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BACKGROUND OF THE INVENTION
The present invention relates to door safety devices and more particularly
to a safety system in which the door is automatically opened when it
strikes an obstruction while being closed.
At the present time the use of safety edge devices on doors, to prevent the
door from being closed when it meets an obstruction, is well known,
particularly in the doors of automatic elevators. For example, if an
elevator door should hit or approach a passenger in its doorway, the
elevator door will automatically open.
Various types of systems have been suggested to control such doors. For
example, a series of light beams and a series of photoelectric detectors,
i.e., "electric eyes," may be used between the door and the door frame.
When one of the beams is interrupted, a controlled motor operates and
opens the door. Alternatively, the door edge may carry an elongated
flexible gas filled bag so that, when the edge strikes an obstruction, the
gas pressure rises and operates a motor control mechanism. As another
alternative, various types of pressure sensitive electrical switches, such
as microswitches, may be used in the door edge. The switches may directly,
or indirectly through an amplifying circuit, control a motor which opens
the door.
It would be desirable to use a door safety system in other types of doors,
particularly in a factory environment. For example, an increased interest
has developed in noise control within factories. This has resulted in an
increased use of enclosures for noisy machines. Such enclosures require
various types of "doors," as that term is used herein, such as vertical
sliding portals, horizontal swinging portals, movable hoods and movable
windows. These "doors" may be dangerous if closed upon an obstruction,
such as a tool or a worker's hand.
However, the door safety systems currently in use present various
difficulties, particularly if employed in a factory environment. Certain
of those door safety systems are not "fail safe," that is, they will not
provide protection if one, or more, of their components should fail. For
example, in the case of a direct contact microswitch, the switch contacts
may become corroded and fail to make electrical contact when the door hits
an obstruction. Other proposed safety door edge systems may be too
delicate or complicated for use in factory safety systems.
SUMMARY OF THE INVENTION
In accordance with the present invention, a safety system for a door is
provided. The system includes an elongated flexible channel member secured
to the free edge of the door. Two normally separated conductive ribbons
are positioned within the flexible channel member. When the flexible
channel member is compressed by an obstruction, the compressive force is
transmitted to the ribbons through a flexible diaphragm and ribs within
the channel member. The compressive force brings the ribbons into
electrical contact.
The ribbons are part of an active circuit, which active circuit also
includes a power source such as a power transformer, a thermal switch, a
resistor and an electromagnetic relay having a coil, a spring-loaded
moving member (an arm) and electrical contacts.
In operation, the transformer supplies power to the relay coil which
energizes a control circuit by pulling the moving member into a closed
position. Upon compression of the door channel member, the ribbons touch
and shunt the relay coil, causing the moving member to open the control
circuit. The control circuit has a solenoid which, when de-energized,
causes an air cylinder to open the door. The resistor in the active
circuit prevents shorting of the circuit should the ribbons remain in
contact. The thermal switch, such as a bimetal lever switch, senses the
temperature of the resistor and opens the active circuit when the resistor
temperature rises and reaches a selected temperature, thereby preventing
over-heating of the resistor.
If any components of the active circuit should fail, or if the power to the
active circuit should fail, the power to the relay coil will be lost,
allowing the moving member to open the control circuit and de-energize the
solenoid causing the door to be opened by the air cylinder. The air
cylinder is operated by compressed air stored in a supply tank. The system
of the present invention, consequently, presents a "fail safe" system
which will open the door upon component or power failure.
OBJECTIVES AND FEATURES OF THE INVENTION
It is an objective of the present invention to provide a safety system for
a door edge, which safety system, upon the edge striking an obstruction,
will initiate automatic opening of the door.
It is a further objective of the present invention to provide such a safety
system which will operate to open the door even though one or more
components of its electrical circuit should fail.
It is a further objective of the present invention to provide such a safety
system for a door edge which, if the power to its electrical system should
fail, will still initiate the automatic opening of the door.
