JP2016139526A - connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connector which meets demands for reduction of size and thickness of a portable device while maintaining predetermined strength and has a waterproof function.SOLUTION: A connector 1 includes: a non-conductive base housing and a contact housing 40 which support a conductive contact 60; a conductive shell which encloses the contact 60 spaced away from the contact 60 and has a cylindrical shape. A peripheral surface of the shell includes a seal material. The seal material 20 includes a seal part 21 at a front side and a filling frame 22 at a rear side. The filling frame 22 includes a side wall and a bottom wall. The side wall forms a peripheral surface of the filling frame 22. The bottom wall is provided in a gap portion between an outer peripheral surface of the shell 10 and an inner peripheral surface of the side wall so as to bury the gap portion. A sealer 50 fills the filling frame 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a connector having a waterproof function used for portable devices and the like.

  Several connectors are assembled in the case of the portable device. It is desired to reduce the size and weight while providing sufficient strength to withstand daily use. In addition, a waterproof function is also required for the assembly gap and the like generated between the case and the case.

A technique described in Patent Document 1 is known as a connector technique having such a function. According to this technique, the periphery of the metal shell covering the terminal is configured by a housing made of a non-conductive synthetic resin, and a sealing material for sealing an assembly gap with the case is provided at the front end of the housing. In addition, at the rear end of the connector, a filling chamber is formed which is filled with a sealing material for filling a gap between the hole opened in the housing and the terminal for supporting the terminal.
Indeed, according to the technique described in Patent Document 1, a connector for a portable device having a waterproof function can be obtained while maintaining strength.

International Publication Number 2011/108679

  However, according to the technique described in Patent Document 1, a housing made of a synthetic resin is used as a constituent element in a skeleton part that covers the entire connector, a metal shell is provided on the inner side, and a waterproofing between the case and the outer side of the tip is provided. Since a sealing material is provided to ensure the function, there is a case where it is not possible to meet the demand for downsizing and thinning of portable devices.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a connector having a waterproof function capable of meeting the demand for downsizing and thinning portable devices while maintaining a predetermined strength.

  The connector according to the present invention is a connector comprising (1) a non-conductive housing that supports conductive terminals and a cylindrical conductive shell that surrounds and separates the terminals. A filling portion that is in contact with the peripheral surface of the housing and further extends toward the anti-fitting surface side by a predetermined amount, the anti-fitting surface side of the housing is a bottom wall, and the shell extension portion is a side wall It has a feature in that a frame is formed and this filling frame is filled with a sealing material.

  According to the present invention, the filling frame filled with the sealing material for filling the gap between the terminal and the hole opened in the housing is constituted by the housing and the extending portion of the shell. As a result, a connector having a waterproof function that does not hinder downsizing and thinning of the portable device can be obtained.

  Preferably, in the connector according to the present invention, (2) the shell described in the above (1) includes a second shell surrounding the peripheral surface thereof, and the shell is in contact with the peripheral surface of the housing, and the shell or the second shell Is provided with an extended portion that complementarily extends to the side opposite to the mating surface, the side facing the mating surface of the housing as a bottom wall, and the shell or the second shell constituting the extension as a side wall The filling frame is formed, and the filling frame is filled with a sealing material.

  According to the present invention, since the second shell is provided around the shell, the strength of the shell is reinforced, and the shell and the second shell complementarily form the extending portion to form the filling frame. Thus, a connector having a waterproof function that does not hinder downsizing and thinning can be obtained.

  Complementary means that the extending portion is not constituted by only the shell or the second shell, but the extending portion is constituted by cooperation of the shell and the second shell. For example, an extension part may be constituted by a half of the circumference of the housing being a shell and the other half being a second shell. Further, the circumference of the housing may be divided into four, and the shell and the second shell may alternately constitute the extending portion.

  Preferably, the connector according to the present invention is characterized in that (3) the extending portions of the shell and the second shell are provided on substantially corresponding sides when the surface of the housing is lined up. It has (2) description.

  According to the present invention, the extending portion of the housing is roughly divided into two parts by the shell and the second shell with the surface where the terminals are arranged as a boundary.

