GB2064128A

GB2064128A - Capacitive level measuring probe

Info

Publication number: GB2064128A
Application number: GB8034182A
Authority: GB
Original assignee: Gustav F Gerdts KG
Current assignee: Gustav F Gerdts KG
Priority date: 1979-11-23
Filing date: 1980-10-23
Publication date: 1981-06-10
Also published as: ES8501877A1; ES496512A0; IT1145295B; IT8050220A0; BE886283A; FR2470367A1; PL228011A1; NL8006169A; SE8008180L; DK498580A; JPS5687820A; DE2953267C2; DE2953267A1

Abstract

A level measuring probe for capacitive level detection comprises an electrode (2) enveloped by an insulating sleeve (5). The sleeve (5) has an open end projecting axially beyond the end of the electrode into which is inserted a closure stopper (7) which tapers (8) over at least part of its length. A thrust ring (12) with an internal contour (13) complementary over at least part of its length to the taper (8) is mounted externally on the sleeve end and the insulating sleeve (5) is clamped between the tapering surfaces (8, 13) of the stopper (7) and thrust ring (12). <IMAGE>

Description

SPECIFICATION Capacitive level measuring probe This invention relates to a level measuring probe for capacitive level detection, comprising an electrode enveloped by an insulating sleeve.

Insulating sleeves for electrodes are preferably produced from a commercial hose or tube material. The hose or tube section used is sealed in pressure-tight manner at the free end of the electrode. This normally takes place by prewelding a base or by adhering in a stopper. However, special machines and skills are required for welding insulating material which are often not available and there are too many limitations on the temperature and pressure of use in the case of adhesion.

The present invention aims to provide a level measuring probe of the aforementioned type, whose closure for the free end of the insulating sleeve is also suitable for use under high operating pressures and temperatures and which can be produced without special machines and skills.

According to the invention, there is provided a level measuring probe for capacitive level detection comprising an electrode enveloped by an insulating sleeve, wherein the insulating sleeve has an open end projecting axially beyond the end of the electrode into which is inserted a closure stopper which tapers over at least part of its length, a thrust ring with an internal contour complementary over at least part of its length to the cone taper being mounted externally on the sleeve end and the insulating sleeve being clamped between the tapering surfaces of the stopper and thrust ring.

A closure is provided for the free end of the insulating sleeve, whose parts can be manufactured with conventional manufacturing equipment (e.g. lathes). The closure can be fitted very simply to the insulating sleeve. There are also no annoying limitations regarding pressure and temperature resistance.

The stopper and thrust ring are preferably provided with facing abutments with a compression spring arranged between the abutments. This arrangement ensures an adequately high clamping force on the closure in spite of possible temperature fluctuations and the resulting thermal expansion of the insulating sleeve.

One abutment is desirably constructed in an axially adjustable manner with a spacer provided between this abutment and the stopper or thrust ring carrying the other abutment. This arrangement facilitates the matching of the sleeve end to the shape of the stopper and the thrust ring during assembly, because it is possible to apply a high initial compressive force which is greater than the force of the compression spring. This is particularly useful with relatively rigid insulating sleeve material, such as e.g. PTFE.

Preferably, the stopper has a central throughhole and a closure member is arranged to seal said hole. This arrangement provides the prerequisites making it possible, if necessary, to introduce a supporting medium into the free inner space of the insulating sleeve which may be present after the complete assembly of the level measuring probe.

The invention will now be further described, by way of example, with reference to the drawing which is a longitudinal section through one embodiment of the capacitive level measuring probe according to the invention.

The level measuring probe has a casing 1 for connection to a pressure vessel (not shown) into which projects an electrode 2 of the level measuring probe in order to monitor the liquid level therein.

The electrode 2 comprises a tubular body fixed in electrically conductive manner to a contact pin 4 leading into the terminal head 3 of the casing 1.

The electrode 2 is surrounded by an electrically non-conductive insulating sleeve 5, preferably a PTFE hose. The insulating sleeve 5 extends axially downwards over the electrode 2.

A stopper 7 is inserted in the open end of the insulating sleeve 5. There is initially a conical thickening as from the end of the stopper facing the electrode 2, which is followed by a taper cone 8. Outside the insulating sleeve 5, the stopper 7 carries an axially adjustably arranged abutment 9 against which bears one end of a compression spring 10. The other end of the spring 10 acts on an abutment 11 on a thrust ring 12 fitted externally to the insulating sleeve 5. Over part of the length of the ring 12 in its internal contour 13 it is shaped in complementary manner to the taper cone 8 of the stopper 7.

On mounting on the insulating sleeve 5, which is supplied in cylindrical form, the thrust ring 12 is initially pressed by a nut 14, the abutment 9 and a tubular spacer 1 5 with a high force onto the insulating sleeve 5, so that the latter precisely adapts to the taper cones 8, 13 of the stopper 7 and thrust ring 1 2. As soon as the insulating sleeve 5 has been introduced into the clamping zone by the force of the compression spring 10, the sleeve 5 is further secured in a pressure-tight manner between the stopper 7 and thrust ring 12.

