Seat under box

Abstract

To obtain an under-seat box that can prevent a box body from jumping out from a pull-out position to a front side when being used, and that facilitates work of removing the box body from a lower side of a seat cushion.SOLUTION: An under-seat box 20 comprises: a pair of rail parts 28 arranged by being spaced apart in a width direction of a seat cushion on a lower side of the seat cushion; a box body 24 to be guided by the rail parts 28 in a slidable manner in a front and rear direction, so as to adopt a storage state of being stored on the lower side of the seat cushion and a pull-out state of being pulled out from the lower side to a front side; and lock mechanisms 30 which are provided on the rail parts 28 for locking portions 26 to be locked provided on the box body 24, when the box body 24 adopts the pull-out state. When the box body 24 adopts a removal state of being removed from the lower side of the seat cushion 12, the lock mechanisms 30 can release the lock with respect to the portions 26 to be locked.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a seat under-box. [Background technology]

[0002] A structure in which an under-box (under-tray) is provided below a vehicle seat so as to be able to be pulled out (slidable) has been conventionally known (see, for example, Patent Document 1). Such an under-box is configured so as not to jump out further forward of the vehicle seat than the pulled-out position during normal use due to inertial force or the like in the event of a vehicle collision or the like.

[0003] For example, a locking portion is provided on a rail portion that guides both sides of the under-box so that the under-box can slide, and the locked portions provided on both sides of the under-box are locked to the locking portion, thereby preventing the under-box from protruding forward of the vehicle seat beyond the pulled-out position during normal use. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-198391 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, although such a configuration can prevent the under-box from jumping out further forward of the vehicle seat (seat cushion) than the pulled-out position during normal use due to inertial force during a collision, it may be difficult to disengage the locked portion from the locking portion when it is necessary to remove the under-box from the underside of the vehicle seat (seat cushion). In other words, the removal work for removing the under-box may be difficult.

[0006] Therefore, an object of the present invention is to provide a seat under-box that can prevent the box body from popping out forward of the seat cushion beyond the pull-out position during normal use due to inertial force, etc., and that can easily remove the box body from the underside of the seat cushion when it is necessary to do so. [Means for solving the problem]

[0007] In order to achieve the above object, the seat under-box according to the present invention is provided below the seat cushion on which the occupant sits. A case arranged in the manner described above and a case In the storage state stored in The above case a drawn-out state in which the seat cushion is pulled out toward the front side of the seat cushion, or Configured The box body, The case includes a top wall, a bottom wall, a left side wall, and a right side wall, the longitudinal direction of which is the front-rear direction of the seat cushion, and rail portions provided on the left side wall and the right side wall, which guide the box body so as to be slidable in the front-rear direction of the seat cushion; a locking mechanism that is provided on the rail portion and that locks a locked portion that is provided on the box body when the box body is in the pulled-out state; Yes The locking mechanism includes: The locking claw is formed integrally with the rail portion so as to be elastically deformable outward in the width direction of the seat cushion, and the locking claw prevents the locked portion from moving forward of the seat cushion, thereby locking the locked portion, and when the box body is in a detached state in which it is detached from the lower side of the seat cushion, the locking claw elastically deforms outward in the width direction of the seat cushion, thereby releasing the lock on the locked portion. It has been done.

[0008] According to the invention described in claim 1, The box includes a case disposed below a seat cushion on which an occupant sits, and a box body configured to be capable of being in a stored state in which the case is stored and in a pulled-out state in which the case is pulled out from the case to the front side of the seat cushion. The case has a top wall, a bottom wall, a left side wall, and a right side wall, the longitudinal direction of which is the front-rear direction of the seat cushion, rail parts provided on the left side wall and the right side wall, respectively, for guiding the box body so as to be slidable in the front-rear direction of the seat cushion, and a locking mechanism provided on the rail parts for locking a locked part provided on the box body when the box body is in the pulled-out state. The locking mechanism is configured to include a locking claw integrally formed on the rail parts so as to be elastically deformable outward in the width direction of the seat cushion, and the locking claw is configured to lock the locked part by preventing the locked part from moving forward of the seat cushion, and to release the lock on the locked part by elastically deforming outward in the width direction of the seat cushion when the box body is in a removed state in which it is removed from the lower side of the seat cushion.

