Field of the Invention

The present invention relates generally to an ear- muff comprising a cup-shaped cap, which has an edge por¬ tion defining an opening, and an annular element which is arranged to extend along said edge portion, the cup- shaped cap and the annular element being secured to one another by a locking means. Background Art

A common type of hearing protector comprises two earmuffs and a headband connecting the earmuffs to one another.

A conventional earmuff usually comprises a cup- shaped cap, an annular bottom plate, a padded sealing ring which is connected to the bottom plate and arranged to abut against a user's head, and stuffing which can be made of foam plastic and is positioned in the cap. The cup-shaped cap and the annular bottom plate are tightly fixed to each other by a conventional snap lock. A con¬ ventional snap lock is provided, for instance, by the cap being provided with a projection extending along the opening portion of the cap. The projection is formed on the inside of the opening portion of the cap. The bottom plate has a connecting portion which is arranged to extend a certain distance into the opening portion of the cap. The connecting portion has on the outside a circum¬ ferential groove. The groove cooperates with the projec¬ tion to tightly hold the cap and the bottom plate toge¬ ther.

However, it has been found that two earmuffs which have been manufactured in the same way according to the description above have a tendency to exhibit different damping properties for sound in different frequency ranges. Differences in damping mean that a first earmuff

damps sound within a certain frequency range quite well while at the same time a second earmuff damps sound with¬ in the same frequency range relatively poorly.

This means in turn that there is a risk that the two earmuffs in one and the same hearing protector exhibit different sound damping capacities, which means that a user catches a certain sound in one way by one ear and in another way by the other ear. This is a drawback since a user has difficulty in determining the direction of sound, which may cause danger on a shopfloor.

Owing to the difference, it is also difficult to adjust an earmuff to a specific purpose. To adjust an earmuff to a specific purpose means, for instance, satis¬ fying a requirement that the capacity of damping sound in a certain frequency range be improved. The problem is, among other things, that different earmuffs of the same type damp, as mentioned above, sound in a certain fre¬ quency range to different degrees. An adjustment of an earmuff so that it has a good capacity of damping sound in a first frequency range means, in practice, that it is necessary to accept an inferior damping capacity in a second frequency range. The difference in the damping capacity of different earmuffs of the type described above can very well be in the same order as the distance between said first and second frequency ranges.

Summary of the Invention

In view of that stated above, an object of the pre¬ sent invention is to provide an improved earmuff. A special object of the invention is to provide ear- muffs which have a consistent sound damping capacity. By consistent sound damping capacity is meant, for instance, that two earmuffs which are of the same type and have been manufactured in the same way have essentially the same sound damping capacity.

A further object of the invention is to provide an earmuff which has improved sound damping capacity.

Another object of the invention is to provide a basic construction of an earmuff which allows great free¬ dom in design.

To achieve at least one of the above objects, and also other objects that will be evident from the follow¬ ing description, an earmuff as claimed in claim 1 is pro¬ vided according to the invention, preferred embodiments being stated in the dependent claims .

In particular an earmuff is provided, comprising a cup-shaped cap, which has an edge portion defining an opening, and an annular element which is arranged to extend along said edge portion, the cup-shaped cap and the annular element being secured to one another by a locking means. The earmuff is characterised in that it further comprises at least one pressure-equalising means, which is arranged between and in contact with the cup- shaped cap and the annular element.

As a result, an improved earmuff is provided, in which tension or pressure between the cup-shaped cap and the annular element is distributed substantially uniform¬ ly around the opening portion of the cap. Effects of dif¬ ferences with respect to geometry, rigidity or the like which, for instance, arise in manufacture and which would result in differences in the transmission of sound between the cap and the annular element are eliminated to a great extent owing to the pressure-equalising means. A particular advantage of the inventive earmuff is that two earmuffs achieve a similar sound damping capacity. A fur¬ ther advantage is that the earmuff can be adjusted to different surroundings and to sound in specific frequency ranges . It also brings the advantage that a user per¬ ceives sound in the same way by both ears, which is advantageous since it will be easier to identify where a source of sound is positioned. It should be noted that annular is not necessarily limited to a circular shape, but the ring shape defines an element which extends around a central opening. The

ring shape can be more or less square or have other shapes. The annular element can be formed with different cross-sectional shapes depending on what other components it is arranged to cooperate with. Said at least one pressure-equalising means is arranged in an engaging surface between the cup-shaped cap and the annular element of said locking means. By the pressure-equalising means being arranged in an engaging surface, it will provide a pressure-equalising power transmission between the cap and the annular element, which adds to consistent transmission of sound.

