Welding auxiliary correction device and welding equipment

Abstract

The present invention discloses a welding auxiliary correction device, comprising a correction base, on which a work station for welding is arranged; a plurality of correction support members, each correction support member comprising a correction pad and a correction support body, the correction pad being fixedly connected to the correction support body, the plurality of correction support members being evenly distributed inside the work station, each correction support body extending in a direction perpendicular to the work station, and each correction support body being fixedly connected to the correction base, for supporting a battery box cover, and compensating for the flatness tolerance of the battery box cover at the position of the work station through the deformation of the correction pad. At the same time, a welding device applying the above-mentioned welding auxiliary correction device is also disclosed, which solves the problem of missing welds or excessively deep weld marks due to flatness tolerance during the welding process of the existing explosion-proof membrane and the battery box cover.

Description

Technical Field

[0001] The present invention relates to the field of battery processing, and in particular to a welding auxiliary correction device and welding equipment. Background Art

[0002] With the development of power batteries and new energy vehicles, the energy density of power batteries continues to increase. However, once thermal runaway occurs, the battery is prone to explosion risk due to its airtightness requirements. Therefore, explosion-proof structures and components are a crucial design feature of power batteries, providing protection, regulating air pressure, and preventing explosions.

[0003] The most critical component of explosion-proof structures and components is the explosion-proof membrane. When a power battery experiences thermal runaway, its internal pressure rises dramatically due to the generation of high-temperature gases. When the internal pressure reaches or exceeds the safe pressure, the membrane pierces through the membrane for immediate and rapid pressure relief, achieving explosion protection.

[0004] Due to the design requirements of power batteries or battery design factors (such as manufacturing, assembly, structural stability, etc.), the explosion-proof structure and explosion-proof components (hereinafter collectively referred to as the explosion-proof structure) will be integrated with the battery box cover. However, the structure of the battery box cover is relatively complex, and there are process errors in the production process of the battery box cover. Therefore, when the explosion-proof membrane is welded and fixed to the explosion-proof structure on the battery box cover, the flatness of the explosion-proof structure cannot be effectively guaranteed, resulting in problems such as missing welds or excessively deep weld marks between the explosion-proof membrane and the explosion-proof structure, which in turn causes the power battery to fail to meet explosion-proof requirements. Summary of the Invention

[0005] In order to overcome at least one of the defects described in the above-mentioned prior art, the present invention provides a welding auxiliary correction device and welding equipment, which solves the problem of missing welds or excessively deep weld marks due to flatness tolerance during the welding process of the existing explosion-proof membrane and the battery box cover.

[0006] The technical solution adopted by the present invention to solve the problem is:

[0007] A welding auxiliary correction device, comprising:

[0008] A correction base, wherein a welding station is provided on the correction base;

[0009] A plurality of correction support members, each of which includes a correction pad and a correction support body, the correction pad is fixedly connected to the correction support body, and the correction support members are evenly distributed inside the workstation, each of the correction support bodies extends in a direction perpendicular to the workstation, and each of the correction support bodies is fixedly connected to the correction base, and is used to support the battery box cover, and compensate for the flatness tolerance of the battery box cover at the position of the workstation through the deformation of the correction pad.

[0010] Furthermore, the welding auxiliary correction device also includes a support auxiliary platform, which is located on one side of the plurality of correction support members and is fixedly connected to the correction base.

[0011] Furthermore, the supporting auxiliary platform includes a buffer pad and a supporting platform, the buffer pad is arranged on the supporting platform, and the supporting platform is fixedly connected to the correction base.

[0012] Furthermore, a plurality of buffer grooves are provided on the buffer pad, and each of the buffer grooves extends toward one side of the workstation.

[0013] Furthermore, the welding auxiliary correction device also includes a plurality of positioning members for inserting and positioning the battery box cover, and the plurality of positioning members are fixedly connected to the correction base.

[0014] Furthermore, four correction supports are evenly arranged inside the workstation to ensure that the battery box cover is evenly stressed at the position of the workstation.