[0009] In this way, when the locking mechanism is composed of a locking claw that is integrally provided on the rail portion and capable of elastically deforming, the configuration of the locking mechanism is simplified compared to when the locking mechanism is composed of a locking claw that is provided on the rail portion as a separate entity from the rail portion.

[0010] Furthermore, if the locking claw is configured to lock onto the locked portion by preventing the locked portion from moving toward the front of the seat cushion, the box body is effectively prevented from popping out toward the front of the seat cushion beyond the pulled-out position during normal use due to inertial forces, etc.

[0011] Furthermore, when it is necessary to remove the box body from the underside of the seat cushion, if the locking claw is configured to move outward in the width direction of the seat cushion to release the lock on the locked portion, there is no need to lift the box body, and the release force required to release the lock is reduced, compared to a configuration in which the locking claw is released by moving, for example, in the vertical direction of the seat cushion.

[0012] therefore, This facilitates the removal operation of the box body from the lower side of the seat cushion. Also, Even if the box body is repeatedly removed from the lower side of the seat cushion, the rate of decrease in the removal force of the box body against the rail portion is suppressed.

[0013] In addition, claims 2 The seat under-box according to claim 1The seat under-box according to the present invention is covered rock Department teeth, The front end surface is formed in a flat shape perpendicular to the front-rear direction in a side view, and the rear end is formed in a substantially semicircular arc shape in a planar cross-sectional view. It has been done.

[0014] Claim 2 According to the invention described in The front end surface of the locked part is formed in a flat surface perpendicular to the front-rear direction in a side view. Therefore, even if a load is applied to the locking claw from the front end surface of the locked part, the load is properly received by the locking claw. Also, the rear end of the locked part is formed in a roughly semicircular arc shape in a horizontal cross section. Therefore, when the box body is returned to the case, the locking claw is smoothly guided to the outside of the locked part. will be done. Effect of the Invention

[0015] As described above, according to the present invention, it is possible to prevent the box body from popping out further forward of the seat cushion than the pulled-out position during normal use due to inertial force, etc., and when it is necessary to remove the box body from the underside of the seat cushion, the removal work can be easily performed. [Brief description of the drawings]

[0016] [Figure 1] 1 is a perspective view showing a vehicle seat including a seat under-box according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a perspective view showing a box body of the seat under-box according to the embodiment. [Diagram 3] 1 is a perspective view showing, in partial cross section, a case having a rail portion that slidably guides the box body of the seat under-box of this embodiment, together with the box body. FIG. [Figure 4] 1 is a perspective view showing a state in which a box body of the seat under-box according to the present embodiment has been pulled out from the case to a pulled-out position during normal use. FIG. [Diagram 5] FIG. 2 is an enlarged perspective view showing a lock mechanism of the seat under-box according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As an example, the seat under-box 20 according to this embodiment is disposed under a vehicle seat 10 such as an automobile. For convenience of explanation, the arrow UP shown in FIG. 1 indicates the upward direction of the vehicle seat 10, the arrow FR indicates the forward direction of the vehicle seat 10, and the arrow RH indicates the rightward direction of the vehicle seat 10. In other words, in the following explanation, when the directions such as up / down, front / rear, and left / right are described without special mention, they indicate the up / down, front / rear, and left / right of the vehicle seat 10.

[0018] 1, the vehicle seat 10 has a seat cushion 12 on which an occupant sits (supporting the thighs and buttocks of the occupant), a seat back 14 that supports the back of the occupant, a head rest 16 that supports the head of the occupant, and an arm rest 18 that supports the arms of the occupant. A resin seat under-box 20 according to this embodiment is disposed below the vehicle seat 10 (seat cushion 12).

[0019] The seat under-box 20 has a case 22 arranged below the seat cushion 12 and a box body 24 configured so as to be capable of being pulled out from within the case 22 to the front side of the seat cushion 12.

[0020] As shown in Figures 1, 3, and 4, the case 22 is formed in a roughly cylindrical shape with the longitudinal direction being the front-to-rear direction, and has a left side wall 22L and a right side wall 22R which are roughly rectangular and flat, a top wall 22U (see Figure 1) which is roughly rectangular and flat, and a bottom wall 22D (see Figure 4) which is suspended between the front lower end of the left side wall 22L and the front lower end of the right side wall 22R.