It is a further objective of the present invention to provide such a safety
edge which utilizes relatively few components so that it may be relatively
readily repaired and may be produced at a relatively low cost.
It is a further objective of the present invention to provide such a safety
edge which is especially adapted to be used connected at the edge of the
sliding doors of noise enclosures.
It is a feature of the present invention to provide a door safety closing
system. The system includes a door frame, a door movably mounted in the
door frame and movable into an open and closed position, control means for
operating an air cylinder, and an air cylinder to open and close the door
upon receiving a control signal from the air cylinder control means. The
door has a free edge which is movable against the door frame in the closed
position. When the free edge strikes an obstruction, the air cylinder
opens the door.
The system also includes an active circuit connected to the air cylinder
control means and including a pair of conductive ribbons. Each of the
ribbons has a first and a second terminal separated by a length of ribbon.
The active circuit also comprises a power source means to provide power to
the active circuit and relay means having a coil, contacts, and a movable
relay arm which opens and closes the contacts. The relay arm is in closed
position energizing the solenoid when the relay is energized. When the
solenoid is energized, the door is moved to the closed position. When the
relay is de-energized, the relay opens the control circuit and
de-energizes the solenoid. When the solenoid is de-energized, the air
cylinder moves the door to the open position.
The door has a safety edge means attached to it which provides an
electrical change when the safety edge strikes against an obstruction
during closing motion of said door. The safety edge means includes the
pair of electrically conductive ribbons. The ribbons are normally
separated and contact each other when the safety edge strikes an
obstruction, the contact of the ribbons shorting the relay coil.
It is a further feature of the present invention that the safety edge means
includes an elongated flexible channel member having an open side, an
outer wall and an interior cavity. The channel member has its open side
attached to the free edge of the door. A diaphragm is attached to the
flexible member within said cavity and a plurality of ribs within the
cavity extends from the diaphragm to the flexible channel member and moves
the diaphragm when the channel member strikes an obstruction. The two
conductive ribbons are positioned within the cavity and on the opposite
side of the diaphragm from the ribs, so that movement of the diaphragm
brings the ribbons into contact and shorts the relay coil.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objectives and features of the present invention may be ascertained
from the detailed description provided below, which gives the inventor's
best presently known mode of practicing the invention. The detailed
description should be taken in conjunction with the accompanying drawings,
in which:
FIG. 1 is a schematic diagram of an electrical circuit which is part of the
safety system of the present invention;
FIG. 2 is a schematic diagram of the same electrical circuit as in FIG. 1
but showing its relay with its contacts in the closed position;
FIG. 3, a perspective view partly in cross-section, is a representation of
a mechanical implementation of the safety system of the present invention
in a door edge; and
FIG. 4 is a perspective view of a noise and safety enclosure which is a
representation of one embodiment of the present invention, the enclosure
including a vertically slidable door.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1, in accordance with the present invention, shows two electrical
circuits -- a safety circuit 10 for sensing door obstructions and a
solenoid operated air cylinder circuit 11 for raising the door 9 (FIGS. 3
and 4) upon contact with an obstruction.
Circuit 10 uses a magnetic core power transformer 12 for its input voltage
supply; for example, it receives 110 volts at its primary and produces 24
volts at its secondary windings. Terminals 33 and 32 of the primary
winding of transformer 12 are connected to external power through fuses
13A and 13B, respectively. Output terminal 30 of the secondary winding of
transformer 12 is connected in series with a fuse 14, an override switch
15, a thermal switch 16, a resistor 17, and the second terminal 18B of a
conductive ribbon 18.
The first terminal 18A of the conductive ribbon 18 is connected to terminal
21A of the coil 22 of an electromagnetic relay 20. Terminal 21B of the
coil 22 of relay 20 is connected to the first terminal 19A of the
conductive ribbon 19. The opposite and second terminal 19B of ribbon 19 is
connected to grounded terminal 31 of transformer 12, thus completing
safety circuit 10. The relay 20 has a controlled arm 29 as its movable
element.
