Patent Description:
Yarns are known, which each include elongated expanded graphites and a tubular member in which the expanded graphites are packed. For example, a yarn disclosed in Patent Literature <NUM> consists of a tubular member filled with fibrous expanded graphites with a constant length.

Fibrous expanded graphites of the yarn disclosed in Patent Literature <NUM> are elongated and straight in the tubular member. Accordingly, the expanded graphites are hardly entangled with each other when they are packed in the tubular member, and thus they provide the shaped yarn with unevenness in thickness. As a result, gland packings made of the yarns can fail to have a sufficient sealing performance.

Patent Literature <NUM> discloses a yarn comprising elongated pieces formed by mica flakes that are packed in a tubular member.

Patent Literature <NUM> discloses a yarn comprising elongated pieces of expanded graphite sheet that are packed in a tubular member.

In view of the above-mentioned problems, the invention is devised. An object of the invention is to achieve the uniformity in thickness of yarns and to enhance the sealing performance of a gland packing made of the yarns.

A yarn according to the invention includes the features of claim <NUM>.

That structure can easily entangle one piece of expanded graphite sheet with another, and thus, it can prevent each piece of expanded graphite sheet from moving relative to others. Even if the tubular member filled with pieces of expanded graphite sheet receives an external force to move the pieces of expanded graphite sheet relative to the tubular member in an axial direction of the tubular member, the pieces of expanded graphite sheet hardly lose their uniformity in density in the tubular member. This enables the yarn to substantially maintain its uniform thickness. As a result, a gland packing made of the yarns can enhance its sealing performance.

Each piece of expanded graphite sheet may be twisted at five turns or less per <NUM>.

Such an appropriate number of turns at which pieces of expanded graphite sheet are twisted can suppress failures of fracture and lack of the pieces of expanded graphite sheet during the shaping of the tubular member filled with the pieces of expanded graphite sheet, although an excessive number of the turns facilitates the failures. Thus, suppression of the failures can be achieved with thickness equalization of the yarns. In addition, a gland packing made of the yarns can further enhance its sealing performance.

A gland packing according to an embodiment of the invention includes the above-mentioned yarns that are knitted, or that are bundled and twisted.

This structure enables the gland packing to enhance its sealing performance.

The invention can achieve the uniformity in thickness of yarns and enhance the sealing performance of a gland packing made of the yarns.

An embodiment of the invention will be explained with reference to the drawings.

<FIG> is a schematically perspective view of a gland packing <NUM> with yarns <NUM> according to an embodiment of the invention. <FIG> is a front elevation view of a portion of the yarn <NUM>.

As shown in <FIG>, the yarns <NUM> are used to form the gland packing <NUM>. The yarns <NUM> may be used to form a product other than the gland packing <NUM>, such as a cloth for heat insulator.

In the gland packing <NUM>, the yarns <NUM> are knitted. The gland packing <NUM> only consists of the yarns <NUM>.

In another gland packing, bundles of the yarns <NUM> may be twisted. The yarns <NUM> may also form a gland packing with other material such as cores prepared separately.

As shown in <FIG>, each of the yarns <NUM> includes a tubular member <NUM> and elongated pieces of expanded graphite sheet <NUM>. In the tubular member <NUM>, the pieces of expanded graphite sheet <NUM> are twisted and packed.

The tubular member <NUM> is formed by knitted fibers. The tubular member <NUM> has a net-like structure. For example, the tubular member <NUM> has a tubular-knitted structure, in which fibers <NUM> are knitted.

The fibers <NUM> included in the tubular member <NUM> are made of metal such as inconel or stainless. The fibers <NUM> have a circular cross section with a diameter of about <NUM>, for example.

The fibers according to the embodiment of the invention are not limited to the metal ones <NUM>, and they may be ones made from silk or cotton, or chemical ones.

The tubular member <NUM> has meshes <NUM> that each have a size to prevent the pieces of expanded graphite sheet <NUM> packed in the tubular member <NUM> from escaping out of the tubular member <NUM>. The tubular member <NUM> allows some pieces of expanded graphite sheet <NUM> to be exposed to the outside through the meshes <NUM>.

In the tubular member <NUM>, the pieces of expanded graphite sheet <NUM> are arranged such that their longitudinal axes extend along the axial direction of the tubular member <NUM> and lie next to each other in the radial directions of the tubular member <NUM>.

<FIG> is a front elevation view of one piece of expanded graphite sheet <NUM> in the yarn <NUM>. <FIG> is a front perspective view of the piece of expanded graphite sheet <NUM> before twisted. <FIG> is a rear perspective view of the piece of expanded graphite sheet <NUM> before twisted.

