Apparatus for manufacturing pouch case and method for manufacturing pouch case

Abstract

The present invention relates to an apparatus for manufacturing a pouch case and a method for manufacturing a pouch case and, more specifically, to an apparatus for manufacturing a pouch case and a method for manufacturing a pouch case, capable of alleviating an edge curling phenomenon of a pouch case caused by cup forming for inserting an electrode assembly. According to one embodiment of the present invention, the method for manufacturing a pouch case comprises: a cup forming step in which a cup is formed on a substrate stopped from traveling by means of a cup forming unit installed on a traveling path of the substrate; an edge forming step in which respective edges of the substrate on which the cup is formed are formed to be upwardly inclined with respect to a side surface of the cup by means of an edge forming unit installed at a rear end of the cup forming unit; and a cutting step in which the substrate having the cup and the respective upwardly inclined edges is cut into the pouch case by means of a cutting unit installed at a rear end of the edge forming unit.

Description

Pouch case manufacturing device and pouch case manufacturing method

[0001] The present invention relates to a manufacturing device for a pouch case and a manufacturing method for a pouch case, and more particularly, to a molding device for a pouch case and a manufacturing method for a pouch case capable of preventing a curling phenomenon of the edges of a pouch case by molding both edges of a substrate into which a cup into which an electrode assembly can be inserted to be inclined upward and then cutting the substrate.

[0002] This application claims the benefit of priority to Republic of Korea Patent Application No. 10-2024-0027479, filed February 26, 2024, the entire contents of which are incorporated herein by reference.

[0003] Recently, demand for secondary batteries capable of repeated charging and discharging has been increasing. A secondary battery consists of an electrode assembly and a case surrounding the electrode assembly. Various types of secondary batteries are available, depending on the shape of the electrode assembly and the type of case.

[0004] The electrode assembly is formed by repeatedly stacking an anode, a separator, a cathode, and a separator, and various methods for manufacturing a single electrode assembly are provided.

[0005] Pouch-type secondary batteries, manufactured by housing electrode assemblies in a pouch case, offer superior power-to-weight ratios. This is because the electrode assembly is wrapped in a thin pouch sheet, reducing the case's weight and minimizing dead space.

[0006] When manufacturing a pouch case using a pouch sheet, a process of forming a cup into which an electrode assembly is inserted and seated in the pouch sheet can be performed.

[0007] Figure 1 is a drawing for explaining the curling phenomenon that occurs at the edge of a pouch case when manufacturing a conventional pouch case.

[0008] As shown in Fig. 1, the manufacturing device (20) of the pouch case includes a die (21) having a mold groove (22) and a punch (26) having a block (27).

[0009] The manufacturing device (20) of the above pouch case can form the two cups (3, 4) on the substrate (1) through the following process. For convenience of explanation, in Fig. 1, the two cups are shown as being formed side by side in the length direction of the substrate (1), but in reality, as shown in Fig. 2, the two cups can be formed side by side in the width direction of the substrate (1).

[0010] First, the die (21) is raised in a direction approaching the punch (26) and the substrate (1) is pressed against the punch (26). The block (27) of the punch (26) stretches the substrate (1) into the mold groove (22) of the die (21). Accordingly, two cups (3, 4) are formed in the substrate (1).

[0011] In the process of forming two cups (3, 4) on the substrate (1), stress is generated in the area where the two cups (3, 4) are formed on the substrate (1) due to the force of the die (21) pressing the punch (26).

[0012] After the cups (3, 4) are formed on the above substrate (1), the die (21) returns to its original position. Then, the substrate (1) on which the cups (3, 4) are formed is cut into a pouch case (2) by a cutting device (30).

[0013] As shown in Fig. 1(b), the edges (5, 6) on both sides of the pouch case (2) can curl in a direction closer to the bottom surface of the cup (3, 4) due to the residual stress of the substrate (1) and different elastic recovery forces depending on the material constituting the substrate (1).

[0014] Referring to enlarged view A of Fig. 1(a), the substrate (1) is a sheet in which a lower resin layer (1a), a metal layer (1b), and an upper resin layer (1c) are laminated in sequence. The lower resin layer (1a), the metal layer (1b), and the upper resin layer (1c) have different materials.

[0015] For example, the lower resin layer (1a) may be made of insulating polyethylene terephthalate (PET) or nylon. The metal layer (1b) may be made of aluminum, which maintains mechanical strength and prevents the penetration of moisture and oxygen. The upper resin layer (1c) may be made of a polyolefin-based material that has thermal adhesive properties and serves as a sealant.

[0016] The lower resin layer (1a), the metal layer (1b), and the upper resin layer (1c) have different elastic recovery forces due to their different material properties. The elastic recovery force is the force by which an object deformed by an external force returns to its original shape and size when the force is removed.

[0017] As described above, when the edge (5, 6) of the pouch case (2) is curled during the molding of the pouch case (2), the following problems may occur.

[0018] For example, referring to Fig. 1(b), a pickup device (40) adsorbs a pouch case (2). The pickup device (40) comes into contact with both edges (5, 6) of the pouch case (2) and provides vacuum pressure (P0) to adsorb the both edges (5, 6) of the pouch case (2).

[0019] Referring to the enlarged view B of Fig. 1(b), when the edges (5, 6) on both sides of the pouch case (2) are curled, the pickup device (40) has a problem in that it cannot stably adsorb the pouch case (2) because atmospheric pressure flows into the gap (g) between the edges (5, 6) on both sides of the pouch case (2).

[0020] In addition, the curling portion (5a, 6a) of the pouch case (2) may be folded to the edge (5, 6) at the stage of folding the pouch case (2) in half. In this way, if a folded portion is formed at the edge (5, 6), it may cause a sealing defect of the pouch case (2).

[0021] The present invention aims to solve the problems of conventional pouch case forming devices and manufacturing methods.

[0022] Through one embodiment of the present invention, it is intended to provide a manufacturing device and manufacturing method for a pouch case that can effectively eliminate curling that occurs by forming a cup on a pouch substrate.

[0023] Through one embodiment of the present invention, it is intended to provide a manufacturing device and manufacturing method for a pouch case that can improve process efficiency by performing curling removal during the transport process of the pouch material rather than as an additional process.

[0024] In one embodiment of the present invention, an apparatus for manufacturing a pouch case and a method for manufacturing a pouch case are provided, which can prevent curling of the edges of a pouch case by forming a cup on a substrate and then cutting the substrate before cutting the substrate, thereby forming both edges of the substrate to be inclined upward relative to the side of the cup.

