JP2009114853A - Weight transporter with built-in propulsive mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of simply loading a driving device on a caterpillar track compactly to a weight transporter and capable of smoothly transporting a heavy article in the forward and opposite directions. <P>SOLUTION: In a weight transporter, the caterpillar track 16 is stretched to a cradle 15 fitted to a pedestal 12, and the heavy article is transported while receiving the load of the heavy article or the reaction of the load by the caterpillar track 16. In the weight transporter, two driving sprockets 28 are fitted on both sides of a shaft section 30, follower sprockets 38 are fitted on both sides of a shaft and a propulsive driving device 17 for the driving sprockets consisting of hydraulic motors 25 and the propulsive driving device 17 for the follower sprockets are mounted on the cradle 15. In the weight transporter, these propulsive driving devices 17 are connected between the shaft section 30 mounting the driving sprockets 28 and the shaft 39 mounting the follower sprockets 38 through clutches respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a propulsion mechanism that is used when a bridge girder or other heavy object is installed by moving it to a predetermined location safely and accurately in either the forward or reverse direction while receiving the load in an endless track. The present invention relates to a built-in heavy goods transfer device.

In bridge construction for rivers, straits, etc., bridge piers are erected at predetermined intervals between one land and the other, and long and heavy objects are sequentially passed over.
In such a bridge construction work, generally heavy objects are made in advance to a predetermined length, rails are laid on one land, the heavy objects are placed on the carriage, and are gradually extended from the sliding device at the tip of the land. First, it is placed on the sliding device on the first pier, and further on the second sliding device while being sent out.

Conventionally, a heavy material transfer device 60 using an endless track 61 as shown in FIG. 8 is known for such heavy material transfer.
In FIG. 8, a sliding plate 65 is slidably mounted on a pedestal 64. On the upper surface of the sliding plate 65, four vertical adjustment jacks 63 are fixed to both sides of the endless track band 61, and a spherical seat at the upper end of the piston rod 66 that advances and retreats to the vertical adjustment jack 63. Is fitted with a pivot 67 on the lower surface of the receiving base 62.

A swinging body 68 that slides on the endless track band 61 is fitted into the swinging body fitting groove of the pedestal 62.
A guide roller 72 and an auxiliary guide roller 73 are provided below the guide roller 72 so as to face both ends of the pedestal 62.
The endless track band 61 is looped around the guide rollers 72 and 73 at both ends. The endless track band 61 is a structure in which a plurality of track band units are sequentially connected to each other by a connecting shaft.

  In the conventional heavy goods transfer device 60 as described above, according to the size and weight of the heavy goods 10, one or more heavy goods transfer devices 60 are fixed with the pedestals 64 arranged sideways and / or vertically. Installed. The heavy article 10 is placed on the heavy article transfer device 60 and is pushed or pulled between the transfer jack 70 such as a double twin jack as shown in FIG. Is slowly transferred.

  In FIG. 8, the heavy article 10 is moved while being placed on the endless track band 61. However, as shown in FIG. At least two heavy-weight transfer devices 60 are attached downward at both ends of the frame, the endless track 61 is brought into contact with the rail 69, and the rail 69 is continuously moved by the transfer jack 70 such as a double twin jack as a reaction force. It is also possible to do so (for example, see Patent Document 1).

JP 2000-351434 A.

Compared to the one in which one roller with a large diameter is rotatably attached to the support base and the one in which a large number of small diameter rollers are connected to the support base with a chain, the endless track 61 is In the heavy load transfer device 60 used, since the endless track band 61 and the bottom surface of the heavy load 10 are in contact with a plurality of surfaces, the load is averaged, and the lower surface on which the heavy load 10 slides is uneven. In such a case, it can be overcome relatively easily.
However, in the heavy load transfer device 60 using the endless track 61, the transfer jack 70 is made as a separate device from the heavy load transfer device 60, and the heavy load transfer device 60 only functions as a roller. there were.

Conventionally, in order to fix the transfer jack 70 such as a double twin jack in a fixed manner, in order to take the reaction force of the heavy object 10, a troublesome and troublesome anchor work has to be performed. Depending on the size and transfer distance, anchor work at a plurality of locations is required. Further, when there are a plurality of transfer jacks 70, it takes several times as much work to install the jacks, and the work efficiency becomes worse.
Therefore, in order to save these troubles, it is conceivable to mount a driving device for driving the rotating shaft of the endless track 61 in the heavy load transport device 60. However, if the driving device is mounted, the limitation on the pier is limited. However, there is a problem that the entire configuration becomes unrealistically large.

