Abstract:
A push button doorbell activator which is for transmitting a radio frequency signal to activate a doorbell chime and which has a metallic outer housing separated into two parts enclosing a transmitter circuit and an antenna and a non-metallic push button integrally interposed between the two housing parts.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention disclosed herein relates to doorbells, and more specifically, to a push button switch with a radio frequency transmitter for activating a remote doorbell.  
         [0003]     2. Discussion of the Prior Art  
         [0004]     In the field of doorbells, it is often desirable to have a doorbell with a chime that is remote from the push button activation switch located at the exterior of the door. It is also often desirable to have a push button switch with a metal cover, such as brass, in order to appear to be of superior quality. It is known to have a doorbell with a push button switch that activates a radio frequency transmitter and a remote chime with a radio frequency receiver so that the chime is activated when the push button switch is pushed.  
         [0005]     One such prior art doorbell assembly includes a push button switch with an RF transmitter and antenna enclosed within a metal housing, as depicted in  FIGS. 1A and 1B . In the doorbell transmitters of  FIGS. 1A and 1B , the metal housing is divided into two unequal parts  12   a ,  12   b  spaced to create a gap  14 , which is filled with a non-metallic substance such as silicon rubber. In the doorbell transmitter of  FIG. 1A , push button  16  for activating the transmitter is metal. In the doorbell transmitter of  FIG. 1B , a gap  18  is located around the push button  16  filled with a non-metallic substance. A problem with this arrangement, however, is that the transmission of the RF signal is significantly impeded by the metal enclosure. Therefore, it would be desirable to have a doorbell button with an RF transmitter and antenna enclosed in an attractive metal housing that has increased transmission range.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention disclosed herein includes a push button doorbell activator for remotely activating a doorbell chime by transmitting a radio frequency signal to a receiver connected to the doorbell chime. The doorbell activator includes a radio frequency transmitter circuit having an antenna for transmitting the signal. The transmitter circuit is carried within a non-metallic casing. A non-metallic push button for activating the transmitter circuit is interposed between opposing spaced apart half parts of a metallic housing, which partially encases the transmitter circuit casing. The antenna is positioned near the gap between the half parts of the metallic housing.  
         [0007]     An object of the invention is to provide a push button doorbell activator for remotely activating a doorbell chime with a radio frequency signal in which the doorbell activator is encased within a metal housing. Another object of the invention is to provide a metallic doorbell push button RF transmitter having an improved transmission range. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     These and other aspects of the invention will become more apparent from the following discussion with reference to the drawings, in which:  
         [0009]      FIG. 1A  depicts a prior art push button doorbell transmitter;  
         [0010]      FIG. 1B  depicts a second prior art push button doorbell transmitter;  
         [0011]      FIG. 2  shows the preferred embodiment of the metal doorbell push button transmitter or activator having a two-piece metal housing in isolation;  
         [0012]      FIG. 3  shows an exploded view of the various subcomponents of the doorbell activator of  FIG. 2 ;  
         [0013]      FIG. 4  is a rear view of a partial assembly of the doorbell activator of  FIG. 2 ;  
         [0014]      FIG. 5  is a longitudinal cross sectional view of the doorbell activator of  FIG. 2 ;  
         [0015]      FIG. 6  is a schematic diagram of the transmitter circuit used in the doorbell activator;  
         [0016]      FIG. 7  shows an alternative push button doorbell transmitter having a one-piece housing.  