[0015] Furthermore, the correction base is provided with a plurality of positioning grooves, each correction support body is provided corresponding to each positioning groove, the correction support body is plugged into the positioning groove, and the correction support body is bolted to the correction base.

[0016] Furthermore, the correction pad is a silicone pad.

[0017] Furthermore, at least one avoidance groove is provided on the correction base.

[0018] The present invention also discloses a welding device, comprising:

[0019] The aforementioned welding auxiliary correction device;

[0020] A welding joint is located above the welding auxiliary correction device.

[0021] In summary, the welding auxiliary correction device and welding equipment provided by the present invention have the following technical effects:

[0022] By using multiple corrective support members to jointly support the battery compartment cover, the force applied to the battery compartment cover is uniform within the orthographic projection of the workstation. Each corrective support member forms an independent force-bearing unit. This not only utilizes the space between two adjacent corrective support members to ensure that the corrective pads of the corrective support members have good deformation capabilities to compensate for the flatness tolerance of the battery compartment cover within the orthographic projection of the workstation, thereby resolving the existing problems of missing welds or excessively deep weld marks caused by flatness tolerance during the welding process between the explosion-proof membrane and the battery compartment cover. Furthermore, it achieves the unexpected effect of reducing the rebound force generated by the corrective pads, thereby avoiding the problem of excessive welding pressure between the explosion-proof membrane and the explosion-proof structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an overall structural diagram of a welding auxiliary correction device according to the first embodiment of the present invention;

[0024] Figure 2 for Figure 1 A partial enlarged schematic diagram of point A in the middle;

[0025] Figure 3 This is a schematic top view of a welding auxiliary correction device according to a first embodiment of the present invention;

[0026] Figure 4 This is a stepped cross-sectional view of a welding auxiliary correction device according to a first embodiment of the present invention;

[0027] Figure 5 This is a first overall assembly diagram of a welding device according to a second embodiment of the present invention;

[0028] Figure 6 This is a second overall assembly diagram of a welding device according to the second embodiment of the present invention.

[0029] Icons: 11-correction base, 12-work station, 13-positioning groove, 14-avoidance groove, 21-correction support, 211-correction pad, 212-correction support body, 31-support auxiliary table, 311-buffer pad, 312-support table, 313-buffer groove, 41-positioning piece, 5-battery box cover, 6-welding joint. DETAILED DESCRIPTION

[0030] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] First embodiment

[0034] At present, the explosion-proof technology and explosion-proof measures of batteries mainly adopt the design and installation of explosion-proof structure - explosion-proof valve on the battery box cover 5. Other explosion-proof measures also include battery quality control and usage management. Since quality control and usage management do not belong to the protection scheme of the present invention, they will not be elaborated here.

[0035] With the continuous improvement of power batteries, the explosion-proof structure will be integrated with the battery compartment cover 5, that is, the explosion-proof structure and the battery compartment cover 5 are integrally formed. The explosion-proof membrane, the core component of the explosion-proof structure, is usually fixed to the explosion-proof structure by hot melt or ultrasonic welding. Because some materials (such as nylon substrates) cannot be integrated with the explosion-proof membrane by hot melt, the explosion-proof membrane is mainly integrated and fixed to the explosion-proof structure of the battery compartment cover 5 by ultrasonic welding.

[0036] Ultrasonic welding is a heating and joining process that uses ultrasound to rapidly fuse molecules at the contact surface of thermoplastic parts. When integrating explosion-proof membranes into explosion-proof structures using ultrasonic welding, the welding pressure must be controlled within an optimal welding pressure value or range. Low welding pressure prevents the contact surfaces from being tightly bonded, leaving large areas of air. Over a period of time, most of the ultrasonic vibrations are lost to the air, resulting in insufficient interface frictional heating, a highly uneven fusion zone, and low heat-sealing strength at the weld joint (6). This can lead to weld defects between the membrane and the structure.

[0037] When welding pressure is too high, the extrusion flow of the molten polymer accelerates, and the polymer chains align horizontally along the weld surface, aggravating the thermal stress concentration at the edge and causing brittle fracture at the weld edge. Furthermore, the edge of the welding head can easily damage the explosion-proof membrane, reducing the heat seal strength and causing a deep weld mark between the explosion-proof membrane and the explosion-proof structure.

