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FIELD OF THE INVENTION 
       [0001]    The present invention relates to an antitheft device that is particularly well suited for use with wheels, e.g., bicycles, motorcycles and automobiles having at least one wheel that can be secured by an unbreakable device passing therethrough. 
       BACKGROUND OF THE INVENTION 
       [0002]    The loss of a bicycle to theft is an economic loss as well as a substantial inconvenience to the now-stranded cyclist. The loss of a favorite, customized or bicycle of exotic manufacture can also represent a substantial emotional loss from the time and energy associated with selecting just the right combination of features for the rider. 
         [0003]    A number of anti-theft devices have been proposed that are intended to secure a bicycle or motorcycle and thereby prevent or impede theft. See, e.g., U.S. Pat. Nos. 3,747,376; 3,908,414; 5,092,142; 5,475,993; 5,487,285; 5,732,577; 5,913,906; 6,820,448; 7,437,898; 7,481,048; 7,712,339; 8,621,898; 8,881,559; US 2014/036233; and U.S. D579,756. 
         [0004]    Despite such devices, those individuals with intent continue to find methods and techniques to defeat such anti-theft devices. Many of those techniques include the use of a handheld bolt cutter with hardened cutting jaws, a portable angle grinder or even a conventional hacksaw to cut through the antitheft device. Such cutters fail the target material in tension, but they induce the tension via the lateral component of the wedge-shaped blades. This means that a bolt cutter is a battle between the compressive strength of the cutting blades versus the compressive strength of the locking device. If both have near-equal hardness, it is difficult to predict which one will win. The battle becomes one of the quantum of pressure that can be applied on the device by the cutting jaws. 
         [0005]    Typical, commercially available bolt cutters exhibit hardened blades of about 62 HRC and can cut 6 mm 48 HRC wire but only HRC 19 rods of 11 mm. This means why traditional chains of interlinked, connected wire stock, even if hardened and/or made of unique alloys, must be made so large and heavy: the bolt cutter acts on the individual wire stock diameter, not the overall chain width. 
         [0006]    Surveillance videos show that members of the public rarely question or interfere with a thief in the act of breaking or cutting through a bicycle locking device, even when obviously using a bolt cutter or cut-off saw. Thus, cyclists cannot rely on help from passersby who might witness acts of theft in progress. The locking device must do more than just buy time—it must actually work. 
         [0007]    It would be desirable to have an anti-theft device that was made from a material that could not be cut, melted, ground or drilled with handheld tools. 
         [0008]    Some antitheft devices, such as the popular U-shaped devices, are defeated because they are large enough to secure only one wheel and the bike frame to a support. This leaves the other wheel vulnerable to removal and theft unless two such devices are carried and used together. This would double the cost and inconvenience of securing a bicycle against theft. 
         [0009]    It would be desirable to have an anti-theft device that was sufficiently long in reach to secure both wheels and the frame to a stationary support. 
         [0010]    Many locking systems are designed with a plurality of flat leg segments joined at a riveted joint that allows one leg segment to rotate and stack closely with the adjacent segments so as to fold into a compact unit that can be stored in a seat bag or on a frame clip. Such design considerations are visually appealing to consumers because they are easy to carry. Unfortunately, all of the currently known designs of this type are made from some version of steel, hardened steel or hard aluminum. 
         [0011]    While titanium may have been suggested for bicycle locks (see, e.g., US Patent Publication Nos. 2014/0109631 and 2014/0260439), no specific grade or type of titanium is specified. 
