JPH04226817A - Spring clamp with clamp holding device - Google Patents

Abstract

PURPOSE:To enhance the clamp holding ability in a spring clamp provided with a device for holding a tool holder in a clamped state even when larger unclamping force than clamping spring force acts on the tool holder in a machining center. CONSTITUTION:A draw bar 28 supported in a main spindle 24 is driven upward by clamping spring force, while the draw bar is driven downward to be unclamped by an output part 35 of a pneumatic/hydraulic booster. A piston 11 is inserted into a cylinder 10 fixed to the upper part of a main spindle 24 to form a liquid sealing chamber 12 to the lower side of the piston 11, and the piston 11 is fixed to the draw bar 28. When the draw bar 28 is held in a clamped state, a check valve 56 is closed to seal oil L in the liquid sealing chamber 12. In this case, when larger pulling-down force than the clamping spring force acts on the draw bar 28, a pressure generated in the liquid sealing chamber 12 counteracts the pulling-down force to prevent the lowering of the piston 11.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a type of clamp that fixes a tool holder to a main shaft using a spring force, for example in a machining center. The present invention relates to a device that holds an object in a clamped state even when a force is applied.

0002

2. Description of the Related Art This type of spring clamp is described in Japanese Utility Model Application Publication No. 150035/1983.

[0003] As shown in FIG. 13, the basic structure is as follows. (a) As shown in the figure, an actuating member B for clamping is supported by a cylindrical housing A so as to be movable in the vertical direction, and the actuating member B is attached to a clamp spring 1.
03, the clamp is driven to the upper clamp position X. On the other hand, as shown in FIG.
is lowered to the lower unclamping position Z against the clamping spring 103 by the pressing force of the unclamping driving means D. A clamp holding device 108 and a switching device 109 are provided across the housing A and the actuating member B. The clamp holding device 108 is switched between a locked state R and an unlocked state U by a switching device 109. In the locked state R shown in (a), the actuating member B is held in the clamp position
In the unlocked state U shown in the figure, the holding is released.

In the above-mentioned basic structure, conventionally, the structures of the clamp holding device 108 and the switching device 109 were as follows. As shown in FIG. 13, the clamp holding device 108 is formed by inserting steel balls 112 into a plurality of guide holes 111 formed in the upper part of the cylindrical wall of the housing A so as to be movable in the radial direction of the cylindrical wall. In the upper part of the actuating member B, a receiving groove 113 for the ball 112, a receiving part 114, and a stepped raised part 115 for extrusion are formed in order from the bottom. Also,
The switching device 109 includes a switching tube 117 that is pressed upward from the housing A by a return spring 116, and a tapered surface 118 for extruding the ball 112 and a retraction groove 119 are formed on the inner peripheral surface of the switching tube 117 in order from the bottom. It forms.

This conventional spring clamp operates as follows. (a) In the clamped state shown in the figure, the switching tube 11
The ball 112 is pressed inward by the extrusion taper surface 118 of No.
is received, and the clamp holding device 108 is in the locked state R.
has been switched to. As a result, even if a pulling force larger than the elastic force of the clamp spring 103 is applied to the actuating member B, the clamp position
is maintained.

During unclamping, the switching tube 117 is driven downward by the unclamping driving means D. Then, as shown in FIG.
12 faces the entrance/exit groove 119. As a result, as shown in FIG.
8 can be switched to the unlocked state U. In this state, the driving means D acts against the clamp spring 103 and the actuating member B
is lowered by an unclamping stroke S, and the actuating member B is switched to the unclamping position Z.

[0007]

[Problems to be Solved by the Invention] The above-mentioned prior art has the following problems. Since the ball 112 supports the receiving portion 114 through point contact, the allowable receiving force must be a small value. Therefore, the clamp holding capacity of the clamp holding device 108 is small.

Furthermore, since the ball 112 is likely to undergo plastic deformation due to high surface pressure due to point contact, smooth forward and backward movement within the guide hole 111 is inhibited at an early stage. Therefore, the clamp holding device 108 has a short lifespan.

Furthermore, since the unlocking stroke T is required to have a large dimension approximately corresponding to the diameter of the ball 112, the stroke of the unclamping drive means D becomes long. As a result, the operation time during unclamping is long.

