JPH0626773B2 - Fluid pressure return type spring clamp - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluid pressure return type spring clamp of a type that is unclamped by a fluid pressure such as hydraulic pressure or air pressure and is clamp-driven by a clamp spring. It is a technology that keeps the clamping force constant even when the position changes.

《Prerequisite basic structure》 This type of fluid pressure return type spring clamp is excellent in that the clamping operation can be performed easily from a remote location, and the reduction of the clamping force due to fluid pressure leakage in the clamped state can be eliminated. Some have a basic structure as follows.

For example, as shown in FIG. 9 to FIG. 11, the piston 6 is vertically and slidably inserted into the clamp body 3 to form the unclamping fluid pressure working chamber 7 on one side of the piston 6, and 6, the clamp spring 9 is attached to the other side, and in the unclamping operation state A in which the working fluid is supplied from the fluid pressure supply / discharge port P to the unclamping fluid pressure working chamber 7, the piston 6 is clamped by the fluid pressure. The clamp tool 4 interlockingly connected to the piston 6 is configured to be driven to the unclamp side by performing a return drive against the spring force of the clamp spring 9 to the fluid pressure supply / discharge port P.
In the clamp operating state C in which the working fluid in the unclamping fluid pressure working chamber 7 is discharged from the unclamping position, the piston 6 is forwardly driven by the spring force of the clamp spring 9 with respect to the clamp body 3 to move the clamp tool 4 to the clamp side. It is configured to drive.

<< Prior Art >> In the above-mentioned basic structure, as a structure of a portion connecting the clamp tool 4 to the piston 6, conventionally, FIG. 9 to FIG.
As shown in FIG. 1, only the input part 4a of the clamp 4 is fixed to the output part 6a of the piston 6.

<< Problems to be Solved by the Invention >> The conventional structure described above operates as shown in FIG.

In each figure of FIG. 11 (a) (b) (c ), reference numeral A is unclamped operating conditions, the code C ₁ is thick clamp actuation state,
Reference numeral C ₂ indicates the thin clamp operating state.

In the unclamping operation state A, as shown in FIG. 1C, the clamp body 3 is unclamped to the right side with respect to the piston 6 by the fluid pressure press-fitted into the fluid pressure operating chamber 7,
The clamp spring 9 is compressed from the free length L _o to the unclamping length L ₁ as shown in the diagram (b), and the clamp spring 9 has the clamping tension F ₁ as shown in the diagram (a). .

When the clamp is driven, the fluid pressure in the fluid pressure working chamber 7 is discharged from the unclamping operation state A. Then, the clamp spring 9 drives the clamp main body 3 to the left, and advances along the spring straight line in FIG. 7A from point A to point O, and the spring force F increases as the spring length increases. While being lowered, the fixed object W is clamped.

When the clamp W is driven, as shown in FIG. 2C, when the object W to be fixed has a large thickness, the thick clamp operation state C ₁ is set. Then, as shown in FIGS. (A) and (b), the clamp spring 9 has a small extension amount m from the unclamping operation state A and a small reduction amount of the spring force F.
The clamp tension F ₂ is only slightly smaller than the clamp tension F ₁ .

On the other hand, as shown in FIG. 3C, when the fixed object W has a small thickness, the thin clamp operating state C ₂ is set. Then, as shown in (a) FIG. And (b) figure, clamp spring 9 has a large decrease of the spring force F larger elongation amount n from the unclamping actuation state A, the clamping tension F ₃ It will be much smaller.

Since the conventional structure operates as described above, it has the following problems.

(A) The clamping force becomes smaller as the fixed object W becomes thinner.

(B) As the thickness of the fixed object W becomes thinner, the clamp spring 9
The amount of expansion is large, and in proportion to this, the required supply amount of the working fluid for unclamping is also large, so that the energy consumption is large.

(C) Further, as described above, since the required supply amount of the working fluid for unclamping is large, the operation time for clamping / unclamping becomes long.

Although the basic structure is different from that of the present invention, a technique similar to the present invention is disclosed in Japanese Utility Model Laid-Open No. 60-117030.

This is because the spring force acting from the movable rod to the adjusting wedge-shaped member is intermittently operated by expanding and contracting the first fluid pressure cylinder, and the second fluid pressure cylinder is expanded and contracted and tightened by the wedge-shaped member. This is a technique to move the piece to the clamp side.

