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Pressurizing device

Pressurizing device description/claims

This patent application is a U.S. National Phase of International Application No. PCT/JP2005/015890, filed Aug. 31, 2005, which claims priority to Japanese Patent Application No. 2005-136322, filed May 9, 2005, the disclosures of which are incorporated herein by reference in their entirety.

The present disclosure relates to a pressure apparatus in which high-speed movement and high-thrust pressurization are compatible on an output shaft.

The present disclosure relates to a pressure apparatus in which high-speed movement and high-thrust pressurization are made compatible in spite of the use of a motor having a small capacity by adding a hydraulic pressure mechanism which makes use of Pascal's principle, that is, a booster mechanism to a screw feed type pressure apparatus driven by a motor (see, for example, International Patent Publication No. WO 02/055291).

As shown in FIG. 11, the pressure apparatus comprises a stationary part 10, an output shaft 20 supported on the stationary part 10 to be made slidable in an axial direction, an input shaft 30 supported on the output shaft 20 to be slidable coaxially with the output shaft 20, a ball screw type drive mechanism 40, which causes a motor (not shown) to directly act the input shaft 30 in the axial direction, a connecting mechanism 50, in which the output shaft 20 and the input shaft 30 are connected to each other by a connecting hook 501, a hydraulic pressure mechanism 60, which increases energization of the input shaft 30 according to Pascal's principle to transmit the same to the output shaft 20, and a control mechanism 70, which controls the operation of the hydraulic pressure mechanism 60.

A pressure receiving piston 201 is formed on the output shaft 20. A first fluid chamber A1 and a second fluid chamber A2, which are compartmented in the axial direction by the pressure receiving piston 201, are defined between the stationary part 10 and the output shaft 20. The first fluid chamber A1 and the second fluid chamber A2 are communicated to each other by communication passages 201a, which are formed on the pressure receiving piston 201. Accordingly, the pressure receiving piston 201 and the output shaft 20 can freely slide relative to the stationary part 10 without being little subjected to resistance by a fluid filled in the both fluid chambers A1, A2. Consequently, the output shaft 20 can be moved at high speed by the drive mechanism 40 in a state of being connected to the input shaft 30 by the connecting mechanism 50.

A pressure applying piston 301 is formed on the input shaft 30. A third fluid chamber A3 pressurized by the pressure applying piston 301 is formed between the output shaft 20 and the input shaft 30. The third fluid chamber A3 is communicated to the second fluid chamber A2 by communication holes 202a. Accordingly, by releasing connection by the connecting mechanism 50 and closing the communication passages 201a, the second fluid chamber A2 and the third fluid chamber A3 function as the hydraulic pressure mechanism 60 capable of transmitting energization of the input shaft 30 to the output shaft 20. A pressure applying area of the pressure applying piston 301 is set to be considerably smaller than a pressure receiving area of the pressure receiving piston 201. Therefore, energization of the input shaft 30 is increased according to Pascal's principle to pressurize the output shaft 20 at high thrust. In addition, when the output shaft 20 is pressurized at high thrust, the first fluid chamber A1 is compressed by the pressure receiving piston 201 to be increased in internal pressure. A pressure absorbing piston 101 is provided in the first fluid chamber A1 to absorb an increase in internal pressure.

The connecting mechanism 50 comprises the connecting hook 501 fixed to an upper surface of the input shaft 30, an engagement 502 provided concavely on an upper surface of the output shaft 20, and a connection hook return roller 503 fixed to an upper portion of the stationary part 10. A pawl is formed on a turning end of the connecting hook 501. As shown in FIG. 11, the pawl engages with the engagement 502 whereby the output shaft 20 and the input shaft 30 are connected to each other so as not to make relative movements. In this connected state, the input shaft 30 moves downward to thereby make the output shaft 20 move at high speed. When the input shaft 30 is stopped in movement after high-speed movement of the output shaft 20 to a predetermined position, for example, a position just before a tip end of the output shaft 20 abuts against a pressurized object, the output shaft 20 is moved downwardly of the input shaft 30 under the influence of an inertial force to stop as shown in FIG. 12. Thereby, the connecting hook 501 is disengaged from the engagement 502 and falls inside due to the bias of a spring (not shown) provided about an axis of turning with the result that connection of the output shaft 20 and the input shaft 30 is released. In addition, when the input shaft 30 returns to an uppermost end (FIG. 11), at which the input shaft 30 is disposed in its origin position, after a series of pressurizing actions are terminated, the connecting hook 501 is returned to a position, in which it engages with the engagement 502, by the connection hook return roller 503 to restore connection of the output shaft 20 and the input shaft 30.

The hydraulic pressure mechanism 60 comprises the control mechanism 70, which controls communication between an interior (the second fluid chamber A2 and the third fluid chamber A3) of the hydraulic pressure mechanism 60 and an outside (the first fluid chamber A1), that is, opening and closing of the communication passages 201a to control the operation of the hydraulic pressure mechanism 60. The control mechanism 70 comprises a pin-shaped valve element 701 and an auxiliary valve element 702. The valve elements 701 are supported slidably by support holes 202 provided on the output shaft 20 and the auxiliary valve elements 702 are supported slidably by support shafts 203 provided on the output shaft 20. When the output shaft 20 and the input shaft 30 are connected to each other by the connecting mechanism 50 to make no relative movements, the valve elements 701 retreat so as to open the communication passages 201a as shown in FIGS. 11 and 12 and the auxiliary valve elements 702 are caused by an attracting force provided by built-in magnets (not shown) to shut off communication between the second fluid chamber A2 and the third fluid chamber A3.