The engaging surface defines a geometric band extending along the opening and having a width, the pressure-equalising means being arranged to extend along the opening along a first portion of the width of the engaging surface. By the pressure-equalising means extending along the opening, consistent force transmis¬ sion is obtained along the entire circumference of the cap and the annular element. The cup-shaped cap and the annular element can, along a second portion of the width of the engaging sur¬ face, abut directly against each other, which brings the advantage of obtaining a dimensionally stable contact between the cap and the annular element. The pressure-equalising means may comprise an annular element, which brings the advantage that the pressure-equalising means can be manufactured in a simple manner. By annular is meant that the pressure-equalising means has in the longitudinal direction the shape of a ring. This also means that the pressure-equalising means helps to ensure tightness in the connection between the cup-shaped cap and the annular element. Thus the tole¬ rances in the manufacture of the cup-shaped cap and the annular element can be increased. The pressure-equalising means may comprise an elas¬ tic insert, which means that the pressure-equalising means can be manufactured in a simple and inexpensive

manner. In addition, the elastic insert may help to main¬ tain tension in the locking means.

The elastic insert can be made of a polymer mate¬ rial, which brings the advantage that it can be manu- factured in a simple and inexpensive manner.

To fasten the cup-shaped cap and the annular element to one another in a simple, inexpensive and time-effec¬ tive manner, the locking means may comprise a snap lock. By snap lock is meant a lock comprising two parts. In locking, one of the parts is pressed onto the other part and snaps, by temporary elastic deformation, onto this other part and locks the two parts relative to one another. In a preferred embodiment, a snap lock is pro¬ vided by the cap being provided with a projection which extends along the opening portion of the cap. The projec¬ tion is formed on the inside of the opening portion of the cap. The annular element has a flange which is arranged to extend a certain distance into the opening portion of the cap. The flange has on its outside a cir- cumferential recess. The recess cooperates with the pro¬ jection to tightly hold the cap and the annular element together.

The pressure-equalising means can be arranged in said recess. The location of the pressure-equalising means brings the advantage that it simplifies mounting since it easily retains its position in the recess. It also brings the advantage that the pressure-equalising means is located in the position in which the greatest power transmission between the cap and the annular ele- ment usually occurs.

The elastic insert can have a circular, square, triangular or H-shaped cross-section. The elastic insert can have a homogeneous or hollow cross-section, such as a tube of various cross-sectional shapes.

Brief Description of the Drawings

A preferred embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings . Components having a similar function have been given the same reference numerals throughout the text.

Fig. 1 is a side view of a hearing protector com¬ prising two inventive earmuffs.

Fig. 2 is an exploded view of an inventive earmuff. Fig. 3 is a cross-sectional view of the earmuff in Fig. 1 along line I-I.

Fig. 4 is a cross-sectional view of an enlarged part of Fig. 3.

Description of a Preferred Embodiment

Fig. 1 illustrates a hearing protector 1 comprising a headband 2 and two earmuffs 3. The earmuffs 3 are con¬ nected to the respective ends of the headband 2. In use, a user (not shown) places an earmuff 3 over each ear, the headband 2 holding the earmuffs 3 in place on the user's head.

An earmuff 3 is shown in more detail in Figs 2-4, to which reference is now made. The earmuff 3 comprises a cup-shaped cap 4, stuffing material 5, a pressure- equalising means 6, an annular element 7 and a sealing ring 8. The stuffing material 5 is arranged in the cavity of the cup-shaped cap 4. A farther side, the side facing away from a user, of the annular element 7 is fixed to the cup-shaped cap 4 by a locking means 9 in the form of a snap lock 9. The snap lock 9 comprises a first and a second part 10, 11. The first part 10 is positioned on the cup-shaped cap 4 and the second part 11 is positioned on the annular element 7. The pressure-equalising means 6 is positioned in an engaging surface between, and is in contact with, both the first and the second part 10, 11 of the snap lock 9, see Fig. 3 and Fig. 4. The sealing ring 8 is fixed by a second snap lock (not shown) to a

front side, the side facing a user, of the annular ele¬ ment 7.