         [0012]    Titanium is available in various grades, based on the material properties. Commercially pure titanium is available in increasing hardness from Grade 1 to grade 4. These grades of titanium can be formed, engraved with conventional machines, and cut so that they can even be used as rings and similar jewelry. Stronger grades of titanium are alloys that have been mixed with one or more Group III-Group VIII materials (e.g., vanadium, molybdenum, nickel, ruthenium, palladium, chromium, zirconium, molybdenum, and aluminum) to increase their hardness. Sometimes referred to as “aircraft grade” titanium alloys, such materials are so hard that they are almost impossible to engrave, form or cut. 
       SUMMARY OF THE INVENTION 
       [0013]    It is an objective of the invention to provide an antitheft device that cannot be cut by handheld bolt cutters. 
         [0014]    It is further an objective to provide a portable antitheft device that can be carried on or by a bicycle without materially compromising the weight and handling of the bicycle in transit when so laden. 
         [0015]    In accordance with these and other objectives of the invention that will become apparent from the description herein, an antitheft device according to the invention comprises an antitheft device comprising a plurality of interlinked titanium alloy arm members, each of which exhibits a hardness of HRC 30 or more and a cross sectional distance of 8 mm or more. 
         [0016]    The security device according to the invention is sufficiently light to be suitable for use with and carried on a bicycle while also exhibiting a high degree of resistance to breach by bolt cutters, saws and angle grinders. Such robust resistance makes the device also suitable for use with motorcycles and automobiles. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  shows an isometric view of an antitheft device according to the invention with two extension members, a locked arm and a lockable arm. 
           [0018]      FIG. 2  is a side view of the device shown in  FIG. 1 . 
           [0019]      FIG. 3  illustrates additional details of an extension arm member. 
           [0020]      FIG. 4  depicts a lockable arm member. 
           [0021]      FIG. 5  is an isometric view of a saddle-shaped washer. 
           [0022]      FIG. 6  is an end view of a connection between extension arm members in which opposing saddle-shaped spacers form a pivot plane and a deformed rivet permanently connects the arm members. 
           [0023]      FIG. 7  is a side view of the connection shown in  FIG. 6 . 
           [0024]      FIGS. 8-10  depict side, bottom and isometric views, respectively, of a saddle washer used in the invention. 
           [0025]      FIG. 11  presents a saddle washer having two bevels or chamfers to round off the upstanding edges of the arcuate side. 
           [0026]      FIG. 12  is a view of a joint connection using two, opposing, rounded off saddle washers to form a planar connection between an extension arm and the locking arm. 
           [0027]      FIG. 13  is a cross sectional view showing the connection of  FIG. 12 . 
           [0028]      FIG. 14  is a sectional view of the lock connecting the locked arm and the lockable arm. 
           [0029]      FIG. 15  is an external view of the connection shown in  FIG. 14 . 
           [0030]      FIG. 16  depicts a security washer that may be used between opposing saddle washers to shield the space between saddle washers from insertion of a blade or prying tool. 
           [0031]      FIG. 17  is a cross sectional view of the security washer of  FIG. 16 . 
           [0032]      FIG. 18  shows the security washer in place between opposing saddle washers at a pivotable connection of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    The present device uses a plurality of connected extension arm members (the number of which determine the overall length available of the device), a locking arm that has a locking device permanently connected thereto, and a lockable arm with a bore through the leading edge thereof. In use, the leading edge of the lockable arm is inserted into a transverse opening in the lock housing and a leading rod member on the lock device is secured into the lock housing so that it passes through the bore in the leading edge of the lockable arm. 
         [0034]    For the present invention, a hard titanium alloy is preferred. One way to measure the hardness of titanium or alloys thereof is with a Rockwell test. Such a test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale. See Table 1. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Rockwell Hardness Scales 
               
