Sunroof unit

In an outer slide type sunroof unit, a first seal member is mounted to a side edge of a molded part provided on an outer peripheral edge of a fixed rear panel; a second seal member is mounted to a rear edge of the molded part and has a lateral end facing forward at a position offset outward relative to a rear end of the first seal member; and a third seal member is provided on an outboard side of the first seal member. The third seal member includes a first portion for resiliently contacting an inner edge of a roof opening and a second portion that resiliently contacts the first seal member and cooperates with the first seal member to define a passage for a stay supporting a slidable front panel, a rear end of the first portion being bonded to the lateral end of the second seal member.

TECHNICAL FIELD

The present disclosure relates to an outer slide type sunroof unit configured to be mounted to a roof of a vehicle such that a front panel slides over a rear panel.

BACKGROUND OF THE INVENTION

There is known an outer slide type sunroof device which includes a front cover and a rear cover constituting a part of a vehicle roof such that the front cover slides over the rear cover (see U.S. Pat. No. 9,114,689B). In this sunroof device, a roof seal is attached on the roof side to surround the roof opening peripherally and a cover seal is attached on the side edge of the rear cover so as to contact the roof seal, whereby the gap between the roof and the rear cover is sealed. When the front cover slides rearward over the rear cover, a lever (support member) of the mounting device of the front cover moves between the roof seal and the cover seal, so that the front cover is allowed to slide a large distance in the rearward direction.

In the sunroof device having such a structure, when installing the sunroof unit to the roof, it is necessary to attach the roof seal to the roof, which is a part of the vehicle body, and thus, the installation work is cumbersome. In other words, a structure in that the all seal members are provided on the sunroof unit is desirable. As an outer slide type sunroof unit having such a structure, a sunroof unit is known in which weather strips (seal members) each including a first seal portion for resiliently contacting an outer peripheral edge of the movable panel (front panel) or the fixed panel (rear panel) and a second seal portion for resiliently contacting an edge of the roof opening are fitted to respective vertical walls formed to stand upwardly from a guide rail or from a front housing or the like, which are part of the sunroof unit (see US2013/0307296A1). In this sunroof unit, a link member supporting the front panel moves in the fore-and-aft direction between the vertical wall and the rear panel by resiliently deforming the first seal portion.

However, in the sunroof unit disclosed in US2013/0307296A1, the seal members and the vertical walls supporting them need to be provided along the entire circumference of the front and rear panels so as to surround these panels, and thus, the seal structure is complex. Further, in a case where there is a manufacturing error in the roof, it is necessary to adjust the heights of the fixed panel and the seal members such that they are aligned with the roof, but in the sunroof unit disclosed in US2013/0307296A1, it is not possible to adjust the heights of the seal members.

SUMMARY OF THE INVENTION

In view of such background art, an object of the present invention is to provide a sunroof unit in which all seal members are provided on the sunroof unit in a simple structure and adjustment of heights of the seal members relative to the roof to which the sunroof unit is to be installed is easy to carry out.

To achieve the above object, one embodiment of the present invention provides a sunroof unit (10) for selectively opening at least a part of an opening (2a) formed in a roof (2) of a vehicle (1), the sunroof unit comprising: a frame (20) configured to be disposed below the roof so as to be aligned with the opening of the roof; a rear panel (12) secured to the frame to close a rear portion of the opening; and a front panel (11) that includes a stay (76) depending from a side portion thereof and is supported by the frame via the stay so as to be slidable between a closed position to close a front portion of the opening and an open position where the front panel overlaps on top of the rear panel to open the front portion of the opening. The rear panel includes a panel main body (16), a molded part (17) provided on an outer peripheral edge of the panel main body, and a seal portion (18) provided on an outer peripheral edge of the molded part. The seal portion includes a first seal member (41) mounted to a side edge (17b) of the molded part, a second seal member (42) mounted to a rear edge (17c) of the molded part and curved forward along a corner portion (33) of the molded part such that the second seal member has a lateral end (42a) facing forward at a position offset in an outboard direction relative to a rear end (41a) of the first seal member, and a third seal member (43) provided on an outboard side of the first seal member. The third seal member includes a first portion (61) configured to resiliently contact an inner edge of the opening of the roof and a second portion (62) that resiliently contacts an outer side of the first seal member and cooperates with the first seal member to define a passage for the stay, a rear end of the first portion (61) being bonded to the lateral end (42a) of the second seal member (42).

