A METHOD FOR AVOIDING UNWANTED SAFETY GEAR TRIPPING IN A SAFETY STOPPING SYSTEM OF AN ELEVATOR SYSTEM, A SAFETY STOPPING SYSTEM, AND AN ELEVATOR SYSTEM
FIELD OF THE INVENTION
The present invention relates toa method for avoiding unwanted safety gear tripping in a safety stopping system of an elevator system, a safety stopping sys¬tem, and an elevator system.
BACKGROUND OF THE INVENTION
In prior art/ an elevator system comprises an elevator car which is connected to a counterweight via suspen¬sion ropes which go over a traction wheel driven by a hoisting machine. The elevator car and thecounter-weight are both guided vertically by respective guide rails inside ashaft. In the following, the elevator car and thecounterweight are referred to as the moving mass.The elevator system further comprises a safety circuit having a plurality ofnormally closed safety switches for monitoring the safety status of the ele¬vator innormal operation. If the safety of the eleva¬tor is somehow compromised, at leastone of the safety switches is opened, the hoisting machine is de-energized andmachinery brakes are engaged so as to de¬celerate the moving mass forguick stop.
The elevator system further comprises an overspeed governor system for the elevator car, which has a'gov-ernor rope loop directed up fromthe elevator car, over an overspeed governor pulley, then down andunder a tension weight pulley connected to a tension weight and thenup again - to the elevator car to be connected to a synchronization linkagefor tripping an elevator car safety gear. A corresponding overspeedgovernor system can be attached to the counterweight.

The synchronization linkage has synchronization levers which make thesafety gear of the moving mass to engage the guide rails of the movingmass when at least a pre-determined force is applied to the synchronizationlin-kage by the governor rope. This predetermined force is acting againstspring forces of synchronization lever springs such that the synchronization lever engages the safety gear when the force applied by the governor rope exceeds the synchronization lever spring force.The overspeed governor system supervises the speed of the moving mass,and, if this speed exceeds a predetermined tripping speed which is above a rateds-peed of the elevator, it activates the machinery quick stop operation and,simultaneously, decelerates the governor rope. This deceleration of thegovernor rope acts against the spring forces of synchronization lev¬er springssuch that the synchronization lever engages the safety gear, bringing theelevator car into an emergency stop.
To summarize, a quick stop operation of the machinery is initiated whenever theelevator safety circuit indi-cates a compromised safety status of the elevator. Additionally, if the compromised safety status is a result of an overspeedcondition of the moving mass, detected.by overspeed governor, an emergencystop oper-ation is activated by engaging the safety gear of the moving mass.
However, in high rise elevators, the elevator travel and speed increase such thatthe inertia of the gover¬nor rope increases substantially. This brings a new challenge during elevator quick stops carried out by the hoisting machine brakes. Namely, when the over-speedgovernor rope having the increased lengthdecele-rate during the above explained quick stop, a large

force is applied to thesynchronization linkage, be¬cause the inertia of the overspeedgovernor rope is-large. As a result, the decelerating governor rope is capable of producingforces to the synchronization lin¬kage which exceed the needed force toengage the safety gear when the moving mass is decelerated. In other-words, the safety gear might be unwantedly engaged or tripped during quickstop although the speed of the moving mass has not exceeded thepredetermined tripping speed for engaging the safety gear.
One solution for preventing unwanted safety gear trip-ping is to increase thesynchronization lever spring' force. However, this has an effect on the design ofthe overspeed governor since the European lift standard EN-81-20 code requires that the tensile force in the overspeed governor -rope produced by the governor, when tripped, shall be twice the force that is necessary to engage the safety gear via the synchronization lin¬kage . Stronger synchronization leads to biggerovers-peed governor rope tensile forces and, consequently a stronger and, thus,heavier overspeed governor rope due to required safety factor. If one wishes to increase the force required for tripping the safety gear by in-creasing the synchronization lever spring force to op-pose the inertial force of the governor rope, then, due to the EN-81-20 code, requirement, the tensile strength of the governor rope would have to be in¬creased which would cause the need for redesigning of the overspeed governor system. It is evident thatthis will finally lead to elevator systems in which there is no more feasible designwindow for overspeed gover¬nor and safety gear system.
Prior art systems, as known from e.g. documents JP 2626408, US 7,128,189, US 7,475,756 utilize springs

