JP7455477B2 - Pulley device for chain lumber collection system and chain lumber collection system - Google Patents

Description

The present invention relates to a pulley device that makes it possible to partially change the chain line in a chain-type lumber collection system that collects felled trees felled in a mountain forest by towing and transporting them on the ground, and a chain lumber collection system using the same.

One of the methods for hauling and transporting felled trees using cables is to use endless chains as cables instead of the conventionally widely used method of using hollow overhead wires. A chain collection method has recently been developed in which a special hook is used to engage and hold the area near one end of a felled tree at an arbitrary position on the chain line that runs on the ground surface, and the chain line is then towed and transported over the ground surface. There is.

As described in Patent Document 1, in such a chain lumber collection method, the ground surface is formed in a straight line between the leading pile and the lumber collection site (dirt area) with a constant interval between the forward and return trips. be done.

Also, depending on the thinning situation, a chain line route may be set up that is far apart on the outbound and return trips between the leading mountain and the lumber collection site (soil yard). However, in any case, when viewed from above, the chain line between the leading mountain that pulls the felled trees and the lumber yard (soil yard) is a straight line that runs along the surface of the mountain forest.

Therefore, there are often unavoidable obstacles when traveling on the ground and towing, such as rocks, stumps, uneven ground, and ridge topography, near the straight chain line that is the towing route. . No matter how a straight route is selected from the first mountain to the dojo, it is often impossible to select a route that avoids all of the obstacles mentioned above over the entire length of the route.

As a countermeasure for such cases, the tip of the felled tree is covered with a hard plastic cap that is roughly shaped like a cannonball so that the tip of the felled tree can avoid and overcome obstacles in the direction of travel, and The tip of the chain may be moved from the obstacle position by manual work, or in some cases, the route of the chain line itself may be changed and set again to pull and slide the ground surface. The tip of the felled tree being transported is towed while avoiding the above-mentioned various ground obstacles. This is because if even the tip of the felled tree being towed is moved and conveyed along the chain line while avoiding obstacles, the other parts of the felled tree will normally follow and slide without any problems.

However, such work in forest areas with poor footing, such as on steep slopes, requires a great deal of labor and time, and greatly impairs productivity in chain lumber collection. Furthermore, if there is a ridge-like topography between the leading mountain and the lumber collecting site, it becomes even more difficult to avoid it, making it considerably difficult to apply the chain lumber collection itself.

Therefore, if such a ground surface condition is unavoidable when setting up a chain line for collecting timber, the cut trees to be pulled by a mounting wire etc. should be One effective measure is to maintain a portion of the chain line offset in the air so that one end portion is lifted into the air from the chain line running on the ground. As long as at least the tip of the cut tree being transported is held and transported floating, the other parts will follow and be transported without any problem.

As a device to hold the cable line that collects and transports such felled trees in the air, a normal wire rope is used as a towing cable, and the hanging object (fallen tree) is fixedly held by a hanging member. A pulley device is known that allows the vehicle to be transported through the vehicle while the vehicle is being moved. For example, a pulley with a pair of cantilever pulley structures facing each other with a certain gap, such as the pulley mechanism described in Patent Document 3 or the roller unit described in Patent Document 2 (see FIG. 5 of Patent Document 2, Split drum-shaped rollers 23a, 23b) in FIG. 6 are known.

JP2020-083485A Japanese Patent Application Publication No. 2010-100150 Japanese Patent Application Publication No. 2015-78064

However, when pulleys with these structures are used for rope lines that use chains, there is almost always a noticeable accumulation of rotational twist in the chain line on the upstream side of the pulley, which eventually leads to the pulling of felled trees fixed to the chain line. The hook for the tree is pulled in by the twist and twists and rotates along with the chain line, and the wire for pulling the felled tree also wraps around the chain line like a vine, resulting in the slit between the pair of cantilever pulleys being pulled in. It becomes impossible for the mounting wire to pass through.

In other words, a pair of cantilever pulley type devices used in the conventional catenary method of collecting materials using wire ropes or the like is not suitable for collecting materials using a chain line.

An object of the present invention is to maintain a part of the running chain line in the air away from the ground, and/or deflect it in the left and right direction in a system for towing and conveying felled trees on the ground surface using a running chain line. The platform cable of appropriate length that holds the felled tree and the hook that connects the platform cable to any position on the chain line can both pass without getting tangled with the chain line. The object of the present invention is to provide a pulley device and a chain lumber collection system using the same.

