Cylindrical petal type core mold tool for fiber winding

Abstract

The invention relates to a cylindrical petal type core mold tool for fiber winding, in particular to the technical field of winding forming, and the cylindrical petal type core mold tool for fiber winding comprises a main shaft, a first core mold petal and a second core mold petal, and the first core mold petal and the second core mold petal surround the main shaft and are alternately arranged; the first core mold section is connected with the main shaft through a first telescopic piece; the second core mold section is connected with the main shaft through a second telescopic piece; the shortening stroke of the first telescopic piece is smaller than the shortening stroke of the second telescopic piece. And the extension distance of the first telescopic piece is equal to that of the second telescopic piece. According to the cylindrical petal type core mold tool provided by the invention, a configuration mode of the movable core mold petals is adopted, so that a good winding effect can be ensured, rapid demolding can be realized through the contraction of the telescopic piece during demolding, the defects that a sand core mold needs to be cleaned and the mold needs to be manufactured again for multiple times are avoided, and the molding efficiency of a fiber winding molded body is favorably improved.

Description

Technical Field

[0001] The invention relates to the technical field of winding molding, and in particular to a cylindrical petal-type core mold tooling for fiber winding. Background Art

[0002] At present, the filament-wound casing of solid rocket engines, especially large-sized filament-wound casings, requires a core mold as a supporting structure during the manufacturing and winding process to complete the filament winding process.

[0003] At present, sand core molds are commonly used for winding molding. For example, CN113123897A discloses a method for molding a solid rocket engine combustion chamber charge column fixing frame, and the molding steps are as follows: S1, design a core mold molding tool, install the charge column fixing frame at a specified position, and then fill the core mold tool with water-soluble sand core filler, put it into a furnace for drying, and finally disassemble the core mold tool to achieve overall molding; S2, brush adhesive on the surface of the core mold charge column fixing frame, form a demoulding layer on the remaining core mold surface, perform inner insulation layer overmolding, perform fiber winding according to a certain winding tension, perform inner insulation layer pre-vulcanization, and remove the fiber; S3, perform fiber winding on the surface of the inner insulation layer, and then solidify the winding layer when the specified thickness is reached; S4, after the combustion chamber shell is solidified, disassemble the winding mandrel, take out the sand core mold to melt, and complete the separation of the core mold and the inner insulation layer.

[0004] CN103883871A discloses a lightweight high-temperature and high-pressure composite gas cylinder and a manufacturing method thereof, comprising nozzles at both ends and a bottle body in the middle, wherein the bottle body comprises, from the inside to the outside, an ablation-resistant thin-walled metal liner, a ceramic tile insulation layer, a rubber insulation layer, and a winding layer, wherein the winding layer is a carbon fiber reinforced resin-based composite material. The manufacturing method comprises the following steps: 1) ellipsoid molding; 2) sand core molding; 3) metal liner molding; 4) insulation layer molding; 5) winding layer molding; 6) demoulding and sand core dissolution.

[0005] However, when using a sand core mold for winding molding, the core mold can only be used once, and a lot of time is needed to clean it after use. At the same time, the sand core mold has to be made again, which makes the entire production cycle of the winding shell longer, which is not conducive to the efficient production of the fiber winding shell. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a cylindrical petal-type core mold tooling for fiber winding, so as to solve the problem that when a sand core mold is used for winding molding, the core mold can only be used once, and a lot of time is required to clean it after use. At the same time, the sand core mold has to be made again, which makes the entire production cycle of the winding shell longer, which is not conducive to the efficient production of the fiber winding shell.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a cylindrical petal-type core mold tool for fiber winding, and the cylindrical petal-type core mold tool for fiber winding comprises:

[0009] A main axis, first core mold halves and second core mold halves arranged alternately around the main axis;

[0010] The first core mold half is connected to the main shaft through a first telescopic member;

[0011] The second core mold half is connected to the main shaft through a second telescopic member;

[0012] The shortening stroke of the first telescopic member is less than the shortening stroke of the second telescopic member;

[0013] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0014] The cylindrical flap-type core mold tooling provided by the present invention can ensure a good winding effect by adopting a configuration method of movable core mold flaps. During demolding, rapid demolding can be achieved through the contraction of the telescopic parts, thereby avoiding the defects of the sand core mold needing to be cleaned and re-molded multiple times, which is beneficial to improving the molding efficiency of the fiber winding molding body.

