GB2140570A - Weight monitoring apparatus - Google Patents

Abstract

Apparatus for monitoring the supply of a free-flowing material being fed from or into a container, comprising a suspension means for supporting the container, the position of which changes according to the weight of material in the container an indicator showing that the apparatus is functioning and an alarm operable on movement of the suspension means to a position corresponding to a predetermined minimum or maximum weight of material in the container. <IMAGE>

Description

SPECIFICATION Weight monitoring apparatus and method This invention relates to weight monitoring apparatus, and especially, though not exclusively, to apparatus for use with a container from which a free flowing material, such as a liquid or powder, is being fed and the exhaustion of which needs to be avoided. The material may, for example, be a fluid, such as blood plasma or saline solution, being supplied to a patient during or subsequent to surgery or parenteral treatment. In such cases the supply of fluid is commonly monitored by periodic visual checks, but the person or persons carrying out the inspection may have other work which could divert attention from the task at a crucial time.As the exhaustion of the supply of fluid could cause serious problems, such as air embolism, it is clearly desirable to prevent it, and one object of the invention is to provide a form of automatic monitoring apparatus which can be used to reduce the risk of this occurring. However, the invention can have other applications as will be apparent from the following description.

A weight monitoring apparatus in accordance with the invention comprises a housing for attachment to a support, a suspension device for supporting a container whose weight is to be monitored and which is movable relative to the housing against biasing means under the weight of the container and its contents and, associated with the housing, an operating circuit, an indicator which is operative to provide a check signal when the circuit is energised, an alarm and means operable to actuate the alarm on movement of the suspension device to an operative position corresponding to a predetermined minimum or maximum weight of material in the container.

The alarm is preferably mounted in or on the housing and may incorporate a lamp or L.E.D.

(light-emitting diode) which, on acutation of the alarm, is either continuously energised or intermittently flashed. The alarm may alternatively or additionally incorporate an audible device which may also be arranged to emit a continuous or intermittent sound warning when the alarm is energised.

The generation of a check signal provides an indication that the apparatus is functioning and the absence of either a check signal or an alarm signal when the apparatus should be operating provides a warning that the apparatus needs to be checked.

The check signal is preferably an intermittent visual signal preferably provided by an L.E.D, arranged to flash in a different colour from that of the visual alarm.

Preferably the operation of the check indicator is inhibited when the alarm is operated.

The biasing means is preferably provided by at least one spring, although in some cases it could be provided by a counterweight acting under gravity the movement of the suspension device in either case being restricted within predetermined limits.

Conveniently the housing has accommodation for one or more electric batteries capable of operating the alarm and the check signal indicator, so that the apparatus constitutes a completely self-contained and portable device. Such a device can be constructed in a compact manner, its power require ments being such that there are no electrical hazards. The use of L.E.D's to give visual check and alarm signals is particularly advantageous, in view of the very low current required to operate them.

This virtually eliminates the risk of sparking on switching their operating circuits, and ensures a long battery life.

The apparatus may, for example, incorporate switch means, for example a microswitch, having a first pair of electrical contacts which are closed to energise the check signal indicator, and a second pair of contacts which are open so as to de-energise the alarm, on displacement of the suspension means from said operative position, the movement of the suspension means into the operative position resulting in the opening of the first pair of contacts and the closure of the second pair, thereby inhibiting the operation of the indicator and actuating the alarm.

Preferably the apparatus is designed to monitor the weight of a container from which a material is being fed, the suspension means being arranged to move upwards as the level of the material falls, and being arranged to actuate the alarm when the weight of the material in the container reaches a preset minimum value.

Preferably adjustment means are provided for varying the setting of the apparatus to cause the alarm to be actuated at different minimum or maximum weight values.

One embodiment of the invention for use in monitoring the weight of a container from which a fluid is supplied to a patient, and for giving a warning signal when the container is nearly empty will now be described by way of example with reference to Figures 1 to 5 of the accompanying drawings, in which Figure 1 represents a perspective view of the monitoring apparatus, Figure 2 represents a perspective view of the rear of the apparatus opened to reveal the interior, Figure 3 illustrates on an enlarged scale the operative part of the apparatus removed from its enclosing housing, Figure 4 illustrates the operating circuit of the apparatus in diagrammatic form, and Figure 5 shows the apparatus in use.

