Grinder pressing device

Description

FIELD OF THE INVENTION

The present invention relates to a grinder pressing device.

DESCRIPTION OF THE RELATED ART

Pressing force applied to an object to be ground by a grinder considerably affects grinding performance, grinding accuracy, life of the grindstone, and the like, and therefore grinding operation by a robot is carried out so as to maintain pressing force predetermined by various means.

There are types of grinder device; an electric grinder and an air grinder. In the former grinder, pressing force is controlled by a servomotor by determining pressing force applied to the object by a grindstone according to current of a grinder motor. In the latter grinder, pressing force is controlled by giving a command to a robot by using a six-axis sensor, for example.

However, in such controlling methods of pressing force, both the devices per se are expensive and, especially in the method of giving the command to the robot by using the six-axis sensor, control is complicated.

It is hence an object of the present invention to provide a grinder pressing device which is, irrespective of types of grinder, inexpensive and capable of compensating wear of a grindstone and/or a slight displacement of an object to be ground.

SUMMARY OF THE INVENTION

In a grinder pressing device according to the present invention, one of a bottom portion of a cylinder main body and a piston rod of an air cylinder in a vertical posture is attached to a fixed plate and the other is attached to a movable plate disposed below the fixed plate, one of a guide table and a guide is mounted on a movable plate side and the other is mounted on an outer peripheral face of the cylinder main body. The guide table is guided on the guide in a vertical direction under the rolling frictional condition through balls. In the air cylinder, hermeticity between outer peripheral walls of a piston and the piston rod and a structural wall of the cylinder main body side is provided by metal seals and friction coefficients between the walls is set low, and the piston rod is supported by a ball bushing in a large area so as to be movable forward and backward. A grinder is mounted to the movable plate directly or through another member, and pressing force of the grinder to an object to be ground can be controlled by adjusting air pressure of upper and lower cylinder chambers separated by the piston.

Moreover, a grinder pressing device of the present invention includes a hanging member having a grinder mounting portion and a partition plate, upper and lower bellows cylinders fixedly disposed on upper and lower faces of the partition plate, and a retaining member for maintaining a constant distance between an upper face of the upper bellows cylinder and a lower face of the lower bellows cylinder. The grinder pressing device is used in a manner that the retaining member is fixed to a fixed portion F or a robot output portion, that a grinder is provided on the grinder mounting portion, and that the upper and lower bellows cylinders are supplied with air of respectively predetermined pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is an explanatory view showing an air circuit of a grinding system using a grinder pressing device in Embodiment 1 of the present invention.

FIG. 2

is a front view of a grinder, the grinder pressing device and the like forming the grinding system.

FIG. 3

is a front view in which a piston rod of an air cylinder in the grinder pressing device is put in a contracted state from the state shown in FIG.

2

.

FIG. 4

is a side view of the grinder pressing device.

FIG. 5

is a sectional view taken along a line V—V in FIG.

3

.

FIG. 6

is an explanatory view of the air cylinder in the grinder pressing device.

FIG. 7

is a partially sectional perspective view of a device formed by combining a guide and a guide table used for the grinder pressing device.

FIG. 8

is a sectional view of the device formed by combining the guide and the guide table taken along line VIII—VIII in FIG.

7

.

FIG. 9

is an explanatory view showing an air circuit of a grinding system using a grinder pressing device in Embodiment 2 according to the present invention.

FIG. 10

is a front view of the grinder, the grinder pressing device and the like forming the grinding system in Embodiment 2 of present invention.

FIG. 11

is a side view of the grinder, the grinder pressing device and the like forming the grinding system in Embodiment 2 of present invention.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

The present invention is described in detail in conjunction with the accompanying drawings.

[Embodiment 1]

As shown in

FIG. 1

, the grinding system of this embodiment includes a grinder pressing device GK for supporting a grinder G and a compressor C for driving the grinder G to rotate and sending air to the grinder pressing device GK. Selector valves K

1

, K

2

, electro-pneumatic proportional valves K

3

, K

4

, and pressure sensors P

1

, P

2

are provided to air lines connecting the compressor C and the grinder G or the grinder pressing device GK.

