Sweeper pickup head

Abstract

A sweeper having an air-assist pickup head in which the exhaust chamber is bounded on three sides by a secondary exhaust chamber. A primary exhaust line extends from the primary exhaust chamber to a debris collecting plenum. A secondary exhaust line extends from the secondary exhaust chamber and joins the primary exhaust line through a small orifice located just ahead of the debris plenum. The secondary exhaust chamber is completely bounded by walls which extend to the surface being cleaned so that the secondary chamber is reasonably well sealed both from the primary exhaust chamber and from the atmosphere. When the pickup head passes over deviations in the surface being cleaned, however, air and dust leaking out through such deviations from the primary exhaust chamber are captured within the secondary exhaust chamber and exhausted to the debris plenum. Air is recirculated from the debris plenum to the pickup head through an air delivery line. A portion of the recirculated air is bled off from the air delivery line through a filter positioned above the pickup head. A chute extends from the filter housing to the pickup head so that collected dust can be shaken off of the filter element downwardly into the pickup head.

Description

BACKGROUND OF THE INVENTION

The present invention relates to sweepers and pick-up heads for sweepers. It is particularly pertinent with respect to sweepers having air-assist pickup heads.

Air-assist pickup heads deliver air under pressure to an exhaust chamber. The air under pressure sweeping over the surface being cleaned tends to loosen debris which is then exhausted through an exhaust line joined to the exhaust chamber. A sweeper having a pickup head of this type is disclosed in U.S. Pat. No. 3,512,206, issuing to Mr. B. W. Young on May 19, 1970, the disclosure of which is hereby incorporated by reference. The exahust chamber is enclosed on all sides with the front wall being a flexible flap so that debris and the like can pass thereunder and into the exahust chamber.

One problem with air-assist pickup heads is that when they pass over deviations in the surface being cleaned, such a potholes and the like, the air being blasted into the exhaust chamber tends to blast dust outwardly underneath the walls of the chamber through the gap provided by the deviations. As a result, sweepers of this nature tend to kick up too much dirt.

One prior art device provides a pressure chamber within the exahust chamber so that air delivered to the pickup head tends to be guided directly from the air delivery conduit to the exhaust conduit by the walls of the pressure chamber. Some air is allowed to flowout into the exhaust chamber underneath a forward wall of the pressure chamber, the forward wall of the pressure chamber being located generally in the middle of the exhaust chamber. The area of the exhaust chamber both in front of and behind the pressure chamber are also in flow communication with the exhaust line through which air in the pressure chamber is exhausted. The effectiveness of this device for stirring up and picking up dust and debris and the effectiveness of this device for purposes of controlling dust are not known. However, to the extent that a portion of the exhaust chamber is positioned behind the pressure chamber, the effectiveness of the exhaust chamber ahead of the pressure chamber is diluted. Further, since the exhaust chamber is in flow communication with the central pressure chamber, the relative vacuum within the exhaust chamber will still be substantially diluted by the air introduced under pressure so that air which leaks out of the pressurized chamber when the pickup head passes over diviations will still tend to leak out under the walls of the surrounding exhaust chamber, thereby kicking up dust.

Another dust problem associated with air-assist pickup heads is created by the bleed-off sometimes employed in such devices. In order to sensure that a slight vacuum exists in the pickup head, a portion of the air being returned by the blower through the air delivery line to the pickup head is bled off to the atmosphere. However, the blower does tend to recicrulate dust as well as air. Accordingly, the bleed-off air tends to carry dust into the atmosphere.

SUMMARY OF THE INVENTION

In the present invention, a secondary exhaust chamber, open at the bottom, is positioned adjacent the primary exhaust chamber, and sealing means are provided at the periphery of the secondary chamber for generally sealing the secondary chamber from the primary exhaust chamber and from the atmosphere when the pickup head is in its normal operative position. Air delivery means and air exhaust means are provided in flow communication with the primary exhaust chamber. A secondary exhaust line is operably joined to the secondary exhaust chamber and to the exhaust means. Becuase the secondary exhaust chamber is generally sealed with respect to the atmosphere and with respect to the primary exhaust chamber, there is normally very little flow of air into the secondary exhaust chamber and through the secondary exhaust line. However, when the pickup head passes over deviations in the surface being cleaned, air and dust escaping out of the primary exhaust chamber are generally captured within the secondary exhaust chamber and are exhausted through the secondary exhaust line. In this way, the extent to which dust escapes into the atmosphere is substantially minimized.

