JPH1182312A - Hydraulically driven piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a shock produced when a drive cylinder operation is switched over and a cylinder comes at a stroke end. SOLUTION: A hydraulically driven piston pump is provided with an oscillating pipe 2, pump cylinders 4L and 4R, drive cylinders 6L and 6R to drive their transfer pistons 71, and 7R, an alternating hydraulic pump 33 to which the operating pipes 25L and 25R of the drive cylinders 6L and 6R are connected and which constitutes a closed circuit. In this case, position detectors 41L and 41R for deceleration command which detect the arrival of the drive pistons 9L and 9R to a deceleration position so as to control the tilt angle of the alternating hydraulic pump in order to decelerate the speed of the drive pistons 9L and 9R and position detectors 42L and 42R which detect the arrival of the drive pistons 9L and 9R to a stop position so as to zero the tilt angle of the alternating hydraulic pump 33 in order to stop the drive pistons 9L and 9R are disposed specified deceleration and stop positions which are before the stroke ends of the drive pistons 9L and 9R of the drive cylinders 6L and 6R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for pumping low-slump concrete or earth and sand with poor fluidity in construction and civil engineering, or for pumping dewatered sludge having a low water content in sewage treatment plants and human waste treatment plants. And a hydraulically driven piston pump.

[0002]

2. Description of the Related Art Generally, a hydraulically driven piston pump is
As shown in FIGS. 5 and 6, a pair of left and right suction and discharge ports 1L and 1R are provided at the lower portion of the back wall 1B of the hopper 1, and one end of each of the suction and discharge ports 1L and 1R is opened at the back of the hopper 1. Pump cylinders 4L and 4R are attached. Each of the pump cylinders 4L and 4R is provided with a transfer piston 7 which is alternately reciprocated by drive cylinders 6L and 6R. A water seal box 5 is provided at the junction between the 4L, 4R and the drive cylinders 6L, 6R.

In the hopper 1, an oscillating tube 2 is installed. The swing tube 2 has a base end 2B rotatably supported by a front wall 1F of the hopper 1 and an intermediate portion of the swing tube 2 rotatably supported by a back wall 1B of the hopper 1. One end of the oscillating tube shaft 10 is fixed. The center of rotation of the swing tube shaft 10 and the center of rotation of the base end 2B of the swing tube 2 are on the same line. Oscillating tube shaft 10 extending outside back wall 1B of hopper 1
A switching lever 11 is fixed to the other end of the switching cylinder 3L, and switching cylinders 3L and 3R are mounted between the switching lever 11 and the hopper 1, and when one of the switching cylinders 3L and 3R is extended, the other contracts. It has become.

When the switching cylinders 3L and 3R expand and contract, the swinging tube shaft 10 rotates, and the swinging tube 2 swings right and left, and the tip 2T of the swinging tube 2 alternately moves the left and right suction discharge ports. 1L, 1
Move to the position facing R.

A replaceable sliding plate 8 having openings corresponding to the suction and discharge ports 1L and 1R is provided at a portion where the tip 2T of the swing tube 2 around the suction and discharge ports 1L and 1R of the hopper 1 is in sliding contact. Is installed. The tip 2T of the swinging tube 2 is slid by being pressed against the sliding plate 8, so that a replaceable wear ring 12 is attached. A wear-resistant material is used for the sliding plate 8 and the wear ring 12.

[0006] A transport pipe (not shown) is connected to the base end 2 B of the swing pipe 2. When transporting an object to be transported such as earth and sand, the object to be transported is put into the hopper 1. Therefore, after one (for example, the right-hand side) transfer piston 7 is retracted to suck the object to be transported into the pump cylinder 4R, the swing tube 2 is swung to move the tip 2T to the pump cylinder 4R.
The transport piston 7 is advanced to discharge the object to be transported in the pump cylinder 4R from the oscillating pipe 2 to the transport pipe by facing the suction discharge port 1R on the side. When one of the pump cylinders 4R is in the discharge stroke, the other pump cylinder 4L retracts the transport piston 7 to suck the transport target into the pump cylinder 4L.

