GB2323775A - Blower-type suction cleaner - Google Patents

Abstract

The portable vacuum cleaner comprises a housing 10A and 12 in which is contained a web of filter material 15 held across a perforated drum 16. Air pump 21 causes air and entrained dirt to be sucked up through inlet 34A. Exhausted air passes into chamber 32A where a portion of it is discharged via a second filter 50 which is finer than main filter web 15; and the other portion is recirculated to a point close to the air inlet to act as as an "air knife" A which impinges on the surface to be cleaned, knocking dirt loose. Whenever the portion of filter web 15 mounted on drum 16 is clogged, the drop in suction pressure activates the diaphragm 28, causing the pawl 24 and ratchet 27 to advance the web so that a fresh portion comes into use, and the spent web is advanced into receptacle 18. Window 35 permits inspection of the web.

Description

IMPROVEMENTS IN OR RELATING TO PORTABLE SUCTION CLEANERS Portable domestic and office suction cleaners of a kind commonly known as cylinder vacuum cleaners" usually comprise a housing having an inlet and an outlet, an air fan or pump driven by an electric motor to draw air from the inlet through a dust collecting filter and to expel the filtered air through the outlet. There are also known suction cleaners of a kind commonly known as "upright vacuum cleaners" which are similar to cylinder vacuum cleaners except primarily in that the inlet is provided with a rotary brush or beater and the dust collecting filter is connected downstream of the pump outlet, usually in a large porous bag.

There are well known variants of such cleaners, in one, known as a "cyclone cleaner", the porous filter is replaced or preceded by flow guide means to cause the air to rotate rapidly in a centrifuging chamber within the housing, for separation of the dust from the air flow.

In another variants commonly known as a "wet and dry cleaner", a liquid collecting chamber is provided in the housing upstream of a water resistant filter or screen, to collect liquids entrained in the suction air flow.

All these known cleaners involve compromises and each kind has its own inherent problems. For example, in cylinder cleaners the filter usually comprises a cloth or paper bag, the paper bags are usually disposable and are intended to remove finer particles than is possible with woven cloth bags, but the paper bags need to be replaced, and can be costly; whereas the cloth bags can become clogged in time unless they are washed or beaten clean at intervals. The same compromises and problems apply to upright cleaners, but because of the much larger volume and filtering area of the bags, the periods between bag replacement or cleaning are greatly extended.

Fine particles are particularly troublesome (see "Health Which" December 1997 pages 194 and 195). When the bags are new or clean their porosity is maximum and they impose minimal resistance to flow of air which is thus also maximum for good picking up of dirt and dust, but the high porosity allows fine particles to pass through the filters.

Only when the accumulating debris and larger particles, particularly of a fibrous nature, have reduced said porosity do the fine particles become trapped, but by this time the air flow and "pick up" power are reduced. In cyclone cleaners, the fine particles (particularly low density particles) are very difficult to remove, and most "wet and dry" cleaners are not designed to remove fine particles to reduce the risk of becoming clogged when sucking up liquids, as can easily happen with fine filters if they are wetted.

Clearly, for a given fan power and air flow, the larger the bag or filtering area, the finer or less porous the filter needs to be, and thus the advantage in this respect lies with upright cleaners, but the commensurate disadvantage is they they are necessarily large, bulky and can be inconvenient to use and manoeuvre.

In order to reduce the aforementioned problems, compromises and costs of filter replacement, the present invention provides a portable suction cleaner comprising a motor to drive an impeller in a housing to propel a flow of air along a flow path within the housing via filter means in the housing, which is characterised in that: (a) the flow path extends or is extended to run from an inlet to an outlet proximal to the inlet so that at least a proportion of said flow is recirculated through the flow path.

Said proportion is preferably a major part of the flow.

The inlet may surround the outlet, and an array of bristles preferably projects downwards along the outer periphery of the inlet. The inlet and outlet are preferably disposed on the underside of the housing, but alternatively a double hose extension may be connected to the body to connect the inlet and outlet flows to a double nozzle which provides the inlet and outlet, and optionally the array of bristles around the inlet.

The cross-sectional flow area of the inlet is preferably arranged so as to be commensurate with that of the outlet so that the vertically acting forces arising in use do not lift the cleaner or nozzle from the floor nor suck the cleaner or nozzle down onto the floor with excessive force.

