US3705640A - Signalling system for mine hoists - Google Patents
Signalling system for mine hoists Download PDFInfo
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- US3705640A US3705640A US110991A US3705640DA US3705640A US 3705640 A US3705640 A US 3705640A US 110991 A US110991 A US 110991A US 3705640D A US3705640D A US 3705640DA US 3705640 A US3705640 A US 3705640A
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- automatic control
- hoist
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- mine
- control system
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- 230000011664 signaling Effects 0.000 title claims description 13
- 239000004020 conductor Substances 0.000 claims description 8
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 230000000881 depressing effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 244000304337 Cuminum cyminum Species 0.000 description 1
- 241001131927 Placea Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66B—ELEVATORS; ESCALATORS OR MOVING WALKWAYS
- B66B19/00—Mining-hoist operation
- B66B19/06—Applications of signalling devices
Definitions
- ABSTRACT in existing mine hoists, much of the complex equipment needed for automatic control is located at the working levels in the mine where environmental con.- ditions are poor.
- the complex equipment needed for automatic control of the hoist is located in the same room as the hoist drive where the environment is warm and dry. This is achievedthrough the use of control equipment of a type that responds to the coded pulses generated in the Bell Pull circuit in the way that the operator responds to the-ringing of his bell or flashing of his light. In essence, this equipment duplicates the responses of the operator in that it counts pulses, distinguishes betweensets of pulses, remembers this, exercises a degree of logic, and applies the information for control purposes.
- the existing Bell Pull system or an equally simple circuit can now.be used for sending the appropriate signals from the various mine levels to the control equipment.
- An operation selector is provided for selecting a mode of hoist operation between automatic or manual through a suitable connection with the Bell Pull circuit. When operation is manual control, the signals sent by the Bell Pull will, of course, be displayed to the operator.
- the Bell Pull' is a simplenormally open switch in which a pair of contacts are biased open and closed by a'person pulling on a rope. It may be a single switch located at the top of the mine shaft and operated by a rope extending from the switch down the mine shaft, during shaft sinking, but in an operating mine a switch is located at every level, each operated by its own rope.
- a person can introduce a sequence of electrical pulses into the system representing a communication that will be heard and seen by those near the indicators.
- Bells and lights are usually used to produce the audible and visible signals respectively, the bells giving a short ring for each pulse and the lights a flash.
- the message is in the form of a code, usually of the three sets of rings or flashes of a number or rings per set. There is relatively long time delay between sets and the rings in each set occur in rapid succession. This enables the operator to count the rings and yet distinguish between sets. In terms of electrical pulses, they occur in rapid. succession in each set but there is a distinguishable time delay between the sets.
- Each message i.e., each hoisting operation that the operator may be called upon to perform and his reply thereto, is
- a call to take some men from the second to the fifth level may be represented by two rings in the first set, five in the second, and two in the third.
- the call to take some men from the second to the fifth level may be represented by two rings in the first set, five in the second, and two in the third.
- the hoist operator replies with the same coded message confirming that he has received the message. However, he does not begin the hoisting operation until he has received the appropriateexecutive signal from the cage tender.
- the expression Bell is intended to include buzzers or like devices that will produce distinguishable sounds.
- the complex equipment needed for automatic control of the hoist is located in a room where the environment is warm and dry, e.g., the hoist room.
- This is achieved through the use of control equipment of a type that responds to the coded pulses generated in the Bell Pull circuit in the way that the operator responds to the ringing of his bell or flashing of his light.
- this equipment duplicates the responses of the operator in that it counts pulses, distinguishes between sets of pulses, remembers this, exercises a degree of logic, and applies the information for control purposes.
- it can be located in the same room as the hoist drive where it is dry and warm.
- the existing Bell Pull system or an equally simple circuit can now be used for sending the appropriate signals from the various mine levels to the control equipment.
- An operation selector is provided for selecting a mode of hoist operation between automatic or manual through a suitable connection with the Bell Pull circuit. When operation is manual control, the signals sent by the Bell Pull will, of course, be displayed to the operator.