  Preferably, the connector according to the present invention is (4) a non-conductive housing that supports conductive terminals, a cylindrical conductive shell that surrounds and separates the terminals, and a peripheral surface of the shell. An elastic sealing material, wherein the sealing material is in contact with the peripheral surface of the housing, and further includes an extension portion extending toward the anti-fitting surface side by a predetermined amount. A storage chamber having a surface side as a bottom surface and an extended portion of the shell as a side wall is formed, and the storage chamber is filled with a sealing material.

  According to this invention, the shell is provided with a sealing material having elasticity, and the sealing material constitutes the extending portion. Thereby, a connector having a waterproof function that does not hinder downsizing and thinning can be obtained.

  Preferably, the connector according to the present invention is characterized in that (5) the seal material includes a projecting seal portion that extends to the vicinity of the front end on the fitting surface side of the shell and extends annularly near the front end ( 4) As described.

  According to this invention, the sealing material constitutes a storage chamber that fills the gap between the terminals, and also constitutes a seal portion that seals the gap between the case and the connector. Thereby, a connector having a waterproof function that does not hinder downsizing and thinning can be obtained.

FIG. 1 is an external perspective view of a connector according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is an external perspective view of the connector shell according to the present embodiment. FIG. 4 is an external perspective view showing a state in which a sealing material is attached to the shell of the connector. 5A is a top view of FIG. 4, and FIG. 5B is a bottom view of FIG. FIG. 6 is an external perspective view showing a state where the base housing is mounted on the shell of the connector according to the present embodiment. FIG. 7 is an external perspective view showing a state in which the contact housing is assembled to the shell of the connector. FIG. 8 is an exploded view of the connector shown in FIG. FIG. 9 is an external perspective view illustrating a state in which the shell rear end of the connector according to the present embodiment is filled with a sealing material. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9, where (1) is before filling with the sealing material and (2) is after filling with the sealing material. FIG. 11 is an external perspective view showing a state in which a tab is assembled to the connector according to the present embodiment. FIG. 12 is a longitudinal sectional view of a connector according to the second embodiment of the present invention. FIG. 13 is a longitudinal sectional view of a connector according to the third embodiment of the present invention.

  A connector according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of a connector according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. Direction indications in the description follow the direction indication definition of the drawing.

<Outline of connector>
The connector 1 according to the present embodiment is composed of a member that is reduced in size and thickness so that it can be assembled to a portable device, and has strength against twisting and a desired waterproof function. As shown in FIGS. 1 and 2, the connector 1 has a pin-shaped contact 60 fixed by a contact housing 40 made of synthetic resin. The contact housing 40 is a base housing in the middle of the axial direction (front-rear direction). 30. The pin-shaped contact 40 is integrally covered with a metal shell 10 so as to hide its entire length, thereby stabilizing communication.

  The metal shell 10 is fixed to the base housing 30, and the distance between the inner peripheral surface of the shell 10 and the contact 60 is kept constant. A sealing material 20 made of a material having an elastic restoring force is attached to the outer peripheral surface of the shell 10. Further, a tab A70 and a tab B75 are mounted on the outer peripheral surface of the shell 10 in order to increase the strength against the twisting of the connector 1.

  <Shell / Sealant> The shell 10 and the sealant 20 will be described with reference to the drawings. FIG. 3 is an external perspective view of the connector shell according to the present embodiment. FIG. 4 is an external perspective view showing a state in which a sealing material is attached to the shell of the connector. 5A is a top view of FIG. 4, and FIG. 5B is a bottom view of FIG. Direction indications in the description follow the direction indication definition of the drawing.

  As shown in FIG. 3, the shell 10 is formed by processing a rolled material of 0.2 mm thickness of stainless steel into an elliptical cylindrical shape. A trapezoidal fitting shape is formed on the abutting surface on the back surface side (lower surface side), and this portion is fixed by caulking. The shell 10 surrounds the periphery of the support portion 41 of the plate-shaped contact housing 40 to which the pin-shaped contacts 60 are fixed in parallel, and is enclosed inside the entire length up to the tip of the contact 60. ing.

