JP7482826B2 - Yarn, gland packing, and manufacturing method thereof - Google Patents

Description

The present invention relates to yarns and gland packings containing the same, and in particular to their structure and manufacturing methods.

A gland packing is a cord-like or annular member with a square or round cross section, and is used to seal gaps around a movable shaft of a pump or valve by adhering closely to the outer surface of the movable shaft. The most common gland packing contains a bundle of yarn as its main component. The yarn is a wire made of a highly heat-resistant material such as expanded graphite. The yarn bundle contained in the gland packing is formed into a cord-like or annular shape by twisting or braiding. There are various yarn structures, and for example, one that contains a single long and thin expanded graphite tape rolled into a cord-like shape as a core (see Patent Document 1), and one in which a tubular member woven with a metallic fiber material is filled with fibrous or strip-like expanded graphite material (see Patent Documents 2 and 3).

When the gland packing contains expanded graphite, the friction with the movable shaft causes the powder of the expanded graphite to peel off from the gland packing and adhere to the movable shaft, which increases the resistance (sliding resistance) that the gland packing exerts on the movable shaft. To prevent this increase, a lubricant is generally incorporated into the gland packing. There are various types of lubricants, including those that are liquid at room temperature (lubricating oil), semi-solid (grease), and solid. When the surface (sliding surface) of the gland packing that contacts the movable shaft wears, the lubricant is supplied to the sliding surface from inside the gland packing. This keeps the sliding resistance of the gland packing against the movable shaft low. There are various methods for incorporating the lubricant into the gland packing, such as one in which the lubricant is impregnated into the gland packing after molding (see Patent Document 4), one in which fibrous lubricant is adhered to a tape made of expanded graphite and the tape is twisted into a string-like shape to form a yarn core (see Patent Document 5), and one in which lubricant powder is mixed with expanded graphite powder and the gland packing is molded from them (see Patent Document 6).

Japanese Patent No. 5205184 Japanese Patent No. 4340647 Patent No. 4378351 Patent No. 3578625 JP 2006-349070 A JP 2012-246973 A

When making yarns from expanded graphite and manufacturing gland packings from bundles of the yarns, it is advantageous to use pre-made expanded graphite sheets to reduce manufacturing costs. However, pre-made expanded graphite sheets generally do not contain lubricants, unlike the powder of expanded graphite disclosed in Patent Document 6. Therefore, it is necessary to incorporate a lubricant into either the expanded graphite sheet, the expanded graphite material cut out from it, the yarns formed therefrom, or the gland packing formed from the bundles of the expanded graphite sheets. However, all of the conventional methods for incorporating a lubricant are cumbersome, and in particular, the work according to the method must be separated in space or time from the work of forming the object to which the lubricant is to be incorporated. For example, in the method disclosed in Patent Document 4, the lubricant cannot be impregnated or applied to the gland packing at the same place as the formation of the gland packing. In the method disclosed in Patent Document 5, the tape made of expanded graphite cannot be rolled and formed into a yarn until the lubricant has been bonded to the tape. Therefore, the lubricant incorporation process makes it difficult to further simplify the manufacturing method of the gland packing. This is detrimental to reducing the manufacturing costs of gland packing.

The object of the present invention is to solve the above problems, and in particular to provide a gland packing that is easy to incorporate lubricant into, and a method for manufacturing the same.

A yarn according to one aspect of the present invention has a tubular member, an expanded graphite material, and a lubricating member. The tubular member is filled with the lubricating member together with the expanded graphite material. The tubular member includes a fiber material woven or braided into a tubular shape. The expanded graphite material is in a strip shape. The lubricating member includes a lubricant, is made of a material having a melting point higher than room temperature and lower than the maximum operating temperature of the gland packing, and is larger in size than both the length and width of the mesh formed by the fiber material of the tubular member. The lubricating member may be in a strip shape.

A gland packing according to one aspect of the present invention includes the above-described yarn according to the present invention.