Main structural portions of this grinding system will be described below.

The grinder G shown in

FIG. 1

is an air-type grinder in which a grindstone g is driven to rotate by compressed air from the compressor C and compressed air is fed through the above selector valve K

2

.

In the grinder pressing device GK, as shown in

FIGS. 2 and 3

, a bottom portion of a cylinder main body

10

of an air cylinder

1

in a vertical posture is fixed to a fixed plate

2

, and a movable plate

3

is attached to an end portion of a piston rod

11

of the air cylinder

1

. A guide table G

2

is mounted to the movable plate

3

side, and a guide G

1

is mounted on an outer peripheral face of the cylinder main body

10

. As shown in

FIGS. 7 and 8

, the guide table G

2

is guided on the guide G

1

in a vertical direction under the rolling frictional condition through balls B (steel balls). As shown in

FIGS. 3

to

5

, the grinder pressing device GK has a linear sensor RS for detecting a position of the movable plate

3

with respect to the fixed plate

2

so that a position of the grinder G can be detected, and further a dust-proof bellows pipe

4

surrounding parts and members present between the fixed plate

2

and the movable plate

3

. As shown in

FIGS. 2 and 6

, by adjusting air pressures in upper and lower cylinder chambers

13

and

14

separated by a piston

12

, pressing force applied to an object to be ground by the grindstone g of the grinder G fixed to the movable plate

3

through a mounting plate

49

can be adjusted.

As shown in

FIG. 6

, the air cylinder

1

is basically formed with the cylinder main body

10

, the piston

12

for dividing an inside of the cylinder main body

10

into the cylinder chambers

13

and

14

, and the piston rod

11

connected to the piston

12

. Supply and discharge of air to and from the cylinder chambers

13

and

14

cause the piston

12

to move to change a projecting portion of the piston rod

11

from the cylinder main body

10

. In this Embodiment, as shown in

FIG. 6

, the cylinder main body

10

is formed by combining members

10

a

to

10

h

and the like, and O-rings OR are disposed between the members where hermeticity is required.

In this air cylinder

1

, as shown in

FIG. 6

, airtightness is provided by metal seals MS between an outer peripheral wall of the piston

12

and an inner peripheral wall of the member

10

d

and between an outer peripheral wall of the piston rod

11

and an inner peripheral wall of the member

10

h

so as to set friction coefficients between the walls low. The piston rod

11

is supported by a ball bushing BS in a large area of the piston rod

11

so that the piston rod

11

can move forward and backward. Reference numeral

19

in

FIG. 6

denotes a grease groove.

The fixed plate

2

has two air lines

20

and

21

extending from a side face to a lower face of the fixed plate

2

as shown in

FIGS. 2 and 3

and is attached to the fixed portion F through another member as shown in FIG.

1

.

As shown in

FIGS. 1 and 2

, air that has passed through the electro-pneumatic proportional valve K

3

is supplied to the cylinder chamber

14

through the air line

20

and a tube Tl, while air that has passed through the electro-pneumatic proportional valve K

4

is supplied to the cylinder chamber

13

through the air line

21

and a tube T

2

.

The movable plate

3

and the mounting plate

49

are united with each other with a bolt and the like, and, as shown in

FIG. 2

, the grinder G is attached to the mounting plate

49

in a manner that a posture of the grinder G can be changeable.

The bellows pipe

4

is made of rubber material and, as shown in

FIG. 2

, core wires are embedded in outer peripheral sharp portions

40

so that the bellows pipe

4

has very small expansion-contraction resistance and shape retention in a diameter direction. A part of the bellows pipe

4

in this Embodiment takes the form of mesh through which air can come into and go out of the bellows pipe

4

.

