WO1990000739A1

WO1990000739A1 - Portable incubator and incubating kit

Info

Publication number: WO1990000739A1
Application number: PCT/GB1989/000789
Authority: WO
Inventors: Philip Graeme Morgan
Original assignee: Welsh Water Authority
Priority date: 1988-07-12
Filing date: 1989-07-11
Publication date: 1990-01-25
Also published as: AU3978389A; GB8816516D0

Abstract

A portable incubator comprises an incubating compartment (4), heating means (16) for heating the compartment and a control system for the heating means, the control system being arranged to maintain the temperature of the compartment (4) at a first selected temperature for a first period of time and subsequently to maintain the temperature of the compartment at a second selected temperature for a second period of time. The incubator may form part of a water testing kit consisting of two individually portable containers. The portable incubator facilitates incubation of samples collected from areas remote from laboratory facilities.

Description

Portable incubator and incubating kit

The present invention relates to incubation apparatus and to apparatus for preparing and incubating samples. It is frequently necessary to test samples in a variety of circumstances for the presence of organisms. For example it is essential to monitor sources of water for human consumption for the presence of organisms which could pose a threat to health. The cultures which are prepared in order to detect the organisms are prefer¬ ably prepared and incubation commenced immediately after collection of the sample. The site at which samples of water for testing are collected is, however, frequently a long way from laboratory facilities. Portable incubators have previously been used for incubation on site, but the known incubators allow only crude control of the incubating temperature and with no or little control. For example, in one known portable water testing kit, an incubator and sample preparation materials are housed in a single unit (International Specification WO85/01579). The unit offers only very limited control of the temperature of the incubator via an aluminium heat block and at two preset temperatures. In particular, there is no provision for automatic adjustment of temperature after a selected time period. The present invention provides a portable incubator, comprising an incubating compartment, heating means for heating the compartment and a control system for the heating means, the control system including first control means for maintaining the temperature of the compartment at a first selected temperature for a first predetermined period of time and second control means for subsequently maintaining the temperature of the compartment at a second selected temperature for a second predetermined period of time, the control system being so arranged that at the end of the first period of time control of the compartment temperature is automati¬ cally transferred from the first control means to the second control means. Using the incubator according to the invention, incubation may be commenced immediately after collection of the sample and preparation of the culture. Further if it is necessary to change the tem¬ perature during incubation, as is frequently desirable, the incubator can be set to change the temperature automatically at the required time. Previously, it has been necessary to reset the temperature manually.

Preferably, the first control means comprises means for varying the first selected temperature and/or means for varying the first predetermined period of time. In addition, the second control means preferably comprises means for varying the second selected tempera- ture and/or means for varying the second predetermined period of time. The means for varying the selected temperatures may be means for selecting one of two or f

more possible temperatures. Preferably, however, the temperature is continuously adjustable over a tempera- ture range, for example by means of dials. For example, each of the temperature varying means may be set at a different temperature in the range of from 20 to 50 C.

Each of the time varying means may, for example, be set at a time in the range of from 0 to 24 hours. The incubator may further comprise a chart recorder that records the temperature of the incubating compartment during use of the incubator. The inclusion of a chart recorder is particularly advantageous for quality control reasons. In particular, by using a chart recorder, the user will be alerted to any accidental variation in temperature which has occurred during incubation, for example if the heating means has malfunctioned.

Preferably, the heating means is arranged so that it can be powered by a battery, for example by a 12V battery. The incubator may further comprise a transformer so that the heating means can also be powered by mains electricity.

The present invention further provides a portable incubator comprising an incubating compartment, heating means for heating the compartment and a control system for the heating means, the compartment having a fan for circulating the air in the compartment. The fan enables an even temperature to be maintained throughout the compartment. While the use of a fan in a small portable incubator would seem unduly sophisticated for a portable incubator and an extra drain on power, it has been found to be suprisingly advantageous.