[0021] 4, bottom wall 22D is formed in a generally rectangular flat plate shape with the left-right direction as the longitudinal direction, and integrally connects the front lower end portion of left side wall 22L and the front lower end portion of right side wall 22R. Then, as shown in FIGS. 3 and 4, a generally rectangular housing-like rear wall 23 with the longitudinal direction in the left-right direction is integrally provided at the rear end portion of case 22.

[0022] Specifically, the rear wall 23 is formed in a hollow block shape having a predetermined thickness, and integrally connects the upper rear end of the left side wall 22L with the upper rear end of the right side wall 22R. Note that, in a front view of the seat cushion 12 seen from the front side, the rear wall 23 protrudes in the left-right direction (outside the width direction of the seat cushion 12) beyond the case 22, and both protruding left and right ends are fixed to predetermined positions below and rearward of the seat cushion 12.

[0023] Further, a pair of left and right rail portions 28 are disposed below the seat cushion 12 and spaced apart in the width direction of the seat cushion 12. That is, at the upper portion of the left side wall 22L and the upper portion of the right side wall 22R of the case 22, the rail portions 28, which are made of resin and have a generally rectangular flat plate shape with the longitudinal direction being the front-to-rear direction, are provided over substantially the entire length of the upper portion of the left side wall 22L and the upper portion of the right side wall 22R.

[0024] 1 and 3 to 5, a plurality of openings 22A are formed at predetermined intervals in the front-rear direction in an upper portion of the left side wall 22L and an upper portion of the right side wall 22R of the case 22. Each opening 22A is formed in a substantially rectangular shape in a side view seen from the width direction of the seat cushion 12.

[0025] Furthermore, a plurality of locking portions 29 are formed at predetermined intervals (at positions corresponding to each opening 22A) on the main body portion 28A of each rail portion 28, and each locking portion 29 is formed in a hook shape that protrudes toward the widthwise outer side of the seat cushion 12 (the outer side of the case 22) (see Figure 5).

[0026] Therefore, each rail portion 28 is attached to the upper portion of the left side wall 22L and the upper portion of the right side wall 22R of the case 22 by inserting each locking portion 29 formed on the main body portion 28A into each opening 22A from the inside of the case 22 and locking with the lower edge portion and the front edge portion or the rear edge portion of each opening 22A. A locking mechanism 30 is provided on each rail portion 28. The locking mechanism 30 will be described in detail later.

[0027] As shown in Figures 1, 3, and 4, the box body 24 is configured to be guided by a pair of left and right rail portions 28 so that it can slide in the front-to-rear direction so as to be able to take a stored state in which it is stored below the seat cushion 12, and a pulled-out state in which it is pulled out from the below side of the seat cushion 12 to the front side of the seat cushion 12.

[0028] 2 to 4, the box body 24 has a left side wall 24L and a right side wall 24R each having a substantially rectangular flat plate shape, a bottom wall 24D having a substantially rectangular flat plate shape, a front wall 24F having a substantially rectangular flat plate shape, and a rear wall 24B having a substantially rectangular flat plate shape. The left side wall 24L, the right side wall 24R, and the rear wall 24B are formed to be at substantially the same height (the upper end faces of the left side wall 24L and the right side wall 24R are substantially flush with the upper end face of the rear wall 24B), and the rear end of the left side wall 24L and the rear end of the right side wall 24R are integrally connected by the rear wall 24B.

[0029] In addition, when viewed from the side in the width direction of the seat cushion 12, the left side wall 24L and the right side wall 24R of the box main body 24 are formed in approximately the same shape as the left side wall 22L and the right side wall 22R of the case 22, respectively, and are configured to be slidable in the fore-and-aft direction at positions close to the inner surfaces of the left side wall 22L and the right side wall 22R.

[0030] The front wall 24F is formed so as to be higher than the left side wall 24L and the right side wall 24R (so as to protrude upward from at least the upper end faces of the left side wall 24L and the right side wall 24R), and integrally connects the front end of the left side wall 24L and the front end of the right side wall 24R. An insertion portion 25 into which an occupant's fingers can be inserted is formed at the upper front surface of the front wall 24F. This insertion portion 25 is configured to make it easier for the box body 24 to be pulled out from inside the case 22.

