Linear position detecting system

Details Linear position detecting system Linear position detecting system

2000-09-13

2001-10-02

Wamsley, Patrick (Department: 2819)

Coded data generation or conversion

Digital pattern reading type converter

Magnetic, inductive or capacitive

C341S005000, C341S011000

Reexamination Certificate

active

06297750

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
The present invention relates to linear position measurement and in particular to linear position encoders.
Linear position encoders are known for measuring the position of a movable element or device along a travel path. One class of linear encoders are electro-optical in which a scale disposed along a travel path contains an array of optically sensible markings which are cooperative with markings on a member movable along the scale. Photosensors associated with the movable member provide electrical signals representative of movement with respect to the scale and provide an output representative of relative position of the movable member in relation to the fixed scale. Such electro-optical encoders can provide accurate linear measurement but are subject to contamination by dirt, dust or debris within the operating environment. Linear encoders are often used in machine tools or in other factory environments in which dust and dirt can be present.
Another class of linear encoders is based on inductive electrical principles. An elongated scale contains an electrical pattern in which a current is caused to flow. A movable member movable along the length of the scale contains an inductive pickup into which current is induced and which is sensed to provide an indication of relative movement of the member in relation to the scale. Such an inductive encoder is subject to electrical interference and is also subject to magnetic and electromagnetic interference which may be caused by the presence of permanent magnets, stray electromagnetic fields and the like.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, a linear position encoder is provided which is not affected by ambient light, smoke, moisture, particulate matter, and also not affected by electrical interference such as may be caused by stray fields or permanent magnets or magnetic particles. The encoder comprises a linear scale having an excitation loop which is composed of a pair of parallel conductors and an interconnecting loop end. The excitation loop is disposed along the length of the scale and has electrical terminals preferably disposed at one end of the scale. An alternating current is applied to the excitation loop to create an alternating magnetic field between the conductors. At least one periodic conductive pattern is provided on an outer side of the excitation loop. The periodic pattern has electrical terminals preferably at the same end of the scale as the terminals of the excitation loop. In a preferred embodiment, a second periodic conductive pattern is provided on the opposite side of the excitation loop from the first periodic conductive pattern. This second periodic pattern has electrical terminals which preferably are on the same end of the scale as the other electrical terminals.
A sensor is provided on a small printed circuit card that is movable in relation to the scale. The card has a central pickup loop which receives energy coupled from the scale excitation loop. The voltage induced in the sensor pickup loop produces a current in two periodic patterns in space quadrature with each other. The resulting magnetic fields are spatially modulated and motion of the sensor in relation to the scale amplitude modulates the output signals to provide an output indication of linear travel along the scale.


REFERENCES:
patent: 3739649 (1973-06-01), Pacini et al.
patent: 4524347 (1985-06-01), Rogers
patent: 4584472 (1986-04-01), Wiblin et al.
patent: 5907200 (1999-05-01), Chitayat

Affiliated with

Also associated with

Rating

Linear position detecting system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Linear position detecting system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Linear position detecting system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2585877