Rotary clamp

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a clamp of the type that rotates a clamp rod.

2. Explanation of Related Art

There is a conventional technique of the rotary clamp of this type which is constructed in the following manner, as disclosed in U.S. Pat. No. 5,820,118.

A clamp rod is inserted into a cylinder tube rotatably around an axis and axially movably. The clamp rod has a halfway height portion in an outer periphery of which there are provided oppositely inclining two helical grooves and a straight groove. An engaging ball is fitted into any one of these three grooves. The engaging ball is supported by a recess provided in a barrel portion of the cylinder tube.

The conventional technique has the following problem.

The clamp rod is supported by the cylinder tube through one engaging ball. Therefore, the clamp rod slightly inclines when it is driven for clamping and for unclamping. This reduces the accuracy of placing a clamp member provided at a leading end of the clamp rod, at a clamping position and at an unclamping position.

SUMMARY OF THE INVENTION

The present invention aims at preventing the inclination of the clamp rod.

In order to achieve the above aim, for example, as shown in

FIGS. 1

to

6

or in

FIGS. 7

to

10

, the present invention has constructed a rotary clamp in the following manner.

A clamp rod

5

is inserted into a housing

3

rotatably around an axis and movably for clamping from one end to the other end in an axial direction. The clamp rod

5

has an outer peripheral portion formed with a plurality of guide groove

26

peripherally. The housing

3

supports a plurality of engaging members

29

which are fitted into these guide grooves

26

, respectively. Each of the guide grooves

26

comprises a rotary groove

27

and a straight groove

28

provided in continuity with each other from the other end to the one end in the axial direction. The rotary grooves

27

as well as the straight grooves

28

are arranged in parallel with one another. A partition wall between the adjacent guide grooves

26

,

26

has a minimum thickness (T) set to a value smaller than a groove width (W) of the guide groove

26

.

The present invention offers the following advantages.

The clamp rod is provided with the guide grooves into which the engaging members are fitted, respectively. This enables the housing to peripherally and substantially evenly support the clamp rod through the engaging members. Therefore, the clamp rod can be prevented from inclining when it is driven for clamping and for unclamping. This results in improving the accuracy of placing a clamp member provided at a leading end of the clamp rod, at a clamping position and at an unclamping position.

Further, the partition wall between the adjacent guide grooves has the minimum thickness set to the value smaller than the groove width of the guide groove. Therefore, it is possible to provide many guide grooves in the clamp rod so as to support the clamp rod peripherally and substantially evenly and at the same time to decrease an inclination angle of the rotary groove. This reduces the stroke required for rotating the clamp rod to result in making the rotary clamp compact. Besides, it becomes possible to arrange a plurality of engaging members, each of which has a large diameter, adjacent one another. Therefore, a rotary mechanism of the clamp can endure a large rotation torque to result in increasing its service lifetime.

The present invention includes a clamp in which the engaging member is formed from a ball. This invention can more smoothly rotate the clamp rod and increase the service lifetime of the rotary mechanism.

Further, in order to accomplish the foregoing object, the present invention has constructed a rotary clamp in the following manner, for example, as shown in

FIGS. 1

to

6

.

A clamp rod

5

is inserted into a housing

3

rotatably around an axis and movably for clamping from one end to the other end in an axial direction. The clamp rod

5

has an outer peripheral portion formed with a plurality of guide grooves

26

peripherally. The housing

3

supports a plurality of engaging balls

29

which are fitted into the guide grooves

26

, respectively. Each of the guide grooves

26

comprises a rotary groove

27

and a straight groove

28

provided in continuity with each other from the other end to the one end in the axial direction. The rotary grooves

27

as well as the straight grooves

28

are arranged in parallel with one another. A partition wall between the adjacent guide grooves

26

,

26

has a minimum thickness (T) set to a value smaller than a diameter (D) of the engaging ball

29

.

This invention also offers the same advantages as those of the above-mentioned invention.

The clamp rod can be prevented from inclining when it is driven for clamping and for unclamping. This results in improving the accuracy of placing a clamp member provided at a leading end of the clamp rod, at a clamping position and at an unclamping position. In addition, it is possible to reduce the stroke required for rotating the clamp rod, which leads to the possibility of making the rotary clamp compact. Besides, it becomes possible to arrange a plurality of engaging balls, each of which has a large diameter, adjacent one another. Therefore, a rotary mechanism of the clamp can endure a large rotation torque to result in increasing its service lifetime.

The present invention, for example, as shown in

FIGS. 1

to

4

or in

FIGS. 7

to

10

, includes the following clamp.

The engaging balls

29

are rotatably supported by through holes

31

provided in the housing

3

and a sleeve

35

is rotatably and externally fitted over the engaging balls

29

. This invention offers the following advantage.

