Note: Descriptions are shown in the official language in which they were submitted.
~L2~7~2~5i
BACKGROUND_OF THE INVENTION
The present invention relates to control switches,
and more particularly to a control switch for automatically
providing a safety function when the main contacts remain fused
or stuck together in the "ON" position after the switch actuator
has been moved to the "OFF" position.
During the operation of electrical equipment,
occasions can arise in which the contacts of a control switch,
e.g., a microswitch, become fused, welded or stuck together in
their ON position. This fused condition can occur under heavy
load when increased current is being drawn at the insta~lt when the
switch is turned OFF, with the result that there is arc;ing across
the ON contacts and therefore fusing or welding of the contacts occurs,
causing them to remain in their closed position, even though the
switch operating means has been moved to OFF position.
For example, a control switch may be used to operate
alternating current electrical equipment including a motor. If
the switch actuator happens to be moved to the OFF position at an
instant during a cycle of the alternating current when peak cur-
rent is flowing in a heavily loaded motor, severe arcing with
consequent welding can occur as the contacts start to part, due
to the energy stored in the magnetlc field of the motor which
momentarily tends to maintain a large current flow through the
contacts as they start to separate. Therefore, the contacts
remain fused together in their ON condition, after the switch
operating means has been turned OFF.
With a switch in this fused or "welded" condition,
the circuit to the electrical equipment is still capable of
energizing the equipment. Further, a switch in this welded con-
--2--
2~5
dition is quite dangerous to the operator of the equipment,since the operator knows that steps have previously been taken
to turn OFF the control switch, which normally opens (de-
activates) the electrical circuit. Moreover, if the operator
visually checks the switch actuating the mechanism, it is seen
to be in its open circuit position. If the switch housing is
visible and the operator visually checks, viewed from the
exterior of the switch housing, the switch appears to be de-
activated or turned OFF, because the visible switch actuating
mechanism, e.g., an actuator or manually movable handle, is in
its OFF position. However, the internal contacts, which are
welded or stuck together, remain in their ON position.
The operator of the electrical equipment is lulled
into a false sense of security when he/she looks at an operating
control or at the switch and sees that the switch actuating
mechanism is in its OFF posi-tion. Consequently, the operator
incorrectly concludes that the circuit to the electrical equip-
ment has been safely de-energized. The operator may then proceed
to perform maintenance or cleaning of the equipment, assuming
that the equipment cannot be activated. In the course of such
service, the operator may accidentally engage a nearby operating
switch. The circuit to the equipment is then completed and the
equipment then proceeds to operate, with possible consequential
damage to the equipment or injury to the operator. Moreover,
if the equipment has been partially disassembled for maintenance,
and then is activated, considerable damage may occur.
The terms "fused", "welded" or "stuck" are used
herein interchangeably in a generic sense to mean that the main
contacts of a switch are remaining together touching or joining
each other in a current-conducting relationship, when these main
~.2~ 3~
contracts are intended to be separated from each other in a non-
conducting relationship by moving the switch operating means to
the OFF position.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there
is provided a safety switch having a housing containing a first
main contact, a second main contact carried by a movable switch
arm and switch operating means being actuatable for moving said
movable arm to an ON position in which said second main contact
touches said first main contact and said switch operating means
being actuatable for moving said switch arm to an OFF position in
which said second main contact is separated from said first main
contact, said safety switch comprising:
a safety contact within aid switch housing,
a movable conductive safety switch element in said housing
movable against said safety contact for completing a
conductive path through said safety contact and said safety
switch element and being movable away from said safety
contact for interrupting said conductive path,
bias spring means in said housing operatively associated with
said safety switch element for urging said safety switch
element away from said safety contact,
control means within said housing interposed between said switch
operating means and said safety switch element normally
holding said safety switch element against said safety
contact in spite of the urging of said bias spring means,
said control means becoming immediately released from holding
said safety switch element against said safety contact if
-- 4 --
~;272~235
said swi-tch operating means is actuated for moving said
switch arm to i-ts OFF position but said second main contac-t
does no-t separate from the first main contact, and
said bias spring means immediately moving said sa~ety swi-tch
elsment away from said safety contact upon said control
means becoming released for immediately interrupting said
conductive path through said safety contact and said safety
switch ele~ent.
In accordance with the present invention in certain of
its aspects safety apparatus is provided comprising a safety
switch having a housing wherein main contacts are closed by
actuator means ~or completing a circuit and are opened by said
actuator means for interrupting the circuit for use in
association with electrical equipment wherein said switch is to
be connected in a circuit with the equipment, and the actuator
means are intended to cause the main contacts of the switch to be
opened for disabling operation of the equipment whenever an
operator moves a barrier protecting a portion of the equipment,
said safety switch comprising:
auxiliary contacts located within the switch housing,
a first pre-stressed spring in said housing associated with said
auxiliary contacts continuously urging said auxiliary
contacts toward an open position,
control means in said housing interposed between said actuator
means and said auxiliary contacts for normally overcoming
said pre-stressed spring for holding said auxiliary contacts
closed,
said control means being released within the switch housing for
allowing said pre-stressed spring immediately to open said
~27%'~
auxiliary contacts if the main contacts remain closed when
the actuator means are operated for opening the main
contacts,
a pair of auxiliary terminals external of the switch housing and
being electrically coupled to said auxiliary contacts within
the switch housing,
said auxiliary contacts completing a current flow path between
said pair of external auxiliary terminals when said
auxiliary contacts are closed,
said auxiliary contacts interrupting said current flow path when
said auxiliary contacts are opened, and
said external auxiliary terminals are adapted to be connected in
series with said circuit for interrupting the circuit for
preventing operation of the equipment, if the main contacts
of the switch remain closed when the operator moves said
barrier.
In accordance with the present invention in certain
aspects, there is provided a switch for automatically
interrupting a circuit when a pair of contacts weld together,
comprising:
a switch housing including the pair of contacts, said pair of
contacts being main contacts, one being fixed in the housing
and the other of said main contacts being movable,
a movable switch arm in said housing carrying said movable
contact,
spring means mechanically coupled to said switch arm for normally
biasing said movable contact away from said fixed contact,
actuator means movable in a first direction for overcoming the
~2~2~
biasing force of said spring means for moving said movable
contact into engagement with said fixed contact,
said actuator means being movable in a second direction for
allowing said spring means to move said switch arm for
separating the movable contact from the fixed contact,
auxiliary contact means within the housing,
a pair of auxiliary terminals external of the housing
electrically connected to said auxiliary contact means,
said external auxiliary terminals being adapted -to be connected
in the circuit to be interrupted,
control means within the housing for normally causing said
auxiliary contact means to be closed for completing a
conductive path be-tween said external auxiliary termina:Ls,
and
said control means causing said auxiliary contact means to open
for interrupting the conductive path between said external
auxiliary terminals if the actuator means is moved in said
second direction but said main switch contacts do not
separate.
In accordance with the present invention in certain
aspects there is provided an electrical switch for automatically
interrupting a conductive path between a pair of external
auxiliary terminals when a movable contact welds to another
contact in the closed position wherein a movable member in a
switch housing carries the movable contac-t, said member being
movable between an open and a closed position in response to
operation of an actuator and in which the movable contact
normally releasably engages the other contact in the closed
~2~72%3~
position and is separated from the other contact in the open
position comprising:
a pair of external auxiliary terminals on the switch housing,
auxiliary contact means within the housing electrically connected
to said external auxiliary terminals,
said auxiliary contact means norma:Lly being closed for completing
a conductive path between said external auxiliary terminals,
said auxiliary contact means being openable for interrupting the
conductive path between said external auxiliary terminals,
said movable member capable of assuming an abnormal position when
the movable contact does not separate from the other contact
and the actuator is operated to move said movable member to
the open position, and
control means in the switch housing responsive to the abnormal
position of said movable member for opening said auxiliary
contact means.
