US3575024A

US3575024A - Key entrapment lock device

Info

Publication number: US3575024A
Authority: US
Inventors: Ernest L Schlage
Original assignee: Schlage Lock Co LLC
Current assignee: Schlage Lock Co LLC
Priority date: 1969-04-14
Filing date: 1969-04-14
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13

Abstract

A key entrapment lock device includes a cylinder plug having a keyway intersected by a passage making a wedging angle therewith. A ball in the passage is spring pressed to engage and wedge a key in the keyway when the key is moved in a withdrawing direction.

Description

United States Patent Inventor Appl. No.

Filed Patented Assignee Ernest L. Schlage Burlingame, Calii. 815,832

Apr. 14, 1969 Apr. 13, 1971 Schlage Lock Company KEY ENTRAPMENT LOCK DEVICE 10 Claims, 9 Drawing Figs.

US. Cl 70/389, 70/386, 70/421 Int. Cl E05b 11/06 Field 01' Search 70/ 356,

References Cited UNITED STATES PATENTS 2/1912 Boone et al 1 l/ 1968 Shiao-Ming l-lsu 1 H1969 Reisner FOREIGN PATENTS 3/1954 Germany Primary ExaminerMarvin A. Champion Assistant Examiner-Robert L. Wolfe Attorney-Lothrop and West Patented April '13, 1971 3,575,024

2 Sheets-Sheet 1 FIG- I VENTOR. Aw Jan/.44:

irrozvi'rs Patented April 13, 1971 3,575,024

2 Sheets-Sheet 2 F 9 INVENTOR.

im iir 4.501444:

KEY ENTRAPMENT LOCK DEVICE In many structures secured by lock devices having pin tumbler mechanisms and actuated by keys it is possible for unauthorized persons to gain access to the space or object secured by a lock device either by stealing the keys for the lock device or borrowing one or more keys temporarily and having additional keys made therefrom. This is particularly bothersome when the key misappropriated happens to be a master key or a key having control over a main entrance to a building or control of several lock sets.

Recently it has become the custom of vandals to enter school buildings, for example, after misappropriating an access key or comparable key from the principals office and either utilizing it directly or having some copies made. This may compromise the security of a large number of lock devices. It is of course possible then to change all of the compromised lock devices so that the previous keys are no longer effective. But this may be an elaborate and expensive operation.

Much of the difficulty is due to vandals who are not professionals and are not intent on entering except by a fairly simple system, such as the one described. It has therefore occurred to me that a lock device, in addition to being altered so that previously effective keys were still received but were no longer effective, also could have the attribute of capturing or entrapping a previously effective key. In this instance it might then be necessary to alter only one or two of the principal lock devices in a system. Upon prompt recovery of the misappropriated keys the rest of the system could safely be left as it was theretofore. As a practical example, a few'keycapturing lock devices were secretly installed in a school complex. Within a 2-week period thereafter some seven unauthorized (previously effective) keys were retrieved. Retention of the previously good keys by the undetected entrapment lock devices was unusual and was unexpected by the miscreants. The retention devices were also psychologically quite effective.

It is therefore an object of the invention to provide a lock device having the ability to prevent the withdrawal of an unauthorized key.

Another object of the invention is to provide a lock device which not only will entrap an unauthorized key but can be operated by an authorized key.

Another object of the invention is to provide a key entrapping lock device which does not markedly differ in external appearance or apparent operation from the normal lock device.

Another object of the invention is to provide a key entrapment lock device that, when knowledgeably handled, will readily release an entrapped key without the necessity of substantial disassembly or access to the rear of the lock device.

Another object of the invention is to provide a key entrapment lock device that can readily be used with lock devices already existing.

Another object of the invention is in general to provide an improved key entrapment lock device.

A further object of the invention is to provide a cylinder unit arranged to trap or capture a key and to be substituted in a lock device for a normal cylinder unit.

Other objects together with the foregoing are attained in the embodiments of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. I is an end view of a door panel on which a key entrapment lock deviceis installed, certain portions being broken away to disclose the interior configuration and reduce the size of the FIG.;

FIG. 2 is a cross section to an enlarged scale, the plane of section being indicated by the line 2-2 of FIG. 1;

FIG. 3 is a cross section, the planes of which are indicated by the lines 3-3 of FIG. 2;

FIG. 4 is an elevation of a releasing tool;

FIG. 5 is a cross section like FIG. 3 but showing an operable key in position;

FIG. 6 is a cross section like FIG. 3 and showing a releasing tool in place;

FIG. 7 is a view like FIG. 3 but showing a modification;

FIG. 8 is an elevation, portions being broken away, of a key for operating the mechanism of FIG. 3; and

FIG. 9 is a cross section like a portion of FIG. 1 showing another form of operating key in position.

