Patent Publication Number: US-2023143140-A1

Title: Unattended trailer hitch lock

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional application Ser. No. 63/057,085 filed Jul. 27, 2020, and is the national phase of application PCT/US21/39605 filed Jul. 29, 2021, the disclosures of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a trailer hitch lock that prevents the theft of boats, lawn care equipment, and snowmobiles that are carried on a trailer but that may be parked and unattended for extended periods of time. 
     BACKGROUND OF THE INVENTION 
     A multitude of vehicles and equipment are carried on a trailer that connects to a towing vehicle with a ball hitch system. In such a system, the towing vehicle has a ball hitch mounted at the rear of the vehicle. The trailer has a forward trailer tongue with a semi-spherical receiver that fits over the rounded top of the ball on the towing vehicle. To aid in guiding the ball into the receiver and to reinforce the receiver, the bottom of the receiver often has a coupling, such as a flared flange. Once in position over the ball, the receiver is secured by an armature that is extended around the lower part of the ball by rotating an external handle down and toward the hitch. Such a system has been used for decades and is prevalent in a wide variety of towed vehicles, equipment, cargo, and mobile homes. 
     A similar system with a square-shaped hollow receiver tube is shown in U.S. Pat. No. 4,807,899 and US Publication 2015/0258866. 
     Trailers and their cargo are often parked in a place where it is convenient for the owner to pull in and disconnect the trailer. A dolly wheel and crank are often used to adjust the height of the connection frame to remain level. If left unprotected, however, there is little that prevents a thief from connecting to the unprotected receiver and pulling off. A trailer hitch lock secures the receiver from connecting to an unauthorized ball hitch. 
     Conventional trailer hitch lock systems engage the semi-spherical opening of the receiver with an obstruction that blocks access by an unauthorized vehicle. See U.S. Pat. Nos. 3,233,913; 5,222,755; and 5,743,549. 
     One type of locking system has an engagement lip that engages the receiver&#39;s flared flange and includes an insert into the receiver portion of the trailer hitch. See, U.S. Pat. Nos. 7,040,646; 7,204,508; 7,909,351; 8,020,885; and 9,701,169 (locking ball insert) and US published application nos. 2006/0163842 (flared flange lock), 2006/0208458, and 2006/0284398 (flange lock with “2” armature). 
     Despite the advances in lock designs that are found in the prior art, trailers continue to be stolen by thieves wielding battery-powered angle grinders. These thieves attack the very material of the lock and can cut through the vulnerable points in minutes. When the trailer is unattended, theft by grinder attack is a very real possibility. 
     It would be advantageous to provide a trailer lock exhibiting an enhanced resistance to angle grinder attacks. 
     Conventional trailer locks also typically have an exposed locking mechanism that makes the system vulnerable to moisture and rusting of crucial parts. There are few things more frustrating to a boat owner than going to great lengths to secure the trailer against theft only to have the lock become rusted shut so as to prevent access by its owner. 
     It would be desirable to have a trailer lock that was also protected against moisture infiltration and rusting or degradation of crucial mechanisms needed to remove the trailer lock. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a trailer hitch lock that would protect the locked hitch from theft and destructive attack by an angle grinder. 
     It is also an object of the invention to have a trailer hitch lock that was protected from internal rusting due to moisture. 
     In accordance with the above and other objectives of the invention that will become apparent from the description herein, a trailer hitch lock according to the invention comprises: (a) a hardened core that includes a locking mechanism operably movable vertically from a first unlocked position into a second locked position, and (b) a grinder resistant shell surrounding said core that is shaped to engage a flared lip of a trailer hitch receiver and is characterized by a plurality of radially extending fins that are made from a soft material that clogs coarse aluminum oxide grit of a cutting disc. Optional additional features include one or more moisture-resistant seals around key movable parts to provide resistance to moisture infiltration and a freely rotating ring around the locking mechanism that foils drill-based attacks on the locking mechanism. 
     The trailer hitch of the invention provides an effective locking system for an unattended trailer that resists destructive attack with an angle grinder, whether battery-powered or AC-powered. Such additional security is enhanced with an anti-drill ring that hinders a direct, drill-based attack on the locking assembly and enhanced moisture resistance with seals at key junctures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross sectional view of a first embodiment of the invention. 
         FIG.  2    is a side sectional view of a first embodiment according to the invention. 
         FIG.  3    is a sectional view of a lock assembly according to the invention. 