[0015] As a preferred technical solution of the present invention, at least two first telescopic members are provided along the axial direction of the main shaft.

[0016] As a preferred technical solution of the present invention, at least two second telescopic members are provided along the axial direction of the main shaft.

[0017] As a preferred technical solution of the present invention, the first telescopic parts and the second telescopic parts are arranged alternately.

[0018] As a preferred technical solution of the present invention, the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold halves and the second core mold halves.

[0019] As a preferred technical solution of the present invention, the first telescopic member is movably connected to the first core mold flap via a hinge.

[0020] Preferably, the second telescopic member is movably connected to the second core mold half via a hinge.

[0021] As a preferred technical solution of the present invention, the first telescopic member is connected to the main shaft through a first sliding member.

[0022] Preferably, the second telescopic member is connected to the main shaft via a second sliding member.

[0023] Preferably, the first telescopic member is movably connected to the first sliding member.

[0024] Preferably, the second telescopic member is movably connected to the second sliding member.

[0025] As a preferred technical solution of the present invention, a guiding and positioning structure is arranged between the first sliding member and the main shaft.

[0026] Preferably, a guiding and positioning structure is arranged between the second sliding member and the main shaft.

[0027] As a preferred technical solution of the present invention, a limited position matching structure is arranged between adjacent first core mold halves and second core mold halves.

[0028] Preferably, the position limiting cooperation structure is provided with a pressure detection device.

[0029] As a preferred technical solution of the present invention, the first telescopic member includes an electric telescopic member and / or a hydraulic telescopic member.

[0030] Preferably, the second telescopic member includes an electric telescopic member and / or a hydraulic telescopic member.

[0031] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0032] The split-flap core mold tooling provided by the present invention has the advantages of convenient assembly and reusability. This type of tooling is used for solid rocket engine composite material shell molding and large aspect ratio non-metallic container winding molding to effectively improve efficiency and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the extension of a cylindrical petal-type core mold tooling for fiber winding provided by an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the contraction of a cylindrical petal-type core mold tooling for fiber winding provided by an embodiment of the present invention.

[0035] In the figure: 100 - main shaft, 210 - first core mold flap, 220 - first telescopic member, 230 - first sliding member, 310 - second core mold flap, 320 - second telescopic member, 330 - second sliding member.

[0036] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0037] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0038] This embodiment provides a cylindrical petal-type core mold tooling for fiber winding, such as Figure 1 and Figure 2 As shown, Figure 1 That is the working state when fiber winding is performed. Figure 2 The state of the core mold tooling when the fiber is wound and molded and then demolded. It can be seen that the tooling is convenient to be taken out of the molded body by shrinking the tooling with the telescopic parts. Specifically, the tooling includes:

[0039] A main shaft 100, a first core mold half 210 and a second core mold half 310 which surround the main shaft 100 and are alternately arranged;

[0040] The first core mold half 210 is connected to the main shaft 100 through a first telescopic member 220;

[0041] The second core mold half 310 is connected to the main shaft 100 through a second telescopic member 320;

[0042] The shortening stroke of the first telescopic member 220 is less than the shortening stroke of the second telescopic member 320;

[0043] The extension distance of the first telescopic member 220 is equal to the extension distance of the second telescopic member 320 .

