VACUUM CLEANER WITH POWDER COLLECTION VESSEL WITH A SCALED SIDE WALL TECHNICAL FIELD The present invention relates in general terms to the field of equipment for the care of floors and more particularly to a vacuum equipped with a dust collection container having a wall Side step that offers a greater cleaning efficiency. BACKGROUND OF THE INVENTION A vacuum cleaner is an electromechanical device used to dry remove dust, dirt and other small residues of carpets, rugs, fabrics and other surfaces in domestic, commercial and industrial environments. To achieve the desired removal of dust and grime, most vacuum cleaners incorporate a rotary agitator. The rotary shaker is provided to shake off dust and debris from the carpet or mat while a pressure drop or vacuum is used to bring the entrained air with this dust or debris into the vacuum cleaner nozzle. The air charged with particles is then attracted to a dust collection container. The air is then pulled through a filter before being directed through the motor of the suction generator to provide cooling. Finally, the air is filtered to remove the fine particles of carbon coming from the brushes of this engine or another type of dirt that can remain in the air stream before being expelled to the environment. Frequently the dust collection container is designed to produce a cyclonic air flow by causing this container to have a powder chamber with a cylindrical side wall and a tangentially directed air inlet. This arrangement forces the air to produce eddies around the dust collection chamber in the form of a cyclone. The centrifugal force produced in this way causes the debris and dust to move towards the cylindrical side wall of the chamber and come in contact with it while the relatively clean air can be extracted from the center of the chamber through a pre-filter towards the chamber. main filter and towards the suction generator. In most operating conditions, most or all of the dust and debris in the air stream is removed through a cyclonic airflow. Sometimes, however, some dust and debris remains trapped in the airstream. Typically, this powder and these residues are relatively thin particles of light weight that are not susceptible to the centrifugal separation force produced by the cyclonic air flow. However, larger debris is sometimes entrained and clogs some of the airflow openings provided in the prefilter. In a circumstance of this type, the cleaning efficiency of the vacuum cleaner becomes affected. The present invention relates to a vacuum cleaner equipped with a dust collection container having a stepped side wall. The stepped side wall works to better separate the dust and debris from the air stream by preventing them from being pulled up into the dust collection chamber after settling to the bottom. As a result, the potential for dust and debris to be attracted to the intake openings or airstream of the prefilter is greatly reduced or eliminated. Therefore the vacuum operates with a peak cleaning efficiency all the time. COMPENDIUM OF THE INVENTION In accordance with the purposes of the present invention as described herein, an improved vacuum cleaner is offered. The vacuum includes a nozzle assembly with a suction inlet and a box assembly. A suction generator is located in one of the nozzle assembly and box assembly. Similarly, a dust collection container is located in one of the nozzle assembly and box assembly. The dust collection container includes a base wall, a side wall and a dust collection chamber. In addition, the dust collection container is characterized in that it has a side wall having a first cylindrical section with a circumference Ci and a second cylindrical section with a circumference C2 where Cx >; C2. In addition, the dust collection container is characterized in that it has a step connecting the first cylindrical section with the second cylindrical section. More specifically, when describing the invention, the circumference Ca is approximately 47.8 centimeters
(18.8 inches) and approximately 63.8 centimeters (25.1 inches). The circumference C2 is between approximately 39.9 centimeters (15.7 inches) and approximately 55.9 centimeters (22.0 inches). In addition, the first cylindrical section has a height Hi comprised between approximately 15.2 centimeters (6 inches) and approximately 17.8 centimeters (7 inches). The second cylindrical section has a height H2 comprised between about 12.7 centimeters (5 inches) and about 15.2 centimeters (6 inches). Together the circumference Ci and the height Ha define a volume Vi comprised between approximately 2,779 cubic centimeters (169.6 cubic inches) and approximately 5,767 cubic centimeters (351.9 cubic inches), while the circumference C2 and the height H2 define a volume V2 comprised between approximately 1,609 cubic centimeters (98.2 cubic inches) and approximately 3,784 cubic centimeters (230.9 cubic inches). In addition, the step has a width between the first cylindrical section and the second cylindrical section comprised between approximately 0.25 centimeters (0.1 inch) and approximately 6.4 centimeters (2.5 inches). In addition, a support is received concentrically in the first cylindrical section. The support is projected from the base wall. The support carries a pre-filter. The prefilter includes a third cylindrical section carrying an angular