<FIG> is a front elevation view of the piece of expanded graphite sheet <NUM> in <FIG> twisted at one turn. For convenience of illustration, the rear surface of the piece of expanded graphite sheet <NUM> is hatched in <FIG>.

As shown in <FIG>, <FIG>, and <FIG>, each piece of expanded graphite sheet <NUM> has an elongated shape and a size to be twisted as shown in <FIG> and packed in the tubular member <NUM>.

More specifically, the piece of expanded graphite sheet <NUM> has a longitudinal length shorter than the axial length of the tubular member <NUM>. The piece of expanded graphite sheet <NUM> has a width, i.e. a transversal length and thickness both smaller than the radial length of the tubular member <NUM>.

As shown <FIG>, each piece of expanded graphite sheet <NUM> before twisted has a thin-plate-like shape whose front view is substantially rectangular. The piece of expanded graphite sheet <NUM> has a width W and a thickness T smaller than the width W.

Each piece of expanded graphite sheet <NUM> before twisted has a length L of <NUM> to <NUM>, a width W of <NUM> to <NUM>, and a thickness T of <NUM> to <NUM>.

The piece of expanded graphite sheet <NUM> is then twisted at one turn. By being twisted at several turns in that manner, the piece of expanded graphite sheet <NUM> forms a final twisted shape.

Twisting the piece of expanded graphite sheet <NUM> at one turn means that its one axial end 7a is rotated <NUM> degrees around a longitudinal center line <NUM>, i.e. its one axial end 7a is flipped while its other axial end 7b is fixed.

Each piece of expanded graphite sheet <NUM> has a length of about <NUM>. The piece <NUM> is twisted at six turns per <NUM>, i.e. three turns per <NUM>.

A twisted piece of expanded graphite sheet <NUM> includes flexed portions <NUM> whose number is the same as the number of twist turns. At each flexed portion <NUM>, a longitudinal intermediate portion of the twisted piece <NUM> is bent.

When twisted pieces of expanded graphite sheet <NUM> are packed into the tubular member <NUM>, their longitudinal directions are arranged to be substantially parallel to each other while their twisted conditions are maintained.

Such an arrangement can easily entangle one piece of expanded graphite sheet <NUM> with another, thus preventing each piece thereof from moving relative to others.

Accordingly, pieces of expanded graphite sheet <NUM> hardly lose their uniformity in density in the tubular member <NUM> filled with the pieces <NUM>, even if the tubular member <NUM> receives an external force to move the pieces <NUM> relative to the tubular member <NUM> in an axial direction of the tubular member <NUM>, for example, even if the tubular member <NUM> filled with the pieces <NUM> are flattened by a pressing member such as a pair of rollers <NUM> and <NUM>, as shown in <FIG>, to form the yarn <NUM> into a flattened shape.

Even in this case, the yarn <NUM> can maintain its substantially uniform thickness. This can enhance the sealing performance of the gland packing made of the yarns <NUM>.

The gland packing according to the invention is preferably made of the yarns according to the invention, but this is not a limited condition. Yarns forming a gland packing only have to partially include the yarns according to the invention.

Each piece of expanded graphite sheet <NUM> is twisted at <NUM> to <NUM> turns per <NUM>, i.e. <NUM> to <NUM> turns per <NUM>.

Preferably, each piece of expanded graphite sheet <NUM> is twisted at six turns per <NUM>, i.e. three turns per <NUM>.

That configuration can prevent failures caused by twisting pieces of expanded graphite sheet <NUM>. The pieces <NUM> twisted at an excessive number of turns tend to be broken at the flexed portions <NUM> when the tubular member <NUM> filled with the pieces <NUM> is flattened. In addition, the broken pieces <NUM> tend to escape from the tubular member <NUM> through the meshes <NUM>. This can cause loss of the pieces <NUM> in the tubular member <NUM> and provide voids therein. If the number of twist turns falls within the above-mentioned range, those failures can be prevented.

While preventing those failures, that configuration can also equalize the thickness of the yarns <NUM> and further enhance the sealing performance of the gland packing <NUM> made of the yarns <NUM>.

The gland packing <NUM> is formed by knitting the yarns <NUM> to enhance its sealing performance.

<FIG> is a first schematic view of a portion of equipment <NUM> for manufacturing the yarns <NUM>. <FIG> is a second schematic view of another portion of the equipment <NUM>. The portion marked by "*" in <FIG> is connected to the portion marked by "*" in <FIG>.

The yarns <NUM> can be manufactured by the equipment <NUM> in <FIG> and <FIG>, which is an example of means for manufacturing the yarns <NUM>.

