JPH04102732A - Dashpot - Google Patents

Abstract

PURPOSE:To improve the stability of the operation characteristics in the case where the pressure of the sealed fluid increases, by fitting a packing so as to be movable in the longitudinal direction and surround a piston rod, in a packing chamber which is formed contiguously to a partitioning wall. CONSTITUTION:When the fluid sealed in the first chamber 21 and the second chamber 22 is expanded by the temperature rise, and the pressure increases, or the pressure in the first chamber 21 is increased temporarily by the spring load of a return spring 38 during the return process of a piston 23, the high pressure fluid is introduced into a packing chamber 13 from the gap of a through hole 3, and a packing 14 is press-shifted forwardly. Then, the capacity of the part which communicates to the first chamber 21 of the packing chamber 13 increases, and absorbes the pressure rise. When the pressure of the fluid lowers, the packing 14 returns to the contact position where the packing 14 contacts a partitioning wall 2, accompanied with the retreat of a piston rod 4. A packing receiving part 15 in front of the packing 14 acts as stopper for preventing the packing 14 from forwardly shifting largely, together with a piston rod 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dashpot used to reduce the operating speed of controlled equipment and prevent sudden changes in force or position.

(Prior art) There are two types of dashpots: pneumatic and liquid type. It is well known that a diaphragm is generally used as a shock absorbing member for a device to be damaged, and a diaphragm or a piston is used for a liquid type device.

Among these, the pneumatic type is, for example,
As disclosed in Publication No. 9 and Japanese Patent Publication No. 59-30898, it is widely used for controlling the closing speed of intake throttle valves in automobile engines because it uses atmospheric air and can be easily installed. It is unavoidable that the diameter is large, and if the stroke is increased, the diameter becomes even larger, which not only limits the installation location, but also has the disadvantage that the initial distortion of the diaphragm causes large variations in the starting point of operation. be. In addition, even if the fluid is liquid, if the temperature changes significantly, the volume and therefore the pressure will change considerably. Therefore, especially in a structure where the fluid is sealed in a closed space, a pressure absorbing means is installed to ensure safety when the pressure increases. It is necessary to take measures to prevent leakage, but since there is no suitable pressure absorbing means other than a diaphragm or bellows, even a piston-type one would be quite large.

(Problems to be Solved by the Invention) The problems to be solved by the present invention are that conventional dashpots are large and have restrictions on installation locations, have unstable operating characteristics and tend to lack reliability, and pressure of the enclosed fluid. The point is that it is difficult to take countermeasures against the increase.

That is, the present invention is a dashpot with a compact configuration that is small in diameter, is less subject to installation location restrictions, and has stable operating characteristics, and is particularly advantageous when the overall size increases when the pressure of the enclosed fluid increases. This design aims to improve the stability of operating characteristics by providing a function to absorb pressure increases without causing any damage.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a cylinder tube having a partition wall that divides the interior into two spaces, front and rear, and a cylinder tube that extends vertically through the front space and penetrates the partition wall. A piston rod inserted into the space, a piston attached to the piston rod and dividing the rear space into a first chamber on the partition wall side and a second chamber on the opposite side, and pushing the piston toward the partition wall. A return spring, a communication passage and a throttle passage that communicate the first chamber and the second chamber, a check valve that opens and closes the communication passage to reduce the movement speed of the piston in the direction of the second window, and a space in front of the It is equipped with packing that maintains the airtightness of the rear space when installed. The banking was inserted into a packing chamber formed adjacent to the partition wall so as to be movable back and forth, surrounding the piston rod.

In addition to the above, the piston rod is provided with a spring holder that is movably fitted in the piston rod and installed in front of the packing, and a push spring that pushes the spring holder rearward.

(Operation) In the non-operating state, the piston is pushed back by the spring to a position where movement is prevented by the partition wall, and the starting point of operation is kept constant. When the controlled device pushes the piston rod, the check valve closes and reduces the operating speed by restricting fluid movement from the second chamber to the first chamber.

When the fluid sealed in the first and second chambers expands due to temperature rise, or the first chamber is compressed by the spring load of the return spring and the pressure increases, the gap between the partition wall and the piston rod increases. The packing moves under the pressure of the fluid that enters the packing chamber, and the spring receiver moves with it to absorb the pressure increase. When the pressure decreases, the packing returns due to the movement of the piston rod, and a push spring assists in the return movement.

(Example) The present invention will be described in detail with reference to the drawings.

The body has a partition wall 2 in the center, and this partition g12 divides the interior into two spaces, front and rear.The cylinder tube 1 has both ends open, and the front space is vertically partitioned from the front open end! ! A piston rod 4 is inserted through the through hole 3 of 2, and this piston rod 4 is fitted into the guide hole 6 of the guide member 5 fixed to the open end, and the piston rod 4 is inserted through the through hole 3 and the guide hole 6. It is supported for linear reciprocating motion. The guide member 5 is made of hard synthetic resin, and includes a flange portion 7 that is fitted into the step #1a at the end of the cylinder tube 1 and fixed by an outer caulking portion 1b, and a collar portion 8 that extends outward.
It has

Further, a small diameter portion 9 having an annular groove 10 is formed at the tip of the piston rod 4 protruding from the cylinder tube 1, and a hard synthetic resin cap 1 having a larger diameter than the piston rod 4 is formed.
1 is engaged with the annular groove 10 and attached to the diameter portion 9, and the protruding portion of the piston rod 4 is fixed at both ends by fitting into the tip of the piston rod 4 and the small diameter portion 8a of the collar part B. It is covered by a bellows-shaped dust cover 12.

