The present disclosure relates to a hearing protection ear cup assembly for partial sound attenuation.

Background of invention

Hearing protection refers to devices used to protect the ear from external noise.

Earmuffs are objects designed cover a person’s ears for hearing protection.

Advantages of using earmuffs, i.e. ear-covering hearing protection cups, include that they are more convenient for intermittent use than earplugs since they are typically more easily placed and removed from a position on the ears, and that they typically do not deform as earplugs do. Moreover, earmuffs tend to provide more efficient sound attenuation than earplugs and may protect against cold weather.

There are also a number of known limitations and disadvantages associated with ear covering cups used as hearing protection. One is the fit. A proper fit of the earmuffs on the head of the wearer is essential for providing adequate hearing protection. The earmuffs should seal well against the head and should fully cover the outer ear. If sound leaks under the earmuff, the effectiveness may be negatively affected.

When an individual wears earmuffs, the device can moreover be displaced from the original and proper position on the ear. This is especially common when the individual moves, which may be the case for example at a workplace, which requires physical movement, or if a child or adolescent wears the device in school.

Another problem of conventional earmuffs is that, although they may well serve the purpose of reducing sound efficiently, but at the same the user is isolated and disconnected from for example speech. For this reason many earmuff wearers, for example at noisy workplaces, wear conventional cups with hard covers and lift them off when they need to communicate. Besides the fact that it adds an extra task to control and perform, it also requires that the user makes a decision about when he needs to communicate. When the cups have been lifted to allow sound to reach the ear and enable communication, after the communication the cup needs to be placed tightly around the ear again with the risk of not being ideally placed in a sealing position every time.

Summary of invention

The present disclosure relates to a hearing protection ear cup assembly for partial sound attenuation, comprising:

- an outer cup member having a rigid portion and at least one opening; and

- a resilient member extending along an inside of the outer cup member, said resilient member comprising at least one distal outer portion, wherein said at least one distal outer portion coincides with the at least one opening of the outer cup member; said resilient member further comprising an proximal flange portion for encircling an ear of a user.

An example of the presently disclosed hearing protection ear cup assembly is shown in fig. 1.

By having an opening in the rigid portion of the outer cup member, and letting a resilient member constitute part of the external surface, the hearing protection ear cup assembly can be made partially sound attenuating in the sense that it can be configured to allow a suitable level of the surrounding sounds to propagate to the wearer’s ears. The idea is that the hearing protection ear cup assembly not necessarily is seen as a tool to block as much as possible of the surrounding sounds, but should allow the wearer to use the hearing protection ear cup in noisy environments and still be able to hear for example speech. Example of typical use environments includes schools, sports and concerts.

Preferably, the resilient member, which may be made of a dampening material, such as rubber or an elastomer, has a distal outer portion which coincides with the opening in the rigid portion of the outer cup member. Seen from the outside, the outer surface of the assembly may therefore be a surface which has a hard portion for blocking as much of the external sound and noise as possible, and a soft portion which attenuates some of the sound but allows the user to hear for example speech. The resilient member may have material and structural properties to improve speech clarity and/or sound quality. The resilient member may be adapted to reduce, but not entirely eliminate, external sounds. Moreover, in the first embodiment of the presently disclosed hearing protection ear cup assembly, the resilient member extends along the inside of the outer cup member and has a proximal flange portion for encircling an ear of a user. The resilient member may thereby be a single piece, including both the soft, partially attenuating portion of the cup and the proximal flange portion for encircling and holding the cup in place on the ear. This arrangement allows for a light an easily manufactured assembly, which is also capable of holding the hearing protection ear cup assembly onto and around an ear of a user.

With the presently disclosed arrangement of an outer cup member in the form of a hard shell with at least one opening and resilient member extending along an inside of the outer cup member and having an outer portion fitting into the opening, it is possible to configure the two areas such that the outer cup member is configured to provide a first attenuation level, and the resilient member is configured to provide a second attenuation level. Similarly, it is possible to configure the assembly such that the outer cup member is configured to attenuate a first frequency range, and the resilient member is configured to attenuate a second frequency range. Thereby a sound filtering device may be obtained.

