The present invention relates to an elevator brake arrange ment as defined in the preamble of claim 1.

When moving people up and down, like in various elevator ar rangements, the passenger safety is the most important as pect. It must be controlled that the elevator car cannot fall freely downwards or move uncontrolled upwards. Also, all accelerations and decelerations must be kept in certain safe limits. Sudden stops even from small speeds can cause injuries for the passengers .

For the reasons mentioned above the authorities in different countries have various regulations related to elevator safe ty issues. The basic principle is that the brake arrangement of an elevator must be able to stop the elevator car from its nominal speed and keep the elevator car in its position in a floor also in overload situations. In addition, the brake arrangement must be fault tolerant so that one mechan ical fault is not able to make the brake arrangement totally inoperative .

Among other things, some safety regulations request that the elevator brake must be mechanically doubled so if one part of the brake failures another part of the brake still works properly. Mechanically doubled elevator brakes are used in normal operation so that both the brakes are always used at the same time. A problem with this kind of a use is that a mechanical failure of one of the brakes in the pair is not necessarily discovered. In that case the elevator may oper- ate a long time hinging on one brake only. This may cause surprisingly dangerous situations .

Some other safety regulations request that the elevator must have one driving machine brake and one emergency brake. In some solutions safety brakes, operating in contact with ele vator guide rails, act as emergency brakes. If the driving machine brake failures the safety brake has to stop the ele vator car within a predetermined displacement so that an un controlled acceleration of the elevator car will not arise. A problem with this solution is that the emergency brake is activated only when a considerable speed or acceleration has been achieved and a dangerous situation has grown up. The emergency brake can prevent fatal injuries of the passen gers, but it is not able to prevent down fallings and/or all nonfatal injuries .

In addition, one problem with the prior art solutions is a need of a big place box depending on the considerably big structure of the brake arrangement .

One object of the present invention is to eliminate draw backs of prior art technology and to achieve a safe and re liable elevator brake arrangement with relatively small sized brake units . The elevator brake arrangement according to 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 inventive content of the application can also be defined differently than in the claims presented below. The in- ventive content may also consist of several separate inven tions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts. Likewise, the different details present ed in connection with each embodiment can also be applied in other embodiments. In addition, it can be stated that at least some of the subordinate claims can, in at least some situations, be deemed to be inventive in their own right.

An aspect of the invention is to provide an elevator brake arrangement, which arrangement comprises at least a brake unit comprising a body, a brake plate assembly, a spring as sembly, an electromagnet arrangement and a counter element, and also a rotating brake disc. Advantageously, the brake plate assembly comprises at least two brake plates and a state detector that is arranged to monitor the operation states of the brake plates.

In order to be able to monitor the operation states of the brake plates the state detector is arranged to measure an instantaneous position of each brake plate in relation to the brake disc. The position here means an instantaneous distance of each brake plate from the brake disc.

A disc brake type brake unit according to the invention is advantageously used as an elevator driving machine brake unit to decelerate and stop the elevator car movement and/or to keep the elevator car in its position during loading and unloading phases and also when being out of use. However, the disc brake unit according to the invention can also be used for various other purposes to stop rotational or linear movements or to prevent an object from moving. Later in this context the term elevator driving machine brake unit or brake caliper is also called shorter only the brake unit.

The invention relates to an elevator brake arrangement with at least one two-plate brake unit that comprises means for monitoring operation states of the two brake plates. In the arrangement the required states of the brake plates of the two-plate brake unit are preferably monitored with a single state detector. The state detector is arranged to provide a signal on the grounds of which it can be deduced which one of the two brake plates are currently braking, are both the brake plates currently braking or are both the brake plates currently free from braking. Thus, the purpose of the moni toring is to secure the reliable operation of the brake unit by checking if both the brake plates are working properly, abnormally or if they do not work at all.

The invention makes it possible to utilize proximity switch es as state detectors or sensors in dramatically smaller space boxes than in prior art solutions.

One advantage of the invention is that the elevator disc brake arrangement according to the invention is reliable, cost effective and requires only a little space. Another ad vantage is higher ride comfort due to decreased deceleration fluctuation as well as a quieter operation of the brakes. Yet another advantage is that the small and simple brake unit is easy to adjust and maintain. Yet one advantage is a robust cast design, resulting in a smaller and cheaper solu- tion, having also more degrees of freedom in the outer shape of the brake unit. In addition, the disc brake arrangement according to the invention has a non-coinciding torque and hence deceleration minimum, resulting in a more stable over all torque. And yet one more advantage is that the cast de sign has also more degrees of freedom in the dimensioning of the brake unit, making the fulfillment of the space box re quirements easier. Yet a further advantage is that thanks to several brake plates a failure of a brake part decreases the usable brake moment only a little, and the brake arrangement remains operable. Yet one more advantage is that smaller brake units lead to a machinery with smaller deceleration, which further leads to better safety and comfort, as well as a smaller space box and price of the brake arrangement.