According to another aspect of this invention there is
provided a switch for automatically interrupting a circuit when a
pair of contacts weld together, comprising:
a switch housing including the pair of contacts, said pair of
contacts being main contacts, one being fixed in the housing
and the other of said main contacts being movable,
a movable switch arm in said housing carrying said movable
contact,
first spring means mechanically coupled to said switch arm
normally acting to hold said switch arm in a first position
for keeping said movable contact away from said fixed
contact,
-- 8 --
~272~3~
actua-tor means movable in a first direction overcoming the action
of said first spring means for moving said switch arm from
said first position to a second position for bringing said
movable contact into engagement with said fixed contact,
said actuator means being movable in a second direction opposite
to said first direction for allowing -the action of said
first spring means to move said switch arm from said second
position back to said first position for separating the
mov~ble contact from the fixed contact,
auxiliary contact means within the housing movable between closed
and open positions,
second spring means stressed within -the housing operatively
associated with said auxiliary contact means and
continuously exerting force for urging said auxiliary
contact means from said closed position to said open
position,
a control member normally in interposed position between said
actuator means and said auxiliary contact means,
said control member acting against the force of said stressed
second spring means for normally keeping said auxiliary
contact means in said closed position,
said control member becominy immediately released from said
interposed position if said actuator means is moved in said
second direction but said movable contact is welded to said
fixed contact preventing said first spring means from moving
said switch arm back to said first position for immediately
releasing said stressed second spring immediately to move
said auxiliary contact means from said closed to said open
- 8a -
.
. ' '~' .
~ ;~r~
~7~7~ 3
position thereby interrupting any circuit through said
auxiliary contact means.
Other objects, aspects and advantages of the present
invention will be understood from the detailed description
considered in conjunction with the drawings, which are presented
herein and should be construed in an illustrative but not in a
limiting sense, as follows:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an enlarged side elevation view of the
components of a switch embodying the present invention showing
the switch electrically coupled to driven electrical equipment
and a deactivating/warning safety circuit, with the housing of
the switch being cut away in section, and the switch is shown in
its normal OFF position;
- ~b -
'~
'
2.3~
FIG. 2 is an enlarged side elevation view of the
switch of FIG. 1, with the switch in its normal ON position;
FIG. 3 is an enlarged side elevational view of the
switch of FIG. 1, with the main switch contacts "welded" together
in their ON position, when externally the switch operating means
give the appearance that the switch is in its OFF position.
Consequently, au~iliary safet:y contact means in the switch have
functioned to give a warning and to deenergize the electrical
driven equipment which is normally controlled by the main contacts
of the switch;
FIG. 4 is an enlarged side elevational view of a
second embodiment of the present invention in which there is only
one auxiliary safety contact with one external terminal.
FIG. 5 is an enlarged side elevational view of
another switch embodying the present invention in another modi-
fication. Three different conditions of this switch are
illustrated, including the normal ON position, the normal OFF
position, and the abnormal "welded" ON position when the switch
is intended to be turned OFF. Consequently, the auxiliary
safety contact means have produced a safety function;
FIG. 6 is an enlarged side elevational view of a
switch comprising another embodiment of the invention, with
the housing of the switch being shown cut away in section and
the switch shown in its OFF position;
FIG. 7 is an enlarged side elevation view of the
switch of FIG. 6, shQwing its ON position,
FIG. 8 is an enlarged side elevational view of the
switch of FIG. 6, with the main contacts of the switch "welded"
together in their ON position, after the switch operating means
~Z7~3~i
has been move~ to OFF position. Consequent]y, auxiliary
safety contact means within the switch have been released to
move into a second relationship for producing a safety function;
FIG. 9 is a further enlargement of a portion of
FIG. 7 showing in greater detail how the auxiliary safety contact
means are being held in their first relationship against the
force of a cocked spring while the switch continues to operate
in normal manner;
FIG. 10 is a further enlargement of a portion of
FIG. 8 showing in greater detail how the auxiliary safety
contact means are released so that the cocked spring can imme-
diately move them into a second relationship for producing
a safety function, when the switch operating means are moved to
OFF position but the main switch contacts remain "welaed" to-
gether in their ON position;
FIG. 11 shows the switch of FIGS. 6 through 10
connected in a circuit including electrical equipment which is
controlled by this switch.
FIG~ 12 is an enlarged side elevational view of a
switch comprising another embodiment of the invention, with the
housing of the switch being shown cut away i~ section and the
switch shown in its OFF position. Auxiliary safety contact
means within the switch housing are normally held closed for
completing a circuit, for example, such as shown in FIG. 1~;
FIG. 13 is an enlarged side elevational view of the
switch of FIG. 12, showing its ON position;
FIG. 14 is an enlarged side elevational view of the
switch of F:CG. 12, with the main contacts of the switch "welded"
together in their ON position, after the switch operating means
has been moved to OFF position. Consequently, the auxiliary
-9A-
~72~3~i
safety contact means within the switch have a~tomatically been
released immediately to open for interrupting the circuit;
FIG. 15 is a further enlargement of a portion of FIG.
12 showing in greater detail how the auxiliary safety contact
means are being he].d closed against the force of a cocked spring
while the switch continues to operate in normal manner;
FIG. 16 is a further enlargement of a portion of FIG.
14 showing in greater detail how the auxiliary safety contact
means are released so that the cocked spring can immediately
move them into open relationship for interrupting a current flow
path, when the switch operating means are moved to OFF position
but the main switch contacts remain "welded" together :in their
ON position;
FIG. 17 is a partial sectional view taken along the
line 17-17 in FIG. 15 showing further details of the auxiliary
safety contacts and the member which normally holds them closed
against the force of a stressed cocked spring;
FIG. 18 shows the switch of FIG. 12 through 16 connect-
ed in a circuit including electrical equipment which is con-
trolled by this switch.
-9B-
~27;~3S
DETAILED DESCRIPTION
It has been a long standing problem that switch
contacts can occasionally unexpectedly become welded or fuséd or
stuck together in their ON or closed circuit condition, when
appropriate steps have been taken by an operator or by control
mechanism which are intended to turn OFF, i~e., to open a cir-
cuit, with consequent possible damage to electrical equipment
controlled by the switch or possible injury to the operator
or both. The present invention has solved this problem in a
practical, compact and feasible manner, and this invention
readily lends itself to be incorporated in various advantageous
embodiments in various switches.
Referring to FIG. 1, a switch embodying the
present invention is illustrated generally at 10. The switch 10
is shown as a master control switch for opening and closing a
control circuit 12 which energizes driven electrical equipment
14, for example, such as an electric motor drive. The switch 10
includes an insulating housing 16 having a common terminal 18
affixed to the housing 16 and extending externally therefrom.
One line 20 from a power source ~not shown), e.g., a 115V, 60 Hz
A.C. voltage source, is electrically coupled to the common
terminal 18.
A pair of spaced ON and OFF terminals 22 and 24
are also affixed to the housing 16 and extend externally there-
from. The external end 26 of the OFF terminal 24 is electrical-
ly connected to the other line 28 from the power source, e.g.
through a lead 30 and brake 32. The external end 34 of the ON
terminal 22 is electrically connected to the driven electrical
equipment 14 and the line 28, e.g. through a lead 36, an oper-
ating switch 38 and relay contacts 40.
--10--
~2~2~3S
The ON terminal 22 has an ON contact 42 affixed
to its internal end 44 located within the housing 16. Similarly,
the OFF terminal ~4 has an OFF contact 46 affixed to its inter-
nal end 48 located within the housing 16. The ON contact 42
and OFF contact 46 are positioned relative to one another to
receive a movable switch arm 50 therebetween. Specifically,
the first end 52 of the movable switch arm 50 is interposed
between the ON contact 42 and the OFF contact 46.
Affixed to the first end 52 of the movable switch
arm 50 is contact 54 which moves with the movable switch arm
50 from a first ("ON") position of engagement with, i.e., touch-
ing, the ON contact 42 (FIG. 2) to a second ("OFF") position
of separation from this ON contact 42 (FIG. 1~. Also shown
affixed to this first end 52 of the movable switch arm 50 is
another contact 55 which moves with the switch arm. When the
switch arm is in its second (OFF) position as shown in FIG. 1,
the movable contact 55 is in engagement with (touches) the OFF
contact 46. The movable switch arm 50 is normally biased up-
wardly by a spring 56, so that the movable contact 55 engages
the OFF contact 46. Advantageously, the spring 56 is mechanic-
ally coupled to the movable switch arm 50 and, e.g., affixed to
the housing 16, or other stationary component of the switch
10, to provide a bias force for urging the switch arm 50 toward
the OFF position.
The ON contact 42 and the movable contact 54 are
the "main" contacts of the switch 10. When these main contacts
42 and 54 touch each other, they enable the electrical circuit
12 which is controlled by the switch 10 and which contains the
equipment 14 to be energized.
7223~i
There is a member 58 forming an extension at the
second end of the movable switch arm, and this member 58 is
positioned proximate to but normally spaced from auxiliary
safety contact means generally indicated at 60. As shown in
FIG. l, the auxiliary safety contact means 60 include a pair
of spaced safety contacts 62 and 64. Contact 62 has a terminal
portion 66 extending externally of the housing 16 and contact
64 also has a terminal portion 68 extending externally of the
housing 16. The terminal portions 66 and 68 of these auxiliary
contacts 62 and 64 are advantageously,affixed to the housing 16,
and these auxiliary contacts are normally separated from each
other, as seen in ~IGS. l and 2.
