JP2020006285A - Liquid jet device - Google Patents

Abstract

To provide a liquid jet device in which a tube is pivotally supported on a rotating body, at a position displaced from a rotation shaft center, which is configured so that the rotating body as well as the liquid jet device are inhibited from vibrating when rotating the rotating body.SOLUTION: The liquid jet device comprises a rotating body that is rotated with a rotating shaft center as a center, a tube that is pivotally supported at a position displaced in a radial direction of the rotating body from the rotating shaft center of the rotating body and a nozzle that jets fluid supplied from the tube, which further comprises a counter mass unit arranged at a position at the opposite side of the tube across the rotating shaft center and fixed to the rotating body when viewed from a direction along the rotating shaft center.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid ejecting apparatus.

  2. Description of the Related Art Conventionally, a liquid ejecting apparatus in which a nozzle is attached to a tip of a shaft has been used in order to be able to eject a fluid ejected from a nozzle in a wider range. For example, in Patent Literature 1, a nozzle connected to the tip of a tube is supported by rotating a rotating body around a rotation axis while supporting the tube at a position displaced from the rotation axis. It is turning. According to such a liquid ejecting apparatus, since the nozzle can be rotated without using a rotary seal or the like, it is suitable for ejecting a liquid such as liquid nitrogen at a very low temperature.

JP-T-2012-533422A

  However, in the liquid ejecting apparatus disclosed in Patent Literature 1, the tube is supported at a position displaced from the rotation axis of the rotating body. Therefore, when the rotating body is rotated, the centrifugal force acting on both sides of the rotating body with respect to the rotation axis is biased, and the rotating body and the entire liquid ejecting apparatus vibrate.

  The present invention has been made in view of the above-described problems, and in a liquid ejecting apparatus in which a tube is supported by a rotating body at a position displaced from a rotation axis, the rotating body is further rotated when the rotating body is rotated. The object of the invention is to prevent the liquid ejecting apparatus from vibrating.

  The present invention employs the following configuration as means for solving the above-mentioned problems.

  According to a first aspect of the present invention, there is provided a rotating body rotated about a rotating axis, a tube supported at a position displaced in a radial direction of the rotating body from the rotating axis of the rotating body, and supplied from the tube. A nozzle for injecting the fluid, wherein the rotary body is disposed at a position opposite to the tube with respect to the rotation axis when viewed from a direction along the rotation axis. Is provided with a counter mass unit fixed to the control unit.

  According to a second aspect, in the first aspect, the counter mass unit has a configuration in which the counter mass unit has a base portion fixed to the rotating body and a detachable weight that can be attached to and detached from the base portion.

  In a third aspect based on the second aspect, the base portion is shaped like a column protruding from the rotating body along the rotation axis, and the countermass unit is provided with a tip end surface of the base portion. And a bolt for fastening the detachable weight to the base portion.

  According to a fourth aspect, in any one of the first to third aspects, the counter mass unit includes a center-of-gravity position adjusting mechanism for adjusting a center-of-gravity position of the counter mass unit in a direction along the rotation axis. Adopt configuration.

  In a fifth aspect based on the fourth aspect, the center-of-gravity adjusting mechanism has a bolt that moves the head in a direction along the rotation axis by rotating the mechanism.

  According to the present invention, the counter mass unit is provided at a position opposite to the tube with respect to the rotation axis of the rotating body. For this reason, the bias in the circumferential direction of the centrifugal force acting on the rotating body is reduced, and it is possible to prevent the rotating body and the liquid ejecting apparatus from vibrating when the rotating body is rotated.

FIG. 2 is a sectional view of the liquid ejecting apparatus according to the embodiment of the present invention. FIG. 2 is an enlarged view of a region A in FIG. 1.

