JPH04357309A - Cylinder for fluid pressure device - Google Patents

Abstract

PURPOSE:To provide a cylinder device for a hydraulic device or a pneumatic device which can generate a large thrust at the beginning of retreating motion of a piston rod without reducing a moving speed on the way of stroke, and also can house a cushion mechanism on a rod end side. CONSTITUTION:A large diametral part 3 is provided on a rod end side of a cylinder tube 1. A floating piston 31 is integrally provided with a piston part 32 fitted to the large diametral part 3, and a ram part 33 fitted to the cylinder tube 1. Fluid chambers on both ends of the floating piston 31 are communicated with each other through a flow passage 37. With regard to a cushion mechanism, a cushion ram 72 which is inserted through the flow passage 37 is provided on a base end of a piston rod 22. Then, there is provided a cushion flow passage 78 provided with a check valve 76 between an intermediate fluid chamber 38 between a piston 21 and the floating piston 31, and a pressure port 8 on the rod end side.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder used as an actuator for a hydraulic or pneumatic device, and more particularly to a cylinder having a structure that increases the initial driving force when a piston rod retracts.

0002

[Prior Art] For example, when using a mold clamping device of an injection molding machine, the mold is clamped by a large-diameter mold clamping cylinder, and the mold is moved by a small-diameter mold opening/closing cylinder or boost cylinder. When moving the mold in the mold closing direction and when moving the mold in the mold opening direction, due to the difference in the pressure receiving area of the piston of the mold opening/closing cylinder, the driving force when opening the mold is smaller than the driving force when closing the mold. The greatest driving force is required of the mold opening/closing cylinder when the movable mold is separated from the fixed mold, and when the piston rod starts moving in the retraction direction. Therefore, the pressure-receiving area on the rod end side of the piston must be determined from the driving force required during mold separation, but in this case, the pressure-receiving area on the head end side of the piston becomes larger than necessary, making it difficult to quickly open and close the mold. Then, a hydraulic pump with a large discharge amount is required.

0003

[Problem to be solved by the invention] Therefore, in this invention,
By providing a cylinder with a structure that can generate a large driving force at the start of movement when the piston rod moves in the retracting direction, it can be used as a mold opening/closing cylinder for an injection molding machine with the above structure, for example. It is an object of the present invention to provide a cylinder which can obtain a mold separation force of a certain magnitude and which does not reduce the moving speed of a piston during mold opening/closing.

Another object of the present invention is to provide only one pressure port on the head end side and one on the rod end side so that the cylinder can be used in place of a conventional cylinder.

[0005]

[Means for Solving the Problems] The cylinder of the present invention has the following features:
A large diameter portion 3 is provided on the rod end side of the cylinder tube 1, and a piston portion 32 is airtightly fitted into the large diameter portion, and a piston portion 32 extends from the piston portion toward the head end side and is airtightly fitted into the cylinder tube 1. A floating piston 31 integrally equipped with a ram portion 33 is installed. and piston rod 2
The pressure port 8 on the rod end side that moves the piston 2 in the retraction direction is opened on the rod end side from the floating piston 31,
A cavity 36 formed between the piston portion 32 and the ram portion 33 of the floating piston is open to the atmosphere, and is provided with a flow path 37 that allows the fluid chambers on both sides of the floating piston 31 to communicate with each other. Since the piston rod 22 passes through the center of the floating piston 31, the flow path 37 is most easily formed by providing a gap in this penetrating portion. The structure of the portion located closer to the head end than the floating piston 31 may be the same as that of the conventional structure.

A cushion mechanism having the following structure can be provided on the rod end side of the cylinder having the above structure. A through hole 71 having an inner diameter larger than the outer diameter of the piston rod 22 is provided at the center of the floating piston 31 to form a flow path 37 that communicates the fluid chambers on both sides of the floating piston 31 with each other. On the other hand, a cushion ram 72 is provided at the connecting portion between the piston 21 and the piston rod 22 and has a length corresponding to a desired cushion stroke, and is inserted into the through hole 71 with a slight play. An intermediate port 74 communicating with the intermediate fluid chamber 38 formed between the piston 21 and the floating piston 31 is provided, and a check valve 76 and a throttle are provided between the intermediate port 74 and the pressure port 8 on the rod end side. A cushion flow path 78 is provided in which valves 75 are connected in parallel. This cushion flow path may be formed by external piping as shown in FIG. 8, or may be built into the cylinder as shown in FIG. 11. The direction of the check valve 76 is such that it blocks fluid flowing from the intermediate fluid chamber 38 to the pressure port 8 on the rod end side.

