AU622820B2

AU622820B2 - Improved grommet screw

Info

Publication number: AU622820B2
Application number: AU59134/90A
Authority: AU
Inventors: Tsun Ping Chern
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-18
Filing date: 1990-07-18
Publication date: 1992-04-16
Anticipated expiration: 2010-07-18
Also published as: AU5913490A

Description

1 I1I1I -i Il~ i I Id I~-YIY-I IJX~II FC 2 8 2 F Ref: 136941 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: t

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Priority: Related Art: Name and Address of Applicant:

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1 Tsun Ping Chern 313-1, Chang Yun Road Chang Hua TAIWAN R.O.C.

I 1 Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia q 0 Complete Specification for the invention entitled: Improved Grommet Screw S The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 ae"~"V CSp~~DP ~s ~~pI

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Abstract An improved grommet screw structure comprising a shank, on whose periphery is formed a spiral auger, a round head formed on one end, and a pair of V-shaped cutting bits conforming in shape with arc sectors of a cone, disposed on the opposite end. An axial cavity extends from a cross-shaped entrance hole, formed on the round head, to a pair of V-shaped inlets defined by the spaces between the V-shaped cutting bits. The axiai cavity comprises a taper section and a level section. The taper section gradually reduces in cross-section from the entrance hole to the adjoining level section which has a constant width cross-section equal with that of the taper section at the point of juncture, whereby a mating screw inserted into grommet screw can threadedly engage the leel section of the axial cavity. A mating nail or screw once inserted into the grommet screw can pierce the tip of the V-shaped .cutting bits, where they join together, so as to cause them to expand outwardly and embed into the material of the wall.

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Title An Improved Grommet Screw Structure Background of the Present Invention The present invention relates to a grommet screw and more particularly to an improved grommet screw that is screwed into a wall made of relatively soft material for the purpose of receiving a mating screw or nail that first passes through an attached article made of a more rigid material, thereby securing the article to the wall.

Referring to Figs. 1 and 2, the first conventional grommet screw comprises a shank 1, a cutting bit 2, an auger 4, ai axial cavity 5, an opening 6, and a screw 7. The cutting bits 2 are relatively long and separated from each other by a small gap, leading to frequent breakages. Moreover, the spidery cutting bits often result in off-center boring. As the chips formed when the *grommet screw is boring into a wall have a relatively long distance to travel before entering the opening 6 to the axial cavity 5, the boring process is often hampered by chips jamming within the cavity formed by the grommet screw.

The second conventional grommet screw, shown in Figs. 3 and 4, has an integral cutting head 8, which obviates the problems of cutting bit breakage and off-center boring, but at a heavy price.

As chips from the bored out material must pass through an side hole "9 positioned to one side of the main body of the grommet screw, the clogging problem is even more severe than with the first conventional grommet screw.

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Summary of the Present Invention It is in view of the aforementioned deficiencies in the prior art that the present invention has been accomplished.

The improved grommet screw structure of the present invention comprises a shank, on whose periphery is formed a spiral auger, a round head formed on one end of the shank, and a pair of V-shaped cutting bits conforming in shape with arc sectors of a cone, formed on the opposite end 'hereof. An axial cavity extends from a cross-shaped entrance hole, formed on the round head, to a pair of V-shaDed cutting bits. Whereby, chips formed when boring into a wall enter the axial cavity through the V-shaped inlets and are expelled out the cross-shaped entrance hole, providing a relatively S* clog-free boring action.

The axial cavity consists of a taper section and a level ssc Ssection, the taper section gradually reducing in cross-section from *the entrance hole to the adjoining level section, which has a constant width cross-section equal with that of the taper section at the point of juncture. A mating scr9w inserted into the grommet of. screw can threadedly engage the level section of the axial cavity to form a strong bond.

Moreover, a mating screw or nail once inserted into the grommet screw can pierce the tip of the V-shaped cutting bits, where they join together, so as to cause them to expand outwardly and embed into the material of the wall, which serves to further strengthen the bond between the wall and grommet screw.

(2) L I I Description of the Drawings Fig. 1 is a perspective view of a first conventional grommet screw.

Fig. 2 is a plan view of a mounted first conventional grommet screw with engaged screw.

Fig. 3 is a perspective view of a second conventional grommet screw.

Fig. 4 is a sectional plan view of a mounted second conventional grommet screw with inserted nail.

Fig. 5 is a perspective view of the grommet screw of the present **ge invention.

Fig. 6 is a bottom projection view of the grommet screw of the present invention.

O0 Fig. 7 is a cross-sectional view of the grommet screw of the present invention taken along line 3-3 of Fig. 5. with an accompanying mating screw.

Fig. 8 is a cross-sectional view of a mounted grommet screw of the present invention with an engaged mating screw.

Fig. 9 is a perspective view detailing the lower end of the grommet screw of the present invention.

Preferred Embodiment of the Present Invention Referring to Figs. 5 and 6, the improved grommet screw 10 of the present invention comprises, a shank 10, with a pair of (3) be.

