EP0305953B1

EP0305953B1 - Reinforced shank plastic key

Info

Publication number: EP0305953B1
Application number: EP88114070A
Authority: EP
Inventors: Robert E. Almblad
Original assignee: Axxess Entry Technologies Inc
Current assignee: Mitsubishi Corp
Priority date: 1987-09-03
Filing date: 1988-08-29
Publication date: 1994-04-27
Anticipated expiration: 2008-08-29
Also published as: NZ225897A; EP0553900B1; DE3889266D1; CA1334797C; PT88419A; DE3889266T2; DE3856046T2; MX172828B; EP0553900A3; EP0553900A2; BR8804530A; KR890005363A; DE3856046D1; AU2154788A; EP0305953A2; PL274407A1; YU168788A; EP0305953A3; JPH01146086A; AU603250B2

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to flat plastic keys according to the preamble of the independent claim and is more particularly concerned with reinforcing such keys against breaking at their shanks due to extraordinary twisting stress applied through the handles of the keys.

DESCRIPTION OF RELATED ART

Conventional metal keys for operating tumbler locks such as in automobiles, building doors, apparatus controls, and the like, have heretofore been generally constructed throughout the shank and bit portions, and generally the handles, or head portion of a uniform thickness common with the bit thickness. Molded plastic keys have also heretofore been constructed of substantially uniform thickness throughout their length similar to comparable metal keys.
The key bit must be fairly snuggly fitted in the key slot in the cylinder plug. Looseness of the bit in the key slot might defeat proper engagement of the lock tumblers in the key notches. On the other hand, especially in the USA, to avoid difficulty in quick insertion of the key bit into the slot, the general practice has been to provide enlarged entrance dimensions. This results in the key shank often having little if any torque support when subjected to the considerable twisting stress which may occur if for any reason there is resistance to turning of the key in the lock. Such resistance may be variously caused such as by faulty cutting of the key notches, binding due to corrosion or icing, and the like. The general tendency of the user, where there is any such resistance to turning of the key in the lock, is to apply additional torque or twisting force to the key through its handle. Metal keys will generally withstand such extraordinary twisting stress.
In a normal U.S. automobile ignition or trunk lock, only about 3.5 to 9.2 cm.Kg of torque are necessary to open the lock; non U.S. automobiles typically require higher torques. A normal uniform thickness molded plastic key will withstand up to 9.2 to 10.4 cm.Kg of torque. If greater torque is applied there is danger of breaking the plastic key shank. An average women can apply up to 8 to 11.5 cm.Kg of torque and an average man can apply up to 11.5 to 16 cm.Kg of torque. Therefore, there has been some key shank breakage experienced in respect to molded plastic keys having a substantially common thickness throughout their lengths.
German Patent Application No. 2,037,071 discloses a key having a reinforcing insert extending through the entire lenght of the bit, the shank and into at least a part of the key head. German Patent No. 1,031,677 discloses a key, parts of which eventually coming under high stress, consisting of metal which is surrounded by plastic material.
German Patent Application No. 3,518,354 discloses another embodiment of a key having a full length reinforcing insert of particularly metal. German Utility Model No. 1,901,655 discloses a key having a rigid cylindrical section extending between the key handle and a lock actuating member of the key. The end of the cylindrical support element of the key includes a partially hollowed-out interior.
U.S. Patent No. 4,677,835 discloses a plastic key inter-connected by a plastic hinge to a plastic card structure. The plastic key disclosed in this patent fails to include any reinforcing materials. U.S. Patent No. 4,637,236 discloses a related type of plastic key detachably connected within a plastic card. The plastic key includes no reinforcing materials.
British Patent No. 1,229,830 discloses a key molded from a thermosetting plastics material which includes a longitudinally extending reinforcing material fabricated from a plurality of flexible glass filaments. The flexible glass filaments extend from a location disposed well within the key head, entirely through the key shank and through the full length of the key bit. The plurality of glass filament reinforcing members because of the inherent flexibility are apparently intended to aid in withdrawing the broken bit of a plastic key rather than to reinforcing the torque transfer capabilities between the key head, key shank and the entrance slot of a cylindrical lock.
German Utility Model No. 1,789,132 discloses a plastics material key with a non-specified steel insert.
By way of a typical disclosure of a metal key and tumbler lock, U.S. Patent No. 4,656,851 is referred to.