Dust escaping with bleed-off air is controlled by connecting a bleed-off line from the air delivery conduit to a filter. Preferably, the bleed-off line extends from the air delivery line just ahead of the juncture of the air delivery line with the pickup head. In order to minimize problems with clogging filters, the filter is positioned above the pickup head and a chute connects the filter to the pickup head such that dust collecting in the filter can be shaken down through the chute and into the pickup head for return to the debris plenum chamber of the sweeper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a sweeper made in accordance with the present invention;

FIG. 2 is a top plan view of the pickup head for the sweeper shown in FIG. 1;

FIg. 3 is a cross-sectional view taken along plane III--III of FIG. 2;

FIG. 4 is a cross-sectional view taken along IV--IV of FIG. 2;

FIG. 5 is a fragmentary side elevational view of the sweeper of the present invention;

FIG. 6 is a fragmentary cross-sectional view taken generally along plane VI--VI of FIG. 5;

FIG. 7 is an enlarged fragmentary side-elevational view of the sweeper taken on the side opposite the side shown in FIG. 5; and

FIG. 8 is a cross-sectional view of the bleed-off filter.

PREFERRED EMBODIMENT

In the preferred embodiment, the sweeper 1 has a pickup head 2 (FIG. 1) which includes a primary exhaust chamber 10 bounded on three sides by a secondary exhaust chamber 20 (FIGS. 2 and 4). An air delivery line 35 delivers air under pressure to an air distribution chamber 40 in the top of pickup head 2. Distribution chamber 40 distributes the air generally along the length of pickup head 2 and delivers it into primary exhaust chamber 10 through an air-blast slot 50. A primary exhaust line 60 exhausts air from the primary exhaust chamber 10 and into a debris plenum chamber 70 (FIGS. 2 and 5). Air is both exhausted from pickup head 2 and delivered to pickup head 2 by means of a blower which is not shown.

A secondary exhaust line 80 extends from secondary exhaust chamber 20 and is joined to primary exhaust line 60 through a small orifice 90 located just ahead of debris plenum chamber 70 (FIGS. 4, 5 and 6). The various walls of secondary exhaust chamber 20 (e.g. numbers 13, 23 and 25 of FIGS. 3 and 4) extend to the level of the surface being cleaned so that secondary chamber 20 is generally sealed both from primary exhaust chamber 10 and from the atmosphere. Thus, very little air is exhausted through secondary exhaust line 80 until pickup head 2 passes over deviations in the surface being cleaned, in which case dust escaping underneath the walls of primary chamber 10 is generally captured within secondary exhaust chamber 20 and is exhausted through secondary exhaust line 80.

Air is bled off of air delivery 35 through a bleed-off line 100 to a filter 110 (FIGS. 7 and 8). Filter 110 is positioned above pickup head 2 and is joined to the primary exhaust chamber 10 by means of a chute 120. Dust collecting in the filter element 112 of filter 110 can be shaken downwardly through chute 120 into primary exhaust chamber 10 of pickup head 2.

Pickup head 2 includes a pair of spaced sheet metal sidewalls 11 and a sheet metal top wall which is bent to define a forward downwardly sloping top wall 14, a generally horizontal top wall 41, a downwardly extending back wall 42 and a rearwardly extending top wall 22 which extends rearwardly from the bottom edge rear wall 42 (FIGS. 2 and 4). The primary exhaust chamber 10 is bounded at its end by side walls 11 and at its top by top wall 14 and by a dividing partition 15 which divides primary exhaust chamber 10 from air distribution chamber 40. The rear of primary exhaust chamber 10 is closed by a downwardly extending flexible rear flap 13. Rear flap 13 is positioned just behind air-blast slot 50. The front of primary exhaust chamber 10 is closed by means of a pair of downwardly extending flexible front flaps 12. Flaps 12 and 13 are made of a flexible material such as rubber or the like. The flexibility in front flaps 12 allows larger pieces of debris and the like to pass thereunder and into exhaust chamber 10.