             
          
           
               
                 Scale 
                 Abbreviation 
                 Load (kg F ) 
                 Indenter 
               
               
                   
               
               
                 A 
                 HRA 
                  60 
                 120° diamond spheroconical †   
               
               
                 B 
                 HRB 
                 100 
                  1/16-inch-diameter (1.588 mm) steel 
               
               
                   
                   
                   
                 sphere 
               
               
                 C 
                 HRC 
                 150 
                 120° diamond spheroconical 
               
               
                 D 
                 HRD 
                 100 
                 120° diamond spheroconical 
               
               
                 E 
                 HRE 
                 100 
                 ⅛-inch-diameter (3.175 mm) steel 
               
               
                   
                   
                   
                 sphere 
               
               
                 F 
                 HRF 
                  60 
                  1/16-inch-diameter (1.588 mm) steel 
               
               
                   
                   
                   
                 sphere 
               
               
                 G 
                 HRG 
                 150 
                  1/16-inch-diameter (1.588 mm) steel 
               
               
                   
                   
                   
                 sphere 
               
               
                   
               
             
          
         
       
     
         [0035]    Materials tested with the HRC protocol are generally harder than those tested with the HRB protocol. There is, however, some overlap between the upper end of the HRB (100 kg) scale and the lower end of the HRC (150 kg) scale, e.g., an HRB (100 kg) of 97 corresponds generally to an HRC (150 kg) of about 20, and an HRB (100 kg) of 120 corresponds with an HRC (150 kg) of about 55 for non-austenitic steels. (See http://www.woodcousa.com/bhn.pdf.) HRC values of less than 20 are said to have questionable accuracy. 
         [0036]    Titanium alloys having a hardness of HRC 30 or more are preferred for use in the present invention, e.g., titanium exhibiting HRC (150 kg) hardness within the range of 30-68 or HRB within the range of 105-120 or more. Even more preferably, the titanium hardness is within the range of HRC (150 kg) 33-50. Such high hardness is generally beyond the ability of hand tools to cut, saw or grind away. Table 1 lists suitable materials and includes unalloyed titanium by way of comparison. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Material Name  
                 HRC 
               
               
                   
                   
               
             
             
               
                   
                 Titanium Grade 7  
                 11.0  
               
               
                   
                 Titanium Grade 7, Annealed  
                 11.0  
               
               
                   
                 Titanium Grade 12  
                 11.0  
               
               
                   
                 Titanium Grade 18 Ti-3Al-2.5V-0.05Pd  
                 15.0  
               
               
                   
                 Titanium Grade 3  
                 16.0  
               
               
                   
                 Titanium Grade 4  
                 23.0  
               
               
                   
                 Titanium Grade 4, Annealed  
                 23.0  
               
               
                   
                 Titanium Ti-3Al-2.5V (Grade 9), alpha  
                 24.0  
               
               
                   
                 annealed  
                   
               
               
                   
                 ATI Allvac ® 3-2.5 Titanium Alloy, Heat  
                 24.0  
               
               
                   
                 Treatment: 704° C. (1300° F.) Anneal  
                   
               
               
                   
                 ATI Allegheny Ludlum Grade 9 Titanium  
                 25.0  
               
               
                   
                 (UNS R56320)  
                   
               
               
                   
                 ATI Allegheny Ludlum Grade 18 Titanium  
                 25.0  
               
               
                   
                 (UNS R56322)  
                   
               
               
                   
                 Titanium Grade 3, Annealed  
                 26.0  
               
               
                   
                 ATI Allvac ® 6-2-4-2-Si UNS R54620 modified  
                 28.0  
               
               
                   
                 Titanium Alloy  
                   
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-0.8Mo (Ti-621/0.8), 
                 30.0  
               
               
                   
                 as-rolled  
                   
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-0.8Mo (Ti-621/0.8),  
                 30.0  
               
               
                   
                 Alpha-Annealed  
                   
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-0.8Mo (Ti-621/0.8),  
                 30.0  
               
               
                   
                 STA-1  
                   
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-0.8Mo (Ti-621/0.8),  
                 30.0  
               
               
                   
                 STA  
                   
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-1Mo  
                 30.0  
               
               
                   
                 Titanium Ti-6Al-2Nb-1Ta-1Mo, Annealed  
                 30.0  
               
               
                   
                 Titanium Ti-13V-11Cr-3Al (Ti-13-11-3)  
                 30.0  
               
               
                   
                 Solution Treated  
                   
               
               
                   
                 ATI Allvac ® 6-4ELI Titanium Alloy, Heat  
                 30.0  
               
               
                   
                 Treatment: 704° C. (1300° F.) Anneal  
                   
               
               
                   
                 ATI Allegheny Ludlum Grade 23 (6-4 ELI)  
                 30.0  
               
               
                   
                 Titanium (UNS R56401)  
                   
               
               
                   
                 Titanium Ti-15V-3Cr-3Al-3Sn ST 850° C.  
                 31.0  
               
               
                   
                 (1560° F.), Aged 545° C.  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-2Mo (Ti-6-2-4-2),  
                 32.0  
               
               
                   
                 Duplex Annealed  
                   
               
               
                   
                 Titanium IMI 829 (Ti-5.5Al-3.5Sn-3Zr-1Nb- 
                 32.0  
               
               
                   
                 0.25Mo-0.3Si)  
                   
               
               
                   
                 Titanium Ti-10V-2Fe-3Al (Ti 10-2-3), Anneal  
                 32.0  
               
               
                   
                 1 hr. 760° C.  
                   