  Hereinafter, an embodiment of a liquid ejecting apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the liquid ejecting apparatus 1 of the present embodiment. FIG. 2 is an enlarged view of a front end region (a region A in FIG. 1) of the liquid ejecting apparatus 1. In the present embodiment, the liquid ejecting apparatus 1 ejects liquid nitrogen X. However, the fluid ejected by the liquid ejecting apparatus of the present invention is not limited to liquid nitrogen. As shown in FIG. 1, the liquid ejecting apparatus 1 of the present embodiment includes a casing 2, a rotating unit 3, a supply tube 4, a nozzle unit 5, a tube holding mechanism 6, an air drill 7, and a power transmission mechanism 8. And

  The casing 2 accommodates the rotating unit 3 and the supply tube 4, and is, for example, a part at least part of which can be gripped by an operator. In the present embodiment, the casing 2 has a rotating body housing 2a, a transmission mechanism housing 2b, and a tube insertion portion 2c. The rotating body accommodating portion 2a is a cylindrical portion in which the rotating unit 3 is accommodated. The rotating body accommodating portion 2a has a central axis arranged so as to overlap with the rotation axis L of the rotating unit 3, a root side is fixed to the transmission mechanism accommodating portion 2b, and a distal end side is an open end.

  The transmission mechanism housing part 2b is a part that houses the power transmission mechanism 8. As shown in FIG. 1, the transmission mechanism housing portion 2b has a rotating body housing portion 2a fixed to an upper end portion and a lower end portion to which an air drill 7 is attached. An opening 2b1 through which the supply tube 4 can pass is provided at the upper end of the transmission mechanism housing 2b.

  The tube insertion portion 2c is a cylindrical portion into which the supply tube 4 is inserted, and is fixed to the upper end of the transmission mechanism housing 2b from the side opposite to the transmission mechanism housing 2b. The tube insertion portion 2c has a closed end at a rear end side, an open end at a front end side, and is concentric with the transmission mechanism housing portion 2b when viewed from a direction along the rotation axis L. Are located in The tube insertion portion 2c is fixed to the transmission mechanism accommodating portion 2b such that the open end on the distal end side is connected to the opening 2b1. The closed end on the rear end side of the tube insertion portion 2c holds the supply tube 4. That is, the supply tube 4 is fixed at an intermediate position to a rear end portion of the tube insertion portion 2 c of the casing 2.

  The casing 2 having such a rotator housing portion 2a, the transmission mechanism housing portion 2b, and the tube insertion portion 2c is formed of, for example, a resin material having heat insulation properties. This suppresses the transfer of cold heat to the worker.

  The rotating unit 3 is housed inside the rotating body housing portion 2a of the casing 2, and includes a front end bearing 3a, a rear end bearing 3b, a rotating cylinder 3c (rotating body), and a counter mass unit 3d. ing. The front end bearing 3a is a bearing arranged closer to the front end of the rotating body housing 2a than the rear end bearing 3b. In this tip side bearing 3a, the outer ring is fixed to the inner peripheral surface of the rotating body housing portion 2a, and the inner ring is fixed to the outer peripheral surface of the rotating cylinder 3c, so that the rotating cylinder 3c can rotate around the rotation axis L. I support it. The rear end side bearing 3b is a bearing arranged closer to the root of the rotating body housing portion 2a than the front end side bearing 3a. The rear end bearing 3b has an outer ring fixed to the inner peripheral surface of the rotating body housing portion 2a, an inner ring fixed to the outer peripheral surface of the rotating cylinder 3c, and is capable of rotating the rotating cylinder 3c about the rotation axis L. I support it.

  The rotating cylinder 3c is a cylindrical part having a closed end closed at the front end by the front wall 3c1 and an open end at the rear end. In the rotating cylinder 3c, the front end wall 3c1 is disposed slightly forward from the front end of the rotating body housing portion 2a, and the rear end side faces the opening 2b1 provided in the transmission mechanism housing portion 2b of the casing 2. As described above, the shaft is supported by the front end bearing 3a and the rear end bearing 3b. The supply tube 4 is inserted through the rotary cylinder 3c as shown in FIG.

  As shown in FIG. 2, the distal wall 3c1 is provided with a through portion 3c2 through which the supply tube 4 can pass and to which the tube holding mechanism 6 is attached. The penetrating portion 3c2 is provided so as to penetrate the distal end wall 3c1, so that the supply tube 4 can pass from the inside of the rotary cylinder 3c to the outside. The tip wall 3c1 is provided with a mounting portion 3c3 for fixing the counter mass unit 3d. The mounting portion 3c3 is provided with a female screw into which a base 3d1 described later of the counter mass unit 3d is screwed.