Next, the swing tube 2 is swung so that the tip 2T faces the suction / discharge port 1L on the other pump cylinder 4L side, and the transport piston 7 is advanced to move the transport object in the pump cylinder 4L. Discharge from the swing tube 2. The object to be transported is continuously transported by alternately performing the suction process and the discharge process on the left and right.

Conventionally, drive circuits for the drive cylinders 6L and 6R include those using an open circuit as shown in FIGS. 7 and 8, and those using a closed circuit as shown in FIG.

In the drive circuit of FIG. 7, the drive cylinder 6L,
The 6R rod-side oil chambers are connected to each other by a communication pipe 21. The head-side oil chambers of the drive cylinders 6L, 6R are connected to the cylinder ports of the pump control valve 22 through operating pipe lines 25L, 25R, respectively, and are connected to the hydraulic pump 23 and the tank 24 via the pump control valve 22. Pump control valve 22
Is a three-position electromagnetic switching valve. By switching the pump control valve 22, the drive cylinders 6L and 6R alternately expand and contract, and the transport pistons 7L and 7R alternately reciprocate.

The working pipelines 25L and 25R are provided with pressure detectors 20L and 20R for detecting the stroke ends of the drive pistons 9L and 9R of the drive cylinders 6L and 6R, respectively. Is sent to the control unit (not shown).

The head-side oil chambers of the switching cylinders 3L and 3R are connected to the cylinder ports of a swing control valve 27 through left and right moving pipelines 26L and 26R, respectively. The driving hydraulic pump 28 and the tank 24 are connected.

The swing control valve 27 is a three-position electromagnetic switching valve. By switching the swing control valve 27, the switching cylinders 3L and 3R expand and contract alternately. Switching cylinder 3
Above L and 3R, a switching position detector 29L for detecting that the switching cylinder 3L has extended and the tip 2T of the swing tube 2 has moved to a position facing the left suction / discharge port 1L, and a switching cylinder 3R. A switching position detector 29R is provided for detecting that the distal end 2T of the swing tube 2 has extended and moved to a position facing the right suction / discharge port 1R. The switching position detectors 29L and 29R are proximity switches, and their detection signals are sent to the control unit.

As shown, one drive piston 9L is at the stroke end of the discharge stroke and the other drive piston 9R
Reaches the stroke end of the suction stroke,
When the pressure of 5L increases, the pressure switch 20L detects that the stroke end has been reached and sends a detection signal to the control unit.

Then, the control unit switches the swing control valve 27,
The right switching cylinder 3R is extended, the left switching cylinder 3L is shortened, and the swing tube 2 is swung to the right, and the tip 2T
To the right suction / discharge port 1R. Therefore, the switching position detector 29R is connected to the suction discharge port 1R of the tip 2T of the swinging tube 2.
, And sends a detection signal to the control unit.

The control unit switches the pump control valve 22, extends the right drive cylinder 6R, and extends the left drive cylinder 6L.
, The transfer piston 7R is advanced, and the transfer piston 7L
Is retracted, the object to be transported is discharged from the pump cylinder 4R to the swing tube 2, and the object to be transported is sucked into the pump cylinder 4L.

When the drive piston 9R reaches the stroke end of the discharge stroke and the drive piston 9L reaches the stroke end of the suction stroke, the pressure in the working line 25R increases, and the pressure switch 20R detects that the stroke end has been reached. To the control unit.

Then, the control unit switches the swing control valve 27,
The right switching cylinder 3R is shortened, the left switching cylinder 3L is extended, and the swing tube 2 is swung to the left, and the tip 2
T faces the left suction and discharge port 1L. Therefore, the switching position detector 29L is connected to the suction / discharge port 1 at the tip 2T of the swing tube 2.
The arrival at the position facing L is detected, and the detection signal is sent to the control unit.

The control unit switches the pump control valve 22, extends the left drive cylinder 6L, and extends the right drive cylinder 6R.
Is shortened and the transfer piston 7L is moved forward, the transfer piston 7R
Is retracted, the object to be transported is discharged from the pump cylinder 4L to the swing tube 2, and the object to be transported is sucked into the pump cylinder 4R.