In order to achieve the above object, a pulley device according to the present invention is a pulley device for a chain lumber collection system, which has a pair of disc-shaped rotating bodies that are cantilevered and whose opposing surfaces face each other with a predetermined gap. One of the disc-shaped rotating bodies has a protrusion that extends beyond the gap toward the other disc-shaped rotating body, with a part of its outer circumferential surface extending, and the other disc-shaped rotating body has It is characterized by having a notch portion for accommodating the protruding portion with a predetermined gap therebetween.

Furthermore, a chain-type lumber collection system according to the present invention is characterized by having the above-mentioned pulley device.

According to the present invention, there are problems such as the presence of obstacles on the ground and unique topography that make it extremely difficult to carry out the timber collection method using an endless chain line that basically slides and pulls felled trees on the ground. In order to avoid this, it is possible to easily change the partial deviation at any position of the chain line, and the drawbacks of the chain-type lumber collection method can be solved.

FIG. 1 is an overall configuration diagram schematically showing a chain-type lumber collection system. 1 is a diagram showing how a pulley device according to an embodiment of the present invention is used as part of a chain line in a chain-type lumber collection system. FIG. 1 is a front view of an example of a pulley device according to an embodiment of the present invention. (b) is a plan view of a disc-shaped rotating body having a protruding part in a pulley mechanism consisting of a pair of disc-shaped rotating bodies in a pulley device according to an embodiment of the present invention, and (a) is a plan view of A of (b). -A sectional view, (c) is a plan view of a disc-shaped rotating body having a notch in the pulley mechanism consisting of a pair of disc-shaped rotating bodies in the pulley device according to the embodiment of the present invention, and (d) is a BB sectional view of (c). It is a figure showing the contact relationship between the running chain and the disk-shaped rotating body of the pulley in the pulley device according to the embodiment of the present invention, and (a) shows the gap (groove) 58 between the pair of disk-shaped rotating bodies. The vertical link 75A of the chain is shown in a pinched state, and (b) shows the state of contact of the chain on a protrusion that forms part of the outer circumferential surface without gaps (grooves) of the disc-shaped rotating body. FIG. 2 is a diagram schematically showing a structure of a mounting wire for towing a felled tree and a towing hook that engages and holds the mounting wire with a chain line in an embodiment of the present invention. FIG. 7 is an explanatory diagram showing the state of the towing hook and the engaged chain line in FIG. 6; FIG. 3 is a diagram showing specific dimensions of a pulley in an example. FIG. 3 is a diagram showing specific dimensions regarding a pair of vertical and horizontal links (a vertical link and a horizontal link) that are connected in large numbers as a chain constituting a chain line in an embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

(Chain wood collection system)
FIG. 1 shows an overview of the conventional chain lumber collection line shown in Patent Document 1 and is a schematic diagram related to the present embodiment, in which 14 is a loop-shaped chain line, which is placed on a dumping ground. It is endlessly driven via a chain drive device 21 (with pulleys 13A and 13B fixed to a standing tree) and pulleys 12A and 12B fixed to a standing tree at the tip of the mountain (chain line turning point).

Arrow A indicates a chain line that tows and conveys a felled tree 3 along the chain line on the ground surface via a hook 30 for towing the chain line and a mounting wire 31 (if necessary, the chain drive device is reversed). (sometimes used).

If there are unavoidably obstacles on the path along which the felled tree 3 is towed and transported, such as rocks, stumps, undulations on the ground, ridge topography, etc., when the tree is towed by traveling on the ground, the pulley of this embodiment FIG. 2 illustrates the use of the apparatus to lift and hold a chain line at least partially in the air.

The pulley device 40 of this embodiment uses a standing tree 2 to lift the original chain line from the ground surface using a sling or the like to at least the extent that the tip of the felled tree 3 to be towed can avoid obstacles on the ground surface. and is held so as to form a new chain line 14A.

In this case, depending on the position of the available standing tree 2, the length of the sling used, etc., the new chain line 14A will be partially deviated from the original chain line not only in the vertical direction but also in the horizontal direction. However, it is also possible to intentionally select a certain degree of deviation in a suitable direction as required.

Note that fixing the pulley device using a sling is also a preferable method in that the direction of the pulley automatically follows the direction of the resultant force of the tension received from the chain line.

FIG. 3 shows an example of a pulley device according to the present invention, and the pulley device 40 includes a pair of disc-shaped rotating bodies 42 and 43 supported by a cantilever on a frame 41 having a hole 59 for hanging from a tree or the like by a sling or the like. Be prepared.

