Note: Descriptions are shown in the official language in which they were submitted.
2178'~~ 8
WO 96/12290 P~LTlUS95/12833
CONTACT BLOCK HAVING CONVERTIBLE NORMALLY OPEN OR
NORMALLY CLOSED ELECTRICAL CONTACTS
FIELD OF THE INVENTION
The invention is related to electrical contacts for
making or breaking an electrical circuit and more
particularly to a-contact block having a stationary set
of contacts which can be selectively converted to either
normally open or normally closed contacts.
HACRGROUND OF THE INVENTION
IS It is common to use a contact block having either a
normally closed or a normally open contact to control the
current flowing in an electrical circuit. The contact
block can typically be used in a limit°switch, with a
push button operator to form a push button switch, or in
any other situation wherein an object can physically move
an actuator thereby causing the normally closed or
normally open contacts to change state. The contact
block generally comprises a first pair of stationary
contacts and a pair of movable contacts attached to the
23 actuator. The actuator is biased such that the movable
contacts are either in the closed or open positicn with
relation to the first stationary contacts. It is also
known to have a second pair of stationary contacts spaced
apart from the first pair of stationary contacts such
that the pair of movable contacts are located between the
first and second stationary contacts, thus allowing the
contact block to have one normally open contact and one
normally closed contact. The extra set of stationary
WO 96/12290 2 PCT/US95112833
contacts increases the physical size of the contact block
and significantly increases; the cost since two additional
_ _
stationary contacts,'two wiring terminals and the bussing
connecting the contacts to the terminals are required.
If an application requires two contacts of the same type ,
it is common to "stack", contact blocks together. This
is accomplished by attached one contact block to another,
such that each subsequent contact block is operated by
the actuator,of-the contact block to which it is
attached. Since the options described above each add
additional cost to the contact block, it would be
desirable to have a contact block which is comparable in
size and cost to a single function contact block of the
prior art and yet is easily converted from a normally
IS open to a normally closed contact block. It is also
desirable to have a contact block which is easily
converted from a normally open normally closed
combination to either two normally closed or two normally
open contacts.
In other types of circuit control devices employing
a stationary contact and a movable contact operated by an
actuator to make or break the circuit it is sometimes
required that an additional control circuit be operated
by the same actuator. For these applications it is
23 common to provide an auxiliary contact. The auxiliary '
contact is generally contained within an enclosure and
includes a pair of stationary contacts, a pair of movable
contacts mounted on an actuator, a biasing spring, and a
pair of wire terminal connectors. The auxiliary contact
CA 02178758 2005-06-03
3
enclosure is mounted on the outside of the circuit control
device enclosure in a location that permits access to the
primary contractor actuator such that the auxiliary contact
can be operated simultaneously with the primary contractor.
Therefore, the trip mechanism of the primary contractor
must be designed to overcome not only the biasing spring
and latching friction of the primary contacts but also the
biasing spring of the auxiliary contact. This increases
the cost of the circuit control device regardless of
whether or not an auxiliary contact is employed. The
auxiliary contacts, like the contact blocks, are available
in either a normally open or a normally closed function and
must be purchased separately as an accessory for the
control device. This means that an inventory of both
normally open and normally closed auxiliary contacts is
required to insure that the desired auxiliary contact is
available when required. It would therefore be desirable
to have a circuit control device with an internal auxiliary
contact that can be easily converted from a normally open
to a normally closed contact and which does not have an
additional biasing spring for the trip mechanism to
overcome.
SUMMARY OF THE INVENTION
A convertible contact is provided which can be
selectively and easily changed between a normally open
function and a normally closed function by the user. The
convertible contact can be used with any electrical control
device capable of having two spaced apart movable contacts
located on a common movable actuator member. The
convertible contact can be used as the primary contact of a
CA 02178758 2005-06-03
3a
contact block or an auxiliary contact of other circuit
control devices.