[0007] The cushion mechanism on the head end side is
It is sufficient to adopt a mechanism similar to the conventional one in which a cushion ram 81 is provided on the side opposite to the rod of the piston 21.

[0008]

[Operation] When fluid pressure is supplied to the head end side of the cylinder, the fluid in the intermediate fluid chamber 38 formed between the piston 21 and the floating piston 31 passes through the flow path 37 to the pressure port 8 on the rod end side. The piston 21 moves to the rod end side and the piston rod 22 advances by the same operation as a conventional cylinder. When the piston reaches near the end of the piston stroke, the piston 21 comes into contact with the end of the floating piston on the ram section 33 side, and the floating piston 31 is pushed by the piston 21 and moved toward the rod end side. The end of the piston portion 32 comes into contact with the stopper 39 on the rod end side, and the movement of the piston 21 toward the rod end is stopped.

Pressure port 8 on the rod end side of the cylinder
When fluid pressure is supplied to the floating piston, the fluid pressure acts on the piston portion 32 of the floating piston, and a force is generated to move the floating piston 31 toward the head end side due to the difference in area with the ram portion 33. Furthermore, this fluid pressure also acts on the rod-side surface of the piston 21, so the piston 21 is ultimately driven by a force equal to the fluid pressure multiplied by the area of the large diameter portion 3 of the cylinder minus the cross-sectional area of the piston rod 22. be done. After the piston portion 32 of the floating piston collides with the end of the cylinder tube 1, the fluid flowing in from the pressure port 8 on the rod end side flows into the intermediate fluid chamber 38 through the flow path 37, and the piston 21 It moves toward the head end only by the fluid pressure acting on the side surface, collides with the stopper on the head end side, and stops.

The volume of the empty chamber 36 increases or decreases as the floating piston 31 moves back and forth.
Since the chamber is opened to the atmosphere, the change in volume of the empty chamber does not hinder the movement of the floating piston 31.

Next, the operation when the cushion mechanism is provided on the rod end side of the cylinder will be explained. When the piston 21 is moving toward the rod end, the floating piston 31 is moving toward the head end because pressure due to the fluid resistance of the return pipe acts on both sides of the floating piston 31. When the tip of the cushion ram 72 at the base of the piston rod 22 is inserted into the through hole 71 of the floating piston 31 in this state, the flow of fluid through this through hole is restricted, and the pressure between the intermediate fluid chamber 38 and the rod end side is A pressure gradient is generated between the piston 31 and the port 8, and the floating piston 31 moves toward the rod end due to the pressure difference. After that, the fluid in the intermediate fluid chamber 38 pushed by the piston 21 which is about to continue its movement flows through the throttle valve 75 to the pressure port 8 on the rod end side, and due to the flow path resistance of the throttle valve 75, the fluid in the intermediate fluid chamber 38 A pressure increase occurs at 38, and this pressure increase causes the piston 21 to gradually decelerate, and then reaches the stroke end, where the piston 21 stops.

On the other hand, when fluid pressure is applied to the pressure port 8 on the rod end side, the fluid pressure acts on the floating piston 3.
1 and the end surface of the cushion ram 72 to cause the floating piston 31 and the piston 21 to simultaneously start backward movement, and the floating piston 31 came into contact with the end of the cylinder tube 1 and stopped moving. After that, check valve 7
6 and flows into the intermediate fluid chamber 38, and the fluid flows from the pressure port 8 on the rod end side through the flow path 37 to the intermediate fluid chamber 3.
The piston 21 separates from the floating piston 31 and moves toward the head end side without receiving any resistance due to the fluid flowing into the piston 8.

[0013]

[Embodiment] Figures 1 to 4 show a first embodiment of the cylinder of the present invention, in which 1 is a cylinder tube, 2 is a cylinder tube, and 2 is a cylinder tube.
is a cylinder block that forms the large diameter part 3 of the cylinder,
Cylinder tube 1 and cylinder block 2 are substantially integral. 4 is a head end flange, 5 is a rod end flange, 6 is a tie rod that connects both flanges 4 and 5 with the cylinder tube 1 and cylinder block 2 in between, 7 is a pressure port on the head end side, and 8 is on the rod end side. pressure port, 9 is the drain port, 10 and 11
is a seal ring.