The cap 4 is in the form of a cup and has an edge portion 12 which defines an opening 13 of the cap. As shown in Fig. 2 and Fig. 3, the opening 13 of the cap 4 defines a space which resembles a space as enclosed by a half-sphere.

On the outside of the cap 4, that is the side facing away from the user and from the enclosed space, two fas- tening means 14 are positioned. The fastening means 14, which can be, for instance, two pins, are arranged to fasten the headband 2 to the cap 4.

On the inside of the cap 4, that is the side facing a user and the enclosed space, the first part 10 of said snap lock 9 is positioned. The first part 10 comprises a projection 15 which extends around the inside of an open¬ ing portion 16 of the cap 4. The opening portion 16 has an engaging surface which in the assembled state is adapted to engage and abut against on the one hand the pressure-equalising means 6 and, on the other, a corre¬ sponding engaging surface of the second part 11 of the snap lock 9.

In the example shown, the projection 5 and the cap 4 are made in one piece of a polymer material. It will be appreciated that the parts can be separately made and subsequently assembled in a suitable manner, for instance by welding or gluing.

The annular element 7 has a front side and a rear side, the front side being the side facing the sealing ring 8 and thus also a user, and the rear side being the side facing the cap 4 and thus also facing away from a user. The annular element 7 which is called bottom plate has a through hole 17 extending from the front side to the rear side. The second part 11 of the snap lock 9 is formed on the rear side of the annular element 7. The second part 11 extends as a circumferential flange 18 around the

annular element 7. The second part 11 has an extent corresponding to the shape of the opening 13 of the cup- shaped cap 4. A recess 19 is formed on the side of the flange 18 which faces away from the through hole 17. The recess 19 has a shape supplementary to the projection 15 of the cup-shaped cap 4. On the same side as the recess 19, the flange 18 has an engaging surface. In Figs 2-4, the surface of the recess 19 is included in the engaging surface, which in the assembled state is in contact with the pressure-equalising means 6 and the engaging surface of the cap 4. It should be mentioned that the second part 11 can be formed with a smaller height relative to corre¬ sponding parts according to prior art, which brings the advantage that the requirements as to the shape of the cap 4 are reduced.

The pressure-equalising means 6 consists in the shown example of an annular flexible insert 6. The insert 6 is circular in cross-section. The insert 6 is arranged between the cup-shaped cap 4 and the annular element 7. The insert 4 is in contact with both the cup-shaped cap 4 and the annular element 7 in the respective engaging surfaces. The location of the pressure-equalising means

6 between the cup-shaped cap 4 and the annular element

7 results in the pressure between the first and the second part 10, 11 of the snap lock 9 being equalised. The pressure-equalisation results in the effect of any irregularities in the first and the second part 10, 11 of the snap lock 9 being eliminated or in any case reduced. The pressure-equalising means 6 also brings the advantage that the tolerances in the manufacture of the cup-shaped cap 4 and the annular element 7 can be increased, which results in reduced costs of manufacture. The reason for this is that the pressure-equalising means 6 also helps to provide a seal between the cap 4 and the annular ele- ment 7.

The pressure-equalising means 6 is positioned in the recess 19 of the second part 11 of the annular element 7,

which is illustrated in Fig. 3 and Fig. 4. In the mounted state, the projection 15 of the snap lock 9 of the cap 4 presses the pressure-equalising means 6 against the recess 19 of the snap lock 9 of the annular element 7. It will be appreciated that the present invention is not limited to the embodiments described above and that a person skilled in the art can modify the above- described earmuff within the scope of the invention as defined in the claims . For instance, it is possible to place the elastic insert also outside the recess which is adapted to pro¬ vide the snap lock function. In such an embodiment, the flange of the annular portion is advantageously provided with a further groove which is adapted to accommodate the annular elastic insert.