GB2141477A - Cylinder barrel lock security device - Google Patents

Abstract

The barrel (2) of a conventional rotatable cylinder lock of the sliding multi plate tumbler type is carried in a housing (1) which contains one or more slideable plates (8) positioned to move tangentially to the axis of the barrel. The slideable plate carries a slot into which the tips of the existing tumbler plates protrude. The slideable plate also carries a sprag type projection (10). If an incorrect key or picking tool is introduced into the lock barrel and a rotational load is exerted in order to defeat the lock, the barrel will be slightly rotated, the tips of the tumbler plates within the barrel will urge the slideable plate tangentially, allowing the sprag projection on the plate to co-operate with a recess or cavity (14) in the lock barrel surface, to prevent further rotation. <IMAGE>

Description

SPECIFICATION Locking cylinder barrel security device Increasing thefts from motor vehicles and thefts from locked premises and security ap pliances demonstrates the need for an im provement in the design of cylinder locks to render them more difficult to open by a thief using special picking tools.

The present invention describes a means to jam or deadlock a rotatable cylinder lock barrei and therefore to resist rotation when subjected to tampering with an incorrect key or picking tool.

The system described can apply to multi plate cylinder barrels of the single entry or double entry key type.

In a known design of cylinder lock there is provided a cylindrical barrel which carries a plurality of slots placed side by side along the axis of the barrel. In each slot is positioned a flat tumbler of generally rectangular shape.

Each tumbler is biased one way by a coil spring. It carries a slot to allow passage of a key. The slots are positioned at different heights relative to the top and bottom edges of the tumbler, so that when the correct key is inserted into the cylinder barrel all the tumblers move into a position to allow free rotation of the barrel within its housing. If an incorrect key is inserted into the barrel some tumblers are over-lifted and other tumblers are underlifted. By means of a "jiggling" movement of an incorrect key or a picking tool and at the same time loading the tumblers by using a rotational load on the picking tool the tumblers can be urged to move within the cylinder barrel and the barrel can then be rotated.

According to the present invention there is provided a housing which carries a cylinder lock barrel containing moving tumblers and also one or more slideable plates positioned to move tangentially to the major axis of the barrel. The slideable plate carries a slot into which the tips of the existing tumblers can protrude. One side of the slot can be considered as a leading edge which is abutted by the tumblers when the cylinder barrel is rotated with a picking tool, the other side of the slot or trailing edge, carries a sprag shape which has means to co-opt into a recess formed within the cylinder barrel surface.So that when the slideable plate is urged tangentially by means of a rotational movement on the cylinder barrel (created by a picking tool) the sprag part of the plate engages with a coopting recess in the face of the cylinder barrel to prohibit further rotation of the barrel. The slideable plate can be fitted with a spring to bias it into its original position.

Following is a description by way of example only and with reference to the accompanying drawings of a method of carrying the invention into effect.

In the drawings: Figure 1 is a section through a cylinder barrel with a plate tumbler shown in a free key out position.

Figure 2 as Fig. 1 but with the plate tumbler biasing the sliding plate.

Figure 3 shows a plan view of the sliding plate.

The following description applies to a double entry key type cylinder lock. Referring to Fig. 1 a cylinder housing (1) contains a locking barrel (2) which contains a plurality of tumblers (3) so that some tumblers move freely in one direction and some in the opposite direction. These tumblers are urged by springs (4) to protrude into cavity (5) in stationary housing (6) in one direction and cavity (7) in moving plate (8) in the other direction.

Moving plate (8) is arranged to slide freely in recess (9) in housing (1) it is generally flat but carries a sprag shape (10) adjacent cavity (7).

Each tumbler carries a slot (11) of rectangular shape to receive a key (not shown).

Fig. 2 shows a situation whereby the lower tumblers (3) are "picked" clear of the cavity (5) in stationary housing (6). The lock barrel (2) is rotated slightly and tumblers (3) moving in an upward direction have a leading edge (12) which abuts edge (13) of cavity (7) in slideable plate (8). This plate will then be urged to move until sprag shape (10) enters a receiving cavity (14) in the surface of the lock barrel (2). The barrel is then in a dead locked or jammed position and cannot be rotated further. If the picking tool torque or rotational load is relaxed the slideable plate (8) will then be urged back to its original position by springs (1 5) which react between the edge of plate (8) and an abutment surface (16) in cylinder housing (1). Plate (8) can be shaped at the sides (1 7) to move readily within edges (18) of recess (9).

1. A security device for rotatable cylinder locks wherein there is provided a housing which carries a rotatable key operated cylinder lock barrel containing moveable tumblers and one or more plates which have means to slide in a tangential direction to the axis of the lock barrel into a position to jam or deadlock the barrel when any tool other than a correct key is inserted into the lock and a rotational movement is applied.

2. A security device for rotatable cylinder locks as claimed in claim 1 wherein the lock barrel has a recess in its surface in line with the axis of the barrel adjacent to the tumbler slots.

