Pick Proof Locking Plate For Padlock

Abstract

A cylinder assembly located in the chamber of a padlock has a key actuated rotating cylinder plug to which is attached a locking plate. Locking lugs at opposite ends of the locking plate engage notches in the long and short legs of a shackle to hold the shackle in locked position. Engagement of the lugs with the notches is such that when the lug engaging the short leg is clear, the lug engaging the long leg is still partly engaged. For that reason the shackle cannot be unlocked by unauthorized manipulation of a shim inserted through the clearance around the short leg of the shackle to release the locking lug from engagement with the short leg.

Description

When a padlock is one equipped with a shackle having one long leg and one short leg the preferred construction is such that there is a reasonably snug fit around the long leg and a rather loose fit around the short leg. What accounts for this is that the long leg is to be fitted in what amounts to a bearing aperture in which some portion of the long leg remains at all times but there should be a relatively greater clearance in the aperture which accepts the short leg so that the short leg can be readily pushed back into the aperture whenever the shackle is to be snapped shut. When a rotating locking plate is made use of to engage both shackles whereby to hold the shackle in locked position, if the lock is to be picked, some unauthorized means such as a thin shim, needs to be used to rotate the locking plate out of its engagement with the legs. Those skilled in the manipulation of padlocks are aware that if such a padlock is to be picked, the shim will need to be manipulated through the relatively large clearance around the short leg, since the bearing-like clearance around the long leg is not normally sufficient to permit such manipulation.

It is therefore among the objects of the invention to provide a new and improved locking means for a padlock which is arranged in such fashion that it cannot be moved from its normally locked position by unauthorized manipulation.

Another object of the invention is to provide a new and improved rotating locking means for locking the legs of a padlock shackle which is arranged in such fashion that the locking means cannot be completely disengaged by manipulation through the clearance around the short leg.

Still another object of the invention is to provide a new and improved double locking means for both legs of a padlock shank which engages the legs through a rotating movement and wherein the rotating means is so constructed and assembled that it inherently resists unauthorized tampering such as might be attempted to rotate the double locking means out of its locked position.

Still another object of the invention is to provide a new and improved simple rotating means capable of engaging both legs of a padlock shackle and which by virtue of its mounting construction is substantially tamper proof.

With these and other objects in view, the invention consists in the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter set forth, pointed out in the appended claims and illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a device partially broken away to show the locking portion.

FIG. 2 is a cross-sectional view on the line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view on the line 3--3 of FIG. 1.

FIG. 4 is a fragmentary cross-sectional view through the short leg revealing the effect of manipulation by an unauthorized shim.

FIG. 5 is a fragmentary cross-sectional view of a long leg showing the continued partial engaged position of the locking lug such as might occur when the short leg locking lug is being tampered with.

FIG. 6 is a view similar to FIG. 4 revealing another effect of manipulation by an unauthorized shim.

In the embodiment of the invention chosen for the purpose of illustration there is shown a padlock indicated generally by the reference character 10, comprising a case or body 11, made up of a multiple number of laminations 12 held together by rivets 13. In the body 11 is a chamber 14 in which is housed a cylinder assembly comprising a cylinder plug housing 15 and a pin tumbler housing 16. In the cylinder plug housing 15 is a rotating cylinder plug 17 to which access is had by way of a key (not shown) and a keyway 17' through an opening in a bottom plate 18. A shackle 19 has a long leg 20 and short leg 21. To accommodate the long leg 20 there is provided a bearing aperture 22 in a top plate 23 and a second axially aligned bearing aperture 24 in an intermediate lamination 25. The clearance between the bearing apertures 22 and 24 and the outer circumference of the long leg 20 is customarily made reasonably close which it can be inasmuch as some portion of the long leg 20 always remains in the apertures 22, 24, removal of the long leg 20 being prevented by engagement of a stop lug 26 with the intermediate lamination 25 when the shackle 19 is released to the extent of its movement.

At the inner end of the cylinder plug 17 is a projection 27 which engages a locking plate 28. Parallel surfaces 29 and 30 are positioned to engage respective stops 31 and 32 on the locking plate 28 so that when the cylinder plug 17 is rotated in a counterclockwise direction as viewed in FIG. 2, the locking plate 28 will likewise be rotated in a counterclockwise direction. A certain amount of lost motion is allowed for when the cylinder plug 17 is rotated in an opposite or clockwise direction until the parallel surface 29 engages a tab 33 which projects downwardly from the intermediate lamination 25.

At one end of the locking plate 28 is a heel locking lug 35 and at the opposite end is a toe locking lug 36. The heel locking lug 35 is adapted to engage in a heel notch 37 in the long leg 20 and the short leg 21 has a toe notch 38 which is adapted to be engaged by the toe locking lug 36. The engaged relationship is shown in FIGS. 1 and 2.

A torsion spring 40 which extends around a boss 41 at the outer end of the projection 27 of the cylinder plug 17, has one end 42 adapted to bear against the toe locking lug 36 and another end 43 adapted to bear against a wall 44 of the chamber 14. Stops 45 and 46 by engagement with the wall 44 prevent the torsion spring 40 from rotating the locking lugs 35, 36 out of engagement with the notches.

To open the lock by normal authorized means a key (not shown) is inserted into a keyway 17' , visible in FIG. 2, and the key is rotated in a counterclockwise direction as viewed in FIG. 2 until the locking lugs 35 and 36 are disengaged entirely from the respective notches 37 and 38. When this occurs the shackle 19 is released and the locking plate 28 remains in rotated position, held there by contact of the round portion of the long leg 20 with an adjacent edge 34 and the heel locking lug 35.