[0044] In the present invention, fiber winding refers to winding the fiber on a core mold according to a set winding trajectory and then molding it. The fiber used is a fiber prepreg or fiber, or the fiber is coated with a resin material after being wound in sections for a set number of layers for curing and molding. The cylindrical fiber shell obtained by molding can be the barrel section of a rocket solid engine shell, etc., or other fiber shells with a columnar structure.

[0045] Specifically, the fibers and bonding materials used can be reasonably selected and designed according to the purpose of the final molded product, and the present invention does not make specific limitations.

[0046] In the present invention, shortening the stroke refers to the shortest contraction distance for the first telescopic member 220 and the second telescopic member 320 to achieve separation of the tooling from the fiber molding. When shortening, the second telescopic member 320 contracts in advance to avoid interference caused by simultaneous contraction and extension, which may lead to damage to the tooling.

[0047] In the present invention, the stretching spacing refers to the radial distance between the core mold halves and the main axis when the core mold halves are stretched and closely adjacent to each other to reach a state where the fiber can be wound.

[0048] In the present invention, the number of the first core mold halves 210 and the second core mold halves 310 is reasonably designed based on actual requirements. In principle, the more the better. The more core mold halves there are, the more conducive it is to configure fiber winding cylinders of different diameters through the number of core mold halves, thereby broadening the scope of use of a single tooling.

[0049] In the present invention, a rigid connection or a movable connection can be selected between the telescopic part and the core mold and the main shaft 100. When a rigid connection is adopted, the connection position between the core mold and the telescopic part, and the connection position between the main shaft 100 and the telescopic part cannot be moved and are in a fixed connection state. At this time, the contraction and extension of the core mold flap can only be controlled by the telescopic part. When a movable connection such as a hinge and a sliding part is adopted for connection, during contraction, the contraction of the core mold flap can be accelerated by controlling the movable connection of the sliding part with the help of the hinge, thereby improving the contraction efficiency and reducing the overall size of the tooling after contraction.

[0050] Furthermore, the telescopic part can be connected to the core mold and the main shaft 100 vertically, or can be connected at a certain acute angle. When more than two telescopic parts are configured and connected at a certain acute angle, the contraction directions of adjacent telescopic parts are ensured to be parallel to avoid interference defects among different telescopic parts.

[0051] In the present invention, the number of telescopic parts can be selected as one or more, one of which can be a rigid connection or a movable connection. When a movable connection is adopted, an interference fit design can be selected between adjacent core mold petals to achieve auxiliary relative fixation and avoid shaking of the core mold petals.

[0052] Wherein, at least two first telescopic members 220 are provided along the axial direction of the main shaft 100 .

[0053] Wherein, at least two second telescopic members 320 are arranged along the axial direction of the main shaft 100 .

[0054] Wherein, the first telescopic members 220 and the second telescopic members 320 are arranged alternately.

[0055] The alternating arrangement of the first telescopic members 220 and the second telescopic members 320 corresponds to the alternating arrangement of the first core mold halves 210 and the second core mold halves 310 .

[0056] The first telescopic member 220 is movably connected to the first core mold half 210 via a hinge.

[0057] The second telescopic member 320 is movably connected to the second core mold half 310 via a hinge.

[0058] The first telescopic member 220 is connected to the main shaft 100 via a first sliding member 230 .

[0059] The second telescopic member 320 is connected to the main shaft 100 via a second sliding member 330 .

[0060] Wherein, the first telescopic member 220 and the first sliding member 230 are movably connected;

[0061] The second telescopic member 320 and the second sliding member 330 are movably connected.

[0062] Wherein, a guiding and positioning structure is configured between the first sliding member 230 and the main shaft 100 .

[0063] Wherein, a guiding and positioning structure is disposed between the second sliding member 330 and the main shaft 100 .

[0064] In the present invention, the guide positioning structure disposed between the sliding member and the main shaft 100 can prevent the sliding member from rotating relative to the main shaft 100 during the sliding process, thereby preventing the instability of the tooling caused by the sliding.