When the clamp rod rotates, almost only rolling friction acts between an inner peripheral surface of the sleeve and the engaging balls, but sliding friction hardly acts therebetween. This reduces a resistance which acts from the sleeve to the engaging balls to result in decreasing a frictional force which acts from the engaging balls to the rotary grooves and therefore smoothly rotating the clamp rod with a light force.

The present invention also includes a clamp which is provided with at least three guide grooves. This invention is preferable due to the fact that it supports the clamp rod peripherally and substantially evenly and decreases the inclination angle of the rotary groove.

The present invention further includes a clamp which has the guide grooves arranged peripherally of the clamp rod at substantially the same spacing. This invention is preferable for supporting the clamp rod more evenly.

Moreover, the present invention, for instance, as shown in

FIG. 4

,

FIG. 5

or

FIG. 6

, includes the following clamp.

The clamp rod

5

has the other end potion provided with the above-mentioned guide grooves

26

. Each of the guide grooves

26

includes the rotary groove

27

provided at its other end portion with a stopper wall

45

which receives the engaging member or ball

29

. The stopper wall

45

has a receiving surface

45

a

which fits with the engaging member or ball

29

. This invention offers the following advantage. When the clamp rod rotates and retreats, the receiving surface of the stopper wall fits with the engaging member or ball to inhibit the clamp rod from rotating. This results in stopping the rotation of the clamp rod with a high accuracy.

Besides, the present invention, for example, as shown in

FIG. 1

, includes the following clamp. An annular piston

15

is inserted into the housing

3

axially movably. The clamp rod

5

is inserted into the piston

15

. A radial bearing

24

is arranged between the piston

15

and the clamp rod

5

. This invention offers another advantage of more smoothly rotating the clamp rod.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1

to

4

show a first embodiment of the present invention;

FIG. 1

is a partial sectional view of a rotary clamp when seen in elevation;

FIG. 2

is a sectional view of a rotary mechanism provided in the clamp when seen in plan;

FIG. 3

is an enlarged view of an essential portion in FIG.

1

and corresponds to a sectional view when seen along a line III—III in

FIG. 2

in a direction indicated by arrows;

FIG. 4

is an enlarged and developed view of a lower slide portion provided in a clamp rod of the clamp;

FIG. 5

shows a first modification of the first embodiment and is similar to

FIG. 4

;

FIG. 6

shows a second modification of the first embodiment and is similar to

FIG. 4

;

FIGS. 7

to

10

show a second embodiment of the present invention;

FIG. 7

is a partial sectional view of the clamp when seen in elevation and is similar to

FIG. 1

;

FIG. 8

is a sectional view of a rotary mechanism provided in the clamp when seen in plan and is similar to

FIG. 2

;

FIG. 9

is an enlarged view of an essential portion in FIG.

7

and corresponds to a sectional view when seen along a line

1

X—

1

X in

FIG. 8

in a direction indicated by arrows;

FIG. 10

is an enlarged and developed view of a lower slide portion provided in a clamp rod of the clamp and is similar to

FIG. 4

;

FIG. 11

shows a clamp according to a third embodiment of the present invention and is similar to

FIG. 7

;

FIG. 12

shows a first modification of the third embodiment and is similar to

FIG. 11

;

FIG. 13

shows a second modification of the third embodiment and is similar to

FIG. 11

;

FIG. 14

shows a clamp according to a fourth embodiment of the present invention and is similar to

FIG. 13

; and

FIG. 15

shows a modification of the fourth embodiment and is similar to FIG.

14

.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention is explained with reference to

FIGS. 1

to

4

. Fist, an explanation is given for a whole structure of a rotary clamp by resorting to FIG.

1

.

FIG. 1

is a partial sectional view of the clamp when seen in elevation.

A housing

3

of a clamp

2

is fixed to a work pallet

1

through a plurality of bolts (not shown). The housing

3

has a cylindrical hole

4

into which a clamp rod

5

is inserted. The clamp rod

5

has an upper end portion to which an arm

6

is secured at a desired rotation position by a nut

7

. The arm

6

has a leading end portion to which a push bolt

8

is fixed.

The housing

3

has an upper end wall (first end wall)

3

a

which supports an upper slide portion (first slide portion)

11

provided in a rod main body

5

a

of the clamp rod

5

slidably and hermetically. Further, a support cylinder

13

forms part of a lower end wall (second end wall)

3

b

of the housing

3

and slidably supports a lower slide portion (second slide portion)

12

which projects downwards of the rod main body

5

a

. The upper slide portion

11

and the lower slide portion

12

are tightly fitted into the upper end wall

3

a

and the lower end wall

3

b

, respectively.

The lower slide portion

12

has an outer diameter set to a value smaller than that of an outer diameter of the upper slide portion

11

.

A means for driving the clamp rod

5

is constructed as follows.

The clamp rod

5

is provided with an input portion

14

in the shape of a flange between the upper slide portion

11

and the lower slide portion

12

. Further, an annular piston

15

is externally fitted onto the clamp rod

5

vertically movably and hermetically through a sealing member

16

. The piston

15

faces the input portion

14

from above. And the piston

15

is inserted into the cylindrical hole

4

hermetically through another sealing member

15

a.