The objects of the present invention are to increase the clamp holding ability of the clamp holding device, to extend the life of the clamp holding device, and to shorten the operation time during unclamping.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention is characterized in that a clamp holding device and a switching device are constructed as follows. For example, as shown in FIGS. 1 and 3 to 7, or FIG. 2 or 8, the clamp holding device 8 is attached to a cylinder 10 extending in the vertical direction, and a piston inserted into the cylinder 10 so as to be slidable in a liquid-tight manner. 11, and a liquid seal chamber 12 formed below the piston 11. The piston 11 is connected to an actuating member B for clamping. The switching device 9 is connected to a liquid supply/discharge chamber 13 that communicates with the liquid seal chamber 12, and to both of these chambers 12 and 1.
It consists of a liquid seal valve 15 provided between three parts, and an operating means 19 for opening and closing the liquid seal valve 15. And the operation means 19
closes the liquid seal valve 15 and seals the liquid L in the liquid seal chamber 12 to switch the clamp holding device 8 to the locked state R, and the same operating means 19 opens the liquid seal valve 15 and seals the liquid L in the liquid seal chamber 12.
By communicating with the liquid supply/discharge chamber 13, the clamp holding device 8 is switched to the unlocked state U.

0012

[Operation] The present invention operates as follows, mainly as shown in FIGS. 1, 6, and 7. In the clamped state shown in FIG. 1, the output portion 35 of the unclamping drive means D returns to the upward position, the actuating member B is upwardly pressed to the clamping position X by the clamp spring 3 (see FIG. 4), and the liquid seal chamber 12 is Seal valve 1
5, and the clamp holding device 8 is switched to the locked state R. In this clamped state, when a pulling force greater than the elastic force of the clamp spring 3 acts on the actuating member B, the actuating member B and the piston 11 tend to be pulled down. Then, the pressure of the liquid L in the liquid seal chamber 12 rises, strongly preventing the piston 11 from being pulled down and holding the actuating member B at the clamp position X.

At the time of unclamping, the clamping state shown in FIG. 1 is switched to the unclamping state shown in FIG. 7 via the switching transient state shown in FIG. 6. That is, in the clamped state shown in FIG.
2 is communicated with the liquid supply/drainage chamber 13, and the clamp holding device 8 is switched to the unlocked state U as shown in FIG. Subsequently, as shown in FIG. 7, the actuating member B is lowered by an unclamping stroke S against the clamp spring by the downward driving force of the unclamping drive means D, and the actuating member B is lowered by an unclamping stroke S.
is switched to the unclamp position Z. In addition, Figure 7
Switching from the unclamped state of FIG. 1 to the clamped state of FIG. 1 is performed by the reverse procedure to that described above.

[0014]

[Effects of the Invention] The present invention has the following effects because it is constructed and operates as described above. Since the clamp holding device receives the pulling force of the actuating member via the piston due to the liquid pressure in the liquid sealing chamber, it is possible to secure an even and large pressure supporting area, and the clamp holding capacity is large.

[0015] Furthermore, since the clamp holding device uses liquid to handle the above-mentioned pull-down force, it does not undergo plastic deformation.
Long lifespan.

Furthermore, when the clamp holding device is switched from the locked state to the unlocked state, the switching device simply opens the liquid seal valve, so that the unlocking stroke is short or no stroke is required. As a result, the stroke of the unclamping drive means becomes shorter, and the operating time during unclamping can be shortened.

[0017]

[Embodiment] First, the outline of the spring clamp will be explained with reference to the system diagram shown in FIG. A housing A of the spring clamp 1 is fixed to a fixed base 2, and a rod-shaped actuating member B is fitted into the housing A so as to be slidable in the vertical direction. The actuating member B presses and fixes the object 4 to be fixed to the lower part of the housing A by being clamped to the upper clamp position X by the elastic force of the clamp spring 3 against the housing A. On the other hand, the actuating member B is a hydraulic cylinder 6 (unclamping drive means D) fixed to another fixed base 5.
The fixed state of the fixed object 4 is released by being driven to the lower unclamping position against the clamp spring 3 by the downward force of the hydraulic piston 7 .