3. A security device for rotatable cylinder locks as claimed in claim 1 wherein a sliding plate carries a slot of sufficient width to enable the tips of the lock tumblers to protrude and urge the plate in a tangential direction

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Locking cylinder barrel security device Increasing thefts from motor vehicles and thefts from locked premises and security ap pliances demonstrates the need for an im provement in the design of cylinder locks to render them more difficult to open by a thief using special picking tools. The present invention describes a means to jam or deadlock a rotatable cylinder lock barrei and therefore to resist rotation when subjected to tampering with an incorrect key or picking tool. The system described can apply to multi plate cylinder barrels of the single entry or double entry key type. In a known design of cylinder lock there is provided a cylindrical barrel which carries a plurality of slots placed side by side along the axis of the barrel. In each slot is positioned a flat tumbler of generally rectangular shape. Each tumbler is biased one way by a coil spring. It carries a slot to allow passage of a key. The slots are positioned at different heights relative to the top and bottom edges of the tumbler, so that when the correct key is inserted into the cylinder barrel all the tumblers move into a position to allow free rotation of the barrel within its housing. If an incorrect key is inserted into the barrel some tumblers are over-lifted and other tumblers are underlifted. By means of a "jiggling" movement of an incorrect key or a picking tool and at the same time loading the tumblers by using a rotational load on the picking tool the tumblers can be urged to move within the cylinder barrel and the barrel can then be rotated. According to the present invention there is provided a housing which carries a cylinder lock barrel containing moving tumblers and also one or more slideable plates positioned to move tangentially to the major axis of the barrel. The slideable plate carries a slot into which the tips of the existing tumblers can protrude. One side of the slot can be considered as a leading edge which is abutted by the tumblers when the cylinder barrel is rotated with a picking tool, the other side of the slot or trailing edge, carries a sprag shape which has means to co-opt into a recess formed within the cylinder barrel surface.So that when the slideable plate is urged tangentially by means of a rotational movement on the cylinder barrel (created by a picking tool) the sprag part of the plate engages with a coopting recess in the face of the cylinder barrel to prohibit further rotation of the barrel. The slideable plate can be fitted with a spring to bias it into its original position. Following is a description by way of example only and with reference to the accompanying drawings of a method of carrying the invention into effect. In the drawings: Figure 1 is a section through a cylinder barrel with a plate tumbler shown in a free key out position. Figure 2 as Fig. 1 but with the plate tumbler biasing the sliding plate. Figure 3 shows a plan view of the sliding plate. The following description applies to a double entry key type cylinder lock. Referring to Fig. 1 a cylinder housing (1) contains a locking barrel (2) which contains a plurality of tumblers (3) so that some tumblers move freely in one direction and some in the opposite direction. These tumblers are urged by springs (4) to protrude into cavity (5) in stationary housing (6) in one direction and cavity (7) in moving plate (8) in the other direction. Moving plate (8) is arranged to slide freely in recess (9) in housing (1) it is generally flat but carries a sprag shape (10) adjacent cavity (7). Each tumbler carries a slot (11) of rectangular shape to receive a key (not shown). Fig. 2 shows a situation whereby the lower tumblers (3) are "picked" clear of the cavity (5) in stationary housing (6). The lock barrel (2) is rotated slightly and tumblers (3) moving in an upward direction have a leading edge (12) which abuts edge (13) of cavity (7) in slideable plate (8). This plate will then be urged to move until sprag shape (10) enters a receiving cavity (14) in the surface of the lock barrel (2). The barrel is then in a dead locked or jammed position and cannot be rotated further. If the picking tool torque or rotational load is relaxed the slideable plate (8) will then be urged back to its original position by springs (1 5) which react between the edge of plate (8) and an abutment surface (16) in cylinder housing (1). Plate (8) can be shaped at the sides (1 7) to move readily within edges (18) of recess (9). CLAIMS

1. A security device for rotatable cylinder locks wherein there is provided a housing which carries a rotatable key operated cylinder lock barrel containing moveable tumblers and one or more plates which have means to slide in a tangential direction to the axis of the lock barrel into a position to jam or deadlock the barrel when any tool other than a correct key is inserted into the lock and a rotational movement is applied.

2. A security device for rotatable cylinder locks as claimed in claim 1 wherein the lock barrel has a recess in its surface in line with the axis of the barrel adjacent to the tumbler slots.

3. A security device for rotatable cylinder locks as claimed in claim 1 wherein a sliding plate carries a slot of sufficient width to enable the tips of the lock tumblers to protrude and urge the plate in a tangential direction when the lock barrel is rotated.

4. A sliding plate as claimed in claim 3 wherein the plate carries a sprag type projection so that when the plate is urged in a tangential direction to the lock barrel the sprag projection co-opts with a recess in the lock barrel surface.

5. A sliding plate as claimed in claim 3 wherein the plate may be fitted with a spring means to bias it into its original position.