[0025] In order to achieve the above-described object, according to one embodiment of the present invention, there is provided a method for manufacturing a pouch case having a cup for inserting an electrode assembly using a pouch substrate, the method including: a cup forming step in which the cup is formed on a substrate that has stopped moving through a cup forming part installed in a moving path of the substrate; a frame forming step in which both sides of the substrate in which the cup is formed are formed to be inclined upward with respect to a side surface of the cup through a frame forming part installed at a rear end of the cup forming part; and a cutting step in which the substrate having the cup and both sides of the cup and the upwardly inclined frames are cut to form the pouch case through a cutting part installed at a rear end of the frame forming part.

[0026] It is preferable that the above-mentioned device repeatedly stops after a certain pitch of driving, and passes through the cup forming part, the frame forming part, and the cutting part in sequence.

[0027] The above-described pitch may correspond to the length of the unit pouch case. Cup forming and cutting may be performed while the substrate is stationary. That is, the cup forming step and cutting step may be performed simultaneously while the substrate is stationary.

[0028] It is preferable that the edge forming step be performed while the substrate is moving from the cup forming section to the cutting section. Since the edge forming is performed while the substrate is moving, no separate process time is added for the edge forming.

[0029] A portion of the substrate on which cup forming has been performed is transported, and the rim forming is performed, and after the rim forming, it is transported and cut.

[0030] It is preferable that the above-mentioned border forming part supports the substrate in the cup forming step and simultaneously forms both sides of the substrate in the border forming step.

[0031] During cup forming, the front end of the substrate may be supported by a conveying roller, and the rear end may be supported by a rim forming portion. The rim forming portion may also be a type of conveying roller, but the rim forming portion may be implemented by a roller that is electrically driven by upper and lower rollers. Therefore, the rim forming portion preferably supports the substrate while also guiding its transport. In particular, it may support both ends of the substrate in the width direction and guide its transport.

[0032] It is preferable that the above-mentioned edge forming part is formed to be inclined upward with respect to the side surface of the cup by pressing both sides of the edge of the substrate in the width direction of the substrate in the above-mentioned edge forming step.

[0033] The above-mentioned edge forming section includes a pair of upper and lower rollers arranged to pressurize and roll the edge of the substrate to form it in an upward slope, and in the edge forming step, the pair of rollers preferably guide the movement of the substrate so that the substrate moves from the cup forming section toward the cutting section and pressurizes and rolls the edge of the substrate at the same time.

[0034] It is preferable that the above pair of rollers be arranged symmetrically on both sides of the above substrate.

[0035] The above pair of rollers can be driven synchronously with the conveying speed of the substrate, and can be driven and stopped in conjunction with the conveying and stopping of the substrate.

[0036] In the above cup forming step, two cups can be formed in parallel in the width direction of the substrate.

[0037] The above cup is formed in a rectangular shape, and it is preferable that the length of the side in the direction of travel of the substrate is longer than the length of the side in the direction of width of the substrate.

[0038] Therefore, the overall length of the unit pouch case is longer than its width. Therefore, the difference in elongation between the uppermost and lowermost layers of the substrate may be more pronounced in the width direction than in the length direction due to cup forming. This may result in severe curling at both edges of the unit pouch case.

[0039] The above pair of rollers can form a convex portion that is sunken upwards in a direction opposite to the direction of cup forming. The cup forming portion repeatedly forms only a portion of the entire substrate. On the other hand, the edge forming portion can continuously form the entire substrate.

[0040] Of course, the spacing between the pair of rollers can be varied. That is, it can be varied between an interval where pressure rolling is performed and an interval where pressure rolling is not performed. Pressure rolling can be performed only on the rim of the cup, and pressure rolling can be omitted on the non-formed portion between the cups in the longitudinal direction of the substrate.

[0041] In order to achieve the above-described object, according to one embodiment of the present invention, there is provided a device for manufacturing a pouch case having a cup for becoming an electrode assembly using a pouch substrate, the device including: a cup forming portion including a mold die and a punch, and configured to form the cup depressed downward in a substrate that is stopped from moving; a cutting portion installed parallel to the width direction of the substrate at a rear end of the edge forming portion and configured to cut the substrate; and an edge forming portion installed between the cup forming portion and the cutting portion, and configured to pressurize both edges of the substrate in which the cup is formed to form the cup so as to be inclined upward with respect to a side surface of the cup.

[0042] The above cups may be formed in two parallel rows in the width direction of the substrate. An electrode assembly may be placed in one cup, a pouch case may be folded between the cups, and then the other cup may cover the electrode assembly. Thereafter, sealing may be performed at the edge of the pouch case.

[0043] The above cup is formed in a rectangular shape, and it is preferable that the length of the side in the direction of travel of the substrate is longer than the length of the side in the direction of width of the substrate.

[0044] The above-mentioned edge forming part may include a first pair of upper and lower rollers provided to pressurize and roll a first edge among the edges on both sides of the substrate to form a convex portion sunken upward; and a second pair of upper and lower rollers provided to pressurize and roll a second edge among the edges on both sides of the substrate to form a convex portion sunken upward.

[0045] It is preferable that the pair of first rollers and the pair of second rollers are provided to support both edges of the substrate in the width direction of the substrate and guide the movement of the substrate from the cup forming portion toward the cutting portion.

[0046] The above pair of rollers includes an upper roller and a lower roller, and a material can be transported and guided between the upper roller and the lower roller. The gap between the upper roller and the lower roller can be varied. It can be divided into a gap for a pressure roller and a gap for simple transport.

[0047] Accordingly, continuous pressure rolling can be performed on the transported material, or pressure rolling can be performed selectively.

[0048] The first roller and the second roller may each include an upper roller having a first outer surface whose diameter decreases from one end to the other along the central axis and a recessed groove portion along the circumferential direction of the first outer surface.

[0049] The first roller and the second roller may each include a second outer surface having a diameter that increases from one end to the other along the central axis, and a lower roller having a protrusion that protrudes convexly along the circumferential direction of the second outer surface and is provided to be insertable into the groove.

[0050] The above-mentioned groove portion has a semicircular cross-section with a predetermined curvature, and the protrusion portion can be provided to be in contact with a part of the groove portion with a curvature smaller than the curvature of the groove portion.

