GB2137351A - Proximity detector - Google Patents

Abstract

A low profile device which can be used to detect the proximity of magnetic materials and is robust and not susceptible to damage by knocks and bangs from external objects consists of a copper winding C wound on a bobbin having unequal diameter flanges B, D, the tails of the winding being secured at two pins on larger flange D. These pins are secured to the twin cores of a screened cable which enters the side of a housing E through a protective grommet. Voids in housing E are filled with resin. The device has a centre pole piece A which passes through the core of the winding and to which is attached magnet N. When a magnetic material is passed over the end of the pole piece an e.m.f. voltage is induced in the coil windings. This e.m.f. voltage can be used by external electronic circuitry to detect the proximity of the magnetic material. <IMAGE>

Description

SPECIFICATION Improved proximity device of low profile and pro- tected side entry cable I, Muriel Millicent Alexander, a British Subject of 105, Hollybush Lane, Hampton, Middlesex. TW12 2QY do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described herein by the following statement.

The present invention relates to the detection of magnetic materials when brought into close proximity to reciprocating arms or rotating vanes. Each time an arm or a vane is made to pass close to the improved proximity device an electrical signal is induced into a coil which is fed out to a cable through the side of the body of the improved proximity device. This signal is the result of the change in magnetic flux through the centre pole piece and permanent magnet and increases to a positive peak as the magnetic metal arm or vane approaches the entre pole piece and decreases to a negative peak as the magnetic metal arm or vane leaves the centre pole piece.

The present invention seeks to provide an improved proximity device by which the cable feeding the signal out is made through a side entry, cushioned for shocks in a rubber grommet in a robust stainless steel body. Also the method by which the very fine copper wire of the coil is attached to the much larger stranded wire of the cable without putting undue stress or strain on the very fine copper wire. The method of side entry cable is also part of the feature of the low profile body which makes the improved proximity device not susceptibie to damage by bangs and knocks from external objects. Also the method of assembly and encapsulation.

Referring now to the single figure of the drawing accompanying the Specification, Figure 1. The centre pole piece A, of magnetic stainless steel is a sliding close fit in the Bobbin B which has different diameter flanges and is made of plastic capable of withstanding high temperatures up to 370 C. The bobbin is wound with very fine enamelled copper wire C of 47 standard wire gauge dimensions up to the diameter of the smaller flange of the bobbin B.

The copper wire is then protected by electrical insulating tape. Two 1 millimeter diameter pins D with retaining heads are inserted in holes drilled in the larger diameter flange of bobbin B such that the heads are towards the copper winding C and the pins D protude on the other side of the flange. The pins are interference fit in the holes and are retained by the tight fit. The holes are on a larger pitch circle diameter than the smaller flange so that the pin heads do not interfere with the main copper winding C. The tails of the copper winding C are brought out through two more holes in the larger flange of bobbin B. These holes are on a pitch circle diameter just above the diameter of the winding C. The enamel is removed from the copper wire and the wire soldered to the protruding pins D.The complete bobbin assembly is placed inside the body E which is made of nonmagnetic stainless steel, with the smaller flange entering first and pushed all the way down into the bore of the threaded part V of the body E. The smaller flange of the bobbin B is a sliding fit into the bore of the threaded part of the body E and the larger flange is a clearance fit in the larger bore of body E whose outer surface F is finely knurled to assist in mounting the device. The rubber grommet G is inserted in an appropriate hole drilled in the side of the knurled part of the body E. A length of twin core screened cable H of seven strands of copper wire of 0.2 inches diameter, each strand is pushed through the grommet which is of such dimensions as to be a tight fit around the outer sheath of the cable.The cable is pushed through until the outer sheath is seen to just protrude through the grommet G on the inside of the body E. The screen braiding J is twisted and connected to he pin K in the side of body E. The two inner core wires L are cut to a suitable length and the insulation is stripped to an appropriate length. These bare ends M of the wires are twisted and tinned with solder, they are then looped around the pins D, one wire to each pin, and solder jointed. The wires L are placed in such a position as to be clear of the flange part of centre pole A. A small drop of cyanoacyralate glue is placed on the flange of centre pole piece A and the round bar magnet N aligned and glued to the centre pole piece A.A small quantity of epoxy resin is placed in the corners P to seal the front face and the viods R in body E is filled with the resin which is allowed to seep down into all spaces. The epoxy resin is poured in till the whole of the body is filled. The cover S, which is made of non-magnetic stainless steel, is then placed in position and pressed down. A small hole T of 1 millimeter diameter drilled in the cover allows any excess epoxy resin to flow out. This is done until the cover bottoms down onto the shoulder U and the inner part of body E and all the components therein, are completely encapsulated.

1. An improved proximity device of low profile and protected side entry cable which can be used to detect the proximity of magnetic materials and is robust and is not susceptible to damage by bangs and knocks from external objects.

2. The method of assembly whereby the copper winding is wound on a bobbin of differing diameter flanges and the tails of the copper winding are secured to pins in the largerdiameter flange, these pins being attached to the twin cores of screened cable, one to each, and the screen to the body of the device, the said cable being brought out through a rubber grommet, for shock protection in the side of the body of the device and the internal voids filled with epoxy resin or other encapsulant.

