A machine brake assembly of a conveyor drive machine, a monitoring system and a conveyor drive machine

Abstract

A machine brake assembly (52) of a conveyor drive machine (5), comprising: at least one brake disc (52-1) of the conveyor drive machine; at least two brake units (52-2A; 52-2B) mounted at opposite sides of the brake disc aligned with and facing each other; each said brake unit (52-2A; 52-2B) comprising on its own: a frame part (52-3); an armature (52-4) movable supported on the frame part; and an actuator configured to move the brake unit either into a braking state in contact with the braking surface of the brake disc (52-1) or into a non- braking state disconnected from the brake disc, in accordance with a control input. A monitoring system of the machine brake assembly. A conveyor drive machine.

Description

FIELD OF THE INVENTION The invention relates to a machine brake assembly of a conveyor drive machine, a monitoring system of the machine brake assembly and a conveyor drive machine. BACKGROUND OF THE INVENTION Elevators have electromechanical hoisting machine brakes as safety devices to apply braking force to a traction sheave or a rotating axis of a hoisting machine to brake movement of the hoisting machine and therefore an elevator car. There are normally two separate brakes, however recently multi-brake hoisting machines, i.e. machines with more than two, such as three or four brakes have been introduced. Depending on the hoisting machine type they can be shoe brakes or disc brakes, for example, engaging against a braking surface or a brake disc of the elevator hoisting machine. Traditionally, different types of hoisting machine brakes have been needed to cover various hoisting machine types. Hoisting machine brakes shall be dimensioned to stop and hold standstill the elevator car with a certain amount of overload. If one brake fails, for safety reasons the remaining ones should still stop and hold the elevator car with suitable safety margin. Thus, it is necessary to make sure that brakes are operating correctly. For example, if the brake does not open correctly, the brake pad may drag against the traction sheave during elevator run, causing e.g. accelerated wear, and may further lead to degradation of the braking force. SUMMARY OF THE INVENTION To address one or more of the above-mentioned problems, the present invention brings forward a new kind of machine brake assembly of a conveyor drive machine, a monitoring system of the machine brake assembly and a conveyor drive machine. An elevator hoisting machine, a drive machine of an escalator and a drive machine of a travelator are preferred implementations of the conveyor drive machine. It is brought forward a new machine brake assembly of a conveyor drive machine according to claim 1. It is also brought forward a new monitoring system of the machine brake assembly according to claim 9. It is also brought forward a new conveyor drive machine according to claim 12. Further embodiments of the invention are described in the dependent claims and the following description. According to a first aspect there is provided a machine brake assembly of a conveyor drive machine, comprising: at least one brake disc of the conveyor drive machine; at least two brake units mounted at opposite sides of the brake disc aligned with and facing each other; each said brake unit comprising on its own: a frame part; an armature movable supported on the frame part; and an actuator configured to move the brake unit either into a braking state in contact with the braking surface of the brake disc or into a non-braking state disconnected from the brake disc, in accordance with a control input. According to an embodiment, the brake units are designed such that similar units can be used both in disc brakes and in shoe brakes, depending on conveyor machine type. According to an embodiment, each said actuator comprises a compression spring located between frame part and armature and adapted to push the armature forward, in contact with the brake disc. According to an embodiment, each said actuator comprises an electromagnet located in the frame part, which electromagnet when energized pulls the armature backwards by resisting force of the compression spring, such that the armature disconnects from the brake disc. According to an embodiment, the brake assembly comprises at least two further brake units of the same type, mounted on the same brake disc with the previous brake units, and located in the same way at opposite sides of the brake disc facing each other. According to an embodiment, the brake assembly comprises two brake discs and four pairs of brake units arranged so that two pairs of brake units are mounted on each brake disc. According to an embodiment, the brake units are dimensioned such that if at least one brake unit of a pair of brake units fails, the remaining pairs of brake units of the brake assembly are still capable of stopping and holding the conveyor, in particular an elevator car. According to an embodiment, the conveyor drive machine comprises an elevator hoisting machine, a drive machine of an escalator, or a drive machine of a travelator. According to a second aspect there is provided a monitoring system of the machine brake assembly as described in this description, comprising: proximity switches associated with each said brake unit and configured to monitoring operation of the state of each individual brake unit; and a control board comprising an ADC (analog-to-digital converter) capable of reading combined proximity switch status and an N+1 bit DAC (digital-to-analog converter), where N denotes the number of monitored proximity switches, capable of converting proximity switch statuses to analog level circuit; and wherein the control board is adapted to convert outputs 0 / 24V of the proximity switches to precise 0 / 18V logic level inputs for the N bits of the DAC. According to an embodiment, the control board comprises an 18V logic AND circuit adapted to combine all proximity switch inputs to N+1 st bit of the DAC. According to an embodiment, the monitoring system further comprises: a conveyor controller configured to control operation of a conveyor and operation of each brake unit; wherein the conveyor controller is adapted to receive analog status signals combined by the control board from each brake unit monitored by a proximity switch. According to