JPH09315780A - Towing winch - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a towing winch capable of absorbing tension fluctuation at the time of towing without using a towing rope. A store winch (2) for winding a towing rope (5) through a traction winch (3) is provided, and a drive circuit for hydraulic motors (10, 11) of the traction winch (3) has a hydraulic pump via hydraulic switching valves (41, 46). The high pressure from 31 is selectively supplied. The towing tension of the rope 5 can be changed when the accumulators 32 to 34 are connected to the hydraulic motor drive circuit so that the pressures from the accumulators 32 to 34 having different set pressures are guided. Control to a predetermined value.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a winch for towing a ship.

[0002]

2. Description of the Related Art When a large vessel or the like is towed by a tugboat or the like, the relative position and speed of both vessels fluctuate, and the tension of the towing rope also greatly fluctuates, especially in stormy weather. Normally, wire ropes are used to tow large vessels,
Keep a distance of 0-500 meters. Due to fluctuations in tension, the wire rope stretches at a maximum of approximately 1%, so 40
A wire rope of 0-500 meters will stretch 4-5 meters. Also, depending on the weight of the wire rope,
Since the suspension curve is drawn and loosened, when the tension increases, the margin due to this suspension curve is added to the elongation of the wire rope, and these absorb the tension fluctuations and avoid breakage or impact of the wire rope.

When the sea is not in the stormy weather, a nylon rope may be towed instead of the wire rope. Nylon rope has greater elongation than wire rope,
~ 20% can be expected. However, due to its light weight, there is little margin due to the suspension curve, and tension fluctuations are absorbed exclusively by elongation.

[0004]

However, although the wire rope is usually paid out by a winch, it is heavy and hard, and its handling is very difficult. On the other hand, lightweight nylon ropes are much easier to handle, but due to aging, the elongation is reduced and the breaking load is also reduced. For this reason, there is a dislike of lack of reliability.

It is an object of the present invention to provide a towing winch capable of absorbing tension fluctuations during towing, regardless of the towing rope.

[0006]

A first invention provides a store winch for winding a towing rope through a traction winch, and two traction drums in which the traction winch is rotated by at least two hydraulic motors. The rope wound between these traction drums is configured to be wound on a store winch, and a high pressure from a hydraulic pump is selectively supplied to a drive circuit of the hydraulic motor via a hydraulic switching valve. On the other hand, it is configured to be switchable so that pressures from a plurality of accumulators with different set pressures are guided, and when the accumulator is connected to the hydraulic motor drive circuit, the towing tension of the rope is set to a predetermined value. I tried to control it.

According to a second aspect of the present invention, for the plurality of accumulators having different set pressures, a circuit for supplying hydraulic pressure from a high pressure circuit is provided with an electromagnetic proportional relief valve so that the accumulator supply pressure can be changed.

According to a third aspect of the present invention, one of the hydraulic motors is a high speed motor and the other is a low speed motor, and is selectively rotatably driven via the hydraulic pressure switching valve when winding and winding the rope. .

[0009]

In the first aspect of the present invention, during towing, the rotational force corresponding to the set pressure of the accumulator acts on the hydraulic motor, and the tension of the rope pulled by the traction winch is determined depending on this. The tension applied to the rope during towing fluctuates periodically depending on the wave conditions, etc., but if the tension is weakened, the traction winch entrains the rope due to the rotation of the hydraulic motor, and conversely, if the tension of the rope becomes stronger, the accumulator becomes stronger. The hydraulic motor reverses while the hydraulic oil flows backward, and the rope is paid out. In this way, the tension of the rope can be maintained substantially constant, and the breakage of the rope and the occurrence of impact due to the fluctuation in tension can be reliably avoided.

In the second aspect of the invention, the hydraulic pressure from the high pressure circuit is supplied to the plurality of accumulators, but the set value thereof is adjusted by the electromagnetic proportional relief valve so that the relief pressure corresponds to the set pressure of the accumulator. You can freely specify the accumulator that determines the rope tension during towing.
Thereby, the rope tension can be easily changed based on the difference in the towing conditions.

According to the third aspect of the invention, when the rope is wound by the traction winch and wound or when it is unwound, a high speed or low speed hydraulic motor can be selected and its speed can be changed.

