Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1998-11-16
2001-07-24
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
C173S181000
Reexamination Certificate
active
06263742
ABSTRACT:
The present invention relates to a method of controlling a screwing spindle of the kind used for screwing stoppers onto packages having threaded necks.
BACKGROUND OF THE INVENTION
Screwing spindles are known that have a linear actuator with a piston connected to a spindle shaft to rotate it. A method commonly used for controlling such spindles consists in subjecting the piston to differential tightening pressure, thereby generating the required torque for tightening the stopper on the neck of the package. A problem comes from the fact that when the stopper begins to be screwed on, there is little friction between the stopper and the neck, such that there is little opposition to rotation of the spindle. The spindle shaft thus acquires a high speed of rotation, and because of its inertia the spindle shaft stores a considerable amount of kinetic energy. The kinetic energy stored in this way causes the stopper to be tightened quickly until it comes into abutment, at which point the spindle shaft is caused to stop suddenly. On stopping, the stored kinetic energy is restored in the form of a dynamic torque which is applied to the stopper and which is greater than the required tightening torque. This dynamic torque can damage the stopper or the neck of the package, and it can make it necessary for a user of the package to have recourse to a tool for loosening the stopper.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to propose a method of controlling a screwing spindle in a manner that enables the required tightening torque to be obtained accurately.
According to the invention, this object is achieved by providing a method of controlling a screwing spindle, the method comprising a step of feeding the screwing spindle with fluid under nominal conditions of pressure and flow rate for generating a required tightening torque, and a prior step during which the screwing spindle is fed under conditions that are weaker than nominal by an amount that is sufficient to ensure that the spindle has a speed of rotation that cannot generate kinetic energy capable of producing a torque that is greater than the required tightening torque.
In particular, with a linear actuator including a piston, the piston is subjected during the prior step to mean differential pressure that is lower than the tightening differential pressure.
Thus, the mean differential pressure serves to rotate the spindle shaft at low speed only, thereby causing little kinetic energy to be accumulated. By the time tightening pressure is applied to the piston, the torque opposing tightening is sufficient to prevent any increase in the speed of rotation of the spindle, such that the stopper comes to rest as soon as the opposing torque is equal to the driving torque which corresponds to the tightening pressure. Kinetic energy is therefore not restored suddenly, so the tightening torque as actually applied to the stopper is indeed equal to the required tightening torque.
In a first implementation of the invention, during the prior step, one face of the piston is subjected in the tightening direction to a constant pressure that is lower than the differential tightening pressure.
Two different pressures are used. Thus, once the tightening operation has been completed, the constant pressure that is lower than the tightening pressure can be used to return the actuator, thereby achieving significant fluid savings.
In a second implementation, the piston is subjected to constant pressure in the tightening direction, and also to a counter-pressure.
The mean differential pressure is then equal to the difference between the constant pressure applied to the face of the piston and the counter-pressure. The constant pressure is preferably equal to the tightening pressure. A single pressure level corresponding to the required tightening torque is then required, and this simplifies regulating the pressure of the fluid fed to the actuator.
In a third implementation, the piston is subjected intermittently to pressure at a constant value.
In this way, the spindle is set into rotation by pressure being applied thereto, and its kinetic energy is restored while pressure is not being applied thereto, thereby making it possible to control the speed of the spindle by acting on the pressure-on times and on the pressure-off times.
In this variant, it is advantageous for the differential pressure to have a value that is constant and equal to the tightening pressure.
As in the preceding case, only one pressure level is used, and it corresponds to the required tightening torque, thereby simplifying regulation of the feed fluid pressure.
Other characteristics and advantages of the invention appear on reading the following description of particular, non-limiting variants of the invention.
REFERENCES:
patent: 3593830 (1971-07-01), Clapp et al.
patent: 3866463 (1975-02-01), Smith et al.
patent: 3939920 (1976-02-01), Hardiman
patent: 4026369 (1977-05-01), Vliet
patent: 4418765 (1983-12-01), Mori et al.
patent: 4620450 (1986-11-01), Yamaguchi
patent: 5129465 (1992-07-01), Rahm
patent: 5167309 (1992-12-01), Albert et al.
patent: 5567886 (1996-10-01), Kettner
patent: 5617924 (1997-04-01), Baron et al.
patent: 637600 (1983-08-01), None
Gruson Bertrand
Ovieve Gerard
Noori Max
Serac Group
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