the first embodiment as shown in fig1 to 8 comprises a cleaning head having an outer housing 10 defining a suction chamber 11 having front and rear side walls 12a , 12b and end walls 12c which define an open planar mouth 13 of substantially rectangular configuration at the underside of the head . the outer housing 10 is formed with an outlet 14 which extends centrally from the suction chamber 11 and is adapted to be connected to an air extraction means by a conventional suction hose ( not shown ). the end walls 12c of the outer housing 10 support between them a structurally separate inner compartment 20 which extends along the entire length of the suction chamber 11 between the ends thereof and which is spaced inwardly from the front and rear side walls 12a , 12b . the outer edges of the front and rear walls 22 of the inner compartment 20 are substantially co - planar with the outer edges of the walls of the suction chamber 11 and define an open planar mouth 23 . the inner compartment 20 is formed with a tubular spigot 21 on its upper face which opens to the interior of the inner compartment 20 and forms a liquid inlet therefor . the upper end of the tubular spigot 21 extends through an aperture in the top wall 12d of the suction chamber 11 when the inner compartment is located within the suction chamber . the inlet is intended to be connected to a source of cleaning liquid by tubing or like means ( not shown ) which source may comprise an unpressurised reservoir . the portion of the inner compartment 20 adjacent to the open mouth 23 accommodates a t - section bar member 30 whereof the transverse web 31 is received innermost and is supported within the inner compartment 20 by abutment against the ends of internal ribs 26 provided on the interior faces of the side walls 22 of the inner compartment 20 . the central leg 32 of the t - section bar member 30 extends downwardly from the web 31 and terminates in the plane of the open mouth 23 of the inner compartment 20 . the lateral edges of the transverse web 31 of the t - section bar member 30 are formed with a plurality of spaced grooves 33 which extend between each face thereof . the transverse web 31 of the t - section bar member 30 forms a separating wall which divides the inner compartment 20 into an internal liquid reception chamber 25 above the transverse web 31 and an outer liquid delivery chamber 29 below the transverse web 31 , between which chambers communication is provided through the grooves 33 . the uppermost region of the inner compartment 20 is provided with a calibrated air - flow passageway comprising in the illustrated embodiment a pair of small apertures 28 which extend between the inner and outer faces of upper wall 22a of the inner compartment 20 and provide communication between the interior of the liquid reception chamber 25 and the upper region suction chamber 11 in the vicinity of the outlet 14 . the outer faces of the side walls 22 of the inner compartment 20 are additionally formed with baffles 24 which abut at their outer edges against the inner faces of the front and rear side walls 12a , 12b of the suction chamber 11 . the baffles 24 in the illustrated embodiment comprise a pair of vanes 24a arranged in shallow v formation centrally of the head and serve to deflect the air - flow entering the suction chamber 11 through the open mouth 13 outwardly towards each end thereof to enhance the equilization of the reduced pressure created across the open mouth 13 of the suction chamber and to evenly direct incoming air - flow into the suction chamber . in the illustrated embodiment the baffles 24 additionally include a vertical vane 24b which extends downwardly from the junction of the vanes 24a to the lower edge of the inner compartment 20 . if desired , the inner compartment may be formed as a set of modules which can be interengaged in end - to - end relationship and to be receivable within suction heads of a variety of dimensions as required . by the use of such separate modules , a conventional suction head may be adapted for use for wet cleaning of floor surfaces . due to the small apertures 28 in the upper wall 22a of the inner compartment 20 , the internal liquid reception chamber 25 is subjected to reduced pressure when the head is connected through the outlet 14 to air extraction means . as a result of such low pressure within the liquid reception chamber 25 , cleaning liquid is drawn through the inlet 21 into the liquid reception chamber 25 , preferably to substantially fill that chamber . when the cleaning head is located in an attitude whereby the open mouth 23 of the inner compartment 20 is not closed by a floor surface whilst suction is applied to the outlet 14 , the pressure in the outer delivery chamber 29 of the inner compartment 20 is greater than the pressure within the liquid reception chamber 25 , which in turn is greater than the pressure in the suction chamber 11 in the region of the outlet 14 . accordingly , there is a net