AU2018260970A1

AU2018260970A1 - Child Restraint for a Vehicle

Info

Publication number: AU2018260970A1
Application number: AU2018260970A
Authority: AU
Inventors: Richard Horsfall
Original assignee: Hbg Ip Holding Pty Ltd
Current assignee: Hbg Ip Holding Pty Ltd
Priority date: 2012-10-09
Filing date: 2018-11-09
Publication date: 2018-11-29
Also published as: AU2017100676A4; AU2016277541C1; AU2020210268A1; AU2012238254C1; AU2017100676B4; AU2012238254A1; AU2012238254B2; AU2016277541A1; AU2016277541B2

Abstract

The present invention provides a child safety seat for a vehicle comprising a seat portion configured to receive a child therein; and a pair of attachment means located on opposing side walls of the seat portion; wherein, each attachment means is located substantially midway between a front of the seat portion and a rear of the seat portion and comprises a recess formed through the side wall to provide a path for a restraining strap to pass so as to extend across the seat portion to facilitate securement of the seat portion to a vehicle seat, said path being the same when the seat portion is orientated in either a forward or a rearward facing position. ,Lo Alp

Description

CHILD RESTRAINT FOR A VEHICLE

FIELD OF INVENTION

The present invention relates generally to a child restraint for a vehicle, and in particular, to a tether system for tethering a lower region of a child restraint to a 5 seat of a vehicle.

BACKGROUND OF THE INVENTION

The use of child restraints to accommodate infants and young children whilst travelling in a vehicle is a well established practice. Most countries have established various laws and regulations that dictate the manner in which infants io and children are to be transported in vehicles, and the types of restraints that are acceptable for such use. Most laws adopted for such purposes require the infant/child to be restrained in a dedicated and approved child safety seat that is anchored or otherwise secured to a rear seat of the vehicle. The child safety seat may include a dedicated harness that restrains the child in position within the 15 seat, or the child safety seat may utilise the vehicle seat belt or a separate harness to restrain the child therein, depending upon the size and/or age of the child.

As such, there exist a variety of types of child safety seats that are approved for use with children of a variety of ages and/or sizes. These types can be broadly characterised as follows. Type A seats typically refer to rear facing seats or 20 capsules suitable for accommodating babies/infants up to around 6 months of age and/or 70 cm in length and up to 12 kg. Type B seats typically refer to forward facing seats used to accommodate toddlers and young children from approximately 6 months to 4 years, or from 8 - 18 kg. Type E seats typically refer to booster seats and booster cushions used to accommodate children 25 between 4-8 years old, or approximately from 14-32 kg, and which are typically used in combination with the vehicle seat belt. There also exist combination Type A/B, B/E and A/B/E seats that are designed to be varied to accommodate the child as the child grows.

The manner in which child restraints are secured in position on a vehicle seat may 30 vary between countries. In Australia, where rear seat lap or lap/sash seatbelts are a mandatory requirement for vehicles, the child restraint is typically secured in position by passing the lap or lap/sash seat belt through the body of the child restraint. In this regard, the vehicle seat belt functions to restrain the lower portion of the child restraint against the vehicle seat. A top tether may also be 35 employed to restrain the upper region of the child restraint in position against the

2018260970 09 Nov 2018 vehicle seat, with the top tether extending to engage with a dedicated vehicle anchorage point provided behind the vehicle seat. Through the use of a top tether in combination with the vehicle seat belt, the child restraint is secured against the vehicle seat at an upper and lower region.

In Europe, the USA, and other countries, a different type of system for securing a child restraint against a vehicle seat is employed. In such countries, vehicles may be fitted with an ISOFIX (Europe) or LATCH (Lower Universal Anchorage System) (USA) anchorage system to aid in securing the safety seat in position. Typically, in such systems, a pair of rigid lower anchorage points are provided in io the bight of the vehicle seat, which provides a means for securing the lower region of the child restraint. In such a system the vehicle seat belt is not required.