Although this technique can solve the above problems (a) to (c), the following new problems arise.

(D) Since two fluid pressure cylinders having different operations are provided, it is necessary to provide a supply / discharge pipe and a switching valve for each fluid pressure supply / discharge port of each fluid pressure cylinder. Thus, since two lines are required, the structure of the supply / discharge device becomes complicated.

An object of the present invention is to solve all of the above problems (a) to (d).

<< Means for Solving the Problems >> To achieve the above object, the present invention provides, for example, as shown in FIG. 1 to FIG. 5, FIG. 6, FIG. 7, or FIG.
The fluid pressure return type spring clamp is configured as follows.

That is, the piston 6 is inserted in the clamp body 3 so as to be vertically and tightly slidable, the unclamping fluid pressure working chamber 7 is formed on one side of the piston 6, and the clamp spring 9 is mounted on the other side of the piston 6. The clamp body 3 is provided with a fluid pressure supply / discharge port P for supplying / discharging the working fluid to / from the fluid pressure working chamber 7, and the elastic force of the clamp spring 9 passes through the piston 6 to clamp the tool 4. A clamp drive start position adjusting tool 14 is provided between the output part 6a of the piston 6 and the input part 4a of the clamp tool 4, and the adjusting tool 14 is provided with the clamp tool 4 and It is configured such that one of the clamp bodies 3 can be switched between an advanced position X for moving the other 3 to the clamp side and a retracted position Y for allowing the other 3 to move to the unclamp side. In the fluid pressure return type spring clamp, the retreat working chamber 24, the check valve seat 28 and the check valve chamber 29 are sequentially connected between the supply / discharge port P and the fluid pressure working chamber 7. The retreat piston 21 is provided in the retreat working chamber 24 so as to be able to slide in a hermetically sealed manner.
The adjusting tool 14 is configured to be switchable from the advanced position X to the retracted position Y by the fluid pressure acting on 1. The adjustable tool 14 is moved from the retracted position Y to the advanced position X.
An advance spring 22 for switching to the check valve chamber 29, a check valve body 31 inserted in the check valve chamber 29 to the check valve seat 28, and a closing valve spring 31 for elastically closing the check valve seat 28. A return spring 25 for elastically pressing the check valve body 30 is provided, and a valve opening operation tool 32 for separating the check valve body 30 from the check valve seat 28 against the check valve spring 31 is provided. It is provided on the piston 21.

<< Operation >> The present invention operates as follows as shown in FIGS. 1 to 5, for example.

As shown in FIG. 1 (a), in the unclamping operation state A, the operation is as follows.

The working fluid supplied from the fluid pressure supply / discharge port P to the retreat working chamber 24 pushes the check valve body 30 open and flows into the unclamping fluid pressure working chamber 7, and the fluid pressure causes the clamp spring 9 to act on the clamp spring 9. The piston 6 is pushed down against it. As a result, the connection state between the output portion 6a of the piston 6 and the input portion 4a of the clamp tool 4 is released, and the fluid pressure in the retract working chamber 24 causes the retract piston 21 to retract the adjuster 14 to the right. The clamp body 3 is moved to the position Y and is moved to the upper unclamp position.

When switching from the unclamping operation state A to the clamping operation state B, the working fluid is discharged from the fluid pressure supply / discharge port P.

Then, since the pressure in the retreat working chamber 24 decreases, the check valve body 30 is kept closed by the valve closing spring 31 (see FIG. 2), and as shown in FIG. The retracting piston 21 is moved to the left by the return spring 25. As a result, the adjuster 14 is moved from the retracted position Y to the advance position X by the advancing spring 22, so that the clamp main body 3 is lowered to the clamp position by the adjuster 14.

Almost at the same time, the valve opening operation tool 32 of the retreat piston 21 opens the check valve body 30.

As a result, as shown in FIG. 1C, the working fluid in the unclamping fluid pressure working chamber 7 is discharged from the fluid pressure supply / discharge port P through the check valve chamber 29 and the retreating working chamber 24. It Then, the elastic force of the clamp spring 9 raises the piston 6 and the clamp body 3 is clamped downward, and the input portion 6 a of the piston 6 is received by the input portion 4 a of the clamp tool 4 via the adjusting tool 14. Then, the clamp body 3 strongly presses the fixed object W.