The secondary exhaust chamber 20 is divided into three parts, a rear compartment 21 and a pair of spaced side compartments 24 (FIGS. 2, 3 and 4). Rear compartment 21 is bounded at the front by rear flap 13 of primary exhaust chamber 10. Rear compartment 21 is bounded at its rear by a downwardly projecting flexible rear flap 23. Both of these flaps are sufficiently long that they normally engage the surface being cleaned when pickup head 2 is in its operative position. Because of their flexibility, these flaps also tend to continuously engage the surface even as one passes over irregularities. The top of rear compartment 21 is closed by top wall 22. Each end of rear compartment 21 is closed by a portion of side wall 11 which projects beyond rear flap 13 and terminates and by the inside wall 25a of side compartments 24. Rear flap 13 and rear flap 23 extend continuously between these end defining walls.

The side compartments 24 are in flow communication with rear compartment 21 through a rectangular shaped communicating aperture 30 in each inside end wall 25a. Each side compartment 24 is defined by a pair of spaced side walls, inside wall 25a and outside wall 25, joined together by means of a generally U-shaped spacer 26. U-shaped spacer 26 includes a top wall 27 and a downwardly depending end wall 28 at each end thereof, the end walls 28 extending to the same level as do the side walls 25 and 25a. Suitable bolts 29 or the like extend through the side walls 25 and 25a and spacer 26 to thereby hold the entire assembly together. The side walls 25 and 25a are made of a sturdy material such as wood since they serve not only to bound side compartments 24, but also serve as shoes upon which the pickup head 2 rides on the surface which is being cleaned. The inside wall 25a of each side compartment 24 is provided with a plurality of vertically spaced adjustment holes 31 whereby each side compartment 24 is joined to a side wall 11 of pickup head 2 (FIG. 3). A pair of spaced bolts 32 pass through the holes 31 on one level and are threadedly received into a clamping bar 33. As the side walls 25 and 25a wear out through continued engagement with the surface being cleaned, one can relocate the side compartments 24 downwardly by passing bolts 32 through a higher set of holes 31.

Since the side walls 25 and 25a and end walls 28 of the side compartments 24 also extend downwardly to the surface being cleaned, the side compartments 24 as well as rear compartment 21 are generally sealed both with respect to the atmosphere and with respect to primary exhaust chamber 10. Accordingly, only a small amount of air tends to flow inwardly under the peripheral walls of secondary exhaust chamber 20 and through secondary exhaust line 80 which is connected thereto. Of course, it will be appreciated that this seal is by no means perfect even when pickup head 2 is resting on a perfectly smooth surface and is not moving. However, it is a sufficiently effective seal that only a slight amount of air is exhausted through exhaust line 80, except when pickup head 2 passes over deviations in the surface being cleaned. In the latter case, air or dust which leaks out from under the walls defining primary exhaust chamber 10 is generally captured within secondary exhaust chamber 20 and exhausted through secondary exhaust line 80. Becuase secondary exhaust line 80 is connected to primary exhaust line 60, air and dust will be drawn through secondary exhaust line 80 when pickup head 2 does pass over deviations. Yet, when the surface being cleaned is relatively smooth and the need for dust control is at a minimum, only a small amount of air will flow through secondary exhaust line 80 becuase of the tendency of secondary exhaust chamber 20 to be sealed with respect to primary exhaust chamber 10 and with respect to the atmosphere. In this way, the effective operation of primary exhaust chamber 10 is not diluted by a continual flow through the secondary exhaust line 80.

