Patent Application
20080067011
The invention relates to a method of checking lift braking equipment, a method for placing a lift installation in operation and equipment for carrying out placing in operation, according to the introductory part of the independent patent claims.
A lift installation is incorporated in a shaft. It substantially consists of a lift cage which is connected by way of support means with a counterweight. The cage is moved along a substantially vertical cage travel path by means of a drive which selectably acts on the support means, directly on the cage or directly on the counterweight. Lift installations of that kind have mechanical braking systems which enable holding of the cage at a desired location, can brake the lift installation or the moved masses thereof in normal operation or can safely stop the lift cage in the case of a fault. Holding at a desired location is, for example, holding of the lift cage at a storey for the purpose of unloading or loading or for waiting for a next travel command. Braking in normal operation is, for example, a stopping process when the cage moves into a storey and braking in the case of fault is required when, for example, a control, the drive or the support means fails.
Until now two braking systems were usually used for these requirements, of which one was arranged at the drive itself and the other on the cage. A check of these systems is costly, because on the one hand two systems have to be checked and on the other hand fully laden cages are normally required for the check. This is complicated inasmuch as a useful load for the cage has to be transported up. This load has to be transported a number of times in small load portions and during the test there is a risk of damage of items of cage equipment by slipping of this useful load.
A braking system is now known from our application EP 05111993.1 which uses only one braking system instead of two braking systems. The illustrated lift braking equipment brakes and holds a lift cage and the lift braking equipment consists of a number of brake units which can be brought into engagement with brake tracks in the case of need, wherein the brake unit for this purpose presses at least one brake plate against the brake track and generates a braking force.
This braking system must now be able to be checked particularly securely and, nevertheless, efficiently.
The object of this invention is accordingly to design a checking method enabling efficient and reliable checking of braking equipment of that kind. Placing of a corresponding lift installation in operation shall be able to be made simple. Preferably there shall be able to be early recognition of possible faults and important installation data shall be able to be verified.
According to the invention these objects are fulfilled in that a number of brake units which are brought into engagement with brake tracks as required and which press at least one brake plate against the brake track are checked in that an effective coefficient of friction, which is generated when the brake plate is pressed against the brake track, of the brake unit is ascertained. Through ascertaining the effective coefficient of friction of the brake unit, deviations can be recognised in good time and the ascertaining allows a reliable statement with respect to the functional capability of the braking unit. The monitoring can, through corresponding ascertaining, be verified continuously, i.e. with each use, which enables a particularly safe construction of a brake unit of that kind.
In an advantageous construction the effective coefficient of friction (μe) of the brake unit is ascertained by means of a braking force measuring device for measuring a braking force and by means of a normal force measuring device for measuring a brake adjusting force which acts. This is particularly advantageous, since force measurements, for example with use of strain gauges, can be constructed economically. In addition, an effective resulting coefficient of friction of a brake unit can be ascertained in very simple manner with use of these measuring magnitudes.
A variant of embodiment proposes that for ascertaining the effective coefficient of friction (μe) of the brake unit the brake unit is brought into engagement with the brake track and adjusted with a brake adjusting force (FNw) having a lesser action, and the lift cage is moved at low speed, wherein the process of movement is continued or repeated until a substantially constant effective coefficient of friction (μe=FB/FNw) of the brake unit sets in. This is particularly advantageous, since during mounting of a lift installation dirt and construction dust can adhere to the brake track. This influences a coefficient of friction and thus also a resulting braking force. With the illustrated method this dirt can be rubbed away and the success of the cleaning can be checked by means of checking the coefficient of friction. At the same time it can be checked whether the measured coefficient of friction corresponds with a value according to experience. This enables coarse assessment of the material used, for example whether the correct brake track material is used.
A very advantageous variant of checking proposes that the ascertaining of the effective coefficient of friction (μe) of the brake unit is carried out at the unladen lift cage. This is of economic interest inasmuch as a useful load does not have to be used for the purpose of checking braking equipment. The time requirement for transport of check weights is eliminated and a risk of damage of lift equipment does not exist.
A helpful variant of embodiment proposes that a sufficient brake safety factor (SB) is evidenced on the basis of the effective coefficient of friction ([Le) and a maximum brake adjusting force (FNm) ascertained by means of the normal force measuring device. A safety factor is a characteristic for the reliability of equipment or the certainty of fulfillment of a task by equipment. Such a brake safety factor is particularly important in the case of braking equipment.