an embodiment, the conveyor comprises an elevator, an escalator, or a travelator. According to a third aspect there is provided a conveyor drive machine, in particular a drive machine of an elevator, an escalator, or a travelator, wherein the drive machine comprises the machine brake assembly as described in this description. A plurality N of conveyor drive machine brake proximity switches can be monitored without adding complexity in a control board comprising an electrical circuit. N denotes the number of monitored proximity switches. N+1 bit DAC (digital-to-analog converter) circuit can be utilized converting switch statuses to analog level circuit. The control board may read combined switch status with an ADC (analog-to-digital converter). A switch interface can convert imprecise switches outputs 0 / 24V to precise 0 / 18V logic level inputs for the N bits of the DAC. An 18V logic AND port can be used to combine all switch inputs to N+1 st bit of the DAC. The invention allows avoiding costly wiring from the proximity switches of a conveyor drive machine to a control board. A single or common control board, eventually located close to drive machine brakes, can be used for reading two proximity switches from conventional machines or for reading a plurality N of proximity switches of multi-brake conveyor drive machines. BRIEF DESCRIPTION OF THE DRAWINGS The invention will in the following be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which: Figure 1 shows an elevator with an elevator hoisting machine, Figure 2 shows an elevator hoisting machine according to a preferred embodiment. Figure 3 shows in detail a single pair of brake units in the hoisting machine of Figure 2. Figure 4 shows a block diagram of an embodiment of a monitoring system comprising a control board for monitoring operation of disc brakes of a conveyor drive machine, Figure 5 shows a first example of an electrical circuit on the control board shown in Figure 4, Figure 6 shows a second example of an electrical circuit on the control board shown in Figure 4, and Figure 7 shows a third example of an electrical circuit on the control board shown in Figure 4. DETAILED DESCRIPTION Figure 1 schematically illustrates some aspects of an exemplary elevator 100 comprising an elevator car 10 and an electric drive 4 operable to drive the car 10 in an elevator shaft 1, to transfer passengers and / or cargo between landings 30. The electric drive 4 in Figure 1 comprises an elevator hoisting machine 5 and an elevator drive unit. The elevator hoisting machine 5 serves as an example of a conveyor drive machine comprising a machine brake assembly 52. The hoisting machine 5 comprises an elevator hoisting motor 51 such as a permanent magnet motor for driving the car 10, as well as hoisting machinery disc brakes 52 configured to apply to a traction sheave 53 or a rotating axis of the hoisting machine, to stop movement of the car or hold the car standstill at a landing 30 in the shaft 1. The elevator in Figure 1 has hoisting ropes 6 supporting the car 10, running via the traction sheave 53, and connected to a counterweight 7. The elevator 100 comprises an elevator controller 110 configured to control elevator operation. Figure 2 shows the elevator hoisting machine 5, representing a conveyor drive machine, according to a preferred embodiment of a first aspect. The example machine brake assembly 52 of a conveyor drive machine comprises a brake disc 52-1. The brake disc 52-1 comprises two braking surfaces. The example machine brake assembly 52 comprises two separate brake units 52-2A, 52-2B mounted at opposite sides of the brake disc aligned with and facing each other. According to an embodiment at least two brake units 52-2A, 52-2B are mounted in connection with at least one brake disc 52-1 to provide braking with at least one braking surface. In the embodiment of Figure 2 the machine brake assembly 52 comprises two separate brake units 52-2A, 52-2B mounted at opposite sides of the brake disc 52-1, particularly aligned with each other and facing each other. Each said brake unit 52-2A, 52-2B comprises on its own: a frame part 52-3; an armature 52-4 movable supported on the frame part; and an actuator configured to move the brake unit either into a braking state in contact with the brake disc 52-1 or into a non-braking state disconnected from the brake disc, in accordance with a control input. Figure 3 shows in detail a single pair of brake units 52-2A, 52-2B in the hoisting machine 5 of Fig. 2. The brake units 52-2A, 52-2B preferably are designed such that similar units can be used both in disc brakes (as is the case in the illustrated embodiment) and in shoe brakes, depending on conveyor machine type. This simplifies machine brake assembly as less variety of brake components is required. Preferably, each said actuator comprises a compression spring (not shown) located between frame part 52-3 and armature 52-4 and adapted to push the armature forward, in contact with the brake disc 52-1. Preferably, the actuator also comprises an electromagnet 52-5 located in the frame part 52-3, which electromagnet when energized pulls the armature 52-4 backwards by resisting force of the compression spring, such that the armature disconnects from the brake disc, enabling rotation of the hoisting machine 5. Preferably, said machine brake assembly comprises at least two further brake units of the same type, mounted on the same brake disc 52-1 with the previous brake units 52-2A, 52-2B, and located in the same way at opposite sides of the brake disc, particularly at opposite sides of the brake disc facing each other. Preferably, said machine brake assembly of the hoisting machine 5 comprises two brake discs 52-1 and four pairs of said brake units 52-2A, 52-2B - so 8 brake units altogether - arranged so that two pairs of said brake units are mounted on each brake disc 52-1. According to an embodiment, the brake units 52-2A, 52-2B are dimensioned such that if one pair fails, i.e. at least one brake unit in the pair of two brake units fails, the remaining pairs of brake units of the machine brake assembly 52 are still capable of stopping and holding the conveyor, in particular the conveying parts of the conveyor, for example the elevator car 10. In case of the elevator hoisting machine 5 with four pairs of said brake units 52-2A, 52-2B, the three remaining pairs are still capable of stopping