  The shell 10 enables the connector 1 to perform high-speed transmission by accommodating the contact 60 over the entire length thereof. The shell 10 has a function of an electromagnetic sealing material 20, and the ground terminal is extended toward a circuit board (not shown) in order to sufficiently achieve this purpose.

  As shown in FIG. 3, the shell 10 is formed by processing a rolled material of stainless steel into a cylindrical shape. The front surface (upper surface) and the rear surface (lower surface) extend in parallel, and the side surface is formed by a curved surface having a semicircular shape. ing. The shell 10 is composed of a flat surface having no uneven structure on both the outer peripheral surface and the inner peripheral surface. The abutting portion of the back surface (bottom surface) is also processed so as not to produce an uneven structure. The shape of the inner peripheral surface corresponds to the shape of the outer peripheral surface of the main body 30a of the base housing 30, and the base housing 30 can be press-fitted and fixed.

  As shown in FIGS. 4 and 5, the outer peripheral surface of the shell 10 is partially covered with a sealing material 20. The sealing material 20 is made of a silicone resin, and is directly formed on the peripheral surface of the shell 10 by simultaneous molding.

  As shown in FIGS. 4 and 5, the seal material 20 includes a seal portion 21 at the front and a filling frame 22 at the rear. The seal portion 21 and the filling frame 22 are connected by a connecting portion 23, and the seal material 20 can be integrally formed.

  As shown in FIG. 5, the seal portion 21 includes a base portion 21 b and two projecting portions 21 a having a triangular cross section extending in an annular shape in parallel with two strips. Since the protruding portion 21a has flexibility and is deformable so as to be restored, a gap generated between the connector 1 and a case (not shown) can be filled. Thereby, the airtightness inside the portable device is improved. Furthermore, since the protrusion 21a is provided with two strips, the airtightness can be improved more effectively.

  As shown in FIG. 4 and FIG. 5, the seal portion 21 is provided from the rear to expose the tip portion of the shell 10. As shown in FIGS. 4 and 5, the connecting portion 23 is provided on the left and right side surfaces of the shell 10 so as to connect the front seal portion 21 and the rear filling frame 22. The connecting portion 23 is provided at a position covering the upper surface side of the left and right side surfaces, and does not extend to the lower surface side.

  As shown in FIGS. 4 and 5, the filling frame 22 is provided at the rear end of the shell 10. The filling frame 22 is provided so as to surround the rear end edge of the elliptical shell 10 having a rectangular shape in a rear view. The filling frame 22 includes a side wall 22a and a bottom wall 22b. As shown in FIG. 4, the side wall 22 a constitutes the peripheral surface of the filling frame 22, and the bottom wall 22 b is provided in such a manner as to fill a gap portion between the outer peripheral surface of the shell 10 and the inner peripheral surface of the side wall 22 a. That is, the bottom wall 22b is not provided on the entire bottom surface, but is provided mainly on the corner portion to fill the gap between the side wall 22a and the shell 10.

  The filling frame 22 is a portion filled with the sealing material 50, and the bottom wall 22 b is a receiving member for the sealing material 50 on the bottom surface of the filling frame 22 in cooperation with the housings 30 and 40, and the bottom wall 22 b. Is a side catch for preventing the seal material 50 from flowing to the periphery.

  <Base Housing> The base housing 30 and the contact housing 40 will be described with reference to the drawings. FIG. 6 is an external perspective view showing a state where the base housing is mounted on the shell of the connector according to the present embodiment. FIG. 7 is an external perspective view showing a state in which the contact housing is assembled to the shell of the connector. FIG. 8 is an exploded view of the connector shown in FIG. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9, where (1) is before filling with the sealing material and (2) is after filling with the sealing material. Direction indications in the description follow the direction indication definition of the drawing.

  As shown in FIG. 6, the base housing 30 is press-fitted to the rear end of the shell 10. The base housing 30 is a synthetic resin injection-molded product. The base housing 30 is attached to the rear end of the shell 10 in order to support and fix the contact housing 40. The base housing 30 may be made of non-conductive synthetic resin, for example, nylon such as 9T nylon.

