IMPROVED DOOR LOCK WITH A HOOK BOLT

The object of the invention is a door lock equipped with a hook bolt according to the preamble of Claim 1.

There are many types of known hook bolt locks. It is advantageous to use a hook bolt or a separate hook part in the bolt because this makes it far more difficult to force the bolt to the releasing position in the lock body as the hook part engages the striker plate in the door frame. Publication FR 2518193 presents a known hook bolt lock. Here, one turning hook part is turnably mounted on a pivot. In this lock, the operation of the hook part is somewhat uncertain because when the hook bolt is moved out of its locking position, the hook part is turned by mere gravity or additionally guided by the top edge of the opening in the striker plate. Friction forces may become a problem so that the hook bolt may even become jammed. Furthermore, the anti-burglar properties of this prior art solution are insufficient, particularly with regard to breaking actions in the lateral direction of the bolt aimed to create tensile load on the bolt.

The objective of the invention is to further develop prior art hook bolt solutions and create a door lock with a hook bolt that has a simple and reliable structure and substantially more advanced break-in properties and strength properties compared to prior art.

The objectives of the invention will mainly be achieved as described in more detail in Claim 1 and the other claims. According to the invention, the hook bolt comprises a plate-like body part with hook parts pivotably mounted on both sides, and in the locking position of the hook bolt, the body part together with the hook parts extends into the striker plate opening. The body part is furnished with side elements arranged at the positions of the hook parts, and in the locking position of the hook bolt, the side elements together with the body part and the hook parts are arranged to substantially fill the striker plate opening.

Furthermore, in the lengthwise direction of the front plate, the body part is dimensioned so that in its locking position, it is wider at the front plate opening compared to other parts of the hook bolt, and the front plate opening has a separate cutout for the body part preferably at both the top edge and the bottom edge of the opening.

The invention provides a substantial improvement in the anti-burglar properties of the door lock and its hook bolt particularly in the case that tensile load is applied to the hook bolt. The hook parts and side elements make the bolt's strength properties good. The additional elements provide the hook with sufficient solid material - that is, material not supported only by the pivot - to resist breaking. Sufficiently strong hook parts ensure a grip on the striker plate opening. The locked hook bolt is too large to go out of the striker plate opening, which means that when locked, the hook bolt cannot be detached from the striker plate but it firmly ties the door to the door frame.

The widened body part protects the hook parts if attempts are made to affect the hook bolt by hitting it with a chisel either upwards or downwards. Furthermore, the widened body part can improve the lock's endurance against lateral load because front plates usually tend to break at the corners of bolt openings. With the bolt and front plate structure according to the invention, load is partially divided across four corners instead of two as previously.

The body part preferably comprises blocking elements that are arranged on both sides of the body part in the lengthwise direction of the front plate and, in relation to the front plate opening, are arranged so that they prevent the hook bolt from being pulled further out of the lock body from the normal locking position. The blocking elements make the hook body too large to go out of the front plate opening in case the sections of the bolt's hook parts located inside the lock body would break due to tensile load applied to the hook body.

The hook parts are mainly U-shaped as is known from prior art, and said side elements are thus shaped to allow turning movement of the hook parts. This design makes it possible to arrange as much material as possible at the hook parts to improve the strength of the hook bolt.

The operation of the hook parts when the hook bolt is moved from the striker plate opening to the lock body can be secured by arranging a control element inside the lock body that is arranged to cooperate with the inner leg of the hook parts so that when the hook bolt is pulled in, it makes the hook parts turn in relation to the striker plate opening to a position in which the hook bolt can be pulled out of the striker plate opening.

In the following, the invention will be described in detail by referring to the enclosed schematic drawings, in which - Figure 1 illustrates a door lock according to the invention together with the striker plate viewed from the side, partially opened and with the hook bolt in the released position,

- Figure 2 illustrates the door lock of Figure 1 viewed from the front,

- Figure 3 illustrates the door lock and striker plate of Figure 1 in a situation in which the hook bolt is partially located inside the striker plate,

- Figure 4 illustrates the door lock and striker plate of Figure 1 in a situation in which the hook bolt is in its fully locked position inside the striker plate, and

- Figure 5 illustrates the door lock of Figure 4 viewed from the front without the striker plate.

In the figures, reference number 1 refers to a door lock for installation in a door or similar turnable wing, and reference number 11 refers to a striker plate in the door frame. For the sake of clarity, the actual door and door frame are not shown.

The door lock 1 comprises a lock body 2 equipped with a front plate 3, the lock body being embedded in a door or similar and containing a hook bolt 4 that can

be moved back and forth using a key or other actuator. The hook bolt includes a plate-like body part 5, hook parts 6 turnably mounted on both sides of the body part with a pivot 7, and side elements 8 attached to the body part 5 below the hook parts 6.

In the situation in Figure 1 , the door lock is in the open position, and the hook bolt 4 is in its released position inside the lock body 2. The inside of the lock body also houses a control element 10 that affects the leg 6a of the U-shaped hook parts 6 and keeps the hook parts 6 in a position that allows the hook bolt 4 to be moved out of the lock body 2.

Figure 3 relates to two situations. When the hook bolt 4 is moved outwards from the lock body 2, the leg 6a of the hook parts contacts the inner surface of the front plate 3, whereupon the hook parts 6 turn around the pivot 7 into the opening 11 a in the striker plate 11 , eventually coming to the locked position illustrated in Figure 4. In case the hook bolt 4 is being moved away from the position illustrated in Figure 4 to its released position inside the lock body 2 in the situation in Figure 3, when the leg 6a of the hook parts contacts the control element 10, it forces the hook parts to turn around the pivot 7 in the opposite direction to a position in which the hook bolt can be pulled out of the opening 11 a in the striker plate 11.

As apparent from Figure 2, the hook parts 6 and side elements 8 are installed on both sides of the body part 5 of the hook bolt 4. However, in the lengthwise direction of the front plate 3, the body part 5 is somewhat wider than other parts of the hook bolt, and for this reason the opening 3a in the front plate 3 also has cutouts 3b. This arrangement improves the strength properties of the hook bolt 4 and the front plate 3 against tensile load applied on the hook bolt from the side in an attempt to break it. A similar purpose is served by blocking elements 9 arranged on both sides of the body part 5, which in a tensile load situation will resist pulling the hook bolt out of the lock body 2 regardless of the legs 6a of the hook parts 6 of the hook bolt. This way the door lock 1 and its hook bolt 4 are

furnished in the best possible way on both the striker plate 11 side and the front plate 3 side against breaking attempts particularly based on tensile load.

It is clear that also the striker plate opening 11 a can be preferably fitted with cutouts corresponding to the cutouts 3b in the front plate opening 3, which will further improve the ability of the striker plate opening to resist tensile load.

The surfaces 8a of the hook parts of the side elements 8 of the hook bolt's body part 5 are shaped so that on the one hand, they allow the turning movements of the hook parts 6, but on the other hand, the additional material represented by them improves the overall strength of the hook bolt 4 at the positions of the front plate opening 3a and the striker plate opening 11 a.

The invention is not limited to the embodiments presented but several variations can be thought of within the scope of the enclosed claims.