Wrist watch having a bracelet attached to the watch casing by a hinge

A wrist watch has a bracelet connected to the watch casing by hinges. Each hinge comprises four lugs which are formed in one piece with the peripheral casing portion and rim portion of the casing, the lugs defining therebetween three spaces which are each occupied by one of three hinge elements provided at one end of the adjacent bracelet half. The casing is made of plastics material. A metal pivot pin extends through holes formed in the elements.

BACKGROUND OF THE INVENTION 
The present invention concerns wrist watches having a bracelet attached to 
the watch casing by hinges. 
The term "hinge" is used to denote a pivot connection between two 
components and comprising at least one first element fixed to one of the 
components, at least one second element fixed to the other component, and 
at least one third element forming a pivot member. 
French Pat. No. 2 251 291 discloses such a wrist watch, wherein the hinges 
are each formed by an element which is fixed to the casing of the watch, 
and two elements which are fixed to the bracelet and which are spaced from 
each other, these two elements flanking the element which is fixed to the 
casing. A pivot pin passes through all three elements, thereby defining a 
pivotal axis. 
Thus, in the known construction, each hinge comprises only a single element 
which is fixed with respect to the watch casing, that element taking up 
the space between the two elements which are fixed to the bracelet. The 
pivot pin subjects the hinge element which is fixed with respect to the 
watch casing not only to tensile stresses which are at right angles to the 
axis of the pin, but also to twisting stresses which are centered at the 
middle of the pin. Accordingly, this known construction cannot be applied 
to watch casings of plastics material, as plastics material generally has 
poor strength against twisting stresses. 
In addition, Swiss Pat. No. 405 170 describes a wrist watch in which the 
bracelet is formed by a plurality of rigid elements, probably of metal, 
which are each held in contact with an adjoining rigid element, and 
non-rigidly connected to the latter. The end elements of the bracelet, 
which are adjacent to the watch casing, are welded to the casing and are 
attached to the adjacent bracelet elements by means of a pin. Such a 
construction, which therefore does not use hinges as defined hereinbefore, 
is also such that it cannot be applied to a casing of plastics material. 
In fact, the end elements of the bracelet, which are welded to the watch 
casing, are subjected to mechanical twisting stresses by the immediately 
adjoining bracelet elements to which they are non-rigidly connected and 
with which they are held in contact. 
SUMMARY OF THE INVENTION 
The main object of the present invention is therefore to provide a wrist 
watch in which the hinges connecting the bracelet to the casing of the 
watch are compatible with using a watch casing made of plastics material. 
In accordance with the invention, at least the peripheral casing portion of 
the watch casing is made of plastics material and each hinge comprises n 
first mutually spaced elements (n being an integer greater than 2) which 
are formed in one piece with the peripheral casing portion, and n-1 second 
elements which are fixed with respect to the bracelet and which each 
occupy a space between two adjacent first elements. 
By virtue of the above-indicated construction, the pivot member of the 
hinge in practice subjects the first elements only to tensile stresses 
which are at right angles to the pivotal axis. 
In accordance with a preferred embodiment, each hinge comprises four first 
hinge elements which are formed integrally with the peripheral casing 
portion of the watch casing, and three second hinge elements which are 
formed integrally with the bracelet half adjoining the hinge, each of said 
elements having a through hole, all the holes being disposed in alignement 
and having a straight pivot member passing therethrough, the pivot member 
being a drive fit in the holes in the second elements while it is engaged 
with clearance in the holes in the first hinge elements.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The wrist watch shown in the drawings comprises a watch casing 1 and a 
bracelet, of which only one bracelet half is shown, at 2. The casing 1 
comprises a bottom or back 3a, and a peripheral casing portion 3b with a 
rim which retains a glass 4. 
In the illustrated embodiment, the back 3a and peripheral portion 3b of the 
casing 1 are made of plastics material in one piece 3, referred to 
hereinafter as the casing body. In this embodiment, the glass 4 is made of 
a transparent plastics material and is fixed on the casing portion 3b in 
fluid-tight manner. 
The casing body 3 is advantageously made from one of the following three 
plastics materials: that which is known as ABS (acryl butadiene styrene), 
that which is known as ASA (acryl styrene acrylester) and that which is 
known as SAN (styrene acrylonitrile), while the glass 4 may be made of a 
transparent acrylic resin such as that known under the trademark 
Plexiglas. The bracelet half 2 may be made either of an elastomer, or a 
plastics material such as PVC (polyvinyl chloride). The back 3a of the 
casing could be made of metal, set into the peripheral portion 3b. 