The present invention further provides a suction cleaner comprising a motor to drive an impeller in a housing to propel a flow of air along a flow path within the housing via filter means in the housing, which is characterised in that: (a) the filter means comprises a feed filter-web store, filter web advance means to draw filter-web from the store to expose fresh portions of the web to the flow path, and to convey used portions of the web to a used filter-web store in the housing to receive used filter-web and deposits thereon.

The filter-web advance means is preferably of automatic form, but may be manually actuated. The automatic form of said means preferably comprises a mechanism responsive to pressure differential between inlet and outlet portions of the air flow, i.e. the pressure differential across the filter means. This pressure differential is a function of the loading or clogging of the filter means.

The advance means preferably comprises a perforate drum located in an opening in the flow path to support the web so that it obscures or occupies said opening.

Said mechanism preferably comprises a pawl movable, against a return bias, by a diaphragm device, and a ratchet wheel associated with the drum.

The filter-web is preferably a roll of fibrous web material commonly sold a "kitchen tissue" or "toilet tissue" or a like porous paper-like web which is relatively inexpensive, and which is preferably adapted to be separated easily into lengths.

Further, according to a first improvement of the invention, the recirculation of air in a recirculating suction cleaner is directed so as to form an air knife which impinges on the floor to direct particles of matter from the floor into the inlet.

In a second improvement a rotary brush is located in the inlet, to engage the floor, and the recirculation of air is directed as an elongate jet onto the brush to cause the brush to rotate and sweep the floor.

The first and second improvements may be combined, and a manually movable air flow controlling member may be provided to selectively control the recirculation flow to provide either the knife or the jet.

The present invention further provides a suction cleaner in which the air sucked into an inlet of the cleaner is filtered by a main filter or filter means and then split into a recirculation flow portion which is fed back to the inlet and a discharge portion which is fed to a discharge filter of a porosity which is finer than that of the filter means or main filter and which is designed to remove particles down to a sub-micron level.

The main filter is preferably designed to remove coarser particles, so that substantially only some particles down to sub-micron levels remain to be removed by the discharge filter.

The splitting of the flow from the main filter ensures that a good suction flow through the inlet is maintained and at the same time reduces the effect of the flow resistance of the discharge filter increasing, in that the inlet flow increases with the reduction in the discharge flow. The discharge filter preferably has a filter area of the same order of magnitude as that of the main filter.

The first improvement of the invention is preferably employed in conjunction with a main filter of self-renewing form, i.e. a main filter in which portions of the filter web are advanced to a filtering position and, when they become laden with particles, are further advanced to a used filter receptacle.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings in which the figures schematically represent the internal arrangements of suction cleaners in accordance with the invention; in which drawings: FIGURE 1 shows a first embodiment; FIGURE 2 shows a second embodiment, and FIGURE 3 shows an enlarged detail of FIGURE 2.

In both of the embodiments the suction cleaner comprises a housing 10 having a substantially rigid frame and chassis lower part 11 and a lid-like upper part 12 attached to the housing 10 by a hinge 13. The lower part 11 is shaped to provide a store in the form of a cradle 14 for a roll 14A of tissue which serves as a filter-web 15 when extended over a perforate winding drum 16 disposed in an opening in a partition 17 in the lower part 11; and is shaped to receive a further store in the form of a receptacle 18 to be disposed below the drum 16 to receive used portions 19 of the web. The partition 17 extends to define a low pressure chamber 20 within the housing.

The chamber 20 houses a motor 21 and an air pump 22 having an impeller 22A driven by the motor 21. The motor 21 has ducts (not shown) in FIGURE 1 which are vented to atmosphere so that it can be cooled by external clean air.

The chamber 20 also houses web advance means of an automatic form comprising a pawl device 23 in which a pawl 24 is biased by a spring 24A about a pivot 25 on a pawl shift member 26 so as to engage a ratchet wheel 27 on the drum 16, which member 26 is connected to a diaphragm 28 in a differential pressure chamber 29 which houses a return bias spring 30 on one side of the diaphragm 28. The chamber 29 on the other side of the diaphragm has a duct 29A which extends through the partition to a suction pressure zone within the housing, which zone is pneumatically separated from the chamber 20 by the air pump 22. The chamber 20 terminates at the pump 22.

In the first embodiment, air pumped from the chamber 20 is discharged via a downwardly open outlet 32 surrounded peripherally by a skirt 33 on the partition 17, and the outlet 32 is also surrounded peripherally by an encircling inlet 34.