- FIG. 1 is a diagram of a mine hoist and the control system for it.
- FIG. 2 is a diagram of an alternate signalling circuit.
- FIG. 1 illustrates a multi level mine hoist comprising a rope winder 10 driven by an electric motor 11, a standard steel rope 12 extending from the winder over a pulley 13 located in the head frame of the mine and down into the mine shaft to a conveyance 14, e.i., cage, suspended by the rope.
- the conveyance is raised or lowered between operating levels in the mine ranging from the ground level to the nth level by means of the winder taking in or letting out rope. This is effected in a well known manner through the motor and a braking system, both of which may be controlled automatically or manually.
- a hoist signalling system may consist of a Bell Pull l5 and an indicator 16 at the hoist operators station and at each level in the mine.
- the Bell Pull is a simple enclosed switch in which a pair of contacts are biased open and closed momentarily by a person pulling and then releasing a cord.
- the indicator if used, may be a bell, buzzer and/or lamps.
- Components 15 and 16 are interconnected by a number of electrical conductors 1'7 and also connected to a mode of hoist operation selector l8.
- Selector 18 is connected in the switching circuit and to the automatic control system 20 for controlling automatic operation of the hoist.
- buttons 25, 26, and 27 in place of a Bell Pull.
- selector 18 is set for manual button is used to generate a different set of pulses.
- a person now depresses and releases button 25 the number of times reqaired for the first set of pulses, following this he does t e same with button 26 for the second set of pulses, and finally the same with button 27 for the third set of pulses.
- the pulses generated by depressing the buttonsare now counted hoist operation the pulses sound a bell and or flash a light in the operators indicator giving him a coded message originating at one of the levels by-a man alterately pulling and releasing the cord of a Bell Full 15.
- the operator Before implementingthe hoisting operation called for, the operator responds by repeating the coded message. It isheard and seen at the level where the call originated.
- System 20 may be one of a number of known systems for processing a sequence of electrical pulses into a machine control signal for implementing a particular machine operation.
- System 20 may include a pulse counter 21 for counting pulses, a means 22 for distinguishing between the sets of pulses; a memory device 23 for recording the sets of pulses and the number of pulses in each set, a logic unit 24 for programming hoist operation when more than one call has been received and not yet acted on, and other control equipment for translating the information "received into actual hoist operations.
- Counter 21 may be a decade counter, means 22 a timer set for a time interval between sets that distinguishes the sets from the individual pulses, memory23 a shift register with a tally for each set of pulses, and unit 24 a device capable of combining two or more calls'intoa single trip if it is logical to do so.
- the automatic control system responds electro-mechanically to the electrical pulses in much the same sense that the operator does to the audible and visible signals, and this is done through the same equipment and wiring down in the mine. Moreover, the same signals are used for either manual or automatic operation by those calling for the conveyance.
- FIG. 2 is an elementary circuit showing another simple way of generating the pulses and counting them.
- each level in the mine has three separate 'Patent of the United States is:
- the tallies are shown as threeseparate registers for-the sake of simplicity.
- the pulses generated by depressing a button 25 are counted by register No. 1, those generated by depressinga button 26 by register No. 2, and those generated by depressing a button27 by register No. 3.
- This circuit retains the simplicity of the Bell Pull circuit in that the buttons are simple and rugged and relatively few conductors are needed for connecting thepush buttons to the automatic control system.
- each one of said switching means is a BellPull and said automatic control system includes means for counting individual pulses and means fordistinguishing the count of one set from the count of another set.
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Abstract
In existing mine hoists, much of the complex equipment needed for automatic control is located at the working levels in the mine where environmental conditions are poor. According to this invention, the complex equipment needed for automatic control of the hoist is located in the same room as the hoist drive where the environment is warm and dry. This is achieved through the use of control equipment of a type that responds to the coded pulses generated in the Bell Pull circuit in the way that the operator responds to the ringing of his bell or flashing of his light. In essence, this equipment duplicates the responses of the operator in that it counts pulses, distinguishes between sets of pulses, remembers this, exercises a degree of logic, and applies the information for control purposes. Moreover, it can be located in the same room as the hoist drive where it is dry and warm. The existing Bell Pull system or an equally simple circuit can now be used for sending the appropriate signals from the various mine levels to the control equipment. An operation selector is provided for selecting a mode of hoist operation between automatic or manual through a suitable connection with the Bell Pull circuit. When operation is manual control, the signals sent by the Bell Pull will, of course, be displayed to the operator.