A checking method of that kind for checking lift braking equipment according to the foregoing embodiments is used with particular advantage for placing in operation a lift installation with lift braking equipment of that kind. The lift installation includes a lift cage for transporting a load, which is to be conveyed, and a counterweight, which is connected with the lift cage by means of support means, and a drive for driving the lift cage, counterweight and support means, wherein counterweight and cage move in a substantially vertical shaft in opposite sense. In the case of a lift installation of that kind the assessment of lift braking equipment is particularly difficult, since a complex mass system is involved. The proposed checking method in this connection offers an efficient and safe possibility for placing the lift installation in operation.
A lift installation is a complex mass system and lift braking equipment has to be appropriate to this complex mass system. As a rule, i.e. in normal operational states, the lift braking equipment of a lift installation has to bring the entire mass system or the total mass (MG), which is to be braked, to a standstill. In a ‘worst case’, for example in the event of failure of support means or support structures, it is necessary, however, for the lift braking equipment to be able to securely brake and hold the residual mass (MV), essentially the mass of the empty lift cage inclusive of the additional load. This latter requirement cannot be actually checked in a lift installation, since for this purpose a ‘worst case’ of that kind—also termed ‘free fall’ in the field of lift construction—would have to be produced. Consequently, in order to make a reliable statement with respect to the safety of lift braking equipment—and a statement of that kind is a constituent of placing the lift installation in operation—the participating masses have to be known. The invention now proposes helpful variants of embodiment for ascertaining these masses.
The first variant of embodiment proposes that the residual mass (MV), which has to be braked by the lift braking equipment in the ‘worst case’, of the lift installation is calculated with input of a permissible weight (MF) of the load, which is to be conveyed, and input of a weight (MK) of the empty lift cage (MV=MK+MF). This can be realised in simple manner and is possible in lift installations with pronounced standardisation, where no customer-specific designs are admitted.
Another variant of embodiment proposes that the residual mass (MV), which is to be braked by the lift braking equipment in the ‘worst case’, of the lift installation is calculated with input of the permissible weight (MF) of the load, which is to be conveyed, and an effective mass part of the drive (MA) and measurement of a lift acceleration (ak), wherein mass determinations at the lift installation, such as an actual imbalance (MB) of the lift installation or an actual weight (MT) of the support means are carried out with use of the braking force measuring device. This variant is advantageous when customer-specific lift installations are concerned, in which, for example, additional apparatus such as image screens, air-conditioning systems or the like or equipment articles such as mirrors, decorative materials or a customer-specific floor covering are installed. This method allows reliable determination of the masses to be braked.
The operative mass parts of the drive (MA) are defined by the drive. These are the inertia masses of the drive inclusive of associated drive pulleys and deflecting rollers. These rotational inertial masses are recalculated in correspondence with the diameter of the drive pulley to an equivalent linear mass proportion of the drive (MA). These values are apparent from lift documents or given in the form of data tables to checking apparatus.
The actual imbalance (MB) denotes the mass difference between counterweight and empty cage. As a rule this mass difference is interpreted as 50% of the permissible load (MF) to be conveyed. However, other interpretations of this imbalance are also known. This imbalance can be ascertained in that initially an actual weight (MT) of-the support means is determined. This is advantageously carried out by measuring the holding force (FBHT) in the rest state with the cage parked at the uppermost stop (HT) and measurement of the holding force (FBHB) in the rest state with the cage parked at the lowermost stop (HT); The measurement of the holding forces (FBHT, FBHB) is carried out in each instance in that the lift cage is fixed at the relevant stop (uppermost or lowermost) solely by the braking equipment and the holding force is measured by means of the braking force measuring device. The actual weight of the support means can be determined from the difference of these two measurements according to the following formula:
Mass Support Means (MT)=(Holding Force (FBHT)−Holding Force (FBHB))/2/g
wherein g is gravitational acceleration (9.81 m/s2).
The actual imbalance (MB) can be determined from, for example, the sum of these two measurements according to the following formula:
Mass Imbalance (MB)=(Holding Force (FBHT)−Holding Force (FBHB))/2/g
wherein g is again the gravitational acceleration (9.81 m/s2). In all cases it is necessary in this determination to take into account a weight (MZ) of a possible useful load of the cage (for example, an installer).
