Patent Description:
Conventionally, it is known that a vacuum suction apparatus for sucking and conveying a sheet-like or plate-like workpiece is equipped with a suction pad made of a porous material in order to suppress wrinkles and distortions of the workpiece.

For example, <CIT> discloses a vacuum suction apparatus including a body having a port to which a negative pressure fluid is supplied, a pad being made of a porous material and having a flat suction surface, and a holding body for holding the pad in such a manner that the pad can be displaced relative to the body. The pad has a body portion and a thin lip portion formed on the periphery of the body portion, and the holding body is disposed between the lip portion and the body of the pad.

<CIT> discloses a vacuum suction device which is capable of attracting a workpiece under a sucking action of a negative pressure fluid.

According to the vacuum suction apparatus, even when the workpiece is inclined with respect to the suction surface of the pad, the suction surface of the pad can be brought into contact with the workpiece.

In the case of the pad of the vacuum suction apparatus, in order to make the lip portion function as a sealing portion, the lip portion is pressed down when the pad is press-molded and as a result, a step is formed between the body portion and the lip portion. Such a pad is liable to deform in the vicinity of the step, and there is a possibility that the suction surface cannot maintain a flat shape.

Further, the pad of the vacuum suction device has a predetermined space between the holding plate attached to the body and the pad in order to allow the pad to be inclined. Therefore, when a high negative pressure is applied, there is a possibility that the pad deforms in a state of being inclined with respect to the holding plate, and the suction surface cannot maintain a flat shape.

The present invention has the object of solving the aforementioned problem.

A suction board having a suction surface configured to come into close contact with a workpiece includes an attaching adapter attached to a vacuum generating device, a nonwoven fabric sheet having a uniform thickness and being formed into a disk shape, and a ring-shaped holding body configured to movably support the nonwoven fabric sheet with respect to the attaching adapter. The suction surface is formed by the flat surface of the nonwoven fabric sheet, and the nonwoven fabric sheet is provided with an air-impermeable region on the outer peripheral portion and an air-permeable region excluding the outer peripheral portion, and the density of the air-impermeable region is higher than the density of the air-permeable region.

According to the suction board of the present invention, because the nonwoven fabric sheet has a uniform thickness, the nonwoven fabric sheet does not easily deform and the flat shape of the suction surface is maintained. Further, by adjusting the density of the nonwoven fabric sheet, it is possible to easily form an air-impermeable region in the outer peripheral portion and an air-permeable region excluding the outer peripheral portion.

A suction board <NUM> according to the first embodiment of the present invention will be described with reference to <FIG>. Moreover, in the following description, when terms in relation to up, down, left, and right directions are used, for the sake of convenience, such terms refer to the directions in the drawings, however, the actual arrangement of the constituent members or the like is not limited thereby.

As shown in <FIG> and <FIG>, the suction board <NUM> includes an attaching adapter <NUM>, a nonwoven fabric sheet <NUM>, a holding plate <NUM>, a holding body <NUM>, and a damper <NUM>. The attaching adapter <NUM> is made of a metal material such as an aluminum alloy and is formed in a disk shape. The attaching adapter <NUM> has a negative pressure supply passage <NUM> extending vertically through a central part of the attaching adapter <NUM> and is attached to a vacuum generating device (not shown). The lower portion of the attaching adapter <NUM> has a step portion <NUM> for mounting the holding body <NUM>. Reference numeral 12a denotes a bolt hole for attaching the attaching adapter <NUM> to the vacuum generating device.

The nonwoven fabric sheet <NUM> contains resin fiber and electrically conductive filler. The nonwoven fabric sheet <NUM> is formed into a disk shape and has a uniform thickness. The flat lower surface of the nonwoven fabric sheet <NUM> constitutes a suction surface <NUM> that can be brought into close contact with a sheet-like or plate-like workpiece. As shown in <FIG>, the nonwoven fabric sheet <NUM> includes an air-impermeable region <NUM> that occupies an outer peripheral portion and has air impermeability, and an air-permeable region <NUM> that occupies a portion excluding the outer peripheral portion and has air permeability. The density of the air-impermeable region <NUM> is higher than the density of the air-permeable region <NUM>.