The present invention further provides a portable water testing kit, comprising first and second individually portable containers, the first container consisting of a portable incubator comprising an incubating compartment, heating means for heating the compartment and a control, system for the heating means, and the second container containing apparatus suitable for preparation of bacteriological samples to be incubated in the incubator. As a result of the provision of the incubator and the sample preparation apparatus in separate, individually portable containers, the portable testing kit consists of two compact containers, which may be transported separately. This is an advantage in cases where, for example, a sample is collected in a remote area; only the second container is then required for collection of the sample, and the incubator may be left in a car in the vicinity of the collection site. The second container may further contain apparatus for the physico-chemical determination of one or more parameters selected from dissociated oxygen, pH, temperature, electrical conductivity and chemical determinands. The determination of one or more of those parameters aids in the monitoring of water quality. Chemical determinands which may advantageously be deter¬ mined include, for example, manganese, iron, chlorine, nitrate.

Advantageously, the apparatus for the preparation of bacteriological samples includes membrane filtration apparatus. The apparatus in the second container may include vacuum filtration means comprising a hand oper¬ able vacuum pump. The apparatus will usually contain other equipment for use in the collection and testing of water samples, for example, a Bunsen burner, sterile petri dishes, ampoules of membrane lauryl sulphate broth, forceps, sealed membrane filters.

Advantageously, the second container comprises a hinged lid and a hinged panel which, when the container is open, may be positioned removably over the open base of the container.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 shows a portable incubator according to the invention;

Fig. 2 shows a plan view of the incubator of Fig. 1, with the lid open;

Fig. 3 shows a front view of the incubator of Fig. 1 ;

Fig. 4 shows a perspective view of the interior of the incubator of Figs. 1 to 3 including the lid interior;

Fig. 5 shows a circuit suitable for the incubator of Fig. 1 ;

Fig. 6 shows a container containing apparatus suitable for preparation of samples.

With reference to Fig. 1 , a portable incubator has a case 1 with a lid 2 which may be attached to the case by a hinge. The case may be of any suitable robust material, for example, plastic coated plywood or fibre glass. A carrying handle 3 is provided on the case. The dimensions of the portable incubator are for example 18 cm by 35 cm by 55 cm. The incubator case 1 may have one or more vents V (not shown in Figs. 1 to 3).

As shown in Fig.2, the case contains a recess which forms the incubating compartment 4, covered by a hinged lid 5. The lid may be of clear plastics material which may, if desired, bear instructions for the use of the incubator. The compartment 4 contains a fan 6, which circulates the air in the compartment, so maintain- ing a substantially constant temperature throughout the compartment. Temperature probes 7a and 7b monitor the temperature in the compartment 4, which is heated by means of heater unit 16.

A control panel 8 has an on/off switch 9, a light indicator 10, which indicates whether the incubator is switched on, and a heater indicator light 11 , which indicates whether or not the heater is on. The control panel also has a first control means including a first timer 12 and a first temperature control dial 13, and a second control means including a second timer 14 and a second temperature control dial 15. A heating unit 16 is located under the control panel (see Fig. 3).

If desired, the lid of the incubator may be provided with one or more closable compartments. Thus with reference to Fig. 4, the lid may include first and second compartments 2a, 2b which may be used to store, for example, operating manuals or electrical connection wires.

As shown in Fig. 5, the heating unit 16, including heater coils 16a is connected to each of the temperature control units CONT 1, CONT 2 via a 12/24V converter 17. The units CONT 1 and CONT 2 include the control dials 13 and 15 respectively. The temperature probe 7a may at any one time be connected to one or other of the temperature control units. The heating unit, in conjunction with the temperature probe 7a is arranged to maintain temperature thermostatically to an accuracy of +0.5 C at the temperature set on the relevant control dial. The timer 12 is so arranged that, after the length of time preset, the circuit connecting the heating unit 16 to temperature control unit CONT 1 is broken. At the same time temperature control CONT 2 becomes connected to the heating unit. Thus, after the period of time which has been preset on timer 12, control of the heater unit is passed from the first control means to the second control means. The second timer 14 does not begin to run until control is passed to the second control means. The fan 6 operates continuously from the time the incubator is switched on until the completion of the second time period.

