This invention relates to an opening mechanism for a door closer of the type comprising a housing which can be fixedly mounted on a wall and which via a rotatable shaft supports a pivot arm which is connectible to a door or the like and which, when the door is opened, bring about tem¬ porary tensioning or compression of a spring mechanism incorporated in said housing, for automatically returning the door to closed position after completion of the open¬ ing movement, said opening mechanism comprising a driver which is movable by means of an electric motor via a mechanical transmission back and forth between an inactive position or initial position and an active position and which, on the one hand, when the door is opened manually remains in its inactive position in which it leaves the pivot arm unaffected and, on the other hand, when the motor is energised causes the pivot arm to move for open¬ ing the door without the need of any manual actuation of the door.

Background of the invention

Conventional door closers are relatively inexpensive and adequately serve their purpose, i.e. after manual opening of the door bring about automatic closure thereof. Especially serviceable are such modern door closers which have a built-in accelerated closure effect, meaning that the door during its return movement towards closed posi¬ tion initially moves at a moderate speed ensuring a uni¬ form closure process, and finally at a substantially in- creased speed with a substantially increased force for a short period of time so as to efficiently overcome the resistance produced by locking bolts, friction and such like, thus bringing about a distinct closure of the door at the final stage of the closure process. For operating doors, use is also made of mechanical door openers, especially on public premises, business pre¬ mises and the like. By means of these door openers, the

door is not only closed but also opened, more specifically by means of some type of remote control system electrical¬ ly activating a hydraulic assembly associated with the door. The remote control system generally consists of manually operable trigger means placed at a certain dis¬ tance in front of the door or of photocells which automa¬ tically sense if a person is approaching the door and then open it. A common feature of prior art door openers how¬ ever is that they involve very high manufacturing and in- stallation costs. Another major drawback is that it is im¬ possible after a power failure to manually open the door before a special switch has been manually switched from one state to another. If a panicky situation should arise on premises subjected to a power failure before the door opener has been switched, most unpleasant consequences may result.

Attempts have previously been made to supplement the simple and inexpensive door closer with a special opening mechanism which can be temporarily activated in order to bring about, if desired, mechanical opening of the door against the action of the door closer. Such an opening mechanism of the type stated by way of introduction is previously known from US Patent 4,348,835. This known mechanism however suffers from several drawbacks. Thus, the mechanism according to US 4,348,835 uses a transmis¬ sion in the form of two cooperating obliquely cut gears or angular gears, one of which is permanently non-rotatably connected to the shaft of the door closer which serves to rotate and tension a spring arrangement in the door closer when the door is opened, and which causes an arm to pivot, while the other angular gear is connected to a remote- controlled electric motor. In order that the second angular gear when in the normal state should be out of en¬ gagement with the door closer, it must be not only rotat- able but also axially movable in a manner not described in more detail in the patent. This means that the known con¬ struction, if practicable at all, will become most expen-

sive and complex. Moreover, the teeth of the two gears must, on each particular occasion of engagement, be hel accurately fitting in with each other, for otherwise bo an irritating noise and a delay of the correct engageme will result. Another drawback inherent in the known con¬ struction is that the opener operates at a constant spee during the entire opening process unless the motor is co trolled in a special manner. It should also be noted tha the construction according to US 4,348,835 requires a sp cial device for holding the door open during the time re quired for allowing a person to pass through the door. Summary of the invention

The present invention aims at overcoming the above- mentioned drawbacks of the opening mechanism.known from 4,348,835 by providing an inexpensive opening mechanism which is reliable and operates without affecting the fun tion of the conventional door closer in respect of the above-mentioned accelerated closure effect. According to the present invention, this is achieved in that the driv is adapted to move rectilinearly between its end positio and, when operated, to act on an auxiliary arm rigidly connected to the rotatable shaft and extending at an ang to the rectilinear path of movement of the driver so as be operated with a relatively large lever arm during the initial stage as well as the final stage of an opening operation, but with a shorter lever arm during an inter¬ mediate stage thereof.

Brief description of the accompanying drawings In the drawings, FIG 1 is a top plan view of a door closer and an openin mechanism according to the invention applied ther to, Fig. 2 is a vertical front view of the opening mechanism and FIG.3 is a perspective view showing an opening mechanis applied to a door.

Detailed description of a preferred embodiment of the in¬ vention

In the drawings, 1 generally designates a door closer comprising in conventional manner a housing 2 which via a rotatable shaft 3 supports a pivot arm 4 in turn articu¬ lated to a link arm 5 having an attachment 6 which can be applied to the pivotal door or door leaf. The housing 2 can be applied to the wall surrounding the door or to the door frame, more specifically in the region immediately above the door. The rotatable shaft 3 may advantageously be a through shaft to permit mounting the pivot arm 4 on either of the sides of the housing to make it possible to apply the door closer to both right-hung and left-hung doors. When the door is manually opened, the arm 4 is swung clockwise in Fig. 1 so as to tension or compress, through the rotatable shaft 3, a spring mechanism (not shown) which is incorporated in the housing 1 and which, after completion of the opening movement, causes the door to automatically return to closed position. To the conventional door closer 1 is added, as spe¬ cial accessory equipment, an opening mechanism according to the invention. This opening mechanism comprises an electric motor 8 mounted on a frame 7, a transmission ge¬ nerally designated 9 and, in this case, two drivers 10, 10'. The drivers 10, 10' advantageously are in the form of wheels or rollers provided with bearings and mounted on a shaft 11 supported by a slide member 12 movable back and forth. More particularly, the slide member 12 is rectili¬ nearly movable back and forth along a guide 13 fixedly mounted on the frame 7. The wheels 10, 10' serving as drivers are adapted to cooperate with a pair of auxiliary arms 14, 14' which are rigidly or non-rotatably connected to one and the same through shaft 3 to which the pivot arm 4 is also rigidly connected. The auxiliary arms 14, 14' extend at an acute angle to the pivot arm 4 and also at an acute angle to the rectilinear path of movement defined by

the wheels 10, 10' when the slide member 12 moves along the guide 13.

