Geometrical instruments – Distance measuring – By flexible tape
Patent
1995-07-31
1997-05-13
Will, Thomas B.
Geometrical instruments
Distance measuring
By flexible tape
33771, 33708, G01B 310, G01B 714
Patent
active
056281200
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for measuring length or angles, in which method use is made of a tapeshaped transmitter element which is provided with markings and is designed to be pulled out of and pushed into a housing, casing or the like, the latter being provided with at least one sensor for detecting the markings on the transmitter element, and with an electronics unit for converting signals from the sensor into length measurements or angle measurements. The invention also relates to equipment for carrying out the method.
PRIOR ART
It is generally known to use markings of a magnetic nature on the transmitter unit of equipment of the abovementioned type. U.S. Pat. No. 4,747,215 describes electronic measuring equipment which comprises a measuring tape with a builtin magnetic strip on which magnetic markings have been recorded, which markings can transmit signals to a sensor in a tape housing. A measuring tape of this type has a number of particular disadvantages. Among these may be mentioned the fact that the magnetic strip has to be embedded in the measuring tape so that the strip is mechanically protected. This is complicated and considerably increases the cost of the product. Nevertheless, there is still a risk of the strip being damaged mechanically. Moreover, in all equipment based on permanent magnetic markings, there is a risk that the markings will be lost or will be altered as a result of demagnetization.
U.S. Pat. No. 4,316,081 is also based on permanent magnetic markings in a measuring tape. In this case the markings are in the form of magnetic spheres arranged at a certain distance from one another. A disadvantage of this measuring equipment is that the degree of resolution is relatively small. In addition, there is a risk of demagnetization in this case too.
It is also known to use magnetoresistive conditions in order to measure lengths or positions. Examples of this technique are described in U.S. Pat. Nos. 4,712,064, 4,612,502, 4,039,936, 4,731,580, 4,053,829, in GB 2 157 831 and in EP-B-0 164 832.
BRIEF DISCLOSURE OF THE INVENTION
An object of the invention is to offer a method and equipment of the type specified in the preamble, which does not presuppose the use of any permanent magnetic markings in the transmitter element. A particular aim of the invention is to offer equipment having a transmitter element which is designed in such a way that it is adapted to magnetoresistive measurement, without markings of a permanent magnetic nature in the transmitter element, which does not, however, preclude the possibility of detection other than magnetoresistive detection being included within the scope of the invention. For example, laser detection or other optical detection of the markings on the transmitter element is conceivable.
A further aim of the invention is to offer a transmitter element which can be massproduced at very low cost and which, in combination with suitable electronics, can nevertheless permit an extraordinarily high degree of resolution and corresponding accuracy of measurement.
BRIEF DESCRIPTION OF THE FIGURES
In the following description of a preferred embodiment, reference will be made to the attached drawings, in which
FIG. 1 is a perspective view of a part of a transmitter element in the form of a measuring tape,
FIG. 2 shows, schematically, the principle of the measuring technique, with a part of the tape being shown on a larger scale in a longitudinal section through II--II in FIG. 1,
FIG. 3 shows, schematically, the main components of the equipment, and
FIG. 4 shows the electronic components of the equipment in the form of a block diagram.
DESCRIPTION OF A PREFERRED EMBODIMENT
In FIGS. 1-3 a measuring tape is generally designated by the reference 1. It consists of coldrolled carbon steel, i.e. a ferromagnetic, but not magnetized, material. The tape 1 has a width which is normal for measuring tapes, i.e. about 15 mm, and a thickness of about 0.12 mm. According to the embodiment, the tape has an S-shaped cross-section, which gi
REFERENCES:
patent: 2875524 (1959-03-01), Bower et al.
patent: 3029518 (1962-04-01), Raymond et al.
patent: 4226024 (1980-10-01), Westerberg et al.
patent: 4658134 (1987-04-01), Okumura
patent: 4747215 (1988-05-01), Waikas
patent: 4926566 (1990-05-01), McMurtry et al.
patent: 5174041 (1992-12-01), Lorenz
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