               
               
                   
                 Titanium Beta C (Ti-3Al-8V-6Cr-4Mo-4Zr)  
                 32.0  
               
               
                   
                 Solution Treated 815° C.  
                   
               
               
                   
                 ATI Allvac ® 6-4 Titanium Alloy, Heat  
                 32.0  
               
               
                   
                 Treatment: 704° C. (1300° F.) Anneal  
                   
               
               
                   
                 ATI Allvac ® 6-7 UNS R56700 Titanium Alloy  
                 32.0  
               
               
                   
                 ATI Allvac ® Grade 15-3-3-3 UNS R58153  
                 32.0  
               
               
                   
                 Titanium Alloy  
                   
               
               
                   
                 ATI Allvac ® 38-644 UNS R58640 Titanium  
                 32.0  
               
               
                   
                 Alloy  
                   
               
               
                   
                 Titanium Ti-5Al-2.5Sn, ELI, Annealed  
                 33.0  
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-2Mo-0.1Si; Duplex  
                 34.0  
               
               
                   
                 Annealed  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-2Mo (Ti-6-2-4-2),  
                 34.0  
               
               
                   
                 Sheet  
                   
               
               
                   
                 Titanium Ti-13V-11Cr-3Al; (Ti-13-11-3)  
                 34.0  
               
               
                   
                 Annealed 800° C., 30 min.  
                   
               
               
                   
                 Titanium Ti-8Mn, Annealed  
                 34.0  
               
               
                   
                 Titanium Ti-7Al-4Mo Annealed  
                 34.0  
               
               
                   
                 ATI Allvac ® 6-2-4-2 Titanium Alloy, Heat  
                 34.0  
               
               
                   
                 Treatment: 982° C. (1800° F.) + Age  
                   
               
               
                   
                 Titanium Ti-8Al-1Mo-1V (Ti-8-1-1) Duplex  
                 35.0  
               
               
                   
                 Anneal  
                   
               
               
                   
                 Titanium IMI 834  
                 35.0  
               
               
                   
                 Titanium Ti-6Al-4V ELI (Grade 23), Annealed  
                 35.0  
               
               
                   
                 ATI Allvac ® 8-1-1 Titanium Alloy, Heat  
                 35.0  
               
               
                   
                 Treatment: 982° C. (1800° F.) + Age  
                   
               
               
                   
                 ATI Allvac ® 6-6-2 Titanium Alloy, Heat  
                 35.0  
               
               
                   
                 Treatment: 718° C. (1325° F.) Anneal  
                   
               
               
                   
                 ATI Allegheny Ludlum Grade 5 Titanium 6Al- 
                 35.0  
               
               
                   
                 4V (UNS R56400)  
                   
               
               
                   
                 Titanium Ti-5Al-2.5Sn (Grade 6)  
                 36.0  
               
               
                   
                 Titanium Ti-8Al-1Mo-1V (Ti-8-1-1)  
                 36.0  
               
               
                   
                 Titanium Ti-8Al-1Mo-1V (Ti-8-1-1) Annealed  
                 36.0  
               
               
                   
                 8 hr at 790° C. (1450° F.)  
                   
               
               
                   
                 Titanium Ti-6Al-4V (Grade 5), Annealed  
                 36.0  
               
               
                   
                 Titanium Ti-6Al-4V (Grade 5), Annealed Bar  
                 36.0  
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6)  
                 37.0  
               
               
                   
                 Annealed  
                   
               
               
                   
                 Titanium Beta C (Ti-3Al-8V-6Cr-4Mo-4Zr ST  
                 38.0  
               
               
                   
                 815° C., Aged 510° C.  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6)  
                 38.0  
               
               
                   
                 STOA  
                   
               
               
                   
                 Titanium Ti-6Al-6V-2Sn (Ti-6-6-2) Annealed  
                 38.0  
               
               
                   
                 Titanium Ti-7Al-4Mo, STA  
                 38.0  
               
               
                   
                 ATI Allvac ® 6-2-4-6 Titanium Alloy, Heat  
                 38.0  
               
               
                   
                 Treatment: 885° C. (1625° F.) + Age  
                   
               
               
                   
                 ATI Allvac ® Ti-17 Titanium Alloy, Heat  
                 38.0  
               
               
                   