Thereafter, switching is controlled so that the above-described suction and discharge strokes are performed alternately on the left and right. In the drive circuit of FIG. 8, in place of the pressure switches 20L and 20R in FIG. 7, proximity switches 30L and 30R are provided in the drive cylinders 6L and 6R to detect the stroke end of the discharge stroke of the drive pistons 9L and 9R. . Other configurations are the same as those in FIG.

In the drive circuit of FIG. 9, the drive cylinder 6L,
The 6R rod-side oil chambers are connected to each other by a communication line 21,
The head-side oil chambers of the drive cylinders 6L and 6R are connected to the swing hydraulic pump 33 by operating lines 25L and 25R, respectively, to form a closed circuit. Working line 25L, 2
The auxiliary pump 32 is connected to 5R via check valves 31L and 31R. Also, the working pipelines 25L, 25L
R is a check valve 34L, 34R and a relief valve 35,
It is connected to the tank 24 via 36.

In this drive circuit, as in FIG.
Driving pistons 9L, 9R are provided in the working pipes 25L, 25R.
The pressure detectors 20L and 20R for detecting the stroke end of the discharge stroke of the above are provided.

As shown, one drive piston 9L is at the stroke end of the discharge stroke and the other drive piston 9R
Reaches the stroke end of the suction stroke,
When the pressure of 5L increases, the pressure switch 20L detects that the stroke end has been reached and sends a detection signal to the control unit.

Then, the control unit switches the swing control valve 27,
The right switching cylinder 3R is extended, the left switching cylinder 3L is shortened, and the swing tube 2 is swung to the right, and the tip 2T
To the right suction / discharge port 1R. Therefore, the switching position detector 29R is connected to the suction discharge port 1R of the tip 2T of the swinging tube 2.
, And sends a detection signal to the control unit.

The control unit switches the discharge direction of the swing hydraulic pump 33, extends the right drive cylinder 6R, shortens the left drive cylinder 6L, advances the transport piston 7R, and retracts the transport piston 7L. The object to be transported is discharged from the 4R to the oscillating pipe 2, and the object to be transported is sucked into the pump cylinder 4L.

When the drive piston 9R reaches the stroke end of the discharge stroke and the drive piston 9L reaches the stroke end of the suction stroke, the pressure in the working line 25R rises and the pressure switch 20R detects the stroke end, and the detection signal To the control unit.

Then, the control unit switches the swing control valve 27,
The right switching cylinder 3R is shortened, the left switching cylinder 3L is extended, and the swing tube 2 is swung to the left, and the tip 2
T faces the left suction and discharge port 1L. Therefore, the switching position detector 29L is connected to the suction / discharge port 1 at the tip 2T of the swing tube 2.
The arrival at the position facing L is detected, and the detection signal is sent to the control unit.

The control unit switches the discharge direction of the swing hydraulic pump 33, extends the left drive cylinder 6L, shortens the right drive cylinder 6R, and advances the pump piston 7L.
The pump piston 7R is retracted, the object to be transported is discharged from the pump cylinder 4L to the swing tube 2, and the object to be transported is sucked into the pump cylinder 4R.

Thereafter, switching is controlled so that the above-described suction and discharge strokes are performed alternately on the left and right.

[0029]

However, FIGS. 7 and 8
When the operation of the drive cylinders 6L and 6R is switched by switching the pump control valve 22, the operating line 25
In each of the oil chambers L, 25R and the drive cylinders 6L, 6R, the pressure changes suddenly and an impact occurs.

Also in the drive circuit of FIG. 9, the drive pistons 9L and 9R of the drive cylinders 6L and 6R reach the stroke end at a high speed, and the hydraulic pressure of the working pipelines 25L and 25R becomes high. 20L, 20R
Since the switching to the next stroke has been performed after the detection in step (1), an impact at the stroke end has occurred.

The present invention is to solve such a problem in a hydraulically driven piston pump, and to provide a hydraulically driven piston pump which can reduce an impact at the time of switching operation of a drive cylinder and at a stroke end. Aim.

