Abstract:
A snow removal device that picks up snow from the ground and flicks the snow into impeller units that transport the snow into a discharge tube whence the snow is expelled from the system. The system primarily includes a pick-up assembly, an impeller assembly, and a discharge tube. The pick-up assembly has a drum array that includes rows of triple-stepped blade-like fingers distributed evenly around each drum of the array of drums. These fingers are stiffly flexible and can cleanly and efficiently pick up snow from uneven ground surfaces and flick the snow into the impeller assembly that is mounted parallel to the axis of the drum array. The impeller assembly includes a plurality of impeller units that transport the snow into the discharge tube. The impeller units are reversible in direction, allowing the snow to be discharged to the right or the left of the system, or to the right and left simultaneously. The discharge tube and the impeller assembly lie in the same plane and are tilted upward approximately 20° relative to the ground. Thus, the snow is discharged at a relatively low height to the ground. The discharge tube and impeller assembly can be pivotally attached to the floating chassis, allowing the plane of the impeller assembly and the discharge tube to be tilted at a steeper angle relative to the ground. The snow removal device may be pulled or pushed by a prime mover and powered by an externally mounted hydraulic system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for removing loose debris from streets and other surfaces. Particularly, the present invention relates to snow or ice removal from regular and irregular surfaces. More particularly, the present invention relates to a system that can be configured to perform various ground cleaning operations. More particularly yet, the present invention relates to a snow removal system that fractures the snow covering a surface, lifts the fractured snow from the surface, and discharges it through an impeller/discharge system. Most particularly, the present invention uses a stiff but flexible stepped triple finger mechanism to fracture and lift the snow and deliver it to an impeller assembly that transfers the snow and laterally discharges it, at an adjustable height above the surface from which it is expelled. 
     2. Description of Prior Art 
     Although the utility of the present invention is not limited to snow removal, the relevant prior art lies in the field of snow removal mechanisms. Among the many different means for removing snow from ground surfaces snowplows are the best known. Nevertheless, snow removal by snowplow has a number of inherent disadvantages. A snowplow typically requires several passes to clear a roadway of snow. In the first pass, it clears a swath, discharging the snow to the side of the plow, thereby creating snowbanks that narrow the roadway and impair visibility for vehicle operators or pedestrians. In a subsequent pass or passes, the plow works at pushing the snowbank further away from the roadway. Furthermore, highway snowplows typically require a certain minimum forward speed if the plows are to impart to the snow the velocity needed for the snow to travel across the face of the plow. In congested traffic conditions in which the snowplow is prevented from maintaining this minimum speed, snow spillage may occur at the edge of the plow not intended to discharge snow, leaving ridges of snow in the middle of the roadway or causing the vehicle to stall. Also, snowplow blades are straight and rigid, designed to remove snow from regular surfaces. When they contact fixed protrusions from the surface, these blades may become bent or damaged in other ways, requiring costly repair or replacement. Also, the plow blade does not remove the snow from the ground cleanly, but rather, leaves surface recesses filled with snow. 
     Snowblowers have certain advantages over plows: they do not require a minimum forward velocity of the prime mover in order to move the snow and, depending on the orientation of the discharge outlet and the throw speed, they may avoid creating snowbanks at the roadside. Yet, there are also disadvantages inherent to snowblowers, existing in all of their many types. Snowblowers typically engage the snow by means of cutters, brushes, or augers, and transport the snow to a blower unit which discharges it to either side of the snowblower at some distance from the roadway. Cole (U.S. Pat. No. 2,103,514; 1937) teaches a system that uses a pair of rotary cutters to engage and then transport the snow or ice to a centrally located blower unit, which then discharges the snow or ice to either side of the vehicle as desired. Another system teaches the use of a rotary drum having blades located around its periphery to cut and lift snow and convey it to a discharge unit Maxfield et al. (U.S. Pat. No. 5,209,003; 1993). The rigidity of augers or cutters, as taught by the systems of Cole or Maxfield et al. creates several difficulties. For one thing, the leading edge of an auger or a rotary cutter is necessarily exposed to allow engagement with the snow; these rigid, churning augers or cutters make such snowblowers inherently dangerous to use. Furthermore, rigid augers and cutters can damage—or be damaged by—roadway protrusions, such as manhole covers or bridge joints, and, consequently, must be operated at some distance above the level of the surface to be cleared. This practice leaves residual snow on the surface. This means that systems that use augers or cutters can be used only in conjunction with other snow removal means, physical or chemical, if the snow is to be completely removed. 
