Abstract:
A new bomb release mechanism which allows an RC aircraft to carry an unlimited number of model bombs. The new bomb release mechanism allows the pilot to release these model bombs in any sequence using only one unused channel on the receiver in the aircraft. The present invention accomplishes these objectives by employing a special alloy metal wire which shrinks when subjected to an electric current. A programmed circuit is used to energize the metal wire upon receipt of the designated control signal.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/011,670 which was filed on Jan. 18, 2008. The provisional application listed the same inventor. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of bomb release systems for Radio Control aircraft. More specifically, the present invention comprises a bomb release system for model aircraft which allows numerous bombs to be released from the airborne aircraft in any sequence on command by an operator using a single channel. 
     2. Description of the Related Art 
     Radio Control (“RC”) aircraft hobbyists enjoy piloting RC aircraft to simulate the flight of traditional manned aircraft. Some hobbyists enjoy equipping RC aircraft with powder-filled break-apart model bombs and dropping these bombs in flight on targets placed on the ground. These powder-filled model bombs break apart when they strike the ground leaving the powder on the ground at the point of impact. It is the pilot&#39;s goal to time the release of the model bombs such that they strike as close to the target as possible. 
     Bomb release mechanisms have been used for many years on RC aircraft. Conventional bomb release mechanisms utilize servos, solenoids or pneumatics to actuate the release of a model bomb in flight. Servo controlled mechanisms limit the number of releasable bombs to the number of “extra” channels available on the RC controller (i.e., channels not dedicated to flight operations). For most RC aircraft, only one or two extra channels are available. 
     Solenoid controlled systems are capable of controlling the release of multiple bombs using only one control channel. In order to actuate independent release of the bombs, a master controller box is used. Each release mechanism requires a separate wiring harness to connect the release mechanism to the master controller box. Thus, the master controller box can only control a defined (and usually small) number of release mechanisms. Due to the high current demands of this type of system, a separate high current battery is generally required to power the solenoids. 
     Pneumatic actuator systems also use a single channel, but the channel must be a rotary control channel to allow for precise positioning of a multi-port air valve. This type of system also requires a high pressure air tank, tubing, actuators and a mechanical bomb release. These mechanisms are relatively heavy compared to the weight of an RC aircraft. 
     As such, a new bomb release mechanism is needed to allow a user to control the timing and sequence of release of numerous model bombs from an RC aircraft. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a new bomb release mechanism which allows an RC aircraft to carry an unlimited number of model bombs. The new bomb release mechanism allows the pilot to release these model bombs in any sequence using only one unused channel on the receiver in the aircraft. The present invention accomplishes these objectives by employing a special alloy metal wire which shrinks when subjected to an electric current. A programmed circuit is used to energize the metal wire upon receipt of the designated control signal. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view, showing the present invention. 
         FIG. 2  is a perspective view, showing the present invention. 
         FIG. 3  is a perspective view, showing the present invention. 
         FIG. 4  is a section view, showing the present invention. 
         FIG. 5  is a section view, illustrating operation of the present invention. 
         FIG. 6  is a section view, illustrating operation of the present invention. 
         FIG. 7  is a perspective view, illustrating two adjacent release assemblies. 
       
         
           
                 
               
                 
                 
                 
                 
               
             
                 
                     
                 
                 
                   REFERENCE NUMERALS IN THE DRAWINGS 
                 
                 
                     
                 
               
               
                 
                     
                 
               
            
             
                 
                   10 
                   release assembly 
                   12 
                   carriage 
                 
                 
                   14 
                   circuit board 
                   16 
                   screw connectors 
                 
                 
                   18 
                   block 
                   20 
                   pins 
                 
                 
                   22 
                   switch 
                   24 
                   holder 
                 
                 
                   26 
                   spring 
                   28 
                   pin 
                 
                 
                   30 
                   pulley 
                   32 
                   surface 
                 
                 
                   34 
                   adjustment rod 
                   36 
                   relief 
                 
                 
                   38 
                   rod tip 
                   40 
                   bomb slots 
                 
                 
                   42 
                   holder clips 
                   44 
                   leads 
                 
                 
                   46 
                   NITINOL wire 
                   48 
                   fix point 
                 
                 
                   50 
                   fix point 
                   52 
                   bomb casing 
                 
                 
                   54 
                   powder 
                   56 
                   bomb clips 
                 
                 
                   58 
                   mount screw 
                   60 
                   mount bore 
                 
                 
                   62 
                   spacer 
                   64 
                   channels 
                 
                 
                   66 
                   conductive strip 
                 
                 
                     