A method for manufacturing a yarn according to one aspect of the present invention includes the following four steps. In the first step, a tubular member is manufactured by weaving or braiding a fiber material into a tubular shape. In the second step, an expanded graphite sheet is cut to manufacture an expanded graphite material. In the third step, a material containing a lubricant and having a melting point higher than room temperature and lower than the maximum operating temperature of the gland packing is molded into a size larger than both the length and width of the mesh formed by the fiber material of the tubular member to manufacture a lubricating member. In the fourth step, the operation of feeding the expanded graphite material into the tubular member and the operation of feeding the lubricating member into the tubular member are performed in parallel. In the fourth step, the expanded graphite material and the lubricating member may be placed in the same funnel and dropped into the tubular member from the leg of the funnel.

A method for manufacturing a gland packing according to one aspect of the present invention includes a step of manufacturing a plurality of yarns by the above-described method according to the present invention, and a step of forming the yarns into a string-like or ring-like shape by twisting or braiding.

In the above yarn according to the present invention, the cylindrical member is filled with a lubricating material together with the expanded graphite material. The material of the lubricating material contains a lubricant, and has a melting point higher than room temperature and lower than the maximum operating temperature of the gland packing. Therefore, in the gland packing made of this yarn bundle, when the temperature rises due to heat generated by friction with the movable shaft or heat transmitted from a high-temperature fluid and reaches the melting point of the lubricating material, the lubricating material melts and diffuses into the surrounding expanded graphite material, covering their surfaces. As a result, the lubricant spreads throughout the inside of the gland packing, so that a sufficient amount of lubricant is supplied from inside the gland packing to the sliding surface of the gland packing, even if the gland packing is considerably worn. In this way, the above yarn according to the present invention can suppress the sliding resistance of the gland packing for a long period of time.

The above-mentioned yarn according to the present invention is manufactured by the above-mentioned manufacturing method according to the present invention. In particular, the incorporation of a lubricant into the yarn is achieved by simultaneously feeding an expanded graphite material into the tubular member and feeding a lubricant into the tubular member, as in the fourth step. This is simpler than any of the conventional methods for incorporating a lubricant into a yarn, and in particular can be carried out simultaneously with the formation of the yarn. Therefore, using this yarn to manufacture a gland packing is advantageous in reducing the manufacturing costs of the gland packing.

In the fourth step, the more similar the shape of the lubricating member is to the expanded graphite material, the easier it is for the lubricating member to mix with the expanded graphite material. Therefore, if the lubricating member is in the shape of a strip, it mixes well with the expanded graphite material. As a result, the uniformity of the lubricant inside the gland packing can be increased, and the period during which the sliding resistance of the gland packing is suppressed can be extended.

When a funnel is used in the fourth step, the lubricating material is easily mixed into the expanded graphite material. Furthermore, since the lubricating material is highly mixed, the uniformity of the lubricant inside the gland packing is increased, and the period during which the sliding resistance of the gland packing is suppressed can be extended.

1A is a perspective view showing the external appearance of a gland packing according to an embodiment of the present invention, FIG. 1B is a perspective view showing the external appearance of a cross section of the gland packing and its vicinity, and FIG. 1C is a perspective view showing the structure of a yarn according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a shaft seal device using the gland packing of FIG. 1. 1 is a process diagram of a method for manufacturing a gland packing according to an embodiment of the present invention. FIG. 1 is a perspective view showing a schematic structure of a yarn manufacturing apparatus according to an embodiment of the present invention; FIG. 2 is a perspective view showing an expanded graphite material and a lubricating member simultaneously fed into a cylindrical member.

Figure 1 (a) is a perspective view showing a schematic appearance of a gland packing 100 according to an embodiment of the present invention. The gland packing 100 is a cord with a rectangular cross section, and has a width and thickness of, for example, several mm to several tens of mm.