     Snow blowers do exist that use brushes rather than rigid augers. E.g., Klauer (U.S. Pat. No. 2,941,223; 1960) teaches a manually operated system that uses two spiral brushes, oppositely wound around a rotating shaft, to transport snow to the center of the shaft. Alternatively, Maisonneuve et al. (U.S. Pat. No. 3,886,675; 1975) teaches the combined use of a rotating brush and an auger to engage snow and transport it to the blower unit. Rotating brushes, unlike rotating cutters and augers, can be operated in direct contact with the ground surface. Brushes, however, have a disadvantage in that the bristles in the brushes are round and, thus, only the snow particles that hit the leading edge of the bristles are propelled forward. All others are deflected laterally to varying degrees. Brushes also require a great deal of power to engage and lift the snow. This is because, typically, every bristle contacts the ground and, thus, every bristle bends, its tip contacting the ground. This results in the leading edge of the bristle actually facing downward before the bristle tip starts its desired forward and then upward movement as the tip loses contact with the surface. As a result, the snow is initially driven downward before it is propelled upward and forward. This results in a packing of the snow, making it more resistant to being passed through the rest of the device. Furthermore, since all the bristles drag on the ground, they encounter a frictional force that works against the direction of the brush rotation. This increases the power demanded to maintain that rotation at an effective rate. 
     As described above, snowblowers with brushes, augers or rotary cutters typically transport the snow to a centrally situated blower unit for expulsion. This means that the snow is handled for an extended period of time, as it travels from the outer edge of the snow collection means to the center, or, when dual snowblowers are used, as it travels from the center of snow collection device to the outer edges. The longer the snow remains in the system, the greater the volume of snow that is being handled or transported at any given time. Thus, snowblower systems must be designed to accommodate these large volumes and provided with the power required to move them. Also, the fact that snowblowers pack the snow as it is handled means that more power is required to transport the snow then would be the case with loose fluffy snow. Furthermore, the high-density, packed snow often causes the equipment to jam, leading to interruptions and potentially hazardous operations to clear the device. 
     Snow or debris removal systems are generally dedicated systems, i.e., a snow removal system is designed to remove only snow, a street sweeper is designed to remove only dirt and loose debris from the ground. As a consequence, cities, towns, and other entities that must be concerned with removing snow or debris from ground surfaces are required to invest in multiple costly devices to perform various necessary ground cleaning operations. It would be of great advantage if a system for removing snow and other debris could be rapidly and easily reconfigured as required to perform various ground surface cleaning operations, such as removal of frozen slush or fallen leaves or other loose debris, in addition to snow removal. 
     Therefore, what is needed is a snow removal device that will cleanly and safely remove snow from ground surfaces and discharge the snow without creating snowbanks that narrow the roadway or impair visibility. What is further needed is such a device that will fracture the snow into small, light units, thereby improving the operating speed, efficiency, and safety of such a device. What is yet further needed is such a device that will cleanly remove snow from irregular ground surfaces. What is still further needed is such a device that can be rapidly and easily reconfigured to perform various ground surface cleaning operations. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a snow removal device that will cleanly and safely remove snow from ground surfaces and discharge the snow without creating snowbanks that narrow the roadway or impair visibility. It is a further object of the invention to provide such a device that will fracture the snow into small, light units. It is yet further an object of the invention to provide such a device that will remove snow from irregular ground surfaces. It is still further an object of the invention to provide a device that can be rapidly and easily reconfigured to perform various ground surface cleaning operations. 
     The apparatus of the present invention provides a novel means for cleanly and efficiently removing snow and other debris from ground surfaces, regardless of whether the surfaces are level. The equipment is safer to operate than either snowplows or auger-using snowblowers, it is easily accessible for cleaning and maintenance, and requires a minimal amount of operating energy. The basic units of the system of the present invention are a novel rotating pick-up assembly mounted in close proximity to an impeller assembly. The system can be contained on its own chassis and pushed in front of, or pulled behind, a prime mover such as a truck, or can be self-propelled, or mounted on another vehicle. 