air - flow into the liquid reception chamber 25 through the grooves 33 in the t - section bar member 30 . while there will also be a flow of cleaning liquid into the liquid reception chamber 25 through the inlet 21 unless a shut - off means is provided in the hose connected to the inlet 21 , any cleaning liquid thus drawn into the liquid reception chamber 25 will , if the chamber 25 becomes full , be drawn through the apertures 28 into the suction chamber 11 and hence back through the outlet 14 . the net air - flow from the liquid delivery chamber 29 into the liquid reception chamber 25 serves to prevent , or at least limit , flow of cleaning liquid from the liquid reception chamber 25 to the liquid delivery chamber 29 under these conditions . when the open mouth 13 of the suction chamber 11 is placed in engagement with a carpet as shown at fig3 air is drawn into the suction chamber 11 through the carpet fibres . in addition , the pressure in the liquid delivery chamber 29 of the inner compartment 20 is reduced to a value lower than the pressure prevailing in the liquid reception chamber 25 , and this assists liquid flow through the grooves 33 into the liquid delivery chamber 29 , and thus into the carpet , subsequently to be extracted from the carpet through the suction chamber 11 . such flow is also assisted by the head of pressure created by the cleaning liquid accumulated in the liquid reception chamber 25 , which serves also as a reservoir within the head and ensures that cleaning liquid is delivered from each of the grooves 33 provided substantially over the full length of the t - section bar member 30 . in addition , cleaning liquid will be constantly drawn into the liquid reception chamber 25 as a result of the low pressure induced above the level of cleaning liquid within the liquid reception chamber 25 by virtue of the apertures 28 in the upper wall thereof and preferably to maintain a sufficient depth of liquid to create an hydrostatic head of pressure in the liquid reception chamber so that the cleaning liquid is delivered to the surface to be cleaned under such head of pressure . in addition , the presence of the side walls 22 of the inner compartment 20 ensures that the cleaning liquid is delivered to the surface to be cleaned rather than being drawn aside into the suction chamber 11 before reaching the surface to be cleaned . when the head is used on carpet , the cleaning liquid is subsequently drawn through the carpet and towards the suction chamber mouth 13 as a result of the reduced pressure created in the suction chamber . this results in the entire surface beneath the head being thoroughly wetted by the cleaning liquid across the full width of the suction chamber and being extracted therefrom by virtue of the air - flow entering the carpet from beneath the lower edges of the walls of the suction chamber 11 and through the carpet backing to provide a uniform and thorough cleaning action without overwetting even when the cleaning head is held stationary for spot cleaning and stain removal . the provision of the apertures 28 serves to prime the liquid reception chamber 25 with cleaning liquid without the need to rely on any other means for delivering the liquid , such as by gravity , air pressure or mechanical pump although such other means may be provided if desired to assist the delivery of liquid . in addition , when not in use ther is substantially no net flow of cleaning liquid to the liquid delivery chamber 29 of the inner compartment 20 and from thence to the floor surface as previously described . in order to prevent wastage of the cleaning liquid , the liquid reception chamber 25 may be provided with an elongate valving and distribution float bar 27 which is disposed within the liquid reception chamber 25 and preferably extends over substantially the full length and width thereof whilst being slidable therein between the uppermost surface of the t - section bar member 30 and the upper wall of the chamber 25 , the float bar 27 being buoyant in the cleaning liquid . the inner ends of the apertures 28 preferably open into respective raised lips 28a which are engageable with the float bar to close the apertures when the float bar is lifted into contact therewith . it will be understood that once the apertures 28 are closed there is no longer any tendency for liquid to be positively drawn into the chamber 25 . in order to prevent passive syphoning of liquid into the chamber , the float bar may also be arranged to engage around the end of the inlet spigot 21 to close it . the float bar 27 when provided also serves to distribute the cleaning liquid from the inlet 21 across the entire area of the liquid reception chamber 25 since the cleaning liquid on entering the chamber 25 initially flows over the float bar and when sufficient liquid has entered the chamber 25 the float bar 27 will then float so that it at all times assists in the distribution of the liquid . the second embodiment as shown in fig1 