In one disc-shaped rotating body 42 and the other disc-shaped rotating body 43, the opposing surfaces 53, 54 face each other with a specified gap between them, and one disc-shaped rotating body 42 has a beak-shaped protrusion 44 that extends beyond the gap toward the other disc-shaped rotating body 43 by extending a portion 52A of its outer circumferential surface 52, and the other disc-shaped rotating body 43 has a notch 48 for accommodating the protrusion 44 across a specified gap. These gaps form a passage for the wire portion of the base-mounted wire 31, one end of which is fastened to the chain line and the other end of which is used to pull felled trees, etc.

In the example shown in FIG. 3, the protrusion 44 has a protrusion outer circumferential surface 45 that is an extension of the outer circumferential surface 52A of a specific position portion of the disc-shaped rotating body 42, and a protrusion-tip tip plane that is close to the other disc-shaped rotating body 43. 47 (a surface perpendicular to the rotational axis), and an inclined surface 46 on the lower surface of the protrusion (the surface opposite to the outer circumferential surface of the protrusion) connected to the opposing surface 53. As can be seen in the figure, the slope portion 46 is formed to form an obtuse angle with the opposing surface 53. The cutout portion 48 has a slope portion 49 of the cutout portion corresponding to the slope portion 46 on the lower surface of the projection portion and a surface perpendicular to the rotation axis (notch portion) corresponding to the flat surface portion 47 of the tip end of the projection portion so as to accommodate the protrusion portion 44 . It consists of a notch (perpendicular surface) 50 and a remaining outer circumferential surface 51.

Note that the gap between the slope portions 46 and 49 of the protrusion and the notch, and the gap between the vertical surface portions 47 and 50 of the above-mentioned one disc-shaped rotating body 42 and the other disc-shaped rotating body 43, The predetermined distance between the facing surfaces 53 and 54 is usually the same, but may be set to a different value as necessary.

The respective outer peripheral parts 52 and 51 of the pair of disc-shaped rotating bodies 42 and 43 at locations other than the beak-shaped protrusion 44 and the corresponding notch 48 have diameters that are opposite to each other on both disc-shaped rotating bodies. Similarly, the outer circumferential surface consisting of the outer circumferential surface 52A of the portion continuous to the protruding portion and the outer circumferential surface 45 of the protruding portion decreases toward the position (the central portion (gap position) in the direction of the rotation axis), and the outer circumferential surface is also disc-shaped. The diameter decreases toward the center of the rotating body in the direction of the rotational axis.

In other words, as shown in FIG. 3 or FIG. 4 described later, the axial cross-sectional shape of the outer circumferential portion of the pair of disc-shaped rotating bodies is The sections 42 and 43, including the gap, have a U-shaped or drum-shaped cross section as a whole, and have a structure in which the cable running on the pulley is naturally centered.

The shapes of these disk-shaped rotating bodies will be further explained using FIGS. 4(a), (b), (c), and (d).

FIG. 4(b) is a plan view of a disc-shaped rotating body having a protrusion in the pulley mechanism consisting of a pair of disc-shaped rotating bodies in the pulley device of this embodiment, and FIG. ) is a sectional view taken along line AA. In FIGS. 4(a) and 4(b), a substantially trapezoidal region indicated by 46 represents a planar sloped surface of the lower surface of the beak-shaped protrusion 44, and a half-moon-shaped region indicated by 47 represents a beak-shaped protrusion. This is the flat end part perpendicular to the axis of rotation of the part.

FIG. 4(c) is a plan view of a disc-shaped rotating body having a notch in the pulley mechanism consisting of a pair of disc-shaped rotating bodies in the pulley device of this embodiment, and FIG. It is a BB sectional view of c). In FIGS. 4(c) and 4(d), the approximately trapezoidal area indicated by 49 represents the planar slope of the notch, and the half-moon-shaped area indicated by 50 is a plane perpendicular to the rotation axis of the notch. (vertical surface of the notch).

The protruding lower surface slope part 46 and the notch part slope part 49 are formed with a predetermined gap when the protruding parts of both disc-shaped rotating bodies and the notch parts that receive the protruding parts face each other without deviation in the circumferential direction. It is designed to be faced with

During actual use, both disc-shaped rotating bodies can rotate independently on the left and right sides, so this gap is not always constant; 49, the rotation of the protruding part is restrained by the notch part depending on the relative rotational position angle of the two, and conversely, the rotation of the notch part is restrained by the protruding part, so the protruding part side and the notch part side are mutually restrained. It cannot rotate freely independently. In the end, the sloped surfaces, that is, the protrusion and the notch rotate in the same phase while remaining substantially facing each other without being significantly deviated. In addition, when the wire portions of the mounting wire pass, they are shifted from each other and rotated, thereby providing a gap necessary for the wire to pass.

