US3136385A

US3136385A - High voltage aerial lift and control therefor

Info

Publication number: US3136385A
Application number: US208029A
Authority: US
Inventors: Jay M Eitel
Original assignee: TELSTA CORP
Current assignee: TELSTA CORP
Priority date: 1962-07-06
Filing date: 1962-07-06
Publication date: 1964-06-09
Anticipated expiration: 1981-06-09

Description

June 9, 1964 J. M. ElTEL 3,136,385

HIGH VOLTAGE AERIAL LIFT AND CONTROL THEREFOR Filed July 6, 1962 3 Sheets-Sheet l INVENTOR. Jay M. E i te! BY Ji @QZQ Attorneys J. M. EITEL 3,136,385

HIGH VOLTAGE AERIAL LIFT AND CONTROL THEREFOR June 9, 1964 3 Sheets-Sheet 2 Filed July 6, 1962 INVENTOR.

Jay M. E i re! Attorneys June 9, 1964 J. M. ElTEL 3,136,385

HIGH VOLTAGE AERIAL LIFT AND CONTROL THEREFOR Filed July 6, 1962 3 She ets-Sheec 5 E MODULATOR OSCILLATOR i F i g. 9

I3! I32 155 I34 DETECTOR INVENTOR.

Jay'M. Eire! F I g. 10

Attorneys United States Patent Ofiice 3,136,385 Patented June 9, 1964 3,136,385 HIGH VOLTAGE AERIAL LIFT AND CONTROL THEREFOR Jay M. Eitel, Los Altos, Califi, assignor to Telsta Corp, San Carlos, Califl, a corporation of California Filed July 6, 1962,Ser. No. 208,029 9 Claims. (Ci. 182-2) This invention relates to a high voltage aerial liftand to a control therefor and more particularly to an aer1al lift of the type having a workmans platform with the controls mounted on the workmans platform.

At the present time, there is a demand for equipment for use in the repair of high voltage transmission lines without interruption of service. In particular, there is a need for an aerial lift in which the workman can be raised from the ground for work on the transmission line and in which he will be adequately insulated so that he can work the transmission lines withoutadditional protective equipment.

In general, it is an object of the present invention to provide an aerial lift and control therefor which can be utilized for working on high voltage transmission lines.

Another object of the invention is to provide an aerial lift and control therefor of the above character in which the workman in the workmans basket can control the operation of the lift.

Another object of the invention is to provide an aerial lift of the above character which can be adequately insulated for work on any existing high voltage transmission lines.

Another object of the invention is to provide a control of the above character for the aerial lift which is relatively inexpensive and which can be readily maintained.

Another object of the invention is to provide a control of the above character which can be utilized with substantially conventional aerial lifts.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a side elevational View of a high voltage aerial lift incorporating my invention.

' FIGURE 2 is an enlarged cross-sectional view of the boom structure used in the aerial lift.

FIGURE 3 is a cross-sectional view taken along the line 33 of FIGURE 2.

FIGURE 4 is a cross-sectional view taken along the line 44 of FIGURE 2.

FIGURE 5 is a diagram with certain of the parts schematically illustrated of the control system utilizedin the aerial lift.

FIGURE 6 is a detailed circuit diagram of the photocell and amplifier circuit.

FIGURE 7 is a partial side elevational view of another aerial lift incorporating my invention. 7

FIGURE 8 is a circuit diagram with certain of the parts schematically illustrated of the control system utilized in the aerial lift shown in FIGURE 7.

FIGURE 9 is a block diagram of the transmitter utilized in the control system in FIGURE 8.

FIGURE 10 is a block diagram of the receiver utilized in the control system shown in FIGURE 8.

In general, my aerial lift which is particularly adapted for use in high voltage work consists of a self-propelled vehicle upon which a workmans lift is mounted. The

. workmans lift has a boom structure with a workmans platform secured to the outer end. The boom structure has portions which are formed of insulating material for insulating the workmans platform from the remainder of the lift. A control assembly is mounted on the lift supporting structure. Motive means is connected to the control assembly for operating the workmans lift so that the workmans platform can be rotated about a vertical axis and raised and lowered about a horizontal axis, and moved toward and away from the vehicle. A control mechanism is mounted on the workmans platform and has electrical switches. Means is provided which is insulated from the remainder of the lift supporting structure for controlling the operation of the control assembly from the control mechanism. This means includes a power supply which is mounted adjacent the workmans platform and circuitry which connects the power supply through the switches of the control mechanism.