In an advantageous embodiment two brake units are attached to the drive machine frame by lugs or other type attaching interfaces. Advantageously each of the brake units comprises two brake plates, the brake plates are arranged to be move between braking contact with the brake disc and a non- contact position apart from the brake disc. In each of the brake units a state detector is arranged to monitor the op eration states of the brake plates.

In the following, the invention will be described in detail by the aid of example embodiments by referring to the at tached simplified and diagrammatic drawings, wherein

Fig. 1 presents in a simplified and diagrammatic oblique top view an elevator machinery with two driving ma chine brake units according to the invention, Fig. 2 presents in a simplified and diagrammatic oblique top view a driving machine brake unit according to the invention,

Fig. 3 presents in a simplified and diagrammatic end view the driving machine brake unit according to Fig. 2,

Fig . 4 presents in a simplified and diagrammatic oblique top view the driving machine brake unit according to Fig. 2 as an exploded view with only main compo nents shown,

Fig. 5 presents in a simplified and diagrammatic front view another advantageous embodiment of the driving machine brake unit according to the invention with out brake plates and a counter element,

Fig . 6 presents in a simplified and diagrammatic oblique top view yet another embodiment of the driving ma chine brake unit according to the invention,

Fig . 7 presents in a simplified and diagrammatic front view a proximity sensor, used in an advantageous embodiment of the invention, in its position in re lation to the brake plates of a driving machine brake unit according to the invention, and

Fig . 8 presents in a simplified and diagrammatic view ed dy-current losses in four different main states of the brake plate combination according to the inven tion .

Figure 1 presents in a simplified and diagrammatic oblique top view an elevator driving machinery 1, which comprises at least a housing la, a drive motor, a traction sheave lc, two driving brake units 2 and a brake disc 3. The drive motor is inside the machinery housing la and is arranged to rotate simultaneously the coaxial traction sheave lc and brake disc 3. The brake units 2 are fastened floatably to fastening lugs lb on the outer periphery of the housing la. The brake units 2 have been arranged to decelerate and stop the rota tional movement of the brake disc 3 and at the same time al so the rotational movement of the traction sheave lc. The brake units 2 act also as holding brakes to keep the eleva tor car in its position during loading and unloading phases and also when being out of use, as mentioned earlier. The brake units 2 can also be called brake calipers as also men tioned earlier.

Figure 2 presents in a simplified and diagrammatic oblique top view a driving machine brake unit 2 according to the in vention. Among other things the brake unit 2 comprises a body 4, a top element 5, a counter element 6 with its fas tening screws 7 and a brake plate assembly 8 having two sep arate brake plates 8a, 8b. The counter element 6 can be also called a caliper plate. The body 4 forms a hollow housing inside which a spring assembly for pressing the brake plates 8a, 8b towards the counter element 6 and brake disc 3 is placed. Also, an electromagnet arrangement comprising a coil assembly causing a magnetic field for pulling the brake plates 8a, 8b free from the brake disc 3 when the brake is opened is placed inside the body 4. For the sake of clarity, the spring assembly and electromagnet arrangement are not presented in figure 2.

The brake unit 2 according to the invention is arranged to operate so that when the electromagnet arrangement compris ing the coil assembly is powered the brake plates 8a, 8b are pulled against the body 4 of the brake unit 2 free from the brake disc 3. In that case the brake is open and the brake disc 3 and the traction sheave lc can be rotated. In this operation state of the brake also both the brake plates 8a, 8b are said to be open. The brake is activated or closed by switching the power off from the electromagnet arrangement. In that case the spring assembly presses the brake plates 8a, 8b against the brake disc 3.

The top element 5 forms an intermediate element between the body 4 of the brake unit 4 and the fastening lugs lb in the housing la of the driving machinery 1 to which lugs lb the brake units 2 are to be floatably fastened so that the brake units 2 are able to move properly when needed in the axial direction of the elevator driving machinery 1.

Figure 3 presents in a simplified and diagrammatic end view the driving machine brake unit 2 according to figure 2. The figure shows a gap 9 between the counter element 6 and the brake plates 8a, 8b. The gap 9 is for the brake disc 3. The brake unit 2 is mounted into its operating location so that the outer circumference of the brake disc 3 is in the gap 9 between the counter element 6 and the brake plates 8a, 8b. Thus, the counter element 6 is arranged to press against the first brake surface of the brake disc 3 on the first side of the brake disc 3, and the brake plates 8a, 8b are arranged to press against the second brake surface of the brake disc 3 on the second side of the brake disc 3.