The felled tree is towed and transported by being engaged and fixed at any position on the chain line by a mounting wire 31 and a towing hook 30 attached to one end thereof.

FIG. 6 shows the construction of a mounting wire with a towing hook. 30 is a towing hook, 31 is a straight wire part of the mounting wire, 32 is an eye part, and 33 is a wire crimping sleeve. Figure 7 shows the structure of the above-mentioned towing hook 30 that can be engaged and fixed at any chain line position, and the chain. This shows the state of engagement with. 71 is a towing hole for connecting the mounting wire 31 to the towing hook 30; 72 is an opening through which the chain is passed in order to engage the chain in the through groove 73; and 75 is an opening for connecting the chain to the towing hook 30. A pair of links of the chain (vertical link 75A and horizontal link 75B shown in FIG. 9) are shown. The vertical link 75A and the horizontal link 75B form one set, and a plurality of these sets are connected to form a chain of a chain line.

As mentioned above, the above-mentioned mounting wire 31 and the towing hook 30 connected thereto are used to tow the felled tree, and the tree is placed oppositely with a certain gap as shown in Patent Document 2 and Patent Document 3. When a pulley with a pair of cantilever pulleys is used to lift a chain line, twisting of the chain accumulates immediately upstream of the pulley, and the twisting force eventually succumbs to the chain line. A phenomenon occurs in which the towing hook 30, which is engaged and fixed to the chain line, becomes entangled with the chain line together with the mounting wire 31.

As a result of detailed observation of the behavior of the pulley section when such a conventional pair of cantilever pulley type is used for lifting a part of an endless chain line or for other partial deviations, the inventor has made the following findings. I gained knowledge. That is, in an endless chain loop, it is generally observed that twist in the chain line tends to occur and accumulate each time the chain passes through the pulleys at both ends.

When a chain line having such a twist passes through a conventional pair of cantilever pulleys that rotate with a constant gap, a pair of vertical and horizontal links 75 (vertical link 75A and horizontal Only one link 75A (for example, a vertical link) in a chain line that is a series of links 75B) continuously falls into (engages with) the gap (groove) 58 and advances. Therefore, the rotation of the chain line about the chain traveling direction is restricted by the groove walls.

As a result, the twist in the chain that enters the pulley is forcibly squeezed by this groove, and the twist accumulates more and more on the upstream side of the pulley.

On the other hand, at the point on the upstream side of the pulley where the mounting wire 31 that pulls the felled tree is fixed to the chain via the towing hook 30, tension is applied to pull the felled tree (heavy object). Because of the towing hook 30, the torsion that has accumulated on the downstream side of the hook (upstream side of the pulley) cannot be relaxed and released to the upstream side beyond the fixed towing hook 30.

As a result, as the towing fixed hook 30 approaches the pulley, the torsion becomes more compressed and accumulated, and eventually, as mentioned above, when the degree of chain torsion exceeds a certain limit, the torsion suddenly returns. As the chain line rotates, the towing fixed hook and mounting wire part are dragged around by the rotation of the chain line and become wrapped around the chain.

In order to prevent this strong twisting compression accumulation from occurring, as shown in Fig. 5(b), if the (gap) groove between the pair of disc-shaped rotating bodies of the pulley is eliminated, the twisted chain line due to the groove should be removed. This eliminates the forced straining of the chain line, and prevents the chain line from accumulating and compressing the chain line toward the upstream side as described above.

In other words, if the chain, which is forcibly bound by the groove and has accumulated twist, is temporarily released by the protrusion 44, it is prevented from being strongly accumulated and compressed to the point that it exceeds its limit.

That is, in this embodiment, the pulley device is used in a chain-type lumber collection system that collects felled trees felled in mountain forests by towing and conveying them on the ground, and is a pulley device that makes it possible to partially change the chain line, and is linked to the chain. A first state in which a part (vertical link 75A) of the link members (vertical link 75A and horizontal link 75B) engages with the gap, and a second state in which the vertical link 75A and horizontal link 75B do not engage with the gap. A state is periodically formed by the rotation of a pair of disk-shaped rotating bodies (a first time period, which is a first state, and a second time period, which is a second state, occur alternately).