21 is a piston fitted into the cylinder tube 1; 22 is a piston rod that is substantially integral with the piston 21; 23 is a seal ring provided at the sliding portion between the piston 21 and the cylinder tube 1; and 24 is a piston. A seal ring 31 provided at the sliding portion between the rod 22 and the rod end flange 5 is a floating piston.

The floating piston 31 is connected to the cylinder block 2
A piston part 32 fitted into the large diameter part 3 of the cylinder formed by the cylinder, and a ram part 33 fitted into the cylinder tube 1.
The fitting portion is sealed by seal rings 34 and 35. Said drain port 9
is open to a cavity 36 formed between the piston part 32 and ram part 33 of the floating piston, and the cavity 36 is communicated with the oil tank and opened to the atmosphere. floating piston 3
A through hole having a diameter larger than the outer diameter of the piston rod 22 is provided in the center of the piston rod 1, and a flow path 37 is formed between the piston rod 22 and the piston rod 22 inserted through the through hole.

FIGS. 2 to 4 are diagrams showing the operation of this cylinder. FIG. 2 shows the state when the piston 21 is at the head end end, and at this time the floating piston 31 is moved from the rod end side. The supplied fluid pressure causes the piston portion 32 to move toward the head end until it comes into contact with the end of the cylinder tube 1. FIG. 3 shows the state when the piston 21 is in the middle of its stroke, and when the piston rod 22 is advanced, the pressure port 7 on the head end side
The fluid in the intermediate fluid chamber 38 formed between the floating piston 31 and the piston 21 is supplied with working fluid from the flow path 3.
7 and flows out from the pressure port 8 on the rod end side. Further, when the piston rod 22 is retracted, the working fluid flowing in from the pressure port 8 on the rod end side flows into the flow path 37.
The fluid flows through the intermediate fluid chamber 38 and moves the piston 21 toward the head end. In any of the above cases, the floating piston 31 is held with the piston part 32 in contact with the end of the cylinder tube 1 due to the difference in pressure receiving area between the piston part 32 and the ram part 33.

FIG. 4 shows the state when the piston 21 has moved to the rod end. At this time, the floating piston 31
is pushed by the piston 21 and moves toward the rod end, and the piston portion 32 collides with a stopper 39 formed on the rod end flange 5, so that the floating piston 31 and the piston 21 are stopped. For details on the operation at this time, see
Since it was explained in the section of the operation above, it will be omitted here.

FIGS. 5 to 7 show an example of a mold clamping device for an injection molding machine using the cylinder having the above structure as a mold opening/closing cylinder. In the figure, 41 is a fixed platen, 42 is a movable platen, 43 is an adjustment plate, 44 is a tie bar,
45 is a nut that fastens the adjustment plate 43 and the tie bar 44, 46 is a motor for moving the adjustment plate 43, and 47 to 49 are for transmitting the rotation of the motor 46 to the nuts 45 of the four tie bars 44. A gear train is schematically shown. 51 is a fixed mold, and 52 is a movable mold.

53 is an ejector cylinder fixed to the movable platen 42, 54 is a mold clamping cylinder, and a mold clamping ram 55 is fitted into the mold clamping cylinder 54. Mold clamping ram 55
A lock ring 58 having a female spline 57 that engages with the male spline is rotatably attached to the adjustment plate 43, and the lock cylinder 5 rotates the lock ring.
9 is provided. The mold opening/closing cylinder 61 having the structure of the present invention is attached to the adjustment plate 43, and the tip of the piston rod 22 is fastened to the movable platen 42.