In addition, a radial bearing

24

is arranged between the input portion

14

and the piston

15

. A snap ring

25

prevents the removal of the piston

15

. Here the radial bearing

24

is composed of many metal balls and can receive not only a radial force but also a vertical thrust.

A first chamber

21

for clamping is provided between the piston

15

and the upper end wall

3

a

. A clamp spring

20

made of an compressed coil spring is attached in the first chamber

21

. A second chamber

22

for unclamping is provided between the piston

15

and the lower end wall

3

b

. Pressurized oil is supplied to and discharged from the second chamber

22

through a pressurized oil supply and discharge port

19

for unclamping and a restricting oil passage

18

.

A fitting gap (G) between a peripheral wall of the second chamber

22

and an outer peripheral surface of the piston

15

limits supply amount of pressurized oil from the oil passage

18

to the second chamber

22

as well as discharge amount of the pressurized oil from the second chamber

22

to the oil passage

18

.

A rotary mechanism is provided over the lower slide portion

12

of the clamp rod

5

and an upper portion of an inner wall

13

a

of the support cylinder

13

. The rotary mechanism is constructed in the following manner as shown in FIG.

1

and

FIGS. 2

to

4

.

FIG. 2

is a sectional view of the rotary mechanism when seen in plan.

FIG. 3

is an enlarged view of an essential portion in FIG.

1

and corresponds to a sectional view when seen along a ling III—III in

FIG. 2

in a direction indicated by arrows.

FIG. 4

is an enlarged and developed view of an outer peripheral surface of the lower slide portion

12

.

The lower slide portion

12

has the outer peripheral surface provided with three guide grooves

26

peripherally at substantially the same spacing. Each of the guide grooves

26

is formed from a groove in the shape of an arc or a segment when seen in section. And it comprises a helical rotary groove

27

and a straight groove

28

which is in upward continuity with the helical rotary groove

27

. The rotary grooves

27

as well as the straight grooves

28

are arranged in parallel with one another. As for the adjacent guide grooves

26

,

26

, a partition wall is minimum in thickness between a lower portion of a right rotary groove

27

and an upper portion of a left rotary groove

27

in FIG.

4

. The minimum thickness (M) of the partition wall is set to a value smaller than a groove width (W) of the guide groove

26

. Further, the rotary groove

27

is inclined at an angle (A) which is set to a small value within a range of about 11 degrees to about 25 degrees. In the exemplified clamp which relies on a spring force, the inclination angle (A) is preferably set to a value within a range of about 11 degrees to about 20 degrees for reducing the rotation stroke.

As such the inclination angle (A) of the helical rotary grove

27

has been made small to result in largely shortening a lead of the rotary groove

27

. This decreases the stroke for rotating the clamp rod

5

.

An engaging ball

29

is fitted into each of the guide grooves

26

. Numeral

29

a

in

FIGS. 3 and 4

designates a fitting portion of the engaging ball

29

. The engaging ball

29

has a diameter (D) (see

FIG. 3

) set to a value larger than the minimum thickness (M) of the partition wall between the adjacent rotary grooves

27

,

27

. The respective engaging balls

29

are rotatably supported by three through holes

31

provided in the upper portion of the inner wall

13

a

of the support cylinder

13

. A sleeve

35

is externally fitted over these three engaging balls

29

rotatably around the axis. Speaking it in more detail, the sleeve

35

has an inner peripheral surface formed with a groove

36

in the shape of a letter ‘V’. The V-shaped groove

36

has two vertical points at which the engaging ball

29

can roll.

The engaging ball

29

is inserted into the through hole

31

via an internally threaded hole

49

which is provided in the sleeve

35

. A closure bolt

50

is attached to the internally threaded hole

49

. A projection

50

a

at a leading end of the closure bolt

50

can receive the engaging ball

29

.

The rotary groove

27

has a lower end portion provided with a stopper wall

45

which receives the fitting portion

29

a

of the engaging ball

29

. The stopper wall

45

has a receiving surface

45

a

which can fit with the engaging ball

29

.

Besides, the guide groove

26

has an opening which is provided at its edge portion with a cutting surface

34

for preventing interference. Owing to this arrangement, even if the opening edge portion of the guide groove

26

undergoes a plastic deformation by a surface pressure of the engaging ball

29

and heaps up, it is possible to prevent the interference between the heaped-up portion and the inner wall

13

a

of the support cylinder

13

. As a result, the clamp rod

5

smoothly rotates for a long period of time.

Further, as shown in

FIG. 1

, an outer wall

13

b

of the support cylinder

13

is attached to a barrel portion

3

c

of the housing

3

through a positioning pin

38

which extends vertically, so as to be prevented from rotating. This makes it possible to accurately determine a rotation phase of the clamp rod

5

with respect to the housing

3

. The support cylinder

13

is secured to the housing barrel portion

3

c

by a lock member

39

made of a snap ring.

