FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to a cleaning robot.
BACKGROUND OF THE DISCLOSURE
[0003] With the development of the level of science and technology and the ever-increasing
improvement of people's living standards, clean robots have become more and more widely
used. In the process of using a conventional cleaning robot, people hold the handle
of the cleaning robot and push and pull the cleaning robot forward and backward. However,
due to the friction between the roller and the floor of the cleaning robot, people
need to overcome the friction when pushing and pulling the cleaning robot, which is
laborious.
SUMMARY OF THE DISCLOSURE
[0004] Based on this, it is necessary to provide a relatively labor-saving cleaning robot.
A cleaning robot includes: the cleaning body, including a handle and a working assembly.
The working assembly is disposed at one end of the handle. The working assembly includes
a roller and a first driving mechanism. The first driving mechanism can drive the
roller to rotate relative to the handle as well as an adjustment mechanism that is
connected with the first drive mechanism. The adjustment mechanism can adjust the
rotational direction and rotational speed of the roller by controlling the first drive
mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In order to more clearly explain the embodiments of the present disclosure or the
technical solutions relative to the prior art, the drawings to be used in the description
of the embodiments or the prior art will be briefly described below. Obviously, the
drawings in the following description are only some embodiments of the present disclosure.
For those skilled in the art, drawings of other embodiments can also be obtained based
on these drawings without any creative work.
Fig. 1 is a schematic structural view of a cleaning robot according to a first embodiment;
Fig. 2 is a schematic structural view of an adjustment mechanism in the cleaning robot
shown in Fig. 1;
Fig. 3 is a block diagram of a partial structure of the cleaning robot shown in Fig.
1;
Fig. 4 is a schematic structural view of an adjustment mechanism of a cleaning robot
according to a second embodiment;
Fig. 5 is a schematic structural view of an adjustment mechanism of a cleaning robot
according to a third embodiment;
Fig. 6 is a block diagram of a partial structure of the cleaning robot shown in Fig.
4;
Fig. 7 is a block diagram of a partial structure of a cleaning robot according to
a fourth embodiment;
Fig. 8 is a block diagram of a partial structure of a cleaning robot according to
a fifth embodiment;
Fig. 9 is a schematic structural view of a roller and a reversing assembly of the
cleaning robot shown in Fig. 1; and
Fig. 10 is a schematic view of the structure of the roller, the first drive mechanism,
and the water tank of the cleaning robot shown in Fig. 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0006] To facilitate the understanding of the present disclosure, the present disclosure
will be described more fully hereinafter with reference to the accompanying drawings.
The preferred embodiments of the present disclosure is given in the accompanying drawings.
However, the present disclosure may be embodied in many different forms and is not
limited to the embodiments described herein. Rather, these embodiments are provided
so that this disclosure will be thorough and complete. It should be noted that when
an element is referred to as being "fixed" to another element, it may be directly
on the other element or there may also be an intervening element. When an element
is considered to be "connected" to another element, it can be directly connected to
another element or there may be an intervening element. The terms "vertical", "horizontal",
"left", "right" and the like are used herein for the purpose of illustration only.
Unless otherwise defined, all technical and scientific terms used herein have the
same meaning as commonly understood by one of ordinary skill in the art to which this
disclosure belongs. The terminology used in the description of the present disclosure
herein is for the purpose of describing particular embodiments only and is not intended
to limit the present disclosure. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed items.
[0007] As shown in Fig. 1, the cleaning robot 10 of an embodiment includes a cleaning body
20 and an adjustment mechanism 30. The cleaning body 20 is used to clean the floor.
The adjustment mechanism 30 can adjust the walking direction and the walking speed
of the cleaning body 20. The adjustment mechanism 30 can be set. The cleaning body
20 can also be wirelessly connected to the adjustment mechanism 30 by remote control.
Specifically, the cleaning body 20 includes a handle 100 and a working assembly 200
disposed at one end of the handle 100. The end of the handle 100 away from the working
assembly 200 is flat and is convenient for a human hand to hold, and the central portion
has a certain degree of curvature in order to make the design of the clean body 20
more ergonomic. The working assembly 200 includes a roller 210 and a first driving
mechanism 220. The roller 210 is made of a flexible material such as a sponge and
has good water absorption. The first driving mechanism 220 can drive the roller 210
to rotate relative to the handle 100. The first driving mechanism 220 can be a brushless
motor or a brush motor.