As shownin the drawings, my insulated or high voltage aerial lift consists of a self-propelled vehicle 11 having front and

rear wheels

12 and 13 and a framework 14 mounted upon the front and rear wheels. A cab 16 is mounted on the framework 14 in a conventional manner. A lifting equipment 18 is mounted on the rear of the vehicle on the framework 14. The lifting equipment 18 can be of any suitable type. For example, it can be of the extensible boom type which is shown in the drawings or it can be of the elbow type, if desired.

The lifting equipment 18 which I have used is provided with a load supporting structure or turret 19 which is mounted upon the framework 14 in the manner shown in US. Patent No. 2,841,404. As disclosed in that patent, the load supporting structure 19 is mounted for rotation about a vertical axis by means which includes a rotating drive assembly 21. A boom structure 22 is pivotally mounted for movement about a horizontal axis formed by a shaft 23 carried by upper portions of the load supporting structure 19 as shown particularly in FIGURE 1. Means is providedfor raising and lowering the outer free end of the boom structure or, in other words, for swing- .ing the boom structure about the horizontal axis provided sections, it is desirable that the inner or telescoping section be formed of a suitable insulating material. One type of insulating material found to be satisfactory for fabricating a telescoping boom section is fibreglass bonded together with epoxy resins. Means is provided for extending and retracting the telescoping boom section 27 with respect to the main or outer section 26 and'includes a telescoping drive assembly 28 of the type which is disclosed in my Patent No. 2,896,750. As disclosed in that patent, this means for extending and retracting the telescoping boom section 27 consists of a sprocket wheel 31 which is driven by the telescoping drive assembly 23. The sprocket 31 drives a chain 32 which, in turn, drives a sprocket 33. The sprockets 31 and 33 are mounted on the mainboom section 26, whereas the two ends of the chain 32 are secured to the inner or telescoping boom section. b

The front end of the outer boom section 26 is provided with a plurality of rollers 36 which engage the side walls of the inner boom section-23 as shown particularly in FIGURE 3. The inner end of the inner or telescoping boom 27 is provided with rollers 37 which engage the inner surface of the outer boom section 26. The inner boom structure includes additional apparatus which will be described in detail in conjunction with the control apparatus utilized in my aerial lift.

A workmans or operators platform or lift 41 is mounted on the outer free end of the boom structure on a pair of arms 42 which are aflixed to the outer end of the telescoping boom section 27. The platform or lift 41 has its upper end secured to the arms 42 by pins 43 so as to permit the workmans platform to continuously assume a level condition as the boom structure is raised and lowered about the horizontal axis provided by the shaft 23.

Control means is provided for controlling the operation of the boom structure, either from the workmans basket or platform 41, or from the ground or from the vehicle itself. Such means includes a motor generator set 46 of a suitable type such as a generator driven by a gasoline engine. The output from the generator is supplied to a control panel 47 which includes an assembly of mechanically interlocked magnetic reversing relays which are protected with thermal overloads. These relays can be controlled either by ground control mechanism 48 or by a control mechanism 49. The ground control mechanism 48 is preferably mounted on the load supporting structure or turret 19 so that the

drive assemblies

21, 24 and 28 can be operated either from the vehicle or from the ground. The control mechanism 49 is mounted in the basket or platform 41 and is utilized for controlling the

drive assemblies

21, 24 and 28 from this position. The control mechanism 49 is of a type which is described in my Patent No. 2,841,404. As disclosed in that patent, it includes a plurality of switches, namely, seven microswitches which are adapted to be operated by the control lever 51.

