CROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

[1] This application claims priority from commonly owned U.S. Provisional Patent Application 62/449424, filed 23 January 2017, and titled A System For Removing Paint And/Or Other Unwanted Material From A Field, And Related Methods, which is currently pending and incorporated herein in its entirety by reference.

BACKGROUND

[2] Many athletic games, such as football, soccer, rugby, baseball, Olympic track and field events, as well as other events, such as fairs and ceremonies involving many people, are played or occur on a large field. Often different athletic games and/or events are played and/or occur on the same field at different times. For example, a high-school football game may be played on a Friday night, a college football game on Saturday the next day, and a professional football game on Sunday the day after.

Likewise, a soccer game may be played on a Friday, and a football game played on Sunday two days later. Each of these games may require different field markings that are typically established by applying a turf paint or chalk to the field. If different football teams will be using the same field, then each of the end zones and the middle of the field may include different colors and/or a logo of the team currently playing. If different sports teams will be using the same field, then the field boundaries as well as the internal field markings may be different.

[3] Changing the markings on such fields first requires removing the old field markings (turf paint or chalk) for the game just played, and then applying the new field markings (turf paint or chalk) for the game about to be played. The removal of the old field markings often depends on the material that the turf is made of. Many fields are made of natural grass and may be thick, that is, have many blades of grass per square inch, or thin, that is, have few blades of grass per square inch. In addition, natural grass fields may include thatch at the base of the turf's blades of grass. Many other fields are made of artificial turf. Artificial turf typically includes many synthetic fibers attached to a mat such that the fibers extend away from the mat like blades of grass in a natural grass field. The artificial turf also often includes infill disposed at the base of the synthetic fibers, much like thatch in a natural grass field, to help keep the synthetic fibers extending up and away from the mat and to provide some cushion or "give" to the artificial turf when one runs, cuts and/or falls during a game. Infill typically consist of small granules of rubber and/or sand.

[4] Extracting field markings from artificial turf is typically done by vacuuming out of the turf the turf paint or chalk. To facilitate this, a solvent is first applied to the field markings on a region of the turf to remove the turf paint or chalk from the synthetic fibers. Next the solvent and the turf paint or chalk that is suspended in the solvent are vacuumed up out of the artificial turf. A vacuum is typically used because the artificial turf's mat is often not very porous and is often placed on top of ground that is not very porous, so it can be difficult to just wash the field markings into the ground below the artificial turf's mat. Extracting a field's markings from natural grass is often easier because one can just cut the grass. But, this technique may not be available if the field's use changes frequently because it takes a while for grass to grow long enough to cut the whole portion of the grass blade that has the turf paint on it. Therefore, a vacuum is also often used to extract turf paint and chalk from grass fields.

[5] When a vacuum is used on artificial turf and natural grass fields, the vacuum process can remove some of the infill from the artificial turf or some of the soil from the natural grass. The vacuum process can also redistribute infill or soil throughout the region of the field being vacuumed and cause some regions of the field to have an excess of infill or soil and other regions of the field to have a depletion of infill or soil. If infill or soil is removed from the field, then it must be replaced. If infill or soil is redistributed, then one has to correct the uneven distribution of infill or soil must be corrected to make it more evenly distributed. Both of these situations add more time and work to the process of changing the markings on a field. SUMMARY

[6] In one aspect of the invention, a device for removing paint and other unwanted material from turf comprises a vacuum head and a compression bar. The vacuum head includes a chamber having an entrance and an exit, wherein when air is urged out of the chamber through the exit, ambient air adjacent to the vacuum head flows into the chamber through the entrance. The compression bar is located adjacent to and outside of the vacuum head's entrance and is operable to exert pressure on the turf to cause fluid in the turf to pool adjacent to the vacuum head's entrance. The fluid includes a solvent applied to the turf to dissolve the turf paint or chalk and remove it from the synthetic fibers of artificial turf or the blades of grass from natural grass turf. When air is urged out of the vacuum head's chamber through the vacuum head's exit, the fluid pooled adjacent to the vacuum head's entrance is urged through the vacuum head's entrance and into the vacuum head's chamber.

