Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to the field of control switches
o the type used in control panels and switch stations in an
industrial environment.
Industrial control switches are characterized by dif-
ferent kinds of operators. In a push button control such as
disclosed in Nelson et al, Canadian Patent No. 966,183
issued April 15, 1975, a momentary operator normally pro-
vides switch actuation for a short time. In a selector
switch, on the other hand, such as disclosed in Wanner,
Canadian Patent No. 971,611, issued July 22, 1975, an
operator is maintained in one of several selectable posi-
tions for a typically longer period.
From these basic control units, other types have been
developed through the addition of a secondary circuit to
li~ht the switch operator. A push button, for example, may
be either constantly lighted or may be the push-to-test
type, wherein the operator is lighted upon the successful
actuation of the primary switch contacts.
One particular class of industrial switches with these
various types of operators must be rugged, reliable, and
sealed against the intrusion of oil and other contaminants
in the industrial environment. Prior devices of this type
such as disclosed in Nos. 966,183 and 971,671 have relied on
mechanical contacts that have been sealed within contact
blocks coupled to the switch operators.
With the introduction of solid state, digital control
equipment there is a need for improved sealed control
switches with low-bounce contacts for switching at d-c logic
signal levels such as 5 volts, 15 volts and 30 volts.
; 30 In the field of digital office equipment, touch-
actuated switching panels have been developed to replace
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traditional key-operated panels. These newer panels com-
monly involve several thin sheets of an insulating material
such as the type sold under the trademark MylarO A spacing
sheet is used between two other sheets on which conductive
areas have been formed by screen printing or other deposition
processes. The spacing sheet contains openings to allow the
conductive areas on the spaced apart sheets to contact one
another when pushed together at the touch of an operator. Such
pressure sensitive switching panels have their functional labels
arranged in patterns and arrays resembling keyboards, yet such
panels are flush with the surface of the control panel or
equipment utilizing them. Such panels have the advantage of
sealed contacts, but in an industrial environment lack the tac-
tility or other form of feedback to the human operator that
is provided by traditional industrial controls. Such mem-
braneous, touch-sensitive switching panels are by the nature
of their construction more readily adapted to arrays and
have not provided suitable individual switches that can be
located apart from control panels.
The invention is provided in an electrical switch that
combines an operator assen~ly, having the look and feel
desired in the manufacturing environment, with a contact
assembly having a thin-layered construction of the general
type seen in membrane switches.
The operator assembly includes an operator housing with
a front end, a rear end, and an opening therethrough from a
housing entrance at the front end to a housing exit at the
rear end. An operator is mounted for movement within the
housing, the operator having a distal end spaced inwardly
from the housing exit and movable towards the housing exit
to actuate the switch. A resilient pad is mounted on the distal
end of the operator~
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A sealed-contact unit extends across the exit of the
housing and includes a substrate of insulating material; a
pair of contact elements spaced apart to provide a switch gap,
the first contact element being supported by the substrate;
a flexible membrane of insulating material on which the
second contact element is disposed on its underside in a position
opposite the first contact element on the substrate; and
spacing means disposed between the flexible membrane and
the substrate for surruounding and sealing the contact ele-
ments within a contact chamber that is formed around the switchgap.
The switch is actuated through an initial movement of the
operator towards the housing exit, and the further movement
of the pad of resilient material against the membrane until
the switch gap is closed.
The distance which the operator must be moved before con-
tacting the membrane provides a measure of switch travel that
is perceptible to the user, and together with the action of
the resilient pad provides a sense of "feel" to the user.
The invention provides an inexpensive contact assembly
that is easily sealed against contaminan-ts. It is contem-
plated that switches of the invention may be located where
they will be subjected to the mists of lubricating fluids
and coolants commonly used in machine shops, as well as the
dust and dirt found in the industrial environment.
The invention also provides a low profile contact assembly.
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The low profile of the contrast assembly reduces the overall
profile of the switch, which increases flexibility in mount-
ing the switch in confined areas. When the switches of the
present invention are mounted on a control panel or other
supporting structure, however, they have sufficient profile
to be clearly observed. The contacts themselves are less
expensive to manufacture than mechanical contacts of the
prior art and are easily replaced if accidentally damaged.
The invented switch construction provides individual
membrane switch units not seen in the prior art, and it is
; also readily adapted to the production of switch arrays
arranged in matrices of two-by-four, three-by-three, three-
by-four, and four-by-four, as examples. An array is pro-
: vided by producing the selected number of pairs of contact
termination areas on a circuit board and by producing a
corresponding number of shorting patches in matching con-
figuration on the membrane.
The invention will enable one to provide a heavy duty,
industrial switch with low-bounce switch contacts that
occupy a minimum of space and are easily sealed against
contaminants in the environment.