         FIG.  4    is an exploded parts view of a hitch lock according to a first embodiment of the invention. 
         FIG.  5    presents a detailed sectional view of an anti-drill feature of the invention. 
         FIG.  6    is an exploded view of a three-piece shell according to an embodiment of the invention. 
         FIG.  7    is an external view of a unitary, cast shell according to an embodiment of the invention. 
         FIG.  8    is a front external view of a finned embodiment of the present invention. 
         FIG.  9    is a rear view of a finned embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A first embodiment of a trailer hitch lock according to the invention is conveniently described with reference to the attached figures. 
     As shown in  FIG.  1   , the grinder-resistant trailer hitch lock according to the invention includes a lock assembly  1  that fits within a vertically-oriented, central chamber within a grinder-resistant shell  2 . Lock assembly  1  includes: (a) lock body  3  that houses lock mechanism  4  and (b) threaded end cap  5  that seals keyhole  6  from dirt and moisture. 
     The present hitch lock is installed onto a trailer&#39;s hitch receiver  101  by slipping slot  10  of shell  2  onto the coupling member of a hitch receiver via channel  101  so that lock assembly  1  becomes positioned below the recess that would receive the semispherical ball of the hitch connection and is thereby positioned to extend vertically up and into the hollow receiver portion. A key is inserted into keyhole  6  to push lock assembly  1  upwardly and into that recess. The coupling member can take the form of a radial flange, cast sleeve coupler, sleeve lock, or ring but is conveniently described with reference to a conventional hitch flange. 
     The Locking Assembly 
     Lock mechanism  4  is disposed within shell  2 . Shell  2  has an upper chamber  23  with a trailer slot  10  that receives a trailer hitch receiver in channel  101  between upper shoulder  19  and lower shoulder  20 . Middle chamber  18  is where the hitch receiver is engaged by lock mechanism  4 . Lower chamber  17  is where lock mechanism  4  retracts when unlocked and withdrawn from middle chamber  18 . Collectively, upper chamber  23 , middle chamber  18 , and lower chamber  17  form lock channel  24 . 
     The lock operates when lock mechanism  4  is pushed upwardly into middle chamber  18 . As the key turns locking cam  16 , first and second arms  11 ,  12  are driven radially outwardly by contact with locking cam  16  as the key turns lock mechanism  4  and cam  16 . When in the locked position ( FIG.  1   ), the cam blocks radial retraction of first and second arms  11 ,  12 . When the key is turned to the unlocked position, cam  16  is turned so as to allow locking arms  11 ,  12  to radially retract and lock mechanism  4  may then be lowered into lower chamber  17 . Once first and second locking arms  11 ,  12  are retracted, the whole lock body  3  can move down into lower chamber  17 . These steps secure the lock over the hitch coupling and obstruct access to the hitch recess until the lock is removed. 
     As shown in  FIGS.  1 - 3   , locking ring  15  is secured in position in middle chamber  18  with opposing set screws  30  that can only be accessed when the lock is in the unlocked position and lock assembly  1  is removed. The lock body slider set screws  30  can be advanced to extend into vertical groove  31  formed in shell  2  to limit the travel of lock body  3 . Retaining ring set screws  32  secure locking ring  15  within middle chamber  18  of shell  2 . Set screws  32  are accessible only when lock body  3  is in its lowest position thus makes the manufacturing process easier because it allows the locking ring  15  to be securely fastened into shell  2  without requiring any post-machining of shell  2 . Additionally, having the set screws accessible only from middle chamber  18  does not expose externally-accessible fasteners that could represent a potential security weak point. 
     Lock mechanism  4  is secured within lock body  3  with lock housing set screw  25  that extends radially inward from lock body  3  into a threaded opening  26  in lock mechanism  4 . Lock mechanism set screw  27  secures tumblers  28  within lock mechanism  4 . 
     Sealing rings are used at junctions to help prevent moisture from intruding into lock assembly. For example,  FIGS.  1 - 3    show an upper seal  21  in the form of a U-cup seal around the base of locking cam  16  and a lower O-ring  22  at the junction between the lock body and its cap. 
     The bottom lock opening of the lock assembly is protected from a drill attach with anti-drilling ring  7 . As shown in  FIG.  4   , freely rotating anti-drill ring  7  is held in position against shoulders  8  of lock mechanism  4 . Anti-drill ring  7  has a tapered central opening  71  of a depth sufficient to allow a key to pass through the central opening  9  and engage lock mechanism  4 . The tapering angle  72  of the inner walls of opening  9  are, however, smaller than the typical angle of a drill bit. Most drills are ground to an angle of about 118° so any opening angle that is substantially less, e.g., an angle  72  within the range of 75° to 100°, will cause the drill bit to engage the tapering sidewalls and spin freely without cutting effect. A drill bit  100  of sufficiently small diameter to pass through opening  9  may grind away internal parts of the lock but cannot extend to the peripheral tumblers so as to drill out the lock as a whole and disengage the internal mechanism that locks the assembly into an obstructing position within the hitch receiver. 
