Universal hearing-aid volute holder with conical extension but without auditory duct, and geometrical method of making the same
The present demands of voice communication require an even closer, less disturbed hearing (see recorders, radio receivers, simultaneous translators, mobile phones, ear prosthesis, etc.) .
For this purpose, several devices to fit transducers of different types on ear have been designed.
Holders supporting such devices, however, do not ever find a suitable location in the ear because of instability, discomfort, and roughness.
Among such holders, those engaging the auditory duct also cause an occlusive effect that prevents people from communicating.
Among the most suitable holders there should be numbered those for hearing aids which are formed of a volute suitably shaped for each user by the cast of the ear so as to reproduce the exact shape thereof .
The manufacturing of such holders can be extremely difficult, then expensive, in any case strictly personal, i.e. not adaptable to an ear other than that of the user concerned.
There are also holders with standard shape. They are provided with an extension fitted to the auditory duct in order to provide a better stability. However, such extension is almost ever a hindrance in the acoustic applications because of the known, troublesome, occlusive effect.
On the other hand, if such extension is lacking, the stability unavoidably fails.
For such reasons, the holders mentioned above did not have further applications. The present industrial invention seeks to provide a standard anatomic device that does not engage with the auditory duct but is only placed into the concha auricolae in a steady, comfortable, safe, functional manner . The technical solutions resulted from a deep study of the ear that allowed some common points to be singled out, such as the intertragic fissure, the slit formed by the anthelix with its upper radix and the almost circular portion formed by the anthelix in its lower tract .
Therefore, the particular shape, the size ratio, the different inclinations, and the relieves of the device are essential to achieve the desired purposes: stability, tightness, comfort, positioning ease, handy use .
The device has been developed considering such parameters detected through the study of a very high number of ears so as to allow a geometrical method to be carried out and a standard volute holder to be proportioned.
It is made of rigid, biocompatible plastic material with two standard sizes so as to be adaptable to almost all of the ears with different size and shape. The volute holder looks like a structure having essentially two faces, one directed to the outside of
the ear, the other to the inside, both faces, in particular the inner face, having particularly complex shapes .
The accompanying drawings show such shapes with the nearest possible approximation.
Fig. 1 shows the outside face remote from the ear having a circular shape formed of a circular crown (1) including a lowered circular portion (2) . The circular crown has two diametrically opposed projections (3) and (4) placed at the upper and the lower sides, respectively: the upper projection (3) has the shape of a semicircular tab and the lower projection (4) has the shape of a cone with two side slots (5) and (6) .
Fig. 2 shows the inside face having a wide groove (7) which extends between two relieves (8) and (9) with different heights, the higher relief (8) having an elongated hole (10) at its top.
Fig. 3 shows a side perspective view of the device in which face (11) of relief (8) can be seen.
Fig. 4 is still a perspective view from a different angle of sight.
Fig. 5 is the section of an ear provided with the volute holder showing that the auditory duct is not crossed by such holder.
Fig. 6 shows a front view of an ear with the volute holder.
Fig. 7 shows an ear for a better understanding of the anatomic parts to which the volute holder is applied, in which the concha is indicated at (12) , the helix at (13) , the anthelix at (14) , the tragus at (15) , the antitragus at (16) , and the antitragic fissure at (17) .
The device described and shown resulted from a careful study of the ear in order to allow a portion of the ear to be used for receiving the device in a steady, comfortable manner.
A geometrical method has been developed for providing a proportional ratio among size, shape and dimension of the volute holder.
Such method is shown in Figs. 8 to 14 and is based upon the consideration that the anthelix has an almost circular curvature.
Starting from such curvature the relative circumference with centre at O is drawn (Fig. 8) . In order to anchor the volute holder being made to the lower portion of the anthelix, the insertion of the holder between tragus and antitragus using the intertragic fissure has been provided. To this
purpose, the conical projection (4) has been applied to the base circumference.
The construction of the latter is as follows : a point A at a distance from O double as long as the radius is determined on the extension of a radius of the circumference mentioned above. Tangents a and b to the circumference are drawn from point A, thus determining the taper of projection (4) having base BC, where B is the intersection of axis Y with the circumference and C is the symmetric point of B with respect to straight line AO.
For the sake of clarity system OXY has been provided so that axis Y is parallel to straight line a. Thereafter, in order to receive the protuberances of tragus and antitragus, side grooves (5) and (6) are formed in the projection by drawing circular arcs which are 2/3 as long as the original circumference and pass through the points of origin of the projection and the points in which the latter is connected to the vertex.