                 
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention, release assembly  10 , is shown in its assembled state in  FIG. 1 . Release assembly  10  includes circuit board  14  which nests in the top portion of carriage  12 . Circuit board  14  includes block  18  which has pins  20 . Pins  20  of block  18  electrically connect to a Radio Control (“RC”) aircraft&#39;s radio signal receiver directly (for one or a single row of release mechanisms) or via a “Y” wiring harness to create two rows of physically separated release mechanisms. The latter is most common with fixed-wing aircraft to afford a balanced load under each wing. In either case, the user would connect a wiring harness to an unused channel on the radio receiver. 
     The electric circuit embedded in circuit board  14  is configured to pass the control signals received via pins  20  to screw connectors  16 . Screw connectors  16  are provided on the top of circuit board  14  to facilitate a common parallel electrical bus for additional release mechanisms within the row. Rigid metal straps are attached to screw connectors  16  to relay control signals sent from the radio receiver to release assembly  10  to other bomb release assemblies on the aircraft (such as shown in  FIG. 7 ). The plurality of release assemblies may be connected in series or parallel. The most common connection method would have a “Y” harness attached to the radio receiver to supply common signals to two release mechanisms (one on each wing) connected each at pins  20 . From this point, an unlimited number of release mechanisms could be connected in a serial fashion utilizing screw connectors  16 . Thus, the reader will appreciate that any number of release assemblies may be employed on the aircraft. 
     A second part of the electric circuit of circuit board  14  processes the control signal to determine whether the user has transmitted a “release bomb” control signal corresponding to the particular release assembly. Each release mechanism is pre-programmed with an “activate number” (e.g., 1, 2, 3 . . . 255) by the operator into non-volatile memory and the activate number will stay in the memory until changed. When the user transmits a “release bomb” control signal, all release mechanisms hear it and count it. Immediately after a count is received, the total count is compared to the programmed “activate number.” When a match occurs, the electronic circuit will activate the release mechanism to release the bomb. 
       FIG. 2  shows the release assembly with circuit board  14  removed from carriage  12  to show the internal components of the release assembly. Holder  24  is situated in the bottom of carriage  12 . Holder  24  moves forward and backward within carriage  12  (toward and away from pin  28 ). Holder  24  is biased (by a spring or other suitable component) to remain in the rearward position until circuit board  14  transmits an energizing charge to NITINOL wire  46  via leads  44 . NITINOL wire  46  is composed of a nickel titanium alloy which is known to shrink in length when subjected to an electric current. NITINOL wire  46  may be replaced by any component that is known to change its shape or size when subjected to a current. NITINOL wire  46  attaches to fix point  48  on holder  24  and fix point  50  (which is fixed to carriage  12 ). NITINOL wire  46  wraps around pulley  30  which is attached to pin  28 . Since NITINOL wire only shrinks approximately 3-5% of its length, pulley  30  allows a longer NITINOL wire to be employed, thereby enabling a greater range of movement of holder  24  to affect a clean release of bomb clips  56  (The released position is shown in  FIG. 6 ). When the circuit is activated, the NITINOL wire shrinks and pulls holder  24  forward with respect to carriage  12 , thereby releasing the bomb. 
     Also shown in  FIG. 2  is “normally open” momentary pushbutton switch  22  and adjustment rod  34 . Switch  22  is placed on the bottom of circuit board  14  and is used to program an identity to each release assembly. The microcontroller program routine tracks how many times switch  22  is pressed and maps the total number of switch closures into the microchip&#39;s non-volatile memory. Each release assembly is programmed with this release code by the user based on the sequence and position of each bomb to be sequentially dropped. For example, the first release assembly may have an identity of ONE, the second release assembly may have an identity of TWO, the third release assembly may have an identity of THREE, and so on. In this example, the first release assembly will release its payload on receipt of the first “release bomb” signal, the second release assembly will release its payload on receipt of the second “release bomb” signal, the third release assembly will release its payload on receipt of the third “release bomb” signal, and so on. Alternatively, multiple release assemblies may be assigned the same identity to cause the release assemblies to drop their payloads simultaneously upon receipt of a single control signal. 
     Adjustment rod  34  is slidably situated in a molded sleeve beneath switch  22 . Turning to  FIG. 3 , the reader will note that rod tip  38  is provided in the bottom of carriage  12  where the pushbutton&#39;s switch adjustment rod  34  extends just below carriage  12  long enough for a finger to push and cause switch closure. The user pushes the adjustment rod  34  into switch  22 , thereby entering desired settings without having to disassemble the device. 
     In  FIG. 3 , the reader will further note that relief  36  is provided on both sides at the top of carriage  12  adjacent to screw connectors  16 . This allows for the attachment of a molded connector to physically connect additional release mechanisms at the proper spacing on either sides (providing sufficient clearance such that adjacent bombs do not touch). Turning to  FIG. 7 , one such connector is illustrated. Spacer  62  attaches between two adjacent release assemblies  10 . Spacer  62  has three channels  64  which extend along the length of the spacer. Channels  64  extend between screws  16  on the two adjacent release assemblies  10  when spacer  62  is attached within relief  36 . Conductive strips  66  are situated within channels  64  and are attached to each circuit board  14  by screw  16 . As such conductive strips  66  provide an electrically conductive pathway for relaying control signals between adjacent bomb assemblies  10 . 