The apparatus comprises a housing 1 in the form of a substantially rectangular openable casing, con venientlyformed of a plastics material such as polypropylene, having front and rear sections 2, 3 connected by an integrally formed hinge, and having a catch, shown diagrammatically at 10, for holding the casing in the closed condition in use. The casing is arranged to be supported with its longer sides vertical, and for this purpose one of the shorter sides of the front section 2 is provided with an outwardly projecting flange 5 having a hole 6 by which the casing can be hooked on to a suitable support, as at 32 in Figure 5.

The casing has, mounted within it, a carrier member in the form of a component board 7, which is shown in more detail in Figure 3, the board carrying a stainless steel or nylon support hook 8 from which the flexible bag of known kind containing fluid to be supplied to a patient is arranged to be supported. The hook 8 projects through an opening formed in the bottom of the casing by two partcircular depressions 9 in the opposed lower edges of the two sections 2,3 of the casing.

The shank 11 of the support hook 8 is supported vertically within a slot 12 formed in the lower part of the component board 7 by means of a pair of longitudinal grooves 13 disposed on opposite sides and into which guide projections 14,15 at the top and bottom of the slot 12 loosely fit, allowing the support hook to move vertically relative to the casing.

An intermediate part of the slot 12 is widened to accommoate a compression spring 16 which surrounds the shank of the support hook 8. The lower end ofthe spring 16 engages a locating hole 17 in the component board 7, and the upper end bears against an internally threaded nut member, such as a thumb wheel 18, screwed on to the threaded upper end of the support hook shank.

The component board 7 carries, above the support hook 8, a microswitch 19, and a resilient actuating arm 21 which is urged downwards away from the switch 19 by the resilience of the arm.

The miroswitch has two pairs of contacts C1, C2, the operation of which will be described later with reference to Figure 4.

The board 7 also carries a pair of L.E.D's 22, 23 and a sound generator 24, together with solid state operating circuits therefor, indicated diagrammatically at 25, and interconnecting conductors which have been omitted from Figures 2 and 3forthe sake of simplicity.

The rear section 3 of the casing 1 has compartments for two electric batteries as at 26, and the operating circuits 25 are connected thereto through an on-off switch 27 mounted on the component board and projecting through an opening in the front face of the casing.

Windows as at 29 and a series of openings as at 30 are also provided in the front of the casing for the emission ofvisual and audible signals from the L.E.D's and sound generator respectively when these are energised.

In use of the apparatus, with a bag 31 containing a supply of plasma, saline solution or other fluid attached to the hook 8, the hook will be pulled downwards against the force of the spring 16, allowing the actuating arm 21 to spring away from the microswitch 19.

The first pair of contacts C1 of the microswitch are arranged to be closed when the switch is unactuated, and the circuit connections are such that when the device is switched on by means of the switch 27, the contacts connect a low frequency oscillator 25' (Figure 4) to the L.E.D 22, which gives an intermittently flashing green light. As fluid is fed from the bottom of the bag 31 to a patient via the usual feed tube 33, the reduction in weight will cause the spring to urge the hook 8, carrying the bag 31 progressively upwards. Thus, when the contents of the bag 31 are nearly depleted or reach a predetermined level the actuating arm 21 will engage and operate the microswitch 19. This will open the contacts C1 and close the second pair of contacts C2.The closure of the second pair of contacts C2 connects the righthand, red-emitting L.E.D 23 to the oscillator 25' and at the same time connects the sound generator to an audio oscillator 25", causing itto emit a discontinuous note in the form of an intermittent "bleep", indicating that the bag 31 will shortly be in need of repiacement.

The point at which the device is actuated to give the warning may be altered by adjustment of the thumb wheel 18, the edge of which also projects through an opening in the front of the casing.

This may be necessary, for example, with different fluids and/or different rates of feed, and the thumb wheel 18 is conveniently provided with suitable markings to facilitate the setting of the wheel to the appropriate position.

If desired the device may be provided with a further switch as at 34 which can be set to give either a quieter or a louder audible signal from the sound generator as may be required, or in some cases into a third position in which the operation of the sound generator is completely suppressed.