[0032]

According to the present invention, there is provided a suction / discharge switching means for a suction / discharge port, a pump cylinder having one end opened at the suction / discharge port, a drive cylinder for driving a transfer piston of the pump cylinder, and a drive cylinder. In a hydraulically driven piston pump including a variable displacement hydraulic pump to which an operating pipe is connected, a deceleration position and a stop position are set before a stroke end of a drive piston of a drive cylinder, and the drive piston is moved to a deceleration position. And a variable displacement hydraulic pump that detects the arrival of the drive piston and controls the amount of oil discharged from the variable displacement hydraulic pump to reduce the speed of the drive piston. The above problem is solved by providing a stop command position detector for stopping the drive piston by setting the discharge oil amount to zero.

In the hydraulically driven piston pump, the suction / discharge port is first switched to the suction side by the suction / discharge switching means, and the transport piston is retracted to suck the object to be transported into the pump cylinder. Next, the suction / discharge port is switched to the discharge side by the suction / discharge switching means, and the transport piston is advanced to discharge the object to be transported in the pump cylinder from the suction / discharge port. The object to be transported is transported by alternately performing the suction and discharge processes.

In this hydraulically driven piston pump, the drive cylinder for driving the transport piston is provided with the deceleration command position detector and the stop command position detector, so that the drive piston is moved to the deceleration position. When it reaches, the position detector for deceleration command controls the amount of oil discharged from the variable displacement hydraulic pump to reduce the speed of the drive piston, and when the drive piston advances further in the decelerated state and reaches the stop position, a stop command is issued. The use position detector sets the discharge oil amount of the variable displacement hydraulic pump to zero, and stops the drive piston before reaching the stroke end.

Therefore, it is possible to avoid an impact at the stroke end when the operation of the drive cylinder is switched.

[0036]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a hydraulically driven piston pump according to an embodiment of the present invention.

Here, the basic structure of the piston pump is as follows.
This is a double-cylinder piston pump similar to the piston pump shown in FIGS. 5 and 6, wherein a pair of left and right suction / discharge ports 1 </ b> L, 1 </ b> R is provided at a lower portion of a back wall 1 </ b> B of the hopper 1. Pump cylinders 4L and 4R each having an open end are attached to the outlets 1L and 1R.
Each of the pump cylinders 4L and 4R is provided with a transfer piston 7 which is alternately reciprocated by drive cylinders 6L and 6R. A water seal box 5 is provided at the junction between the 4L, 4R and the drive cylinders 6L, 6R.

In the hopper 1, an oscillating tube 2 is installed. The swing tube 2 has a base end 2B rotatably supported by a front wall 1F of the hopper 1 and an intermediate portion of the swing tube 2 rotatably supported by a back wall 1B of the hopper 1. One end of the oscillating tube shaft 10 is fixed. The center of rotation of the swing tube shaft 10 and the center of rotation of the base end 2B of the swing tube 2 are on the same line. Oscillating tube shaft 10 extending outside back wall 1B of hopper 1
A switching lever 11 is fixed to the other end of the switching cylinder 3L, and switching cylinders 3L and 3R are mounted between the switching lever 11 and the hopper 1, and when one of the switching cylinders 3L and 3R is extended, the other contracts. It has become.

When the switching cylinders 3L and 3R expand and contract, the swing tube shaft 10 rotates, and the swing tube 2 swings right and left, and the tip 2T of the swing tube 2 alternately moves the left and right suction discharge ports. 1L, 1
Move to the position facing R.

A replaceable sliding plate 8 having openings corresponding to the suction and discharge ports 1L and 1R is provided at a portion where the tip 2T of the swinging tube 2 around the suction and discharge ports 1L and 1R of the hopper 1 is in sliding contact. Is installed. The tip 2T of the swinging tube 2 is slid by being pressed against the sliding plate 8, so that a replaceable wear ring 12 is attached. A wear-resistant material is used for the sliding plate 8 and the wear ring 12.