  In the present invention, the propulsion drive device for driving the endless track zone can be easily and compactly mounted on the heavy load transfer device, and the loaded heavy load can be smoothly transferred in the forward and reverse directions. The purpose is to provide what was done.

In the present invention, an endless track band 16 is stretched over a pedestal 15 provided on a pedestal 12, and the heavy load is transferred while receiving the load of the heavy load 10 or the reaction force of the load at the endless track band 16. In the device
The endless track band 16 has a chain shaft 47 that is rotatably attached to an elongated load receiving member 48 and link plates 51 are attached to both ends of the chain shaft 47 protruding from the load receiving member 48. And a drive sprocket 28 that is engaged with the two rows of chains 24 so as to face one end and the other end of the receiving base 15. Two driven sprockets 38 are provided, the two drive sprockets 28 are provided on both sides of the shaft 30, the driven sprockets 38 are provided on both sides of the shaft, and the cradle 15 includes a hydraulic motor 25. A propulsion drive device 17 and a propulsion drive device 17 for a driven sprocket are provided, and a shaft portion 30 to which the drive sprocket 28 is attached and a propulsion drive device for the drive sprocket. 7, between the driven sprocket 38 shaft 39 and the driven sprocket for propulsion drive 17 fitted with a heavy transport device incorporating a propulsion mechanism characterized by being connected via a clutch.

According to the first aspect of the present invention, the endless track band is attached to the elongated load receiving member through the chain shaft so as to be rotatable, and the link plate is attached to the end protruding from the load receiving material of the chain shaft. A plurality of attached ones are sequentially connected, the load receiving member is provided with a chain, facing one end and the other end of the receiving base, and provided with a driving sprocket and a driven sprocket that mesh with the chain, the driving A sprocket is provided on the shaft portion, the driven sprocket is provided on the shaft, a propulsion drive device for a driving sprocket and a propulsion drive device for a driven sprocket, each comprising a hydraulic motor, are provided on the cradle, and the shaft portion and the driving sprocket to which the driving sprocket is attached And a propulsion drive unit for the driven sprocket and a shaft to which the driven sprocket is attached via a clutch. Because it is connected, when the drive sprocket at one end during normal operation is driving, the driven sprocket at the other end is disengaged from the clutch and runs idle, and the heavy object beyond the transfer point is reversed. When returning to the direction, the drive sprocket on one end side should be able to control the transfer according to the purpose of use such as disengaging the clutch and idling to drive the driven sprocket on the other end side. Can do.
In addition, the endless track band is integrated with the chain, the configuration of the endless track band is simplified, and the propulsion drive device that drives the endless track band can be easily and compactly mounted on the heavy goods transfer device. Further, since the chain meshes with the tooth portion of the drive sprocket at a plurality of points, the tensile load in the endless track band is dispersed, and the loaded heavy object can be smoothly transferred.

  According to the second aspect of the present invention, the endless track band is attached to the elongated load receiving member through the chain shaft so as to freely rotate, and the link plate is attached to both ends protruding from the load receiving material of the chain shaft. Drive sprockets and driven sprockets that are connected in series with a plurality of attached ones and that have a chain on both sides of the load receiving material, face one end and the other end of the cradle and mesh with the two rows of chains. Two drive sprockets are provided on both sides of the shaft portion, the driven sprockets are provided on both sides of the shaft, and the propulsion drive device for the drive sprocket and the propulsion for the driven sprocket, each comprising a hydraulic motor in the cradle. A drive device is provided, between the shaft portion to which the drive sprocket is attached and the propulsion drive device for the drive sprocket, and to the shaft to which the driven sprocket is attached and the driven sprocket. Between the use propulsion drive, since the respectively connected via a clutch, heavy object placed on the endless track by a drive sprocket which meshes with the two rows of chain can be transported without lateral displacement.