The shackle 19 can be re-engaged by merely pushing the short leg 21 into access apertures 48 and 49, respectively, in the top plate 23 and intermediate lamination 25. As soon as the notches 37 and 38 coincide in position with the locking lugs 35 and 36, the torsion spring 40 will again take over and rotate the locking plate 28 clockwise, as viewed in FIG. 2, into an engaging position with the shackle legs 20, 21.

Those experienced in lock construction and who might undertake to disengage the locking plate 28 from engagement with the legs of the shackle 19 understand that clearance between the access apertures 48 and 49 and the exterior circumference of the short leg 21 is customarily made sufficiently wide for ease of re-entry of the short leg 21. A known expedient is to inject a relatively thin, stiff shim 50, shown in FIGS. 3 and 4, through the clearance and undertake to pry the toe locking lug 36 out of its engagement with the toe notch 38 by rotating it.

As shown to good advantage in FIG. 6, the toe locking lug 36 is provided with a corner cut-out 39 to provide a still further obstacle to unauthorized release of the shackle. The location of the cut-out 39 is such that when the shim 50 is initially pressed into engagement with the toe locking lug 36 the shim will be trapped in the cut-out 39. The direction of applied pressure is at an angle with respect to the location of the toe locking lug such that one component acts along the longitudinal axis of the locking plate 28 which, since the locking plate is not shiftable axially, additionally discourages the prospect of dislodging it from locked position by shim action.

Although in the device herein disclosed such a manipulation might be made possible by moving the shim 50 to the position shown in FIGS. 3 and 4, wherein the disengagement of the toe locking lug 36 is complete, the locking plate 28 is so constructed that the heel locking lug 35 remains in engagement with the heel notch 37 as shown in FIGS. 3 and 5. This remains true even though a substantial part of the heel locking lug 35 has been shifted from its position of full engagement. As long as any portion of the heel locking lug 35 remains in the notch 37, the long leg 20 is not released and the padlock 10 remains locked. Clearance between the exterior of the long leg 20 and the bearing apertures 22 and 24 is customarily made so snug that it will not admit injection of a second shim of sufficient size or strength to manipulate the heel locking lug.

Moreover, in spite of the tampering which might be undertaken, no damage is done to the lock and once the shim 50 is removed the lock can be unlocked and relocked in the customary fashion.

While the invention has herein been shown and described in what is conceived to be a practical and effective embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

Claims

Having described the invention, what is claimed as new in support of Letters Patent is:

1. An anti-tamper padlock construction comprising a padlock body having a chamber therein, a shackle having a long leg and a short leg, said body having a bearing aperture on one side in which said long leg is rotatably and slidably secured and an access aperture on the other side for reception of the short leg, a cylinder lock assembly mounted in said chamber and having a cylinder plug extending into the chamber adjacent said apertures, a locking plate in operating engagement with said cylinder plug and adapted to be rotated thereby out of a locked position, said long leg having an inwardly facing heel notch and said short leg having a toe notch facing said heel notch, said locking plate having a radially outwardly extending heel locking lug adapted to engage in said heel notch and an opposite radially outwardly extending toe locking lug adapted to engage in said toe notch, the relationship of the heel locking lug, the toe locking lug, the heel notch and the toe notch being one wherein when the toe locking lug is clear of the toe notch and adjacent thereto the heel locking lug is in engagement with the heel notch, whereby unauthorized disengagement separately of said toe locking lug will fail to release said shackle.

2. An anti-tamper padlock construction as in claim 1 wherein the locking lugs are diametrically opposite each other and the trailing edge of the heel locking lug is laterally offset relative to trailing edge of the toe locking lug.

3. An anti-tamper padlock construction as in claim 1 wherein clearance between the short leg and the access aperture is greater than clearance between the long leg and the bearing aperture.

4. An anti-tamper padlock construction as in claim 1 wherein there is a top end plate forming part of said body and closing said chamber and wherein when the shackle is in locked position the notches in the legs are locked adjacent an inside face of said top end plate.

5. An anti-tamper padlock construction as in claim 1 wherein there is a cut-out in a portion of said toe locking lug on the side thereof facing the short leg access aperture and a side of said cut-out extending into and out of said access aperture whereby to trap movement of an unauthorized instrument inserted between the short leg and said short leg access aperture when the shackle is in locked position.

6. An anti-tamper padlock construction comprising a padlock body having a chamber therein, a shackle having a long leg and a short leg, said body having a bearing aperture on one side in which said long leg is rotatably and slidably secured and an access aperture on the other side for reception of the short leg, a cylinder lock assembly mounted in said chamber and having a cylinder plug extending into the chamber adjacent said apertures, a locking plate in operating engagement with said cylinder plug and adapted to be rotated thereby out of a locked position, said long leg having an inwardly facing heel notch and said short leg having a toe notch facing said heel notch, said locking plate having a radially outwardly extending heel locking lug adapted to engage in said heel notch and an opposite radially outwardly extending toe locking lug adapted to engage in said toe notch, said toe locking lug having a cut-out at a portion thereof facing the short leg access aperture with a side extending into said access aperture in locked position of said toe locking lug whereby to trap movement of an unauthorized instrument inserted between the short leg and said short leg access aperture when the shackle is in locked position and guide movement of said instrument in a direction nonproductive of release of said toe notch.

7. An anti-tamper padlock construction as in claim 6 wherein said side of the cut-out has a portion at a location greater in radial distance from the axis of rotation of said locking plate and outside said access aperture than is the bottom of the cut-out, said side having a potential direction of movement against said unauthorized instrument when said locking plate is subjected to unauthorized rotation.