In one practical form the key entrapment lock device of the invention is mounted on a door panel 6 hinged to swing in the customary fashion. The lock device includes a latch bolt 8 adapted to be projected from and retracted to the end face of the panel 6. The latch bolt 8 is connected in the usual way for operation by a driver bar 9 extending along the axis 11 of a spindle 12 mounted for rotation as part of the lock device. An actuating knob I3 is connected to the spindle and carries within it a key cylinder unit I4 of the usual sort. The cylinder body I5 of the cylinder unit has a tongue 16 within which the customary springs 17 and tumbler pins 18 are enclosed. Also included in the cylinder unit I4 is a cylinder plug 19 rotatable about the axis Ill within the cylinder body 15. It is the plug 19 that is directly connected to the driver bar 9 and is effective to produce retraction of the latch bolt 8.

The plug I9 in the customary fashion is pierced from endto-end to afford a keyway 21. This is an axially extending passageway having a number of different surfaces 22 on one side and 23 on the other to define a transverse cross section of any predetermined configuration. It is customary to have at least a part of the cross section, such as the wall 24, of a generally planar character extending throughout all or most of the length of the keyway.

To facilitate the insertion of a key by axial movement toward the keyway, the knob 13 is formed with a conical depression 26 leading to the entrance to the keyway at the flanged end 27 of the plug. The cooperating key 28 has a bow 20 merging with a shank 3I conforming in cross section to the configuration of the keyway 21. Along one edge 32 the shank has a number of serrations to correspond with the tumbler pins 18. The key customarily is long enough and is so contoured as to actuate all of the five or more tumbler pins 18 arranged in line within the cylinder tongue I6.

In the normal use of the structure, the key 28 is inserted fully into the keyway, thus positioning all of the tumblers 18 so that a uniform shear line exists between the plug 19 and the cylinder body 15. A following rotation of the key produces rotation of the plug and likewise of the driver bar 9. This releases the latch bolt 8 and permits swinging of the door panel 6. Following the unlocking operation the key is rotated to initial position and can be withdrawn in an axial direction. The tumblers I3 under influence of the springs 17 return to their positions across the shear line between the rotatable plug and the cylinder.

Pursuant to the present invention, the entrapment cylinder plug is preferably provided, as particularly shown in FIGS. 2 and 3, with a passage 36 generally circular cylindrical in character arranged approximately at the level of the flat wall 24 and having its own axis 37 intersecting the axis 11 of the rotatable plug at a relatively small angle a; for example, about 8". This angle is referred to as a wedging angle to distinguish between a small angle of this sort at which a wedging operation can readily occur and a larger angle at which no wedging occurs. The difference between the small wedging angle and a larger nonwedging angle is, in many instances, only a relatively few degrees. In the present instance, the axis 37 is not parallel to the axis II in side elevation. The actual angle between the axes is thus not exactly the angle measured in plan. The difference is slight and not material.

Disposed in the passage 36 is a jamming or wedging body 38 preferably a ball, such as a bearing ball. Behind the ball there is located a helical spring 39. At one end the spring abuts the ball and at the other end carries a cap 41 serving as a seat and stop for the spring. The cap abuts the end of the driver bar 9. The spring 39 urges the ball toward and even part way into the keyway 21. The ball is large enough when stopped against the end of the passage 36 to emerge slightly into the keyway.

With this mechanism, a regular key 28 can be introduced by axial movement into the keyway 21 without any apparent difference to the user. In entering the keyway, the key first displaces the projecting ball farther into the intersecting passage 36. However, the spring pressure on the ball continually urges the ball into immediate contact with the flat surface of the key. In an instance in which the lock device is installed overhead with the axis ll vertical, the spring may not be needed, gravity being sufficient to hold the ball into contact with the key. Prior to the substitution of the present entrapment cylinder unit 14 in the lock device, the earlier cylinder unit cooperated fully with the key 28 to rotate the driver bar 9. The entrapment cylinder unit I4, although having a keyway cross section capable of receiving the key 28, has a different arrangement of the pins I8 and so no plug or driver bar rotation is possible. The key can be inserted but not turned and so cannot unlock the lock device. The frictional engagement between the key and the ball is sufiicient so that, when the user attempts to withdraw the key by a retracting movement along the axis 11, the ball wedges between the wall of the passage 36 and the key. In fact, the withdrawal motion, though minute, tends to displace the key laterally in a direction away from the passage 36. The wedging engagement is sufficient so that the key cannot be withdrawn.

There are various ways of removing the key from its entrapped or captured condition or position.