The assembly may further comprise an acoustic foam member arranged on the inside of the resilient member. The design of the resilient member, which extends along the inside of the outer cup member and finishes in a proximal flange portion, which may extend inwardly towards the center, may create a recess in which an acoustic foam element can be held in place. The resilient member may thus have three functions in one single piece: attenuate noise (soft attenuation by outer portion), holding the device onto the ear (flange portion) and holding the acoustic foam element in place.

These and other aspects of the invention are set forth in the following detailed description if the invention.

Description of drawings

Figs. 1 A-B show a cross-section of one embodiment of the presently disclosed hearing protection ear cup assembly.

Figs. 2A-B show a front view and a perspective view of one embodiment of the presently disclosed hearing protection ear cup assembly.

Fig. 3 shows a perspective view of one embodiment of the presently disclosed hearing protective device comprising two hearing protection ear cup assemblies. Figs. 4A-B show an embodiment of a headband connection member connecting a first headband part and a second headband part.

Detailed description of the invention

The present disclosure relates to a hearing protection ear cup assembly for partial sound attenuation. The hearing protection ear cup assembly comprises an outer cup member having a rigid portion and at least one opening; and a resilient member, wherein one outer portion of the resilient member is arranged in the opening of the rigid portion. Preferably, the resilient member extends along an inside of the outer cup member. The resilient member may end in a proximal flange portion oriented towards the user (in a wearing position) for encircling an ear of a user. The resilient portion may have several functions, as explained below. One is to balance the partial sound attenuation of the device. The hard shell may be arranged to block as much of external sound and noise as possible, whereas the resilient portion may be configured to function as a filter or dampening element.

As can be seen in for example fig. 2B, the at least one distal outer portion of the resilient member and the rigid portion of the outer cup member may form a

substantially smooth outer surface. The at least one outer portion of the resilient member and the rigid portion of the outer cup member may thereby be arranged to form one outer surface without substantial height differences and/or gaps between the at least one outer portion of the resilient member and the rigid portion of the outer cup member. If the outer cup member and the resilient member have the same color, it may give the impression that the outer shell is one single piece. However, given the different attenuation properties of the materials, a modified sound profile may be obtained in relation to a single piece made of the same material. The at least one outer portion of the resilient member and the rigid portion of the outer cup member form a substantially airtight surface.

Resilient member

The resilient member may be a single piece that serves a number of purposes in the assembly. In addition to providing a softer dampening of noise than the rigid cup, it may be used to hold the device onto the ear and hold a supplementary acoustic foam element in place. The at least one outer portion of the resilient member may have the shape of a membrane or a plate. This portion may have for example a substantially round or oval shape. The sound attenuation characteristics of the outer portion of the resilient member typically depend on the material and thickness of the outer portion, which, accordingly, may be selected to obtain certain sound profiles for specific user groups or specific noise environments. In one embodiment the resilient member is made of a rubber material or an elastomer.

Preferably, the resilient member extends along the inside of the outer cup member, as shown in for example fig. 1 A. Preferably, the resilient member is attached to the outer cup member. This can be achieved in a number of ways. For example the resilient member may be glued to the inside of the outer cup member and/or attached, such as clipped and/or glued to a proximal rim of the outer cup member.

The resilient member may be adapted to hold the hearing protection ear cup assembly onto and around an ear of a user. Preferably, the resilient member is configured to hold the hearing protection ear cup assembly in a fixed position on the ear of the user, preferably without further elements for holding the hearing protection ear cup assembly in place. This allows for a light design, which may comprise only the outer cup member and the resilient member for providing the partial sound attenuation. The fact that the resilient member may be adapted to hold the hearing protection ear cup assembly in place on the ear of the user allows the user to use one or two of the assemblies without an additional headband or strap.

