The present invention relates to a lock mechanism for locking a door, as more particularly a metallic fire door, which lock mechanism comprises a latch mechanism which is mounted in the body of the door, on the upper and/or lower edge of it, and in its latching position locks the door to the door frame, an opening means, such as a handle or a push-button for unlocking the lock mechanism, and a vertical pull rod, disposed within the body of the door, which by means of its vertical movement transmits the movement of the opening means to the latch mechanism.

The fire doors are made of metal as are also the latch mechanisms and the pull rods. When they bump against each other, the metallic parts cause considerable noise problems, for instance at work places.

In the lock mechanisms, the pull rods have traditionally served as both pull and locking rods, and have therefore had to be sturdy, inflexible and heavy, and naturally also expensive.

In new lock arrangements, separate pull rods for transmitting the command of the opening means to unlock, and locking latch element for locking the door have been used. Then, the pull rods do not have to be as solidly built and heavy as before. Essential is only that the rod is capable of unlocking a locked latch mechanism by pulling. These pull rods made of lighter and thinner bar material are flexible. The pull rods can even, depending on the design of the latch mechanism, be connected to the latch mechanism so that the pull rod can move laterally. The pull rods of this kind can easily, when the door is opened or closed, vibrate or swing in the body of the door and hit the structural parts of the door causing noise.

It is therefore a principal object of this invention to eliminate the above problem and to provide an improved lock mechanism which does not have the above mentioned drawbacks. The invention is characterized by the features set forth in the appended claims.

In the lock mechanism according to the invention, in which the pull rod is made of a flexible material, such as a wire or the like, and/or connected movably to the latch mechanism so that it can move also laterally inside the body of the door, one or several damping members, such as rubber or plastic rings, which prevent the pull rods from laterally hitting the structural parts of the door, are disposed on the pull rod.

The dampening member made of rubber or plastics is preferably ring-shaped but can also be cylindric or have a quadratic, polygonal or completely asymmetric cross section. A rubber or plastic ring, in which there is an opening which is slightly smaller than the cross section of the pull bar, can by stretching it be slipped on the rod, where it stays firmly in place. It is essential that the dampening member, due to its size, shape or the manner of fastening it, stays firmly in place on the rod, and that it forms laterally a large enough dampening layer between the pull rod and the wall structure of the door. The dampening layer should preferably prevent contact between the pull rod and the structural parts of the door. The dampening members can be made of other soft material than rubber or plastics.

An exemplary embodiment of the present invention will now be described in more detail with reference to the accompanying drawing, which shows schematically a cross- sectional view of a portion of the body of a door, in which

a latch mechanism and a pull rod according to the invention is disposed.

The figure shows a body 10 of a door, in the upper part of which is disposed an upper latch mechanism 12, in which there is a locking latch 14 and a slide 16 moving vertically, by means of which the locking latch 14 can be unlatched. In the lower part of the door there is a corresponding latch mechanism, which is not shown. A push- button 20, by means of which the lock mechanism can be unlocked, is disposed on the surface 18 of the door in the middle of the door. Pull rods 22, 24, which transmit the movement of the push-button to the latch mechanisms, are further disposed in the body of the door 10. The pull rods 22, 24 are connected to the push-button by means of a pulling mechanism 26, of which only a portion can be seen in the figure.

The pull rod 22, which is a wire, is disposed to move near the wall structure 28 of the door. The pull rod is further connected relatively freely to the slide 16 of the latch mechanism 12 so that the wire in its rest position can swing laterally relatively freely. On the pull rod 22 or pull wire, which it also could be called, there is disposed two dampening members 30, such as two rubber rings, which when the wire is swinging, break the force against the wall structures and prevent the wires from coming into contact with them. The pull rod is provided with a suitable number of damping members along the whole length of the same.

The arrangement according to the invention renders it possible to eliminate the noise problems caused by the lateral movements of the pull rod.