Means is provided for connecting the control mechanism 49 to the control panel 47 which, at the same time, will provide suitable high voltage insulation for a purpose hereinafter described. This means consists of a suitable power supply such as a battery 52 which is mounted in a suitable location adjacent the control mechanism 49 such as within the workmans basket 41. As shown in FIGURE 5, one side of the battery 52 is connected to the control mechanism 49 in such a manner so that it is connected to all six of the switches which are utilized for operating the

drives

21, 24 and 28 through the safety switch. The other side of the battery is connected to one side of lamps 54 by a conductor 56 which forms a part of a cable 57 which extends from the workmans platform 41 to the outer end of the telescoping boom section 27 as shown particularly in FIGURE 2. The other sides of the lamps 54 are connected to the other sides of the six switches within the control mechanism 49 by conductors 58 which also form a part of the cable 57. The lamps 54 serve as means for emitting light rays. Suitable means is provided for transmitting the light rays from each of the lamps and consists of a plurality of light conducting rods or members 61 of a suitable insulating material such as Lucite. The Lucite rods can be of any desired dimension. For example, I have found that Lucite rods each having a diameter of A inch and a length of approximately 4 ft. are suitable. The length of the Lucite rods is primarily determined by the voltages which are to be encountered by the apparatus. The members 61 must be formed of an insulating material which will not break down under high voltages. Each of the Lucite rods 61 is preferably shrouded in a suitable light reflecting casing 62 to prevent light from entering any one of the rods from the other rods. It is also preferable that all the rods 61 be mounted in a unitary assembly and that the entire assembly be enclosed in a light-tight housing 63 which is connected to the housing 64 which carries the lamps 54.

Photosensitive means in the form of photosensitive elements 66 are provided at the end of each of the light conducting members 61. The elements 66 sense when light is present or when light is not present in the associated light transmitting member 61. In my embodiment, I have chosen to utilize the photosensitive elements 66 to sense when the lamps 54 are energized. These photosensitive elements are carried within a housing 67 mounted on the other end of the housing 63.

From the construction shown, it can be seen that the

housings

63, 64 and 67 are formed as a unitary structure which is mounted in the forward end on one side of the telescoping boom section 27 as shown particularly in FIGURES 2 and 4. This makes it possible to readily remove the entire assembly for maintenance and replacement when desired. The photosensitive elements 66 are connected by conductors 71 and a common conductor 72 provided in a cable 73 to an amplifier and power supply assembly 74 which is mounted in a housing 75 secured to the outer boom section 26 as shown in FIGURE 2. The amplifier and power supply 74 is connected by a cable 76 to the control assembly in panel 47 for control operations as hereinafter described.

A take-up assembly is provided within the inner boom section 27 for taking up the cable 73 as the telescoping section 27 is extended and retracted. It consists of a dolly assembly 81 which includes wheels 82 which ride in the four corners of the inner boom section 27, as shown particularly in FIGURE 4. Movement of the dolly within the inner boom section 27 is controlled by a cable 83. One end of the cable 83 is secured to a turnbuckle 84 which is yieldably restrained in its movement by a spring 86 mounted within a bracket 87 secured to a reel support member 88. The cable 83 is reeved over a pulley 89 which is mounted in the front end of the dolly assembly 81. It then passes over a pulley 91 which is rotatably mounted in a pulley support 88 provided in the front end of the telescoping boom section 27. The cable then extends rearwardly and is reeved over a pulley 91 which is mounted in an opening 92 provided in the boom section 27. The other end of the cable 83 is then secured to the outer boom section 26 by a bolt 93 as shown particularly in FIGURE 2. The cable 73, after it passes from the housing 67, extends rearwardly and passes over a sheave 96 which is mounted on the rear end of the inner telescoping section 27 and then passes forwardly over a sheave 97 mounted within the dolly assembly 81. It then extends rearwardly to the housing 75.

It can be seen that as the inner boom 27 is extended and retracted with respect to the outer boom section by movement of the sprocket wheel 31 and the associated chain and sprocket 33, that the dolly assembly 81 will be caused to travel by the cable 83 within the inner boom section 27 to take up all the slack in the cable 73.

