Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FLUIDTIGHT PUSH-BUTTON SWITCH
The present invention relates to a fluidtight push-button
switch.
In particular, the present invention relates to a fluid-
tight switch especially, but not exclusively, suitable for
fitment to a motor vehicle for indicating imperfect clos-
ure of a door.
Fluidtight switches of the aforementioned type usually com
prise an outer casing, and a button extending through a
wall on the casing and designed to perform a given work
stroke in relation to the same, between a normal extracted
position and a withdrawn position.
The button iB usually fitted with a cap of resilient mate-
rial connected in fluidtight manner to the outer casing,
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and a number of fixed conta~ts are usually fitted in fluidtight manner through the opposite wall on the casing to
the one fitted with the button. Said contacts are designed
~o cooperate with at least one contacit-carrying~element
mounted in mobile manner inside the casing and connected
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to the button so as to perform, in relation to the fixed
contacts, the same work stroke as the button, between the
open and closed position. Known fluidtight switches of the
aforementioned type present a number of drawbacks in terms
of both cost and performance.
The resilient waterproof cap on the button involves rela- -
tively high production and assembly co~ts, whereas direct
connection of the button and contact-carrying element in-
variably results in sealing problems. In connection with
the latter, it should be noted that the button/contact-
carrying element assembly operates like a piston, sliding
in fluidtight manner inside the outer casing of the switch.
As, on known fluidtight switches of the aforementioned
type, the work stroke of the button is usually relatively
long, to compensate for varying amounts of slack between
the vehicle bodywork and door, said piston produces a re-
latively high vacuum on the fixed contact side, whenever
the door is opened and the button released. As a re~ult,
the sealing materials on the fixed contact openings inside
the switch casing are subjected to fatigue, and soon lose
their capacity to seal out any condensate on the outside
terminals of the fixed contacts.
The aim of the present invention is to provide a fluid-
tight switch designed to overcome the aforementioned draw
backs.
With this aim in view, according to the present invention,
there is provided a fluidtight push-button switch compris-
ing a casing; a button extending through said casing, and
designed to perform, in relation to the same, a first gi-
ven work stroke between a normal extracted position and a
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withdrawn position; a number of fixed contacts extendingthrough said casing; and at least one conducting contact-
carrying ele~ent housed inside said casing and connected
to said button so as to perform, in relation to said fix-
ed contacts, a second work stroke between an open and closed position; characterised by the fact that it alæo com-
prises a substantially fluidtight chamber formed inside
said casing and housing said contact-carrying element and
at least part of said fixed contacts; a control member
housed inside said casing and connected in sliding manner
to the same so as to perform said second work stroke to- -
gether with said contact-carrying element; said button be-
ing connected in sliding manner to said control member;
first and second elastic means being provided respectively
between said control member and said casing, and between
said button and said control member; and said second work
stroke being relatively short as compared with said first
work stroke.
According to a preferred embodiment of the invention as de
scribed above, said fluidtight chamber comprises a wall de
fined by a flexible diaphragm; said first elastic means be
ing housed inside said fluidtight chamber and cooperating :
axially with said-end portion of said control member via
the interposition of said contact-carryign element and
said diaphragm.
Said control member preferably comprises an end portion
penetrating in fluidtight manner inside said fluidtight
chamber; æaid diaphragm presenting a hole engaged in
fluidtight manner by said end portion of said control mem
ber.
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Stop means are also preferably provided inside said fluid
tight chamber, for cooperating with said contact-carrying
element; said fixed contacts comprising, inside said
fluidtight chamber, a bent portion facing said stop means,
and said contact-carrying element moving into contact with
said stop means in said open position.
According to a particularly advantageous embodiment of the
invention as described above, both said casing and said
control member are in the form of hollow cylinders, said
control member being mounted in sliding manner inside said
casing; and said button being connected telescopically to
said control member via the interposition of said second
elastic means.
A non-limiting embodiment of the present invention will be
described by way of example with reference to the accompa-
nying drawings, in which :
Fig.1 shows a bottom plan view of a preferred embodiment
of the switch according to the present invention;
Fig.2 shows a section along line II-II in Fig.1;
Fig.3 shows a section along line III-III in Fig.1;
Fig.4 shows a section along line IV-IV in Fig.2.
Number 1 in Fig.2 indicates a fluidtight push-button switch
comprising a substantially cylindrical outer casing 2 de-
fined by a lateral wall 3 consisting of a substantially cy
lindrical rear portion 4 and a cylindrical front portion 5
coaxial with rear portion 4~ Front portion 5 present exter
nal longitudinal strengthening ribs 6 and a smaller out-
side diameter than rear portion 4 to which it is blended
via annular shoulder 7.
Casing 2 also comprises a flat transverse front wall 8
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closing off front portion 5 and projecting outwards of la-
teral wall 3 so as to form a flange 9 having a member 10
for clicking casing 2 on to a supporting wall (not shown).
Casing 2 also comprises a cup-shaped body 11 having its
concave æide facing wall 8, and consisting of a substan-
tially cylindrical lateral wall 12 closed off at the rear
by a flat wall 13 forming an outer flange 14 and parallel
with wall 8.
As shown in Fig.3, wall 12 is fitted inside rear portion
4 of wall 3 with flange 14 contacting the rear end of por-
tion 4, and is clicked on to portion 4 by means of radial
appendices 15 projecting radially outwards from the outer
surface of wall 12 and clicked inside respective slots 16
formed in portion 4.
A front annular edge of wall lZ cooperates with annular
shoulder 7 so as to lock axially, and in fluidtight man-
ner, the outer annular rib 17 of a flexible undulated an-
nular diaphragm 18 defined internally by a second annular
rib 19 coaxlal with rib 17 and defininB a center through
hole 20 coaxial with wall 12. Unlike Fig.s 1 and 3, dia-
phragm 18, when undistorted, is perfectly symmetrical in
relation to its mid plane, so as to enable troublefree as-
sembly.