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0 C 9 0 r~ V-shaped cutting bits 11, conforming in shape with arcuate sectors of a cone, disposed on the lower end thereof, a round head 12 disposed on the other end, and a spiral auger 13, formed on the periphery of the shank 10. The V-shaped cutting bits 11 meet at an apex to define a tip 111.

Referring to Fig. 9, the cutting edge 112 of the cutting bits 11 can efficiently bore into a plaster surface. The empty space between the pair of cutting bits 11 form the V-shaped lower inlets to an axial cavity 15, serrated by grooves along its axis, that leads to a cross-shaped entrance hole 14 on the center of the round head 12. When the grommet screw is boring into a material, the chips from the displaced material will enter the axial cavity through the inlets between the pair of cutting bits 11, and are expelled out through the entrance hole 14. Moreover, the pair of V-shaped cutting bits 11 gives the grommet screw a self-centering effect while boring, greatly reducing the possibility of breakage.

Referring to Fig. 7, showing the grommet screw in cross-section along an axial plane, the interior of the grommet screw, which defines the axial cavity 15, has a taper section 101 that is widest near the entrance hole 14 of the round head 12 and tapers downwards until, after a suitable distance, the level section 102, of constant width, is reached. The level section 102 has a diameter slightly smaller than the thread diameter of a mating screw 20 inserted into the grommet screw. Being of a larger diameter, the threads of a mating screw 20, rotatingly inserted int, the grommet screw, will cut into the sides of the level .tion 102 and secure the mating screw 20 to the grommet screw.

It is worthy to note that in a conventional grommet screw, the axial cavity tapers continuosly from the head to the terminal end, _7 to which a mating screw would have to reach before engaging its threads. Thus the mating screw of a conventional grommet screw would have to be very long and, moreover, has a fixed depth of penetration within the grommet screw when secured. The improved grommet screw of the present invention obviates these shortcomings, allowing the use of a shorter mating screw that can be adjusted in depth while secured to the grommet.

As shown in Fig. 8, the grommet screw is embedded in a wall, with mating screw 20 passing through a layer of attachment material and engaging the grommet. Moreover, the mating screw 20 has reached the pair of cutting bits 11, pushing them apart as it penetrates the material of the wall itself. As the pair of cutting bits 11 expand outwardly they embed into the material of the wall to further strengthen its joint with the grommet screw. Moreover, as the grommet screw becomes open ended, there is no limitation on *the length of the mating screw.

The main advantages of the unique design of the grommet screw of the present invention are listed below: *4e* ee', A) The pair of V-shaped cutting bits 11 have sharp cutting edges 112 not go eschew when boring.

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B) The cutting bits 11 are relatively short and close to the shank of the grommet screw. Hence, they are highly resistant to twisting and breakage.

C) Chips from the bored out material enter the axial cavity which has a relatively large diameter, through the entrances on the sides of the cutting bits and are expelled i PP~ i..

out the cross-shaped entrance hole 14 as the gronmet screw drills into a wall. Thus, the chips almost never cause blockage within the cavity.

D) The tip 111 where the pair of cutting bits 11 meet is pierced, and the pair of cutting bits 11 pushed apart, by a screw or nail that passes through. This serves to further strengthen the bond between the wall and grommet screw.

E) The specially designed cross-section of the axial cavity of the grommet screw allows the use of a variety of screws or nails for insertion.

F) Including the the cutting bits 11, the main body of the improved grommet screw is manufactured single-piece from a zinc-aluminum alloy. The cutting bits, which come together at the small tip 1 where the two cutting bits are joined together, have sufficient strength to resist breakage when drilling but readily separate when pierced by a mating screw or nail to embed into the material of the wall.

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Claims

1. An improved grommet screw comprising: a shank on whose outer surface is formed a spirat auger; a round head formed on one end of said shank; an axial cavity extending from an entrance hole on said round head to the opposite end thereof, having a substantially cross-shaped cross section; a pair of cutting bits, substantially conforming in shape with arcuate sectors of a cone, are disposed on the end of said shank opposite from said round head, ,joining together at an apex co-axial with said axial cavity, and define a pair of V-shaped inlets to said axial cavity: whereby, upon boring into a material, concomitantly formed chips enter through said V-shaped inlets into said axially cavity and are expelled out through said entrance hole, aid; after penetrating a pre-determined distance, an inserted mating element, selected from the group consisting of screws or nails, pierces said apex of said pair of cutting bits, pushing said cutting bits outwards to embed in wall material.

2. An improved grommet screw structure as in claim wherein; said axial cavity is divided into a taper section and a level (7) .L I I C. 4 S. P C. 4' 9r~~ section, said taper section being longer than said level section; said taper section extends from said entrance hole, with a gradually reduced cross-sectional width therefrom, to said level section; said level section extends from said V-shaped inlets, with a constant cross-section substantially equal with the minimum cross-section of the adjoining said taper section; whereby, a threaded said mating element, formed from a material of greater hardness than that of said axial cavity, and of a suitable diameter, can pass throught said entrance hole and said taper section to threadedly engage said level section of said axial cavity. DATED this EIGHTEENTH day of JULY 1990 Tsun Ping Chern Patent Attorneys for the Applicant SPRUSON FERIUSON (8)