JP2004000561A - Floor care machine having reactionary action force - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floor care machine for maintaining automatically uniform pressure to a floor. <P>SOLUTION: The floor care machine 50 that includes a deck 54 having a motor, a rotatable floor care element for engaging a floor surface, and a handle device 64 pivotally mounted to the deck 54. Additionally, there are first and second sets of wheels 108, 110 toward the rear of the deck 54 and on opposite sides of handle apparatus pivot attachment points. In addition to the attachment points, the handle apparatus and the deck 54 are coupled together by a rigid handle link mechanism 76 which is pivotally attached to the deck 54 at one end and pivotally attached to the handle apparatus at the other end. The handle link mechanism 76 communicates deck pivot forces between the deck 54 and the handle apparatus, and communicates such forces resulting from a compressing or decompressing of a compressible component provided along the length of the handle device. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to floor care machines, and more particularly to floor care machines that automatically maintain a substantially uniform pressure on the floor by means of floor care parts mounted on the apparatus.
[0002]
[Prior art]
In order to operate the floor care machine, such as to polish, wax, clean, or polish the floor, the floor care machine must be installed on the floor during the care of the floor, against contact pads and other floor care parts of the equipment. It is preferred to control the applied weight. Such weight control is important in controlling the pressure applied to the floor surface and in controlling the amperage flowing to the motor of the floor care machine. In the past, such weight control has generally been achieved by the operator of the floor care machine using the fixed handle of the floor care machine to manually determine the amount of pressure applied to the various floor areas. Specifically, the operator controls the pressure of the floor care component by lifting or pushing the handle.
[0003]
The problem with this type of operator intervention is that, for example, different operators have different pressures on the floor grooming parts, and the pressure of the floor grooming parts changes due to the fatigue of the operators as well as the height of the operators. That is. Floor care machines are disclosed in U.S. Pat. No. 4,658,459, filed Jan. 27, 1986, for the purpose of reducing the reliance on operators to apply appropriate floor care parts pressure to the floor. A torsion spring including a torsion spring as an "biasing member" is disclosed. However, due to the requirement that the torsion spring must be pre-loaded before shipment, the floor polisher of U.S. Pat. No. 4,658,459 is not suitable for unskilled and / or Due to the danger of splattering of components during assembly by a person without a jig, they cannot generally be sold in partial assembly. In addition, the free end of the torsion spring exerts a high compressive force on the floor care machine chassis. As a result, under such high compression forces, some materials, such as rotationally molded resins, may not be able to withstand without reinforcement.
[0004]
To remedy this drawback, U.S. Pat. No. 5,674,120, filed Sep. 30, 1996, uses a gas spring instead of a torsion spring. The gas spring has one end pivotally connected to the handle of the device and the other end pivotably connected to the vehicle body of the device. The pivot point of the gas spring on the vehicle body is different from the pivot point of the handle of the device.
[0005]
[Patent Document 1]
US Patent No. 4,658,459 [Patent Document 2]
US Patent No. 5,674,120
[Problems to be solved by the invention]
Although various designs have been developed to achieve uniform pressure on the floor using floor care machines, they are cost-effective, stylish and have all the other necessary mechanical functions, while at the same time providing such uniformity. It is desirable to provide a floor care machine capable of providing a high pressure.
[0007]
[Means for Solving the Problems]
The present invention relates to a floor care machine provided with a connector or a handle connection mechanism between a vehicle body of a floor care machine and a handle device pivotally mounted on the vehicle body. The handle coupling is part of a force generating system having an elastic compressible component (e.g., a compression spring) along the length of the handle device, wherein the compressible component cooperates with the handle coupling. And biasing the body (or deck) of the floor care machine to pivot about the axis of the first wheel set, thereby biasing the front of the deck upward. The force urging the deck to pivot is caused by the weight of the deck and the floor suction resulting from the rotation of the floor care components that contact the floor while rotating to provide the desired floor care during operation of the equipment. Used to balance opposing swiveling forces.
[0008]
Accordingly, it is an object of the present invention to provide a new machine for floor surface care.
It is a further object of the present invention to provide a novel floor care machine in which the floor care parts exert a substantially uniform pressure on the floor, regardless of the pivot position of the handle device relative to the deck of the floor care machine. .