The clamp holding device 8 is formed by inserting a piston 11 into a cylinder 10 fixed to the upper part of the housing A so as to be slidable vertically in a liquid-tight manner. A liquid seal chamber 12 for generating high pressure is formed below the piston 11, and the piston 11 is fixed to the actuating member B. The switching device 9 also includes a low-pressure liquid supply and discharge chamber 13 formed above the piston 11, a communication passage 14 that communicates this liquid supply and discharge chamber 13 with the liquid seal chamber 12, and a communication passage 14 that is connected to the communication passage 14. It consists of a liquid seal valve 15 (here configured as an electromagnetic opening/closing type).

The spring clamp 1 operates as follows. When clamping the object 4, the pressure oil in the hydraulic chamber 6a of the hydraulic cylinder 6 is discharged from the pressure oil supply/discharge valve 17, and the hydraulic piston 7 is raised by the return spring 18. Then, the actuating member B is pressed to the clamp position X by the clamp spring 3 and presses and fixes the object 4 to be fixed.

In this clamped state, the liquid seal valve 15 is operated by the operating means 19 (here configured as an electrically controlled type).
The valve is closed to seal the liquid L in the liquid seal chamber 12. In the locked state R of the clamp holding device 8, even if a pulling force greater than the elastic force of the clamp spring 3 acts on the fixed object 4, the pressure of the liquid L in the liquid seal chamber 12 increases and the piston 11 and prevents the actuating member B from descending. As a result, the actuating member B is held at the clamp position X, and the object 4 to be fixed is held in the clamped state. Note that when the liquid seal chamber 12 becomes abnormally pressured due to a rise in temperature or the like, the relief valve 20 is designed to operate safely.

On the other hand, when unclamping the fixed object 4,
First, the liquid seal valve 15 is opened by the operating means 19,
The liquid seal chamber 12 is communicated with the liquid supply/discharge chamber 13, and the clamp holding device 8 is switched to the unlocked state. In this state,
Pressure oil is supplied from the pressure oil supply/discharge valve 17 to the hydraulic working chamber 6a of the hydraulic cylinder 6 to lower the hydraulic piston 7, thereby driving the piston 11 and the actuating member B downward against the clamp spring 3.

Note that the liquid supply and discharge chamber 13 can also be arranged in the external space of the cylinder 10. The cylinder 10
may be fixed to the fixing base 2 instead of being fixed to the housing A. Furthermore, the actuating member B is
Instead of being fitted inside the housing A, it may be placed on the outer circumferential side of the housing A. Further, the liquid L to be introduced into the liquid seal chamber 12 and the liquid supply/discharge chamber 13 is preferably oil, but may be other fluid liquid such as glycerin.

(First Embodiment) FIGS. 1 and 3 to 7 show a first embodiment, in which the spring clamp 1 described above is applied to a tool locking device of a machining center. In this first embodiment, members having the same configuration as in FIG. 2 described above are given the same reference numerals.

3 to 5, inside the casing 23 fixed to the spindle head 22 of the vertical machining center 21,
The main shaft 24, which is the housing A, has a plurality of bearings 25.
It is rotatably supported by a motor 26 and rotated at high speed by a motor 26. The main shaft 24 includes an actuating member B
A draw bar 28 is fitted inside the draw bar 28 so as to be vertically slidable, and a collet 29 is connected to the lower part of the draw bar 28.

When clamping the tool holder 30 to the main shaft 24, the draw bar 28 is pressed upward against the main shaft 24 by a plurality of disc springs 31 (clamp springs 3), the collet 29 is reduced in diameter and raised, and the tool holder 30 on the holder receiving surface 24 of the spindle 24.
Press and fix to a. Note that the reference numeral 33 is a tool. On the other hand, when unclamping the tool holder 30,
The push-down force of the output part 35 of the pneumatic hydraulic booster 34, which is the unclamping driving means D, drives the drawbar 28 downward against the disc spring 31, and at the same time expands the diameter of the collet 29 and lowers it, allowing the tool holder 30 to be removed. Let it happen.

The cylinder 10 of the clamp holding device 8 is screwed and fixed to the upper part of the main shaft 24, and the switching device 9 is provided in the internal space of the cylinder 10. In addition, in the pneumatic-hydraulic booster 34, the code|symbol 36 is a compressed air supply nozzle. In addition, an air blow channel 3 is provided in the draw bar 28.
9 is formed through the air passage 39, and the upper end of the flow path 39 can communicate with an air supply hole 40 in the output section 35 of the booster 34.

