Abstract:
A control mechanism is provided for coupling/interrupting two transmission leads. A first cam configured for spring-loaded rotation in a direction of rotation is positioned between the two leads. A lead coupler attached to the first cam couples the two leads to one another when the first cam achieves a prescribed position. A second cam is disposed adjacent to the first cam for, in sequential fashion, i) maintaining the first cam in a first position different than the prescribed position prior to rotation of the second cam, ii) permitting the spring-loaded rotation of the first cam from the first position to the prescribed position after rotation of the second cam commences, iii) inhibiting the spring-loaded rotation of the first cam from the prescribed position for a prescribed period of time during continued rotation of the second cam, and iv) permitting the spring-loaded rotation of the first cam from the prescribed position during continued rotation of the second cam after completion of the prescribed period of time.

Description:
ORIGIN OF THE INVENTION 
     The invention described herein was made in the performance of official duties by an employee of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon. 
     FIELD OF THE INVENTION 
     The invention relates generally to mechanisms used to complete/interrupt a transmission line capable of transmitting electricity or an explosive reaction, and more particularly to a simple mechanical device that only completes such a transmission line during a prescribed window of time and assures that the transmission line is interrupted at all other times. 
     BACKGROUND OF THE INVENTION 
     In many explosive devices, detonation must occur at a particular time in a prescribed sequence of events. Should some malfunction occur during the prescribed sequence of events, it may be desirable to prevent detonation from every occurring thereby permanently “safing” the malfunctioned device. For example, underwater explosive devices are often placed in a shallow-water environment to clear a military landing zone. Typically, not all devices explode at time of detonation. To prevent later inadvertent detonation, unexploded devices are preferably removed from the zone. It is desirable to have confidence that any unexploded devices can be safely retrieved/removed from the area without harm to personnel. Accordingly, many fuze systems incorporate complex electronic or electromechanical components for completing a detonation train only at the appropriate time in a prescribed sequence of events. However, the complex or electric nature of such components are often the source of malfunction in harsh water environments. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a device that can be used to complete a detonation train at a prescribed time. 
     Another object of the present invention is to provide a device that completes a detonation train at a prescribed time and subsequently interrupts the detonation train such that detonation can only occur at the prescribed time. 
     Still another object of the present invention is to provide a simple mechanical device that can be used to complete a detonation train. 
     Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings. 
     In accordance with the present invention, a control mechanism has a first cam configured for spring-loaded rotation in a direction of rotation. The first cam is positioned between two leads which can conduct an energetic transmission therealong when coupled to one another. A lead coupler made of a material capable of conducting the energetic transmission is coupled to the first cam. The lead coupler is sized and shaped such that the two leads are coupled to one another by the lead coupler when the first cam achieves a prescribed position. A second cam configured for rotation is disposed adjacent to the first cam for, in sequential fashion, i) firstly maintaining the first cam in a first position different than the prescribed position prior to rotation of the second cam, ii) secondly permitting the spring-loaded rotation of the first cam from the first position to the prescribed position after rotation of the second cam commences, iii) thirdly inhibiting the spring-loaded rotation of the first cam from the prescribed position for a prescribed period of time during continued rotation of the second cam, and iv) fourthly permitting the spring-loaded rotation of the first cam from the prescribed position during continued rotation of the second cam after completion of the prescribed period of time. A cam rotator is coupled to the second cam for rotating same. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan schematic view of the energetic transmission line coupler/interrupter control mechanism of the present invention shown in its pre-detonation safe position; 
     FIG. 2 is a plan schematic view of the control mechanism of the present invention shown in its detonation position; and 
     FIG. 3 is a plan schematic view of the control mechanism of the present invention shown in its post-detonation safe position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, FIGS.  1 - 3  depict an embodiment of an energetic transmission line coupler/interrupter control mechanism of the present invention at three positions during its sequence of operation. By way of example, the present invention will be described for its use in coupling and subsequently interrupting a detonation train. More specifically, the present invention will be used to couple two detonation leads  101  and  102  to one another at a precise time to allow an energetic (e.g., explosive) transmission to travel therealong (i.e., from lead  101  to lead  102  or vice versa) between other components of a fuze (not shown). However, leads  101  and  102  could also be electrical leads in which case the present invention could be configured to couple leads  101  and  102  to allow an electrical transmission to travel therealong. 
