JPH08116755A - Power transmission mechanism - Google Patents

Abstract

PURPOSE: To provide a mechanism enabling smooth transmission of the power from an engine to two rotary blades, etc. CONSTITUTION: This power transmission mechanism is composed of a 1st belt 21 loosely stretched between a 1st pulley 20 for a 1st rotary blade and a driving pulley 19, a 1st tension roller 22, a 2nd pulley 27 for the 1st rotary blade interlocked with the 1st pulley 20 for the 1st rotary blade, a pulley 28 for a 2nd rotary blade, a 2nd belt 29 loosely stretched between the pulley 28 for the 2nd rotary blade and the 2nd pulley 27 for the 1st rotary blade, a 2nd tension roller 48, an action lever 61 tiltably supported on a machine body and a spring 64 placed between the action lever 61 and the 1st tension roller 22 and transmitting the tilting force of the action lever 61 as a pressing force of the 1st tension roller 22 against the 1st belt 21 until the tension of the 1st belt 21 reaches a prescribed level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission mechanism suitable for use in a mower equipped with two rotary blades as a rotary working member.

[0002]

2. Description of the Related Art For example, there is known a mower of a type in which a main rotary blade and a sub rotary blade are provided on the left and right as rotary working members, and both rotary blades are operated by the power of a prime mover mounted therein.

In such a mower, transmission of power to the main rotary blade and the sub rotary blade has been performed as follows, for example.

A prime mover pulley is fixed to the output shaft of the prime mover. The first rotary blade first pulley and the main rotary blade second pulley are coaxially fixed to the rotary shaft of the main rotary blade. A sub rotary blade pulley is fixedly attached to the rotary shaft of the sub rotary blade.

A first belt is loosely wound between the driving pulley and the first rotary blade first pulley. A second belt is loosely wound between the main rotary blade second pulley and the sub rotary blade pulley.

A first tension roller is displaceably provided near the first belt. The first tension roller performs a pressure contact operation with the first belt and a separation operation from the first belt. These displacement operations are performed by operating an operation lever provided near the handle of the mower. The first tension roller controls the power transmission from the prime mover to the main rotary blade by controlling the tension of the first belt.

A second tension roller is provided near the second belt. The second tension roller is constantly pressed against the second belt by a spring. The second tension roller constantly applies a predetermined tension to the second belt to keep the main rotary blade and the sub rotary blade connected in operation.

The above-described power transmission mechanism is disclosed, for example, in JP-A-5-30837, column 3, line 24 to line 4.
1 line, column 5, line 22 to line 36, and FIGS. 3 and 4.

The conventional power transmission mechanism operates as follows. When it is desired to transmit the power of the prime mover to the rotary blades, the operation lever is operated to bring the first tension roller into pressure contact with the first belt and apply tension to the first belt. When a predetermined tension is applied to the first belt, the driving pulley and the main rotary blade first pulley are operatively connected and power is transmitted.

On the other hand, the main rotary blade second pulley and the sub rotary blade pulley are operatively always connected by the second belt and the second tension roller.
Therefore, the power of the prime mover is also transmitted to the sub rotary blade via the main rotary blade, and the sub rotary blade is started at the same time when the main rotary blade is started.

By operating the second tension roller, the rotation of the auxiliary rotary blade can be controlled to be turned on and off as required.

[0012]

According to the conventional power transmission mechanism, when the operation lever is operated to apply tension to the first belt, the main rotary blade and the sub rotary blade are simultaneously moved. Operationally connected to the prime mover. For this reason,
In addition to a sudden load being applied to the prime mover, an excessive load was also applied to the rotary shaft of each rotary blade. Further, the impact at the time of starting the both rotary blades was also large.

In order to withstand such a large shock at the time of starting, it is possible to mount a high-power prime mover and adopt means such as enlarging the diameter of each of the rotary shafts. In this case, the mower becomes heavy and the operability deteriorates, and the cost increases.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a power transmission mechanism which is capable of smoothly transmitting power from a prime mover to two rotary working members and which is suitable for use in a mower, a floor polisher or the like.

