Obstruction-responsive brake actuator for fire door or the like

A brake actuator for use in conjunction with a door barrier for preventing closure of the door barrier when the actuator comes in contact with an obstruction. The brake actuator includes a bumper mounted on a leading edge of the barrier and movable between an operative position and an inoperative position. A load carrying linkage is provided which is activated when the bumper is moved to the operative position. The linkage is connected to a brake which becomes engaged when the linkage is activated, thus preventing movement of the door barrier to a closed position when the bumper contacts the obstruction.

RELATED APPLICATIONS 
This application claims priority from provisional application Ser. No. 
60/009,429 filed on Dec. 29, 1995. 
FIELD OF THE INVENTION 
The present invention relates to an obstruction-responsive brake actuator 
and, more particularly, to an obstruction-responsive brake actuator for a 
safety barrier, such as a fir door, which prevents further closure of the 
safety barrier when an obstruction is encountered. 
BACKGROUND OF THE INVENTION 
Safety barriers, such as fire doors, for buildings and the like 
automatically close in response to certain emergencies, such as a fire. 
Safety barriers which automatically close by falling downwardly under the 
force of gravity may close with considerable force because of the 
substantial weight of the barrier. Safety barriers which close by sideways 
or upward displacement may also close with considerate force owing to the 
powerful spring mechanisms employed to close such safety barriers. Objects 
struck by such safety barriers during automatic closure thereof may be 
severely damaged and, in the case of persons, severely injured. 
Because of this potential hazard, safety edge devices often include one or 
more sensors, such as a switch, for generating an electrical signal upon 
contact with an obstruction. The sensors are electrically connected to a 
motor which controls movement of the door such that when a sensor engages 
an object upon closure of the door, the motor stops movement of the door 
toward its closed position and, in some cases, reverses the direction of 
movement of the door. 
A problem with such safety edge devices arises when they are used with 
safety barriers which automatically close in response to certain 
emergencies. Some such emergencies, such as fires, are accompanied by 
electrical power failures. Because known safety edge devices require 
electricity for operation, such devices may be inoperable during the very 
emergencies when they may do the most good. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention, an obstruction-responsive 
brake actuator is used with a safety barrier of the type including a 
curtain having a leading edge. A brake is operatively engageable with the 
curtain for preventing closure thereof, the brake being biased against 
operative engagement with the curtain. The curtain is of the type which, 
when not in operative engagement with the brake, is biased to close. 
The obstruction-responsive brake actuator comprises a support and a bumper 
carried by the support and movable to and from an operative position 
relative thereto. The brake actuator also includes a continuous 
load-carrying linkage carried by the support in abutting relation to the 
bumper. The linkage includes an actuator movable into and out of an 
actuating position relative to the support. The linkage has sufficient 
load-carrying capacity such that when a force is applied to the bumper 
sufficient for movement thereof to its operative position, the force is 
transmitted through the linkage to the actuator for movement thereof to 
the actuating position. Movement of the bumper out of its operative 
position reduces the force applied by the linkage to the actuator 
sufficiently to allow movement thereof out of its actuating position. 
The support is securable to the leading edge of the curtain and engages the 
bumper. The actuator is coupled to the brake such that movement of the 
actuator to its actuating position operatively engages the brake with the 
curtain. The actuator is movable to its actuating position when the bumper 
is urged against an obstructing object by a force greater than the force 
biasing the brake out of operative engagement with the curtain. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages, and specific objects attained by its use, reference 
should be made to the following detailed description in conjunction with 
the accompanying drawings in which there are illustrated and described 
currently preferred embodiments of the invention. It is to be understood, 
however, that the detailed description and drawings are intended to 
illustrate and not to define the limits of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, FIG. 1 illustrates a brake actuator and, 
more particularly, an obstruction-responsive brake actuator identified by 
the general reference number 20 and constructed in accordance with the 
teachings of the present invention. The motor controlled fire door 
assembly shown in FIG. 1 and generally designated by the reference number 
22 is disclosed in U.S. Pat. No. 5,245,879, the entire disclosure of which 
is expressly incorporated by reference herein. 