Description
Eastcott SIGNALLING SYSTEM FOR MINE HOISTS- inventor? Peter Hertel Eastcott, Peterborough, Ontario, Canada 7 [73] Assignee: Canadian General Electric Company Limited, \Vest Toronto, Ontario,
Canada [.22] Filed: Jun. 29, 1071 [21] Appl. No.: 110,991
[30 Foreign Application Priority om Feb. 18, 1970 Canada .....75l42 [52] US. Cl. ..18'1/29 R [51] Int. Cl. ..B66b 1/16 I [58] Field of Search ..l87 /29 [S6] I References Cited UNITED STATES PATENTS 1,962,009 6/1934 Gale ..1a7/29 2,602,524 7/1952 Shirley ..l87/29 3,203,506 8/1965 Cummins ..l87/29 Primary Examiner-Bernard A. Gilheany 5] 1451 Dec. 12,1972
[57] ABSTRACT in existing mine hoists, much of the complex equipment needed for automatic control is located at the working levels in the mine where environmental con.- ditions are poor. According to this invention, the complex equipment needed for automatic control of the hoist is located in the same room as the hoist drive where the environment is warm and dry. This is achievedthrough the use of control equipment of a type that responds to the coded pulses generated in the Bell Pull circuit in the way that the operator responds to the-ringing of his bell or flashing of his light. In essence, this equipment duplicates the responses of the operator in that it counts pulses, distinguishes betweensets of pulses, remembers this, exercises a degree of logic, and applies the information for control purposes. Moreover, it can be located in the same room as the hoist drive where it is dry and warm. The existing Bell Pull system or an equally simple circuit can now.be used for sending the appropriate signals from the various mine levels to the control equipment. An operation selector is provided for selecting a mode of hoist operation between automatic or manual through a suitable connection with the Bell Pull circuit. When operation is manual control, the signals sent by the Bell Pull will, of course, be displayed to the operator.
4 Claims, 2 Drawing Figures Qgi 2ND LEVEL PATENTED m 12 I972 OPERATION SELECTOR GROUND LEVEL CAGE SHEET 1 OF 2 FOR HOIST OPERATOR 2 Ts s s 2 2 2 2 'l'l'l AUTOMATIC CONTROL SYSTEM n TH LEVEL I NVENTOR.
PETER DEH. EASTCOTT QQFLM Patent Age P'A'TE'N'TED DEC 12 m2 SHEET 2 0F 2 REGISTER 1 REGISTER 2 REGISTER 3 25 Po -o4 26 27 N X Iii];- 0-0 D 26 PO 43 27a ANOTHER LEVEL :fiiilgo- FIG. 2
IN-VENTOR. PETER DEH. EASTCOTT Patent A ent 1 SIGNALLING SYSTEM FOR MINE IIOIS'IS I This invention relates to a signalling system for mine hoists, and in particular to a system suitable for use during either manual or automatic operation of the hoist.
- In Canada and elsewhere, all mine hoists must be capable of manual control, even though they are autoknown as a Bell Pull and an indicator on each level in the mine 'near the. stop for the conveyance, an indicator and a signalling switch in the hoist room for use by the operator of the hoist,- and a few electrical conductors running from the signalling equipment in the hoist room down the mine shaft to the signalling equipment at the different levels. The Bell Pull'is a simplenormally open switch in which a pair of contacts are biased open and closed by a'person pulling on a rope. It may be a single switch located at the top of the mine shaft and operated by a rope extending from the switch down the mine shaft, during shaft sinking, but in an operating mine a switch is located at every level, each operated by its own rope.