     In its Preferred Embodiment, the removal system of the present invention is mounted on a floating chassis attached to and suspended from a “fixed” chassis that can be pulled or pushed. The fixed chassis is designed to support floating chassis of varying widths. The moving components of the system are powered by a hydraulic power unit, or other power means, that can be incorporated into the system, or provided externally. The basic units of the removal system are a pick-up assembly, an impeller assembly, and a discharge tube. The pick-up assembly consists of a drum array mounted on a drum shaft that runs parallel to the ground surface and perpendicular to the direction the system is intended to move. The drum array may be formed from a plurality of interconnected drums, or it may consist of an individual drum. Most importantly, each drum carries an array of finger modules and each finger module includes an array of flat fingers, each of which is an elongated, thin element. Fingers offer distinct advantages over snow removal equipment that uses plow blades, augers, cutters, or rotary brushes. Made of a stiff, yet flexible material, they will flex when they come into contact with fixed protrusions on the surface, unlike rigid plow blades, augers or cutters. As a result, the fingers are much less likely to be damaged by objects on road surfaces; also, they will not damage protrusions on the ground surfaces such as manhole covers and bridge joints. This finger module is the heart of the present invention, which thereby provides advantages over rigid, straight-edged plow blades, rotary brushes and augers and cutters with respect to its ability to sweep surfaces clean of debris, including snow. In the Preferred Embodiment, these stepped finger modules have three fingers: a leading finger, a middle finger, and a trailing finger, each successively longer. In the operating position, the distance of the pick-up assembly from the ground is adjusted so that the middle finger just grazes the mean level of the ground surface. With the drum rotating in a direction that causes the snow to be flicked forward to the impeller openings, the leading finger does not touch the road surface at all, but rather strikes the snow at some short distance above the ground. As this leading finger hits the snow, it fractures it, i.e., it breaks the snow into small particles and, as the finger continues through into its forward and upward rotation, it lifts the snow particles into the vicinity of the impeller assembly intake. With the apparatus operating in this manner, the middle finger just grazes the ground surface and conveys forward and upward the snow that the leading finger left behind. The trailing finger, having a length greater than the distance needed to reach the ground, flexes and drags when it contacts a flat surface. Thus, it is able to scoop snow out of depressions in the road or ground surface. In short, the leading finger fractures and displaces the snow down to within an inch or so above the ground. Because it is just moving through snow, without scraping against the road surface, this lead finger encounters minimal “back forces” and, consequently, presents minimal drag on the drum rotation. The middle finger fractures and lifts the snow left by the leading finger, also transmitting little back force to the drum, since it just grazes the surface and does not have to flex and drag on the ground. The trailing finger, when it contacts the ground, does flex and scrape the ground, thus creating a back force on the drum. However, since it is not lifting any significant amount of snow (the bulk of the snow having already been cleared away by the leading and middle fingers), the ground resistance is about all that contributes to its drag. Thus, in contrast to snowblower systems or plows that compact the snow in the pick-up process, the pick-up assembly of the present invention breaks the snow into small units while it lifts it from the surface, cleanly and with a minimal force on the drum. The fingers offer a further advantage in that individual fingers can easily be replaced when they eventually become worn or damaged, in contrast to the large snowplow, auger, or brush assemblies, each of which can be very costly to replace. 
     The snow removal device of the present invention is intended to be used in connection with new snowfall as well as with packed snow. In normal operating mode, the lower half of the drum is rotating in the direction of travel of the system, with the shorter finger being the leading finger. For light fluffy snow, the direction of the rotation of the drum can easily be reversed, so that the lower half of the drum is rotating opposite the direction of travel. In this mode of operation, the longer finger becomes the leading finger, with the middle and shorter fingers providing a stiffening and strengthening of the leading finger. The snow is swept backward and upward, propelled around the drum, and driven from above into the impeller assembly. The advantages of operating the system in this reverse mode are twofold: the system can be operated at greater travel speeds, and less power is required to operate the drum. 
     The impeller assembly includes one or more impeller units. In the Preferred Embodiment, four impeller units are arranged in an array such that an axis that passes through the centers of them all is perpendicular to the direction of travel of the snow-removal apparatus and parallel to the pick-up assembly&#39;s drum shaft. The impeller assembly is mounted on the floating chassis adjacent to the pick-up assembly. The impellers are similar to fans that move large volumes of air. In this case, the action of the impellers creates a pressure gradient such that all snow brought near the intakes is sucked into them. Each impeller unit includes an impeller blade array attached to an impeller shaft and to an impeller base plate, and an impeller chamber formed by an impeller chamber cover and impeller chamber walls. The impeller blades rotate in impeller chambers and, as an impeller blade approaches the opening between the chamber and the discharge tube, the rotational impeller action flings the snow into the discharge tube whence It is expelled from the system. The direction of impeller rotation is reversible, therefore the snow can be discharged to either side of the system, as desired. The discharge tube lies in the same plane and is parallel to the impellers and, thus, discharges the snow transversely at a relatively low height, using to advantage the fling momentum of the impellers and reducing the danger of snow cloud formation. 
