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Patent Searching and Data


Title:
IMPROVED DOOR SYSTEM
Document Type and Number:
WIPO Patent Application WO/2010/118984
Kind Code:
A1
Abstract:
A door system (100) comprises a door (102), a direct current, DC, electric motor (104) configured to operate the door and a control unit (114). The DC motor comprises a first pair of brushes arranged at a commutator of the DC motor and configured to be connected to at least a first source of electric power (108), and a second pair of brushes arranged at the commutator of the DC motor and configured to be connected to at least a second source of electric power (112). The control unit is configured to detect damage to the first pair of brushes and, in dependence of such detection, disconnect the first pair of brushes from the first source and connect the second pair of brushes to the second source. That is, a redundant channel of power is provided that can be utilized when a first channel of power has been damaged, thereby maintaining safety critical functionality.

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Inventors:
DREYER ROGER JUEL (SE)
Application Number:
EP2010/054676
Publication Date:
October 21, 2010
Filing Date:
April 09, 2010
Export Citation:
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Assignee:
ASSA ABLOY IP AB (SE)
DREYER ROGER JUEL (SE)
International Classes:
E05F15/10; G01R31/34; H01R39/58; H01R39/62
Foreign References:
US20060244271A12006-11-02
DE19619728A11997-11-20
DE740379C1943-10-19
US2775717A1956-12-25
US6873083B22005-03-29
Attorney, Agent or Firm:
AURELL, Henrik (PO Box 4289, Malmö, SE)
Download PDF:
Claims:
Claims

1. A door system (100) comprising a door (102), a direct current, DC, electric motor (104) configured to operate the door and a control unit (114), where the DC motor comprises:

- a first pair of brushes (222) arranged at a commutator (230) of the DC motor and configured to be connected to at least a first source of electric power (108), and

- a second pair of brushes (224) arranged at the commutator of the DC motor and configured to be connected to at least a second source of electric power (112), and where:

- the control unit is configured to detect damage to the first pair of brushes and, in dependence of such detection, disconnect the first pair of brushes from the first source of electric power and connect the second pair of brushes to the second source of electric power.

2. The door system of claim 1 , wherein:

- the first pair of brushes is configured to be connected to an alternating current, AC, source via a rectifier unit (110), and

- the second pair of brushes is configured to be connected to a battery.

3. The door system of claim 1 or 2, wherein:

- the control unit is configured to detect damage to the first pair of brushes by way of performing a measurement of at least one electric property of the first pair of brushes.

4. A method of controlling a door system (100) that comprises a door (102), a direct current, DC, electric motor (104) configured to operate the door, the method comprising:

- detecting (201 ) damage to a first pair of brushes (222) arranged at a commutator (230) of the DC motor,

- in dependence of the detection, disconnecting (205) the first pair of brushes from a first source of electric power (108) and connecting (207) a second pair of brushes (224) arranged at the commutator of the DC motor to a second source of electric power (1 12).

5. The method of claim 4, wherein:

- detecting damage to the first pair of brushes comprises performing a measurement of at least one electric property of the first pair of brushes.

Description:
Improved door system

Technical field

The present invention relates to a door system with an electric motor that is configured to operate a door in the door system.

Background

Doors that open and close automatically have been widely used for a long time now. Such doors are in most implementations operated by electric motors, such as direct current (DC) motors. The door operation motors are often controlled by control devices that sense an approaching person and/or control devices that electronically authenticates and authorizes persons before controlling the motor to open or close the door.

Depending on where such automatic doors are situated, i.e. depending on the number of open and close cycles experienced by the doors, the lifetime of the electric components of the motors may vary to a large extent. This is a safety issue that has been recognized and the use of automatic doors in escape routes has in some legislations resulted in directives pointing out requirements regarding redundancy. Such requirements are often fulfilled by the use of plural independent systems to ensure that the door always can open in event of escape. A common way of solving that is to apply two motors and two electronic control systems connected to the motors for ensuring the safety critical functionality.

US 2,775, 717 and US 6,873,083 address the problem of how to extend the lifetime of a brush assembly in a DC motor by incorporating two or more carbon brushes, a first brush and a second brush. As the motor is used the first brush is worn away until approaching end of useful life, when a trip mechanism arranged at the brushes causes the first brush to retract from the commutator and the second brush to get in contact with the commutator.

A drawback of such arrangements is that, although they may be used to extend the operational lifetime of an automatic door system, they do not provide the redundancy that is needed in order to fulfill many safety requirements in escape routes.

Summary

In order to improve on prior art solutions there is provided, according to a first aspect, a door system comprising a door, a direct current, DC, electric motor configured to operate the door and a control unit. The DC motor comprises a first pair of brushes arranged at a commutator of the DC motor and configured to be connected to at least a first source of electric power, and a second pair of brushes arranged at the commutator of the DC motor and configured to be connected to at least a second source of electric power. The control unit is configured to detect damage to the first pair of brushes and, in dependence of such detection, disconnect the first pair of brushes from the first source of electric power and connect the second pair of brushes to the second source of electric power.

