BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the bottom of a detachable body of a sensor device;
FIG. 2 is a plan view of a mounting base corresponding to the body of the sensor device shown in FIG. 1;
FIG. 3 is a cross sectional side elevational view of the mounting base taken along line CC shown in FIG. 2;
FIG. 4 is a cross sectional side elevational view of the sensor device, the body and mounting base as a unit, taken along line AA shown in FIG. 1;
FIG. 5 is a cross sectional side elevational view of the sensor device, the body and mounting base as a unit, taken along line AA shown in FIG. 1 showing a detailed view “A” of the plunger and printed circuit board; and
FIG. 6 is a cross sectional, side elevational detail view at “A” in FIG. 5 depicting the plunger and conductive pads on the printed circuit board.
DETAILED DESCRIPTION OF THE INVENTION
The tamper detection device according to the present invention acts as a switch for detecting when a sensor device has been opened. The tamper detection device can also detect if the sensor device is removed from a wall or ceiling. According to the present invention, the tamper detection device is located at the center of rotation of the sensor device, so that there are no frictional side-thrust loads which can cause damage and malfunction to the mechanism during rotation. This assures proper activation/de-activation over the life of the product. The present invention enables blind assembly of the body and mounting base of an example circular-housed sensor, independent of any required angular alignment, and a simple rotation until locked. This is especially desirable for an installer on a ladder, without good visibility.
The sensor device 500 according to the present invention allows an exemplary circular packaged sensor, such as a carbon monoxide, smoke or heat detector, to be easily installed into its' mounting base, which is permanently affixed to the wall or ceiling. The sensor is initially installed by a security system installer, and is removed from time to time by an end-user for battery replenishment. It is necessary for it to be easy to replace the sensor to the mounting base after the necessary service has been completed.
The embodiment of the present invention, depicted in FIGS. 1-6, allows the sensor to be placed against the mounting base without visually aligning any tabs or appurtenances and requires a simple clockwise rotation to lock it in position. In the present invention, the tamper detection resilient element/plunger 400, is preferably installed into the center of the base 100. When the base 100 is rotated into its' mounting surface, the plunger 400 is compressed which forces it in the direction opposite to the mounting surface. The plunger is compressible, so that when the sensor is attached to the mounting base 100, the plunger compresses inward, which assures a continuous pressure of the contact disk 117 on the end of the plunger 400 with the printed circuit board electrically conductive pads 452, which completes the tamper circuit.
An embodiment of the sensor device body 10 and mounting base 100 according to the present invention is shown in FIGS. 1 and 2. The sensor device body 10 is circular and can be blindly placed against its' mating circular mounting base 100 and rotated until locked, without the need for viewing or alignment of tabs or locating structure to secure the body 10 to the mounting base 100. The body 10 includes a battery compartment 14 for housing a battery which provides power to a printed circuit board (PCB) and associated circuitry for detecting a tamper situation and producing a signal according to the detection mechanism, which may be a smoke, or carbon monoxide, etc., detection mechanism. Further, when tampering is detected, the battery provides power to a signal means for emitting a signal which may include, for example, a siren, or a wireless transmission. Tabs 18 are positioned on opposite sides of the body 10 and are adapted to matingly slide under the elements 114 on the bottom of the mounting base 100. The tabs 18 and elements 114 comprise a locking mechanism for removable coupling the body 10 and mounting base 100 together.
Contact surface 22, shown in FIG. 1, on the body 10 is an exposed part of the PCB 450 (shown in FIG. 5) and includes electrically conductive pads 452. Referring to FIG. 5, the PCB 450 is protected by a printed circuit board cover 460. The printed circuit board 450 is a sub-assembly that is mounted to a heat detector (not shown) in the body 10 of the sensor unit 500. The heat detector, printed circuit board 450 and printed circuit board cover 460, and the screws 483 that hold the printed circuit board to the heat detector are a sub-assembly housed in the body 10 of the sensor device 500. The sub-assembly as part of the body 10 is placed against the mounting base 100 and rotated to lock the sub-assembly into the mounting base which has been fastened to a mounting surface, e.g. a ceiling or a wall.
Referring to FIG. 2, the resilient element 400 is substantially centrally located on the mounting base 460. The contact disk 117 of the resilient element 400 (shown in FIGS. 2 and 6) mate with the printed circuit board 450 contact surface 22 pads 452 (shown in FIGS. 1 and 6). The resilient element 400 and the locking mechanism comprising the tabs 18 and the elements 114 are independent of the initial orientation of the body 10 and the mounting base 100. During assembly, the body 10 overlays the base 100 and the tabs 18 are positioned adjacent to the elements 114. The body 10 and the mounting base 100 lock into position by two outward tabs 18 on the sensor device body 10 rotating along a circular raised surface 116 within the mounting base 100. The body is then twisted in a clockwise direction to slide the tabs 18 under the element 114 thereby locking the body 10 to the base 100 as a unit 600 (shown in FIG. 5). Eventually, portions 19 of the tabs 18 abut stops 119 on the mounting base 100 at the end of the rotation. Above the stops is a retaining ledge for holding the two tabs securely. The locking tabs 18 of the sensor body 10 can be aligned blindly, without extensive adjustment, and twisted until the body of the sensor locks to the base.
Resilient element/plunger 400 (shown in FIG. 5) is resilient and extends through shaft 424 and terminates at end 504. The shape is determined by a combination of factors including the initial memory of the molded elastomeric product, whether a mounting surface (e.g. a wall or ceiling) is pushing up against it, and the force of the printed circuit board pressing back and resilient plunger 400. The shaft 424 maintains the plunger 400 perpendicular to the circuit board 450 to ensure that the end 504 remains at the shaft's bottom while the distal contact disk 117 contacts the pads 452 on the contact surface 22 of the circuit board 450 completing the tamper circuit.