flange. The flange and the third cylindrical section are joined at a vertex V which defines an included angle A2 between about 135 and about 165 degrees. The vertex V is received concentrically within the second cylindrical section. In addition, the flange includes a straight continuous face. An annular space is provided between the flange and the end of the second cylindrical section. The space has a width between approximately 1.3 centimeters (0.5 inch) and approximately 6.4 centimeters (2.5 inches). In addition, a filter is provided in the dust collection chamber. The filter is carried in the prefilter. A lid including an upper wall closes one end of the dust collection container opposite the base wall. The lid includes an inlet in communication with the dust collection chamber and an outlet in communication with an upstream side of the filter. In a possible embodiment, the nozzle assembly is pivotally connected to the box assembly. In addition, a rotating agitator can be found in the nozzle assembly adjacent to the suction inlet. In addition, the box assembly may include a control handle. In accordance with another aspect of the present invention, the step between the first cylindrical section and the second cylindrical section may include a channel opening toward the base wall. In one embodiment of this type, this channel could be defined by the first cylindrical section, the second cylindrical section and the step. The channel could include a back wall in the shape of an arch. In the following description, several preferred embodiments of the invention are shown and described, simply by way of illustration of some of the best embodiments of the invention. As will be appreciated, the invention may be embodied in different embodiments and various details may be modified in several obvious aspects without departing from the present invention. Accordingly, the drawings and descriptions are considered as illustrative by nature and not restrictive. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing that is incorporated and forms part of this specification illustrates various aspects of the present invention and together with the description serves to explain certain principles of the invention. In the drawing:
Figure 1 is a partially open, perspective view of the floor cleaning apparatus of the present invention; Figure 2 is an open perspective view of the dust collection container, filter and flow control valve assembly of the apparatus illustrated in FIG.
Figure 1; Figure 3 is a cross-sectional view of the dust collection container, filter and flow control valve assembly in the first position allowing normal operation of the vacuum cleaner; Figure 4 is a schematic plan view illustrating the first flow valve in the first position that allows normal operation of the vacuum cleaner; Figure 5 is a cross-sectional view similar to the
Figure 3 but illustrating the flow control valve assembly in the second position allowing the cleaning of a section of the filter; Figure 6 is a schematic plan view similar to Figure 4 but showing the first flow valve in the second position that allows air to be sucked through the clean air inlet; Figure 7 is a detailed top perspective view of the filter assembly; Figure 8 is a schematic illustration of an additional filter cleaning characterized that can be used to clean dust and debris from the filter in situ in the dust collection container; and Figures 9a-9c are detailed schematic illustrations of three possible modes of the stepped side wall for a dust collection container. Reference will now be made in detail to the presently preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION Reference is now made to Figure 1 illustrating the floor cleaning apparatus 10 of the present invention. In the illustrated embodiment, the floor cleaning apparatus 10 comprises a vertical vacuum cleaner. It will be noted, however, that the apparatus 10 can also be easily a box vacuum or a manual vacuum cleaner. As illustrated, the apparatus 10 includes a housing 12 that includes both a nozzle assembly 14 and a box assembly 16. The nozzle assembly 14 includes a suction inlet 18 through which air entraining dust and debris is attracted to the vacuum cleaner. A rotary agitator 20 is mounted on a nozzle assembly 14 and extends through the suction inlet 18. The box assembly 16 includes a handle 22 having a handle 24. An actuator switch 26 for turning the vacuum cleaner on and off It is adjacent to the handle. In addition, the box assembly 16 includes a cavity or receiver 28 for receiving and containing a dust collection container 30. A suction generator 32 is mounted in a compartment in the box assembly 16. During operation, the rotary stirrer 20 Shake the dust and residue from the hair from the carpet or carpet that is being cleaned. The suction generator 32 pulls the air that drags dust and debris through the suction inlet 18 into the dust collection container 30. The dust and debris are trapped in the dust collection container 30 and the air is now relatively Clean passes through and over the motor of the suction generator 32 to provide cooling before being expelled through an exhaust port (not shown) back into the environment. As best illustrated in Figure 2, the dust collection container 30 comprises a powder container section 36 and a cover