and holding the elevator car 10. According to a second aspect there is provided a monitoring system of the abovementioned machine brake assembly 52. The monitoring system of the machine brake assembly comprises proximity switches PS1 ...PSN associated with each said brake unit 52-2A; 522B and configured to monitoring operation of the state of each individual brake unit; and a control board 70 comprising an ADC (analog-to-digital converter) capable of reading combined proximity switch status and an N+1 bit DAC (digital-to-analog converter), where N denotes the number of monitored proximity switches, capable of converting proximity switch statuses to analog level circuit; and wherein the control board 70 is adapted to convert outputs 0 / 24V of the proximity switches PS1...PSN to precise 0 / 18V logic level inputs for the N bits of the DAC. According to an embodiment, the control board 70 comprises an 18V logic AND circuit adapted to combine all proximity switch inputs to N+1st bit of the DAC. According to an embodiment, the monitoring system further comprises: a conveyor controller 110 configured to control operation of a conveyor and operation of each brake unit 52-2A; 52-2B; wherein the conveyor controller is adapted to receive analog status signals Output 1 -S1; Output 2-S2 combined by the control board 70 from each brake unit 52-2A; 52-2B monitored by a proximity switch PS1...PSN. In the example of Figure 4 the monitoring system is described along a hoisting machine 5 comprising two brake discs 52-1 and four pairs of said brake units 52-2A, 52-2B - so 8 brake units altogether - arranged so that two pairs of said brake units are mounted on each brake disc 52-1. Eight brake switches PS1...PS4, PS5...PS8 are configured for monitoring operation of the individual 8 brake units, respectively. Said monitoring system comprises a monitoring unit 90, arranged as conveyor drive machine 5 auxiliary equipment, configured to obtain information of operating state of the individual brake switches, such that operation of each brake unit can be monitored individually. Figure 4 shows a block diagram of the monitoring system for monitoring operation of disc brakes 52 of the conveyor drive machine 5. Figure 4 shows left a conveyor controller 110 that measures status of proximity switches PS1... PS8. In the middle there is a control board 70 providing interface between the conveyor controller 110 and a group 60 of brake proximity switches PS1... PS8. The control board 70 acts as a combiner board for the signals of the brake proximity switches PS1 ...PS8 and provides from Output 1 and Output 2 status information as input for the conveyor controller 110 switch interfaces S1 and respectively S2. The monitoring unit 90 comprises the control board 70 provided with electrical circuits depicted exemplary on Figures 5, 6 and 7, and further the proximity switches group 60. On the right are shown the brake proximity switches PS1...PS8, grouped under reference number 60. It can be seen that the proximity switches are split into two groups PS1...PS4 and PS5...PS8. The advantage of this is that eight proximity switches PS1...PS8 can be managed with two switch interface channels S1; S2 conventionally available in the conveyor controller 110 and by this there is resolution to separate different switch combination. Each proximity switch PS1...PS8 has 3 wires (power, signal, ground) giving in total 24 output signals from the proximity switches group 60. The proximity switches PS1...PS8 have an output stage that adds inaccuracy to voltage displacement ratio. Also there is voltage drop in the cabling. I.e. a fully closed brake can produce variable voltage. To convert imprecise 24V to precise 18V level, there is provided two blocks: “18V ref” and “18V logic level”. “18V ref’ creates accurate reference voltage for the discrete logic. Each bit input has a level shifter with an example shown by the electrical circuit in Figure 5. Figure 5 shows a first example of an electrical circuit on the control board 70 shown in Figure 4. Vcc is the voltage produced by the block “18V ref”. In Figure 5 “bit3” which is received by the block “Input 1” is the output signal from the proximity switch PS4. In Figure 5 “bit3_out” is input for respective “bit3” in the R-2R ladder circuit of the block “5-bit DAC 24V”. The bitsO, 1,2,3 of the proximity switches PS1... PS8 are sent to an 18V AND circuit. The advantage of this is to have clear separation of “all brakes open” to “partial brakes open” statuses. Figure 6 shows the 18V AND circuit arranged on the control board 70 shown in Figure 4. So the level shifter pulls respective bit0,1,2,3 in the R-2R ladder circuit of the 18V AND block to ground or push to 18V reference voltage. The 18V AND block pulls bit4 in the R-2R ladder circuit to ground or push to 18V reference voltage. By the monitoring system for monitoring operation of the conveyor drive machine disc brakes a plurality N brake proximity switches PS1... PSN can be monitored without adding complexity in a control board 70 comprising an electrical circuit. N denotes the number of monitored proximity switches PS. N+1 bit DAC (digital-to-analog converter) circuit can be utilized converting proximity switch statuses to analog level circuit. The control board 70 may read combined proximity switch status with an ADC (analog-to-digital converter). A switch interface can convert imprecise outputs 0 / 24V of the switches to precise 0 / 18V logic level inputs for the N bits of the DAC. An 18V logic AND circuit can be used to combine all switch inputs to N+1st bit of the DAC. The use of the invention is not limited to the embodiments disclosed in the figures. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various 5 ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A machine brake assembly (52) of a conveyor drive machine (5), comprising:at least one brake disc (52-1) of the conveyor drive machine;at least two brake units (52-2A; 52-2B) mounted at opposite sides of the brake disc aligned with and facing each other;each said brake unit (52-2A; 52-2B) comprising on its own: a frame part (52-3); an armature (52-4) movable supported on the frame part; and an actuator configured to move the brake unit either into a braking state in contact with the braking surface of the brake disc (52-1) or into a non-braking state disconnected from the brake disc, in accordance with a control input.