The guide G

1

and the guide table G

2

are assembled with each other through balls B as shown in

FIGS. 7 and 8

. When the guide table G

2

moves on the guide G

1

, the balls rotatively circulate. The balls B have angular-contact structure of 45° with respect to the guide G

1

and are applied with well-balanced preload. Therefore, the balls B have the same rated load in vertical and horizontal directions and maintain a constantly low coefficient of rolling friction.

As shown in

FIGS. 2 and 3

, the guide G

1

is mounted on an outer face of the cylinder main body

10

of the air cylinder

1

in a vertical posture and the guide table G

2

is mounted on a bracket

39

erectly provided on the movable plate

3

. A range of movement of the guide table G

2

with respect to the guide G

1

is determined by upper-limit and lower-limit stoppers.

The linear sensor RS detects a position of the movable plate

3

with respect to the fixed plate

2

in order to detect a position of the grinder G, as described above. As shown in

FIGS. 4 and 5

, the linear sensor RS is disposed in a manner that a main body RS

1

thereof is mounted to the cylinder main body

10

and a rod RS

2

thereof is mounted on the movable plate

3

. The rod RS

2

of the linear sensor RS is movable with small resistance to the main body RS

1

.

With the structure of the grinder pressing device GK as stated above, air pressure to the cylinder chambers

13

and

14

can be adjusted by changing voltage or current to the electro-pneumatic proportional valves K

3

and K

4

. As a result, the pressing force of the grindstone g to the object to be ground can be set at a desired value.

In the air cylinder

1

used for the grinder pressing device GK, friction coefficients between the outer peripheral wall of the piston

12

and the inner peripheral wall of the member

10

d

and between the outer peripheral wall of the piston rod

11

and the inner peripheral wall of the member

10

h

are respectively set low, and the piston rod

11

is supported by a ball bushing BS in a large area of the piston rod

11

so that the piston rod

11

can move forward and backward. Therefore, the pressing force of the grindstone g to the object to be ground can be compensated irrespective of wear of the grindstone g or a slight displacement of the object to be ground.

Furthermore, use of the grinder pressing device GK eliminates an expensive device and enables very easy control, thereby cost being lowered.

In this Embodiment 1, design modifications of the following (1) to (6) may be made.

(1) In the above Embodiment, the vertical movement of the grinder G and the pressing force of the grindstone g to to the object to be ground are set by changing internal pressures in the cylinder chambers

13

and

14

of the air cylinder

1

by using the two electro-pneumatic proportional valves K

3

and K

4

. Alternatively, air pressure fed to one of the cylinder chambers

13

and

14

is fixed while air pressure fed to the other is variable.

(2) In a system in which the grindstone g presses the object to be ground while the object being moved vertically, both of the air pressures fed to the cylinder chambers

13

and

14

of the air cylinder

1

may be fixed.

(3) The grinder G used in the system of the above Embodiment is an air type one. However, an electric grinder may be selectively employed in the system.

(4) The grinder G is, although not limited thereto, attached to the fixed portion F through the grinder pressing device GK in the system of the above Embodiment. Optionally, for example, the grinder G may be attached to an output portion of a robot through the grinder pressing device GK.

(5) Different from the above Embodiment, the end portion of the piston rod

11

of the air cylinder

1

in the vertical posture may be fixed to the fixed plate

2

and a bottom portion of the cylinder main body

10

may be mounted on the movable plate

3

to form the grinder pressing device GK.

(6) Different from the above Embodiment, the guide G

1

may be attached to the movable plate

3

side and the guide table G

2

may be mounted on the outer peripheral face of the cylinder main body

10

.

[Embodiment 2]

The grinding system in this Embodiment, as shown in

FIG. 9

, includes a grinder G, a grinder pressing device GK for supporting the grinder G, a compressor C for driving the grinder G to rotate and feeding air to the grinder pressing device GK, and further as shown in

FIG. 10

, a frame

99

(corresponding to the fixed portion F) for supporting the grinder pressing device GK. Selector valves K

1

and K

2

, electro-pneumatic proportional valves K

3

and K

4

, and pressure sensors P

1

and P

2

are provided to air lines connecting the compressor C and the grinder G or the grinder pressing device GK.