According to this configuration, because the first and second seal members are mounted to the molded part provided on the outer peripheral edge of the main panel body of the rear panel, there is no need to form a vertical wall on the frame to support the first and second seal members. Further, the third seal member is mounted to the main panel body of the rear panel via the rear end bonded to the second seal member. Thus, the all seal members are provided on the sunroof unit in a simple structure. In addition, in the above configuration, not only the positions (heights) of the first and second seal members relative to the panel main body but also the position (height) of the third seal member relative to the panel main body is fixed. Therefore, when the height of the panel main body of the rear panel relative to the frame is adjusted such that the panel main body is aligned with the roof of the vehicle to which the sunroof unit is installed, the heights of the first to third seal members are automatically adjusted, and therefore, the height adjustment can be carried out easily.

Preferably, in the above configuration, an outer edge of the rear end of the first portion (61) of the third seal member (43) is aligned with an outer edge of the lateral end (42a) of the second seal member (42).

According to this configuration, it is ensured that the outer edges of the third seal member and the second seal member at the connection therebetween tightly contact the inner edge of the opening of the roof, and thus, the sealing performance at the connection between the third seal member and the second seal member is improved.

Preferably, in the above configuration, the rear end of the first portion (61) of the third seal member (43) is bonded to the lateral end (42a) of the second seal member (42) by welding.

According to this configuration, the third seal member and the second seal member are bonded to each other firmly and reliably.

Preferably, in the above configuration, the first portion (61) and the second portion (62) of the third seal member (43) are formed to be symmetric to each other.

According to this configuration, arrangement of the third seal member is easy because the direction of arrangement of the third seal member is not limited.

Preferably, in the above configuration, the side portion (31) of the molded part (17) is provided with a cutout (35) extending from a position that coincides with the lateral end (42a) of the second seal member (42) to a front edge (17a) of the molded part (17), and the first seal member (41) is disposed in the cutout.

According to this configuration, the width of the lateral end of the second seal member can be reduced, and therefore, the panel main body can be made larger correspondingly.

Preferably, in the above configuration, the second portion (62) of the third seal member (43) is disposed in the cutout (35).

According to this configuration, the width of the lateral end of the second seal member can be reduced further, and thus, the panel main body can be made even larger correspondingly.

Preferably, in the above configuration, the rear panel (12) is mounted to the frame (20) such that a height of the rear panel is adjustable.

According to this configuration, in a case where there is a manufacturing error in the roof, the height of the rear panel relative to the frame can be adjusted such that the rear panel is aligned with the roof. Therefore, it is unnecessary to adjust the height of the frame relative to the roof, and thus, the installation of the sunroof unit to the roof is easy to carry out.

Preferably, in the above configuration, the third seal member (43) is supported by a support bracket (70) mounted to the frame (20), wherein a height of the support bracket is adjustable.

According to this configuration, the support rigidity of the third seal member is improved, and thus, the reliability of the seal is improved.

Preferably, in the above configuration, the frame (20) includes a guide rail (24) for guiding the front panel (11) via the stay (76), and the support bracket (70) includes a lower end portion (71) secured to the frame (20) at a position on an outboard side of the guide rail, an intermediate portion (72) extending from the lower end portion in an inboard direction, and an upper end portion (73) extending upward from the intermediate portion and supporting the third seal member (43) above the guide rail.

According to this configuration, it is possible to prevent the support bracket from interfering with the movement of the front panel.

Preferably, in the above configuration, the support bracket (70) is constituted of a plate member bent along bend lines (74) each extending in a fore-and-aft direction.

According to this configuration, the support bracket can be manufactured easily by processing a plate member to have a desired cross-sectional shape. In addition, by using a plate member with a length necessary to support the third seal member, it is possible to manufacture a support bracket in accordance with the length of the third seal member.