As shown in <FIG> and <FIG>, the equipment <NUM> includes a supply system <NUM>, a transport system <NUM>, a cutting system <NUM>, a guiding system <NUM>, a knitting machine <NUM>, and a pressing machine <NUM>. The equipment <NUM> also includes a control device <NUM> that can control the above-listed portions.

The supply system <NUM> has a sheet member <NUM>, i.e. a roll of expanded graphite sheet and a core <NUM>. Most part of the sheet member <NUM> is a portion 41a rolled around the core <NUM>.

The rolled portion 41a of the sheet member <NUM> rotates by the action of the transport system <NUM>, and then, the rolled portion 41a is gradually unwound from the core <NUM> and carried toward a longitudinal end 41b of <FIG>, i.e. toward the cutting system <NUM>.

The transport system <NUM> has a pair of rollers <NUM> and <NUM> and a driving unit <NUM> to rotate the rollers <NUM> and <NUM>.

Between the rollers <NUM> and <NUM>, the transport system <NUM> places the sheet member <NUM> sent from the supply system <NUM>.

The transport system <NUM> rotates the rollers <NUM> and <NUM> by the driving unit <NUM> to pull and send the sheet member <NUM> from the supply system <NUM> toward the longitudinal end 41b of <FIG>, i.e. toward the cutting system <NUM>.

The cutting system <NUM> has a chopping blade <NUM>, a driving unit <NUM> to move the chopping blade <NUM>, and a platform <NUM>.

The cutting system <NUM> reciprocates the chopping blade <NUM> such that the blade <NUM> approaches or separates from the sheet member <NUM>.

The cutting system <NUM> cuts the sheet member <NUM> reaching the platform <NUM> along the direction perpendicular to the traveling direction of the sheet member <NUM>. Each strip cut from the longitudinal end 41b of the sheet member <NUM> is separated from the rest of the sheet member <NUM>.

The guiding system <NUM> has a hopper <NUM> with an upper opening <NUM> and a lower opening <NUM>. The upper opening <NUM> has a larger diameter than the lower opening <NUM>. The hopper <NUM> is arranged so that the upper opening <NUM> is positioned below the cutting system <NUM>.

The guiding system <NUM> receives pieces of expanded graphite sheet <NUM> cut by the cutting system <NUM> through the upper opening <NUM>, then guiding the pieces <NUM> from the upper opening <NUM> to the lower opening <NUM> and sending them to the knitting machine <NUM>.

The knitting machine <NUM> can form the tubular member <NUM> by knitting the fibers <NUM>. The knitting machine <NUM> causes the knitted tubular member <NUM> to extend downward so that the opening of the tubular member <NUM> faces the lower opening <NUM> of the hopper <NUM>.

In the knitting machine <NUM>, pieces of expanded graphite sheet <NUM> sent from the guiding system <NUM> enter the knitted tubular member <NUM>. The knitting machine <NUM> sends the tubular member <NUM> filled with the pieces <NUM> to the pressing machine <NUM>.

The pressing machine <NUM> has a pair of rollers <NUM> and <NUM> and a driving unit <NUM> to rotate the roller <NUM> and <NUM>. The pressing machine <NUM> presses the tubular member <NUM> filled with pieces of expanded graphite sheet <NUM> after the tubular member <NUM> is sent from the knitting machine <NUM>.

The pressing machine <NUM> places the tubular member <NUM> filled with pieces of expanded graphite sheet <NUM> between the rotating rollers <NUM> and <NUM>, thus flattening the tubular member <NUM>.

In that manner, the equipment <NUM> can form the yarns <NUM> into a flattened shape. During the process of manufacturing by the equipment <NUM>, more specifically, at the cutting step by the cutting system <NUM>, pieces of expanded graphite sheet <NUM> are twisted before packed in the tubular member <NUM>.

<FIG> is a schematic, cross-sectional view of a first step of forming a piece of expanded graphite sheet <NUM> by the cutting system <NUM>. <FIG> is a schematic, cross-sectional view of a second step of forming the piece of expanded graphite sheet <NUM> by the cutting system <NUM>.

<FIG> is a schematic, cross-sectional view of a third step of forming the piece of expanded graphite sheet <NUM> by the cutting system <NUM>. In the order shown in <FIG>, the process of forming each piece of expanded graphite sheet <NUM> progresses. <FIG> are views of the piece of expanded graphite sheet <NUM> in <FIG>, respectively, from the traveling direction of the sheet member <NUM>.

