Patent Publication Number: US-4546345-A

Title: Theft preventing device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a theft preventing device, and more particularly to a theft preventing device of a chain locking type which employs a cable member therein. 
     2. Description of Relevant Art 
     Theft preventing devices of a chain locking type are already known in which one end of a cable member having the other end fixed to a lock body is linked around an object, such as a bicycle or the like, and is lockably fastened to the lock body to prevent the object from being stolen. The lock body is additionally provided with an alarm or warning device which will alert as to possible breakage of the cable member when the device is in a locking position to perfect the theft preventing function of the device. 
     In such conventional theft preventing devices, a cable has an electric conductor extending therealong which completes an inhibiting circuit for inhibiting operation of an alarm or warning device, and is energized when the device is in its locking position. These theft preventing devices, however, are disadvantageous in that an additional bypass circuit can easily be provided to such an electric circuit, which will render the warning or alarm device inoperable. 
     The present invention resolves such problems of these conventional theft preventing devices. 
     SUMMARY OF THE INVENTION 
     The present invention provides a theft preventing device comprising a lockable lock body, a cable member having one end thereof secured to the lock body, and the other end thereof fastenable to the lock body. At least one light-conducting member extends through and along the cable member. An alarm system is housed in the lock body. The alarm system includes an alarm device, a drive circuit operable to drive the alarm device when the lock body is in its locking position, and an inhibiting circuit for inhibiting operation of the drive circuit, the inhibiting circuit being completed by the light-conducting member. 
     It is an object of the present invention to provide a theft preventing device of a chain locking type in which ordinary deceiving means cannot substantially hinder generation of warning sound. This makes it difficult to steal the protected object, and gives maximized alarming effects against various means of theft, so that the object can be suitably prevented from being stolen. 
     The above and other objects, details and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention, when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an illustrative representation showing the entire system of a theft preventing device according to a preferred embodiment of the present invention. 
     FIG. 2 is a block diagram showing an alarm system of the theft preventing device of FIG. 1. 
     FIG. 3 is a front elevational view of a lock cylinder portion of the theft preventing device of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a preferred embodiment wherein a portable and self-contained theft preventing device includes a chain locking wire cable 1 consisting of steel strands as its main stock. An end 1a of the cable 1 extends into and is secured to a fastening metal member 2a formed as a cylindrical body having a flange at an end thereof. 
     The metal member 2a has at least one circumferential groove 2c formed around a substantially intermediate portion thereof in an axial direction thereof. In a locking position of the theft preventing device, the metal member 2a is inserted in a receiving hole 4a formed in one side portion of a housing of a lock body 3 and is fastened thereto as described hereinbelow. 
     The other end 1b of the cable 1 extends into and is secured to a mounting metal member 2b. End 1b extends into an interiorly widened recess 4b formed in a side portion of the housing 4 in opposing relationship relative to the receiving hole 4a, and is secured thereto. 
     The cable 1 has at least one optical fiber 11 twisted therewith which serves as a light beam conducting member. The optical fiber 11 extends through and along the cable 1 in a coextensive relationship to one end 11a thereof at an outer end face of the end 1a of the cable 1 so that, when the metal member 2a is fastened, it faces a light-emitting element 5. Element 5 is disposed within the housing of the lock body in confronting relation to an inner proximal end of the receiving hole 4a, and serves as a light source. The other end 11b of the fiber 11 similarly extends to an end face of the other end 1b of the cable 1 and faces a light-receiving element 6 mounted in the interior of the recess 4b and serving as a detector. 
     The housing 4 of the lock body 3 further has securely contained therein an electric circuit unit 7, a sound generating member 8 serving as an alarm member which generates an alarm sound when the cable 1 is broken, a power source 9 which electrically supplies required energy, and a lock cylinder 10 which constitutes a main locking mechanism. The housing 4 is covered with a cover member 4c to protect the same from the environment and includes a key receiving hole adjacent the cable receiving hole 4a. 
     The lock cylinder 10 has at least one lock pin 10a mounted for movement into and out of the lock cylinder 10 in a radial direction. When a key 12 inserted into the cylinder 10 is turned for locking motion, the pin 10a is moved to extend outwardly into the receiving hole 4a to engage in the groove 2c formed in the metal member 2 so as to fasten the end 1a of the cable 1 to the lock body 3. 
     Referring now to FIG. 2, the lock cylinder 10 has an ON-OFF switch 13 contained therein which is disposed for operation by the pin 10a such that the switch 13 is turned ON when the device is brought into a locked position. Upon turning ON of the switch 13, the power source 9 is connected to the light-emitting element 5. An oscillator 15 acts as a drive circuit for the sound generator 8. An amplifier circuit 14 functions as an inhibit circuit for inhibiting oscillation of the oscillator 15 when outputting a predetermined output therefrom. Thus, the timing at which the power circuit is completed by a locking operation of the key 12 is synchronized with the timing at which the lock pin 10a is moved into engagement with the groove 2c of the metal member 2a. 
     The light-emitting element 5 emits light by the completion of the power circuit including power source 9. The light is conducted by and along the optical fiber 11 to pass through the cable 1, and is projected onto the light-receiving element 6. This excites the element 6 so that the light-receiving element 6 generates a voltage in accordance with the amount of light received. Thus, when the device is in the locking position, a closed condition of the amplifier circuit 14 is established due to the photo coupling by the optical fiber 11. Accordingly, so long as the cable 1 is not broken and the locking condition is maintained properly, the light-receiving element 6 will receive a substantially constant amount of light and maintain a predetermined output so that the sound generating member 8 will produce no alarm sound. 
     On the other hand, if the output of the light-receiving element 6 is reduced so low or even to zero from some cause, then the oscillator 15 will operate to bring the sound generating member 8 into operation to generate an alarm sound. In this respect, it can be considered that causes of reduction of the output of the light-receiving element 6 to such a low level or even to zero include breakage of the cable 1. 
     Referring now to FIG. 3, the lock cylinder 10 has at a front face thereof a key slot 10b for receiving the key 12 therein and marks &#34;OFF&#34; and &#34;LOCK&#34; for pointing out clearly an initial position and a locking position. The initial position &#34;OFF&#34; provides for opening of the switch 13 and the locking position &#34;LOCK&#34; provides for closing of the switch 13. 
     Although there has been described what are at present considered to be a preferred embodiment of the invention, it will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential character thereof. The preferred embodiment is therefore to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description.