The motor-controlled fire door assembly 22 includes a frame 24 which 
horizontally supports a low speed output shaft 26 at an elevated position 
relative to ground 28, which is typically, though not necessarily, a 
structurally reinforced floor. A curtain 30 is wound around the output 
shaft 26 which is rotatable about its longitudinal axis for raising and 
lowering the curtain 30. Frame 24 includes vertical tracks 32 for engaging 
and guiding the side edges of curtain 30 during raising and lowering 
thereof. Curtain 30 has a leading edge 34 and, as will be described in 
detail hereinbelow, the brake actuator 20 is secured to the curtain 30 in 
depending relation to its leading edge 34. 
Rotation of output shaft 26 is controlled by a motor-operator unit, such as 
the motor-operator unit disclosed in U.S. Pat. No. 5,245,879. Only that 
part of the motor operator unit considered pertinent to the present 
invention is disclosed in FIG. 1 and generally designated at 40. 
Motor-Operator Unit 
The motor-operator unit 40 includes a motor 42 secured to a conventional 
hand chain assembly 44. The motor 42 is coupled to rotatable drive shaft 
46. Alternatively, the shaft 46 may be rotated by pulling a hand chain 52 
when, for example, motor 42 is unavailable due to a power interruption. 
Hand chain 52 is operatively engaged with shaft 46 for effecting rotation 
thereof by a lever 50 which, in turn, is activated by pulling a lever cord 
47. 
The shaft 46 engages a coupling 48 which, in turn, drives a shaft 49 
passing through a hole 54 in a support plate 56 of a brake controller 58. 
The other end of input shaft 49 is connected to a splined shaft 60 which, 
in a manner more fully described in U.S. Pat. No. 5,245,879, drives output 
shaft 26 for raising and lowering curtain 30. 
The motor-operator unit 40 includes a cast iron drum 62 secured to shaft 49 
for rotation therewith. A brake 64 secured to support plate 56 is disposed 
within the drum 62 and is independent of rotation thereof. The brake 64 
includes a pair of pivotally connected brake shoes 66 for selectively 
engaging drum 62 for blocking rotation of input shaft 49 and output shaft 
26 coupled thereto. A pair of tension springs 68 bias the brake shoes 66 
out of engagement with drum 62, the bias of the tension springs being 
overcome when the brake is actuated, as will be more fully explained 
below. 
The motor-operator unit 40 further includes a speed governor 70 connected 
by a pin 72 to drum 62 for rotation therewith. Governor 70 includes a pair 
of pivotally connected brake shoes 74 and a pair of tension springs 76 
which bias brake shoes 74 out of engagement with a stationary housing (not 
shown) until shaft 49 rotates above a predetermined speed whereupon 
centrifugal forces separate brake shoes 74 for applying a braking friction 
against the inside of the stationary housing to slow the rotational speed 
of shaft 49 and output shaft 26 coupled thereto. For example, automatic 
closure of curtain 30 may result in shaft 49 reaching an unacceptably high 
rotational speed thereby actuating governor 70 for preventing the curtain 
from slamming shut at an undesirably high speed. 
As illustrated in FIGS. 1, 2a and 2b, brake controller 58 includes a brake 
solenoid 78 mounted on support plate 56 and having a core 82 terminated 
with a cross pin 84. A take-up spring 90 is hooked at one end to cross pin 
84 and at the other end to an upstanding flange 92 on brake control lever 
88 such that the spring 90 couples the cross pin and brake control lever. 
The intermediate portion 94 of brake control lever 88 is fixed to a 
rotatable brake control shaft 96 for rotation therewith. 
The core 82 of brake solenoid 78 includes a plurality of laminates 98, one 
of which 99 extends beyond the others as shown in FIGS. 2a and 2b. Secured 
to laminate extension 99 is a brake cable 100 which, in turn, is connected 
to brake actuator 20 as described further hereinbelow. 