Thus, according to the foregoing configuration, it is possible to provide a sunroof unit in which all seal members are provided on the sunroof unit in a simple structure, and adjustment of heights of the seal members relative to the roof to which the sunroof unit is to be installed is easy to carry out.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1is a perspective view showing a closed state of a sunroof unit10installed to a roof2of a motor vehicle1. A rectangular opening2ais formed in the roof2of the motor vehicle1, and the sunroof unit10is installed to the roof2to close the opening2a. In the following description, the directions such as front, rear, left, right, up, and down are defined with respect to the motor vehicle1. With respect to the vehicle width direction of the motor vehicle1, which corresponds to the lateral direction, a side closer to the center of the motor vehicle1may be referred to as an inboard side, and an outer side of the motor vehicle1may be referred to as an outboard side. The sunroof unit10is substantially left and right symmetric, and the details of the symmetric structures will be described while showing the structures on the left side in the drawings.

The sunroof unit10includes a front panel11for closing a front portion of the opening2aand a rear panel12for closing a rear portion of the opening2a. The front panel11and the rear panel12are arranged along the roof2such that their upper surfaces are aligned with the upper surface of the roof2. The front panel11is a movable panel that is movable relative to the roof2, while the rear panel12is a fixed panel that is not movable relative to the roof2.

The front panel11includes a front panel main body13formed of a glass plate, an annular front molded part14made of resin and provided on an outer peripheral edge of the front panel main body13, and a front seal portion15made of an elastic material and provided on an outer peripheral edge of the front molded part14. The rear panel12includes a rear panel main body16formed of a glass plate, an annular rear molded part17made of resin and provided on an outer peripheral edge of the rear panel main body16, and a rear seal portion18made of an elastic material and provided on an outer peripheral edge of the rear molded part17. The front seal portion15and the rear seal portion18cooperate with each other to form an annular seal portion around an outer circumference of the front panel11and the rear panel12and to form a seal portion between the front panel11and the rear panel12.

In this embodiment, the front seal portion15is provided to extend along both side edges and the front edge of the front molded part14(these edges are part of the outer peripheral edge of the front molded part14) and has a U-shape. On the other hand, the rear seal portion18is provided to extend annularly along the entire outer peripheral edge of the rear molded part17. Namely, the seal portion between the front panel11and the rear panel12is formed as a part of the rear seal portion18. In another embodiment, the seal portion between the front panel11and the rear panel12may be formed as a part of the front seal portion15.

When driven by a known slide mechanism in an opening direction, the front panel11is moved from a closed position shown inFIG. 1, at which the front panel11closes the front portion of the opening2a, to a tilt-up position shown inFIG. 2, at which the rear portion of the front panel11is raised, and then, slides over the rear panel12rearward to move to an open position shown inFIG. 3, at which the front panel11overlaps on top of the rear panel12and opens the front portion of the opening2a. On the other hand, when driven by the slide mechanism in a closing direction, the front panel11slides forward over the rear panel12from the open position shown inFIG. 3to the closed position shown inFIG. 1via the tilt-up position shown inFIG. 2. Thus, the front panel11is configured to be slidable between the closed position shown inFIG. 1and the open position shown inFIG. 3, and the sunroof unit10can selectively open the front portion of the opening2a.

As shown inFIG. 3, a frame20that supports the front panel11and the rear panel12is mounted below the roof panel3such that the frame20is aligned with the opening2aof the roof2. The frame20is formed to have an annular shape extending along the inner peripheral edge of the opening2a, and includes left and right side frames21extending in the fore-and-aft direction along the respective inner side edges of the opening2a, a front frame22(FIG. 4) connecting the front ends of the left and right side frames21to each other, and a rear frame23(FIG. 4) connecting the rear ends of the left and right side frames21to each other. Each side frame21is integrally provided with a guide rail24extending in the fore-and-aft direction.

FIG. 4is a perspective view showing a part of the sunroof unit10before being installed to the roof2. As shown inFIG. 4, a drive source27including an electric motor25and a reduction mechanism26is mounted at an intermediate portion of the rear frame23in the lateral direction. The output end of the drive source27is engaged with left and right push-pull cables28(FIG. 5) for driving the front panel11. The push-pull cables28extend from the output end of the drive source27along the rear frame23in the outboard direction, are passed through left and right guide pipes29to be curved forward, and then extend forward in the left and right guide rails24, respectively.

The rear panel main body16has a substantially rectangular shape, with the rear left and right corners thereof being rounded. The rear molded part17includes left and right side portions31(FIG. 1) extending in the fore-and-aft direction along left and right outer side edges of the rear panel main body16, respectively, a front portion32connecting the front ends of the left and right side portions31to each other, and a rear portion34connecting the rear ends of the left and right side portions31to each other via left and right curved corner portions33.