According to the third aspect of the present invention, the driven sprocket, the driven sprocket, and the guide sprocket for driving, which are engaged with the two rows of chains, facing the one end portion, the other end portion, and the lower portion of the cradle, respectively. Two guide sprockets for driving are provided integrally with the shaft, and two sets of propulsion driving devices consisting of hydraulic motors are provided on the cradle so as to be vertically adjustable by a jack for tension. Since the rotating plate provided in the hydraulic motor is fixed to each part, if the sprocket when acting as a guide is shrunk with a tensioning jack, the endless track can be easily attached and detached during assembly to the cradle The guide sprocket can be extended with a tensioning jack to apply tension according to the weight of the heavy load on the endless track. Drive sprocket, guide sprocket, it can be adjusted to the optimum state loosening or hardness of the time of engagement of the driven sprocket.
Also, two guide sprockets are provided integrally with the shaft, and two sets of propulsion drive devices consisting of hydraulic motors are provided on the cradle so as to be vertically adjustable by means of tension jacks. When the rotating plate provided on the motor is fixed to act as a drive, a heavy thrust drive device is installed at the lower part of the cradle to lower the emphasis of the heavy object transfer device and to obtain a sense of stability of the device itself This leads to a stable transport of heavy objects.

It is a partially cutaway plan view showing an embodiment of a heavy goods transfer device incorporating a propulsion mechanism according to the present invention. FIG. 2 is a side view partially cut away in FIG. 1. FIG. 2 is a partially cutaway front view in FIG. 1. FIG. 2 is a partially cutaway rear view in FIG. 1. FIG. 2 is a front view in which the endless track 16 in FIG. 1 is partially cut away. FIG. 2 is a side view in which the endless track 16 in FIG. 1 is partially cut away. FIG. 5 is an enlarged view of the tension jack 42 and the guide sprocket 37 in FIG. 4 partially cut away. It is the side view in which the conventional heavy article transfer device 60 was partially cut away. It is explanatory drawing at the time of transferring with the endless track 61 in the conventional heavy goods transfer apparatus 60 facing down.

  In the heavy goods transfer device for transferring a heavy object while receiving the load of the heavy object 10 or the reaction force of the load on the endless orbital band 16 over the cradle 15 provided on the pedestal 12. The orbital belt 16 has a chain shaft 47 that is pivotably attached to an elongated load receiver 48, and a plurality of link shafts 51 attached to both ends of the chain shaft 47 protruding from the load receiver 48. Drive sprockets 28 and driven sprockets 38 that are sequentially connected to each other with the chain 24 on both sides of the load receiving member 48 and face one end and the other end of the receiving base 15 and mesh with the two rows of chains 24. Two drive sprockets 28 are provided on both sides of the shaft portion 30, the driven sprocket 38 is provided on both sides of the shaft 39, and the cradle 15 includes a hydraulic motor 25. A drive sprocket propulsion drive unit 17 and a driven sprocket propulsion drive unit are provided. Between the shaft portion 30 to which the drive sprocket 28 is attached and the drive sprocket propulsion drive unit 17, and a shaft 39 to which the driven sprocket 38 is attached. The heavy-duty transfer device having a built-in propulsion mechanism that is connected to a propulsion drive device for a driven sprocket via a clutch.

  The chain 24 of the endless track band 16 may be in a single row, but if possible, two rows can be formed by sequentially connecting a plurality of link plates 51 attached to both ends protruding from the load receiving member 48 of the chain shaft 47. It is more preferable to provide two drive sprockets 28 and two driven sprockets 38 each having a chain 24 and meshing with the two rows of chains 24.

  Further, two drive sprockets 28, two driven sprockets 38, and two guide sprockets 37 that respectively engage with the two rows of chains 24 are provided facing one end, the other end, and the lower part of the cradle 15. By providing the guide sprocket 37 so that it can be adjusted up and down by the tension jack 42, the endless track 16 can be given an optimum tension according to the load.

An embodiment of a heavy load transfer device incorporating a propulsion mechanism according to the present invention will be described with reference to FIGS.
In FIG. 1 to FIG. 4, 12 is a pedestal that is directly attached to the upper end of the pier or the land. The pedestal 12 has a rotating plate 13 for changing the direction through a sliding thin plate for improving the sliding on the upper surface. Is slidably mounted, and the long hole at the substantially center of the pedestal 12 and the downward rotation shaft at the substantially center of the lower surface of the rotating plate 13 are fitted in a movable and rotatable manner.

