Patent Publication Number: US-2022236033-A1

Title: Propelling device

Description:
TECHNICAL FIELD 
     The present invention relates to a propelling device. 
     BACKGROUND ART 
     As a method of propelling a propelling section, such as a bullet and an arrow, there are, for example, a method using explosive power of a bursting explosive as described in PTL 1 and a method using elastic energy of an elastic material, such as a spring, as described in PTL 2. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2018-159492 A 
     PTL 2: JP 2004-230929 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the method using explosive power of a bursting explosive and the like has a possibility of unintentionally initiating the bursting explosive, causing a safety problem. In the method using elastic energy, the elastic force is constantly applied from the elastic material and there is a risk of unintentionally propelling a propelling section due to detachment of a stopper to inhibit release of the elastic material and the like. 
     It is an object of the present invention to provide a propelling device that is excellent in safety during storage and securely propels a propelling section during operation. 
     Solution to Problem 
     To solve the above problems, an aspect of the present invention provides a propelling device including: a fixed section; a propelling section; a shape memory alloy placed between the fixed section and the propelling section; and a coupling member coupling the fixed section, the propelling section, and the shape memory alloy with each other, wherein the shape memory alloy is in a state of a compressed martensite phase, and the shape memory alloy is transformed from the state of the martensite phase to a state of an austenite phase, causing strain energy to be stored, and action of the strain energy is used to break at least part of the coupling member and also impart a propelling force to the propelling section, and action of the propelling force causes the propelling section to be propelled in a direction away from the fixed section. 
     The coupling member may have a notched portion in an indent or recess shape. The shape memory alloy may have a cylindrical shape with a bush, the coupling member may be a notched bolt having the notched portion, the fixed section may have an internal thread screwed to the notched bolt, the notched bolt may have a head engaged with the propelling section, the notched bolt may have a threaded portion screwed to the internal thread of the fixed section through the bush of the shape memory alloy, and the notched bolt may be fastened to couple the fixed section, the propelling section, and the shape memory alloy with each other. 
     The shape memory alloy may be a single crystal shape memory alloy. The single crystal shape memory alloy is a Cu—Al—Ni single crystal shape memory alloy. 
     It should be noted that Summary of Invention above does not list all the characteristics essential to the present invention. In addition, sub-combinations of these characterizing groups may also constitute the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a propelling device  100  as an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 . 
         FIG. 3  is a side view illustrating details of a notched bolt shown as an example of a coupling member  140 . 
         FIG. 4  is a photograph of an experimental device for propellant experiment of a propelling section  120 . 
         FIG. 5  is a graph of a reaction force during propellant measured with a load sensor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention is described below with embodiments of the present invention while the embodiments below do not limit the invention according to the scope of the claims. In addition, not all combinations of the characteristics described in the embodiments have to be essential for the means of solution of the invention. 
       FIG. 1  is a top view of a propelling device  100  as an embodiment of the present invention, and  FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 . The propelling device  100  in the present embodiment has a fixed section  110 , a propelling section  120 , a shape memory alloy  130 , and a coupling member  140 . 
     The fixed section  110  is fixed to a mass not to be moved by reaction of propelling the propelling section  120 . The fixed section  110  itself may configure the mass. A connection mechanism between the fixed section  110  and the mass is exemplified by screwing in this description while it is arbitrary. For example, it may be welding, clamping, and the like. 
     The propelling section  120  is a member to be propelled from the propelling device  100 . Together with the shape memory alloy  130 , the propelling section  120  is coupled to the fixed section  110  by the coupling member  140 . The material for the propelling section  120  is arbitrary as long as it has mechanical strength to allow coupling by the coupling member  140 . For example, it may be exemplified by metal, such as iron and stainless steel, ceramic, rigid plastics, and the like. 
     The shape memory alloy  130  is placed between the fixed section  110  and the propelling section  120  and is coupled, together with the propelling section  120 , to the fixed section  110  by the coupling member  140 . The shape memory alloy  130  is in a state of a compressed martensite phase. 
     The coupling member  140  couples the fixed section  110 , the propelling section  120 , and the shape memory alloy  130  with each other. The coupling member  140  may have a notched portion, such as an indent and a recess. When the coupling member  140  has the notched portion, it is possible to focus breaking of the coupling member  140  during operation on the notched portion to control the breaking and stabilize propelling of the propelling section  120 . 
       FIG. 3  is a side view illustrating details of a notched bolt shown as an example of the coupling member  140 . The notched bolt (coupling member  140 ) illustrated in  FIG. 3  has a head  142 , a threaded portion  144 , and a notched portion  146 . As described above, when the notched bolt is broken, the breaking occurs in the notched portion  146 . 
     When the notched bolt in  FIG. 3  is used as the coupling member  140 , the shape memory alloy  130  has a cylindrical shape with a bush, the fixed section  110  has an internal thread formed to be screwed to the notched bolt, the head  142  of the notched bolt is engaged with the propelling section  120 , the threaded portion  144  of the notched bolt is screwed to the internal thread of the fixed section  110  through the bush of the shape memory alloy  130 , and thus the notched bolt is fastened to allow coupling of the fixed section  110 , the propelling section  120 , and the shape memory alloy  130  with each other. 
     In the propelling device  100  thus configured, the shape memory alloy  130  is transformed from the state of the martensite phase to a state of an austenite phase, causing strain energy to be stored, and action of the strain energy is used to allow breaking of at least part of the coupling member  140 , for example the notched portion  146 . This allows impartation of a propelling force to the propelling section  120 , and action of the propelling force causes the propelling section  120  to be propelled in a direction away from the fixed section  110 . It should be noted that the shape memory alloy  130  from the martensite phase to the austenite phase may be transformed by heating. 
     According to the propelling device  100  in the present embodiment, the propelling section  120  is not propelled unless the shape memory alloy  130  is heated by a heater and the like and it is thus possible to provide the propelling device  100  that is excellent in safety during storage and securely propels the propelling section  120  during operation. 
     It should be noted that the shape memory alloy  130  is preferably a single crystal shape memory alloy and more preferably a Cu—Al—Ni single crystal shape memory alloy. Use of such a single crystal shape memory alloy or a Cu—Al—Ni single crystal shape memory alloy allows storage of more strain energy and an increase in a propelling rate of the propelling section  120 . 
     EXAMPLES 
       FIG. 4  is a photograph of an experimental device for propellant experiment of the propelling section  120 . The fixed section  110  was fixed to a base via a load sensor, and a heater arranged near the shape memory alloy  130  was turned on to heat the shape memory alloy  130 . The heated shape memory alloy  130  was transformed to the austenite phase to release the strain energy, and as a result, the notched portion  146  of the notched bolt as the coupling member  140  was broken to cause the propelling section  120  to be propelled in the right direction of  FIG. 4 . 
       FIG. 5  is a graph of a reaction force during propellant measured with the load sensor. A large reaction force measured at 4E−03 sec (4 msec) is assumed to indicate the moment of breaking the notched bolt and propelling the propelling section  120 . 
     Three kinds of experiment (Experimental Examples 1 through 3) were performed by varying the length of the shape memory alloy. In the respective experiment of Experimental Examples 1 through 3, the maximum reaction force, the impulse, the electric energy, and the propelling rate were measured. The propelling rate was calculated from measurement by camera imaging or the angle of a hanging strap. In the respective experiment, the measurement was performed three times and the average was defined as the result of measurement. 
     The results are shown in Table 1. In Experimental Example 3, the weight of the propelling section was so heavy as 275 g, and thus the propelling rate is indicated by converting to the case of the weight of the propelling section of 110 g same as the other Experimental Examples (the value in the parentheses is the actually measured value with the weight of the propelling section of 275 g). 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Length of 
                 Weight of 
                 Maximum 
                   