[7] By exerting pressure on the region of the turf being cleaned, much of the infill in artificial turf or soil in a natural grass turf is forced out of suspension in the fluid that includes the solvent, turf paint and chalk, or is prevented from becoming suspended in this fluid. Thus, one can remove markings from a field in preparation for the application of a different set of markings to the field with a minimal amount of disturbance to an artificial turf's infill or a natural grass turf's soil.

[8] In another aspect of the invention, a method for removing paint and other unwanted material from turf comprises: a) locating an entrance of a vacuum head of a device over a region of the turf to be cleaned; b) exerting pressure on the region of the turf with a compression bar of the device that is located adjacent to and outside of the vacuum head's entrance to cause fluid in the turf to pool adjacent to the vacuum head's entrance; and c) reducing pressure inside a chamber of the vacuum head to urge: 1 ) ambient air adjacent to the vacuum head's entrance, and 2) the pooled fluid adjacent to the vacuum head's entrance to flow through the entrance and into the chamber.

[9] In yet another aspect of the invention, a machine for removing paint and other unwanted material from turf comprises a vacuum device operable to remove paint and other material from turf, a scrubbing device operable to strip paint from the turf, and a chassis that carries the vacuum device and scrubbing device across the turf. The vacuum device includes a vacuum head and a compression bar. The vacuum includes a chamber having an entrance and an exit, wherein when air is urged out of the chamber through the exit, ambient air adjacent to the vacuum head flows into the chamber through the entrance. The compression bar is located adjacent to and outside of the vacuum head's entrance and operable to exert pressure on the turf to cause fluid in the field to pool adjacent to the vacuum head's entrance.

BRIEF DESCRIPTION OF THE DRAWINGS

[10] FIG. 1 shows a perspective view of a machine for removing paint and other unwanted material from artificial and/or natural grass turf, according to an embodiment of the invention.

[11] FIG. 2 shows a left, side view of the machine shown in FIG. 1 , according to an embodiment of the invention.

[12] FIG. 3 shows a right, side view of the machine shown in FIG. 1 , according to an embodiment of the invention.

[13] FIG. 4 shows a different perspective view of the machine shown in FIG. 1 , according to an embodiment of the invention.

[14] FIG. 5 shows a perspective view of a vacuum device and a scrubbing device included in the machine shown in FIGS. 1 - 4, according to an embodiment of the invention.

[15] FIG. 6 shows a cross-sectional view of the vacuum and scrubbing devices shown in FIG. 5, according to an embodiment of the invention.

[16] FIG. 7 shows a different cross-sectional view of the vacuum device shown in FIGS. 5 and 6, according to an embodiment of the invention. [17] FIG. 8 shows a perspective view of a vacuum device and scrubbing device, according to another embodiment of the invention.

[18] FIG. 9 shows a cross-sectional view of the vacuum and scrubbing devices shown in FIG. 8, according to another embodiment of the invention.

[19] FIG. 10 shows a brush that may be included in the scrubbing device shown in FIGS. 8 and 9, according to another embodiment of the invention.

[20] FIG. 11 shows a brush that may also be included in the scrubbing device shown in FIGS. 8 and 9, according to yet another embodiment of the invention.

