Metal deforming – With use of control means energized in response to activator... – Sensing tool or tool-linked part
Patent
1998-11-16
2000-12-26
Crane, Daniel C.
Metal deforming
With use of control means energized in response to activator...
Sensing tool or tool-linked part
72 3101, 72416, 29720, 81313, H01R 43042
Patent
active
061641065
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a pressing device, in particular for joining a pipe with a press fitting, having at least two pressing jaws and a drive for moving the pressing jaws or a part thereof relative to one another from an open position into a final pressed position.
It is known, in order to join pipes, to use sleeve-like press fittings that are made of plastic or metal. To produce a pipe joint, the press fitting is slid over the pipe ends and then radially compressed, both the press fitting and the pipe being plastically deformed. Pipe joints of this kind and the pertinent press fittings are known, for example, from DE-C-11 87 870 and EP-B-0 361 630.
Pressing of the press fitting and the pipe is accomplished with the aid of pressing devices such as are known in various embodiments, for example from DE-C-21 36 782, DE-A-34 23 283, EPA-0 451 806, EP-B-0 361 630, and DE-C-42 40 427. The pressing devices have at least two, and in some cases even more pressing jaws, at least a portion of which can be moved radially inward during the pressing operation to form a closed pressing space. A hydraulic piston, which can be acted upon by hydraulic pressure via a manually driven or electric motor-driven pump, is often provided as the drive to move the pressing jaws.
The pipe joints described above are produced, in particular, when installing water-carrying pipework in buildings. It is obviously extremely important that the press fitting and pipe ends be compressed so as to guarantee absolute tightness. The material deformation must therefore be uninterrupted over the circumference of the press fitting. To achieve this result, the pressing jaws are displaced until their respective opposing pairs of end faces come into contact, or at least until only a slight gap remains between said end faces.
To achieve this, the drive is displaced into its final position. The desired and predefined final pressed position of the pressing jaws is not necessarily, however, achieved thereby. The forces which occur lead to elastic deformations at the levers on which the pressing jaws sit or which are used to contract a pressing jaw ring. In addition, the pressing jaws, press fittings, and pipes are subject to tolerances which, if they add up unfavorably, mean that compression is insufficient when the final position of the drive is reached. In order nevertheless to be able to produce a leakproof pipe joint, the pressing jaws are acted upon by a pressing force which is designed, with the addition of a sufficient safety factor, so that in normal circumstances an adequate and therefore leakproof pressing is achieved.
Problems can nevertheless still occur, and result in an incomplete pressing. For example, it is difficult to maintain a constant final force for the drive. Achieving the final force is in most cases the responsibility of a release member acting as switching member, for example a torque coupling for rotating drives, a pressure relief valve for hydraulic devices, and an overcurrent release for electrically driven devices. Since the release member does not measure the drive force directly, but rather measures a converted magnitude (torque, pressure, or current) which represents only a fraction of the magnitude of the final force, any inaccuracy in the manufacture of the release member, and any wear, can have major effects on the final force of the drive and thus ultimately on pressing quality. The latter is also influenced by the ambient temperature and operating temperature. A particular difficulty is that the change in the final force, due primarily to wear, proceeds gradually, and therefore remains unnoticed by the control system.
A further reason for an incomplete pressing may lie in wear on the bearings for the transfer levers between the drive and the pressing jaws. This then causes an elongation of the pivot axes, with the result that in their final positions, the pressing jaws no longer constitute the desired contour, so that the predefined final pressed position is no longer reached. This again remains unnoticed by the contro
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PCT, WI 9601092, PCT/EP97/00533, Int'l. Filing Date Jun. 2, 1997--International Preliminary Exam.
German Pat Application, G 93 12 808.8, filed Aug. 26, 1993.
Lohmann Gert
Nghiem Xuan Luong
Crane Daniel C.
Novopress GmbH Pressen und Presserkzeuge & Co. KG
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