     Before describing the operation of the present invention, its component parts will first be described. Common reference numerals will be used for all views of the present invention. A first rotatable member or cam  10  is positioned between leads  101  and  102 . Cam  10  is rotatable about its central axis  12  and is spring-loaded for rotation in one of a clockwise or counterclockwise direction of rotation. For clarity of illustration, the spring used to load cam  10  is not shown. However, the spring-loading is illustrated by arrow  14  which, in the illustrated embodiment, is configured for counterclockwise spring-loading. That is, if and when cam  10  is unrestrained, cam  10  will rotate counterclockwise about axis  12  brought about by spring-loading  14 . The choice of spring can be selected based on the application and/or the amount of spring-loading needed. Examples of suitable springs could include coil springs used in clock mechanisms. 
     Cam  10  is essentially circular with protuberances or tabs  16  and  18  extending therefrom. Tab  16  lies in a first plane that is perpendicular to a axis  12 . Tab  18  lies in a second plan (i.e., further into the paper) parallel to the plane in which tab  16  resides. For ease of description, it will be assumed that tabs  16  and  18  are similarly sized in terms of how far they extend radially from cam  10 . While the exact shape and size of tabs  16  and  18  can be other than shown, the angle θ made between a side (e.g., side  16 A of tab  16 ) of a tab and the adjoining periphery of cam  10  is typically 90° or less for reasons that will be apparent below. Tabs  16  and  18  are further angularly offset with respect to one another such that tab  16  will lead tab  18  during rotation of cam  10  brought about by spring-loading  14 . 
     Mounted on or attached to cam  10  is a lead  20  that will be used to couple leads  101  and  102  to one another only when cam  10  is appropriately positioned. For the illustrated embodiment, lead  20  is made form a material that conducts an explosive reaction. If, however, leads  101  and  102  are electrical leads, lead  20  is made from a material that conducts electricity. To prevent the inadvertent “jumping” of any energetic transmission across cam  10 , the material used to construct cam  10  should not be conductive of such energetic transmission. Note that although lead  20  is illustrated linearly, this need not be the case. Lead  20  can be sized and shaped to conform to a size and position necessary to couple leads  101  and  102  to one another when cam  10  is appropriately positioned. For a linear lead  20  that is initially positioned 90° out of alignment with a linear arrangement of leads  101  and  102 , tabs  16  and  18  are angularly offset from one another by 90°. 
     Adjacent to cam  10  is a rotatable controlling member or cam  30 . Cam  30  is rotatable about its central axis  32  and is used to control both the inhibition and release of spring-loading  14  thereby controlling rotational movement of cam  10 . Rotational movement of cam  30  is indicated by arrow  34  which is in the same direction (e.g., counterclockwise) as spring-loading  14 . Similar to cam  10 , cam  30  is essentially circular and presents controlling peripheral surfaces on each of two planes that are parallel to one another and perpendicular to axis  22 . The two controlling peripheral surfaces cooperate with tabs  16  and  18 . Accordingly, a first controlling peripheral surface of cam  30  resides on a plane that is coincident with the plane in which tab  16  resides. The second controlling peripheral surface of cam  30  resides on a plane that is coincident with the plane in which tab  18  resides. 
     The first controlling surface of cam  30  residing on the plane coincident with tab  16  is defined in the illustrated example by three contiguous regions  36 A,  36 B and  36 C, each of which is defined by a constant radius. Specifically, region  36 A is defined by constant radius R 1 , region  36 B is defined by a constant radius R 2  and region  36 C is defined by a constant radius R 3  where R 3 &gt;R 1 &gt;R 2 . Radius R 1  is selected such that region  36 A can only contact cam  10  at tab  16  as region  36 A and tab  16  oppose one another as will be explained further below. Radius R 2  is selected such hat region  36 B will not contact any portion of cam  10  (including tab  16 ) as it rotates. With respect to the direction of rotation  34 , region  36 A leads region  36 B which leads region  36 C. 
     The second controlling surface of cam  30  residing on the plane coincident with tab  18  is defined in the illustrated example by two contiguous regions  38 A and  38 B, each of which is defined by a constant radius. In the illustrated example, region  38 A is defined by a constant radius equal to R 1  and region  38 B, which defines the remainder of the second controlling surface, is defined by a constant radius equal to (or less than) R 2 . When viewed relative to the direction of rotation  34 , the leading edge  39  of region  38 A is coincident with the trailing edge  37  of region  36 A. 