DETAILED DESCRIPTION

[21] Each of FIGS. 1 - 4 shows a view of a machine 20, according to an embodiment of the invention. One may use the machine 20 to remove field markings, such as paint and/or chalk, and other unwanted material from any field that includes artificial turf and/or natural grass turf. Each of FIGS. 1 and 4 shows a perspective view of the machine 20, and each of FIGS. 2 and 3 shows a side view of the machine 20. The machine 20 includes a scrubbing device 22 (discussed in greater detail in conjunction with FIGS. 5 and 6) to agitate the turf and help separate field markings from the synthetic fibers of artificial turf and/or the blades of grass from natural grass turf, as well as loosening up other unwanted material lying in the turf. The machine 20 also includes a vacuum device 24 to extract the separated field markings and other loosened material from the turf. The vacuum device 24 (discussed in greater detail in conjunction with FIGS. 5 - 8) includes a compression bar 26 (shown in FIGS. 2 and 3), and a filter 27 (shown in FIGS. 2 and 3). The compression bar 26 exerts pressure on the turf to pool fluid next to the vacuum device's entrance 28 (shown in FIGS. 2 and 3). The filter 27 helps prevent infill, soil and/or thatch from flowing through the vacuum device's entrance 28 and into the vacuum device 24. When the machine 20 is used to remove field markings from a field's turf, the fluid that the compression bar 26 pools next to the vacuum device's entrance 28 typically includes a solvent 38 that dissolves turf paint and/or chalk, and a liquid that holds the solvent and dissolved turf paint and/or chalk in suspension. With the fluid pooled next to the vacuum device's entrance 28, the vacuum device 24 can extract the fluid from the field's turf. Although the machine 20 shown here is configured to be self-propelled and driven by a person, the machine 20 may be configured as a remote-controlled machine or an autonomous machine, or as a machine that is pushed over the turf much like a conventional push-mower.

[22] In operation, the machine 20 travels in the direction indicated by the arrow 30 and is maneuvered to locate the scrubbing device 22 and the vacuum device 24 over the region of the field's turf to be cleaned. When using the machine 20 to remove markings on a field, the machine 20 is maneuvered to align the direction that the scrubbing device 22 and vacuum device 24 travel (arrow 30) with the direction that the field's marking extends. After the scrubbing device 22 and the vacuum device 24 are located as desired, the scrubbing device 22 and vacuum device 24 are lowered onto the turf such that the two front wheels 32, the brushes 34, and the compression bar 26 contact the turf. As shown in FIGS. 1 - 4, the scrubbing device 22 and vacuum device 24 are located in an elevated position in which the wheels 32, brushes 34, and compression bar 26 do not contact the turf. In this elevated position, the machine 20 can be more easily maneuvered to a desired region of the field to be cleaned. After the scrubbing device 22 and vacuum device 24 are lowered to their cleaning position, the machine 20 pushes both devices 22 and 24 over the region of the turf to be cleaned. While the devices 22 and 24 are pushed over the region, nozzles 36 spray onto the turf a solvent 38 and/or another liquid 39, such as water, that can hold the solvent 38 and dissolved turf paint in suspension; the brushes 34 agitate the region; and the

compression bar 26 exerts pressure on the region and causes the solvent and/or other liquid to pool at the vacuum device's entrance 28. There the pooled fluid and other unwanted material in the turf is then sucked into the vacuum device 24 and carried to a holding tank 40.

[23] With the scrubbing device 22, the machine 20 can quickly and effectively position debris and other unwanted material in a field's turf for extraction via the vacuum device 24. And, when the scrubbing device 22 is used in conjunction with a solvent 38 that dissolves turf paint and/or chalk, the machine 20 can quickly and effectively remove field markings from the field's turf via the machine's vacuum device 24. With this ability, a field's markings can quickly be changed to accommodate different events, such as multiple football games played by different teams, different sports played by different teams, and different fairs and ceremonies. Although the machine 20 is particularly effective at removing field markings with the help of a solvent 38 applied to the field markings, the machine 20 is also effective at removing field markings without the help of a solvent.

[24] To generate a vacuum at the vacuum device's entrance 28, the machine 20 includes a blower 42 (shown in FIGS. 1 - 4). The blower 42 may be any desired blower capable of moving a desired amount of air through the vacuum device's entrance 28. For example, in this and other embodiments, the machine 20 includes two blowers 42, each capable of moving air at a rate of 230 cubic feet per minute (cfm). As discussed in greater detail in conjunction with FIG. 7, each blower 42 generates a vacuum in approximately half of the vacuum device 24 and at approximately half of the

cross-sectional area of the vacuum device's entrance 28. When fluid pooled in front of the vacuum device's entrance 28 and other unwanted material is sucked through the entrance 28, the moving air generated by each of the blowers 42 carries the fluid and material through a respective one of the tubes 44 and into the holding tank 40, which in this embodiment has a capacity of 55 gallons. A portion of each of the tubes 44 has been omitted from FIGS. 1 - 4 to provide clarity for portions of the machine 20 the view of which would otherwise be obstructed.

