Flat plastic key with rigid torque transfer insert

Claim 2

A flat plastic key for actuating a rotary cylinder lock having lock tumblers, an elongated key receptacle for receiving the key and a rotary lock face including a rectangular lock entrance slot with spaced apart sidewalls, the key and the lock including alignable longitudinal axes, the plastic key comprising: a. a head for receiving a lock actuating input torque within a force input area and having an end surface, a head thickness, a head width and a head length; b. a shank having a substantially rectangular cross section with substantially parallel sides defining a shank thickness, the shank further including a width, a length, a first end surface joined to the end surface of the head and a spaced apart second end surface, the shank thickness, width and length configured to enable the shank to extend through the entrance slot of the lock face when the key is fully inserted into the lock receptacle, the resulting area of overlap between the sides of the fully inserted shank and the lock entrance slot defining a shank torque transfer surface where torque is transferred from the shank to the sidewalls of the lock entrance slot; c. a solid plastic bit having an edge surface for receiving notches to actuate the lock tumblers and including a thickness, a width and a first end surface joined to the second end surface of the shank, selected notches penetrating into the edge surface of the bit toward the key longitudinal axis by a first distance; and d. a rigid metal insert imbedded in the head and the shank of the key, having a thickness and rigidity adequate to resist torsional bending and a length less than the combined length of the head and the shank, the insert including an insert head section with an end displaced into the force input area of the key head and an insert shank section with an end terminating before the second end of the key shank; whereby application of the lock actuating input torque to the force input area of the key head transfers the input torque through the plastic key head and key shank and through the head section and shank section of the rigid metal insert across the shank torque transfer surface to the sidewalls of the lock entrance slot to enable the lock actuating input torque to rotate the lock face and thereby actuate the lock while limiting torsional bending of the key head relative to the key shank.

Claim 3

The plastic key of claim 1 wherein the thickness of the rigid metal insert is uniform within the head and shank sections of the key.

Claim 4

The plastic key of claim 2 wherein the thickness of the rigid metal insert is approximately equal to the thickness of the notch receiving edge surface of the key bit.

Claim 5

The plastic key of claim 3 wherein the rigid metal insert includes parallel oriented first and second side surfaces defining the thickness of the insert.

Claim 6

The plastic key of claim 4 wherein the rigid metal insert includes a width defined by first and second spaced apart insert edges and wherein the width of the shank section of the rigid metal insert is substantially constant.

Claim 7

The plastic key of claims 1 or 5 wherein penetration of the notches into the notch receiving edge surface of the key bit at a selected notch location reduces the bit width at that notch location to a minimum bit width and wherein the width of the shank section of the rigid metal insert exceeds the minimum bit width.

Claim 8

The plastic key of claim 6 wherein the key shank includes first and second spaced apart edges defining the shank width and wherein the rigid metal insert is centrally located between the first and second edges of the key shank.

Claim 9

The plastic key of claim 7 wherein the insert shank section includes first and second spaced apart edges defining the width of the insert shank section.

Claim 10

The plastic key of claim 8 wherein the spacing between the first edge of the insert shank section and the key longitudinal axis is greater than the spacing between an edge which defines the minimum bit width and the key longitudinal axis.

Claim 11

The plastic key of claim 1 wherein the end of the insert shank section extends through and beyond the lock entrance slot when the key is fully inserted into the key receptacle of the lock.