     In normal operation, the plane of the impeller intake is tilted only slightly upward toward the pick-up assembly; however, the section of the floating chassis that supports the impeller/discharge assembly can be pivotally attached to the section of the floating chassis that supports the pick-up assembly so as to allow the plane of the impeller intake to be tilted at a steeper angle. Increasing the angle of the plane of the impeller assembly/discharge tube relative to the ground brings the impeller intake closer to the pick-up assembly, thereby decreasing the distance the snow must travel between the exit point of the pick-up assembly and the impeller assembly intake. This is advantageous when clearing wet snow. Increasing the tilt of the impeller intake plane also raises the height of the discharge tube, changing the height and angle of discharge, which may be desired in certain conditions. The use of multiple impellers has distinct advantages over systems that utilize only a single or two blower units. The pick-up assembly does not need to transport the snow as far to deliver it to the impeller unit because of the proximity of the impeller assembly intake to the pick-up system. Also, the “negative” pressure that is created along the length of the pick-up assembly by the impeller action assists the delivery process by sucking the snow into the impellers. Furthermore, the snow is handled for a much shorter period of time before it is dumped into the discharge tube and, consequently, the use of multiple impellers reduces the volume of snow that is within the system at any one time. Thus, the impeller assembly handles the snow more efficiently and can be much more compact in design relative to other known snowblower systems of equivalent capacity. 
     Separate housings enclose the pick-up assembly and the impeller assembly/discharge tube so that during operation all sides, with the exception of the bottom of the pick-up assembly, are enclosed. This enhances the operating safety of the system because no moving parts of the apparatus are exposed during operation. Removable access covers can be opened to provide access to the pick-up assembly and the impeller assembly and discharge tube from above, making the assemblies readily accessible for cleaning and maintenance. 
     The apparatus of the present invention has three operating positions: an idle position in which the fingers of the pick-up assembly only reach to within one or two inches of ground level; a working position in which the middle finger just grazes the ground; and a transport position in which the entire device is raised and supported so that the fingers only come to within six to eight inches of the ground. For cleaning and maintenance operations, the floating part of the apparatus can be raised still further above ground level or the fixed chassis can be lifted from above to provide easy access to the pick-up assembly and the impeller assembly and discharge tube. 
     The device of the present invention is a versatile system that can be used for purposes other than snow removal. For example, the pick-up assembly with the finger modules can also be used for cleaning streets of debris in the summer. Furthermore, the drum with the finger modules can be easily and conveniently removed and replaced with another drum, such as a drum fitted with special blades or chains for removing ice, or with a brush for removing sand from the road in the spring. Furthermore, the versatility of the system is enhanced by the fact that the fixed chassis of the system can support varying widths of a floating chassis and the fact that the drum can rotate in a forward or reverse direction relative to the direction of translational travel. 
     In summary, the present invention includes a pick-up assembly and an assembly that includes an impeller assembly and a discharge tube, both of which are mounted on a floating chassis that in turn is mounted on a fixed pullable or pushable chassis, with the drum of the pick-up assembly and the blades of the impeller assembly driven by hydraulic motors mounted on the floating chassis. All moving parts of the system are enclosed in housings or under hoods during operation, greatly improving the safety of operating such a system. As the drum in the pick-up assembly rotates, the stepped, triple-finger modules fracture the snow and lift it into the vicinity of the impeller assembly, where it is sucked into the impellers and discharged to either side of the system through the discharge tube. The use of stepped fingers allows the snow to be broken up into small units, rather than be compacted, as is the case with snowplows and brush, auger, or cutter snowblowers. This offers several advantages: the snow is lighter and easier to transport, less power is required for its transportation, and the fracturing action of the fingers reduces the probability of the snow packing while being handled, thus increasing safety and efficiency. The use of flexible-yet-stiff fingers offers further advantages in that the fingers clean uneven road surfaces of snow efficiently and without damage to the snow removal equipment or to protrusions from the road surface such as manhole covers and bridge joints. The use of fingers is also cost effective, as the fingers can be replaced individually should they become worn or damaged. The use of multiple impellers provides a more efficient, compact design than the use of simply one or two impellers and also creates a suction force that aids in delivering the snow into the discharge assembly. Furthermore, the location of the discharge tube allows for relatively low transverse discharge, thus reducing the formation of snow cloud and improving visibility for other vehicles and pedestrians in the vicinity of the operating system. A device for removing snow or other debris from ground surfaces which has several different, easily and rapidly interchangeable drums, each configured to perform a certain ground cleaning operation, offers cost-saving advantages to entities that must acquire several different devices to perform the various typical cleaning operations on roads and other ground surfaces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of the system, shown as it appears during operation, fully enclosed in housings and with access covers closed. 
     FIG. 2 is a side view of the system, shown as it appears during operations, fully enclosed in housings and with access covers closed. 