As will be seen from the drawings, the bracelet half 2 is attached to the 
watch casing 1 by a hinge 5. The hinge 5 comprises an array of four first 
fixing elements or lugs 6 which are moulded with the casing body 3, the 
elements 6 being disposed in a side-by-side and spaced relationship and 
each having a through hole 7 of circular section, the holes 7 all being of 
the same diameter and being mutually aligned. The hinge 5 further 
comprises three second fixing elements 8 which are formed in one piece 
with the bracelet 2, each element 8 being respectively engaged in a space 
9 defined between two adjacent first elements 6. Each element 8 has a 
through hole 10 of circular section. The holes 10 are aligned with each 
other and, when the elements 8 are set into the spaces 9, they are also 
aligned with the holes 7 in the first hinge elements 6. A straight metal 
rod or pin 11 of circular section passes through the aligned holes 7 and 
10, to form the pivot member of the hinge. In order to prevent any 
tangential stress from being applied to the first hinge elements 6, the 
rod 11 is a drive or interference fit in the holes 10, while it is a free 
fit in the holes 7. 
In order to hide the hinge elements 6 and 8, at its side towards the glass 
4, the peripheral casing portion 3b is provided with a cover wall portion 
3c which is of such a size as to overhang and mask the hinge elements 6 
and 8, when viewed from above. 
The cover portion 3c which is formed by moulding with the casing body 3 
connects the first hinge elements 6 together and thus contributes to 
enhancing the mechanical strength of the first hinge elements 6. The cover 
portion 3c has a free edge as shown at 3d, which is formed by a part of 
the external surface of the cover wall portion, that faces towards the 
back of the watch casing, the edge 3d being disposed at a position remote 
from the centre 1a of the watch casing 1. The free edge 3d, the 
cross-section of which is substantially in the form of a circular arc, 
lies substantially flush with the end 6a of the hinge elements 6, which is 
remote from the centre 1a of the watch casing. 
As will be better seen from FIGS. 2 to 4, transversely with respect to the 
hole 10, each second hinge element 8 is of a cross section, the periphery 
of which comprises a first arcuate portion 12 centered on the geometrical 
axis of rotation 5a of the hinge 5, a straight portion 13 substantially 
normal to the general plane 2a of the bracelet half 2, a second arcuate 
portion 14 which is also centered on the axis 5a, and a second straight 
portion 15 which constitutes an extension of the internal surface 2b of 
the bracelet half 2. The internal surface 2b is the surface which is 
intended to be in contact with the wrist of the person wearing the watch. 
The first arcuate portion 12 has a radius R that is substantially equal to 
the distance between the geometrical axis 5a of the hinge 5 and the free 
edge 3d of the cover portion 3c. That particular dimension avoids a space 
remaining between the elements 8 and the edge 3d, which is unattractive 
from the aesthetic point of view. The first arcuate portion 12 is 
connected to the upper surface 2b of the bracelet half 2, by a regular 
curve 16. At its opposite end, the arcuate portion 12 is connected to the 
substantially straight portion 13. 
The radius r of the second arcuate portion 14 is less than the radius R of 
the arcuate portion 12. The radius r is substantially equal to the 
distance between the geometrical axis 5a of the hinge 5 and an external 
and substantially flat surface 17 of the peripheral casing portion 3b, the 
surface 17 delimiting each space 9, in a direction towards the centre 1a 
of the casing 1. The second arcuate portion 14 is connected on the one 
hand to the first straight portion 13 and on the other hand to the second 
straight portion 15 of the cross section of an element 8. The straight 
portions 13 and 15 are spaced from the geometrical axis 5a by a distance 
substantially equal to r. Finally, in the illustrated embodiment, the two 
arcuate portions 12 and 14 of the cross section of an element 8 are each 
of an angular extent that is substantially equal to 90.degree.. 
By virtue of the particular configuration of the hinge elements 8 and the 
particular configuration, as shown in the drawings, of the wall portions 
defining the spaces 9, the bracelet half 2 can be pivoted relative to the 
watch casing 1 through a maximum angle of 90.degree. from a first limit 
position as shown in FIGS. 1 and 2, in which the bracelet half 2 extends 
parallel to and substantially in the line of the general plane 1b of the 
casing 1, to a second limit position as shown in FIG. 4, in which the 
bracelet half 2 extends substantially perpendicularly to the general plane 
1b of the casing 1. The bracelet half 2 is stopped in its first limit 
position by the flat surface 13 (defined by the cross-sectional portion 
13), coming into a position of abutment with the external surface 17. The 
bracelet half 2 is stopped in its second limit angular position by the 
flat surface 15 (defined by the cross sectional portion 15), coming into a 
position of abutment with the surface 17 which thus forms a 
counter-abutment means. 
It will be appreciated that the invention is not limited to the embodiment 
described hereinbefore with reference to FIGS. 1 to 4 but that in contrast 
it extends to any other embodiment which falls within the scope of the 
principle defined by the claims accompanying this description. In 
particular, it would be possible for the pivot member 11 not to be a drive 
fit in the holes 10 in the hinge elements 8, but to be simply held axially 
in the holes 10 by any suitable means. For example, in the portions of the 
member 11 which are disposed in the holes 10, the member 11 may be smaller 
in diameter than the diameter of the portions thereof that are fitted in 
the holes 7 in the first hinge elements 6. If in addition the diameter of 
the holes 10 is smaller than the diameter of the abovementioned portions 
of the member 11, the annular steps which are thus formed between the 
parts of the axis member 11 which are of different diameters act as means 
for axially stopping the member 11 with respect to the second hinge 
elements 8.