  The penetrating part 3c2 and the mounting part 3c3 are arranged at point-symmetric positions about the rotation axis L. For this reason, the supply tube 4 held by the tube holding mechanism 6 attached to the penetrating portion 3c2 and the counter mass unit 3d attached to the attachment portion 3c3, when viewed from the direction along the rotation axis L, have the rotation axis L Are arranged in between. That is, when viewed from the direction along the rotation axis L, the counter mass unit 3d fixed to the rotation cylinder 3c is disposed at a position opposite to the supply tube 4 with respect to the rotation axis L.

  As shown in FIG. 2, the outer edge of the distal end wall 3c1 is formed as a flange 3c4 which bulges radially outward with respect to the rotation axis L from the peripheral wall of the rotary cylinder 3c. The flange 3c4 is provided over the entire circumference of the rotary cylinder 3c with the rotation axis L as a center. Such a flange portion 3c4 is provided so as to cover a gap between the rotating cylinder 3c and the rotating body accommodating portion 2a of the casing 2 when viewed from the outside of the casing 2, and is always rotated including during rotation of the rotating cylinder 3c. Foreign matter is prevented from entering the gap between the cylinder 3c and the rotator housing 2a from outside.

  The counter mass unit 3d includes a base 3d1, a detachable weight 3d2, and a weight fixing bolt 3d3 (bolt, center-of-gravity position adjusting mechanism). The base portion 3d1 is screwed to a mounting portion 3c3 provided on the distal end wall 3c1 of the rotary cylinder 3c. The base portion 3d1 is a weight member that is a main portion of the counter mass unit 3d. The mass of the base portion 3d1 acts on the rotating cylinder 3c due to the centrifugal force acting on the rotating cylinder 3c due to the mass of the supply tube 4 and the tube holding mechanism 6 when the rotating cylinder 3c rotates, and acts on the rotating cylinder 3c due to the mass of the counter mass unit 3d. And the centrifugal force to be applied are set to be substantially the same. Such a base portion 3d1 has a substantially cylindrical shape, and is fixed to the distal end wall 3c1 of the rotating cylinder 3c so as to protrude from the rotating cylinder 3c toward the front of the rotating cylinder 3c. A bolt hole 3d4 for screwing the weight fixing bolt 3d3 is provided on the distal end surface of the base portion 3d1.

  The detachable weight 3d2 is a disk-shaped member having substantially the same diameter as the base portion 3d1 when viewed from a direction along the rotation axis L, and has an opening in the center portion through which the weight fixing bolt 3d3 can pass. . The attachment / detachment weight 3d2 can be attached to / detached from the base portion 3d1 by weight fixing bolts 3d3. By selecting attachment / detachment, the total mass of the counter mass unit 3d (that is, the counter mass unit 3d is rotated when the rotary cylinder 3c rotates). The centrifugal force acting by the mass) can be adjusted.

  Such a detachable weight 3d2 may be in a state where it is not provided for the countermass unit 3d, or may be a state where a plurality of such weights are provided for the countermass unit 3d. When a plurality of attachment / detachment weights 3d2 are provided in the countermass unit 3d, the mass and shape of these attachment / detachment weights 3d2 need not be the same.

  The weight fixing bolt 3d3 has a shaft portion screwed into a bolt hole 3d4 of the base portion 3d1, and the detachable weight 3d2 is pressed against the base portion 3d1 with the head portion, thereby fastening the detachable weight 3d2 to the base portion 3d1. . Such a weight fixing bolt 3d3 can be used as a center of gravity position adjusting mechanism for adjusting the position of the center of gravity in the direction along the rotation axis L of the counter mass unit 3d, in addition to fixing the detachable weight 3d2. For example, by inserting a shim between the weight fixing bolt 3d3 and the base portion 3d1 (or the detachable weight 3d2), and adjusting the position of the head of the weight fixing bolt 3d3 in the direction along the rotation axis L, the counter can be used. The position of the center of gravity of the mass unit 3d in the direction along the rotation axis L can be adjusted.

