U.S. patent number 3,714,644 [Application Number 05/092,673] was granted by the patent office on 1973-01-30 for alarms for night latch.
Invention is credited to Harold Richard Hellstrom.
United States Patent |
3,714,644 |
Hellstrom |
January 30, 1973 |
ALARMS FOR NIGHT LATCH
Abstract
An alarm system includes a latch mechanism having a flexible
connective member with one end anchored for example to a wall or
door frame and the other end detachably securable to the door.
Sensory means are extended along at least a portion of the flexible
member, and circuit means are coupled to the sensory means for
energizing an alarm mechanism upon occurrence of a malfunction in
the sensory means.
Inventors: |
Hellstrom; Harold Richard
(Pittsburgh, PA) |
Family
ID: |
22234471 |
Appl.
No.: |
05/092,673 |
Filed: |
November 25, 1970 |
Current U.S.
Class: |
340/508;
200/61.62; 292/264; 340/542; 340/556; 340/652 |
Current CPC
Class: |
E05B
45/005 (20130101); E05C 17/365 (20130101); Y10T
292/283 (20150401) |
Current International
Class: |
E05B
45/00 (20060101); E05C 17/36 (20060101); E05C
17/00 (20060101); G08b 013/08 (); G08b
013/12 () |
Field of
Search: |
;340/274,276,280,380,256,273 ;200/61.62,61.81,61.93,61.08
;174/34,36 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Caldwell; John W.
Assistant Examiner: Partridge; Scott F.
Claims
I claim:
1. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securable to the other of said frame
and said door to latch said door to said frame, said flexible
connective member having a length sufficient to permit opening of
said door to a predetermined and limited extent, an alarm
mechanism, continuous conductive means extended along at least a
portion of said flexible member, and circuit means coupled to said
continuous conductive means and to said alarm mechanism for
energizing said alarm mechanism upon stretching or breaking of the
flexible connective member and occurrence of a malfunction in said
continuous conductive means.
2. The combination according to claim 1 wherein said sensory means
define a circuit path for arming said circuit means, and said
circuit means include fail-safe means for energizing said alarm
mechanism upon occurence of a break in said path.
3. The combination according to claim 1 wherein said sensory means
include an electrically conductive circuit path and electrical
shield means extended along said flexible member and juxtaposed to
that portion of said path extending along said flexible member,
said shield means and said path when shorted together by an attempt
to break said flexible member providing said malfunction.
4. The combination according to claim 1 wherein switch means are
provided for arming and disarming said circuit means, a keeper and
keeper plate are provided as part of said latch arrangement, said
switch means including at least one conductive strip located
adjacent a slot in said keeper plate, said keeper being
electrically conductive so as to arm said circuit means by a
circuit path through said keeper and said strip upon engagement of
said keeper and said keeper plate and so as to disarm said circuit
means upon disengagement of said keeper and said keeper plate.
5. The combination according to claim 4 wherein said switch means
include at least one elongated conductive strip substantially
coextending with a keeper slot in said keeper plate.
6. The combination according to claim 1 wherein said sensory means
include a continuity conductor passed back and forth at least once
each way along said flexible member.
7. The combination according to claim 1 wherein said flexible
member is a length of chain, and a length of said sensory means is
interwoven with and passed along the length of said chain.
8. The combination according to claim 1 wherein said sensory means
is secured at spaced positions along its length to the end portions
of said flexible member respectively to aid in creating said
malfunction in said sensory means when said flexible member is
stretched or broken.
9. The combination according to claim 8 wherein an expansible
member is incorporated in said flexible member to ensure
malfunctioning of said sensory means upon striking of said flexible
member but before severance thereof.
10. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securable to the other of said frame
and said door, an alarm mechanism, sensory means extended along at
least a portion of said flexible member, and circuit means coupled
to said sensory means for energizing said alarm mechanism upon
occurrence of a malfunction in said sensory means, said circuit
means being armed through a photoelectric relay, and said sensory
means including a light source and a fiber optic elongated bundle
extending from said light source to said photoelectric relay and
along said flexible member.
11. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securable to the other of said frame
and said door, said flexible connective member having a length
sufficient to permit opening of said door to a predetermined
extent, an alarm mechanism, sensory means extended along at least a
portion of said flexible member, circuit means coupled to said
sensory means and to said alarm mechanism for energizing said alarm
mechanism upon occurrence of a malfunction in said sensory means,
said flexible member terminating in a conductive keeper, and a
conductive keeper plate for detachably securing said flexible
member to said other of said door and said frame, said sensory
means including electrical conductors electrically connected to
said keeper and to said keeper plate respectively so that said
keeper and keeper plate are connected in a circuit including said
sensory means and so that unauthorized disengagements of said
keeper and keeper plate also results in said malfunction.
12. The combination according to claim 11 wherein switch means are
provided for said circuit means for disarming said circuit means
upon intentional disengagement of said keeper and said keeper
plate.
13. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securably to the other of said frame
and said door, an alarm mechanism, sensory means extended along at
least a portion of said flexible member, circuit means coupled to
said sensory means for energizing said alarm mechanism upon
occurrence of a malfunction in said sensory means, an anchor member
for said flexible member fabricated from a conductive material, an
electrical contact inserted between said anchor member and a
non-conductive support therefor, and said sensory means including
an electrical continuity loop having said anchor member and said
electrical contact electrically connected therein so that said
sensory means malfunctions upon breakage of said flexible member or
upon loosening of said anchor member.
14. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securable to the other of said frame
and said door, an alarm mechanism, sensory means extended along at
least a portion of said flexible member, circuit means coupled to
said sensory means for energizing said alarm mechanism upon
occurrence of a malfunction in said sensory means, said latch
mechanism including a keeper and an elongated keeper plate, said
plate having an elongated keeper slot therein, said sensory means
including an electrical continuity loop, said keeper and said
keeper plate being fabricated from electrically conductive material
and being electrically connected in said continuity loop, and
biasing means extended along said slot for urging said keeper into
electrical contact with said keeper plate as it is moved along said
slot.
15. An alarm system including a latch mechanism, said latch
mechanism having a flexible connective member with one end capable
of being anchored adjacent one of a door frame and an entrance door
and the other end detachably securable to the other of said frame
and said door, an alarm mechanism, sensory means extended along at
least a portion of said flexible member, circuit means coupled to
said sensory means for energizing said alarm mechanism upon
occurrence of a malfunction in said sensory means, said sensory
means defining a circuit path for arming said circuit means and
said circuit means including fail-safe means for energizing said
alarm mechanism upon occurrence of a break in said path, said
fail-safe means including a relay having normally closed contact
means connected in series with said alarm mechanism and a source of
electrical potential, said relay having an energizing coil capable
of holding said contact open when energized, and said coil being
connected in series with said path and said source.
16. The combination according to claim 15 wherein said relay
includes normally open contact means connected in series with said
path and said coil so that said relay is latched to an open circuit
condition upon a momentary break in said path.
17. The combination according to claim 15 wherein electrical shield
means are extended along that portion of said path which coextends
with said flexible member, said shield means being so connected to
said source that said relay coil is dropped from said circuit means
when said shield means are short-circuited to said path.
18. The combination according to claim 17 wherein dropping
resistance means are connected in said circuit means to said relay
coil and to said shield means such that current is limited through
said relay coil and said shield means both during normal operation
of said coil and when said shield means are short-circuited to said
path.
19. The combination according to claim 16 wherein electrical shield
means are extended along said flexible member and the adjacent
portion of said path, said shield means being connected to said
circuit means generally in by-passing relation to said normally
open contact means so that said relay is latched to an open circuit
condition upon a momentary short circuit between said shield means
and said path.
20. An alarm system including a latch mechanism, said latch
mechanism being mountable one one of a door frame and an entrance
door, an anchor member for said latch mechanism mounted on the
other of said door and said frame, an alarm mechanism, electrical
sensory means for mounting between said anchor member and said
other of the door and frame, circuit means coupled to said sensory
means for energizing said alarm mechanism upon occurrence of a
malfunction in said sensory means as by loosening or removing said
anchor member from said other of the door and frame said anchor
member being fabricated from a conductive material, said sensory
means including an electrical contact insertable between said
anchor member and said other of the door and frame, and said
sensory means further including an electrical continuity loop
having said anchor member and said contact electrically connected
therein when said anchor member is so mounted so that said sensory
means malfunctions upon loosening of said anchor member.
Description
The present invention relates to burglar or tampering alarm devices
and more particularly to a device of the character described
incorporated in a night latch using a flexible connective member
such as a chain. The alarm is arranged to indicate breakage of or
tampering with the night latch connective member or associated
components such as the anchor and keeper plates.
A chain type night latch is widely used on entrance doors to
private and multiple dwellings, multiple unit apartments, offices
and office suites and the like. In the usual forms of this type of
night latch, a short length of chain is usually affixed to the door
frame or the wall adjacent thereto. The free end of the chain
terminates in a keeper which can be keyed into an elongated slot in
a keeper plate usually attached to the door. The arrangement of
parts can be and frequently is reversed. In the usual configuration
the remote end of the slot is enlarged such that a keying portion
of the chain keeper can be inserted therethrough where upon the
keeper is retained in the slot as it moves therealong toward the
adjacent edge of the entrance door. In most cases the chain is only
of sufficient length to permit insertion of its keeper into the
remote end of the keeper plate slot when the door is completely
closed. When the entrance door is set slightly ajar the keeper is
moved to the nearer end of the keeper plate slot to afford a narrow
opening of not more than an inch or two. This affords the occupant
of the dwelling, office or other space visual access to ascertain
the identity of any caller or visitor or to receive small articles
through the visual access opening such as letters, newspapers,
prescriptions and the like without fully unlatching the door and
subjecting the premises to the possibility of forceful, violent, or
other unwanted entrance.
The chain type night latch or lock also secures the entrance to the
dwelling or other space protected thereby against the possibility
of an occupants' having lost his key, which may have been found by
an adverse or other undesirable person. Use of a chain lock or some
other form of night latch is a double check against an occupant's
forgetting to set the night latch usually forming part of a
conventional key lock customarily used for entrance doors.