' By momentarily pulling and then releasing the rope a number of times, a person can introduce a sequence of electrical pulses into the system representing a communication that will be heard and seen by those near the indicators. Bells and lights are usually used to produce the audible and visible signals respectively, the bells giving a short ring for each pulse and the lights a flash. The message is in the form of a code, usually of the three sets of rings or flashes of a number or rings per set. There is relatively long time delay between sets and the rings in each set occur in rapid succession. This enables the operator to count the rings and yet distinguish between sets. In terms of electrical pulses, they occur in rapid. succession in each set but there is a distinguishable time delay between the sets. Each message, i.e., each hoisting operation that the operator may be called upon to perform and his reply thereto, is
represented by a different combination of rings making up a three-setcode. For example, a call to take some men from the second to the fifth level may be represented by two rings in the first set, five in the second, and two in the third. In response to this call, the
hoist operator replies with the same coded message confirming that he has received the message. However, he does not begin the hoisting operation until he has received the appropriateexecutive signal from the cage tender. The expression Bell is intended to include buzzers or like devices that will produce distinguishable sounds.
When a mine hoist is equipped with automatic controls as many hoist are to-day, automatic operation requires a control system separate and distinct from the Bell Pull system described above. The automatic system employed in an elaborate system incorporating a multiplicity of pushbuttons and indicators at every level interconnected electrically by means of multi conductor cables. As the number of levels increase, the complexity of the system multiplies at a rate out of all proportion to the increase in number of levels. The automatic control. equipment is far less rugged, much more complex, and has many more vital components located in the damp regions than the Bell Pull scheme. The extreme dampness in a mine along with rough usage of more delicate equipment makes the automatic system more vulnerable to failure. As a result, the automatic control system requires a great deal, more maintenance than the Bell Pull system.
According to this invention, the complex equipment needed for automatic control of the hoist is located in a room where the environment is warm and dry, e.g., the hoist room. This is achieved through the use of control equipment of a type that responds to the coded pulses generated in the Bell Pull circuit in the way that the operator responds to the ringing of his bell or flashing of his light. In essence, this equipment duplicates the responses of the operator in that it counts pulses, distinguishes between sets of pulses, remembers this, exercises a degree of logic, and applies the information for control purposes. Moreover, it can be located in the same room as the hoist drive where it is dry and warm. The existing Bell Pull system or an equally simple circuit can now be used for sending the appropriate signals from the various mine levels to the control equipment. An operation selector is provided for selecting a mode of hoist operation between automatic or manual through a suitable connection with the Bell Pull circuit. When operation is manual control, the signals sent by the Bell Pull will, of course, be displayed to the operator.
A method of practicing the invention will now be described in more detail with reference to the accompanying drawings, in which FIG. 1 is a diagram of a mine hoist and the control system for it; and
FIG. 2 is a diagram of an alternate signalling circuit.
FIG. 1 illustrates a multi level mine hoist comprising a rope winder 10 driven by an electric motor 11, a standard steel rope 12 extending from the winder over a pulley 13 located in the head frame of the mine and down into the mine shaft to a conveyance 14, e.i., cage, suspended by the rope. The conveyance is raised or lowered between operating levels in the mine ranging from the ground level to the nth level by means of the winder taking in or letting out rope. This is effected in a well known manner through the motor and a braking system, both of which may be controlled automatically or manually.
A hoist signalling system according to the invention may consist of a Bell Pull l5 and an indicator 16 at the hoist operators station and at each level in the mine. As pointed out earlier, the Bell Pull is a simple enclosed switch in which a pair of contacts are biased open and closed momentarily by a person pulling and then releasing a cord. The indicator, if used, may be a bell, buzzer and/or lamps. Components 15 and 16 are interconnected by a number of electrical conductors 1'7 and also connected to a mode of hoist operation selector l8. Selector 18 is connected in the switching circuit and to the automatic control system 20 for controlling automatic operation of the hoist.