The resilient member may end in a proximal flange portion.‘Proximal’ shall be construed as the side or direction towards the ear when the user wears the assembly. Consequently,‘distal’ refers to the opposite side or direction, i.e. away from the ear of the user. The flange portion of the resilient member for encircling the ear may have an annular shape. Moreover, the flange portion of the resilient member for encircling the ear may have a substantially oval shape or may be ear-shaped. In order to be held in place on the ear by itself, in addition to the flexible nature of the resilient material of which it is made, the resilient member may comprise a proximal section that is curved towards the center of the resilient member, thereby forming a shape for encircling the ear. Fig. 1 A shows an example of a proximal section (14) of the resilient member (4), wherein the proximal section (14) is slightly curved towards the center of the resilient member in the proximal end. This design may, if properly sized, be directly placed on the ear of a user without further elements for holding the hearing protection ear cup assembly in place. The flange portion of the resilient member may form an inwardly extending (towards the center) annular flange. The proximal flange portion may also be adapted to seal the hearing protection ear cup assembly against skin around the ear of the user. The inventor has realized that one piece made of a resilient material may suitable both for attenuating external sound, wherein the resilient element constitutes part of the outer surface of the assembly, to a suitable level, and for sealing the assembly against the skin of the wearer.

Outer CUD member

The outer cup member may be provided in the form of a cup-shaped hard shell. The shell may be made of any suitable material, such as a hard plastic material. One of ordinary skill in the art would be able to select a suitable material for this application.

The outer cup member preferably has a substantially oval shape, as shown in for example figs 2A and B. The opening(s) of the outer cup member may be centered on the rigid portion of the outer cup member.

The outer cup member comprises at least one opening in order to let some sound be less attenuated, or at least differently attenuated, than the rest of the cup. In one embodiment the presently disclosed hearing protection ear cup, the outer cup member comprises two openings. The openings may be through-openings. An example of an outer cup member having two openings (3) is shown in fig. 2A. In this embodiment the two openings are separated by an integral separation bar (15) of the outer cup member. In addition to blocking as much as much as possible of the external sound, the outer cup member functions as a rigid frame for the assembly.

Attenuation

The presently disclosed hearing protection ear cup assembly may be a passively attenuating device. This means that the material and structure of the device is used to decrease the sound level. By choosing specific properties of the parts of the presently disclosed hearing protection ear cup assembly and by arranging the parts in a specific way, specific filtering and/or sound profiles may be obtained. In one embodiment, the outer cup member is configured to provide a first attenuation level, and the resilient member is configured to provide a second attenuation level. Alternatively, or in combination, the outer cup member may be configured to attenuate a first frequency range, and the resilient member is configured to attenuate a second frequency range, preferably wherein the first frequency range and the second frequency are not the same.

In order to obtain the above functionality and features, the outer portion of the resilient member may be configured to attenuate external sound waves less than the rigid portion of the outer cup member. In one embodiment of the presently disclosed hearing protection ear cup assembly the resilient member is made of a material having lower attenuation efficiency than the outer cup member. By having an external surface, wherein a first area has a first set of properties and a second area has a second set of properties a specific attenuation profile may be obtained. In one embodiment the resilient member provides a sound filtering function. The partitioning of the first and second areas will typically have an impact on the attenuation profile of the assembly. In one embodiment the distal outer portion of the resilient member constitutes 10-50% of the total area of the external surface of the assembly, preferably 15-40% of the total area, more preferably 20-30% of the total surface.

In order to achieve suitable attenuation levels of the rigid portion of the outer cup member and the outer portion of the resilient member, the material and thickness of the rigid portion of the outer cup member and the outer portion of the resilient member have to be selected such that the outer cup member provides a predefined attenuation level and such that the outer portion of the resilient member provides a predefined attenuation level. In one embodiment, the rigid portion of the outer cup member is configured to attenuate external sound waves by a minimum predefined attenuation level, such at least 20 dB, preferably at least 30 dB, more preferably at least 40 dB, even more preferably at least 50 dB, most preferably at least 70 dB. The outer portion of the resilient member may be arranged to attenuate external sound waves less than the rigid portion of the outer cup. In one embodiment the outer portion of the resilient member is configured to attenuate external sound waves by a maximum predefined attenuation level, such not more than 50 dB, preferably not more than 40 dB, more preferably not more than 30 dB, even more preferably not more than 25 dB, most preferably not more than 20 dB.

Acoustic foam member

The hearing protection ear cup assembly may further comprise a foam member, such as an acoustic foam member, arranged on the inside of the resilient member. Fig. 1 B shows and example of a foam member (8) arranged on the inside of the resilient member (4). The foam member may be made of for example silicone foam, which is a synthetic rubber material. The foam member may comprise acoustic foam, which is a lightweight material, usually made from polyurethane foam, and/or polyether and/or polyester. Acoustic foam may be particularly useful to insert in the presently disclosed hearing protection ear cup assembly since it may be capable of improving speech clarity and sound quality. The purpose is to reduce, but not entirely eliminate, external sounds.

