Geometrical instruments – Gauge – Circular size
Reexamination Certificate
2001-06-08
2003-09-09
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Circular size
C033S732000, C033S512000
Reexamination Certificate
active
06615504
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for determining the circumference of a body.
DESCRIPTION OF THE RELATED ART
In virtually all technical areas, it is often necessary to determine or check the circumference of a body. In the area of production a circumference measurement is often part of a quality check on products. In this case, it is often important that this circumference determination is carried out as exactly as possible, but at the same time also quickly and simply, since it is most often only one measurement which accompanies the actual process and, in terms of time, is not intended to have a very detrimental effect on the fault-free progress of the process. A further application for a circumference meter is in the medical area. Here, for example in the area of venous occlusion plethysmography, it is necessary to be able to determine the exact circumference of any desired extremities of a patient.
DE 3 223 711 describes an apparatus and a method for measuring the lower extremities, for example as a basis for the preparation of medical compression hose, the circumferential measurement being carried out by using a measuring tape loop whose circumference can be varied by an electric-motor drive and which, when recording the circumferential dimension, encloses the extremities with a constant, electronically regulated contact pressure. With the aid of an electronic eye module sensing the measuring tape scale and a counter electrode, the measured result is displayed digitally. The drawback with this apparatus and this method is the complicated handling, since a closed measuring tape loop has to be slipped over or guided over the extremities to be measured. A further drawback consists in a measurement inaccuracy which increases with time as a result of the measuring tape moving to and fro during a measuring operation.
It is an object of the present invention to provide an apparatus and a method with which rapid, simple and accurate determination of the circumference of a body is possible.
According to the invention, this object is achieved by the apparatus described in the claims and by the method described in the method claims.
SUMMARY OF THE INVENTION
Within the context of the present invention, an apparatus for determining the circumference of a body is provided, the apparatus having at least the following elements:
a) a wire which has a known length section of length L
D
,
b) a position sensor, which is in operative contact with the wire such that it outputs a signal S, as soon as the wire exerts at least a predetermined tensile force Z on the position sensor,
c) a drive device for tensioning the length section of the length L
D
of the wire along the circumference of the body, the drive device being connected to the position sensor such that when the signal S is output, the tensioning of the wire by the drive device can be stopped,
d) a distance meter, in operative contact with the drive device, for measuring the distance W
D
traced by the wire as it is tensioned along the circumference of the body by the drive device,
e) so that the circumference of the body can be determined by the length L
D
, the distance W
D
and an apparatus-dependent geometry factor G.
It is preferable if the apparatus according to the invention has a unit for the calculation and output of the circumference of the body from the length L
D
, the distance W
D
and an apparatus-dependent geometry factor G. This ensures rapid and simultaneously exact determination of the circumference. It is preferable if the distance meter is coupled directly to a signal processing unit, preferably to a microprocessor or, particularly preferably to a computer, in which the measured distance W
D
traced by the wire as it is tensioned along the circumference of the body by the drive device can be read in and evaluated directly. The parameters of the apparatus which are known in advance, such as the length L
D
of the known length section of the wire and the apparatus-dependent geometry factor G, can be stored in the signal processing unit as fixed variables and called up at any time, or, preferably, integrated directly into a program used for the evaluation. The resulting circumference then preferably appears on a monitor or display connected directly to the processing unit.
In another preferred embodiment of the apparatus according to the invention, the drive device is a mangle mechanism with a drive roller and a traction roller. The introduction of the wire between the drive roller and the traction roller means that the apparatus becomes intrinsically self-contained. The drive device, the wire and the position sensor therefore form an intrinsically self-contained, complete system for determining the circumference of a body around which the wire wraps. After the drive roller has been set operating, the wire functions as a transmitter of the torque from the drive roller to the traction roller, so that the two rollers rotate synchronously with each other and, in so doing, simultaneously draw in the wire. The length by which the wire is drawn in between the two rollers can simultaneously be measured at any time with the aid of the distance meter coupled to the traction roller. As soon as the wire has been tensioned, that is to say as soon as it rests directly on the body whose circumference is to be measured, the wire exerts a finite tensile force on the position sensor, with which it is in operative contact. The position sensor reacts to this tensile force acting on it by generating a signal. This signal is preferably in turn coupled back to the drive roller which, when the signal appears, stops operating, so that the wire is not drawn in further by the two rollers, that is to say the drive roller and the traction roller.
The position sensor used is preferably an inductive distance sensor, whose impedance changes as a function of the force acting on it, as a result of the wire in this case. Here, the force which is necessary for the position sensor to respond, lies far below the compressibility limit of the body, whose circumference is to be determined. This ensures that the body is not compressed by the wire, and therefore changes its circumference, before the position sensor responds, that is to say provides a signal. In order to ensure that the compressibility limit of the body still has not been reached during the circumference measurement, after the first signal provided by the position sensor, the wire is preferably drawn in further by the drive device by a specific amount. The comparison of the length of the wire that is drawn in and can be read off on the distance meter after the first signal provided by the position sensor, together with the corresponding length extension of the position sensor which occurs simultaneously after the first signal as the wire is drawn in further by the drive device, offers a good possible means of checking; this is because the two distances must be identical if the body has not been compressed by the wire now resting directly on the circumference of the body.
In a preferred embodiment, the drive device has an electric motor.
In a preferred embodiment of the apparatus according to the invention, at least part of the surfaces of the drive device which come into contact with the wire as it is tensioned along the circumference of the body has a roughening which can be achieved by photomechanical or mechanical or chemical or electrochemical treatment. In the previously mentioned preferred refinement of the drive device as a mangle mechanism, such deliberate roughening of the traction roller achieves good adhesion of the wire on the traction roller and therefore ensures that the wire is drawn in simple, continuously and steadily. In the case of the mangle mechanism, good adhesion between wire and traction roller is also indispensable for its satisfactory functioning, that is to say for the interplay of traction roller, drive roller and wire.
While the adhesion between wire and traction roller should be comparatively high, the adhesive and
Courson Tania C.
DOMED Medizintechnik GmbH
Gutierrez Diego
Hood Jeffrey C.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
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