Suitable circuitry is provided for the amplifier and power supply 74 and for the photosensitive element 66. Typical circuitry is shown in FIGURE 6. Only one channel has been provided in FIGURE 6. However, it is readily apparent that seven similar channels can be readily provided. The circuitry forms a bridge in which the potentiometer 101 forms two of the legs of the bridge, the photosensitive element 66 forms another leg and the battery 102 in series with the winding of the relay 103 forms the last leg. The battery 104 is connected across the input terminals of the bridge. The output from the bridge is supplied across the emitter and base elements of a transistor 106. The collector element of the transistor 106 is connected to one end of the Winding of the relay 103. The potentiometer 101 is set so that when light rays shine on the photosensitive element 66, the transistor 106 will be triggered to operate the relay 103. The transistor 106 is forward biased by the differential between the two batteries 102 and 104. Resistor 107 is provided for stabilization. Operation of the relay 103 closes its normally open contacts to supply power to energize the associated relay in the control panel 47.

In one embodiment of my apparatus, the circuitry shown in FIGURE 6 was comprised components:

of the following Photosensitive element 66-Clairex type CL 6041..

Transistor-2N35 Relay 103Advance Electric & Relay Co. SVIC 5500B. Resistor 107l.3 megohms. Potentiometer 101-50 K. ohms.

Battery 102-15 v.

Battery 104-22.5 v.

Operation and use of my insulated or high voltage aerial lift may now be briefly described as follows. Let it be assumed that it is desired to utilize the aerial lift for replacing insulators on a high voltage transmission line such as that shown in the drawing which includes towers 116 which carry insulators 117 and in which the conductors 118 are carried by the insulators. Let it also be assumed that this is an operating transmission line and it is very undesirable to deenergize the lines, and

for that reason it is necessary to work the lines hot. Let

I it also be assumed that the transmission lines 118 carry anism 49 or the ground control mechanism 48. Thus, as

described in my Patent No. 2,841,659, the control lever 51 of the control mechanism can be operated like a joy stick to selectively operate desired switches to obtain the desired motion of the boom structure and to thereby position the workmans basket 41 in the desired position. For example, as described in my Patent No. 2,841,659, the controlmechanism 49 can be actuated to operate the

drive assemblies

21, 24 and 23, either, singly or in any desired combination, and in either forward or reverse. When one of the-switches is closed, power is supplied from the battery 52 to energize the lamp 54. The lamp 54 transmits light rays down the associated Lucite rod 61 to the associated photosensitive element which, in turn, causes operation of the associated amplifier circuitry to operate the proper relay within the control panel 47 and to thereby operate the proper drive assembly. The circuitry utilized to obtain the desired operation of the

drive assemblies

21,24 and 28 is described in detail in my Patent No. 2,936,847, and for that reason will not be described in detail. Thus, it can be seen that with the construction shown, the workmans basket 41 and the outer end of the boom structure can be rotated about a vertical axis, raised and lowered about a horizontal axis, and moved toward and away from the vehicle.

From this construction, it can be seen that the operator in the Workmans platform is safe because the workmans platform 41 is insulated from ground by the use of' the insulated boom structure 27 and the use of the Lucite rods 61. V

The operator, of the vehicle and an operator utilizing the ground control mechanism 48 should also be safe from high voltage on the transmission lines because the outer endof 'theboom structure which could possibly come in contact with the transmission lines is insulated from the remainder of the boom structure and the vehicle so thatthey will not be subjected to the high voltages.

Other means may be providedfor obtaining the desired high voltage insulation between the control mechanism 49 and the control panel 47. For example, apparatus utilizing electromagnetic waves, infrared, microwaves, ultrasonic waves and other known modes of communication can be used. Thus, I have shown a transmitter 121 which is mounted on the outer end of the telescoping boom 27 and a receiver 122 which is mounted on the outer boom 26. As shown in FIGURE 8, the control mechanism 49 is connected to the transmitter 121, whereas the receiver 122 is connected to the control panel 47 p A block diagram of a suitable transmitter is shown in FIGURE 9. It is of the ultrasonic type and consists of a modulator 126 which modulates the carrier provided by the oscillator 127 'to provide the necessary side bands. The output of the oscillator is supplied to a suitable radiator 128. A block diagram of the receiver is shown in FIGURE 10 and consists ofa microphone 131 which is connected to an amplifier 132. The output of the amplifier is supplied to adetec'tor 133 which is connected to a tunedrelay 134. The output of the tuned relay 134 is connected to the control panel 47. Ultrasonic apparatus of this type is now available. For example,