According to an aspect of the current invention there
is provided a contact block having at least one set of
electrical contacts convertible between a normally open and
normally closed state comprising: a housing defining a
generally hollow interior; an actuator partially received
within the housing and being slidably movable between a
first position and a second position; means for biasing the
actuator to the first position; at least one pair of
contact cavities being defined by the housing and being
positioned immediately adjacent to and on opposite sides of
the actuator; at least one pair of movable contacts, the
movable contacts being attached to the actuator such that
the movable contacts are movable between a first position
and a second position within the contact cavities; means
for attaching the movable contacts to the actuator; first
and second pairs of access apertures providing access to
the contact cavities such that the first pair of access
apertures generally coincides with the first position of
the movable contacts and the second pair of access
apertures generally coincides with the second position of
the movable contacts; and stationary contact module having
at least one pair of stationary contacts which can be
received through either of the first and second pairs of
access apertures for being selectively engaged with the
movable contacts in one of the first or second positions.
According to a further aspect of the current invention
there is provided an electrical control device having a set
of auxiliary electrical contacts convertible between a
CA 02178758 2005-06-03
3b
normally open and normally closed state, the control device
comprising: a housing having a generally hollow interior
and defining a pair of terminal apertures, a first pair of
access apertures and a second pair of access apertures,
each of the apertures providing access to the generally
hollow interior; a base enclosed by the housing; an
actuator being supported by the base such that the actuator
is slidably movable between a first position and a second
position; means for biasing the actuator to the first
position; at least one pair of contact cavities being
defined by the base, each the contact cavity being
immediately adjacent the actuator such that the pair of
contact cavities is separated by the actuator, the base
being positioned within the housing such that the access
apertures provide an external access to the contact
cavities; a pair of stationary contacts supported by the
base; a first pair of movable contacts being attached to
the actuator such that the first movable contacts are
movable between a first position and a second position
relative to the pair of stationary contacts; means for
attaching the first pair of movable contacts to the
actuator; two second pairs of movable contacts, the movable
contacts being attached to the actuator such that the
second movable contacts are movable between a first
position and a second position within the contact cavities;
means for attaching the second pairs of movable contacts to
the actuator; and a stationary contact module having at
least one pair of stationary contacts which can be received
through either the first or second pairs of access
apertures for being selectively engaged by one of the
CA 02178758 2005-06-03
4
second pairs of movable contacts in one of the first or
second positions.
Other features and advantages of the invention will
become apparent to those skilled in the art upon review of
the following detailed description, claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an interior view of a typical normally closed
contact block of the prior art. Figure 2 is an interior
view of a typical normally open contact block of the prior
art.
Figure 3 is an exterior view of a typical contact
block of the prior art.
Figure 4 is a front view of a convertible auxiliary
contact constructed in accordance with the present
invention.
Figure 5 is an end view of a convertible auxiliary
contact constructed in accordance with the present
invention.
Figure 6 is an interior view of a contact block
constructed in accordance with the present invention.
Figure 7 is an exterior view of a contact block
constructed in accordance with the present invention.
Figure 8 is exterior view of a contact block
constructed in accordance with the present invention with
~~.~8'~5~
R'O 96112290 5 PCTIUS95112833
a convertible stationary contact installed in th.e
normally open position.
Figure 9 is an exploded view of a circuit control
device having a conventional dedicated contact and a
convertible auxiliary contact in accordance with the
present invention operated by a common actuator.
Figure 10 is an isometric view of an alternate
construction for a contact carrier/acturator for
supporting two sets of movable contacts.
t0 Figure 11 is an end view of the assembled contact
carrier/actuator of Figure 10.
Figure 12 is an exploded view of the contact
carrier/actuator of figure 10.
Before one embodiment of the invention is explained
in detail, it is to be understood that the invention is
not limited in its application to the details of
construction and description or illustrated in the
drawings. The invention is capable of other embodiments
and of being practiced or being carried out in various
other ways. Also, it is to be understood that the
phraseology and terminology used herein is for the
purpose of description and should not be regarded as
limiting.