  As shown in FIG. 1, the supply tube 4 is a flexible metal tube for guiding the liquid nitrogen X from a supply source (not shown) to the nozzle unit 5. The supply tube 4 is inserted from the inside of the tube insertion portion 2c of the casing 2 through the opening 2b1 of the transmission mechanism housing 2b into the inside of the rotary cylinder 3c of the rotary unit 3 (that is, the inside of the rotary body housing 2a). . The supply tube 4 has a distal end that is drawn out of the rotary cylinder 3c through a penetrating part 3c2 provided on a distal end wall 3c1 of the rotary cylinder 3c, and has a diameter from the rotation axis L by the tube holding mechanism 6 at the penetrating part 3c2. The nozzle unit 5 is pivotally supported at a position displaced in the direction and is connected to a tip end portion. The supply tube 4 is fixed to the rear end of the tube insertion section 2c. When the rotary cylinder 3c is rotated about the rotation axis L, the distal end of the supply tube 4 pivots about the rotation axis L with the intermediate portion fixed to the tube insertion portion 2c. Is rotated as follows. As described later, the distal end of the supply tube 4 is rotatably supported by the tube holding mechanism 6 with respect to the rotary cylinder 3c. For this reason, the supply tube 4 is not rotatable by the rotation of the rotary cylinder 3c, and is rotatable so that the distal end always rotates around the rotation axis L.

  The nozzle unit 5 is fixed to the tip of the supply tube 4. As shown in FIG. 2, the nozzle unit 5 has a base part 5a, a first nozzle 5b, and a second nozzle 5c. The base portion 5a is a block body connected to the supply tube 4 and having an internal flow path connected to the first nozzle 5b and the second nozzle 5c. The internal flow path of the base portion 5a is single at the root side (the supply tube 4 side) of the base portion 5a and is branched into a plurality at the distal end side. The number of branches of the internal flow path is arbitrary. Further, a configuration in which the internal flow path is not branched can also be adopted.

  The first nozzle 5b is fixed to the base 5a so as to be connected to the internal flow path. The first nozzle 5b injects the liquid nitrogen X supplied from the supply tube 4 to the outside through the internal flow path of the base 5a. The second nozzle 5c is fixed to the base 5a so as to be connected to the internal flow path. The second nozzle 5c injects the liquid nitrogen X supplied from the supply tube 4 to the outside through the internal flow path of the base portion 5a. That is, in the present embodiment, the liquid nitrogen X is jetted outward from the first nozzle 5b and the second nozzle 5c.

  The tube holding mechanism 6 is attached to a penetrating portion 3c2 provided on the distal end wall 3c1 of the rotating cylinder 3c, and rotatably supports the supply tube 4. The holding position and holding angle of the supply tube 4 by the tube holding mechanism 6 and the length of the supply tube 4 are set so that a large stress does not act locally on the supply tube 4. For example, it is assumed that the nozzle unit 5 has a single injection opening for injecting the liquid nitrogen X on an extension of the axis at the connection end of the supply tube 4. Further, the distance from the rotation axis L in the radial direction about the rotation axis L of the rotary cylinder 3c to the tip end position of the nozzle unit 5 is defined as δ. The angle formed between the injection axis of the nozzle unit 5 (the axis of the supply tube 4 at the connection end) and the rotation axis L is α. Further, the distance from the holding position of the supply tube 4 of the tube insertion portion 2c to the tip end position of the nozzle unit 5 in the direction along the rotation axis L is d. In this case, first, the distance δ and the angle α are set based on the specifications required for the liquid ejecting apparatus 1. Further, the distance d is set so that the maximum bending stress acting on the supply tube 4 is equal to or less than half the fatigue limit value of the supply tube 4. The holding position and the holding angle of the supply tube 4 by the tube holding mechanism 6 and the length of the supply tube 4 are set so that the distance δ, the angle α, and the distance d set as described above are realized. As described above, by setting the holding position and the holding angle of the supply tube 4 by the tube holding mechanism 6 and the length of the supply tube 4, it is possible to more reliably prevent the supply tube 4 from being damaged by fatigue. .

  Returning to FIG. 1, the air drill 7 receives the compressed air supplied from the outside and generates rotational power for rotating the rotary cylinder 3 c, and is connected to the lower end of the transmission mechanism accommodating portion 2 b of the casing 2. I have. In such an air drill 7, as shown in FIG. 2, an output shaft 7 a is disposed inside the transmission mechanism housing 2 b, and the output shaft 7 a is connected to the power transmission mechanism 8.