When the cutting system <NUM> cuts one piece of expanded graphite sheet <NUM>, the chopping blade <NUM> moves to bring its edge 47a into contact with an upper surface of the sheet member <NUM> as shown in <FIG> and <FIG>.

The chopping blade <NUM> is placed such that its edge 47a extends to the direction perpendicular to the traveling direction of the sheet member <NUM>. The edge 47a of the chopping blade <NUM> is inclined at an angle from the upper surface of the sheet member <NUM>. In other words, the straight line along the edge 47a is not parallel to the upper surface of the sheet member <NUM> but inclined at an angle from the upper surface. The edge 47a of the chopping blade <NUM> has its tip located downstream in the traveling direction of the sheet member <NUM>.

The edge 47a of the chopping blade <NUM> brings its tip into contact with the upper surface of the sheet member <NUM> when the longitudinal end 41b of the sheet member <NUM> moves by a distance downstream in the traveling direction from a point <NUM> where the chopping blade <NUM> should cut the sheet member <NUM>.

The platform <NUM> on which the sheet member <NUM> is placed is located upstream in the traveling direction from the point <NUM> such that the longitudinal end 41b of the sheet member <NUM> after passing through the point <NUM> floats on air, i.e. the platform <NUM> forms a void <NUM> below the longitudinal end 41b.

As shown in <FIG> and <FIG>, the edge 47a of the chopping blade <NUM> moves downward at the point <NUM> from the position in contact with the sheet member <NUM>, and then starts to cut a first transversal end 41c of the sheet member <NUM>, i.e. an end located at a deep position in <FIG>.

As shown in <FIG> and <FIG>, the edge 47a of the chopping blade <NUM> completely cuts the first transversal end 41c of the sheet member <NUM>. After that, the edge 47a of the chopping blade <NUM> further moves downward and cuts a second transversal end 41d of the sheet member <NUM>, i.e. an end located at a front position in <FIG>.

When the sheet member <NUM> is cut, the longitudinal end 41b of the sheet member <NUM> located downstream in the traveling direction from the point <NUM> is kept floating in air, i.e. the void <NUM> is kept below the longitudinal end 41b.

In that manner, the chopping blade <NUM> brings its edge 47a in contact with the upper surface of the sheet member <NUM> such that the edge 47a crosses the upper surface at a substantially right angle, and then, the edge 47a cuts the sheet member <NUM> into thin strips, i.e. pieces of expanded graphite sheet <NUM>.

Since the edge 47a of the chopping blade <NUM> is inclined at an angle from the upper surface of the sheet member <NUM>, there is a time delay from the start of cutting the first transversal end of the sheet member <NUM> to the end of cutting the second transversal end thereof.

Since the sheet member <NUM> is thin, i.e. <NUM> to <NUM> in thickness, strips cut from the sheet member <NUM>, i.e. pieces of expanded graphite sheet <NUM> are also thin, i.e. <NUM> to <NUM> in thickness.

Accordingly, each strip, i.e. each piece of expanded graphite sheet <NUM> starts to curl at the start of cutting the sheet member <NUM>, and the strip is twisted at the end of cutting the sheet member <NUM>.

Thus, twisted strips, i.e. twisted pieces of expanded graphite sheet <NUM> are formed and thrown into the hopper <NUM> of the guiding system <NUM>. In that manner, pieces of expanded graphite sheet <NUM> can be twisted during the cutting step by the cutting system <NUM> of the equipment <NUM>.

The number of turns at which each piece of expanded graphite sheet <NUM> is twisted per <NUM> can be adjusted by change in size of a strip cut at the cutting step, e.g. changing the transversal width of the sheet member <NUM> or the width of the strip.

In view of the above-described teaching, it is obvious that the invention has many variations and modifications within the scope of the attached claims. Accordingly, it should be understood that the invention can be embodied in manners other than the embodiments described in this specification within the scope of the attached claims.

Claim 1:
A yarn (<NUM>) comprising elongated pieces of expanded graphite sheet (<NUM>) that are packed in a tubular member (<NUM>) made of knitted or braided fibers,
wherein each of the elongated pieces of expanded graphite sheet (<NUM>) has a shape like an elongated, thin plate characterized in that the yarn (<NUM>) has a flattened shape and each elongated piece of expanded graphite sheet (<NUM>) is twisted around its own longitudinal center line (<NUM>) at one or more turns the shape having flexed portions (<NUM>) and a longitudinal intermediate portion that is bent at each of the flexed portions (<NUM>); and
a longitudinal end (7a) of the shape is rotated by <NUM> degrees per turn around the longitudinal center line (<NUM>) while another longitudinal end (7b) of the shape is fixed.