[0015]

In order to solve the above-mentioned problems, a power transmission mechanism of a mower according to the present invention is operatively connected to a driving pulley and a first rotary working member. And a first belt for the first rotating work member, a first belt loosely wound between the first pulley for the first rotating work member and the driving pulley, and pressed against the first belt. And a first tension roller displaceable in a direction in which the tension is applied and a direction in which the tension is released, and a first rotary working member first roller operatively connected to the first rotary working member first pulley. Two pulleys, a second rotary working member pulley operatively connected to the second rotary working member, and between the second rotary working member pulley and the first rotary working member second pulley. The second belt loosely wrapped around the A second tension roller that is displaceable in a direction in which the tension is applied by pressing it against the belt and a direction in which the tension is released, an operating lever rotatably supported by the machine body, the operating lever and the first tension. A spring body which is provided between the first belt and the roller and transmits the rotational force of the operating lever as a pressure contact force of the first tension roller to the first belt until the first belt has a predetermined tension; The operating lever and the second tension roller are associated with each other so that the second tension roller comes into pressure contact with the second belt after the first belt has a predetermined tension. It is characterized by

The above-mentioned relationship between the operating lever and the second tension roller is rotatably supported by the machine body, has the second tension roller at one end thereof, and has the other end contacting the operating lever. It is preferable to perform it through a second tension roller arm that is rotated in contact therewith.

[0017]

According to the present invention, when the prime mover operates, the prime mover pulley rotates. The rotation of the driving pulley is not immediately transmitted to the first rotary working member and the second rotary working member. That is, between the drive pulley and the first rotary work member first pulley, and between the first rotary work member second pulley and the second rotary work member pulley, the loose first and This is because they are linked by the second belt.

When the actuating lever is rotated to transmit power to each of the rotary working members, first, the turning force of the actuating lever displaces the first tension roller via the spring body. Then, the first tension roller comes into pressure contact with the first belt, the first belt has a predetermined tension suitable for power transmission, and the first rotating work member starts to rotate.

After the first rotating work member starts to rotate, when the actuating lever is further swung in the same direction, the second tension roller comes into pressure contact with the second belt, and the second tension roller comes into contact with the second belt. A predetermined tension suitable for power transmission is applied to the belt. As a result, the second rotary working member also starts to rotate.

After the first belt has a predetermined tension due to the action of the spring body, even if the operating lever is further rotated, the first tension with respect to the first belt is increased. The pressure contact force of the roller does not become excessive. Therefore, in order to start the second rotating work member as well, even if the actuating lever is rotated further largely after the first rotating work member starts to rotate, the first belt is stretched. There is no inconvenience caused.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power transmission mechanism according to an embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, reference numeral 13 (13a, 13b)
FIG. 4 shows a body of a mower equipped with a power transmission mechanism according to an embodiment of the present invention.

The machine body 13 carries a prime mover 1 such as an air-cooled two-cycle gasoline engine. The body 13
Has a guide wheel 2 at the front and a drive rear wheel 3 at the rear.
have. The driving rear wheel 3 is given a driving force by the prime mover 1. At the rear of the fuselage 13,
It has an operation handle 4 extending in a bifurcated manner obliquely rearward and upward.

Between the guide wheel 2 and the drive rear wheel 3, there are provided a flat cutting blade 5 as a first rotary working member and a slope cutting blade 6 as a second rotary working member. There is. These cutting blades 5 and 6 are rotated by the prime mover 1.

The slope cutting blade 6 is located diagonally rearward of the plane cutting blade 5 (in the illustrated example, diagonally leftward rearward as shown in FIG. 7). The plane cutting blade 5 and the slope cutting blade 6 are
They overlap each other in the left-right direction by a predetermined width X. The slope cutting blade 6 part includes a support shaft 26 extending in the front-rear direction.
The outer side portion is tilted in the vertical direction as shown in FIG.

The driving of the driving rear wheel 3 will be described with reference to FIG. The prime mover 1 is arranged with its output shaft 1a facing downward. A wheel drive pulley 7 is fixed to the output shaft 1a. On the other hand, a transmission pulley 8 is arranged near the drive rear wheel 3 with its support shaft oriented in the vertical direction. The transmission pulley 8 is drivingly connected to the drive rear wheel 3 via a speed reducer 10. A wheel drive belt 9 is loosely wound between the transmission pulley 8 and the wheel drive pulley 7.