The above-mentioned clamp holding device 8 and switching device 9 will be explained in detail with reference to FIGS. 1, 6, and 7. The clamp holding device 8 holds the cylindrical piston 11 and the cylindrical piston rod 43 with upper and lower seal members 45 and 4, respectively.
6, 47 and 48, and are slidably inserted into the cylinder 10 in a fluid-tight manner. Piston 11 and piston rod 4
3 is fixed to the drawbar 28 via a cylindrical pressing tool 49, a washer 50, and a nut 51 in this order. Piston 11
A liquid seal chamber 12 is formed below the piston 11, and a liquid supply/discharge chamber 13 is formed above the piston 11.

Liquid (oil in this case) is supplied to both chambers 12 and 13 from an oil supply hole 53 provided in the upper wall 10a of the cylinder 10.
L is supplied. The oil supply holes 53 and their plugs 54 are provided at a plurality of locations symmetrically with respect to the axis of the piston 11 to maintain rotational balance. Among the seal members of the piston 11 and the piston rod 43, the first seal members 46 and 47 on the side closer to the liquid seal chamber 12 function as seal members for medium and high speed rotation, and the first seal members 46 and 47 on the side farther from the liquid seal chamber 12 function as seal members for medium and high speed rotation. The second seal members 45 and 48 are configured to function as seal members for low-speed rotation or during rotation stop.

The switching device 9 includes a communication passage 14 formed in the piston 11 and communicating the upper and lower chambers 12 and 13, and a check valve 56 (liquid seal valve 15) interposed in the communication passage 14. It becomes. That is, an annular check valve chamber 57 and a check valve seat 58 are formed in the annular communication passage 14 formed around the axis of the piston 11 in order from the bottom. The check valve seat 58 is pressed by the pressing tool 49
It is placed facing downward in the middle of the height. Check valve chamber 57
The check valve body 59 inserted vertically in a liquid-tight manner is pressed against the check valve seat 58 by a check spring 60 to close the check valve body.

Further, a cylindrical unclamping input member 63 is fitted onto the upper part of the pressing tool 49 so as to pass through the upper wall 10a of the cylinder 10 and to be slidable vertically in a liquid-tight manner. The input member 63 is pressed against the washer 50 by a return spring 67 and faces the booster output section 35 . Further, a check valve opening tool 66 constituting the operating means 19 is fixed to the lower part of the input member 63. The valve opening tool 66 is driven downward against the return spring 67 by the downward force of the booster output section 35, thereby separating the check valve body 59 from the check valve seat 58. And the above-mentioned pressing tool 49
An unclamping start stroke M, which is a contact gap between the unclamping input part 69 provided at a mid-height part and the above-mentioned input member 63, is a gap between the valve opening tool 66 and the check valve body 59. It is set to a value larger than the stroke N for starting valve opening, which is the abutment clearance.

The cross-sectional area for oil storage of the liquid supply and discharge chamber 13 is such that the pressing tool 4 is placed inside the straight cylinder 10.
9 and the input member 63, the cross-sectional area of the liquid seal chamber 12 is smaller than that of the cylinder upper wall 10a.
The lack of cross-sectional area is compensated for by forming a liquid relief chamber 71 in the lateral area. This liquid relief chamber 71 is also connected to the piston 11.
Multiple locations are provided symmetrically about the axis of Furthermore, a disk-shaped partition wall 73 for preventing gas-liquid mixing is provided to protrude from the valve opening tool 66 toward the cylinder inner circumferential surface 10b.

The above spring clamp operates as follows. In the clamped state shown in FIG.
), and the unclamping input member 63 and the valve opening tool 66 are urged to the raised position by the return spring 67. As a result, the check valve body 59 is brought into close contact with the check valve seat 58 by the check spring 60, the oil L is sealed in the liquid seal chamber 12, and the clamp holding device 8 is in the locked state R. .

[0033] In the clamped state, the main shaft 24 is driven to rotate at high speed, and the workpiece is machined. Here, if the machining conditions such as the feed rate, rotation speed, and depth of cut of the tool 33 (not shown here) do not match the material of the workpiece, or if the tool 33 (not shown) gets tangled with chips during pocket machining, etc. When the cutting performance deteriorates, a pulling force greater than the elastic force of the disc spring 31 acts on the tool 33 and attempts to pull down the drawbar 28 and the piston 11. Then, the internal pressure of the liquid seal chamber 12 increases, preventing the piston 11 from being pulled down and holding the drawbar 28 at the clamp position X. This strongly prevents the tool holder 30 from falling off the holder receiving surface 24a of the main shaft 24.