The rotary clamp

2

operates as follows.

In a state of

FIG. 1

, pressurized oil is supplied to the second chamber

22

for unclamping, thereby raising the clamp rod

5

to an illustrated rotation and retreat position.

When switching over the clamp

2

to a clamping condition, the pressurized oil in the second chamber

22

is discharged to push down the input portion

14

of the clamp rod

5

by the clamp spring

20

. Then the clamp rod

5

goes down along the rotary grooves

27

while rotating in a clockwise direction when seen in plan. Subsequently, it descends straightly along the straight grooves

28

. This enables the clamp rod

5

to switch over to a clamping position (not shown).

As shown by an arrow in

FIG. 2

, when the clamp rod

5

rotates in the clockwise direction when seen in plan, every engaging ball

29

fitted into the rotary groove

27

rolls in a counter-clockwise direction when seen in plan and at the same time the sleeve

35

externally fitted over the respective engaging balls

29

freely rotates in the counter-clockwise direction. This allows almost only rolling friction to act between an inner peripheral surface of the sleeve

35

and every engaging ball

29

, but hardly allows sliding friction to act therebetween. This reduces a resistance which acts from the sleeve

35

to every engaging ball

29

, which results in decreasing a frictional force which acts from every engaging ball

29

to the rotary groove

27

and therefore smoothly rotating the clamp rod

5

with a light force.

Here, the sleeve

35

has an inner diameter set to a value which is about one and half times a value of an outer diameter of the lower slide portion

12

of the clamp rod

5

. Thus in the case of rotating the clamp rod

5

by 90 degrees, the sleeve

35

rotates by about 60 degrees.

When switching over the clamp

2

from the clamping condition to a rotated and retreated condition in

FIG. 1

, the pressurized oil is supplied to the second chamber

22

for unclamping. Then, first, the piston

15

goes up by an upward oil pressure force which acts on an annular sectional area of the piston

15

. Simultaneously, the clamp rod

5

straightly ascends along the straight grooves

28

by an upward oil pressure force which acts on an inner sectional area of the sealing member

16

. Subsequently, the clamp rod

5

ascends along the rotary grooves

27

while rotating in the counter-clockwise direction when seen in plan, whereby the clamp rod

5

and the arm

6

switch over to the rotation and retreat position in FIG.

1

.

In this case, as mentioned above, the upward force which acts from the pressurized oil in the second chamber

22

to the piston

15

does not apply to the clamp rod

5

. This prevents an excessive force from acting on the rotary grooves

27

and the engaging balls

29

.

At the above time of rotating and retreating, if the clamp rod

5

rotates in the counter-clockwise direction, every engaging ball

29

and the sleeve

35

rotates in a direction opposite to the direction indicated by the arrow in FIG.

2

.

Further, at the above time of rotating and retreating, as shown in

FIGS. 1 and 4

, the stopper wall

45

has the receiving surface

45

a

fitted with the fitting portion

29

a

of the engaging ball

29

, thereby inhibiting the rotation of the clamp rod

5

. This results in stopping the rotation of the clamp rod

5

with a high accuracy. Moreover, the clamp rod

5

is provided with the stopper wall

45

and therefore offers the following advantage, when compared with a case where the barrel portion

3

c

of the housing

3

is provided with the stopper wall

45

.

The cylindrical hole

4

of the housing

3

need not be provided with a stepped portion for the stopper wall and therefore can be formed straight. This can facilitate the machining of the cylindrical hole

4

and besides can make the clamp spring

20

large and strong.

The first embodiment further offers the following advantages.

The clamp rod

5

is provided with the guide grooves

26

, into which the engaging balls

29

are fitted, respectively. This enables the support cylinder

13

to support the clamp rod

5

peripherally and substantially evenly through the engaging balls

29

. Accordingly, when driven for clamping and for unclamping, the clamp rod

5

can be prevented from inclining. This results in improving the accuracy of placing the push bolt

8

provided in the arm

6

at a clamping position and at an unclamping position.

The partition wall between the adjacent guide grooves

26

,

26

has the minimum thickness (T) set to the value smaller than the groove width (W) of the guide groove

26

. Consequently, many guide grooves

26

can be provided in the clamp rod

5

to result in the possibility of peripherally and substantially evenly supporting the clamp rod

5

and at the same time decreasing the inclination angle (A) of the rotary groove

27

. This can reduce the stroke required for rotating the clamp rod

5

to thereby make the rotary clamp

2

compact.

The clamp rod

5

is provided with the upper slide portion (first slide portion)

11

and the lower slide portion (second slide portion)

12

outside the opposite ends of the piston

15

. Therefore, notwithstanding the existence of a fitting gap of the piston

15

, the two slide portions

11

,

12

axially spaced apart from each other can prevent the inclination of the clamp rod

5

. In consequence, the housing

3

can surely guide the clamp rod

5

with a high accuracy.