One way is to release the door panel 6 from the interior, then dismantle the entire lock device to gain access to the cylinder unit. Disassembly of the cylinder unit permits removal of the spring and ball from the plug interior. The key can then be withdrawn. This, however, is a time consuming and may be an expensive proceeding. Instead I prefer slightly to enlarge, if necessary, the transverse dimension of the keyway and to provide a piece of shim stock 44 (FIG. 4) of a thickness just sufficient to be insertable into the space alongside the key 28 in the keyway 21 (FIG. 6) when the key is moved sideways under the influence of the ball or any lateral force. A person having knowledge of the mechanism can insert the piece of shim stock 44 from the entrance end of the keyway alongside the flat portion thereof and by engaging the ball from the entrance end can displace the ball inwardly and correspondingly somewhat transversely, thereupon compressing the spring slightly and releasing the ball from the key. The key can then be withdrawn from the front.

A variation on this arrangement is afforded by a special bore 46 in the plug (FIG. 7) opening into the passage 36 and emerging alongside the keyway at the plug surface. A wire 47 can be introduced from the front to dislodge and release the ball and so to free the key. This variation avoids any necessity of partially enlarging the keyway to receive the piece'of shim stock 44, but does make a visible change in the looks of the front of the plug and so may mark its unique character.

As an expedient for those authorized, there can be provided to actuate this particular lock device a special key 48 as shown in FIG. 5. In this instance the key, in all parts which might be contacted by the ball, has a taper portion 49 so that the resulting angle b between the surface 49 of the key and the axis of the ball passage 36 is greater than the wedging angle. This tapered key, although generally in appearance not notably distinguished from the previously effective key, will not be captured since the angle is too great for the ball and key blank to wedge. As another expedient, the bottom portion of an authorized key 51 can be cut away (FIG. 8) so that it has no part in position to be engaged by the ball although it can actuate all the tumbler pins 18. Furthermore, a short key 52 (FIG. 9) can be provided to stay out of the path of the ball if various of the inner tumbler pins I8 are omitted.

With an entrapment lock device of this sort it is possible to provide a new system of security simply by changing one or two of the most likely lock devices. These can still be actuated, despite changes in their pin tumbler setup, by special keys known to those authorized, yet are effective to capture previously effective keys and prevent their further use.

Iclaim:

I. A key entrapment lock device comprising a cylinder plug having an axis, means in said plug defining a keyway having a first wall extending parallel to said axis, means in said plug defining a passage having a second wall intersecting said first wall at a wedging angle to said axis, and a body in said passage movable into and away from a position in said passage in which said body is wedged between said first wall and a key wall on a key in said passage and disposed substantially parallel to said first wall. I

2. A key entrapment lock device as in claim 1 including a spring in said passage urging said body toward said keyway.

3. A key entrapment lock device as in claim 1 in which said body is a ball.

4. A key entrapment lock device as in claim I in which said keyway extends into said plug a predetermined distance and said passage intersects said keyway at a point about midway of said distance.

5. A key entrapment lock device as in claim I in which said keyway is proportioned with respect to said key to leave an access channel between said key and said plug from the entrance end of said plug to said body.

6. A key entrapment lock device as in claim 5 in which said access channel and said body are on the same side of said keyway.

7. A key entrapment device as in claim 1 in combination with a key having a surface which when said key is in said keyway abuts said body at an angle less than a wedging angle between said key surface and said body.

8. A key entrapment device as in claim I in combination with a key having a surface which when said key is in said keyway abuts said body at an angle greater than a wedging angle between said key surface and said body.

9. A key entrapment device as in claim 1 in combination with a key having a surface which when said key is in said keyway is spaced away from said body but if continued would abut said body at a wedging angle.

I0. A key entrapment device as in claim 1 including means defining a bore in said plug extending from the exterior thereof substantially to said passage.

Claims

1. A key entrapment lock device comprising a cylinder plug having an axis, means in said plug defining a keyway having a first wall extending parallel to said axis, means in said plug defining a passage having a second wall intersecting said first wall at a wedging angle to said axis, and a body in said passage movable into and away from a position in said passage in which said body is wedged between said first wall and a key wall on a key in said passage and disposed substantially parallel to said first wall.

3. A key entrapment lock device as in claim 1 in which said body is a ball.

4. A key entrapment lock device as in claim 1 in which said keyway extends into said plug a predetermined distance and said passage intersects said keyway at a point about midway of said distance.

5. A key entrapment lock device as in claim 1 in which said keyway is proportioned with respect to said key to leave an access channel between said key and said plug from the entrance end of said plug to said body.

8. A key entrapment device as in claim 1 in combination with a key having a surface which when said key is in said keyway abuts said body at an angle greater than a wedging angle between said key surface and said body.

10. A key entrapment device as in claim 1 including means defining a bore in said plug extending from the exterior thereof substantially to said passage.