The invention will further enable one to provide such a
switch with contacts that are inexpensively manufactured and
easily replaced, if necessary.
The invention will further enable one to provide a
switch of higher profile than a membrane switch but of lower
profile than other prior switches of the type which are
assembled in arrays in control panels or other supporting
structures.
In drawings which illustrate two embodiments of the
invention:
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Fig. 1 is an exploded perspective view of a push button
switch that embodies the present invention;
Fig. 2 is a sectional view of the push button switch of
Fig. 1 looking vertically downward through a horizontal
plane that bisects the switch, with certain interior parts
being broken away;
Fig. 3 is a rear end view of the push button operator
forming a part of the invention taken in the plane indicated
by line 3-3 in Fig. 2;
Fig. 4 is a detail exploded view in perspective of a
contact assembly that is the upper left component seen in
Fig. l;
Fig. 5 is an exploded perspective view of a circuit
board assembly seen in assembled form in Fig. 6;
Fig. 6 is a partially exploded perspective view of an
array of switch operator assemblies seen in Fig. 3, which
are combined with the circuit board assembly of Eig. 5; and
Fig. 7 is a side view in elevation showing a switch in
the assembled array of Fig. 6, with parts broken away.
~eferring to Figs. 1 and 2, an electrical switch 10
adapted for attachment to a control panel 12 or other sup-
porting structure, includes an operator assembly 13 and a
contact assembly 14. The operator assembly 13 ïs housed in
a bezel 15 molded from a thermoplastic insulating material
and having a forward box-shaped portion 16 with an entrance
into a rectangular opening 20, which is framed by four
rounded edge surfaces. A barrel portion 17 of the bezel 15
extends from a rear wall 18 of the rectangular portion 16,
the barrel portion 17 having a cylindrical opening 19 that
extends from the rectangular opening 20 to a housing exit at
the rear end of the bezel 15. An annular spring seat 21 is
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formed in the rear wall 18 of the rectangular portion 16
around the entrance into the barrel opening 19.
As seen in Fig. 1, an operator 22 includes an elon-
gated, cylindrical plunger 23 which has been removed from a
cap assen~ly 24. Referring to Fig. 2, a plunger-receiving
cavity 25 is formed in a hollow, cylindrical cap stem 26 to
receive the plunger 23 when the operator 22 is assembled. A
complex lens assembly 27 with a plurality of light-trans-
mitting members is mounted on a rectangular flange 28 at the
front end of this cap stem 26. The lens assembly 27 forms a
head for the operator cap 24 that fills the rectangular
opening 20 in the bezel 15 and is flush with the front edges
of the bezel 15. The head of the cap 24 could, of course,
be positioned rearwardly from the front edges of the bezel
15 to provide a guard for the operator 22. As seen in Figs.
1 and 2, the lens assembly 27 includes a rectangular lens
frame 33 that snap fits over projections 30 formed on the
lens 32 and has a rectangular opening in which a portion of
the lens 32 is received. The lens 32 in turn snap fits over
projections 29 formed on the rectangular flange 28 (as seen
in Fig. 2).
When the operator button is assembled in the bezel 15
as seen in Fig. 2, a return spring 35 is captured between
the spring seat 21 and the cap stem flange 28. The return
spring 35 is compressed when the operator 22 is moved
through the opening l9, 20 towards the rear of t-he bezel 15,
and the spring 35 stores energy that exerts a return force
on the head of the operator cap 24, when the operator 22 is
released by a user. The operator stem 26 has a channel 36
encircling it midway between the stem flange 28 at its
forward end and the opening into the plunger cavity 25 at
its rear end. A U-cup seal 37 of thin elastomeric material
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is fitted into this channel, the seal 37 tapering from a
; wider effective width to a narrower effective width as it
extends rearwardly through the barrel opening lg. This seal
37 protects the barrel opening l9 against the intrusion of
oil or other contaminants.
As seen in Figs. 1 and 3, the cap stem 26 is formed
with two flexible barbed fingers 38, to hold the operator 24
in position within the bezel 15. The barbed fingers 38 are
formed by a plurality of slots extending axially into the
cap stem 26 from its rear end, the stem 26 being terminated
in four segments, two of which form the retaining fingers
38. The barbed ends of these fingers 38 snap over an inte-
gxally formed annular retaining ring 39 seen partially in
perspective in Eig. 1, and seen in cross section in Fig. 2,
where the barrel opening 19 is narrowed at its entrance.