Referring to FIG. 1, the motor-operator unit 40 also includes a sheet metal 
cylindrical housing 102 having an intermediate circular plate 106 defining 
a chamber on either side thereof, one of which 104 is shown in FIG. 1. The 
support plate 56 and the components of brake controller 58 mounted thereon 
are received in one chamber (not shown). The other chamber 104 receives 
the coupling 48 when the housing 102 is secured to the housing of the hand 
chain assembly 44. 
Mounted on the side wall of housing 102 is a boss 108 having a longitudinal 
passage therethrough for connecting electrical conductors 110 to brake 
solenoid 78. The side wall of housing 102 also includes an opening (not 
shown) through which brake cable 100 extends. 
The brake cable 100 extends between laminate extension 99 and brake 
actuator 20 through a sleeve 114 shown schematically in FIGS. 1, 2a and 
2b. One end of the sleeve abuts housing 102 and an opposite end is fixed 
to the brake actuator, as further described hereinbelow. Brake cable 100 
is preferably steel or other metal, and sleeve 114 is preferably plastic, 
such as PVC, although other materials may be used provided they are 
transversely flexible but longitudinally-stiff such that longitudinal 
translation of one end of the brake cable relative to sleeve 114 produces 
concomitant translation at the opposite end thereof. 
The brake solenoid 78 is electrically connected, via conductors 110, to 
electrical source 115. Referring to FIG. 2b, when electrical source 115 
supplies power to brake solenoid 78, core 82 is retracted. Because core 82 
is secured via cross pin 84 and spring 90 to lever 88, retraction of core 
82 effects counterclockwise rotation of lever 88 and of brake control 
shaft 96 secured thereto. The brake control shaft 96 extends through a 
hole (not shown) in support plate 56 and into a cavity 116 in brake 64. 
The free end of brake control shaft 96 interlocks with the walls of cavity 
116 in a key-type engagement such that counterclockwise rotation of the 
brake control shaft 96 causes brake shoes 66 to pivot outwardly into 
engagement with drum 62 for blocking rotation of output shaft 26 thereby 
blocking closure of curtain 30. 
In a known manner, the take-up spring 90 compensates for wear of brake 
shoes 66 by allowing brake control lever 88 to be set relative to brake 
control shaft 96 to outwardly pivot the brake shoes, even when in a worn 
condition, sufficiently to produce engagement thereof with drum 62. This 
setting may also be used when brake shoes 66 are new, and normally 
thicker, since take-up spring 90, by deflecting, limits the force exerted 
on the brake shoes by movement of brake solenoid 78. 
The tension springs 68 connected between brake shoes 66 resist the outward 
pivoting thereof attendant engagement of the brake shoes with drum 62. 
Thus, when a force exerted on brake shoes 66 causing engagement thereof 
with drum 62 is removed, the brake shoes are pivoted inwardly to a 
position in which the brake shoes are disengaged from the drum. 
Brake controller 58 also includes a spring-loaded plunger 118 slidably 
mounted in a bracket 120 attached to support plate 56. The plunger 118 is 
held in a retracted position by a chain 122 located externally to 
motor-operator unit 40. The chain 122 includes a fusible link 124 with a 
melting temperature of about 135 degrees Fahrenheit. When fusible link 124 
melts, the plunger 118 is driven by the spring-loading thereof into 
engagement with an emergency actuator 126 for depressing the latter. 
Depression of emergency actuator 126 opens an emergency switch 128 which 
interrupts power to brake solenoid 78 thereby releasing the brake 64 and 
allowing curtain 30 to close. The emergency switch 128 may also be opened 
for releasing brake 64 by pulling a hand cable 130 connected thereto. When 
brake controller 58 is disposed in housing 102, plunger 118 and hand cable 
130 extend through respective openings in the side wall of housing 102. 
Brake Actuator 
The obstruction-responsive brake actuator 20, shown generally in FIG. 1 and 
in detail in FIGS. 3, 4 and 5, comprises a support 132 including an 
elongate shelf member 134 preferably formed of extruded aluminum. As shown 
in FIG. 3, shelf member 134 has a top wall 136 and a pair of opposed 
depending side wells 138, the end of each side wall having an inturned lip 
140. 