The holding plate <NUM> is made of a metal material such as stainless steel and is formed in a disk shape. The outer diameter of the holding plate <NUM> coincides with the outer diameter of the nonwoven fabric sheet <NUM>. The holding plate <NUM> is joined to the nonwoven fabric sheet <NUM> with, for example, an electrically conductive double-sided tape. As shown in <FIG>, a central part of the holding plate <NUM> has a first hole 26a that is aligned with the negative pressure supply passage <NUM> of the attaching adapter <NUM>. The holding plate <NUM> has a plurality of arc-shaped second holes 26b surrounding the first hole 26a. The plurality of second holes 26b are formed at portions corresponding to the air-permeable region <NUM> of the nonwoven fabric sheet <NUM>.

The nonwoven fabric sheet <NUM> has a uniform thickness and a shape without steps. Thus, the nonwoven fabric sheet <NUM> does not easily deform. Further, since the nonwoven fabric sheet <NUM> is supported by the holding plate <NUM> having high rigidity, the nonwoven fabric sheet <NUM> does not deform even when a large negative pressure (high vacuum pressure) acts on the nonwoven fabric sheet <NUM>, and thus the flat shape of the suction surface <NUM> is reliably maintained. Further, since the holding plate <NUM> has a plurality of second holes 26b corresponding to the air-permeable region <NUM> of the nonwoven fabric sheet <NUM>, the permeability of the nonwoven fabric sheet <NUM> is not obstructed by the holding plate <NUM>.

The holding body <NUM> is a rubber sponge body formed by foaming a rubber material such as chloroprene rubber to which electrically conductive filler such as carbon or metal has been added, thereby making the rubber material porous. The holding body <NUM> has a large number of closed cells (closed bubbles) therein and does not have air permeability. The holding body <NUM> is formed into a ring shape and is disposed between the attaching adapter <NUM> and the holding plate <NUM>. The holding body <NUM> is attached to the step portion <NUM> of the attaching adapter <NUM> and protrudes downward from the attaching adapter <NUM>. The nonwoven fabric sheet <NUM> and the holding plate <NUM> are movably supported with respect to the attaching adapter <NUM> by the holding body <NUM>.

The holding body <NUM> has a notch groove <NUM> that encircles the holding body <NUM> on the outer peripheral surface of the holding body <NUM>. That is, the holding body <NUM> includes a first flange portion 28b extending radially outward from an upper portion of a main body portion 28a, and a second flange portion 28c extending radially outward from a lower portion of the main body portion 28a. The upper surface of the holding body <NUM> is joined to a stepped surface 16a of the step portion <NUM> of the attaching adapter <NUM>, and the lower surface of the holding body <NUM> is joined to the upper surface of the outer peripheral portion of the holding plate <NUM>.

The damper <NUM> is made of a rubber material such as NBR, and is molded in a ring shape. The damper <NUM> is mounted on the lower portion of the attaching adapter <NUM> and protrudes slightly downward from the lower surface of the attaching adapter <NUM>. The damper <NUM> faces the upper surface of the holding plate <NUM> with a predetermined gap therebetween. When the holding plate <NUM> is displaced upward, the damper <NUM> comes into contact with the holding plate <NUM>.

It is preferable to use the holding body <NUM> having a closed-cell structure at a squishing ratio of <NUM>% or less. In other words, the holding body <NUM> is preferably used at a squishing ratio of <NUM>% or less, which is within the range of elastic deformation. In repeated use, if the squishing ratio greatly exceeds <NUM>%, the cells inside the holding body <NUM> burst, and the cushioning property and the air impermeability of the holding body <NUM> are impaired.

Therefore, it is preferable that the value of (H-L)/H is <NUM> or less, where H denotes the height (vertical thickness) of the main body portion 28a of the holding body <NUM> and L denotes the vertical distance from the stepped surface 16a of the attaching adapter <NUM> to a protruding end of the damper <NUM>. Thus, the desired cushioning property and air impermeability of the holding body <NUM> can be maintained for a long period of time. The cushioning property of the holding body <NUM> depends on the main body portion 28a, and the first flange portion 28b and the second flange portion 28c do not contribute to the cushioning property of the holding body <NUM>.

The upper surface of the holding body <NUM> is joined to the stepped surface 16a of the attaching adapter <NUM> by using an electrically conductive double-sided tape (not shown). The lower surface of the holding body <NUM> is joined to the upper surface of the outer peripheral portion of the holding plate <NUM> joined to the nonwoven fabric sheet <NUM> by using an electrically conductive double-sided tape (not shown). Specifically, a double-sided tape is placed between the upper surface of the holding body <NUM> and the stepped surface 16a of the attaching adapter <NUM>, and a hard jig (not shown) is inserted into the notch groove <NUM> of the holding body <NUM> while the double-sided tape is placed between the lower surface of the holding body <NUM> and the upper surface of the holding plate <NUM>.