         [0017]      FIG. 8  schematically depicts the set up for testing the doorbell activator and prior art activators;  
         [0018]      FIG. 9  is a chart comparing the test results of the two-piece housing doorbell activator of  FIG. 2  with the one-piece housing doorbell activator of  FIG. 7 ; and, 
     
    
     DETAILED DESCRIPTION  
       [0019]     Turning now to the drawings, in the preferred embodiment of the invention, as depicted in  FIGS. 2-6 , a metallic push button doorbell transmitter or activator  20  includes an exterior housing made of metal, preferably brass, which is divided into two spaced apart symmetrical half parts  22 ,  24 . A silicone rubber push button  26  includes a pair of integral side extension parts  28 ,  30  which protrude from opposite sides of the bush button. Push button  26  and side extensions  28 ,  30  are sandwiched in the gap  31  between housing half parts  22 ,  24  with the extensions following the contours of the housing half parts. The silicon rubber material for push button  26  and extensions  28 ,  30  preferably has a luminous or fluorescent property such that the material absorbs light energy when exposed to light and then emits light in the dark.  
         [0020]     A transmitter circuit  32  is encased between an opposing pair of plastic casing parts  34 ,  36 . Transmitter circuit  32  is secured between casing parts  34 ,  36  within housing half parts  22 ,  24  with fasteners  38 . A hole  33  in casing part  34  allows the back end of push button  26  to contact a switch  40 , which is preferably a metal dome button, for activating transmitter circuit  32 . When assembled, casing parts  34 ,  36 , housing parts  22 ,  24 , and push button  26  form a sealed environment for transmitter circuit  32 .  
         [0021]     A mounting plate  42  for mounting the doorbell transmitter  20  to a mounting surface includes a resilient barbed tab  44 . Mounting plate  42  may be secured to a mounting surface such as a wall or door frame. Doorbell transmitter  20  is then snap-fitted onto mounting plate  42  with barbed tab  44  snapping into a complementary groove  46  in casing part  36 . A gasket seal  48  around the periphery of the junction between mounting plate  42  and casing part  36  prevents water from seeping downwardly into the space behind casing part  36 .  
         [0022]     Transmitter circuit  32  is a SAW resonator based transmitter circuit tuned to fifty ohm impedance matching. Transmitter circuit includes a printed circuit board (PCB)  50 , a power source such as a battery  52  located within battery compartment  53 , an antenna  54 , and switch  40 . PCB  50  includes integrated circuit (IC)  56  and associated electronic components as shown in  FIG. 6  such that when push button  26  closes switch  40 , a radio frequency signal is emitted from antenna  54 . This radio frequency signal is transmitted to a receiver (not shown) used to activate a remote doorbell chime in a fashion known in the art. Antenna  54 , shown here as a helically wound coil, is positioned on PCB  50  within casing parts  34 ,  36  adjacent the gap  31  between housing parts  22  and  24  aligned directly underneath push button  26  and button extensions  28 ,  30  to enhance the transmission range of the RF signal. The circuitry on PCB  50  is ground plain incorporated referring to one of the metal housings  22 ,  24  to form a steady environment.  
         [0023]     In  FIG. 7 , an alternative embodiment of a metal doorbell button transmitter  60  is shown. This transmitter  60  has a single piece metal housing  62  with an opening in its front side where a non-metallic button  64 —preferably made of silicon rubber—for activating the RF transmitter switch is located. The transmitter circuitry is the same as already described herein such that, when button  64  is pushed, an RF signal is transmitted to a receiver to activate a remote chime. The transmitter has an antenna (not shown), which is within housing  62  and aligned behind push button  64  to maximize the effective transmission range of the RF signal.  
         [0024]     Turning now to  FIGS. 8 and 9 , tests were performed on the two-part brass housing doorbell actuator  20  of  FIGS. 2-6  and the one-part brass housing doorbell actuator  60  of  FIG. 7 . Each test specimen  20  and  60  was set up individually within an anechoic chamber  70  with the test specimen located a fixed distance from a receiving antenna  72 . The signal transmission of each doorbell transmitter specimen  20  or  70  was then recorded and analyzed. From the resulting analysis of the test data thus obtained, as shown in  FIG. 9 , the two-piece housing doorbell transmitter  20  was able to transmit a usable signal more effectively than the one-piece housing doorbell transmitter  60 .  
         [0025]     The description of the preferred embodiment related herein is not meant to act as a limitation on any obvious and minor variations on the invention as claimed.