Referring to FIG. 5, a mounting structure/bracket 480 is connected to the body 10 of the sensor device 500. The mounting bracket 480 has the printed circuit board (PCB) affixed to it. There are two dropped arms 482 which rotate into the seat 484 locking the mounting bracket 480 and PCB to the wall mounting base 100. The bracket suspends the PCB at the correct level and also serves as a mounting surface for the heat detector module. Screws 483 go through the PCB, making contact with the PCB and fasten the PCB to the mounting bracket 480 through the threaded holes in the heat detector.
There is electrical contact via the two fastening screws 483, between the PCB 450 and the heat detector. When there is a thermal alarm, there is the equivalent of an electrical switch closure at the two threaded holes in the heat detector, which contacts the PCB through the screws. The circuitry on the PCB 450 interprets that switch closure as an alarm situation and sends out a suitable message.
Further, referring to FIG. 5, the mounting structure 480 is secured by arm 482 to the seat 484 on the body 10. Stop arm 486 contacts plate 488 to prevent the mounting structure 480 from over compressing and damaging the PCB 450 or contact 117 on the plunger 400. The mounting structure 480 is biased outwardly such that the coupling of the mounting base 100 and body 10 as a unit on a structure, e.g., a wall or ceiling, pushes the PCB 450 toward the contact disk 117 on FIG. 6 on the end of the plunger 400. If the sensor device 500 as a unit is removed from the structure, the natural bias of the mounting structure 480 pulls the PCB away from the contact disk 117 at the end of the plunger 400, thus, the circuit is opened which the PCB senses as a tampering. The present invention satisfies the need for a front tamper indication, when the body 10 and the mounting base 100 of the sensor device 500 is removed, but also serves as a rear tamper indicator if the entire sensor unit 500 is pried from the mounting surface.
The tamper detection device shown in FIGS. 4 and 5, includes a tamper detection plunger 400 preferably made of an elastomeric material, such as rubber, and is shaped into the form of a plunger. On one end are necessary grooves and appurtenances required to fix the device to a backing or mounting plate 460 on the mounting base 100. On the other end of the tamper detection plunger/device 400 is the centrally located conductive contact disk 117 that is used to complete the circuit of the two adjacent electrically conductive pads 452 (shown in FIG. 6) on the PCB 450.
More specifically, the resilient element/plunger 400 is inserted into the mounting base 100 and snapped into the a base portion 460 using a circular depressed retainer groove located along the length of the resilient element perpendicular to the cylindrical axis of the element. A proximal part 504 of the resilient element 400 protrudes behind the base portion 460 and is compressed when the mounting base 100 is pushed up against the mounting surface (e.g., wall or ceiling).
The compression of the resilient element/plunger 400 causes the element to extend further inward, eventually contacting the printed circuit board 450 which completes the circuit. There is over-travel designed into the resilient element/plunger 400, which ensures positive pressure against the printed circuit board 450, so that the conductive element 117 at the end of the resilient element/plunger 400 contacts both electrically conductive pads 452 (shown in FIGS. 1 and 6) on the printed circuit board 450 which completes the tamper circuit.
Over-travel, in this case, occurs when the resilient element 400 would extend beyond the normal mounting plane of the printed circuit board if the PCB were not present in the body 10. Thus, under normal operating conditions when the PCB 450 is in place in the body 10, the resilient element/plunger 400 exerts a positive pressure against the printed circuit board 450 contact surface 22 resulting in contact resistance between the two printed circuit electrically conductive pads 452 on the contact surface 22 of the tamper circuitry when the pads 452 are bridged by the contact disk 117 at the end of the resilient element 400.
The resilient element 400 is compressed by the force of the mounting surface against the mounting base 100 which pushes the mounting base 100, and thereby the resilient element, toward the PCB 450 affixed in the body 10. While the force against the mounting surface and the resulting application of pressure against the PCB continues, the resilient element remains locked into its' hole in the mounting base because the groove in the mounting base has a diameter approximately the diameter of the hole that it is inserted into, and on either side of the groove, the diameter is larger which results in a retention of the resilient element in the hole. The resilient element can easily be forced into the hole during manufacture because the element is resilient, and snapped into position.
When the body 10 and the mounting base 100 are assembled as a unit (as shown in FIG. 5), the contact disk 117 completes the circuit of the adjacent pads 452 and acts as a switch. If the sensor device 500 is disassembled, the circuit is opened electrically which is interpreted as a “tamper” condition. When a tamper condition is sensed by the PCB, wireless circuitry, for example, may transmit a message indicating tampering. Also, for example, a sound may be emitted or a light, or all of the indicators together.
A wireless transmission according to an embodiment of the present invention may include a custom integrated circuit, such as an RF-Encoder, which senses when a tamper situation has occurred. The RF-Encoder sends two signals to a transmitter circuit. One signal from the Encoder powers up an oscillator which is running at the selected transmitter frequency. This stays engaged until the full message is sent. The other signal from the RF-Encoder, switches power amplifier circuitry on and off, forming a burst transmission of pulses. These pulses are received by a receiver that decodes the digital message sent. To ensure a satisfactory transmission, there are multiple redundant transmissions of the same data. In addition to housekeeping data for the product, tamper and alarm data, a relatively unique serial number is transmitted which identifies which unit is transmitting. This is transmitted from the RF Amplifier through a small antenna within the unit.
An alternative to wireless transmission, is replacing the wireless transmitter radio with “hard wiring” which would route the wires to the alarm system's control panel.
While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in forms and details may be made without departing from the spirit and scope of the present application. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated herein, but falls within the scope of the appended claims.
Patent Application
20070290845