DESCRIPTION OF THE PREFERRED
Figure 1 illustrates the inside of a contact block
of the prior art generally and is indicated by reference
numeral 10. The contact block 10 includes a housing 14
which defines a generally hollow interior for supporting
21~~r~e~8
R'O 96112290 s PCT/U595/12833
and enclosing at least one pair of stationary contacts
18, at least one pair of bussing members 22, a portion of
an actuator 26, at least one flexible member 30 supported
by the actuator 26, at least one pair of movable contacts
34, and an actuator biasing,spring 38. ,
Each pair of stationary contacts 18 is positioned
within the housing 14 such that--one stationary contact 18
is spaced apart from the other stationary contact 18 a
preselected distance and both lie in a common plane.
IO Each stationary contact 18 is connected to one end of an
associated bussing member 22. A terminal end 42 of each
bussing member 18 extends outboard of the housing 14
through a passage 44 in the housing 14., Each flexible
member 30 is generally rectangular in shape and is
supported at its approximate midpoint by the actuator 26
such that it has two opposing ends 46 being spaced apart
a preselected distance. Each flexible member 30 is
positioned generally perpendicular to the longitudinal
axis of the actuator 26 and parallel to the plane of the
pairs of stationary contacts 18. At least one movable
contact 34 is attached at each of the opposing ends 46 of
the flexible member 30.
The actuator 26 has a distal end 50 which extends
outboard of the housing 14 through a passage 54 in the
housing 14. The actuator 26 is slidably movable along
its longitudinal axis between a first position and a
second position. The biasing spring 38 is located
between a portion of the housing 14 and the actuator 26
urging the actuator 26 to maintain its first position.
21~~7~8
WO 96/12290 ~ PCT/US95/12833
An external force exerted on the distal end 50 of the
actuator 26 is required to move the actuator 26 to its
second position. In the configuration of Figure 1, the
stationary contacts 18 are positioned within the housing
14 such that when the actuator 26 is biased by the spring
38 to its first position, the movable contacts 34 are in
contact with the stationary contacts 18 thereby providing
a contact block having normally closed contacts.
In the configuration of the prior art contact block
shown in Figure 2, the stationary contacts l8 are
positioned within the housing 14 such that when the
actuator 26 is biased by the spring 38 to its first
position, the movable contacts 34 are spaced apart from
the stationary contacts 18 thereby providing a contact
block having normally open contacts.
Figure 3 illustrates an assembled prior art contact
block with a terminal clamp 58 and a screw 62 fitted to
each of the extending terminal ends 42.
Figures 4 and 5 illustrate a convertible stationary
contact module 66 constructed in accordance with the
present invention. The contact module 66 includes a
housing 70 which is generally rectangular in shape. The
housing 70 has a generally flat top surface 74, a front
surface 78 and a back surface 82. The front and back
~ 25 surfaces, 78 and 82 respectively, are generally parallel
to one another and spaced apart by the top surface 74. A
generally rectangular handle 86 extends upward from a
middle portion of the top surface 74. Two generally flat
bussing conductors 90 are supported by and partially
2 :~'~ ~'~ 5 8 ~ r
WO 96/12290 8 PCTIUS95112833
enclosed by the contact module housing 70. A portion of
each bussing conductor 90 extends outwardly from and
generally perpendicular-to a bottom surface 94 of the
housing 70 to a distal end 98. The bussing conductors 90
3 pass through the housing 70 at.a~.point between the ,
longitudinal center line of'~he contact module 66 and the
,..,
back surface 82 of the housing 70. The distal end 98 of
each bussing conductor 90 has a contact pad 102. A
stationary contact 106 is fixed to the side of the
t0 contact pad 102 facing toward the front surface 78 of the
housing 70. A contact indicator 110 extends outwardly
from and generally perpendicular tn the top surface 74 at
a point between the longitudinal center line of the
contact module 66 and the back surface 82. The contact
t5 indicators 110 indicate the position of the bussing
conductors 90 and the stationary contacts 106. Two
passages 114, each communicating between the front and
back surfaces, 78 and 82 respectively, and each located
adjacent one of the bussing conductors 90, provide access
20 to a wire terminal screw 118 for external wiring to the
contact module 66.