[0065] In the present invention, the guiding and positioning structure can be selected to achieve guidance through a concave-convex matching structure, such as setting a protrusion on the main shaft 100, and then configuring a corresponding groove on the sliding part, so that the protrusion and the groove match to prevent the sliding part from rotating around the main shaft 100.

[0066] In the present invention, the first sliding member 230 and the second sliding member 330 may be selected to share a sliding member, or may be configured separately.

[0067] Wherein, a limited position matching structure is arranged between the adjacent first core mold halves 210 and second core mold halves 310 .

[0068] Wherein, the limit matching structure is configured with a pressure detection device.

[0069] In the present invention, through the configuration of the limit matching mechanism and the pressure detection device, good matching of the core mold halves can be achieved, and damage to the core mold halves caused by excessive stretching during the stretching process due to interference from the matching structure can be avoided.

[0070] Wherein, the first telescopic member 220 includes an electric telescopic member and / or a hydraulic telescopic member.

[0071] Wherein, the second telescopic member 320 includes an electric telescopic member and / or a hydraulic telescopic member.

[0072] In the present invention, the core mold petals are petals obtained by dividing the side of the cylinder into n equal parts, where n≥3. Specifically, the side of the hollow cylindrical winding body is divided into equal parts based on the bottom circle of the cylinder, and the side is divided along the generatrix of the cylinder.

[0073] In the present invention, each of the petals obtained by dividing the petals into n equal parts is independently provided with a corresponding telescopic member.

[0074] In the present invention, the materials of the core mold flap, the main shaft 100 and the telescopic member can be reasonably determined according to actual needs under the premise of ensuring that the fiber body is formed during the winding process. For example, light alloys, mold steel and other metal materials can be selected.

[0075] Further, in order to illustrate the effect that can be achieved by the cylindrical split-petal core mold tooling for fiber winding provided by the present invention, the following actual example is used for illustration, as follows:

[0076] Example 1

[0077] This embodiment provides a cylindrical petal-type core mold tool for filament winding, and the cylindrical petal-type core mold tool for filament winding includes:

[0078] A main axis, a first core mold half and a second core mold half arranged alternately around the main axis;

[0079] The first core mold half is connected to the main shaft through a first telescopic member;

[0080] The second core mold half is connected to the main shaft through a second telescopic member;

[0081] The shortening stroke of the first telescopic member is 0.5 times the shortening stroke of the second telescopic member;

[0082] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0083] Among them, the first telescopic member and the second telescopic member are both fixedly connected to the main shaft and the core mold petal, and the movement of the core mold petal is controlled only by the contraction of the telescopic member along the radial direction of the main shaft, the telescopic member is perpendicular to the inner surface of the core mold petal, and the telescopic member is perpendicular to the axial direction of the main shaft; the first telescopic member and the second telescopic member are alternately arranged; the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold petal and the second core mold petal; the core mold petals are equally divided according to the cylindrical bottom circle, and there are 18 petals in total, including 9 first core mold petals and 9 second core mold petals, corresponding to 9 first telescopic members and 9 second telescopic members.

[0084] Example 2

[0085] This embodiment provides a cylindrical petal-type core mold tool for filament winding, and the cylindrical petal-type core mold tool for filament winding includes:

[0086] A main axis, a first core mold half and a second core mold half arranged alternately around the main axis;

[0087] The first core mold half is connected to the main shaft through a first telescopic member;

[0088] The second core mold half is connected to the main shaft through a second telescopic member;

[0089] The shortening stroke of the first telescopic member is 0.8 times the shortening stroke of the second telescopic member;

[0090] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0091] Among them, the first telescopic member and the second telescopic member are both fixedly connected to the main axis and the core mold petal, and the movement of the core mold petal is controlled only by the contraction of the telescopic member along the radial direction of the main axis, the telescopic member is perpendicular to the inner surface of the core mold petal, and the telescopic member is perpendicular to the axial direction of the main axis; the first telescopic member and the second telescopic member are alternately arranged; the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold petal and the second core mold petal; the core mold petal is equally divided according to the cylindrical bottom circle, and there are 18 in total, the first core mold petal is 9, the second core mold petal is 9, corresponding to 18 first telescopic members and 18 second telescopic members, that is, each core mold petal corresponds to 2 telescopic members, and is equipped with a head end and an end of the core mold petal.