In the space in front of the cylinder tube 1, that is, the inside between the partition wall 2 and the guide member 5, a packing chamber 13 with a small diameter on the partition wall 2 side is formed by a stepped portion 1c. The collar portion 16 of the spring receiver 15, which is loosely fitted to the piston rod 4, is inserted and is slightly separated from the end surface of the packing 14. The flange portion 17 of the spring receiver 15 is located at the large diameter portion of the guide member 5@, and is moved in the direction in which it contacts the stepped portion 1c by the push spring 1B, which is a compression coil spring inserted between the flange portion 7 of the guide member 5. receives the power of

The rear open end of the cylinder tube l is hermetically sealed by a plug 20 having an O-ring 19 that engages with the stepped portion 1d and is pressed and fixed by the outer caulking portion 1c. The space behind the cylinder tube l, that is, the partition wall 2 and the plug 20
The inside between the two has a uniform diameter, and is partitioned into a first chamber 21 on the partition wall 2 side and a second chamber 22 on the plug 20 side by a piston 23 attached to a piston rod 4 protruding from this part.

That is, a retaining ring 24 is attached and fixed to a portion of the piston rod 4 that protrudes from the partition wall 2 to the rear space, and a bowl-shaped piston stopper 25, a piston 23, and a piston retainer 26 are sequentially attached to the piston rod 4 on the tip side thereof. It is fitted. The piston 23 is made of synthetic rubber, synthetic resin, or leather;
The disc-shaped main body g23m sandwiched between the piston stopper 26 and the piston retainer 26 and the second chamber 2 from its outer periphery
The cylindrical peripheral part 23b has an elastic cylindrical peripheral part 23b which becomes larger in diameter toward the cylinder part 2 and is inscribed in the cylinder part 11, and the cylindrical peripheral part 23b is inscribed in the cylinder part 1 to such an extent that it can be rotated by hand. The piston retainer 26 is made of hard synthetic resin, and a metal sleeve 27 is embedded and fixed by insert molding on the inner peripheral surface of the tip portion that is fitted into the piston rod 4, and this sleeve 27 is press-fitted into the piston rod 4. The piston stopper 25 and the piston 23 are
is pressed and fixed to the retaining ring 24.

The piston retainer 26 consists of a flange portion 28 overlaid on the main body portion 23m of the piston 23, a cylindrical portion 29 extending rearward of the piston rod 4, and a bottom portion 30 at the rear end, and has a fluid inlet/outlet 31 in the bottom portion 30. The piston rod 4 has a communication passage 32 that is open to the rear end surface and the outer circumferential surface facing the first chamber 21, and the communication passage 32 is connected to the piston rod 4 in a small diameter portion behind the press-fitting point of the sleeve 27. It has a throttle passage 33 consisting of an orifice communicating with a valve chamber 34 surrounded by a piston retainer 26. Further, a valve body 35 made of a ball that opens and closes the communication passage 32 is inserted into the valve chamber 34, and a valve seat 3 at the end of the fluid inlet/outlet 31 and the communication passage 32 is inserted.
6. The valve chamber 34 and the valve body 35 constitute a check valve 37.

Furthermore, a return spring 38 made of a compression coil spring is press-fitted between the flange portion 28 and the plug 20.

Incidentally, a screw 39 for attachment is provided on the outer peripheral surface of the cylinder tube 1.

In this embodiment configured in this manner, the piston stopper 25 hits the partition wall 2 due to the spring load of the return spring 38 in the non-operating state as shown in FIG. 1, thereby minimizing the volume of the first chamber 21. The piston 23 moves to the position, and the piston rod 4
The tip of the cylinder protrudes the most from the cylinder tube 1.

When the controlled device comes into contact with the cap 11 and moves the piston rod 4 backward, the first chamber 21 expands and the second chamber 22 contracts, increasing its internal pressure, so the valve body 35 closes the communication path 32. The fluid in the second chamber 22 is transferred from the throttle passage 33 to the communication passage 3.
2 and is gradually introduced into the first chamber 21 to reduce the operating speed of the controlled equipment. When the controlled device leaves, the return spring 3
The piston 23 and piston rod 4 move forward due to the spring load B, and the valve body 35 opens the communication passage 32 to contract the first chamber 21 and increase its internal pressure, allowing the fluid in the first chamber 21 to flow into the second chamber 22. Return the piston rod 4 to the inoperative position by moving it without resistance.