It is a further object of the present invention to provide a novel floor care machine which applies a uniform polisher to the floor surface with the floor care parts irrespective of the unevenness of the floor surface. It is a further object of the present invention to provide a novel floor care machine that automatically maintains a uniform polishing pressure.
[0009]
It is a further object of the present invention to provide a novel floor care machine that maintains a uniform floor care component pressure without relying on operator intervention.
It is a further object of the present invention to provide a novel floor care machine having a floor care component pressure that does not vary with operation of different operators.
It is a further object of the present invention to provide a novel floor care machine that has a floor care component pressure that does not substantially fluctuate due to operator fatigue.
The above and other objects and advantages of the present invention will be apparent in light of the accompanying drawings and detailed description.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The same numbers used in the figures of the drawings indicate the same or similar parts. Further, when terms such as "lower", "upper", "upper", and other locations are used, these terms shall be understood in the positional relationship and orientation illustrated in the accompanying drawings.
[0011]
An embodiment of the floor care machine 50 is shown in FIG. The floor care machine 50 generally includes a body portion or deck 54 adapted to move along a floor 58 (FIG. 2), mounted on the deck, for example, polishing pads, brushes, polishing pads, Abrasive discs, waxing pads, floor scouring components or other of the type that make contact with the floor in a rotating motion when the floor care machine 50 is operable. Further, a handle device 64 for guiding and controlling the deck 54 is attached to the deck 54. The handle device 64 includes, for example, (i) an operating position (the handle 68 described below is generally within a range of 30 to 60 degrees from a horizontal position, but may be outside the range) and (ii). 3.) Pivotally mounted to deck 54 at various locations on the deck (described below) so that it can pivot to and from a movement position (handle 68 is substantially vertical).
[0012]
Among the components included in the handle device 64 are:
(A) an operator grip 66 used by an operator to control the floor care machine 50;
(B) a handle 68 whose length extends downwardly from the grip 66 and the other end of the length connects to the assembly 70 described immediately below; and (c) (i) a handle device 64 pivotally mounted on the deck 54. (Ii) providing a force-generating system 72 (or simply a force system) that produces a force that is a counter-swirl to the gravity and floor suction generally generated in front of the wheels 108 during operation of the floor care machine 50. An assembly or section 70 that serves both purposes (FIG. 1, hereinafter also referred to as “mounting assembly” and “reaction assembly (counterforce assembly)”). Here, the latter two forces (gravity and floor suction force) are applied to at least the deck 54 and the floor care part 62 so as to turn counterclockwise around the rotation axis of the wheel 108 in the orientation in FIG. It is two forces to gain momentum.
[0013]
Note that the force system 72 includes:
(I) a force generating device 74 (FIG. 1), which is a further extension of the handle 68, generally in the direction of the deck 54; The force generator 74 may apply a force in the longitudinal direction of the handle (e.g., to the shaft 118 of FIG. 2 as described below) to balance the floor suction caused by the weight of the deck 54 and the rotation of the floor care component 62. Along) a component such as a compressible elastic component for generating;
(Ii) A substantially rigid handle coupling 76 that transmits the force generated by the force generator 74 to the deck 54, as described further below.
[0014]
Deck 54 also includes a housing 78 that substantially contains floor care components 62. The housing 78 includes an inclined chassis 82 having a skirt extending downwardly from its outer periphery, the skirt including a first skirt portion 86 surrounding the floor care component 62 and a second skirt portion extending rearward to attach, for example, a handle device 64. The second skirt portion includes a pair of planar side surfaces (88aL, 88aR), (88bL, 88bR) and a rear skirt 88c (eg, FIG. 3). A motor 90 is mounted at the center of the chassis 82 and roughly at the top. The floor care component 62 is operably connected to the motor 90 to rotate within the housing 78.
[0015]
Deck 54 further includes a substantially inverted cup-shaped housing or motor side plate 94 mounted on housing 78 for housing motor 90. In one embodiment of the present invention, housing 94 includes a generally cylindrical portion 98 and a generally box-shaped portion 102. Portion 102 includes a generally sealed upper end 106 and a bottom that is generally open for receiving and fitting over chassis 82.