[0092] Example 3

[0093] This embodiment provides a cylindrical petal-type core mold tool for filament winding, and the cylindrical petal-type core mold tool for filament winding includes:

[0094] A main axis, a first core mold half and a second core mold half arranged alternately around the main axis;

[0095] The first core mold half is connected to the main shaft through a first telescopic member;

[0096] The second core mold half is connected to the main shaft through a second telescopic member;

[0097] The shortening stroke of the first telescopic member is 0.6 times the shortening stroke of the second telescopic member;

[0098] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0099] Among them, the first telescopic member and the second telescopic member are connected to the main shaft through a sliding member, and the first telescopic member and the second telescopic member are connected to the core mold petal through a hinge, the first telescopic member and the first sliding member are movably connected; the second telescopic member and the second sliding member are movably connected; the first telescopic member and the second telescopic member are alternately arranged; the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold petal and the second core mold petal; the core mold petals are equally divided according to the cylindrical bottom circle, totaling 20, 10 first core mold petals, 10 second core mold petals, corresponding to 30 first telescopic members, 30 second telescopic members, that is, each core mold petal corresponds to 3 telescopic members, and is equipped with a head end, middle end and end end of the core mold petal.

[0100] Example 4

[0101] This embodiment provides a cylindrical petal-type core mold tool for filament winding, and the cylindrical petal-type core mold tool for filament winding includes:

[0102] A main axis, a first core mold half and a second core mold half arranged alternately around the main axis;

[0103] The first core mold half is connected to the main shaft through a first telescopic member;

[0104] The second core mold half is connected to the main shaft through a second telescopic member;

[0105] The shortening stroke of the first telescopic member is 0.5 times the shortening stroke of the second telescopic member;

[0106] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0107] Among them, the first telescopic member and the second telescopic member are connected to the main shaft through a sliding member, and a guiding and positioning structure is configured between the sliding member and the main shaft, the first telescopic member and the first sliding member are movably connected; the second telescopic member and the second sliding member are movably connected; the first telescopic member and the second telescopic member are connected to the core mold petal through a hinge; the first telescopic member and the second telescopic member are alternately arranged; the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold petal and the second core mold petal; the core mold petals are equally divided according to the cylindrical bottom circle, totaling 30, with 15 first core mold petals and 15 second core mold petals, corresponding to 45 first telescopic members and 45 second telescopic members, that is, each core mold petal corresponds to 3 telescopic members, and is configured with a head end, middle end and end end of the core mold petal.

[0108] Example 5

[0109] This embodiment provides a cylindrical petal-type core mold tool for filament winding, and the cylindrical petal-type core mold tool for filament winding includes:

[0110] A main axis, a first core mold half and a second core mold half arranged alternately around the main axis;

[0111] The first core mold half is connected to the main shaft through a first telescopic member;

[0112] The second core mold half is connected to the main shaft through a second telescopic member;

[0113] The shortening stroke of the first telescopic member is 0.5 times the shortening stroke of the second telescopic member;

[0114] The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

[0115] Among them, the first telescopic member and the second telescopic member are connected to the main shaft through a sliding member, a guiding and positioning structure is configured between the sliding member and the main shaft, the first telescopic member and the second telescopic member are connected to the core mold flap through a hinge, the first telescopic member and the first sliding member are movably connected, and the second telescopic member and the second sliding member are movably connected; the first telescopic member and the second telescopic member are alternately arranged; the alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold flap and the second core mold flap; the core mold flap is equally divided according to the cylindrical bottom circle, a total of 20, 10 first core mold flaps, 10 second core mold flaps, corresponding to 20 first telescopic members, 20 second telescopic members, that is, each core mold flap corresponds to 2 telescopic members, respectively, configured with a head end and an end of the core mold flap, a limited position matching structure is arranged between adjacent first core mold flaps and second core mold flaps; the limited position matching structure is configured with a pressure detection device.