As described above, in the pulley device of this embodiment, the protrusion provided on one of the disc-shaped rotating bodies has a structure in which there is no gap (groove) periodically with respect to the chain running according to the rotation of the protrusion. As shown in FIG. 5(b), each time the chain link is freed from the constraint of the groove, the twist is released and returned, and the towing hook 30 and the mounting wire 31 that follow it are released. Accumulation of strong torsion that would cause the chain line 14A to wrap around the chain line 14A is prevented from occurring.

Actually, using the pulley device of this embodiment, the chain line was lifted as shown in FIG. 2, and the chain line was lifted as shown in FIG. The felled tree was towed and transported by the chain line 14A. As a result, strong twisting that would cause the part of the mounting wire that is pulling the felled tree to wrap around the chain will not accumulate on the upstream side just before the pulley, and the chain line 14A will no longer be twisted around the outer periphery of the disc-shaped rotating body of the pulley device. The straight wire portion of the mounting wire 31 that travels through the towing hook 30 together with the towing hook 30, and then pulls up and tows the tip of the felled tree, passes through the gap between the opposing surfaces 53 and 54 of the pair of disc-shaped rotating bodies, Next, the felled tree passes through the gap between the protrusion 44 and the notch 48 on the slopes 46 and 49, and passes through the installation position of the pulley device 40 with the tip raised above the ground, that is, various obstacles on the ground. The material was towed and collected while avoiding obstacles.

From the above observation, the protrusions extending from one side to the other across the gap between the disc-shaped rotating bodies periodically release the restraint of the longitudinal links of the chain by the grooves and cause strong twisting of the chain. It is thought that it provides a function that allows the animal to return to its natural state without being restrained.

There are no particular restrictions on the structure or size of the protrusion 44 and the corresponding notch 48 as long as they can withstand the load from the chain and allow the mounting wire 31 to pass through smoothly. The gap between the pair of disc-shaped rotating bodies for the wire to pass through is, of course, large enough that the chain line 14A and the hook 30 cannot pass therethrough, and that the mounting wire 31 can pass therethrough.

Furthermore, as shown in Fig. 5(b), in order to make it easier for the chain to release its twist, the outer circumferential surface that receives the chain on the upper side of the protrusion may be U-shaped or a drum-shaped bottom that is close to a flat surface. desirable.

(Example 1)
An example in which the pulley device of this embodiment was used to tow and transport a felled tree will be described below. A pulley device 40 was installed in a part of a linear chain line placed on a slope in a forest in the manner shown in FIG. 2. The chain was passed through the pulley device 40 by loosening the fastening nut on the top of the frame and opening it left and right.

Of course, depending on the case, it is also possible to cut off a part of the chain, pass it through the pulley section, and then reconnect the chain. The specific dimensions (see FIG. 8) and other conditions of the pulley device 40 used in this example are as follows.

Dimensions of pulley device 40:
Diameter of disc-shaped rotating body: maximum outer circumference diameter is 163 mm, minimum diameter excluding protrusion 44 and notch 48 is 108 mm,
Thickness of disc-shaped rotating body: 34mm.

Gap between the opposing surfaces of both rotating bodies: 12 mm, the gap between the protrusion 44 and the notch 48 is also the same (both between the slope parts and the vertical face parts are 12 mm)
The proportion of the protrusion 44 in the outer periphery is approximately 60°, which corresponds to the center of the gap between the two rotating bodies.

Height from the ground of the pulley device 40 fixedly held on a standing tree with a sling: 1 to 2 m
Mounting wire 31 used: Wire diameter 8-10mm, wire length 2m,
External dimensions of the towing hook 30 tied to one end of the mounting wire 31: 140 mm (length), 50 mm (width), 16 mm (thickness)
Conditions of chain line 14A used:
Chain type: Link chain Dimensions (see Figure 9)
Wire diameter d = 7.1mm Width b = 23.2mm or less Pitch p = 20.2mm
Chain line length between Sakiyama and Doba: Approximately 60 m (Pulley device 40 of this embodiment is installed along the way)
Chain running speed: 35-40m/min
Chain traction force: 2 tons
Towed felled tree: Weight approx. 1 ton, length approx. 30 m
The mountain forest area where chain towing is performed is an uphill slope of approximately 30 degrees.Under the above conditions, an attempt was made to pass the pulley device 40 of the towing hook 30 and platform wire 31 that were towing and transporting the felled tree. As a result, the towing hook 30 in front of the pulley device 40 and the subsequent mounting wire 31 do not become entangled with the chain line 14A, and the chain line 14A moves on the outer periphery of the rotating body of the pulley device 40 to the towing hook 30. The straight wire portion of the mounting wire 31 that is pulling up and pulling the tip of the felled tree passes through the gap between the opposing surfaces 53 and 54 of the pair of disc-shaped rotating bodies and the protrusion 44. The felled tree passes through the gap between the slopes 46 and 49 between the cutout and the notch 48, and the gap between the flat end of the protrusion 47 and the vertical face of the cutout 50, with the tip of the felled tree raised above the ground. In this state, the wood passed through the installation position of the pulley device 40, that is, was towed and conveyed while avoiding various obstacles on the ground surface, and was collected.