Considering the circuit of Fig. 5 in more detail, the temperature control unit CONT 1 controls the disposition of the contact C. and the temperature control unit CONT 2 controls the disposition of contact C₂- When the on/off switch 9 is closed, the timer 12 is energised, contact T-,-1 is closed and contact T--2 is opened. The closed contact T.,-1 energises control unit CONT 1 and the relay R,/4 causing contacts R-.-1 and R.,-4 (upper) to be closed and contacts R.-4 (lower), R..-2 and R.,-3 to be opened. The contacts T~-1 and T-,-2 (upper) remain closed and T--2 (lower) remains open.

In this state the timer 12 is energised and begins timing, the timer 14 is de-energised, the control unit CONT 1 is energised and connected to the temperature probe 7a. The control unit CONT 1 controls the contact C- , while the timer 12 is operating, to switch the heater 16 on and off as required to maintain the temperature of the bath thermostatically at a value which has been preset on the temperature control dial 13. The fan 6 is energised.

At the end of the period which has been preset on timer 12, the timer 12 causes contact T..-1 to open and contact T-_j-2 to close. On opening of contact T.-1 relay R-./4 is de-energised so that contacts R,-1 and R--4 (upper) are opened and contacts R.-4 (lower), R..-2 and R--3 are closed. Thus, the timer 12 remains energised but the time period has expired and the timer 14 is energised and begins timing. At the same time the control unit CONT 1 is de-energised and is disconnected from the temperature probe; the control unit CONT 2 is energised and connected to the temperature probe. The fan 6 remains energised. The control unit CONT 2 controls the contact C-, while the timer 14 is operating, to switch the heater 16 on and off as required to maintain the bath temperature thermostatically at a temperature which has been preset on the temperature control dial 15.

At the end of the period which has been preset on timer 14, the control unit CONT 2 switches off the heater

16. The contact T--2 (upper) is opened to switch off the fan 6 and the contact T~-2 (lower) is closed to switch on the light 10 to indicate that the cycle is over.

The incubator shown in Figs. 1 to 4 also contains a chart recorder 19 which records the temperature in the compartment 4 as monitored by the probe 7b. For the sake of simplicity, however, the chart recorder and probe 7b have been omitted from Fig. 5. The incubator shown may be powered by a battery or by a 240V mains supply. The power supply is connected to a power input switch 20a. A 240/12 V transformer 20b, which is preferably located within the case 1 , as shown, is provided for use when the incubator is to be powered by mains supply. A fan may be provided to cool the transformer.

Fig. 6 shows a kit including apparatus suitable for preparing bacteriological samples and apparatus for monitoring physico-chemical determinands. The kit is housed in a lidded container 21 similar to that of the incubator. In the kit shown the apparatus for preparing bacteriological samples is stored in the base of the con¬ tainer and includes a filtration assembly 22, a receiving chamber 23 for use with unit 22, a hand operated vacuum pump 24, a gas torch 25a and a gas lighter 25b. Consum¬ able microbiological apparatus, for example, sterile petri dishes, an ampoule breaker, forceps, individually sealed membrane filters and ampoules of membrane lauryl sulphate broth (culture media) may be provided in a compartment 26. In addition to the items mentioned above, or instead of one or more of.those items, the kit may contain other items for use in water testing, for example, a lighter, an absorbent pad, a pencil torch. r The apparatus for monitoring physico-chemical determinands is received in the lid of the container 21 and includes, shown generally by the reference numeral 27, a dissolved oxygen probe, a pH/temperature probe and an electrical conductivity probe as well as a spectro- photometer 28 and reaction tubes and reagents 29 for determining for example manganese, iron, chloride, aluminium and nitrate content. The container 21 may include a panel which can be placed removably over the open base of the container to provide a work surface for preparation of samples. An edge of the panel may be hingedly attached to the upper rear edge of the base of the container (see panel 30a in Fig. 6) or the panel may be hingedly attached to an upper side edge of the base (see panel 30b in Fig. 6). The container may include either, or both of the panels 30a, 30b.

