Sensing edge having a pressure sensitive switch for a door

A sensing edge for a door comprised of a pressure sensitive switch. The sensing edge protects persons, equipment and the door from impact damage. The sensing edge includes an outer sheath which is compressible upon application of external pressure. An elongate inner tubular member fabricated of resiliently compressible air impervious material is longitudinally positioned and enclosed within the sheath. A pressure sensitive switch is operatively associated with the inner tubular member. Upon application of external pressure to the sheath, pressure within the tube is increased and thereby communicated to the pressure switch for actuation of the switch to effect a desired result. A substantially rigid transverse structure within a portion of the outer sheath proximate the pressure switch prevents damage to the pressure switch.

FIELD OF THE INVENTION 
The present invention relates to a sensing edge for a door and, more 
particularly, to a sensing edge having a pressure switch to protect 
persons, equipment and the door from impact damage. 
BACKGROUND OF THE INVENTION 
Employing pressure switches in sensing edges for doors is generally known. 
Such sensing edges generally include a sheath having several openings or 
chambers therein in fluid communication with each other, in order to 
transmit therebetween pressure changes in response to the application of 
external pressure to the sheath. The problem associated with such edges is 
that in order to construct several openings or chambers in fluid 
communication with each other, a plurality of different types and 
structures of foam must be used within the sheath to provide the proper 
sensitivity and path to communicate the pressure changes therebetween. 
Therefore, constructing and assembling door edges of this type is costly. 
Other types of more conventional door edges include a pair of upper or 
lower, flexible, electrically conductive sheets (e.g., aluminum foil) 
positioned on the upper and lower sides of a bridge. Upon application of 
pressure to the sheath, the conductive sheets are deflected into 
electrically conductive engagement with each other to thereby function as 
a switch to actuate suitable control circuitry for controlling the door. 
Sensing edges with this type of construction may not be as sensitive as 
that contemplated by the present invention. For instance, before the 
control circuitry is actuated, the conductor sheets must travel the full 
distance therebetween in order to make electrical connection. Whereas, in 
the present invention, the control circuit may be actuated without forcing 
the control tube to deflect a significant amount, as will be apparent from 
the description hereinafter. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention comprises a sensing edge for a door 
to protect persons, equipment and the door from impact damage. The sensing 
edge comprises an elongate outer sheath compressible upon application of 
external pressure and fabricated of flexible air impervious material for 
attachment to a door edge. An elongate inner tubular member fabricated of 
resiliently compressible air impervious material is longitudinally 
positioned and enclosed within the sheath. The inner tubular member has a 
first end and a second end, the second end being sealingly closed. A 
substantially rigid, incompressible transverse structure is positioned 
within a portion of the outer sheath and has a configuration which 
complements the interior cross section of the sheath to effectively 
prevent deformation of the sheath thereabout. A pressure sensitive switch 
having a switch element is protectively located within the portion of the 
sheath proximate to the transverse structure for sensing pressure change 
within the inner tubular member without subjecting the switch element to 
direct external pressure, whereby upon application of external pressure to 
the sheath, anywhere therealong except at the portion encompassing the 
transverse structure, pressure within the tubular member is increased and 
thereby communicated to the pressure switch for actuation thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Certain terminology is used in the following description for convenience 
only and is not limiting. The words "right," "left," "lower," and "upper" 
designate directions in the drawings to which reference is made. The words 
"inwardly" and "outwardly" refer to directions toward and away from, 
respectively, the geometric center of the sensing edge and designated 
parts thereof. The terminology includes the words above specifically 
mentioned, derivatives thereof and words of similar import. 
Referring to the drawings, wherein like numerals indicate like elements 
throughout, there is shown in FIG. 1 a building wall 10 having a doorway 
11 provided with a door 12. While the door 12, as illustrated, is an 
overhead door, having a sensing edge 13 in accordance with the present 
invention along its lower side or leading edge, it is within the spirit 
and scope of the invention to incorporate the sensing edge described 
hereinafter along the edge of any door structure, such as vertically 
disposed or horizontally movable doors, as desired. 
Referring now to FIG. 2, sensing edge 13 extends substantially along the 
lower or leading edge 15 of door 12. Sensing edge 13 and door 12 include 
securing means 16 for fixing sensing edge 13 to leading edge 15 of door 
12. In the presently preferred embodiment, securing means are a pair of 
T-shaped members 16 which complement T-shaped slots in the lower surface 
of door 12. Of course, sensing edge 13 may be secured to door 12 in any 
other suitable manner, for instance, with a traditional dovetail slot 
configuration (not shown). 