[0031] The bottom wall 24D is integrally joined at its periphery to close the lower end of the substantially rectangular frame formed by the left side wall 24L, the right side wall 24R, the rear wall 24B, and the front wall 24F. The space on the upper surface side of the bottom wall 24D and surrounded by the left side wall 24L, the right side wall 24R, the rear wall 24B, and the front wall 24F forms the storage space S of the box main body 24 (seat under-box 20).

[0032] Further, guide portions 27 guided by rail portions 28 are integrally formed over almost the entire length of the upper ends of the left side wall 24L and the right side wall 24R at the upper ends of the left side wall 24L and the right side wall 24R. Each guide portion 27 is formed into a substantially "L" shape in a cross section perpendicular to the longitudinal direction, and a lower portion of each guide portion 27 is formed as a protruding portion 27D protruding outward in the width direction of the seat cushion 12.

[0033] The height positions of each guide portion 27 and each rail portion 28 are set so that rail portion 28 is disposed on the upper surface side of overhang portion 27D when box body 24 is housed in case 22. Also, as shown in Figures 2 and 5, a cutout portion 27A having a generally rectangular shape in side view is formed near the rear end portion at the upper portion of each guide portion 27, and a locked portion 26 is integrally provided on the upper surface of overhang portion 27D rearward of each cutout portion 27A.

[0034] The locked portion 26 is formed in a generally rectangular flat plate shape having a predetermined thickness whose normal direction is the width direction of the seat cushion 12, and has a certain degree of rigidity. The front end surface 26F of the locked portion 26 is formed in a flat shape along the up-down direction (perpendicular to the front-rear direction in side view), and the rear end surface 26B of the locked portion 26 is formed in a generally semicircular arc shape in a horizontal cross-sectional view (see FIG. 5). The outer surface 26A of the locked portion 26 is also formed in a flat shape.

[0035] 3 to 5, the rail portion 28 is provided with a locking mechanism 30 that locks the locked portion 26 formed on the box body 24 when the box body 24 is in the pulled-out state. The locking mechanism 30 has a locking claw 32 as a locking portion that prevents the locked portion 26 (box body 24) from moving forward by coming into contact with a front end face 26F of the locked portion 26.

[0036] 5, the locking claw 32 is formed in a substantially "L" shape in a planar cross section, with its front end 32F being integral with the main body 28A of the rail portion 28 and being provided so as to be elastically deformable in the width direction of the seat cushion 12. The rear end 32B of the locking claw 32 is formed so that its bent portion 32A is on the upper surface side of the protruding portion 27D and protrudes toward the cutout portion 27A, and a rear end surface 32C facing the rear side is formed in a flat shape along the up-down direction (perpendicular to the front-rear direction in a side view).

[0037] Therefore, when the box body 24 is pulled out from within the case 22, the front end surface 26F of the locked portion 26 comes into surface contact with the rear end surface 32C of the locking claw 32, so that the box body 24 pulled out from within the case 22 does not protrude forward of the seat cushion 12 beyond the pulled-out position during normal use.

[0038] In addition, the locking mechanism 30 is configured to be able to release the lock on the locked portion 26 when the box body 24 is in a detached state in which it is detached from the lower side of the seat cushion 12 (inside the case 22). In other words, the locking claw 32 functions not only as a locking portion but also as an unlocking portion.

[0039] Specifically, openings 22A are formed in the left and right walls 22L and 22R of the case 22 at locations facing the locking claws 32 in the left-right direction (the width direction of the seat cushion 12). Therefore, when the box body 24 is to be removed, the occupant presses the bent portions 32A of the locking claws 32 toward the outside in the width direction of the seat cushion 12 with the fingers. Then, the rear end portions 32B of the locking claws 32 move toward the outside in the width direction of the seat cushion 12 (into the openings 22A) with the elastically deformable front end portions 32F as a fulcrum.

[0040] As a result, the rear end surface 32C of the locking claw 32 retreats from the front end surface 26F of the locked portion 26, and the locking claw 32 is released from the locked portion 26. In this state, the box body 24 is pulled out from inside the case 22, whereby the box body 24 is removed from the lower side of the seat cushion 12 (inside the case 22).