[0051] A convex portion can be formed on the substrate by the shape matching between the groove portion and the protrusion portion. It is preferable that the convex portion is formed by being sunken in the opposite direction to the cup.

[0052] The upper roller preferably has a truncated cone shape with the first outer surface inclined at an angle of 10° to 20° relative to the central axis. This angle of inclination forms the inclination angle of the edge, and can prevent the edge from sagging due to a load even after the unit pouch is formed by cutting later.

[0053] It is preferable that the lower roller has a truncated cone shape with a second outer surface provided to be in contact with the first outer surface.

[0054] According to one embodiment of the present invention, after forming a cup on a substrate, before cutting the substrate, the edges of both sides of the substrate are formed to be inclined upward relative to the side of the cup, and then the substrate is cut, thereby effectively preventing curling of the edges of the pouch case.

[0055] According to one embodiment of the present invention, a border forming part is installed between a cup forming part and a cutting part, so that the existing configurations of the forming device can be used as is without change, and thus a very economical effect can be expected.

[0056] According to one embodiment of the present invention, by preventing curling of the edge of a pouch case during molding of the pouch case, it is possible to prevent in advance manufacturing defects of a secondary battery that may be caused by curling of the edge of the pouch case.

[0057] According to one embodiment of the present invention, the edge of the unit pouch case is prevented from being bent downward due to its own weight, so that the subsequent assembly process can be expected to be facilitated.

[0058] Figure 1 is a drawing for explaining the curling phenomenon that occurs at the edge of a pouch case when manufacturing a conventional pouch case.

[0059] FIG. 2 is a plan view of a manufacturing device for a pouch case according to one embodiment of the present invention, and is a drawing for explaining the arrangement of a cup forming part, a frame forming part, a cutting part, and a grip transfer part.

[0060] Figure 3 is a drawing for explaining the process of forming two cups on a substrate by a cup forming part.

[0061] Fig. 4(a) is a perspective view of a substrate in which two cups are formed, and Fig. 4(b) is a cross-sectional view taken along line aa of Fig. 4(a).

[0062] Figure 5 is a cross-sectional view taken along line bb of Figure 2, and is a drawing for explaining the process of forming a border by a border forming part.

[0063] Fig. 6 is a cross-sectional view taken along line cc of Fig. 2, which is a drawing for explaining a state in which the grip transfer unit holds the edges of both sides of the substrate.

[0064] Fig. 7 is a cross-sectional view taken along line dd of Fig. 2, and is a drawing for explaining the process of the pickup unit vacuum-absorbing the pouch case.

[0065] FIG. 8 is a drawing for explaining a molding process of a pouch case according to one embodiment of the present invention.

[0066] FIG. 9 is a drawing for explaining a process of transporting a molded pouch case to a folding section and sealing the pouch case by a sealing section according to one embodiment of the present invention.

[0067] Hereinafter, with reference to the attached drawings, a manufacturing device for a pouch case according to a preferred embodiment of the present invention will be described.

[0068] The above manufacturing device can be said to be a manufacturing device for manufacturing a unit pouch while a roll-shaped pouch sheet (hereinafter referred to as a “substrate”) is transported.

[0069] FIG. 2 is a plan view of a manufacturing device for a pouch case according to one embodiment of the present invention, and is a drawing for explaining the arrangement of a cup forming part, a frame forming part, a cutting part, and a grip transfer part, FIG. 4(a) is a perspective view of a substrate on which two cups are formed, FIG. 4(b) is a cross-sectional view taken along line aa of FIG. 4(a), and FIG. 5 is a cross-sectional view taken along line bb of FIG. 2, and is a drawing for explaining the process of the frame forming part forming a frame.

[0070] As illustrated in FIG. 2, a pouch case manufacturing device (100) according to one embodiment of the present invention includes a cup forming part (120) and a cutting part (140), and may include a border forming part (200) provided between the cup forming part (120) and the cutting part (140).

[0071] After the cup is formed in the cup forming section (120), the curling is removed through the edge forming section (200), and then it can be cut into a unit pouch case through the cutting section (140).

[0072] The inventors were able to confirm that curling can occur significantly after cutting from a substrate into a unit pouch case. That is, while the curling tendency is hidden by the tension applied to the substrate in a continuous substrate state, it was confirmed that the tension is released in the unit pouch case state, and the curling tendency becomes extremely apparent.

[0073] Removing curling from a single-piece pouch case is quite cumbersome. Therefore, the present embodiment was able to deduce that it is more effective to alleviate or eliminate the curling tendency before the single-piece state, i.e., in the continuous-material state.

[0074] The cup forming unit is for forming a pouch case (2) having a cup (3, 4) into which an electrode assembly can be inserted, and may include a mold die and a punch. Specifically, the cup forming unit may include a mold die having a mold groove and a punch having a block provided to be insertable into the mold groove. The cup forming unit (120) may be defined as a forming device configured to form the cup (3, 4) on a substrate (1) that is stopped from moving.

[0075] The cutting section (140) is installed parallel to the width direction (W) of the substrate (1) at the rear end of the border forming section (200), and can be said to be a cutting device designed to cut the substrate (1).

[0076] The edge forming part (200) is installed between the cup forming part (120) and the cutting part (140), and can be said to be a edge forming device that presses the edges (5, 6) on both sides of the substrate (1) on which the cup (3, 4) is formed to form the cup (3, 4) so ​​as to be inclined upward with respect to the side surface.

[0077] The manufacturing device (100) of the above pouch case includes a driving unit (110) that drives the substrate (1) from the cup forming unit (120) toward the cutting unit (140) while repeatedly driving at a certain pitch and then stopping. The driving unit (110) includes the edge forming unit (200) and the grip transfer unit (130).

[0078] The manufacturing device (100) of the above pouch case may include a control unit (160) that controls the operation of a cup forming unit (120), a frame forming unit (200), a driving unit (110), a cutting unit (140), and the grip transfer unit (130). The cup forming unit (120) and the cutting unit (140) operate when the driving of the base material (1) is stopped. The frame forming unit (200) operates when the base material (1) is moving. Therefore, the additional process time for frame forming can be eliminated. In addition, since the frame forming unit can be installed by utilizing the driving space between the cup forming unit and the cutting unit, it can be said to be very economical.

[0079] The above cup forming part (120), the frame forming part (200), and the cutting part (140) can be sequentially arranged along the running direction (MD) of the substrate (1). The running direction (MD) of the substrate is parallel to the longitudinal direction (L) of the substrate (1).