Air delivery line 35 comprises a flexible conduit approximately 6 inches in diameter joined to the output side of the blower means and to a suitable connecting sleeve at the top of pickup head 2. The point of connection is to top wall 31 and into air distribution chamber 40. Air distribution chamber 40 is defined by top wall 41, back wall 42 and the generally L-shaped partition 15 (FIG. 4). Air distribution chamber 40 extends generally the length of pickup head 2, except that it does terminate short of the point where exhaust line 60 is connected to pickup head 2. The end wall 43 of air distribution chamber 40 is shown in hidden lines in FIG. 2. Thus, air distribution chamber 40 does not interfere with the communication of exhaust line 60 with primary exhaust chamber 10.

Air distribution chamber 40 is open at its rear along its length to define an air blast slot 50 at the rear of primary exhaust chamber 10. A downwardly and forwardly inclined guide flap 51 sweeps the air in a forward direction generally horizontally underneath a forward guide flap 52 (FIG. 4). This sweeps the air forwardly into primary exhaust chamber 10.

Primary exhaust line 60 includes a conduit 61 of approximately 6 inches in diameter joined by a suitable connector sleeve to one end of pickup head 2 (FIG. 5). Exhaust line 60 is located at the end opposite end delivery line 35 so that air tends to sweep into one end of primary exhaust chamber 10 and across primary exhaust chamber 10 into primary exhaust line 60. Conduit 61 is connected at its other end to the upper portion 62 of exhaust line 60 by suitable connector sleeve. The upper portion 62 of exhaust line 60 is actually defined by sheet metal partitions. The upper portion 62 opens into the debris plenum chamber 70. A viewing port 65 can be opened to inspect primary exhaust line 60, particularly for purposes of making sure that orifice 90 has not been clogged.

Debris plenum chamber 70 is an enlarged debris collecting chamber in which the rapidly moving air coming through primary exhaust line 60 has a chance to expand and slow down. Dust and debris settle out into debris plenum chamber 70. Located on the opposite side of debris plenum chamber 70 is the blower which is not shown in the drawings. This blower maintains a vacuum within debris chamber 70 and thereby maintains an exhausting flow of air through primary exhaust line 60.

Secondary exhaust line 80 comprises a flexible conduit joined at one end by means of a suitable connector sleeve to generally the center of the rear compartment 21 of secondary exhaust chamber 20 (FIG. 5). At its upper end, the conduit is joined to a metal connector sleeve 82 which in turn is fastened onto the upper portion 62 of primary exhaust line 60. Secondary exhaust line 80 is preferably a conduit of approximately 3 inches in diameter. This allows air to move readily through secondary exhaust line 80. Yet, orifice 90 is preferably only about one-third the diameter of secondary exhaust line 80, or approximately 1 inch in diameter. This combination of a larger secondary exhaust line 80 with a smaller diameter orifice 90 allows air and dust to flow freely through primary exhuast line 60, but without substantially diluting the exhausting force of primary exhaust line 60. While no precise theory can be formulated for successful operation of this combination, it is believed that the ratio of the diameter of the secondary exhaust line to the diameter of the orifice 90 should be approximately 3 to 1. Further, the primary exhaust line 60 should have a diameter of approximately 6 inches, or a relationship to secondary exhaust line 80 and orifice 90 of approximately 6 to 3 to 1.

In order to ensure that a smaller amount of air is delivered into pickup head 2 than is withdrawn, thereby ensuring a slightly negative pressure within primary exhaust chamber 10 with respect to the atmosphere, a small amount of air is bled off of air delivery line 35 through a bleed-off line 100 (FIGS. 4 and 7). Preferably, bleed-off line 100 joins air delivery line 35 at a point just upstream or ahead of the juncture of air delivery line 35 with pickup head 2. At this point, the air which is bled off of air delivery line 35 will be as clean as possible, most of the dust and debris having settled out in debris plenum chamber 70.

To further control dust emission, bleed-off line 100 is joined to the bottom of filter 110 (FIGS. 7 and 8). Bleed-off line 100 constitutes a flexible conduit of approximately 2 inches in diameter. It is joined to connector sleeve 101 on air delivery line 35 and to a suitable connector sleeve at the bottom of filter 110.