Sensing edge 13 is comprised of an outer casing or sheath 18 of elongate, 
generally constant cross-sectional outline configuration, extending 
closely along the underside or edge 15 of door 12. In the presently 
preferred embodiment, sheath 18 is generally of square cross section, but 
may be of any other suitable shape, such as circular or semi-circular (not 
shown). 
Sheath 18 is advantageously fabricated of form-retaining, but flexible air 
impervious material, such as rubber, having a bottom wall 22 for 
engagement with the door threshold or ground (see FIG. 1). Sheath 18 
further includes side walls 24 and 26 upstanding integrally from opposite 
side edges of bottom wall 22 and a top wall 28 extending between upper 
edges of side walls 24 and 26 in close facing or complementary relation 
with leading door edge 15. T-shaped members 16 are formed with sheath 18 
along top wall 22 for releasably interconnecting engagement with leading 
edge 15, thereby facilitating quick and easy mounting or removal and 
replacement of sensing edge 13 with respect to door 12. 
Referring now to FIG. 3, end walls 30 close and seal sheath 18. Provided on 
a portion of the interior of sheath 18 at one end thereof is a relatively 
stiff or rigid incompressible transverse structure 32 extending completely 
across sheath 18, so as to effectively prevent or minimize compression and 
deformation of the sheath 18 at that location. In the presently preferred 
embodiment, transverse structure 32 is generally L-shaped in cross section 
and positioned at the left-hand end of sheath 18 (when viewing FIG. 3). 
The L-shaped transverse structure 32 is of a configuration which 
complements the internal cross-sectional configuration of sheath 18, and 
is fabricated of relatively stiff, incompressible material, such as firm 
rubber, metal or plastic. Transverse structure 32 may be of any other 
shape, such as C-shaped, as long as it effectively prevents compression 
and deformation of the surrounding portion of sheath 18. For instance, the 
transverse structure of the presently preferred embodiment may include 
bores or holes (not shown) to decrease shipping weight, without detracting 
from the requirement of a rigid structure. 
Disposed generally centrally within sheath 18 is an elongate inner tubular 
member 34 fabricated of resiliently compressible air impervious material, 
such as rubber or closed cell foam. Tubular member 34 extends almost the 
complete length of sheath 18 and is longitudinally positioned and 
completely enclosed within sheath 18. In the presently preferred 
embodiment, tubular member 34 is generally of circular cross section (see 
FIG. 2), but may be of other cross-sectional shape such as square or oval 
(not shown). Tubular member 34 has first and second ends and extends 
longitudinally into abutting engagement with second or right-hand end wall 
30 of sheath 18 (when viewing FIG. 3). Positioned within this second end 
of tubular member 34 is a plug 36 which is of a configuration conformable 
to the internal cross-section of tubular member 34 and sealingly 
positioned therein so as to prevent air from escaping between plug 36 and 
tubular member 34. In the presently preferred embodiment, plug 36 is 
sealed in position with epoxy, however, any suitable sealant (e.g., glue 
or cement) may alternatively be employed. Plug 36 may be constructed of 
any suitable rigid or stiff material. In the presently preferred 
embodiment, plug 36 is constructed of firm rubber, but may be constructed 
of plastic. If desired, tubular member 34 may be formed with the second or 
right-hand end permanently sealed (not shown). 
The other or first end of the tubular member 34 preferably extends up to 
the transverse structure 32. Positioned within the other end (left-hand 
end when viewing FIG. 3) of tubular member 34 is a second plug 38 which is 
also of a configuration conformable to the internal cross-sectional 
configuration of tubular member 34, and fabricated of relatively stiff 
material, such as firm rubber or plastic. Plug 38 is sealingly secured 
within tubular member 34 as with plug member 36. Plug 38 further includes 
a generally centrally disposed bore 40 for receiving pressure sensing 
means 42 for sensing pressure change within tubular member 34. 