When pressure oil is supplied to the head end side of the mold opening/closing cylinder 61 from the mold opening state, the movable platen 42 moves forward, and when the molds 51 and 52 come into contact, the piston 21 of the mold opening/closing cylinder 61 moves forward. When the rod end is reached (more precisely, there is a gap left to absorb the elongation of the tie bar during mold clamping), the male spline 56 of the mold clamping ram comes off from the female spline 57 of the lock ring. In this state, the lock ring 58 is rotated by the lock cylinder 59 to shift the phase of the male spline 56 and the female spline 57 (FIG. 7), thereby preventing the male spline 56 from retreating. Then, pressure oil is supplied to the hydraulic chamber 62 of the mold clamping cylinder 54, and the mold clamping ram 55 is advanced by an amount corresponding to the elongation deformation of the tie bar 44 and the compressive deformation of the molds 51, 52, etc. to close the molds 51, 52. Clamp the mold. In this state, the molds 51 and 52
After the molten resin is cooled and solidified, the hydraulic pressure in the hydraulic chamber 62 of the mold clamping ram is released, and pressure oil is supplied to the back pressure chamber 63 of the mold clamping ram, and the rear end of the male spline 56 is The pressing force between the lock ring 58 and the lock cylinder 59 is released.
Then, the lock ring 58 is rotated so that the phases of the male spline 56 and the female spline 57 match.

Then, pressurized oil is supplied to the rod end side of the mold opening/closing cylinder 61 to open the molds 51 and 52. At this time, the mold opening/closing cylinder 61 having the structure of the present invention exerts a large force at the beginning of mold opening to separate the molds 51 and 52.
Thereafter, the movable platen 42 is quickly moved to the mold opening position. When separating the molds 51 and 52, it is necessary to separate the molds against the adhesive force of the resin, and a strong force is required. By increasing the diameter of the piston 32, the force of the mold opening/closing cylinder 61 at the start of mold opening can be increased as much as possible, and after the molds 51 and 52 are separated, the size of the piston portion 32 of the floating piston Regardless of the situation, the piston 21 can be quickly retreated, which is extremely convenient.

FIGS. 8 to 11 show an embodiment in which a cushion mechanism is provided on the rod end side of the cylinder. Hereinafter, only the parts that are different from the first embodiment described above will be explained.

Reference numeral 71 denotes a through hole provided at the center of the floating piston 31, and the through hole 71 has a diameter larger than the outer diameter of the piston rod 22. A cushion ram 72 and a stopper ring 73 are formed at the connecting portion between the piston 21 and the piston rod 22, with diameters changing in two stages. The cushion ram 72 is connected to the through hole 7 of the floating piston.
1 with a slight play, and by inserting the cushion ram 72 into the through hole 71,
The flow of oil through the through hole 71 is restricted. The cushion ram 72 may have a slightly conical outer diameter so that the flow of oil through the through hole 71 is gradually restricted.

The cylinder tube 1 has an intermediate port 7 that opens into an intermediate fluid chamber 38 formed by the piston 21, the ram portion 33 of the floating piston 31, and the cushion ram 72 when the piston 21 approaches the rod end side.
4 is provided. The stopper ring 73 is provided to prevent the intermediate port 74 from being closed by the ram portion 33 of the floating piston or the piston 21 when the floating piston 31 moves from side to side. This intermediate port 74 is communicated with the pressure port 8 on the rod end side through an external pipe 77 in which a throttle valve 75 and a check valve 76 are connected in parallel.

A cushion ram 81 is provided on the opposite rod side of the piston 21 to provide a cushioning effect to the piston 21 at the stroke end on the head end side. When this cushion ram 81 is inserted into the cushion hole 82 provided in the head end flange 4, it restricts the flow rate of fluid flowing from inside the cylinder tube 1 to the pressure port 7 on the head end side, thereby reducing the impact on the head end side. It has a known structure that absorbs.

The operation of the cushion mechanism constructed as above is as explained in the section of the operation above, and FIG. 8 shows that the tip of the cushion ram is connected to the through hole 71 of the floating piston 31
9 shows a state in the middle of the cushion, and FIG. 10 shows a state in which the piston 21 reaches the end of its stroke and stops.

From the state shown in FIG. 8, the floating piston 31 moves to the stroke end on the rod end side due to the pressure increase in the intermediate fluid chamber 38, and after the floating piston 31 stops, the pressure in the intermediate fluid chamber 38 increases rapidly, resulting in a cushioning action. is started. The piston 21 then stops at the end of its stroke after passing through the intermediate state shown in FIG. The stroke end of the piston 21 may be regulated by the stroke end of the cylinder itself or by the moving end of a member driven by the piston rod 22. FIG. 10 shows the latter case, for example, when the advancing stroke of the piston 21 is restricted by the contact between the movable mold and the fixed mold of the injection molding machine described above. The stroke allowance Tp at this time is a stroke that absorbs the elongation of the tie bar 44 when the mold is fastened by the mold clamping cylinder, for example in the above-mentioned injection molding machine.