[0038] However, the structure of the battery box cover 5 is relatively complex, and there are process errors in the production process of the battery box cover 5. When the battery box cover 5 is clamped in the existing welding equipment, it is easy to cause a large flatness tolerance problem of the explosion-proof structure. In addition, the contact surface of the explosion-proof membrane itself also has a flatness tolerance. Therefore, during the welding process of the explosion-proof membrane and the explosion-proof structure, there are problems of missing welds and excessively deep weld marks in local positions. The inventor urgently needs to make improvements and solutions to this problem.

[0039] Please combine the specific Figure 1 and Figure 2 As shown, the present invention discloses a welding auxiliary correction device, comprising:

[0040] The correction base 11 is provided with a welding station 12. After the battery box cover 5 is clamped and fixed on the correction base 11, the explosion-proof structure of the battery box cover 5 is located within the orthographic projection range of the station 12.

[0041] A plurality of correction support members 21 are provided, each correction support member 21 includes a correction pad 211 and a correction support body 212, the correction pad 211 is fixedly connected to the correction support body 212, and the plurality of correction support members 21 are evenly distributed inside the work station 12, each correction support body 212 extends in a direction perpendicular to the work station 12, and each correction support body 212 is fixedly connected to the correction base 11, and is used to support the battery box cover 5, specifically to support the explosion-proof structure of the battery box cover 5, and to compensate for the flatness tolerance of the battery box cover 5 at the position of the work station 12 through the deformation of the correction pad 211.

[0042] Specifically, the shape and size of the correction pad 211 are preferably adapted to the shape and size of the correction support 212, or the shape and size of the correction pad 211 may be slightly larger than the shape and size of the correction support 212. Among them, the correction pad 211 has a certain elastic property so that the correction pad 211 can produce a certain deformation. The center line of each correction support 212 is perpendicular to the correction base 11, and the top surface of the correction base 11 is set as the reference plane. In this way, it is not only convenient for each correction support 21 to be accurately and quickly installed and fixed to the correction base 11, but also each correction support 21 can guide the force along the center line of the correction support 21 to the correction base 11 to ensure the stability of the force applied to the battery box cover 5 at the position of the work station 12.

[0043] In this embodiment, the battery cover 5 is clamped to the welding auxiliary correction device, and the explosion-proof structure of the battery cover 5 is brought into contact with the correction support members 21. The elasticity and softness of the correction pads 211 effectively prevent the battery cover 5 from contacting the rigid correction support members 21, thereby preventing problems such as collision wear or surface indentation. This effectively protects the battery cover 5 during the clamping process.

[0044] More importantly, when the welding joint 6 welds the explosion-proof membrane to the explosion-proof structure, the welding joint 6 applies welding pressure to the explosion-proof structure, and the explosion-proof structure then transmits the welding pressure to the plurality of corrective supports 21. At this point, each corrective support 21 acts as an independent force-bearing unit, and the plurality of corrective supports 21 collectively support the explosion-proof structure at multiple locations. At the same time, two adjacent corrective supports 21 form an adjustment space for the correction pad 211 to deform. Thus, compared to forming a single annular corrective support 21, each corrective pad 211 has more ample adjustment space, and each corrective pad 211 has better deformation capabilities.

[0045] In this way, when the welding joint 6 abuts against the raised position, a large force is generated between the raised position and the welding joint 6. At this time, the corresponding correction pad 211 at the raised position quickly produces a large deformation to form a space to accommodate the height of the raised position, thereby avoiding the risk of high welding pressure value and thermal stress concentration at the raised position, and eliminating the problem of excessively deep weld marks at the raised position.

[0046] When the welding joint 6 abuts against the concave position, the corresponding correction pad 211 at the concave position quickly deforms to form a convex structure that fills the depth of the concave, so that the explosion-proof membrane and the explosion-proof structure are tightly combined, eliminating the air area between the explosion-proof membrane and the explosion-proof structure, thereby eliminating the problem of missing welds at the concave position.