                   
                   
               
               
                   
                 Shape Memory 
                 Propelling 
                 Reaction 
                 Impulse 
                 Electric 
                 Propelling 
               
               
                   
                 Alloy (mm) 
                 Section (g) 
                 Force (N) 
                 (NmSEC) 
                 Energy (Ws) 
                 Rate (m/s) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Experimental 
                 10 
                 110 
                 1443 
                 343 
                 630 
                 2.9 
               
               
                 Example 1 
               
               
                 Experimental 
                 20 
                 110 
                 2012 
                 589 
                 709 
                 5.0 
               
               
                 Example 2 
               
               
                 Experimental 
                 30 
                 275 
                 1837 
                 1150 
                 709 
                 7.1 
               
               
                 Example 3 
                   
                   
                   
                   
                   
                 (4.5) 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, with the increase in the length of the shape memory alloy  130  as 10 mm, 20 mm, and 30 mm, the propelling rate increased and the indicated values were sufficiently large as 2.9, 5.0, and 7.1 m/s, respectively. 
     While the present invention has been described with reference to the embodiments, the technical scope of the present invention is not limited to the description of the above embodiments. Those skilled in the art clearly understand that various modifications and improvement may be made to the above embodiments. It is also clearly understood from the scope of the appended claims that the embodiments processed with such a modification or improvement are also included in the technical scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           100  Propelling Device 
           110  Fixed Section 
           120  Propelling Section 
           130  Shape Memory Alloy 
           140  Coupling Member 
           142  Head 
           144  Threaded Portion 
           146  Notched Portion