[25] Other embodiments are possible. For example, each of the blowers 42 may move air at a rate that is greater than 230 cfm or less than 230 cfm depending on the cross-section of the vacuum device's entrance 28 and the amount and weight of the fluid and other unwanted material to be extracted from the turf. For another example, one blower 42 may be desired, or more than two blowers 42 may be desired. For another example, the holding tank 40 may include an infill separator that separates and isolates any infill and/or sand that is extracted from the turf. The infill separator may include a container that has its exit at its top so that infill can settle to the bottom of the container while the fluid continues through the container and into the holding tank 40. [26] Still referring to FIGS. 1 - 4, the nozzles 36 may be positioned throughout the machine 20 as desired, and may spray a solvent 38, a liquid 39 that can hold the solvent and dissolved turf paint in suspension, or both at the same or at different times during the operation of the machine 20. For example, in this and other embodiments, the machine 20 includes three groups of two nozzles 36, each group located ahead of a respective one of the three brushes 34 in the direction of the arrow 30. Each of these nozzles 36 sprays water 39 to help spread solvent 38 that was previously sprayed onto the turf so that the agitating action of each brush 34 can help remove turf paint from the turf's artificial fibers and/or natural blades of grass. The machine 20 also includes ten nozzles 36 located between the brushes 34 and the vacuum device 24. Each of these nozzles 36 also sprays water 39 to help suspend the solvent 38, dissolved turf paint and/or chalk, and any other material to be extracted via the vacuum device 24.

Adjacent to the wheels 48 of the machine 20, nozzles 36 spray water 39 onto the wheels 48 to rinse them of any paint, infill, soil, or other debris picked up from the turf. And finally, four nozzles 36 located at the rear of the machine 20 spray solvent 38 onto the turf to dissolve the turf paint and other materials used to mark the field. With all of the nozzles 36 configured in this way, a single machine 20 may be used to clean the turf by making two passes over the region of the turf to be cleaned. During the first pass, the four nozzles at the rear spray solvent 38 onto the region. Then, during the second pass, all of the nozzles ahead of the vacuum device 24 spray water on the region just before and just after the brushes 34 scrub the region. If two or more machines 20 are used to clean a region of turf, then a first machine 20 may travel over the region while spraying solvent 38; and a second machine may travel over the region while spraying water 39, rotating the brushes 34, and extracting fluid and other material through the vacuum device 24.

[27] Other embodiments are possible. For example, one or more of any of the nozzles 36 may spray solvent 38, or a mix of solvent 38 and water 39. For another example, the machine 20 may include fewer than 25 nozzles 36 or more than 25 nozzles 36, and each may be located in any other desired position on the machine 20. [28] In this and other embodiments, the machine 20 also includes a tank 50 that holds the water 39 and a pump 52 (here two) that urges the water 39 toward the nozzles 36. The tank's capacity is 1 10 gallons and the rate at which the two pumps 52 move the water 39 through the nozzles 36 is nine gallons per minute. The machine 20 also includes a solvent tank 54, a pump 56, and a wand (not shown but similar to a wand at a self-service car wash used to rinse a car) that may be used to spray solvent 38 and/or liquid that can hold the dissolved paint and/or chalk in suspension onto a region of the turf that the nozzles 36 can't reach while the machine 20 travels over a region of the field. The solvent tank's capacity is 16 gallons; and the pump 56 urges solvent 38 and/or liquid that can hold the dissolved paint and/or chalk in suspension to the nozzles 36 or the wand at a rate of 2.2 gallons per minute.