[0047] From the above, it can be seen that, with the coordinated action of the plurality of correction pads 211 and the adjustment space between two adjacent correction supports 21, not only is the purpose of uniform stress on the battery box cover 5 achieved during the welding process, but also the stability of stress during the welding process of the explosion-proof membrane to the explosion-proof structure is ensured. At the same time, the excellent deformation ability of the correction pads 211 is also utilized to compensate for the flatness tolerance between the explosion-proof membrane and the explosion-proof structure, ensuring that when the weld joint 6 reaches the welding pressure value, the interface between the explosion-proof membrane and the explosion-proof structure is quite tightly bonded, thereby facilitating a rapid increase in the interface temperature and the rapid diffusion of the polymer chains, thereby improving the heat seal strength, and thus forming a dense structure in the weld area between the explosion-proof membrane and the explosion-proof structure, thereby ensuring the welding quality between the explosion-proof membrane and the battery box cover 5.

[0048] What is even more unexpected is that compared to forming a single annular correction support 21, since the deformation adjustment space is formed between two adjacent correction supports 21, the rebound force generated by each correction pad 211 is relatively small, thereby achieving the premise of compensating the flatness tolerance by deformation while avoiding the problem of excessive welding pressure between the explosion-proof membrane and the explosion-proof structure.

[0049] As one of the preferred embodiments, please refer to Figure 1 、 Figure 3 and Figure 4As shown, the number of correction supports 21 is set to four, that is, four correction supports 21 are evenly arranged inside the work station 12. Specifically, the four correction supports 21 are evenly distributed around the center line of the work station 12, and the four correction supports 21 are evenly distributed around the circumference of the explosion-proof structure. At this time, the explosion-proof structure has force points evenly distributed at four positions in the orthogonal directions centered on the central axis, so that the explosion-proof structure can support force in each direction, so that the explosion-proof structure reaches the most stable force state. At the same time, the deformation of the correction pad 211 in the orthogonal directions centered on the central axis of the explosion-proof structure can compensate for the flatness tolerance of the explosion-proof structure, which effectively ensures the welding quality between the explosion-proof membrane and the explosion-proof structure.

[0050] It should be explained that Figure 1 and Figure 4 As shown, the correction base 11 is provided with a plurality of positioning grooves 13, and each correction support 212 is provided corresponding to each positioning groove 13. The number of positioning grooves 13 correspondingly provided here is preferably adapted to the number of correction supports 212, and the shape and size of the positioning grooves 13 are preferably adapted to the shape and size of the correction supports 212. Of course, the size of the positioning grooves 13 is larger than the size of the correction supports 212 within the assembly tolerance range. In this way, the risk of loosening, deflection or shaking of the correction support 21 during the force application process is effectively avoided, which is conducive to the correction pad 211 to stably and accurately compensate for the flatness tolerance of the battery box cover 5 at the position of the work station 12. At the same time, it is also conducive to the efficient and accurate assembly of the correction support 21 to the correction base 11.

[0051] It should also be noted that the correction pad 211 is preferably a silicone pad. To ensure that the correction pad 211 has good elasticity, the silicone pad is preferably a soft silicone pad. As a conventional replacement for the silicone pad, the correction pad 211 can also be a rubber pad.

[0052] The above solution effectively addresses the flatness tolerance issues between the explosion-proof membrane and the explosion-proof structure within station 12, as well as the force balance between the welded joint 6 and the explosion-proof structure within station 12. In essence, since the battery compartment cover 5 and the explosion-proof structure are integrally formed, the assembly stability of the battery compartment cover 5 also affects the flatness tolerance of the explosion-proof structure. For example, if the force applied to the battery compartment cover 5 during welding is unstable, weld offset between the explosion-proof membrane and the explosion-proof structure may occur.

[0053] In view of the above problems, the inventor provides a further solution. Figure 1 As shown, the welding auxiliary correction device further includes a support auxiliary platform 31 , which is located on one side of the correction support members 21 and is fixedly connected to the correction base 11 .