' push buttons 25, 26, and 27 in place of a Bell Pull. Each divided into sets of rapidly occurring pulses of a' number of pulses per set specified by the instruction, the sets being distinguishable one from another by a pause between successive sets substantially longer in time than the pausebet'ween the pulses themselves. As many as three sets of pulses maybe needed for deep mine having many levels. If selector 18 is set for manual button is used to generate a different set of pulses. To placea call, a person now depresses and releases button 25 the number of times reqaired for the first set of pulses, following this he does t e same with button 26 for the second set of pulses, and finally the same with button 27 for the third set of pulses. The pulses generated by depressing the buttonsare now counted hoist operation, the pulses sound a bell and or flash a light in the operators indicator giving him a coded message originating at one of the levels by-a man alterately pulling and releasing the cord of a Bell Full 15. Before implementingthe hoisting operation called for, the operator responds by repeating the coded message. It isheard and seen at the level where the call originated.
If, instead, selector 18 is set for automatic control of the hoist, the three sets of pulses will be fed into automatic control system 20 where they are processed for control of the hoist through electro-mechanical means rather than through human endeavor. System 20 may be one of a number of known systems for processing a sequence of electrical pulses into a machine control signal for implementing a particular machine operation. System 20 may include a pulse counter 21 for counting pulses, a means 22 for distinguishing between the sets of pulses; a memory device 23 for recording the sets of pulses and the number of pulses in each set, a logic unit 24 for programming hoist operation when more than one call has been received and not yet acted on, and other control equipment for translating the information "received into actual hoist operations. Counter 21 may be a decade counter, means 22 a timer set for a time interval between sets that distinguishes the sets from the individual pulses, memory23 a shift register with a tally for each set of pulses, and unit 24 a device capable of combining two or more calls'intoa single trip if it is logical to do so. In practice, the automatic control system responds electro-mechanically to the electrical pulses in much the same sense that the operator does to the audible and visible signals, and this is done through the same equipment and wiring down in the mine. Moreover, the same signals are used for either manual or automatic operation by those calling for the conveyance.
In the scheme shown in FIG. 1 only the rugged call and indicator equipment necessary for manual control is located down in the mine whereoperating conditions are poor. The more complex and delicate equipment necessary for automatic control is now located in the hoist room where the environment is warm and dry. This should reduce failures of the automatic equipment, and when failures do occur make repairs easier and faster. I I
FIG. 2 is an elementary circuit showing another simple way of generating the pulses and counting them. In this figure, each level in the mine has three separate 'Patent of the United States is:
directly by a different one of the three tallies of the memory device,.and there is no longer any need for a means such as timer 22 in the automatic control system for distinguishingthe individual pulses from the sets of pulses; thisis inherent in the circuit. In FIG. 2 the tallies are shown as threeseparate registers for-the sake of simplicity. The pulses generated by depressing a button 25 are counted by register No. 1, those generated by depressinga button 26 by register No. 2, and those generated by depressing a button27 by register No. 3. This circuit retains the simplicity of the Bell Pull circuit in that the buttons are simple and rugged and relatively few conductors are needed for connecting thepush buttons to the automatic control system.
I What I claim as new and desire to secure by Letters 1. A signalling system fora multilevel mine hoist having a mine shaft conveyance and a drive therefore, said signalling system comprising means for controlling said drive manually; an automatic control system for controlling operation of said drive; selector means for selecting a mode of hoist operation between either manual or automatic control; indicator, means for use by the hoist operator; said automatic control system, selector means and indicator means being located in a hoist building; electrical conductors interconnecting I said automatic control system, selector means and inble switching means located at the hoist operators station and at each one of different levels in the mine; conductors electrically interconnecting said switching means with said circuit; each one of said switching means being adapted for manual operation to produce in said circuit a number of sets of electrical pulses representing a hoisting instruction of the sender; when said selector means is set for automatic control said automatic control system utilizing said pulses for automatic control of said drive, and when said selector means is set for manual control said automatic control system being rendered inoperable and said indicator means displaying said pulses in either or both audible and visible form.
2. The system defined in claim 1 wherein each one of said switching means is a BellPull and said automatic control system includes means for counting individual pulses and means fordistinguishing the count of one set from the count of another set.
