Plug drawing of tubes and other hollow items
First Claim
1. A method of plug-drawing an elongated tubular workpiece in a forward direction, comprising the following method steps:
- providing such an elongated tubular workpiece presenting an inner wall and a transverse dimension;
forming a plug comprising a forward region with which said inner wall of said workpiece makes contact as its said transverse dimension diminishes in the course of drawing, a rearward region adapted to lie with a clearance within the undrawn part of said workpiece at all times, an intermediate region between said forward surface region and said rearward region;
providing a flexible and deformable ring seal and supporting said seal on said rearward region of said plug, said seal having a first and relaxed state in which it offers minimum resistance to relative movement of said plug and said undrawn part of said workpiece and a second and deformed state in which it is adapted to make a firm contact with both said plug and said inner wall of said workpiece;
and providing through said plug a fluid passage having an outlet in said intermediate region and an inlet formed in said plug rearward of said seal so as to be accessible from that part of the interior of the said undrawn part of said workpiece lying rearward of said plug;
forming a cylindrical space bounded at the forward end thereof by the contact between said plug and said workpiece, at its inner radius by the surface of said intermediate region, at its outer radius by said inner wall of said workpiece and at its rearward end by said seal;
connecting said inlet to a source of lubricant under pressure, and so filling said cylindrical space with said lubricant; and
drawing said workpiece over said plug, and in so doing exerting a forward force on at least part of said plug; and
by the action of at least one of said above method steps, causing said seal to deform from its said first state to its said second state, whereby it seals said rearward end of said cylindrical space and so enhances the pressure at which said lubricant can be contained within said space without escaping from it by way of said rearward end.
1 Assignment
0 Petitions
Accused Products
Abstract
A plug for use in the plug drawing of hollow tubes or other stock. A flexible and deformable seal is mounted on the rearward part of the plug. In its relaxed state this seal allows easy insertion of the plug into the stock before drawing begins. In its deformed state, which it is caused to adopt in use, it effectively seals the rearward end of a cylindrical clearance between the plug and the stock, so enabling this clearance to be filled with pressurized lubricant to improve drawing efficiency. The lubricant is supplied through passages formed in the plug and connected to a hollow conduit extending backwards within the undrawn stock. The conduit may be flexible, or may be rigid and then act as a plug bar. The plug may be in two parts which are caused, as drawing begins, to move relative to each other and in so doing to deform the seal.
6 Citations
5 Claims
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1. A method of plug-drawing an elongated tubular workpiece in a forward direction, comprising the following method steps:
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providing such an elongated tubular workpiece presenting an inner wall and a transverse dimension; forming a plug comprising a forward region with which said inner wall of said workpiece makes contact as its said transverse dimension diminishes in the course of drawing, a rearward region adapted to lie with a clearance within the undrawn part of said workpiece at all times, an intermediate region between said forward surface region and said rearward region; providing a flexible and deformable ring seal and supporting said seal on said rearward region of said plug, said seal having a first and relaxed state in which it offers minimum resistance to relative movement of said plug and said undrawn part of said workpiece and a second and deformed state in which it is adapted to make a firm contact with both said plug and said inner wall of said workpiece; and providing through said plug a fluid passage having an outlet in said intermediate region and an inlet formed in said plug rearward of said seal so as to be accessible from that part of the interior of the said undrawn part of said workpiece lying rearward of said plug; forming a cylindrical space bounded at the forward end thereof by the contact between said plug and said workpiece, at its inner radius by the surface of said intermediate region, at its outer radius by said inner wall of said workpiece and at its rearward end by said seal; connecting said inlet to a source of lubricant under pressure, and so filling said cylindrical space with said lubricant; and drawing said workpiece over said plug, and in so doing exerting a forward force on at least part of said plug; and
by the action of at least one of said above method steps, causing said seal to deform from its said first state to its said second state, whereby it seals said rearward end of said cylindrical space and so enhances the pressure at which said lubricant can be contained within said space without escaping from it by way of said rearward end. - View Dependent Claims (2, 3, 4, 5)
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Specification