The support 132 further includes a structure for securing shelf member 134, 
preferably in a releasable fashion, to leading edge 34 of curtain 30. 
Those skilled in the art will appreciate that numerous structures within 
the scope of the invention will serve this purpose. One such structure, 
shown in FIG. 3, includes a hanger slat 141 attached to top wall 136. The 
upper edge of hanger slat 141 is hook-shaped for hanging from the 
lip-shaped leading edge 34 of curtain 30 in a known manner as depicted in 
FIG. 3. The interlocking engagement between the hook-shaped upper edge of 
hanger slat 141 and leading edge 34 facilitates mounting and removal of 
brake actuator 20 on curtain 30. 
It will be appreciated that hanger slat 141 may extend along the entire 
length of top wall 136 or only along discrete portions thereof. Similarly, 
the upper edge of hanger slat 141 may be hooked, as shown in FIG. 3, along 
its entire length or only along discrete portions thereof. All such 
embodiments are within the scope of the present invention. Preferably, 
shelf member 134 has a length which is substantially the same as that of 
leading edge 34 of curtain 30. It will be understood, however, that the 
invention contemplates embodiments in which the length of shelf member 34 
is less than that of the leading edge 34. 
As best seen in FIG. 3, and as is conventional, a pair of steel angles 142 
are bolted to opposite sides of hanger slat 141 in abutting relation to 
the upper surface of top wall 136. As with slat 141, it will be 
appreciated that angles 142 may extend along the entire length of top wall 
136 or only along discrete portions thereof. Those skilled in the art will 
appreciate that hanger slat 141 and extensions 142 are conventionally 
found on the bottom of fire door except, of course, that in the 
conventional arrangement hanger slat 141 is not integral with shelf member 
134 is proposed herein. 
Still referring to FIG. 3, brake actuator 20 further includes a bumper 
generally designated at 143 and preferably formed is an aluminum 
extrusion. Bumper 143 has a bottom wall 144 and a pair of opposing 
upstanding side flanges 146. Confronting upper portions of side flanges 
146 are inwardly recessed as indicated at 148, each recessed portion 148 
being defined, in part, by upper and lower walls 150, 152. 
The length of upper walls 150 preferably slightly exceeds the length of the 
lips 140 such that when bumper 143 is amounted on shelf member 134, 
substantially the entire length of upper walls 150 seats on the lips 140. 
It will be apparent that bumper 143 may be mounted on shelf member 134 by 
sliding one extrusion into the other so that upper wall 150 rests on lip 
140, as shown in FIG. 3 and that when the bumper 143 is so mounted, the 
recesses 148 accommodate vertical displacement of bumper 143 relative to 
the shelf member 134. 
End caps 191, which may be made of metal, plastic or any other suitable 
material, are preferably secured to the ends of shelf member 134 after 
bumper 143 is mounted thereon to block movement of the bumper relative to 
the shelf member. As the construction of such end caps and their 
securement to the shelf member 134 will be readily apparent to those of 
ordinary skill in the art who have read this description, a further 
description thereof is deemed unnecessary. 
The support 132 further includes an elongate central flange 154 depending 
from top wall 136 between and parallel to side walls 138. The central 
flange 154 is rigidly fixed to top wall 136 as, for example, by welding, 
high-strength adhesive or the like, and may be formed of the same or a 
different material than shelf member 134. Most importantly, shelf member 
134 and central flange 154 are extruded as an integral, unitary part. 
While central flange 154 may, as shown in FIG. 3, bisect the channel 
defined by shelf member 134, this is not necessary and central flange 154 
may be offset such that it is closer to one side wall 138 than the other. 
This may be desirable if one or more microswitches 156, described 
hereinbelow, are disposed on one side of central flange 154, in which 
event offsetting central flange 154 facilitates access to the 
microswitches for adjustment, repair or replacement. 
The length of central flange 154 is preferably the same as that of shelf 
member 134. Central flange 154 may have cutouts or discontinuities therein 
which may advantageously reduce the weight thereof. Also, if the cutouts 
or discontinuities are located adjacent to one or more microswitches 156, 
access thereto may be facilitated. 