5 (a) (b) (c) schematically shows the operation of the spring clamp. Hereinafter, description will be given with reference to FIG.

(c) In the unclamping operation state A shown in FIG.
As shown in the figure (b), the clamp spring 9 is compressed from the free length L ₀ to the unclamping length L ₁ , and as shown in the figure (a), the spring force F is applied to the clamp spring 9. The tension for clamping is F ₁ .

When the clamp W is driven, as shown in FIG. 2C, when the object W to be fixed has a large thickness, the thick clamp operation state C ₁ is set. When the unclamping operation state A is switched to the thick-walled clamp state C ₁ , the clamp spring 9 moves along with the leftward movement of the clamp body 3 as shown in FIGS. While keeping the force F at the clamping tension F ₁ , it moves from the point A to the left side by the idling distance l ₁ as a whole, then extends by the clamping extension e and the piston 6 with the clamping tension F _2. Drive the clamp.

Also, when switching from the unclamping operating state A to the thin clamp operating state C ₂ in FIG. 3C, the same operation is performed. That is, as shown in FIGS.
The clamp spring 9 keeps its spring force F at the clamp tension F ₁ as the clamp body 3 moves to the left,
It moves from the point A to the left side by the idling distance l ₂ as a whole, then extends by the extension amount e for clamping and the piston 6 is clamp-driven by the tension F ₂ for clamping.

Thus, even in thin clamp actuation condition C _2, since the elongation of the clamp spring 9 requires only the same amount of extension e thicker clamp actuation condition C _1, it does not occur decrease of the clamping force.

Further, the spring force of the clamp spring 9 in the clamp operating state C is reduced from the spring force F _{1 in the} unclamping operating state A by an amount corresponding to the elongation e for clamping. Since the amount of spring extension e is a minute amount for connecting and disconnecting the piston output part 6a and the clamp tool input part 4a, the clamp spring 9 has a small decrease in the spring force F and is in the unclamping operation state. The same strong spring force as A can be obtained.

<< Effects of the Invention >> The present invention has the following effects because it is configured and operates as described above.

(A) Even if the thickness of the fixed object changes, the amount of extension of the clamp spring does not change, so the clamping force can be kept constant.

Moreover, since the above-mentioned amount of expansion is a minute amount for connecting and disconnecting the piston output part and the clamp tool input part, the amount of decrease in spring force is small and the spring force is almost the same as in the unclamped state. can get. Therefore, the spring clamp can secure a strong clamping force.

(B) Also, since the extension amount of the clamp spring does not change even when the thickness of the fixed object becomes thin, the required supply amount of working fluid for unclamping can be as small as in the case of the thick clamp. , Low energy consumption.

(C) Further, as described above, since the required supply amount of the working fluid for unclamping is small, the operation time for clamping / unclamping is short.

(D) Since the spring clamp only needs to be provided with one fluid pressure supply / discharge port, only one system of supply / discharge piping and supply / discharge switching valve connected to the fluid pressure supply / discharge port is required. Therefore, the structure of the device for supplying and discharging the working fluid is simple. Moreover, since only one supply / discharge switching valve is required, the configuration of the means for controlling the supply / discharge device is simple.

«Examples» Examples of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 to 5 show a first embodiment.

In the longitudinal sectional view of FIG. 2, a work (fixed object) W placed on the upper surface of a fixed base 1 such as a work pallet can be pressed and fixed by a hydraulic (fluid pressure) return type spring clamp 2. This spring clamp 2 drives the clamp tool 4 to return to the unclamp side by supplying pressure oil (working fluid) to the clamp body 3, and discharges the pressure oil from the clamp body 3 to cause the clamp tool 4 to move by spring force. It is designed to drive to the clamp side. The piston 6 is inserted in the clamp body 3 so as to be vertically oiltightly slidable. An unclamping fluid pressure working chamber 7 is formed on the upper side, which is one side of the piston 6. A clamp spring 9 is mounted in a spring chamber 8 formed on the lower side, which is the other side of the piston 6. The clamp spring 9 is formed by stacking a large number of disc springs. In addition, the T leg 11 of the clamp tool 4 is fitted and fixed in the T groove 1a of the fixed base 1, and the middle height portion 12 of the clamp tool penetrates the piston 6 slidably.