Notwithstanding the inspectional aspects of the use of a chain type
latch, there are certain disadvantages inherent in such use. For
example if an intruder or other adverse party possesses a key to
the house or apartment or other dwelling whose entrance door is
protected by a chain type night latch, frequently the entrance door
can be opened, after the intruder unlocks the usual entrance key
lock, sufficiently to permit insertion of a wire or other object
for the purpose of removing the chain keeper from the remote end of
the keeper plate slot. By this means, a burglar or other intruder
can gain entrance to the premises without arousing the sleeping
occupants. In any event the entrance door can be opened
sufficiently (taking advantage of the aforementioned visual access)
to permit a burglar, robber, or other intruder to insert a tool or
weapon for the purpose of breaking the chain latch or otherwise
dislodging components thereof or in some cases to permit a direct
attack upon the occupant or occupants of the premises. For example,
an intruder may knock at the entrance door in the ordinary manner,
whereupon the occupant opens the entrance door but only to the
extent permitted by the chain latch to ascertain who the expected
or unexpected caller might be. The intruder or attacker may then
swing a tire iron or other weapon through the visual access opening
permitted by the chain lock for the purpose either of attacking the
occupant if he or she remains within reach or for striking and
severing the chain to gain access to the premises.
With the exponential increases in criminal activities, apparently
engendered by the modern "enlightenment" of our latterday
civilization, the incorporation of an alarm system in conjunction
with a conventional and widely used chain type or similar night
latch becomes increasingly undesirable.. Such alarm system can be
arranged to sound an internal alarm, i.e. an alarm only within the
premises, for the purpose of awakening sleeping occupants to the
activities of a burglar or other sneak thief. Alternatively the
alarm system can be arranged to sound an external alarm, for
example in the building managers office or apartment, house
detectives office, or the like in the case of an apartment house or
other multiple dwelling, or an alarm in a nearby police or fire
station. The latter alarm system would of course be more
advantageous in the case of attempted entrance by robbers or
burglars attempting to gain access by violence either against the
occupant or by mutilating the chain latch through the visual access
opening afforded thereby. An ultimate in protection can be afforded
by use of a combination of these systems.
I am aware of course of the efforts of others in this and related
fields. The U.S. Pats. to Chick et al No. 3,340,522 and to Hawkins
No. 3,406,386, and British Patent No. 636,985 each relate to an
alarm device in conjunction with a night latch such as a chain
lock. In every case, however, the alarm device is unable to
distinguish between an inadvertant opening of the door (to the
extent permitted by the chain or other flexible member) and an
actual breaking or attempt at breaking the chain. Moreover the
aforementioned alarm systems and also the differently-actuated
alarm system disclosed in U.S. Pat. to Fruh No. 2,607,866 depends
upon a mechanical switch actuation, i.e. the pulling of some
flexible or essentially flexible member, to operate the alarm.
The U.S. Pats. to O'Connor No. 883,335; Ferris No. 1,765,223; Lee
No. 2,913,712; Cremer No. 3,090,948; and Lewin et al. No. 3,127,597
relate to various types of shoplifting alarms in connection with
the display of various types of merchandise. The idea of intimately
associating an alarm system with a chain lock or similar type of
night latch is not disclosed in or obvious from these references.
None of the aforementioned references discloses the association of
a sensor such as a continuity loop with a flexible night latch
member such as a chain, in order to activate an alarm when an
intruder or attacker tampers with the night latch.
I overcome these disadvantages of the prior art by providing a
burglar alarm for use with a conventional chain type night latch or
the like by extending a sensing element (forms of which are
described hereinafter) either along or through the chain. The
sensing element is coupled to suitable circuitry designed to
energize either a local or a remote alarm or a combination of these
for the purpose of warning of an intrusion or attempted intrusion,
if the chain is broken or if an attempt be made to break the chain.
Alternatively, or preferably in conjunction therewith, a sensing
element can also be incorporated with the keeper plate or other
components of the chain lock to activate such alarm or combination
of alarms when the keeper plate or other night latch component is
either loosened or removed from its normal location on the entrance
door or doorframe.
The sensing element can be colored or textured or otherwise
configured to conceal its presence and/or its function in
conjunction with the chain lock. When the sensing element takes the
form of one or more electrical conductors I contemplate the use of
a holding or latching feature in the alarm circuit which will
continue the energation of the alarm although the intruder may
succeed in splicing or otherwise rejoining the broken ends of the
conductors. Alternatively, a number of dummy or superfluous
conductors can be added to the energized or functional conductors
to make the splicing or other rejoining operation more confusing
and less likely, particularly when there is inadequate light for
the operation. An electrical shield formed from similar-appearing
wires can be disposed adjacent an electrically conductive sensory
loop or conductor to obfuscate any attempt at splicing broken
conductors. Additional features of my invention involve the use of
a spring or other biasing arrangement to make it more difficult to
remove the keeper end of the chain from the keeper plate from the
outside of the entrance to the premises and to sound an alarm, in
any event, should this be accomplished. I also contemplate a switch
arrangement incorporated in conjunction with the keeper plate slot
such that the alarm system is energized automatically but only when
the chain keeper has been inserted into the keeper plate slot by
the occupant or occupants of the premises. To minimize the
possibility of shock to occupants of the premises, the alarm
circuit can be battery-operated or it can be coupled to other
sources of low potential electric current, such as a door-chime
power supply. If a battery system is used an automatic recharging
arrangement can be provided therefor, which can be automatically
coupled to the battery when the chain latch is deactivated.