The floor care machine 50 further includes a first wheel set 108 having a rotational axis intermediate the motor 90 and the second wheel set 110. When the floor care machine 50 is in the operable position, the first wheel set 108 is located at a position substantially equal to or slightly lower than the height of the floor care part 62. When the floor care component 62 is rotated by the motor 90, at least two-thirds of the front of the floor care component 62 (i.e., from its 8 o'clock to 4 o'clock position) engages the floor surface 58, and more preferably. Note that substantially the entire surface of the floor care component 62 facing the floor 58 engages or contacts the floor. Further, the wheel 108 is rotatably fixed to the skirt 84 of the housing 78.
[0016]
To attach the handle device 64 to the deck 54, the reaction force assembly 70 includes a mount 116 extending from a central axis 118 (FIG. 3) of the handle device 64 and spanning a rear skirt 88c. The mounting base 116 is pivotally fixed to the deck 54 via an axle 120 (FIG. 3) provided through the planar skirt side surfaces 88bL and 88bR and further through the axle hole 122 of each mounting base 116. Reaction force assembly 70 as described above, and in turn, includes a force system 72 that includes a force generator 74 (FIG. 1) provided generally along central axis 118 and below handle 68. Specifically, the force generating device 74 includes an adjacent lower handle side 130 (FIG. 3) between which there is provided a substantially cylindrical chamber 136 (FIG. 2), which comprises (a) a pair of Extend from the end cap halves 142 (only one shown in FIG. 3) to (b) bracket 146.
[0017]
Note that cylindrical chamber 136 has its central axis aligned with central axis 118 of handle device 64. In addition, each lower handle side surface 130 extends approximately one-third of the length of the cylindrical chamber 136 in the direction of the central axis 118 toward the end cap halves 142 vertically below the bracket 146. Note that it has a guiding slot 152 that extends. Also, in the area 158 (FIG. 3) between the upper end of each guide slot 152 and the corresponding bracket 146, the cylindrical chamber 136 has a radius below the area 158 that is greater than the lower portion 160 of the cylindrical chamber 136 (see FIG. 3). FIG. 2) Each lower handle side surface 130 is provided. The lower end of handle 68 is secured within the enlarged radius provided by the two sections 158 when the two sections 158 are secured by any of a variety of securing devices, such as bolt assembly 164. Note that (FIG. 3). Specifically, the bolt assembly 164 is positioned within the bolt holes 168, 172 and 176 to secure the adjacent lower handle side 130 to the handle 68.
[0018]
Provided in the lower portion 160 (and as part of the force generating device 74) are force generating components for causing the above-mentioned reverse turning force. Specifically, the reverse pivoting force is provided by the compression of a compressible component, such as a compression spring 182, that produces a force linearly along the central axis 118. However, it is within the scope of the present invention that other components such as wave springs or other resilient components may be used in place of the compression spring 182, and such resilient components may be used, for example, on floors. Depending on the desired action of the care machine 50, it may have different elastic properties. Additionally, within the lower portion 160 but above the spring 182 in the force generator 74, a compression block 186 is included that compresses the spring 182 within the lower portion 160.
[0019]
Thus, the compression block 186 has a diameter smaller than the diameter of the lower portion 160 only to be slidable within the lower portion 160. The compression block 186 is slidably secured to the guide slot 152 by a bolt assembly 190 (FIG. 3), also included in the force generating device 74, and the bolt shaft 194 and the sleeve 198 of the bolt assembly are compressed with both guide slots 152. It is fixed to the bolt hole 204 of the block 186 and bridged. Similarly, the first end 208 (via the bolt hole 212) of the handle connection mechanism 76 is pivotally fixed to the bolt shaft 194 and the sleeve 198, and the other end 220 of the handle connection mechanism will be described below. Is pivotally attached to the deck 54. As seen in FIG. 1, the side flanges 226 and the cross members 230 of the handle coupling mechanism 76 fit over the lower portion 160.
[0020]
With respect to the other end 220 of the handle coupling mechanism 76, this end is pivotally secured to the deck 54 such that when the angular orientation between the handle device 64 and the deck 54 changes, the bolt assembly 190 is positioned in the guide slot 152. Each end 208 and 220 of the handle coupling mechanism 76 pivots to change. Thus, when the angle between the handle 68 and the horizontal surface of any of the decks 54 decreases (eg, decreases in a 90 degree direction), the bolt assembly 190 is biased toward the upper end of the guide slot 152 and the spring 182 is depressurized. Is done. On the other hand, if the angle between the handle 68 and the aforementioned horizontal plane increases (e.g., in the 180 degree direction), the bolt assembly 190 is biased toward the lower end of the guide slot 152, thereby compressing the spring 182.