The weight (MK) of the empty lift cage can now be ascertained in that, for example, an intrinsic acceleration (ak) of the lift cage is measured by means of an acceleration sensor. In this connection the empty cage is parked at the lowermost stop (HB), then the braking equipment released, whereby the empty lift cage automatically accelerates upwardly. This acceleration (ak) and a possible residual braking force (FBR) are measured and subsequently the brake is applied again.
The actual weight (MK) of the empty lift cage can now be determined, for example, with use of the values ascertained as aforesaid or values which are known, according to the following formula:
MK=((MB−MT−MZ)*g−(MT+MZ+MA+MB)*ak−FBR)/ak.
The residual mass (MV), which is to be braked by the lift braking equipment in the ‘worst case’, can now be calculated:
MV=MK+MF.
This method allows secure ascertaining of the actual mass proportions of a lift installation.
Advantageously, a maximum required brake adjusting force (FNe) is determined with consideration of the total mass (MV) to be braked in the ‘worst case’, the effective coefficient of friction (μe) of the brake unit, the number (N) of brake units used, a requisite minimum retardation (ake) and a correction factor (KB1), wherein the correction factor (KB) takes into consideration empirical values such as speed of braking, contamination or anticipated overload:
FNe=KB1*MG*(ake+G)/(N*(μe).
This allows an effective prediction of the required adjusting force (FNe) with little effort. The required measurements can be undertaken by one person alone and no test weights are required.
A further refinement proposes that the brake unit is adjusted with a maximum force and the maximum brake adjusting force (FNm), which is achievable in that manner, is measured by means of the normal force measuring device and this maximum brake adjusting force (FNm) is compared with the maximum required brake adjusting force (FNe), evidence of sufficient braking function being designated fulfilled when the maximum brake adjusting force (FNm) is greater by the safety factor (SB) than the maximum required brake adjusting force (FNe). This embodiment allows a statement with respect to an actually present safety of the braking equipment. This gives very safe braking equipment.
Alternatively, the brake unit is adjusted with a maximum force and the maximum brake adjusting force (FNm), which is achievable in this manner, is measured by means of the normal force measuring device and a maximum possible braking force is determined with consideration of the effective coefficient of friction (μe) of the brake unit, the number (N) of brake units used and a correction factor (KB2), wherein the correction factor (KB2) takes account of characteristic empirical values such as speed of braking or contamination:
FBm=KB2*2*FNm*N*te.
This allows a direct statement with respect to maximum possible braking capacity of the braking equipment, which is used, in a specific lift installation.
Advantageously, based on the preceding statement with respect to maximum possible braking force (FBm), a maximum required braking force (FBe) is determined with consideration of the weight (MV) which is to be braked in the ‘worst case’, a required minimum retardation (ake) and a correction factor (KB2′):
FBe=KB2′*MV*(ake+G).
The correction factor (KB2′) takes into account characteristic empirical values such as anticipated overload. The maximum possible braking force (FBm) is now compared with the maximum required braking force (FBe) and evidence of sufficient braking function is designated fulfilled when the maximum possible braking force (FBm) is greater than the maximum required braking force (FBe) by the safety factor (SB).
This method gives a comprehensive overview of braking safety of a lift installation.
In an advantageous refinement of the method for placing a lift installation in operation the braking function is generally verified in that the empty cage is accelerated in controlled or uncontrolled manner, preferably in upward direction, until a travel curve or speed monitoring system activates the braking equipment and the braking equipment brakes the cage to a standstill by means of an associated brake unit or associated brake units and holds it at standstill. During the braking process the brake adjusting forces and braking forces are measured and a coefficient of friction (μb), which is ascertained from these measurements, of the brake unit is compared with the previously determined effective coefficient of friction (μe) of the brake unit. Placing of the braking equipment in operation is designated fulfilled when the ascertained coefficient of friction (μb) substantially corresponds with the effective coefficient of friction (μe), if need be with consideration of the correction factor (KB1, KB2). The advantage of this refinement is to be seen in that the overall function of the safety system of the lift installation can be carried out by simple means by only one person.
A further advantageous refinement of the method of placing in operation proposes that a correct equilibration of a lift system is undertaken or verified with use of the braking force measuring device. This is economic, since no separate measuring instruments are required.