Figure 4 presents in a simplified and diagrammatic oblique top view the driving machine brake unit 2 according to fig ure 2 as an exploded view with only main components shown. For the sake of clarity, the brake plates 8a, 8b are slight ly separated from each other. The brake plates 8a, 8b are substantially flat plates comprising a group of friction pads or linings 10 on the surface that is facing to the ro tating brake disc 3. The counter element 6 comprises sub stantially similar friction pads or linings on its surface that is facing to the rotating brake disc 3. Those pads or linings are not presented in figures.

Preferably, the size and shape of the brake plates 8a, 8b are substantially equal but the thickness is different so that, for example, the first brake plate 8a is thicker than the second brake plate 8b. For that reason, the horizontal gap between the braking surface of the first brake plate 8a and the braking surface of the brake disc 3 is smaller than the corresponding gap between the braking surface of the second brake plate 8b and the braking surface of the brake disc 3. That feature makes it possible to achieve a sequen tial brake arrangement where the brake plates 8a, 8b hit the brake disc 3 at a different time, one after the other. Due to a smaller gap the first brake plate 8a hits the brake disc 3 slightly earlier than the second brake plate 8b when a braking is actuated and the brake is closed by the spring assembly after the magnetic force provided by the coil as sembly is weakened or removed. This sequential braking ar rangement gives a higher ride comfort due to decreased de celeration fluctuation, as well as a quieter operation be cause there are only two minor clicks instead of one louder slam .

Figure 4 also presents a coil 11 of the coil assembly for an electromagnet arrangement that is arranged to open the brake by pulling the brake plates 8a, 8b free from the brake disc 3. The electromagnet arrangement is placed inside the body 4. In this embodiment the body 4 comprises only one coil 11 that is common for both the brake plates 8a, 8b. Therefore, the coil 14 extends, preferably symmetrically, to the area of each brake plate 8a, 8b and is arranged to interact with both the brake plates 8a, 8b.

Figure 5 presents in a simplified and diagrammatic front view another advantageous embodiment of the driving machine brake unit 2 according to the invention without the brake plates 8a, 8b and the counter element 6. The structure of this embodiment is otherwise similar to the structure of the embodiment according to figure 4 but now the coil assembly of the brake unit 2 comprises a separate coil 11a, lib for each brake plate 8a, 8b. Preferably in this embodiment the brake arrangement comprises adjusting means for adjusting each brake plate 8a, 8b separately. Thus, the first brake plate 8a is interacted by the first coil 11a and the second brake plate 8b is interacted by the second coil lib. In this embodiment the operation of the two brake plates 8a, 8b can be freely adjusted.

Figures 6 - 8 present in a simplified and diagrammatic view yet another advantageous embodiment of the driving machine brake unit 2 according to the invention. In this embodiment a single detector 12 comprising at least a processor unit 13 and an antenna 14 is used as a state indicator to make moni toring the operation states of the brake unit 2 possible by measuring instantaneous locations of the two brake plates 8a, 8b in relation to the brake disc 3. Advantageously, the state detector 12 is a proximity sensor. The term "operation state'' in this context preferably means a horizontal dis tance of the brake plates 8a, 8b from the brake disc 3. Figure 6 presents the state detector 12 fastened to its place in the brake unit 2, and figure 7 presents in a sim plified and diagrammatic front view the antenna 14 of the state detector 12 in its offset position in relation to the brake plates 8a, 8b of the driving machine brake unit 2 ac cording to the invention. Figure 8 presents measured eddy- current losses in four different main operation states of the brake unit 2 or the brake plates 8a, 8b.

An advantageous monitoring system for the operation states of the brake unit 2 according to the invention comprises a single state detector 12, such as a proximity sensor, having an LC resonator circuit that is arranged to provide a vi- brating magnetic field in its vicinity. When the brake is open both the brake plates 8a, 8b are at their maximum dis tance from the brake disc 3. In that case the losses in the magnetic field provided by the LC resonator circuit are min imal, almost non-existent. When the brake is closed for the braking operation both the brake plates 8a, 8b have come closer to the state detector 12. In that case a large por tion of the flux of magnetic field goes through the brake plates 8a, 8b causing eddy-currents that are subject to damp because of the resistance of the material of the brake plates 8a, 8b. The processor unit 13 of the state detector

12 comprises measuring means to measure the dampening by measuring losses in eddy-currents. The losses are at their minimum when the brake is open and at their maximum when the brake is closed and the brake plates 8a, 8b are close to the state detector 12. Advantageously, the processor unit 13 of the state detector 12 is fastened, for example, to the counter element 6, and the antenna 14 is placed so that it is able to receive the signal emitted by the LC resonator circuit in order to ob tain the instantaneous operation states of the two brake plates 8a, 8b. The state detector 12 or at least its antenna 14 is placed in the brake unit 2 with an offset 16 in rela tion to the line 15 of the facing surfaces of the brake plates 8a, 8b. The offset 16 is essential because it makes it possible to separate the proximity or the operation state of the first brake plate 8a from the proximity or the opera tion state of the second brake plate 8b. In that case an ad equate number of operation states, namely four main opera tion states, are obtained to reliably monitor the functions of the brake units 2.