In order to anchor the volute holder to the upper portion of the anthelix, the characteristic slit of the latter is used by forming the semicircular tab (3) . Such tab is located at the portion diametrically opposed to projection (4) and is limited by an arc ED of a circumference with centre at B and radius equal to the diameter of the original circumference, and by the tangent to such circumference parallel to straight line a.
The geometrical drawing of Fig. 8 gives the main reference points for the construction of the inside face of the device.
This face is essentially characterized by the presence of relief (8) which is integral with projection (4) and is so shaped as to take up the portion near the auditory duct. The relief has an almost prismatic shape and an almost flat face (11) on one side of groove (5) (Fig. 3) and ends at the upper side in the elongated hole (10) .
In order to form such relief (Fig. 8) it is necessary first to determine point F on axis Y at a distance from 0 which is 3/4 as long as the diameter of the original circumference and then to draw the parallel to tangent b from such point by a length FG which is 9/10 as long as the radius of the original circumference .
The inclinations of face (11) and consequently the relief (8) with respect to the base plane are obtained from height h of face (11) over such plane (Fig. 10 and Fig. 11) which is 3/5 as high as the original diameter and by connecting points G and F to points H and A, respectively.
In the detail of Fig. 11 there is shown the elongated hole (10), the dimension ratio of which is 2:1 and, as shown, it takes up the whole top of relief (8) and is formed by drawing the perpendiculars to tangent b at points F and G (Fig. 9) .
In order to obtain the maximum curvature of relief (8) (Fig. 12) an arc of circumference connecting points I
and N1 is drawn with a radius which is 9/10 as long as the diameter of the original circumference . Fig. 12 shows a section of the relief along a plane perpendicular to the base passing through the centre of hole (10) and crossing the relief along its length, as shown also in Fig. 9.
Fig. 12 also shows the plane LI of hole (10) which is perpendicular to face (11) and the intersection of arc IN' which determines the maximum height of the relief. In order that the remaining inside part of the device adheres to the profile of the concha auricolae, relief (9) and groove (7) are formed.
Relief (9) is situated remote from projection (3) and is shown as a plane with two main inclinations. In order to form such inclinations (Fig. 13 and Fig. 14) point E' is connected to point N' and the centre O' of the circumference.
The heights of points E' and N" over the plane are 1/2 and 1/5 as high as the base diameter, respectively, and the height of 0 ' is 3/4 as high as the radius.
Fig. 13 also shows point E situated at a distance from base plane which is 1/3 as long as the diameter of the original circumference, the thickness of tab (3) being obtained by the difference between such distance and the distance of point E' from such plane.
In order that the device can better adhere to the wall of the concha auricolae, groove (7) receiving the radix of the helix is formed. It is formed by a wide depression connecting relieves (8) and (9) at both sides. Its slightly curved profile is formed by
connecting point N1 to O' and the latter to middle point Q of arc H'P' (Fig. 9) .
Points N' , O' and Q', the first two points having a known height, the third point having a height which is 1/4 as high as the radius of the base circumference, define the not even profile of the groove by their different heights.
At last, should the application require a tight sealing of the auditory duct, a fixed end (18) is provided at the top of relief (8) surrounding hole (10) capable of receiving an elastic seal (Fig. 15) . The size of the fitting members is omitted because the latter are not important for the dimensioning, and the circular portion (2) (Fig. 1) is also omitted because it is only the outline of a fixed joint which is dimensioned according to the type of application. The volute holder is applied by the simple operation of directing relief (8) to the auditory duct and fitting projection (3) into the fissure of the anthelix owing to the resilience of the auricle (Fig. 16) .
Once the device is located into the ear, hole (10) is situated at the entrance of the auditory duct without engaging the same and its positioning is steady, safe and functional.
The described volute holder can be used in a plurality of applications. One example is shown in Fig. 17 where it is used as support for receiving an acoustic transducer and another example is shown in Fig. 18 where an application as hearing aid can be seen.
According to what described and illustrated, the advantages of the volute holder of the present invention are self-evident:
- owing to its universal shape, it can be manufactured at an extremely low cost as it need not any cast;
- owing to the conical projection its positioning in the ear is steady and safe;
- it does not cause the troublesome occlusive effect because of the lacking of the extension normally inserted into the auditory duct;
- its positioning is readily and easily carried out as its anchoring points are situated only in the concha auricolae ;
- its safe, steady positioning allows it to be used for the application of particularly expensive, delicate devices, for example, hearing aids, radio receivers, caps, etc.;
- owing to the presence of the elastic seal, it can also be used in case a tight sealing is necessary. Shape and construction changes can be made to the present invention within the scope of the inventive concept which is defined by the appended claims.