Metal working – Means to assemble or disassemble – Tube and coextensive core
Reexamination Certificate
2000-10-25
2004-02-24
Vidovich, Gregory (Department: 3726)
Metal working
Means to assemble or disassemble
Tube and coextensive core
C029S237000, C029S272000, C029S282000, C029S283500, C029S03300H
Reexamination Certificate
active
06694586
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of European Patent Application No. EP20000123080, filed Oct. 24, 2000; German Patent Application DE200001019701, filed Apr. 20, 2000; and Swiss Patent Application CH19990001951, filed Oct. 26, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a press tool and a method for connecting by cold forming.
Such press tools are also known as press chains, press loops or press rings and are used in particular for connecting pipe sections. For this purpose, the pipe ends to be connected are pushed into a deformable sleeve, a so-called press fitting. For connecting by cold forming, the press jaws are first placed around the press fitting in the manner of a collar that remains open in one area, the two chain ends of the press tool being opposite one another across the open area. The introduction of the drive forces causes the two chain ends to be drawn together. Consequently, the insides of the press jaws are moved together as far as they will go to form an annular press space, and the cold-forming forces are transmitted to the press fitting. To ensure radial cold forming of the fittings that is as uniform as possible, at least three press jaws, generally arranged in the manner of a chain, are typically used for connecting pipes with a diameter greater than 54 mm by cold forming.
2. Description of Related Art
European patent EP627,273 describes a press tool comprising more than two press jaws that are partially movable in a connecting link guide in the circumferential direction. As a result, the press jaws are arranged uniformly over the circumference of the press fitting, which thus permits a uniform radial distribution of the forming forces and prevents flash formation between the press members.
As described in EP627,273, press tools for cold-formed pipe connections having relatively large external cross-sectional diameters, in particular for pipe systems with high internal pressure stresses, require more than two press jaws. More than two press jaws help prevent “run-out” of the press fittings or formation of a flash between the end faces of the press jaws on closing the press tool. Run-out of the fittings or formation of a flash makes complete closing and consequently reliable connection impossible.
Such press tools are described, for example, in German Patent DE4,240,427 and European Patent EP992,537. Such tools also available in so-called self-holding versions, which move together even before the introduction of the drive forces. Such tools move together prior to the introduction of the drive forces by pretensioning forces exerted by spring elements. These tools, therefore, need not be additionally held on the workpiece, for example with a hand, to prevent slipping or falling down from the connecting point.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a press tool that is easy to handle, has a simple design and can be used flexibly. The present invention also includes a method for connecting, by cold-forming, workpieces that are inserted one into the other. The method of the present invention permits safe and reliable connection of workpieces having relatively large external cross-sectional shapes and facilitates connections with relatively extensive cold forming. Such press tools should preferably be capable of being used even where there is limited space and should, if necessary, surround, in a nonfrictional manner, the workpieces to be connected.
A press tool according to the present invention is preferably formed with at least two arms, the press jaws advantageously also being used for transmitting the drive forces introduced. The press jaws must be capable of being moved toward one another, the connection of ends of the press jaws by means of bearing bolts having proven a simple and reliable connection concept in terms of design.
The cold-forming forces exerted by the press jaws on the workpieces are initiated by drive forces introduced into the tool. For the introduction of drive forces, engagement regions such as recesses, holes, projections, eyes, hooks, etc. should be provided in at least one area of the press tool. These can be provided at the non-bearing ends of press jaws for application of a drive means that can be optionally coupled.
When, for example, optionally tubular workpieces having predetermined, in particular circular, external cross-sectional shapes are mentioned, it is always to be understood as meaning workpieces having connection regions formed in this manner.
A press tool according to the present invention preferably exerts the cold-forming forces via the insides of the press jaws on the workpieces in a manner such that, when the press jaws move toward one another, “run-out” of the outer workpiece and thus the formation of a flash between the press jaws are substantially prevented. To prevent the ends of the inside edges of the press jaws from cutting into the workpiece thus causing the formation of flash, widening recesses in the form of bevels angled outward (i.e., widening toward the end faces) are provided at least on one side (optionally on both sides) in those regions of the insides of the press jaws that are adjacent to the end faces. The insides of the press jaws may be both angled outward toward the end inside edges and may also be convex. Optionally, the insides of the press jaws may be gradually increasingly curved toward the inside edges, turning outward. The optionally angled insides of the press jaws beveled outward may be in the form of insertion bevels adjacent to the end inside edges. These angled insertion bevels are preferably flat but may also be slightly concave, depending on the machining. If the insertion bevels are slightly concave, their curvature is less pronounced than that of the remaining inside of the press jaw. In particular, the insertion bevel have a curvature that is less pronounced than that of a lateral surface segment of a rotational body, and optionally also smaller than the external cross-sectional diameter of the outer workpiece before the cold forming. The curvature of the inside regions of the press jaws adjacent to the inside of the insertion bevels at least approximately corresponds to the remaining external cross-sectional diameter of the cold-formed workpiece.
As a result of these features, the insertion bevels of the insides of the press jaws are shaped at their end inside edges in such a way that, when placed on the workpiece, the insides do not rest on the end inside edges but lie on the outer lateral surface of the workpiece under their inside surface, optionally tangentially, optionally a distance away from the end inside edges.
The extent of the outward angling of the outer end inside regions depends on the external cross-sectional diameter of the respective workpieces coordinated with the press tool. In the case of external cross-sectional diameters between 54 mm and 108 mm, the insertion bevels may be angled, for example, at an angle of 5 to 250 degrees outward relative to the lateral surface directly adjacent to it.
At least two press jaws are required for the operation of a press tool according to the invention. The two press jaws can be mounted around a common bearing bolt, the baring bolt optionally being eccentric. An eccentric bearing bolt results in those end faces of the press jaws that are not on the bearing side experiencing an additional translational movement apart when the press tool is opened. Consequently, the required opening angle for surrounding the workpieces and the spacing of the end faces in the initially clamped state of the tool can be reduced.
The two press jaws can also each be individually mounted by means of two bearing bolts held in a bearing holder. Once again, at least one bearing bolt can optionally be eccentric. The two bearing bolts can be mounted in the bearing holder both rigidly and coupled to one another. For example, it is possible to provide for each bearing bolt, for relative displacement in he bearing holder, a guide slo
Compton Eric
Emerson Electric Co.
Howrey Simon Arnold & White , LLP
Vidovich Gregory
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