Output part 6a of the piston 6 and input part 4 of the clamp tool 4
A clamp drive start position adjuster 14 composed of an inclined cam is interposed between the clamp drive start position adjuster 14 and a. The clamp drive start position adjusting tool 14 is elastically pressed toward the upper wall 7a of the unclamping hydraulic chamber 7 by the clamp body returning means composed of the pressing spring 15, and the clamp tool 4 is operated by the fluid pressure control operation device 17. With respect to the advance position X (see FIG. 1 (b) or (c)) that moves the clamp body 3 to the clamp side, and the retracted position Y (Fig. 1) that allows the clamp body 3 to move to the unclamp side. 1 (see (a)).

Fluid pressure supply / discharge port P of the unclamping fluid pressure working chamber 7
1 is selectively connected to a hydraulic pressure source S or an oil tank T by a supply / exhaust oil valve V, as shown in FIG.

In the unclamping operation state A shown in FIG. 1A, the piston 6 is first unclamped downward with respect to the clamp body 3 by the fluid pressure supplied from the fluid pressure supply / discharge port P, Piston output part 6a and clamp tool input part 4
The clamp main body returning means 15 clamps the clamp body 3 by releasing the connection with a and subsequently driving the clamp drive start position adjuster 14 to the right retracted position Y by the fluid pressure control type operating device 17. An unclamping idling distance 1 is formed between the lower surface of the clamp body 3 and the upper surface of the work W by urging the tool 4 upward.

In the initial stage of the clamp operating state C shown in FIG. 1 (b), the fluid pressure is discharged from the fluid pressure supply / discharge port P, and the clamp drive start position adjuster 14 is moved to the left side advance position by the fluid pressure control operation device 17. By driving to advance to X, the clamp body 3 is lowered by the idle distance 1 with respect to the clamp tool 4, and the lower surface of the clamp body 3 is brought into contact with the upper surface of the work W.

At the end of the clamp operating state C shown in FIG. 1 (c), the fluid pressure is discharged from the unclamping fluid pressure operating chamber 7, and the spring force of the clamp spring 9 causes the piston output portion 6a and the clamp drive start position adjuster 14 to operate. Is transmitted to the clamp tool input section 6a via. As a result, the work W is pressed and fixed on the upper surface of the fixed base 1 by the clamp body 3.

The fluid pressure control type operating device 17 operates as follows.
That is, in the unclamping operation state A of FIG. 1A, the hydraulic pressure in the fluid pressure operating chamber 7 causes the piston 6 to start unclamping downward, and then the clamp drive start position adjuster 14 is retracted to the retracted position Y. On the other hand, in the clamp operating state C of FIG. 1 (c), the clamp drive start position adjuster 14 is provided before the clamp spring 9 clamp-drives the piston 6 upward.
Is advanced to the advance position X side. Hereinafter, the fluid pressure control type operating device 17 will be described in detail with reference to FIGS. 2 to 4.

This allows the clamp drive start position adjuster 14 to be moved backward by the adjuster retracting piston 21 of the single-acting hydraulic cylinder 20 to the retracted position Y, and the adjuster advance pressing springs 22 and 22 to move the advance position X. It is designed to drive into. On the left side of the retracting piston 21 in FIG. 2, an adjusting tool retracting hydraulic oil chamber 24, which is a retracting operating chamber, is formed, and a return spring 25 is mounted on the right side. And
The clamp drive start position adjuster 14 is pressed by the hydraulic pressure of the adjuster retracting hydraulic oil chamber 24 to the retracted position Y via the adjuster retracting piston 21 and the piston rod 26.
A return spring 25 is used to return the adjuster retracting piston 21. Further, the fluid pressure supply / discharge port P is communicated with the unclamping fluid pressure working chamber 7 through the adjusting device retracting working oil chamber 24, the check valve seat 28, and the check valve chamber 29 in this order. The check valve body 30 in the check valve chamber 29 is brought into close contact with the check valve seat 28 by the valve closing spring 31, and the check valve body 30 is opened from the hydraulic fluid chamber 24 for retracting the adjusting tool. The tool 32 is opposed. This valve opening operation tool 32 is the piston 2 for retracting the adjustment tool.
It is fixed at 1.

