The present invention relates to an electric switch operating
mechanism of the rocker type.
Referring first to Figure 1, a conventional switch operating
device of the rocker type comprises a pivotable operating member
(1) typically having an operating surface (2) for operation by
finger pressure, and having two opposing side surfaces (3)
extending downwardly from the operating surface, the side faces
having, for example, outwardly extending projections (4) which
cooperate in formations of the switch body so that the operating
member may pivot. A surface (5) opposite the operating surface
has a recess (6 - See Figure 2) which typically forms a seat for
a spring (7) and plunger (8), the plunger (7) being urged
outwardly from the operating member by the spring (8). In this
conventional arrangement, the spring is of metal, and the plunger
and operating member are of plastics material.
A moving switch contact (10) has a first end portion (11) which
alternatively makes and breaks contact with a counterpart contact
member (18). The moving contact member has the form of a strip
of, for example, brass, the strip having a generally-planar
portion (12) bounded at both ends by respective fold regions
(13,14), one of which (13) extends into a contiguous second end
portion (15) opposite the contact-making region (11). The other
fold region extends to a contiguous ridge portion (16) which is
itself contiguous with the contact region. The substantially
planar region, together with the second end portion and the ridge
region form a generally channel-shaped portion having the planar
portion (12) as base and the second end portion (15) and one side
of the ridge portion (16) forming the walls thereof. The plunger
of the switch operating member is disposed within the channel
such that rocking of the switch operating member between two end
positions causes the plunger to move between the two fold
regions. To this end, the contact member is pivotably supported
at a fulcrum point on the underside of the base of the channel
portion thereof, the support being provided by a conductive
member (30).
Referring now to Figure 2, in a first position of the operating
member, the plunger is engaged between the fulcrum and the second
fold region (13) of the moving contact, which is thereby pivoted
so that the first end portion (11) thereof does not make contact
with the counterpart contact (18). Finger pressure at one end
(21) of the operating surface urges the operating member to
pivot, which pivoting motion requires the plunger to retract
against the pressure of the spring and then to extend under the
action of spring pressure as the plunger moves along the base
(11) of the channel of the moving contact, towards the first fold
region (13). As the plunger passes the fulcrum (see Figure 3),
the moving contact snaps to a closed position wherein the contact
(11) at the first end thereof makes contact with the counterpart
contact (18). Subsequent pressure at the opposite end (22) of the
operating surface re-opens the contacts by snapping the moving
contact back to the position of Figure 2 as the plunger passes
the fulcrum again.
The plunger may move from engagement in the first fold region to
engagement in the second fold region, but normally it will only
move from a position intermediate the fulcrum and the first fold
region to a position intermediate the fulcrum and the second fold
region, and vice versa.
Such switch arrangements, and other similar arrangements are well
known in the art. They are however relatively difficult to
manufacture. The need for at least three separate parts of the
switch operating member - i.e. the rocker member, the plunger and
the spring, is disadvantageous, both because of the number of
components and because of the difficulty in assembling them.
It is therefore an object of the present invention to provide a
rocker switch operating mechanism which at least partly overcomes
the above-mentioned difficulties.
According to the present invention there is provided a rocker
switch operating device comprising a rocker member adapted to be
supported in a switch body, the rocker member having a contact-engaging
member depending therefrom, the material of the contact-engaging
member providing resilience whereby the contact-engaging
member may urge the contact between an open and closed position.
Preferably the material of the contact-engaging member is
plastics material.
Advantageously the rocker member is of plastics material and the
contact-engaging member is of the same plastics material.
Alternatively the rocker member may be of a first plastics
material and the contact-engaging member of a second, different,
plastics material.
Conveniently the rocker member and the contact-engaging member
are formed in consecutive moulding steps whereby the rocker
member and contact-engaging member form an integral device.
Alternatively the rocker member may be a first component and the
contact-engaging member be a second component, wherein one of the
components has engagement means whereby it may be secured to the
other component.
Embodiments of the invention will now be described with reference
to the accompanying drawings in which:-
Figure 1 shows a partial perspective view of a conventional
switch.
Figure 2 shows the switch in a first, open, state.
Figure 3 shows the switch in a second, closed, state.
Figure 4 shows a side elevation of a first embodiment of the
present invention.