Main structural portions of the grinding system will be described below.

As shown in

FIG. 9

, an air-type grinder in which compressed air from the compressor C drives a grindstone g to rotate is employed as the grinder G. The compressed air is fed through the above selector valve K

2

.

As shown in

FIGS. 10 and 11

, the grinder pressing device GK has a hanging member

5

on which the grinder G is hung, upper and lower bellows cylinders

6

and

7

fixedly disposed on upper and lower faces of a partition plate

51

of the hanging member

5

that will be described later, a retaining member

8

for maintaining a constant distance between an upper face of the upper bellows cylinder

3

and a lower face of the lower bellows cylinder

7

, a linear sensor RS for detecting a position of the grinder G, and a guide mechanism

9

for allowing the grinder G to move smoothly and vertically with keeping its posture.

As shown in

FIGS. 10 and 11

, the hanging member

5

is formed by connecting a grinder mounting portion

50

and the partition plate

51

by four connecting bars

52

.

As shown in

FIGS. 10 and 11

, the retaining member

8

includes a thick upper plate

80

, a thick lower plate

81

, and four connecting bars

82

which connect the upper and lower plates

80

and

81

.

The upper and lower bellows cylinders

6

and

7

are formed by closing opposite end faces of bellows pipes with plate members. As shown in

FIGS. 10 and 11

, the upper bellows cylinder

6

is fixedly disposed between the upper plate

80

and the partition plate

51

and the lower bellows cylinder

7

is between the partition plate

51

and the lower plate

81

. As shown in

FIGS. 10 and 11

, air from the compressor C can be supplied respectively to the upper bellows cylinder

6

through an air line

80

a formed in the upper plate

80

and to the lower bellows cylinder

7

through an air line

81

a

formed in the lower plate

81

. The upper bellows cylinder

6

may be formed by closing the opposite end faces of the bellows pipe with the upper plate

80

and the partition plate

51

and the lower bellows cylinder

7

may be formed by closing the opposite end faces of the bellows pipe with the partition plate

51

and the lower plate

81

.

As shown in

FIG. 11

, the linear sensor RS includes a main body RS

1

provided on a plate

83

hung across between the connecting bars

82

and

82

, and a rod RS

2

provided on an upper face portion of the grinder mounting portion

50

at its end portion. The position of the grinder G can be detected according to forward and backward movement of an input shaft portion

51

due to vertical movement of the grinder G. In a state in which the grindstone g is pressed against an object W to be ground, in order to cancel elastic returning force of the upper and lower bellows cylinders

6

and

7

generated when a position of the grinder G is shifted from a preset position, air pressure supplied to one of the upper and lower bellows cylinders

6

and

7

is changed by the electro-pneumatic proportional valve in response to output information of the linear sensor RS that has detected the position of the grinder G, thereby wear of the grindstone g or a slight displacement of the object W to be ground being compensated.

As shown in

FIGS. 10 and 11

, the guide mechanism

9

includes a bearing portion

90

mounted on the partition plate

51

and a shaft portion

91

hung from the upper plate

80

. The shaft portion

91

is closely and slidably inserted into a bore in the bearing portion

90

. Therefore, weight of the grinder G produces moment on the partition plate

51

. However, the partition plate

51

moves vertically while maintaining a horizontal state and the posture of the grinder G is not affected by the moment.

With the above structure of the grinder pressing device GK, the device GK has the following functions.

In order to move the grinder G upward, voltage or current to the electro-pneumatic proportional valves K

3

and K

4

is changed so as to make the internal pressure of the lower bellows cylinder

3

higher than that of the upper bellows cylinder

6

. In order to bring the grindstone g of the grinder G into contact with the object W to be ground, the voltage or the current to the electro-pneumatic proportional valve K

3

is reduced so as to gradually lower the internal pressure of the lower bellows cylinder

7

.