[0041] In this manner, the locked portion 26 is locked by the locking claw 32, and is also unlocked by the locking claw 32. In other words, the locking portion that locks the locked portion 26 and the unlocking portion that unlocks the locked portion 26 are both integrally configured as the locking claw 32.

[0042] Next, the operation of the seat under-box 20 according to this embodiment configured as above will be described.

[0043] When using the seat under-box 20 arranged below the vehicle seat 10 (seat cushion 12), the occupant inserts his / her fingers into the insertion portion 25 of the front wall 24F and pulls out the box body 24 from within the case 22. At this time, the front end surface 26F of the locked portion 26 provided on the box body 24 hits the rear end surface 32C of the locking claw 32 constituting the locking mechanism 30, so that the forward movement of the box body 24 is restricted to a predetermined position.

[0044] Therefore, even if the box body 24 is caused to jump out from within the case 22 toward the front side of the seat cushion 12 due to inertial force or the like during a vehicle collision, the box body 24 is prevented from jumping out further toward the front side of the seat cushion 12 than the pulled-out position during normal use (from falling out of the case 22).

[0045] Moreover, the locked portion 26 has a certain degree of rigidity, and the front end face 26F of the locked portion 26 and the rear end face 32C of the locking claw 32 are both flat surfaces along the vertical direction, so that even if a load (pressure that compresses the locking claw 32 forward) is applied from the front end face 26F of the locked portion 26 to the rear end face 32C of the locking claw 32, the load can be appropriately received by the locking claw 32.

[0046] When the occupant pulls out the box body 24 from the case 22, he or she stores items in the storage space S of the box body 24 (on the upper surface of the bottom wall 24D) and then moves the box body 24 rearward (into the case 22). As a result, the items are stored in the seat under-box 20.

[0047] On the other hand, when it is necessary to remove the box body 24 from within the case 22, the box body 24 is pulled out from within the case 22 until the front end surface 26F of the locked portion 26 abuts against the rear end surface 32C of the locking claw 32. Then, the occupant uses his or her fingers to push the bent portion 32A of the locking claw 32 outward in the width direction of the seat cushion 12 (into the opening 22A), and moves the rear end surface 32C of the locking claw 32 away from the front end surface 26F of the locked portion 26.

[0048] This releases the lock on the locked portion 26 by the locking claw 32, and in this state, if the box body 24 is pulled further toward the front side of the seat cushion 12, the box body 24 is removed from within the case 22 (from the lower side of the seat cushion 12).

[0049] When returning the box body 24 into the case 22, the box body 24 is inserted into the case 22 from the front side of the case 22. Then, the rear end 26B of the locked portion 26 abuts against the bent portion 32A of the locking claw 32, but because the rear end 26B is formed in a substantially semicircular arc shape in a plan cross-sectional view, the bent portion 32A can be smoothly guided to the outer surface 26A of the locked portion 26.

[0050] The locked portion 26 presses the bent portion 32A of the locking claw 32 outward in the width direction of the seat cushion 12 while causing the bent portion 32A to slide against the outer surface 26A of the locked portion 26. When the box body 24 further moves rearward and the front end surface 26F of the locked portion 26 passes over the bent portion 32A of the locking claw 32, the locking claw 32 is returned to its original position (on the upper surface side of the protruding portion 27D and on the cutout portion 27A side) by its elastic restoring force.

[0051] Therefore, when the box body 24 is next pulled out from within the case 22, as described above, the front end surface 26F of the locked portion 26 provided on the box body 24 abuts against the rear end surface 32C of the locking claw 32 that constitutes the locking mechanism 30, and the forward movement of the box body 24 is restricted to a predetermined position.

[0052] As described above, the locking mechanism 30 (locking claw 32) that locks the locked portion 26 provided on the box body 24 when the box body 24 is in the pulled-out state is configured to be able to release the lock on the locked portion 26 when the box body 24 is in the detached state in which it is removed from the lower side of the seat cushion 12.

[0053] Therefore, as described above, in the event of a vehicle collision or the like, the box body 24 can be prevented from flying out toward the front side of the seat cushion 12 from the pulled-out position during normal use due to inertial forces, etc., and when it is necessary to remove the box body 24 from the lower side of the seat cushion 12, the removal work can be easily performed.