As best seen in FIG. 4-5, the brake actuator 20 further includes a 
continuous, uninterrupted load-carrying linkage designated generally by 
the reference number 160 and including one or more linkage levers 158 each 
of which is individually attached to central flange 154 by a pivotal 
connection such as, but not limited to, a pin 197, rivet, stud or bolt, 
for rotation in a common plane parallel to the central flange. Each 
linkage lever 158 has a dog-leg shape including a forward portion 162 
having an outer edge 164 and an actuation edge 166. 
Each outer edge 164 is preferably bevelled relative to its respective 
actuation edge 166 such that when bumper 143 is in its fully downward 
position relative to shelf member 134 and the linkage levers 158 are 
rotated clockwise (solid lines in FIG. 5), the outer edges 144 are flush 
with or, preferably, slightly spaced from bottom wall 144. With reference 
to FIG. 3, it will be apparent that when the bumper is in its fully 
downward position upper walls 150 of bumper 143 abut inturned lips 140 of 
shelf member 134. The angle between each outer edge 164 and its adjoining 
actuation edge 166 also results in bottom wall 144 of bumper 143 being 
flush with the actuation edges 166 when the bumper 143 is in its upward or 
operative position (dashed lines in FIG. 5) as more fully described below. 
The linkage levers 153 are preferably equally spiced along central flange 
154 with the linkage levers nearest to the ends of shelf member 134 being 
approximately equivalent from their respective ends. The distance between 
adjacent linkage levers 153 is preferably approximately 24 to 30 inches 
although other distances as well as unequal spacings are within the scope 
of the invention. 
The load-carrying linkage 160 includes an elongate substantially flat rigid 
arm 168. Brake cable 100 extending from brake controller 58 is secured to 
one end 170 of arm 168, though it will be appreciated hereinafter that 
brake cable 100 may be attached to another portion of arm 168. As depicted 
in FIG. 4 and as noted above, one end of sleeve 114 for brake cable 100 is 
secured to an end cap at one end of shelf member 134 and cable 100 extends 
through a hole in the end cap for attachment to arm 168. A spring 190 
secured to the end cap 191 and to the arm 168 biases the arm to the right 
as seen in FIGS. 4 and 5. Other placements of spring 190 and other devices 
for biasing arm 168 to the right will be readily apparent to those who 
have read the description and all such placements and devices are within 
the contemplation of the present invention. For example, springs disposed 
between arm 168 and levers 158 which bias the levers 158 to their solid 
line positions in FIG. 5 and hence urge arm 168 to the right may be 
employed. In addition, and as is presently preferred, a spring 196 
positioned on pin 197 and connected between pins 197 and lever 158 may be 
employed for biasing levers 158 to the solid line position of FIG. 5 
Each linkage lever 158 is attached to arm 168 by a pivotal connection such 
as, but not limited to, a pin, rivet, stud or bolt. The pivotal 
connections between arm 168 and linkage levers 158 are at the end of the 
linkage levers opposite the forward portions 162. 
Because each linkage lever 158 is pivotally secured to central flange 154 
and to rigid arm 168, it will be apparent that displacement of bumper 143 
toward shelf member 134 will cause each linkage 158 lever to rotate 
counterclockwise about its respective pivotal attachment to central flange 
154 thereby displacing arm 168 leftwardly as viewed in FIGS. 4 and 5. 
Similarly, when arm 168 is displaced rightwardly as viewed in FIGS. 4 and 
5 the linkage levers 158 are rotated clockwise about their respective 
pivotal attachments to central flange 154. 
The length of brake cable 100 between arm 168 and laminate extension 99, 
shown generally in FIG. 1 and in greater detail in FIGS. 2a and 4, is such 
that the translation of the brake cable 100 to the position illustrated in 
FIG. 2a upon release of brake 64 is sufficient to pull the arm 160 to the 
right as is viewed in FIGS. 4 and 5 thereby rotating the linkage levers 
158 clockwise about their respective pivotal attachments to central flange 
154. 