                 Treatment: 899° C. (1650° F.) + Age  
                   
               
               
                   
                 Titanium Ti-13V-2.7Al-7Sn-2Zr, ST 815° C.,  
                 39.0  
               
               
                   
                 Aged 540° C. (1000° F.)  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6)  
                 39.0  
               
               
                   
                 STA-1  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6)  
                 39.0  
               
               
                   
                 STA-2  
                   
               
               
                   
                 Titanium Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6)  
                 39.0  
               
               
                   
                 BSTA  
                   
               
               
                   
                 Titanium Ti-6Al-4V (Grade 5), STA Bar  
                 39.0  
               
               
                   
                 Titanium Ti-10V-2Fe-3Al (Ti 10-2-3) ST  
                 40.0  
               
               
                   
                 760° C.; Age 525° C. (980° F.)  
                   
               
               
                   
                 Titanium Ti-11.5Mo-6Zr-4.5Sn, ST 720° C.,  
                 40.0  
               
               
                   
                 Aged 495° C.  
                   
               
               
                   
                 Titanium Ti-8Mo-8V-2Fe-3Al ST 800° C.,  
                 40.0  
               
               
                   
                 Aged 540° C. (1000° F.)  
                   
               
               
                   
                 Titanium Ti-5-5-8-3 (Ti-5Mo-5V-8Cr-3Al),  
                 40.0  
               
               
                   
                 1 to 3 mm Sheet  
                   
               
               
                   
                 Titanium Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17)  
                 40.0  
               
               
                   
                 Alpha-Beta Processed  
                   
               
               
                   
                 Titanium Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17)  
                 40.0  
               
               
                   
                 Beta Processed  
                   
               
               
                   
                 Titanium Ti-6Al-4V (Grade 5), STA  
                 41.0  
               
               
                   
                 Titanium Ti-13V-11Cr-3Al (Ti-13-11-3) Aged  
                 42.0  
               
               
                   
                 400° C.  
                   
               
               
                   
                 Titanium Ti-6Al-6V-2Sn (Ti-6-6-2) STA  
                 42.0  
               
               
                   
                 870° C./565° C.  
                   
               
               
                   
                 Titanium Ti-13V-11Cr-3Al; (Ti-13-11-3)  
                 43.0  
               
               
                   
                 Annealed 850° C. (1560° F.) + Aged 510° C.  
                   
               
               
                   
                 8 hr 
                   
               
               
                   
                 Titanium Ti-13V-2.7Al-7Sn-2Zr, ST 760° C.,  
                 44.0  
               
               
                   
                 Aged 440° C.  
                   
               
               
                   
                 Titanium Ti-6Al-6V-2Sn (Ti-6-6-2) STA  
                 44.0  
               
               
                   
                 910° C./540° C. (1000° F.)  
                   
               
               
                   
                 Titanium Ti-13V-11Cr-3Al (Ti-13-11-3)  
                 46.0  
               
               
                   
                 SolnTreat; Age 450° C.  
                   
               
               
                   
                 Titanium Ti-13V-11Cr-3Al (Ti-13-11-3) Aged  
                 50.0  
               
               
                   
                 490° C. 
               
               
                   
                   
               
             
          
         
       
     
         [0037]    The most preferred titanium for use as the extension members, rivets and spacer elements in the present invention has a hardness of HRC 35 or higher. Such a material can be found in a Grade 5 titanium alloy (Ti-6Al-4V). 
         [0038]    The specific shape of the rod member can exhibit a round or rectangular cross section, but a preferred shape exhibits a cross sectional diameter or length of 8 mm or more, preferably a diameter within the range of 10-20 mm. Such a shape and diameter are sufficiently hard and exhibit such a high tensile strength that they are not readily cut by bolt cutters or saws (hand-operated or battery-operated). Such dimensions and hardness are also a visual deterrent for those intent on using a portable angle grinder that may serve as a psychological deterrent and redirect the would-be thief toward other lock systems that do not have such a robust system. 
         [0039]    The ultimate tensile strength of the titanium alloy can also be used as an indicator for suitability in the present invention. This tensile strength may help avoid potential variances due to surface absorption of oxygen from annealing. An exemplary listing of the ultimate tensile strengths of various titanium alloys is found in Table 3. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Alloy 
                 Designation 
                 Tensile Strength (MPa) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Commercially Pure 
                 ASTM Grade 1  
                 241  
               