[29] Still referring to FIGS. 1 - 4, in this and other embodiments, the machine 20 also includes an engine (not shown) to generate power, and a chassis 58 to carry the engine, the scrubbing device 22, the vacuum device 24 and all of the other components while the machine travels over a field. The engine may be any desired engine capable of generating enough power to propel the machine 20 over a field's turf while fully loaded with solvent 38 and/or liquid for holding the solvent 38, dissolved paint and other material in suspension, fuel for the engine and a person driving the machine 20, as well as powering a generator 60 capable of generating 2,600 watts of electrical power to run the pumps 52 and 56, the blowers 42, and the brushes 34. For example, in this and other embodiments, the engine is a conventional, naturally aspirated engine that uses the Otto cycle to generate power. In other embodiments, the engine may be a conventional, naturally aspirated engine that uses the Diesel cycle to generate power. In yet other embodiments, the engine may be an electric motor that receives electrical power from an outlet at the field, or from a battery carried by the chassis 58; or the engine may use propane or any other low-pressure gas to generate power.

[30] FIG. 5 shows a perspective view of the vacuum device 24 and the scrubbing device 22 included in the machine 20 shown in FIGS. 1 - 4, according to an

embodiment of the invention. FIG. 6 shows a cross-sectional view of the vacuum and scrubbing devices 24 and 22, respectively, shown in FIG. 5, according to an embodiment of the invention. And FIG. 7 shows a different cross-sectional view of the vacuum device 24 shown in FIGS. 5 and 6, according to an embodiment of the invention. The scrubbing device 22, which will be discussed first followed by the vacuum device 24, includes a brush 34 that moves relative to the turf to agitate the turf and help separate field markings from the synthetic fibers of artificial turf and/or the blades of grass from natural grass turf, as well as loosening up other unwanted material lying in the turf. The vacuum device 24 includes a vacuum head 66 to extract the separated field markings and other material from the turf, a compression bar 26 that exerts pressure on the turf to pool fluid next to the entrance 28 of the vacuum head 66, and a filter 27 that helps prevent infill, soil and/or thatch from flowing through the entrance 28 into the vacuum head 66.

[31] Referring to FIGS. 5 and 6, the scrubbing device 22 may be configured as desired to perform its function. For example, in this and other embodiments, the scrubbing device 22 includes three brushes 34 each mounted to a frame 68 and configured to rotate about a respective one of three axes 70 to agitate the turf. The scrubbing device 22 also includes three motors 72 each coupled to a respective one of the brushes 34 to rotate the brushes as desired. Each motor 72 may rotate its respective brush 34 independent of the other two motors 72 so that the speed and direction that each brush rotates may be the same or different than one or more of the other brushes 34. For example, one may want the middle brush 34 to rotate clockwise (when viewed from above) at a speed of 100 revolutions per minute (rpms), while the other two brushes 34 rotate counterclockwise (when viewed from above) at a speed of 75 rpms. For another example, one may want the middle brush 34 to oscillate between clockwise rotation and counterclockwise rotation at a speed of 40 rpms, while one of the outer brushes 34 rotates clockwise at 100 rpms and the other outer brush 34 rotates counterclockwise at 100 rpms.

[32] In this and other embodiments, each brush 34 is mounted to the frame 68 such that each brush 34 is independently suspended. That is, each brush moves up or down relative to the frame 68 independent of the other two brushes 34 movement relative to the frame 68. This allows each of the brushes 34 to remain in contact with a field's turf while traveling over a region of the turf that has bumps, mounds, grooves and/or valleys, which is common in turf that includes natural grass. To provide this

independent suspension, each motor 72 is directly coupled to its respective brush 34and is bolted to a suspension plate 74. The suspension plate 74 is in turn bolted to the frame 68 with a coil torsion spring 76 positioned between the suspension plate 74 and the head 78 of the bolt coupling the two. The spring 76 urges the head 78 of the bolt away from the suspension plate 74 and compresses when the brush 34 is pushed up toward the frame 68 by a bump in the turf.