[0054] Specifically, when the explosion-proof structure of the battery box cover 5 abuts against the plurality of correction supports 21, the battery box cover 5 also simultaneously abuts and is fixed to the auxiliary support platform 31. Because the supporting surface of the auxiliary support platform 31 is much larger than that of the correction supports 21, the battery box cover 5 forms a surface contact with the auxiliary support platform 31, ensuring uniform and stable force on the battery box cover 5 during welding and eliminating the risk of the battery box cover 5 shifting during welding.

[0055] It should be noted that the bottom of the auxiliary support platform 31 is provided with at least one bolt hole, and the correction base 11 is provided with a countersunk hole corresponding to each bolt hole. Bolts pass through the countersunk holes and are bolted to the bolt holes, thereby achieving the purpose of bolting the auxiliary support platform 31 to the correction base 11. However, this connection is not limited to bolts, and the auxiliary support platform 31 and the correction base 11 can also be welded.

[0056] Please combine the specific Figure 1 and Figure 2 As shown, the auxiliary support platform 31 includes a cushion pad 311 and a support platform 312. The cushion pad 311 is disposed on the support platform 312, and the support platform 312 is fixedly connected to the correction base 11. The cushion pad 311 is preferably a silicone pad, a rubber pad, or other elastic pad. The elasticity of the cushion pad 311 can effectively cushion and eliminate the collision caused by the battery box cover 5 when it is placed and clamped to the auxiliary support platform 31, thereby protecting the battery box cover 5.

[0057] For further details, please refer to Figure 1 and Figure 2 As shown, the buffer pad 311 is provided with a plurality of buffer grooves 313, and each buffer groove 313 extends toward one side of the work station 12. Specifically, the plurality of buffer grooves 313 are evenly arranged in an array along the length extension direction of the buffer pad 311, so that the buffer pad 311 forms a long strip-shaped serrated shape, wherein the shape of the buffer groove 313 can be a rectangular groove, an arc groove, or a V-shaped groove. At this time, the buffer groove 313 forms an adjustment space for the deformation of the buffer pad 311, that is, when the battery box cover 5 is placed on the top of the buffer groove 313 and welding pressure is applied to the battery box cover 5 during the welding process, the battery box cover 5 generates a certain pressure on the buffer pad 311, and the groove wall of the buffer groove 313 will deform toward the inside of the buffer groove 313, thereby improving the elastic deformation capacity of the buffer pad 311.

[0058] Unexpectedly, the buffer groove 313 structure of the buffer pad 311 cooperates with the buffer pad 311 being set on one side of several correction support members 21, so that during the welding process of the battery box cover 5, the side of the buffer pad 311 close to the correction support member 21 can produce compression deformation in a timely and rapid manner, so that the buffer pad 311 can gradually diffuse and decrease along the extension direction of the buffer groove 313 after being subjected to welding pressure. In this way, when the correction pad 211 is deformed to compensate for the flatness tolerance, the buffer pad 311 can produce deformation to assist the correction pad 211 in supplementing the flatness tolerance.

[0059] For further details, please refer to Figure 1 and Figure 2 As shown, the welding auxiliary correction device also includes two positioning members 41 for inserting and positioning the battery box cover 5. Both positioning members 41 are fixedly connected to the correction base 11. The fixed connection referred to here is preferably a bolt connection, and the positioning members 41 are preferably positioning pins. The central axis of the positioning members 41 is perpendicular to the correction base 11. The battery box cover 5 is provided with positioning holes corresponding to the two positioning members 41. When each positioning hole of the battery box is inserted and matched with the corresponding positioning member 41, the battery box can be quickly clamped to the welding auxiliary correction device.

[0060] It should be noted that the number of positioning members 41 is not limited to two, and the number of positioning members 41 can also be three, four, five, etc.

[0061] In addition, according to Figure 1 As shown, at least one avoidance groove 14 is provided on the correction base 11, and the avoidance groove 14 avoids part of the raised structure on the battery box cover 5, thereby effectively ensuring the flatness of the explosion-proof structure.