[0080] As illustrated in Fig. 3, the cup forming part (120) includes a mold die (125) and a punch (121). The mold die (125) has a first mold groove (126) and a second mold groove (127) parallel to the first mold groove (126). The punch (121) is installed on the upper portion of the mold die (125). The punch (121) has a first block (122) that is provided to be insertable into the first mold groove (126) and a second block (123) that is provided to be insertable into the second mold groove (127).

[0081] The above mold die (125) is raised and lowered toward the punch (121) along the height direction (H) and presses the substrate (1) with the punch (121). At this time, the first block (122) of the punch (121) stretches the substrate (1) into the first mold groove (126) to form a first cup (3) on the substrate (1). Then, the second block (123) of the punch (121) stretches the substrate (1) into the second mold groove (127) to form a second cup (4) on the substrate (1).

[0082] The first cup (3) and the second cup (4) may be formed in a rectangular shape. The length of the side of the first cup (3) and the second cup (4) with respect to the direction of travel of the substrate (1) may be longer than the length of the side with respect to the width direction (W) of the substrate (1). The first cup (3) and the second cup (4) are provided so that an electrode assembly (9a, see (e) of FIG. 9) can be inserted therein.

[0083] In this specification, for the convenience of explanation, the edge extending from the first long side (L1) of the first cup (3) is referred to as the first edge (5). And, the edge extending from the second long side (L2) of the second cup (4) is referred to as the second edge (6). The second edge (6) is parallel to the first edge (5) along the longitudinal direction (L) of the substrate (1) and is spaced apart from the first edge (5) along the width direction (W) of the substrate (1).

[0084] In this specification, drawing numbers 5 and 7 indicate the first edge (5), and specifically, drawing number 5 indicates the first edge (5) of the substrate (1) before passing through the edge forming section (200), and drawing number 7 indicates the first edge (5) that is inclined upward with respect to the first cup (3) while passing through the edge forming section (200).

[0085] In addition, drawing number 6 indicates the second edge (6) of the substrate (1) before passing through the edge forming section (200), and drawing number 8 indicates the second edge (6) that is inclined upwards with respect to the second cup (4) while passing through the edge forming section (200).

[0086] The above-mentioned border forming part (200) is installed between the above-mentioned cup forming part (120) and the above-mentioned cutting part (140).

[0087] As illustrated in FIG. 5, the edge forming part (200) may include a pair of first rollers (210) provided to form a first edge (5) among the edges on both sides of the substrate (1) to be inclined upward by applying pressure and rolling, and a pair of second rollers (260) provided to form a second edge (6) among the edges on both sides of the substrate (1) to be inclined upward by applying pressure and rolling.

[0088] The first edge (5) can be formed to be inclined upward with respect to the side surface (3b) of the first cup (3) while passing through the pair of first rollers (210). In addition, the second edge (6) can be formed to be inclined upward with respect to the side surface (4b) of the second cup (4) while passing through the pair of second rollers (260).

[0089] The above pair of first rollers (210) and the above pair of second rollers (260) may be provided to support the edges (5, 6) on both sides of the substrate (1) in the width direction (W) of the substrate (1), respectively, and guide the movement of the substrate (1) from the cup forming portion (120) toward the cutting portion (140).

[0090] The pair of first rollers (210) and the pair of second rollers (260) may be arranged symmetrically. The pair of first rollers (210) includes a first upper roller (220) and a first lower roller (230). The pair of second rollers (260) includes a second upper roller (270) and a second lower roller (280).

[0091] The first upper roller (220) and the second upper roller (270) have the same shape. The first lower roller (230) and the second lower roller (280) have the same shape. In order to avoid repetition of explanation in this embodiment, the description will focus on the first upper roller (220) and the first lower roller (230).

[0092] The first upper roller (220) has a first outer surface (225) whose diameter decreases from one end to the other along the first central axis (CL1) and a recessed groove (223) along the circumferential direction of the first outer surface (225).

[0093] The above-mentioned groove (223) has a semicircular cross-section with a predetermined curvature. The groove (223), together with the protrusion (233) described later, serves to fix the boundary between the first cup (3) and the first frame (5).

[0094] The first upper roller (220) may have a truncated cone shape. The first upper roller (220) has a first reference plane (221) perpendicular to the first central axis (CL1), a first opposite surface (227) parallel to the first reference plane (221), and a first outer surface (225) connecting the first reference plane (221) and the first opposite surface (227).

[0095] The first reference surface (221) has a cross-sectional area larger than that of the first opposite surface (227). The first outer surface (225) is a surface connecting the first reference surface (221) and the first opposite surface (227). The first outer surface (225) is inclined within a range of 10° to 20° with respect to the first central axis (CL1).

[0096] The first upper roller (220) is arranged so as to be in contact with the upper surface of the first frame (5). The first upper roller (220) is arranged so that the first central axis (CL1) is parallel to the width direction (W) of the substrate (1).

[0097] A first upper driving unit (241) may be mounted on the first upper roller (220). The first upper driving unit (241) may be a motor that rotates the first upper roller (220).

[0098] A first height adjustment member (243) is mounted on the first upper roller (220). The first height adjustment member (243) is for adjusting the height of the first upper roller (220) along the height direction (H).

[0099] The first height adjustment member (243) can be tightened with a bolt type to adjust the gap between the first upper roller (220) and the first lower roller (230). Alternatively, the first height adjustment member (243) can be a reciprocating cylinder that can move along the height direction (H).

[0100] The first lower roller (230) has a second outer surface (235) whose diameter increases from one end to the other along the second central axis (CL2) and a protrusion (233) that protrudes convexly along the circumferential direction of the second outer surface (235).

[0101] The above protrusion (233) has a curvature smaller than that of the groove (223). The protrusion (233) protrudes convexly along the circumferential direction of the second outer surface (235). The protrusion (233) is provided so as to be in contact with a portion of the groove (223).

[0102] The first lower roller (230) may have a cone shape in which the second outer surface (235) is provided to be in contact with the first outer surface (225) of the first upper roller (220).

[0103] The first lower roller (230) has a second reference plane (231) perpendicular to the second central axis (CL2), a second opposite surface (237) parallel to the second reference plane (231), and a second outer surface (235) connecting the second reference plane (231) and the second opposite surface (237).