Four vertical adjustment jacks 14 are fixed to the upper surface of the rotating plate 13 so that two of them are located on both sides of an endless track 16 described later, and pistons that advance and retreat to the cylinders 20 of these vertical adjustment jacks 14. A spherical seat is provided at the upper end of the rod 21.
The rotating plate 13 controls the hydraulic rod 25 of the propulsion drive unit 17 and the tension jack 42 of the guide sprocket 37, which will be described later, as well as controlling the advance and retreat of the piston rod 21 of the four vertical adjustment jacks 14. The supply port and the stop valve are connected via an oil feed pipe.

  A pedestal 15 is mounted via a pivot 23 by a spherical seat of the four piston rods 21. In the center of the upper surface of the cradle 15, a swinging body fitting groove is provided from the front end portion to the rear end portion corresponding to the moving direction. In this swinging body fitting groove, as shown in FIG. Two sliding plates 18 sliding on 16 are fitted in front and rear in the moving direction. On the upper surface of the sliding plate 18, a sliding groove 19 is formed in the moving direction, and a sliding body 22 is interposed. On the side of the endless track 16 is provided a guide plate 36 that guides when the heavy object 10 is transferred and prevents displacement.

  As shown in FIGS. 1 to 4, vertical frames 34 and 35 are fixed to the lower surface of the cradle 15 so as to face one end side and the other end side, respectively, and one vertical frame 34 has a propulsion drive device. 17 is provided, and the other vertical frame 35 is provided with a support frame 33 for supporting the driven sprocket shaft 39 of the driven sprocket 38.

  The endless track band 16 returns to the other end side through a driven sprocket 38 on the other end side, two sliding plates 18, a drive sprocket 28 on one end side, and a guide sprocket 37 on the lower part of the cradle 15. It is stretched around once. As shown in FIGS. 5 and 6, the endless track band 16 is rotatably fitted with two chains 24 formed at both ends of the chain shaft 47 and a gap 50 between the chains 24. Load receiving material 48. More specifically, the load receiving member 48 has a rectangular plate shape whose width is slightly narrower than the pitch of the chain 24, and the lower sliding surface 31 provides friction resistance to the sliding groove 19 of the sliding plate 18. The chain shaft 47 is engaged with the sliding body 22 for lowering, and the chain shaft 47 penetrates in the center in the longitudinal direction. The link plates 51 are fitted into the portions projecting from both ends of the chain shaft 47 and sequentially connected. A chain 24 is formed. Further, a height adjusting plate 49 is fixedly attached to the upper surface of the load receiving member 48 so that the surface on which the heavy article 10 is placed is slightly higher than the chain 24.

Next, as shown in FIGS. 1 and 2, a driven sprocket shaft 39 is horizontally attached to the support frames 33 on both sides on the other end side by a support plate 40, and the driven sprocket shaft 39 includes A driven sprocket 38 that meshes with the chains 24 on both sides is rotatably provided.
Further, as shown in FIGS. 1, 2, and 3, hydraulic motors 25 as the propulsion drive devices 17 are fixedly attached to the support frames 32 on both sides on the one end side by mounting plates 27, respectively. A part of the hydraulic motor 25 is rotatably fitted in the cylindrical portion 29, and the cylindrical portion 29 and the rotating plate 26 of the hydraulic motor 25 are fixedly coupled. The cylinder portions 29 on both sides are formed by integrally forming the drive sprockets 28 on both sides and the horizontal shaft portion 30, and the chains 24 on both sides are engaged with the drive sprockets 28 on both sides.

  As shown in FIGS. 2, 4, and 7, tension jacks 42 for adjusting the vertical position of the guide sprocket 37 are attached to both sides of the lower surface of the center of the cradle 15. The cylinder 43 and the piston 44 in the tension jack 42 are respectively provided downward on the lower surface of the cradle 15, and the lower end of the piston 44 is connected to a horizontal shaft via a vertical movement guide plate 45, a bearing cover 46, and a bearing 53. 41, guide sprockets 37 are attached to both sides of the shaft 41 by keys 52, and both chains 24 are engaged with the guide sprockets 37 on both sides.