An important advantage of my invention is that it is associated
with a familiar and widely used type of night latch and does not
require the manipulation of unfamiliar devices of components on the
part of the occupants of the premises to energize the alarm system.
Instead, the alarm system is incorporated with a conventional latch
system and can be energized automatically, whenever the chain latch
or similar latch is utilized by the occupants. In certain forms my
alarm system can be continuously armed as it is a low-drain system,
and peaceful removal of the chain or other connective member from
the keeper plate by the occupant is not sensed by the sensory
member of the alarm. There is no necessity for the occupants to
turn on various activating switches (which can be readily
forgotten) when protection is desired and to turn off switches when
it is desirable or necessary to deenergize the alarm system. My
alarm system is particularly advantageous in this respect, when a
remote or external alarm (such as in a police station) is connected
to the alarm system. In other embodiment of my invention, whenever
the night latch chain or similar component is attached to utilize
the latch, the alarm system is automatically activated or armed
and, thus, is not armed continuously. By the same token, the alarm
system is disarmed whenever the chain element or other component of
the latch arrangement is disengaged. A most significant advantage
of my alarm system is the impossibility of disarming the system by
an intruder from outside of the entrance door of the protected
premises.
It should be noted that the purpose of the usual chain type night
latch or other night latch is to protect the occupants of the
premises, rather than the premises themselves, as the usual night
latch of this type cannot be closed or engaged from outside the
entrance. However, it is contemplated that my novel alarm
arrangement can be incorporated with various key-operated chain
devices and similar locks, which can be engaged and disengaged from
outside the entrance of the premises. In such case, the alarm
circuit of the invention desirably is coupled to a remote alarm
such as a building manager's office or a nearby police station.
I accomplish these desirable ends by providing an alarm system
including a latch mechanism, said latch mechanism having a flexible
connective member with one end anchored adjacent one of a door
frame and an entrance door and the other end detachably securable
to the other of said frame and said door, an alarm mechanism, a
sensory means extended along at least a portion of said flexible
member, and circuit means coupled to said sensory means for
energizing said alarm mechanism upon occurence of a malfunction in
said sensory means.
I also desirably provide a similar alarm system wherein said
sensory means define a circuit path for arming said circuit means,
and said circuit means include fail-safe means for energizing said
alarm mechanism upon occurrence of a break in said path.
I also desirably provide a similar alarm system wherein said
sensory means include an electrically conductive circuit path and
electrical shield means extended along said flexible member and
adjacent that portion of said path extending along said flexible
member, said shield means and said path when shorted together by an
attempt to break said flexible member providing said
malfunction.
I also desirably provide a similar alarm system wherein switch
means are provided for arming and disarming said circuit means, a
keeper and keeper plate are provided as part of said latch
arrangement, said switch means being located adjacent a slot in
said keeper plate so as to be actuated to arm said circuit means
upon engagement of said keeper and said keeper plate and to be
actuated to disarm said circuit means upon disengagement of said
keeper and said keeper plate.
I also desirably provide a similar alarm system wherein said
flexible member is a length of chain, and a length of said sensory
means is interwoven with and passed along the length of said
chain.
During the foregoing discussion, various objects, features and
advantages of the invention have been set forth. These and other
objects, features and advantages of the invention together with
structural details thereof will be elaborated upon during the
forthcoming description of certain presently preferred embodiments
of the invention and presently preferred methods of practicing the
same.
In the accompanying drawings, I have shown certain presently
preferred embodiments of the invention and have illustrated certain
presently preferred methods of practicing the same, wherein:
FIG. 1 is an elevational view illustrating one form of alarm system
arranged in accordance with my invention and in conjunction with a
conventional chain latch;
FIG. 2 is an enlarged partial view of a conventional chain latch
having another form of my invention incorporated therewith;
FIG. 2A is a still further enlarged, partial view of the alarm
system of the invention and similar in its broad outlines to the
FIG. 2 arrangement;
FIG. 2B is a schematic circuit diagram of one form of alarm circuit
which can be utilized with the alarm systems of my invention as
disclosed therein;
FIG. 2C is a schematic electrical and optical circuit arranged in
accordance with my invention and illustrating another form of my
novel alarm system;
FIGS. 2 and 3A are partial elevational views of modified forms of a
flexible latch member forming part of the invention in these
modifications;
FIG. 4 is an elevational view of another form of my alarm system
incorporating in this example automatic switch means for arming and
disarming the alarm circuit;
FIG. 4A is an elevational and electrical schematic view of still
another arrangement of my novel alarm system;
FIG. 5 is an elevational view and circuit diagram of a protected
night latch arrangement similar to those illustrated in the
preceding figures, but incorporating modified sensing means capable
of detecting the loosening or removal of either or both of the
anchor plate and the keeper plate of the night latch assembly;
FIG. 5A is an edge view of a portion of the alarm system shown in
FIG. 5 and taken along reference line VA--VA thereof;
FIG. 5B is a partial elevational view of another form of the
invention having a modified flexible member; and
FIG. 6 is a schematic and pictorial arrangement of one form,
arranged in accordance with my invention, of alarm circuit which
can be utilized with any of the aforementioned alarm systems.