A transport pipe (not shown) is connected to the base end 2B of the swing pipe 2. When transporting an object to be transported such as earth and sand, the object to be transported is put into the hopper 1. Therefore, after one (for example, the right-hand side) transfer piston 7 is retracted to suck the object to be transported into the pump cylinder 4R, the swing tube 2 is swung to move the tip 2T to the pump cylinder 4R.
The transport piston 7 is advanced to discharge the object to be transported in the pump cylinder 4R from the oscillating pipe 2 to the transport pipe by facing the suction discharge port 1R on the side. When one of the pump cylinders 4R is in the discharge stroke, the other pump cylinder 4L retracts the transport piston 7 to suck the transport target into the pump cylinder 4L.

Next, the rocking pipe 2 is rocked so that the tip 2T faces the suction / discharge port 1L on the other pump cylinder 4L side, and the transport piston 7 is advanced to move the object to be transported in the pump cylinder 4L. Discharge from the swing tube 2. The object to be transported is continuously transported by alternately performing the suction process and the discharge process on the left and right.

As shown in FIG. 1, in the drive circuit of this piston pump, the rod-side oil chambers of the drive cylinders 6L and 6R are connected to each other by a communication pipe 21, and the drive cylinders 6L and 6R are connected to each other.
The oil chamber on the head side of R is connected to a variable displacement type double swing hydraulic pump 33 via working lines 25L and 25R, respectively, to form a closed circuit. The double swing hydraulic pump 33 swings the tilt angle left and right, thereby turning the left and right working pipelines 25L, 2L,
The direction of ejection to 5R can be switched.

An auxiliary pump 32 is connected to the operation pipes 25L and 25R via check valves 31L and 31R. Further, the high pressure sides of the working pipelines 25L, 25R are connected to the tank 24 via check valves 34L, 34R and relief valves 35, 36. The low-pressure sides of the working pipelines 25L and 25R are connected to the tank 24 via a relief valve 37.

The drive cylinders 6L and 6R are provided with deceleration command position detectors 41L and 41R and deceleration command position detectors 41L and 41R, respectively, at a deceleration position and a stop position set before the stroke end of the drive pistons 9L and 9R on the forward side. Position detector 42L,
42R. Deceleration command position detector 41
L, 41R and the stop command position detectors 42L, 42R are proximity switches for detecting the proximity of the heads of the drive pistons 9L, 9R.
When L and 41R detect that the drive pistons 9L and 9R have reached the deceleration position, they send detection signals to a control unit (not shown). The control unit controls the swing hydraulic pump 33 to reduce the amount of discharged oil and reduce the speed of the drive pistons 9L and 9R. When the stop command position detectors 42L and 42R detect that the drive pistons 9L and 9R have reached the stop positions, they send detection signals to a control unit (not shown). The control unit sets the discharge oil amount of the swing hydraulic pump 33 to zero and stops the drive pistons 9L and 9R before reaching the stroke end.

The head-side oil chambers of the switching cylinders 3L and 3R are connected to the cylinder ports of the swing control valve 27 through left and right moving pipelines 26L and 26R, respectively. The driving hydraulic pump 28 and the tank 24 are connected.

The swing control valve 27 is a three-position electromagnetic switching valve, and by switching the swing control valve 27, the switching cylinders 3L and 3R alternately expand and contract. Switching cylinder 3
Above L and 3R, a switching position detector 29L for detecting that the switching cylinder 3L has extended and the tip 2T of the swing tube 2 has moved to a position facing the left suction / discharge port 1L, and a switching cylinder 3R. A switching position detector 29R is provided for detecting that the distal end 2T of the swing tube 2 has extended and moved to a position facing the right suction / discharge port 1R. The switching position detectors 29L and 29R are proximity switches, and send detection signals to the control unit. The control unit switches the discharge direction of the swing hydraulic pump 33 in the reverse direction based on the detection signal to move the drive pistons 9L and 9R in the reverse direction.

In the discharge stroke of the left pump cylinder 4L, that is, the forward travel of the left drive cylinder 6L, when the drive piston 9L reaches the deceleration position, the deceleration command position detector 41L shifts the drive piston 9L to the deceleration position. When the arrival is detected, the swinging hydraulic pump 33 is controlled to drive the driving piston 9L.
, And the retreat speed of the drive piston 9R is reduced. When the drive piston 9L reaches the stop position, the stop command position detector 42L detects that the drive piston 9L has reached the stop position, and sets the discharge oil amount of the double swing hydraulic pump 33 to zero, thereby setting the drive pistons 9L and 9R. Is stopped, and the swing control valve 27 is switched to switch the left switching cylinder 3L.
, The right switching cylinder 3R is extended, the swing tube 2 is swung to the right, and the tip 2T is moved to the right suction and discharge port 1.
Face R.