As shown in FIG. 10, the base housing 30 includes a main body 30a that is press-fitted into the shell 10, and a support 30b that extends forward from the main body 30a. As shown in FIG. 6, the base housing 30 includes a storage portion 34 that penetrates in the front-rear direction, and an insertion port 31 is formed at the rear end of the storage portion 34. Further, as shown in FIG. 6, press fitting grooves 33 are provided on the left and right side surfaces of the accommodating portion 34, and the press fitting grooves 33 extend along the front-rear direction. Further, as shown in FIG. 6, contact grooves 32 are provided on the upper and lower surfaces of the accommodating portion 34.

  The press-fitting groove 33 is provided for press-fitting and fixing the contact housing 40 to the base housing 30. The contact groove 32 is a space in which a protruding portion of the contact 60 assembled to the contact housing 40 press-fitted into the base housing 30 is accommodated. The contact groove 32 allows the contact 60 to be smoothly mounted without interfering with the base housing 30. Can be done.

  As shown in FIG. 10, the outer peripheral surface of the main body 30 a is in contact with the inner peripheral surface of the shell 10, and the inner press-fitting groove 33 is in contact with the press-fitting portion 42 of the contact housing 40. The shell 10 is provided with a predetermined clearance and is press-fitted and fixed by sliding the outer peripheral surface of the main body 30a. As shown in FIG. 10, the rear end surface of the base housing 30 with the insertion port 31 is at a slightly lower level than the rear end edge of the shell 10 in the normal press-fitting position, and cooperates with the filling frame 22 of the sealing material 20. Thus, a portion filled with the sealing material 50 is formed.

  As shown in FIG. 6, the outer peripheral surface of the main body 30 a is configured in a shape corresponding to the inner peripheral surface of the shell 10, and when the base housing 30 is press-fitted to the shell 10 to the normal press-fitting position, the contact The surface is in close contact with the inner peripheral surface of the shell 10.

  <Contact Housing> As shown in FIGS. 7 and 8, the contact housing 40 is press-fitted and fixed to the base housing 30 with the contacts 60 disposed on the front and back surfaces. The contact 60 is surrounded by the shell 10 via the contact housing 40 and the base housing 30. The contact housing 40 is a non-conductive synthetic resin injection-molded product, and may be a nylon-based synthetic resin such as 9T nylon, for example.

  As shown in FIGS. 7 and 8, the contact housing 40 includes a main body portion 40a in which pin-shaped contacts 60 are arranged in parallel, a support portion 41 provided in front of the main body portion 40a, and left and right of the main body portion 40a. And an extending flange 43. Between the main body portion 40a and the support portion 41, press-fit portions 42 are provided at the left and right end portions. The flange 43 has a screw hole 44 for fixing the connector 1 to the portable device.

  As shown in FIG. 8, pin-like contacts 60 are arranged in parallel on the front and back surfaces of the contact housing 40. The contact 60 has a connection portion with a terminal of a circuit board (not shown) arranged in the main body portion 40a, and a contact portion that comes in electrical and mechanical contact with a mating contact (not shown) extends forward and is received by the support portion 41 over the entire length. Yes.

  As shown in FIG. 8, the contact housing 40 is press-fitted in a posture in which the support portion 41 faces the insertion port 31 with respect to the base housing 30 attached to the shell 10. The press-fitting is performed by a method of pushing the press-fitting portion 42 of the contact housing 40 into the press-fitting groove 33 of the base housing 30.

  As shown in FIG. 7, the contact housing 40 is held by the base housing 30 at the normal press-fitting position. There is a gap between the contact housing 40 and the base housing 30 at the normal press-fitting position. Specifically, between the main body portion 40 a of the contact housing 40 and the accommodating portion 34 of the base housing 30, particularly between the contact 60 disposed in the main body portion 40 a and the contact groove 32 of the accommodating portion 34. A gap is generated, and the airtightness of this part is not ensured. Further, there may be a gap between the outer peripheral surface of the main body 30 a of the base housing 30 and the corresponding inner peripheral surface of the shell 10.

<Sealing Material> The filling of the sealing material 50 will be described with reference to the drawings. FIG. 9 is an external perspective view illustrating a state in which the shell rear end of the connector according to the present embodiment is filled with a sealing material. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9, where (1) is before filling with the sealing material and (2) is after filling with the sealing material. Direction indications in the description follow the direction indication definition of the drawing.

