GB2084401A

GB2084401A - Flow responsive switch

Info

Publication number: GB2084401A
Application number: GB8031546A
Authority: GB
Original assignee: MITCHELL CRAIG CLENACHAN
Current assignee: MITCHELL CRAIG CLENACHAN
Priority date: 1980-09-30
Filing date: 1980-09-30
Publication date: 1982-04-07

Abstract

A flow responsive switch comprises a housing (1) having a liquid inlet (2) and a liquid outlet (3), and a magnetic float (4) received within the housing (1). The float (4) is movable in a translational fashion between a first position in which it floats when liquid is present in the housing and a second position which it adopts when liquid is absent from the housing. A magnetically responsive contact unit (8) is responsive to the position of the magnetic float. Pins (7) ensure that the device allows liquid to flow through the housing past the float at least when the float is in the first position. One particular application of the switch device is in monitoring the supply of processing chemicals to a photographic processing apparatus. <IMAGE>

Description

SPECIFICATION Device for detecting the presence or absence of a liquid.

This invention relates to a device for detecting the presence or absence of a liquid at a location where the liquid is to flow or is flowing.

According to the invention there is provided a device for detecting the presence of absence of a liquid at a location where the liquid is to flow or is flowing, which comprises a housing having a liquid inlet and a liquid outlet, a magnetic float received within the container and movable in a translational fashion between a first position in which it floats when liquid is present in the housing and a second position which it adopts when liquid is absent from the housing, and a switch responsive to the position of the magnet, the device being such as to allow liquid to flow through the housing past the float at least when the float is in the first position.

An embodiment of the invention is shown in the accompanying diagrammatic drawings, in which: Figure 1 is a longitudinal section; and Figure 2 is a cross-section through the casing and float.

Figure 1 shows a device, hereinafter referred to as a sensor, which comprises a housing 1 having an inlet 2 at its lower end and an outlet 3 at its upper end. A float 4 of dumbell shape is received within the housing and a bar magnet 5 is mounted inside the float. It will be appreciated that the float 4 need not be dumbell in shape, and that other shapes, for example a cylinder tapered or rounded at its ends, could be used instead. Each end of the housing has a respective lid 6 which is provided with pins 7. The purpose of the pins is to prevent the float 4 approaching the inlet or outlet too closely and so blocking it. A reed switch 8 which is diagrammatically illustrated, is mounted on the outside of the housing and is responsive to the position of the float 5.

When a liquid is present in the housing, either flowing or static, the float 5 floats therein and is in the upper position illustrated. If no liquid is present the float falls to the bottom of the housing. The reed switch detects which of these two positions the float is in and sends a signal which may actuate, for example, an alarm system or may act on a mechanism forming part of whatever apparatus the sensor may form a part.

A particular form of casing is shown in Figure 2.

The shape of the interior cross-section is such as to allow liquid to flow freely past the float. The float responds essentially to the presence or absence of a liquid rather than to the liquid pressure or liquid flow rate. It will be appreciated that other suitable cross-sections could be used instead of the one illustrated.

The sensor may be made of any suitabie material, though conveniently the major part of it may be made of a plastics material such as polypropylene.

One particular application of the sensor is in machines used for processing photographic materials. Such machines comprise a plurality of baths into which the material being processed is successively introduced. Some of these baths contain a solution of appropriate chemicals or mixtures of chemicals, and must be replenished to allow for the chemicals consumed by the processing operation as photographic material passes through them. Accordingly, such baths have connected to them a supply of replenishment solution. Traditionally, replenishment solutions have been made up in bulk by the user, but a method more recently introduced is for the replenishment solution to be made up in a semicontinuous fashion as it is required.The second method involves the use of a substantially closed system in which there is connected containers of the various chemicals which are to be dissolved and a supply of water. In both the traditional and newer types of machine, though particularly in the latter, it is important to ensure that the supply of replenishment liquid does not run out, since if it did the amount and/or concentration of the solution in the bath would deviate from what is required, with potentially serious results as far as the processing operation was concerned.

The device of the present invention may be used with particular advantage in machines for processing photographic materials, a respective device according to the invention being inserted in each line which carries replenishment solution. If at any time one of the devices detects that there is no replenishment solution in the line it may emit a warning signal, for example an audible warning, or it may be used to cause the processing machine to cease operation.