2. The machine brake assembly according to claim 1, wherein the brake units (52-2A; 52-2B) are designed such that similar units can be used both in disc brakes and in shoe brakes, depending on conveyor machine type.

3. The machine brake assembly according to claims 1 or 2, wherein said actuator comprises a compression spring located between frame part (523) and armature (52-4) and adapted to push the armature forward, in contact with the brake disc (52-1).

4. The machine brake assembly according to claim 3, wherein said actuator comprises an electromagnet (52-5) located in the frame part (52-3), which electromagnet when energized pulls the armature (52-4) backwards by resisting force of the compression spring, such that the armature disconnects from the brake disc (52-1).

5. The machine brake assembly according to any of preceding claims, wherein the brake assembly (52) comprises at least two further brake units (52-2A; 52-2B) of the same type, mounted on the same brake disc (52-1) with the previous brake units (52-2A; 52-2B), and located in the same way at opposite sides of the brake disc facing each other.

6. The machine brake assembly according to any of preceding claims, wherein the brake assembly (52) comprises two brake discs (52-1) andfour pairs of brake units (52-2A; 52-2B) arranged so that two pairs of brake units are mounted on each brake disc (52-1).

7. The machine brake assembly according to any of preceding claims, wherein the brake units (52-2A; 52-2B) are dimensioned such that if at least one brake unit of a pair of brake units fails, the remaining pairs of brake units of the machine brake assembly (52) are still capable of stopping and holding the conveyor, in particular an elevator car (10).

8. The machine brake assembly according to any of preceding claims, wherein the conveyor drive machine (5) comprises an elevator hoisting machine, a drive machine of an escalator, or a drive machine of a travelator.

9. A monitoring system of the machine brake assembly according to any of the preceding claims, comprising:proximity switches (PS1... PSN) associated with each said brake unit (52-2A; 52-2B) and configured to monitoring operation of the state of each individual brake unit; anda control board (70) comprising an ADC (analog-to-digital converter) capable of reading combined proximity switch status and an N+1 bit DAC (digital-to-analog converter), where N denotes the number of monitored proximity switches, capable of converting proximity switch statuses to analog level circuit; and wherein the control board (70) is adapted to convert outputs 0 / 24V of the proximity switches (PS1... PSN) to precise 0 / 18V logic level inputs for the N bits of the DAC.

10. The monitoring system according to claim 9, wherein the control board (70) comprises an 18V logic AND circuit adapted to combine all proximity switch inputs to N+1 st bit of the DAC.

11. The monitoring system according to claim 9 or 10 further comprising:a conveyor controller (110) configured to control operation of a conveyor and operation of each brake unit (52-2A; 52-2B); whereinthe conveyor controller is adapted to receive analog status signals (Output 1-S1; Output 2-S2) combined by the control board (70) from each brake unit (52-2A; 52-2B) monitored by a proximity switch (PS1...PSN).5             12. A conveyor drive machine, in particular a drive machine of anelevator, an escalator, or a travelator, wherein the drive machine comprises the machine brake assembly according to any of claims 1-8.

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