Untitled record

The present invention relates to a cylinder lock provided with means for indicating damage, which i.a. comprises a cylinder housing with a cylinder arranged therein and provided with a carrier and one or more electric circuits, each in the form of an electric current conductor, arranged to be connected to a current source for obtaining a quiescent current and so placed that a short circuit or breakage occurs in the respective circuit, when the lock is exposed to damage.

The object of the invention is to provide a lock of the type mentioned, which indicates attempts at damage, so that alarms can be triggered, for example in the event of a burglary, or so that the contents of a locked box or the like can be caused to be destroyed, e.g. by staining. To enable this, it is advisable in the first instance to provide means for indication, as the most vulnerable parts of the lock are exposed to damage. These parts are located in connection with the mounting plate mounting screws, the cylinder - especially its recesses and pins - and the cylinder housing.

A cylinder lock of the type mentioned in the introductory paragraph is characterized according to the invention mainly in that a current conductor consisting of two twisted and separately insulated conductor wires runs through one or more cylinder holes, which open at the end of the cylinder adjacent to the carrier.

The invention will now be described in more detail below in the form of a preferred embodiment with reference to the accompanying drawing.

Figure 1 shows in perspective and partly in cut-away form a conventional cylinder lock, which is supplemented with the indicating means designed according to the principles of the invention. Locking details in the form of locking pins and associated springs and recesses etc. do not appear from the figure, since they are not essential for understanding the invention.

Figure 2 shows on an enlarged scale a detail from figure 1.

The cylinder lock illustrated in Figure 1 is in its basic form of traditional type but has been provided with supplementary means, which make it possible to obtain the intended indication effect mentioned in the introduction. The drawing thus shows the conventional elements in the form of a front plate 10, which is arranged to be mounted at the outer end of a cylinder housing 12. The cylinder housing 12 is provided with a cylinder 14 rotatable therein, which can be rotated around with a key 16. At the inner end of the cylinder · 14 is a flat carrier

18 fixed, which in a conventional manner can affect and control a locking piston (not shown).

In the illustrated embodiment of the invention, three circuits intended for indication are included. However, it should already be noted here that the number of circuits can be varied as desired within the scope of the invention. Two or more circuits can also, if desired, be connected in series.

When attaching the front plate 10 to a base, two fixing screws, which extend from the inside of the base, through the base and into the mounting plate 10 are normally used. For this purpose, two corresponding screw holes 20 are received in the plate. The circuits are intended for connection over a power source (not shown), from which a small quiescent current is obtained. According to FIG. 1 the first circuit in the form of an electrical conductor 22 runs in at the edge of a recess 24 at the inside of the faceplate 10, follows the recess edge and then passes into a non-through-going bore 26 adjacent and radially outside the hole 20 of the single mounting screw. The conductor 22 passes back into the same bore 26. It is thus double-folded and runs after passing out of the bore 26 further next to the countersunk edge.

. The conductor 22 then runs into a similar bore 26, which is arranged radially outside the second fixing screw. Here, too, the leader is 22

7710862-9 double weight and its two ends are connected across the power source.

The drawing, in particular Fig. 2, shows a particularly suitable design of conductors, which comprises two twisted and separately insulated wires 28, 30. One conductor wire always has earth potential.

Through this arrangement, a safe indication of injury is obtained. The conductor is sensitive both to breakage and to short circuits between the wires 28, 30, which consist of lacquered 32 copper wires. The lacquer is so complex that it obtains a low melting point. This causes a short circuit between the conductors 28, 30 when heating them. Short circuits can occur in this way when drilling in the lock, before the wires are exposed to a direct mechanical damage.

A second circuit is connected across a current source, the corresponding electrical conductor 34 extending via a plate 36 attached to the carrier 18, which extends across the axis of the cylinder 14.

The plate 36 is provided with conductive coatings 38, 40, 42, against which the wire ends of the conductor 34 abut using a trailing contact arrangement. From the plate 36, the conductor 34 passes into a non-through hole 44, which is drilled in the cylinder 14 on one side of its recesses (not shown) for locking pins. The conductor 34 passes out of the same hole 44 - it is thus also double-weighted here - and into a similar hole 44 on the other side of the 1ås pin recesses. The conductor 34 then runs out again and back to the plate 36. It ^;is not absolutely necessary to use the arrangement with trailer contacts in all applications. Instead, for example, flexible wires with fixed ends can be used, especially when the locking cylinder rotation is small. On the outside of the cylinder housing 12 there is a third circuit. This consists of tightly wound turns of the used two-wire conductor 46 and extends across the mantle surface of the housing 12. The wire ends are connected across the power source.

In the embodiment shown, it is suitable to connect the three circuits 22, 34, 46 to one and the same power source. The circuits 22, 46 of the faceplate 36 and the cylinder housing 12 are suitably connected in series.