[0008] The adjustment mechanism 30 is connected with the first drive mechanism 220, and
the adjustment mechanism 30 can adjust the rotational direction and rotational speed
of the roller 210 by controlling the first drive mechanism 220.
[0009] As shown in Fig. 2 and Fig. 3, the adjustment mechanism 30 includes a movable member
300 and a controller 400. The movable member 300 is disposed at an end of the handle
100 away from the working assembly 200. The movable member 300 is slidable relative
to the handle 100, and the movable member 300 is opposite to the handle 100. When
the handle 100 slides, the controller 400 can control the rolling state of the roller
210; that is, the controller 400 can control the rotational direction and rotational
speed of the roller 210. When the movable member 300, in an initial position, is pushed
forward with the user's position using the cleaning robot 10 as a reference, the roller
210 rotates in the forward direction; that is, the cleaning body 20 moves forward
and the movable member 300 moves forward. The greater the distance, the greater the
rotational speed of the roller 210. Conversely, when the movable member 300 in the
initial position is pushed backward, the roller 210 rotates in the reverse direction;
that is, the cleaning body 20 moves backward. The larger the distance of the movable
member 300 moving backward, the greater the rotational speed of the roller 210. Therefore,
when cleaning the floor, the user only needs to slide the movable member 300 to adjust
the cleaning direction and speed of the cleaning body 20, which is convenient and
effortless.
[0010] In an embodiment, the movable member 300 includes a first sliding portion 310 and
a second sliding portion 320 that are connected to each other. The handle 100 is provided
with a groove 110. The first sliding portion 310 is disposed in the groove 110, and
the second sliding portion 320 is formed outside the groove 110. The adjustment mechanism
30 further includes a sensing component 500 connected to the controller 400. The sensing
component 500 includes a sensor head 510 and a sensor band 520. The sensor head 510
is disposed on the first sliding portion 310, and the sensor band 520 is located on
a bottom wall of the groove 110. A plurality of spaced-apart nodes 522 are disposed
on the sensor band 520. When the movable member 300 slides relative to the handle
100, the sensor head 510 can correspond to different nodes 522, so that the controller
400 can change the rolling state of the roller 210. As shown in Fig. 2 as the viewing
angle, there are a total of 8 nodes on the sensor band 520. In order from left to
right, it is assumed that the eight nodes correspond to +4, +3, +2, +1, -1, -2, -3,
and -4, respectively. When the sensor head 510 is located between the +1 node and
the -1 node, the movable member 300 is in the initial position, and at this time,
the roller 210 does not rotate. When the sensor head 510 is located between any two
nodes from +1 to +4, the roller 210 rotates clockwise to achieve the advancement of
the cleaning body 20. In addition, the further leftward the movable member 300 is
with respect to the initial position, the greater the rotational speed of the roller
210. When the sensor head 510 is located between any two nodes between -1 and -4,
the roller 210 rotates counterclockwise to achieve the retraction of the cleaning
body 20. In addition, the movable member 300 is positioned further to the right with
respect to the initial position, and the rotational speed of the roller 210 is larger.
[0011] It can be understood that the number of nodes 522 may be an even number or an odd
number. When the number of nodes 522 is an even number, the initial position of the
sensor head 510 is between two intermediate nodes. When the number of nodes 522 is
an odd number, the initial position of the sensor head 510 corresponds to one node
in the middle. In this embodiment, the adjustment mechanism 30 further includes a
telescoping assembly connected with the handle 100 and the movable member 300 to assist
in resetting the movable member 300. Specifically, the telescoping assembly includes
a first spring 610 and a second spring 620, and both the first spring 610 and the
second spring 620 are accommodated in the groove 110. One end of the first spring
610 is connected with the sidewall of the groove 110, and the other end is connected
with the first sliding portion 310. One end of the second spring 620 is connected
with the sidewall of the groove 110, and the other end is connected with the first
sliding portion 310. The first sliding portion 310 is located between the first spring
610 and the second spring 620. When the first spring 610 is compressed, the second
spring 620 is elongated.
