US 3045468 A
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Description (OCR text may contain errors)
July 24, 1962 N. A. WELCH ETAL 3,045,468
PICK RESISTANT LOCK CYLINDER Filed April e, 1960 J J J D INVENTORS /V/c//oLHs H. Ww. cH
13g/mines /fz/wvgr/fPaBz'Pn PICK RESISTANT LCK CYLINDER Nicholas A. Welch, West Hartford, Conn., and Charles Kenneth Roberts, East Canton, Ohio, assignors, by mesne assignments, to Charles K. Roberts, Baltimore,
Filed Apr. 6, 1960, ser. No. 20,443 3 claims. (ci. '1o- 421) This invention relates to a lock `cylinder and more particularly to a lock cylinder of the pin tumblervtype which is especiallyr adapted to resist picking.
The present invention provides a pin tumbler lock cylinder which is especially well suited for use in locking devices such as padlocks, door locks, drawer locks, cabinet locks and the like where a' high degree of security is required. While most `such locking devices may be defeated by actually destroying the lock mechanism or physically altering the lock cylinder as by drilling or the like, such methods are likely to attract immediate attention as they are being carried out and are, in any event, thereafter easily detected. Picking techniques, on the other hand, leave no telltale evidence that the lock has been tampered with, but are usually thwarted if success cannot be quickly achieved. lIt is therefore apparent that the degree of pick resistance inherent in a lock cylinder is of singular importance.
Most pin tumbler lock cylinders hereto-fore devised can be successfully picked in a relatively short time and hence do not afford a very high degree of security. Of
. course, lock cylinders have been made which were difcult to pick, but these generally involved complicated mechanisms, odd shaped keyways and keys, compound tumbler sets or other such unusual structure, and were so expensive to manufacture that they were rarely commercially successful.
The present invention therefore has as its primary object the provision of a pin tumbler lock cylinder which is extremely diicult, if not impossible, to pick, is comparatively inexpensive to manufacture and is yet reliable in action so that it may be easily operated by the proper key.
A further object of this invention is to provide a lock cylinder 'which is highly pick resistant and yet does not involve the use of complicated and expensive structure.
Another object of the present invention is to provide a pin tumbler lock construction which may be readily ernbodied in conventional locking devices of the type mentioned above .without requiring radical changes in the structure of the locking devices.
As is well known to those skilled in the lockart,
'Y conventional techniques for picking pin tumbler lock cylinders require the application of torque to the key plug of the lock cylinder to effect fractional turning movement thereof while the pin tumblers are manipulated to bring them into unlocking or shear position. In one method, commonly known as up picking, torque is applied to the key plug and the pin tumblers are then successively raised against their springs wit-h a picking tool inserted into the keyway until all of the tumblers have been moved into shear position. The reverse of this method, known as down picking, involves simultaneously raising all of the tumblers as far as possible and then exerting torque on the key,plug. The tumblers are then permitted to move downwardly under the inlluence of their respective tumbler springs while an attempt is made to catch the proper tumblers on the exposed edge portions of the tumbler bores in the key plug to thereby release the key plug for turning movement. In other picking methods, the tumblers are Vibrated rapidly up and down with a suitable tool or by striking the locking device -With a mallet while simultaneously exerting a flice torque on the key plug in order to trap the tumblers in locking position.
Pin tumbler lock cylinders may also be picked by skilled persons using the well known impression method. This method is essentially a down picking technique and involves the use of an uncut key blank of the proper cross-sectional shape to it the keyway of the lock cylinder. This key blank is usually provided with a burnished top edge and is inserted into the keyway to lift all of the pin tumblers above their normal shear positions. Heavy torque is then applied to the key plug to clamp the pins in position and an up and down, in and out rocking motion is applied to the key blank to cause the clamped pins to mark lthe edge of the key'blank. Thekey blank is then examined and several fine file cuts are made at each mark on the edge of the key blank. This operation is repeated until the key blank has been cut deeply enought to lower all of the pins to shear position.
In order to prevent picking by4 these and other wellknown methods, we provide a lock cylinder having means therein which prevent the tumblers from being properly manipulated when torque is applied during pickv ing operations and which also serve to bale and confuse for Vlimited rotation in the body of the lock cylinder,l
the amount of rotation permitted the control member being ineffective to cause operation of the mecha nism of the locking device in which the lock cylinder is contained. The cylinder body, the control member and the key plug have the usual rows of tumbler bores which are normally aligned and contain a series of tumbler elements including conventional pin tumblers. In the normal locking position of said tumblers, thekey plug 'and the control member are locked together bythe pin tumblers and are adapted to rotate in said cylinder body so that the application of a torque to the key plug, regardless of how slight it may be, will cause the control member to rotate therewith.