1. A device for detecting the presence or absence of a liquid at a location where the liquid is to flow or is flowing, which comprises a housing having a liquid inlet and a liquid outlet, a magnetic float received within the housing and movable in a translational fashion between a first position in which it floats when liquid is present in the housing and a second position which it adopts when liquid is absent from the housing, and a switch responsive to the position of the magnet, the device being such as to allow liquid to flow through the housing past the float at least when the float is in the first position.

2. A device according to claim 1, wherein the float is of dumb-bell shape.

3. A device according to claim 1, wherein the float has the shape of a cylinder tapered or rounded at its ends.

4. A device according to any preceding claim, wherein the cross-section of the interior of the housing differs from the maximum cross-section of the float in such a way as to define at least one passage for liquid to flow past the float.

5. A device for detecting the presence or absence of a liquid, substantially as herein described with reference to the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Device for detecting the presence or absence of a liquid. This invention relates to a device for detecting the presence or absence of a liquid at a location where the liquid is to flow or is flowing. According to the invention there is provided a device for detecting the presence of absence of a liquid at a location where the liquid is to flow or is flowing, which comprises a housing having a liquid inlet and a liquid outlet, a magnetic float received within the container and movable in a translational fashion between a first position in which it floats when liquid is present in the housing and a second position which it adopts when liquid is absent from the housing, and a switch responsive to the position of the magnet, the device being such as to allow liquid to flow through the housing past the float at least when the float is in the first position. An embodiment of the invention is shown in the accompanying diagrammatic drawings, in which: Figure 1 is a longitudinal section; and Figure 2 is a cross-section through the casing and float. Figure 1 shows a device, hereinafter referred to as a sensor, which comprises a housing 1 having an inlet 2 at its lower end and an outlet 3 at its upper end. A float 4 of dumbell shape is received within the housing and a bar magnet 5 is mounted inside the float. It will be appreciated that the float 4 need not be dumbell in shape, and that other shapes, for example a cylinder tapered or rounded at its ends, could be used instead. Each end of the housing has a respective lid 6 which is provided with pins 7. The purpose of the pins is to prevent the float 4 approaching the inlet or outlet too closely and so blocking it. A reed switch 8 which is diagrammatically illustrated, is mounted on the outside of the housing and is responsive to the position of the float 5. When a liquid is present in the housing, either flowing or static, the float 5 floats therein and is in the upper position illustrated. If no liquid is present the float falls to the bottom of the housing. The reed switch detects which of these two positions the float is in and sends a signal which may actuate, for example, an alarm system or may act on a mechanism forming part of whatever apparatus the sensor may form a part. A particular form of casing is shown in Figure 2. The shape of the interior cross-section is such as to allow liquid to flow freely past the float. The float responds essentially to the presence or absence of a liquid rather than to the liquid pressure or liquid flow rate. It will be appreciated that other suitable cross-sections could be used instead of the one illustrated. The sensor may be made of any suitabie material, though conveniently the major part of it may be made of a plastics material such as polypropylene. One particular application of the sensor is in machines used for processing photographic materials. Such machines comprise a plurality of baths into which the material being processed is successively introduced. Some of these baths contain a solution of appropriate chemicals or mixtures of chemicals, and must be replenished to allow for the chemicals consumed by the processing operation as photographic material passes through them. Accordingly, such baths have connected to them a supply of replenishment solution. Traditionally, replenishment solutions have been made up in bulk by the user, but a method more recently introduced is for the replenishment solution to be made up in a semicontinuous fashion as it is required.The second method involves the use of a substantially closed system in which there is connected containers of the various chemicals which are to be dissolved and a supply of water. In both the traditional and newer types of machine, though particularly in the latter, it is important to ensure that the supply of replenishment liquid does not run out, since if it did the amount and/or concentration of the solution in the bath would deviate from what is required, with potentially serious results as far as the processing operation was concerned. The device of the present invention may be used with particular advantage in machines for processing photographic materials, a respective device according to the invention being inserted in each line which carries replenishment solution. If at any time one of the devices detects that there is no replenishment solution in the line it may emit a warning signal, for example an audible warning, or it may be used to cause the processing machine to cease operation. CLAIMS

2. A device according to claim 1, wherein the float is of dumb-bell shape.

6. An apparatus for processing photographic materials, which comprises at least one bath for containing a processing liquid connected by a line to a source of processing liquid for replenishing the bath, the or each line having inserted therein a device according to any preceding claim.