and US 4,083,432 utilizes a spring loaded weight for the same purpose.
OBJECTIVE OF THE INVENTION
The objective of the invention is to alleviate the disadvantages mentioned above.
In particular, it is an objective of the present in-vention to provide a simple and cost-effective measure and means for preventing the overspeed governor rope inertia from unwantedly engaging the safety gear.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a method for avoiding unwanted safety gear tripping in a safety stopping system of an elevator system. The safety stopping system comprises a machi¬nery brakefor decelerating a moving massso as to per¬form a guick stop of the moving mass, a safety gear-mounted to the moving mass, an overspeed governor, an overspeed governor ropeconnected to the moving mass of the elevator system, and a synchronization linkage-mounted to the moving mass for tripping the safety gear, the synchronization linkage comprising a lever armhaving a first endpivotally connected to the over-speed governor ropeand a second endfixedly connected to a spindle shaftto which a safety gear tripping arm-for tripping the safety gear is connected. According to the invention kinetic energy caused by inertia of the overspeed governor ropeto the lever armis dissi¬pated by implementing fluid viscous damping to dampen the rotary movement of the spindle shaftto prevent un¬wanted safety gear tripping when the upwards movement of the moving massis decelerated by the machinery bra-keto perform a guick stop of the moving mass.
The technical effect of the invention is that it pre¬vents the overspeed governor rope inertial forces from

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unwantedly engaging the safety gear. Further, existing overspeed governor components can be used to higher travels in high-rise elevatorswithout redesigning them because unintended and unwanted activation of the 5 safety gears does not happen in case of unplanned rap¬id stopping upwards.
In an embodiment of the method, the fluid viscous damping is performed by a fluid viscous damper acting 10 on a member of the synchronization linkage.
n an embodiment of the method,the fluid viscous damp¬ing is performed' by a fluid viscous damper cylinder acting on an arm or a rod connected to the spindle 15 shaft.
In an embodiment of the method,fluid viscous damping is performed by an oil damper cylinder.
2 0 In an embodiment of the method,the damping force is a non-linear function of velocity of a piston relative to a cylinder of the fluid viscous damper cylinder.
In an embodiment of the method, in velocities of the 2 5 piston relative to the cylinder of the fluid viscous damper cylinder smaller than a predetermined velocity the damping force is arranged to increase more forci¬bly than in higher velocities.
30 In an embodiment of the method, themoving mass is an elevator car.
In an embodiment of the method, themoving mass is a counterweight. 35
According to a second aspect, the present invention provides a safety stopping arrangement for an elevator

6
system for stopping the movement of a moving mass. T the safety stopping arrangement comprises a machinery brakefor decelerating a moving massso as to perform a quick stop of the moving mass, a safety gearmounted to 5 the moving mass, an overspeed governor,an overspeed governor rope attached to a moving massof the elevator system, and a synchronization linkagemounted to the moving mass for tripping the safety gear, the synchro¬nization linkage comprising a lever armhaving a first
10 endpivotally connected to the overspeed governor ro-peand a second end,a spindle shaft to which the second end of the lever arm is fixedly connected, and a safe¬ty gear tripping arm for tripping the safety 'gear, the safety gear tripping arm being fixedly connected to
15 the spindle shaft. According to the invention the safety stoppingarrangement comprises a fluidviscous damper arranged to dissipate kinetic energy caused by inertia of the over speed governor rope to the lever arm to dampen the rotary movement of the spindle
20 shaft.
In an embodiment of the safety stopping arrangement, the fluid viscous damper is arranged to act on a mem-ber of the synchronization linkage -
25
In an embodiment of the safety stopping arrangement, the fluid viscous damper is a fluid viscous damper cy-linder acting on an arm or a rod connected to the spindle shaft.
30
In an embodiment of the safety stopping arrangement, the fluid viscous damper is an oil damper cylinder.
In an embodiment of the safety stopping arrange-3 5 ment,the damping force is a non-linear function of ve¬locity of a piston relative to a cylinder of the fluid viscous damper cylinder.