In Australia, the LATCH or ISOFIX system is being introduced into new vehicles such that parents will be able to use either the Latch/ISOFIX system and the vehicle seat belt to restrain the child safety seat in position. Where such a dual 15 means for restraint exists, challenges arise for child safety seat manufacturers to provide a child restraint that is able to be used with a vehicle seat belt and a LATCH system which is easy to use and offers the benefits of both systems.

Thus, there is a need to provide a child restraint that accommodates a variety of restraining devices in a simple and convenient manner. Further, there is a need to 20 provide a child safety seat that provides a common path for securing the child safety seat in position in either a forward or rearward facing manner, irrespective of the orientation of the safety seat.

The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

so STATEMENT OF INVENTION

The invention according to one or more aspects is as defined in the independent claims. Some optional and/or preferred features of the invention are defined in the dependent claims.

Accordingly, in a first aspect here is provided a child safety seat for a vehicle

2018260970 09 Nov 2018 comprising:

a seat portion configured to receive a child therein; and a pair of attachment means located on opposing side walls of the seat portion;

wherein, each attachment means is located substantially midway between a front of the seat portion and a rear of the seat portion and comprises a recess formed through the side wall to provide a path for a restraining strap to pass so as to extend across the seat portion to facilitate securement of the seat portion to a vehicle seat, said path being the same when the seat io portion is orientated in either a forward or a rearward facing position.

In an embodiment, the restraining strap is a vehicle seat belt. The vehicle seat belt may comprise a lap and sash belt combined together. In another form, the vehicle seat belt may comprises a lap belt only.

In another embodiment, the restraining strap may comprise a length of strap 15 having an engagement member located at or adjacent each end thereof, each engagement member being configured to engage with an anchor point provided in a bight of the vehicle seat. Each engagement member may engage with its corresponding anchor point on each opposing side of the seat portion to secure the seat portion to the vehicle seat.

The seat portion may comprise a seat shell mounted on a base. Each attachment means may be provided on side walls of the seat shell.

A clip or retaining member may be mounted within the recess to engage with the restraining strap to substantially secure the restraining strap in position with respect to the attachment means so as to prevent sliding movement of the 25 restraining strap when the clip or retaining member is engaged therewith.

Accordingly, in a second aspect of the invention there is provided a child safety seat for a vehicle comprising:

a seat shell configured to receive a child therein; and a pair of attachment means located on opposing sides of the seat shell;

wherein, each attachment means is configured for use with either a

LATCH style anchorage system or a vehicle seat belt, to facilitate securement of the seat shell against a seat of a vehicle

2018260970 09 Nov 2018

The pair of attachment means may be centrally located on the opposing sides of the seat to facilitate both forward and rearward facing use of seat shell. The attachment means may comprise a recess formed through the side of the seat shell to provide a path for the seat belt and/or a strap of the LATCH style anchorage 5 system to pass therebetween.

The attachment means may each comprise a cover member received within the recess, the cover member may be configured to engage with the seat belt and/or the strap of the LATCH style anchorage system to lock the seat belt and/or the strap of the LATCH style anchorage system in position with respect to the io attachment means.

In a third aspect of the present invention, there is provide an attachment means for facilitating securement of a child safety seat to a vehicle by way of a seat belt and/or the strap of the LATCH style anchorage system, the attachment means comprising:

is a recess formed in a side of a shell of the child safety seat, the recess being configured to receive the seat belt and/or the strap of the LATCH style anchorage system therein; and a cover member mounted within the recess, the cover member being configured to lock the seat belt and/or the strap of the LATCH style 20 anchorage system in position with respect to the recess.

In a fourth aspect of the present invention, there is provide a securement system for securing a child safety seat to a seat of a vehicle, comprising an attachment means mounted to opposing sides of the child safety seat, the attachment means being configured to receive either a LATCH style anchorage system or a vehicle 25 seat belt to facilitate securement of the child safety seat to the seat of the vehicle, wherein the attachment means is located centrally of the child safety seat such that the child safety seat can be used in either a front facing or rearward facing position.