In use of the kit, cultures may be prepared from a sample and incubation commenced at the site of collec¬ tion of the sample. For example, Coliform and E. Coli cultures may be prepared as follows. The assembled filtration assembly 22 (Sartorius unit) and receiving chamber 23 are sterilised using the gas torch. A membrane filter is removed from its pack and placed on the filter base, the filter then being secured in the filter unit with the locking mechanism of the Sartorius unit. The required volume of the water sample is poured into the funnel and drawn through the membrane using the vacuum pump 24. An ampoule of the culture media is broken and poured onto an absorbent pad in a petri dish. The filter membrane is removed from the filter unit with forceps and placed onto the pad. Any excess culture media is poured off. The petri dish is placed in a container to minimise evaporation and the container is placed in the portable incubator. The first timer 12 and first temperature control dial 13 are then set for a first desired heating period. The second timer 14 and second temperature unit 15 are then similarly set for a further period. The incubator may advantageously be set, in the case of Coliform/ E. Coli cultures to incubate the cultures for a first period of 4 hours at a temperature of 30 C, followed by a second period of 16 hours at a temperature of 37 C.

The dissolved oxygen and chlorine, pH, temperature, electrical conductivity and other chemical determinands may be determined in known manner using the apparatus received in the lid container.

Claims

Claims :

1. A portable incubator, comprising an incubating compartment,heating means for heating the compartment and a control system for the heating means, the control system including first control means for maintaining the temperature of the compartment at a first selected temperature for a first predetermined period of time and second control means for subsequently maintaining the temperature of the compartment at a second selected temperature for a second predetermined period of time, the control system being so arranged that at the end of the first period of time control of the compartment temperature is automatically transferred from the first control means to the second control means.

2. A portable incubator as claimed in claim 1, wherein the first control means comprises means for varying the first selected temperature and/or means for varying the first predetermined period of time.

3. A portable incubator as claimed in claim 1 or claim 2, wherein the second control means comprises means for varying the second selected temperature and/or means for varying the second predetermined period of time.

4. A portable incubator as claimed in any one of claims 1 to 3, which further comprises a chart recorder that records the temperature of the incubating compartment during use of the incubator.

5. A portable incubator as claimed in any one of claims 1 to 4, wherein there is provided in the compartment a fan for circulating the air in the compartment.

6. A portable incubator as claimed in any one of claims 1 to 5, wherein the heating means is arranged so that it can be powered by a battery.

7. A portable incubator as claimed in claim 6, wherein the incubator further comprises a transformer so that the heating means can be powered by mains electricity.

8. A portable incubator comprising an incubating compartment, heating means for heating the compartment and a control system for the heating means, the compartment having a fan for circulating the air in the compartment.

9. A portable water testing kit comprising first and second individually portable containers, the first container comprising a portable incubator according to any of claims 1 to 8 and the second container containing apparatus suitable for preparation by membrane filtration of samples to be incubated in the incubator.

10. A portable water testing kit, comprising first and second individually portable containers, the first container consisting of a portable incubator comprising an incubating compartment, heating means for heating the compartment and a control system for the heating means, and the second container containing apparatus suitable for preparation of bacteriological samples to be incubated in the incubator.

11. A kit as claimed in claim 10, wherein the second container further contains apparatus for the physico- chemical determination of one or more parameters selected from dissociated oxygen, pH, temperature, electrical conductivity and chemical determinants.

12. A kit as claimed in claim 10 or claim 11, wherein the apparatus for the preparation of bacterio¬ logical samples includes membrane filtration apparatus.

13. A kit as claimed in claim 12, wherein the apparatus in the second container includes vacuum filtra- tion means comprising a hand operable vacuum pump.

14. A kit as claimed in any of claims 8 to 10, wherein the second container comprises a hinged lid and a hinged panel which, when the container is open, may be positioned removably over the open base of the container for use as a work surface.