2 is a cross-sectional view of a shaft seal device 500 that uses a gland packing 100. The shaft seal device 500 is a device for sealing the gap around the rotating shaft 510 of the pump, and includes a stuffing box 520 and a packing gland 530. The stuffing box 520 is a cylindrical member that coaxially surrounds the rotating shaft 510, with one axial end (left end in FIG. 2) 521 facing the pump chamber 540 and the other end (right end in FIG. 2) 522 exposed to the outside of the casing 550 of the pump. A rib 523 protrudes from one end 521 of the stuffing box 520 in the inner circumferential direction. Between the rib 523 and the other end 522 of the stuffing box 520, the gland packing 100 is packed into the gap between the inner circumferential surface 524 of the stuffing box 520 and the outer circumferential surface 511 of the rotating shaft 510. The gland packing 100 is cut into five rings and is wound coaxially around the rotating shaft 510. The packing gland 530 is a ring member that coaxially surrounds the rotating shaft 510 and closes the gap between the other end 522 of the stuffing box 520 and the outer circumferential surface 511 of the rotating shaft 510. One axial end face (left end face in FIG. 2) 531 of the packing gland 530 is in contact with the gland packing 100. A flange 532 protrudes from the other axial end (right end in FIG. 2) of the packing gland 530 in the outer circumferential direction and is fixed to the other end 522 of the stuffing box 520 by a plurality of bolts 533. The packing gland 530 presses the gland packing 100 against the rib 523 by the axial pressure of the bolt 533. As a result, the gland packing 100 is compressed in the axial direction and expands in the radial direction. As a result, the gland packing 100 adheres closely to the outer circumferential surface 511 of the rotating shaft 510, sealing the gap between the rotating shaft 510 and the rib 523.

Figure 1 (b) is a perspective view showing a cross section of the gland packing 100 and the appearance of the vicinity thereof. The gland packing 100 includes one core material 110 and eight yarns 120. The core material 110 is an expanded graphite material formed into a string shape. The yarn 120 is a cylindrical member 121 filled with expanded graphite material 122 and formed into a string shape. The eight yarns 120 are eight-stranded around the core material 110. Although not shown, the cross section of both the core material 110 and the yarn 120 is a circle with a diameter of several mm before being braided. On the other hand, after being braided as shown in Figure 1 (b), the cross section is significantly distorted from a circle due to pressure applied during braiding and during molding of the gland packing 100.

(c) of FIG. 1 is a perspective view showing a schematic structure of the yarn 120. The cylindrical member 121 includes a fiber material 123 woven into a cylindrical shape. The fiber material 123 is made of metal such as Inconel or stainless steel, and has a cross section that is, for example, a circle with a diameter of 0.1 mm. The stitches 124 formed by the fiber material 123 are, for example, several mm in length and width, and are arranged in a spiral shape along the axial direction of the cylindrical member 121. The cylindrical member 121 maintains its shape when the yarn 120 is woven, and improves the mechanical strength of the gland packing 100. The expanded graphite material 122 is expanded graphite formed into a strip shape. Here, "strip shape" means a shape in which the length is, for example, one to three orders of magnitude larger than the width and thickness. Specifically, the cross section of the expanded graphite material 122 is rectangular with a width of 0.5 mm to 2.5 mm, a thickness of 0.2 mm to 1.0 mm, and a length of 100 mm to 300 mm. The weight of the expanded graphite material 122 is, for example, several g/m.

The yarn 120 further includes a plurality of lubricating members 125 intermingled among the plurality of expanded graphite materials 122. Each of the lubricating members 125 is larger in size than both the length and width of the stitches 124 of the tubular member 121. The lubricating members 125 are preferably rectangular, and in particular, like the expanded graphite material 122, the length is one to three orders of magnitude larger than both the width and thickness. Specifically, the cross section is rectangular, the width and thickness are a few tenths of a millimeter to a few millimeters, and the length is several hundred millimeters.

The material of the lubricating member 125 is preferably paraffin. This paraffin has a melting point higher than room temperature and lower than the maximum operating temperature of the gland packing 100, for example, several hundred degrees Celsius. Therefore, when the gland packing 100 raises its own temperature above the melting point of paraffin, i.e., to several hundred degrees Celsius, for example, due to heat generated by friction with the rotating shaft 510 or heat transmitted from the high-temperature fluid in the pump chamber 540, the paraffin that has been melted and made fluid diffuses from the lubricating member 125 to the surrounding expanded graphite material 122. The fluidized paraffin further functions as a lubricant by covering the surface of the expanded graphite material 122 to which it has been diffused. In other words, when the expanded graphite material 122 is exposed to the sliding surface of the gland packing 100, it suppresses friction between the expanded graphite material 122 and the rotating shaft 510.