The present invention is characterized in that the packing 14 has a pressure absorbing function. That is, the first chamber 21 and the second chamber 22
When the fluid sealed in the through hole 3 expands due to a rise in temperature and the pressure increases, or when the pressure in the first chamber 21 increases temporarily due to the spring load of the return spring 38 when the piston 23 returns, the pressure in the first chamber 21 increases. High-pressure fluid is introduced into the packing chamber 13 from the gap and presses the packing 14 forward,
The volume of the portion of the packing chamber 13 communicating with the first chamber 21 is increased to absorb the pressure increase. When the pressure of the fluid decreases, the piston rod 4 retreats and the packing 14 closes against the partition wall 2.
Return to the position where it touches.

The spring receiver 15 placed in front of the packing 14 also works as a stopper to prevent the packing 14 from moving forward too much together with the piston rod 4, but the pressure of the fluid increases greatly and the packing 14 comes into contact. After that, the push spring 18 is compressed and moved forward to further increase the volume of the rear part of the banking 14 to absorb the pressure, and when the pressure decreases, the spring load of the push spring 18 changes the position of the piston rod 4. Its main function is to move the spring receiver 15 and the packing 14 rearward and return them to their initial positions regardless of their movement.

In this way, since the packing 14 is movable in response to pressure, there is no need to press it against the piston rod 4 with strong force in order to seal in high-pressure fluid, and an inexpensive packing 14 can be used, and the piston rod 4 can be moved. By reducing the resistance to the reciprocating motion of 4, it is possible to appropriately control the controlled device.

In this embodiment, the maximum compression length of the push spring 18 is set so that the packing 14 can move to the tip of the packing chamber 13, so as not to impair airtightness (FIG. 3).

According to the configuration of this embodiment, firstly, the tip of the piston rod 4 is made into a small diameter portion 9 and a cap 11 made of synthetic resin is attached. By inserting the unattached piston rod 4 from the rear space, assembly is facilitated, there is no inconvenience such as the packing 14 being hooked on the piston rod 4 and causing damage, and the cap 11 is in contact with the controlled equipment. This has the advantage of reducing wear.

Second, by fitting the piston stopper 25, piston 23, and piston retainer 26 as separate parts to the piston rod 4, the piston rod 4 can be made smaller in diameter, and since the piston stopper 25 is in contact with the partition wall 2, the piston The actuation starting point of the rod 4 can be kept constant, and since the piston 23 is inscribed in the cylinder tube 1 so that it can be rotated by hand, it is necessary to assemble the piston after it is assembled. It has the advantage that it can be confirmed by turning the rod 4.

Thirdly, since the piston rod 4 and the piston retainer 26 form a valve chamber 34 containing a valve body 35, the check valve 3
7 has a compact configuration, especially the piston retainer 2.
6 is made of synthetic resin, which has the advantage of being lightweight.

(Effects of the Invention) Since the dashpot of the present invention has a cylinder or piston shape, it has a small diameter and is less subject to restrictions in its installation location. In addition, the movement of the piston, which is a buffer member, is prevented by the partition wall, and the shaft sealing packing is installed on the opposite side of the piston across the partition wall, so that the piston is kept in a fixed position by the partition wall when not in operation. The starting point of operation does not change. Moreover, even if the fluid is liquid, the amount of sealed liquid is small, so there is almost no bubble generation at high temperatures, so there is little concern that the characteristics will fluctuate, and furthermore, the piston rod is supported by the partition wall, so it operates stably. .

In particular, according to the present invention, since the packing is inserted into the packing chamber so as to be movable back and forth according to the pressure of the sealed fluid, the pressure increase of the sealed fluid can be absorbed very skillfully without increasing the size of the entire device. Even if the packing is not brought into contact with the piston rod with strong force, it does not cause leakage of the sealed fluid or suction of outside air, and the resistance to the piston rod is small, improving the stability of operating characteristics and properly controlling the controlled equipment. . In addition, when a spring support and a push spring are provided, the packing can be moved and returned to the initial position in response to pressure fluctuations regardless of the movement of the piston rod, and the loose check valve 38...return spring ,

Claims (1)

[Scope of Claims] 1. A cylinder tube having a partition wall that divides the interior into two front and rear spaces, and a piston rod that traverses the front space, penetrates the partition wall, and is inserted into the rear space. a piston attached to the piston rod and dividing the rear space into a first chamber on the partition wall side and a second chamber on the opposite side; a return spring that pushes the piston toward the partition wall; A communication passage and a throttle passage that communicate the first chamber and the second chamber, a check valve that opens and closes the communication passage to reduce the movement speed of the piston toward the second chamber, and is installed in the space in front of the chamber. packing for keeping the rear space airtight;
The dashpot is characterized in that the packing is placed in a packing chamber formed adjacent to the partition wall so as to be movable back and forth surrounding the piston rod. 2. In addition to the structure described in claim 1, a spring receiver is fitted in the piston rod so as to be movable back and forth and installed in front of the packing;
A dash pot characterized by comprising a push spring that pushes the spring holder backward.