FIG. 5is an enlarged perspective view showing a detailed structure of the sunroof unit10, with a part thereof broken away along line V-V inFIG. 4. As shown inFIGS. 4 and 5, each of the left and right side portions31of the rear molded part17has a smaller width than the front end of the associated corner portion33and is connected to an inboard-side part of the front end of the corner portion33. In other words, each side portion31of the rear molded part17is provided with a cutout35that extends in the fore-and-aft direction from the front end of the associated corner portion33to the front edge17aof the rear molded part17. The inboard-side edge of the cutout35extending in the fore-and-aft direction makes a side edge17bof the rear molded part17(outer edge of the side portion31).

The rear seal portion18includes a pair of first seal members41respectively extending along the left and right side edges17bof the rear molded part17, a second seal member42extending along the rear edge17cof the rear molded part17and curved forward along the corner portions33of the rear molded part17, a pair of third seal members43extending along the outer sides of the respective first seal members41, and a fourth seal member44(FIG. 4) extending along the front edge17aof the rear molded part17.

The front ends of the left and right first seal members41are connected with each other by the fourth seal member44via left and right corner members45(FIG. 4) each bent at a right angle. Each first seal member41extends in the fore-and-aft direction in the associated cutout35and the rear end41athereof is positioned at the rear end of the cutout35.

The second seal member42has lateral ends42aeach facing forward at a position offset in the outboard direction relative to the front end of the associated corner portion33of the rear molded part17, namely, relative to the rear end41aof the associated first seal member41. In other words, each cutout35is formed to extend from a position that coincides with the associated lateral end42aof the second seal member42to the front edge17aof the rear molded part17.

Each third seal member43is provided on the frame20such that the outer end thereof is aligned with the outer end of the associated lateral end42aof the second seal member42. Specifically, each third seal member43is mounted to the frame20via an associated one of left and right support bracket70respectively attached to the left and right side frames21, and is disposed such that only an inner portion thereof (second portion62, which will be described later) extends in the fore-and-aft direction in the cutout35. The detailed structure of the third seal member43will be described later. An end member46(FIG. 4) is welded to the front end of each third seal member43. The rear end of each third seal member43is bonded to the associated lateral end42aof the second seal member42at least partially.

As shown inFIG. 5, the rear panel12is secured to the frame20by means of support posts47that extend downward from the four corners of the rear molded part17. Each support post47is provided with a height adjustment mechanism48of a known structure. Namely, the rear panel12is mounted to the frame20such that the height of the rear panel12is adjustable.

FIG. 6is a cross-sectional view taken along line VI-VI inFIG. 1. As shown inFIG. 6, the second seal member42is an extrusion molded product made of an elastic material, and has a constant cross-sectional shape. The second seal member42includes a main body49in the shape of letter D convex in the outboard direction and a fitting portion50formed integrally on the inboard side of the main body49so as to be fitted in a mounting groove17dformed in the peripheral edge of the rear molded part17. The main body49of the second seal member42resiliently contacts the inner edge of the opening2aof the roof2.

FIG. 7is a cross-sectional view taken along line VII-VII inFIG. 1. As shown inFIG. 7, similarly to the second seal member42, each first seal member41is an extrusion molded product made of an elastic material, and has a constant cross-sectional shape. The first seal member41includes a main body51in the shape of letter D convex in the outboard direction and a fitting portion52formed integrally on the inboard side of the main body49so as to be fitted in the mounting groove17dof the rear molded part17.

Each third seal member43includes a first portion61in the shape of letter D convex in the outboard direction and a second portion62in the shape of letter D convex in the inboard direction, where the second portion62is connected with an upper part of the first portion61via a connecting portion63. The first portion61, the second portion62, and the connecting portion63are formed integrally with each other. The first portion61has a cross-sectional shape substantially the same as that of the main body49of the second seal member42(FIG. 6), and the entirety of the rear end thereof is bonded to the associated lateral end42aof the second seal member42by welding. The first portion61and the second portion62are formed to be symmetric to each other, and a mounting groove64opening out on the underside of the third seal member43is defined below the connecting portion63that connects the first and second portions61,62.

