Water purification device

Abstract

A water purification device includes an expandable water collecting device having a variable volume, wherein at least part of the surface of the water collecting device includes a filter area, the filter area being permeable to water and allowing water to enter the water collecting device when the filter area is submerged in water. The device further includes a mechanically driven expansion means for exerting a force for increasing the volume of the water collecting device and thereby drawing water through the filter area into the water collecting device. In use, the water collecting device is submerged and the expansion means is released, drawing water into the water collecting device through the filter membrane.

1 . A water purification device, comprising:
 a water collecting device having a surface defining a variable volume,   wherein at least part of the surface of the water collecting device comprises a filter area, the filter area being permeable to water and allowing water to enter the water collecting device when the filter area is submerged in water,   wherein the device further comprises a mechanically driven expansion means for exerting a force for increasing the volume of the water collecting device and thereby drawing water through the filter area into the water collecting device.   
     
     
         2 . The device of  claim 1 , further comprising an outlet for removing clean water accumulated in the water collecting device. 
     
     
         3 . The device of  claim 1 , wherein the volume of the water collecting device is defined by a flexible sheet material. 
     
     
         4 . The device of  claim 3 , wherein the water collecting device comprises at least two sections of a filter membrane material that are joined in a watertight manner along edges of the sections, forming in the expanded state of the water collecting device, a substantially pillow-shaped bag. 
     
     
         5 . The device of  claim 1 , wherein at least a quarter of the surface of the water collecting device is made of a material serving as the filter. 
     
     
         6 . The device of  claim 1 , wherein, when the water collecting device is in a first configuration, comprising a reduced volume, the expansion means comprises stored energy, and release of said stored energy causes the volume of the water collecting device to increase. 
     
     
         7 . The device of  claim 6 , wherein the first configuration corresponds to an essentially flat configuration of the expansion means, and the increase of volume of the water collecting device corresponds to the expansion means assuming a three-dimensional configuration. 
     
     
         8 . The device of  claim 1 , wherein the expansion means is arranged inside the water collecting device and, when released, causes the water collecting device to expand, increasing the volume of the water collecting device. 
     
     
         9 . The device of  claim 1 , wherein the expansion means comprises at least one resilient element which releases stored energy by changing its shape, in particular by at least one of bending or unbending or expanding or contracting. 
     
     
         10 . The device of  claim 1 , wherein the expansion means comprises one or more struts that form a frame supporting the water collecting device, which struts themselves constitute resilient elements for releasing stored energy or are arranged in co-operation with resilient elements for releasing stored energy. 
     
     
         11 . The device of  claim 10 , wherein, in a transport configuration of the water collecting device, the resilient elements are not loaded (i.e. they are in a minimum energy state), and, in a ready-for-use configuration, the resilient elements are arranged such that they are loaded by bringing the water collecting device into a reduced volume configuration. 
     
     
         12 . The device of  claim 10 , wherein the expansion means comprises, in addition to the struts, resilient elements that are arranged to
 effect a change of angle between adjacent struts; or   push sections of the struts away from each other; or   pull sections of the struts towards each other;   
       and thereby increase the volume of the water collecting device. 
     
     
         13 . The device of  claim 9 , wherein the energy in the resilient elements is stored by bending or otherwise deforming the resilient elements. 
     
     
         14 . The device of  claim 13 , wherein the expansion means comprises two flat, star-shaped structures arranged inside a pillow-like water collecting device and pressed apart by a spring. 
     
     
         15 . The device of  claim 11 , wherein the expansion means comprises a frame of flexible wires that is bendable into a flat shape and when released expands to a three-dimensional shape supporting the water collecting device. 
     
     
         16 . The device of  claim 9 , wherein the energy in the resilient elements is stored by inflating a volume which is part of the resilient elements. 
     
     
         17 . The device of  claim 1 , wherein the water collecting device comprises a means for attaching a weight or to attach it to an external structure. 
     
     
         18 . The device of  claim 1 , further comprising a watertight outer envelope in which the water collecting device may be arranged. 
     
     
         19 . A method for water purification, using a water purification device that includes a water collecting device having a surface defining a variable volume, wherein at least part of the surface of the water collecting device comprises a filter area, the filter area being permeable to water and allowing water to enter the water collecting device when the filter area is submerged in water, wherein the device further comprises a mechanically driven expansion means for exerting a force for increasing the volume of the water collecting device and thereby drawing water through the filter area into the water collecting device, the method comprising the steps of
 in the case that the water collecting device is not in a reduced volume configuration, compressing the water collecting device such that it is in the reduced volume configuration;   submerging at least the filter area of the water collecting device in water;   releasing the expansion means, allowing the water collecting device to expand, whereby water enters the water collecting device through the filter area;   when a predetermined amount of filtered water has accumulated inside the water collecting device, removing the water collecting device from the water;   draining the accumulated filtered water from the water collecting device.