The weight ratio of the lubricating member 125 to the yarn 120 is preferably 5% to 15%. The lower limit of this weight ratio is determined by the condition that "seizing of the sliding surface of the gland packing 100 is sufficiently prevented," and the upper limit is determined by the condition that "the tightening pressure of the gland packing 100 is maintained sufficiently high regardless of the deformation (flow) of the yarn 120 caused by the melting of the lubricating member 125."
[Manufacturing method of gland packing]

Figure 3 is a process diagram of the method for manufacturing the gland packing 100. This manufacturing method includes five steps 201, 202, 203, 204, and 205. The first step 201 to the fourth step 204 are the method for manufacturing the yarn 120. In the first step 201, the fiber material 123 is woven into a cylindrical shape to produce a cylindrical member 121. In the second step 202, the expanded graphite sheet is cut to produce the expanded graphite material 122. In the third step 203, the lubricating member 125 formed in a sheet shape, for example a paraffin sheet, is cut into fibers. In the fourth step 204, the expanded graphite material 122 and the lubricating member 125 are fed simultaneously into the cylindrical member 121. In this way, one yarn 120 is completed. In the fifth step 205, the bundle of yarns 120 is formed into the gland packing 100. Specifically, a bundle of expanded graphite material is first formed into a string-like shape to produce the core material 110. Next, eight yarns 120 are braided around the core material 110 to form the bundle of core material 110 and yarns 120 into a string-like shape. The bundle is then pressurized to form its cross section into a square shape. In this way, the gland packing 100 is completed.

Figure 4 is a perspective view showing a schematic structure of a manufacturing device 300 for yarn 120. This manufacturing device 300 includes a first supply section 310, a first cutting section 320, a second supply section 330, a second cutting section 340, a filling section 350, and a control section (not shown).

The first supply section 310 includes a first reel 311, a first conveying roller pair 312, and a first driving mechanism 313. The first reel 311 is a cylindrical frame supported rotatably around its central axis, and an expanded graphite sheet 314 is wound around it. The expanded graphite sheet 314 has a width of, for example, several tens to several hundreds of mm and a thickness of 0.2 mm to 1.0 mm. The conveying roller pair 312 is a pair of cylindrical members supported with their central axes parallel to each other, and their outer circumferential surfaces face each other across a narrow gap approximately equal to the thickness of the expanded graphite sheet 314. The tip portion of the expanded graphite sheet 314 pulled out from the first reel 311 is sandwiched in the gap. The first driving mechanism 313 supports the first conveying roller pair 312 rotatably around their respective central axes, and rotates the first conveying roller pair 312 in opposite directions to each other using the rotational force of a built-in motor (not shown). As a result, the leading end of the expanded graphite sheet 314 is sent out from the gap between the first transport roller pair 312 to the first cutting section 320, and the trailing portion of the expanded graphite sheet 314 is pulled out from the first reel 311 into the gap between the first transport roller pair 312.

The first cutting section 320 includes a first receiving table 321 and a first flat blade 322. The first receiving table 321 has a rectangular horizontal upper surface and includes a linear slit 323. The tip portion of the expanded graphite sheet 314 sent from the first supply section 310 is placed on the upper surface of the first receiving table 321 and intersects with the slit 323. The first flat blade 322 is a plate-shaped member with a blade on one side, and is supported by a first linear actuator (not shown) above the receiving table 321 so that the cutting edge faces downward and the plate surface is perpendicular to the plate surface of the receiving table 321. The first linear actuator moves the first flat blade 322 up and down, and moves the cutting edge into and out of the slit 323 of the first receiving table 321. As a result, the portion of the expanded graphite sheet 314 located above the slit 323 is cut. The rectangular pieces cut off from the expanded graphite sheet 314, i.e., the expanded graphite material 122, are pushed out of the first receiving tray 321 and fall by the subsequent portion of the expanded graphite sheet 314 being transported from the first supply section 310 to the first receiving tray 321.

The second supply unit 330 includes a second reel 331, a second transport roller pair 332, and a second drive mechanism 333. The second reel 331 is a cylindrical frame supported rotatably around its central axis, and a paraffin sheet 334 is wound around it. The paraffin sheet 334 has a width of, for example, several tens of mm to several hundreds of mm, and a thickness of several tenths of mm to several mm. The second transport roller pair 332 is a pair of cylindrical members supported with their central axes parallel to each other, and their outer circumferential surfaces face each other across a narrow gap approximately equal to the thickness of the paraffin sheet 334. The tip portion of the paraffin sheet 334 pulled out from the second reel 331 is sandwiched in the gap. The second drive mechanism 333 supports the second transport roller pair 332 rotatably around its respective central axis, and rotates the second transport roller pair 332 in opposite directions to each other using the rotational force of a built-in motor (not shown). As a result, the leading end of the paraffin sheet 334 is sent from the gap between the second transport roller pair 332 to the second cutting section 340, and the trailing portion of the paraffin sheet 334 is pulled from the second reel 331 into the gap between the second transport roller pair 332.