In a fifth aspect of the present invention, there is provided a child safety seat for a 30 vehicle comprising:

a seat shell adapted to be positioned on a vehicle seat and configured to receive a child therein, the seat shell having a backrest portion and a seat portion; and a restraining means for restraining the seat shell in position against the

2018260970 09 Nov 2018 vehicle seat, the restraining means comprising a length of strap having an engagement member located at or adjacent each end thereof, each engagement member being configured to engage with an anchor point provided in a bight of the vehicle seat;

wherein, an attachment means is provided in opposing sides of the seat shell thereby defining a path between which the restraining means passes across the seat shell to facilitate engagement of each engagement member with its corresponding anchor point on each opposing side of the seat shell.

io In an embodiment of the fifth aspect, the strap of the restraining means may be adjustable in length. The engagement member may be a hook or latch member.

The attachment means may comprise a recess formed in the seat shell. A clip or retaining member may be mounted in the recess to engage with the strap of the restraining member to substantially secure the strap in position with respect to the is attachment means so as to prevent sliding movement of the strap when the clip or retaining member is engaged therewith.

The attachment means may be centrally located in the opposing sides of the seat shell to facilitate use of the child safety seat in both a forward and a reverse orientation. The attachment means may further provide a path for receiving a 20 vehicle seat belt to secure the seat shell against the vehicle seat.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

Fig. 1 is a side view of a prior art arrangement showing a child safety seat being secured against a seat of a vehicle using a LATCH securing system;

Fig. 1A is an enlarged view showing the manner in which the anchorage system of Fig. 1 is configured;

Fig. 2 shows a side view of a child safety seat according to one embodiment of the present invention;

Fig. 3 shown an enlarged view of an attachment means for use with the child safety seat of Fig. 2;

Fig. 4 is a top perspective view of a child safety seat using the attachment

2018260970 09 Nov 2018 means of the present invention in a forward facing position;

Fig. 5 is a rear perspective view of a child safety seat of the present invention in a rearward facing manner; and

Fig. 6 shows a side view of a child safety seat of the present invention 5 being secured against a vehicle seat using a conventional vehicle seat belt.

DETAILED DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be io construed as limiting on the scope of the invention.

Referring to Fig. 1, there is shown a prior art child safety seat 10 fitted to a vehicle seat 5 in a conventional manner by way of a LATCH system. The LATCH system generally comprises a pair of anchors 15 in the form of a small bar, as shown. The anchors 15 are located in the bight of the vehicle seat 5 on 15 each side of the child safety seat 10. A pair of straps 12 are fixed to either side of the body of the child safety seat 10 by bolts 13 or the like. Each strap 12 is adjustable in length and terminates in a hook 14 or similar fastening element. The hook 14 engages with the anchor 15 of the LATCH system as shown in Fig. 1A, and the strap 12 is able to be tightened to secure the child safety seat in 20 position as shown. A top tether 16 is also provided to engage with an upper vehicle anchorage point 9, as is well known in the art.

Referring to Fig. 1, it can be readily appreciated that the arrangement as shown relies upon the integrity of the bolt 13 to attach the strap 12 to the wall of the shell 22 of the child safety seat 10. As the shell 11 of the child safety seat 10 is 25 typically made from a plastic material, the material may fracture under the loads experienced in a accident situation thereby significantly compromising the safety of the child seated therein, as well as other occupants of the vehicle in the general vicinity of the child safety seat.

Further to this, the child safety seat 10 of Fig. 1 also shows a conventional path 30 18 for accommodating a seat belt of the vehicle, when the child safety seat 10 is to be used without the LATCH system. As is shown, the path 18 for use in a forward facing mode is essentially provided in a lower rear region of the child safety seat 10, remote from the straps 12. Hence, as the seat belt path 18 is in a separate position to the location of the straps 12 of the LATCH system, there is

2018260970 09 Nov 2018 an increased likelihood of confusion by the consumer when installing the seat, depending upon the system to be employed. If used in a rearward facing mode, another seat belt path located at the front of the child safety seat (not shown) would have to be used, providing additional confusion to the consumer in 5 determining the correct path to use when securing the child safety seat 10 in a desired position.