SUMMARY OF THE INVENTION

The present invention provides an improved plastics material key. The plastics material key of the present invention can be used alone, or it can be used in combination with means for holding the key, such as a card-like holder. The improved plastics material key of the present invention includes means for substantially lessening the likelihood that the plastics material key will break or fail when unusual resistance or torque is encountered then the plastics material key is utilized in a lock or the like.
To this end, the plastics material key includes means for reinforcing the key. The means for reinforcing the key increases the strength of the key over that of a key which is essentially only a plastic duplicate of a standard metal key.
The means for reinforcing the plastics material key is so constructed and arranged that it does not interfere or hinder the cutting of notches or slots in the key that are necessary along at least one side of the bit to actuate the tumblers of a lock. Accordingly, the present invention provides a means for reinforcing the key that does not hinder or hamper some of the advantages of a plastic material key. For example, a plastics material key imay be easier for a key cutter to cut than a corresponding metal key. However, if a rigid insert were placed within the plastics material key and extended along the entire length of the key any advantages inherent in the ability to cut a plastics material key would be lost. Furthermore, the plastics material key provides a lightweight key when compared to some typical metal keys. An extending rigid member throughout the entire length of the key would increase the weight of the key and limit some of the advantages of a plastics material key.
The present invention also provides a plastics material key having a reinforcement member that can be used with a variety of different keys. There are a variety of different key blanks having different shank and bit constructions with varying groove configurations. The present invention provides means for reinforcing plastics material key that can utilized with a majority of the known typical key structures.
An important object of the present invention is to provide a new and improved molded key constructed from a plastics material which is strengthened against torque induced breakage of the shank portion of the key.
A further object of the present invention is to provide a new and improved molded plastic key provided with a shank reinforcing insert.
A still further object of the present invention is to provide a new and improved molded plastics material key in which the shank is strengthened through the addition to the plastic material of a strengthening material.
In accordance with the principles of the present invention, there is provided a flat plastic key according to the attached claim 1.
Fig. 1 is a plan view of another embodiment of a molded plastics material key having a rigid insert of the present invention.
Fig. 2 is a perspective view of the rigid insert embodied in the molded plastics material key and insert of Fig. 1.
Fig. 3 is a cross-sectional view of the molded plastics material key of Fig. 1 taken along lines XXXVIII-XXXVIII of Fig. 1.
Referring now to Figs. 1-3, a further embodiment of a molded plastics material key and reinforcing means of the present invention is illustrated. As illustrated, again, the plastics material key 301 includes a head portion 315, shank portion 311, and bit portion 303. A rigid insert 313 for reinforcing the shank is embedded within a portion of the head 315 and the shank 311 of the plastics material key 301. As further illustrated, as in the previous embodiment, the head 315 includes a slot 371 or hole that provides means for supporting the insert 313 during molding. The slot 371 further functions to provide means for stress relieving portions of the key adjacent the insert 313 so that the key 301 does not substantially deform as the plastics material of the key cools after molding.
The embodiment of the rigid insert 313 illustrated has a substantially Z-shaped cross-section. To this end, the rigid insert 313 includes a body portion 314 having extending side portions 341 and 343 having a reduced cross-sectional thickness. These side portions 341 and 343 are located in planes offset from each other with respect to a thickness of the shank 311. Accordingly, the side portions 341 and 343 can be received within reduced thickness offset side portions 319 and 321 of the molded plastics material key 301. This construction allows the rigid insert 313 to be utilized with keys that have longitudinal side areas that do not lie within the same horizontal plane. As illustrated, the offset side portions 341 and 343 extend all the way from one end of the rigid insert 313 to approximately a second end allowing the insert relatively easy movement into a portion of the slot 371 during the shrinking of the plastics material of the key 301 after molding.
Referring to Fig. 2, as illustrated, preferably, the rigid insert 313 includes an extending flange portion 373. As in the previously discussed embodiment, the flange 373 provides an interlock with the plastics material of the key 301. Again, because in certain embodiments of the key 301 and rigid insert 313, the extended side portions 341 and 343, or body portion 314 of the rigid insert, may be coplanar, or approximately coplanar, with a portion of the bit 303 of the key 301, the flange 373 ensures that the rigid insert 313 is secured within the key.
In the embodiment illustrated, the flange 373 includes a semi-circular cut-out portion 374. The semi-circular cut-out portion 374 is utilized to at least partially receive a locater pin that allows the rigid insert 313 to be securely positioned within the mold cavity during the molding process of the key 301.
Due to its construction, the rigid insert 313 illustrated in Fig. 2 has been found to function satisfactorily in at least certain types of automobile keys.
From the foregoing it will be apparent that the present invention provides means that afford substantial reinforcement protection against torque damage to the critical areas of the molded plastic keys.

Claims

A flat plastic key (301) for actuating a rotary cylinder lock (17) including a head (315) 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; a shank (311) 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 (315) and a spaced apart second end surface; a solid plastic bit (305) having an edge surface and including a thickness, a width and a first end surface joined to the second end surface of the shank (311); a rigid metal insert (313) imbedded in the head (315) and the shank (311) of the key (301); whereby application of the lock actuating input torque to the force input area of the key head (315) transfers the input torque through the plastic key head (315) and key shank (311) and through the head section and shank section of the rigid metal insert (313) to the sidewalls of the lock entrance slot (22) to enable the lock actuating input torque to rotate the lock face and thereby actuate the lock (17) while limiting torsional bending of the key head (315) relative to the key shank (311), the plastic key (301) being characterized by the rigid metal insert having a thickness and rigidity adequate to resist torsional bending and a length less than the combined length of the head (315) and the shank (311), the insert (313) including an insert head section with an end displaced into the force input area of the key head (315) and an insert shank section with an end terminating before the second end of the key shank (311).
The plastic key of Claim 1 characterized in that the thickness of the rigid metal insert (313) is uniform within the head (315) and shank (311) sections of the key (301).
The plastic key of Claim 2 characterized in that the thickness of the rigid metal insert (313) is equal to the thickness of the key bit (305).
The plastic key of Claim 3 characterized in that the rigid metal insert (313) includes parallel oriented first and second side surfaces defining the thickness of the insert.
The plastic key of Claim 4 characterized in that the rigid metal insert (313) includes a width defined by first and second spaced apart insert edges.
The plastic key of one of the preceding claims characterized in that the key shank (311) includes first and second spaced apart edges defining the shank (311) width and that the rigid metal insert (313) is centrally located between the first and second edges of the key shank (311).
The plastic key of Claim 6 characterized in that the insert shank section includes first and second spaced apart edges defining the width of the insert shank section.