Thereafter, the first flange portion 28b of the holding body <NUM> is sandwiched between the attaching adapter <NUM> and the jig, whereby the holding body <NUM>, the double-sided tape, and the attaching adapter <NUM> are press-joined to each other. Thereafter, the second flange portion 28c of the holding body <NUM> is sandwiched between the holding plate <NUM> and the jig, whereby the holding body <NUM>, the double-sided tape, and the holding plate <NUM> are pressed-joined to each other. The order of these two press-joining steps may be reversed.

In the press-joining step, the first flange portion 28b of the holding body <NUM> is pressed to a large extent and adheres to the double-sided tape. Similarly, the second flange portion 28c of the holding body <NUM> is pressed to a large extent and adheres to the double-sided tape. Thus, the holding body <NUM> and the attaching adapter <NUM> are reliably joined by the double-sided tape, and the holding body <NUM> and the holding plate <NUM> are reliably joined by the double-sided tape.

Next, with reference to <FIG> and <FIG>, an operation in which a plate-like workpiece W such as a glass substrate is sucked and held by the suction board <NUM> will be described. It is assumed here that the workpiece W has a size larger than the suction surface <NUM> of the suction board <NUM> and is sucked and held by a plurality of suction boards <NUM>. Hereinafter, a vacuum generating device (not shown) to which a plurality of suction boards <NUM> are attached is referred to as a "vacuum suction device".

The vacuum suction device is operated to supply negative pressure (vacuum pressure) to the negative pressure supply passage <NUM> of the suction board <NUM>, and the vacuum suction device is moved so that the suction board <NUM> approaches the workpiece W. When the negative pressure is supplied to the negative pressure supply passage <NUM>, the negative pressure acts on the upper surface of the nonwoven fabric sheet <NUM> through the first hole 26a and the second holes 26b of the holding plate <NUM>. Through the air-permeable region <NUM> of the nonwoven fabric sheet <NUM>, this negative pressure further acts on the workpiece W that faces the lower surface of the nonwoven fabric sheet <NUM>.

When the weight of the workpiece W is relatively small, the workpiece W is displaced upward (lifted) and adheres to the suction surface <NUM> of the suction board <NUM> even if the workpiece W is not pressed onto the suction board <NUM>. When the weight of the workpiece W is relatively large, the suction board <NUM> is pressed onto the workpiece W, whereby the suction surface <NUM> of the suction board <NUM> is brought into close contact with the workpiece W.

Once the workpiece W is brought into close contact with the suction surface <NUM> of the suction board <NUM>, the differential pressure between the negative pressure acting on the upper surface of the workpiece W and the atmospheric pressure acting on the lower surface of the workpiece W rapidly increases. Due to this differential pressure, the workpiece W pushes up the nonwoven fabric sheet <NUM> and the holding plate <NUM>, and displaces upward while squishing the holding body <NUM>. When the holding plate <NUM> comes into contact with the damper <NUM>, the displacement of the workpiece W stops. In this way, the workpiece W is sucked and held by the suction board <NUM> in a stable state. The impact at the time of lifting the workpiece W is absorbed by the holding body <NUM> being squished and by the holding plate <NUM> being in contact with the damper <NUM>.

Since the nonwoven fabric sheet <NUM> has an air-impermeable region <NUM> in the outer peripheral portion thereof, and the holding body <NUM> having a closed-cell structure has air impermeability, vacuum leak does not occur. Joint portions between the holding body <NUM> and the attaching adapter <NUM>, between the holding body <NUM> and the holding plate <NUM>, and between the holding plate <NUM> and the nonwoven fabric sheet <NUM> are sealed so that vacuum leak does not occur.

<FIG> shows a state in which the nonwoven fabric sheet <NUM> and the holding plate <NUM> are displaced upward without changing the posture and also the workpiece W is sucked and held. When the upper surface of the workpiece W having high rigidity has a plane with relatively high accuracy and the plurality of suction boards <NUM> are attached to the vacuum generating device with high accuracy, the workpiece W is sucked and held in the state shown in <FIG> by all the suction boards <NUM>.