  In addition to attaching the propulsion drive device 17 to the drive sprocket 28 on one end side of the endless track band 16, two units can be transferred to the two driven sprockets 38 on the other end side of the endless track band 16 in the direction opposite to the one end side. The propulsion drive unit 17 is installed. Normally, when the driving sprocket 28 on one end side is driven, the driven sprocket 38 on the other end side is disengaged so as to idle and the heavy object 10 beyond the transfer point is moved in the reverse direction. When returning, the drive sprocket 28 at one end is disengaged from the clutch so as to idle, and the driven sprocket 38 at the other end is driven.

  The propulsion drive unit 17 is mounted on the drive sprocket 28 and the driven sprocket 38, respectively, and the propulsion drive unit 17 is installed on each of the two guide sprockets 37 below the endless track 16 to be used as a drive sprocket. . That is, the drive sprocket 28 on one end side and the driven sprocket 38 on the other end side of the endless track 16 are made to act as followers, and the guide sprocket 37 is used as the drive side. More specifically, the sprocket 37 for driving is fixedly attached to the shaft 41, the rotating plate 26 of the hydraulic motor 25 is connected to the end of the shaft 41, and the non-rotating main body portion of the hydraulic motor 25 is a tension jack. It can also be attached to the lower end of the piston 44 in 42 so that the vertical position can be adjusted.

The operation of the apparatus according to the present invention configured as described above will be described.
Depending on the size and weight of the heavy load 10, one or more heavy load transfer devices according to the present invention, in which the propulsion drive 17 is built in the land, the pier, etc., the pedestal 12 in the horizontal and / or vertical direction. The heavy objects 10 are placed in a fixed manner so as to be arranged, and the heavy objects 10 are placed on spacers placed on or fixed on the endless track 16.
Further, pressure oil is sent to the tension jack 42, the piston 44 is advanced and retracted from the cylinder 43, and the shaft 41 is moved up and down to adjust the tension between the guide sprocket 37 and the chain 24.

  In such a state, when the endless track 16 is to be transferred to the left in FIGS. 1 and 2, the clutch on the drive sprocket 28 side is engaged, and the hydraulic oil 25 is applied to the hydraulic motor 25 of the propulsion drive device 17. To rotate. At this time, the driven sprocket 38 is disengaged from the clutch. Then, the rotating plate 26 of the hydraulic motor 25 rotates counterclockwise in FIG. 2, so that the cylindrical portion 29, the shaft portion 30, and the driving sprocket 28 fixed integrally with the rotating plate 26 rotate, and this drive The endless track 16 starts to move through the chain 24 meshing with the sprocket 28, and the heavy article 10 starts to move in one direction.

As the hydraulic motor 25 continuously rotates, the heavy article 10 is continuously transferred.
If the heavy load transfer device according to the present invention is detached from the rear end portion of the heavy load 10 to be transferred in accordance with the transfer of the heavy load 10, the heavy load transfer device is transferred to the lower surface of the tip portion and transferred to the target position.
Here, when the heavy object 10 that has passed the transfer point is returned in the reverse direction, the drive sprocket 28 on one end side is disengaged to idle and the driven sprocket 38 on the other end side is driven to move in the other direction. Transport to.
The four vertical adjustment jacks 14 move up and down in conjunction with each other, thereby adjusting the height of the endless track 16 and adjusting the front, rear, left, and right inclinations of the endless track 16.

  In the above-described embodiment, the heavy object 10 is moved while being placed on the endless track band 16, but a heavy load transfer device incorporating a propulsion mechanism using the endless track band 16 is shown in FIG. Similarly, two or more heavy goods transfer devices with built-in propulsion drive devices 17 are attached to both ends of the heavy load 10 downward, and the endless track 16 is brought into contact with the rail 69 to propel and drive the rail 69 as a reaction force. It can also be used such that it is continuously moved by making the heavy-duty transfer device incorporating the device 17 self-propelled.

In the above embodiment, the chains 24 are provided in two rows on the left and right sides, so that the propulsion drive devices 17 are installed on the drive sprockets 28 on both sides on one end side of the endless track band 16 respectively. Even in a row, the propulsion drive device 17 may be installed only in one of the drive sprockets 28.
When the chain 24 is in one row, the chain 24 may be provided at the center of the endless track band 16 and the load receiving members 48 may be disposed on both sides of the chain 24.