While the main shaft 24 is rotating, the oil in the liquid supply/discharge chamber 13 is pressed against the peripheral wall of the cylinder 10 by centrifugal force, as shown by the chain double-dashed line K in FIG. However, since the partition wall 73 prevents the upper space of the check valve body 59 from communicating with the gas phase part (air part),
Air in the liquid supply and discharge chamber 13 is prevented from mixing with the oil L in the liquid seal chamber 12. Thereby, the incompressibility of the oil L in the liquid seal chamber 12 can be prevented from being impaired, and the clamp holding function can be maintained well.

When replacing the tool, the rotation of the main shaft 24 is stopped in the clamped state shown in FIG. 1, and then the switching state shown in FIG. 6 is changed to the unclamped state shown in FIG. 7. That is, in the clamped state of FIG. 1, the booster 34 (not shown)
By driving the booster output section 35 downward, the output section 35 starts to drive the input member 63 downward.

Then, the input member 63 first descends by the contact gap N and comes into contact with the check valve body 59, and then pushes down the check valve body 59 to separate it from the check valve seat 58. While releasing the seal of the liquid seal chamber 12 and switching the clamp holding device 8 to the unlocked state U, it further descends by a distance (M-N) and contacts the input part 69, and switches to the switching transient state shown in FIG. .

Subsequently, the input member 63 is driven downward by the booster output section 35, so that the oil L in the liquid seal chamber 12 passes through the communication path 14 and is supplied with liquid, as shown in the unclamped state in FIG. The piston 11 is allowed to descend into the discharge chamber 13, and the draw bar 28 descends by an unclamping stroke S and switches to the unclamping position Z. Note that switching from the unclamped state shown in FIG. 7 to the clamped state shown in FIG. 1 is performed by the reverse procedure to that described above.

According to the above structure, the liquid supply and discharge chamber 13 is formed in the space above the piston 11, and the communication passage 14 is formed in the space above the piston 11.
1, the switching device 9 can be made compact. In addition, since the check valve element opening tool 66 is fixed to the lower part of the unclamping input member 63, the liquid seal structure is simplified compared to the case where both 63 and 66 are provided separately. The structure for sequentially raising and lowering 66 is also simplified. Further, since the communication passage 14 and the check valve 56 are formed in an annular shape, the clamp holding device 8 has a large flow passage cross-sectional area for supplying and discharging oil, resulting in a faster switching speed and better rotational balance.

Furthermore, as described above, by applying the spring clamp 1 to the tool locking device of the machining center 21,
The housing A is composed of the main shaft 24 and the operating member B.
When configured with the drawbar 28, the following advantages can be obtained. That is, in order to increase the clamp holding ability, it is sufficient to simply connect the draw bar 28 to the piston 11 of the clamp holding device 8, and there is no need to modify the main shaft 24, the clamp spring 3, and the unclamping drive means D of the machining center 21. Therefore, it is easy to newly install the clamp holding device 8 in the existing machining center 21, or to change a conventionally structured clamp holding device to the clamp holding device 8 of the present invention. Note that the present invention is of course applicable not only to machining centers but also to other machine tools.

(Second Embodiment) FIG. 8 shows a second embodiment of a clamp holding device 8 used in a relatively large machining center. Upper flange 7 of main shaft 24
4, the lower part of the cylinder 10 is fixed with a plurality of bolts 75. In addition, the piston 11 and the piston rod 43
A cylindrical bolt 96 is inserted through the cylindrical bolt 96 . By screwing the lower part of the bolt 96 to the upper part of the draw bar 28, the piston 11 and the piston rod 43 are held and fixed between the cylindrical pressing tool 49 and the draw bar 28.

A rotor 97a of a rotary joint 97 for supplying cutting fluid is fixed to the upper part of the cylindrical bolt 96. During machining operation of the machining center, the above rotary joint 97
As shown by the solid line arrow, the cutting fluid that has been pumped to the tool 33 (see FIG. reference). Thereby, the tool 33 can be powerfully cooled when performing deep hole drilling or heavy cutting.