In each of the tumbler bores of the control member we provide a unique control tumbler which is responsive to the torque applied to said control member to prevent successful manipulation of the pin tumblers. The control tumblers are preferably in the form of balls and are capable of acting in diverse and unpredictable ways to defeat various picking techniques as will be hereinafter described.
The basic conce-pt of our invention may be embodied in many physical forms, and several of these forms are shown by way of example in the accompanying drawing in which:
FIG. l is an elevational view, partly in central vertical section, illustrating a lock cylinder embodying our invention, said lock cylinder being shown in its normal, locked condition.
lFIG. 2 is a sectional end view of the lock cylinder taken on line 2--2 of IFIG. l.
IFIG. 3 is a sectional end view illustrating one manner in which up picking operations are defeated by the control tumblers of our invention.
FIG. 4 `is a diagrammatic view further illustrating the principle of operation of the control tumblers.
FIG. 5 is a sectional end view illustrating one manner in lwhich down picking operations are defeated.
FIG. 6 is a view similar to FIG. 1, but illustrating the normal operation of the lock cylinder of the proper key.
FIG. 7 is a fragmentary sectional end View illustrating a modified form of control tumbler for use in the lock cylinder.
FIG. 8 is a similar view illustrating another type of control tumbler which maybe used in the lock cylinder.
The lock cylinder embodying our invention and illustrated in the drawing comprises a body including a cylinder portion -6 and an integral chamber portion 7 which extends radially from said cylinder portion. The cylinder portion 6 contains an axial bore which is Open at the inner end of said body and terminates short of its outer end to provide an outer wall `6-a thereon. A longitudinal row of aligned, equally spaced driver `bores 9 extend radially from the bore 8 into the chamber 7 and said bores are closed at their upper ends by a plate 7-a.
In accordance with the present invention, a control member in the form of a sleeve 10 is rotatably mounted in the bore 8 of the body 5 and the control sleeve contains a row of radially extending tumbler bores 11 which are alignable with the driver bores 9 as shown in FIGS. l and 2.
A key plug 12 is mounted to rotate in the control sleeve 10 and extends through a coaxial opening 13 in the outer wall 6-a of the body 5. At its outer end, said key plug is provided with a flange 1'4 which rotates in a recess 15 in said outer wall and prevents inward axial movement of the key plug. The inner end of the key -plug has an axial extension 16 of reduced diameter which projects from the inner end of the control sleeve 10 and receives a cap 17. The said cap is secured to the key plug extension 16 by a pin 18 and is provided with an annular flange 19 which engages the inner end of the control sleeve 10. It will be seen that the cap 17 prevents outward axial movement of the key plug and inward axial movement of the control sleeve to thereby maintain the lock cylinder in assembled condition. The cap 17 is, in the present illustration, provided -with a stud 20 which is adapted to operate the lock mechanism of the locking device in which the lock cylinder is contained.
The key plug 12 has an axially extending keyway 21 of irregular cross-sectional shape, and it will be noted that said keyway is contained entirely within the key plug so that it is closed along its bottom to prevent access to the control sleeve 10 through the keyway. The key plug also contains a row of radially extending pin tumblers bores 22 which communicate with the keyway and are normally aligned with the tumbler bores 11 and 9 in the control sleeve 10 and the body 5 respectively.
Each of the aligned sets of tumbler bores of the lock cylinder slidably contain a series of tumbler elements of predetermined lengths which are normally disposed in the positions illustrated in FIG. 1. In the present embodiment, each series of tumbler elements includes a change pin 23 and an intermediate pin 24 which are slidably disposed in the tumbler bores 22 and 11 of the key plug and the control sleeve respectively. The intermediate pin tumblers 24 normally extend across the shear line 25, defined by the adjacent surfaces of the key plug and the control sleeve, and lock these parts together.
Each series of tumbler elements also includes a novel control tumbler 26 which is preferably in the form of a -sphere or ball as shown in IFIGS. 1 to 6. The control 'tumblers are normally disposed in the tumbler bores 11 in the control sleeve, but project slightly above its peripheral surface. 'In this position, the upper segment of each sphere extends across the shear line 27, defined by the peripheral surface of the control sleeve and the wall of the bore8, and into the aligned tumbler bore 9 in the body 5 as best shown in FIG. 2. The control tumblers 26 and the pin tumblers 24 and 23 are yieldingly held in normal locking position by driver tumblers 28 which are slidable in the tumbler bores 9 of the body 5 and are biased downwardly into engagement with the control tumblers by tumbler springs 29.
hereinafter described, such rotation must be limited to an amount less than that required to operate the mechanism of the locking device in which the lock cylinder is contained. In order to accomplish this, we provide a slot 30 in the periphery of the control sleeve and a stop pin 31 in the body 5. The stop pin 31 extends into said slot and is engageable by the sidewalls thereof to limit rotation of the control sleeve to a predetermined num ber of degrees.