7
In an embodiment of the safety stopping arrange¬ment, moving mass is an elevator car.
5 In an embodiment of the safety stopping arrange¬ment, moving mass is a counterweight.
According to a third aspect, the present invention provides an elevator system comprising a moving mass
10 guided by a pair of guide rails to be vertically mova¬ble in an elevator shaft, a suspension rope attached to the moving mass, a traction wheel over which the suspension rope ■ is lead, a hoisting machine for driv¬ing the traction wheel to move the moving mass. Ac-
15 cording to the invention the elevator system comprises a safety stopping arrangement according to the second aspect.
It is to be understood that the aspects and embodi-2 0 ments of the invention described above may be used in any combination with each other. Several of the as¬pects and embodiments may be combined together to form a further embodiment of the invention.
2 5 BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to pro¬vide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the de-30 scription help to explain the principles of the inven¬tion . In the drawings:
Figure lschematically shows an elevator system accord-
ing to one embodiment of the invention,
35
Figure 2shows a detail A from Figure 1,

n \->
Figure 3 is an axonometric view of the safety stopping arrangement according to one embodiment of the inven-tion, and
5 Figure 4 is a diagram showing schematically the damp¬ing force being a non-linear function of the velocity of the piston relative to the cylinder of the fluid viscous damper cylinder in accordance with one embodi¬ment of the invention.
10
DETAILED DESCRIPTION OF THE INVENTION
In the following, description will be made to embodi-ments of the present invention. It 'is to be unders¬tood, however, that the description is given by way of
15 example only, and that the described embodiments are by no means to beunderstood as limiting the present j.nvention thereto.
.In particular, different exemplifying embodiments will
2 0 be described using, as anexample of an elevator system
to which the embodiments may be applied, an elevator system as depicted and explained in connection with Figs. 1 to 3.
25 It is to be noted that the following examples and em¬bodiments are to beunderstood only as illustrative ex-amples . Although the specification may refer to"an", "one", or "some" example(s) or embodiment(s) in sever¬al locations, thisdoes not necessarily mean that each
30 such reference is related to. the sameexample(s) or em-bodiment (s), or that the feature only applies to a singleexample or embodiment. Sinale features of dif¬ferent embodiments may also becombined to provide oth¬er embodiments. Furthermore, terms like "compris-
3 5 ing"and "including" should be understood as not limit-
ing the described embodimentsto consist of only those features that have been mentioned; such examples an-

9
dembodiraents may also contain features, structures, units, modules etc. thathave not been specifically mentioned.
5 The general elements and functions of described eleva¬tor systems, details ofwhich also depend on the actual type of elevator system, are known to thoseskilled in the art, so that a detailed description thereof is omitted.herein.However, it is to be noted that several 10 additional devices and functions besidesthose de¬scribed below in further detail may be,employed in an elevator system.
Figure 1 shows an elevator system and Figure 2 and 3
15 show details of the same. The elevator system has an elevator car 2 and a counterweight3, which are both acting as a moving mass and are connected to each oth-er bysuspension ropes 19. The suspension ropes 19 are going around a traction wheel20 which is driven by a
2 0 hoisting machine 21. A machinery brake 1 is arranged in connection with the hoisting machine for. decelerat¬ing amoving mass2, 3. so as to perform a quick stop of the moving mass. Because of the heavymass hanging on both ends of the suspension ropes 19, the suspension
25 ropes 19 do not slide on the traction wheel 20. When the traction wheel 20 is driven bythe hoisting machine 21 and rotates, the elevator car 2 and the counter¬weight 3 move. The elevator car 2 and the counter¬weight 3 are guided by guide rails 16 and 17 which are
30 mounted to the walls of the shaft 18 in which theele-vator system 1 is provided.
Figure 1 further shows an overspeed governor system 15 for the elevator car 2which comprises an overspeed 35 governor rope 5 both ends of which are connected to theelevator car 2 (the moving mass). The governor rope 5 goes around a governorpulley 22on the top side of

the elevator system and goes around a tension weightpulley 23 connected to a tension weight 24 on the bottom side of the elevator system. The governor rope 5 is connected to the elevator car 2 via a lever 5 arm 8 of a synchronization linkage 7 having tripping arms12 for tripping a safetygear 4 against both guide rails 16 of the elevator car 2.
Figure 1 further shows an overspeed governor system 15 10 for thecounterweight 3, which is similar to that ex¬plained for the elevator car 2. The overspeed governor system 15for the counterweight 3 comprises an over-speed 'governor rope 6 both ends of ' which areconne'cted to the counterweight 7 (the moving mass) . The over-15 speedgovernor rope 6 goesaround a governor pulley 22 on the top side of the elevator system and goesaround a tension weight pulley 23 connected to a tension weight 24 on thebottom side of the elevator system. The governor rope 6 connected to thecounterweight 7 2 0 via a lever arm 8 of a synchronization linkage 7 hav¬ing tripping arms 12 for tripping a safety gear 4 against both guide rails of the counterweight 7.
Referring to Figures 2 and 3, a safety stopping ar-
2 5 rangement. has a synchronization linkage 7. is mounted
to the moving mass, such as the elevator car 2 or counterweight 3 for tripping the safety gear 4. In this example of Figure 2 and 3 the synchronization linkage 7 is explained in connection with the elevator
3 0 car 2, but the counterweight 3 can be equipped with
similar synchronization linkage 7 as shown in Figure X. The synchronizat ion linkage 7 is arranged in the lower beam 25 of the sling 26 of the elevator car 2.
3 5 The synchronization linkage 7 comprises a lever arm 8. The lever arm 8 has a first end 9 pivotally connected to the over speed governor rope 5. A spindle shaft 11

