Wastewater treatment apparatus with ice resistant adjustable friction drive

A wastewater treatment apparatus comprising a generally circular tank having a wall; a rotatable driven bridge having one end positioned above the center of the tank and an opposite end supported above the tank wall; a sludge moving member supported by the bridge and movable in response to movement of the opposite end of the bridge along the tank wall; and a drive apparatus for moving the opposite end of the bridge along the tank wall. The drive apparatus includes a rail extending along the top of the wall, a frame supporting an end of the bridge, an idler wheel supporting the frame for movement along the top of the wall, a drive wheel rotatably supported on the frame, means for urging the drive wheel into frictional engagement with the surface of the rail, and a drive motor operably connected to the drive wheel for driving the drive wheel along the rail. Preferably, the means for urging the drive wheel is adjustable for controlling the frictional engagement of the drive wheel with the surface of the rail. The apparatus preferably further includes heating apparatus for heating one of the rail and drive wheel to prevent accumulation of ice and snow, and, more preferably, the heating apparatus includes the rail being a hollow member for containing heated fluid. Also, the surface of the rail and the drive wheel preferably are curved to provide a large surface area for frictional engagement of the rail and the drive wheel.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to wastewater treatment apparatus, and, more 
particularly, to such apparatus including a drive apparatus for propelling 
a rotating bridge. 
2. Reference to Prior Art 
One common type of wastewater treatment apparatus for separating liquids 
and solids, frequently described as a clarifier, includes a generally 
circular wastewater treatment tank, a rotatable driven bridge, a sludge 
moving member supported by the bridge and a drive apparatus. The tank 
includes a wall having a top surface. The rotatable driven bridge includes 
one end supported above the center of the tank and an opposite end 
supported above the tank wall and is supported such that the opposite end 
of the bridge can move along the tank wall and rotate the bridge about the 
center. The sludge moving member is supported in the tank by the bridge 
and is movable in response to movement of the opposite end of the bridge 
along the tank wall. The drive apparatus for moving the bridge along the 
tank wall typically includes a frame supported by a pair of drive wheels. 
The frame supports the end of the bridge for movement along the top of the 
tank wall. The drive wheels rest on the top surface of the tank wall and 
support the frame for movement along the tank wall. A drive motor is 
operably connected to the drive wheels for driving the drive wheels along 
the top surface of the tank wall. 
In such an arrangement, in order to move the bridge the drive wheels must 
have secure frictional engagement or traction with the top surface of the 
tank wall. When snow or ice accumulates on either the drive wheels or the 
top surface of the tank wall, traction declines. When traction declines, 
movement of the bridge may be interrupted, resulting in malfunction or 
shutdown of the wastewater treatment apparatus. Thus it is frequently 
necessary for the drive apparatus to include a cowling extending ahead of 
the drive wheels to push snow out of the path of the drive wheels. It is 
also necessary for personnel to scrape ice and snow accumulations from the 
top wall to improve traction. Spreading sand and salt on the tank wall is 
also frequently required to improve traction and minimize the rate of ice 
and snow accumulation. 
U.S. Pat. No. 2,418,189 issued to Nordell relates to a clarifier for 
separating liquids and solids wherein a truss provided with a plurality of 
scraper blades is supported by two wheels on the upper side of a rail. A 
pinion engages a rack on the lower edge of the rail to move the truss. 
U.S. Patent Reissue No. 23,415 also issued to Nordell relates to a traction 
drive wherein a wheel riding on the upper surface of a rail moves a 
rotating bridge. When the force required for moving the bridge is greater 
than can be secured by the wheel alone, a second wheel can be mounted in 
contact with the lower edge of the rail. 
U.S. Pat. No. 4,859,346 issued to Wood relates to a traction drive which is 
mounted on a circular support base at ground level below and exterior of 
the vertical walls of an above ground tank. A continuous rail and rack are 
mounted on the base, and a wheel and pinion assembly are provided so that 
the wheel rolls on the rail and the pinion meshes with the rack. 
German Patent 2,812,525 relates to a settling tank including a scraper 
drive trolley having drive wheels with V-shaped tread for straddling the 
top of a rail and crushing any ice which forms on the rail. 
SUMMARY OF THE INVENTION 
The invention provides a wastewater treatment apparatus including a 
rotatable bridge driven by an ice resistant drive apparatus, so that ice 
and snow accumulation does not prevent rotation of the bridge. The ice 
resistant drive apparatus avoids the application of materials such &s sand 
and salt, so that corrosion of the wastewater treatment apparatus does not 
occur. 
The invention also provides a rotatable bridge driven by an adjustable 
friction drive apparatus with the degree of frictional engagement of the 
drive wheels being adjustable to accommodate different operating 
conditions. 
Other features and advantages will become apparent to those skilled in the 
art upon review of the following drawings, detailed description and 
claims. 