In the grinding process of the object W by the grindstone g of the grinder G, a constant relationship between the internal pressures of the upper bellows cylinder

6

and the lower bellows cylinder

7

is maintained to make the pressing force of the grindstone g to the object W to be ground constant. In case the pressing force is made constant as described above, regardless of wear of the grindstone g or a slight displacement of the object W to be ground, the pressing force applied to the object W to be ground by the grindstone g is compensated by the linear sensor RS and the like.

Furthermore, in this grinder pressing device GK, it is possible to know the position of the grinder G by the linear sensor RS and the like and to detect when to replace the grindstone g. Under the grinding process of the object W, an overload can be detected by the pressure sensors P

1

and P

2

. Moreover, the grinder pressing device GK in this Embodiment necessitates no expensive device and enables very easy control, thereby resulting in a lower cost.

In this Embodiment, design modifications of the following (1) to (6) may be made.

(1) In the above Embodiment, in the state in which the grindstone g is pressed against the object W to be ground, in order to cancel the elastic returning force of the upper and lower bellows cylinders

6

and

7

generated when the position of the grinder G is shifted from the preset position, air pressure supplied to one of the upper and lower bellows cylinders

6

and

7

is changed by the electro-pneumatic proportional valve in response to the output information of the linear sensor RS that has detected the position of the grinder G. However, such a system is not required in case elastic moduli of the upper and lower bellows cylinders

6

and

7

are set to small values. This is because the elastic returning force of the upper and lower bellows cylinders

6

and

7

generated when the position of the grinder G is shifted from the preset position are extremely small as compared with the pressing force of the grindstone g to the object W to be ground.

(2) In the above Embodiment, vertical movement of the grinder G and pressing force of the grindstone g to the object W to be ground are set by changing the internal pressures in the upper and lower bellows cylinders

6

and

7

by using the two electro-pneumatic proportional valves K

3

and K

4

. Alternatively, a system can be employed in which air pressure fed to one of the upper and lower bellows cylinders

6

and

7

is fixed while air pressure fed to the other is variable.

(3) In a system in which the object W to be ground is moved vertically and the grindstone g is pressed against the object W, air pressures respectively fed to the upper and lower bellows cylinders

6

and

7

may be fixed.

(4) The grinder G used for the system in the above Embodiment is an air type grinder. However, this system may be applied to an electric grinder.

(5) In the system of the above Embodiment, the grinder G m is, although not limited thereto, attached to the fixed portion F, or the frame

99

, through the grinder pressing device GK. Alternatively, for example, the grinder G may be attached to an output portion of a robot through the grinder pressing device GK.

INDUSTRIAL APPLICABILITY

As stated above, the grinder pressing device according to the present invention is, regardless of types of grinder, inexpensive and suitable for grinding a portion where wear of the grindstone and the slight displacement of the object to be ground have to be compensated.