Referring now more particularly to FIGS. 1 and 2 of the drawings
the alarm system 11 of my invention, including sensory means, in
this case a continuity loop, is associated with a conventional
chain lock denoted generally by reference character 14 or other
suitable latch arrangement. The chain lock 14 conventionally
includes a chain 16 which is somewhat slack when door 18 is fully
closed, an anchor plate 20, and a keeper plate 22. The otherwise
free end of the chain 16 terminates in a keeper 24, which has a
projection 26 (see FIG. 2A) insertable into an enlarged slot
portion 28 of keeper slot 30 in the keeper plate 22. Normally, the
circuit plate 22 is affixed to the door 18 while the anchor plate
20 is affixed to door frame 32 or to wall surface 34 adjacent
thereto.
The alarm circuit 10 can be mounted on the wall 34 adjacent the
night latch arrangement 14, as shown in FIG. 1 or as better shown
in FIG. 2 the alarm circuit 10 can be remotely located, for example
in a bedroom of one or more of the occupants of the premises thus
protected. In the arrangement as shown in FIG. 2 the sensor 12'
includes conductors 13 connected to the alarm circuit 10.
Alternatively, the alarm circuit 10 (or the alarm mechanism 38
(FIG. 2B) thereof) can be located outside of the premises serviced
by the alarm system 11, (FIG. 1) for example in the manager's or
house detective's apartment or office of a multi-unit building or
in a nearby police or fire station. Alternatively the alarm circuit
10 can be coupled to a pair of alarm mechanisms in parallel, with
one of the mechanisms being located within the premises and the
other located externally of the premises as foresaid.
The alarm system 11 in accordance with the feature of my invention
presently under discussion include a very low-drain circuit 10,
which therefore can be left energized or activated continuously.
The occupants of the premises are not forced continuously to arm
and disarm the circuit 10 as they enter and leave the premises.
Suitable circuitry for use as part of the alarm system 11 is
described below in connection with FIGS. 2B, 2C, and 6 of the
drawings.
The sensory means 12, which is coupled to the alarm circuit 10 and
forms part thereof is arranged in this example of the invention as
a continuity loop, which when subject to a malfunction such as
breakage causes the alarm forming part of the alarm system 11 to be
energized. Although not essential to the basic feature of my
invention, various arrangements can be provided for preventing an
intruder from reestablishing the continuity loop 12 and thus
terminating the energization of the alarm mechanism.
The sensory means 12, which in this example is in the form of a
continuity loop or circuit path can be threaded through the chain
16 of the latch arrangement 14 in such manner as to be unapparent
to the casual observer. As better shown in FIG. 2 the loop 12 can
be affixed at one end to the chain keeper 24 and adjacent its other
end to anchor plate 20. The loop 12 can be affixed to the keeper 24
by passage through a small hole 35 therein. At the anchor plate 20
the loop can be secured thereto for example by wrapping about a
chain retaining ring 37. Thus, if the chain 16 is severed the
continuity of the circuit path 12 is destroyed, which energizes an
alarm mechanism in the alarm circuit 10, as described below.
To further conceal the presence of the sensor 12, the latter can be
provided with the same color as that of the chain 16. Alternatively
the chain 16 can be replaced by a suitable length of a hollow
flexible material such as a braided and tubular metal mesh (not
shown) through which the sensor 12 can be passed.
Alternatively, again, the chain 16 can be replaced with another
flexible member made, as shown in FIG. 5B, from conductive loop
12a. The loop 12a can be heavily stranded for strength and
flexibility or can be a mixture of copper and steel strands for
added strength. The bight of the loop 12a passes through keeper 24a
and the other end of the sensor 12a is secured to anchor plate 20a
by wrapping about ring 37a and/or by securing to terminals 39. This
provides a unitary sensor and flexible member structure, the
purpose of which is concealed by insulation 13a.
It is also contemplated that a lock-type chain latch can be
substituted for any of the chain latches depicted in the drawings
and described herein. As such latches generally unlock the chain at
the anchor plate end, it would be desirable to pass the continuity
loop or the sensor directly to this end of the chain (or other
flexible member) without passage through the anchor ring or in any
way securing the sensor to the anchor plate.
As evident from FIGS. 2B and 2C of the drawings (and from FIG. 6
described below), the alarm circuit means 10 and the sensor 12
forming part thereof can be provided in accordance with my
invention in a variety of forms. For example as shown in FIG. 2B
the alarm circuit 10 comprises a source of electric potential 36, a
conventional alarm device 38, such as a bell or buzzer, and a relay
coil 40.
The alarm mechanism 38 is coupled across the source 36, which can
be a battery as shown or a conventional line voltage connection
(not shown), in series with a pair of normally closed contacts 42.
The contacts 42, however, are held open in the usual manner by the
relay coil 40 when energized. In the arrangement of FIG. 2B the
relay coil 40 is normally energized from the source 36 through a
dropping resistor 44, and, in this case, both the resistor 44 and
the coil 40 are connected in series with the sensor 12. Here, the
sensor 12 is a conductive loop or wire arranged to complete a
circuit through the source 36, dropping resistor 44, and the relay
coil 40.