     FIG. 2 a  is a schematic drawing of the drum mounting and drum motor drive. 
     FIG. 3 is a perspective view of a finger module. 
     FIG. 4 shows a drum shaft with finger modules. 
     FIG. 5 shows a fully assembled drum array. 
     FIG. 5 a  shows a partially assembled drum array of the Preferred Embodiment. 
     FIG. 6 is a frontal view of a bracket with finger modules. 
     FIG. 7 is a top view of the system with housings and covers removed. 
     FIG. 8 is a frontal view of the impeller assembly. 
     FIG. 8 a  is a top view of the chamber wall and blade set of an impeller unit. 
     FIG. 8 b  is a frontal view of the impeller blade attached to the impeller shaft. 
     FIG. 9 is a perspective view of an impeller assembly and discharge tube. 
     FIG. 10 is a partial cut-away view of the system according to the invention, showing the pick-up assembly, the impeller assembly, and the discharge tube. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In its Preferred Embodiment, the apparatus of the present invention is configured to be a snow removal system  1  FIG.  1  and FIG. 2 show the snow removal system  1  as it appears during operation. A pick-up assembly  4  is enclosed under a curved pick-up assembly housing  6  having a removable access cover  7 ; an impeller assembly  5  and discharge tube  70  are enclosed under an impeller assembly/discharge tube housing  8  having a removable access cover  9 . During operation, the pick-up assembly  4  picks up snow and conveys it to the impeller assembly  5 , which expels the snow into the discharge tube  70  whence it is discharged from the system  1  through discharge tube end  71 . As can be seen in FIG.  1  and FIG. 2, the sides and tops of the pick-up assembly  4  and the impeller assembly  5  are fully enclosed during operation, thus preventing any unintended contact of operators or pedestrians with moving parts of the system  1 . FIG. 10 is a partial cut-away view of the snow removal system  1  and illustrates the arrangement of the pick-up assembly  4 , the impeller assembly  5 , and the discharge tube  70 . 
     The heart of the invention lies in the use of a finger module  33  as a snow pick-up device on the pick-up assembly  4 . As can be seen in FIG. 3, the finger module  33  of the Preferred Embodiment includes a triad of blade-like fingers including a long trailing finger  33   a , a middle finger  33   b , and a short leading finger  33   c . The fingers  33   a ,  33   b ,  33   c  are fabricated of band or spring steel or any other material that is sufficiently strong to allow the fingers  33   a ,  33   b ,  33   c  to fracture and lift snow, yet flexible enough to allow them to bend when they contact the ground or fixed objects. Referring again to the Preferred Embodiment, the fingers  33   a ,  33   b ,  33   c  are approx. 1″ in width, the trailing finger  33   a  is approximately 1″ longer than the middle finger  33   b  and 2″ longer than the leading finger  33   c . Although the finger module  33  in the Preferred Embodiment has a triad of fingers, it is still within the scope of the present invention to have a pick-up drum  35  having a plurality of finger modules that include one or more fingers. Such a pick-up drum  35  is shown in FIG.  4 . FIG. 5 shows a fully assembled drum array  17  of the pick-up assembly  4  and FIG. 5 a  shows a partially assembled drum array  17   a  according to the Preferred Embodiment The drum array  17  contains a plurality of drums  18   a ,  18   b ,  18   c , . . . , a drum shaft  12 , and an inner shaft  12   a  having shaft ends  13 . In the Preferred Embodiment, the drum shaft  12  is fabricated of schedule  80  steel pipe, 4″ in diameter and approx 87″ in length, but could be made of any suitable length and be fabricated of any other material that is strong enough to withstand the forces applied to the shaft. The drum shaft  12  is fitted over the inner shaft  12   a . This inner shaft  12   a  is a solid steel shaft  2  {fraction (7/16)}″ in diameter that extends the entire length of the drum array  17  with shaft ends  13  fitting into support bearings  206  (not shown) mounted on the floating chassis  2 . FIG. 5 a  shows a partially assembled drum array  17   a  according to the Preferred Embodiment. A first drum  18   a  is formed by mounting a first drum disk  20   a  and a second drum disk  20   b  rigidly on the drum shaft  12  and mounting a plurality of first brackets  27   a  between the first drum disk  20   a  and the second drum disk  20   b  so that the plurality of first brackets  27   a  is distributed evenly around and aligned parallel to the drum shaft  12  and perpendicular to the first drum disk  20   a  and the second drum disk  20   b . A plurality of first finger modules  34 a is removably attached to each of the plurality of brackets  27   a . A second drum  18   b  is formed by mounting an additional drum disk  20   c  on the drum shaft  12 , then mounting a plurality of second brackets  27   b  between the second drum disk  20   b  and the additional drum disk  20   c . A plurality of second finger modules  34   b  is removably attached to each of the plurality of second brackets  27   b . Subsequent drums  18   c , . . . , are formed in a similar manner. As shown in FIG. 5, in the Preferred Embodiment the plurality of first brackets  27   a  of the first drum module  18   a  is radially offset to the plurality of second brackets  27   b  of the second drum  18   b , and this manner of offsetting is continued in the subsequent drums  18   c , . . . . This arrangement distributes in time the load on the drum shaft  12 , reducing maximum torsional stress and also vibrations. In the Preferred Embodiment, the diameter of the completely assembled drum array  17  is about 30 inches. Although the drum array  17  according to the Preferred Embodiment of the invention as shown in FIG. 5 a  includes a plurality of drums  18   a ,  18   b ,  18   c , . . . , the scope of the invention is not limited to the drum array  17 . A pick-up assembly could comprise a single drum mounted on a shaft. 