Filter 110 comprises a housing 111 having a filter element 112 mounted therein (FIG. 8). Housing 111 is formed of metal or the like. Filter element 112 comprises a plurality of cloth sleeves 113 with adjacent sleeves being sewn togehter along their bottom edges. The sleeves 113 are suspended at their top on a carriage rod 114 which passes through the top of housing 111. Carriage rod 114 is mounted in oversized holes and includes a handle 117 projecting upwardly through the top of housing 111. One can grasp handle 117 and move carriage rod 114 up and down, thereby shaking filter element 112. Housing 111 has a sloped bottom floor 116 such that dust which is shaken out of filter element 112 tends to fall down the sloped floor 116 and into chute 120 which joins housing 110 at the bottom of sloped floor 116. The side walls of housing 111 include vent apertures 115 such that air tends to flow into housing 110 and upwardly through the sleeves 113 of filter element 112 and out through vent apertures 115.

Chute 120 is a flexible conduit which extends downwardly from the bottom of housing 110 and which is joined to a connector sleeve 123 in top wall 14 of primary exhaust chamber 10 (FIGS. 2, 4 and 7). During the operation of the sweeper 1, the operator occasionally shakes filter element 112 by grasping handle 117 and shaking it up and down. This causes collected dust to fall downwardly through chute 120 into primary exhaust chamber 10 where it is exhausted through primary exhaust line 60 back into debris collecting plenum chamber 70.

OPERATION

In operation, pickup head 2 is lowered until the walls 25 and 25a engage the surface to be cleaned. The blower is activated and sweeper 1 is driven over the surface to be cleaned. Air is blasted into primary exhaust chamber 10 through air-blast slot 50. This loosens dust and debris to be cleaned and sweeps them down toward the end of primary exhaust chamber 10 adjacent primary exhaust line 60. Dust and debris are exhausted upwardly through primary exhaust line 60 into debris collecting plenum chamber 70. Dust and debris tend to settle out of the air and debris plenum chamber 70 and the air is then blown back through air delivery line 35 into air distribution chamber 40 and back through air blast slot 50.

When pickup head 2 passes over deviations in the surface to be cleaned, the escaping air and dust are gnerally captured within either of the side compartments 24 or rear compartment 21 of secondary exhaust chamber 20. Most of the escaping dust will escape underneath rear flap 13 into rear compartment 21. This air and dust is drawn upwardly through secondary exhaust line 80, through the smaller orifice 90 and into primary exhaust line 60 just ahead of debris collecting planum chambers 70. In this manner, the amount of dust escaping from pickup head 2 is minimized. That dust which escapes into either side of chamber 24 will be drawn through aperture 30 in inside wall 25a, into rear compartment 21 and then through secondary exhaust line 80.

Dust control of bleed-off air is affected in that the bleed-off air passes through bleed-off line 100 into filter 110. In order to prevent the filter element 112 of filter 110 from clogging, the operator occasionally shakes it by grasping handle 117 and moving it up and down. This shakes the dust loose and cuases it to fall downwardly onto sloped bottom floor 116 and into chute 120. The dust travels through chute 120 downwardly into primary exhaust chamber 10 where it is again exhausted through primary exhaust line 60.

Of course, it will be understood that the above is merely a preferred embodiment of the invention and that various changes and alterations can be made without departing from the spirit and broader aspects of the invention.

Claims

The embodiments of the invention in which an exlusive property or privilege is claimed are defined as follows:

1. A surface cleaning apparatus including a pickup head, said apparatus comprising: said pickup head having a first chamber and a second chamber, said second chamber being adjacent said first chamber; said first chamber being open at the bottom; air delivery means in flow communication with said first chamber of said first and second chambers only; air exhaust means in flow communication with said first chamber; said second chamber being open at the bottom and including sealing means at the periphery of said second chamber for generally sealing said second chamber from said first chamber and from the atmosphere when said pickup head is in an operative position whereby the flow of air through said second chamber is normally minimal; a secondary exhaust line operably joining said second chamber to said exhaust means at a point substantially downstream from said first chamber whereby when said pickup head passes over a deviation in the surface being cleaned, air and dust escaping out of said first chamber are generally captured in said second chamber and exhausted through said secondary exhaust line.