section 38. The powder container section comprises a stepped side wall 35 and a bottom wall. The benefits provided by the stepped side wall 35 will be discussed in more detail below. The lid section 38 comprises a first element 40, a second element 42 and a third element 43. The first element 40 includes the dirty air inlet 44 and a filter cavity 46. The second element 42 includes a clean air outlet 48. and a clean air inlet 50. A filter, generally designated by the reference number 52, is received in the filter cavity 46 of the first element 40. The filter 52 includes a side wall 54., a center 56 and multiple divisions 58 extending between the center and the side wall (see also Figure 7). The divisions 58 serve to divide the filter 52 into several sections 60. A filter means 62 of a type well known in the art extends between the side wall 54, the center 56 and the divisions 58 that define each section 60. A support inner 64 extends upward in the powder container section 36 from the bottom wall 37. A prefilter 66 rests on the internal support 64. The prefilter 66 includes a series of intake openings 68 which allow the flow of air enter in a way that will be described in more detail below. In the illustrated embodiment, the dust collection container 30 is designed to produce a cyclonic air flow and therefore use centrifugal force to improve the efficiency with which dust and debris are removed from the air stream. More specifically, as clearly illustrated in Figure 2, the powder container section 36, the cover section 38, the internal support 64, the prefilter 66 and the filter 52 all have a substantially cylindrical shape. As illustrated in Figures 3 and 5, the internal support 64 and the prefilter 66 are received concentrically in the stepped side wall 35 of the powder container section 36. The filter 52 is concentrically received in the filter cavity 46 of the first element 40 of the lid section 38. The dirty air inlet 44 is directed tangentially in the annular space S formed between (a) the first element 40 and the stepped side wall 35 on the outside and (b) the internal support 64 and the prefilter 66 on the inside. The air current flows around the annular space S in a circular or vortex-like pattern generating a centrifugal force which causes the dust and debris in the air stream to move outwards towards the stepped side wall 35 thereby causing the dust and debris are collected in the dust storage section 36. Simultaneously, the relatively clean air is pulled through the intake openings 68 provided in the prefilter 66 along the inner wall of the annular space S where it is then directed upwards through the filter 52. Specifically, the air passes through the filter medium 62 where the dust and fine debris remaining in the air stream are stopped while the clean air passes through the medium through the clean air outlet 48 towards the suction generator 32. The direction of the air flow during the normal operation of the vacuum is shown through the action arrows in Figure 3. The flow control valve assembly of the present invention is general designated by the reference number 70. As can best be illustrated in Figure 2, the control valve assembly flow 70 comprises a first flow valve 72 carried by a cooperative valve body 71 that covers the clean air inlet 50. As best illustrated in Figures 4 and 6, two first flow valves 72 are each connected in a manner pivoting to the valve body 71 by a pivot pin 74. A torsion spring 75 is provided in each first flow valve 72. The torsion springs 75 function to push the first flow valves 72 in a first position and illustrated in FIG. Figure 4, wherein the first flow valves 72 close the two opposite ports 73. Each first flow valve 72 includes a first light follower 76. Each cam follower 76 engages a first cam 78 mounted or integrally formed on the underside of a first driving gear 80. The driving gear 80 is driven by an actuator. In the illustrated embodiment, the actuator comprises a second driving gear 82 and a stepper motor 84 cooperating. In alternative modalities, the actuator may comprise, for example, a manual twist button / dial wheel or an electric solenoid and an activation switch. The operation of the stepper motor 84 and the first flow valve 72 will be described in greater detail below. As illustrated in Figure 2, an air guide 86 is engaged in the first driving gear 80. More specifically, the first driving gear 80 includes a hexagonal shaft 85 which is received in a hexagonal opening 87 provided in the center 89 of the air guide 86. As will also be seen, the air guide 86 includes an inlet 88 and an outlet 90. The inlet 88 extends concentrically about the center 89 while the outlet 90 projects radially outwardly in an arc of A ° (see also Figure 7). With reference again to the filter 52, each section 60 also has an A ° tree. In the illustrated embodiment, the filter 52 includes eight divisions 58 that divide the filter 52 into eight equal sections 60, each spanning an arc of 45 °. Thus, the outlet 90 of the air guide 86 also comprises an arc of 45 °, corresponding to the arc of each individual section 60 of the filter 52. Obviously, sections of other sizes could be provided (for example 12 sections each of an arc of 30 °, 10 sections each of an arc of 36 °, 9 sections each of an arc of 40 °, 6 sections each of an arc of 60 °).
