Symmetrical side bar lock and key therefor

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in cylinder locks of the type having dual locking mechanisms including tumblers and a side bar. More particularly this invention relates to improvements in twisting tumbler-side bar cylinder locks.

2. Prior Art

Medeco Security Locks, Inc. of Salem, Va., a wholly owned subsidiary of Hillenbrand Industries, Inc., makes and sells a twisting tumbler-side bar cylinder lock under the Medeco trademark. The Medeco cylinder lock is fully disclosed in U.S. Pat. No. Re. 30,198 reissued Jan. 29, 1980 and such disclosure is incorporated herein by reference.

In the Medeco lock the side bar which rests in a camming slot of the cylindrical shell must have its tumbler locking lugs positioned above a horizontal center line through a center of the plug since the side bar lugs or legs must be able to avoid interference with a proper bitted key when they move into the tumbler slots.

While the Medeco twisting tumbler-side bar cylinder lock has been a significant commercial success for a number of years, it, like many successful products, could be improved.

In the Medeco lock, because the side bar legs or lugs must avoid the key, they are of necessity of a small dimension in height and because the legs are asymetrical with regard to a radial line through the camming slot they will not bear the same forces in either direction. Also, if larger and symmetrically-positioned side bar legs or lugs could be used, the lock would offer more strength against forcing. However, if the side bar legs were made larger and the side bar were positioned symmetrically with regard to a horizontal line through the center of the plug, the side bar legs would intersect the key and not operate properly, thus rendering the lock inoperative.

SUMMARY OF THE INVENTION

This invention relates to improvements in the dual locking cylinder locks of the type including twisting tumblers and a side bar in which the side bar legs are symmetrical with a line through the center of the key plug perpendicular to the plane of the keyway so as to provide larger side bar legs which resist forcing equally in opposite directions and are stronger than legs which extend only to one side of the center line, combined with a unique key which allows operation of the cylindrical side bar by having vertical slots perpendicular to the longitudinal axis of the keyblade at the position of each tumbler.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse sectional elevation view taken through the improved lock of this invention at one tumbler pin location.

FIG. 2 is a transverse sectional elevation view similar to FIG. 1 illustrating the position of the tumbler upon insertion of a proper key.

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a transverse sectional view similar to FIG. 2 showing the lock plug turned toward an unlocking position.

FIG. 5 is a sectional view taken along line 5--5 of FIG. 4.

FIG. 6 is an exploded perspective view of an improved key of this invention with the cylinder plug and side bar of the lock.

FIG. 7 is a transverse sectional view of the prior art Medeco lock.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Because the entire Medeco lock is so well known and is completely described in U.S. Pat. No. Re. 30,198, reissued Jan. 29, 1980 (the Medeco patent), a complete description of the lock cylinder will not be given, but only the improvements which are incorporated in this invention with regard to the symmetrical side bar and the unique key.

With reference to FIG. 1 there is shown a key plug 10 rotatable within a cylindrical bore 12 of a lock cylinder 14. The lock cylinder 14 has a plurality of tumbler holes 16 therein for reception of driver pins 18 which together with the tumblers 20 are biased downwardly by driver spring 17. A cap or other suitable means 19 closes each tumbler.

Each tumbler 20 has a chisel-shaped lower tip 22 as in the Medeco lock of U.S. Pat. No. Re. 30,198 and also has a slot 24 extending along one side of the tumbler as disclosed in the Medeco patent. A suitable keyway 26 of unique profile is provided horizontally into the plug. The keyway is preferably selected so that it is not of the same profile as any other commercial keyway so as to avoid the possibility of using different manufacturer's keys in the cylinder lock, as is known in the art. The key 28 has a key bit 30 for each tumbler slot and the key bits are either center cut, skew-cut right or skew-cut left as disclosed in the Medeco patent.

A side bar 32 extends substantially the length of the cylinder plug and includes a projection 34 on one side thereof for mating with a cam groove 36 in the shell. A plurality of lugs or legs 38 extend from the other side of the side bar toward the tumblers. There is a lug at each tumbler position. Springs 40 bias the side bar away from the tumblers and normally hold the projection 34 in the groove 36.

It should be noted that the keyway extends upwardly above a horizontal line 50 through the center of the plug and that the lugs or legs 38 of the side bar extend equally and symmetrically above and below the line 50 so that in normal operation with a prior art Medeco key when the lugs 38 move toward the slots 24 of the twisting tumbler, they would intersect the key. The line 50 is perpendicular to a plane of the keyway and extends through the axis of rotation of the plug. The plane of the keyway is a vertical plane in the FIG. 2 position which extends through the center of the plug and the tumbler holes.

The key used in this invention is shown more fully in FIG. 6. The key 28 has a blade portion 42 with a longitudinal axis and a bow 44 as is conventional. The key bits 30 on top of the blade portion 42 can include one or more skew-cut bits 46 which can be skewed in either direction as is known in the Medeco lock and one or more center cut bits.

The key blade 42 has a plurality of slots 48 in one side face thereof positioned adjacent to the bits and at the location of each tumbler. These slots 48 are on the same side of the key as the side bar. Each slot 48 extends into the profile of the keyway and the key blade can therefore accommodate the symmetrical lugs or legs 38 of the side bar as shown in FIGS. 4 and 5.

FIG. 1 shows the position of a tumbler when the lock is in a locked position with the side bar projection 34 in the groove 36 and the driver pin 18 blocking rotation of the key plug 10. This is the condition prior to insertion of a proper key.

FIG. 2 shows the situation at the time of insertion of a proper key and prior to the turning of the plug. The proper key 28 will twist each of the tumblers 20 by virtue of the chisel point on the tumblers and the straight or skew bits on the key so that the slots 24 on the tumblers line up with the side bar legs 38 as shown in FIG. 3. The side bar legs then have suitable space for movement to the left as shown in FIG. 3 upon turning of the key. When the key is turned the side bar projection 34 cams out of slot 36 as shown in FIG. 4 and moves inwardly to a position so that the tips of the legs 38 are accommodated by the slots 24 of the tumblers 20 and by the slots 48 of the keyblade 42 as shown in FIG. 5.

FIG. 6 shows the interaction of the key with its cross sectional profile fitting into the keyway in the cylindrical plug and the side bar removed from the plug but positionable therein.

FIG. 7 shows the prior art Medeco lock with each reference numeral of the prior described parts indicated with a prime and showing the Medeco key inserted to twist and lift the tumbler so that the tumbler 20' is positioned at the shear line and the tumbler slot 24' is positioned to receive the lug 38' of the side bar 32'. However, the lug 38' of the side bar 32' is asymmetrical and is above a radius perpendicular to a plane of the keyway. That is, lug 38' is above line 50 because if it were to extend below line 50 it would intersect the keyway and the key and render the lock inoperable.

With this invention the side bar lugs are symmetrical on either side of a radius perpendicular to the plane of the key. Thus, the side bar lugs 38 can be wider to enhance interaction with the shell slot and provide the same action and resistance in either direction of rotation of the plug. Furthermore, with larger legs the legs are stronger and provide more resistance to forcing. Additionally, the unique construction requires a key with parallel slots so that one can be sure that a key with parallel slots fits a lock of the invention and enables the key to be better identified on a key ring.

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