In FIG. 7, reference numeral 11 is a traveling clutch. The traveling clutch 11 includes a swing lever 14. The swing lever 14 is pivotally fixed to the machine body 13 by a pin 12 at its base end. Links 16 and 17 are connected to the base end side of the swing lever 14. The link 17 is operatively connected to a traveling clutch lever 18 attached to the operation handle 4.

On the other hand, a tension roller 15 is provided at the swing end of the swing lever 14 so as to press the wheel drive belt 9 and apply a predetermined tension thereto.

In the above construction, when the traveling clutch lever 18 is not pulled, the wheel drive belt 9 is loose. Therefore, even when the prime mover 1 is started, the wheel drive pulley 7 is rotated. It is not transmitted to the transmission pulley 8. On the other hand, when the traveling clutch lever 18 is pulled after the start of the prime mover 1, the link 1
The tension roller 15 is brought into pressure contact with the wheel drive belt 9 via 7, 16 and the swing lever 14. As a result, a predetermined tension is applied to the wheel drive belt 9, and the wheel drive pulley 7 and the transmission pulley 8 are operatively connected. As a result, the drive rear wheels 3 are rotationally driven through the speed reducer 10 so as to advance the machine body 13.

Next, a power transmission mechanism from the prime mover 1 to the plane cutting blade 5 and the slope cutting blade 6 will be described.

As shown in FIGS. 1 and 7, a cutting blade drive pulley 19 is fixed to the output shaft 1a of the prime mover 1 as a drive pulley. On the other hand, a first pulley 20 for a flat cutting blade is fixed to a rotary shaft 5a of the flat cutting blade 5. A first V belt 21 for driving the cutting blade is provided between the first pulley 20 for the flat cutting blade and the cutting blade driving pulley 19.
(A flat belt is shown for simplification of the drawing.) It is loosely wrapped around.

A rotatable first tension roller 22 is arranged outside the first belt 21. The first tension roller 22 is used for the first belt 2
It can be displaced in a direction in which it is pressed against 1 to give a predetermined tension and a direction in which the tension is released.

A second pulley 27 for a flat cutting blade is fixed to the rotary shaft 5a of the flat cutting blade 5. A sloped cutting blade pulley 28 is provided on the side (on the left side in the illustrated example) of the second planar cutting blade pulley 27. The slope cutting blade pulley 28 is attached to the machine body 13 with its rotating shaft 28a oriented vertically.

A second V-belt 29 for driving the cutting blade (illustrated as a flat belt for simplification of the drawing) is provided between the second pulley 27 for the flat cutting blade and the pulley 28 for the slope cutting blade. .) Is loosely wrapped around. This second belt 2
On the outside of 9, the second tension roller 48 which is rotatable
Is arranged. This second tension roller 48
Are displaceable in a direction in which the second belt 29 is brought into pressure contact with the second belt 29 to apply tension and a direction in which the tension is released.

As shown in FIG. 7, a drive bevel gear 30 is fixed to the rotary shaft 28a of the slope cutting blade pulley 28. A driven bevel gear 32 fixed to the front end of the transmission shaft 31 meshes with the drive bevel gear 30. The transmission shaft 31 is horizontally supported along the machine body 13 in the front-rear direction. An intermediate drive timing pulley 33 is provided at the rear end of the transmission shaft 31.

A movable rod 34 having a rectangular tube shape is attached to the machine body 13 in the left-right direction. This movable rod 34
Inside the base end of the
3 are accommodated. The movable rod 34 extends forward of the slope cutting blade 6. The movable rod 34 is configured such that an outer end side of the movable rod 34 can be vertically swung about the intermediate drive timing pulley 33 (see FIG. 6).

An intermediate driven timing pulley 35 having a support shaft in the front-rear direction is housed inside the swinging end (outer end) of the movable rod 34. A timing belt 36 is wound around the intermediate driven timing pulley 35 and the intermediate drive timing pulley 33.

A connecting rod 37 in the shape of a rectangular tube extending inward is connected to the outer end of the movable rod 34. Inside the outer end of the connecting rod 37, the drive timing pulley 3
8 are accommodated. This drive timing pulley 38
Is provided coaxially with the intermediate driven timing pulley 35. The connecting rod 37 is configured such that an inner end side of the connecting rod 37 can swing freely up and down about a support shaft of the drive timing pulley 38.