  The power transmission mechanism 8 is a mechanism that connects the air drill 7 and the rotary cylinder 3c and transmits rotational power from the air drill 7 to the rotary cylinder 3c. As shown in FIG. 2, the power transmission mechanism 8 includes a drive gear 8a fixed to the output shaft 7a of the air drill 7, a driven gear 8b fixed to the peripheral surface of the rotary cylinder 3c and meshed with the drive gear 8a. have.

  In the liquid ejecting apparatus 1 of the present embodiment employing such a configuration, when compressed air is supplied to the air drill 7 from outside, the air drill 7 generates rotational power. The rotating power generated by the air drill 7 is transmitted to the rotating cylinder 3c of the rotating unit 3 by the power transmission mechanism 8. As a result, the rotary cylinder 3c is rotated about the rotation axis L.

  When the rotary tube 3c is rotated, the supply tube 4 is a part held by the tube holding mechanism 6 that is rotated with the rotary tube 3c in a state where the connection portion with the tube insertion portion 2c of the casing 2 is fixed. Is rotated (turned) about the rotation axis L. At this time, since the supply tube 4 is rotatably held by the tube holding mechanism 6, the distal end portion is continuously rotated without the supply tube 4 being greatly twisted. As a result, the nozzle unit 5 connected to the tip of the supply tube 4 is rotated about the rotation axis L.

  Further, when liquid nitrogen X is supplied to the supply tube 4 from a supply device (not shown), the liquid nitrogen X is supplied to the rotating nozzle unit 5 and is ejected from the first nozzle 5b and the second nozzle 5c. For example, when liquid nitrogen is injected into concrete, the concrete can be processed by the expansion force when the liquid nitrogen enters the porous material of the concrete and vaporizes after the injection. By injecting the liquid nitrogen X from the nozzle unit 5 rotated in this way, it becomes possible to inject the liquid nitrogen X over a wide range without moving the liquid ejecting apparatus 1 by the operator.

  Here, in the liquid ejecting apparatus 1 according to the present embodiment, when viewed from the direction along the rotation axis L, the liquid ejection apparatus 1 is disposed at a position opposite to the supply tube 4 with respect to the rotation axis L and is attached to the rotation cylinder 3c. A fixed counter mass unit 3d is provided. According to the liquid ejecting apparatus 1 of the present embodiment, the bias of the centrifugal force acting on the rotating cylinder 3c in the circumferential direction is reduced by the mass of the counter mass unit 3d, and the rotation when the rotating cylinder 3c is rotated is reduced. Vibration of the cylinder 3c can be suppressed. Therefore, according to the liquid ejecting apparatus 1 of the present embodiment, it is possible to suppress the vibration of the liquid ejecting apparatus 1 when the rotary cylinder 3c is rotated.

  Further, in the liquid ejecting apparatus 1 of the present embodiment, the counter mass unit 3d includes the base 3d1 fixed to the rotary cylinder 3c, and a detachable weight 3d2 detachable from the base 3d1. For this reason, according to the liquid ejecting apparatus 1 of the present embodiment, the mass of the counter mass unit 3d can be adjusted by attaching and detaching the attaching and detaching weights 3d2. Therefore, even when the rotation speed of the rotary cylinder 3c is changed or the flow rate of the liquid nitrogen X to be injected is changed, the mass of the counter mass unit 3d is appropriately adjusted according to these changes. It is possible to do.

  Further, in the liquid ejecting apparatus 1 of the present embodiment, the base portion 3d1 is shaped like a column protruding from the rotary cylinder 3c along the rotation axis L, and the countermass unit 3d is connected to the front end surface of the base portion 3d1. And a weight fixing bolt 3d3 for fastening the detachable weight 3d2 to the base 3d1. Therefore, the detachable weight 3d2 can be easily attached to the base 3d1 only by rotating the weight fixing bolt 3d3 with respect to the base 3d1. Further, a plurality of detachable weights 3d2 can be stacked between the head of the weight fixing bolt 3d3 and the base portion 3d1. Therefore, the plurality of detachable weights 3d2 can be fixed to the base 3d1 by the single weight fixing bolt 3d3.