As depicted in FIGS. 3 and 4, the brake actuator 20 may include one or more 
springs (not shown) disposed between top wall 136 of shelf member 134 and 
upper walls 150 of recessed portions 148 for biasing bumper 143 to its 
fully downward position. The number of and placement of such springs for 
accompanying their stated objective is well within the capabilities of the 
person of ordinary skill in the art. 
Microswitches 
As shown in FIG. 3, the obstruction-responsive brake actuator 20 also 
includes one or more electrical switches, preferably microswitches 156, 
affixed to the bottom of top wall 136, the microswitches forming part of 
an electrical circuit as is explained hereinbelow. Preferably, 
microswitches 156 are equally spaced along the length of top wall 136 such 
that the distance between adjacent microswitches is approximately 24 to 30 
inches. However, other distances as well as unequal spacings are within 
the scope of the invention. The microswitches 156 may be affixed to top 
wall 136 on either or both sides of central flange 154. 
As is more fully explained below, each microswitch 156 is normally biased 
in an open switch condition and is movable to a closed switch condition 
when bumper 143 moves upwardly relative to shelf member 134 by a 
predetermined distance. Microswitches operating in this fashion are well 
known in the art. One such microswitch 156, shown schematically in FIG. 3, 
includes a housing 180 and a post 182 axially moveable relative to the 
housing through a hole (not shown) at the lower end thereof. The post 182 
is biased outwardly from housing 180 by a spring (not shown) disposed in 
the housing and a stop on the end of post 182 inside housing 180 prevents 
the post from escaping the housing. The housing 180 also includes the 
usual conductive pathway (not shown) which is open when the post 182 is 
biased outwardly and is closed by the post when the post is pushed 
sufficiently into the housing against the bias of the spring. 
One or more microswitches 156 may be served to top wall 136 as depicted in 
FIG. 3 such that when bumper 143 moves upwardly a predetermined distance, 
the post 182 is pushed by upper wall 150 sufficiently into housing 182 to 
close the conductive pathway. 
Of course, the microswitches 156 may be replaced by other types of 
electrical sensors. For example, one or more microswitches 156 may be 
replaced by confronting electrical contacts mounted on top wall 136 of 
shelf member 134 and upper walls 150, respectively. In such an embodiment 
it will be apparent that a conductive pathway is established when bumper 
143 is displaced toward shelf member 134 sufficiently for the confronting 
contacts to touch. Alternatively, optical sensors may be employed to 
service when bumper 143 has moved upwardly toward field member 134 by a 
predetermined distance. An electrically conductive cable 176 is in 
electrically conductive relation with microswitches 156. A cable 176 
suitable for this purpose includes a pair of conductors 177, represented 
schematically in FIG. 1, connected in parallel with microswitches 156. The 
cable 176 may be insulated, as by a braided insulation sleeve shown in 
FIG. 4. In the embodiment depicted in FIG. 4, the insulation extends to 
one end cap of shelf member 134 with the conductors 177 extending through 
an opening (not shown) in the end cap to the microswitches 156. As 
schematically illustrated in FIG. 1, cable 176 and microswitches 156 are 
in an electrical circuit with motor 42 such that the motor 42 is activated 
when one or more of the microswitches is closed as a result of upward 
movement of bumper 143. 
Operation 
During normal operation, curtain 30 is raised and lowered by motor-operator 
unit 40 driving output shaft 26 in response to a conventional switching 
arrangement (not shown) for activating motor 42 for clockwise or 
counterclockwise rotation. Normally, when curtain 30 is raised or lowered, 
brake 64 is released and core 82, brake control shaft 96 and cable 100 are 
in the positions shown in FIG. 2a and discussed hereinabove. When brake 
cable 100 is in the position shown in FIG. 2a arm 168 (FIGS. 4 and 5) is 
pulled sufficiently to the right to rotate the linkage levers 158 
clockwise to the position illustrated in solid lines in FIG. 5. 