(Modified example)
Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention.

For example, in the embodiment described above, the chain line is lifted and maintained in the hollow using a single pulley device, but the chain line can be shifted not only in the vertical direction but also in the left and right horizontal directions as necessary. It is clear that it can be used for

In addition, in the case of topography where there is a large ridge between the leading mountain and the land where timber is collected, the ground surface changes from an uphill slope to a downhill slope. This is basically impossible as the material will be pushed against the surface of the chain line itself. In this case, by appropriately installing and using the pulley device according to the present invention in a plurality of positions, it becomes possible to maintain the chain line completely floating from the ridgeline, and it is possible to maintain the chain line in such a terrain. Materials can be easily made available.

2 Standing tree 3 Felled tree 14 Chain line 14A Lifted chain line 21 Chain drive device 30 Towing hook 31 Mounting wire 32 Eye of mounting wire 33 Wire crimping sleeve 40 Pulley device 41 Frame 42 of pulley device Disc with protrusion Rotating body 43 Disc-shaped rotating body 44 having a notch Protruding part 45 Outer circumferential surface of the protruding part 46 Slanted surface of the lower surface of the protruding part 47 Flat end of the protruding part 48 Notch part 49 Slanted part of the notched part 50 Vertical part of the notched part Surface 51 Outer circumferential surface 51A of the disc-shaped rotating body having a notch portion Remaining part of the outer circumferential surface of the notch portion 52 Outer circumferential surface 52A of the disc-shaped rotating body having a protrusion portion Outer circumferential surface 53 of a portion continuous to the protrusion portion Outer peripheral surface 51A of the disc-shaped rotating body having a protrusion portion Opposing surface 54 Opposing surface 58 of a disc-shaped rotating body having a notch portion Gap (groove) between a pair of disc-shaped rotating bodies
59 Hanging hole 71 Towing hole 72 Opening 73 Through hole 75 Vertical and horizontal pair of links 75A Chain vertical link 75B Chain horizontal link

Claims (5)

A pulley device for a chain lumber collection system having a pair of disk-shaped rotating bodies that are cantilever-supported with opposing surfaces facing each other with a predetermined gap, one of the disk-shaped rotating bodies being a part of its outer peripheral surface. has a protrusion extending beyond the gap toward the other disc-shaped rotating body, and the other disc-shaped rotating body has a cutout for accommodating the protrusion with a predetermined gap therebetween. A pulley device characterized by having a notch. The pulley device according to claim 1, wherein the lower surface of the protrusion of the one disc-shaped rotating body has an inclined surface whose cross section from the tip of the protrusion toward a position near the rotational axis of the opposing surface is flat. . In one of the disk-shaped rotating bodies, the diameter of the outer circumference at the location where the protrusion is located and the diameter of the outer circumference at a location other than the location where the protrusion is located are at the center of both disc-shaped rotating bodies in the direction of the rotational axis. decreases towards the
2. The diameter of the outer circumferential portion of the other disc-shaped rotating body at a location other than the notch portion decreases toward the center in the rotational axis direction of both disc-shaped rotating bodies. 2. The pulley device according to 2. A pulley device that is used in a chain-type lumber collection system that collects felled trees in mountain forests by towing and transporting them on the ground, and allows the chain line to be partially changed,
In the chain line which is a series of a pair of vertical and horizontal links, a first state in which the vertical link of the vertical and horizontal links constituting the pair of vertical and horizontal links engages with the gap; The pulley according to any one of claims 1 to 3, wherein the second state in which the horizontal link does not engage with the gap is periodically formed by rotation of the pair of disc-shaped rotating bodies. Device. A pulley device according to any one of claims 1 to 4, which makes it possible to partially change a chain line in a chain-type timber collection system that collects felled trees felled in a mountain forest by towing and transporting them on the ground. A chain-type lumber collection system characterized by having a pulley device.

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