[0054] Moreover, in this locking mechanism 30, the locking portion that locks the locked portion 26 and the unlocking portion that unlocks the locked portion 26 are both configured integrally as the locking claw 32. Therefore, the configuration of the locking mechanism 30 can be simplified compared to when the locking portion and the unlocking portion are configured separately.

[0055] Furthermore, since the locking claw 32 is configured to be integrally provided on the rail portion 28 so as to be capable of elastically deforming, the configuration of the locking mechanism 30 can be further simplified compared to a configuration in which the locking claw 32 is provided on the rail portion 28 as a separate body from the rail portion 28, and the manufacturing cost of the locking mechanism 30 (rail portion 28) can be reduced.

[0056] Moreover, the locking claw 32 (locking portion) prevents the locked portion 26 from moving forward, thereby locking the locked portion 26. Therefore, the box body 24 can be effectively prevented from jumping out (coming out of the case 22) forward of the seat cushion 12 beyond the pulled-out position during normal use.

[0057] Moreover, the locking claw 32 (unlocking portion) unlocks the locked portion 26 by moving outward in the width direction of the seat cushion 12. Therefore, compared to a configuration in which the locking claw 32 unlocks the locked portion 26 by moving, for example, in the vertical direction, there is no need to lift the box body 24, and the unlocking force required for unlocking can be reduced. This makes it even easier to remove the box body 24 from the lower side of the seat cushion 12.

[0058] Even if the box body 24 is repeatedly removed from the lower side of the seat cushion 12, the rate of decrease in the removal force of the box body 24 against the rail portion 28 can be suppressed. In other words, deterioration of the elastic deformation of the locking claws 32 can be suppressed, and the locking force of the locking claws 32 against the locked portion 26 can be suppressed from being weakened, which makes it difficult for the box body 24 to come off from within the case 22.

[0059] Although the seat under-box 20 according to this embodiment has been described above with reference to the drawings, the seat under-box 20 according to this embodiment is not limited to the one shown in the drawings, and the design can be appropriately changed without departing from the scope of the present invention. For example, the outer shapes of the case 22 and the box body 24 are not limited to the shapes shown in the drawings.

[0060] In addition, the unlocking direction of the locking claw 32 with respect to the locked portion 26 is not limited to the outer side in the width direction of the seat cushion 12, and may be the up-down direction of the seat cushion 12 as long as it is not necessary to lift the box body 24. In addition, the seat under-box 20 according to this embodiment is not limited to being disposed on the lower side of the vehicle seat 10. Although not shown in the drawings, the seat under-box 20 according to this embodiment may be disposed on the lower side of a seat of an airplane, for example. [Explanation of symbols]

[0061] 12 Seat cushion 20 Seat under box 24 Box body 26 Locked part 28 Rail section 30 Locking mechanism 32 Locking claw (locking part / unlocking part)

Claims

1. A case disposed below a seat cushion on which an occupant sits; a box body configured to be capable of assuming a stored state in which the box is stored in the case and a drawn state in which the box is drawn out from the case toward a front side of the seat cushion; Equipped with The case is A top wall, a bottom wall, a left side wall, and a right side wall, the longitudinal direction of which is the front-rear direction of the seat cushion; a rail portion provided on each of the left side wall and the right side wall, the rail portion configured to guide the box body so as to be slidable in a front-rear direction of the seat cushion; a locking mechanism that is provided on the rail portion and that locks a locked portion that is provided on the box body when the box body is in the pulled-out state; having The locking mechanism includes: a lock claw formed integrally with the rail portion so as to be elastically deformable outward in the width direction of the seat cushion; The locking claw is The seat under-box is configured to lock onto the locked part by preventing the locked part from moving toward the front side of the seat cushion, and to release the lock on the locked part by elastically deforming outward in the width direction of the seat cushion when the box body is removed from the underside of the seat cushion to assume a detached state.

2. A seat under-box as described in claim 1, wherein the front end surface of the locked portion is formed in a plane perpendicular to the fore-and-aft direction when viewed from the side, and the rear end surface is formed in an approximately semicircular arc shape when viewed in cross-section.

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