LOCK FOR INTERNAL DOOR

The invention relates to a lock for internal door in accordance with the preamble of claim 1.

Locks for internal doors are used in doors, which primarily separate various kinds of interior spaces from another so that the doors may easily be locked temporarily, if so required. One typical application is a toilet door. As these locks are manufactured in large volumes and may be in frequent use, their construction is important in terms of dependability on one hand and manufacturing costs on the other hand. Prior art locks for internal doors have, in spite of their fairly simple locking operations as such, a quite complicated structure, which tends to increase the manufacturing costs. On the market, there is e.g. a lock for internal door, which has two separate bolts operated from their respective operating axes.

A purpose of the invention is to provide an improved lock for internal door, in which the above needs are taken into account better than before.

The objects of the invention are achieved as disclosed in the appended claim 1 , and more closely as explained in the other claims. According to the invention, the lock casing is provided with a locking piece, which is removable independent on the latch bolt and which may be moved by means of a second follower from a first position, where it allows the retraction of the latch bolt, to a second position, where it is adapted to prevent the retraction of the latch bolt and to provide dead-locking of the latch bolt. Thus, one single bolt in the lock may be actively deadlocked in a simple manner.

A force transmission means and a first follower are preferably arranged with respect to one another so that the force transmission means can be turned to a position, in which force transmission from the first follower to the force transmission means is disconnected and the force transmission means is spring-loaded toward said position disconnecting the force transmission. Further, the locking piece is provided with a guide surface, which is adapted to determine the turning freedom of the force transmission means in each case in said spring-loaded direction. This arrangement makes it possible to manage the position of the force transmission means at each specific time by means of the locking piece. The arrangement is also advantageous for the reason that the latch bolt itself cannot be affected by exertion of force on the lever handle.

In a preferred embodiment, the locking piece is provided with a first and a second restricting member, which are adapted to cooperate with said second follower in order to make the locking piece move. At the same time, the restricting members may preferably define the turning freedom of said second follower.

It is advantageous to arrange the latch bolt, in a manner known as such, so that it can be pulled outwards, from the lock casing against the force of a spring for turning the latch bolt 180- in order to change between right-hand and left-hand usage of the lock. To this end, said second restricting member, which is located farther away from the protruding end of the latch bolt, is adapted to allow said pulling of the latch bolt. In a practical application, said second restricting member, which is located farther away from the protruding end of the latch bolt, is given a resilient construction.

The locking piece may also with advantage be provided with a spring, which urges said second follower into its extreme position in each case. This tends to secure the operation of the lock.

For guiding the movements of the locking piece there may be stationary stoppers in the lock casing and moreover, said second follower may preferably be shaped so as to guide the locking piece.

A cost-effective solution is provided, if the locking piece as well as the restricting and resilient members therein are manufactured of plastic as one piece by using injection moulding. Thus, a plurality of members and components may be united as one piece. This manufacturing method may naturally be applied also to the manufacture of several other parts of the lock casing. For instance the latch bolt and the spring for changing it between right-hand and left-hand usage may, depending on the application, also be manufactured as one piece, if so required.

In the following, the invention is explained by way of example with reference to the appended drawings, in which

Figure 1 depicts a lock for internal door according to the invention with the cover of the lock casing open, illustrating the normal state thereof, in which the latch bolt is not locked;

Figure 2 depicts the lock for internal door according to Figure 1 illustrating similarly the state, in which the latch bolt is locked; and

Figures 3a - 3d depict a locking piece included in the lock for internal door according to the invention, shown from various perspectives.

In the drawings the reference number 1 refers to a lock casing in a lock for internal door provided with a front plate 1 a, through the opening of which a reciprocable latch bolt 2 protrudes. The latch bolt is guided by the opening of the front plate and a stopper 1 b in the lock casing. A spring 3 urges the latch bolt 2

into its protruding position. Further, the lock casing comprises a first operating axis 4, on which a handle-actuated follower 5 is most suitably mounted, which follower is by means of a turnable force transmission means 7 arranged to move the latch bolt 2 to a retracted position inside the lock casing (not shown) for opening the door. The lock casing also comprises a second operating axis 1 1 , on which a second follower 12 is similarly mounted, which follower is turnable by a key, turning knob or the like, depending on the application, for locking the latch bolt 2 from the other side of the door optionally into its protruding position.

