Patent GB-1468309-A (GB)
Title: Fastener
IPC: F16B19/10
Filed: 1975-01-08
Abstract: 1468309 Stud and socket fasteners HARTWELL CORP 8 Jan 1975 [25 Jan 1974 11 Dec 1974] 728/75 Heading E2B A fastener for releasably securing first and second perforated members 24, 25 comprises an expansible grommet 1 and an expander plunger 2 which are initially joined by connection 23 for initially positioning the plunger 2 in extended relation to the grommet 1 and which are shearable to permit a shank 16 of the plunger 2 to move inwardly of the grommet 1 to cause spreading of stem portions 6 of the grommet 1 to secure the members 24, 25 together; the plunger 2 may subsequently be moved outwardly from the grommet 1 to permit contraction of the stem portions 6 but complete withdrawal of the plunger 1 from the grommet 2 is prevented by at least one stop lug 13. In the embodiment illustrated in Figures 1-12 the grommet 1 has a pair of head portions 3 connected by a web 4, and the stem portions 6 which extend from the head portions 3 have confronting walls 7 which are provided with opposed retainer flanges 11 and with cam shoulder 12, and one or both of the stem portions are provided with a said stop lug 13. The expander plunger 2 has a handle head 14 and the shank 16 which extends therefrom has flat sides 17 for sliding fit between walls 7. The shank 16 has opposed V-shaped channels 18 for interengagement with flanges 11, and the shank has recess portions 19 with a stop shoulder 20 therebetween. In use the grommet stem portions 6 are first inserted in the perforation 26 in the first member 24. The member 24 is then placed over the member 25 with the perforation 27 in alignment with perforation 26 (see Figure 8) and sufficient force is then exerted on handle head 14 to break connections 23 and to move the shank 16 between stem portions 6 to engage cam shoulders 12 to spread the stem portions 6 and thereby fasten the members 24, 25 together the shank 16 being held by the cam shoulders 12 engaging recesses 21 (see Figure 10), and a projection 15 on a shank 16 being held in a recess (5) in grommet 1. During this movement shoulder 20 snaps past lug 13 and if the plunger is now moved outwardly the stem portions 6 may be withdrawn from perforation 27 to permit release of member 25 but the grommet and plunger remain attached by the action of stop lug 13. In the modification of Figures 13-15 (not shown) a stop lug (13a) is provided on shank (16). A projection (13b) may also be provided on shank (16) which offers resistance to the movement of the plunger to prevent engagement of the shank with the cam shoulders until the grommet has been forced through the second member 25. In the embodiment of Figures 16-24 the head portions 3 of the grommet 1 are not connected by a web but the stem portions 6 are connected by a web 28. The shank 16 of the plunger 2 has lateral projections 29 to be received in the space between head portions 3 and opposite sides of the shank have stop shoulders 20 for engagement by stop lugs 13. The embodiment of Figures 1-12 may also include the web 28 and the embodiment of Figures 16-14 may also include the web 4. Figures 16-14 may also include the modification of Figures 13-15. The fastener may be formed from plastics material or metal. In the embodiment of Figures 25-29 the shank 16 has a radial projection 29 having cam surfaces 32 for engagement with complementary head portions 30 on the grommet 1.