Disposed in the area between sheath 18 and tubular member 34 is a 
resiliently compressible inner formation 44 which extends generally along 
the entire length of tubular member 34 (see FIG. 3). In the presently 
preferred embodiment, compressible formation 44 is preferably fabricated 
essentially of open cell foam and is substantially co-extensive with 
sheath 18, except for the space occupied by transverse structure 32. It is 
within the spirit and scope of the invention to construct compressible 
formation 44 of other materials, such as a closed cell foam. While on the 
other hand, it should be understood that formation 44 is not necessary for 
operation of the sensing edge 13 and, therefore, may not be included and 
the area between the inner tubular member 34 and the sheath 18 may be 
open. However, without formation 44, the sensitivity of edge 13 decreases. 
Referring now to FIG. 3, protectively located between transverse structure 
32 and the left-hand or other end of tubular member 34 is a pressure 
sensing means 42. Pressure sensing means 42 senses pressure change within 
the interior of tubular member 34. In the presently preferred embodiment, 
pressure sensing means 42 comprises a fluid pressure sensitive switch 
element, in which electrical contact is made or broken in response to 
pressure changes. The switch element is of a type well known in the art. 
Such pressure sensitive elements are manufactured by Micro Pneumatic 
Logic, Inc. of Fort Lauderdale, Fla. The pressure sensitive switch element 
is effectively protected from direct pressure and/or impact damage by 
embedding or otherwise enclosing the switch element within transverse 
structure 32. If desired, the switch element may also be encased with 
protective material, such as foam (not shown) which may be installed 
within the open area of the outer sheath 28 proximate the transverse 
structure 32. The switch element includes a pressure port or nipple 46 
extending through plug bore 40 and communicating with the interior of 
tubular member 34. Thus, the switch element is in pneumatic communication 
from its mounting in the transverse structure 32 with the interior of 
tubular member 34. Pressure sensitive switch means 42 is provided with 
electrical conductors or leads 48 and 50 which extend outwardly in sealed 
relation from sheath 18 for connection with desired control circuitry (not 
shown) in a manner well known in the art. 
In operation, the application of external pressure to sheath 18 caused by 
an obstruction to the closing of door 12 anywhere therealong (except at 
the location of transverse structure 32) is communicated by compressible 
formation 44 (or the air within the outer sheath if no compressible 
formation is employed) to tubular member 34, which is depressed an amount 
proportional to the magnitude of the external pressure. A slight 
depression in tubular member 34 increases the internal pressure 
therewithin and is sensed by the pressure sensing means 42 which actuates 
by making or breaking electrical contact in a manner well known in the art 
to effect a desired result, generally, the automatic opening of door 12 or 
automatically inhibiting door 12 from closing any further. Further, the 
sensing means 42 is protectively enclosed in transverse structure 32, 
which also serves upon normal ground engagement of door 12, to prevent the 
pressure within tubular member 34 from increasing and, thus, the actuation 
of the switch element. It is within the spirit and scope of the invention 
to incorporate a plurality of incompressible rigid transverse structures 
anywhere along sheath 18, for instance, adjacent plug 36. 
The sensitivity of sensing edge 13 is adjustable. The switch element can be 
adjusted to actuate (make or break electrical contact) at any desired 
pressure change. In the presently preferred embodiment the switch element 
is set to a desired sensitivity before it is installed. In addition, by 
changing the material or size of the compressible inner formation 44 
and/or tubular member 34 their density and thickness can be varied to 
adjust sensitivity prior to installation. In the presently preferred 
embodiment, the switch element is adjusted and the density and thickness 
of the elements 44 and 34 is selected such that sensing means 42 is 
actuated before the inner surfaces 20 of tubular member 34 contact each 
other. Therefore, sensing edge 13 actuates quickly in response to a slight 
depression in sheath 18 and is, therefore, highly sensitive to external 
pressure. 
It is also within the spirit and scope of the invention to include a second 
pressure sensing means (not shown) as a redundant or back-up system. 
Furthermore, the two sensing means may operate in sequence with each 
other, as for controlling a plurality of separate functions, such as the 
stopping and reversing of door movement, or other desired functions. 
From the foregoing description, it can be seen that the present invention 
comprises a sensing edge for a door to protect persons, equipment and the 
door from impact damage. The sensing edge of the present invention 
overcomes the problems of the prior art by providing a highly sensitive 
sensing edge with a pressure chamber within tubular member 34, which is 
less costly and easier to manufacture. It will be appreciated by those 
skilled in the art that changes could be made to the embodiment described 
above without departing from the broad inventive concepts thereof. It is 
understood, therefore, that this invention is not limited to the 
particular embodiment disclosed, but it is intended to cover all 
modifications which are within the scope and spirit of the invention as 
defined by the appended claims.