On the other hand, when part of the plurality of suction boards <NUM> is not attached to the vacuum generating device in an accurate posture (when an attachment error is not less than a predetermined value), the workpiece W is sucked and held in the state shown in <FIG> by the part of the suction boards <NUM>. Similarly, even when the upper surface of the workpiece W having high rigidity is not a flat surface, the workpiece W is sucked and held in the state shown in <FIG> at some of the suction boards <NUM>. Thus, the workpiece W can be brought into close contact with the suction surfaces <NUM> of all the suction boards <NUM>.

As shown in <FIG>, the nonwoven fabric sheet <NUM> and the holding plate <NUM> are inclined with respect to the attaching adapter <NUM>, and the workpiece W adheres to the inclined nonwoven fabric sheet <NUM>. The amount of squishing the holding body <NUM> is the largest at the right end that is one end in the diameter direction, and the amount of squishing the holding body <NUM> is the smallest at the left end that is the other end in the diameter direction. At the beginning of the description of the suction holding action, it was described that the suction board <NUM> approaches the workpiece W while the negative pressure is supplied to the negative pressure supply passage <NUM> of the suction board <NUM>. However, after the suction board <NUM> is pressed onto the workpiece W, the negative pressure may be supplied to the negative pressure supply passage <NUM>.

According to the suction board <NUM> of the present embodiment, since the nonwoven fabric sheet <NUM> has a uniform thickness, the nonwoven fabric sheet <NUM> does not easily deform and the flat shape of the suction surface <NUM> is maintained. Moreover, since the nonwoven fabric sheet <NUM> is supported by the holding plate <NUM> having high rigidity, the nonwoven fabric sheet <NUM> does not deform even when a large negative pressure (high vacuum pressure) acts on the nonwoven fabric sheet <NUM>.

In addition, by adjusting the density of the nonwoven fabric sheet <NUM>, it is possible to easily form the air-impermeable region <NUM> in the outer peripheral portion and the air-permeable region <NUM> excluding the outer peripheral portion. Vacuum leak does not occur because the nonwoven fabric sheet <NUM> is provided with an air-impermeable region <NUM> and also the holding body <NUM> is air-impermeable.

Further, since the nonwoven fabric sheet <NUM> and the holding plate <NUM> are movably supported with respect to the attaching adapter <NUM> by the holding body <NUM> having a closed-cell structure, an impact at the time of lifting the workpiece W is absorbed. Moreover, even if there is an error larger than a predetermined value in the attachment of the suction board <NUM> to the vacuum generating device, the workpiece W certainly adheres to the suction surface <NUM> of the suction board <NUM>.

Further, since the holding body <NUM> has the notch groove <NUM> for inserting the jig, it is possible to reliably join the holding body <NUM> by means of the double-sided tape while the ratio of squishing the main body portion 28a in use is set to a preferable value. Further, since the nonwoven fabric sheet <NUM>, the holding body <NUM>, and the double-sided tape is electrically conductive, it is possible to release to the outside static electricity caused by sucking and holding of the workpiece W.

Next, a suction board <NUM> according to a second embodiment of the present invention will be described with reference to <FIG> and <FIG>. In the suction board <NUM> according to the second embodiment, the same or equivalent components as those of the above-described suction board <NUM> are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in <FIG> and <FIG>, the suction board <NUM> includes the attaching adapter <NUM>, the nonwoven fabric sheet <NUM>, a holding plate <NUM>, and the holding body <NUM>.

The holding plate <NUM> is made of a metal material such as stainless steel and is formed in a disk shape. The holding plate <NUM> is joined to the attaching adapter <NUM> using, for example, a double-sided tape having electric conductivity. A central portion of the holding plate <NUM> is provided with a first hole 42a that is aligned with the negative pressure supply passage <NUM> of the attaching adapter <NUM>. The holding plate <NUM> has a plurality of arc-shaped second holes 42b surrounding the first hole 42a. The plurality of second holes 42b are formed at positions corresponding to the air-permeable regions <NUM> of the nonwoven fabric sheet <NUM>. The holding plate <NUM> faces the nonwoven fabric sheet <NUM> with a predetermined gap therebetween. When the nonwoven fabric sheet <NUM> is displaced upward, the nonwoven fabric sheet <NUM> comes into contact with the holding plate <NUM>.

