Press tool

Details Press tool Press tool

1995-06-02

1997-12-16

Watson, Robert C.

Metal working

Means to assemble or disassemble

Coupling to conduit

7240901, B23P 1904

Patent

active

056971354

DESCRIPTION:

BRIEF SUMMARY
The invention involves a press tool for pressing tubular, nested workpieces, in particular a pipe end upon which is slid a press fitting, having several clamping components which bear clamping jaws with a continuous circumferential pressing groove shaped in their inner side, and containing a pressing land extending along only one side.
One known-in-the-art process for joining the ends of tubular workpieces involves using tubular press fittings that are ductile and are comprised of metal, preferably of steel. Such pipe joints and the associated press fittings can be found, for example, in DE-C-1 187 870 and DE-C-40 12 504.
A wide variety of designs has been developed for press tools that are intended for pressing a press fitting and a pipe end together radially. These press tools contain clamping components with clamping jaws, which in the pressing process are moved radially to form a closed pressing space. In addition to press tools having two clamping jaws (DE-A-34 23 283; DE-A-38 33 748), press tools having more than two clamping jaws, which permits greater insertion depths, are also known-in-the-art. The latter type of press tools can be found, specifically, in EP-A-0 451 806. In relation to this, the press tools illustrated in FIGS. 7 and 8 are of particular interest, as they are suited for the joining of pipe ends that are large and very large in diameter.
As may be found in the similar type DE-C2-38 33 748, the clamping jaws in such press tools contain on their inner side a specific cross-sectional shape that conforms to the shape of the press fitting. Because such press fittings have at their open end an annular ring that protrudes toward the outside, and on the inner side of which a conical nipple is inserted, the clamping jaw contains a pressing groove that is shaped to receive this annular ring. The individual segments of the pressing groove in the clamping jaws join to form a continuous circumferential pressing groove.
In order that the annular ring is not simply pressed onto the pipe end, effecting instead a pressing process between the press fitting and the pipe end, in addition to the annular ring, pressing lands extend on both sides of the pressing groove, which become pressed during the pressing process into the material of the press fittings, and thereby also the nested pipe end. As may also be found in DE-C2-38 33 748, the inclusion of pressing lands on both sides of the pressing groove is not an absolute requirement for the pressing process. However, handling is foolproof when the cross-section of the clamping jaw is symmetrical, that is, when pressing lands extend on both sides of the pressing groove, because it then becomes irrelevant in which position the press tool is applied to the point that is to be pressed.
In the application of a press tool of the type described in the beginning, in which the cross-section of the clamping jaws is symmetrical, it has been shown that the pressing land that lies on the open end of the press fitting, in the final phase of the pressing process, also comes to be applied to the pipe, where it causes a constriction of the pipe. Aside from the fact that this increases the amount of pressing force that must be applied, the elastic tension of the conical nipple is reduced via the pressing of the annular ring, so that the maintenance of the required tightness over a period of years can no longer be ensured. In the worst case, a fissure could even form in the area of the seal, which would result in leakage.
It is thus the object of the invention to design a press tool of the type described at the beginning, that will allow the maintenance of mounting safety while permitting pressing that will not affect tightness.
This object is attained in accordance with the invention in that a template which fits over the nested workpiece but not over the slid-on workpiece is positioned toward the other side of the groove.
With a press tool of this type, foolproof handling is ensured, despite the fact that a pressing land is positioned along only one side of the groove. T

REFERENCES:
patent: 3756064 (1973-09-01), Erdmann
patent: 3934318 (1976-01-01), Mertens
patent: 4934673 (1990-06-01), Bahler
patent: 5121625 (1992-06-01), Unewisse et al.
patent: 5148698 (1992-09-01), Dischler
patent: 5209100 (1993-05-01), Dischler
patent: 5307664 (1994-05-01), Homm

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