  The rear end of the shell 10 is filled with a sealing material 50 as shown in FIGS. The base housing 30 is press-fitted into the shell 10 on the rear end side of the shell 10, and the contact housing 40 is press-fitted into the base housing 30. In both of the normal press-fitting positions, a gap is formed between the outer peripheral surface of the main body portion 30 a of the base housing 30 and the inner peripheral surface of the shell 10, and the main body portion 40 a of the contact housing 40 and the accommodating portion 34 of the base housing 30. There is also a gap between them. In particular, a gap is formed between the contact 60 disposed in the contact housing 40 and the contact groove 32 formed in the base housing 30.

  As shown in FIGS. 9 and 10, the sealing material 50 is generated in a normal press-fitted state between the shell 10 and the base housing 30 and between the base housing 30 and the contact housing 40. For filling the gap, for example, UV curable resin is generally known.

  As shown in FIGS. 9 and 10, the sealing material 50 is filled in the filling frame 22 at the rear end of the sealing material 20. Since the bottom wall 22 b of the filling frame 22 is constituted by the shell 10, the base housing 30, and the contact housing 40, the space between the shell 10 and the base housing 30, and between the base housing 30 and the contact housing 40. The bottom surface includes a portion where the gap is generated. Thereby, the permeable sealing material 50 permeates into these gaps by its own weight filled in the filling frame 22 and fills the gaps. Further, since the side surface of the filling frame 22 is constituted by the side wall 22a, the sealing material 50 can be filled up to the height of the side wall 22a.

  Accordingly, as shown in FIGS. 9 and 10, the sealing material 50 covers the bottom surface of the filling frame 22 and is filled with the bulk along the side wall 22 a of the filling frame 22. The gap between the main body 40a is filled. Since the sealing material 50 has good compatibility with the sealing material 20 and the contact housing 40, there is a gap between the sealing material 50 and the filling frame 22 and between the sealing material 50 and the contact housing 40. Fill without any occurrence. Further, since the sealing material 50 itself has a characteristic of not allowing moisture to pass therethrough, the airtightness behind the connector 1 can be ensured by the sealing material 50.

  Further, since the airtightness in front of the connector 1 can be ensured by filling the gap between the case (not shown) and the connector 1, the effect is exhibited by the seal portion 21 provided in front of the sealing material 20. is there.

  Therefore, the airtightness between the connector 1 and the case (not shown) and the airtightness behind the connector 1 can be ensured by the sealing material 20, the sealing material 20, and the sealing material 50. The waterproof property required for the connector 1 is provided in the connector according to this embodiment.

  In this embodiment, a UV curable resin is used for the sealing material 50, but a material having other characteristics may be used. For example, there are a thermosetting resin and a photo-curing resin. An elastomer may also be used. As a method of filling such a resin into the filling frame 22, there is a potting method by injection, and the working conditions of filling and curing can be performed in accordance with the material used.

  <Reinforcement> Reinforcing the connector 1 against twisting will be described with reference to the drawings. FIG. 11 is an external perspective view showing a state in which a tab is assembled to the connector according to the present embodiment. Direction indications in the description follow the direction indication definition of the drawing.

  As shown in FIG. 11, the connector 1 is reinforced by tabs A70 and B75. The tab A70 reinforces the upper half of the connector 1, and the tab B75 reinforces the lower half of the connector 1. The tab A70 and the tab B75 are caulked with the left and right caulking pieces, and are integrated together. Both the tab A 70 and the tab B 75 are in direct contact with the peripheral surface of the shell 10 and are not related to the seal material 20. Tab A70 and tab B75 are obtained from a stainless rolled material.

  <Effect> In the connector 1 according to the present embodiment, the filling frame 22 of the sealing material 50 is configured by the sealing material 20. Thereby, since there is followability to deformation, a connector having a waterproof function enhanced as well as strengthening against twisting can be obtained. In the connector 1 according to this embodiment, the filling frame 22 of the sealing material 50 is configured by the sealing material 20. Thereby, since the housing surrounding the shell 10 can be removed from the configuration, the connector 1 which can be reduced in size, particularly reduced in height, can be obtained.