The flow control valve assembly 70 also includes a second flow valve 92. The second flow valve 92 includes an external side wall 94 and a mounting center 96 received concentrically in this external side wall. A second cam 88 is provided in the air guide 86. A second cam follower 100 cooperating engages the second cam 98. The second cam follower 100 includes a mounting shaft 102 having a pointed end 104 and a channel 106. The pointed end 104 extends into the mounting center 96 of the second flow valve 92 and this center engages the channel 106 to hold the second flow valve on the mounting shaft 102. As further illustrated in section 2 , the second cam follower 100 includes a hexagonal head 108. The hexagonal head 108 is received in the hexagonal opening 110 in the first element 40 such that the second cam follower 100 is engaged in the cover section 38 to prevent a relative rotation. A coil spring 112 is located around the shaft 102 and is held in the hexagonal opening 110 in the center of the first element 40. The spring 102 pushes the second cam follower 100 in engagement with the second cam 98 all the time. As best illustrated in Figures 3 and 5, the second flow valve 92 is concentrically received within the prefilter 66. An annular seal 114 is connected between the lower margin of the second flow valve 92 and the wall of the prefilter 66. The annular seal 114 extends completely circumferentially between these two components. The operation of the flow control valve assembly 70 will now be described in detail. During normal operation of the vacuum cleaner, the suction generator 32 pulls air from the suction inlet 18 through the dust collection container 30 where the dust and debris is trapped and then the clean air exits through the port escape To do this, the flow control valve assembly 70 is placed in accordance with that illustrated in Figures 3 and 4 in such a manner that the first flow valve 72 closes the ports 73 leading to the clean air inlet 50 and the second flow valve 92 opens the annular passage 116 between the angular flange 118 at the top of the second valve 92 and the side wall of the prefilter 66 in such a way that the air can pass from the annular space S through the openings of intake 68 and filter means 62 of filter 52 before passing through outlet 48 to suction generator 32. As the cleaner continues to operate, fine dust particles not removed from the air stream by cyclonic action in the annular space S are removed from the air stream and trapped by the filter medium 62 of the filter 52. With the passage of time, these fine dust particles begin to clog the pores in the filter medium 62 by restricting or consequently the air flow. This not only causes the motor of the suction generator 32 to be hot and present a lower efficiency, it also reduces the air flow which negatively affects the cleaning efficiency of the vacuum cleaner. Consequently, the air flow can be so restricted that the vacuum cleaner is prevented from functioning properly. It is then necessary either to clean the filter 52 or to replace it. The present invention allows to clean the filter 52 in situ in a very comfortable and efficient manner. Specifically, stepper motor 84 can be activated to rotate air guide 86 to a 45 ° arc by means of driving gears 80, 82 engaged. This functions to rotate the air guide 86 in such a way that the outlet 90 thereof is exactly aligned with one of the sections 60 of the filter 52. The rotation of the first driving gear 80 simultaneously causes the first cam 78 to rotate from the position illustrated in Figure 4 towards the position shown in Figure 6. As this occurs, the cam followers 76 rise above the first cam 78 and the first flow valves 72 pivot around the pins 74 opening the ports 73 leading to the clean air inlet 50. As the stepper motor 84 rotates the drive gear 80, first cam 78 and air guide 86, second cam 98 rotates as well. The second cam follower 100 passes over the cam 98 by raising the second flow valve 92 in such a way that the upper edge thereof hooks the prefilter 66 above the intake openings 68 around its entire circumference. In this way it will be noted that as the ports 73 are opened through the movement of the first flow valve 72, the second flow valve 92 closes the air passage from the prefilter 66 to the outlet 48. Accordingly, the generator suction 32 pulls clean air through the ports 73 and through the clean air inlet 50. This air is then pulled through the inlet 88 of the air guide 86 and then directed through outlet 90 thereof through the single individual section 60 of the filter 52 with which the outlet is aligned. Since the clean air is moving through the selected section 60 of the filter 52 in a direction opposite to the normal operating direction, the powder (and particularly the fine powder from the pores of the filter) is removed from the medium. filter 62. The powder expelled from the section 60 of the filter 52 being cleaned has a tendency to be trapped in the lumen or particle trap 120 of the internal support 64. This is largely due to the shape to the shape of the support that it includes a frusto-conical upper end 122 connected to a substantially cylindrically shaped lower end 124 through an intermediate neck section 126 of circumferential opening smaller than the lower end. The relatively clean air is then carried through the other sections 60 of the filter 52 not aligned with the outlet 90 of the air guide 86 before passing through the outlet 48 and continuing towards the suction generator 32. As will be recalled , the outlet 90 of the air guide defines an arc only as wide as a section 60 of the filter 52. In the currently illustrated embodiment, this section has an arc of 45 °. This means that the remaining sections of the filter 52 not aligned with the air guide 86 define an arc of 315 °. This is a cross sectional area much larger than the 45 ° arc through which it initially passes into the air. The resulting pressure drop helps to ensure that the dust and debris cleaned from the filter section 60 that is aligned with the air guide 86 fall from the downstream air stream into the particulate trap 120 of the support 64 where they are retained. Accordingly, the fine dust and grime