A lead 69 electrically connects the line 20 to the
terminal portion 68. Lead 70 connects the terminal portion 66
to the line 28 through an audio or visual alarm 72 and/or elec-
trical equipment deactivating means 74, illustrated as a relay
76, which opens relay contacts 40 for deactivating the electric-
al equipment 14, and through lead 84. Advantageously, the
electrical equipment deactivating means 74 may also provide for
permanent deactivation by using a quick-acting heating element
at the location of the relay winding 76 for heating a nearby fuse
incorporated in the control circuit 12 in place of the relay
contact 40. This burnt fuse is replaced when the malfunctioned
switch 10 is replaced.
This switch 10 includes operating means for moving
its main contacts 42 and 5~ into closed ("ON") position and into
open ("OFF") position. These switch operating means include a
movable actuator shown in the form of a manually or mechanically
actuatable plunger 78 which is accessible from the exterior of
the housin~ 16, and is mechanically coupled to the movable
switch arm 50. However, it is to be understood that the
-12-
~27223~i
actuator may also be automatically actuated. The movable switch
arm 50 is included in the switch operating means, and the
actuator 78 is capable of moving this switch arm 50 from its
open to its closed position, when the actuator 78 is moved by
external means to cause the main contact 54 affixed to the first
end 52 of the movable switch arm 50 to engage the ON main contact
42. Upon release of the actl~ator 78, the spring force of
the spring 56 returns the movable switch arm 50 to its open posi
tion, as shown in FIG. 1, with contact 55 engaging contact 46.
It is to be understood that conductive means are
included in the switch housing 16 for providing an electrically
conductive path continuously existing between the common terminal
18 and the movable switch arm 50, for example, this terminal 18
is mechanically and electrically connected to a conduct:ive
element 82 which, in turn, is mechanically and electrically
coupled as desired to the switch arm 50, for example, by abutting
against the arm for maintaining sliding contact therewith or
through a hinged linkage (for example, such as shown at 104 in
FIG. 5) or through the spring 56. Thus, the common terminal 19
is continuously electrically connected to the movable arm 50
during its movement and when the contact 54 or 55 carried by
this arm is respectively engaging the ON contact 42 or the OFF
contact 46.
Referring to FIG. 2, when the actuator 78 is
depressed, the main contact 54 is moved into engagement with
the ON main contact 42, with movable switch arm 50 now moved to
its closed position. Thus, the normal sequence of operation
for a correctly functioning switch 16 is illustrated in FIGS.
1 and 2 with the movable switch arm 50, spring 56 and actuator
78 moving the main contact 54 into engagement with the ON main
contact 42 to place the switch 10 in the ON position as shown in
-13-
7~:23~i
FIG. 2, when the actuator 78 is depressed; and moving the con-
tact 55 into engagement with the OFF contact 46, as shown in
FIG. 1, when the actuator 78 is released. The member 58
of the movable switch arm 50 advantageously includes an insulat-
ing element 80 which moves with the movable switch arm 50, but
is dimensioned so that it does not normally affect the auxiliary
safety contact means 60, the latter remaining open so that the
circuit to the alarm 72 and deactivating means 74 remain in-
operative.
However, should sufficient current be flowing
through the lines 20 and 28,so that arcing occurs between the
main contact 54 and ON main contact 42, as they are being
separated, the contacts 54 and 42 may become fused or welded to-
gether. If fusing occurs, the contact 54 will remain electric-
ally connected to the ON contact 42, when the actuator 78 is
in its released or open position as shown in FIG. 3. That is,
with the main contact 54 and ON main contact 42 fused together
as shown in FIG. 3, upon release of the actuator 78, it will
move upward under the force of the spring 56 to the same posi-
tion as shown in FIG. 1. Thus, viewed from the exterior of
the housing 16, it appears that the movable switch arm 50 and
contact 54 are in th~ OFF position as shown in FIG. 1 with the
master control switch 10 open, so that the electrical equipment
14 cannot be energized even upon intentional or accidental
closure of the operating switch 38. However, in actuality, as
seen from the interior of the housing in FIG. 3,the contact 54
remains fused to the ON contact 42, and the master control switch
10 remains ON in its closed condition.
--14-
~2~2:2~5
Advantageously, if the contact 54 remains fused
to the ON contact 42 when the actuator 78 is released, the
movable switch arm 50 is dimensioned so that the spring 56 will
force the movable switch arm 50 upward causing it to effectively
pivot about the weld or fusion between the contact 54 and the ON
contact 42, with the result that the insulating element 80 on the
member 58 forming an extension at the second end o~ the movable
switch arm 50 pushes safety contact 62 deflecting its terminal
portion 66 and thus forcing it into engagement with safety con-
tact 64.
In summary, the member 58 is operatively associate-
ed with the switch operating means 78, 50 and 56. When these
switch operating means are moved to OFF position, but the main
contacts 54, 42 remain together in their ON position, then the
auxiliary safety contact means 60 are moved by the member 58
into a second relationship, as shown in FIG. 3 for producing a
safety function. Thus, a circuit is completed through the
safety contacts 62 and 64 to the alarm 72 and relay 76 to pro-
vide a visual or audible war-ning of this switch malfunction and/-
or to deactivate the electrical equipment control circuit 12 by
opening the relay contacts 40, see FIG. 3. Further, it is to
be understood that closure of safety contacts 62 and 64 may also
be utilized to provide a signal to a remote location for indicat-
ing this switch malfunction.
Referring to FIG. 4, an alternative embodiment
of the present invention is illustrated as switch 10A, with
components of this switch 10A which are similar to corresponding
components of the switch 10 being given similar reference
numerals. However, with this embodiment of the present
invention, the auxiliary safety contact means 60A include only
a single external terminal 66A with a contact 90 which is closed
by engagement with a conductive contact portion 92 affixed to
-15-
~2~:3~i
the member 58A forming an extension at the second end of the
movable switch arm 50A and thus being operatively associated
with the switch operating means 78A, 50A and 56A. When the
switch operatin~ means 78A, 50A and 56A are moved to their OFF
position, but the main contacts 54A and 52A remain together in
their ON position, then the member ~8A causes the auxiliary
safety contact means 60A to move into a second relationship as
shown in FIG. 4 for producing a safety function. The auxi-
liary contacts 92 and 90 are moved together for completion
of the circuit including the lead 70A to the alarm 72A and de-
activating relay 76A to provide an audible.or visual alarm of
the welded condition of the contacts 54A and 42A and/or for de-
activation of the electrical circuit 12A including equipment 14A.
The circuit including the lead 70Ais completed
from the supply line 20A through the common terminal 18A, through
the conductive element 82A, through the switch arm 50A and member
58A, through closed contacts 92, 90 and terminal 66A to the lead
70Ato the alarm 72A and the deactivating means 74A, 76A for the
circuit 12A and through the lead 84A to the other electrical
supply line 28A. By virtue of the fact that the circuit 12A
has been deactivated by the opening of the relay contacts 40A,
the equipment 14A cannot become energized by accidental or in-
tentional closure of the operating switch 38A. It is to be
understood that the deactivating means 74A for the circuit 12A
may comprise a fuse (not shown) at the location of the relay
contacts 40A. Such a fuse is associated with a quick-acting
heater (not shown) at the location of the relay winding 76A,
with this heater being near the fuse for immediately burning out
this fuse when the auxiliary safety contacts 92 and 90 touch
each other.
-16-
Referring to FIG. 5, another embodiment of the
present inventon is illustrated as switch 10B, with com-
ponents of this switch 10B which are similar to corresponding
components of the switches 10 and 10A being given similar
reference numerals. Common terminal 18B includes an elec-
trically conductive element portion 82B mounted internal~y of the
housing 16B, and its end 100 is secured within the housing by
being received within housing slot 102. A second electrically
conductive element 104 in the form of a movable hinged linkage is
mechanically coupled and hinged at one end to the electrically
conductive portion 82B at a slot or socket 106 and at the other
end to the movable switch arm 50B at a second slot or socket 108.
A spring means in the form of a bow spring 56B is
mechanically coupled at one end to the movable switch arm 50B at
a slot or socket 110 and is mechanically coupled at its other end
to the electrically conductive portion 82B at a slot or socket
112. The bow spring 56B is under compression, and thus it
normally applies an upward component of force to the movable
switch arm 50B to bias its contact 55B into engagement with the
OFF contact 46B. The OE'F or open position of the movable switch
arm 50B is shown in dashed outline at 50B" in FIG. 5.