[0012] Still referring to Fig. 2 as the viewing angle, when the movable member 300 is in
the initial position, both the first spring 610 and the second spring 620 are original
lengths. When the movable member 300 slides to the left, the first spring 610 is compressed
and the second spring 620 is elongated. When the movable member 300 is released, the
movable member is acted upon by the urging force of the first spring 610 and the tension
of the second spring 620. The movable member 300 can return to the initial position
in time. Similarly, when the movable member 300 slides to the right, the movable member
300 can be restored to the initial position in time under the joint action of the
first spring 610 and the second spring 620, so that the action of manually resetting
the movable member 300 can be reduced. Moreover, the first spring 610 and the second
spring 620 can also act as a buffer to prevent the movable member 300 from resetting
excessively beyond the initial position and causing the roller 210 to reverse. It
can be understood that in this embodiment, the first spring 610 and the second spring
620 may be omitted.
[0013] In one embodiment, referring to Fig. 1 and Fig. 4 to Fig. 6, the rolling state of
the roller 210 may also be controlled by detecting the force of the sidewall of the
groove 110 or the first sliding portion 310. Specifically, the adjustment mechanism
30 further includes a first force sensor 530 and a second force sensor 540. The first
force sensor 530 is located at one end of the first spring 610. The first force sensor
530 may be mounted on the first spring 610 and the groove 110. The sidewalls may also
be disposed between the first spring 610 and the first sliding portion 310. The second
force sensor 540 is disposed at one end of the second spring 620. Similarly, the second
force sensor 540 may be disposed between the second spring 620 and the sidewall of
the groove 110, and may also be disposed between the second spring 620 and the first
sliding portion 310. The first force sensor 530 and the second force sensor 540 are
both connected to the controller 400, and the controller 400 can determine the rotational
direction and rotational speed of the roller 210 based on the detection results of
the first force sensor 530 and the second force sensor 540.
[0014] In this embodiment, both the first force sensor 530 and the second force sensor 540
are pressure sensors, or both the first force sensor 530 and the second force sensor
540 are tension sensors. As shown in Figs. 1 and 4 as viewing angles, when the first
force sensor 530 and the second force sensor 540 are both pressure sensors, the movable
member 300 is pushed to the left, and the first force is generated because the first
spring 610 is compressed. The first force sensor 530 can detect the elastic force
of the first spring 610, and the second spring 620 is elongated so that the value
of the second force sensor 540 does not change. The controller 400 can issue a command
to rotate the roller 210 clockwise at a corresponding rotational speed based on the
detection results of both. Moving the movable member 300 to the right, the working
principle of the first force sensor 530, the second force sensor 540, and the controller
400 is similar to the above principle, and will not be repeated here.
[0015] When both the first force sensor 530 and the second force sensor 540 are tension
sensors, the movable member 300 is moved to the left. Because the first spring 610
is compressed, the value of the first force sensor 530 is unchanged, and the second
spring 620 is changed. Being elongated, the second force sensor 540 can detect the
elastic force of the second spring 620, and the controller 400 can issue an instruction
that the roller 210 needs to rotate clockwise at a corresponding rotational speed
according to the detection result of both. For the contrary, the same reasoning applies.
Of course, it can be understood that in other embodiments, either the first spring
610 or the second spring 620 may be selected. For example, when there is only the
first spring 610, the first force sensor 530 and the second force sensor 540 are provided
at both ends of the first spring 610, respectively. In this case, when the first force
sensor 530 is a pressure sensor, the second force sensor 540 is a tension sensor.
Pushing the movable member 300 to the left, since the first spring 610 is compressed,
the first force sensor 530 can detect the elastic force of the first spring 610, and
the controller 400 can issue instructions instructing the roller 210 to rotate according
to the detection result of the first force sensor 530. The roller 210 is therefore
instructed to rotate clockwise at the corresponding speed. When the movable member
300 is pushed to the right, since the first spring 610 is elongated, the second force
sensor 540 can detect the elastic force of the first spring 610, and the controller
400 can issue instructions instructing the roller 210 to rotate according to the detection
result of the second force sensor 540. The roller 210 is therefore instructed to rotate
counterclockwise at a corresponding rotational speed.