Desirably the dropping resistor 44 is a relatively high resistance
for use with a low voltage type relay including the normally closed
contacts 42 and the relay coil 40. Thus, the current drain on the
source 36 is very low and the relay coil 40 can be energized
continually if desired. Accordingly, as noted above there is no
necessity for switching the alarm circuit 10 on and off, and the
alarm system can remain continuously armed. However, as described
below, means in accordance with another feature of the invention
are provided for automatically activating and deactivating the
alarm circuit 10 or its equivalent.
As noted previously when the chain 16 is broken, the circuit path
including the continuity loop 12 is also broken, and this
deenergizes the relay coil 40. In consequence, the relay contact
means 42 are closed and the alarm 38 is energized. It is possible
but not extremely likely that the intruder could reconnect the
broken ends of the continuity loop 12. To further decrease the
possibility of this occurrence the sensing loop can be passed
several times through the chain 16' (FIG. 2A) to form, in effect,
two or more sensor loops 12' in series. The series loops 12' can be
fastened to the anchor plate 20.degree. and keeper 24' in the
manner described previously. The series loops 12' can be connected
directly through conductors 13' for this purpose to an appropriate
one of the alarm circuits described herein. With the use of four or
more conductors passing through the chain 16', it is much less
likely that the intruder will attempt to locate and reconnect the
broken ends.
It is contemplated by my invention that one or more additional
sensing members can be employed for or in conjunction with the
sensory means 12, as further shown in FIG. 2B of the drawings. The
additional sensing arrangement can be in the form of a metallic
shield of tubular woven or braided metallic mesh surrounding and
extended along at least that portion of the loop 12, which extends
along the chain 16. Alternatively, one or morenon-looped conductors
similarly extended along the sensory means 12 can be used. In
either of these cases or in the case of any reasonably equivalent
structure, the auxilliary sensing arrangement will be referred to
as a shield, in this instance an electrical shield denoted
generally by the chain outline 46 thereof in FIG. 2B. Specifically,
the shield 46 can take the form of one or more (in this example,
three) of the aforementioned conductors, desirably extended or
woven through the chain 16 in generally parallel relation to the
adjacent portion of the loop 12. The shield 46 is positioned very
close and preferably coextensive with that part of the sensory loop
12 which is extended along or through the chain 16.
One end of the shield 46 is connected in series with the dropping
resistor 44 and more or less in by-passing relation to the relay
coil 40. In the event that a short circuit should occurr between
the conductive shield 46 and the conductive sensory loop 12 the
relay coil 40 would drop out of the circuit. Such short circuit
would not draw a significant current as it would, like the relay
coil 40, be in series with the dropping resistor 44. With such
malfunction of the sensory means (including the loop 12 and the
shield 46) and with the relay coil 40 thus shorted out, the
normally closed contacts 42 would permit the alarm mechanism 38 to
be energized, as the contacts 42 no longer would be held open by
the relay coil 40.
With the use of the auxillary sensing means 46 it is likely that
the alarm 38 would be energized before the intruder succeeds in
severing the chain 16 or 16', as one or more blows upon the chain
16, particularly with a metal tool or weapon such as a tire iron,
would tend to short-circuit the conductive shield 46 to the
conductive sensory loop 12. The alarm would not only arouse the
occupants of the premises before the intruder succeeds in breaking
the chain lock, but also would tend to frighten off the intruder
before he succeeded in gaining access to the premises.
The use of the shield 46, in any of its variety of forms, also
renders it less likely that the intruder would be able to reattach
the broken ends of the sensing arrangement in order to silence the
alarm mechanism, when once energized.
Modified forms of the chain lock or similar latch arrangement are
shown in FIGS. 3 and 3A of the drawings, and these are arranged to
ensure breakage or severance of the continuity loop 12, or
equivalent sensory means, prior to actual severance of the night
latch chain or other flexible connecting element, by an intruder or
attacker. In each of these arrangements the circuit path member 12
is affixed at one end to the chain keeper 24 and adjacent its other
end to the anchor plate 20, for example in the manner described
above. The chain 16, however, is provided with a relatively stout
spring or other expansible resilient member. The expansible member
is positioned in and forms part of the chain 16 such that any
reasonably hard blow thereof which is substantially less than that
required to break the chain will sufficiently elongate the chain,
by virtue of the expansion of its expansible member, to break the
sensory loop 12. The aforementioned expansible member, illustrated
in FIGS. 2 and 3A as a stout spring 48 or 48', can be located
adjacent the keeper 24 as shown in FIG. 3 or adjacent the anchor
end of the chain 12 as shown in FIG. 3A, or elsewhere along the
length of the chain 16. I also consider that the chain spring 48 or
48' can be made longer and less stout so that the flexible member
must be stretched slightly to reach the enlarged keeper end of the
keeper plate slot 30. It is therefore, much more difficult to
remove the keeper 24 from the far end of the slot 30 from the
outside of the door 18.
