Stethoscopic headphone set

A stethoscopic headphone set comprising two identical arms each provided with an earphone, Which arms terminate in a hinged connecting element including a wire spring. The connecting element essentially comprises two mirror-symmetrical identical coupling members which cooperate with each other via a gear transmission and which fully enclose the wire spring. The wire spring may comprise two helical springs which are mirror-symmetrical, each helical spring being incorporated in a coupling member.

The invention relates to a stethoscopic headphone set comprising two 
identical arms each provided with an earphone, which arms terminate in a 
hinged connecting element including a wire spring. 
Such a headphone set is already known from Swiss Pat. No. 3343. The arms of 
this headphone set form part of a wire spring bent in the same manner as a 
safety pin. 
In order to obtain an identical deflection of the two arms, the present 
invention is characterized in that a hinged connecting apparatus (element) 
essentially comprises two identical coupling members arranged in mirror 
image which cooperate with each other via a gear transmission and which 
fully enclose the wire spring. 
This construction has the advantage that the tendency of the headphone set 
to become lopsided is substantially reduced and that an equal light 
pressure will be experienced on both of the ears of a user. 
An embodiment of the invention is characterized in that the wire spring 
arrangement comprises two helical springs, which are mirror-symmetrical, 
each helical spring being incorporated in a coupling member. 
Preferably, each coupling member comprises a disc which is provided with 
teeth along a part of its circumference so that said discs, i.e. coupling 
members, cooperate with each other via said teeth. Each disc has a 
cylindrical recess which is adapted to accommodate a respective one of the 
two helical springs with one tangentially extending end of the helical 
spring being retained behind a cam of the disc. An oblong mount for 
receiving an arm is secured to the disc. 
The two helical springs can be manufactured from a single wire; for this 
purpose the two adjacently and mirror-symmetrically disposed ends are 
interconnected. In other words, a wire spring arrangement is provided for 
exerting a force on the arms of the headphone set and which comprises a 
wire spring having first and second helical spring parts with their axes 
in parallel and mechanically coupled to first and second disc-shaped 
coupling members, respectively, and wherein said axes coincide with the 
axes of rotation of the corresponding coupling members, respectively. Each 
coupling member may include a recess in which the respective spring part 
is located. By having one of the coupling members cooperate with a switch 
in the supply lead to the headphone set, the earphones can be switched off 
in a rest position. 
By way of example, an embodiment of the invention will be described in more 
detail with reference to the accompanying drawings.

In FIGS. 1 and 2, which are depicted on an enlarged scale, the coupling 
members 1 and 2 are constructed and arranged mirror-symmetrically. Each 
coupling member comprises a disc 3 and 4 respectively, which is provided 
with teeth 5 and 6 respectively over an angle of approximately 120.degree. 
along the circumference. These discs 3, 4 constitute a linking gear 
transmission which is effective through this angle. 
Furthermore, the discs 3, 4 are provided with tapered tubular mounts 7 and 
8 respectively, in which mounts tubular metal arms 9 and 10 are clamped. 
The other ends (see FIG. 3) of the arms are each provided with an earphone 
30, which in this example is a mini-electret capacitor loudspeaker. The 
sound of each earphone 30 is transmitted to the ear of the person wearing 
it via a perforated ball-joint 31 and an earphone 32 which is secured 
thereto. 
Each disc 3 and 4 has on one major surface a cylindrical recess 11 and 12 
respectively, in which the cylindrical helical springs 13, 14 are mounted, 
respectively. The axis of spring 13 coincides with the axis of the disc 3, 
i.e. the axis of coupling member 1, whereas the axis of spring 14 
coincides with the axis of disc 4 or coupling member 2. The two helical 
springs 13 and 14 are manufactured from a single piece of wire. The spring 
ends 15, 16 are disposed behind associated cams 17, 18, which form a part 
of the discs 3, 4. The other ends of the springs constitute a kinked 
connection spring 19. 
The coupling members 1 and 2 are accommodated in a flat thin-walled housing 
20 which consists of two shells. This housing furthermore comprises a 
number of electrical connectors 21, to which the two earphones are 
connected by leads via arms 9, 10 and coupling members 1 and 2 (leads not 
shown). 
This connector includes a microswitch 22 which cooperates with the coupling 
member 1 and which is open in the rest position, that is when the arms 9 
and 10 are disposed nearest one another, and which is closed in the 
operating position, that is with the arms in the spread position. 
In the first (rest) position the earphones are disconnected from the 
electrical connectors 21. 
In FIG. 3 an additional box 33 which contains an infrared receiver 34 is 
depicted for use in a system that includes a transmitter operating at 
frequencies in the infrared frequency domain. This box may be connected to 
the same connector 21 as the lead for direct connection to for example an 
associated dictation machine. 
The wire spring arrangement exerts a force on the arms that counteracts the 
deflection of the arms 9 and 10. This deflection is the same for each of 
the arms and can be adjusted very smoothly as a result of the gear 
transmission which is provided.