[0016] Similarly, when the first force sensor 530 is a tension sensor, the second force
sensor 540 is a pressure sensor. In an embodiment, as shown in Fig. 1 and Fig. 7,
it is also possible to control the rolling state of the roller 210 by detecting the
position of the movable member 300. Specifically, the adjustment mechanism 30 further
includes a position sensor 550 disposed on the movable member 300 and connected with
the controller 400. The position sensor 550 can detect the position of the movable
member 300 in real time, and feedback the detection result to the controller 400.
The controller 400 can determine the rotational direction and rotational speed of
the roller 210 based on the detection result of the position sensor 550. In an embodiment,
as shown in Fig. 1 and Fig. 8, the adjustment mechanism 30 further includes a gyroscope
560 and an accelerometer 570. The gyroscope 560 and the accelerometer 570 are both
disposed on the movable member 300 and are all connected to the controller 400. The
gyroscope 560 can detect the change in the orientation of the movable member 300,
the accelerometer 570 can detect the magnitude of the acceleration of the movable
member 300, and the controller 400 can determine the rotational direction and rotational
speed of the roller 210 based on the detection results of the gyroscope 560 and the
accelerometer 570. In the present embodiment, the gyroscope 560 may be independent
from the accelerometer 570, and the accelerometer 570 may also be integrated in the
gyroscope 560.
[0017] Further, in addition to the movable member 300 being capable of sliding back and
forth with respect to the handle 100, the movable member 300 can also be deflected
leftward and rightward relative to the handle 100. That is, the adjustment mechanism
30 can control the cleaning in addition to the movement of the cleaning body 20 in
the front-rear direction. The cleaning body 20 performs commutation. For example,
when the movable member 300 is deflected to the left front with respect to the handle
100, the cleaning body 20 will turn leftward and the like. Specifically, in an embodiment,
referring to Fig. 1, Fig. 8, and Fig. 9, the cleaning body 20 further includes a reversing
component. The reversing component includes a first direction wheel 710, a second
direction wheel 720, a second driving mechanism, and a third driving mechanism. The
roller 210 is disposed between the first direction wheel 710 and the second direction
wheel 720, the second driving mechanism can drive the first direction wheel 710 to
rotate, and the third driving mechanism can drive the second direction wheel 720 to
rotate. The second driving mechanism and the third driving mechanism are both connected
with the controller 400. The controller 400 controls the second driving mechanism
to control the first direction wheel 710, and controls the third driving mechanism
to control the second direction wheel 720. The differential rotation of the first
direction wheel 710 and the second direction wheel 720 can achieve the turning commutation
of the cleaning body 20.
[0018] Specifically in this embodiment, the first direction wheel 710 and the second direction
wheel 720 are coaxially arranged, and the second drive mechanism and the third drive
mechanism are both brushless motors. When the movable member 300 moves linearly, the
controller 400 also controls the linear movement of the cleaning body 20. At this
time, the rotational speed of the first direction wheel 710 is equal to the rotational
speed of the second direction wheel 720. When the movable member 300 is deflected
to the left front, the gyroscope 560 and the accelerometer 570 respectively send the
orientation and the acceleration of the movable member 300 to the controller 400,
and the controller 400 causes the first direction wheel 710 to rotate at a lower speed
than the second direction. The rotational speed of the second direction wheel 720
is such that a forward left turn of the cleaning body 20 is achieved. When the movable
member 300 is deflected to the right front, the controller 400 causes the rotational
speed of the first direction wheel 710 to be smaller than the rotational speed of
the second direction wheel 720, thereby achieving a forward turning right of the cleaning
body 20. Similarly, when the movable member 300 is deflected to the left rear, the
cleaning body 20 will turn left and right, and when the movable member 300 is deflected
to the right rear, the cleaning body 20 will turn rightward.
[0019] In an embodiment, the working assembly 200 further includes a reversing wheel. When
the cleaning body 20 is straight, the axis of the reversing wheel is parallel to the
axis of the roller 210. When the cleaning body 20 turns, the angle between the axis
of the reversing wheel and the axis of the roller 210 is set. The reversing wheel
is connected with the movable member 300. When the movable member 300 is deflected
with respect to the handle 100, the reversing wheel can be deflected together with
the movable member 300 to realize the turning of the cleaning body 20. The connection
between the reversing wheel and the movable member 300 is mainly a mechanical connection,
and the movable member 300 can be connected with the hub of the reversing wheel through
a connecting rod.