     Threaded end cap  5  is then screwed into the threaded bore  37  at the bottom of lock body  3 . This protects lock assembly  4  from fouling by water, dirt, grit, and the like. 
     The Outer Shell 
     Surrounding locking assembly  1  is a grinder-resistant shell  2 . Shell  2  interferes with, and preferably prevents, destructive attack against the lock assembly  1  by an angle grinder disc. This shell  2  can be made of a relatively softer metal that clogs the grit of a grinding wheel or it can be made from a relatively hard metal that is not readily cut, ground, or scored by typical grinding wheel grit. Shell  2  can be cast as a single, unitary piece ( FIG.  1   ) or formed in separate parts that are joined together ( FIG.  5   ). 
     Permanent mold casting is the preferred process to make the grinder resistant shell  2  of the present invention. 
     A second embodiment of the invention is shown in  FIG.  5    which shows the use of a three-piece shell. This design uses a hardened steel core coupler  33  sandwiched between a top shell piece  34  and a bottom shell piece  35  that are joined together around core coupler  33 . Top shell piece  34  and bottom shell piece  35  may be solid or exhibit internal fins (not shown) in the same manner as discussed above. 
     The top and bottom shell pieces  34 ,  35  may be made of a material that is relatively softer than the grit of an angle grinder wheel to clog the grit to reduce the grinder&#39;s cutting efficiency and thereby drain the tool&#39;s battery with little cutting to show for the efforts. Conversely, the top and bottom shell pieces  34 ,  35  may also be made of a material that is hard and relatively hard to scratch with a typical carborundum cutting disk. 
     A wide variety of metal joining methods can be used to join the top and bottom shell pieces  34 ,  35 , such as, thermoset adhesives such as epoxy, mechanical fasteners such as rivets, and fusion methods such as welding. Welding is preferred. 
     Once positioned and secured to each other, the three-piece shell is preferably greater than 35 mm, preferably 37-55 mm, and even more preferably 40-50 mm in thickness from any direction that is accessible once the lock is installed on a trailer hitch. A typical angle grinder disc penetrates about 35 mm so a shell thickness that is greater than this depth will act as a visual and functional deterrent in the decision of whether to attempt to attack this lock. 
     A third embodiment of a lock according to the invention is shown in  FIG.  6   . In this embodiment, the cast shell  40  surrounds the locking core  41  and middle section  42  of the coupler. Preferably, the cast shell  40  is made from steel or aluminum. This embodiment allows cast shells of ever greater diameter to defeat even the largest of portable grinder disks while also eliminating the need for lock assembly. This shell can be hollow or internally finned. 
     Shell  2  protects lock assembly  1  from destructive attack with a series of 7-15 vertical ribs  43 . In the exposed side of the lock (as shown in  FIGS.  2 ,  3 ,  7 , and  8   ), ribs  43  extend between upper horizontal support  44 , central horizontal support  45  and lower horizontal support  46 . On the side that faces the trailer ( FIG.  3   ), some of ribs  43  only extend between a lower central support  47  and lower horizontal support  46  so as to leave slot  10  unobstructed and able to receive the hitch coupling in channel  101 . Ribs  43  may, or may not, extend to a surface on the bottom or top of the rib. 
     Outer shell  2  is preferably made from a material that is relatively softer than the metal of the lock assembly  1  and is preferably chosen to clog the aluminum oxide grinding wheels most commonly used. Suitable materials include aluminum, aluminum alloys, aluminum-containing polymeric composites, and brass. Aluminum and its alloys are preferred. It is also useful, however, to make outer shell  2  from a material or metal that is relatively hard to cut or scratch with the grit on a conventional grinder. 
     Die casting is a cheaper and faster process for casting aluminum parts. Die cast parts are also too porous to weld. 
     The preferred alloys that are suitable shell materials have a copper content less than 0.5%. It is essential that the copper content of the alloys is low in order for it to be welded in a commercially viable process. The main purpose of copper in aluminum alloys is to increase the alloys reactivity to heat treatment, however, increased copper also decreases weldability and reduces corrosion resistance. Table 1 below identifies some of the suitable aluminum alloys for use in the shell of the invention. The values indicate maximum limits unless shown as a range or a minimum. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Chemical Composition Limits for Aluminum Alloys (Wt %) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 OTHERS 
                 OTHERS 
                 Al 
               