[0012]

1 shows an embodiment of the present invention. As shown in FIG. 1, a store winch 2, a traction winch 3 and a guide roller 4 are provided on a deck of a hull 1.
And a towing rope (for example, a nylon rope) 5 are wound around the store winch 2 via the guide roller 4 and the traction winch 3.

The traction winch 3 rotates with the store winch 2 at a predetermined low speed or high speed when the rope 5 is wound or unwound, and when the ship is towed, a predetermined tension is applied to the rope 5 by the action of an accumulator described later. To absorb and mitigate tension fluctuations based on changes in relative position and speed between ships, while maintaining a constant towing distance.

2 to 4 show the structure of a traction winch 3 which is the main part of the present invention. The traction winch 3 is provided with first and second hydraulic motors 10 and 11, and their motor shafts 10A and 11A, respectively. Traction drums 12 and 13 are mounted on the same axis.

A plurality of grooves 15 are formed around the traction drums 12 and 13, and the towing rope 5 is wound between them. Two traction drums 12 and 1
In order to rotate 3 in the same direction, an intermediate gear 17 meshing with each other is provided between gears 10B and 11B fixed to both motor shafts 10A and 11A. A pressure roller 18 for holding the rope is provided at the winding start position of the traction drum 13,
A pressure roller 19 for pressing the rope is also arranged at the end of winding, and the hydraulic cylinders 20 and 21 respectively press the rope 5 with a predetermined biasing force to prevent the rope 5 from deviating from the groove 15. Also, the hydraulic motors 10 and 11
Are provided with brakes 22 and 23, and the rotation of the hydraulic motors 10 and 11 can be braked by hydraulic brake cylinders 24 and 25.

The guide roller 4 is composed of two pairs of rollers 4A and 4B which are perpendicular to each other and are orthogonal to each other.
The rope 5 is stably guided to the traction winch 3 in a predetermined towing angle range.

FIG. 5 shows a hydraulic circuit for driving the traction winch 3, in which the first hydraulic motor 10 is set in the low speed range and the second hydraulic motor 11 is set in the high speed range. When the hydraulic pressure is supplied, the towing rope 5 is wound or unwound so that the rope is rotated at a low speed and a high speed, and when connected to the accumulators 32 to 35, tension maintenance control is performed based on each set pressure. I do.

The hydraulic motor 37 of the store winch 2
Similarly winds or unwinds the rope 5 in accordance with the supply of hydraulic pressure from the hydraulic pump 31, and the tension of the rope 5 is loosened between the store winch 2 and the traction winch 3 at the time of tension control due to the connection with the accumulator 38. Absorbs.

Drive circuits 40A and 4 of the hydraulic motor 10
OB is selectively connected to the high pressure circuit 42 from the pump 31 and the low pressure circuit 43 communicating with the accumulator 35 having the lowest pressure via the hydraulic pressure switching valve 41.

For example, when the port a of the hydraulic pressure switching valve 41 is switched, the drive circuit 40A has a high pressure and the drive circuit 40B has a low pressure, and the hydraulic motor 10 normally rotates at a low speed. Similarly, when the port is switched to the b port, the hydraulic motor 10 reversely rotates at a low speed.

On the other hand, the drive circuit 4 of the hydraulic motor 11
5A and 45B are selectively connected to the high pressure circuit 42 and the low pressure circuit 43 through the hydraulic pressure switching valve 46. For example, when the hydraulic pressure switching valve 46 is switched to the a port, the hydraulic motor 11 rotates at high speed in the forward direction, and b When switched to a port, it rotates in reverse at high speed.

Since the other hydraulic motor 11 is driven when the hydraulic motor 10 is rotating at a low speed, the pair of reverse direction check valves 48 are provided in the circuit that short-circuits the drive circuits 45A and 45B. 49 is provided and the hydraulic motor 11
To rotate. Similarly, when the hydraulic motor 11 is rotating at a high speed, the other hydraulic motor 10 is rotated together, so that each pair of reverse check valves 57 and 58 is provided in the circuit that short-circuits the drive circuits 40A and 40B. It is provided.