Referring to Figure 2, a child safety seat 20 in accordance with an embodiment of the present invention is shown. The child safety seat 20 comprises a seat shell 22 which into which a child is to be received, and a base 24 which supports the seat io shell 22 thereon. The child safety seat 20 is configured to be used in either a forward or rearward facing manner, depending upon the safety requirements of the child located therein.

A dedicated attachment means 30 is provided in opposing sides of the seat shell 22 to provide a common point for accommodating the straps 12 of the LATCH is system as well as a path for the vehicle seat belt to be used when the child safety seat 20 is to be used with a vehicle without a LATCH system fitted. The attachment means 30 is located in a central location of the seat shell 22. This enables the child safety seat 20 to be used in a forward or rearward manner without the straps 12 of the LATCH system being restricted by the seat shell 22, 2o as is shown by the dashed lines.

Referring to Figure 3, the attachment means 30 is shown in detail. The attachment means 30 generally comprises a semi-circular recess 31 formed through the side walls of the seat shell 22 on opposing sides of the seat shell. The recesses 31 provide a path for the strap 12 or the vehicle seat belt 40 (shown in dashed lines) to pass therethrough and across the seat shell 22 where it can be secured in position.

In the embodiment as shown in Figs. 2-5, rather than the LATCH system having two separate straps 12 as is shown in the prior art system of Fig. 1, the strap 12 of the LATCH system may be a single length of strap having a hook 14 located

3o adjacent either end. An adjustment means may be provided in either or both ends of the strap 12 for tightening purposes, as is shown more clearly in Fig. 4.

The attachment means 30 may comprise a cover or clip member 32 that is pivotally mounted within the recess 31 to at least partially close about or over the strap 12 (and/or the seat belt 40) of the LATCH system, as shown. The cover or clip members 32 of the attachment means are then closed to lock, or securely retain the strap 12 of the LATCH system in position. Such locking of the cover

2018260970 09 Nov 2018 member 32 may be provided by a lug 33 provided to engage within a recess formed in the cover or clip member 32 to retain the cover member 32 in a locked position about the strap 12. In this locked position, the cover member 32 applies a holding force against the strap 12 of the LATCH system to reduce the 5 likelihood of the strap undergoing lateral movement within the recesses 31.

Referring to Figure 4, the path of the strap 12 of the LATCH System across the seat shell is shown with the child safety seat 20 in a forward facing position. It will be appreciate that the dashed line represents that the strap 12 travels under the seat covering and any internal harness so as to be substantially hidden from io view when in use. Similarly, Fig. 5 shown the child safety seat 20 in use in a rearward facing manner to depict the manner in which the strap 12 is able to be employed.

In the event that the child safety seat 20 is not being used in a vehicle equipped with a LATCH system, the attachment means 30 is able to accommodate the 15 vehicle seat belt system 40 in a similar manner, as is shown in Fig. 6. In this regard, the vehicle seat belt is able to be passed through the recess 31 provided in the attachment means 30 to pass over and through the seat shell 22 to be secured to a clip member, in a conventional manner. Once the vehicle seat belt 40 is engaged, the cover member 32 of the attachment means 30 may be able to be 20 locked in position about the vehicle seat belt 40, as discussed above. In situations where the vehicle seat belt 20 is being used to restrain the child safety seat 20 in position, it may be possible to store the LATCH components in a device such as a pocket or the like, located on the child safety seat 20. This may be in the form of a pocket formed in the cover 50 of the child safety seat, as is shown in Fig. 6.

Whilst the above embodiments of the present invention have been shown and described in relation to the strap 12 of the LATCH system being a continuous piece of strap threaded through the attachment means 30 for use, it will be appreciated that the strap 12 may be separate lengths of strap securely attached at the attachment means 30 at either sides of the seat shell 22. In this regard, the recesses 31 of the attachment means 30 are provided for receiving the vehicle seatbelt only.

It will be appreciated that the arrangement of the present invention provides a child safety restraint that can be readily adapted for use with either a LATCH system or a conventional seatbelt system to restrain the child restraint against the vehicle seat. By providing the attachment means in a central location, the child safety seat is able to be used in either a forward or rearward facing manner,

2018260970 09 Nov 2018 without hindering or impacting the effectiveness of the anchorage system being used.