3. A proximity device for the detection of magnetic material substantially as described herein with reference to the drawing, Figure 1, accompanying the Specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improved proximity device of low profile and pro- tected side entry cable I, Muriel Millicent Alexander, a British Subject of 105, Hollybush Lane, Hampton, Middlesex. TW12 2QY do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described herein by the following statement. The present invention relates to the detection of magnetic materials when brought into close proximity to reciprocating arms or rotating vanes. Each time an arm or a vane is made to pass close to the improved proximity device an electrical signal is induced into a coil which is fed out to a cable through the side of the body of the improved proximity device. This signal is the result of the change in magnetic flux through the centre pole piece and permanent magnet and increases to a positive peak as the magnetic metal arm or vane approaches the entre pole piece and decreases to a negative peak as the magnetic metal arm or vane leaves the centre pole piece. The present invention seeks to provide an improved proximity device by which the cable feeding the signal out is made through a side entry, cushioned for shocks in a rubber grommet in a robust stainless steel body. Also the method by which the very fine copper wire of the coil is attached to the much larger stranded wire of the cable without putting undue stress or strain on the very fine copper wire. The method of side entry cable is also part of the feature of the low profile body which makes the improved proximity device not susceptibie to damage by bangs and knocks from external objects. Also the method of assembly and encapsulation. Referring now to the single figure of the drawing accompanying the Specification, Figure 1. The centre pole piece A, of magnetic stainless steel is a sliding close fit in the Bobbin B which has different diameter flanges and is made of plastic capable of withstanding high temperatures up to 370 C. The bobbin is wound with very fine enamelled copper wire C of 47 standard wire gauge dimensions up to the diameter of the smaller flange of the bobbin B. The copper wire is then protected by electrical insulating tape. Two 1 millimeter diameter pins D with retaining heads are inserted in holes drilled in the larger diameter flange of bobbin B such that the heads are towards the copper winding C and the pins D protude on the other side of the flange. The pins are interference fit in the holes and are retained by the tight fit. The holes are on a larger pitch circle diameter than the smaller flange so that the pin heads do not interfere with the main copper winding C. The tails of the copper winding C are brought out through two more holes in the larger flange of bobbin B. These holes are on a pitch circle diameter just above the diameter of the winding C. The enamel is removed from the copper wire and the wire soldered to the protruding pins D.The complete bobbin assembly is placed inside the body E which is made of nonmagnetic stainless steel, with the smaller flange entering first and pushed all the way down into the bore of the threaded part V of the body E. The smaller flange of the bobbin B is a sliding fit into the bore of the threaded part of the body E and the larger flange is a clearance fit in the larger bore of body E whose outer surface F is finely knurled to assist in mounting the device. The rubber grommet G is inserted in an appropriate hole drilled in the side of the knurled part of the body E. A length of twin core screened cable H of seven strands of copper wire of 0.2 inches diameter, each strand is pushed through the grommet which is of such dimensions as to be a tight fit around the outer sheath of the cable.The cable is pushed through until the outer sheath is seen to just protrude through the grommet G on the inside of the body E. The screen braiding J is twisted and connected to he pin K in the side of body E. The two inner core wires L are cut to a suitable length and the insulation is stripped to an appropriate length. These bare ends M of the wires are twisted and tinned with solder, they are then looped around the pins D, one wire to each pin, and solder jointed. The wires L are placed in such a position as to be clear of the flange part of centre pole A. A small drop of cyanoacyralate glue is placed on the flange of centre pole piece A and the round bar magnet N aligned and glued to the centre pole piece A.A small quantity of epoxy resin is placed in the corners P to seal the front face and the viods R in body E is filled with the resin which is allowed to seep down into all spaces. The epoxy resin is poured in till the whole of the body is filled. The cover S, which is made of non-magnetic stainless steel, is then placed in position and pressed down. A small hole T of 1 millimeter diameter drilled in the cover allows any excess epoxy resin to flow out. This is done until the cover bottoms down onto the shoulder U and the inner part of body E and all the components therein, are completely encapsulated. CLAIMS

1. An improved proximity device of low profile and protected side entry cable which can be used to detect the proximity of magnetic materials and is robust and is not susceptible to damage by bangs and knocks from external objects.

2. The method of assembly whereby the copper winding is wound on a bobbin of differing diameter flanges and the tails of the copper winding are secured to pins in the largerdiameter flange, these pins being attached to the twin cores of screened cable, one to each, and the screen to the body of the device, the said cable being brought out through a rubber grommet, for shock protection in the side of the body of the device and the internal voids filled with epoxy resin or other encapsulant.

3. A proximity device for the detection of magnetic material substantially as described herein with reference to the drawing, Figure 1, accompanying the Specification.

4. A proximity device used in the detection of various materials and said proximity device assembled and manufactured according to the methd of assembly herein described with reference to the drawing, Figure 1, accompanying the Specification.