The foam member may be provided in the form of a replaceable foam cushion.

Preferably, it is not necessary to attach the foam member in a permanent position in the hearing protection ear cup assembly. The proximal flange portion of the resilient member may form a recess in which the foam member can be placed without falling out of the assembly.

Earmuff device with headband/strap

The present disclosure further relates to a hearing protective device comprising two hearing protection ear cup assemblies in any version described above. The hearing protective device comprises a headpiece in the form of a headband or a strap, wherein the headband/strap has a first end a second end, wherein the first end is connectable to a first of the two hearing protection ear cup assemblies and the second end is connectable to a second of the two hearing protection ear cup assemblies.

Preferably, the two ear cup assemblies do not need a headband or strap to stay on the ears, as described above. Preferably, the resilient member is configured to hold the hearing protection ear cup assembly onto the ear without further support. However, the headband/strap may be configured to provide pressure on the two hearing protection ear cup assemblies towards the head of the user, thereby ensuring proper airtight sealing of the hearing protection ear cup assemblies against the skin of the user.

As stated above, the outer cup member may comprise two openings separated by an integral separation bar of the outer cup member. Even if the outer cup member has two openings, on single resilient member can be used, as shown in for example fig. 1 A.

The outer portion of the resilient member may comprise two outer portions formed by a single resilient member, wherein the two outer portions are connected by a bridging section arranged on the inside of the separation bar. Moreover, the integral separation bar of the outer cup member may have an attachment opening. The resilient member, more specifically the bridging section of the resilient member, may comprise a receiving portion adapted to fit into the attachment opening. The receiving portion may be adapted to receive a connection member of a headband or strap of a headset or pair of earmuffs. The receiving portion may comprise the socket part of a ball and socket joint. The headband or strap may accordingly comprise the ball part of the same ball and socket joint.

In a further embodiment the headband further comprises a first headband part connectable to the first hearing protection ear cup assembly and a second headband part connectable to the second hearing protection ear cup assembly, the first and second headband parts connected to each other through a headband connection member. The headband connection member may comprise two attachment parts, wherein a first attachment part is connected to the first headband part and a second attachment part is connected to the second headband part. The first and second attachment parts may by slidably turnable in relation to each other, as shown in figs. 4A-B. This can be sued to fold the hearing protective device efficiently. The headband connection member may be configured in a use configuration, as shown in fig. 3, and in a storage configuration, as shown in fig. 4B. The first attachment part may have at least one tongue and the second attachment accordingly at least one corresponding groove for snap locking of the first and second attachment parts. More preferably, the first attachment part has two tongues, one in each end, whereas the second attachment part has two corresponding grooves. In this configuration there is a snap lock function both in the use configuration and in the storage configuration, wherein the first and second attachment parts have been turned 180° in relation to each other. The headband connection member may further comprises a central connection member between the first and second attachment parts, around which the first and second attachment parts can rotate, which also may hold the two parts together.

Detailed description of drawings

The invention will in the following be described in greater detail with reference to the accompanying drawings. The drawings are exemplary and are intended to illustrate some of the features of the presently disclosed hearing protection ear cup assembly, and are not to be construed as limiting to the presently disclosed invention. Figs. 1 A shows a cross-section of one embodiment of the presently disclosed hearing protection ear cup assembly (1 ). The assembly (1 ) has an outer cup member (2) having a rigid portion (2) and two openings (3). The outer cup member (2) has a proximal rim (7). A resilient member (4) has a distal outer portion (5). It can be seen that the resilient member (4) extends along the inside of the outer cup member (2). The resilient member (4) has a proximal section (14) which is slightly curved towards the center of the resilient member (4) in the proximal end. The proximal section (14) is exposed at a proximal side of the proximal rim (7) of the outer cup member (2). The resilient member (4) further comprises a proximal flange portion (6) for encircling an ear of the wearer. The assembly of the example further comprises a foam member (8) arranged on the inside of the resilient member (4). The proximal flange portion (6) of the resilient member (4) forms a recess in which a proximal rim (9) of the foam member (8) is held in place. A bridging section (1 1 ) of the resilient member (4) bridges the two outer surfaces of the distal outer portion (5). The bridging section (1 1 ) of resilient member (4) also serves as receiving portion (1 1 ) (socket) for receiving a ball (10). The ball part (10) is connected to a strap (12) through attachment element (13).‘C’ denotes the meaning of‘center’ or direction towards the center of the assembly.‘P’ and Ό’ denote the meaning of‘proximal’ and‘distal’, respectively. Fig. 1 B shows a different cross-sectional view of the same hearing protection ear cup assembly (1 ).