The drive circuit 40A of the hydraulic motor 10 includes three accumulators 3 having different set pressures.
2 to 34 are connected to a high pressure accumulation circuit 47, a high pressure accumulation circuit 48 is also connected to the drive circuit 45A of the hydraulic motor 11, and switching valves 51 and 52 interposed in the high pressure accumulation circuits 47 and 48 are illustrated. When the port is switched to the open port,
The hydraulic pressures of the accumulators 32 to 34 are guided through the one-way speed control valves (parallel orifices and check valves) 53, respectively. However, when the switching valves 51 and 52 are switched to the shutoff ports, the communication with the accumulators 32 to 34 is shut off.

The accumulators 32 to 34 are high voltage circuits 42.
Is communicated with a branch high-voltage circuit 54 branched from, and an electromagnetic proportional relief valve 55 is interposed in this branch high-voltage circuit 54,
The set pressure of the accumulators 32 to 34 is kept the same as the pressure set in the electromagnetic proportional relief valve 55.

For example, the first accumulator 32 has 16
A gas having a pressure of 2 bar is filled, the second accumulator 33 is also 124 bar, and the third accumulator 3 is the same.
4 is filled with 93 bar of gas, and the set pressure of the electromagnetic proportional relief valve 55 is now set to the first accumulator 3
If it is the same as the filled gas of No. 2, the discharge pressure from the pump 31 guided to the branch high-voltage circuit 54 does not rise above the relief set pressure. In this state, only the first accumulator 32 functions as an accumulator, and the other second and third accumulators 33 and 34 have their built-in free pistons moved to the full rising limit, and the second and third set pressures are kept. It does not function as an accumulator unless

Similarly, the electromagnetic proportional relief valve 55
When the set pressure of is set to be the same as the set pressure of the second accumulator 33, the free piston of the first accumulator 32 does not move at all while moving to the lower limit (because the enclosed gas is higher), Three accumulators 34
The free pistons of the above-mentioned move to the upper limit and stop their functions as accumulators respectively. This means that even when the set pressure of the third accumulator 34 is matched, the free accumulators of the third accumulator can be similarly operated. 34 only works and the other first and second accumulators 32 and 3
3 substantially stops functioning.

On the other hand, the drive circuit 4 for the hydraulic motors 10 and 11
0B and 45B are connected to the lowest pressure accumulator 35 via the low pressure accumulator circuits 57 and 58. However, a pair of operating check valves 60 and 61 are provided in the low pressure accumulating circuits 57 and 58, respectively, and when the operating pressure is introduced by the switching valve 62, the operating check valves 60 and 61 lose their functions and are relieved. The valve 36 allows free communication between the accumulator 35 having a low set pressure of, for example, 10 bar.

Therefore, the hydraulic pressure switching valves 41 and 4 described above are used.
In the state where 6 is set to the neutral shut-off position, the drive circuits 40A and 45A of both hydraulic motors 10 and 11 have high pressure accumulating circuits 47 and 48.
And the drive circuits 40B and 45B are connected to the low pressure storage circuit 5
7 and can be connected to the hydraulic motor 10 in this state.
And 11 are normally or reversely rotated based on the relationship between the motor driving force that depends on the set pressure of the accumulators 32 to 35 and the motor load, that is, the tension applied to the rope 5.

For example, when the tension of the rope 5 becomes lower than the pressure set by the accumulators 32 to 35,
The hydraulic motors 10 and 11 rotate in the normal direction, and the rope 5 is wound up,
On the contrary, when the tension of the rope 5 becomes stronger than the set pressure, the hydraulic motors 10 and 11 are reversed and the rope 5 is paid out. In this way, the tension is kept constant so that excessive tension does not act on the rope 5. To do.

The high pressure accumulator circuits 47 and 48 are also provided with a pair of operating check valves 63 and 64, respectively, and their functions disappear when the operating pressure is supplied by the switching valve 65.

Next, the brake 2 of the hydraulic motors 10 and 11
When high pressure from the accumulator 72 is introduced via the brake switching valve 71 to the hydraulic brake cylinders 24 and 25 that control 2 and 23, the brake cylinders 24 and 25 operate and the brakes 22 and 23 are released. On the contrary, when the pressure is released to the low pressure, the braking operation is performed by the spring force.

Further, for the cylinders 20 and 21 which control the operation of the pressure rollers 18 and 19, a switching valve 73 is provided.
When high pressure is supplied by the pressure rollers 18, 1,
9 pushes the rope 5 against the traction drums 12, 13 and prevents it from deviating.