Resistor 17 of safety circuit 10 has a resistance value equal to,
preferably, about 10% of the coil resistance in the coil of relay 20. This
resistance value difference allows the relay coil 22 to receive the full
circuit voltage without a large voltage drop across the resistor 17.
Shorting of the ribbons 18,19 by contacting one ribbon with the other
causes the circuit relay 20 to be shunted out of the circuit 10. The coil
of the relay 20 is thus placed in a de-energized state. The resistor 17 of
circuit 10 then picks up the shunted voltage, preventing a short circuit.
The resistance of resistor 17 should be in the range of about 5-20% of the
resistance of the relay coil, and preferably about 10% of that resistance.
To prevent over-heating of the resistor 17 due to extended shorting or
shunting of the coil 22 of the relay 20, the thermal switch 16 in safety
circuit 10 will detect an over-heating of the resistor 17 and open,
removing power from the resistor 17 and safety circuit 10. This feature is
necessary to allow the use of a resistor 17 with a circuit handling
(wattage) value within the switching capability of the ribbon switch
(ribbons 18 and 19).
The solenoid operated air cylinder of the control circuit 11 of FIG. 1, for
raising door 9 (FIGS. 3,4) upon contact with an obstruction, is comprised
of a power source 27, shown as a d.c. battery, and a three-way solenoid 25
connected to the controlled switch contacts (terminals 23 and 24) of the
relay 20.
The three-way solenoid 25 directs air to an air cylinder 26 which has an
air piston 26a disposed therein. When the solenoid 25 is de-energized, a
spring-loaded spool in the solenoid causes compressed air entering the
solenoid to be directed to one side of the air cylinder 26, causing the
door 9 to be moved to the open position. When the solenoid 25 is
energized, the spool in the solenoid shifts and directs air to the
opposite side of the air cylinder, causing the door to move to the closed
position. When the relay 22 is de-energized because of ribbon contact due
to an obstruction, or if the relay 22 is de-energized due to power
failure, the spring-biased relay arm moves to the open position, thereby
de-energizing the solenoid and causing the door to move to the open
position. The unconnected terminal 34 of the relay 20 may be connected in
series with a light and/or other status indication device to the terminals
of power source 27.
FIG. 2 shows the same safety circuit 10 and air cylinder control circuit 11
as shown in FIG. 1, but with the controlled arm (movable element) 29 of
relay 20 held in a closed position against relay coil 22. In other words,
the relay coil is activated and the switch terminals 23,24 are closed.
FIG. 3 depicts one embodiment of a mechanical implementation utilizing the
circuits of FIGS. 1 and 2, which is a perspective view partly in
cross-section. The door 9 has as an end projection a flexible and
resilient channel member 43, for example, of rubber or synthetic rubber.
The open side of channel member 43 is mounted on the free side of the door
9, the free side being the bottom edge in a downwardly closable,
vertically slidable door. The flexible channel member 43 is held
semi-rigid through the plastic ribs 42 which are attached to a flexible,
resilient and movable diaphragm 44. The normally open ribbon switch,
comprised of the ribbons 18 and 19, is enclosed within the flexible
channel member 43 and positioned between the diaphragm 44 and the edge of
the door 9. The ribbons 18 and 19 are separated, for example, 0.015 inch,
by either (i) spring-loaded tension along their length, i.e., between
their respective first terminals 18A, 19A and the second terminals 18B,
19B; and/or (ii) thin foam washers of a minimal thickness. The minimal
spacing 39 is elastic such that the ribbons 18 and 19 may be brought into
contact through application of pressure, but will revert to their original
position once the pressure is released.