to 14 is of a generally similar form to that of the first embodiment and like reference numerals are used in these figures to denote corresponding parts , and the following description will be confined to features of difference from the first embodiment . in the second embodiment the open mouth 23 of the inner compartment 20 is arranged substantially parallel to the open mouth 13 of the suction chamber 11 but is spaced somewhat inwardly therefrom . in addition , the lower edges of the side walls 22 of the inner compartment 20 are formed with a plurality of equi - distant grooves 22b . the effect of the grooves 22b is to cause mechanical agitation of the carpet fibres as they pass between the grooves due to the reduced compression of the carpet fibres in the location of the grooves . such reduced compression serves to assist in the wetting of the carpet fibres which , with the mechanical agitation , enhances the cleaning process . as a result of the inward spacing of the open mouth of the inner compartment 20 in this embodiment , when the head is applied to carpet , that part of the carpet which is surrounded by the open mouth of the suction head is caused to be lifted such that it becomes engaged with the inner compartment 20 and as a result air is caused to flow into the suction chamber 11 through the carpet in the region abutting lower edges of the side walls 12a , 12b of the suction chamber 11 and also from underneath the carpet through the backing and fibres . this upward cleaning action serves to assist in preventing overwetting of the carpet backing and underlay which could otherwise result in permanent damage to the carpet . the upward flow further combines with the cleaning liquid being drawn downwards into the carpet from the inner compartment 20 to create a turbulence in the form of bubbles of air which expand rapidly as they rise through the carpet fibres due to the decrease of pressure on entry to the suction chamber 11 . this agitation assists the detergent action of the cleaning liquid in penetrating and releasing soil from the carpet fibres . the action is further combined with the mechanical agitation of the fibres by the groove 22b in the outer edges of the inner comparment 20 which act on the fibres as the cleaning head is moved in both forward and reverse directions . it will be appreciated that the scope of the present invention need not be limited to the particular embodiments described above . in particular , whilst the inner compartment is most conveniently formed as a structurally separate unit which is inserted into the suction head , it will be understood that it may be integrally formed within the suction head . whilst the calibrated air - flow passageway in the illustrated embodiments comprises a pair of small apertures 28 which extend through the upper wall of the inner compartment and open into the upper region of the suction chamber 11 , other arrangements are possible . for example , there may be a single opening in the upper region of the side wall 22 of the inner compartment 20 in register with the opening afforded by the outlet 14 , or a tube may extend from the inner compartment into and along the length of the outlet 14 . one particular advantage of the embodiments of head as illustrated , which includes the apertures 28 so as to obviate the need for a pressurised liquid delivery system , is that such heads can be used with conventional wet pick - up cleaners in order to convert such cleaners to carry out a cleaning process in which the cleaning liquid is applied to the surface to be cleaned through the cleaning head and simultaneously extracted in a single operation . it will be understood that for this purpose it is merely necessary to replace the conventional cleaning head of such wet pick - up cleaners with the head in accordance with the invention and to connect the inlet 21 to a source of cleaning liquid , which may be contained in a bucket or other suitable container .
a suction cleaning head , including a body defining a suction chamber having a boundary wall defining an open mouth and having an outlet adapted to be connected to an air extraction means , and an inner compartment extending across the suction chamber and having a substantially planar open mouth substantially in the plane of the open mouth of the suction chamber , wherein the inner compartment is divided by a separating wall into an outer liquid delivery chamber adjacent to the open mouth of the inner compartment and an internal liquid reception chamber which extends across the suction chamber and which has an inlet adapted to be connected to a supply of cleaning liquid , and a plurality of liquid flow passageways extending through the separating wall between the liquid reception chamber and the liquid delivery chamber , and wherein an air - flow passageway extends from the interior of the liquid reception chamber to a position within a low pressure zone downstream of the open mouth of the suction chamber .