As shown in FIG. 2C, my invention contemplates other forms of
sensing means beyond the electrical arrangements noted previously
and their equivalents. For example, in the alarm circuit of FIG. 2C
a sensory member 50 can form part of an optical circuit and
includes an elongated fiber optic bundle, which can be looped as
shown in FIG. 2C and then passed along or through the chain 16, in
much the same manner as the electrical conductor loop 12 of FIGS. 1
and 2. For example, the central or return portion of the loop can
be affixed to the keeper 24 while the lead in portions of the loop
can be wrapped about the anchor ring 37 and then passed to an alarm
circuit 52. Of course, a well known characteristic of a fiber optic
bundle is its capability of conducting light along a tortuous
path.
The alarm circuit 52 is generally similar to a circuit 10 and
includes an alarm mechanism 38', potential source 36', relay coil
40', and normally closed relay contacts 42'. In the circuit 52,
however, energization of the relay coil 40' is controlled by an
electro-optical system including the aforementioned fiber optic
sensor 50. Thus, the relay coil 40' is connected electrically in
series with the source 36' and with a conventional photoelectric
relay 54. A dropping resistor 44' is utilized as before to minimize
current drain of the source 36', when the alarm system is on
standby or armed. The photoelectric relay includes a pair of
normally open contacts 56, which are maintained in the contact
closed position as shown by light passing from light source 58
through the fiber optic loop 50 to photocell 60 forming part of the
photoelectric relay 54. Preferably the light source 58 is a low
voltage lamp and is likewise connected across the voltage source
36' through a dropping resistor 62 to minimize drain.
The fiber optic loop 50 can be provided with a relatively small
diametric dimension and can be otherwise colored or configured so
as to be virtually unnoticable when extended through the chain 16
(FIGS. 1 and 2). When the chain 16 is broken the fiber optic bundle
50 is of course severed with the result that light from the source
58 no longer passes through the bundle 50 to the photoelectric
relay 54. The normally open photoelectric relay contacts 56 then
open to interrupt the flow of low voltage current to the relay coil
40'. This permits the normally closed alarm relay contacts 42' to
close thereby energizing the alarm 38'. As the fiber optic bundle
50 comprises a relatively large number of very fine
light-conducting filaments, it is extremely unlikely that the
intruder or attacker can reassemble the broken ends in such manner
as to reestablish an adequate level of illumination at the
photocell 60 in order to reenergize the photoelectric relay 54 and
thereby to deenergize the alarm 38'.
In conjunction with the feature of my invention as shown in FIG.
2C, I also contemplate the use of means such as the expandible
members 48 or 48' of FIG. 3 or 3A respectively to ensure breakage
or malfunction of the fiber optic continuity circuit 50 prior to
actual breakage of the chain 16 or other connected member.
In the modification of my invention as illustrated in FIG. 4, I
provide means for automatically activating and deactivating an
alarm circuit 64. The alarm circuit 64 can be provided in the same
general arrangement as that of the circuit 10 (FIGS. 1 and 2) or
the circuit 52 (FIG. 3C) or the circuit 66 (FIG. 6). The alarm
circuit 64, of course, includes battery 67 or other source of
suitable electric potential such as the line voltage customarily
supplied to the premises. The alarm circuit 64 is coupled in the
manner mentioned previously to a suitable sensor 69, which may take
the form of one of the sensors described previously.
Automatic activation and deactivation of the alarm circuit 64 is
accomplished by a pair of conductive strips 70, 72, which are
secured to the entrance door 74 and preferably alligned with and
behind the keeper slot 30' of the keeper plate 22'. The contact
strips 70, 72 can be spring loaded or otherwise biased toward the
keeper slot 30' to ensure contact with the keeper 24', when the
latter is inserted into the keeper slot 30' in the usual
manner.
As evidenced in FIG. 4 the contact strips 70, 72 are connected in
series with the alarm circuit 64 and its source 68, which is
preferably a low-voltage source to obviate shock hazard. Thus, the
circuit 64 is automatically activated when the keeper 24' is
inserted into the keeper plate 22' during use of the latch 14' and
is automatically deactivated when the keeper 24' is removed, i.e.
when the latch 14' is not in use. A low voltage alarm mechanism
(not shown) can be incorporated into the alarm circuit 64, and a
dropping resistor 76 can be employed, if desired, further to
minimize shock hazard at the contact strips 70, 72. Alternatively
or in conjunction therewith that portion of the keeper 24' which is
to be grasp by the occupant or occupants of the premises can be
electrically insulated (not shown). Other forms of contact means
can, of course, be substituted for the contact strips 70, 72. For
example one of the contact strips 70, or 72 can be eliminated and
the associated conductor 78 or 80 can be electrically connected
directly to the keeper plate 22'. Where the keeper plate 22' is
secured to the door 74, the conductor 78, 80 can be extended across
the door in an unobtrusive manner and around one of the door
hinges, for example the upper door hinge 82 as shown in FIG. 4, to
the source 68 and other components respectively of the alarm
circuit 64.
As evident from FIG. 4A, it is not essential that the sensing means
be a continuous or reentrant loop insofar as the chain 84 is
concerned. In the last-mentioned arrangement of the invention a
conductor wire 86 is extended from the alarm circuit 10' (the
circuit of FIG. 2B or 6 or equivalent circuit can be utilized for
this purpose) to the anchor plate 87. Desirably the conductor 86 is
attached to the anchor plate 87 for example by wrapping about
anchor ring 88 thereof. From the ring 88 the wire is passed through
and along the chain 84 to the keeper 90. The conductor 86 is
electrically connected to the keeper 90 as denoted by reference
character 92. For this arrangement of the invention, the keeper 90
and keeper plate 94 are each fabricated from an electrically
conductive material. Conductor 96 is electrically connected to the
keeper plate 90 and completes the circuit path or continuity loop
to the alarm circuit 10', when the keeper is engaged in the keeper
plate slot 98.