Various modifications can be made to the arrangement described. For example a photo-electric device could replace the contacts C1, C2, the support hook 8 then carrying a shutter arranged to be moved across the photo-electric device, to cause it to initiate the operation of the alarm devices 23,24, and inhibit the operation of the L.E.D 22, when the support reaches a predetermined position.

Similar forms of apparatus could be used for other applications where a free flowing material is being fed from a container to give a warning signal when only a predetermined minimum amount of the material remains in the container.

In addition for some applications the device could be modified to operate in the reverse manner and actuate an alarm when material which is being fed into a container supported by the device reaches a predetermined maximum weight, for example blood from a blood donor.

Although monitoring apparatus in accordance with the invention is capable of being constructed as a self-contained unit, the visual or audible alarms may, if desired, be located at a position remote from the main body of the apparatus if desired.

Claims (16)

1. Aweight monitoring apparatus comprising a housing for attachment to a support, a suspension device for supporting a container whose weight is to be monitored and which is movable relative to an operating circuit, an indicator which is operative to provide a check signal when the circuit is energised, an alarm, and means operable to actuate the alarm on movement of the suspension device to an operative position corresponding to a predetermined minimum or maximum weight of material in the container.

2. Apparatus according to Claim 1 incorporating adjustment means for varying the setting of the apparatus to cause the alarm to be actuated at different maximum or minimum weight values.

3. Apparatus according to Claim 1 or 2 in which the biasing means is provided by at least one spring.

4. Apparatus according to Claim 1,2 or 3 wherein the housing accommodates the alarm and one or more electric batteries capable of actuating the alarm.

5. Apparatus according to Claim 4 wherein the said indicator and the alarm each incorporates at least one L.E.D.

6. Apparatus according to Claim 4 wherein the alarm incorporates at least one electrically operable audible device.

7. Apparatus according to any preceding Claim incorporating switch means having a first pair of electrical contacts which are closed to energise the check signal indicator, and a second pair of contacts which are open so as to de-energise the alarm, on displacement of the suspension means from said operative position, the movement of the suspension means into the operative position resulting in the opening of the first pair of contacts and the closure of the second pair, thereby inhibiting the operation of the indicator and actuating the alarm.

8. Apparatus according to Claim 7 wherein the switch is a microswitch.

9. Apparatus for monitoring the weight of a container from which a free flowing material is arranged to be fed, comprising a housing, a suspension device for supporting said container and which is movable relative to the housing under the weight of the container and its contents against biasing means, an operating circuit incorporating first and second pairs of electrical contacts arranged to be closed and open respectively when there is more than a predetermined weight of material in the container, the closure of the first pair of contacts giving rise to the operation of a visual indicator and movement of the suspension means under the biasing means into a position corresponding to a preset minimum weight of material into the container resulting in the opening of the first pair of contacts, and the closure of the second pair of contacts, and an alarm operable by closure of the second pair of contacts.

10. Apparatus according to Claim 9 wherein the housing comprises a casing accommodating the contacts the indicator and the alarm, and the suspension means is supported for vertical sliding movement relative to the housing when the latter is mounted in its operative position, and is movable downwards against spring means by the weight of material in the container.

11. Apparatus according to Claim 10 wherein the contacts, indicator, alarm and suspension means are carried by a carrier member mounted within the casing.

12. Apparatus according to Claim 11 wherein the suspension means comprises a hook having a straight shank slidably supported by guide means on said carrier member.

13. Apparatus according to Claim 12 wherein the shank of the hook has a pair of longitudinal grooves disposed opposite each other and into which guide elements of the carrier member project.

14. Apparatus according to Claim 11 or 12 wherein the shank of the hook is at least partly threaded and carries an internally-threaded nut member screwed on to it, the spring means being in the form of a compression spring disposed so as to urge the internally-threaded nut member, and hence the hook, upwards, the position of the nut member on the hook being adjustable.

15. A method of monitoring the supply of a free flowing material comprising automatically monitoring the weight of a container into which or from which such material is flowing, and causing the actuation of an alarm device when the monitored weight reaches a predetermined level.

16. Aweight monitoring apparatus substantially as shown in and as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.