Figs. 2A-B show a front view and a perspective view of one embodiment of the presently disclosed hearing protection ear cup assembly (1 ). In addition to the features shown in fig. 1 , fig. 2 discloses the two openings (3) separated by an integral separation bar (15) of the outer cup member (2).

Fig. 3 shows a perspective view of one embodiment of the presently disclosed hearing protective device (16) comprising two hearing protection ear cup assemblies (1 ). The hearing protective device (16) comprises a headband (17A-B) comprising a first headband part (17A) and a second headband part (17B). The first and second headband parts (17A-B) are connected to each other through a headband connection member (18).

Figs. 4A-B show an embodiment of a headband connection member (18) connecting a first headband part (17A) and a second headband part (17B). Fig. 4A shows the headband connection member (18) in a partly folded configuration. Fig. 4B shows the headband connection member (18) in a completely folded, storage configuration. The headband connection member (18) has first attachment part (19) and a second attachment part (20). The first attachment part (19) has two extending tongues (21 ) and the second attachment part (20) has two corresponding grooves (not visible).

Further detail of the invention

1. A hearing protection ear cup assembly for partial sound attenuation,

comprising:

- an outer cup member having a rigid portion and at least one opening; and

- a resilient member extending along an inside of the outer cup member, said resilient member comprising at least one distal outer portion, wherein said at least one distal outer portion coincides with the at least one opening of the outer cup member; said resilient member further comprising a proximal flange portion for encircling an ear of a user.

2. The hearing protection ear cup assembly according to any of the preceding items, wherein the at least one outer portion of the resilient member and the rigid portion of the outer cup member form a substantially smooth outer surface, preferably wherein the at least one outer portion of the resilient member and the rigid portion of the outer cup member are arranged to form one outer surface without substantial height differences and gaps between the at least one outer portion of the resilient member and the rigid portion of the outer cup member.

3. The hearing protection ear cup assembly according to any of the preceding items, wherein the at least one outer portion of the resilient member and the rigid portion of the outer cup member form an airtight surface.

4. The hearing protection ear cup assembly according to any of the preceding items, wherein the at least one outer portion of the resilient member has the shape of a membrane or a plate.

5. The hearing protection ear cup assembly according to any of the preceding items, wherein the resilient member is made of rubber or an elastomer. 6. The hearing protection ear cup assembly according to any of the preceding items, wherein the resilient member is configured to hold the hearing protection ear cup assembly onto and around an ear of a user. 7. The hearing protection ear cup assembly according to item 6, wherein the resilient member is configured to hold the hearing protection ear cup assembly in a fixed position on the ear of the user, preferably without further elements for holding the hearing protection ear cup assembly in place. 8. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer cup member is configured to provide a first attenuation level, and the resilient member is configured to provide a second attenuation level.

9. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer cup member is configured to attenuate a first frequency range, and the resilient member is configured to attenuate a second frequency range, preferably wherein the first frequency range and the second frequency are not the same.

10. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer portion of the resilient member is configured to attenuate external sound waves less than the rigid portion of the outer cup member.

1 1 . The hearing protection ear cup assembly according to any of the preceding items, wherein the resilient member is made of a material having lower attenuation efficiency than the outer cup member.

12. The hearing protection ear cup assembly according to any of the preceding items, wherein the resilient member provides a sound filtering function.

13. The hearing protection ear cup assembly according to any of the preceding items, wherein the rigid portion of the outer cup member is configured to attenuate external sound waves by a minimum predefined attenuation level, such at least 20 dB, preferably at least 30 dB, more preferably at least 40 dB, even more preferably at least 50 dB, most preferably at least 70 dB.

14. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer portion of the resilient member is configured to attenuate external sound waves by a maximum predefined attenuation level, such not more than 50 dB, preferably not more than 40 dB, more preferably not more than 30 dB, even more preferably not more than 25 dB, most preferably not more than 20 dB.

15. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer cup member is a cup-shaped hard shell.

16. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer cup member has a substantially oval shape.

17. The hearing protection ear cup assembly according to any of the preceding items, wherein the outer cup member comprises two openings separated by an integral separation bar of the outer cup member.

18. The hearing protection ear cup assembly according to any of item 17, wherein the at least one outer portion of the resilient member comprises two outer portions formed by a single resilient member, wherein the two outer portions are connected by a bridging section arranged on the inside of the separation bar.

19. The hearing protection ear cup assembly according to any of items 17-18, wherein the integral separation bar has an attachment opening, and wherein the resilient member comprises a receiving portion adapted to fit into the attachment opening.

20. The hearing protection ear cup assembly according to item 19, wherein the receiving portion is adapted to receive a connection member of a headband or strap of a headset or pair of earmuffs.

21 . The hearing protection ear cup assembly according to any of items 19-20, wherein the receiving portion comprises a socket of a ball and socket joint. 22. The hearing protection ear cup assembly according to any of the preceding items, the at least one opening being one or two through-openings.

23. The hearing protection ear cup assembly according to any of the preceding items, wherein the at least one opening(s) of the outer cup member are located at the center of the rigid portion of the outer cup member.

24. The hearing protection ear cup assembly according to any of the preceding items, wherein the flange portion of the resilient member for encircling an ear of a user is annular.

25. The hearing protection ear cup assembly according to any of the preceding items, wherein the flange portion of the resilient member for encircling an ear of a user has a substantially oval shape or is ear-shaped.

26. The hearing protection ear cup assembly according to any of the preceding items, preferably wherein a proximal section of the resilient member is curved towards the center of the resilient member, thereby forming a shape for encircling the ear.

27. The hearing protection ear cup assembly according to any of the preceding items, wherein the flange portion of the resilient member forms an inwardly extending annular flange.

28. The hearing protection ear cup assembly according to any of the preceding items, wherein the resilient member is a single piece.

The hearing protection ear cup assembly according to any of the preceding items, wherein the flange portion for encircling an ear of a user is adapted to seal the hearing protection ear cup assembly against skin around the ear of the user.

30. The hearing protection ear cup assembly according to any of the preceding items, further comprising a foam member, such as an acoustic foam member, arranged on the inside of the resilient member. 31. The hearing protection ear cup assembly according to item 30, wherein the foam member is adapted to further attenuate external sounds.

32. The hearing protection ear cup assembly according to any of items 30-31 , wherein the foam member is a replaceable foam cushion.

33. The hearing protection ear cup assembly according to any of items 30-32, wherein the foam member has a proximal rim arranged in a fixed position in a recess formed by the proximal flange portion of the resilient member.

34. A hearing protective device comprising two hearing protection ear cup

assemblies according to any of items 1 -33 and a headpiece in the form of a headband or a strap, said headband/strap having a first end a second end, wherein the first end is connectable to a first of the two hearing protection ear cup assemblies and the second end is connectable to a second of the two hearing protection ear cup assemblies.

35. The hearing protective device according to item 34, wherein the headband/strap is configured for providing a pressure on the two hearing protection ear cup assemblies towards the head of the user, thereby improve sealing of the hearing protection ear cup assemblies against the skin of the user.

36. The hearing protective device according to any of claims 34-35, wherein the headband further comprises a first headband part connectable to the first hearing protection ear cup assembly and a second headband part connectable to the second hearing protection ear cup assembly, the first and second headband parts connected to each other through a headband connection member.

37. The hearing protective device according to claim 36, wherein the headband connection member comprises a first attachment part connected to the first headband part and a second attachment part connected to the second headband part, wherein the first and second attachment parts are connected to each other and slidably turnable in relation to each other. The hearing protective device according to claim 37, wherein the first attachment part has at least one tongue and the second attachment part has at least one corresponding groove for snap locking of the first and second attachment parts. The hearing protective device according to any of claims 37-38, wherein the headband connection member further comprises a central connection member between the first and second attachment parts, around which the first and second attachment parts can turn.