[0021]
More specifically, end 220 is pivotally mounted to deck 54 (by pin subassembly 236 having components identified by the same reference numerals) within raised wall 244 of the deck. Accordingly, if the operator changes the angle of the handle device 64 relative to the horizontal during operation, the linear movement of the bolt assembly 190 (as well as the spring 182 and the compression block 186) in the lower portion 160 causes the shaft 120 to move. The pivoting force of the centered deck 54 causes a responsive movement by the handle linkage that at least temporarily changes the pressure exerted by the rotating floor care component 62. Conversely, if the deck 54 is moved during operation, for example, onto a portion of the floor that rises or descends abruptly, the deck 54 will usually pivot about the axis 120 and on the pin subassembly 236 the handle coupling mechanism 76 Corresponding responsive pivoting and repositioning of the handle linkage end 208 along the axis 118 occurs correspondingly, causing movement of the bolt assembly 190 (and also the spring 182 and compression block 186) at the lower portion 160. .
[0022]
Note that the response induced by the deck 54 to the movement of the handle device 64 (or vice versa) is weakened, for example, by the compression and elastic properties of the spring 182. For example, a spring 182 that requires a very high force for compression may cause the handle linkage 54 to move closer to maintaining the handle linkage end 208 in a fixed pivot position along the axis 118, resulting in a handle Any angle changes (relative to horizontal) between the device 64 and the deck 54 will be transmitted substantially completely between the two assemblies. However, if the spring 182 requires a very small force to compress, the angle change (relative to the horizontal) between the handle device 64 and the deck 54 will hardly be transmitted from one of the two assemblies to the other. . Thus, by adjusting the compression characteristics of the spring 182 (eg, increasing or decreasing the range of movement within the chamber 136), or by replacing the spring with a different spring, the floor against the angle change between the handle device 64 and the deck 54 can be changed. The responsiveness of the care machine 50 can be changed.
[0023]
A latch mechanism for latching the handle device 64 in a substantially vertical position to retract the floor groom 50 when the floor groom 50 is not in use (e.g., at rest) substantially within the raised wall 244. There is also a group of components that function as. The group of components for the latching mechanism is to rotate the handle coupling mechanism 76 (and accordingly the handle 68) clockwise (in the orientation in FIG. 2) about this pin subassembly so that A torsion spring 254 (FIG. 3) is disposed on the pin subassembly 236 to bias (shift) to the operating position rather than the retracted position. Thus, when retracting the floor care machine 50, the handle device 64 overcomes the bias of the torsion spring 254 and causes the latch mechanism to substantially lock the handle device 64 in a substantially vertical position. Rotated to a vertical position.
[0024]
Further, a group of components for the latch mechanism is pivotally provided on the pin subassembly 236 and in the raised surrounding wall 244 to receive the latch striker 262 provided at the end of the handle device 64 opposite to the grip 66. Latch 258 (FIG. 3). Note that latch 258 and latch striker 262 cooperate to secure handle device 64 in a substantially vertical position for storing floor care machine 50.
[0025]
In operation of at least one embodiment of floor care machine 50, wheels 110 are positioned slightly above the height of floor care parts 62. In one embodiment, wheels 110 are located in the range of 1/2 to 3/4 inch above the height of wheels 108. In addition, the force system 72 may include: (a) a counter-swirl force against the gravity and floor suction force that the deck 54 exerts about the axis 120, and (b) when a wave undulation is encountered, for example, at the floor 58 and / or Pivoting forces, such as reducing the likelihood (or degree) of floor care components 62 to contact the floor disproportionately or differently when different handle device 64 orientations are used by different floor care machine operators. This can occur at axis 120. Thus, for different operators, both the tall operator holding the handle device 64 at a substantially constant 50 degrees and the short operator holding the handle device 64 at a substantially constant 35 degrees. The personnel can cause the floor care component 62 to exert substantially the same pressure on the floor 58 during operation of the floor care machine 50. However, for the force system 72 to achieve the benefits of (a) and (b) above, the spring 182 (or other compressible component) must be matched to the weight and suction generated by the deck 54.