particles cleaned from the selected section 60 of the filter 52 are not deposited on the other sections of the filter during the cleaning cycle. The cleaning cycle can last, for example, from about 1 second to about 30 seconds and more typically from about 3 to about 15 seconds. The stepper motor 84 can then be activated again to rotate the first and second drive gears 80, 82, the first cam 78 and the second cam 98 to thereby move the first flow valves 72 from the open position towards the closed position and the second flow valve 72 from the closed position to the open position (i.e., moving the flow valves 72, 92 from the positions illustrated in Figures 5 and 6 to the positions illustrated in Figures 3 and 4 ). This returns the vacuum 10 to normal operation where dust and debris are attracted from the suction inlet 18 through the dirty air inlet 44 towards the dust collection container 30. There, an air flow cyclonic It uses centrifugal force to effectively remove dust and debris from the airstream. This dust and these debris are captured in the annular space S of the powder container section 36 as relatively clean air is pulled through the inlet openings 68 of the prefilter 66. This air then passes through the passage 116 towards the filter 52 wherein the remaining fine particles are removed from the air stream before it passes through the outlet 48 and moves to the suction generator 32. The air stream then cools the motor of the suction generator 32 before being expelled back to the environment through the escape port. Evidently, it can be seen that stepper motor 84 can be activated equally easily to clean any number of filter sections 60 before returning to normal operation mode, according to the criteria of the vacuum cleaner operator. Reference is now made to Figure 8 which schematically illustrates an optional additional feature of the present invention that can be provided for the purpose of further improving the cleaning of the filter 52. A ratchet 130 can be provided. In the illustrated embodiment, the ratchet 130 includes an elongated mounting arm 131 held in a short shaft 132 clamped over the lid section 38. A resilient fin 134 is provided at each end of the arm 131. As illustrated, the tips of the fins 134 engage the filter means 62 52 between the side wall 54 and the center 56. An impeller motor 136 is provided. As illustrated in the full line in FIG. 8, the drive motor may be connected to the pawl 130 and activated to rotate the pawl relative to the cross section. cap 38 and filter 52. As ratchet 130 rotates, the tips of the fins 134 engage the peaks of the filter material with ribs 62 so that the material filter vibrates and effectively shakes dust and debris from the filter pores. While the vibration offers a good cleaning action when used alone, it is particularly effective when used with the pneumatic cleaning mechanism previously described in this document. In an alternative arrangement also illustrated in Figure 8, the drive motor is connected to the filter 52 (note the dotted line in the drawing of Figure 8). In this arrangement, the filter 52 rotates while the ratchet 130 and the lid section 38 remain stationary. The result is the same inasmuch as the tips of the fins 132 engage the peaks of the filter medium with ribs 62 as the filter rotates so that the medium is vibrated and the dust and debris are released therefrom. Reference is now made to Figures 9a-9c schematically illustrating three possible embodiments of a stepped side wall 35. As illustrated in Figure 9a, the stepped side wall 35 of the powder container section 36 includes a first cylindrical section 150. and a second cylindrical section 152 connected together through an annular step 154. As illustrated, the step 154 and the first cylindrical section 150 define an included angle Ai of 90 degrees. In the embodiment illustrated in Figure 9b, the stepped side wall 35 again includes a cylindrical section 150, a second cylindrical section 152 and an annular shoulder 154 interconnecting these two cylindrical sections. In this embodiment, the annular step 154 in the first cylindrical portion 150 defines an included acute angle i, that is, an angle i less than 90 degrees. As a result a channel 156 is formed between the step 154 in the first cylindrical section 150 of the side wall 35. This channel 156 opens towards the base wall 37 of the powder container section 36. Figure 9c illustrates another possible embodiment of the stepped side wall 35. In this embodiment, the stepped side wall 35 includes a first cylindrical section 150, a second cylindrical section 152 and an annular step 154 connecting the first cylindrical section and the second cylindrical section. Together, the cylindrical sections 150, 152 and the annular step 154 define a channel 156 that opens toward the base wall 37 of the powder container section 36. As illustrated in phantom line on the right hand side of Figure 9c, this channel 156 may have a bow-shaped bottom wall if desired. In any of the embodiments illustrated in Figures 9a-9c, the first cylindrical section 150 has a circumference Ci between approximately 47.8 centimeters (18.8 inches) and approximately 63.8 centimeters (25.1 inches). The second cylindrical section 152 has a circumference C2 between approximately 39.9 centimeters
(15.7 inches) and approximately 55.9 centimeters (22.0 inches). The first cylindrical section has a height Hi between about 15.2 centimeters (6 inches) and about 17.8 centimeters (7 inches) and the second cylindrical section 152 has a height H2 between about 12.7 centimeters (5 inches) and about 15.2 centimeters (6 inches) . The first cylindrical section 150 therefore defines a volume Vi between approximately 2779 cubic centimeters (169.6 cubic inches) and approximately 5,767 cubic centimeters (351.9 cubic inches), while the second cylindrical section 152 defines a volume V2 between approximately 1.609 cubic centimeters (98.2 cubic centimeters). cubic inches) and approximately 3,784 cubic centimeters (230.9 cubic inches). The annular step 154 has a width between the first cylindrical section 150 and the second cylindrical section 152 of about 0.25 centimeters (0.1 inch) and about 6.4 centimeters (2.5 inches).