[0062] Second embodiment

[0063] Based on the welding auxiliary correction device disclosed in the first embodiment, specifically combined with Figure 5 and Figure 6 As shown, the inventors also disclosed a welding device, which includes:

[0064] The aforementioned welding auxiliary correction device and welding joint 6, wherein the welding joint 6 is located above the welding auxiliary correction device. During use of the welding equipment, the positioning holes on the battery box cover 5 are aligned with the corresponding positioning members 41, and the battery box cover 5 is placed so that the positioning members 41 are inserted into the positioning holes until the battery box cover 5 abuts the cushioning pads 311 of the auxiliary support platform 31. At this point, the explosion-proof structure of the battery box cover 5 abuts the correction pads 211 of the correction supports 21, completing the purpose of positioning and clamping the battery box to the welding auxiliary correction device.

[0065] When the welding equipment enters the welding process, the welding joint 6 of the welding equipment moves to the top of the explosion-proof structure, that is, the welding joint 6 moves to the top of the work station 12 of the welding auxiliary correction device, and the welding joint 6 moves downward and performs the welding process according to the optimal welding pressure set by the system equipment.

[0066] From the above, it can be seen that the welding auxiliary correction device can effectively eliminate the problems of under-welding and over-welding of explosion-proof membranes caused by flatness tolerances of welding equipment during the automated welding process, ensuring that the power battery meets explosion-proof requirements and thereby improving the quality of power batteries in automated production. Furthermore, during the clamping process, the battery compartment cover 5 only needs to be positioned and fixed, which does not affect the clamping efficiency of the battery compartment cover 5 and also saves time in repeated positioning and verification.

[0067] The technical means disclosed in the solutions of the present invention are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A welding auxiliary correction device, characterized in that: include: A correction base (11), wherein a work station (12) for welding is provided on the correction base (11); A plurality of correction support members (21), each of the correction support members (21) includes a correction pad (211) and a correction support body (212), the correction pad (211) is fixedly connected to the correction support body (212), the plurality of correction support members (21) are evenly distributed inside the work station (12), each of the correction support bodies (212) extends in a direction perpendicular to the work station (12), and each of the correction support bodies (212) is fixedly connected to the correction base (11), and is used to support the battery box cover (5), and compensate for the flatness tolerance of the battery box cover (5) at the position of the work station (12) through the deformation of the correction pad (211).

2. The welding auxiliary correction device according to claim 1, characterized in that: It also includes a supporting auxiliary platform (31), which is located on one side of the plurality of correction support members (21), and the supporting auxiliary platform (31) is fixedly connected to the correction base (11).

3. The welding auxiliary correction device according to claim 2, characterized in that: The supporting auxiliary platform (31) comprises a buffer pad (311) and a supporting platform (312), the buffer pad (311) is arranged on the supporting platform (312), and the supporting platform (312) is fixedly connected to the correction base (11).

4. The welding auxiliary correction device according to claim 3, characterized in that: A plurality of buffer grooves (313) are provided on the buffer pad (311), and each of the buffer grooves (313) extends toward one side of the work station (12).

5. The welding auxiliary correction device according to claim 1, characterized in that: It also includes a plurality of positioning members (41) for inserting and positioning the battery box cover (5), and the plurality of positioning members (41) are all fixedly connected to the correction base (11).

6. The welding auxiliary correction device according to claim 1, characterized in that: Four correction support members (21) are evenly arranged inside the work station (12) to ensure that the battery box cover (5) is subjected to a balanced force at the position of the work station (12).

7. The welding auxiliary correction device according to claim 1 or 6, characterized in that: The correction base (11) is provided with a plurality of positioning grooves (13), each correction support body (212) is provided corresponding to each positioning groove (13), the correction support body (212) is plugged into the positioning groove (13), and the correction support body (212) is bolted to the correction base (11).

8. The welding auxiliary correction device according to claim 1 or 6, characterized in that: The correction pad (211) is a silica gel pad.

9. The welding auxiliary correction device according to claim 1, characterized in that: At least one avoidance groove (14) is provided on the correction base (11).

10. A welding device, characterized in that: include: The welding auxiliary correction device according to any one of claims 1 to 9; A welding joint (6), wherein the welding joint (6) is located above the welding auxiliary correction device.

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