Furthermore, during unclamping driving, after the booster output section 35 comes into contact with the unclamping input member 63, the compressed air that is force-fed to the air supply port 35a of the output section 35 flows as shown by the broken line arrow. Then, the air flows downward from the receiving hole 63a of the input member 63 through the distribution fitting 81 and the air blowing channel 39 in the pipe 82 in order to clean the holder receiving surface 24a (see FIG. 4). In addition,
The fitting gap between the check valve body 59 of the check valve 56 and the piston 11 is sealed by an X ring 98. Further, the check spring 60 for the check valve body 59 described above is constituted by one spring that is fitted onto the pressing tool 49.

(Third Embodiment) FIGS. 9 and 10 show a third embodiment. As shown in FIG. 9, an annular relief valve 76 is provided in series in a space above the check valve 56 in the communication path 14. That is, the relief valve chambers 77 are arranged in series above the check valve chambers 57, and the check valve seat 58 is formed below the relief valve body 79 inserted into the relief valve chamber 77. 78 is provided on the check valve body 59. The relief valve body 79 is pressed closed against the relief valve seat 78 by a relief spring 80 which also serves as the return spring 67.

If the cylinder 10 is heated due to heat received from the main shaft 24 and the internal pressure of the liquid seal chamber 12 rises excessively, the relief valve body 79 will close due to the abnormal pressure, as shown in FIG. It is spaced apart from the check valve body 59 against the relief spring 80 to release abnormal pressure in the liquid seal chamber 12 to the liquid supply/discharge chamber 13.

(Fourth Embodiment) FIG. 11 shows a fourth embodiment. A plurality of communicating passages 84 are formed through the piston 11 symmetrically about its axis. A check valve chamber 85 and a check valve seat 86 are formed in each communication passage 84 in order from the bottom. The check valve body 87 in the check valve chamber 85 is pressed to close by the check valve seat 86 by the check spring 88, and the protruding upper part of the check valve body 87 is made to face the unclamping input member 63. There is. A plurality of relief valves 90 are provided in separate communication passages 91 within the piston 11 symmetrically with respect to the piston axis.

(Fifth Embodiment) FIG. 12 shows a fifth embodiment. A check valve body 94 is supported within the check valve chamber 92 on the inner peripheral surface of the annular communication passage 14 so as to be vertically slidable. Further, the check valve seat 93 is integrally formed with the piston 11.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a clamped state of a spring clamp according to a first embodiment, and is an enlarged view of the main part of FIG. 4. FIG.

FIG. 2 is a system diagram showing the concept of the spring clamp.

FIG. 3 is a front view of a machining center provided with the spring clamp.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a schematic diagram corresponding to FIG. 4.

FIG. 6 is a longitudinal cross-sectional view showing a transient state of switching of the spring clamp.

FIG. 7 is a longitudinal sectional view showing the spring clamp in an unclamped state.

FIG. 8 is a diagram showing a second embodiment and corresponding to FIG. 1;

FIG. 9 is a diagram showing a third embodiment and corresponding to FIG. 1;

FIG. 10 is a partial diagram showing a relief state of the third embodiment.

FIG. 11 is a diagram showing a fourth embodiment and corresponding to FIG. 1;

FIG. 12 is a diagram showing a fifth embodiment and corresponding to FIG. 1;

FIG. 13 shows a conventional example, (a), (b), and (c).
The figures correspond to FIGS. 1, 6, and 7, respectively.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Spring clamp, 3 (31)... Clamp spring, 8... Clamp holding device, 9... Switching device, 10... Cylinder, 1
0a...Top wall, 10b...Inner peripheral surface, 11...Piston, 12...
Liquid sealing chamber, 13...Liquid supply/drainage chamber, 14...Communication path, 15...Liquid sealing valve, 19...Operation means, 24...Main shaft of machine tool, 28...Drawbar, 56...Check valve, 57...Check valve chamber , 58... Check valve seat, 59... Check valve body, 60... Check spring, 63... Input member for unclamping, 66... Valve opening tool for check valve body, 67... Return spring, 71... Liquid relief chamber , 73... Partition wall, 76... Relief valve, 77... Relief valve chamber, 78... Relief valve seat, 7
9... Relief valve body, 80... Relief spring, A... Housing, B... Operating member, D... Drive means for unclamping, M.
N... Contact gap, X... Clamp position, Z... Unclamp position.