               
                 Alloy 
                 Si 
                 Fe 
                 Cu 
                 Mn 
                 Mg 
                 Cr 
                 Zn 
                 Ti 
                 EACH 
                 TOTAL 
                 MIN. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1070 
                  0.20 
                 0.25 
                 0.04 
                 0.03 
                 0.03 
                 — 
                 0.04 
                 0.03 
                 0.03 
                 — 
                 99.70 
               
               
                 1100 
                 0.95 Si + Fe 
                   
                 0.05-0.20 
                 0.05 
                 — 
                 — 
                 0.10 
                 — 
                 0.05 
                 0.15 
                 99.00 
               
               
                 3003 
                 0.6 
                 0.7 
                 0.05-0.20 
                 1.0-1.5 
                 — 
                 — 
                 0.10 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 3004 
                  0.30 
                 0.7 
                 0.25 
                 1.0-1.5 
                 0.8-1.3 
                 — 
                 0.25 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 3005 
                 0.6 
                 0.7 
                 0.30 
                 1.0-1.5 
                 0.20-0.6  
                 0.10 
                 0.25 
                 0.10 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 3104 
                 0.6 
                 0.8 
                 0.05-0.25 
                 0.8-1.4 
                 0.8-1.3 
                 — 
                 0.25 
                 0.10 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 4004 
                 9.0-10.5 
                 0.8 
                 0.25 
                 0.10 
                 1.0-2.0 
                 — 
                 0.20 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 4104 
                 9.0-10.5 
                 0.8 
                 0.25 
                 0.10 
                 1.0-2.0 
                 — 
                 0.20 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 4043 
                 4.5-6.0  
                 0.8 
                 0.30 
                 0.05 
                 0.05 
                 — 
                 0.10 
                 0.20 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 4045 
                 9.0-11.0 
                 0.8 
                 0.30 
                 0.05 
                 0.05 
                 — 
                 0.10 
                 0.20 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 5005 
                 0.30 
                 0.7 
                 0.20 
                 0.20 
                 0.50-1.1  
                 0.10 
                 0.25 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 5050 
                 0.40 
                 0.7 
                 0.20 
                 0.10 
                 1.1-1.8 
                 0.10 
                 0.25 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 5052 
                 0.25 
                 0.40 
                 0.10 
                 0.10 
                 2.2-2.8 
                 0.15-0.35 
                 0.10 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 5252 
                 0.08 
                 0.10 
                 0.10 
                 0.10 
                 2.2-2.8 
                 — 
                 0.05 
                 — 
                 0.03 
                 0.10 
                 Rem. 
               