Depression of the movable actuator 78B, which may
advantageously be accomplished through means of manually or auto-
matically depressing a generally L-shaped lever 111 which over-
lies the movable actuator 78B r causes the electrically conductive
linkage 104 and movable switch arm 50B to move downwardly~ over-
coming the upward bias force of the bow spring 56B to move the
movable main contact 54B into engagement with the ON main contact
42B. The normal ON or closed position of the switch arm 50
is shown at dashed outline 50'B.
Upon release of the actuator 78B the movable switch
arm 50B normally assumes the open position 50B" with the movable
contact 54B engaging the OFF contact 46B as shown in dashed out-
line in FIG. 5. However, should fusing or welding of the main
contacts 54B and 42B occur, then the movable switch arm 50Bwill
assume the abnormal tilted or canted position shown in solid
outline in FIG. 5.
Auxiliary safety contact means 60B are illustrated
in FIG. 5 to include two spaced contact elements 62B and 64B
and their respective external terminals 66B and 68B. However,
it is to be understood that the auxiliary safety contact means
60B may optionally include only one contact element 62B and its
external terminal 66B, similar to FIG. 4. In the event there
is only the one auxiliary safety contact element 62B with its
external terminal 66B, then the associated alarm and/or de~
activation circuit is closed by a conductive leaf spring member
116 ~FIG. 5)to be described touching a contact 113 of the con-
tact element 62B. The two spaced contact elements 62B and 64B
are positioned proximately to leaf spring member 116 associated
with the second end 58B of the movable switch arm 50B. Contact
elements 62B and 64B include contact portions 113 and 114, res-
pectively. The leaf spring member 116 has a generally U shaped
configuration with a short arm portion 118 and a long arm
portion 120, and is positioned wlth its bight extending around a
mounting pin 122 af:Eixed to the housing 16B. The end 124oE the
short arm portion 118 is positioned in pressure contact with the
contact port:ion 114 of the contact 64B. The end 126 of the
long arm port:ion 120is positioned inpressure contact with a
notched portion 128 formed near the end 58B of the movable
switch arm 50B.
-18-
~2~ 3~
The spring 116is configured so that upon
depression of the actuator 7~B by the lever 111 to place the
switch lOB in the ON position, the long arm portion 120 of the
spring 116will be deflected downwardly as shown in dashed out-
line at 120' as the movable switch arm 50B is moved downwardly to
the generally horizontal ON position shown in dashed outline 50B'
in FIG. 5. The end 124 of the spring 116 will remain in engage-
ment with the contact portion 114 of contact 64B; however, there
is no engagement between the deflected spring 120' and the contact
portion 113. Thus, the circuit between contacts 62B and 64B
and thus between terminals 66B and 68B remains open when the
switch lOBis in the ON position.
Upon release of the actuator 78B by the release of
the lever 111, the movable switch arm 50BWill move upwardly
under the biasing force of the bow spring 56B. 2~ormally, when
the contacts 54B and 42B are not welded or fused together, upon
release of the actuator 78B, the bow spring 56Bwill move the
movable switch arm 50B to the generally horizontal OFF loPen)
position, as shown in dashed outline at 50B". The ~novable con-
tact 54Bis now in engagement with the OFF contact 46B, and the
spring 116, specifically its long arm portion 120 is positioned
slightly below the contact portion 113 in spaced non-contacting
relationship. Thus, auxiliary safety contact means 60B remains
electrically open, when the switch arm is in its normal OFF
(open) position 50B".
In the event that the contacts 5~B and 42B become
fused or we]Lded together, when the actuator 7~B is released,
the bow spring 56Bwill move the movable switch arm 50B upwardly
causing the movable switch arm 50B to effectively pivot about
the welded region to assume an abnormal canted or tilted posi-
tion, as shown in solid outline in FIG. 5. In this canted
--19--
~72%35i
arm position, the long arm portion 120 of the spring 116
effectively moves upwardly higher than normal, thereby touch-
ing the contact portion 113 for completing a circuit between
the terminals 66B and 68B.
The long arm spring portion 120 is allowed by
canted switch arm 50B to move higher than normal, because the
second (left) end 58B of the canted arm 50B i5 above its normal
OFF (open) position 50B". Also, the long arm spring portion
120 is now allowed to move slightly forward (leftward) in the
notched portion 128, since the end 58B of canted switch arm 50B
has tilted up slightly above its normal horizontal OFF position,
with the result that the point of application of the downward
force on the long arm portion 120 is further rearward ~rightward)
toward the end 126 of the long arm portion 120, thereby allowing
the long arm portion 120 to bow upward into engagement with the
contact portion 113 to complete a circuit through the auxiliary
safety contacts 62B and 64B, and thus through the terminals 66B
and 68B. The circuit between the contacts 62B and 64B is now
completed through the conducti~e leaf spring member 116 touching
contact portion 113 and 114.
It is to be understood that the switch 10B of
FIG. 5 can be connected into any desired electrical control cir-
cuit, for example, such as the circuit 12 shown in FIGS. 1 and
3 or,for example, such as the circuit 12A shown in FIG. 4. In
other words, the switch 10B can be substituted for the switch
10 in FIGS. 1, 2 and 3, and this switch 10B can be substituted
for the switch 10A in FIG. 4.
In operation, referring first to FIGS. 1 through
3, when the actuator 78 is in its released position, as shown
-20-
~2'~
in FIG. 1, the spring force from sprin~ 56 biases the movable
switch arm 50 upwardly so that the contact 55 normally engages
the OFF contact 46. Thus, a circuit is completed from the
power source (not shown) through the line 20, the common
terminal 18, electrically conductive element 82, movable switch
arm 50 and its contact 55, OFF contact 46, OFF terminal 26, lead
30, brake 32, and line 28 to activate the brake 32
and stop the driven electrical equipment 14. Moreover, with
the master control switch 10 in the position illustrated in FIG.
1, the electrical equipment 14 cannot be energized even when the
operating switch 38 is closed.
However, upon depression of the actuator 78, the up-
ward biasing force of the spring 56 is overcome, and the movable
switch arm 50 is moved downwardly under the influence of the
force of the actuator 78, so that the contact 54 engages the ON
contact 42, as seen in FIG. 2. The circuit to the brake 32 is
now open, and the circuit to the electrical equipment 14 is
placed in a ready state by completion of a circuit to one side of
the operating switch 38 through line 20, common terminal 18,
electrically conductive element 82, movable switch arm 60, ON
contact 42, and ON terminal 34. The other side of the oper-
ating switch 38 is electrically coupled to the power source
through the line 28, the electrical equipment 14, and the relay
contacts 40. Thus, upon closure of the operating switch 38 by
the operator the electrical equipment 14 is energized to run.
In the event that the main contact 54 and the
ON main contact 42 remain fused or welded together, when the
actuator 78 is released, the brake 32 is not energized and the
electrical equipment 14 remains in the dangerous condition of
being capable of being energized upon intentional or accidental
closure of the operating switch 38. Further, the brake 32 is
~2~2~3S
not being energized to stop any coasting of the electrical
equipment 14. However, advantageously, the auxiliary safety
contact means 60 are closed by the movable member 58 on the
movable switch arm 50 in its abnormal position for causing the
circuit to the alarm 72 and relay 76 to be completed from the
power source through line 20, lead 68, safety contacts 65 and
62, and lead 70 through alarm 72 and relay 76 and lead 84 to
line 28. Thus, an audible or visual alarm is provided, and the
electrical equipment 14 is deactivated by opening relay contacts
40, or a fuse as described earlier. Therefore, even in the
presence of intentional or accidental closure of the operating
switch 38, the electrical equipment 14 remains deactivated.
Further, a safety indication 72 is provided to the operator
that the brake 32 has not been energized to stop the electrical
equipment 14 if it is coasting after the switch operating means
has been moved to OFF position.
The operation of the auxiliary safety contact means
60A in FIG. 4 is similar to that shown in FIGS 1-3, with the
exception that the contact 90 is closed through engagement with
an electrically conductive contact 92 by the movable member 58A
on the movable switch arm 50A. A circuit is completed from the
power source through line 20A, common terminal 18A, electrically
conductive element 82A, movable switch arm 50A, safety contact
92, safety contact 90, lead 70A, through alarm 72A, relay 74 and
lead 84A to line 2 8A back to the power sourae.