The second cutting unit 340 includes a second receiving table 341 and a second flat blade 342. The second receiving table 341 has a rectangular horizontal upper surface and includes a linear slit 343. The tip of the paraffin sheet 334 sent from the second supply unit 330 is placed on the upper surface of the second receiving table 341 and intersects with the slit 343. The second flat blade 342 is a plate-shaped member with a blade on one side, and is supported by a second linear actuator (not shown) above the second receiving table 341 so that the cutting edge faces downward and the plate surface is perpendicular to the plate surface of the second receiving table 341. The second linear actuator moves the second flat blade 342 up and down, and moves the cutting edge into and out of the slit 343 of the second receiving table 341. As a result, the part of the paraffin sheet 334 located above the slit 343 is cut. The rectangular piece cut off from the paraffin sheet 334, i.e., the lubricating member 125, is pushed out of the second receiving tray 341 and falls by the subsequent portion of the paraffin sheet 334 transported from the second supply unit 330 to the second receiving tray 341.

The filling section 350 includes a funnel 351 and a circular knitting machine 352. The cone section 353 of the funnel 351 extends below both the first receiving stand 321 and the second receiving stand 341. The expanded graphite material 122 dropped from the first receiving stand 321 and the lubricating member 125 dropped from the second receiving stand 341 are put into the cone section 353. The put-in expanded graphite material 122 and the lubricating member 125 are in a position where their respective ends are inclined downward as a result of collision with the inner surface of the cone section 353 of the funnel 351, and slide down along the inner surface of the cone section 352 in that position. The legs 354 of the funnel 351 are cylindrical, and the lower end is inserted into the inside of the circular knitting machine 352. Inside the legs 354, the expanded graphite material 122 and the lubricating member 125 are both approximately parallel to the vertical direction and fall into the inside of the circular knitting machine 352. The circular knitting machine 352 produces the tubular member 121 from the fiber material 123 (see FIG. 1C). Inside the circular knitting machine 352, the tubular member 121 is supported so that its central axis is parallel to the vertical direction. The lower end of the leg 354 of the funnel 351 is placed directly above the cavity of the tubular member 121, and the inner diameter of the lower end of the leg 354 is designed to be equal to or smaller than the inner diameter of the tubular member 121. As a result, the expanded graphite material 122 and the lubricating member 125 that have passed through the leg 354 fall inside the tubular member 121 while remaining approximately parallel to the vertical direction.

The control unit is an electronic circuit system that controls the operation of the transport roller pairs 312, 332, the flat blades 322, 342, and the circular knitting machine 352, and includes a control circuit and a drive circuit. The control circuit is an industrial computer such as a motherboard or a personal computer, and sends instructions to the drive circuit by executing various software. The drive circuit is a combination of a logic circuit such as a microprocessor (MPU/CPU), an application specific integrated circuit (ASIC), or a programmable programmable gate array (FPGA), and a power circuit such as a switching converter, and is installed in each of the drive mechanisms 313, 333 of the supply units 310, 330, the linear actuators of the cutting units 320, 340, and the circular knitting machine 352. The logic circuit sets the target value of the output of actuators such as motors and solenoids in response to instructions from the control circuit. The power circuit adjusts the power supplied to the actuators to maintain the output of the actuators at the target value.