The holding body <NUM> that is a rubber sponge body has a large number of closed cells therein and does not have air permeability. The holding body <NUM> is formed into a ring shape and is disposed between the attaching adapter <NUM> and the nonwoven fabric sheet <NUM>. The outer diameter of the holding body <NUM> coincides with the outer diameter of the nonwoven fabric sheet <NUM>. The holding plate <NUM> is disposed on an inner side of the holding body <NUM>. The holding body <NUM> is mounted on the step portion <NUM> of the attaching adapter <NUM> and projects downwardly beyond the holding plate <NUM>. The nonwoven fabric sheet <NUM> is movably supported by the holding body <NUM> with respect to the attaching adapter <NUM>.

The holding body <NUM> has a notch groove <NUM> that encircles the holding body <NUM> on the outer peripheral surface of the holding body <NUM>. The first flange portion 28b of the holding body <NUM> is joined to the stepped surface 16a of the attaching adapter <NUM>. The second flange portion 28c of the holding body <NUM> is joined to the upper surface of the air-impermeable region <NUM> of the nonwoven fabric sheet <NUM>.

It is preferable to use the holding body <NUM> having a closed-cell structure at a squishing ratio of <NUM>% or less. Therefore, assuming that the height of the main body portion 28a of the holding body <NUM> is H and the distance in the vertical direction from the stepped surface 16a of the attaching adapter <NUM> to the lower surface of the holding plate <NUM> is L', it is preferable that a value of (H-L')/H is <NUM> or less. Thus, the desired cushioning property and air impermeability of the holding body <NUM> can be maintained for a long period of time.

The upper surface of the holding body <NUM> is joined to the stepped surface 16a of the attaching adapter <NUM> by using a double-sided tape having electric conductivity. The lower surface of the holding body <NUM> is joined to the upper surface of the nonwoven fabric sheet <NUM> by using an electrically conductive double-sided tape. Specifically, a double-sided tape is placed between the upper surface of the holding body <NUM> and the stepped surface 16a of the attaching adapter <NUM>, and a hard jig is inserted into the notch groove <NUM> of the holding body <NUM> while the double-sided tape is placed between the lower surface of the holding body <NUM> and the upper surface of the nonwoven fabric sheet <NUM>.

Thereafter, the first flange portion 28b of the holding body <NUM> is sandwiched between the attaching adapter <NUM> and the jig, whereby the holding body <NUM>, the double-sided tape, and the attaching adapter <NUM> are press-joined to each other. Thereafter, the second flange portion 28c of the holding body <NUM> is sandwiched between the nonwoven fabric sheet <NUM> and the jig, whereby the holding body <NUM>, the double-sided tape, and the nonwoven fabric sheet <NUM> are press-joined to each other. The order of these two press-joining steps may be reversed.

In the press-joining step, the first flange portion 28b of the holding body <NUM> is pressed to a large extent and adheres to the double-sided tape. Similarly, the second flange portion 28c of the holding body <NUM> is pressed to a large extent and adheres to the double-sided tape. Thus, the holding body <NUM> and the attaching adapter <NUM> are reliably joined by the double-sided tape, and the holding body <NUM> and the nonwoven fabric sheet <NUM> are reliably joined by the double-sided tape.

When a negative pressure is supplied to the negative pressure supply passage <NUM>, the negative pressure acts on the upper surface of the nonwoven fabric sheet <NUM> through the first hole 42a and the second holes 42b of the holding plate <NUM>. Through the air-permeable region <NUM> of the nonwoven fabric sheet <NUM>, this negative pressure further acts on the workpiece W that faces the lower surface of the nonwoven fabric sheet <NUM>.

Claim 1:
A suction board (<NUM>, <NUM>) including a suction surface (<NUM>) configured to come into close contact with a workpiece, the suction board (<NUM>, <NUM>) comprising:
an attaching adapter (<NUM>) attached to a vacuum generating device;
a nonwoven fabric sheet (<NUM>) having a uniform thickness and being formed into a disk shape; and
a ring-shaped holding body (<NUM>) configured to movably support the nonwoven fabric sheet (<NUM>) with respect to the attaching adapter (<NUM>),
wherein
the suction surface (<NUM>) is formed by a flat surface of the nonwoven fabric sheet (<NUM>),
the nonwoven fabric sheet (<NUM>) is provided with an air-impermeable region (<NUM>) on an outer peripheral portion and an air-permeable region (<NUM>) excluding the outer peripheral portion, and
a density of the air-impermeable region (<NUM>) is higher than a density of the air-permeable region (<NUM>).