The rotary mechanism which comprises the rotary grooves

27

and the engaging balls

29

is provided between the support cylinder

13

which has the above-mentioned guiding strength, and the lower slide portion

12

. Therefore, it can fully endure a rotary torque and increase its service lifetime. In addition, the engaging balls

29

are provided in the support cylinder

13

, thereby enabling portions for installing the engaging balls

29

to serve as a portion for supporting the lower slide portion

12

. Thus it is possible to reduce a height of the housing

3

and make the rotary clamp

2

compact.

Moreover, the lower slide portion

12

has the outer diameter set to the value smaller than that of the outer diameter of the upper slide portion

11

to result in shortening the lead of the rotary groove

27

formed in the lower slide portion

12

. This further reduces the stroke for rotating the clamp rod

5

and as a result can make the rotary clamp

2

more compact. Additionally, the pressurized oil for driving the piston

15

is decreased in supply and discharge amount.

FIG. 5

shows a first modification of the first embodiment and is similar to FIG.

4

. In

FIG. 5

, the partition wall between the adjacent rotary grooves

27

,

27

has the minimum thickness (M) set to a value smaller than that shown in FIG.

4

. The adjacent cutting surfaces

34

,

34

overlaps one another at a portion of the minimum thickness (M). Further, in

FIG. 5

, the inclination angle (A) of the rotary groove

27

is set to a value within a smaller range (about 11 degrees to about 15 degrees) than that of FIG.

4

.

FIG. 6

shows a second modification of the first embodiment and is similar to FIG.

4

. In this case, the clamp rod

5

has the lower slide portion

12

provided with four guide grooves

26

. A pair of the adjacent guide grooves

26

,

26

and the corresponding engaging balls

29

are displaced not only peripherally of the clamp rod

5

but also axially thereof. And the partition wall between a pair of the adjacent rotary grooves

27

,

27

has the minimum thickness (M) set to a value smaller than the groove width (W). The partition wall between a pair of the adjacent straight grooves

28

,

28

has a minimum thickness (N) set to a value smaller than the groove width (W). Additionally, the latter minimum thickness (N) is set to a value smaller than that of the former minimum thickness (M). Thus the partition wall between the adjacent guide grooves

26

,

26

has a minimum thickness (T) set to a value smaller than the groove width (W) and the diameter of the engaging ball

29

.

The first embodiment and its modifications can be modified as follows.

It is possible to provide the through holes

31

which rotatably support the engaging balls

29

, in the barrel portion

3

c

of the housing

3

and the like instead of providing them in the support cylinder

13

(lower end wall

3

b

) as exemplified.

The inner peripheral surface of the sleeve

35

may be provided with a U-shaped groove or an arcuate groove instead of the exemplified V-shaped groove

36

. Further, it may be a straight inner peripheral surface. With the straight inner peripheral surface, in order to inhibit the vertical movement of the sleeve

35

with respect to the engaging balls

29

, it is considered to provide a snap ring or the like stopper between the inner wall

13

a

of the support cylinder

13

and the sleeve

35

.

The helically formed rotary groove

27

is inclined at the angle (A) preferably within a range of 10 degrees to 30 degrees and more preferably within a range of 11 degrees to 20 degrees.

FIGS. 7

to

10

show a second embodiment and

FIGS. 11

to

13

illustrate a third embodiment. Further,

FIGS. 14 and 15

show a fourth embodiment. In these separate embodiments, the members similar to the constituent members in the first embodiment are, in principle, designated by the same characters.

In the second embodiment shown in

FIGS. 7

to

10

,

FIG. 7

is a partial sectional view of the rotary clamp

2

when seen in elevation and is similar to FIG.

1

.

FIG. 8

is a sectional view of the rotary mechanism provided in the clamp

2

when seen in plan and is similar to FIG.

2

.

FIG. 9

is an enlarged view of an essential portion in FIG.

7

and corresponds to a sectional view when seen along a line IX—IX in

FIG. 8

in a direction indicated by arrows.

FIG. 10

is an enlarged and developed view of the lower slide portion

12

provided in the clamp rod

5

of the clamp

2

.

The second embodiment is different from the first embodiment on the following points.

The driving means for the clamp rod

5

is formed into a double-acting system. More specifically, pressurized oil for clamping is supplied to and discharged from the first chamber

21

provided upwards of the piston

15

, through a pressurized oil supply and discharge port

17

for clamping. Further, pressurized oil for unclamping is supplied to and discharged from the second chamber

22

provided downwards of the piston

15

, through a pressurized oil supply and discharge port for unclamping (not shown) and the oil passage

18

.

