Case middle/horn connection device for a watch

1. A case middle/attachment piece connection device for a watch, comprising:

an attachment piece having a first connector; and

a case middle having a second connector, the first connector being configured to cooperate with the second connector to attach the attachment piece to the case middle, wherein:

the first connector comprises a tongue with a recess,

the second connector comprises a groove with an undercut portion, the undercut portion being configured to lodge inside the recess of the tongue,

the case middle and the attachment piece are configured to be made integral when the undercut portion of the second connector is lodged inside the recess of the tongue of the first connector, and

wherein the case middle and the attachment piece are irreversibly joined to each other.

2. The case middle/attachment piece connection device claimed in claim 1 , wherein the tongue has a rest position, and wherein the tongue is configured to deform elastically when inserted into the groove, the tongue and the undercut portion being configured such that the tongue returns to its rest position when the undercut portion lodges in the recess of the tongue.

3. The case middle/attachment piece connection device claimed in claim 2 , wherein the groove also comprises an undercut portion on which the tongue is configured to bend elastically when the tongue is inserted into the groove.

4. The case middle/attachment piece connection device according to claim 1 , wherein the recess is a through recess.

5. The case middle/attachment piece connection device according to claim 1 , wherein the case middle and the attachment piece are irreversibly joined to each other.

6. The case middle/attachment piece connection device according to claim 1 , wherein the first connector comprises a tenon and the second connector comprises a mortise, the mortise being configured to guide the tenon when the first connector of the attachment piece is placed in contact with the second connector of the case middle.

7. The case middle/attachment piece connection device according to claim 6 , wherein the first connector comprises two or more tenons and the second connector comprises two or more mortises, the mortises being configured to guide the tenons when the first connector of the attachment piece is placed in contact with the second connector of the case middle.

8. The case middle/attachment piece connection device according to claim 1 , wherein the second connector comprises one or more support parts for the tongue of the first connector in order to limit the elastic deformations of the tongue when the undercut portion is lodged in the tongue recess.

9. The case middle/attachment piece connection device according to claim 1 , wherein the tongue is made of steel.

10. The case middle/attachment piece connection device according to claim 1 , wherein the attachment piece is moulded around the tongue, the moulding being made from a plastic material.

11. The case middle/attachment piece connection device according to claim 1 , wherein the case middle is machined, and the second connector is machined.

12. A method of attachment of a case middle and an attachment piece with the case middle/attachment piece connection device according to claim 1 , the method comprising:

insertion of the first connector of the attachment piece into the second connector of the case middle such that the undercut portion lodges inside the recess of the tongue.