Figure 5 shows a perspective view of the embodiment of Figure 4.
Figure 6 shows a view similar to that of Figure 1, but
incorporating the switch operating device of Figures 4 and 5.
Figure 7 shows an alternative embodiment of the invention.
Figure 8 shows yet another embodiment of the present invention.
Figure 9 shows a further embodiment of the rocker device of the
present invention in which two contact-engaging members are
disposed within the confines of the main body portion.
In the figures, like reference numerals indicate like parts.
Referring first to Figure 4 and 5 the rocker (40) has a main body
portion (41) having an operating surface (42), to whose ends
pressure - e.g. finger pressure - may be applied to move the
rocker between two end positions. In the embodiment shown, the
main body is trapezoid in cross-section parallel to the
longitudinal axis thereof, and is generally rectangular in cross-section
in an orthogonal direction thereto. However it will be
understood by one skilled in the art that any desired shape could
be used and indeed it is possible to use a hollow main body if
so desired.
Depending from the main body opposite to the operating surface,
there is a rib portion (43) which extends perpendicular to the
longitudinal axis of the body and which has end projections (44)
adapted for pivotable engagement - see Figure 5 - with
counterpart recesses (46) in the main body (47) of the switch.
It will be understood by one skilled in the art that the
projections are not essential and could be replaced by recesses
or other formations performing the same function.
In this embodiment, the rib portion extends beyond the confines
of the main body so as to provide sufficient spacing to operate
two switch contacts as described below. The end projections (44)
have a generally triangular form, with one apex rounded to
provide pivoting. The recesses (46) of the main body (47) of the
switch are open on one side to allow for engagement therein by
the projections (44) so that the rocker (40) is not retained in
the recesses, nor secured to the main body of the switch but
rather is urged into engagement with the main body of the switch
by spring pressure as more fully described below.
This embodiment therefore provides some assembly difficulties
again as will be later more fully described.
The rib portion supports two contact-engaging members (45). In
this present embodiment, the two contact-engaging members (45)
may be integrally moulded with the rocker main body, or may be
separate components which are secured to the rib portion thereof.
Each contact-engaging member is generally symmetrical and has a
downwardly depending V-shaped portion (50) extending into two
contiguous hook portions (80,81) which are mutually inwardly
directed. In the case of an integrally moulded device, each of
the hook portions extends into the rib portion (43) of the
rocker, whereas in the case of a two-part device, the hook
portions engage with the rib portion.
The material of the contact-engaging member together with its
configuration enable the rocker and contact-engaging members to
perform similarly to the conventional body-spring-plunger
assembly. Specifically, an apex portion (53) of the V of the
contact-engaging member is enabled to be moved against a
resilience of the hooked portions towards the rib portion of the
rocker, during the course of which the hooked portions behave
similarly to leaf springs so enabling the apex portion to pass
along the base portion of the moving contact and past the fulcrum
position. Once the apex of the V has passed this position, the
resilience and configuration of the contact-engaging member urges
it outwardly towards the undeformed condition thus causing the
moving contact to snap to the open or respectively closed
position.
The resilience of the contact-engaging member not only serves to
move the moving contact between its open and closed positions but
also serves to urge the rocker itself into engagement with the
main body (47) of the switch (47) in the recesses (46) thereof.
In practice, the resilience of the contact-engaging portions also
serves to retain the moving contact member within the body of the
switch. Thus, during assembly the rocker (40) is first inserted
into the switch body (47) with the projections (44) of the rocker
engaged in the recesses (46) and then the contact-supporting
portion of the switch body is offered to the main switch body
(47). It will be seen that care is required during this assembly
operation because the rocker will tend to fall out from the
recesses (46) when the switch body is tilted, and the contacts
(being otherwise free to move until held in position by the
contact-engaging members (45)) will also tend to be dislodged if
the contact-supporting portion of the body is tilted.
Figure 6 shows the embodiment of Figures 4 and 5 in use with the
V portion engaged with the moving contact member (10) near to the
second fold region (14) thereof whereby the moving contact is
held in the open position.
It will be understood that the V form of this embodiment is not
essential to the invention. For example the contact-engaging
member may have the form of a solid pillar supported by resilient
hook portions, or other forms as desired.