The electric motor 8, which in practice may be a con¬ ventional windscreen-wiper motor, has an output drive shaft 15 provided with a gear rim 16 non-rotatably con¬ nected to the shaft. In the illustrated embodiment, the transmission 9 consists of a chain which is passed around the gear rim 16 and one end of which is fixedly connected to the slide member 12 by means of an attachment 17, while the other end of the chain is fixed to a relatively weak tension spring 18 whose end remote from the chain is fixed to the frame 7 at a point designated 19. To the attachment or member 17 is further fixed one end of a second tension spring 20 whose oppposite end is fixed to the frame 7 at a point 21. The second tension spring 20 is advantageously more powerful than the first spring 18. In practice, the motor 8 is suitably controlled by an electronic circuit with a built-in time relay or the like by means of which the drive shaft 15 can be caused first to rotate counter- clockwise in Fig. 2, and then remain stationary in a given position for a predetermined period of time and finally caused to rotate in the opposite direction of rotation.

As appears from Fig. 2, the slide member 12 may be guided in a manner known per se along the guide 13 by means of a plurality of balls 22 arranged in an endless configuration.

The opening mechanism now described operates in the following way. If it is desirable to open a door mechani¬ cally by means of the inventive opening mechanism, the motor 8 is energised in a suitable manner, for instance by operating a trigger mechanism or the like. The shaft 15 is then caused to rotate counterclockwise in Fig. 2, the por¬ tion of the chain 9 extending between the gear rim 16 and the point of attachment 17 imparting to the slide member 12 a rectilinear movement to the left in Fig. 2. The wheels 10, 10' serving as drivers will then entrain the auxiliary arms 14 and cause them to pivot, thereby rotat-

ing the shaft 3, such that the pivot arm 4, together with the associated link arm 5 is also caused to pivot for opening the door. The movements of the slide member and the drivers 10, 10' between the two opposite end positions may in practice be determined by two limit switches 23, 24, the distance therebetween being selectable so that the mechanism opens the door e.g. to a position at 90° to the closed position. When the door has been opened, e.g. through 90°, the motor 8 is stopped and is allowed to re- main stationary for a suitable period of time, for in¬ stance 5-30 seconds, whereupon it is reversed so that the drive shaft is rotated clockwise in Fig. 2. The tension spring 20 acting as return spring will then return the slide member 12 to the initial position shown in Fig. 2. During both the forward movement and the return movement of the slide member, the spring 18 ensures that the chain passing around the gear rim 16 is held properly stretched. Advantageously, the speed of rotation of the drive shaft 15 of the motor is so selected that the driver wheels 10, 10' move faster than the auxiliary arms 14, such that the driver wheels leave their engagement with the auxiliary arms as soon as the return movement of the slide member is started. In this manner, the ordinary closure characteris¬ tics of the door closer 1 remain unaffected by the driver wheels, whereby the accelerated closure effect integrated in the door closer is automatically provided at the end of the door closing process without any interference from the driver wheels. Another advantage of the opening mechanism now described is that the opening movement becomes re- latively smooth in both the initial stage and the final stage, but faster during the intermediate stage, since the driver wheels 10, 10' during their rectilinear movement act on the auxiliary arms 14, 14' with a relatively large lever arm during the initial stage and the final stage, whereas with a shorter lever arm during the intermediate stage when the auxiliary arms in fact extend at nearly 90° to the rectilinear path of movement of the driver wheels.

If a person who is to pass through the door does not wish to use the opening mechanism, the two driver wheels 10, 10' remain in their inactive positions or initial positions according to Figs. 1 and 2, and manual opening of the door in entirely conventional manner entails that the spring mechanism in the housing 1 is compressed for subsequent automatic closure of the door. This can be achieved since the auxiliary arms 14, 14', in connection with manual opening of the door, simply leave their en- gagement with the driver wheels 10, 10' and passively ac¬ company the shaft 3 during the rotary movement thereof. As compared to the opening mechanism known from US Patent 4,348,835, the inventive opening mechanism is most inexpensive and, in combination with the also inexpensive door closer, offers an economically very competitive al¬ ternative to the conventional door opener. It may be pointed out that the inventive opening mechanism not only can be designed as a separate accessory unit which can be mounted on an existing door closer, but also can be de- signed as an integrated part of the door closer.

It goes without saying that the mechanism can be mo¬ dified in may different ways. Although it is preferred to provide it with two driver means and two auxiliary arms (producing a distributed action of force on the opposite sides of the slide member), it is conceivable to provide the mechanism with one such means only. Further, it may consist of a projection other than a wheel.