The invention provides a wastewater treatment apparatus including a 
generally circular wastewater treatment tank, a rotatable driven bridge, a 
sludge moving member supported by the bridge and a drive apparatus. The 
tank includes a wall having a top surface. The rotatable driven bridge 
includes one end supported above the center of the tank and an opposite 
end supported above the tank wall such that the opposite end of the bridge 
can move along the tank wall and rotate the bridge about the center. The 
sludge moving or removing member is supported in the tank by the bridge 
and is movable in response to movement of the opposite end of the bridge 
along the tank wall. 
The drive apparatus for moving the bridge along the tank wall includes a 
rail extending along the top of the wall, a frame supported by an idler 
wheel and supporting the opposite end of the bridge for movement along the 
top of the wall, a drive wheel rotatably supported by a drive wheel 
mounting arm, means for urging the drive wheel upwardly for frictional 
engagement with the bottom surface of the rail, and a drive motor operably 
connected to the drive wheel for driving the drive wheel along the rail. 
In one embodiment of the invention, the opposite end of the bridge is 
supported on the frame and includes a pressure rod for urging the drive 
wheel upwardly. In another embodiment, the opposite end of the bridge is 
connected to the inner end portion of the drive wheel mounting arm for 
supporting the bridge and urging the drive wheel upwardly. In still 
another embodiment of the invention, the bridge is pivotally connected to 
the drive wheel mounting arm, and the distance between the pivotal 
connection of the drive wheel mounting arm to the frame and the pivotal 
connection of the drive wheel mounting arm to the bridge is adjustable to 
control the frictional engagement of the drive wheel with the bottom 
surface of the rail. 
In one embodiment of the invention, the drive apparatus includes heating 
apparatus for heating either the rail or drive wheel to prevent 
accumulation of ice and snow. Preferably, the heating apparatus includes 
the rail being a hollow member for containing heated fluid.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Illustrated in FIGS. 1 and 2 is a wastewater treatment apparatus 2 of the 
invention. The wastewater treatment apparatus 2 includes a generally 
circular wastewater treatment tank 4, a rotatable driven bridge 6, a 
sludge moving member 8, and a drive apparatus 10. 
The wastewater treatment tank 4 includes a floor 12 having a center 14 and 
a wall 18 having a top surface 20. Wastewater and sludge are contained in 
the tank. Although other suitable materials could be used, in the 
illustrated embodiment of the invention the tank 4 is constructed from 
concrete. The bridge 6 includes an end 22 rotatably supported above the 
center 14 of the tank 4 and an opposite end 24 supported above the tank 
wall 18. While other arrangements for rotatably supporting the end 22 of 
the bridge 6 are possible, in the illustrated embodiment of the invention 
a support 25 extends upwardly from the floor 12 and rotatably supports the 
end 22. As described in detail below, the opposite end 24 of the bridge 6 
is supported for movement along the tank wall 18 to rotate the bridge 6 
about the support 25. In the illustrated embodiment of the invention, the 
bridge 6 is constructed of a pair of horizontally extending steel "H" 
beams or trusses. 
The sludge moving member 8 is supported in the tank 4 by the bridge 6 and 
is movable in response to movement of the opposite end 24 of the bridge 6 
along the tank wall 18. Although the sludge moving member 8 can include 
any member suitably adapted for moving or removing sludge, in the 
embodiment of the invention illustrated in FIGS. 1 and 2, the sludge 
moving member 8 includes a scraper blade supported for scraping sludge 
from the floor 12. 
As shown most clearly in FIGS. 3 and 4, the drive apparatus 10 for moving 
the opposite end 24 of the bridge 6 along the tank wall 18 includes a 
fixed rail 26, movable frame 28, idler wheels 30, drive wheel mounting arm 
32, drive wheel 34, and drive motor 36. The rail 26 is rigidly supported 
by rail supports 38 to extend along and above the top surface 20 of the 
wall 18. As described in detail below, the rail 26 includes an upper 
surface 39 and a bottom surface 40 spaced above the top surface 20 of the 
wall 18. Although other suitable materials could be used, in the 
illustrated embodiment of the invention the rail 26 is constructed from 
steel. A pair of idler wheels 30 contact the wall top surface 20 and 
support the frame 28 for movement along the tank wall 18. While the frame 
28 can be constructed differently, in the embodiment of the invention 
illustrated in FIGS. 1-4, the frame 28 includes a horizontally extending 
frame beam 28a supported above the idler wheels 30, a first pivotal 
connection apparatus 28b on the beam 28a, and a drive motor mounting 
portion 28c also mounted on the beam 28a. 
The drive wheel 34 is mounted on a pivotable drive wheel mounting arm 32. 
The drive wheel mounting arm 32 includes opposed outer and inner end 
portions 42,44 and is pivotally connected to the frame beam 28a by the 
first pivotal connection apparatus 28b intermediate the end portions 
42,44. The first pivotal connection apparatus 28b can include any suitable 
connector, and in the illustrated embodiment of the invention is a pin 
pivotally engaging an aperture in the drive wheel mounting arm 32 and an 
aperture 28e in the frame beam 28. 