Using the above-mentioned functional units 310-350, the manufacturing apparatus 300 performs the operations from the first step 201 to the fourth step 204 shown in FIG. 3 as follows.
(First step 201)

The control circuit sends a knitting start command to the drive circuit of the circular knitting machine 352. In response to this command, the drive circuit starts the circular knitting machine 352 to produce the tubular member 121. After that, when the time required for the tubular member 121 to extend to a predetermined length, for example to the length of the expanded graphite material 122, has elapsed, the control circuit sends a knitting interrupt command to the drive circuit of the circular knitting machine 352. In response to this command, the drive circuit stops the circular knitting machine 352.
(Second step 202 and third step 203)

The control circuit sends a command to start conveying to the drive circuits of the drive mechanisms 313 and 333 of the supply units 310 and 330. In response to this command, those drive circuits start the motors of the drive mechanisms 313 and 333, intermittently rotating the conveying roller pairs 312 and 332. As a result, the expanded graphite sheet 314 repeats the operation of stopping for a predetermined time each time it advances by the width of the expanded graphite material 122, and the paraffin sheet 334 repeats the operation of stopping for a predetermined time each time it advances by the width of the lubricating member 125.

In sync with the timing of sending the above-mentioned conveyance start command, the control circuit sends a cutting start command to the drive circuits of the linear actuators of the cutting units 320 and 340. In response to this command, those drive circuits start the linear actuators, causing the flat blades 322 and 342 to repeat reciprocating motion at regular time intervals.

The time when the control circuit sends a command to start conveying and a command to start cutting, the time when the pair of conveying rollers 312, 332 rotate and stop, and the time intervals for the flat blades 322, 342 to reciprocate are designed as follows: The first flat blade 322 waits above the first receiving tray 321 while the expanded graphite sheet 314 is moving, and makes one reciprocating motion to cut the expanded graphite sheet 314 while the expanded graphite sheet 314 is stopped. The second flat blade 342 waits above the second receiving tray 341 while the paraffin sheet 334 is moving, and makes one reciprocating motion to cut the paraffin sheet 334 while the paraffin sheet 334 is stopped.
(Fourth step 204)

The expanded graphite material 122 separated from the expanded graphite sheet 314 is fed from the first receiving tray 321 into the funnel 351 one by one each time the first transport roller pair 312 rotates. The lubricating members 125 separated from the paraffin sheet 334 are fed from the second receiving tray 341 into the funnel 351 one by one each time the second transport roller pair 332 rotates. Since the second process 202 and the third process 203 proceed simultaneously, the multiple expanded graphite materials 122 are mixed with the multiple lubricating members 125 inside the legs 354 of the funnel 351.

Figure 5 is a perspective view showing the expanded graphite material 122 and the lubricating member 125 that are fed into the tubular member 121 at the same time. Inside the circular knitting machine 352, the expanded graphite material 122 and the lubricating member 125 fall into the tubular member 121 from the lower end 355 of the leg 354 of the funnel 351. Although not shown in Figure 5, the lower end of the tubular member 121 is closed by, for example, a member of the circular knitting machine 352, so that the fallen expanded graphite material 122 and the lubricating member 125 are accumulated in the tubular member 121. The expanded graphite material 122 and the lubricating member 125 are larger in size than both the length and width of the stitches 124 of the tubular member 121, so they do not slip out of the stitches 124 to the outside of the tubular member 121.

When a first predetermined time has elapsed since the time when the instruction to start conveying was sent, the control circuit sends an instruction to stop conveying to the drive circuits of the drive mechanisms 313 and 333 of the supply units 310 and 330. In response to this instruction, the drive circuits stop the motors of the drive mechanisms 313 and 333. Furthermore, when a second predetermined time has elapsed since the time when the instruction to start cutting was sent, the control circuit sends an instruction to stop cutting to the drive circuits of the linear actuators of the cutting units 320 and 340. In response to this instruction, the drive circuits stop the linear actuators. The first and second predetermined times are set so that when they have elapsed, the expanded graphite material 122 and the lubricating member 125 are produced in the amounts necessary to fill the cavity of the cylindrical member 121 of a predetermined length. Therefore, when the conveying roller pairs 312 and 332 and the flat blades 322 and 342 stop, the cylindrical member 121 is filled with the expanded graphite material 122 and the lubricating member 125.