Throughout the specification and claims the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the 5 contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

io Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the child safety seat uppermost.

is It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.

Claims

Claims

1. A child restraint for use in a vehicle in each of a forward facing and a rearward facing orientation, the child restraint including a seat shell configured to receive a child, the seat shell having:

5 a backrest portion securable to a vehicle anchorage point through a top tether;

a seat portion having a seating surface; and opposing sides;

wherein:

each opposing side has one only attachment means for a restraining strap to facilitate

10 securement of the child restraint to a vehicle seat; and each attachment means has an aperture which is located in a substantially central location of the seat shell, whether the child restraint is in use in the forward facing or the rearward facing orientation, such that the apertures provide a path for the restraining strap to extend over and across the seating surface for securing the child

15 restraint to the vehicle seat in each of the forward facing and rearward facing orientations.
2. A child restraint for use in a vehicle, comprising:

a seat shell including a seating surface configured to receive a child; and a single attachment means, for a restraining strap being a vehicle seat belt to facilitate

20 securement of the child restraint to a vehicle seat, located on each of opposing sides of the seat shell;

wherein each attachment means includes an aperture, having a continuous boundary, located substantially midway between a front of the seat shell and a rear of the seat shell in use, whether the child restraint is in a forward facing or a rearward facing

25 orientation, so as to provide a path for the vehicle seat belt to extend over and across

2018260970 09 Nov 2018 the seating surface, said path being substantially the same when the child restraint is in the forward facing and the rearward facing orientations.
3. A child restraint according to claim 1 or 2, wherein the restraining strap is a vehicle seat belt comprising a lap and sash belt combined together.
5 4. A child restraint according to claim 1 or 2, wherein the restraining strap is a vehicle seat belt comprising a lap belt.

5. A child restraint according to claim 1, wherein the restraining strap is a length of strap having an engagement member located at or adjacent each end thereof, each engagement member being configured to engage with an anchor point provided in a

10 bight of the vehicle seat.
6. A child restraint according to claim 5, wherein each engagement member engages with its corresponding anchor point on each opposing side of the seat shell to secure the child restraint to the vehicle seat.
7. A child restraint according to claim 1 or 2, wherein the seat shell is mounted on a base.

15
8. A child restraint according to claim 1 or 2, wherein the attachment means are provided on side walls of the seat shell.
9. A child restraint according to any one of claims 1, 5 and 6, wherein a clip or retaining member is mounted with respect to the aperture to engage with the restraining strap to substantially secure the restraining strap in position with respect to the

20 attachment means so as to prevent sliding movement of the restraining strap when the clip or retaining member is engaged therewith.
10. A child restraint according to any one of claims 1 to 9, wherein each aperture has a semi-circular profile having a curved portion and a flatter portion.
11. A child restraint according to claim 10, wherein the semi-circular profile is configured

25 so that in use the flatter portion is at the base of the aperture.

2018260970 09 Nov 2018
12. A child restraint according to claim 6, wherein in use the restraining strap is configured to engage with its corresponding anchor point directly after exiting the aperture.
13. A child restraint for use in a vehicle, comprising:

5 a seat shell including a seating surface configured to receive a child; and a single attachment means, for a restraining strap not being a vehicle seat belt, to facilitate securement of the child restraint to a vehicle seat, located on each of opposing sides of the seat shell;

wherein each attachment means includes an aperture, having a continuous boundary,

10 located substantially midway between a front of the seat shell and a rear of the seat shell in use, whether the child restraint is in a forward facing or a rearward facing orientation, so as to provide a path for the restraining strap to extend over and across the seating surface, said path being substantially the same when the child restraint is in the forward facing and the rearward facing orientations.
15 14. A child restraint according to claim 13, wherein the restraining strap is a length of strap having an engagement member located at or adjacent each end thereof, each engagement member being configured to engage with an anchor point provided in a bight of the vehicle seat.