A driven timing pulley 39 having a front-rear rotating shaft 42 is housed inside the swinging end (inner end) of the connecting rod 37. A timing belt 40 is wound around the driven timing pulley 39 and the drive timing pulley 38.

The rotary shaft 42 of the driven timing pulley 39 extends rearward from the swinging end of the connecting rod 37. A drive bevel gear 43 is fixed to the rear end of the rotary shaft 42. This bevel gear 43
The driven bevel gear 44 fixed to the upper end of the rotary shaft 6a of the slope cutting blade 6 meshes with the driven bevel gear 44.

In FIG. 7, 41 is a cover for covering the slope cutting blade 6 from above.

Reference numeral 45 is a support rod for adjusting and maintaining the inclined state of the slope cutting blade 6. The support rod 45 is attached to the machine body 13 so that an outer end portion of the support rod 45 can swing up and down. The outer end portion of the support rod 45 is pivotally supported by the cover 41. At the inner end of the support rod 45,
An appropriate number of adjustment holes are provided on the arc. The support rod 4
5 is an adjustment hole for maintaining the required inclination,
The pin 46 provided on the 3 side is inserted and fixed.

Reference numeral 47 is a gripping rod for assisting the operation of vertically moving the slope cutting blade 6 when adjusting the inclination state of the slope cutting blade 6.

Next, an embodiment of the power transmission mechanism according to the present invention will be described with reference to FIGS. 1 to 4.

The machine body 13a includes a vertical support shaft 60.
The actuating lever 61 is rotatably attached by. The actuating lever 61 is for operating the first tension roller 22 so as to come into pressure contact with the outer peripheral surface of the first belt 21.

A torsion coil spring-shaped spring body 64 is provided between the operating lever 61 and the first tension roller 22. The spring body 64 acts to transmit the turning force of the actuating lever 61 as a pressure contact force of the first tension roller 22 to the first belt 21.

The spring force of the spring body 64 is set so that the turning force of the operating lever 61 is applied to the first belt 21 until the first belt 21 has a predetermined tension suitable for power transmission. The pressure is transmitted as the pressure contact force of the first tension roller 22, but when the tension of the first belt 21 reaches a predetermined level, the force is not further transmitted.

In the illustrated example, a first tension roller arm 62 is rotatably attached to the support shaft 60 of the operating lever 61 at the base end side thereof. On the tip side of the first tension roller arm 62,
The first tension roller 22 is rotatably provided by a vertical support shaft 63.

The first tension roller arm 62.
As the spring body 64, a torsion coil spring 64 for urging them in directions opposite to each other is provided between and the operating lever 61. In the coil spring 64, the first tension roller 22 is used for the first belt 21.
The first tension roller arm 62 is constantly urged in a direction in which the first tension roller arm 62 is pressed against and applied with tension. The coil spring 64 has its winding start end 64a hooked on the first tension roller arm 62, and its winding end 6
4b is hooked on the operating lever 61, and is provided around the support shaft 60 of the operating lever 61.

The first tension roller arm 62.
Has integrally an extending portion 65 extending upward toward the operating lever 61 side. The first tension roller arm 62 and the operating lever 61 are urged in the opposite rotational directions by the coil spring 64, and the extension portion 65 and the swinging end 61a side of the operating lever 61 are normally in contact with each other. Are integrated with each other by abutting each other.

A front end portion 25 of an operating push-pull cable 25 is provided on the operating end 61b side of the operating lever 61.
a is connected. The operating cable 25 extends rearward of the machine body 13, and a cutting blade clutch lever 24 is connected to a rear end portion 25b of the operating cable 25. The cutting blade clutch lever 24 is swingable in the front-rear direction along the lever guide groove 24d of the lever guide 24c attached to the operation handle 4.

The lever guide 24c is formed with a first stage locking portion 24a and a second stage locking portion 24b. The clutch lever 24 has the locking portions 24a, 24
It is locked by b and stopped.

In the structure as described above, the prime mover 1
When the clutch lever 24 is pulled to stop the first-stage locking portion 24a, the operating cable 25 is pulled rearward, and the operating end 61b side of the operating lever 61 is pulled rearward. Get burned. Then, the operating lever 61 rotates around the support shaft 60, and the swing end 61a side thereof rotates forward. The operating lever 61
Of the swing end 61a is transmitted to the first tension roller arm 62 via the coil spring 64, and the first tension roller 22 is pressed against the outer peripheral surface of the first belt 21. Be punished.