     A variety of mechanisms can be used to rotate cam  30  thereby control rotation of cam  10  as brought about by spring-loading  14 . By way of example, rotation of cam  30  is accomplished by the combination of a simple spring and mechanical timer. The spring (not shown for clarity of illustration) can be, for example, a simple coil or clock spring coupled to cam  30  for spring-biasing cam  30  to rotate in the direction of rotation  34 . To control the release of the spring force in the direction of rotation  34 , a mechanical timer  40  is coupled to cam  30  by, for example, gear tooth engagement. That is, gear teeth  42  of timer  40  mesh with gear teeth  31  on cam  30 . Gear teeth  31  reside on a plane parallel to and spaced apart from the first controlling surface (defining regions  36 A,  36 B and  36 C) and the second controlling surface (defined by regions  38 A and  38 B). 
     In operation, cam  10  is positioned with lead  20  out of alignment with leads  101  and  102  while cam  30  is positioned to maintain the position of cam  10 , i.e., inhibit release of spring-loading  14 . To do this, cam  30  is spring-loaded for the direction of rotation  34  with region  36 A engaging tab  16  as illustrated in FIG.  1 . The spring-bias of cam  30  in the direction of rotation  34  is initially restrained by, for example, the non-movement of gear teeth  42 . Alternatively, gear teeth  42  could be configured for continual rotation and a mechanical stop (not shown) could be used to inhibit such rotation to thereby inhibit the spring-bias of cam  30 . 
     When timer  40  is activated so that gear teeth  42  move clockwise, cam  30  begins to rotate counterclockwise with region  36 A continuing to engage tab  16  to prevent the release of spring-loading  14 . As region  36 A rotates past tab  16 , spring-loading  14  is released as tab  16  opposes region  36 B of radius R 2  thereby allowing cam  10  to quickly assume counterclockwise rotation. When lead  20  has rotated 90° so that it is in alignment with and couples leads  101  and  102 , tab  18  engages region  38 A as illustrated in FIG. 2 to again inhibit the release of spring-loading  14 . In this way, cam  10  snaps into alignment with leads  101  and  102 . Meanwhile, the shapes of tab  18  and regions  38 A allow for the continued rotation of cam  30  in the direction of rotation  34 . The arc length of region  38 A determines how long lead  20  stays in alignment with leads  101  and  102 . That is, region  38 A defines the prescribed window of time during which an explosive reaction (or electricity as the case may be) can travel from lead  101  and lead  102  or vice versa. 
     As the trailing edge of region  38 A rotates past tab  18 , spring-loading  14  is again released as tab  18  opposes region  38 B of radius R 2 . Thus, cam  10  again quickly assumes counterclockwise rotation to snap lead  20  out of coupled alignment with leads  101  and  102 . For the linear arrangement of leads  101  and  102 , lead  20  is preferably moved to a position that is 90° out of alignment with leads  101  and  102  as illustrated in FIG.  3 . This minimizes the possibility that any energetic transmission could “jump” between leads  101  and  102  using lead  20 . 
     To positively inhibit spring-loading  14  once lead  20  is rotated out of alignment, a mechanical stop can be provided to cooperate with one or both of tabs  16  and  18 . In the illustrated embodiment, a single mechanical stop  50  is provided to engage tab  16  to prevent any further counterclockwise rotation of cam  10  as illustrated in FIG.  3 . The above-described angle θ that tab  16  makes with the adjoining periphery of cam  10  allows tab  16  to positively engage stop  50 . Cam  30  continues to rotate in the direction of rotation  34  until region  36 C contacts cam  10  at which point timer  40  is stopped. 
     The advantages of the present invention are numerous. A simple mechanical control mechanism allows two energetic transmission lines to only be coupled during a prescribed window of time. Before and after this window, the mechanism assures that the lines are not coupled to one another to prevent any inadvertent energy transmissions. The mechanism will be of great use in explosive systems that may need to be retrieved should they malfunction during the prescribed window of time. 
     Although the invention has been described relative to a specific embodiment thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. For example, the shape and material used for lead  20  can be changed for a particular application. The angular spacing between tabs  16  and  18  could also be changed. Similarly, the arc lengths of the various controlling surface regions of cam  30  could be changed. For example, the arc length of region  38 A could be increased to increase the window of time during which leads  101  and  102  are coupled to one another. Still further, rotation of cam  30  might be controlled by a single device, e.g., just a mechanical timer, if spring-loading  14  was a weak force that could be controlled by the rotational force delivered by the mechanical timer. Note also that the direction of rotation for each of cams  10  and  30  could be clockwise. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.