[33] The brush 34 of the scrubbing device 22 may be any desired brush having any desired stiffness. For example, in this and other embodiments each brush 34 has a diameter of 18 inches and a ring of bristles 80 that are moderately stiff to provide sufficient contact pressure between the ends of the bristles 80 and the turf's synthetic fibers and/or blades of grass. The brushes 34 are releasably mounted to their respective motors 72 so that a currently mounted brush34 can be quickly and easily removed and replaced with a different brush 34. This may be desirable when the machine 20 is used to remove field markings from artificial turf whose synthetic fibers are soft, and then subsequently used to remove field markings from natural grass turf whose grass is substantially stiffer, such as Bermuda grass, than the synthetic fibers of the artificial turf.

[34] Other embodiments are possible. For example, the scrubbing device 22 may include fewer than three brushes or more than three brushes. For another example, the arrangement of the brushes may be different than that shown in FIGS. 1 - 5.

[35] Referring to FIGS. 5, 6 and 7, the vacuum device 24 includes a vacuum head 66 to extract separated field markings and other loosened material from the turf, a compression bar 26 that exerts pressure on the turf to pool fluid next to the entrance 28 of the vacuum head 66, and a filter 27 that helps prevent infill, soil and/or thatch from flowing through the entrance 28 into the vacuum head 66. The vacuum head 66 may be configured as desired to perform its function. For example, in this and other embodiments, the vacuum head 66 includes two chambers 84. Each chamber 84 has an entrance 86, and an exit 88; and each chamber's entrance 86 lies next to the other chamber's entrance 86 to form a single rectangular entrance to the vacuum head 66 that spans both chambers 84. When air is urged (here pulled) by the blowers 42 (FIGS. 1 - 4), air flows out of the chambers 84 through the exits 88. This causes the air pressure in the chambers 84 to drop, which in turn causes ambient air outside of the chambers 84 to flow through the entrances 86 and into the chambers 84. When this happens, the flowing air urges the fluid pooled up in front of the entrances 86 to also enter the chambers 84 and continue to flow through the chambers 84 toward the holding tank 40.

[36] Other embodiments are possible. For example, the vacuum head 66 may include a single chamber 84, or the vacuum head 66 may include more than two chambers 84. For another example, the entrance 86 of each of the chambers 84 may not combine to form a single, continuous entrance for the vacuum head 66, but may instead remain separate from each other to form two separate entrances for the vacuum head 66. Similarly, the two entrances 86 may overlap each other to form a single continuous entrance for the vacuum head 66 whose cross-sectional area is equal to the cross-sectional area of one of the chamber's entrances 86.

[37] In this and other embodiments, the vacuum head 66 is mounted to the frame 68 such that the vacuum head 66 is independently suspended. That is, the vacuum head 66 may move up or down relative to the frame 68 independent of the movement of each of the brushes 34 relative to the frame 68. In addition, one end of the vacuum head 66 may move up or down relative to the other end of the vacuum head 66. This allows the vacuum head 66 to remain in contact with a field's turf while traveling over a region of the turf that has bumps, mounds, grooves and/or valleys. To provide this independent suspension, four coil torsion springs 90 (FIGS. 6 and 7) are positioned between the vacuum head 66 and the frame 68, and bolts couple the three together. The springs 90 urge the vacuum head 66 away from the frame 68 and compress when the respective end of the vacuum head 66 is pushed up toward the frame 68 by a bump in the turf.

[38] The compression bar 26 may also be configured as desired to perform its function. For example, in this and other embodiments, the compression bar 26 extends the length of the combined entrances 86 of the chambers 84 that form the entrance to the vacuum head 66, and is located outside of and adjacent to the entrance to the vacuum head 66. More specifically, the compression bar 26 includes a cylinder having a smooth surface that contacts the turf. Moreover, the compression bar 26 is releasably coupled to the vacuum head 66 and includes bearings so that the compression bar 26 may roll over the turf when the compression bar 26 is urged against the turf. By releasably coupling the compression bar 26 to the vacuum head 66, the current compression bar 26 may be quickly and easily removed and replaced with a

compression bar 26 that has a different configuration possibly more suited to the type of turf to be cleaned. For example, a compression bar 26 having a smaller or larger diameter than the current compression bar 26 may be desired. Or, a compression bar

26 that includes a rough or carefully arranged set of ridges and/or grooves on the surface that contacts the turf may be desired. Or, a compression bar 26 that does not roll over the turf but slides or skids over the turf and may have a flat or differently curved surface that contacts the turf, may be desired.