In Fig. 3, two other oppositely disposed segments carry
rounded, inwardly extending projections 40 that are radially
spaced 180 degrees apart. These projections 40 are received
in detents 41 (seen best in Fig. 2) formed in a tapered
annular flange 42 seen best in Fig. 1 where it encircles the
middle of the plunger 23. The detents 41 are also spaced
180 degrees apart, as seen in Fig. 3, to cooperate in Xeying
the position of the plunger 23 within the stem cavity 25.
As seen best in Eig. 1, the beveled flange 42 also forms an
annular surface 43 at its forward end, and in Fig. 2 with
the plunger 23 inserted in the stem cavity 25, this surface
43 engages an annular stop surfaca 44 formed in the interior
of the cap stem 26. The upper end of the plunger ~3 forms
ribs 50 that provide an interference fit against the surface
30 defining the upper end of the plunger-receiving cavity 25,
to securely hold the plunger 23 against axial displacement
relative to the cap stem 26. The plunger 23 is completed by
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a pad 45 of resilient insulating material which is mounted
on its distal end and extends toward the housing exit.
Referring to Fig. 4, the contact assembly 14 includes a
contact support cup 53 of thermoplastic insulating material
with an octagonal cavity that forms eight interior walls.
Four rectangular slots 51 are formed in the bottom of the
cup and arranged in opposing pairs along orthoganal a~es.
The slo*s 51 are each parallel to a respective wall, and
these four walls are alternated with four obliquely disposed
walls formed around the octagonal cavity. A breather ring
52 of elastomeric material is disposed in the bottom of the
cup 53 and an octagonal substrate 54 is disposed over the
breather ring 52 as seen in cross section in Fig. 2. The
substrate 54 has a centrally located aperture 55 for reasons
that are more fully explained in Baran et al, U.S. Patent No.
4,331,852, issued May 25, 1982, and entitled "Industrial
Membrane Switch with Breather."
Refarring again to Fig. 4, two spiralling termination
areas 56 are deposited on the front face of the substrate
54, which is made of an insulating glass-epoxy material with
electrolytic copper on one side, using an etching technique
of a type well known in the art of making printed circuit
boards. The etched circuit pattern is then electroplated
with small amounts of nickel and gold. The ends of the
spiralling termination areas 56 are electrically cGnnected
to the upper ends of a pair of switch terminals 57 which are
anchored near the outside edge of the substrate 54 and which
are radially spaced 180 degrees apart. These switch term-
inals 57 have neck-and-shoulder portions connecting their
upper ends to two-legged portions. As seen in Fig. 2, the
terminals 57 have their neck portions positioned in the
slots 51, where their two-legged portions are twisted about
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the longitudinal axes of the terminals 57, to anchor them in
position in the support cup 53.
Referring to Figs. 2 and 4, an insulating, octagonal,
Mylar spacer 59 with a thickness of five mils is adhesively
secured to the front face of the substrate 54 between the
outside edges of the spiral configuration and the upper ends
of the terminals 57, the spacer 59 having a circular aper-
ture in it for access to the contact termination areas 56.
On top of the spacer 59 a flat, flexible membrane 60 of in-
sulating material is adhesively secured, the membrane 60 inthis instance being an octagonal sheet of Mylar with a
thickness of five mils and with a circular shorting patch 61
formed on its back side by screen printing or otherwise
depositing a dot of conductive ink or paint thereon. With
the membrane 60 in position on the spacer 59, as seen in
Fig. 2, the shorting patch 61 opposes the contact termination
areas 56 but is spaced apart by a gap of approximately
twelve mils occupied by the spacer 59 and two iayers 62, 63
of adhesive on opposite sides of the spacer 59. The thick-
nesses of the layers have been exaggerated in Fig. 2 as anaid in disclosing the invention.
Referring to Figs. 1 and 4, the contact cup 53 has
integrally formed, coupling members 53a with barbed ends
that are received in a pair of rectangular detents 17a
formed within the interior of barrel 17, one of the detents
being seen in phantom in Fig. 1. The barbs extend radially
outward with the coupling members being flexed towards one
; another as they are forced axially into the exit end of the
barrel 17. The result of this arrangement is that the
contact cup 53 abuts the exit end of the barrel 17, as seen
in Fig. 2, to seal the contact elements 56 and 61 within
an insulated switch housing.