In the second embodiment, air pumped from the chamber 20 is discharged into a plenum 32A bounded by a skirt 33A on the partition 17 and a bottom l0A, which also forms a support for a discharge filter 50 and defines part of a discharge outlet 51. An elongate non-encircling air inlet 34A is disclosed at one end of the housing. An air recirculation outlet 52 is disposed immediately adjacent to one side of the air inlet 34A, and is provided with an air flow control member 53. A rotary cylindrical brush 54 is disposed in the inlet 34A.

In both embodiments, the inlet 34,34A leads to a dust conveying zone 31 via which dust laden air is conveyed to the filter and from which the filtered air enters the chamber 20 after passing through the filter-web 15 and the perforate drum 16. As the filter-web 15 removes particles from the flow of air, its resistance to flow will increase thus increasing the differential pressure across the diaphragm 28 which responds by shifting the pawl device 23 against the return bias provided by the spring 30 so that the pawl 24 steps anticlockwise around the wheel 27 by one or more teeth. Then, when the motor is switched off, the pressure in the suction pressure zone and chamber 20 will equalise allowing the spring 30 to drive the pawl device bodily to the left, thus causing the pawl to shift the wheel and drum in a clockwise direction to pull a fresh length of web 15 from the roll 14A, to expose fresh web on the drum and to shift some of the used portion 19 of tissue with dust thereon into the receptacle 18.

The upper part 12 is provided with a window 35, so that the user can view the web 15 and ascertain visually when the receptacle 18 needs to be emptied. Releasable retaining means is provided to retain the parts 11 and 12 in a closed together condition (in which they are depicted), and to allow the part 11 to be swung upwards about the hinge 13 to expose the roll 14A, the web 15, portion 19 and receptacle 18, whereby to enable the user to tear the web 15 and empty the receptacle and thereafter to draw fresh tissue from the roll 14A and drape it over the drum 16.

In the first embodiment the outlet 32 and inlet 34 have approximately equal floor covering areas whereby to bring the resultant pressure induced vertical forces on the cleaner into near equality, so that the cleaner is not forcibly sucked down onto the floor and the proximity of the skirt 33 to the floor results in a high velocity flow thereunder and a substantial pressure differential between the inlet and the outlet, in order to drive dust and particles from the floor into the inlet 34.

However, this, under some circumstances can give rise to a transient condition in which some of the high velocity flow can escape past the inlet blowing the surface dirt away from the inlet.

To reduce the risk of such transient conditions arising, an array of flexible bristles 41 is provided on the body around the inlet 34.

In the second embodiment, the suction flow to the inlet 34A is always greater than the return (recycle) flow by the amount of the discharge flow, thus greatly reducing the risk of said transient conditions arising and reducing the unwanted effects thereof.

Referring to FIGURES 2 and 3, the discharge flow enters a discharge filter chamber 55 over the filter 50 via a flow control opening 56 in the skirt 33A, from the plenum 32A. The return flow can be directed by the member 53 being placed in an "up" position (FIGURE 2) to produce an air knife" (arrow A) directed towards the floor below the brush 54 which is carried by a support 57 on which the member 53 is carried. The support is also movable to a "down" position (FIGURE 3) in which the member 53 abuts the bottom 10A to shut off the air knife and opens a turbine jet gap between itself and a tapered extension 58 of the skirt 33A, which causes the return flow (arrow B) to impinge on the brush 54 (also lowered to abut the floor) so that the brush rotates. In the lowered "down" position the brush may rest or ride on the floor so that it can rise over any object covered by the inlet, and in so doing will cause the air knife to come into operation to impinge on said object.

This rotary brush arrangement, greatly further reduces the risk of return air escaping from the area bounded by the bristles 41.

When the bin 18 is removed, the filter 50 can be pulled upwards for removal and replacement. The filter is supported by a perforate screen 59. The opening below the bin 18 is sealed by a sealing ring 60.

FIGURE 2 also shows that the motor 20 draws fresh air in through a cooling duct 43 and discharges the air into the filter chamber 55 via a duct 44.

The invention is not confined to details of the foregoing examples, and many variations and modifications are possible within the scope of the invention.