[0104] The second reference surface (231) has a cross-sectional area smaller than that of the second opposite surface (237). The second outer surface (235) is inclined within a range of 10° to 20° with respect to the second central axis (CL2).

[0105] The first lower roller (230) is arranged so as to be in contact with the lower surface of the first frame (5). The first lower roller (230) is arranged so that the second central axis (CL2) is parallel to the width direction (W) of the substrate (1).

[0106] A first lower driving unit (245) is mounted on the first lower roller (230). The first lower driving unit (245) may be a motor that rotates the first lower roller (230).

[0107] A second height adjustment member (247) is mounted on the first lower roller (230). The second height adjustment member (247) is for adjusting the height of the first lower roller (230) along the height direction (H).

[0108] The second height adjustment member (247) is a bolt type member that can adjust the degree of tightening to adjust the gap between the first lower roller (230) and the first upper roller (220). A reciprocating cylinder can be used as the second height adjustment member (247).

[0109] The first lower roller (230) pressurizes and rolls the first edge (5) while rotating in the opposite direction to the first upper roller (220). At this time, the protrusion (233) can extend a portion of the first edge (5) to the groove (223) to form a convex shape toward the upper portion of the side surface of the first cup (3). In addition, the second outer surface (235) of the first lower roller (230) can extend the remaining portion of the first edge (5) to the first outer surface (225) to form an upward slope with respect to the side surface (3b) of the first cup (3).

[0110] The above protrusion (233) presses a portion of the first frame (5) including the first long side (L1) of the first cup (3) along the height direction (H) toward the groove (223), thereby preventing the substrate (1) from being displaced from its original position along the width direction (W) of the substrate (1) when the first upper roller (220) and the first lower roller (230) rotate.

[0111] When the first upper roller (220) and the first lower roller (230) rotate, the protrusion (233) pressurizes and rolls a portion of the first edge (5) together with the groove (223), and extends a portion of the first edge (5) upward in the height direction (H) to form a first convex portion (7a) having a predetermined curvature.

[0112] The first convex portion (7a) is formed between the vertical surface of the cup and the first rim (5), and the first rim can be formed to be inclined upward by the first convex portion (7a).

[0113] In addition, the first upper roller (220) and the first lower roller (230) can pressurize and roll the remaining area of ​​the first edge (5) located between the first inclined surface (225) and the second inclined surface (235) while rotating in opposite directions to form an upper slant of the side surface (3b) of the first cup (3).

[0114] The first convex portion (7a) may form a line dividing the side surface (3b) of the first cup (3) and the upwardly inclined first edge (7) along the first long side (L1) of the first cup (3). The first convex portion (7a) is provided to be convex upward in the height direction (H) from the side surface (3b) of the first cup (3). The first convex portion (7a) may have a semicircular cross-section.

[0115] The first upwardly inclined edge (7) is bent upward in the height direction (H) from the first convex portion (7a), and may be provided so as not to be parallel or perpendicular to the bottom surface (3a) and the side surface (3b) of the first cup (3), respectively.

[0116] The above-mentioned upwardly inclined first edge (7) is inclined within a range of 10° to 20° with respect to the side surface (3b) of the above-mentioned first cup (3).

[0117] The above-mentioned upwardly inclined first edge (7) is a part of the substrate (1) extending from the first cup (3). The above-mentioned upwardly inclined first edge (7) is provided to be inclined toward the upper portion of the side surface (3b) of the first cup (3) and may have a predetermined elasticity.

[0118] The second upper roller (270) is equipped with the second upper driving unit (291) and the third height adjustment member (293). The second upper driving unit (291) may be a motor that rotates the second upper roller (270). The third height adjustment member (293) is for adjusting the height of the second upper roller (270) with respect to the second lower roller (280).

[0119] The second lower roller (280) has the same shape as the first lower roller (230). The second lower roller (280) is arranged symmetrically with the first lower roller (230) in the width direction (W) of the substrate (1) on the lower surface of the second edge (6). The second lower roller (280) can pressurize and roll the second edge (6) together with the second upper roller (270).

[0120] The second lower roller (280) is equipped with the second lower driving unit (295) and the fourth height adjustment member (297). The second lower driving unit (295) may be a motor that rotates the second lower roller (280). The fourth height adjustment member (297) is for adjusting the height of the second lower roller (280) with respect to the second upper roller (270).

[0121] The second upper roller (270) and the second lower roller (280) can pressurize and roll the second edge (6) of the substrate (1) to form a second convex portion (8a) and to form an upward slope with respect to the side surface (4b) of the second cup (4).

[0122] The second convex portion (8a) may form a line dividing the side surface (4b) of the second cup (4) and the second rim (8) formed to be inclined upward along the second long side (L2) of the second cup (4). The second convex portion (8a) is provided to be convex upward in the height direction (H) from the side surface (4b) of the second cup (4). The second convex portion (8a) may have a semicircular cross-section.

[0123] The second edge (8) formed upwardly inclined is bent upward in the height direction (H) from the second convex portion (8a), and may be provided so as not to be parallel or perpendicular to the bottom surface (4a) and the side surface (4b) of the second cup (4), respectively.

[0124] The second edge (8) formed to be inclined upwardly can be inclined within a range of 10° to 20° with respect to the side surface (4b) of the second cup (4). The second edge (8) formed to be inclined upwardly is formed symmetrically with respect to the first edge (7) formed to be inclined upwardly.

[0125] The second edge (8) formed to be inclined upwards may be inclined upwards toward the upper portion of the side surface (4b) of the second cup (4) and may have elasticity. Even if the lower resin layer (1a), the metal layer (1b) and the upper resin layer (1c) constituting the substrate (1) have different elastic recovery forces, the first and second edges (7, 8) formed to be inclined upwards have a predetermined elasticity and may not be bent in a direction approaching the bottom surfaces (3a, 4a) of the first and second cups (3, 4) when the substrate (1) is cut.

[0126] Fig. 6 is a cross-sectional view taken along line cc of Fig. 2, which is a drawing for explaining a state in which the grip transfer unit holds the edges of both sides of the substrate.

[0127] The grip transfer unit (130) above grips the edges (5, 6) on both sides of the substrate (1) and moves the substrate (1) in the travel direction (MD). The grip transfer unit (130) can reciprocate between a preset cutting position (P1) and a transfer position (P2) along the longitudinal direction (L) of the substrate (1) at the rear end of the edge forming unit (200).