2. The apparatus of claim 1 including: said exhaust means including a primary exhaust line in flow communication with a blower; said secondary exhaust line being operably connected to said primary exhaust line at a point substantially downstream from the juncture of said primary exhaust line with said first chamber.

3. The apparatus of claim 2 comprising: a plenum chamber for collecting debris; said primary exhaust line exhausting into said plenum chamber; said secondary exhaust line being joined to said primary exhaust line just ahead of said plenum chamber.

4. The apparatus of claim 3 comprising: said secondary exhaust line being of a sufficiently large diameter that air flows relatively easily theretrhough; said secondary exhaust line being joined to said primary exhaust line through an orifice, said orifice being of a smaller diameter than the diameter of said secondary exhaust line whereby dilution of the exhausting force through said primary exhaust line is minimized and whereby just enough exhausting force is maintained in said second chamber to effect dust control when said pickup head passes over deviations in the surface being cleaned.

5. The apparatus of claim 3 in which said secondary exhaust line is joined to said primary exhaust line through an orifice whose diameter is smaller than the diameter of said secondary exhaust line; the ratio of the diameter of said secondary exhaust line to the diameter of said orifice being approximately 3 to 1.

6. The apparatus of claim 5 in which the diameter of said secondary exhaust line is approximately 3 inches and the diameter of said orifice is approximately 1 inch.

7. The apparatus of claim 5 in which the ratio of the diameter of said primary exhaust line to said orifice is approximately 6 to 1.

8. The apparatus according to claim 7 in which the diameter of said primary exhaust line is approximately 6 inches, the diameter of said secondary exhaust line is approximately 3 inches and the diameter of said orifice is approximately 1 inch.

9. The apparatus of claim 3 in which said second chamber bounds said first chamber on three sides of said first chamber; said first chamber being closed at the front by a generally flexible flap whereby said first chamber is generally sealed with respect to the atmosphere but whereby debris can pass into said first chamber underneath said generally flexible flap.

10. The apparatus according to claim 9 in which said second chamber includes a rear portion at the rear of said first chamber and a side portion at each of the sides of said first chamber; said secondary exhaust line being joined to said second chamber generally at the center of the rear portion of said second chamber.

11. The apparatus according to claim 10 in which said side portions of said second chamber comprise a pair of plates joined to the opposite sides of a generally U-shaped spacer, one of said plates including an aperture therein whereby said side portions of said second chamber communicate with said rear portion thereof.

12. The apparatus of claim 10 in which said air delivery means includes a slot in said first chamber through which air is delivered, said slot being positioned immediately adjacent said rear portion of said second chamber.

13. The apparatus of claim 2 comprising: said secondary exhaust line being of a sufficiently large diameter that air flows relatively easily therethrough; said secondary exhaust line being joined to said primary exhaust line through an orifice, said orifice being of a smaller diameter than the diameter of said secondary exhaust line whereby dilution of the exhausting force through said primary exhaust line is minimized and whereby just enough exhausting force maintained in said second chamber to effect dust control when said pickup head passes over deviations in the surface being cleaned.

14. The apparatus of claim 2 in which said secondary exhaust line is joined to said primary exhaust line through an orifice whose diameter is smaller than the diameter of said secondary exhaust line; the ratio of the diameter of said secondary exhaust line to the diameter of said orifice being approximately 3 to 1.

15. The apparatus of claim 14 in which the ratio of the diameter of said primary exhaust line to said orifice is approximately 6 to 1.

16. The apparatus according to claim 15 in which the diameter of said primary exhaust line is approximtely 6 inches, the diameter of said secondary exhaust line is approximately 3 inches and the diameter of said orifice is approximately one inch.

17. The apparatus of claim 1 in which said second chamber bounds said first chamber on three sides of said first chamber; said first chamber eing closed at the front by a gnerally flexible flap whereby said first chamber is generally sealed with respect to the atmosphere but whereby debris can pass into said first chamber underneath said generally flexible flap.