Claims (12)

[Claims] Claim 1: When the spring clamp (1) is viewed in a vertical position, the housing (A) supports an actuation member (B) for the clamp so as to be movable in the vertical direction, and the actuation member (B) A clamp spring (3) is provided to drive the above to the upper clamp position (X), and the above actuating member (B) is driven to the lower unclamp position (Z) against the clamp spring (3). A clamp holding device (8) which is provided with an unclamping drive means (D) and holds the above-mentioned operating member (B) at the above-mentioned clamp position (X) is connected to a cylinder (10) extending in the vertical direction and the cylinder (10). ) and the piston (11) slidably inserted in a fluid-tight manner.
1) and a liquid seal chamber (12) formed on the lower side, and the piston (11) is connected to the actuating member (B),
A switching device (9) for switching the clamp holding device (8) is installed between the liquid supply and discharge chamber (13) that communicates with the liquid seal chamber (12) and these two chambers (12) and (13). It is characterized by comprising a liquid seal valve (15) provided in the liquid seal valve (15) and an operating means (19) for opening and closing the liquid seal valve (15).
Spring clamp with clamp retention device. 2. The spring clamp according to claim 1, wherein the liquid supply/discharge chamber (13) is formed above the piston (11) within the cylinder (10). 3. In the spring clamp according to claim 2, the cross-sectional area of the liquid supply/drainage chamber (13) is equal to the cross-sectional area of the liquid seal chamber (12).
), and a liquid escape chamber (71) is formed in the upper wall (10a) of the cylinder (10). 4. The spring clamp according to claim 2, wherein the liquid seal valve (15) is constituted by a check valve (56), and the liquid seal chamber (12) and the liquid supply/drain chamber (13) A communication passage (14) is provided in the piston (11) that communicates with the check valve chamber (57) and the check valve seat (58).
and a check spring (60) that presses the check valve body (59) inserted into the check valve chamber (57) against the check valve seat (58), and performs the above operation. The means (19) includes a check valve opening tool (66) that faces the check valve body (59) from above, and a valve opening tool return that presses the valve opening tool (66) upward. It consists of a spring (67) and the valve opening tool (
66), with the unclamping drive means (D) facing from above. 5. The spring clamp according to claim 4, wherein the communication passage (14) and the check valve chamber (57) are arranged annularly around the axis of the piston (11). 6. In the spring clamp according to claim 4, an annular unclamping input member (63) driven by the unclamping drive means (D) is connected to the upper end of the operating member (B) and the unclamping input member (63). The upper wall (10) of the cylinder (10)
a), and its input member (6
3) Fix the above-mentioned valve opening tool (66) for the check valve body to the lower end part, and connect the unclamping input part (66) of the above-mentioned operating member (B).
9) and the above input member (63) (M)
is set to a value larger than the contact gap (N) between the valve opening tool (66) and the check valve body (59). 7. The spring clamp according to claim 4, wherein a relief valve (76) is provided in the communication path (14) between the liquid seal chamber (12) and the liquid supply/drainage chamber (13). )
The relief valve (76) is provided with a relief valve seat (7
8) and a relief valve chamber (77) formed in order from the bottom, and a relief spring (80) that presses a relief valve body (79) inserted into the relief valve chamber (77) against a relief valve seat (78). What was set up. 8. The spring clamp according to claim 7, wherein the communication passage (14) and the relief valve chamber (77) are arranged annularly around the axis of the piston (11). 9. The spring clamp according to claim 8, wherein the relief valve chamber (77) is provided above the check valve chamber (57).
) are arranged in series, and the check valve seat (58) is provided at the lower end of the relief valve body (79). 10. The spring clamp according to claim 4, wherein the housing (A) is configured to be rotatable at high speed around an axis. 11. The spring clamp according to claim 10, wherein a gas-liquid mixing prevention valve is provided from the check valve element opening tool (66) toward the inner circumferential surface (10b) of the cylinder (10). One with a protruding partition wall (73). 12. The spring clamp according to claim 10 or 11, wherein the housing (A) is attached to a main shaft (2) of a machine tool.
4), and the actuating member (B) is connected to the main shaft (
It consists of a drawbar (28) fitted inside the drawbar (24).