[0128] The above grip transfer unit (130) is provided to hold both edges (5, 6) of the above substrate (1). The transfer position (P2) is a position spaced apart from the cutting position (P1) by the length of the pouch case (2).

[0129] The above grip transfer unit (130) includes a first gripper (131) and a second gripper (135).

[0130] The first gripper (131) is arranged to hold the first frame (5). The first gripper (131) includes a first upper grip bar (132) and a first lower grip bar (133). The first upper grip bar (132) and the first lower grip bar (133) are arranged to hold the first frame (5) in a forceps manner.

[0131] The first gripper (131) is equipped with a first transfer unit (134). The first transfer unit (134) is provided to move the first gripper (131) in the driving direction (MD) or the reverse direction (MDR). The first transfer unit (134) may be a driving device such as a linear motor or a reciprocating cylinder.

[0132] The second gripper (135) is arranged to hold the second frame (6). The second gripper (135) includes the second upper grip bar (136) and the second lower grip bar (137). The second upper grip bar (136) and the second lower grip bar (137) are arranged to hold the second frame (6) in a forceps manner.

[0133] The second transfer unit (138) can move the second gripper (135) in the driving direction (MD) or the reverse direction (MDR). The second transfer unit (138) can be a driving device such as a linear motor or a reciprocating cylinder.

[0134] The manufacturing device (100) of a pouch case having the above structure can form the edges (5, 6) of both sides of the substrate (1) to be inclined upward by installing a border forming part (200) between the cup forming part (120) and the cutting part (140).

[0135] The border forming part (200) can be stopped during the forming operation of the cup forming part (120) and hold the substrate (1) at the rear end of the cup forming part (120) so that the substrate (1) can be stretched in the height direction (H) during the forming operation of the cup forming part (120).

[0136] In addition, the above-mentioned edge forming part (200) can pressurize and roll the base material (200) while the base material (1) in which the cups (3, 4) are formed moves toward the cutting part (140), thereby forming the edge (5, 6) of the base material (1) to be inclined upward in succession to the forming of the cups (3, 4).

[0137] The manufacturing device (100) of a pouch case can improve the forming efficiency of a pouch case by continuously performing forming of a cup (3, 4) and forming of a frame (5, 6).

[0138] In addition, the manufacturing device (100) of the above pouch case can prevent curling of the edge of the pouch case (2) by cutting the substrate (1) after forming the substrate (1) into cups (3, 4) and upwardly inclined edges (7, 8) on both sides while the substrate (1) repeats moving and stopping at a certain pitch.

[0139] The curling occurrence mechanism and curling prevention mechanism are explained as follows through Figure 1.

[0140] First, the elongation of the upper resin layer (1c) and the lower resin layer (1a) are different due to cup forming. That is, the inner surface of the cup is formed by the upper resin layer (1c) and the outer surface of the cup is formed by the lower resin layer (1a) due to cup forming. The elongation of the lower resin layer (1c) becomes greater than that of the upper resin layer (1c) due to cup forming. Therefore, after cup forming is completed, the restoring force of the lower resin layer (1c) becomes greater than that of the upper resin layer (1a). As a result, curling as illustrated in FIG. 1 may occur at the edge portion after cup forming is completed.

[0141] Considering the mechanism of curling occurrence, it can be understood that an anti-curling mechanism can be implemented by performing forming in the opposite direction to the mechanism of curling occurrence. That is, if the elongation of the upper resin layer (1c) is small due to cup forming, the elongation of the upper resin layer (1c) can be increased through edge forming.

[0142] That is, an upwardly convex convex portion can be formed between the cup and the rim. For example, the cup has a downwardly convex shape, and the convex portion has an upwardly convex shape. By forming the convex portion, the elongation of the upper resin layer (1c) in the convex portion becomes greater than that of the lower resin layer (1a). Therefore, the difference in elongation between the upper and lower resin layers is minimized overall, so that curling can be alleviated or eliminated.

[0143] Additionally, it is highly desirable to have the edges or wings slope upward as they move outward during the edge forming process. This is because, in a unit pouch case, the edges inevitably sag downward due to their own weight. Therefore, by sloping the edges upward, this downward sagging can be prevented. This facilitates the operation of subsequent grippers and can also facilitate the assembly process of covering and sealing subsequent pouch cases.

[0144] Below, a method for manufacturing a pouch case by forming a pouch case (2) using a pouch case manufacturing device (100) will be described.

[0145] FIG. 8 is a drawing for explaining a process of forming a pouch case according to one embodiment of the present invention, and FIG. 9 is a drawing for explaining a process of transporting a formed pouch case to a folding section and sealing the pouch case by a sealing section according to one embodiment of the present invention.

[0146] Referring to FIG. 8, a method for manufacturing a pouch case according to an embodiment of the present invention is for forming a pouch case (2) having a cup (3, 4) into which an electrode assembly can be inserted, and may include a cup forming step in which the cup (3, 4) is formed on a stopped substrate (1) in a cup forming part (120) installed in a travel path of the substrate (1), a frame forming step in which the frame (5, 6) on both sides of the substrate (1) in which the cup (3, 4) is formed is formed to be inclined upward with respect to the side surface of the cup (3, 4) in a frame forming part (200) installed at the rear end of the cup forming part (120), and a cutting step in which the substrate (1) having the cup (3, 4) and the frame (7, 8) inclined upward on both sides is cut to form the pouch case (2) in a cutting part (140) installed at the rear end of the frame forming part (200).

[0147] The above-mentioned device (1) can pass through the cup forming part (120), the frame forming part (200), and the cutting part (140) in sequence while repeating stopping after a certain pitch.

[0148] The cup forming step can be performed while the above-mentioned substrate (1) is stopped from moving. In the cup forming step, the control unit (160) can stop the moving unit (110), the edge forming unit (200), and the grip transfer unit (130) to stop the moving of the substrate (1).

[0149] Referring to FIG. 3, the cup forming part (120) moves upward and downward in a direction in which the mold die (125) approaches the punch (121) along the height direction (H).

[0150] The above mold die (125) presses the stopped substrate (1) by the punch (121) while being raised and lowered along the height direction (H). At this time, the substrate (1) is pulled in the direction in which the mold die (125) presses, and the first cup (3) and the second cup (4) are formed by the punch (121).

[0151] Specifically, the first block (122) of the punch (121) stretches the substrate (1) into the first mold groove (126) to form a first cup (3) on the substrate (1). Then, the second block (123) of the punch (121) stretches the substrate (1) into the second mold groove (127) to form a second cup (4) on the substrate (1).