Diaphragm 18 closes off the front of cup-shaped body 11 so
as to define, inside the same, a substantially fluidtight
chamber 21 housing, as shown clearly in Fig.4, two block~
22 extending from the inner surface of wall 13 and having
a substantially C-shaped cross section. Each of blocks 22
presents an axial slot 23 into which clicks in fluidtight
manner (Fig.3) a respective electric termianl 24 project-
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ing rearwards of wall 13 through a respective slot 25 andfitted on the front end with a curved plate 26 lying in a
plane perpendicular to the axis of wall 12.
Blocks 22 combine to define a duct 27 coaxial with wall 12
and housing a helical spring 28 compressed between the in-
ner surface of wall 13 and a conducting contact-carrying
element 29 defined by an elongated, substantially flat me-
tal plate extending diametrically across chamber 21 and
fitted on its opposite ends with two movable contacts 30,
each designed to cooperate frontally with the rear surface
of end portion 31 of respective plate 26.
The front end of each block 22 projects frontwards of re-
spective plate 26, and presents a rib 32 projecting inside
duct 27 and designed to click on to the center portion 33
of contact-carrying element 29 in such a manner as to axi~
ally lock the same against the thrust exerted by spring 28
during assembly.
Rearwarda of contact-carrying element 29, blocks 22 define
two coplanar stop shoulder~ 34 facing both end portions 31
and defining, with the same, a relatively short work stroke
(roughly a millimetre)) of contact-carrying element 29 be-
tween a front closed position, contacting end portions 31,
and a rear open position contacting ahoulders 34.
Inside front portion 5 of wall 3, diaphragm 18 defines a
cylindrical chamber 35 coaxial with chambér 21 and housing
a hollow cylindrical body 36 comprising a cylindrical late
: ral wall 37 connected in sliding manner to the inner sur-
face of portion 5 and closed off at its opposite ends by
a front wall 38 and a rear wall 39 parallel to each other
and to wall 8. Body 36 is slightly shorter than chamber
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35, and forms part of a control member 40 also comprising
a hollow pin 41 coaxial with wall 37 and integral with
wall 39. The front end of pin 41 engages, in radially
slack manner, a through hole 42 formed axially through
wall 38, and located facing and coaxial with a hole 43
having substantially the same diameter and formed through
wall 8. The rear end of pin 41 projects rearwards of wall
39 so as to form an appendix 44 constituting the rear end
portion of control member 40 and engaged in fluidtight man
ner through hole 20. Appendix 44 fits through hole 20 into
chamber 21, with its free end contacting the front surface
of center portion 33 of contact-carrying element 29. :
Control member 40 is connected telescopically to a button
45 consisting of a cup-shaped body having its concave side
facing diaphragm 18 and comprising a substantially cylin-
drical lateral wall 46 extending in sliding manner through
holes 42 and 43 and closed off at the front by a substan-
tially flat transverse wall 47. The rear end of wall 46
presents an annular outer flange 48, the outer ed8e of
which is connected in sliding manner to the inner surface
of wall 37.
Pin 41 is wound with a helical spring 49 less flexible ~:
than and coaxial with spring 28. Spring 49 is compressed
between walls 39 and 47 so as to normally maintain flange
25 48 contacting the inner aurface of wall 38, and is locat- :-
ed with its rear end contacting a center portion of wall
39 surrounded by a number of vent holes 50 in chamber 35. ..
Clearly, therefore, whereas button 45 is designed to per-
form, in relation to cylindrical body .36 of control member
30 40 and against the action of spring 49, a relatively long ~ .
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work stroke (roughly a centimetre) wherein wall 47 is
brought into contact with the front end of pin 41, the
work stroke of control member 40 and contact-carrying ele
me~t 29 connected to the same is relatively short.
In actual use, any axial pressure applied on button 45 in
the extracted position shown in Fig.2 is transmitted by
spring 49 to spring 28 by control member 40 and contact-
carrying element 29 connected to the same. By virtue of the
increased flexibility of spring 28 a~ compared with ~pring
49, axial displacement of button 45 in relation to casing
2 results, firstly, in distortion of spring 28 and, conse-
quently, axial displacement of the button 45 and control
member 40 assembly in the direction of wall 13, so as to
set contact-carrying element 29 in the closed position con
tacting shoulders 34, and, secondly, in axial displacement
of button 45 in relation to control member 40 against the
action of spring 49. In other words, the 40-45 assembly
acts as a shock absorber mounted in sliding manner inside
casing 2 and designed to perform, in relation to the same
and in undistorted manner, a relatively short stroke for
setting contact-carrying element 29 in the open or closed
position, but capable of distortion for absorbing any over
travel of button 45.
The advantages of the above 6tructure will be clear from
the foregoing description. Firstly, said shock absorber is
located substantially outside fluidtight chamber 21, which
;~ occupies only a small portion of the volume of casing 2 un
affected by operation of button 45 in relation to control
member 40. Secondly, displacement of the moving parts in-
side chamber 21 is extremely small, as is the "pump effect"
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originated by the same. In other words, the vacuum formed
inside chamber 21 by contact-carrying element 29 moving
from the open to the closed position, is so small as to . .
rule out any possibility of damp being sucked into chamber
21 through slots 25.
In connection with chamber 21, according to an obvious va-
riation (not shown), hole 20 through diaphragm 18 may be
eliminated by forming, in diaphragm 18 itself, a center
cap for receiving end portion 44 of control member 40, or
by eliminating end portion 44 and providing diaphragm 18
with a corresponding center boss.
