Joints and connections – Member ends joined by inserted section – Expansible section
Reexamination Certificate
1998-03-20
2001-02-13
Browne, Lynne H. (Department: 3629)
Joints and connections
Member ends joined by inserted section
Expansible section
C403S408100, C403S292000, C411S061000, C411S055000, C411S072000
Reexamination Certificate
active
06186695
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a dowel for securing objects to construction elements, in particular gypsum plaster boards, with an expandable dowel body which has an inner bore into which a fastening screw can be screwed. At an insertion front area, the dowel body is subdivided into at least two head segments by slots starting at a front end and has at the front area along the outer surface a continuous necking. At the rear end opposite to the front end, the dowel body includes a stopping plate extending transversely to a dowel longitudinal axis.
The invention also relates to a method for making a dowel with an inner bore and an inner thread.
2. Description of the Related Art
From U.S. Pat. No. 3,869,959 there is known a dowel for securing objects to construction elements, in particular to gypsum plaster boards, with a spreadable dowel body which has an inner bore into which a fastening screw can be screwed, wherein the dowel body is subdivided into at least two head segments by slots starting at a front end and includes at the front area along its outer surface a continuous necking, and wherein the dowel body at the rear end opposite to the front end includes a stopping plate extending transversely to a dowel longitudinal axis.
The dowel known from U.S. Pat. No. 3,869,959 is made of a uniform dowel body with a cylindrical section which corresponds to a bore in the construction part to which the dowel is to be secured. At the rear end of the dowel body, there is disposed a threaded inner bore and a stopping plate. At the rear area opposite to the front area, the dowel body has a collar which is connected with the rear area through a conical necking. At the front area, the dowel body has a plurality of slots which can spread radially when a fastening screw is inserted in the inner bore. On the circumference of the dowel body there are arranged a plurality of ribs for preventing rotation of the dowel in the dowel bore. With the known dowel, the fastening screw can disadvantageously be pulled out of the inner bore when tensile forces are applied along the longitudinal axis of the dowel. To making it more difficult for the fastening screw to be pulled out, the known dowel has to be provided with a relatively coarse thread which makes it hard to turn the screw. The dowel may disadvantageously also rotate together with the fastening screw when the fastening screw tightened. To counteract this situation, additional ribs are provided on the circumference. These ribs, however, can damage the construction element surrounding the dowel.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to improve the known dowel so that the resistance to tensile forces and the load bearing capacity, respectively, are increased in the axial direction and the fastening screw can be tightened easily without causing rotation of the dowel. The object is solved by the invention in that the inner bore includes a recess located in a rear area opposite to the front area, wherein the recess holds an insert with a female thread. Since the insert is immovably installed in the recess, a fastening screw which is easy to turn can be used, while the load bearing capacity in the axial direction is simultaneously increased. More particularly, by using the insert, the material for the dowel body can be selected for the required speadability and resiliency, and the material for the insert can be selected for the strength necessary to prevent stripping of the thread. Since the fastening screw can now be tightened easily and the dowel body can be spread apart easily, ribs or other protruding elements can be eliminated from the outside diameter.
It is yet another object of the invention to provide a simple method for manufacturing a dowel with an inner bore and a female thread.
This object is solved with the invention in that the dowel is made of two vertical halves with a recess adapted to receive an insert with a female thread, wherein the insert is inserted into the first half and the second half is then joined with the first half. With the method of the invention, the dowel body can be manufactured by injection molding preferably from plastic—without the need for cutting a thread in the dowel. Moreover, the insert does not have to be inserted in the mold form prior to molding. The insert is particularly easy to install since the dowel body is constructed from two halves.
In another advantageous embodiment, the two halves are joined with each other at a longitudinal side in such a way that, after insertion of the insert, the two halves can be folded together by pivoting the two halves about the joined portion and then secured by, for example, pushing a ring over the dowel body.
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patent: 2221141 (1940-11-01), Kindt
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patent: 4287807 (1981-09-01), Pacharis et al.
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patent: 5106225 (1992-04-01), Andre et al.
patent: 5702216 (1997-12-01), Wu
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patent: 24 52 398 (1976-05-01), None
patent: 3202433 A1 (1983-08-01), None
patent: 31 07 153 A1 (1982-09-01), None
patent: 8571 (1909-12-01), None
Browne Lynne H.
Cottingham John R.
Darby & Darby
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