18. The apparatus of claim 1 in which said air delivery means includes an air delivery line connected with said pickup head; a bleed-off line joined to said air delivery line for bleeding of a portion of the air passing through said air delivery line beofre it reaches said pickup head; a filter on said bleed-off line, said filter being positioned above said pickup head; a chute joining said filter with said pickup head whereby dust collected in said filter can fall down through said chute into said pickup head.

19. The apparatus of claim 18 in which said apparatus includes means for shaking said filter whereby dust which has collected therein can be loosened by shaking so that it falls downwardly through said chute into said pickup head.

20. The apparatus of claim 1 in which said air delivery means includes an aperture in said first chamber through which air is delivered, said aperture being positioned immediately adjacent said second chamber.

21. A surface cleaning apparatus including a pickup head, said surface cleaning apparatus comprising: said pickup head including first and second chambers; said first chamber having peripheral wall means generally enclosing said first chamber, said first chamber being open at the bottom; air delivery means in flow communication with said first chamber of said first and second chambers only for delivering air under pressure into said first chamber; exhaust means in flow communication with said first chamber for exhausting air, duct and the like therefrom; said second chamber being adjacent said first chamber; said second chamber being open at the bottom and having peripheral wall means extending around the entire periphery thereof and extending downwardly generally to the surface being cleaned when said pickup head is in an operative position for generally sealing said second chamber from said first chamber and from the atmosphere whereby the flow of air through said second chamber is normally minimal; a secondary exhaust line operably connecting said second chamber with said exhaust means at a point substantially downstream from said first chamber whereby when said pickup head passes over a deviation in the surface being cleaned, air and dust escaping out of said first chamber are generally captured in second chamber and exhausted through said secondary exhaust line.

22. The apparatus of claim 21 including: said exhaust means including a primary exhaust line in flow communication with a blower; said secondary exhaust line being operably connected to said primary exhaust line at a point substantially downstream from the juncture of said primary exhaust line with said first chamber.

23. The apparatus of claim 22 comprising: a plenum chamber for collecting debris; said primary exhaust line exhausting into said plenum chamber; said secondary exhaust line being joined to said primary exhaust line just ahead of said plenum chamber.

24. The apparatus of claim 23 comprising: said secondary exhaust line being of a sufficiently large diameter that air flows relatively easily therethrough; said secondary exhaust line being joined to said primary exhaust line through an orifice, said orifice being of a smaller diameter than the diameter of said secondary exhaust line whereby dilution of the exhausting force through said primary exhaust line is minimized and whereby just enough exhausting force is maintained in said second chamber to effect dust control when said pickup head passes over deviations in the surface being cleaned.

25. The apparatus of claim 24 in which said second chamber bounds said first chamber on three sides of said first chamber; said first chamber being closed at the front by a generally flexible flap whereby said first chamber is generally sealed with respect to the atmosphere but whereby debris can pass into said first chamber underneath said generally flexible flap.

26. The apparatus of claim 21 in which said second chamber bounds said first chamber on both sides and the rear of said first chamber; said first chamber being closed at the front by a generally flexible flap whereby said first chamber is generally sealed with respect to the atmosphere but whereby debris can pass into said first chamber underneath said generally flexible flap.

27. The apparatus of claim 26 in which said air delivery means includes a slot in said first chamber through which air is delivered, said slot being positioned immediately adjacent said rear portion of said second chamber.

28. The apparatus of claim 21 in which said air delivery means includes an air delivery line connected with said pickup head; a bleed-off line joined to said air delivery line for bleeding off a portion of the air passing through said air delivery line before it reaches said pickup head; a filter on said bleed-off line, said filter being positioned above said pickup head; a chute joining said filter with said pickup head whereby dust collected in said filter can fall down through said chute into said pickup head.

29. The apparatus of claim 28 in which said apparatus includes means for shaking said filter whereby dust which has collected therein can be loosened by shaking so that it falls downwardly through said chute into said pickup head.

30. The apparatus of claim 21 in which said air delivery means includes an aperture in said first chamber through which air is delivered, said aperture being positioned immediately adjacent said second chamber.