If an object 178 illustrated schematically in FIG. 1 situated beneath 
curtain 30 during lowering thereof is engaged by bumper 143, continued 
lowering of the curtain collapses shelf member 134 on the bumper such that 
inturned lips 140 of the shelf member 134 move away from the upper walls 
150 of the bumper. Upon sufficient movement of shelf member 134 relative 
to bumper 143, one or more of the microswitches 156 are moved to their 
closed positions as upper walls 150 urge posts 182 into housings 180. 
As schematically illustrated in FIG. 1, closure of one or more of the 
microswitches 156 operates to stop position of motor 42 which halts 
further descent of curtain 30. Optionally, motor-operator unit 40 may 
automatically reverse its direction of position in response to closure of 
one or more microswitches 156 thereby to raise the curtain 30 away from 
object 178. Suitable circuitry for accomplishing these objectives is well 
known to those skilled in the art. 
If, however, there is a power failure during closure of curtain 30, such as 
may occur in the case of an emergency, closure of microswitches 156 will 
have no effect on blocking closure of curtain 30 as motor 42 will be 
inoperative. In such event the present invention nevertheless arrests 
downward movement of curtain 30 when it strikes an object 178. As 
discussed hereinabove, collapsing shelf member 134 on bumper 143 is a 
result of engagement of the bumper with an object 178 causes central 
flange 154 to move toward bottom wall 144 of bumper 143. Such relative 
movement produces counterclockwise rotation of linkage levers 158 (is 
viewed in FIGS. 4 and 5) thereby causing arm 168 to translate leftwardly 
against the bias of spring 198. Leftward translation of arm 168 results in 
corresponding movement of brake cable 100 which draws laminate 99 of brake 
controller 58 upwardly as viewed in FIGS. 2a and 2b. Sufficient 
counterclockwise rotation of one or more linkage levers 158 causes brake 
cable 100 to move core 82 upward to the position shown in FIG. 2b which, 
as explained hereinabove, results in engagement of brake 64 which halts 
further closing of curtain 30. It will be apparent that the recesses 148 
accommodate relative movement between shelf member 134 and bumper 143 and 
that the receivers are sufficiently high that linkage levers are moved to 
their dashed line positions in FIG. 5 before lower walls 152 of bumper 143 
contact inturned lips 140 of shelf member 134. 
The spacing between posts 182 of microswitches 158 and the upper walls 150 
of bumper 143 is such that the microswitches are closed before the linkage 
levers 158 are rotated sufficiently to effect engagement of brake 64. 
Therefore, provided motor-operator unit 40 and microswitches 156 are 
functioning properly, descent of curtain 30 is halted and optionally 
reversed by motor 42 before brake 64 is engaged. However, if 
motor-operator unit 40 and/or microswitches 156 are inoperable, closing of 
the microswitches 156 will have no effect on descent of the curtain 30. 
Under such circumstances, continued descent of curtain 30 results in 
sufficient counterclockwise rotation of the linkage levers 158 to the 
position illustrated by dashed lines in FIG. 5 whereupon the brake 64 is 
engaged for arresting descent of the curtain as explained hereinabove. 
It will be apparent, therefore, that brake actuator 20 provides curtain 30 
with obstruction-responsive sensitivity during normal operation and in the 
event of a power interruption. 
If the object 178 is removed from the path of travel of brake actuator 20, 
bumper 143 drops away from shelf member 134 to its solid line position in 
FIG. 3. If only microswitches 156 had been engaged, movement of bumper 143 
away from shelf member 134 returns microswitches 156 to their open 
condition whereupon motor 42 is restored to normal operation. If closure 
of curtain 30 was effected by linkage levers 158 rotating sufficiently to 
engage brake 64, upon movement of bumper 143 away from shelf member 134 
spring 190 moves arm 168 to the right in FIGS. 4 and 5 thereby returning 
linkage levers to their solid line positions (FIG. 5). Movement of arm 168 
to the right results in corresponding translation of brake cable 100 which 
urges core 82 to the position shown in FIG. 2A whereupon brake 64 is 
disengaged and curtain 30 is free to move to its fully closed position as 
explained hereinabove. 