Claim 12

A flat plastic key for actuating a rotary cylinder lock having lock tumblers, an elongated key receptacle for receiving the key and a rotary lock face including a rectangular lock entrance slot with spaced apart sidewalls, the key and the lock including alignable longitudinal axes, the plastic key comprising: a. a head for receiving a lock actuating input torque within a force input area and having an end surface, a head thickness, a head width and a head length; b. a shank having a substantially rectangular cross section with substantially parallel sides defining a shank thickness, the shank further including a width, a length, a first end surface joined to the end surface of the head and a spaced apart second end surface, the shank thickness, width and length configured to enable the shank to extend through the entrance slot of the lock face when the key is fully inserted into the lock receptacle, the resulting area of overlap between the sides of the fully inserted shank and the lock entrance slot defining a shank torque transfer surface where torque is transferred from the shank to the sidewalls of the lock entrance slot; c. a solid plastic bit having an edge surface for receiving notches to actuate the lock tumblers and including a thickness, a width and a first end surface joined to the second end surface of the shank, wherein penetration of a selected notch into the notch receiving edge surface of the key bit at a selected notch location reduces the bit width at that notch location to a minimum bit width and wherein the width of the shank section of the key exceeds the minimum bit width; and d. a rigid metal insert imbedded in the head and the shank of the key, having a thickness at least approximately equal to or greater than the thickness of the notch receiving edge surface of the key bit, a rigidity adequate to resist torsional bending and a length less than the combined length of the head and the shank, the insert including parallel oriented first and second side surfaces defining the insert thickness, an insert head section with an end displaced into the force input area of the key head and an insert shank section with an end terminating before the second end of the key shank, the insert shank section further including first and second spaced apart edges defining a width of the insert shank section, wherein the spacing between the first edge of the insert shank section and the key longitudinal axis is greater than the spacing between an edge which defines the minimum bit width and the key longitudinal axis; whereby application of the lock actuating input torque to the force input area of the key head transfers the input torque through the plastic key head and key shank and through the head section and shank section of the rigid metal insert across the shank torque transfer surface to the sidewalls of the lock entrance slot to enable the lock actuating input torque to rotate the lock face and thereby actuate the lock while limiting torsional bending of the key head relative to the key shank.

Claim 13

A flat plastic key for actuating a rotary cylinder lock having lock tumblers, an elongated key receptacle for receiving the key and a rotary lock face including a rectangular lock entrance slot with spaced apart sidewalls, the key and the lock including alignable longitudinal axes, the plastic key comprising: a. a head for receiving a lock actuating input torque within a force input area and having an end surface, a head thickness, a head width and a head length; b. a shank having a substantially rectangular cross section with substantially parallel sides defining a shank thickness, the shank further including a width, a length, a first end surface joined to the end surface of the head and a spaced apart second end surface, the shank thickness, width and length configured to enable the shank to extend through the entrance slot of the lock face when the key is fully inserted into the lock receptacle, the resulting area of overlap between the sides of the fully inserted shank and the lock entrance slot defining a shank torque transfer surface where torque is transferred from the shank to the sidewalls of the lock entrance slot; c. a solid plastic bit having an edge surface for receiving notches to actuate the lock tumblers and including a thickness, a width and a first end surface joined to the second end surface of the shank, wherein penetration of a selected notch into the notch receiving edge surface of the key bit at a selected notch location reduces the bit width at that notch location to a minimum bit width and wherein the width of the shank section of the key exceeds the minimum bit width; and d. a rigid metal insert imbedded in the head and the shank of the key, having a thickness at least approximately equal to or greater than the thickness of the notch receiving edge surface of the key bit, a rigidity adequate to resist torsional bending and a length less than the combined length of the head and the shank, the insert including parallel oriented first and second side surfaces defining the insert thickness, an insert head section with an end displaced into the force input area of the key head and an insert shank section with an end terminating before the second end of the key shank, the insert shank section further including first and second spaced apart edges defining a width of the insert shank section, wherein the spacing between the first edge of the insert shank section and the key longitudinal axis is greater than the spacing between an edge which defines the minimum bit width and the key longitudinal axis; whereby application of the lock actuating input torque to the force input area of the key head transfers the input torque through the plastic key head and key shank and through the head section and shank section of the rigid metal insert across the shank torque transfer surface to the sidewalls of the lock entrance slot to enable the lock actuating input torque to rotate the lock face and thereby actuate the lock while limiting torsional bending of the key head relative to the key shank.

Claim 14

The plastic key of claim 11 wherein the end of the insert shank section extends through and beyond the lock entrance slot when the key is fully inserted into the key receptacle of the lock.