Motors: expansible chamber type – Torque responsive motive fluid control
Patent
1996-04-25
1998-04-14
Nguyen, Hoang
Motors: expansible chamber type
Torque responsive motive fluid control
91361, 91459, 91465, F01C 2112, F15B 1316
Patent
active
057379920
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for controlling a double-acting cylinder actuated by a pressurized fluid in an assembly, such as a hydraulic tightening wrench and its control unit, in which a to-and-fro movement of a piston may be repeated, an active stroke of which piston provides a desired maximum force and a so-called passive stroke, in the reverse direction to the active stroke, causes the piston to return for the repetition.
When using a hydraulic tightening wrench described, for example, in U.S. Pat. No. 4,201,099 or in DE-A-3,620,753 and DE-A-3,416,881, it is necessary, on the one hand, to monitor the moment when the supply pressure for the cylinder in the tightening active-stroke direction reaches a desired value corresponding to the desired tightening torque (the tightening torque obtained is proportional to the force caused by the cylinder and this force is itself proportional to said supply pressure) and, on the other hand, to check that this value is reached during said active stroke and not at the end of it. The reason for this is that, at the end of this active stroke, as the supply for the cylinder is maintained in this direction, the pressure of this supply increases to the point where it may be confused with the pressure corresponding to the desired tightening torque. In order to avoid this confusion, an end-of-active-stroke sensor could be provided and the signal communicated by this sensor could be used.
The object of the present invention is to avoid the use of such a sensor, or of any other auxiliary device of this kind, which it is necessary to mount in the tightening wrench, which it is necessary to supply with power from the outside in order for it to operate and from which it is necessary to extract the end-of-stroke signal in order to bring it to a means for using the latter. The costs of installing such a sensor in the tightening wrench are considerable compared to those of the wrench itself and the incorporation of this sensor into the latter, often used under high stress conditions, especially in the active-stroke direction, increases the risk of the tightening wrench malfunctioning, for example through false information being provided by said sensor.
The method of the present invention is developed in order to exploit, to the maximum and in a reliable manner, preferably automatically by means of programmable devices, the information supplied by means of detection and of measurement of the hydraulic pressure, these means being provided outside the hydraulic wrench proper.
For this purpose, the method according to the invention comprises: maximum force; active stroke: fluid reaches the set pressure; fluid, for the passive return stroke; stroke; and the moment when the completion of the passive return stroke is detected; corresponding substantially to that of a complete passive return stroke; and is substantially less than the determined time.
The present invention also )relates to a device for implementing the abovementioned method.
According to the invention, the device comprises: maximum force desired during an active stroke of the piston of the cylinder; the fluid during the active stroke of the piston, and optionally its passive return stroke, and of the set pressure; signal of the pressure supplied to the cylinder during its active stroke and optionally its passive return stroke; cylinder for the active stroke and for the passive return stroke; passive return stroke; elapsed between the start of the passive return stroke and the completion thereof; and determined as corresponding substantially to that of a complete passive return stroke.
Other details and features of the invention will appear from the secondary claims and from the description of the drawings which are appended to the present document and which illustrate, by way of nonlimiting examples, the method and particular embodiments of the device according to the invention.
FIG. 1 diagrammatically represents the main constituent elements of a tightening wrench which can be employed in the method according
REFERENCES:
patent: 4201099 (1980-05-01), Junkers
patent: 4628499 (1986-12-01), Hammett
patent: 4805496 (1989-02-01), Wagner et al.
patent: 5105719 (1992-04-01), Yoshikawa
patent: 5230272 (1993-07-01), Schmitz
patent: 5421240 (1995-06-01), Ohta et al.
Pacco Didier
Torrekens Daniel Octaaf Ghislain
Nguyen Hoang
Torrekens Daniel Octaaf Ghislain
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