[0152] When the first cup (3) and the second cup (4) are formed on the substrate (1) through the above process, the mold die (125) moves downward in the direction away from the punch (121) along the height direction (H) and returns to the original position.

[0153] In the above cup forming step, two cups (3, 4) can be formed in parallel in the width direction (W) of the substrate (1). The cups (3, 4) are formed in a rectangular shape, and the length of the side with respect to the running direction of the substrate (1) can be longer than the length of the side with respect to the width direction (W) of the substrate (1).

[0154] After the above cup forming step, the driving unit (110) and the grip transfer unit (130) drive the substrate (1) in the driving direction (MD). The driving direction (MD) is a direction from the cup forming unit (120) toward the cutting unit (140). When the driving unit (110) is in operation, the substrate (1) passes through the edge forming unit (200) while driving in the driving direction (MD).

[0155] The border forming step can be performed while the above-mentioned substrate (1) moves from the cup forming portion (120) to the cutting portion (140).

[0156] The above-mentioned border forming part (200) supports the substrate (1) in the cup forming step, and can continuously form the borders (5, 6) on both sides of the substrate (1) in the border forming step.

[0157] The above-mentioned edge forming part (200) can form the edge (5, 6) of the substrate (1) in the width direction of the substrate (1) in the edge forming step so as to be inclined upward with respect to the side surface of the cup (3, 4).

[0158] The above pair of first rollers (210) and the above pair of second rollers (260) guide the movement of the substrate (1) so that the substrate (1) moves from the cup forming portion (120) toward the cutting portion (140) and can simultaneously pressurize and roll both edges (5, 6) of the substrate (1).

[0159] In the above-described border forming step, the pair of first rollers (210) can form a first area (A1) including a first long side (L1) of the first cup (3) so as to be inclined upward with respect to a side surface (3b) of the first cup (3). In addition, the pair of second rollers (260) can form a second area (A2) including a second long side (L2) of the second cup (4) so ​​as to be inclined upward with respect to a side surface (4b) of the second cup (4).

[0160] Through the above process, the two sides of the edge (7, 8) of the substrate (1) can be formed symmetrically in the width direction (W) of the substrate (1).

[0161] In the above-described border forming step, the grip transfer unit (130) grabs the ends of both sides of the border (5, 6) of the substrate (1) at a preset cutting position (P1) and moves backward in the driving direction (MD).

[0162] Referring to Fig. 6, the first gripper (131) grabs the end of the first frame (5) at the cutting position (P1). And, the second gripper (135) grabs the end of the second frame (6) at the cutting position (P1).

[0163] The first gripper (131) and the second gripper (135) move from the cutting position (P1) to the transfer position (P2) while holding the first edge (5) and the second edge (6). The first gripper (131) and the second gripper (135) are stopped at the transfer position (P2). The distance between the cutting position (P1) and the transfer position (P2) may be the length of the pouch case (2).

[0164] Referring to FIG. 5, in the edge forming step, the pair of first rollers (210) and the pair of second rollers (260) pressurize and roll the edges (5, 6) on both sides of the substrate (1) in the traveling direction (MD), thereby forming them to be inclined upward with respect to the side surface (3b) of the first cup (3) and the side surface (4b) of the second cup (4).

[0165] The substrate (1) passing through the above-mentioned border forming section (200) has a first border (7) inclined upward with respect to the side surface (3b) of the first cup (3) and a second border (8) inclined upward with respect to the side surface (4b) of the second cup (4).

[0166] The above-mentioned upwardly inclined first edge (7) is inclined within a range of 10° to 20° with respect to the side surface (3b) of the first cup (3) toward the outer side of the side surface (3b) of the first cup (3).

[0167] The upwardly inclined second edge (8) is inclined within a range of 10° to 20° with respect to the side surface (4b) of the second cup (4) toward the outer side of the side surface (4b) of the second cup (4). The upwardly inclined second edge (8) may be arranged symmetrically with respect to the upwardly inclined first edge (7).

[0168] The cutting step can be performed while the above-mentioned substrate (1) is stopped from moving. In the cutting step, the control unit (160) can stop the moving unit (110), the edge forming unit (200), and the grip transfer unit (130) to stop the moving of the substrate (1).

[0169] In the above cutting step, the grip transfer unit (130) is stopped while holding the substrate (1) at the transfer position (P2). Then, in the cutting step, the cutting unit (140) moves in a direction approaching the substrate (1) along the height direction (H) from the cutting position (P1) and cuts the substrate (1) along an imaginary cutting line (C1) parallel to the width direction (W) of the substrate (1).

[0170] After completion of the above cutting step, the cutting portion (140) moves away from the substrate (1) along the height direction (H) and returns to the original position. Then, the grip transfer portion (130) is separated from the two sides of the pouch case (2) at the transfer position (P2).

[0171] Fig. 7 is a cross-sectional view taken along line dd of Fig. 2, and is a drawing for explaining the process of the pickup unit vacuum-absorbing the pouch case.

[0172] The pickup unit (150) can pick up the pouch case (2) at the transfer location (P2) and transport it to a subsequent process for manufacturing a secondary battery (9). The subsequent process includes a process of storing the electrode assembly (9a) in the first cup (3) of the pouch case (2) and a folding process of folding the pouch case (2) in half.

[0173] The above pickup unit (150) includes a first adsorption member (151) and a second adsorption member (152). The pickup unit (150) can vacuum-adsorb the upwardly inclined first edge (7) and second edge (8) of the pouch case (2) by applying vacuum pressure (P0) to the first and second adsorption members (151, 152).

[0174] The pouch case (2) manufactured through the above process can be stably absorbed by the first and second absorption members (151, 152) without curling the edges (7, 8).

[0175] The above pouch case (2) is provided with a folding part (170) after the electrode assembly (9a) is accommodated in the first cup (3). The folding part (170) is a device that folds the pouch case (2) in half so that the second cup (4) covers the first cup (3) and the first edge (7) and the second edge (8) come into contact.

[0176] The above folding member (170) includes a first folding member (171) on which a portion of the pouch case (2) including the first cup (3) is placed, and a second folding member (172) on which the remaining portion of the pouch case (2) including the second cup (4) is placed. The first folding member (171) and the second folding member (172) are rotatably connected at a predetermined angle by a hinge axis (173).