As further illustrated in Figures 9a-9c, the internal support 64 projects from the base wall 37 and carries the prefilter 66. The prefilter 66 includes a third cylindrical section 158 incorporating the various intake openings 68 (for simplicity for illustration only eight openings are shown). An angular flange 160 depends on the third cylindrical section 158. The third cylindrical section 158 and the angular flange 160 are joined at a vertex V which defines an angle included in A2 comprised between approximately 135 and approximately 165 degrees. The vertex V is received concentrically within the second cylindrical section 152: that is, it is placed on top of the step
154 in the illustrated modes. As illustrated, the angle flange 160 also has a straight continuous face 162. An annular space 162 is provided between the flange 160 and the end 166 of the second cylindrical section 152. The space
164 has a width between approximately 1.3 centimeters (0.5 inch) and approximately 6.4 centimeters
(2.5 inches). In addition, the geometry of the prefilter 66, first cylindrical section 150 and angular flange 160 are such that the dimension E is equal to the dimension F. In any of the embodiments illustrated in the Figures
9a-9c, the stepped sidewall 35 offers a more efficient and effective cyclonic separation of the dust and debris found in the air stream. More specifically, the air is supplied to the dust collecting container 30 through the tangentially directed inlet 44. As a result, the air stream moves in a vortex pattern in the annular space S. As a consequence, the centrifugal force acts on the dust and debris in the air stream causing it to move towards the surface of the side wall 65. As the air stream is pushed and moves towards the base wall 47 of the dust collection container 30, the dust and the residues previously flowing against the second cylindrical section 152 pass through the step 154 and begin to move in engagement with the first cylindrical section 150. The annular step 158 in the embodiment of Figure 9a and the channel 156 in the embodiments of the Figures 9b and 9c then act as a physical barrier that prevents dust and debris moving along the first cylindrical section 150 rise and move along the second cylindrical section 152. Accordingly, dust and debris are essentially captured in the portion of the dust collection container 30 defined between the first cylindrical section 150, the step 154 and the base wall 37. Accordingly, dust and debris can not rise towards the intake opening 68 in the prefilter 66. As a consequence, dust and debris can not interrupt or otherwise interfere with the air passage through the opening. of intake 68 and the peak cleaning efficiency is improved all the time. The above description of a preferred embodiment of the present invention has been presented for the purpose of illustration and description. It is not intended to be complete or to limit the invention to the precise form disclosed. Modifications or obvious variations are possible taking into account the teachings above. For example, an air guide 86 of the embodiment illustrated and described extends through an angle of A ° corresponding to each section 60 of the filter 52. The air guide 86 can, in fact, have an arc which is a multiple of A ° to allow cleaning of more than one filter section at a time. In addition, the cleaning function of the filter can be automatic. It can be started automatically after a certain period of time of operation or when an event occurs, for example the movement of the control handle 22 in the vertical or storage position. In addition, it will be noted that clean air from the outlet of the suction generator can be recycled to clean the filter. The modality was selected and described in order to offer the best illustration of the principles of the invention and its practical application to thereby enable a person with ordinary knowledge in the art to use the invention in various modalities and with several suitable modifications for the invention. private use contemplated. All these modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the magnitude to which they have fair, legal and equitable rights. The drawings and the preferred embodiments do not limit or intend to limit in any way the ordinary meaning of the claims and their broad and fair interpretation.