REINFORCED SHANK PLASTIC KEY

Abstract: A molded plastic key (10) having a handle (11), a shank (12) and a bit (13) has the shank (12) reinforced to withstand extraordinary torque applied through the head when resistance to turning is encountered after the key (10) is inserted into a lock. The reinforcement may comprise integrally molded thickening throughout the length of the shank (12) and extending at least partially on to the handle (11), and the thickening termination short of the adjacent end of the bit (13) of the key (10). If preferred, the reinforcement may comprise a metallic reinforcing insert having an extension from the handle (11) into the shank (12).

Description: The present invention relates to a molded plastic key with a shank reinforcement of the type described in the preamble of claim 1. 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, at least, and generally also the handles, of a thickness common with the bit thickness. Molded plastic keys have also heretofore been constructed of substantially uniform thickness throughout their length similarly as comparable metal keys. The key bit must be fairly snuggly fitted to 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 reception of the key bit into the slot, 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 considerable twisting stress, 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. 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 automobile ignition or trunk lock, only about 3.5 to 5.8 cm.kg (three to five inch pounds) of torque are necessary to open the lock. A normal uniform thickness molded plastic key will withstand up to 9.2 to 10.4 cm.kg of torque (eight to nine inch pounds). 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 (seven to ten inch pounds) and an average man can apply up to 11.5 to 16 cm.kg of torque (ten to fourteen inch pounds). 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 application. In both of those patents the keys are shown as of a common thickness throughout their lengths. By way of a typical disclosure of a metal key and tumbler lock, U.S. Patent No. 4,656,851 is referred to. DE-U-16 69 387 shows a laminated plastic key having a lengthwise sandwiched reinforcing material which extends along the entire length of the key. DE-A-20 37 071 discloses a key according to the preamble of claim 1 having a reinforcing insert extending from an intermediate location in the key head through the shank and through the entire length of the key bit. An important object of the present invention is to provide a new and improved molded plastic key which is strengthened against torque induced breakage of the shank portion of the key. In accordance with the principles of the present invention, there is provided a molded plastic key of said type according to the features of the characterizing portion of claim 1. Other objects, features and advantages of the present invention will be readily apparent from the following description of preferred embodiments threof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which: Fig. 1 is a plan view of a molded plastic key blank embodying a reinforced shank according to the present invention; Fig. 2 is an enlarged cross-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 generally schematic illustration of the key of Fig. 1 located operatively within one form of tumbler lock; Fig. 5 is a plan view of a modified form of molded plastic key embodying the present invention but having a somewhat shorter shank than in the form of Fig. 1; Fig. 6 is an enlarged tansverse sectional detail view taken sustantially along the line VI-VI in Fig. 5; Fig. 7 is an enlarged longitudinal sectional detail view taken substantially along the line VII-VII in Fig. 5; Fig. 8 is a schematic illustration showing the key of Fig. 5 in a typical tumbler lock; Fig. 9 is a plan view of a plastic card/key combination embodying a key according to the invention; Fig. 10 is a sectional detail view taken substantially along the line XV-XV of Fig. 9; Fig. 11 is a sectional detail view taken substantially along the line XVI-XVI of Fig. 9; Fig. 12 is a plan view of the opposite side of the combination plastic card/key combination of Fig. 9; Referring to Figs. 1-4, a one-piece molded plastic key 10 is disclosed having a head or handle 11, typically of substantially greater width than an integral shank 12 connecting the handle to a blade or bit 13. In this instance, the bit 13 is of the type which may have tumbler notches 14 cut along either or both edges, and for this purpose the cross-sectional geometry of the shank and bit may, as best seen in Fig. 2, be provided with longitudinal rabbet grooves 15 providing thinner margins along both edges. Illustratively, the key 10 has the shank 12 and the bit 13 elongated for reception in a tumbler lock 17 (Fig. 4) having a tumbler barrel cylinder or plug 18 extending from a housing 19 defining a chamber 20 of ample size to accommodate a spring-biased flapper closure 21 which is adapted to be pushed aside by the key from the dash position to the full line position when the key is inserted through an entrance 22. It may be noted that the entrance 22 affords ample clearance to facilitate entry of the key therethrough for reception in a key slot 23 which for practical reasons is fairly closely dimensioned relative to the key bit 13. A tolerance clearance of only about 0.01 cm (.005 inch) is desirable between the bit 18 and the slot 23. An entrance 24 into the key slot 23 flairs towards its outer end in a generally lead-in cam fashion to facilitate reception of the key bit 13 into the slot 23. From this it will be apparent that should there by extraordinary torque applied through the handle 11 after the key bit 13 has been introduced into the slot 23, there is no torque support for the shank 12, although the bit 13 fits closely in the slot 23. In order to equip the shank 12 against twisting, torque-stressed breakage, the shank is reinforced. By way of example, where there is ample lock entrance clearance, e.g. as in Fig. 4, reinforcement for the shank 12 may be advantageously provided by an integrally molded thickening 25 of the shank. Such thickening 25 is preferable effective throughout the length of the shank from adjacent to but clear of the proximal area of the bit 13 to be notched. Thus, the thickening avoids interference with close reception of the bit 13 in the key slot 23. By preference the thickening 25 is effected about .020 inch on both faces of the shank 12 and extends to at least a limited distance onto the adjacent portion of the handle 11. For utmost integrity of reinforcement, the thickening 25 extends over substantially the entire width of both the shank 12 and the portion of the handle 11 provided with the thickening. At the bit end of the shank 12, the thickening 25 may end abruptly, as shown at 26 (Fig. 3) as close as practicable to the area of the bit to be notched, so as to gain maximum advantage the thickening for its reinforcing function. At the handle end of the thickening 25 it may taper for smoothness both at the sides and at the handle end, substantially as visualized in Figs. 2 and 3. Although the thickening 25 could cover the entire handle 11 on both faces of the handle, that is not necessary and plastic material is saved by having the thickening extend only partway onto the remainder of the handle. In any event, the thickening provides ample digital grip area for transmission of torque to the reinforced shank. In Figs. 5-8, 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. Reinforcement of the key 27 against torque breakage of the shank 29 is, similarly as described in connection with the key 10 in Fig. 1, provided by means of thickening 39 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. 6. Although the key may be utilized independently, it may also provide the key for a plastic card/key combination as depicted in Figs. 9-12. To this end, the key 40 is located within a complementary recess 53 within a preferably generally wallet size holder 54. Desireably the recess 53 is located as conveniently near one side of the card 54 so that the remaining area of the face, or both faces, of the card can be utilized for any desired legends or indicia as schematically shown at 55. For retaining the key 40 integrally with the card 54, integral multidirectional hinge means 55 is provided comprising a unitary part of the molding and formed from the same material as the key and the molded card, and integrally connecting an edge of the key head or handle 41 to an edge of the card 54 in the recess 53. Desirably the hinge means 55 comprises a generally elongated element which permits the key to be not only swung out of the plane of the card 54 but also to be twisted relative to the card on and about the hinge without breaking away from the card. In the preferred form, the hinge 55 comprises a generally rod shaped element which may be of cylindrical cross section and is longer than its diameter. Although the hinge 55 may be of slightly smaller diameter than the thickness of the head 41, as best seen in Fig. 10 the hinge diameter may be slightly greater than the thickness of the card 54. A reinforcement extension 57 extends from the attached end of the hinges 55 onto the adjacent portion of the card 54 and is connected to a reinforcing rib 58 which runs along the edge of the card and stiffens the card in this area against undue flexibility. Molded plastic keys of the kind described may be formed from an acetal resin, comprising a polymerized formaldehyde formulation, such as may be obtained from E.I. Dupont De Nemours & Company under the registered trademark "Delrin 500". As to the reinforcing inserts for the keys, suitable material comprises sheet steel stampings such as cold rolled steel which may be hardened if desired, or a C1095 spring steel annealed and hardened to 55-57 Rockwell prior to molding in place in the plastic keys. From the foregoing it will be apparent that the present invention provides substantial reinforcement protection against torque damage to the critical shank areas of the molded plastic keys.