In the embodiment shown in FIGS. 8 to 10, the check valve 76 and the throttle valve 75 are formed by external piping 77, but as shown in FIG. The throttle valve 75 and check valve 76 can also be built into the cylinder itself. The throttle valve shown in FIG. 11 is a needle valve, and the check valve is a ball check valve, and the intermediate fluid chamber 38 and the pressure port 8 on the rod end side, respectively.
It is provided in the middle of cushion channels 78 and 79 that connect the two. The structure shown in FIG. 11 has a structure in which the strength of the cushion can be adjusted by rotating a screw 84 provided with a needle 83, but if such adjustment is not necessary, the floating piston By managing the play between the through hole 71 and the cushion ram 72,
It is also possible to have a structure in which the throttle valve 75 and its cushion flow path 78 are omitted.

[0029]

[Effects of the Invention] According to the structure of this invention explained above,
When moving the piston in the direction of retracting the piston rod, the pressure-receiving area of the floating piston on the rod side of the piston is added at the beginning of the movement, so the retracting movement of the piston rod can be started with a large force. After the piston rod starts to retreat, it will move back with a force and speed corresponding to the pressure receiving area on the rod side of the piston, similar to a normal fluid pressure cylinder, and a large force is required at the start to move the piston rod back. It is extremely useful as a fluid pressure cylinder for use in locations where:

Furthermore, since the arrangement of the pressure ports is the same as that of a conventional double-acting cylinder, there is no need to change the hydraulic circuit when using the cylinder of the present invention in place of a conventional cylinder.
It has the feature of not complicating the hydraulic circuit.

[0031] Also in such a structure in which a floating piston is provided, it is possible to provide a cushion mechanism at the end of the rod, and it is also possible to obtain a cylinder in which no impact occurs at the end of the stroke.

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view of the cylinder of the first embodiment

[Figure 2] Cross-sectional view when the piston is on the head end side

[Figure 3] Cross-sectional view when the piston is in the middle of its stroke

[Figure 4] Cross-sectional view when the piston moves to the rod end end

[Figure 5] Cross-sectional side view of the mold clamping device of an injection molding machine

[Figure 6] Rear view of mold clamping ram in unlocked state

[Figure 7] Rear view of mold clamping ram in locked state

[Fig. 8] Cross-sectional view of the cylinder of the second embodiment

[Figure 9] Cross-sectional view of the state in the middle of cushioning operation

[Figure 1
0] Cross-sectional view when the piston reaches the rod end

[Fig. 11] Partial sectional view of the cylinder of the third embodiment

[Explanation of symbols]

1 Cylinder tube 3 Large diameter part 8 Pressure port 31 Idle piston 32 Piston part 33 Ram part 37 Flow path 61 Mold opening/closing cylinder 71 Through hole 72 Cushion ram 75 Throttle valve 76 Check valve

Claims (2)

[Claims] Claim 1: A large diameter part (3) is provided on the rod end side of the cylinder tube (1), and a piston part (32) is airtightly fitted into this large diameter part, and from the piston part to the head end side. A floating piston (31) integrally equipped with a ram part (33) that extends and is hermetically fitted into the cylinder tube (1) is installed, and a pressure port (8) on the rod end side is connected to the floating piston (31). ) is opened toward the rod end side, and the empty chamber (36) between the piston part and the ram part of the floating piston (31) is open to the atmosphere, and the fluid chambers on both sides of the floating piston (31) are communicated with each other. A cylinder of a fluid pressure device, in which a flow path (37) is provided. 2. The flow path (37) according to claim 1 is formed by providing a through hole (71) in the center of the floating piston (31) with a diameter larger than the outer diameter of the piston rod (22), Piston (21) and piston rod (22)
A cushion ram (72) is provided at the connecting portion of the through hole (71) to be inserted into the through hole (71) with a slight play.
The intermediate fluid chamber (38) formed between the piston (21) and the ram portion (33) of the floating piston (31) when the piston (21) is located near the stroke end on the rod end side and the rod end side A cushion flow path (78) in which a check valve (76) and a throttle valve (75) are connected in parallel is provided between the pressure port (8) and the check valve (76).
Cylinder according to claim 1, characterized in that the intermediate fluid chamber (38) blocks the flow from the intermediate fluid chamber (38) to the rod end pressure port (8).