The operation of the auxiliary sa~ety contact means
60B in FIG. 5 to close a circuit to the power source is similar
to that shown in FIG. 1 to 3. However, in the embodiment of
FIG. 5, th~ abnormal upward canting movement of the movable
switch arm 50B allows the long arm portion 120 of the spring
member 116 to come into engagement with the contact portion 113
of the contact terminal 62B for completing a circuit between
- 22 -
2;~3~
the contact portions 114 and 113 and thus completing a circuit
between the terminals 66B and 68B, when ~he contacts 54B and
42B are fused or welded together and the actuator 78Bis
released.
A modified embodiment similar to FIG. 5 may be
employed which includes only a single contact member 62B, and
external terminal 66B, and the second contact 64B and terminal
68B as shown in FIG. 5 would be eliminated. With such a modi-
fied embodiment, the external electrical connections would be
similar to those in FIG. 4. The end 124 of the short arm
portion 118 of the spring 116 would rest against an insulating
portion of the housing 16B. Completion of the electric:al cir-
cuit to the various safety devices would occur when the long a~
portion 120 engages the contact portion 113 of the contact 62B,
with the circuit through the master control switch lOB being
completed through the terminal 66B, contact portion 113, spring
member 116, movable switch arm 58B, electrically conductive
elements 104 and 82B, and terminal 18B.
The various switch embodiments of the present
invention are described as including an OFF contact 46, 46A or
46B and an OFF external terminal 26, 26Aor26B. It is to be
understood that the intended meaning of "OFF contact" is to be
broadly construed to include either a conductive or a non-con-
ductive element against which a portion of the first end 52, 52A
or 52B of the switch arm 50, 50A or 50B comes to rest when the
switch arm is in its normal OFF (open) position. For example,
the OFF contact 46, 46A or 46B can be omitted entirely to be
replaced by a non-conductive abutment or fixed post serving
merely as a mechanical stop in the housing 16, 16A or 16B, and
then the external OFF terminal 26, 48 or 26A, 48A or 26B, 48Bis
also omitted. In other words, the described embodiments of
-23-
~2~223~
the present invention solve the problem of main switch contacts
42, 54 or 42A, 54A or 42B, 54B becoming fused, welded or struck
together in their ON position, regardless of whether the OFF
contact is conductive or non-conductive or omitted or non-
existent or is present but not utilized in any external circuit.
It is to be understood that the OFF contact (or button element)
55 or 55A or 55B carried by the first end 52, 52A or 52B of the
switch arm 50 or 50A or 50B serves as a mechanical stop which
abuts against an opposed element, such as a contact or stop 46,
46A or 46B, when the switch arm is moved to its normal OFF posi-
tion, for limiting and defining the amount of upward travel of
this first end of the switch arm when it is moved to its open
(OFF) position as pushed upwardly by the spring means 56, 56A or
56B. The shoulders 79B on the actuator 78B normally serve as
stop means for limiting the upward travel of the second end of
the switch arm. In the switches 10 and 10A, the upward travel
of the second end of the switch arm 50 or 50A is limited by the
length of the spring 56 or 56A. If desired, shoulders similar
to those at 79B in FIG. 5 can be provided on the actuator 78 or
78A.
Referring to FIGS. 6 through 10, a further embodi-
ment of the present invention is illustrated as switch 10C,
with components of this switch 10C which are similar to corres-
ponding components of the switch 10 or 10A or 10B being given
similar reference numerals. The right half of this switch 10C
is very similar to the right half of the switch 10B, except
that the contact element 46C merely serves as a mechanical stop
and does n~t perform any electrical function. This stop contact
46C is mounted upon a support 48C which is anchored in the wall
of the housing 16C. The housing 16C is molded of durable rigid
-24-
~72~3S
insulating plastic material in two mating parts. After the
switch components have been assembled in the interior of the
housing, its two mating parts are secured together by fastening
means, for example, rivets or screws or bolts and nuts, which are
inserted through appropriate mounting holes, for example, at 94
and 96. It is to be understood that the other switch housings
16, 16A and 16B can similarly be assembled from two mating parts.
The left half of this switch 10C is different from
the left half of the switch 10B, as will now be explained. There
is a control leg 130 extending diagonally from the left (second)
end of the movable switch arm 50C. The foot end 129 of this
diagonal control leg 130 is received loosely in a recess 132 at
the lower left corner of the housing 16C. The purpose of this
diagonal control leg 130 is to stabilize, define and mechanically
control the desired movement of the switch arm 50C for making its
motion behave in a predetermined manner as will now be explained.
In FIG. 6, the switch arm 50C is shown in its
normal open ~OFF) position with its main contact 54C separated
from the ON main contact 42C. The foot end 129 of the control
leg is abutting at 134 against the top of the recess 130, while
the button element 55C abuts against the stop 46C. In other
words, the bow spring 56C is exerting an upward component of
force, and the upward travel of the switch arm 50C is stopped
at 134 and at 46C. Also, the shoulders 79C serve as stops for
limiting upward travel of the actuator 78C and of the switch
arm.
In FIG. 7, the switch arm 50C is shown in its
normal closed (ON) position with the main contacts 54C and 42C
firmly touching each other. As the actuator 78C is moved
-25
~2235i
downwardly (arrow 135) in going from its initial outer position
shown in FIG. 6 to its fully depressed position shown in FIG. 7,
the foot end 129 initially moves down in its recess 132 until
it touches the lower side of lhis recess at 136 as shown in
FIG. 7. This mechanical abutting at 136 arrests the downward
movement of the control leg 130 and thereby positively causes the
right (first) end 52C of the switch arm 50C to swing down firmly
for bringing the main contacts 54C and 42C together in firm con-
tact as shown in FIG. 7.
Summarizing, during the downward motion 135 of the
actuator 78C, the foot end 129 moves down until it abuts against
the housing wall at 136. Thereafter, this foot end 12~ acts
like a fulcrum pivot, forming a pivot point at 136 for positively
causing the first end 52C of the switch arm 50C to swing down
firmly into the closed position, as shown in FIG. 7. The bow
spring 56C plus the hinged link 104 produce a quick-acting
toggle-like action. Consequently, after the fulcrum pivot has
been established at 136 and after the first end 52C of the switch
arm has begun to swing down and while the hinged link 104 is
swinging down about its fixed pivot point at 106~ the bow
spring moves past its toggle position, and then the first end 52C
of the switch arm swings down quickly with a snap-like action into
its fully closed position, as shown in FIG. 7. The spring 56C
continues to exert an upward component of force, but the main
contacts are held firmly closed by the depressed 135 actuator
78C.
Conversely, as the actuator 78C is allowed to move
upwardly for turning the switch 10C OFF, the foot end 129
initially rises being pushed upwardly by the u~rd component of
-26-
~272Z35
bow spring force, until this foot end 129 forms an abutting
fulcrum at 134 (FIG. 6). While the pivotable link 104 is
swinging upwardly about its fixed pivot point 106 and when the
first end 52C of the switch arm begins to move upwardly, the
bow spring 56C passes its toggle point, and the first end of
the switch arm then quickly snaps up to its fully open position
as shown in FIG. 6.
At the left (second) end of the housing 16C are
auxiliary safety contact means generally indicated at 60C.
These auxiliary safety contact means 60C include the pair of
spaced auxiliary safety contacts 62C and 64C which slope inwardly
toward each other and have external terminal portions 66C and 68C
respectively. Positioned between the two contacts 62C and 64C
is a movable conductive safe~y switch element 140 having a
truncated conical cup-shape for conforming with these contacts,
as seen most clearly in FIGS. 9 and 10. This safety switch
element 140 is normally in open position; that is, spaced from
its contacts 62C and 64C, as shown in FIGS. 6, 7 and 9, so long
as the main contacts 54C, 42C do not become fused together as
they are shown in FIG. 8.
A coil spring 142 seating in a recess 144 presses
against the switch element 140 for urging it toward closed posi-
tion wherein it bridges across between its contacts 62C, 64C, as
shown in FIGS. 8 and 10. In order to control the auxiliary
safety switch means 60C by normally restraining the switch
element 140 against the switch-closing bias force of the spring
142, there is a rod-like control member 150, as illustrated most
clearly in FIGS. 9 and 10. As will be explained later, this
control member 150 is operatively associated with the switch
operating mechanism, which includes the actuator 78C, the switch
-27-
~2~22~
~.J
arm 50C and its leg 130 and the hinged link 104 plus bow spring
56C. This control member 150 has one of its ends 152 ~FIGS. 9
and 10) inserted in loose-fitting relationship through a hole
in the center of the switch element 140, and it has a pair of
shoulders 154 (only one is seen) against which the switch
element 140 is pushed by the spring 142.