Outside upper and lower opposite sides of another sealing member

15

a

attached to an outer periphery of the piston

15

in fitting relationship, there are formed relatively large fitting gaps between the outer peripheral surface of the piston

15

and the cylindrical hole

4

. This enables the housing

3

to smoothly support the clamp rod

5

with a good accuracy at vertical two portions of the upper slide portion

11

and the lower slide portion

12

.

The lower slide portion

12

has the outer peripheral surface provided with four guide grooves

26

peripherally at substantially the same spacing. Likewise the first embodiment, each of the guide grooves

26

comprises the helical rotary groove

27

and the straight groove

28

which is in upward continuity with the rotary groove

27

. However, the rotary groove

27

has a lower portion opened to an under surface of the clamp rod

5

through a vertically extending groove (designated by no numeral). The engaging ball

29

can be inserted into the guide groove

26

through the opening.

Likewise the first embodiment, as for the adjacent guide grooves

26

,

26

, the partition wall is minimum in thickness between a lower portion of a right rotary groove

27

and an upper portion of a left rotary groove

27

in FIG.

10

. The partition wall has the minimum thickness (M) set to a value smaller than the groove width (W) of the guide groove

26

and the diameter of the engaging ball

29

.

The engaging balls

29

fitted into the respective guide grooves

26

are rotatably supported by the four through holes

31

provided in the upper portion of the inner wall

13

a

of the support cylinder

13

. The sleeve

35

is externally fitted over these four engaging balls

29

rotatably around the axis. The rotary groove

27

is concaved to provide an arcuate recess

37

. Every engaging ball

29

is rollable in the rotary groove

27

at two vertical outside positions of the recess

37

.

A cylindrical spacer

32

is attached between a lower portion of a peripheral wall of the second chamber

22

for unclamping and an upper surface of the support cylinder

13

. The spacer

32

has an upper surface formed with a restricting groove

33

. The restricting groove

33

controls supply amount of the pressurized oil from the oil passage

18

to the second chamber

22

. A though hole or the like is employable instead of the groove

33

.

The support cylinder

13

is pushed and fixed to the housing barrel portion

3

c

by the lock member

39

made of an externally threaded cylinder.

Likewise the first embodiment, the lower slide portion

12

has the outer diameter set to a value smaller than that of the outer diameter of the upper slide portion

11

. This shortens the lead of the helical rotary groove

27

to result in reducing the rotation stroke of the clamp rod

5

.

FIG. 11

shows a third embodiment of the present invention.

FIG. 11

is a partial sectional view of the rotary clamp when seen in elevation and is similar to FIG.

7

.

The third embodiment of

FIG. 11

is distinct from the structure shown in

FIG. 7

merely on the following point.

The sleeve

35

in

FIG. 7

is omitted. And the spacer

32

prevents the removal of the engaging balls

29

supported by the inner wall

13

a

of the support cylinder

13

.

FIG. 12

shows a first modification of the third embodiment and is similar to FIG.

11

.

The first modification of

FIG. 12

differs from the structure of

FIG. 11

on the following points.

The piston

15

is integrally formed with the clamp rod

5

. Downwardly provided between the piston

15

and the lower end wall

3

b

are the second chamber

22

and a cylinder hole

41

for rejecting receipt of pressure in the mentioned order. The cylinder hole

41

is defined by an inner peripheral surface of an adaptor cylinder

42

. The clamp rod

5

has an enclosed portion

5

b

inserted into the cylinder hole

41

hermetically by a sealing member

43

.

Owing to the above arrangement, an upward force which acts on the clamp rod

5

upon unclamping is only an oil pressure force acting on an annular sectional area which appears by deducting a cross sectional area of the enclosed portion

5

b

from a cross sectional area of the second chamber

22

. Therefore, any excessive force does not act on the rotary grooves

27

and the engaging balls

29

.

It is sufficient if the enclosed portion

5

b

has a diameter set to a value smaller than that of a diameter of the second chamber

22

. Here it is set to substantially the same value as that of the diameter of the upper slide portion

11

of the clamp rod

5

.

It is preferable to set the diameter of the enclosed portion

5

b

to a value larger than that of the diameter of the upper slide portion

11

. In this case, the upward force which acts on the clamp rod

5

upon unclamping can be further decreased to result in extending the service lifetime of the rotary groove

27

and the engaging ball

29

.

Likewise

FIG. 11

, a relatively large fitting gap is formed between the outer peripheral surface of the piston

15

and an upper half portion of the cylindrical hole

4

as well as between the enclosed portion

5

b

of the clamp rod

5

and the cylinder hole

41

.

The oil passage

18

has a lower end surface formed with the restricting groove

33

.

A rod

46

which detects the clamping condition and the unclamping condition projects downwards of the lower slide portion

12

. The rod

46

is formed with an internally threaded hole

47

which engages with a detected member (not shown) in screw-thread fitting. A limit switch or the like sensor (not shown) opposes to the detected member.