It has been found that the degree of pick resistance of lock cylinders constructed in accordance with the present invention is directly proportional to the number of control tumblers 26 provided therein. Experimental models with a single series of tumbler elements arranged as shown could easily be picked. When two series of tumbler elements were provided, picking became more difficult, but could be accomplished. Look cylinders with three series of tumbler elements could not be successfully picked in the time allotted, and exhaustive tests have shown that lock cylinders constructed as shown in `FIG. 1 are capable of resisting indefinitely all presently known picking techniques.
While the spherical control tumblers 26 act in diverse and unpredictable ways to prevent proper manipulation of the pin tumblers during picking operations, FIGS. 3 and 4 of the drawing illustrate one manner in which up picking is prevented. As previously mentioned, the tumbler elements normally occupy their lowermost positions, as shown in FIGS. 1 to 4, wherein the key plug l2 is locked to the control sleeve 10 by the intermediate pin tumblers 24, and the upper segments of the spherical control tumblers 26 project into, but are spaced from, the lower edges of the tumbler bores 9. When torque is applied to the key plug 12, say in la clockwise direction as shown by the arrow 32 in FIG. 4, both the key plug and the control sleeve will rotate together and the control tumblers 26 will be carried into engagement with the lower edges of the tumbler 4bores 9. Since the centers of the spherical control tumblers are disposed below the edges of the tumbler bores 9, the surfaces of said control tumblers which engage said edges are disposed angularly thereto and act as cam surfaces which cause said control tumblers to be cammed or thrust downwardly, as indicated by the Iarrow 33, to prevent the pin tumblers 23 and 24 from being raised. If the torque is increased, the downward force exerted by the control tumblers is Ialso increased proportionately which makes raising of the pin tumblers that much more diiiicult. Should the upward force exerted on the pin tumblers 23 with vthe picking tool `and the torque applied to the key plug be so proportioned as to pennit raising `of one or more series of 'tumbler elements, the control tumblers 26 will cam the control sleeve back toward its normal position as they are forced upwardly in the tumbler bores 11 and into the tumbler bores 9. As soon as the centers of one or more of the control tumblers move past the shear line 27, they will be cammed upwardly by the left-hand edges of the tumbler bores 11 in the control sleeve which will cause them to pop upwardly into the tumbler bores 9 in the cylinder body, thus permitting the control sleeve to turn slightly before the person attempting to pick the lock has time to realize what has happened. The control tumblers so affected will then be trapped up in the tumbler bores 9, as shown in FIG. 5, and will prevent the force exerted by the tumbler springs 29 from being transmitted to the pin tumblers 23 and 24. In the absence of such spring pressure the pin tumblers 23 and 24 are free to move up `and down in their bores and it is then impossible to feel their positions with respect tothe shear line 25.
FIG. 5 .also illustrates what may happen when down picking techniques are employed in an attempt to pick the lock cylinder. In such ya case, all of the tumbler elements are rst raised as far as possible with the picking tool thus moving the ycontrol tumblers 26 into the tumbler bores 9 in the cylinder body. Torque is then applied to the key plug, say in la clockwise direction as shown, but
since the key plug will be locked to the control sleeve by one or more of the pin tumblers 23, the control sleeve will rotate with the key plug when the torque is applied. It will be apparent, therefore, that the edges of the tumbler bores 11 in the control sleeve will then be positioned as shown in FIG. 5 to engage and prevent the descent of the control tumblers when the upward pressure on the pin tumblers is released. Asa result, the tumbler springs are prevented from acting upon the pin tumblers 23 and 24 so that their positions with respect to the shear line 25 cannot be determined. All in all, the described 4and other functions of the control tumblers 26 serve -to baflle and confuse the person attempting to pick the lock .and make picking extremely difficult if not impossible.