The second end 156 of the control member 150 is
normally being pushed toward the right by the bias spring 1~2, so
that this end 156 thrusts against the upper end 159 of the hinged
link 104. This end 159 of the link 104 extends up through an
opening or slot 108 in the switch arm 50C. Thus, the control
member 150 is normally prevented from moving toward the right
under the bias force of the spring 142, because its second end 156
is abutting against the upper end 159 of the link 104 which acts
as a mechanical stop. Preferably, to electrically isolate the
auxiliary safety contact means 60C from the remainder of the
switch components, then the control member 150 is formed from
riyid insulating material.
In addition to the switch-closing compression spring
142, there is a leaf spring 160 which serves as a trigger spring.
This trigger spring 160 has its second end 158 anchored in a
socket 162, while its first end 164 continually exerts an upward
force on the control member 150, i.e. exerts a force in a
direction generally transverse with respect to the length of said
control member.
When the actuator 78C is depressed as shown by arrow
135 (FIGS. 7 and 9) turning the switch ON, the control member
150 swings (tilts) downwardly as its second end 156 (FIG. 9) is
pushed down by the actuator. Its first end 152 is sufficiently
-28-
~272~3S
loosely received in the hole in the switch element 140 for allow-
ing this slight tilting movement of the control member 150 with-
out also tilting the switch element. Conversely, when the
actuator is moved to OFF position, the control member 150 swings
back up to a more nearly horizontal position as shown in FIG. 6.
Thus, in this normal ON and OFF operation, the second end 156 of
the control member always remains abutting against the upper end
159 of the hinged link 104. The rightward thrust of the safety
switch-closing spring 142, which causes a rightward thrust of
the control member 150 against the end 159 of the hinged link
104 whi~h, in turn, causes a rightward thrust of the hlnged
link 104, is ultimately resisted by the fixed pivot at 106
where the end of link 104 is hingedly received in a socket slot
in the portion 82C of the fixed com~on terminal 82C.
In the event that the main contacts 54C, 42C remain
welded, fused, or stuck together as shown in FIG. 8 when the
actuator 78C is allowed to move upwardly as indicated by arrow
137 for turning the switch OFF, then these joined-together con-
tacts 54C-42C act as a hinge or pivot point to prevent the first
end 52C of the switch arm 50C from rising. The upward component
of force exerted by bow spring 56C causes the second end of the
switch arm to swing up until the foot end 129 of leg 130 abuts
against the recess wall at 136 preventing further upward movement
of the switch arm. That is, the upward motion of the switch arm
50C is now totally arrested at both of its ends, but the first
end 164 of the trigger spring 160 continues to lift upwardly on
the control member 150 as indicated by the curved arrow 166 (FIGS.
8 and 10).
-29-
~2~223S
Thus, the switch operating means has assumed an ab-
normal position when the upward motion of the switch arm 50C is
arrested at both ends while the actuator 58C is being moved
toward ~FF position.
As seen most clearly in FIG. 10, this trigger spring
now causes the second end 156 of the control member ].50 to be
lifted as shown by arrow 167 above the end 159 of the link 104,
thus immediately releasing the control member i50 to move to the
right as indicated by arrow 168, thus allowing the compressed or
cocked spring 142 to quickly move the switch element 140 into its
closed position bridging across between safety contacts 62C and
64C for automatically effecting a desired safety funct:ion. The
desired safety function(s) which is (are) effected by closure of
the auxiliary safety contact means 60C is (are) determined by the
particular arrangement of the associated control circuit, for
example, such as the circuit 12C shown in FIG. 11, for de
activating the electrical equipment 14 and for giving an alarm
signal.
The control circuit 12C shown in FIG. 11 is similar
to the control circuit 12 shown in FIGS. 1 and 2, except that
the OFF terminal 24 and the brake 32 are omitted. Also, the
deactivating means 74 is shown as including a fast-acting heater
76C near a fuse 40C.
It is to be understood that the switch 10C is
adapted to include an L-shaped actuator lever for depressing
the actuator 78C, similar to the lever 111 in FIG. 5. The
fixed end of this actuator lever is mounted in an external
socket 170 in the housing 16C.
-30-
~.~72~:;35
Referring to FIG. 12, a safety switch embodyiny the
present invention is illustrated generally at 10D. This switch
10D is shown by way of example as a control switch used with an
interlock mechanism 211 (FIG. 18) for opening and closing a cir~
cuit 212, for example as shown in FIG. 18, which energizes elec-
trical equipment 214, for example such as an ele~tric motor dri~e
for driving a tool or other machinery 215.
This interlock mechanism 211 is illustratively shown
associated as indicated by the dashed line 217 with a cover or
door 219 which blocks access to the tool or machinery 2L5, until
this access barrier 219 is opened. The interlock mechanism in-
cludes a plunger 221 which depresses a switch operating level
223 and an actuator 225 for keeping the switch 10D in its ON
condition, so long as the access barrier 219 is closed. When the
operator opens the barrier 219 to obtain access to the tool or
machinery 215, the interlock mechanism 211 causes the plunger 221
to oe raised, thus allowing the actuator 225 to move upwardly as
explained later fox turning OFF the switch 10D for preventing
the motor drive 214 from becoming energized.
The switch 10D includes an insulating housing 216 hav-
ing a fixed common terminal 218 extending externally from the
housing. A pair of fixed spaced ON and OFF terminals 222 and
224 also Pxtend externally from the housing.
The ON terminal 222 has an ON contact 232 fastened to
its internal end 236 located within the housing 216. Similarly,
the OFF termlnal 224 has an OFF contact 234 fastened to its
internal end 218 located within the housing 216. The ON contact
-31-
~%~23~i
232 and OFF contact 234 are spaced relative to one another to
receive the end of a movable switch arm 240 between them.
Specifically, the first end 242 of the movable switch arm 240
is interposed between the ON contact 232 and the OFF contact 234.
Affixed to this first end 242 of the movable switch arm
240 is a contact 244 which moves with the arm between an ON posi-
tion of engagement with, i.e., touching the ON contact 232 (FIG.13)
to an OFF position of separation from this ON contact (FIG. 12).
~lso shown affixed to this first end 242 of the switch arm is a
movable contact 245 which moves with the arm. When the switch
arm is in its OFF position, as shown in FIG. 12, the movable con-
tact 245 is in engagement with (touches) the OFF contact 234.
The movable switch arm 240 is biased upwardly by a bow spring 246,
so that the movable contact 245 normally engages the OFF contact
234. This spring 246 is mechanically coupled to the movable
switch arm 240 and thrusts at a location 227 against the station-
ary internal end 228 of the common terminal 218 for providing a
bias force urging the switch arm 240 toward the OFF position.
This inner end portion 228 of the common terminal is anchored in
a recess 229 in the wall of the switch housing, and there is a
notch or concave bend at the location 227 for receiving the end
of the bow spring 246. The other end of the bow spring hooks at
231 into a slot in the switch arm 240. If desired, the switch
operating level 223 may be omitted from the switch 10D as is
shown in FIGS. 12-14, in which case the plunger 221 is directly
aligned over the actuator 225 for depressing it. Although this
switch actuator 225 is illustratively shown to be moved by an
interlock mechanism, it is to be understood that this actuator
may be moved down or depressed by external operation of the
switch in a variety of ways, such as manually or mechanically,
depending upon the particular installation in which the switch
is used.
~2~ S
When the actuator 225 is pushed down as shown by the
arrow 247 in FIG. 13, the switch arm 240 is caused to move down
into its closed (ON) position against the force of the bow spring
246 for bringing the main contacts 244 and 232 together for com-
pleting a conductive path between the common terminal 218 and
the ON terminal 222.
The ON contact 232 and the movable contact 244 are
considered the "main" contacts of the switch 10D, because the
closure of these main contacts enables the electrical circuit 212,
which is controlled by the switch 10D and which contains the
equipment 214, to be energized by closure of an operating switch
230 (FIG. 18) which is included in the circuit 212.