Besides, the support cylinder

13

has the lower portion into which a plug

51

is hermetically fitted. A breathing passage

52

provided within the plug

51

communicates an interior space of the cylinder hole

41

with an exterior area. The breathing passage

52

, as shown in a schematic view, is provided with a trap valve

53

which comprises a check valve of spring type.

The trap valve

53

functions as follows.

When the clamp rod

5

has ascended to expand the interior space of the cylinder hole

41

, checking function of the trap valve

53

prevents the cutting lubricant and the like present in the exterior atmosphere from invading into the cylinder hole

41

. Further, when the clamp rod

5

has descended to contract the interior space of the cylinder hole

41

, the trap valve

53

smoothly discharges to the exterior area the pressurized oil which has invaded from the second chamber

22

to the interior space of the cylinder hole

41

.

FIG. 13

shows a second modification of the third embodiment and is similar to FIG.

11

.

FIG. 13

shows the rotary clamp

2

of single-acting and spring-return type, which is different from the structure shown in

FIG. 11

on the following points.

The piston

15

is formed integrally with the clamp rod

5

. A return spring

56

for unclamping is attached within the second chamber

22

formed between the support cylinder

13

and the piston

15

. The return spring

56

urges the clamp rod

5

upwards. Here the return spring

56

is composed of a compressed coil spring. The spring

56

has a lower end brought into contact with the support cylinder

13

and has an upper end received by the piston

15

through a thrust ball bearing

57

.

In addition, the sleeve

35

is rotatably and externally fitted over the engaging balls

29

.

The trap valve

53

is attached to a bolt

58

which engages with a mid portion of the support cylinder

13

in screw-thread fitting.

FIG. 14

illustrates a fourth embodiment of the present invention.

FIG. 14

is a partial sectional view of the rotary clamp

2

when seen in elevation and is similar to FIG.

13

.

The fourth embodiment of

FIG. 14

is distinct from the structure of

FIG. 13

on the following points.

The engaging balls

29

are prevented from removing, by the sleeve

35

externally fitted over the inner wall

13

a

of the support cylinder

13

. The sleeve

35

is fixed to the inner wall

13

a

through a pin

69

.

A torsion spring (resilient member)

61

composed of a coil spring is attached in an annular gap between the clamp rod

5

and the return spring

56

. The torsion spring

61

has an upper end connected to the clamp rod

5

through the piston

15

. Further, the torsion spring

61

has a lower end connected to the sleeve

35

, thereby connecting the lower end of the torsion spring

61

to the housing

3

through the support cylinder

13

.

The torsion spring

61

urges the clamp rod

5

(and the arm

6

) to the rotation and retreat position shown in

FIG. 14. A

preload is applied to the torsion spring

61

, for example, according to the following procedures.

The clamp rod

5

has an upper end surface opened to provide an internally threaded hole (not shown). By utilizing the internally threaded hole, the clamp rod

5

is twisted by a predetermined angle in the clockwise direction when seen in plan and the torsion spring

61

makes its urging force act in the counter-clockwise direction when seen in plan.

The rotary clamp

2

is, for instance, assembled according to the following procedures.

In advance, the clamp rod

5

, the support cylinder

13

, the torsion spring

61

and the return spring

56

are provisionally assembled. Speaking it in more detail, each of the engaging balls

29

is inserted into a predetermined rotation position (for example, the rotation position shown in

FIG. 14

) of every guide groove

26

. In that state, the support cylinder

13

and the sleeve

35

are formed into an integral structure by the pin

69

.

Next, the bolt

58

is removed from a female screw

60

of the support cylinder

13

. An operation bolt (not shown) is inserted into the female screw

60

. The operation bolt is fitted into a threaded hole

63

of the clamp rod

5

. The operation bolt is rotated to pull the clamp rod

5

toward the support cylinder

13

, thereby compressing the return spring

56

(and the torsion spring

61

) by a predetermined amount.

Subsequently, with the arm

6

removed from the clamp rod

5

, the clamp rod

5

and the support cylinder

13

are inserted into the housing

3

from below. The support cylinder

13

is attached to the lower portion of the housing

3

through the pin

38

so that it does not rotate. This can automatically determine the rotation phase of the clamp rod

5

. Thereafter, the lock member

39

made of a male screw fixes the support cylinder

13

to the housing

3

.

The rotary clamp

2

works as follows.

In a state shown by

FIG. 14

, the pressurized oil in the first chamber

21

is discharged. The clamp rod

5

rotates in the counter-clockwise direction when seen in plan by the torsion spring

61

and goes up through the return spring

56

.

When switching over the rotated and retreated clamp

2

to the clamping condition, the pressurized oil is supplied to the first chamber

21

, thereby enabling the piston

15

to push down the clamp rod

5

. Then the piston

15

compresses the return spring

56

and at the same time the clamp rod

5

descends along the rotary grooves

27

while rotating in the clockwise direction when seen in plan to enhance a torsional force of the torsion spring

61

. Subsequently, the piston

15

further compresses the return spring

56

and the clamp rod

5

descends straightly along the straight grooves

28

. This switches over the clamp rod

5

to the clamping position (not shown).