As a result, a predetermined tension suitable for power transmission is applied to the first belt 21, and the cutting blade drive pulley 19 and the flat surface cutting blade first pulley 20 are operatively connected. When the first plane cutting blade pulley 20 rotates, the plane cutting blade 5 rotates via the rotation shaft 5a.

In the present embodiment, the clutch lever 24 is further pulled from the first-step engaging portion 24a and moved to the second-step engaging portion 24b, so that the above-mentioned method in addition to the flat cutting blade 5 can be achieved. The chamfering blade 6 also starts to rotate.

That is, near the operating lever 61,
By the vertical support shaft 66 fixed to the machine body 13b,
The second tension roller arm 67 is rotatably supported. This second tension roller arm 67
As shown in FIG. 4, are arranged so that the vertical position thereof is offset from the operating lever 61. The second tension roller 48 is rotatably attached to the swing end 67a side of the second tension roller arm 67 by a vertical support shaft 68.

On the operating end 61b side of the operating lever 61, an extending portion 69 extending upward toward the second tension roller arm 67 side is bent and formed at a right angle. The extension portion 69 has a predetermined tension suitable for power transmission to the first belt 21 due to the pressure contact of the first tension roller 22 when the operation lever 61 rotates counterclockwise as viewed in FIG. Is abutted against the operation end 67b side of the second tension roller arm 67. The extending portion 69 causes the turning force of the operating lever 61 to be applied to the second tension roller arm 6
7 to rotate the arm 67.

In the above structure, when the clutch lever 24 is further pulled and moved from the first-step engaging portion 24a to the second-step engaging portion 24b, the actuating lever 61 rotates further. . However, since the magnitude of the spring force of the coil spring 64 is as described above, the pressure contact force of the first tension roller 22 with respect to the first belt 21 does not change significantly. That is,
The degree of tension of the first belt 21 does not change, and the transmission of power to the flat blade 5 is not hindered.

When the actuating lever 61 is further rotated by moving the clutch lever 24 from the first-stage engaging portion 24a to the second-stage engaging portion 24b, the extension of the operating lever 61 is increased. The projecting portion 69 is the operation end 67b of the second tension roller arm 67.
They rotate together while contacting the side. That is,
The turning force of the operating lever 61 is transmitted to the second tension roller arm 67 via the extending portion 69, and the arm 67 is rotated in the same direction as the operating lever 61. As a result, the second tension roller 4
8 comes into pressure contact with the outer peripheral surface of the second belt 29, and the second belt 29 has a predetermined tension suitable for power transmission.

When a predetermined tension suitable for power transmission is applied to the second belt 29 as described above, the second plane cutting blade pulley 27 and the slope cutting blade pulley 28 operate. The upper is connected. Therefore, the power of the prime mover 1 is transmitted to the slope cutting blade pulley 28 via the rotary shaft 5 a of the plane cutting blade 5.

When the pulley 28 for the slope cutting blade rotates,
Drive bevel gear 30, driven bevel gear 32, transmission shaft 31, intermediate drive timing pulley 33, timing belt 36, intermediate driven timing pulley 35, drive timing pulley 38, timing belt 40, driven timing pulley 39, rotary shaft 42, drive bevel gear in order. 43, the rotational power is transmitted to the driven bevel gear 44, and the slope cutting blade 6 is rotated in the same direction as the plane cutting blade 5.

When the clutch lever 24 is removed from the second-stage locking portion 24b and returned to the first-stage locking portion 24a, the operating end 61b of the operating lever 61 is moved through the forward movement of the operating cable 25. The side is pushed back forward, and first, the second tension pulley arm 67 is released. For this reason, the pressure contact force of the second tension roller 48 against the second belt 29 is lost, and the power transmission from the second plane cutting blade pulley 27 to the slope cutting blade pulley 28 is cut off. .