[0177] Referring to FIGS. 9(c) to 9(e), the folding part (170) folds the pouch case (2) in half so that the second cup (4) covers the first cup (3) while the second folding member (172) rotates in a direction closer to the first folding member (171) while the first folding member (171) and the second folding member (172) vacuum-absorb the lower surface of the pouch case (2).

[0178] Referring to Fig. 9(f), after folding the pouch case (2), the edges (7, 8) of the pouch case (2) can be sealed by heat (Q) fusion by the sealing portion (180).

[0179] The present invention can prevent curling of the edge of a pouch case (2), thereby preventing poor absorption of a pickup unit (150) for transporting the pouch case (2) to a subsequent process, and furthermore, can prevent repetitive warning alarms due to the poor absorption.

[0180] In addition, the present invention prevents curling of the edge of the pouch case (2), thereby preventing a folding phenomenon in which a part of the edge of the pouch case (2) is folded to another part during the folding step of folding the pouch case (2) in half, thereby preventing a folding defect of the pouch case (2).

[0181] In addition, the present invention can improve the productivity of the secondary battery (9) by preventing sealing failure due to poor folding of the pouch case (2).

[0182] The preferred embodiments of the present invention described above are disclosed for illustrative purposes. Those skilled in the art will appreciate that various modifications, variations, and additions can be made within the spirit and scope of the present invention. Such modifications, variations, and additions should be deemed to fall within the scope of the following claims.

[0183] As described in the detailed description of the invention.

Claims

1. A method for manufacturing a pouch case having a cup into which an electrode assembly is inserted using a pouch substrate, A cup forming step in which a cup is formed on a stopped vehicle through a cup forming unit installed in the vehicle's travel path; A border forming step in which the borders on both sides of the substrate in which the cup is formed are formed to be inclined upward relative to the side of the cup through a border forming part installed at the rear end of the cup forming part; and A method for manufacturing a pouch case, comprising a cutting step in which a substrate having the cup and upwardly inclined edges on both sides is cut to form the pouch case through a cutting portion installed at the rear end of the above-mentioned edge forming portion.

2. In paragraph 1, A method for manufacturing a pouch case, characterized in that the above-mentioned material repeatedly stops after a certain pitch travel and passes through the cup forming part, the frame forming part, and the cutting part in sequence.

3. In paragraph 2, A method for manufacturing a pouch case, characterized in that the edge forming step is performed while the substrate runs from the cup forming section to the cutting section.

4. In paragraph 3, A method for manufacturing a pouch case, characterized in that the cup forming step and the cutting step are performed during the stoppage of the above-described device.

5. In paragraph 1, A method for manufacturing a pouch case, characterized in that the above-mentioned edge forming part supports the substrate in the cup forming step and forms both sides of the substrate simultaneously in the edge forming step.

6. In paragraph 5, A method for manufacturing a pouch case, characterized in that the above-mentioned edge forming part forms the edges of the substrate on both sides in the width direction of the substrate in the edge forming step to be inclined upward relative to the side of the cup.

7. In paragraph 6, The above-mentioned edge forming part includes a pair of upper and lower rollers arranged to pressurize and roll the edge of the substrate to form it in an upward slope, A method for manufacturing a pouch case, characterized in that, in the above-mentioned edge forming step, the pair of rollers guide the movement of the substrate so that the substrate moves from the cup forming portion toward the cutting portion and simultaneously pressurizes and rolls the edge of the substrate.

8. In paragraph 7, A method for manufacturing a pouch case, characterized in that the pair of rollers are arranged symmetrically on both sides of the substrate.

9. In paragraph 1, A method for manufacturing a pouch case, characterized in that in the above cup forming step, two cups are formed parallel in the width direction of the substrate.

10. In paragraph 9, A method for manufacturing a pouch case, wherein the cup is formed in a rectangular shape, and the length of the side in the direction of travel of the substrate is longer than the length of the side in the width direction of the substrate.

11. In a manufacturing device of a pouch case having a cup for becoming an electrode assembly using a pouch substrate, A cup forming section including a mold die and a punch, and configured to form the cup sunk downward into a stopped moving substrate; A cutting part installed parallel to the width direction of the substrate at the rear end of the above-mentioned border forming part and provided to cut the substrate; and A pouch case manufacturing device including a border forming unit installed between the cup forming unit and the cutting unit and configured to pressurize both sides of a substrate on which the cup is formed to form an upward slope with respect to a side of the cup.

12. In paragraph 11, A pouch case manufacturing device characterized in that the above cups are formed in two parallel rows in the width direction of the above substrate.

13. In paragraph 12, A pouch case manufacturing device characterized in that the cup is formed in a rectangular shape, and the length of the side in the direction of travel of the substrate is longer than the length of the side in the width direction of the substrate.

14. In paragraph 11, The above frame forming part A pair of upper and lower first rollers provided to pressurize and roll the first edge among the two edges of the above-mentioned device to form a convex portion sunken upward; and A pouch case manufacturing device characterized by including a pair of upper and lower second rollers provided to pressurize and roll a second edge among the edges on both sides of the above-mentioned device to form a convex portion sunken upward.

15. In paragraph 14, A pouch case manufacturing device characterized in that the pair of first rollers and the pair of second rollers are provided to support both edges of the substrate in the width direction of the substrate and guide the movement of the substrate from the cup forming portion toward the cutting portion.

16. In paragraph 15, A pouch case manufacturing device characterized in that the first roller and the second roller each include a first outer surface having a diameter that decreases from one end to the other along a central axis and an upper roller having a recessed groove portion along the circumferential direction of the first outer surface.

17. In paragraph 16, A pouch case manufacturing device characterized in that the first roller and the second roller each include a second outer surface whose diameter increases from one end to the other along a central axis and a lower roller having a protrusion that protrudes convexly along the circumferential direction of the second outer surface and is provided to be insertable into the groove.

18. In paragraph 17, The above home portion has a semicircular cross-section with a predetermined curvature, A pouch case manufacturing device characterized in that the protrusion has a curvature smaller than the curvature of the groove and is provided to be in contact with a part of the groove.

19. In paragraph 18, A pouch case manufacturing device characterized in that the upper roller has a truncated cone shape with the first outer surface inclined within 10° to 20° with respect to the central axis.

20. In paragraph 19, A pouch case manufacturing device characterized in that the lower roller has a truncated cone shape with a second outer surface provided to be in contact with the first outer surface.

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