For instance, the web of tissue may be a concertina stack instead of a roll, and the web advance means may include a limit switch 40, actuable by the pawl device 23 to switch off the motor when the pawl device has been moved to the right (in the drawing) into a predetermined limit position so that subsequent pressure equalisation advances the filter web and allows the switch to reset and restart the motor 21. The housing 10 may be wholly or partially supported by gliders, castors, wheels or rollers. The array of bristles 41 also serves as a brush to detach fibres, e.g. from a carpet. In both embodiments the margins of web may be pressed against the drum by guides, e.g. spring foils mounted on the lid 12, and the margins of the drum may be imperforate and provided with end seals, to avoid air bypassing the filter.

The releasable retaining means may comprise catches or detent formations on the housing, or magnetic elastomeric strips 42 on the parts 11 and 12. The air pump 22 may comprise a plurality of stages each including an impeller.

The cleaner may further comprise a hose assembly, which, preferably, comprises, for example, a nozzle, which functionally replicates the inlet and recirculation air outlet, a double hose for suction supply and return air flows, and a connector to connect the hose to the inlet 34 and outlet 32 and, except for the flows to and from the hose, to blank off the inlet and outlet 34/32 of the first embodiment. A functionally equivalent hose assembly may be provided for the second embodiment, which may be suitably adapted, e.g. by providing a return air connector to the chamber 32A.

The housing and partition may be formed as an integral plastics moulding or an assembly of plastics mouldings.

The invention further includes and provides a cleaner having any novel part, functional arrangement of parts and/or operational feature disclosed herein or in the accompanying drawing, and/or any novel mechanical or functional equivalent thereof.

Claims (15)

1. A portable suction cleaner comprising a motor to drive an impeller in a housing to propel a flow of air along a flow path within the housing via filter means in the housing, which is characterised in that: (a) the flow path extends or is extended to run from an inlet to an outlet proximal to the inlet so that at least a proportion of said flow is recirculated through the flow path.

2. A cleaner as claimed in Claim 1 wherein said portion is a major part of the flow.

3. A cleaner as claimed in Claim 1 or 2 wherein an array of bristles projects downwards along the outer periphery of the inlet.

4. A cleaner as claimed in Claim 1, 2 or 3 wherein a part of the flow which is not recirculated is fed to a discharge outlet via a discharge filter.

5. A suction cleaner in which the air sucked into an inlet of the cleaner is filtered by a main filter or filter means and then split into a recirculation flow portion which is fed back to the inlet and a discharge portion which is fed to a discharge filter of a porosity which is finer than that of the filter means or main filter and which is designed to remove particles down to sub-micron level.

6. A cleaner as claimed in Claim 5 wherein the filter means or main filter is designed to remove coarse particles, so that substantially only some particles down to sub-micron levels remain to be removed by the discharge filter.

7. A cleaner as claimed in Claim 4, 5 or 6 wherein the discharge filter has a filter area of the same order of magnitude as that of the filter means or main filter.

8. A cleaner as claimed in Claim 4, 5, 6 or 7 wherein the filter means or main filter is of self-renewing form, i.e. a main filter in which portions of the filter web are advanced to a filtering position and, when they become laden with particles, are further advanced to a used filter receptacle.

9. A suction cleaner comprising a motor to drive an impeller in a housing to propel a flow of air along a flow path within the housing via filter means in the housing, which is characterised in that: (a) the filter means comprises a feed filter-web store, filter web advance means to draw filter-web from the store to expose fresh portions of the web to the flow path, and to conveying used portions of the web to a used filter-web store in the housing to receive used filter-web and deposits thereon.

10. A cleaner as claimed in Claim 9 wherein the filterweb advance means is of automatic form.

11. A cleaner as claimed in Claim 9 or 10 wherein the automatic form of said means comprises a mechanism responsive to pressure differential across the filter means

12. A cleaner as claimed in Claim 9, 10 or 11 wherein the advance means comprises a perforate drum located in an opening in the flow path to support the web so that it obscures or occupies said opening.

13. A cleaner as claimed in Claim 9, 10, 11 or 12 wherein said mechanism comprises a pawl movable, against a return bias, by a diaphragm device, and a ratchet wheel associated with the drum.

14. A cleaner as claimed in any preceding claim having a rotary brush in the inlet which is driven to rotate by the recirculated air flow.

15. A portable suction cleaner substantially as hereinbefore described with reference to FIGURE 1, FIGURE 2 or FIGURES 3 and 4 of the accompanying drawings.