               
                 Commercially Pure 
                 ASTM Grade 2  
                 345  
               
               
                 Commercially Pure 
                 ASTM Grade 3  
                 448  
               
               
                 Commercially Pure 
                 ASTM Grade 4  
                 552  
               
               
                 Ti-3%Al-2.5%V 
                 ASTM Grade 9  
                 621  
               
               
                 Ti-0.8%Ni-0.3%Mo 
                 ASTM Grade 12 
                 483  
               
               
                 Ti-3%Al-8%V-6%Cr-4%Zr- 
                 Beta C 
                 1172  
               
               
                 4%Mo 
                   
                   
               
               
                 Ti-15%Mo-3%Nb-3%Al- 
                 Timetal 21 S a   
                 792  
               
               
                 0.2%Si 
                   
                   
               
               
                 Ti-6%Al-4%V 
                 ASTM Grade 5  
                 897  
               
               
                 Ti-2.5%Cu 
                 IMI 230 
                 540  
               
               
                 Ti-4%Al-4%Mo-2%Sn-0.5%Si 
                 IMI 550 
                 1104  
               
               
                 Ti-6%Al-6%V-2%Sn 
                   
                 1035  
               
               
                 Ti-10%V-2%Fe-3%Al 
                   
                 1241  
               
               
                 Ti-15%V-3%Cr-3%Sn-3%Al 
                   
                 1000  
               
               
                 Ti-8%Al-1%Mo-1%V 
                   
                 897  
               
               
                 Ti-6%Al-5%Zr-0.5%Mo- 
                 IMI 685 
                 850  
               
               
                 0.2%Si 
                   
                   
               
               
                 Ti-6%Al-2%Sn-4%Zr-2%Mo 
                   
                 931  
               
               
                 Ti-6%Al-2%Sn-4%Zr-6%Mo 
                   
                 1172  
               
               
                 Ti-5.5%Al-3.5%Sn-3%Zr- 
                 IMI 829 
                 960  
               
               
                 1%Nb-0.3%Mo-0.3%Si 
                   
                   
               
               
                 Ti-5.8%Al-4%Sn-3.5%Zr- 
                 IMI 834 
                 1030  
               
               
                 0.7%Nb-0.5%Mo-0.3%Si 
               
               
                   
               
               
                   a Solution treated 
               
             
          
         
       
