IMPROVEMENTS IN OR RELATING TO WATERING INDICATORS FOR PLANTS

Abstract: The invention is a watering indicator for plants or the like, said indicator comprising a base strip 4 which carries a hygro­ scopic layer 5. The hygroscopic layer 5 can be viewed to ascertain the presence of water in the medium being moni­ tored and means (5a, 9) is provided to permit the viewed hygroscopic layer 5 to vent to atmosphere.

Description: Improvements in or relating to watering indicators for Plants This invention relates to a watering indicator for plants. The indicator is intended to be inserted into the soil surrounding a plant in order to indicate the moisture content thereof. Such indicators have previously been proposed and in particular British Patent No. 2059077 discloses one form of indicator in which a base member is coated with a layer of hygroscopic material substantially over its total surface area. The hygroscopic layer changes from an opaque to a translucent state in the presence of water. At its upper end the layer of hygroscopic material is provided with a discontinuity which effectively prevents moisture travelling up the hygroscopic layer for passage to the atmosphere. The discontinuity acts as a seal along the upper edge. In order to prevent evaporation from the sides of the upper portion of the layer, said upper side edges of the hygroscopic layer are sealed by means of adhesive tape. Accordingly, the upper end of the indicator is sealed on both its upper edge and its side edges. A transparent window is applied over the hygroscopic layer at the upper end of the indicator so that any change in the colour of the hygroscopic material can be observed. It has been found that the arrangement as described in British Patent No. 2059077 has the disadvantage that because the upper portion is sealed to the atmosphere in order to prevent evaporation of water travelling up the indicator, the indicator can in fact give an incorrect reading. This is due to the fact that the sealing of the upper end of the indicator traps and retains water moisture at said upper end and a favourable reading can be given suggesting that the soil being tested is adequately watered when, in fact, the actual soil surrounding the plant at the lower end of the indicator is dry and requires watering. An object of the present invention is to provide an indicator of the type disclosed in British Patent 2059077 but in which the aforesaid disadvantage is obviated or mitigated. According to the present invention there is provided a watering indicator for plants or the like comprising a base member adapted to be inserted into a medium to be monitored; a layer of hygroscopic material carried by said base member and adapted to vary in character in the presence of water in the medium;and viewing means overlying at least a portion of said hygroscopic layer for observing variation in the character thereof characterised in that venting means is provided to permit loss of water located in the hygroscopic layer between the viewing means and the base member. Preferably, said venting means comprises a portion or portions of the hygroscopic layer which extend to the free edges of the viewing means. Preferably also, the viewing means is provided with a first window area displaying constant colour for enabling ready comparison with a second window area displaying a portion of the hygroscopic layer which is subject to colour variation. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing in which: Fig. 1 is a perspective view of a watering indicator in accordance with the present invention; Fig. 2 is an exploded perspective view of the indicator; and Fig. 3 is a side view of the indicator shown in Figs. 1 and 2. Referring to the drawings, a watering indicator for plants comprises a coloured base strip 4 of synthetic plastics material, the lower end of the strip being pointed to facilitate insertion into the soil. One face of the base strip 4 is coated with a layer 5 of hygroscopic material which, as shown best in Fig. 2, extends continuously from the pointed lower end of the strip 4 to the upper edge 4a of the strip 4 and also laterally to the two side edges 4b of the upper portion of the strip. Those portions Sa of the layer 5 which extend to the upper and side edges 4a and Ab respectively act as vents to allow water travelling up the layer to evaporate to the atmosphere. Discontinuous or discrete areas 6 from which the hygroscopic layer has been removed or omitted are provided towards the upper end of the strip 4 and to these discontinuous areas which are free from hygroscopic material is adhesively secured a transparent viewing window or film 7 of any suitable material e.g. a synthetic plastics material. If desired, the window 7 can be provided with any suitable design. Through the window 7 there can be viewed the hygroscopic layer. A small area 8 of one or more of the areas 6 which are free of hygroscopic material is also left free of adhesive so that the colour of the base strip 4 can be viewed through the window 7 at this location. This permits a ready visual colour comparison between the area 8 and that portion of the hygroscopic layer 5 which is viewed through window 7 and which will, of course, change its character e.g. colour, depending upon whether the layer 5 is wet or dry. In the above-described embodiment, the vents 5a are constituted by portions of the hygroscopic layer extending to the upper and side edges of the window 7 of the indicator. It will be readily appreciated that other forms of vent can be provided so long as the desired result is achieved of allowing evaporation of water from the hygroscopic layer where it is sandwiched between the base strip 4 and the viewing window 7. For example, the layer may only extend to the side edges or upper edge of the window 7. Alternatively, the window 7 can be provided with a plurality of venting perforations. In an alternative embodiment of the invention as shown in Fig. 4, the upper and side edges of the window 7 may be sealed i.e. portions of the hygroscopic layer do not extend to the upper and side edges of the window 7 of the indicator. In this case the vents are provided by spaced perforations 9 formed through the window 7. These perforations 9 allow the layer 5 of hygroscopic material between the window 7 and base strip 4 to communicate with the external atmosphere thereby permitting evaporation of water therefrom. In operation of the indicator, the lower pointed end is inserted into the soil or other growing medium to be tested so that the lower part of the hygroscopic layer 5 is in contact with the soil. If water is present, water travels upwardly through the layer 5 by capillary action and the hygroscopic material changes from an opaque whitish colour to a translucent form which allows the colour of the base strip to be viewed through the window 7 as the water travels up the indicator. Due to the fact that the hygroscopic layer 5 extends continuously to the upper and side edges of the indicator and thereby allowing evaporation through vents 5a, the indicator gives a true indication that water is present in the soil and not as a result of residual water being retained in the indicator itself. Any suitable hygroscopic material can be employed for the purposes of the present invention. One such suitable hygroscopic material is calcium hydroxide in a liquid carrier. Examples of other hygroscopic materials which may be used are magnesium, hydroxide, calcium carbonate and paper.

Claims: CLAIMS 1. A watering indicator for plants or the like comprising a base member adapted to be inserted into a medium to be monitored; a layer of hygroscopic material carried by said base member and adapted to vary in character in the presence of water in the medium; and viewing means overlying at least a portion of said hygroscopic layer for observing variation in the character thereof characterised in that venting means is provided to permit loss of water located in the hygroscopic layer between the viewing means and the base member. 2. A watering indicator as claimed in claim 1, in which said venting means comprises a portion or portions of the hygroscopic layer which extend to the free edges of the viewing means for communication with the atmosphere. 3. A watering indicator as claimed in claim 1, in which said venting means comprises one or more perforations in said viewing means for permitting communication of the hygroscopic layer with the atmosphere. 4. A watering indicator as claimed in any of claims 1 to 3, in which the viewing means is provided with a first window area displaying constant colour for enabling ready comparison with a second window area displaying a portion of the hygroscopic layer which is subject to colour variation. 5. A watering indicator as claimed in claim 1, in which the hygroscopic material comprises calcium hydroxide. 6. A watering indicator as claimed in any preceding claim1 in which the viewing means comprises a sheet of transparent material secured at discrete locations to the base member. 7. A watering indicator for plants or the like, substantially as hereinbefore described with reference to Figs. 1 to 3 or Fig. 4 of the accompanying drawing.

Inventors: CROWTHER, ALBERT
Applicants: CROWTHER DISPLAY LIMITED
Application year: 1986
Main classification: G01N31
IPC codes: G01N21, G01N31