Advantageously the equilibration of the lift system is carried out in that a required equilibration factor is input into an evaluating unit. The actual imbalance (MB) can be ascertained, as described in the foregoing, with use of the braking force measuring device. An effective equilibration factor (Bw) is determined in that the actual imbalance (MB) is correlated with the permissible useful load (MF) of the lift cage. A possible required additional weight can be calculated in simple manner as the difference of the required equilibration factor (Bg) minus the effective equilibration factor (Bw) and multiplication by the permissible useful load, and the counterweight can be charged with this additional weight or, in the case of a negative result, correspondingly relieved. The advantage of this embodiment is that an equilibration can be checked and/or corrected in simple, secure and efficient manner.
Advantageously the number of brake units used is two or a multiple of two. This is of advantage, since usually two brake tracks are present and thus the brake units can be distributed symmetrically on the brake tracks. It is also possible to use, instead of large brake units, several small brake units. This is economic, since modular items of braking equipment can be combined to form a system.
Advantageously characteristic magnitudes, which are detected within the scope of placing in operation, of the brake unit are checked for correspondence with preset values. For the purpose of checking a function in normal operation these placing-in-operation values, or characteristic magnitudes ascertained in the placing in operation, are stored and a continuous status check evaluates the characteristic values in each braking use of the braking equipment in normal operation. The status check continuously compares ascertained characteristic values with the placing-in-operation values and, in the case of unexpected deviations, generates a recalibration, a service notification or a fault report. This allows guaranteeing of the function of the braking equipment over a long period of time and permits focussed maintenance.
Advantageously the ascertained effective coefficient of friction (μe) is used as characteristic magnitude. Alternatively or additionally an ascertained normal force characteristic curve, which is stored as a function of an adjustment measuring device or an adjustment path, is used as characteristic magnitude. These characteristic magnitudes are basic magnitudes which enable a safe statement with respect to braking capability and thus with respect to the safety state of the braking equipment and thus the lift installation.
In an advantageous refinement a correct functioning of the braking force measuring equipment is checked by means of comparison of a measured braking force (FB) with a drive force (FA) required for moving the lift cage, wherein for this purpose a static braking force (FBst) is measured when the lift cage is stationary and a dynamic braking force (FBdyn) is measured at constant travel speed and brake adjusting force (FBw) with smaller action and the difference of these two measurements (FBdyn−Fbstat) is compared with the required driving force (FA), for example a motor torque (TA). This method allows a further or alternative assessment of the safety state of the lift installation or of the measuring system.
Advantageously, for carrying out the method of placing in operation use is made of equipment which is connectible with the braking equipment and which controls the course of the placing in operation. This is particularly advantageous, since by means of this equipment it is possible, for example, to give instructions to the person carrying out the work. Calculations can be performed automatically and the results of the placing in operation stored or can be issued in a report. This is safe and efficient.
Further details of the invention and supplementary advantages thereof are explained in more detail in the following part of the description.
The invention is explained in more detail in the following by way of examples of embodiment in conjunction with the figures. The figures are shown schematically and not to scale. Equivalent parts are denoted in the same way in the figures.
There:
a shows a plan view of the lift cage and counterweight of the lift installation according to
a shows mass distribution of a lift installation with cage at the lowermost stop,
b shows mass distribution of a lift installation with cage in a centre position and,
c shows mass distribution of a lift installation with cage at the uppermost stop.
The braking equipment 11 comprises at least one brake unit 12 which can be brought into engagement with a brake track 6. In the illustrated example according to
a shows the lift installation, which is illustrated in
During braking the brake unit 12 slides along the brake track 6 at a speed v, the speed v being equal to zero in the case of stopping. This embodiment allows an efficient regulation of the braking equipment 11 in the operational case, since the brake control unit 13 can preset a desired normal force FM at each brake unit 12 and the brake unit 12 can automatically set this value. In the case of placing in operation these values can be used in simple manner for calculation of an effective brake safety SB.
The equipment 9 for controlling the method of placing in operation controls the inspection process and gives required instructions to operating personnel.
a to 6c give an illustration of possible measuring points for placing the braking equipment 11 or the lift installation 1 in operation. The cage is unladen, i.e. the instantaneous mass MF is zero.
In
In
In
With knowledge of the present invention the lift expert can change the set forms and arrangements as desired. For example, the illustrated arrangement of a drive in a shaft head can be replaced by a drive on the cage or at the counterweight or the braking equipment can be arranged at the upper end of the cage or below and above the cage or also laterally of the cage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06115686.5 | Jun 2006 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| 60805125 | Jun 2006 | US |