The first pair of brushes may configured to be connected to an alternating current, AC, source via a rectifier unit, and the second pair of brushes may be configured to be connected to a battery.

Furthermore, the control unit may be configured to detect damage to the first pair of brushes by way of performing a measurement of at least one electric property of the first pair of brushes.

Similarly, in a second aspect, there is provided a method of controlling a door system. The method comprises detecting damage to a first pair of brushes arranged at a commutator of the DC motor and, in dependence of the detection, disconnecting the first pair of brushes from a first source of electric power and connecting a second pair of brushes to a second source of electric power.

The detection of damage to the first pair of brushes may comprise performing a measurement of at least one electric property of the first pair of brushes.

In other words, the drawbacks as discussed above are addressed by providing a door system with a redundant second channel of power that can be utilized when a first channel of power has been damaged. That is, safety critical functionality is maintained in an automatic door even when the main brushes in the DC motor are worn out.

The control unit has the ability to identify, e.g. by making electrical measurements, that one pair of brushes is worn out or damaged. The control system can then disconnect power from the first channel and connect power from the second channel and then enable use of the second pair of brushes to drive the door to a selected safe position or performing a final, maybe critical, action, during an emergency situation such as an evacuation.

The second pair of brushes that may be considered as spare, or only used in case of a failure, is not worn out to the same degree as the first pair that is used for normal use. There is no current floating through the second pair of brushes, possibly with the exception during testing of the redundant second power channel provided via the second pair of brushes. This means that the second pair of brushes lasts longer, and since both pairs of brushes operate with one and the same commutator and windings in the DC motor, the solution as summarized will be simple and cost efficient.

Brief description of the drawings

Embodiments will now be described with reference to the attached drawings, where: figure 1 is a block diagram that schematically illustrates a door system, figure 2 is a perspective view that schematically illustrates a DC motor, and figure 3 is a flowchart of a control sequence.

Detailed description of embodiments

Figure 1 is a block diagram of a door system 100 as summarized above. The door system 100 comprises a door 102 and a DC motor 104 that is configured to open and close the door 102 via mechanical interface means 106. The mechanical interface means 106 typically comprises gears and levers that are capable of converting rotary motion in the motor 104 to appropriate motion of the door 102, noting that the door 102 may be any type of door known in the art that is capable of being operated by a motor. Examples of such door types include swing doors, sliding doors and revolving doors.

An electronic control unit 114, connected to the motor 104, is configured such that it is capable of, by help of an electric switch 116, connecting and disconnecting the motor 106 to a first electric power source 108 and a second electric power source 112. The door system 100 is in this embodiment capable of being connected to an AC outlet 108 via a rectifying unit 110 as well as a DC source in the form of a battery 1 12.

Turning now to figure 2, a DC motor 204 that is suitable for use in a door system, such as the system 100 of figure 1 , will be described in some more detail. It is to be noted that the motor 204 is schematically represented in figure 2 and many details that are common to most DC motors have been omitted for the sake of clarity.

The motor 204 comprises a rotation axle 206, a commutator 230 and winding 220. The axle 206 is configured to be interfaced, via mechanical interface means such as the mechanical interface means 106 in figure 1 , to a door such as the door 102 in figure 1. A first pair of brushes 222 and a second pair of brushes 224 are arranged at the commutator 230. Electric power is provided to the first pair of brushes 222 via first electric leads 226 and electric power is provided to the second pair of brushes 224 via second electric leads 228. Although not explicitly shown in figure 2, the electric leads 226, 228 are connected via an electric switch, such as the switch 1 16 in figure 1 controlled by a control unit such as the control unit 1 14 in figure 1 , to a respective power source such as the first power source 108 and the second power source 112 in figure 1. Any of the first pair of brushes 222 and the second pair of brushes 224 may be connected to any power source, such as any of the first power source 108 and the second power source 1 12 in figure 1.

Turning now to figure 3, control of a DC motor such as the motor 104 in figure 1 and the motor 204 in figure 2 will be described. The control is performed by means of a control unit such as the control unit 1 14 in figure 1 , together with sensors and actuators suitable for detecting electric characteristics in the motor and operating switching units such as the switching unit 1 16 in figure 1. As the skilled person will realize, the control is typically realized by way of software that is stored in memory and executed by a processing unit within the control unit.

An initial state is that of the motor being provided with electric power from a first electric power source through a first pair of brushes, as described above in connection with figure 1. In a measuring step 201 , sensing and detecting of electric characteristic is performed together with processing of these characteristics to the extent that it can be determined whether or not the first pair of brushes are damaged. A decision based on this measurement is then taken in a decision step 203. If it is found that the first pair of brushes are damaged, the first pair of brushes are disconnected from the first power source in a disconnection step 205, and the second pair of brushes are connected to the second power source in a connection step 207.