11
is rot at ably bearing-mounted to the lower beam 25. The second end 10 of the lever arm 8 is fixedly con¬nected to the spindle shaft 11. A safety gear tripping arm 12 is also fixedly connected to the spindle shaft 5 11 so that turning of the lever arm 8 rotates the spindle shaft and turns the safety gear tripping arm 12. Another safety gear tripping arm 12 is arranged (on the right side of Figures 2 and 3) for tripping another safety gear 4 acting in co-operation with
10 another guide rail 16. The synchronization linkage 7 comprises a connecting rod 27 which transmits the mo¬tion of the spindle shaft 11 to said another safety gear tripping arm 12'.' An extension' spring 28 is ' ar¬ranged in the synchronization linkage 7 to oppose the
15 tripping action. A viscous fluid damper cylinder 13 is arranged to dissipate kinetic energy caused by inertia of the overspeed governor rope 5to the lever arm 8 to dampen the rotary .movement of the spindle shaft 11.The fluid viscous damper dissipates energy by pushing flu-
20 id through an orifice, producing a damping pressure which creates a force.The fluid viscous damper cylind¬er acts on an auxiliary arm 14 which is also fixedly ' attached to the spindle shaft 11.In some other {not shown embodiments) the fluid viscous damper may ar-
25 ranged to act on any suitable moving member of the synchronization linkage 7, such as arm 14 or tripping arm 12 or connecting rod 27 connected directly or in¬directly to the spindle shaft 11. In this example the fluid viscous damper cylinder 13 compresses when the
3 0 Inertia of the overspeed governor rope 5 urges the lever arm 8 to turn the spindle shaft 11 in a clock¬wise direction. In some other embodiment the fluid viscous damper cylinder 13 may be arranged to rebound in that situation.
35
Preferably, the fluid viscous damper 13 is an oil dam-per cylinder.

The fluid viscous damper cylinder 13 has at least two damping ratios depending on the velocity of the fluid viscous damper cylinder 13.The damping ratio of the fluid viscous damper cylinder may be adjustable.
Figure 4 shows an example of how the damping force of the fluid viscous cylinder 13 can be arranged to vary in function of the velocity of the piston relative to the cylinder of the fluid viscous damper cylinder. The horizontal axis of the diagram represents the compres-sion (or rebound) velocity of the fluid viscous damper cylinder. The vertical axis' of the diagram represents the damping force F. The damping force F increases as a function of the velocity v. In the shown example, the damping force is a non-linear function of velocity of a piston relative to a cylinder of the fluid visc¬ous damper cylinder. In smaller velocities the damping force is arranged to increase more forcibly than in higher velocities where the damping force increase is lightened. For example, the damping force function F(v) may be parabolic.
This ensures that the damping force will not be too high in a normal emergency stop situation wherein .the overspeed governor system trips the safety gears, and this operation will not be substantially delayed due to the provision of the fluid viscous damping.
Although the invention has been the described in con¬junction with a certain type of the elevator system, it should be understood that the invention is not li¬mited to any certain type. While the present inven¬tions have been described in connection with a number of exemplary embodiments, and implementations, the present inventions are not so limited, but rather cov¬er various modifications, and equivalent arrangements, which fall within the purview of prospective claims.