Further, the drive circuits 81A and 81B of the hydraulic motor 37 of the store winch 2 described above include the hydraulic switching valve 8
2 is selectively connected to the medium-voltage circuit 44 and the low-voltage circuit 43, whereby the rope 5 is wound and unwound on the store winch 2 together with the traction winch 3.

Further, at the shut-off position of the hydraulic pressure switching valve 82, the pressure accumulator circuit 84 is so arranged that the pressure from the pressure accumulator circuit 84 connected to the accumulator 38 whose set pressure is regulated by the relief valve 89 is guided to the drive circuit 81A. The interposed switching valve 85 is in the open position, and hydraulic pressure acts via the one-way speed control valve 86. The pair of operation check valves 87 stop their functions and are opened when the operating pressure from the switching valve 88 is supplied. Further, the low-pressure accumulator 90 absorbs the hydraulic oil from the drive circuit 81B via the check valve 93, and supplies the hydraulic oil to the drive circuit 81B via the check valve 94.

As a result, the hydraulic motor 37 is reversibly rotated along with the operation of the traction winch 3 so as to prevent the rope 5 between the traction winch 3 and the store winch 2 from being loosened during the towing of the ship.

Reference numeral 91 is a brake cylinder of the store winch 2, and when hydraulic pressure is supplied through the switching valve 92, the brake is released as in the above.

The circuit pressure of the high pressure circuit 42 is set to a predetermined high pressure (for example, 210b) by the high pressure relief valve 95.
ar), the low-pressure circuit 43 is connected to the low-pressure relief valve 96.
Is set to a predetermined low pressure (for example, 15 bar), and the intermediate pressure circuit 44 is set to a predetermined intermediate pressure (for example, 70 bar) by the intermediate pressure relief valve 97.

Further, in the figure, 101, 102, 103, 1
Reference numeral 04 is a check valve that blocks a reverse flow from each circuit to the hydraulic pump 31.

With the above construction, the operation will be described.

First, when towing by the rope 5, for example, 4
The vessel is towed via the traction winch 3 while maintaining the tension of the rope 5 that has been fed out by about 00 to 500 meters at a constant value set by the accumulators 32 to 34.

Which of the accumulators 32 to 34 is used depends on the towing conditions at that time, and the tension of the rope 5 increases as the towing vessel becomes larger and the towing speed becomes faster.

For example, a case where the second accumulator 33 is towed with a tension determined by the gas pressure of 124 bar will be described.

At the time of towing, the hydraulic pressure switching valves 41, 46, 8 of the hydraulic motors 10, 11, 37 of the traction winch 3 are driven.
2 in the shut-off position and the hydraulic motors 10, 1
1 and 37 are brought into a state in which they can be driven by accumulator pressure. At this time, hydraulic pressure is applied to the brake cylinders 24, 25, 91 to release the brake. In addition, the hydraulic pressure is supplied to the hydraulic cylinders 20 and 21, and the pressure roller 1
The rope 5 is pressed by 8 and 19 so as not to deviate from the traction drums 12 and 13 of the traction winch 3.

The set pressure of the electromagnetic proportional relief valve 55 is made to match the set pressure of the second accumulator 33, the hydraulic pump 31 is driven, and the discharge pressure thereof is supplied from the high pressure circuit 42 to the branch high pressure circuit 54. When the hydraulic pressure is supplied until the electromagnetic proportional relief valve 55 performs the relief operation, the hydraulic pump 31 is stopped. In this state, as described above, the first accumulator 32 and the third accumulator 35 stop functioning, and only the second accumulator 33 holds the free piston at the intermediate position due to the balance with the gas pressure. Since the check valves 101, 102, 103 and the like prevent the reverse flow, this pressure is contained in the high pressure circuit 42.

The hydraulic pressure is also supplied to the low pressure circuit 43 and the intermediate pressure circuit 44, and the accumulators 35 and 3 are respectively supplied.
The pressure set by the relief valves 36 and 89 at 8 is accumulated.

Then, the switching valves 51 and 52 of the high pressure accumulator circuits 47 and 48 connected to the drive circuits 40A and 45A of the hydraulic motors 10 and 11 are switched to the open position, and the drive circuit 4 similarly.
Also for the low pressure storage circuits 57 and 58 of 0B and 45B, the switching valve 62 supplies the operating pressure so as to cancel the functions of the operating check valves 60 and 61, and maintains the communication state.

