GB2383829A

GB2383829A - Expansion screw assembly

Info

Publication number: GB2383829A
Application number: GB0200015A
Authority: GB
Inventors: Bright Precision Ind Co Lt Sun; Sha-Lan Kao
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-24
Filing date: 2002-01-02
Publication date: 2003-07-09
Also published as: NL1019220C2; GB0200015D0; DE20119135U1; FR2832193A3

Abstract

An expansion screw assembly includes an expansion sleeve (3) having an conical plug (4) assembled to an expandable front part, a locating sleeve (2) screwed to a rear part of the expansion sleeve (3), and a screw (1) adapted to screw into the locating sleeve (2). The expansion sleeve includes retaining means such as a rib or groove between the expandable front part and the rear part for receiving a locking ring (5) provided with a plurality of claws (51) that catch a front end of the screw (1) to firmly hold the screw (1) to the expansion sleeve (3). In another embodiment the locating and expansion sleeves may be formed as a single piece and include an inward depression for preventing the screw from becoming loose.

Description

EXPANSION SCREW BACKGROUND OF THE INVENTION An expansion screw is frequently used to fasten or hold something to a building structure, particularly to a wall. A conventional expansion screw A is shown in Fig.

1 and mainly includes a screw Al, a sleeve A2, and a conical plug A3. The screw Al is screwed into a rear part of the sleeve A2 and the conical plug A3 is plugged into a front opening of an expandable front part of the sleeve A2. When the sleeve A2 is forced into the wall, the conical plug A3 in front of the sleeve A2 is stopped by the wall and the sleeve A2 is gradually pushed toward the conical plug A3 to expand its expandable front part along a conical wall of the conical plug A3. The expanded sleeve A2 is therefore tightly pressed against the wall surrounding it and firmly held to the wall.

While the sleeve A2 is firmly forced into the wall to tightly contact with the latter at the expanded front part, the screw Al screwed into. the sleeve A2 tends to gradually rotate relative to and loosen from the sleeve A2 and eventually separate therefrom due to vibrating forces constantly acted on the building.

That is, while the expandable sleeve A2 keeps tight contact with the wall, the screw Al might have become loosened from the sleeve A2 and no longer effectively

holds the previously fastened item to the wall. There p is great latent danger in the conventional expansion screw endangering the safety of persons in and surrounding the building.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved expansion screw that includes components more securely connected to one another to ensure firm and safe fastening of any item to the building structure via the expansion screw and accordingly, the safety of people's life and properties.

To achieve the above and other objects, the expansion screw of the present invention includes an expansion sleeve having a conical plug assembled to an expandable front part thereof, a locating sleeve screwed to a rear part of the expansion sleeve, and a screw adapted to screw into the locating sleeve. The expansion sleeve includes an annular retaining groove between the expandable-front part and the rear part thereof for receiving an 0-ring therein. The Coring is provided

along its circumference with a plurality of claws that catch threads at the most front end of the screw to firmly hold the screw to the expansion sleeve.

4'".

Therefore, the screw would not rotate and thereby loosen or separate from the locating and the expansion sleeves due to vibration caused by any external force, ensuring a secure and safe fastening of an item to, for example, a wall via the expansion screw.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein Fig. 1 is an exploded perspective view of a conventional expansion screw ; Fig. 2 is an exploded perspective view of an expansion screw according to a preferred embodiment of the present invention ; Fig. 3 is an assembled sectional view of the expansion screw of Fig. 2; and

Fig. 4 is a fragmentary, assembled sectional view of an expansion screw according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Please refer to Figs. 2 and 3, in which an expansion screw according to a preferred embodiment of the present invention is shown. The expansion screw of the present invention mainly includes a screw 1, a locating sleeve 2, an expansion sleeve 3, a conical plug 4, and an 0-ring or locking ring 5.

1 The screw 1. is a general standard screw element having screw threads 11 provided around a shank of the screw 1.

The locating sleeve 2 includes a front part provided with external threads 21 and an inner wall surface provided with internal threads 22 for engaging with the threads 11 of the screw 1.

The expansion sleeve 3 includes a front part that is radially outward expandable, and a rear part that is internally provided with threads 31 for engaging with the external threads 21 at the front part of the locating

sleeve 2, so that the locating sleeve 2 is connected to a rear end of the expansion sleeve 3. An annular retaining rib 32 is formed inside the expansion sleeve 3 between the expandable front part and the internally threaded rear part.

The conical plug 4 is a commercially available element for an expansion screw and has been assembled to a front opening of the expandable front part of the expansion sleeve 3.

,.. - The 0-ring 5 is provided along its circumference with a plurality of claws 51 and is pre-positioned against the annular retaining rib 32 in the expansion sleeve 3.