Claims: A molded plastic key (10, 27, 40) having a handle (11, 28, 41), a shank (12, 29, 42) and a bit (13, 30, 43) comprising a shank reinforcement against breakage due to unusual torque applied through said handle (11, 28, 41) when resistance to turning is encountered after the bit (13, 30, 43) is inserted into a lock (17, 33), characterized in that said shank reinforcement is a thickening (25, 39) molded integrally with said shank (12, 29, 42), said thickening (25, 39) extending throughout substantially the length of said shank (12, 28, 42), and said thickening (25, 39) continuing at least a limited distance onto the adjacent portion of said handle (11, 28, 41). A molded plastic key according to claim 1, which is molded from an acetal resin. A molded plastic key according to claim 1 or 2, wherein said thickening (25, 39) extends over substantially the entire area on both faces of said shank (12, 29, 42). A molded plastic key according to one of the claims 1 to 3, wherein said thickening (25, 39) ends abruptly adjacent to the proximal end of said bit (13, 30, 43) and in clearance relation to a key notch area (14, 32) of said bit (13, 30, 43). A molded plastic key according to one of the preceding claims, wherein said thickening (25, 39) tapers toward a head end of said handle (11, 28, 41). A molded plastic key according to one of the preceding claims, wherein said thickening (25, 39) extends sufficiently onto said handle (11, 28, 41) for digital engagement by a user applying torque to the key (10, 27, 40) when the key (10, 27, 40) is located in a lock (11, 33). A molded plastic key according to one of the preceding claims, including a card-like key (40) holder (54) having a single recess (53) offset adjacent to one side and leaving a substantial card face area between said recess (53) and a second side of the holder, said key (40) being in said recess (53), and a hinge (55) connecting said key (40) handle (41) to said holder (54) in a manner permitting the key (40) to be swung hingedly into and out of said recess (53).

Inventors: ALMBLAD, ROBERT
Applicants: MITSUBISHI CORPORATION
Application year: 1987
Main classification: E05B19
IPC codes: E05B19, A45C11, E05B15