Figures 6 illustrates the interior of a contact
block 122 constructed in accordance with the present-
invention. As in the prior art discussed above, the
23 contact block 122 of the present invention has a housing
126 which defines a generally hollow interior for
supporting and enclosing an actuator 130, at least one
flexible member 134 supported by the actuator 130, two
pairs of movable contacts 138 and an actuator biasing
21'~8'~~8
WO 96112290 9 PCT/US95/12833
spring 142. However, in accordance with the present
invention, a generally rectangular contact cavity 146 is
defined on each side of the actuator 130. The contact
cavities 146 receive the stationary contacts 106 of the
contact module 66 shown in Figures 4 and 5.
Each flexible member 134 is generally rectangular in
shape and is supported at its approximate midpoint by the
actuator 130 such that it has two distal ends 150 being
spaced apart a preselected distance. Each flexible
member 134 lies in a plane generally perpendicularly to
the longitudinal axis of the actuator 130. At least one
movable contact 138 is attached to each side of the
flexible member 134 at each of the distal ends 150.
The actuator 130 has a distal end 154 which extended
outboard of the housing 126 through a passage 158 in the
housing 126. The actuator 130 is slidably movable along
its longitudinal axis between a first position and a
second position. The biasing spring 142 is located
between a portion of the housing 126 and the actuator
130, thereby urging the actuator 130 to maintain its
first position. An external force exerted on end 154 or
the actuator 130 is required to move the actuator 130 to
its second position.
Figure 7 illustrates an assembled contact block 122
of the present invention. The housing 126 includes
indicia indicating normally closed (NC) 162 and normally
open (NO) 166. Two generally rectangular apertures 170
generally adjacent to the NC indicia 162 provide access
to the two contact cavities 146 at a location coinciding
21'~8r158
R'O 96/12290 ~~ , PCT/US95112833
with the location of the movable contacts 138 when the
actuator 130 is in the first position. Two generally
rectangular apertures 174 generally adjacent to the NO
indicia 166 provide access~to the two contact cavities
146 at a location coinciding with the location of the
movable contacts 138 when the actuator 130 is in the
second position. The stationary contacts 106 and their
associated bussing conductors 90, shown in Figures 4 and
5, are received in apertures-170 when a normally closed
contact block is desired and in apertures 174 when a
normally open contact block is desired. An aperture 178
is provided for receiving a contact module mounting screw
178.
Figure 8 illustrates a contact block 122 of the
present invention with a contact module 66 of the present
invention installed. The contact module 66 is in the
normally closed position as indicated by the contact
indicator 110 adjacent to the NC indicia 162. The
contact module is attached to the contact block housing
126 by the mounting screw 178. The contact block is
easily changed from normally closed to normally open by
removing the mounting screw 178, removing the contact
module 66 from the contact block 122, rotating the
contact module 66 180° and reinstalling the contact
module 66 on the contact block 122.