The stopper 7 has a central through hole 1 7 which is closable by a closure member 16. By means of this hole, the inner space 1 8, 1 9 of the insulating sleeve 5 can, if necessary, be completely filled with a supporting liquid.

1. A level measuring probe for capacitive level detection comprising an electrode enveloped by an insulating sleeve, wherein the insulating sleeve has an open end projecting axially beyond the end of the electrode into which is inserted a closure stopper which tapers over at least part of its length, a thrust ring with an internal contour complementary over at least part of its length to the cone taper being mounted externally on the sleeve end and the insulating sleeve being clamped between the tapering surfaces of the stopper and thrust ring.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Capacitive level measuring probe This invention relates to a level measuring probe for capacitive level detection, comprising an electrode enveloped by an insulating sleeve. Insulating sleeves for electrodes are preferably produced from a commercial hose or tube material. The hose or tube section used is sealed in pressure-tight manner at the free end of the electrode. This normally takes place by prewelding a base or by adhering in a stopper. However, special machines and skills are required for welding insulating material which are often not available and there are too many limitations on the temperature and pressure of use in the case of adhesion. The present invention aims to provide a level measuring probe of the aforementioned type, whose closure for the free end of the insulating sleeve is also suitable for use under high operating pressures and temperatures and which can be produced without special machines and skills. According to the invention, there is provided a level measuring probe for capacitive level detection comprising an electrode enveloped by an insulating sleeve, wherein the insulating sleeve has an open end projecting axially beyond the end of the electrode into which is inserted a closure stopper which tapers over at least part of its length, a thrust ring with an internal contour complementary over at least part of its length to the cone taper being mounted externally on the sleeve end and the insulating sleeve being clamped between the tapering surfaces of the stopper and thrust ring. A closure is provided for the free end of the insulating sleeve, whose parts can be manufactured with conventional manufacturing equipment (e.g. lathes). The closure can be fitted very simply to the insulating sleeve. There are also no annoying limitations regarding pressure and temperature resistance. The stopper and thrust ring are preferably provided with facing abutments with a compression spring arranged between the abutments. This arrangement ensures an adequately high clamping force on the closure in spite of possible temperature fluctuations and the resulting thermal expansion of the insulating sleeve. One abutment is desirably constructed in an axially adjustable manner with a spacer provided between this abutment and the stopper or thrust ring carrying the other abutment. This arrangement facilitates the matching of the sleeve end to the shape of the stopper and the thrust ring during assembly, because it is possible to apply a high initial compressive force which is greater than the force of the compression spring. This is particularly useful with relatively rigid insulating sleeve material, such as e.g. PTFE. Preferably, the stopper has a central throughhole and a closure member is arranged to seal said hole. This arrangement provides the prerequisites making it possible, if necessary, to introduce a supporting medium into the free inner space of the insulating sleeve which may be present after the complete assembly of the level measuring probe. The invention will now be further described, by way of example, with reference to the drawing which is a longitudinal section through one embodiment of the capacitive level measuring probe according to the invention. The level measuring probe has a casing 1 for connection to a pressure vessel (not shown) into which projects an electrode 2 of the level measuring probe in order to monitor the liquid level therein. The electrode 2 comprises a tubular body fixed in electrically conductive manner to a contact pin 4 leading into the terminal head 3 of the casing 1. The electrode 2 is surrounded by an electrically non-conductive insulating sleeve 5, preferably a PTFE hose. The insulating sleeve 5 extends axially downwards over the electrode 2. A stopper 7 is inserted in the open end of the insulating sleeve 5. There is initially a conical thickening as from the end of the stopper facing the electrode 2, which is followed by a taper cone 8. Outside the insulating sleeve 5, the stopper 7 carries an axially adjustably arranged abutment 9 against which bears one end of a compression spring 10. The other end of the spring 10 acts on an abutment 11 on a thrust ring 12 fitted externally to the insulating sleeve 5. Over part of the length of the ring 12 in its internal contour 13 it is shaped in complementary manner to the taper cone 8 of the stopper 7. On mounting on the insulating sleeve 5, which is supplied in cylindrical form, the thrust ring 12 is initially pressed by a nut 14, the abutment 9 and a tubular spacer 1 5 with a high force onto the insulating sleeve 5, so that the latter precisely adapts to the taper cones 8, 13 of the stopper 7 and thrust ring 1 2. As soon as the insulating sleeve 5 has been introduced into the clamping zone by the force of the compression spring 10, the sleeve 5 is further secured in a pressure-tight manner between the stopper 7 and thrust ring 12. The stopper 7 has a central through hole 1 7 which is closable by a closure member 16. By means of this hole, the inner space 1 8, 1 9 of the insulating sleeve 5 can, if necessary, be completely filled with a supporting liquid. CLAIMS

2. A level measuring probe according to claim 1, wherein the stopper and thrust ring are provided with facing abutments and a compression spring is arranged between said abutments.

3. A level measuring probe according to claim 2, wherein one abutment is constructed in an axially adjustable manner and a spacer is provided between this abutment and the stopper or thrust ring carrying the other abutment.

4. A level measuring probe according to any preceding claim, wherein the stopper has a central through-hole and a closure member is arranged to seal said hole.

5. A level measuring probe substantially as described herein with reference to the drawing.