The connector 1 according to the present embodiment has a single sealing material 20 that ensures the airtightness between the case (not shown) and the connector 1 and the airtightness of the connector 1 itself. Thereby, the connector 1 provided with the waterproof function with few work parts and good work efficiency is obtained.
The connector 1 according to the present embodiment ensures the airtightness behind the connector 1 by filling the filling frame 22 with the sealing material 50. Thereby, the connector 1 which can aim at commonality of the components of the housings 30 and 40 with a non-waterproof connector is obtained.

  The connector 1 according to the present embodiment includes a tab A 70 and a tab B 75 around the shell 10. As a result, the connector 1 with enhanced strength is obtained.

  Second Embodiment The present invention is not construed as being limited to the present embodiment, and the configuration can be changed as appropriate without departing from the technical idea of the present invention. For example, it is within the technical scope of the present invention that the filling frame has the configuration shown in the second and third embodiments, and similar modifications are also within the technical scope of the present invention.

A connector 1 according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a longitudinal sectional view of a connector according to the second embodiment of the present invention.
In the connector 1 according to the second embodiment, as shown in FIG. 12, a filling frame 220 of the sealing material 50 is formed by the shell 100. The sealing material 200 is provided only at the front end of the connector 1 and constitutes the sealing portion 21. Even in such a configuration, the above-described effects can be generally obtained.

<Third Embodiment> A connector 1 according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a longitudinal sectional view of a connector according to the third embodiment of the present invention.
As shown in FIG. 13, the connector 1 according to the third embodiment includes a shell 110 and a tab B750 that form a filling frame 2200. A tab A700 and a tab B750 for reinforcing the twisting strength of the connector 1 are provided. The upper side of the filling frame 2200 is constituted by the shell 110, and the lower side of the filling frame 2200 is constituted by the tab B750. Even in such a configuration, the above-described effects can be generally obtained.

DESCRIPTION OF SYMBOLS 1 Connector 10 100 Shell 20 200 Sealing material 21 Sealing part 21a Protruding part 21b Base part 22 220 2200 Filling frame 22a Side wall 22b Bottom wall 23 Connection part 30 Base housing 30a Main part 30b Support part 31 Insertion slot 32 Contact groove 33 Press-fit groove 34 Housing portion 40 Contact housing 40a Main body portion 41 Support portion 42 Press-fit portion 43 Flange 44 Screw hole 45 Base portion 50 Sealant 60 Contact 70 700 Tab A
75 750 Tab B

Claims (5)

A connector comprising a non-conductive housing that supports conductive contacts and a cylindrical conductive shell that surrounds and separates the contacts,
The shell is provided with an extending portion that is in contact with the peripheral surface of the housing and further extends a predetermined amount toward the non-fitting surface side, the anti-fitting surface side of the housing is a bottom wall, and the extending portion of the shell is A connector having a feature that a filling frame is formed as a side wall, and a sealing material is filled in the filling frame.   2. The shell according to claim 1, further comprising a second shell surrounding the peripheral surface thereof, wherein the shell is in contact with the peripheral surface of the housing, and the shell or the second shell is complementarily extended toward the non-fitting surface side by a predetermined amount. And forming a filling frame with the shell or the second shell constituting the extending portion as a side wall and sealing the sealing frame to the filling frame. A connector characterized by where the material is filled.   The connector according to claim 2, wherein the extending portions of the shell and the second shell are provided on substantially corresponding sides when the contact surface of the housing is lined up. A connector comprising a non-conductive housing that supports conductive contacts, a cylindrical conductive shell that surrounds and separates the contacts, and an elastic sealing material that attaches to the peripheral surface of the shell,
The seal material is provided with an extension portion that is in contact with the peripheral surface of the housing and extends a predetermined amount toward the non-fitting surface side, the anti-fitting surface side of the housing as a bottom surface, and the extension portion of the shell. A connector having a feature that a filling frame is formed as a side wall, and a sealing material is filled in the filling frame.   The connector according to claim 4, wherein the seal material includes a projecting seal portion that extends to the vicinity of the front end of the shell on the fitting surface side and extends in an annular shape near the front end.

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