In operation, when the free door edge meets an obstruction, such as a
worker's hand or a tool left in the door frame, the flexible channel 43,
when it encounters the obstruction, will bend, causing the ribs 42 to push
the diaphragm 44 inwardly toward the free edge of the door 9. The inward
pressure of diaphragm 44 will cause the ribbons 18 and 19 to contact,
thereby shunting relay 20 and thus de-energizing the relay coil 22. The
de-energization of the relay coil 22 allows the spring-biased relay arm 29
to move from terminal 23 to terminal 34. This will de-activate air
cylinder control circuit 11, de-energizing solenoid 25, causing the air to
drive the piston to open the door. However, once door edge 43 has cleared
the obstruction, the ribbons 18 and 19 are no longer in contact and the
relay 20 is no longer shunted. The relay 20 is again energized; however, a
latching circuit prevents the solenoid 25 from being re-energized and
closing the door again. A relatching switch must be actuated to again
re-energize the solenoid 25 and allow the door to reclose.
The particular fail safe characteristic of the circuit is that, upon
de-energizing the solenoid, the door will open. Thus, (i) plant electric
power failure, (ii) electrical component failure, (iii) opening of
override switch 15, or (iv) safety edge contact with an obstruction, will
cause door 9 to open. In situations 1 to 3 the door will be opened until
the failure is corrected, i.e., the replacement of the component, the
restoring of power, or the closing of the switch 15. There is no danger of
door damage as door opening is accomplished through an air driven piston
which stops as the door reaches its fully open position. An adequate air
supply is maintained to open the door, even though there may be an
electrical power failure.
FIG. 4 depicts one embodiment of the mechanical implementation of the
system of the present invention as applied to a machine enclosure 50. The
interior walls of the enclosure 50 are padded with sound-absorbing
material. The enclosure acoustically isolates a machine, located therein,
from the plant when its door 51 is closed. The door 51 may be operated
either vertically as shown in FIG. 4, or laterally (not shown).
The door 51 has a handle 63, which may be either recessed or surface
mounted, a safety edge 53 consisting of a flexible channel attached on its
open side to the free side 54 of door 51 and a sound insulated perimeter
57 sufficient to cause the enclosure 50 to be acoustically isolated upon
closing of the door 51. The door 51 is vertically slidable in track 56 and
closes against jamb 58. The jamb 58 has a safety edge recess 59 which
accepts safety edge 53 so that the door 51 may close without compression
of the safety edge 53.
A control box 60 containing a door operation switch 61 is located on the
exterior of the enclosure 50. FIG. 4 also shows an obstruction 55, placed
across the jamb 58 and the safety edge recess 59.
The operation of the preferred and described embodiment of the present
invention is as follows: As a result of the obstruction across the jamb 58
and the safety edge recess 59, the door 51 may not be closed but rather is
automatically opened. Upon contact with the obstruction the safety edge 53
compresses. As shown in FIG. 3, an inward force is transmitted to the
diaphragm 44 through the ribs 42. The diaphragm 44 flexes inwardly,
forcing the ribbons 18 and 19, which are normally separated by minimal
spacers 39, to come into contact. The contact of ribbons 18,19 shunts
relay 20. This causes the coil 22 of the relay 20 to become de-energized,
thus allowing controlled switch terminals 23,24 to assume their open
position.
The resistor 17 provides a voltage drop path for the shunted voltage, upon
closure of the ribbons 18,19, so that the safety circuit 10 is not
short-circuited. When the resistor 17 becomes heated, the thermal switch
16 opens, removing power from the resistor 17 -- if the ribbons 18,19
remain in contact for a period of time.
Once the door 9 has cleared the obstruction, the channel member 43 is no
longer compressed and is no longer exerting an inward pressure on the
diaphragm 44 through ribs 42. The ribbons 18 and 19 are no longer under
pressure and will revert to their original spacing, thus removing the
shunt to the relay 20. The coil 22 is energized, causing the controlled
switch arm to contact terminal 23, closing the circuit 11. However, the
latching circuit (not shown) prevents the solenoid 25 from being
re-energized and reclosing the door. A relatching switch must be actuated
to re-energize the solenoid 25.
The term "door" as used herein is intended broadly to cover various types
of portals such as horizontal or vertical slidable hoods.
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