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The resilient pad 45 is spaced from the exit of the
barrel 17, so that it moves through a pre-travel distance
before engaging the front side of the membrane 60. The pad
45 is then moveA through an additional distance to deflect
the membrane 60 and bridge the gap between the spiral con-
tact areas 56 using the shorting patch 61 as the bridging
contact element. The double spiral configuration of the
contact areas 56 eliminates potential blind spots at which
deflection of the shorting patch 61 might fail to make a
bridging connection; however, this desirable feature is not
absolute to the practice of the invention in its broader
aspects. When the membrane 60 is deflected, air is circu-
lated through the aperture 55 in the substrate 54 to the
void in the middle of the breather ring 52, and when the
operator 22 is released, the air returns to the switch air
gap between the substrate 54 and the membrane 60 to breaX
contact. Besides the measure of pre-travel, several other
factors contribute to a sense of feel to the user when the
switch 10 is operated. The return spring 35 extends a
sufficient distance to provide a measure of over-travel for
the switch operator 22, and the resilient pad ~5 emulates,
to some extent, the action of the user's fingertip.
As seen in a second embodiment in Fig. 5, the structure
and method of making the contact assembly 14 is adapted to
an array o~ contacts for a plurality of switches. A plural-
ity of double spiral configurations 56 in a three-by-three,
two-by-four, three-by-four, four-by-four, or other matrix
configuration is etched in the manner described above on a
circuit board 65 which serves as the substrate for the
array. The pattern seen in Fig. 5 is a three-by-three
common bus arrangement where one termination area 56 in each
double spiral configuration is connected to a common ground
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circuit path 66 while the other contact termination area 56
in each spiral configuration has its own respective clrcuit
path 67 leading to a terminal 68a in an edge connector 68
mounted on one edge of the circuit board 65~ Besides a
common bus configuration, other configurations are possible,
such as a set of circuit paths connecting pairs of spiral
switch termination areas 56 to binary coded I/O terminals in
the edge connector 68. In those embodiments a termination
strip (not shown) is used, in addition to the edge connector
68, to terminate some of the circuit paths. A spacing sheet
69 of file mils thickness with circular apertures 70 in a
corresponding array is then adhesively mounted on the cir-
cuit board 65. This spacing sheet 69 has channels 64 con-
necting the apertures 70 in each row to provide a path for
circulating air from an actuated switch to and from its
neighbors. Next, a membrane overlay 71 of five mils thick-
ness with shorting patches 61 formed in corresponding con-
figuration is adhesively secured to the spacer 69 so that
each shorting patch 61 will oppose a respective double
spiral pair of contact termination areas 56.
Referring to Fig. 6, the circuit board assembly 80 just
described is assembled with a plurality of switch operator units
13, such as push buttons, pilot lights and lighted push button
units that are mounted in a control panel 12 or other supporting
structure. The latter two types of switch units are constructed
according to the disclosure in Fillus et al, U.S. Patent No.
4,350,857, iscued September 21, 1982, and entitled "Illuminated
Membrane Switch"~ To mount the switch operator units a plurality
of circular apertures (not seen) are provided in the panel 12,
with the switch operator unit 13 being positioned as seen
in Fig. 2 with the back side of the rectangular portion 16 of
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the rectangular portion 16 of the bezel 15 meeting the front
side of the panel. As seen in both Figs. 1 and 2, an annular
gasket 76 of a synthetic elastomeric material and a metal
washer 77 are slipped over the outside of the barrel 17 and
held against the back side of the control panel by an annular
lock ring 78 with an interior thread that engages a thread
running around the circumference of the barrel 17. The
outer surface of the lock ring 78 is knurled for a better
grip.
With a plurality of operators assembled in the panel as
seen in Fig. 6, the circuit board assembly 80 is attached.
The circuit board 65 has holes 81 in its four corners which
are aligned with corresponding countersunk holes 82 in the
control panel 12. Circuit board standoffs 83 are inserted
; through the holes in the panel 12 and sealing lock nuts 84
are threadingly turned onto the standoffs 83 until posi-
tioned a~ainst a panel gasket 86 seen in Fig. 7 on the back
side of the panel 12. External prong retainers 85 are
attached to the ends of the standoffs 83, which extend
through the aligned holes 81 in the circuit board assembly
80, these ends being specially adapted to receive such
retainers 85.
Referring again to Fig. 7, one of the push buttons 10
in the assembled array is seen with its actuator pad 45 in
registration with the shorting patch 61 on the overlay 71.
The circuit board assembly 80 is mounted at a distance from
the panel 12 where tha exit ends of tha bezels 15 abut the
overlay 71 and complete the seal around the contact struc-
ture formed in the circuit board assembly 80.
It can be seen that the present invention provides a
switch with a lower profile than prior switches used in a
manufacturing environment, yet with the look and feel de-
sired by industrial customers. The contact assembly 14 in
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the individual switch completes the sealed switch structure,
and is easily removed if the conductive contact areas are
accidentally damaged. The contact structure is easily
produced in multiple units for use in control panel arrays.
While the foregoing description provides the details of
making and using two embodiments of the invention, the full
scope of embodiments contemplated by the invention is de-
scribed by the following claims.
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