To detect elevator overspeed, the speed of the elevator car is monitored during both downward and upward travel by means of an overspeed governor, which, when an overspeed situation occurs, reacts e. g. by activating a safety de- vice called safety gear mounted on the elevator car, which stops the elevator car safely before the car reaches an excessive overspeed. In most cases this happens in a situation where, after the occurrence of a disturbance, the elevator car starts falling downwards at an increasing speed. The overspeed governor is usually a device based on centrifugal force and comprising a rope loop connected to a safety gear mounted on the elevator car, in which loop a rope runs around diverting pulleys of the overspeed gover- nor with the motion of the elevator car. If the elevator car reaches an excessive speed, then the overspeed gover- nor will be locked by the action of centrifugal force, stopping the said rope, with the result that the safety gear is activated and stops the elevator car by gripping an elevator guide rail with a wedge.

In prior-art overspeed governors based on centrifugal force, the overspeed governor rope passes around an over- speed governor rope pulley placed in the upper part of the shaft or in the machine room and runs through the whole length of the shaft to the lower part of the shaft, where the rope passes around a diverting pulley. The rope is tensioned by a counterweight attached to the diverting pulley in the lower part of the shaft and pulling the lower diverting pulley downwards. Between the overspeed governor and the diverting pulley in the lower part of the shaft, the rope is fastened to the safety gear mounted on the elevator car, so that the rope runs along with the

elevator car.

A problem with the use of overspeed governor rope counter- weights is the space taken up by the counterweights espe- cially when a limited space is available below the eleva- tor car. The counterweights take up space in the vertical direction, so when the shaft space below the elevator car is low, it is difficult to find room for the counter- weights below the overspeed governor diverting pulley, which has to be located substantially below the lower position of the elevator car. A further problem is that, in prior-art solutions based on centrifugal force, the overspeed governor can only be placed in the upper part of the rope loop, which constitutes a limitation of flexibil- ity of design and layout.

The object of the present invention is to overcome the above-mentioned drawbacks and achieve a simple, safe and compact safety gear arrangement in which the overspeed governor can be disposed either in the upper or in the lower end of the shaft and which can also be used as an installation-time safety gear. A further object of the invention is to achieve an economical and versatile safety gear arrangement that can also be used for detecting an elongation or rupture of the overspeed governor rope. The safety gear arrangement of the invention is characterized by what is disclosed in the characterization part of claim 1. Other embodiments of the invention are characterized by what is disclosed in the other claims.

The solution of the invention has the advantage that the overspeed governor need not be placed only in the upper part of the shaft or in the machine room, but, depending on the case, the overspeed governor may be located at either the upper or lower end of the overspeed governor rope loop. A further advantage is that no space consuming rope weights for rope tensioning are needed, which is why

the solution can be installed in a small space and is therefore very well suited for use in situations where the space above or below the elevator is limited. In addition, the solution of the invention is simpler and more economi- cal in structure than prior-art solutions. This is due, among other things, to the fact that the safety gear con- tactor and the tensioning contactor can be combined. An additional advantage is that the elevator safety gear is capable of gripping when necessary even in cases where the overspeed governor rope is broken or elongated and the overspeed governor would therefore normally be no longer operational in an overspeed situation. Another advantage is that the new safety gear arrangement can also be used during installation as an installation safety gear in combination with a pedal.

In the following, the invention will be described in de- tail with reference to an embodiment example and the at- tached drawings, wherein Fig. 1 presents a simplified side view of the safety gear arrangement of the invention, and Fig. 2 shows in magnified side view how the overspeed governor rope is fastened in the safety gear arrangement presented in Fig. 1.

The figures present an elevator car 1 arranged to travel upwards and downwards along vertical guide rails 2, guided by guides 12. The figure does not show the elevator drive machine or suspension structures, which are inessential to the present invention. The elevator car is provided with a safety gear 3 comprising at least a safety lever 7, whose movement causes a wedge to move in a gripping device hous- ing 13 so that the wedge gets wedged between the gripping device housing 13 and the guide rail 2, thus stopping the elevator car 1.

The movement of the safety lever 7 is usually originated by an overspeed governor 4 based on centrifugal force, which in this embodiment has been installed in the lower part of the elevator shaft. The rotating overspeed gover- nor 4 is driven by a rope 6 placed in the elevator shaft and having its first end fastened to the free end of the safety lever 7. From the safety lever 7, the rope 6 goes to the overspeed governor 4 and passes under the diverting pulley of the overspeed governor 4, after which the rope 6 goes upwards and passes around a diverting pulley 5 mounted in the upper part of the elevator shaft and then goes downwards again and is connected by its second end to the safety lever 7, the rope being tensioned by a tension- ing spring 8 placed below the safety lever. When the ele- vator car 1 is moving at normal speed, the overspeed gov- ernor rope 6 moves along with the elevator car 1 and the safety lever 7 remains in the normal position.

The tensioning spring 8 works like a prior-art counter- weight, keeping the rope 6 tight. The safety gear arrange- ment also comprises a back stop 9 placed below the ten- sioning spring. If the back stop 9 is disposed at a suit- able distance from the spring, the tensioning spring 8 will activate the safety gear 3 even when the rope 6 be- comes slack or breaks. In such a situation, the rope 6 will no longer compress the tensioning spring 8 towards the safety lever 7 but the released spring will hit against the stop face of the back stop 9, with the result that the supporting force lifts the safety lever 7 upwards and the wedge of the safety gear 3 is pushed between the gripping device housing 13 and the guide rail 2, stopping the motion of the elevator car.

The safety gear 3 is additionally provided with a contac- tor 10, which is activated in a when the safety gear grips and also in situations where the rope 6 of the overspeed

governor 4 becomes slack or breaks. Upon activation of the contactor 10, the elevator control system receives infor- mation regarding the disturbance and reacts according to the situation, e. g. by switching off the driving power to the elevator.

The safety gear 3 also comprises a back stop 11 in the elevator car to support the safety lever 7, which rests on it in a normal situation.

The safety gear arrangement of the invention can also be utilized as an installation safety gear at installation time. In this case, the brake pedal of the safety gear used during installation is connected by a rod to the safety lever 7, so that when the pedal is pressed down, the safety gear 3 is activated and the falling movement of the elevator car 1 is stopped. The connecting rod is not shown in the figures.

It is obvious to the person skilled in the art that the invention is not limited to the example described above, but that it may be varied within the scope of the claims presented below. Thus, for example, the overspeed governor may also be mounted in the upper part of the elevator shaft if this is more sensible in a given situation. Like- wise, the structure of the safety gear 3 may differ from that described above.