Claims

1. A grinder pressing device comprising an air cylinder (1) in a vertical posture, a guide table (G2) and a guide (G1), wherein one of a bottom portion of a cylinder main body (10) and a piston rod (11) of said air cylinder (1) is fixed to a fixed plate (2) and other is mounted to a movable plate (3) disposed below said fixed plate (2), one of said guide table (G2) and said guide (G1) is mounted to a movable plate (3) side and other is mounted on an outer peripheral face of said cylinder main body (10), said guide table (G2) is guided on said guide (G1) in a vertical direction under a rolling frictional condition through balls (B), said air cylinder (1) is formed in a manner that hermeticity is provided by metal seals (MS) between outer peripheral walls of a piston (12) and said piston rod (11) and a structural wall of said cylinder main body (10) side so as to set friction coefficients between said walls low and that said piston rod (11) is supported by a ball bushing (BS) in a large area to move forward and backward, said movable plate (3) is provided directly or through another member with a grinder (G), and pressing force applied to an object to be ground by said grinder (G) can be controlled by adjusting air pressure of upper and lower cylinder chambers (13, 14) separated by said piston (12).
2. A grinder pressing device according to claim 1, wherein a linear sensor (RS) for detecting a position of said movable plate (3) with respect to said fixed plate (2) is provided so as to detect a position of said grinder (G).
3. A grinder pressing device according to claim 2, wherein a main body (RS1) side of said linear sensor (RS) is mounted on said cylinder main body (10) and a shaft portion (RS2) of said linear sensor (RS) is mounted on said movable plate (3).
4. A grinder pressing device according to claim 1, wherein a dust-proof bellows pipe (4) for surrounding a part and a member disposed between said fixed plate (2) and said movable plate (3) is provided and expansion-contraction resistance of said bellows pipe (4) is set very small.
5. A grinder pressing device comprising a hanging member (5) having a grinder mounting portion (50) and a partition plate (51), upper and lower bellows cylinders (6) (7) fixedly disposed on upper and lower faces of said partition plate (51), and a retaining member (8) for maintaining a constant distance between an upper face of said upper bellows cylinder (6) and a lower face of said lower bellows cylinder (7), wherein said retaining member (8) is mounted to one of a fixed portion (F) and a robot output portion, said grinder mounting portion (50) is provided with a grinder (G), and said upper and lower bellows cylinders (6)(7) are supplied with air of respectively predetermined pressures.
6. A grinder pressing device according to claim 5, wherein said upper and lower bellows cylinders (6)(7) are respectively supplied with air so as to cause lifting force to act on said partition plate (51) of said hanging member (5).
7. A grinder pressing device according to claim 5 , wherein at least one of air pressures supplied respectively to said upper and lower bellows cylinders (6)(7) is changeable.
8. A grinder pressing device according to claim 5, wherein at least one of air pressures supplied to said upper and lower bellows cylinders (6)(7) is changeable in response to output information of a linear sensor (RS) for detecting a position of said grinder (G) so as to cancel elastic returning force of said upper and lower bellows cylinders (6)(7) generated when said position of said grinder (G) in a state in which a grindstone (g) is pressed against an object (W) to be ground is shifted from a predetermined position.
9. A grinder pressing device according to claim 7, wherein at least one of air pressures supplied to said upper and lower bellows cylinders (6)(7) is changeable in response to output information of a linear sensor (RS) for detecting a position of said grinder (G) so as to cancel elastic returning force of said upper and lower bellows cylinders (6)(7) generated when a position of said grinder (G) in a state in which a grindstone (g) is pressed against an object (W) to be ground is shifted from a predetermined position.
10. A grinder pressing device according to claim 8, wherein when said linear sensor (RS) outputs information that a position of said grinder (G) is shifted more than a certain amount from said predetermined position, a warning means is put into an output state or said grinder (G) is set to stop.
11. A grinder pressing device according to claim 9, wherein when said linear sensor (RS) outputs information that a position of said grinder (G) is shifted more than a certain amount from said predetermined position, a warning means is put into an output state or said grinder (G) is set to stop.
12. A grinder pressing device according to claim 5, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.
13. A grinder pressing device according to claim 7, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.
14. A grinder pressing device according to claim 8, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.
15. A grinder pressing device according to claim 9, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.
16. A grinder pressing device according to claim 10, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.
17. A grinder pressing device according to claim 11, wherein said upper and lower bellows cylinders (6)(7) have a same diameter and are disposed on a same vertical axis.

Priority Claims (2)

Number	Date	Country	Kind
10-010487	Jan 1998	JP
10-268085	Sep 1998	JP

PCT Information

Filing Document	Filing Date	Country	Kind
PCT/JP99/00198		WO	00

Publishing Document	Publishing Date	Country	Kind
WO99/37442	7/29/1999	WO	A

US Referenced Citations (5)

Number	Name	Date	Kind
5095662	Grimm et al.	Mar 1992	A
5299389	Yonaha et al.	Apr 1994	A
5509847	Jinno et al.	Apr 1996	A
5565749	Jinno et al.	Oct 1996	A
5711697	Taninaga et al.	Jan 1998	A

Foreign Referenced Citations (3)

Number	Date	Country
57-178663	Feb 1982	JP
60-58841	Apr 1985	JP
06-109006	Apr 1994	JP

Grinder pressing device

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US