When switching over the clamp rod

5

from the clamping condition to the rotated and retreated condition in

FIG. 1

, the pressurized oil in the first chamber

21

is discharged.

Then, first, the piston

15

and the clamp rod

5

straightly go up along the straight grooves

28

through the urging force of the return spring

56

. Subsequently, the piston

15

and the clamp rod

5

ascend while strongly rotating in the counter-clockwise direction by a force resultant from a component force of rotation produced by the urging force of the return spring

56

, and the urging force of the torsion spring

61

. The clamp rod

5

and the arm

6

are smoothly switched over to the rotation and retreat position.

The fourth embodiment of

FIG. 14

offers the following advantages.

When performing an unclamping rotation, the clamp rod

5

strongly rotates to the rotation and retreat position by the force resultant from the component force of rotation produced by the urging force of the return spring

56

, and the urging force of the torsion spring (resilient member)

61

. Consequently, in order to smoothly rotate the clamp rod

5

, a gradient of the rotary groove

27

need not be increased and therefore the rotation stroke of the clamp rod

5

is small. This results in reducing the height of the rotary clamp

2

and besides decreases the consumption amount of the pressurized oil when it is driven for clamping.

Further, the return spring

56

is externally fitted onto the clamp rod

5

with an annular gap interposed therebetween. The torsion spring

61

is attached in the annular gap. Accordingly, by effectively utilizing a redundant space within the housing

3

, the rotary clamp

2

can be made more compact.

FIG. 15

shows a modification of the fourth embodiment and is similar to FIG.

14

.

The modification of

FIG. 15

supplies to the clamp

2

, pressurized oil of a higher pressure than the structure of FIG.

14

and is distinguished from the structure of

FIG. 14

on the following points.

The horizontal positioning pin

38

is provided between the lock member

39

made of the male screw and a lower portion of the housing barrel portion

3

c

. The torsion spring

61

is attached between the lock member

39

and the piston

15

. The support cylinder

13

is secured to the lock member

39

through a plurality of bolts

70

(only one of which is shown here). A spring retainer

71

is brought into contact with an under surface of the piston

15

from below. The return spring

56

is attached between a lower flange

72

of the spring retainer

71

and the lock member

39

through the thrust ball bearing

57

.

Downwardly projecting from the lower slide portion

12

is a rod

73

which detects the clamping condition and the unclamping condition. The rod

73

is formed with the threaded hole

63

. The threaded hole

63

engages with a detected member (not shown) in screw-thread fitting. The detected member opposes to a limit switch or the like sensor (not shown).

The fourth embodiment and its modification can be modified as follows.

The resilient member which urges the clamp rod

5

peripherally may be a cylindrical or columnar spring, rubber or the like instead of the exemplified coiled torsion spring

61

. The resilient member may be attached in an interior space of the clamp rod

5

.

The piston

15

may be formed separately from the clamp rod

5

instead of integrally therewith.

The respective embodiments and modifications can be further modified as follows.

The clamp rod

5

is preferably provided with three or four guide grooves

26

, but it may be provided with two guide grooves. Further, at least five guide grooves may be provided. And the guide groove

26

may have a groove in the shape of a cam instead of the exemplified helical rotary groove

27

.

It is sufficient if the minimum thickness (T) of the partition wall between the adjacent guide grooves

26

,

26

has a value smaller than the diameter of the engaging ball

29

. In consequence, the minimum thickness (T) can be made to have a value larger than the groove width (W) of the guide groove

26

.

Besides, the engaging member which is fitted into the guide groove

26

may be a columnar pin or the like instead of the exemplified ball

29

.

The pressurized fluid which is supplied to and discharged from the first chamber

21

or the second chamber

22

may be other kinds of liquid, and air or the like gas, instead of the exemplified pressurized oil.

On performing clamping operation, the clamp rod

5

rotates in the clockwise direction when seen in plan. Instead, on performing the clamping operation, it may rotate in the counter-clockwise direction when seen in plan. Further, it is a matter of course that the rotation angle of the clamp rod

5

may be set to a desired angle, for example, such as 90 degrees, 60 degrees and 45 degrees.

Number	Date	Country
P 2001-346977	Nov 2001	JP
P 2001-383987	Dec 2001	JP
P 2002-100851	Apr 2002	JP

Number	Name	Date	Kind
4351516	Ersoy et al.	Sep 1982	A
4508327	Ersoy	Apr 1985	A
5013015	Fatheree	May 1991	A
5192058	VanDalsem et al.	Mar 1993	A
5820118	Craft	Oct 1998	A
5927700	Yonezawa	Jul 1999	A
5954319	Yonezawa	Sep 1999	A
6113086	Yonezawa	Sep 2000	A

Rotary clamp

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (3)

US Referenced Citations (8)