While the control tumblers 26 provided by our invention effectively defeat picking, they cause no interference with the normal operation of the lock cylinder. Referring now to FIG. 6, it will be seen that when the proper key 34 is inserted into the keyway 21 the tumbler elements Iare lifted to align the abutting ends of the pin tumblers 23 and 24 with the shear line 25 whereupon the key plug may be -rotated relatively to the control sleeve. Rotation of the control sleeve during key operation of the lock cylinder may be prevented by providing an intermediate pin tumbler 24 which is long enough to extend into its respective tumbler bore 9 to lock thel control sleeve to the cylinder body.
While the spherical control tumblers 225 provide the maximum pick resistance, other types of tumbler elements may be used in our lock cylinder to defeat picking. FIG. 7, for example, illustrates a modied control tumbler which is in the form of a pin tumbler 24-1 having a spherical, or spheroidal, upper end por-tion 24J). Preferably, one such pin tumbler is provided in each of the tumbler bores 11 of the control sleeve 1li immediately above the pin `tumbler 23. ln the normal locking positions of the tumbler elements, the lower portion of each pin tumbler 24-a extends across the shear line 25 to lock the key plug |12 and the control sleeve `lil together. The
` upper segment of the spherical end portion 2li-In of each said tumbler projects slightly above the .peripheral surface of the control sleeve 10` and thus extends across the shear line 27 and into the aligned tumbler bore 9 in the cylinder body. The pin tumblers 23 land 24a are normally yieldingly maintained in locking position by the spring-pressed driver tumblers 23 as previously described.
The control tumblers 24-a function in the same manner as the spherical control tumblers 25 to defeat up picking, for when the control sleeve is rotated upon the application o-f a picking torque to the key plug their spherical end portions 2li-b are carried into engagement with the edges of the tumbler bores 9. This results in the application of a downward force on said control tumblers which prevents the pin tumblers 23 `from being raised. The ability of the lock cylinder to resist down picking and other picking techniques may be effectively increased by using Icontrol tumblers ot the well known spool or mushroom type whose `function will be apparent to .those skilled in the art.
FIG. 8 illustrates a further modificationof our invention wherein the control tumblers are in the form of wafers 35-35 having opposed spherical surfaces 36-36- Preferably, a pair of said wafers are provided in each of the tumbler bores 11 in the control sleeve between the intermediate pin tumbler 24 and the driver tumbler 2b as shown. In the normal locking position of the tumbler elements, the spheroidal surfaces of the upper wafers 35 project slightly above the peripheral surface of the control sleeve il@ and into the aligned tumbler bore 9 in the cylinder body. When the control sleeve is rotated, it will be apparent that theA upper wafers will engage the edges of the tumbler bores 9 whereupon they will be cammed downwardly to prevent manipulation of the pin tumblers 23 and 24. The wafer control tumblers will also act much in the same way as the balls 25 to prevent down picking as above described.
From the preceding description, it will be apparent to those skilled in the art that our invention is capable of many other embodiments than those shown. For example, the body 5 may be a padlock body or the body of a door knob having the bore `9 and the tumbler bores 9 formed directly therein. The important features of our invention reside in the other elements described herein and the particular type of lock body in which they are used is of little signicance.
l. A' pick resistant lock including a lock body having a bore, a tubular control sleeve rotatable in said bore, means limiting the rotation of said control sleeve in said bore, a key plug mounted to rotate in said control sleeve and having an axial keyway, said key plug, control sleeve and lock body having radial tumbler bores which are alignable and communicate with said keyway, a series of tumblers slidable in said tumbler bores including pin tumblers normally positioned to lock said key plug and said control sleeve together and being movable by a key inserted into said keyway to unlocking position to release said key plug for free rotation relatively to said.
control sleeve, tumbler control means normally occupying a position in the tumbler bore in said control sleeve radially outwardly of the pin tumblers in said series, said tumbler control means including at least one lens-shaped wafer having opposed spheroidal surfaces and in the normal locking position of said tumblers being disposed so that the upper segment of the upper spheroidal surface projects into the tumbler bore in said lock body in spaced vrelation to the edge portiony thereof to permit rotation of said control sleeve when picking pressure is applied to said key plug in an attempt to pick said tumblers, the'spheroidal surface of said tumbler control means being carried into engagement .with said edge portion upon rotation of said control sleeve thereby preventing movement of said series of tumblers to unlocking position, said tumbler control means responsive to applied torque of said key plug producing a locking action and `false indications removed from the operating shear line which serves to baffle and confound picking attempts.
2. The subject matter set forth in claim l wherein said tumbler control means includes at least one substantially spherical shape that may have an irregular surface.
3. The subject matter set forth in claim 1 wherein said tumbler control means and said control sleeve may be-of a plastic or resilient material.
References Cited in the tile of this patent UNITED STATES PATENTS