Figure 9 illustrates a circuit control device
generally indicated by reference numeral 182 having a
pair of dedicated nonconvertible stationary contacts 186
supported by a base 190, a first pair of movable contacts
21'~8°~~8
WO 96112290 ~~ PCTIUS95112833
194 supported by a first flexible member 198 which is
attached to an actuator 202, two pair of second movable
contacts 206 supported by a second flexible member 2I0
which is also attached to the actuator 202 and a pair of
contact cavities 214 defined by the base 190. The
actuator 202 is biased to a first position by a spring
218 and slidably movable to a second position by a force
exerted on an end 222 of the actuator 202. The base 190
and its associated components are enclosed within a
housing 226. The housing 226 defines a pair of terminal
apertures 230 for receiving the terminal ends 234 of the
dedicated stationary contacts 186, a first pair of access
apertures 238 and a second pair of access apertures 242
which provide access to the contact cavities 214. The
first pair of access apertures 238 are associated with
the second pairs of movable contacts 206 when the
actuator 202 is in the first position and the second pair
of access apertures 242 are associated with the second
pair of movable contacts 206 when the actuator 202 is in
the second position. The housing 226 also includes NC
indicia 246 adjacent the first pair of access apertures
238 and NO indicia 250 adjacent the second pair of access
apertures 242. The pairs of access apertures 238 and 242
receive the bussing conductors 98 and stationary contacts
106 of the convertible contact module 66, thereby
providing the circuit control device 182 with a
convertible auxiliary contact which is easily selectable
between a normally closed contact and a normally open
contact.
21'~ $'7 ~ 8
WO 96112290 ~ 2 PCTlUS95112833
A contact carrier/actuator assembly generally
indicated as reference numeral 254 and illustrated in
Figures 10, 11 and 12 provides a simple easily assembled
method of supporting two flexible members 258 each of
which has two movable contacts 262 attached to opposing
sides of each of its opposing ends. ,The contact
,W ,
carrier/actuator assembly 2.54 consists of two identical
opposing halves 266 which snap together and thereby
captivate one flexible member 258 at each end of the
IO assembly 254. Each half 266 has a generally E-shaped
cross-section wherein a first outside leg 270, a second
outside leg 274 and a center leg 278 each extending
outwardly from and generally perpendicular to a base leg
282. The first outside legs 270 is shorter in length
than the second outside leg 274 by an amount
approximately equal to the thickness of the base leg 282.
The center leg 278 is slightly shorter than the first and
second outside legs, 270 and 274 respectively, and is not
centered between the first and second outside legs, 270
and 274 respectively. The first outside leg 270 has a
generally flat outside surface 286 from which a generally
rectangular rib 290 extends outwardly and
perpendicularly. The rib 290 is located approximately at
the middle of the first outside leg 270 and runs
generally parallel to a distal end 294 of the first
outside leg 270. The outside second leg 274 defines a
generally squareslot298 which extends inward from a
distal end 302 of the second outside leg 274. The slot
298 is dimensioned to slidingly receive the rib 290 of
2~.'~8'~~g
WO 96112290 ~3 Pn17U595/12833
said first outside leg 270. The cen~er'leg 278 includes
a generally wedge-shaped distal end 306 which defines a
hook 310. The center leg 278 is positioned such that
when the two halves 266 are assembled together, the rib
290 of one half 266 is slidably received within the slot
298 of the opposing half 266 and the hooks 310 of the
opposing center legs 278 interlock, thereby holding the
contact carrier /actuator assembly 254 together. The
flexible members 258 each have a slot 314 which is
dimensioned to closely receive the rib 290 on the
cooperating first outside leg 270. To assemble the
contact carrier/actuator assembly 254, one flexible
member 258 with its attached movable contacts 262 is
placed on the generally flat outside surface 286 of the
first outside leg 270 of each of the opposing halves 266
such that the rib 290 is received through the slot 314.
The two opposing halves 266 are then aligned such that
the ribs 290 of each first outside leg 270 are slidably
received within the slots 298 of the second outside leg
274 of the opposing half 266. As the two halves 266 are
pressed together the hooks 310 of both center legs 278
become latched together. The flexible members 258 are
capitivated between the generally flat surfaces 286 of
the first outside legs 270 and the second outside legs
274 such that the ribs 290 prevent them from sliding out.
Because the contact carrier/actuator assembly 254 is
symmetrical, no special positioning is required during
assembly.