The drive wheel 34 is rotatably supported by a U-shaped bracket 45 fixed to 
the outer end 42 of the drive wheel mounting arm 32 for frictional 
engagement with the bottom surface 40 of the rail 26. The drive motor 36 
is operably connected to the drive wheel 34 for selectively driving the 
drive wheel 34 along the rail 26. Although the drive motor 36 may be 
connected to the drive wheel 34 in any suitable manner, in the embodiment 
of the invention shown in FIGS. 1-4, the drive motor 36 is connected to 
the drive wheel 34 by a chain and sprocket assembly 46. 
The opposite end 24 of the bridge 6 is supported by the drive apparatus 10 
for movement along the top 20 of the tank wall 18. Although they may be 
connected differently, in the embodiment of the invention illustrated in 
FIGS. 1-4, the opposite end 24 of the bridge 6 is connected to the inner 
end portion 44 of the drive wheel mounting arm 32 by second pivotal 
connection apparatus 48. Although different connection apparatus can be 
used, in the illustrated embodiment of the invention, the second pivotal 
connection apparatus is a pin 48 pivotally housed in one of a plurality of 
horizontally spaced first apertures 50 in the drive wheel mounting arm 32 
and one of a plurality of horizontally spaced second apertures 51 in 
U-shaped brackets 52 on the bridge 6. Although the distance between the 
first and second pivotal connections 28b,48 may be fixed, in the 
embodiment of the invention illustrated in FIGS. 1-4, the distance 28b-48 
between the first pivotal connection 28b of the drive wheel mounting arm 
32 to the frame beam 28a and the second pivotal connection 48 of the 
bridge 6 to the drive wheel mounting arm 32 is adjustable by selecting 
different first and second apertures 50,51 for connection by the second 
pivotal connection apparatus 48. Adjusting the distance 28b-48 between the 
first and second pivotal connections 28b,48 controls the frictional 
engagement of the drive wheel 34 with the bottom surface 40 of the rail 
26. When the distance 28b-48 is relatively small, the upward force exerted 
by the drive wheel 34 against the bottom surface 40 of the rail 26 is 
relatively small, so that the corresponding frictional engagement of the 
drive wheel 34 with the bottom surface 40 is also small. When the distance 
28b-48 is increased, the upward force and corresponding frictional 
engagement increase. 
As the drive wheel 34 is turned by the drive motor 36, the drive wheel 34 
frictionally engages the bottom surface 40 of the rail 26 and moves the 
opposite end 24 of the bridge 6 along the tank wall 18. While different 
configurations of the rail 26 and drive wheel 34 are possible, in the 
embodiment of the invention illustrated in FIGS. 1-4, the bottom surface 
40 of the rail 26 and the drive wheel 34 are curved in a complementary 
manner so that a large surface area of the bottom surface 40 is contacted 
by the drive wheel 34. The curvature of the bottom surface 40 and drive 
wheel 34 provide increased frictional engagement compared to flat 
surfaces. Although other materials, such as nylon, which are resistant to 
the adhesion of ice could be used, in the illustrated embodiment of the 
invention the drive wheel 34 is constructed from polyurethane to 
facilitate frictional engagement with the bottom surface 40. 
Although the illustrated configuration minimizes the accumulation of 
falling snow and ice that might otherwise hinder frictional engagement 
between the bottom surface 40 and the drive wheel 34, preferably the rail 
26 and drive wheel 34 are heated to resist accumulation of ice and snow. 
While other arrangements are possible for heating the rail 26 and drive 
wheel 34, in the embodiment of the invention illustrated in FIGS. 1-4 the 
rail 26 is a hollow tubular member having an internal cavity 60 for 
containing a heated fluid 62. The heated fluid 62, which may be gaseous or 
liquid, preferably is heated air and more preferably is a heat transfer 
liquid. As shown generally in FIG. 1, the fluid 62 is heated in a heater 
64, introduced into the rail cavity 60 through piping 66, and circulated 
through the internal cavity 60 to heat the rail 26. 
Illustrated in FIG. 5 is a second embodiment of a drive apparatus 10. In 
the embodiment illustrated in FIG. 5, the opposite end 24 of the bridge 6 
is fixedly supported on the frame beam 28a by bridge mounting apparatus 
28f. The drive wheel mounting arm 32 is pivotally connected to the frame 
beam 28a at first pivotal connection 28b, and a vertically extending 
pressure rod 68 on the bridge 6 engages the inner end portion 44 of the 
drive wheel mounting arm 32. The pressure rod 68 includes a handle 68a and 
is threadably mounted on the bridge 68 by threads 68b and a threaded 
connector 68c. The end of the rod 68 engages the mounting arm 32 at a 
second connector 68d. The length of the rod 68 extending below the bridge 
6 can be adjusted by moving the handle 68a to control the amount of 
downward pressure on the inner end portion 44 of the drive wheel mounting 
arm 32 and thereby control the frictional engagement of the drive wheel 34 
with the bottom surface 40 of the rail 26. In other embodiments of the 
invention (not shown), the drive wheel 34 may be urged upwardly by 
weights, springs or other suitably adapted urging means connected to the 
drive wheel mounting arm 32 or drive wheel 34.