The manufacturing apparatus 300 repeats the above-described operations from the first step 201 to the fourth step 204. As a result, every time the circular knitting machine 352 stretches the tubular member 121 by a predetermined length, the expanded graphite material 122 and the lubricating member 125 are filled into the stretched portion. In this manner, the manufacturing apparatus 300 completes one yarn 120.
Advantages of the embodiment

In the fourth step 204 of the method for producing the yarn 120, the expanded graphite material 122 is put into the funnel 351 and falls from its leg 354 into the tubular member 121. At the same time, the lubricating member 125 is put into the same funnel 351 and falls from its leg 354 into the tubular member 121. As a result, the expanded graphite material 122 is filled into the tubular member 121 to form the yarn 120, and at the same time, the lubricating member 125 is incorporated into the yarn 120. In this way, the incorporation of the lubricant, i.e., paraffin, into the yarn 120 is simple, and is particularly performed at the same time as the formation of the yarn 120. This is advantageous for further reducing the manufacturing cost of the gland packing 100.

In the funnel 351, the lubricating material 125 easily mixes with the expanded graphite material 122. Furthermore, since the lubricating material 125 is in the same rectangular shape as the expanded graphite material 122, the degree of mixing of the lubricating material 125 is high. Therefore, as the operating temperature of the gland packing 100 increases, the melted paraffin spreads throughout the inside of the gland packing 100. As a result, a sufficient amount of paraffin is supplied to the sliding surface of the gland packing 100 from the inside of the gland packing 100, even if the sliding surface is considerably worn. In this way, the yarn 120 can suppress the sliding resistance of the gland packing 100 for a long period of time.

The weight ratio of the lubricating member 125 to the yarn 120 is mainly determined by the weight ratio of one lubricating member 125 to one expanded graphite material 122 and the ratio of the number of lubricating members 125 to the number of expanded graphite materials 122 contained in the yarn 120. Therefore, the weight ratio depends on the width of the lubricating member 125 and the number of lubricating members 125 that fall into the funnel 351 per unit time. The width of the lubricating member 125 can be adjusted by the speed or time at which the second transport roller pair 332 rotates, and the number of lubricating members 125 that fall into the funnel 351 per unit time can be adjusted by the cycle at which the second transport roller pair 332 turns on and off. In this way, the manufacturing apparatus 300 can relatively freely change the weight ratio of the lubricating member 125 to the yarn 120 even after it is assembled. This is advantageous for further reducing the manufacturing cost of the gland packing 100.
[Modification]

(1) The gland packing 100 is string-shaped and has a square cross section. However, in addition to this shape, the gland packing according to the present invention may be annular and may have a round cross section.

(2) The bundle of yarn 120 contained in the gland packing 100 is eight-strand braided. However, in the gland packing of the present invention, the bundle of yarn may be formed into a string or ring shape by other braiding processes such as bag braiding or lattice braiding, or by twisting.

(3) The gland packing 100 includes a bundle of expanded graphite material as the core material 110. The core material may also be made by laminating tapes made of expanded graphite and forming them into a string shape. Note that the core material is not an essential component and may therefore be omitted from the gland packing according to the present invention.

(4) The main material of the yarn 120 is expanded graphite. However, any other material that has heat resistance, corrosion resistance and sealing ability against the fluid to be sealed, workability, mechanical strength, etc. equivalent to expanded graphite can be used as the main material of the yarn according to the present invention.

(5) The shape and dimensions of the stitches 124 of the tubular member 121 shown in FIG. 1(c) are merely examples, and other shapes or dimensions may be used. In addition, the tubular member of the yarn according to the present invention may be one in which multiple fiber materials are woven.

(6) The material of the lubricating member 125 is paraffin. However, any other material having the following properties (A) and (B) can be used as the material of the lubricating member according to the present invention. (A) The melting point is higher than room temperature and lower than the maximum use temperature of the gland packing. (B) In the molten state, it diffuses from the lubricating member to the surrounding expanded graphite material and covers their surfaces, thereby functioning as a lubricant. Examples of such materials include boron oxide, diboron trioxide, zinc, zinc bromide, silver bromide, cesium bromide, copper bromide, lithium carbonate, magnesium, and lithium amide. The lubricating member according to the present invention may also be a base material having a melting point higher than room temperature and lower than the maximum use temperature of the gland packing, such as paraffin, in which lubricating oil, grease, or powder of solid lubricant is dispersed. As the use temperature of the gland packing increases, the base material that has been fluidized by melting diffuses into the surrounding expanded graphite material, and the lubricating oil, grease, or powder of solid lubricant is attached to the surface of the expanded graphite material.