[0116] The tooling obtained by the above embodiment is used to carry out winding and molding of the cylindrical fiber body, as follows: the telescopic parts of the cylindrical split-flap core mold tooling used for fiber winding are controlled to extend so that the core mold flaps fit together, and then the fiber is wound and molded. After the molding is completed, the telescopic parts are controlled to contract so that the core mold flaps are separated from the molded fiber profile.

[0117] In summary, the cylindrical petal-type core mold tooling provided by the present invention can ensure a good winding effect by adopting a configuration method of movable core mold petals. During demolding, rapid demolding can be achieved through the contraction of the telescopic parts, thereby avoiding the defects of the sand core mold that needs to be cleaned and re-molded multiple times, which is beneficial to improving the molding efficiency of the fiber winding molding body.

[0118] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0119] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0120] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A cylindrical flap-type core mold tooling for fiber winding, characterized in that: The cylindrical petal-type core mold tooling for fiber winding comprises: A main axis, first core mold halves and second core mold halves arranged alternately around the main axis; The first core mold half is connected to the main shaft through a first telescopic member; The second core mold half is connected to the main shaft through a second telescopic member; The shortening stroke of the first telescopic member is less than the shortening stroke of the second telescopic member; The extension distance of the first telescopic member is equal to the extension distance of the second telescopic member.

2. The cylindrical petal-type core mold tooling for fiber winding according to claim 1, characterized in that: At least two first telescopic members are arranged along the axial direction of the main shaft.

3. The cylindrical petal-type core mold tooling for fiber winding according to claim 1, characterized in that: At least two second telescopic members are arranged along the axial direction of the main shaft.

4. The cylindrical flap-type core mold tooling for fiber winding according to claim 1, characterized in that: The first telescopic parts and the second telescopic parts are arranged alternately.

5. The cylindrical flap-type core mold tooling for fiber winding according to claim 4, characterized in that: The alternating arrangement of the first telescopic member and the second telescopic member corresponds to the alternating arrangement of the first core mold halves and the second core mold halves.

6. The cylindrical petal-type core mold tooling for fiber winding according to any one of claims 1 to 5, characterized in that: The first telescopic member is movably connected to the first core mold petal via a hinge; Preferably, the second telescopic member is movably connected to the second core mold half via a hinge.

7. The cylindrical petal-type core mold tooling for fiber winding according to any one of claims 1 to 6, characterized in that: The first telescopic member is connected to the main shaft via a first sliding member; Preferably, the second telescopic member is connected to the main shaft via a second sliding member; Preferably, the first telescopic member is movably connected to the first sliding member; Preferably, the second telescopic member is movably connected to the second sliding member.

8. The cylindrical flap-type core mold tooling for fiber winding according to claim 7, characterized in that: A guiding and positioning structure is arranged between the first sliding member and the main shaft; Preferably, a guiding and positioning structure is arranged between the second sliding member and the main shaft.

9. The cylindrical petal-type core mold tooling for fiber winding according to any one of claims 1 to 8, characterized in that: A limited position matching structure is provided between adjacent first core mold halves and second core mold halves; Preferably, the position limiting cooperation structure is provided with a pressure detection device.

10. The cylindrical petal-type core mold tooling for fiber winding according to any one of claims 1 to 9, characterized in that: The first telescopic member includes an electric telescopic member and / or a hydraulic telescopic member; Preferably, the second telescopic member includes an electric telescopic member and / or a hydraulic telescopic member.

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