The locating sleeve 2 is connected to the rear part of the expansion sleeve 3 by engaging the external threads 21 with the internal threads 31, so that the 0-ring 5 fixedly located against the retaining rib 32 between the locating sleeve 2 and the expandable front part of the expansion sleeve 3 together with the connected locating and expansion sleeves 2,3 provide a semi-assembly of the-expansion screw ready for use.

To use the expansion screw of the present invention,

first force the semi-assembly of the expansion screw into a pilot hole (not shown) pre-formed on a wall.

When the expansion sleeve 3 "-5 forced against the conical plug"4 that is an element located at the most front of the semi-assembly of the expansion screw, the expandable front part of the expansion sleeve 3 is radially expanded to tightly press against the wall surrounding it and thereby securely holds the semi-assembly of the expansion screw to the wall. And then thread the screw 1 into the locating sleeve 2 via a rear opening thereof to engage the threads 11 of the screw 1 with the internal threads 22 of the locating sleeve 2 to fasten a desired item to the wall with the expansion screw. When the screw 1 is fully threaded into the locating sleeve 2, threads 11 that are located at the most front end of the shank of the screw 1 are tightly caught by the claws 51 on the 0-ring 5, enabling the screw 1 to firmly and stably connect to the expansion sleeve 3. The engagement of the threads 11 with the claws 51 of the 0-ring 5 protects the screw 1 from undesired rotation and loosening relative to the expansion sleeve 3 and the locating sleeve 2 when the whole expansion screw of the present invention in the wall is subject to vibration due to external forces. That is, the whole expansion screw is able to maintain a firmly assembled structure without the risk of a

loosened or even separated screw 1 from the locating sleeve 2 and the expansion sleeve 3 of the expansion screw.

Fig. 4 shows an expansion screw according to another embodiment of the present invention. In this embodiment, the locating sleeve 2 is locally deformed at a predetermined position with an external force, so as to produce, for example, an annular depression that directly applies a tight pressure on the screw 1 threaded into the locating sleeve 2 and thereby firmly holds the screw 1 in place in the locating sleeve 2.

The pressure applied on the screw 1 by the annular depression on the locating sleeve 2 is large enough to prevent the screw 1 from rotating relative to or loosening from the locating sleeve 2 when the whole expansion screw on the wall is subject to any vibration. The expansion screw of the present invention is therefore structurally safe for use.

Holding means, such as deformation may accordingly be employed in place of the ring 5. When there is no need to hold the ring 5 in place, for example when the arrangement shown in Fig. 4 is employed, the locating sleeve 2 and expansion sleeve 3 may be fabricated unitarily. The 0-ring or locking ring 5 may be held in

place inside the expansion sleeve 3 by retaining means other than the rib 32 such as by a shoulder or an annular groove.

Claims

CLAIMS : 1. An expansion screw assembly comprising: a screw;

a locating sleeve including a front part provided -' with external threads and an inner wall surface provided with internal threads for engaging with external threads provided around a shank of said screw; an expansion sleeve including a front part that is radially outward expandable, a rear part that is internally provided with threads for engaging with said external threads at the front part of said locating sleeve, and a retaining means formed inside said expansion sleeve between said expandable front part and said internally threaded rear part; a conical plug being assembled to a front opening of said expandable front part of said expansion sleeve; and an 0-ring or locking ring positioned by said retaining means in said expansion sleeve; whereby when said screw is threaded into said locating sleeve, said external threads of said screw located at a frontmost end thereof are caught by

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said ring, enabling a firm and stable connection of said screw to said locating sleeve and said expansion sleeve and thereby protecting said screw from rotating or loosening relative to said locating sleeve and said expansion sleeve due to any vibration caused by external forces.
2. The expansion screw assembly as claimed in claim 1 wherein said retaining means comprises an annular rib.
3. The expansion screw assembly as claimed in claim 1 wherein said retaining means comprises an annular retaining groove in which said ring is retained.
4. The expansion screw assembly as claimed in claim 1 wherein said retaining means comprises a shoulder against which said ring is held.
5. The expansion screw assembly as claimed in any preceding claim wherein said ring has a plurality of claws provided along a circumference thereof for engaging said screw.
6. An expansion screw assembly comprising: a screw; a sleeve including a front part that is radially outward expandable and an inner wall surface provided with internal threads for engaging with external threads provided around a shank of said screw

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said sleeve being locally deformed at a predetermined position to produce at least a radial depression that applies a tight pressure on said screw threaded into said sleeve and thereby firmly hold said screw in place in said sleeve, preventing said screw from loosening or separating from said sleeve due to any vibration; and a conical plug assembled to a front opening of said expandable front part of said sleeve.
7. The expansion screw assembly according to claim 6 wherein said sleeve comprises a locating sleeve and an expansion sleeve connected together, said locating . sleeve including said internal threads and a front part provided with external threads, and said expansion sleeve includes said radially outwardly expandable front part and a rear part that is internally provided with threads for engaging with said external threads at the front part of said locating sleeve.