[0020] It is worth mentioning that for the cleaning robot 10 of the present embodiment,
the rotational speed of the first driving mechanism 220 is controlled between the
first speed and the second speed, wherein the first speed is 60 revolutions per second
and the second speed is 154 revolutions per second. In this range, the cleaning robot
10 can obtain reasonable cleaning performance. As shown in Fig. 1 and Fig. 10, in
the present embodiment, the working assembly 200 further includes a water tank 230,
a brush 240, and a garbage collection box 250. The water tank 230 is used for supplying
the clean water to the roller 210 and for recovering the sewage absorbed by the roller
210. The brush 240 is disposed on one side of the roller 210 and is in contact with
the surface of the roller 210. The garbage collection box 250 is used to collect garbage
separated from the roller 210 by the brush 240.
[0021] The bottom wall of the water tank 230 is provided with a protrusion 232. The protrusion
232 is in contact with the roller 210, and the protrusion 232 can make the portion
of the roller 210 abutting the protrusion 232 be recessed toward the axis of the roller
210 so that the protrusion 232 can squeeze out the sewage absorbed when the roller
210 cleans the ground, and the sewage is pushed out into the water tank 230 after
being extruded.
[0022] In the present embodiment, the brush 240 can also rotate so as to facilitate the
sweeping of the trash on the surface of the roller 210 and into the garbage collection
box 250. The mechanism for driving the brush 240 to rotate may be an additionally
provided motor or a first driving mechanism 220. The first driving mechanism 220 may
be connected to the brush 240 through a gear pair or other transmission mechanism.
[0023] In order to increase the cleaning effect, the working assembly 200 includes two rollers
210, the axes of the two rollers 210 are parallel to each other, and the rotational
directions of the two rollers 210 are the same. It can also be said that two rollers
210 are arranged at intervals in the front-rear direction. When the cleaning body
20 advances, the roller 210 located at the rear can clean the garbage still remaining
on the ground after the roller 210 located at the front passes by, and achieve the
purpose of secondary cleaning. Correspondingly, two brushes 240 are also provided,
corresponding one-to-one to the roller 210. The axes of the two brushes 240 are located
between the axes of the two rollers 210, and the rotational direction of the two brushes
240 is opposite one another. As shown in Fig. 1 as the viewing angle, regardless of
whether the two rollers 210 rotate clockwise or counterclockwise, the brush 240 on
the left side rotates counterclockwise, and the brush 240 on the right side rotates
clockwise.
[0024] In the present embodiment, the work assembly 200 further includes a bearing roller
260 capable of supporting the garbage collection box 250 to increase the load-bearing
capacity of the garbage collection box 250.
[0025] The technical features of the above-described embodiments may be combined arbitrarily.
To make the description succinct, all the possible combinations of the technical features
in the above embodiments are not described. However, as long as there is no contradiction
in the combination of these technical features, all should be considered as described
in this specification. The above-mentioned embodiments merely represent several embodiments
of the present disclosure, and the description thereof is more specific and detailed,
but it should not be construed as limiting the scope of the disclosure. It should
be noted that, for those skilled in the art, several variations and improvements may
be made without departing from the concept of the present disclosure, and these are
all within the protection scope of the present disclosure. Therefore, the scope of
protection of the present disclosure shall be subject to the appended claims.
1. A cleaning robot comprising:
a cleaning body including a handle and a working assembly, wherein the working assembly
is disposed at one end of the handle, the working assembly includes a roller and a
first driving mechanism, and the first driving mechanism drives the roller to rotate
relative to the handle; and
an adjustment mechanism connected with the first driving mechanism, wherein, when
a rotational speed of the roller is between a first speed and a second speed, the
adjustment mechanism can adjust rotational direction and the rotational speed of the
roller by controlling the first driving mechanism.
2. The cleaning robot according to claim 1, wherein the adjustment mechanism comprises
a movable member and a controller, the movable member is disposed at an end of the
handle away from the working assembly, and the movable member movable relative to
the handle, when the handle is slid and the movable member slides relative to the
handle, the controller controls a rolling state of the roller based on a relative
position of the movable member and the handle.