[39] The filter 27 may also be configured as desired to perform its function. For example, in this and other embodiments, the filter 27 is mounted to the leading edge of the entrance 86 to the vacuum head 66 and includes a brush with many fine bristles that functions much like a whale's baleen except that the filter 27 prevents material from entering the vacuum head chambers 84, while a whale's baleen prevents material from exiting the whale's mouth. The filter 27 is configured such that when the compression bar 26 contacts the turf and the vacuum head 66 travels in the direction indicated by the arrow 30, the filter 27 forms an arc that covers much of the entrance 86 but leaves a portion of the entrance 86 uncovered. In this manner the filter 27 can help prevent infill, soil, and thatch from passing through the entrance 86 when ambient air and fluid flows through the entrance 86 toward the holding tank 40.

[40] Other embodiments are possible. For example, the filter 27 may be mounted inside one or more of the vacuum head's chambers 84. For another example, the filter

27 may include a mesh of material instead of many bristles.

[41] Still referring to FIGS. 5 and 6, the vacuum device 24 may also include a brush 92 to more evenly disperse infill, soil or thatch that has congregated as a result of the cleaning process, back across the turf. The brush 92 also helps straighten out or erect artificial fibers and/or grass blades that have been matted down by the agitating action of the brushes 34 and the contact of the compression bar 26. The brush may be any desired brush capable of performing this function. For example, in this and other embodiments, the brush 92 includes many bristles 94 that contact infill, soil and/or thatch that has congregated after being cleaned, and artificial fibers and blades of natural grass that have been matted down. When the bristles contact infill, soil and/or thatch, the stiffness of the bristles pushes the materials it contacts into a more even distribution across the region of the turf. And, when the bristles contact artificial fibers and blades of grass, the stiffness of the bristles moves some of them into alignment with the direction that the machine travels and urges some of them to straighten out and extend upward.

[42] Each of FIGS. 8 and 9 shows a view of a vacuum device 100 and a scrubbing device 102, each according to another embodiment of the invention. FIG. 8 shows a perspective view of the devices 100 and 102, and FIG. 9 shows a cross-sectional view of the devices 100 and 102. The vacuum device 100 is similar to the vacuum device 24 (FIGS. 1 - 7) except that the compression bar 104 is located in a different position in the vacuum head 106, and the vacuum head's entrance 108 includes a filter 1 10. The compression bar 104 is located in the vacuum head 106 such that less of the bar 104 protrudes below the bottom of the vacuum head 106. The filter 1 10 is similar to the filter 27 (FIGS. 2, 3 and 6).

[43] Still referring to FIGS. 8 and 9, the scrubbing device 102 is similar to the scrubbing device 22 (FIGS. 1 - 6) except that the device includes two longitudinal brushes 120, each of which rotates in a respective one of two, opposite directions indicated by the arrows 122 and 124, and about an axis that lies parallel to the turf, not perpendicular to the turf as is the case with the brushes 34 of the device 22. Configured and rotating in this manner, the brushes 120 help prevent infill, soil, and thatch from congregating in undesirable regions of the turf while the devices 100 and 102 remove field markings from the turf. The nozzles 126 spray water to help suspend solvent, dissolved turf paint and/or chalk, and any other unwanted material to be extracted via the vacuum device 100.

[44] Each of FIGS. 10 and 11 shows a view of the brush 120 in FIGS. 8 and 9, according to different embodiments of the invention. FIG. 10 shows a brush 120 that includes four rows of bristles 130, each row extending the longitudinal length of the brush 120 and forming a helix along the brush's length. FIG. 11 shows a brush 120 that may include a single row of bristles 132 that extends along the longitudinal length of the brush 120 in a much tighter helix than the brush 120 shown in FIG. 10.

[45] The preceding discussion is presented to enable a person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.