15. A child restraint according to claim 14, wherein each engagement member engages

20 with its corresponding anchor point on each opposing side of the seat shell to secure the child restraint to the vehicle seat.
16. A child restraint according to any one of claims 13 to 15, wherein a clip or retaining member is mounted with respect to the aperture to engage with the restraining strap to substantially secure the restraining strap in position with respect to the 25 attachment means so as to prevent sliding movement of the restraining strap when the clip or retaining member is engaged therewith.

2018260970 09 Nov 2018
17. A child restraint according to claim 14, wherein in use the restraining strap is configured to engage with its corresponding anchor point directly after exiting the aperture.
18. A child restraint for a vehicle, the child restraint comprising:

5 a seat shell configured to receive a child, the seat shell having a backrest and a seating surface within opposing sides: and attachment means located on each opposing side;

wherein each attachment means includes an aperture, the aperture located in the side to allow a vehicle seat belt to extend over and across the seating surface to facilitate

10 securement of the child restraint in each of a forward facing orientation and a rearward facing orientation.
19. A child restraint for a vehicle, the child restraint comprising:

a seat shell configured to receive a child, the seat shell having a backrest and a seating surface within opposing sides: and

15 attachment means located on each opposing side;

wherein each attachment means includes an aperture, the aperture located in the side to allow a restraining strap, not being a vehicle seat belt seat belt, to extend over and across the seating surface to facilitate securement of the child restraint in each of a forward facing orientation and a rearward facing orientation.
20 20. A child restraint according to claim 18 or 19, wherein in use the attachment means is located substantially in a central location of the seat shell.
21. A child restraint according to claim 18, wherein the vehicle seat belt comprise a lap and sash belt combined together or a lap belt.
22. A child restraint according to claim 19 or 20, wherein the restraining strap is a length

25 of strap having an engagement member located at or adjacent each end thereof, each engagement member being configured to engage with an anchor point provided in a bight of the vehicle seat.

2018260970 09 Nov 2018
23. A child restraint according to claim 22, wherein each engagement member engages with its corresponding anchor point on each opposing side of the seat shell to secure the child restraint to the vehicle seat.
24. A child restraint according to any one of claims 13 to 23, wherein the seat shell is

5 mounted on a base.
25. A child restraint for a vehicle, the child restraint being adapted for use in a rearward facing mode and a forward facing mode, the child restraint comprising:

a seat shell configured to receive a child therein, the seat shell having a backrest and a seating surface within opposing sides; and

10 an attachment means located on each opposing side;

the child restraint being adapted for use with a covering for the seating surface;

wherein each attachment means includes a hole having a continuous boundary, the hole comprising a recess formed through the side to provide a path for a vehicle seat belt to extend over the seating surface and beneath the covering when used;

15 and wherein the attachment means located on each opposing side is the sole attachment means in the child restraint for providing the path for the vehicle seat belt to facilitate securement of the seat shell to a vehicle seat in each of the forward facing and rearward facing modes.
26. A child restraint for a vehicle, the child restraint being adapted for use in a rearward

20 facing mode and a forward facing mode, the child restraint comprising:

a seat shell configured to receive a child therein, the seat shell having a backrest and a seating surface within opposing sides; and an attachment means located on each opposing side;

the child restraint being adapted for use with a covering for the seating surface;

25 wherein each attachment means includes a hole having a continuous boundary, the hole comprising a recess formed through the side to provide a path for a restraining

2018260970 09 Nov 2018 strap, not being a vehicle seat belt, to extend over the seating surface and beneath the covering when used;

and wherein the attachment means located on each opposing side is the sole attachment means in the child restraint for providing the path for the restraining strap 5 to facilitate securement of the seat shell to a vehicle seat in each of the forward facing and rearward facing modes.
27. A child restraint according to claim 25 or 26, wherein in use the attachment means is located substantially in a central location of the seat shell.
28. A child restraint according to claim 25 or 27, wherein the vehicle seat belt comprises

10 either a lap and sash belt combined together or a lap belt alone.
29. A child restraint according to any one of claims 25 to 28, wherein the seat shell is mounted on a base.
30. A child restraint according to any one of claims 2, 13 to 17 and 26 to 29, wherein an upper part of the boundary is curved.