It will be apparent that if during closure of the curtain 30 the curtain is 
permitted to move downwardly until the bumper 143 strikes the floor 28 or 
other confronting surface the bumper 143 will activate the brake mechanism 
in the manner described hereinabove. This is undesirable because it 
results in unnecessary actuation of linkage levers 158 and arm 168 which, 
over time, may fail. Accordingly, and as is known in the art, the fire 
door assembly 22 preferably includes a limit switch which is tripped as 
the bumper 143 approaches the floor 28. In a manner well known in the art, 
tripping of the microswitch applies power to solenoid 78 for activating 
the brake 64 in the manner more fully described above such that movement 
of the door is halted before the brake actuator 20 is actuated by movement 
of bumper 143 relative to shelf member 134. In a preferred embodiment 
activation of the limit switch upon closing of the curtain 30 deactivates 
the microswitches 156. As suitable circuitry for accomplishing this 
objective will be readily apparent to those of ordinary skill in the art 
who have read this description, a further description thereof is deemed 
unnecessary. In any event, even if bumper 143 strikes the floor 28 with 
sufficient force to actuate brake actuator 20, such action is merely 
redundant as the sole effect is actuation of brake 64 if it has not 
already been activated by the limit switch. 
As long as power is applied to motor 42 or, upon restoration of power to 
motor 42 in the event of a power failure, curtain 30 may be raised and 
lowered in the manner described hereinabove by activating motor 42 to 
rotate in the appropriate direction. That is, there is no requirement of 
resetting the brake actuator 20 each time it is actuated upon striking an 
object 178 or floor 28. Rather, and as will be apparent from the foregoing 
description, brake actuator 20, even when operating in its fully 
mechanical mode i.e., in response to pivoting of linkage levers 158, 
automatically resets. 
Manually Driven Fire Door 
The brake actuator 20 of the present invention is also applicable to 
manually driven safety barriers including, but not limited to, the 
manually driven fire door assembly 22' illustrated in FIG. 6 and fully 
described in a copending U.S. Provisional Patent Application titled Drive 
Mechanism With Automatically Resetting Emergency Closing Device For Fire 
Door Assembly And The Like. 
In the manually driven fire door assembly 22', brake 64' is released for 
emergency closing of curtain 30' by movement of cable 216 to the left as 
viewed in FIG. 6. As explained in said copending U.S Provisional Patent 
Application, cable 216 is released forleftward movement either by melting 
of fusible link 225', movement of lever 224' in a counterclockwise 
direction, i.e. to the solid line position in FIG. 6, or by any other 
suitable mechanism such as by actuation of a solenoid. 
To incorporate the brake actuator 20 of the present invention in such a 
manually driven fire door cable 100' is coupled to cable 216 by a 
mechanical couple 220 diagrammatically illustrated in FIG. 6. 
Consequently, actuation of brake actuator 20' by linkage levers 158 in the 
manner described above results in rightward movement of cable 216 for 
actuating brake 64'. 
It will therefore be apparent that during emergency closing of curtain 30' 
upon disengagement of brake 64', brake 64' will be reactivated by brake 
actuator 20' when bumper 143' strikes an object 178'. As with the brake 
actuator 20 described above in connection with FIGS. 1-5, once the object 
178' is removed the brake 64' is again deactivated. 
It will be further apparent that inasmuch as fire door assembly 22' is 
manually driven, there may be no available power source, in which event 
microswitches 156 depicted in the embodiment of FIGS. 1-5 may be dispensed 
with in which event brake actuator 20' will only be actuated upon rotation 
of linkage levers 158' as is more fully described above. 
Thus, while there have been shown and described and pointed out fundamental 
novel features of the invention as applied to preferred embodiments 
thereof, it will be understood that various omissions and substitutions 
and chances in the form and details of the devices illustrated, and in 
their operation, may be made by those skilled in the art without departing 
from the spirit of the invention. For example, it is expressly intended 
that all elements and/or method steps which perform substantially the same 
function in substantially the same way to achieve the same result as the 
elements specifically disclosed in the specification.