When the clamp operating state C is switched to the unclamping operating state A, first, the adjusting tool retracting hydraulic chamber 24 is opened.
The pressure oil is press-fitted into the check valve body 30 by the oil pressure.
Is pressed to open the hydraulic fluid chamber 24 for retracting the adjuster to the fluid pressure operating chamber 7 for unclamping, and the piston 6 is unclamped downward against the clamp spring 9. Subsequently, the adjusting member retracting piston 21 and the piston rod 2
6, the clamp drive start position adjusting tool 14 is driven to be pushed to the retracted position Y (see FIG. 1 (a)).

On the other hand, at the time of switching from the unclamping operation state A to the clamping operation state C, at the initial stage of the discharge of the pressure oil from the fluid pressure supply / discharge port P, the check valve body is operated due to the pressure drop of the adjusting tool retracting operation oil chamber 24. The valve 30 is kept closed, and the hydraulic pressure in the unclamping fluid pressure working chamber 7 is maintained at the clamp pressure. On the other hand, in the latter stage of discharge of the pressure oil from the fluid pressure supply / discharge port P, the adjuster retracting piston 21 returning to the adjuster retracting hydraulic oil chamber 24 side reverses the valve opening operation tool 32. The stop valve body 30 is opened. As a result, the pressure oil in the unclamping fluid pressure working chamber 7 is discharged from the fluid pressure supply / discharge port P (see FIG. 1 (b)), and the piston 6 clamps the clamp spring 9 to drive the clamp tool 4 upward. To do. (See FIG. 1 (c)).

FIGS. 6 to 8 show other embodiments, respectively, and a configuration different from that of the first embodiment will be described. The first
The members having the same functions as those in the embodiment are designated by the same reference numerals.

(Second Embodiment) FIG. 6 shows a second embodiment, in which the clamp main body 3 is fixed to the upper surface of the fixed base 1, and the clamp tool 4 extends vertically between the clamp main body 3 and the fixed base 1. Is penetrated.
Then, the clamp tool input portion 4a formed on the upper part of the clamp tool 4 is clamped upward by the piston output portion 6a via the clamp drive start position adjusting tool 14 and the pressing tool 41, so that it can be detachably attached to the leg screw portion 42. The work W is pressed and fixed to the lower surface of the fixed base 1 by the nut 43 attached to the.

(Third Embodiment) FIG. 7 shows a third embodiment, in which an intermediate part of a swing type clamp tool 4 is pivotally supported so as to be vertically swingable on an upper portion of a clamp body 3 placed on an upper surface of a fixed base 1. A clamp tool input portion 4a is formed at the right swing end in the figure, and a clamp tool output portion 4b is formed at the left swing end. Then, the clamp tool input section 4a is clamp-driven upward by the piston output section 6a via the clamp drive start position adjusting tool 14 and the pressing tool 45, so that the work W at the clamp tool output section 4b.
Is pressed and fixed on the upper surface of the fixed base 1. When the piston 6 is returned, the clamp tool 4 is unclamped by the clamp tool return spring 46.

(Fourth Embodiment) FIG. 8 shows a fourth embodiment, which is the same as that shown in FIG. 7 except that a part thereof is changed as follows.

That is, the clamp tool input portion 4a is directly driven by the clamp start position adjuster 14 mounted on the upper left surface 3a of the clamp body 3 so as to be slidable in the left and right directions. In the unclamping operation state A, the supply of pressure oil from the fluid pressure supply / discharge port P causes the piston output portion 6a to move the piston output portion 6a to the upper left surface 3a of the clamp body 3.
Clamp drive start position adjuster 1
4 is a piston 21 for retracting the adjusting tool and a piston rod 50
Is retreated to the retreat position Y. On the other hand, when the pressure oil is discharged from the fluid pressure supply / discharge port P, the clamp drive start position adjustment tool 14 is advanced by the adjustment tool advancement pressing spring 22, and the piston output section 6a is moved from the clamp body upper surface 3a. It projects and drives the clamp tool 4 to the clamp side via the clamp drive start position adjusting tool 14.

In each of the above embodiments, the working fluid is pressure oil, but the working fluid may be a gas such as air.