     Each of the plurality of first brackets  27   a  and of the plurality of second brackets  27   b  has the form of a bracket  27 , shown in FIG.  6 . According to the Preferred Embodiment, a group of nine finger modules  34  is removably attached to the bracket  27 . FIG. 6 also shows a bracket overlap  28  that extends laterally beyond the mounting width of the bracket  27 . An overlap finger module  36  is attached to this bracket overlap  28 . The purpose of the bracket overlap  28  is to allow the finger module  36  to pick up snow spillage from an adjoining drum module  18 . 
     Another key component of the invention is the impeller assembly  5 . As shown in FIG. 7, FIG. 8, FIG. 8 a , and FIG. 9, the impeller assembly  5  of the Preferred Embodiment includes four impeller units  67 , each of the four impeller units  67  includes an impeller chamber  52  formed by an impeller wall  63  and an impeller chamber cover  59 , an impeller intake  63  formed by a divider plate  60 , an impeller exit  66 , an impeller shaft  56 , an impeller blade array  64 , and an impeller base plate  57 . As shown in FIG. 8, the impeller base plate  57  is rigidly and permanently connected to the impeller shaft  56  which is rotatably mounted on a lower support bearing  51 . The impeller blade array  64  is rigidly and permanently attached to the impeller shaft  56  and the impeller base plate  67 . In the Preferred Embodiment, the impeller blade array  64  includes six blades  58 , each of which is flat and substantially rectangular. As can be seen in FIG. 8 b , the upper blade edge  58   a  is notched to improve the flow of the snow down into the impeller chamber and, also, to reduce noise. In the Preferred Embodiment, a notch  58   b  has an outer leg  58   c  and an inner leg  58   d , the ratio of the length of the outer leg  58   c  to the length of the inner leg  58   d  being 2:3. The four impeller units  67  are mounted such that an axis passing through each of the four impeller units  67  lies parallel to the discharge tube  70  and the pick-up assembly  4 . FIG. 9 shows the divider plate  60  mounted vertically between the impeller cover plate  59  of any two of the four impeller units  67 . As seen in FIG.  8  and FIG. 9, the divider plate  60  creates a separate impeller intake  63  above each impeller unit  67  and serves to reduce the amount of air crossflow across the four impeller units  67 , thereby improving the suction and reducing the amount of snow spillage. As shown in FIG. 1, snow is discharged to the right through the discharge tube end  71 . The impeller action is reversible in direction and, therefore, in other embodiments the snow can be discharged to the left or to the left and the right simultaneously, as desired. When snow is discharged to one side only, a guide plate can be installed in the discharge tube  70  at the end opposite the discharge tube end  71  or the shape of the impeller assembly/discharge tube housing  8  can be modified to prevent snow from accumulating in a comer area of the non-discharging end of the discharge tube  70 . FIG. 8 shows a Teflon disk  65  placed between the impeller assembly housing floor  8   a  and the base impeller plate  57  to prevent the impeller base plate  57  from freezing to the impeller assembly housing floor  8   a . Other means for preventing ice from forming in the gap between the base plate  57  and the impeller assembly housing floor  8   a  can also be used. 