[0026]
In general, many of the springs 182 have a non-trivial angular range relative to the horizontal, where only a small change in the linear force generated by the spring 182 occurs. For example, such a range may correspond to a handle device 64 that varies from 35 degrees to 50 degrees (eg, counterclockwise in FIG. 2) relative to the horizontal. Beyond such a range, however, the linear force generated by the spring 182 will begin to change significantly, and such changes will correspond to different floor conditions, for example, extraordinarily dirty areas of the floor 58, and will require floor care. The components are beneficial in that the pressure on the floor 58 can be explicitly changed by the operator.
[0027]
After moving the floor care machine 50 from the storage location to the desired floor 58 location, the latch striker 262 is disengaged from the latch 258 and the handle device 64 including the handle 68 and a force generator 74 such as a compression spring 182. Can pivot relative to deck 54 about pivot pin subassembly 236 and axis 120. It should be appreciated that the torsion spring 254 biases the handle device 64 from a substantially vertical position toward a position that is relatively angled relative to horizontal (eg, 45 degrees). When the handle device 64 is lowered to the operating position as shown in FIG. 2, the handle device 64 loads the spring 182. This load or force is clocked (in the orientation in FIG. 2) on wheels 108 such that a downward pressure is created at the rear of chassis 82, resulting in an upward lifting force at the front of chassis 82. Turns into a turning force.
[0028]
If the motor 90 for rotating the floor care component 62 is not operated and the handle device is in the operating position, no floor suction force is applied in front of the floor care device 50, so that the front of the deck 54 and the floor care component 62 are not applied. It should be appreciated that the deck 54 pivots about the wheels 108 so that the front of the deck 54 is higher than the floor 58. In addition, the operator may then move the floor groom 50 rearward so that the floor groom 50 can be moved on and off of both the wheel sets 108 and 110, for example, between different floor areas and / or to / from the hangar. Can be tilted.
[0029]
The wheels 110 of the floor care machine 50 perform a dual function. First, the wheels limit the amount of upward movement of the biased floor care component 62 by the force generator 74 and consequently reduce the front of the floor care component 62 during the initial rotation of the floor care component 62. A local negative pressure is created to create a suction effect for pulling down. Second, the wheels 110 serve as transport wheels when moving the floor care machine 50 from one position to the next.
[0030]
Although the invention disclosed herein can be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of the forms are shown, but the described embodiments are It should be regarded as illustrative only and not limiting. The scope of the invention is indicated by the appended claims rather than by the preceding specification, and all changes that come within the spirit and equivalent scope of the claims are intended to be covered by the appended claims. I have.
[Brief description of the drawings]
FIG. 1 is an external perspective view of a floor care machine of the present invention;
FIG. 2 is a side view of a floor care machine;
FIG. 3 is a partially exploded view of the floor care machine, illustrating internal components.