3. The system defined in claim 1 wherein said switch means at each level consists of a push button for each set of pulses; and wherein said automatic control system has a counter for each set of pulses.
4. The system defined in claim 1 wherein said automatic control system includes logic means for programming hoist' operation in response to two or more calls to be acted on.
II 8 II 4
Claims (4)
1. A signalling system for a multi level mine hoist having a mine shaft conveyance and a drive therefore, said signalling system comprising means for controlling said drive manually; an automatic control system for controlling operation of said drive; selector means for selecting a mode of hoist operation between either manual or automatic control; indicator, means for use by the hoist operator; said automatic control system, selector means and indicator means being located in a hoist building; electrical conductors interconnecting said automatic control system, selector means and indicator means in an operable circuit; manually operable switching means located at the hoist operator''s station and at each one of different levels in the mine; conductors electrically interconnecting said switching means with said circuit; each one of said switching means being adapted for manual operation to produce in said circuit a number of sets of electrical pulses representing a hoisting instruction of the sender; when said selector means is set for automatic control said automatic control system utilizing said pulses for automatic control of said drive, and when said selector means is set for manual control said automatic control system being rendered inoperable and said indicator means displaying said pulses in either or both audible and visible form.
2. The system defined in claim 1 wherein each one of said switching means is a Bell Pull and said automatic control system includes means for counting individual pulses and means for distinguishing the count of one set from the count of another set.
3. The system defined in claim 1 wherein said switch means at each level consists of a push button for each set of pulses; and wherein said automatic control system has a counter for each set of pulses.
4. The system defined in claim 1 wherein said automatic control system includes logic means for programming hoist operation in response to two or more calls to be acted on.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA75142 | 1970-02-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3705640A true US3705640A (en) | 1972-12-12 |
Family
ID=4086349
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US110991A Expired - Lifetime US3705640A (en) | 1970-02-18 | 1971-01-29 | Signalling system for mine hoists |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3705640A (en) |
| CA (1) | CA906617A (en) |
| ZA (1) | ZA71129B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2776644A1 (en) * | 1998-03-30 | 1999-10-01 | Otis Elevator Co | Control plate for lift with special provision for visually handicapped people |
| CN105151971A (en) * | 2015-09-30 | 2015-12-16 | 枣庄矿业(集团)有限责任公司田陈煤矿 | Multi-level signal promotion system for underground coal mine inclined lane |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1962009A (en) * | 1930-07-31 | 1934-06-05 | Gurney Elevator Co | System of control for elevators |
| US2602524A (en) * | 1950-05-23 | 1952-07-08 | Joshua E Shirley | Remote-control system for cars moving in a defined path of travel |
| US3203506A (en) * | 1961-08-16 | 1965-08-31 | Ace Machinery Ltd | Radio communication means between elevator cage and motor control |
-
1970
- 1970-02-18 CA CA906617A patent/CA906617A/en not_active Expired
-
1971
- 1971-01-11 ZA ZA710129A patent/ZA71129B/en unknown
- 1971-01-29 US US110991A patent/US3705640A/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1962009A (en) * | 1930-07-31 | 1934-06-05 | Gurney Elevator Co | System of control for elevators |
| US2602524A (en) * | 1950-05-23 | 1952-07-08 | Joshua E Shirley | Remote-control system for cars moving in a defined path of travel |
| US3203506A (en) * | 1961-08-16 | 1965-08-31 | Ace Machinery Ltd | Radio communication means between elevator cage and motor control |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2776644A1 (en) * | 1998-03-30 | 1999-10-01 | Otis Elevator Co | Control plate for lift with special provision for visually handicapped people |
| US6105729A (en) * | 1998-03-30 | 2000-08-22 | Otis Elevator Company | Elevator car operating panel |
| CN105151971A (en) * | 2015-09-30 | 2015-12-16 | 枣庄矿业(集团)有限责任公司田陈煤矿 | Multi-level signal promotion system for underground coal mine inclined lane |
Also Published As
| Publication number | Publication date |
|---|---|
| CA906617A (en) | 1972-08-01 |
| ZA71129B (en) | 1971-10-27 |
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