With the arrangement just described any severance of the chain 84
will also sever the conductor 86 and cause the alarm circuit 10' to
energize the alarm mechanism forming part thereof, in the manner
described above. The FIG. 4A arrangement in addition will energize
the alarm, if a thief succeeds in disengaging the keeper from the
keeper plate. The alarm circuit 10' is armed and disarmed by means
of manual switch 100 in series with the alarm circuit 10' and a
power supply 102 therefor. Alternatively, the alarm circuit can be
activated and deactivated automatically for example after the
manner of FIG. 4. To ensure electrical contact between the keeper
90 and the keeper plate 94 along the length of the keeper slot 98,
a leaf spring 104 or the like can be mounted behind the slot 98 to
ensure such electrical contact as the keeper 90 is moved.
In FIGS. 5 and 5A of the drawings modified sensing means are
provided for detecting tampering with one or more of the latch
components, in addition to the chain 106. In many entrance
arrangements it is possible for an intruder to pry loose anchor
plate 108 after opening door 110 to the limit permitted by the
chain 106. One form of a dual purpose sensing means includes a
conductive loop 112 extended through the chain 106 and physically
attached to keeper 114 after the manner described previously.
However, the conductor loop 112 in this example is interrupted at
116 and one of the ends adjacent the interruption is secured
electrically to the anchor plate 108 as denoted by reference
character 118. The other end is electrically secured to an
electrical contact member 120 secured to a wall or other
nonconductive support on which the anchor plate 108 is mounted.
When properly mounted the anchor plate electrically engages the
contact member 120 to complete the conductive loop 112.
Accordingly, the alarm circuit 10" energizes the alarm mechanism
forming part thereof when either the chain 106 is broken or when an
attempt is made to pry the anchor plate 108 loose from the wall or
other support. If the latching type alarm circuit 66 of FIG. 6 be
employed in place of the alarm circuit 10" only a momentary
separation of the conductive anchor plate 108 and the electrical
contact 120 is sufficient for continued energization of the alarm
mechanism. It is also contemplated that the chain 106 can be
provided with a spring such as the spring 48 or 48' mentioned above
or other expansible member so that the loop 112 is broken when the
chain is struck a solid blow or otherwise pryed or jimmied
sufficiently to elongate the expansible member.
It is contemplated that the keeper plate 117, for example, can be
more securely fastened to the door than the anchor plate 108 is to
the wall of the premises, such that the anchor plate would be
preferentially loosened thereby interrupting the continuity loop
112. Alternatively a similar contact arrangement such as
chain-outlined contact 119 can be secured between the keeper plate
117 and the door 110. Assuming that the keeper plate 117 is
fabricated from a conductive material the keeper plate 117 and the
contact 119 likewise can be series-connected to the conductive loop
112 as denoted by chain-outlined conductors 121.
In FIG. 6 of the drawings, the aforementioned latching type alarm
circuit is illustrated, as arranged in accordance with another
feature of my invention. The alarm circuit 66 of FIG. 6 is shown
with latching relay coil 122 in its energized state. Thus, normally
open latching contacts 124 are closed while the normally closed
alarm contacts 126 are open. As in the previously described alarm
circuits, the circuit 66 thus incorporates a fail-safe feature. The
relay coil 122 is energized as shown from the source 36' by means
of a circuit path through dropping resistor 44', latching contacts
124, and sensory means such as continuity loop 12'. If a break
occurs in the continuity loop the relay coil 122 is deenergized
such that the alarm contacts 126 are closed and the latching
contacts 124 are open. The alarm mechanism 38' then is energized
continually although the broken ends of the loop 12' may be
reconnected. After passage of the emergency or correction of the
situation which tripped the alarm circuit, the latching relay 122
can be reenergized by operation of a manual reset switch 128 by an
occupant of the premises.
If desired an electrical shield such as the guard wires 46' can be
utilized in the alarm circuit 66 after the manner of FIG. 2B. The
shield 46' (whenever shorted to the continuity loop 12') is
connected in series-parallel with the relay coil 122 and its
latching contacts 124 to the source 36'. Thus, a short circuit
(limited by dropping resistor 44') between the loop 12' and the
electrical shield 46' will short out the relay coil 122 causing its
deenergization and concomitant disengagement of the latching
contacts 124 and engagement of the alarm contacts 126, without the
occurance of a break in the continuity loop 12'. The alarm
mechanism 38', then, will be energized in the case of either type
of malfunction in the sensory means, albeit of a momentary
character.
From the foregoing it will be apparent that novel and efficient
forms of Alarms for Night Latch have been described herein. While I
have shown and described certain presently preferred embodiments of
the invention and have illustrated presently preferred methods of
practicing the same it is to be distinctly understood that the
invention is not limited thereto but may be otherwise and variously
embodies and practiced within the spirit and scope of the
invention.
* * * * *