3. The cleaning robot according to claim 2, wherein the adjustment mechanism further
comprises a gyroscope and an accelerometer, wherein the gyroscope and the accelerometer
are both disposed on the movable member, and both are connected to the controller,
and the gyroscope and the accelerometer respectively configured to detect an orientation
and an acceleration of the movable member to generate a detection result, and the
controller controls the rolling state of the roller according to the detection result.
4. The cleaning robot according to claim 3, wherein the cleaning body further comprises
a reversing component, wherein the reversing component comprises a first direction
wheel, a second direction wheel, a second drive mechanism and a third drive mechanism,
the roller is disposed between the first direction wheel and the second direction
wheel, the second drive mechanism drives the first direction wheel to rotate clockwise
or counterclockwise, and the third drive mechanism drives the second direction wheel
to rotate clockwise or counterclockwise, the second driving mechanism and the third
driving mechanism are both connected to the controller, the roller provides main power
for forward and backward movement, and the first direction wheel and the second direction
wheel provide power for steering.
5. The cleaning robot according to claim 2, wherein the working assembly further comprises
a reversing wheel, the reversing wheel is located behind the roller, and an axis of
the reversing wheel is parallel to an axis of the roller when the cleaning body is
moving straight, when the cleaning body turns, an angle between the axis of the reversing
wheel and the axis of the roller is set to generate a biasing force, and the movable
member is deflected relative to the handle and the reversing wheel is connected with
the movable member and deflected together with the movable member to achieve turning
of the cleaning body.
6. The cleaning robot according to claim 2, wherein the movable member comprises a first
sliding portion and a second sliding portion that are connected with each other, a
groove is formed in the handle, and the first sliding portion is inserted in the groove,
wherein the second sliding portion is external to the groove.
7. The cleaning robot according to claim 6, wherein the adjustment mechanism further
comprises a sensing component connected to the controller, and the sensing component
comprises a sensor head and a sensor band, and the sensor head is disposed in the
first sliding portion, the sensor band is located on a bottom wall of the groove,
and a plurality of nodes are arranged at intervals on the sensor band, when the movable
member slides relative to the handle, the sensor head corresponds to different nodes,
so that the controller changes the rolling state of the roller.
8. The cleaning robot according to claim 6, wherein the adjustment mechanism further
comprises a first spring, the first spring is accommodated in the groove, and one
end of the first spring and a sidewall of the groove is connected, and the other end
is connected to the first sliding portion.
9. The cleaning robot according to claim 8, wherein the adjustment mechanism further
comprises a second spring, the second spring is accommodated in the groove, the first
sliding portion is located between the first spring and the second spring, and when
the first spring is compressed, the second spring is elongated.
10. The cleaning robot according to claim 9, wherein the adjustment mechanism further
comprises a first force sensor and a second force sensor, and the first force sensor
is located at one end of the first spring, and the second force sensor is disposed
at one end of the second spring, and the first force sensor and the second force sensor
are both connected to the controller.
11. The cleaning robot according to claim 8, wherein the adjustment mechanism further
comprises a first force sensor and a second force sensor, and the first force sensor
and the second force sensor are respectively disposed at both ends of the first spring,
the first force sensor and the second force sensor are both connected to the controller,
when the first force sensor is a pressure sensor, the second force sensor is a tension
sensor, when the first force sensor is the tension sensor, the second force sensor
is the pressure sensor.
12. The cleaning robot according to claim 2, wherein the adjustment mechanism further
includes a position sensor that is provided on the movable member and is connected
to the controller.
13. The cleaning robot according to claim 1, wherein the working assembly further comprises
a water tank, a brush and a garbage collection box, the water tank providing clean
water to the roller and recovering sewage absorbed by the roller, wherein the brush
is disposed on one side of the roller and is in contact with a surface of the roller,
wherein the garbage collection box is used to collect trash separated from the roller
by the brush.
14. The cleaning robot according to claim 13, a bottom wall of the water tank is provided
with a protrusion, the protrusion abuts against the roller, and the protrusion can
make a site on the roller abutting against the protrusion recessed toward an axis
of the roller.
15. The cleaning robot according to claim 13, two rollers are provided, wherein axes of
the two rollers are parallel to each other, and rotational directions of the two rollers
are the same, and brushes are arranged in a one-to-one correspondence with the rollers,
wherein axes of the two brushes are located between the axes of the two rollers, and
rotational directions of the two brushes are opposite.