Further, instead of the disc spring, the clamp spring 9 may be made of an elastic body such as rubber, a sealed liquid such as silicon oil, a sealed gas having a high compressibility.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention. 1 to 5 show the first embodiment, FIG. 1 is an explanatory view of the clamp operation, FIG. 1 (a) is a view showing an unclamping operation state, and FIG. 1 (b) is a clamp operation. FIG. 1 (c) shows the final state of the clamp operation, FIG. 2 shows a longitudinal sectional view of the fluid pressure return type spring clamp, and FIG. 3 shows the III-III line of FIG. 4 is a sectional view taken along the line IV-IV of FIG. 2, FIG. 5 is an operation explanatory view of the clamp spring, and FIG. 5 (a) shows a spring force and a spring compression amount. Fig. 5 (b) is a diagram showing the change in spring length, Fig. 5 (c) is a diagram showing changes in the clamp state, and Fig. 5 (c) is an unclamping operation state. FIG. 4C is a view showing a thick clamp operating state, and FIG. 3C is a thin clamp operating state. 6 to 8 show another embodiment, FIG. 6 is a view corresponding to FIG. 2 showing a second embodiment, FIG. 7 is a view corresponding to FIG. 2 showing a third embodiment, and FIG. FIG. 8 is a view corresponding to FIG. 2 showing a fourth embodiment. 9 to 11 show a conventional example. 9 is a view corresponding to FIG. 2, FIG. 10 is a view corresponding to FIG. 1, FIG. 10 (a) is a view showing an unclamping operation state, and FIG. 10 (b) is a view showing a clamping operation state, FIG. 11 corresponds to FIG. 5, FIG. 11 (a) corresponds to FIG. 5 (a), FIG. 11 (b) corresponds to FIG. 5 (b), and FIG. 11 (c) corresponds to FIG. It is a view corresponding to FIG. 5 (c). 3 ... Clamp body, 4 ... Clamping tool, 4a ... Clamping tool input section, 6 ... Piston, 6a ... Piston output section, 7 ... Unclamping fluid pressure working chamber, 9 ... Clamp spring, 14 ...... Clamp drive start position adjuster, 21 ...
… Reverse piston, 22 …… Advance spring (Adjustment tool advancing spring), 24 …… Reverse working chamber (Adjustment tool retracting hydraulic chamber), 25 …… Return spring, 28 …… Check valve seat, 29 ……
Check valve chamber, 30 ... Check valve body, 31 ... Valve closing spring, 32
…… Valve opening operation tool, P …… Fluid pressure supply / discharge port, X …… Advance position, Y …… Reverse position.

Claims (1)

[Claims] 1. A piston (6) is inserted into a clamp body (3) so as to be vertically and slidably sealed, and a fluid pressure working chamber (7) for unclamping is formed on one side of the piston (6). A clamp spring (9) is attached to the other side of the piston (6), and a fluid pressure supply / discharge port (P) for supplying or discharging a working fluid to / from the fluid pressure working chamber (7) is provided in the clamp body (3). ), The elastic force of the clamp spring (9) can be transmitted to the clamp tool (4) through the piston (6), and the output part (6a) of the piston (6) and the clamp tool (4)
A clamp drive start position adjusting tool (14) is provided between the input section (4a) of (4) and the adjusting tool (14) is the clamp tool.
(4) and one of the clamp body (3) (4), the other (3) moves to the clamp side, and the other (3) moves to the unclamp side. In a fluid pressure return type spring clamp configured to be switchable to a retracted position (Y) that allows the
The reverse working chamber (24), the check valve seat (28), and the check valve chamber (29) are provided in order to communicate with each other, and the reverse piston (21) is tightly slid on the reverse working chamber (24). It is movably inserted, and the piston (2
The adjusting tool (14) is configured to be switchable from the advanced position (X) to the retracted position (Y) by the fluid pressure acting on 1), and the adjustable tool (14) is moved from the retracted position (Y) to the above-mentioned retracted position (Y). Providing an advancing spring (22) for switching to the advancing position (X), the check valve body (30) inserted in the check valve chamber (29) is closed to the check valve seat (28) to close and elastically close the valve. A spring (31) is provided, and a return spring (25) for elastically pressing the retracting piston (21) toward the check valve body (30) is provided, and the check valve body (30) is closed as described above. A fluid pressure return type spring clamp, characterized in that a valve opening operation tool (32) for separating the check valve seat (28) from the valve spring (31) is provided on the piston (21).