Therefore, the hydraulic motors 10 and 11 have high pressures from the high pressure accumulation circuits 47 and 48, and low pressure accumulation circuits 57 and 5.
A rotating force is generated according to the pressure difference between the low pressure and the low pressure of 8, and the traction winch 3 drives the rope 5 in the winding direction. At this time, a load is applied to the rope 5 in the payout direction according to the size, speed, and the like of the towed ship, and the rope 5 is balanced by the balance between the take-in force and the payout force. if,
When the tension of the rope 5 temporarily increases from the equilibrium state, the hydraulic motors 10 and 11 reversely rotate due to this load, and the rope 5
To prevent the load on the rope 5 from becoming excessive.

At this time, the reverse rotation of the hydraulic motors 10 and 11 causes the drive circuits 40B to 40A to move in the same manner as the drive circuit 45.
The hydraulic oil flows from B to 45A, and these are absorbed by the accumulator 33, respectively.

On the contrary, if the tension of the rope 5 is temporarily weakened,
The hydraulic motors 10 and 11 rotate the rope 5 in the winding direction to absorb the slack of the rope 5.

In this case, the drive circuits 40B and 45, respectively.
The hydraulic fluid flowing to B is absorbed by the low-pressure accumulator 35 via the low pressure accumulation circuits 57 and 58.

In this way, the tension applied to the rope 5 is maintained in a constant state according to the set pressure of the accumulator 33 (electromagnetic proportional relief valve 55), and an excessive stress acts on the rope 5 due to the tension fluctuation during towing. It is also possible to absorb and relax the impact of impact.

The store winch 2 applies a certain amount of weak tension to the rope 5 in order to prevent the rope 5 from loosening and tension between the traction winch 3 and the traction winch 3 as the traction winch 3 is wound and unwound. That is, the hydraulic motor 3
If a relatively low pressure of the accumulator 38 acts on the drive circuit 81A of No. 7 to cause slack in the rope 5, the rope 5 is wound up, and if the tension of the rope 5 is increased by unwinding the traction winch 3, a hydraulic motor is generated. Three
7 is reversed and the rope 5 is paid out.

In this description, the tension is controlled by the set pressure of the second accumulator 33. However, when towing a larger ship or when the towing speed is fast, the rope 5 is used.
Since the tension applied to the vehicle also becomes large, in this case, the first accumulator 32 can be used to tow with a stronger tension. On the contrary, when the required tension of the rope 5 is lower, the tension control may be performed based on the low set pressure by the third accumulator 34. The pressure setting at this time is performed by the electromagnetic proportional relief valve 55.

This means that when the towing distance is gradually shortened during towing, the tension applied to the rope 5 is too strong. Therefore, the accumulator set pressure may be lowered, or conversely, the towing distance may be reduced. If it becomes longer, increase the set pressure or decrease the towing speed.

Next, a case where the rope 5 is wound after the towing is completed will be described.

In this case, it is not necessary to control the tension of the rope 5 to be constant, and the rope 5 is wound at low speed or high speed by the traction winch 3.

For example, when winding is performed by the hydraulic motor 10 rotating at a low speed, the hydraulic switching valve 41 is set to the hydraulic motor 1.
Switch to the direction in which 0 rotates forward. At this time, the high pressure accumulation circuit 4
7 and 48, and further, each switching valve 51, 52, 62, 65, etc. is switched so that each circuit of the low pressure accumulation circuit 57 is shut off, and the hydraulic switching valve 4 of the hydraulic motor 11 rotating at a high speed.
6 is held in the blocking position.

By driving the hydraulic pump 31, the high pressure circuit 42
The hydraulic fluid sent to the hydraulic fluid flows from the hydraulic pressure switching valve 41 to the drive circuit 40A to rotate the hydraulic motor 10. This hydraulic oil flows from the drive circuit 40B to the low pressure circuit 43, and is returned to the tank via the low pressure relief valve 36.

As a result, one traction drum 12 of the traction winch 3 rotates, but the other traction drum 13 also tries to rotate in the same direction via the intermediate gear. At this time, since the hydraulic switching valve 46 of the other hydraulic motor 11 is in the shut-off position, high pressure is not supplied from the pump 31, but the hydraulic motor 10 is forcibly driven by the rotation of the hydraulic motor 10 and sucks hydraulic oil from the drive circuit 45A. , To the drive circuit 45B. Since both drive circuits 45A and 45B are connected by a pair of check valves 48 and 49,
The hydraulic oil is sucked from the drive circuit 45B to 45A, and the hydraulic motor 11 is allowed to continue the same rotation.