Therefore, the switching position detector 29R is connected to the swing tube 2
Of the leading end 2T of the swinging hydraulic pump 33 in the opposite direction by detecting the arrival of the leading end 2T at the position facing the suction / discharge port 1R, and retreats the drive piston 9L, thereby reversing the drive piston 9R.
, The discharge stroke of the right pump cylinder 4R,
That is, the process proceeds to the forward travel of the right drive cylinder 6R.

The same control is performed when the right drive piston 9R reaches the deceleration position and reaches the stop position. Thereafter, the suction and discharge strokes are alternately repeated. The deceleration position and the stop position are appropriately set according to the specifications and operating conditions of the piston pump so that no impact occurs at the stroke end.

In this hydraulically driven piston pump, even when the piston speed is changed in order to increase or decrease the discharge amount of the object to be transported, when the drive pistons 9L and 9R reach the deceleration positions, the speed is reduced to a predetermined speed. The stroke is stopped at the stop position before the stroke end, so that the switching of the stroke is reliably performed without the drive pistons 9L and 9R colliding with the stroke end.

Therefore, a sudden increase in pressure and an impact caused by the collision of the drive pistons 9L and 9R with the stroke end are prevented. FIGS. 2 to 4 are hydraulic circuit diagrams showing another embodiment of the present invention.

In the drive circuit shown in FIG. 2, the deceleration command position detectors 41L and 41R and the stop command position detectors 42L and 42R are used.
R is for detecting the proximity of the rod end portions of the drive pistons 9L and 9R, and is arranged to detect the drive pistons 9L and 9R reaching the deceleration position and the stop position before the retreat-side stroke end. Have been.

In the drive circuit shown in FIG. 3, the deceleration command position detectors 41L and 41R detect the proximity of the rod end portions of the drive pistons 9L and 9R.
It is arranged to detect the reaching of the deceleration position just before the stroke end on the retreating side of 9R.

The stop command position detectors 42L and 42R are
It detects the proximity of the heads of the drive pistons 9L and 9R, and is arranged to detect that the drive pistons 9L and 9R have reached the stop positions before the forward stroke ends.

In the drive circuits shown in FIGS. 2 and 3, the deceleration command position detectors 41L and 41R and the stop command position detector 42 are used.
The arrangement of L and 42R is different from that of FIG. 1, but the operation is the same.

The piston pump shown in FIG. 4 is a single-cylinder type piston pump having one pump cylinder 4 and a drive cylinder 6.
A suction / discharge switching valve 50 is provided below the hopper 1.

Here, the rod-side oil chamber and the head-side oil chamber of the drive cylinder 6 are connected to the swing hydraulic pump 33 by operating pipe lines 25L and 25R, respectively, to form a closed circuit. Other circuit configurations are the same as those in FIG.

The position detector 41F for deceleration command and the position detector 42F for stop command are proximity switches,
And detects the approach of the drive piston 9 to the deceleration position and the stop position before the stroke end of the drive piston 9 on the forward side.

The deceleration command position detector 41B and the stop command position detector 42B are proximity switches which detect the proximity of the rod end of the drive piston 9 to the position.
The drive piston 9 is arranged to detect the reaching of a deceleration position and a stop position before the stroke end on the retreating side.

The valve-side hydraulic chamber for valve switching is connected to the rod-side oil chamber and the head-side oil chamber of a valve switching cylinder 51 for switching between the suction side and the discharge side of the suction / discharge switching valve 50 via a valve control valve 52. 53 and the tank 24.