Each side frame21is an extrusion molded product made of an aluminum alloy, and has a pair of guide portions66,67for guiding a slider80(FIG. 8) from both left and right sides. The pair of guide portions is constituted of an outer guide portion66disposed on the outboard side and an inner guide portion67disposed on the inboard side. The outer guide portion66is provided with a cable guide groove68for guiding the push-pull cable28. An extending portion69is formed integrally at an intermediate part of the outer guide portion66in the height direction so as to extend out in the outboard direction.

As shown inFIGS. 4 and 5, each support bracket70is a press-formed product produced by press-forming a steel plate, has a fore-and-aft length substantially the same as that of the third seal member43, and has an identical cross-sectional shape over its entire length.

As shown inFIGS. 5 and 7, the support bracket70extends in the lateral direction such that the support bracket70includes a lower end portion71secured to the extending portion69of the side frame21at a part on the outboard side of the pair of guide portions66,67, an intermediate portion72that is bent upward at the inboard-side end of the lower end portion71and further bent inward to extend in the inboard direction across above the outer guide portion66, and an upper end portion73that is bent upward at the inboard-side end of the intermediate portion72to extend upward from the intermediate portion and supports the third seal member43between the first seal member41and the inner edge of the opening2aof the roof2opposing the first seal member41. The plurality of bent portions including the bent portion between the lower end portion71and the intermediate portion72, the bent portion between the intermediate portion72and the upper end portion73, and the multiple bent portions formed in the intermediate portion72, constitute bend lines74each extending in the fore-and-aft direction. Namely, the support bracket70is formed of a plate member bent along bend lines74each extending in the fore-and-aft direction. The lower end portion71is secured to the extending portion69of the side frame21by any known securing means such as a bolt and nut. The height of the support bracket70is adjustable by inserting a shim75having an appropriate thickness between the lower end portion71and the extending portion69. It is to be noted that when the height adjustment is unnecessary, the shim75may not be inserted.

The third seal member43is mounted to the support bracket70such that the upper end portion73is received in the mounting groove64, and is secured to the support bracket70with the first portion61and the second portion62being bonded to the upper end portion73with an adhesive. In the state where the third seal member43is mounted to the support bracket70, the first portion61resiliently contacts the inner edge of the opening2athe roof panel3(FIG. 7), and the second portion62resiliently contacts the outer side of the first seal member41.

FIG. 8is a cross-sectional view taken along line VIII-VIII inFIG. 3, which is a cross-sectional view corresponding toFIG. 7but showing the sunroof unit10in the open state. As shown inFIG. 8, the front panel11includes a pair of stays76depending from left and right side portions thereof, respectively, and is guided by the guide rails24via a pair of sliders80supporting the respective stays76, whereby the front panel11is slidably supported by the frame20via the stays76and the sliders80. When the front panel11is moved from the tilt-up position shown inFIG. 2to the open position shown inFIG. 3, each stay76lifting up the rear portion of the front panel11enters between the first seal member41and the second portion62of the third seal member43on the same lateral side of the sunroof unit10. Namely, the second portion62of the third seal member43cooperates with the first seal member41to define a passage for the stay76.

The sunroof unit10is configured as described above. In the following, The operation and effect of the sunroof unit10will be described.

As shown inFIG. 5, the rear seal portion18includes a first seal member41mounted to the side edge17bof the rear molded part17, a second seal member42mounted to the rear edge17cof the rear molded part17and curved forward along the corner portion33of the rear molded part17such that the second seal member42has a lateral end42afacing forward at a position offset in the outboard direction relative to the rear end41aof the first seal member41, and a third seal member43provided on the outboard side of the first seal member41. Thus, the first to third seal members41-43are all provided on the sunroof unit10, and therefore, installation of the sunroof unit10to the roof2is easy to carry out. Further, because the first and second seal members41,42are mounted to the rear molded part17provided on the outer peripheral edge of the rear panel main body16of the rear panel12, there is no need to form a vertical wall on the frame20to support the first and second seal members,41,42, and thus, the seal structure is simple.