     
         [0040]    An ultimate tensile strength of 700 MPa or more (at 20° C.) is preferred for the titanium members and parts use in the present invention. Even more preferable is a tensile strength of about 930 MPA or more. 
         [0041]    The specific shape of the rod member can exhibit any number of potential geometric shapes in cross section, e.g., round, triangular, rectangular, hexagonal, octagonal, etc. provided that the cross sectional distance is sufficiently large to be impractical to cut with handheld bolt cutters, e.g., a cross sectional distance of at least 8 mm, preferably a cross sectional distance within the range of 9-20 mm, and even more preferably a cross sectional distance of 10-14 mm. A preferred shape uses commercially available rod stock that exhibits a cross sectional diameter within the range of 8-12 mm. 
         [0042]    Turning now to the figures,  FIGS. 1 and 2  shows an antitheft device  1  according to the invention. Two extension rod members  3 ,  4  (also called “first rod members” herein) are interconnected with each other and with locked rod member  5  (referenced as “third rod member” herein) and lockable rod member  2  (referred to as “second rod member” herein) at first ends  6 . Any number of extension rods  3 ,  4  may be used to provide additional length to antitheft device  1 . 
         [0043]    An opposing pair of saddle washers  7  have an arcuate side that contacts the round external surfaces of each rod and an opposing flat or planar side that provides a planar interaction surface  8  in which each rod can pivot relative to the rod with which it is connected by rivet  9 , e.g., between rod  2  and rod  3 . Saddle washers  7  also serve to protect rivets  9  from attack using the connected rods as cutting guides by a saw blade or bolt cutter jaws. 
         [0044]    Locked rod member  5  is permanently secured to lock  10 . Lockable rod member  2  can become secured by lock  10  when lockable rod  2  is inserted into lock hole  11  and lock mechanism  12  is engaged. See also  FIG. 13 . 
         [0045]      FIGS. 3 and 4  show additional details of extension rod  3 . As shown extension rod  3  is cylindrical with a substantially circular cross sectional shape having a length  17  and rod diameter  18 . Substantially parallel, transverse bores  13 ,  14  with countersink bores  15 ,  16  that exhibit greater diameter than bores  13 ,  14 . Bore centers  19 ,  20  of bores  13 ,  14  respectively are desirably located at least one third and preferably at least one half of a rod diameter from the terminal ends  21 ,  22  of rod  3 . 
         [0046]      FIGS. 5-13  illustrate additional details of the saddle washers  7  and the pivotable connections between connected rods, e.g., extension rods  3 ,  4 . As shown, saddle washer  7  has a planar side  23  and an arcuate side  24 . Arcuate side  24  preferably exhibits a radius of curvature  25  that is substantially the same as rods  3 ,  4  to provide a good fit. Washers  7  also exhibit a transverse bore  26  having a close tolerance fit for securing rivet  9  without undue play between rivet  9  and spacer  7  when assembled. 
         [0047]    As shown in  FIGS. 6 and 7 , the ends of rivet  9  are exposed above the outer diameter of rods,  3 ,  4 . While exposed ends are operative to secured rods  3 ,  4  together they also provide a potential vulnerability for attack by a portable angle grinder that might remove the deformation flanges  27  on either end of rivet  9 . To that end, rivet  9  may also be set at or below the outer surface  31  of the connected rods, e.g., rods  4  and  5 , in countersink boring  32 . 
         [0048]    The outer diameter  28  of spacer  7  may be the same or substantially the same as the rod diameter  18 . The rising edges  29  of washer  7  can present a sharp edge for users. First and/or second chamfers  30 ,  31  can be used to reduce incidents of cutting or snagging at edges  29  while also retaining the security and planar motion features of saddle washers  7  between connected rods. 
         [0049]      FIGS. 14 and 15  illustrate additional details of lock  10 . As shown, distal end  33  of lock body  35  extends through rod  5  and into countersink bore  32  where it is deformed in-situ to make enlarged end  34  that permanently holds lock body  35  to locking rod  5 . 
         [0050]    Within lock body  35 , locking member  36  is able to be removed vertically and axially from within lock body  35  by operation of a key (not shown) in keyhole  37  from a secured position  38  to an unsecured position (not shown). Locking member  36  also exhibits a distal pin  39  that engages the transverse bore  14  of lockable rod  2  when in secured position  38  and disengages from rod  2  when moved axially within lock body  35  or removed completely from lock body  35 . Secured bushings  40 ,  41  within lock body  35  are used to center and secured locking member  36  within lock body  35 . Preferably, the external surface  42  of locking member  39  and the corresponding internal surfaces  43 ,  44  of bushings  40 ,  41  exhibit mating threads that allow locking member  36  to be threaded into and secured within lock body  35 . 
         [0051]      FIGS. 16-18  illustrate the optional use of a security washer  45  between opposing saddle washers  7 . Preferably, at least one security washer is used in the antitheft device according to the invention and even more preferably a security washer is used at each joint connection in the device. Security washer  45  preferably exhibits a shaped radial edge  46 , such as counter-sloping sections  47 ,  48  that meet in an acute or obtuse angle  49  at substantially the vertical mid-point  50  of the height of security washer  45 . Such a profile shape makes it more difficult for a blade or saw edge to attack the joint at the intersection of the opposing saddle washers  7 . The inner area  51  of security washer  7  preferably has opposing countersink portions  52  to receive saddle washers  7  and centered on a central bore  53  for passing rivet  9  therethrough. 
         [0052]    The foregoing illustrations and descriptions are not intended to serve as limitations on the scope of the appended claims. 
         [0053]    Each of the patents and published applications that have been cited herein are hereby incorporated by reference.

Summary:
The invention relates to an anti-theft device that is both highly resistant to attack by hand-carried bolt cutters and saw blades while also exhibiting a weight suitable for use with bicycles. The device is made with a plurality of interlinked titanium alloy arm members, each of which exhibits a hardness of HRC 30 or more and a cross-sectional distance of 8 mm or more.