               
                 5056 
                 0.30 
                 0.40 
                 0.10 
                 0.05-0.20 
                 4.5-5.6 
                 0.05-0.20 
                 0.10 
                 — 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 5657 
                 0.08 
                 0.10 
                 0.10 
                 0.03 
                 0.6-1.0 
                 — 
                 0.05 
                 — 
                 0.02 
                 0.05 
                 Rem. 
               
               
                 5182 
                 0.20 
                 0.35 
                 0.15 
                 0.20-0.50 
                 4.0-5.0 
                 0.10 
                 0.25 
                 0.10 
                 0.05 
                 0.15 
                 Rem. 
               
               
                 6061 
                 0.40-0.8  
                 0.7 
                 0.15-0.40 
                 0.15 
                 0.8-1.2 
                 0.04-0.35 
                 0.25 
                 0.15 
                 0.05 
                 0.15 
                 Rem. 
               
               
                   
               
            
           
         
       
     
     Table 2 lists the hardness of suitable alloys. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Hardness 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Tensile 
                 Hardness 
                 Hardness 
               
               
                 Alloy 
                 Temper 
                 Strength (MPa) 
                 Brinell HB 
                 Vickers HV 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 AA1050A 
                 H2 
                 100 
                 30 
                 30 
               
               
                   
                 H4 
                 115 
                 35 
                 36 
               
               
                   
                 H6 
                 130 
                 39 
               
               
                   
                 H8 
                 150 
                 43 
                 44 
               
               
                   
                 H9 
                 180 
                 48 
                 51 
               
               
                   
                 0 
                 80 
                 21 
                 20 
               
               
                 AA2011 
                 T3 
                 365 
                 95 
                 100 
               
               
                   
                 T4 
                 350 
                 90 
                 95 
               
               
                   
                 T6 
                 395 
                 110 
                 115 
               
               
                   
                 T8 
                 420 
                 115 
                 120 
               
               
                 AA3103 
                 H2 
                 135 
                 40 
                 40 
               
               
                   
                 H4 
                 155 
                 45 
                 46 
               
               
                   
                 H6 
                 175 
                 50 
                 50 
               
               
                   
                 H8 
                 200 
                 55 
                 55 
               
               
                   
                 H9 
                 240 
                 65 
                 70 
               
               
                   
                 0 
                 105 
                 29 
                 29 
               
               
                 AA5083 
                 H2 
                 330 
                 90 
                 95 
               
               
                   
                 H4 
                 360 
                 100 
                 105 
               
               
                   
                 H6 
                 380 
                 105 
                 110 
               
               
                   
                 H8 
                 400 
                 110 
                 115 
               
               
                   
                 H9 
                 420 
                 115 
                 120 
               
               
                   
                 0 
                 300 
                 70 
                 75 
               
               
                 AA5251 
                 H2 
                 210 
                 60 
                 65 
               
               
                   
                 H4 
                 230 
                 65 
                 70 
               
               
                   
                 H6 
                 255 
                 70 
                 75 
               
               
                   
                 H8 
                 280 
                 80 
                 80 
               
               
                   
                 H9 
                 310 
                 90 
                 90 
               
               
                   
                 0 
                 180 
                 45 
                 46 
               
               
                 AA5754 
                 H2 
                 245 
                 70 
                 75 
               
               
                   