     As shown in  FIG. 4 , bomb slots  40  are provided in the bottom of carriage  12  to receive the matching serrated mating clips of model bombs. Holder  24  has a pair of holder clips  42  which are positioned above bomb slots  40 . Spring  26  exerts a force on holder  24  biasing holder  24  toward the right in the orientation shown in the view (which is actually toward the rear of the carriage). 
     Turning to  FIG. 5 , a representative model bomb is shown attached to carriage  12 . The model bomb has a break-apart bomb casing  52  which can optionally be filled with powder  54  or other desired contents. Powder  54  may be talcum powder, flour, baking soda, or any other substance suitable for marking the bomb&#39;s impact point. Bomb clips  56  are provided on one side of bomb casing  52 . Bomb clips  56  insert into bomb slots  40  and engage holder clips  42  of holder  24 . When holder  24  is in the illustrated position, the model bomb is securely held to the model aircraft by holder  24 . Bomb clips  56  of the model bomb are clamped between holder clips  42  and surfaces  32  (labeled in  FIG. 4 ) which are integrated into the base of the internal cavity of carriage  12 . 
       FIG. 6  illustrates release of the model bomb. When the appropriate “release bomb” control signal is received, circuit board  14  energizes NITINOL wire  46  via leads  44 . Leads  44  are electrically connected to NITINOL wire  46  at fix points  48  and  50 . When energized, NITINOL wire  46  shrinks to approximately 95% of its original length. Fix point  50  remains fixed, but the tensile force exerted by the shrinking of NITINOL wire  46  pulls holder  24  forward toward pin  28 . This tensile force is sufficient to compress spring  26  and provide sufficient clearance for bomb clips  56  of the model bomb to drop through bomb slots  40  when bomb clips  56  disengage from holder clips  42 . 
     With the present invention now described, the reader can appreciate how the present invention is used. The user first electrically connects one or more release assemblies to an unused channel of the model aircraft&#39;s radio receiver as previously described. The release assemblies are then attached to the aircraft at the desired locations. Turning to  FIG. 4 , the reader will note that the release assembly may be mounted to the aircraft with mount screws  58  which pass through mount bores  60 . Each release assembly is then assigned a desired identity by pushing on adjustment rod  38  an appropriate number of times. Model bombs are then filled with an appropriate substance (or left empty) and attached to the respective holders  24  by inserting bomb clips  56  into bomb slots  40 . The model bombs are now ready for release. 
     The user then flies the RC aircraft using the normal flight controls of the RC transmitter. The user may then take aim at targets placed on the ground and actuate the release of the model bombs in the desired sequence using the appropriate control button on the RC corresponding to the channel employed for the bomb release assemblies. The user drops each payload in the programmed sequence. If the release assemblies were programmed as previously described (i.e. the first release assembly given the identity of ONE, the second release assembly given the identity of TWO, etc.), the first release assembly will drop its payload upon the transmission of the first “release bomb” signal transmitted on the channel. The second release assembly will drop its payload upon the transmission of the second “release bomb” signal transmitted on the channel. 
     The reader should now appreciate that no master controller is needed to coordinate the release of the model bombs using the present invention. Each release mechanism operates independently, allowing the user to easily add or remove bomb release assemblies to the aircraft when desired. Thus, the controller for each release assembly is contained on circuit board  14 . The circuit board includes a microprocessor, a voltage regulator, a thermistor and a MOS power switch. The microprocessor counts “release bomb” command signals, and when the number of command signals received is equal to its identity, the microprocessor actuates the MOS power switch to energize NITINOL wire  46 . 
     In one embodiment, the microprocessor stores in its memory the number of times switch  22  is pressed. The electrical signal passing to each release assembly through the wiring harnesses are pulses that vary between 1.0 ms and 2.0 ms in length. The controller is configured to remain idle if the pulse length is smaller than 1.8 ms. If the controller sees a signal that exceeds 1.8 ms, the controller interprets this as a “release bomb” signal. Before releasing its payload, the controller first compares the “release bomb” signal count to the number of times switch  22  was pressed during the programming stage. If there is no match, nothing happens and the circuit continues to monitor for more pulses that are over 1.8 ms. If any particular release assembly has the same identity as the signal count, the controller energizes the NITINOL wire for that assembly. 
     In addition to interpreting control signals and actuating the release of its payload, each release assembly also monitors the main receiver battery for critical low voltage. When a specific low voltage is measured, each circuit shuts down until it has been turned off and back on again. This prevents the circuit from further reducing battery voltage which could cause a crash of the aircraft due to battery failure. 
     The preceding description contains significant detail regarding the novel aspects of the present invention. It should not be construed, however, as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.