(7) In the third step 203 of the method for manufacturing the yarn 120, the paraffin sheet 334 is cut to form the lubricating member 125 into a strip shape. In this case, a ready-made product can be used as the paraffin sheet 334. This is advantageous in reducing the manufacturing cost of the gland packing 100. However, the lubricating member only needs to be larger in size than both the length and width of the stitches 124 of the tubular member 121, and it is not essential for the present invention that the lubricating member be strip-shaped. Therefore, in the third step, for example, a powder of the material may be solidified into the desired shape.

(8) In the fourth step 204 of the method for producing the yarn 120, the expanded graphite material 122 and the lubricating member 125 are simultaneously put into the funnel 351, mixed inside the leg 354, and dropped into the tubular member 121 from the lower end 355 of the leg 354. However, the term "simultaneously" should not be interpreted too strictly. In the fourth step according to the present invention, it is sufficient to carry out the operation of feeding the expanded graphite material into the tubular member and the operation of feeding the lubricating member into the tubular member in parallel. For example, a period in which only the expanded graphite material 122 falls into the tubular member 121 through the funnel 351 and a period in which only the lubricating member 125 falls into the tubular member 121 through the funnel 351 may be alternated in small increments. In this case, the expanded graphite material 122 and the lubricating member 125 are mixed in the tubular member 121. Also, the path along which the expanded graphite material 122 falls into the cylindrical member 121 and the path along which the lubricating member 125 falls into the cylindrical member 121 may be separate. In this case as well, the expanded graphite material 122 and the lubricating member 125 are mixed in the cylindrical member 121. Alternatively, the expanded graphite material 122 immediately after being cut off from the expanded graphite sheet 314 and the lubricating member 125 immediately after being cut off from the paraffin sheet 334 may be temporarily collected in the same place and mixed, and then sent together into the cylindrical member 121.

100 Gland packing 110 Core material 120 Yarn 121 Cylindrical member 122 Expanded graphite material 123 Fiber material 124 Stitch 125 Lubricating member 201 First step of manufacturing method of gland packing 202 Second step of manufacturing method of gland packing 203 Third step of manufacturing method of gland packing 204 Fourth step of manufacturing method of gland packing 205 Fifth step of manufacturing method of gland packing 300 Yarn manufacturing device 310 First supply unit 311 First reel 312 First conveyor roller pair 313 First driving mechanism 314 Expanded graphite sheet 320 First cutting unit 321 First receiving table 322 First flat blade 323 Slit of first receiving table 330 Second supply unit 331 Second reel 332 Second conveyor roller pair 333 Second driving mechanism 334 Paraffin sheet 340 Second cutting section 341 Second receiving tray 342 Second flat blade 343 Slit of second receiving tray 350 Filling section 351 Funnel 352 Circular knitting machine 353 Cone of funnel 354 Leg of funnel 355 Lower end of leg of funnel

Claims (6)

A tubular member including a woven or braided fiber material in a tubular shape;
A rectangular expanded graphite material;
a lubricating member made of a material containing a lubricant and having a melting point higher than room temperature and lower than the maximum use temperature of the gland packing, the lubricating member being larger in size than both the length and width of the mesh formed by the fiber material;
The yarn is characterized in that the tubular member is filled with the lubricating material together with the expanded graphite material. The yarn according to claim 1, wherein the lubricating member is strip-shaped. A gland packing comprising the yarn according to claim 1 or claim 2. 1. A method of making a yarn, comprising:
A first step of producing a tubular member by weaving or braiding a fiber material into a tubular shape;
A second step of cutting the expanded graphite sheet to produce rectangular expanded graphite materials;
a third step of producing a lubricating member by molding a material containing a lubricant, the material having a melting point higher than room temperature and lower than the maximum use temperature of the gland packing, into a size larger than both the length and width of the mesh formed by the fiber material;
and a fourth step of feeding the expanded graphite material into the tubular member and feeding the lubricating material into the tubular member in parallel. The method according to claim 4, wherein in the fourth step, the expanded graphite material and the lubricating member are placed in the same funnel and allowed to fall from the foot of the funnel into the cylindrical member. producing a plurality of yarns according to the method of claim 4 or claim 5;
and forming the plurality of yarns into a string-like or annular shape by twisting or braiding the yarns.

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