The switch 10D includes operating means for moving its
main contacts 244, 232 into the closed ~ON) position and into the
open (OFF) position. These switch operating means include the
actuator 225 already described (plus the level 223 if it is
present) and the bowed spring 246 and also a movable link 248 to
be described. This movable link 248 is formed of electrically
conductive material having the lower of its ends hingedly sealed
at 249 to the inner portion 228 of the common terminal 218. For
example, this hinged relationship at 249 is provided by receiving
the end of the link 248 into a recess or slot in the fixed termi-
nal portion 228. The upper end 250 of this movable link 248 is
hingedly sealed at 251 on the switch arm. For example, this
hinged relationship at 251 is provided, as seen most clearly in
FIGS. 15 and 16, by extending the link end 250 up through an
opening 252 in the switch arm 240 for the edge of this opening
to rest in a notch in the side of the link end 250. Thus, this
hinged link 248 serves as a component of the switch operating
means for it swings down with the switch arm about its fixed
hinge location at 249, as seen in FIG. 13, when the switch arm
-33-
3r~
240 is moved down to the closed (ON) position by depressing the
actuator 225 as shown by the arrow 247. The bow spring 246 con-
tinues to exert an upward component of force on the switch arm
240, regardless OI whether the switch arm is in its opne (FIG.12)
or closed (FIG. 13) position.
Forming part of the operating means for the switch arm
240, there is a control leg 260 extending diagonally from the
left (second) end of the movable swithc arm 240. The foot end
258 of this diagona.l control leg 260 is received loosely in a
recess 262 at the lower left corner of the housing 216. The
purpose of this diagonal control leg 260 is to define and mech
anically control the desired movement of the switch arm 240.
In FIG. 13, the switch arm 240 is shown in il:s normal
closed (ON) position with the main contacts 244 and 232 firmly
touching each other. As the actuator 225 is moved downwardly
(arrow 247) in going from its initial outer position shown in
FIG. 12 to its fully depressed position shown in FI~. 13, the
foot end 258 initially moves down in its recess 262 until it'
touches the lower side of this recess at 264 as shown in FIG.
13. This abutting at 264 arrests the downard movement of the
control leg 260 and thereby positively causes the right (first)
end 242 of the switch arm to swing down for bringing the main
contacts 244 and 232 together in firm contact as shown in FIG.
13.
In operation, during the downward motion 247 of the
actuator 225, the foot end 258 moves down until it abuts against
the housing wall at 264. Thereafter, this foot end acts like a
fulcrum pivot at 264 for positively causing the first end 242 of
the switch alrm 240 to swing down firmly into the closed position,
as shown in FIG. 13. The bow spring 246 plus the hinged link 248
-34-
~2t7223~i
produce a quick, toggle-like action. Consequently, after the
fulcrum pivot has been established at 264 and after the first
end 242 of the switch arm ha.s begun to swing down and while the
hinged link 248 is swinging down about its fixed pivot point at
249, the bow spring moves past its toggle position, and then the
first end 242 of the switch arm swings down quickly with a snap~
like action into its fully c:Losed position, as shown in FIG. 13.
The spring 246 continues to exert an upward component of force,
but the main contacts are held firmly closed by the depressed
(arrow 247) actuator 225.
Conversely, as the actuator 225 is allowed to move
upwardly for turning OFF the switch 10Dj the foot end 258 ini-
tially rises being pushed upwardly by the upward component of
bow spring force, until this foot end forms an abutting fulcrum
at 266 (FIG. 14). While the link 248 is swinging upwardly about
its fixed pivot point 249 and when the first end 242 of the
switch arm begins to move upwardly, the bow spring 246 passes
its toggle point, and the first end of the switch arm then
~uickly snaps up to its fully open position as shown in FIG. 12.
If sufficient current happens to be flowing through
the electrical equipment 214 (FIG. 18), so that arcing occurs
between the main contacts 232 and 244 as they are being separated
when the switch is being turned OFF, then these main contacts
may become fused or welded together. If fusing occurs, the con-
tact 244 will remain electrically connected to the ON contact
232 when the actuator 225 is in its released or open position as
shown in FIG. 14.
In order advantageously to disable or interrupt the
electrical circuit 212, which is under control of the switch 10D,
in the event that its main contacts 244 and 232 remain together
when the act:uator 225 is released as shown by the arrow 256,
~ ~7;~23S
auxiliary safety contact means, generally indicated at 70, are
provided in the housing 16. The auxiliary safety contact means
70 include a pair of spaced auxiliary safety contacts 272 and
274 which extend toward each other and have respective external
terminal portions 276 and 278. Positioned near these two con-
tacts 272 and 274 is a movable conductive safety swithc element
280 having a cup-shape with a flat circular flange 282 (FIGS.
15 and 16) for pressing flat against these contacts in good con-
ductive relationship as seen in FIG. lS for providing a highly
conductive path through the switch element 280 bridging across
these contacts. This safety switch element 280 is normally in
closed position; that is, engaging both contacts 272 and 274 so
long as the main contacts 244, 232 do not become fused together
as they are shown in FIG. 14.
A larger diameter coil spring 284 has one end pressing
against the flange 282 for urging the switch element 280 toward
closed position wherein it bridges across between contacts 272,
274, as shown in FIGS. 12, 13, and 14. The other end of this
coil spring 284 (FIG. 17) presses against a pair of shoulders
286 on a movable rigid insulating member 288 which serves to
control the position of the switch element 280 be being opera-
tively associated with the switch operating means, as will be
explained later. This control member 288 has one of its ends
290 ~FIG. 15, 16 and 17) inserted in loose-fitting relationship
through an aperture 292 in the center of the switch element 280.
A smaller diameter coil spring 294 seating in a recess
296 in the switch housing presses against a pair of shoulders
298 on the control member 288 for continuously urging or biasing
the control rnember toward the right, namely toward opening the
auxiliary safety contact means 270. Thus, the second end 300 of
this control member is normally being pushed toward the right by
the bias spring 294, so that this end 300 thrusts against the
upper end 250 of the hinged link 248. The control member 288 is
normally prevented from moving toward the right under the bias
-~.6-
~7223~
force of the switch-opening spring 294, because its second end
300 is abutting against the upper end of the link 248 which is
acting as a mechanical stop having a ~ixed hinge point 249.
In addition to this switch-opening compression spring
294, there is a leaf spring :310 which serves as a trigger spring.
This trigger spring has its second end 308 anchored in a socket
312, while its first end 314 continually exerts an upward force
on the control member 288, i e., exerts a force in a direction
generally transverse with respect to the length of said control
member.
When the actuator 225 is depressed as shown by arrow
247 ~FIG. 13) turning the switch ON, the control member 288
swings (tilts) downwardly as its second end 300 is pushed down
by the actuator. Its first end 290 is sufficiently loosely re-
ceived in the aperture in the switch element 280 for allowing
this slight tilting movement of the control member without also
tilting the switch element. Conversely, when the actuator is
moved to OFF position, the control member 288 swings back up to
a more nearly horizontal position as shown in FIGS. 12 and 15.
Thus, in this normal ON and OFF operationS the second
end 300 of the control member 288 always remains abutting against
the upper end 250 of the hinged link 248. The rightward thrust
of the switch-opening spring 294, which causes a rightward thrust
of the control member 288 against the end 250 of the hinged link
248 which, in turn, causes a rightward thrust of the hinged link
248, is ultimately resisted by the fixed pivot at 2~9.
In order to assure that the control member end 300 will
remain normally abutting against the side surface of the hinged
link end serving as stop 250, the switch actuator 225 has a
special configuration on its lower portion. There is an elevated
central clearance recess 316 (FIG. 15) defining a downwardly pro-
truding leg 318 which normally holds the control member end 300
~27223~
down below the upper extremity of the stop 250, where the control
member end cannot normally slip past this stop.
In the event that the main contacts 244,232 remain
welded, fused, or stuck together as shown in FIG. 14 when the
actuator 225 is allowed to move upwardly as indicated by arrow 256
for turning the switch OFF, then these joined-together contacts
244-232 prevent the first end 242 of the switch arm 240 from ris-
ing. The upward component of force exerted by bow spring 246
causes the second end 254 of the switch arm to swing up until the
foot end 258 of the leg 260 abuts against the recess wall at 266
preventing further upward movement of the switch arm. That is,
the upward motion of the switch arm 240 is now totally arrested
at both of its ends, but the first end 314 of the trigger spring
310 continues to lift upwardly on the control member 288 as in-
dicated by the curved arrow 320 (FIG. 16).
The switch operating means has assumed an abnormal
position when the upward motion of the switch arm 240 is arrested
at both ends while the actuator 225 is being moved 256 toward OFF
position.
Rs seen most clearly in FIG~ 16, this trigger spring
310 now causes the second end 300 of the control member 285 to
be lifted as shown by arrow 322 above the stop end 250 of the
link 248, thus immediately releasing the control member to move
to the right as indicated by arrow 324, thus allowing the com-
pressed spring 294 suddenly to lengthen to quickly move the switch
element 280 into its open position. The circular shaped of the
end of the coil spring 294 does not fit through the slotted ap-
erture 292, even though the strip-shaped control member 288 can
slide freely through the aperture as seen in FIGo 16. Consequent-
ly, the spring 294 moves the switch element 280 to the right as
-38-
235
seen in FIG. 16, and the conductive path between the auxiliary
safety terminals 276 and 278 is interrupted.