                 H4 
                 270 
                 75 
                 80 
               
               
                   
                 H6 
                 290 
                 80 
                 85 
               
               
                   
                 H8 
                 315 
                 90 
                 90 
               
               
                   
                 H9 
                 340 
                 95 
                 100 
               
               
                   
                 0 
                 215 
                 55 
                 55 
               
               
                 AA6063 
                 0 
                 100 
                 25 
                 85 
               
               
                   
                 T1 
                 150 
                 45 
                 45 
               
               
                   
                 T4 
                 160 
                 50 
                 50 
               
               
                   
                 T5 
                 215 
                 60 
                 65 
               
               
                   
                 T6 
                 245 
                 75 
                 80 
               
               
                   
                 T8 
                 260 
                 80 
                 85 
               
               
                 AA6082 
                 0 
                 130 
                 35 
                 35 
               
               
                   
                 T1 
                 260 
                 70 
                 75 
               
               
                   
                 T4 
                 260 
                 70 
                 75 
               
               
                   
                 T5 
                 325 
                 90 
                 95 
               
               
                   
                 T6 
                 340 
                 95 
                 100 
               
               
                 AA6262 
                 T6 
                 290 
               
               
                   
                 T9 
                 360 
               
               
                 AA7075 
                 0 
                 225 
                 60 
                 65 
               
               
                   
                 T6 
                 570 
                 150 
                 160 
               
               
                   
                 T7 
                 505 
                 140 
                 150 
               
               
                   
               
            
           
         
       
     
     Preferred materials for the shell are weldable aluminum alloys having a Knoop hardness of at least 50, and more preferably a Knoop hardness within the range of 70-140. 
     The most preferred aluminum alloys for the shell include Aluminum A356.0-T6 (Rockwell B Hardness=49; Knoop Hardness=103), Aluminum A356.0-F (Knoop Hardness=78), Aluminum A357.0-F, Aluminum A357.0-T6 (Rockwell B Hardness=56; Knoop Hardness=114), and Aluminum 6061-T6 (Rockwell B Hardness=60; Knoop Hardness=120). 
     The radial thickness of fins  23  and horizontal supports  24 ,  25 ,  26 ,  27  should be sufficient to exceed the reach of a typical battery-operated angle grinder disk. Such disks can typically cut to a depth of about 35 mm so fins  23  should extend at least 35 mm from the outer surface of the hardened lock assembly  1 . Preferably, fins  23  extend radially away from the outer surface of lock assembly  1  by a distance within the range of 36-100 mm, more preferably a distance within the range of 40-75 mm. 
     Similarly, fins  43  should be spaced around the lock so that a grinder blade must engage at least two, and preferably three of the fins as it cuts toward the lock assembly. The additional material hastens the rate of clogging of the coarse blade grit as well as the drain on the battery as the user presses harder to continue to see the same rate of cut but with an even more dull disk. 
     Surprisingly, the presence of horizontal supports introduces an extra level of difficulty when a thief attempts to defeat the lock of the present invention. Compared to a planar cut test through just a set of only vertical fins, the connection of the horizontal members with all of the fins requires the attacker to make twice the number of cuts to remove any singular fin. Additionally, the distribution of the fins around the surface (e.g., a radial fin-to-fin distribution angle within the range of 30-40°, preferably an angle of about 36° fin-to-fin distribution) limits the advantage of removing any singular fin when attacking with an angle grinder. Instead, the attacker must remove at least two neighboring fins to gain any sort of geometric advantage with an angle grinder disc. As noted above, this accelerates the clogging actions on the disk and increases the battery drain of the device. 
     The external fins are preferably straight although it is within the scope of the invention to provide fins that are non-straight, e.g., exhibiting a wavy pattern or which are not at right angles relative to an adjacent fin. 
     It is understood however that the description above is intended to describe preferred embodiments and is not intended to limit the scope of the appended claims.