Connection by the connecting mechanism 50 is released and the input shaft 30 is moved downward whereby the control mechanism 70 begins the operation of the hydraulic pressure mechanism 60. Owing to downward movement of the input shaft 30, the pressure applying piston 301 raises a hydraulic pressure in the third fluid chamber A3 closed by the auxiliary valve elements 702. As the hydraulic pressure in the third fluid chamber A3 rises, the valve elements 701 are pushed down to close the communication passages 201a. Further, when a hydraulic pressure in the third fluid chamber A3 rises, the auxiliary valve elements 702 are pushed up to provide a communication between the second fluid chamber A2 and the third fluid chamber A3. Thereby, as shown in FIG. 13, the input shaft 30 provided with the pressure applying piston 301, which has a small pressure applying area, and the output shaft 20 provided with the pressure receiving piston 201, which has a large pressure receiving area, are connected hydraulically to each other to enable increasing energization of the input shaft 30 according to Pascal's principle to transmit the same to the output shaft 20. In addition, the magnets built in the auxiliary valve elements 702 are set in attracting force so that after the valve elements 701 closes the communication passages 201a, the auxiliary valve elements 702 provide a communication between the second fluid chamber A2 and the third fluid chamber A3. Also, pins (not shown) are provided upright on upper surfaces of the auxiliary valve elements 702. When the output shaft 20 returns to its origin position, the pins abut against an upper lid body 102 of the stationary part 10 and the auxiliary valve elements 702 are pushed down to an initial position, in which a communication between the first fluid chamber A1 and the second fluid chamber A2 is shut off.

In the case where the output shaft 20 in the pressure apparatus makes high-speed movement and high-thrust pressurization, the connecting mechanism 50 first connects between the output shaft 20 and the input shaft 30 to move the input shaft 30 to a predetermined position at high speed. Subsequently, the input shaft 30 is stopped in the predetermined position whereby the connecting hook 501 turns to release connection of the output shaft 20 and the input shaft 30 as shown in FIG. 12. Thereafter, when downward movement of the input shaft 30 is begun again, pressurization by the pressure applying piston 301 raises the internal pressure in the third fluid chamber A3. Owing to an increase in internal pressure in the third fluid chamber A3, the control mechanism 70 operates to cause the valve elements 701 to close the communication passages 201a and to cause the auxiliary valve elements 702 to provide a communication between the second fluid chamber A2 and the third fluid chamber A3 as shown in FIG. 13. A fluid pushed out from the third fluid chamber A3 by the pressure applying piston 301 having a small pressure applying area flows into the second fluid chamber A2 to push the pressure receiving piston 201, which has a large pressure receiving area, thereby pressurizing the output shaft 20 at high thrust.

When high-thrust pressurization is terminated, a fluid compressed in the first fluid chamber A1 causes a reaction force from the pressure absorbing piston 101 to push back the valve elements 701 to open the communication passages 201a. Thereby, a fluid can move to the first fluid chamber A1 from the second fluid chamber A2. Accordingly, by moving the input shaft 30 upward, the output shaft 20 can be returned to the origin position. When the output shaft 20 is returned to the origin position, the auxiliary valve elements 702 are pushed down to an initial position, in which a communication between the second fluid chamber A2 and the third fluid chamber A3 is shut off.

The pressure apparatus makes high-speed movement and high-thrust pressurization compatible in spite of the use of a motor having a small capacity, but involves the following problems.

Firstly, the auxiliary valve elements 702 provided in order to shut off a communication between the second fluid chamber A2 and the third fluid chamber A3 makes the control mechanism 70 complex in construction causing an increased risk of generation of a failure.

Secondly, there is a need of surely returning the output shaft 20 to the origin position in order to return the auxiliary valve elements 702 to an initial position, in which a communication between the second fluid chamber A2 and the third fluid chamber A3 is shut off. Accordingly, in the case where it is unnecessary to retreat the output shaft 20 so much, there is a need of returning the output shaft 20 to the origin position, for example, even when it suffices that a spacing between the output shaft 20 and a pressurized object be not considerably large, with the result that loss in time is caused.

Thirdly, the valve elements 701 are held by slide resistance between the valve elements 701 and the support holes 202. When the slide resistance becomes too large, there is a fear that at the time of switchover to high-thrust pressurization from high-speed movement the auxiliary valve elements 702 act prior to the valve elements 701 to be unable to close the communication passages 201a. Therefore, it is necessary to strictly control the dimensional relationship between the valve elements 701 and the support holes 202 at the time of manufacture.

Fourthly, while the valve elements 701 are pushed back by a hydraulic pressure in the first fluid chamber A1 after high-thrust pressurization is terminated, the valve elements 701 are formed in a pin-shaped manner to be inserted into the communication passages 201a and small in pressure receiving area. Therefore, there is a fear that only the hydraulic pressure in the first fluid chamber A1 does not return the valve elements 701 fully to the initial position. That is, the communication passages 201a are incompletely opened and so there is a possibility that the output shaft 20 becomes later in returning, which is accompanied by movement of a fluid to the first fluid chamber A1 from the second fluid chamber A2.

In view of the problems, the present disclosure constructs a control mechanism which controls the operation of a hydraulic pressure mechanism, so as to make the control mechanism simple in construction and to enable the control mechanism to surely operate while the control mechanism is easy to manufacture. Also, a pressure apparatus is provided in which an output shaft is not necessarily returned to an origin position and a stroke of operation can be changed appropriately.

• Provisional Patent
• Utility Patent

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