In order to arrest the rightward movement 324 of the
mem~er 288, the lower portion of the actuator 225 has a second
downwardly protruding leg 328 which is long enough to extend down
into the opening 252 in the switch arm 240. The end 300 of the
control member 288 is stopped by this leg 328.
The actuator 225 is made of rigid insulating material.
The housing 216 is molded of durable rigid insulating plastic
material in two mating parts. After the switch components have
been assembled in the interior of the housing, its two mating
parts are secured together by fastening means, for example,
rivets or screws or bolts and nuts, which are inserted through
appropriate mounting holes, for example, at 329 and 330.
As shown in FIG. 18, an advantageous way to connect the
switch 10D into a circuit 212 is to include the auxiliary safety
contact means 270 in series with the electrical equipment 214.
One electrical supply line 332 (FIG. 18) from a power source (not
shown), e.g., a 115V, 60 Hz A.C. ~oltage source, is shown elec-
trically connected to the common terminal 218. The operating
switch 230 may be included in this supply line, if desired. The
OFF terminal 224 is shown electrically connected to the other
supply line 334 from the power source, e.g., through a lead 336
to a brake 338 and through a lead 340 to the supply line 334.
Thus, the brake 338 is applied whenever the swithc 10D is OFF.
The ON terminal 222 is connected through a lead 342 to one of
the safety terminals 276 or 278, and another lead 334 is connect-
ed from the other safety terminal to the equipment 214 being
controlled, with a lead 346 from the equipment to the other sup-
ply line 334. Therefore, the auxiliary safet contact means are
-39-
~27~:3~
connected directly in series with the electrical load 214. In-
terrupting the conductive path between the terminals 276, 278
will immediately disable the circuit 212 so that the equipment
will not become energized by closure of the operating switch 230.
This operating switch may be included at any desired location in
circuit in series with the electrical load 214. For example,
this operating switch may be located at 230' in the lead 344 in-
stead of being at 230 in the supply line 332.
The switch embodiment 10D of the present invention has
been described as including an OFF contact 234 and an OFF external
terminal 224.
It is to be understood that the intended meaning of
"OFF contact" is to be broadly construed to include either a
conductive or a non-conductive element 234 against which a por-
tion 245 of the first end 242 of the switch arm 240 comes to rest
when the switch arm is in its normal OFF (open) position. For
example, the OFF contact can be omitted entirely to be replaced
by a non-conductive abutment or fixed post serving merely as a
mechanical stop in the housing 216, and then the external OFF
terminal 224 and the brake circuit 336, 338 and 340 are omitted.
In other words, the described embodiment of the present inven-
tion solves the problem of main switch contacts 244, 232 becom-
ing fused, welded or stuck together in their ON position, regard-
less of whether the OFF contact is conductive or non-conductive
or omitted or non-existent or is present but not utilized in any
external circuit. It is to be understood that the contact (or
button element) 245 carried by the first end 242 of the switch
arm 240 serves as a mechanical stop which abuts against an op-
posed element, such as a contact or stop 234 when the switch arm
is moved to its normal OFF position, for limiting and defining
-40-
2~3~
the amount of upward travel of this first end of the switch arm
when it is moved to its open (OFF~ position as pushed upwardly
by the spring means 246. The shoulders 348 on the actuator 225
serve as stio means for limiting the upward travel of the second
end 254 of the switch arm.
An example of an application wherein the present in-
vention may be used to advantage is a food processor. In such
an example, the food processing tool 215 is driven by a motox
drive 214. A removable cover 219 is located on a working bowl
(not shown) in which the rotatable tool 215 processes various
food items. The interlock mechanism 211 includes a vertical
plun~er 221 mounted in the working bowl with a spring urging this
plunger upwardly away from the switch actuator 225 and includes
an element on the cover 219 which depresses the plunger 221 for
turning ON switch lOD only when the cover has been properly
placed by the operator on the rim of the bowl in readiness for
food processing operation. In a food processor, the plunger 221
is direct~y aligned with the actuator 225, and the lever 223 is
omitted. The operator uses an operating switch 230 or 230' for
running the motor drive 214 after the cover 21g has been appro-
priately placed on the bowl. When the cover 219 is removed by
the operator from the bowl, the plunger 221 moves upwardly for
turning OFF the switch lOD, and thus closure of the operating
switch 230 or 230' can not energize the motor dxive 214 until
the cover 219 is again placed on the bowl in readiness for fur-
ther food processing operation.
In the event that the main contacts 244, 232, in the
switch lOD happen to become welded, fused or stuck together,
then the auxiliary safety contact means 270, which are connected
in the main circuit 324, 344, 346 in series with the motor drive
214, are automatically triggered and moved into open position
-41-
~2~ 23~i
for interrupting this main circuit. This opening of the auxiliary
safety contact means 70 prevents further operation of the motor
drive until the food processor appliance has been serviced by
replacing the malfunctional interlock switch 10D with a new
switch.
It is to be understood that physical
orientation terms, such as "horizontal", "up", "upper", "upward",
"upwardly", "rises", "higher", "above", "down", "downward",
"downwardly", "lower", "below", "right", "rightward", "left",
"leftward", "leftwardly", and similar terms, are set forth for
convenience of the reader in readily understanding the descrip-
tion with reference to the drawings as shown and these terms are
not intended to be limiting. The switches 10, 10A, 10B, 10C
can be installed and mounted and will operate properly in any
desired orientation, because their various components are oper-
ated by mechanical motions and by spring foxces without any sig-
nificant effect by the earth's gravity.
It is to be understood by those skilled in the art
that various modifications may be made in the described embodi-
ments of the present invention, without departing from the spirit
and scope of the present invention, as described in the specifica-
tion and defined in the appended claims, which provides a switch
with auxiliary safety contact means which are changed in position
when the switch actuator means is turned (moved) ~F~,if the ON con~acts
remain fused, welded or stuck together, for automatically effecting a ~dr~ty
function, for example to prevent operation of the electrical
equipment, to protect the operator or maintenance personnel from
injury from unexpected actuation of the electrical equipment in
question, and/or infornung them that the switch has malfunctioned.
-42-
JCI ~31~ '> t~
It is to be recognized that there is provided in the
embodiment a switch which automatically provides a safety
function if its main contacts remain fusecl, welded or stuck
together in their ON position, ~hen the switch actuator is moved
to the UFF position, for example the safety function may be to
give an alarm signal or to interrupt the circuit which is
controlled by the switch.
There is also provided auxiliary contact means within
the housing of a switch which become moved if the switch actuator
is turned or moved to OFF position but its main contacts remain
in their ON position.
The embodiments further provide a safety switch having
spring-biased auxiliary safety contact means within the swit~h
housing which become triggered and released from a first position
to a second position for producing a safety function, when the
switch operating means are moved to OFF position but the main
contacts of the switch remain together in their ON position. In
an embodiment of this invention the auxiliary contact are
triggered into a closed position for producing a safety function,
for example for giving an alarm signal or for operating a relay,
and in another embodiment the auxiliary contacts are triggered
into an open position for producing a safety function, for
example for interruptlng a circuit, for example for interrupting
the main circuit.
Among the advantages of the present embodiments are
those resulting from safety apparatus to be incorporated in a
- 43
~%~ZZ35
switch. This safety apparatus includes auxiliary contacts which
are moved from a first relationship to a second relationship for
producing a safety function in the event the main switch contacts
remain together in their closed or ON position after the switch
operating means have been moved to the OFF position.
There is provided a switch having auxiliary safety
contacts for automatically deactivating a circuit controlled by
the switch to prevent energization of equipment in the circuit
when the main switch contacts remaln together in their ON
condition, after the switch has been turned OFF, for example the
main circuit may be deactivated.
There is also provided a switch having auxiliary safety
contacts for producing an audible andJor visible alarm signal
when its main contacts remain together, after the switch
operating means are turned OFF.
The embodiments show a switch having auxiliary safety
contacts for automatically energizing a circuit to transmit a
signal to a remote location for alerting personnel that the
control switch has malfunctioned by its main contacts remaining
in their ON position, after the switch actuator has been moved to
OFF position.
The switches illustrate advantageously protect the
operator of driven electrical e~uipment from acridental injury
when the contacts of the switch remain together in their ON
position, after the switch actuator has been moved to its OFF
position.
- 44
,
.
~ ' '' "':': , '
` ~
: . :