Therefore, in the discharge stroke of the pump cylinder 4, that is, in the forward movement of the drive cylinder 6, when the drive piston 9 reaches the deceleration position, the deceleration command position detector 41F detects that the drive piston 9 reaches the deceleration position. Detecting and controlling the amount of oil discharged from the swing hydraulic pump 33 reduces the forward speed of the drive piston 9. When the drive piston 9 reaches the stop position, the stop command position detector 42F detects that the drive piston 9 has reached the stop position, and
The drive piston 9 is stopped by setting the discharge oil amount to zero, and the valve switching control valve 52 is switched to switch the suction / discharge switching valve 50 to the suction side.

When the suction / discharge switching valve 50 is switched to the suction side, the discharge direction of the swing hydraulic pump 33 is switched to the opposite direction, and the drive piston 9 is moved backward, so that the suction stroke, that is, the drive cylinder 6 is moved backward.

When the drive piston 9 reaches the deceleration position,
The deceleration command position detector 41B detects that the drive piston 9 has reached the deceleration position, controls the amount of oil discharged from the swing hydraulic pump 33, and reduces the retreat speed of the drive piston 9.
When the drive piston 9 reaches the stop position, the stop command position detector 42B detects that the drive piston 9 has reached the stop position, and stops the drive piston 9 by setting the discharge oil amount of the double swing hydraulic pump 33 to zero. At the same time, the valve switching control valve 52 is switched to switch the suction / discharge switching valve 50 to the discharge side.

When the suction / discharge switching valve 50 is switched to the discharge side, the discharge direction of the double swing hydraulic pump 33 is switched to the opposite direction to advance the drive piston 9 and enter the discharge stroke, that is, the forward travel of the drive cylinder 6. Thereafter, the suction and discharge processes are repeated alternately on the left and right.

In the piston pumps shown in FIGS. 1 to 4, the swing hydraulic pump 33 is used. However, any variable displacement pump other than the swing hydraulic pump 33 can be used. In such a case, a direction switching valve is provided in the working pipeline to switch the supply direction of the discharge oil.

[0067]

As described above, the hydraulically driven piston pump of the present invention is decelerated to a predetermined speed when the drive piston reaches the deceleration position, and is stopped at the stop position before reaching the stroke end. The stroke is reliably switched without the drive piston colliding with the stroke end. Therefore, it is possible to avoid an impact at the time of switching operation of the drive piston and at the stroke end.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a hydraulically driven piston pump according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing another embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing another embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram showing another embodiment of the present invention.

FIG. 5 is a plan view of a conventional piston pump.

FIG. 6 is a longitudinal sectional view taken along the center of a swing pipe of a hopper of a conventional piston pump.

FIG. 7 is a hydraulic circuit diagram of a conventional hydraulically driven piston pump.

FIG. 8 is a hydraulic circuit diagram of a conventional hydraulically driven piston pump.

FIG. 9 is a hydraulic circuit diagram of a conventional hydraulically driven piston pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hopper 2 Oscillating pipe 1L, 1R Suction and discharge port 3L, 3R Switching cylinder 4L, 4R Pump cylinder 6L, 6R Driving cylinder 7L, 7R Transfer piston 8 Sliding plate 9L, 9R Driving piston 10 Oscillating pipe shaft 11 Switching lever 21 Communication line 25L, 25R Working line 26L Left moving line 26R Right moving line 27 Swing control valve 28 Swing hydraulic pump 29L, 29R Switching position detector 33 Double swing hydraulic pump 41L, 41R Deceleration command position detector 42L, 42R Stop command position detector

Claims (1)

[Claims] 1. A suction / discharge switching means for a suction / discharge port, a pump cylinder having one end opened at the suction / discharge port, a drive cylinder for driving a transport piston of the pump cylinder, and a variable connection line connected to an operating line of the drive cylinder. A hydraulically driven piston pump comprising a displacement hydraulic pump, wherein a deceleration position and a stop position are set before a stroke end of the drive piston of the drive cylinder, and the drive piston reaches the deceleration position. Control the amount of oil discharged from the variable displacement hydraulic pump to reduce the speed of the drive piston, and a position detector for deceleration command, and detects the arrival of the drive piston at the stop position to determine the amount of oil discharged from the variable displacement hydraulic pump. A hydraulically driven piston pump, comprising: a stop command position detector for stopping the drive piston at zero.