The four main operation states obtained are:

Osl. Both brakes plates 8a, 8b open: Losses minimum = LI Os2. The first brake plate 8a closed: Losses small = L2 Os3. The second brake plate 8b closed: Losses medium = L3 Os4. Both brakes plates 8a, 8b closed: Losses maximum = L4

The four operation states Osl-Os4 of the brake can be de duced by the single state detector 12 that is placed in the brake unit 2 with an offset 16 in relation to the line 15 of the facing surfaces of the brake plates 8a, 8b. For the de duction the losses in the vibrating magnetic field created by the LC resonator are measured.

Figure 8 presents an example of the measured losses in the four operation states Osl-Os4 mentioned above. Line LI indi- cates that the losses are minimal, either zero or almost ze ro. The measured value of LI tells that both the brakes plates 8a, 8b are open, and in the operation state Osl. In that case the brake is open.

Correspondingly, the measured value of L2 is relatively small that tells that the first brake plate 8a is close to the brake disc 3 but the second brake plate 8b is further, closer to the body 4 of the brake unit 2. In that case it can be said that the first brake plate 8a is closed and the second brake plate 8b is open. The small value of L2 is based on the smaller resistance because only a smaller area of the antenna 14 is facing the closer brake plate that is now the first brake plate 8a.

Further, the measured value of L3 indicates medium losses telling that the second brake plate 8b is close to the brake disc 3 but the first brake plate 8a is further, closer to the body 4 of the brake unit 2. In that case it can be said that the second brake plate 8b is closed and the first brake plate 8a is open. The medium value of L3 is based on the greater resistance because a greater area of the antenna 14 is facing the closer brake plate that is now the second brake plate 8b. This is clearly seen in figure 7.

Finally, the measured value of L4 is relatively great and tells that there is a lot of material causing a great deal of losses to the eddy-currents. This means that both the brake plates 8a, 8b are close to the brake disc 3, and, as a matter of fact, the brake is closed. The measured value L4 of the losses is substantially equal to the sum of measured losses L2 and L3 , i.e. L4 · L2+L3. The monitoring arrangement mentioned above can be applied with proximity sensors that are placed so that when the braking is activated the brake plates 8a, 8b come closer to the sensor and/or its antenna 14, and when the brake is open the brake plates 8a, 8b are further from the sensor and/or its antenna 14. With other types of sensors or other kinds of positioning the sensors, the monitoring arrangement may be different .

In general, it is characteristic to the arrangement accord ing to the invention that each brake unit 2 comprises at least two separate brake plates 8a, 8b that are placed one after the other or adjacent to each other in the direction of rotation of the brake disc 3. In that case both the brake plates 8a, 8b are on the same side of the brake disc 3. Preferably each brake unit 2 comprises a single state detec tor 12, such as the proximity sensor with its processor unit 13 and antenna 14 as mentioned above, or a corresponding as- sembly, to measure and monitor the instantaneous operation states of the brake plates 8a, 8b. The instantaneous opera tion states correspond instantaneous distances of both the brake plates 8a, 8b from the brake disc 3. Preferably, the instantaneous distances of both the brake plates 8a, 8b from the brake disc 3 are measured, and based on the measuring results the monitoring is applied.

Also essential is the asymmetrical positioning of the state detector 12 or at least its antenna 14. By doing so, ade- quate measuring results can be obtained with a simpler way. The corresponding results can be obtained also by using sen sors with a non-homogenous field distribution. In that case the asymmetrical positioning of the sensor and/or its anten na is not necessary. The thickness of the brake plates 8a, 8b can also be equal when using a non-homogenous field dis tribution .

Thus, as mentioned earlier, the state detector 12 is ar ranged to recognize also which one of the brake plates 8a, 8b is closed and which one is open, utilizing either the offset 16 of the antenna 14 or the non-homogenous field dis tribution or both, or some other advantageous arrangement. The open and closed states have been described above.

Instead of proximity sensors also other advantageous sensors or detectors may be used to measure the operation states of the brake plates 8a, 8b.

It is obvious to the person skilled in the art that the in vention is not restricted to the examples described above but that it may be varied within the scope of the claims presented below. Thus, for instance, the structures and com ponents of the brake units may differ from what is presented above. In that case the brake plates can also be somewhere else than in the outer periphery of the brake disc. The brake plates can be, for example, on the side face of the brake disc and at maximum one brake plate can be a semicir cle or almost a semicircle.