[Explanation of symbols]
Reference Signs List 50 floor care machine 54 deck 58 floor 62 floor care parts 64 handle device 66 grip 68 handle 70 reaction force assembly 72 force generation system 74 force generation device 76 handle coupling mechanism 78 housing 82 inclined chassis 84 skirt 86 first skirt portion 88 Second skirt part 90 Motor 94 Motor side plate 98 Cylindrical part 102 Part 106 Sealed upper end part 108 First wheel set 110 Second wheel set 116 Mounting stand 118 Center axis 120 Axis 130 Lower handle side surface 136 Chamber 142 End cap Half body 146 Bracket 152 Guide slot 158 Area 160 Lower part 164, 190 Bolt assembly 168, 172, 176 Bolt hole 182 Compression spring 186 Compression block 194 Bolt shaft 198 Sleeve 204 Bolt hole 2 8 first end 212 bolt hole 226 side flange 208 and 220 end 230 crosspiece 236 pin subassembly 244 uplift handle connecting mechanism enclosure 254 torsion spring 258 latch 262 latch striker

Claims (23)

A floor care machine,
deck,
Floor care components operatively connected to the deck,
A handle having a central longitudinal axis and operably attached to the deck; and a force generating portion extending along the central longitudinal axis of the handle and used to apply a force to the deck. Power system,
Floor care machine equipped with. The floor care machine of claim 1, wherein the force system includes a handle coupling coupled to the deck, the handle coupling applying the force to the deck. The handle connecting mechanism has a first part and a second part, the first part is connected to the deck, and the second part is connected to at least one of the handle and the force generating part. The floor care machine according to claim 2, characterized in that: The floor care machine of claim 1, wherein the force system is part of a reaction force assembly including a mount extending from the force system and coupled to the deck. The floor care machine according to claim 4, wherein the reaction force assembly, the force generator and the handle are part of a handle device. The floor care machine of claim 1, wherein the force generator generates a force in a substantially linear direction. The floor care machine according to claim 1, wherein the force generator includes at least one of the following: an elastic component, a compression spring, a wave spring, and a movable part. When the handle has a storage position and at least a first operation position and a second operation position, and when the handle is in the storage position, the handle is substantially vertical and floor care pieces are at rest, and the handle is When selected in each of the first operating position and the second operating position, the handle is not vertical and the floor care component is activated,
The floor care machine according to claim 1, wherein the force generated by the force generation unit is different between the first non-storage position and the second non-storage position. A latch mechanism for holding the handle in a stowed position, the latch mechanism including a torsion spring used to hold the handle in a non-stowed position and being overcome when the handle is in the stowed position; The floor care machine according to claim 1, wherein: The floor care machine according to claim 1, wherein the handle pivots about a horizontal axis, and the force generating unit also pivots about the horizontal axis. The floor care machine according to claim 10, wherein the force generator includes at least one of a compression spring and a wave spring. A handle is connected to a deck adjacent to one end of the handle connection mechanism, and is connected to a slot of the handle adjacent to the other end of the handle connection mechanism, and the other end of the handle connection mechanism is used to move the force generating unit. The floor care machine according to claim 1, wherein the force generating unit includes a handle coupling mechanism to be used. A floor care machine,
deck,
Floor care components operatively connected to the deck,
A handle system including a handle pivotable about a horizontal axis, and a floor system including a force generator used to apply a force to the deck, the force generator also being pivotable about the horizontal axis. ,
Floor care machine equipped with. The deck is connected to a first set of wheels and a second set of wheels, the second set of wheels is located closer to the handle device than the first set of wheels, and the second set of wheels is 14. The floor care machine of claim 13, wherein the floor care machine is coupled to the deck along a horizontal axis. 14. The floor care of claim 13, wherein the handle has a central longitudinal axis, the force generating portion includes a compressible spring, and the spring is disposed along the central longitudinal axis. Machine. The handle has a slot and the floor system includes a handle coupling mechanism having first and second ends, the handle coupling mechanism being coupled to the deck adjacent the first end and the handle 14. The floor care machine of claim 13, wherein a coupling mechanism is coupled to the handle slot adjacent the second end. The floor care machine of claim 16, wherein the handle coupling mechanism extends offset from the longitudinal central axis. A method for controlling the position of a floor component,
Providing a floor care machine including a deck, a floor care component, a handle device having a slot and a force generator coupled to the handle device,
Generating at least a first force using the force generator, and a handle coupling mechanism offset from the force generator to oppose suction when the floor care component is actuated; Applying at least a portion of the first force to the deck using a handle coupling mechanism coupled to the force generator using a slot;
Having a method. 19. The method of claim 18, wherein the force generating portion includes a compressible spring, and the generating step includes compressing the spring when the handle device is moved to at least a first operating position. the method of. The force generating unit includes one of a compression spring and a wave spring, and the generating step includes compressing one of the compression spring and the wave spring by operation of the handle device and the handle coupling mechanism. The method of claim 18 wherein: The handle device has a longitudinal central axis and includes a handle, and a force generating portion is disposed along the longitudinal central axis, and the generating step applies the first force substantially to the longitudinal central axis. 19. The method of claim 18, comprising generating along. 19. The method of claim 18, wherein the handle device has a central longitudinal axis and includes a handle, and the generating step includes generating the first force substantially along the central longitudinal axis. The method described in. 19. The method of claim 18, further comprising pivoting the handle device and the force generator about the same horizontal axis.

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