Reinforced shank plastic key

Abstract: A flat plastic operational key (27) replaces a corresponding metal key, but is geometrically dissimilar to the metal key. The plastic key (27) includes a shortened key alignment groove (31) relative to the length of the key alignment groove utilized in the corresponding metal key. The shortened key alignment groove (31) increases the volume and strength of the plastic key shank (29) by eliminating a part of the decreased key thickness created by the penetration of the alignment groove (31) into the shank (29) of the plastic key (27).

Description: FIELD OF THE INVENTION The present invention relates to molded plastic keys, whether individual keys, or plastic card/key combinations on the order of the disclosure in my U.S. Patent No. 4,677,835 dated July 7, 1987, 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 (3 to 8 inch pounds) 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 (8 to 9 inch pounds) of torque. If greater torque is applied there is a danger of breaking the plastic key shank. An average woman can apply up to 8 to 11.5 cm·kg (7 to 10 inch pounds) of torque and an average man can apply up to 11.5 to 16 cm·kg (10 to 14 inch pounds) 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. Molded plastic keys have been disclosed in U.S. patent of Donald F. Almblad No. 4,637,236, and in U.S. Patent No. 4,677,835 of the present applicant. In both of those patents the keys are shown as of a common thickness throughout their lengths. German Patent No. 1,031,677 discloses at FIGS. 3 and 4 a plastic key including a laminate consisting of first and second plastic layers 4 with an intervening, reinforcing metal layer 3. The area of the metal layer 3 is equal to the area of plastic laminate layers 4. 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 when 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. The present invention also provides a plastics material key having reinforcing means 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. To this end, the present invention provides a flat plastic key according to claim 1. Other objects, features and advantages of the present invention will be readily apparent from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a form of molded plastic key embodying the present invention; Fig. 2 is an enlarged transverse sectional detail view taken substantially along the line II-II in Fig. 1; Fig. 3 is an enlarged longitudinal sectional detail view taken substantially along the line III-III in Fig. 1; Fig. 4 is a schematic illustration showing the key of Fig. 1 in a typical tumbler lock. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS In Figs. 1-4, a modified shorter molded plastic key 27 is depicted having a handle 28, a short shank 29 and a bit 30 of a suitable length for the intended purpose. In this instance, the bit 30 has a rabbet groove 31 along only one side providing a thin longitudinal side area for receiving tumbler pin notches 32. The key 27 is especially adaptable for operating a tumbler lock 33 of the kind having an escutcheon 34 providing an entrance with lead-in surfaces 35 and 37 of wider dimensions than a key slot 38 within the plug of the lock and into which the bit 30 fits fairly snuggly. There is provided a thickening 39 of shank 29 which stops short of the notch 32 located in the bit 30 nearest to the shank. In that portion of the thickening 39 which extends over onto the handle 28 on each face of the key, the thickening tapers toward the handle substantially as shown. The thickening 39 on each face of the key extends from side-to-side of the key as is clearly evident in Fig. 2. As illustrated in Fig. 1, the groove g that runs along a portion of the length of the blade of the key 27, for indexing with internal configurations of a slot of a tumbler, does not extend all the way to a head end of the shank 29. This functions to reinforce the shank 29 and make it stiffer. In this regard, it should be noted that by terminating the groove g prior to an end portion of the shank 29 one can reinforce a key having such a groove. Accordingly, if desired, the shank of the plastic key can be reinforced merely by shortening the length of the groove without the necessity of making the shank thicker than remaining portions of the key.

Claims: A flat plastic key (27) configured to actuate a rotary cylinder lock (33) having lock tumblers, an elongated key receptacle (38) disposed along a lock longitudinal axis for receiving the key (27) and a rotary lock face (34) including a lock entrance slot (37) with spaced apart sidewalls, the longitudinal axis of the key being aligned with the longitudinal axis of the key receptacle when the key is inserted in the lock, the plastic key (27) comprising a head (28) 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 (29) having a substantially rectangular cross section with substantially parallel sides defining a shank thickness, the shank (29) further including a width, a length, a first end surface joined to the end surface of the head (28) and a spaced apart second end surface; a bit (30) 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 (29); the plastic key (27) being further provided with a key alignment groove (g) disposed in a side of the key (27) creating a decreased key thickness along the groove (g); characterized by: a. the groove (g) being oriented parallel to, but offset by a first distance from the key longitudinal axis and extends along the entire length of the bit (30), but terminates at a groove termination point spaced away from the first end of the shank (29) as to limit the penetration of the alignment groove (g) into the shank (29) to thereby increase the strength of the plastic key and its capacity to transfer the input torque to the lock; b. the thickness of the shank along substantially the entire length of the shank exceeding the thickness of the head and the bit; and c. the head including an area located in proximity to the first end of the shank having a thickness exceeding the thickness of the remainder of the head. The plastic key of one of the Claim 1 characterized in that the groove termination point is located in proximity to the second end surface of the shank (29). The plastic key of Claim 2 characterized in that the bit (30) includes a length and that the groove length is approximately equal to the bit (30) length. The plastic key of one of Claims 1 to 4 characterized in that the groove termination point is positioned within the lock (33) at a longitudinal location beyond the lock entrance slot (37) when the key (27) is fully inserted into the key receptacle (38) of the lock (27).

Inventors: ALMBLAD ROBERT E, ALMBLAD, ROBERT E.
Applicants: AXXESS ENTRY TECH, AXXESS ENTRY TECHNOLOGIES
Application year: 1988
Main classification: E05B19
IPC codes: E05B19, A45C11