     The pick-up assembly  4  with the pick-up assembly housing  6  and the impeller-assembly/discharge-tube housing  8  including the impeller assembly  5  and the discharge tube  70  are mounted on the floating chassis  2  that is suspended from a fixed chassis  3 . In the Preferred Embodiment, the floating chassis front end  2   a  is attached to the fixed chassis front end crossbar  3   a  by means of a clevis pin  80  which allows the front end  2   a  to pivot about the fixed chassis front end crossbar  3   a . As shown in FIG.  1  and FIG. 2, a pair of standard dolly wheels  110 , a lifting frame  112 , and a known lifting means, such as a lifting ram  111 , can be used to adjust the height of the floating chassis rear end  2   b . In the Preferred Embodiment, the dolly wheels  110  are mounted on each side of the floating chassis rear end  2   b  and the lifting frame  112  is mounted in the center of the floating chassis rear end  2   b . The lifting ram  111  is mounted on a power deck  300  and attached to the lifting frame  112 . In the Preferred Embodiment, the floating chassis rear end  2   b  has three operating positions: (a) In its working position, the floating chassis rear end  2   b  rests on the dolly wheels  110 . The dolly wheels  110  are sized such that the tip of the middle finger  33   b  of the finger module  33  just grazes the ground when the floating chassis rear end  2   b  is supported by the dolly wheels  110 . As the system is operated, the dolly wheels  110  follow the contour of the ground surface, allowing the pick-up assembly  4  to follow the same contour. To adjust the working position of the floating chassis  2 , the length of the lifting ram  111  is adjusted until the dolly wheels  110  touch the ground and is then retracted approximately another inch. If the dolly wheels  110  should drop down into a recession in the ground, such as into a large pothole, the floating chassis rear end  2   b  will drop down only the distance that the lifting ram  111  was retracted after adjusting the height of the floating chassis rear end  2   b  because the lifting frame  112  will come to rest on the lifting ram  111 , preventing the floating chassis rear end  2   b  from dropping further. This is done to protect the drum array  17  from being damaged by hitting the ground surface. (b) For an idle position, the lifting ram  111  can be extended to push up against the lifting frame  112 , raising the floating chassis rear end  2   b  until the tip of the trailing finger  33   a , at its lowest position, is one to two inches above ground. (c) When the system is in transit, the lifting ram  111  can be used to raise the position of the floating chassis rear end  2   b  high enough so that the lowest position of the trailing finger  33   a  is six to eight inches above ground. For maintenance and repair work, the floating chassis rear end  2   b  can be raised still higher by the lifting ram  111  or the fixed chassis  3  can be raised to provide easy access to the pick-up assembly  4 , the impeller assembly  5 , and the discharge tube  70 . 
     The fixed chassis  3  can be hitched to or mounted on a prime mover which pushes or pulls the system  1  along the surface to be cleared of snow. In the Preferred Embodiment, the system  1  is hitched to a prime mover which pulls the system and powered by a commercially available hydraulic power unit that is carried external to the system on a power deck  300  shown schematically in FIG.  1  and FIG.  2 . The fixed chassis rear support  3   b  is mounted on the power deck  300 . The drive motors for the drum and the impeller assembly are mounted externally on the floating chassis  2  and are shown in FIG. 1, FIG. 2, and FIG.  7 . Although the hydraulic power unit is shown carried on the power deck  300  in the Preferred Embodiment, it may be mounted externally to the snow removal system  1  in a variety of ways. Such power units and the methods of powering such equipment as that of the present invention are well-known to those skilled in the art and are not included within the scope of this invention. The belt shields  201  that cover the two hydraulic drum-shaft-drive motors  40  and the belt shields  207  that cover the two hydraulic impeller-drive motors  61  can be seen in FIGS. 1 and 2. Any commercially available hydraulic motor that provides sufficient power to drive the drum shaft, such as 20 HP hydraulic drive motors, can serve as the drive motors  40  to drive the drum shaft  12  of the pick-up assembly  4 . Commercially available motors, such as White Hydraulics RS-Series, Model 10, can serve as drive motors  61  to drive the impeller units  67  of the impeller assembly. Although this invention uses a hydraulic power system with two drive motors  40  for the drum assembly and two drive motors  61  for the impeller assembly, it is understood that it is within the scope of this invention if a different number of motors or other suitable means of driving the drum shaft and the impeller shafts are used. 