  In the liquid ejecting apparatus 1 of the present embodiment, the countermass unit 3d includes the weight fixing bolt 3d3 that functions as a center-of-gravity position adjusting mechanism that adjusts the center-of-gravity position of the countermass unit 3d in the direction along the rotation axis L. Have. Therefore, by adjusting the position of the head of the weight fixing bolt 3d3 in the direction along the rotation axis L, the position of the center of gravity of the countermass unit 3d in the direction along the rotation axis L can be adjusted.

  Further, by using the weight fixing bolt 3d3 as the center of gravity adjusting mechanism, the center of gravity of the counter mass unit 3d can be easily adjusted by rotating the weight fixing bolt 3d3 with respect to the base 3d1. For this reason, it is not necessary to move the base portion 3d1 directly fixed to the rotating cylinder 3c, and it is possible to reduce the influence of the work of adjusting the position of the center of gravity, such as a decrease in the mounting accuracy of the rotating cylinder 3c.

  As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to the above embodiments. The shapes, combinations, and the like of the constituent members shown in the above-described embodiments are merely examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

  For example, in the above embodiment, the configuration in which only one counter mass unit 3d is provided has been described. However, the present invention is not limited to this, and a configuration in which a plurality of counter mass units 3d are provided can be employed. For example, when a plurality of counter mass units 3d are provided, the plurality of counter mass units 3d may be arranged in a circumferential direction around the rotation axis L. Thereby, the centrifugal force acting when the rotary cylinder 3c is rotated is equalized in the circumferential direction around the rotation axis L, and the vibration of the rotary cylinder 3c can be further suppressed.

  Further, for example, when processing the concrete by the liquid ejecting apparatus 1 of the present embodiment, the concrete pieces scattered during the processing will collide with the base 3d1 of the countermass unit 3d. For this reason, as a result of long-term use, there is a possibility that the base portion 3d1 is gradually shaved and the mass changes. Therefore, a protection member that can be easily replaced and covers the base portion 3d1 may be provided on the counter mass to prevent the base portion 3d1 from being scraped.

  In the above embodiment, the configuration in which the fluid ejected by the liquid ejecting apparatus 1 is liquid nitrogen has been described. However, the invention is not limited. As the fluid to be injected, liquid at extremely low temperature other than liquid nitrogen, water, blasting agent, and the like can be used. That is, the liquid ejecting apparatus 1 of the present invention can be applied to a water jet apparatus and a polishing apparatus.

1 Liquid ejecting device 2 Casing 2a Rotating body housing 2b Transmission mechanism housing 2b1 Opening 2c Tube insertion unit 3 Rotating unit 3a Rotating unit 3a Rear bearing 3b End side bearing 3c ... Rotary cylinder (rotary body)
3c1... Tip wall 3c2... Penetration part 3c3... Mounting part 3c4... Flange part 3d...
3d4 bolt hole 4 supply tube (tube)
5 Nozzle unit 5a Base part 5b First nozzle 5c Second nozzle 6 Tube holding mechanism 7 Air drill 7a Output shaft 8 Power transmission mechanism 8a Drive gear 8b … Driven gear L… rotation axis X …… liquid nitrogen

Claims (5)

A rotating body rotated about a rotating axis, a tube supported at a position displaced in a radial direction of the rotating body from the rotating axis of the rotating body, and a nozzle for ejecting a fluid supplied from the tube A liquid ejecting apparatus comprising:
A liquid jet, comprising: a counter mass unit disposed at a position opposite to the tube with respect to the rotation axis as viewed from a direction along the rotation axis and fixed to the rotating body. apparatus. The counter mass unit includes:
A base portion fixed to the rotating body,
The liquid ejecting apparatus according to claim 1, further comprising: a detachable weight that can be attached to and detached from the base portion. The base portion is shaped like a column protruding from the rotating body along the rotation axis,
The liquid ejecting apparatus according to claim 2, wherein the counter mass unit has a bolt that is screwed to a tip end surface of the base portion and fastens the detachable weight to the base portion.   The liquid jet according to any one of claims 1 to 3, wherein the counter mass unit includes a center-of-gravity position adjusting mechanism that adjusts a center-of-gravity position of the counter mass unit in a direction along the rotation axis. apparatus.   The liquid ejecting apparatus according to claim 4, wherein the center-of-gravity position adjusting mechanism includes a bolt that moves a head in a direction along the rotation axis by rotating the center of gravity.

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