  The heavy load transfer device incorporating the propulsion mechanism according to the present invention is effective not only as a bridge girder but also as a transfer device for large buildings, ships, oil tanks, transformers, large vehicles, and other heavy loads.

DESCRIPTION OF SYMBOLS 10 ... Heavy article, 12 ... Base, 13 ... Rotating plate, 14 ... Vertical adjustment jack, 15 ... Base, 16 ... Endless track belt, 17 ... Propulsion drive device, 18 ... Sliding plate, 19 ... Sliding groove, 20 ... Cylinder, 21 ... Piston rod, 22 ... Sliding body, 23 ... Pivot, 24 ... Chain, 25 ... Hydraulic motor, 26 ... Rotary plate, 27 ... Mounting plate, 28 ... Drive sprocket, 29 ... Cylinder, 30 ... Shaft , 31 ... sliding surface, 32 ... support frame, 33 ... support frame, 34 ... vertical frame, 35 ... vertical frame, 36 ... guide plate, 37 ... guide sprocket, 38 ... driven sprocket, 39 ... shaft for driven sprocket, 40 ... support plate, 41 ... shaft, 42 ... tension jack, 43 ... cylinder, 44 ... piston, 45 ... vertical movement guide plate, 46 ... bearing cover, 47 ... chain shaft, 48 ... load receiving material, 49 ... height adjustment Board, 50 ... Gap DESCRIPTION OF SYMBOLS 51 ... Link board, 52 ... Key, 53 ... Bearing, 60 ... Heavy goods transfer apparatus, 61 ... Endless track belt, 62 ... Base, 63 ... Vertical adjustment jig, 64 ... Base, 65 ... Rotating plate, 66 ... Piston rod , 67 ... Pivot, 68 ... Oscillator, 69 ... Rail, 70 ... Jack for transfer, 71 ... Rod or rope, 72 ... Guide roller, 73 ... Guide roller.

Claims (3)

  In the heavy goods transfer device for transferring the heavy goods while receiving the load of the heavy goods or the reaction force of the heavy goods in the endless orbit bands, the endless orbit bands are elongated. A chain shaft is pivotally passed through and attached to the load receiving material of the chain, and a plurality of the chain shafts having a link plate attached to the end projecting from the load receiving material of the chain shaft are sequentially connected to the chain. There are provided a drive sprocket and a driven sprocket that mesh with the chain so as to face one end and the other end of the cradle, the drive sprocket is provided on a shaft portion, the driven sprocket is provided on a shaft, A drive sprocket propulsion drive unit and a driven sprocket propulsion drive unit comprising a hydraulic motor are provided on the cradle, and a shaft portion to which the drive sprocket is attached and a propulsion drive unit for the drive sprocket. During a heavy transport device incorporating a propulsion mechanism characterized by being connected via a clutch, respectively and between the, shaft and driven sprocket for propulsion drive fitted with the driven sprocket with.   In the heavy goods transfer device for transferring the heavy goods while receiving the load of the heavy goods or the reaction force of the heavy goods in the endless orbit bands, the endless orbit bands are elongated. A chain shaft is pivotally passed through and attached to the load receiving material of the chain, and a plurality of link shafts attached to both ends protruding from the load receiving material of the chain shaft are sequentially connected to both sides of the load receiving material. Two drive sprockets and two driven sprockets that mesh with the two rows of chains are provided so as to face one end and the other end of the cradle, and the two drive sprockets are connected to the shaft portion. The driven sprocket is provided on both sides of the shaft, the cradle is provided with a propulsion drive device for a driving sprocket and a propulsion drive device for a driven sprocket comprising a hydraulic motor, and the drive sprocket is provided. And a drive sprocket propulsion drive device, and a shaft to which the driven sprocket is attached and the driven sprocket drive device are connected via a clutch, respectively. Heavy goods transfer device with built-in propulsion mechanism.   Two driven sprockets, two driven sprockets, and two guide sprockets for driving, which are respectively engaged with two rows of chains, are provided facing one end, the other end, and the lower part of the cradle. The guide sprocket is provided integrally with the shaft, and two sets of propulsion drive devices consisting of a hydraulic motor are provided on the cradle so that it can be adjusted up and down by a tension jack, and each end of the shaft is provided on the hydraulic motor. 3. A heavy article transfer device incorporating a propulsion mechanism according to claim 2, wherein said rotating plate is fixed.

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