Referring again to Figures 4 and 5, intermediate the contact-engaging
members of the rocker, the rib portion has generally
rounded portions (56) extending in the same direction as the
contact-engaging members.
The previously described v-shaped portions (50) also provide a
positive mechanical break, now described:-
Referring to Figure 6, it will be seen that when the rocker (40)
is moved from the closed-contact position to the open-contact
position the rocker is disposed such that the v-shaped portion
(50) of the contact-engaging member (44) is in close proximity
to the ridge portion (16) of the contact. If the contacts remain
undesirably closed, for example due to contact-welding caused by
arcing, in which case the movement of the contact-engaging
portion past the fulcrum may not cause sufficient leverage to
open the contacts, then the continued contact-opening pressure
on the rocker (40) further urges a side of the v-shaped portion
(50) intermediate the apex portion (53) and the hook portion (81)
to engage with the ridge portion (16) of the contact to
mechanically move the contact from the closed to the open
position.
Figures 7 and 8 shows alternative embodiments in which the
contact-engaging member is asymmetrical. In Figure 7, the
contact-engaging member (65) has a first half which is similar
to one half of the contact-engaging member shown in Figure 4, but
the other side is truncated at the remote extremity of the V-portion
so that the end (66) of the V-portion (68) is supported
on the bearing portion (67) of the rib portion (44) but only
connected to the rib portion via the remainder of the V-portion
(68) and the single hook portion (69).
Turning to Figure 8 the contact-engaging portion (181) shown is
integrally moulded with the body portion and consists of a first
part (182) contiguous with the body portion which extends
generally parallel to the longitudinal axis thereto and is
connected to the body portion via a resilient fold portion (183)
at one end thereof, the other end thereof providing a second
resilient-fold portion (184) which extends into a downwardly-depending
finger portion (185) adapted to engage with the base
portion of the trough of the moving contact member. The third
embodiment is particularly advantageous where the entire rocker
device is moulded in a single step, for example using
polycarbonate materials.
Turning now to Figure 9, a fourth embodiment of the rocker switch
operating member of the invention has, instead of the triangular-like
projections (44) of the other embodiments instead circular
projections (101), which snap fit into corresponding circular
recesses in the main switch body. This rocker, which is of an
increased width by comparison with those already disclosed, has
two contact-engaging portions within the confines of the main
body of the rocker each for operating a contact corresponding to
a respective one of two poles of a two-pole switch. The fourth
embodiment may be made of nylon, especially filled nylon, and is
especially suitable for relatively high current switching.
A number of different techniques may be used to manufacture
rocker operating mechanisms in accordance with the invention.
Specifically, a single moulding operation may be used, having the
results that the main body of the rocker and the contact-engaging
portions are of the same material - for example filled nylon.
Alternatively a two-shot moulding technique may be used in which
the contact-engaging portion(s) is/are moulded first and then
overmoulded with the main body portion of the rocker, or vice
versa depending upon the relative melting temperatures of the
plastics used for the two components. (The highest melt
temperature component would be moulded first.) Thirdly, it is
envisaged that the main body of the rocker be moulded in one
operation, and the contact-operating member or members be moulded
as a separate moulding operation with the two components secured
together for example by press fitting or by snapping into a slot.
Where the two-shot moulding technique is used, contrasting
colours may be used for the two moulding materials. In such a
case, the material of the contact-engaging portion may be carried
through to be visible in a portion of the main body, for example
an end region thereof, so as to provide an on, or respectively
off indication. This may be most effective when the material of
the contact-engaging portions is red, in which case a red
indicator portion is arranged to become visible when the rocker
is on the on condition. However, where the rocker is used in
other than mains-switching situations, for example used in
automotive situations, different colour end "windows" may be
provided to distinguish between different loads, the colour of
the material of the window being repeated in the contact-engaging
portion.
Examples of materials have been indicated but these are not
intended to be restrictive. Many other materials could be used
instead, notably acetal copolymer, which is stable and not
susceptible to water absorption.
Thus there has been disclosed four embodiments of an advantageous
rocker switch operating member, the operating member being of
reduced component count in comparison to the rocker operating
members of the prior art, the resilience of the rocker device
being provided by the material and configuration of the device
itself rather than requiring the use of external metal springs.