In this way, the traction winch 3
The rope 5 is wound while the traction drums 12 and 13 of FIG.

At this time, the hydraulic switching valve 82 is switched in the forward direction of the hydraulic motor 37 so that the store winch 2 winds up the rope 5 wound by the traction winch 3 without slackening, and the intermediate pressure circuit 44. It receives the supply of hydraulic oil from and rotates.

At this time, the switching valves 85 and 88 are in the shut-off position to prevent the backflow to the accumulator 38.

The rope 5 wound up by the traction winch 3 in this way is wound around the store winch 2, and the rotational force of the store winch 2 is smaller than the rotational force of the traction winch 3 because the supplied hydraulic pressure is low. , Therefore store winch 2 forced rope 5
Also does not pull in.

The above is the case where the low speed hydraulic motor 10 is used for winding. However, when the winding speed is desired to be increased, the high speed hydraulic motor 11 may be used. At this time, the hydraulic pressure switching valve 46 of the hydraulic motor 11 is switched,
High pressure is supplied to the traction winch 3 and the other parts are controlled in the same manner as described above, whereby the traction winch 3 rotates at high speed while the other hydraulic motor 10 rotates in the same direction.

When the rope 5 is unwound, the rotation directions of the traction winch 3 and the store winch 2 may be reversed from those described above, and these hydraulic pressure switching valves 41, 45, 8 may be used.
It will be easily understood what can be done by switching the two.

Although not specifically described, it goes without saying that the operation of each brake is released when the rope 5 is wound and unwound.

[0067]

According to the first aspect of the invention, when the tension applied to the rope fluctuates during towing, and the tension is weakened, for example, the traction winch wraps the rope by the rotation of the hydraulic motor, and conversely the tension of the rope is increased. When this happens, the hydraulic motor reversely flows back the hydraulic oil to the accumulator, and the rope is paid out.In this way, the tension of the rope is always kept almost constant, and it is possible to avoid the occurrence of rope breakage and impact due to tension fluctuation. can do.

According to the second aspect of the invention, the rope tension can be easily changed based on the difference in the towing conditions by the action of the plurality of accumulators and the electromagnetic proportional relief valve.

According to the third aspect of the present invention, when the rope is wound by the traction winch and wound or unwound, the rope can be operated at high speed or low speed as required, and efficient operation can be performed.

[Brief description of drawings]

FIG. 1 is an overall plan view showing an embodiment of the present invention.

FIG. 2 is a plan view of a traction winch.

FIG. 3 is a front view of the same.

FIG. 4 is a side view of the same.

FIG. 5 is a hydraulic drive circuit of a winch.

[Explanation of symbols]

 2 Store winch 3 Traction winch 5 Rope 10 Hydraulic motor 11 Hydraulic motor 12 Traction drum 13 Traction drum 31 Hydraulic pump 32 Accumulator 33 Accumulator 34 Accumulator 41 Hydraulic switching valve 46 Hydraulic switching valve 55 Electromagnetic proportional relief valve

Claims (3)

[Claims] 1. A store winch for winding a towing rope through a traction winch, the traction winch being equipped with two traction drums which can be rotated by at least two hydraulic motors, and wound between these traction drums. The rope is configured to be wound around a store winch, and a high pressure from a hydraulic pump is selectively supplied to a drive circuit of the hydraulic motor through a hydraulic switching valve, while the set pressure is different. It is configured such that it can be switched and connected so that pressures from a plurality of accumulators are guided, and when the accumulator is connected to the hydraulic motor drive circuit, the towing tension of the rope is controlled to a predetermined value. Towing winch. 2. The electromagnetic proportional relief valve is provided in a circuit for supplying hydraulic pressure from a high pressure circuit to the plurality of accumulators having different set pressures, and the accumulator supply pressure can be changed. Towing winch. 3. The hydraulic motor according to claim 1, wherein one of the hydraulic motors is a high speed motor and the other is a low speed motor, and the rotary motor is selectively rotatably driven through the hydraulic pressure switching valve when winding and winding the rope. Towing winch described in.