     When the system  1  is operating in its normal mode, the drum array  17  of the pick-up assembly  4  rotates as illustrated by a directional arrow  102  in FIG. 2. A directional arrow  101  indicates the direction of travel of the system. For purposes of illustration, FIG. 7 shows the system  1  with the pick-up assembly access cover  7 , and the impeller assembly/discharge tube access cover  9  removed. The finger modules  33  on the drum array  17  pick up snow as the drum array  17  rotates around the drum shaft  12  and convey the snow to the impeller intake  63  of each of the four impeller units  67  of the impeller assembly  5 . The impeller intake  63  is an open chamber extending across all four impeller units  67 , as shown in FIG.  8 . In the Preferred Embodiment, the impeller units  67 , rotating in the direction indicated by arrow  103 , transport the snow around the impeller chamber  52  and fling the snow into the discharge tube  70 , whence it is then discharged at right angles to the direction of travel of the system  1  through a discharge tube end  71 . In the Preferred Embodiment, and as shown in FIG. 2, the discharge tube  70  is formed by the impeller assembly/discharge tube housing  8 , and the discharge tube end  71  is located at the right end of the discharge tube  70 . It is understood that the discharge tube end  71  can be located at either the left or right end of the discharge tube  70 . In the Preferred Embodiment, the plane of the impeller assembly  5  and the discharge tube  70  is tilted upward approximately 20° relative to the ground so that the plane of the impeller intakes  63  is tilted toward the pick-up assembly, as shown in FIG.  2 . It is possible to adjust the tilt of the plane of the impeller assembly  5  and discharge tube  70  to a greater angle relative to the ground. For example, a first section of the floating chassis  2   c  that supports the impeller assembly  5  and the discharge tube  70  can be pivotally attached to a second section of the floating chassis  2   d  that supports the pick-up assembly, as shown in FIG. 2 at  2   e . A hydraulic piston (not shown) can be mounted on each side of the floating chassis  2  on the second section of the floating chassis  2   d  and attach to each side of the discharge tube  70  such that, when the piston is retracted the tilt the plane of the impeller assembly  5  and the discharge tube  70  is adjusted to a steeper tilt. 
     FIG. 2 shows a side view of the pick-up assembly  4  and the impeller assembly  5  with the discharge tube end  71 . In the Preferred Embodiment, as shown in FIG. 2, a rear pick-up plate  11 , hingedly attached to the floating chassis  2  and extending parallel to the pick-up assembly  4 , extends below the pick-up assembly housing  6 . This rear pick-up plate  11  is flexible so that it can drag across protrusions in the ground surface. The purpose of the rear-pick-up plate  11  is to keep within the pick-up assembly area any snow that is not engaged and lifted by the pick-up assembly  4  so that the snow can be picked up during the continuing rotation of the pick-up assembly  4 . Also seen in FIG. 2 is an inclined feed plate  10 , fabricated of a rigid, smooth material such as steel, and hingedly attached to the floating chassis  2  so that it extends parallel to the axis of the pick-up assembly  4  and, as can be seen in FIG. 2, extends below the pick-up assembly housing  6 . The lower inclined feed plate edge  10   b  is a distance from the ground that corresponds to the depth of snow the system  1  is designed to clear, which, in this Preferred Embodiment, is approximately four inches. Thus, the inclined feed plate  10  skims across the surface of the snow, providing a smooth, non-sticky surface against which the snow that is being lifted by the pick-up assembly  4  can slide and creep upward toward the impeller assembly  5 . 
     The system  1  of the present invention is designed to be a versatile, multi-purpose system for removing snow and other debris from ground surfaces. To this end, the drum array  17  of the Preferred Embodiment can be easily and quickly exchanged for a drum or drum array configured for a cleaning operation other than snow removal mounted. FIG. 2 a  shows a drive arrangement  200 . To exchange the drum array  17  for another drum or drum array, the belt shield  201  and the pick-up assembly housing end shield  6   a , attached to pickup assembly housing  6  at each end of the pickup assembly  4 , are removed. The belt tensioner  202 , the drive belt  204 , and the main drive pulley  203  are removed from each end of the drum array  17 , exposing each end of the inner drive shaft  12   a . Two standard, commercially available rolling carriages, each fitted with a pillow block bearing, are positioned at each end of the drive shaft  12  and adjusted in height until the rolling carriages a bearing the weight of the drum array  17 . Fasteners are removed from a drum mounting plate  205  which is arranged at each shaft end  12   a  for mounting the drum array  17  on the floating chassis  1 . The rear pick-up plate  11  and the inclined feed plate  10  are loosened so as to allow the rear pick-up plate  11  and the inclined feed plate  10  to s down and free of the drum array  17 . Using the hydraulic ram  111 , the floating chassis rear end  2   b  can be raised until the pick-up assembly housing  6  clears the drum array  17 . The drum array  17  can now be wheeled out from under the pickup assembly  4 . To install another drum or drum array, the process is reversed. In the Preferred Embodiment, the time estimated to exchange drums is approximately 1 hour. 
     While a Preferred Embodiment is disclosed herein, this is not intended to be limiting. Rather, the general principles set forth herein are considered to be merely illustrative of the scope of the present invention and it is to be further understood that numerous changes may be made without straying from the scope of the present invention.