The lock casing is provided with a spring 6 for the first follower 5 for holding the handle (not shown) mounted on the operating axis 4 normally in a horizontal position. The follower has a cam member 5a, which is in cooperation with a cam member 7a of the force transmission means 7 for turning the force transmission means 7 counter-clockwise around a guiding pin 8 against the force of a spring 9 in Figs. 1 and 2. Then, a protrusion 7b of the force transmission means moves the latch bolt 2, by means of a stopper 2a arranged therein, to the right in the figures, i.e. into the lock casing 1.

The second follower 12 is provided with a guide opening 12a, which is shaped so as to enable the operation of the follower 12 by either a key or a turning knob or the like equipped with a quadratic spindle. The lock casing is also provided with a locking piece 13, which may be moved by a cam member 12b of the follower 12 from the position according to Fig. 1 over to the position according to

Fig. 2, in which it locks the latch bolt 2 by means of a locking member 13a into its protruding position. The movements of the locking piece 13 are guided by the stopper 1 b in the lock casing, the stopper 2a on the body of the latch bolt and a guide surface 12c of the second follower 12. In the normal situation according to

Fig. 1 , a recess 13f in the locking piece allows the turning movement of the protrusion 7b on the force transmission means for retracting the latch bolt 2.

To bring about the movements, the locking piece 13 is provided with a first restricting member 13c and a second restricting member 13d. At the same time these define the turning freedom of the cam member 12b and thus also that of the follower 12, since the locking piece 13 is, in its extreme positions shown in Figs. 1 and 2, in contact with the inner surfaces of the lock casing 1. The locking piece is also provided with a spring 13e, which urges the cam member 12b in both extreme positions of the locking piece 13 toward the respective extreme positions of the follower 12.

The locking of the lock occurs as follows. While the follower 12 in Fig. 1 is turned anti-clockwise by a key or a turning knob installed on the operating axis 1 1 , the cam member 12b of the follower turns at the same time against the force of the spring 13e and, when hitting the restricting member 13c, moves the locking piece 13 until it takes the position according to Fig. 2, in which it is located immediately behind the enlarged end of the latch bolt 2. In this position the latch bolt 2 is locked. The suitable shaping of the cam member's 12b end and the spring 13e also prevent any attempts to move the latch bolt 2 into the lock 1 casing by manipulating it by a tool.

It appears from Figs. 1 and 2 that simultaneously with the movement of the locking piece 13 to its position, which locks the latch bolt, also the force transmission means 7 turns into the position according to Fig. 2, as the spring 9 acts on the protrusion 7b of the force transmission means keeping it constantly in contact with the guide surface 13b of the locking piece. As a consequence of this turning movement the cam member 7a of the force transmission means moves into the position of Fig. 2, in which the force transmission from the follower 5 to the force transmission means 7 is disconnected. Thus, exertion of force from the operating axis 4 does not have any effect on the locking of the latch bolt 2.

It is possible to choose and, if necessary, change between the right-hand and left-hand usage of the lock in a manner known per se without opening the lock casing. This is performed by pulling the latch bolt 2 from its end further outwards against the force of the spring 10 so that the entire enlarged end of the latch bolt 2 comes out of the lock casing. Then the latch bolt may be turned 180°, whereby the lock is changed from right-hand usage to left-hand usage or vice versa. As Fig. 1 reveals, the restricting member 13d of the locking piece would, in principle, prevent this, since at the same time as the latch bolt is pulled outwards, its stopper 2a acts on the protrusion 7b of the force transmission means, which seeks to move the locking piece 13 accordingly. On account of this, the restricting member 13d is made resilient. In the embodiment of the figures the restricting member 13d is by means of a resilient arm 13d' and a stationary pin 13d" in contact with the locking piece 13. The structure of the locking piece 13 appears from Figs. 3a - 3d.

The invention is not limited to the shown embodiment, but several variations are conceivable within the scope of the appended claims.