Next, when the clutch lever 24 is disengaged from the first-step engaging portion 24a and returned to the front, the swinging end 61a side of the operating lever 61 extends toward the extending portion 65 of the first tension roller arm 62. And the first tension roller arm 62 is returned and rotated in a direction in which the first tension roller 22 separates from the first belt 21. As a result, the pressure contact force of the first tension roller 22 with respect to the first belt 21 is lost, and the power transmission from the driving pulley 19 to the first plane cutting blade first pulley is also cut off.

In the figure, 50 is an engine throttle lever, 51 is a recoil starter, and 52 is an auxiliary wheel provided on the slope cutting blade 6 part.

As described above, according to the power transmission mechanism of this embodiment, the power of the prime mover 1 is smoothly transmitted to the plane cutting blade 5 and the slope cutting blade 6 with a time difference.
Therefore, there is no sudden load on the prime mover 1,
Excessive load is not applied to various rotary shafts, and the impact when starting the cutting blade is small.

Further, since the power transmission switching operation from the prime mover 1 to the plane cutting blade 5 and the slope cutting blade 6 can be operated by one clutch lever 24, workability is good.

Further, by stopping the clutch lever 24 in the first-stage engaging portion 24a, it is possible to operate only the plane cutting blade 5 to perform mowing work.

[0068]

According to the present invention, the power of the prime mover can be sequentially transmitted from the first rotary working member to the second rotary working member with a time difference. Therefore, it is possible to prevent a sudden load from being applied to the prime mover at the time of starting, and it is possible to smoothly transmit power.

If necessary, only one rotary working member can be used.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a main part of an embodiment of the present invention.

FIG. 2 is a perspective view showing a relationship between an operating lever and a first tension roller.

FIG. 3 is a perspective view showing a relationship between an operating lever and a second tension roller.

FIG. 4 is a vertical cross-sectional side view of essential parts showing a vertical positional relationship among an operating lever, a first tension roller arm, and a second tension roller arm.

FIG. 5 is a perspective view of a mower equipped with a power transmission mechanism according to an embodiment of the present invention.

6 is a front view of the mower of FIG.

FIG. 7 is a schematic plan view showing a drive system of the mower of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Prime mover 5 1st rotary working member 6 2nd rotary working member 13a, 13b Machine body 19 Driving pulley 20 1st rotary working member 1st pulley 21 1st belt 22 1st tension roller 27 1st rotation Working member second pulley 28 Second rotating working member pulley 29 Second belt 48 Second tension roller 61 Actuating lever 64 Spring body 67 Second tension roller arm 67a One end of second tension roller arm 67b The other end of the second tension roller arm

Claims (2)

[Claims] 1. A prime mover pulley (19) operatively connected to a prime mover (1) and a first rotary working member first pulley (20) operatively connected to a first rotary working member (5). When,
A first belt (21) loosely wound between the first pulley (20) for the first rotary working member and the driving pulley (19) and pressed against the first belt (21). And a first tension roller (22) which is displaceable in a direction in which the tension is applied and a direction in which the tension is released, and a first tension roller (22) operatively connected to the first pulley (20) for the first rotary working member. A second rotary working member pulley (27), a second rotary working member pulley (28) operatively connected to the second rotary working member (6), and a second rotary working member pulley ( 28) and the second pulley for the first rotary working member (2)
Second belt (29) loosely wrapped between 7)
And a second tension roller (48) which is displaceable in a direction in which the second belt (29) is pressed to apply tension and a direction in which the tension is released, and is rotatably supported by the machine body (13a). The operating lever (61) is provided between the operating lever (61) and the first tension roller (22) until the first belt (21) has a predetermined tension. A spring body (64) for transmitting the turning force of the operating lever (61) as a pressure contact force of the first tension roller (22) to the first belt (21).
And the second tension roller (4) after the first belt (21) has a predetermined tension.
8) so that the actuating lever (61) and the second tension roller (4) are pressed against the second belt (29).
8) A power transmission mechanism characterized by being associated with 2. A body (13b) is rotatably supported and has the second tension roller (48) at one end (67a) side thereof, and the other end (67b) side contacts the operating lever (61). A second tension roller arm (67) that is rotated by contact is provided.
7) allows the first belt (21) to have a predetermined tension, and then the second tension roller (4).
2. The actuating lever (61) and the second tension roller (48) are associated with each other such that 8) presses against the second belt (29). Power transmission mechanism.