Further, as shown inFIG. 8, the third seal member43includes a first portion61configured to resiliently contact the inner edge of the opening2aof the roof2and a second portion62that resiliently contacts the outer side of the first seal member41and cooperates with the first seal member41to define a passage for the stay76. Thereby, the stay76, which depends from the side portion of the front panel11, can pass through the passage between the first seal member41and the second portion62of the third seal member43, and therefore, the front panel11is allowed to slide a large distance in the rearward direction, as shown inFIG. 3.

Further, as shown inFIG. 5, the rear end of the first portion61of the third seal member43is bonded to the lateral end42aof the second seal member42. Thereby, not only the positions (heights) of the first and second seal members41,42relative to the rear panel main body16but also the position (height) of the third seal member43relative to the rear panel main body16is fixed. Therefore, when the height of the rear panel main body16relative to the frame20is adjusted such that the rear panel main body16is aligned with the roof2of the vehicle1to which the sunroof unit10is installed, the heights of the first to third seal members41-43are automatically adjusted, and therefore, the height adjustment can be carried out easily.

As described above, the outer edge of the rear end of the first portion61of the third seal member43is aligned with the outer edge of the lateral end42aof the second seal member42. Thereby, it is ensured that the outer edges of the third seal member43and the second seal member42at the connection therebetween tightly contact the inner edge of the opening2aof the roof2, and thus, the sealing performance at the connection between the third seal member43and the second seal member42is improved.

In the illustrated embodiment, the rear end of the first portion61of the third seal member43is bonded to the lateral ends42aof the second seal member42by welding. Thereby, the third seal member43and the second seal member42are bonded to each other firmly and reliably.

The first portion61and the second portion62of the third seal member43are formed to be symmetric to each other. Thereby, the direction of arrangement of the third seal member43is not limited, and therefore, arrangement of the third seal member43is easy.

The side portion31of the rear molded part17is provided with a cutout35extending from the position that coincides with the lateral ends42aof the second seal member42to the front edge17a(FIG. 4) of the rear molded part17, and the first seal member41is disposed in the cutout35. Thereby, the width of the lateral end42aof the second seal member42can be reduced, and therefore, the rear panel main body16can be made larger correspondingly.

Further, in addition to the first seal member41, the second portion62of the third seal member43also is disposed in the cutout35. Thereby, the width of the lateral ends42aof the second seal member42can be reduced further, and thus, the rear panel main body16can be made even larger correspondingly.

The rear panel12is mounted to the frame20by the support post47such that the height of the rear panel12is adjustable. Thereby, in a case where there is a manufacturing error in the roof2, the height of the rear panel12relative to the frame20can be adjusted such that the rear panel12is aligned with the roof2. Therefore, it is unnecessary to adjust the height of the frame20relative to the roof2, and thus, the installation of the sunroof unit10to the roof2is easy to carry out.

Further, the third seal member43is supported by the support bracket70mounted to the frame20, wherein a height of the support bracket70is adjustable. Thereby, the support rigidity of the third seal member is improved, and thus, the reliability of the seal is improved.

The frame20includes a guide rail24for guiding the front panel11via the stay76. Further, the support bracket70includes a lower end portion71secured to the frame20at a position on an outboard side of the guide rail24, an intermediate portion72extending from the lower end portion71in an inboard direction, and an upper end portion73extending upward from the intermediate portion72and supporting the third seal member43above the guide rail24. Thereby, it is possible to prevent the support bracket70from interfering with the movement of the front panel11, as shown inFIG. 8.

As shown inFIGS. 5 and 7, the support bracket70is constituted of a plate member bent along bend lines74each extending in the fore-and-aft direction. Thereby, the support bracket70can be manufactured easily by processing a plate member to have a desired cross-sectional shape. In addition, by using a plate member with a length necessary to support the third seal member43, it is possible to manufacture a support bracket70in accordance with the length of the third seal member43.

The description of the concrete embodiment has been provided in the foregoing, but the present invention is not limited to the foregoing embodiment and can be carried out with various modifications and alterations. For example the concrete structure, arrangement, number, material, etc. of the members or parts may be changed appropriately without exceeding the spirit of the present invention. It is also to be noted that not all of the component parts shown in the foregoing embodiment are necessarily indispensable, and they may be selectively used as appropriate. For example, in the foregoing embodiment, some of the component parts, such as the guide rails, stays, first seal members, third seal members, etc. are provided symmetrically on both left and right sides of the sunroof unit, but they may be provided on only one lateral side.