CLAIMS
1-A method for avoiding unwanted safety gear tripping in a safety stopping system of an elevator system, thesafety stopping system comprising
a machinery brake (1) for decelerating a mov-ing mass [2, 3) so as to perform a quick stop of the moving mass,
a safety gear (4) mounted to the moving mass,
anoverspeed governor (15),
anoverspeedgovernor rope (5, 6) connected to the moving mass of the elevator system,
a synchronization linkage (7) mounted to the moving mass for tripping the safety gear, the synchro-nization linkage comprising a lever arm (8) having a first end (9) pivotally connected to the overspeed governor rope (5, 6) and a second end (10) fixedly connected to a spindle shaft (11) to which a safety gear tripping arm (12) for tripping the safety gear is connected, characterized in that kinetic energy caused by inertia of the overspeed governor rope (5, 6) to the lever arm (8) is dissipated by im¬plementing fluid viscous damping to dampen the rotary movement of the spindle shaft (11) to prevent unwanted safety gear tripping when the upwards movement of the moving mass (2, 3) is decelerated by the machinery brake (1) to perform a quick stop of the moving mass.
2. A method according to claim 1, characte-rized in that the fluid viscous damping is per-formed by a fluid viscous damper acting on a member of the synchronization linkage (7) ■-
3. A method according to claim 2, characte-rized in thatthe fluid viscous damping is performed by a fluid viscous damper cylinder (13) acting on an

arm (14, 1,2) or a rod (27) connected to the spindle shaft (11).
4. A method according to any one■of the claims 1 to3, characterized in that the fluid viscous damp¬ing is performed by an oil damper cylinder (13).
5. A method according to claim 3 or 4, characte¬rized .in that the damping force is a non-linear function of velocity of a piston relative to a cylind;-er of the fluid viscous damper cylinder (13).
6. A method according to claim 5, characte¬
rized in that in velocities of the piston relative
to the cylinder of the fluid viscous damper cylinder
(131 smaller than a predetermined velocity the damping
force is arranged to increase more forcibly than in
higher velocities.
7. A method according to any one of the claims 1 to 6,
characterize, d in thatthe moving mass' is an
elevator car (2).
8,. A method according to any one of the claims 1 to 7, characterized in thatthe. moving mass is a counterweight (3) .
9. A safety stopping arrangement for an elevator sys¬tem for stopping the movement of a moving mass (2, 3), the safety stopping arrangement comprising
a machinery brake (1) for decelerating a mov-ing mass (2, 3) so as to oerform a auick stop of the moving mass,
a safety gear (4) mounted to the moving mass,
an overspeed governor (15),
anoverspeed governor rope (5, 6) attachedto a moving mass (2, 3)~ of the elevator system, and

a synchronization linkage (7) mounted to the moving mass for tripping the safety gear, the synchro-nization linkage comprising a lever arm (8) having a first end (9) pivotal ly connected to the over speed governor rope (5, 6)and a second end (10) , a. spindle shaft (11) to which the second end of the lever arm is fixedly connected, and a safety gear tripping arm (12) for tripping the safety gear, the safety gear trip¬ping arm being fixedly connected to ■ the spindle shaft
(11) ,characterized in that the safety stop-pingarrangement comprises a fluid viscous damper (13) -arranged to dissipate kinetic energy caused by inertia of the overspeed governor rope (5; 6) to the lever arm
(8) to dampen the rotary movement of the spindle shaft
10. A safety■ stopping arrangement according to claim■ 9, characterized in that the fluid viscous damper (13) is arranged to act on a member of the syn-chronization linkage (7).
11. A safety stopping arrangement according to claim 9 or 10, characterized in that the fluid visc¬ous damper (13) is a fluid viscous damper cylinder acting on an arm (14, 12) or rod (27) connected to the spindle shaft (11) .
12. A safety stopping arrangement according to any one of the claims9 to 11, c haracterized in that the fluid viscous damper (13) .is an oil damper cylind¬er.
13. A safety stopping arrangement according to any one of the claims 9 to 12, characterized in thatthe damping force is a non-linear function of ve¬locity of a piston relative to a cylinder of the fluid viscous damper cylinder .(13) .

14. A safety stopping arrangement according to any one of the claims 9 to 13, characterized in thatthe moving mass is an elevator car (2).
15. A safety stopping arrangement according to any one of the claims 9 to 14, characterized in thatthe moving mass is a counterweight (3).
16. An elevator system comprising a moving'mass (2, 3) guided by a pair ofguide rails (16, 17) to be verti¬cally movable in an elevator shaft (18), a suspension rope (19) attached to the moving' mass (2, 3) , a trac¬tion wheel (20) over which the suspension rope is lead, a hoisting machine (21) tor driving the traction wheelto move the moving mass, wherein the elevator system comprises a safety stopping arrangement accord¬ing to any one of the claims 8 to 15.