to a shear position;

a first bore hole through the side of said housing;

a second bore hole through said cylinder of smaller diameter than said first bore hole and having an axis intersecting the plane of said slot said bore holes being coaxially aligned and defining a shoulder upon said cylinder at their juncture;

a spring-biased safety tumbler within said aligned bore holes having a flanged base portion within said first bore hole, and a shank end extending through said second bore hole into said slot, the juncture of said flanged base portion and said shank end of said tumbler being the shear plane thereof and said tumbler being at its shear position to unlock said cylinder with said base portion against said shoulder;

a key having a flat cammed blade portion to engage said series of tumblers and having a tip portion and a bevelled side on the end of said tip portion of said key adapted to engage and move said safety tumbler to a non-shear position, said key having a cross bore through said flat blade portion intermediate the ends thereof at a point rcgisterable with the end of said safety tumbler in the fully inserted position of said key in said slot, whereby with said safety tumbler in the fully inserted position of said key in said slot, said safety tumbler is allowed to move free of said key in said cross bore against said shoulder to its shear position as said series of tumblers are moved to their shear position to unlock said cylinder.

References Cited UNITED STATES PATENTS MARVIN A. CHAMPION, Primary Examiner R. L. WOLFE, Assistant Examiner US. Cl. X.R. 70-364, 378