the oscillator 127 can operate at a carrier frequency of utilized in the oscillator 127 as a radiator 128 and also as a precision frequency control for the oscillator. The microphone 131 and the receiver can be a barium titanate tranducer, the output of which can be amplified and detected in transistorized amplifiers and detectors. The detected audio signal is fed into the magnetic tuned relay 134'which has one tuned reed for each of the modulating frequencies. In addition, the relay has a magnetic holding circuit which is excited from the detector. Therefore, when any reed begins to vibrate, it is held by a magnetic holding circuit. Apparatus of a similar type is presently being used for remotely operating slide projectors.

Operation and use of the control system and apparatus shown in FIGURES 7-10 is very similar to that hereinbefore described. Operation of the control mechanism 49 will cause the carrier frequency of the oscillator 127 to be modulated with the appropriate frequencies. These frequencies are received by the receiver and will cause operation of the associated relays in the control panel 47 to thereby control the

drive assemblies

21, 24 and 28 in the manner desired.

It is also apparent that this control will provide the desired insulation in view of the fact that the transmitter and receiver are separated by relatively great distances by air and also because the transmitter 121 is mounted on the insulated telescoping boom section 27 and the receiver 122 is mounted on the main section 26.

As hereinbefore pointed out, it is readily apparent that other transmitting and receiving systems'can be utilized ,of the aerial lift, while at the same time retaining the same method of control which is well known to those I utilizing this type of equipment.

I claim: 1. In an aerial lift, a self-propelled vehicle, a workmans lift mounted on the vehicle and having a'boomstructure with a workmans platform secured to its outer end, the

- boom structure having itsv outer extremity formed of insulating material for insulating the workmans platform from the remainder of the lift, a power supply mounted adjacent the outer end of said boom structure and insulated from the remainder of the boom structure, a control mechanism mounted on the workmans platform and having a plurality of electrical switches connected to said power supply, a control assembly mounted on the lift, motive means connected to the control assembly and operated by the control assembly for operating the workmans lift so that the outer end of the boom structure and the workmans platform can be rotated about a vertical axis, raised and lowered about a horizontal axis and moved toward and away from the vehicle, and means connecting the control mechanism to the control assembly so that the control assembly will be operated in accordance with the conditioning of the switches in the control mechanism and having good insulating qualities serving to electrically insulate the control mechanism from the control assembly.

2. In an aerial lift, a self-propelled vehicle, a workmans lift mounted on the vehicle and having a boom structure with a workmans platform secured to the outer end, the boom structure having portions formed of insulating material for insulating the workmans platform from the remainder of the lift, a control mechanism mounted on the workmans platform, a control assembly mounted adjacent the workmans lift, motive means connected to the control assembly for operating the workmans lift so that the outer end of the boom structure and the workmans platform secured thereto can be rotated about a vertical axis, raised and lowered about a horizontal axis and moved toward and away from the vehicle, control circuitry connecting the control mechanism in the workmans platform to the control assembly and serving to electrically insulate the control mechanism from the control assembly, and a power supply mounted adjacent the outer end of the boom structure and insulated from the remainder of the boom structure, the control mechanism having a plurality of electrical switches, circuitry connecting the power supply to the electrical switches, control means mounted on the outer end of the boom structure and circuitry connecting the switches in the control mechanism to the control means.

3. In an aerial lift, a self-propelled vehicle, a workmans lift mounted on the vehicle and having a boom structure with a workmans platform secured to the outer end, the boom structure having portions formed of insulating material for insulating the workmans platform from the remainder of the lift, a control mechanism mounted on the workmans platform, a control assembly mounted adjacent the workmans lift, motive means connected to the control assembly for operating the workmans lift so that the outer end of the boom structure and the workmans platform secured thereto can be rotated about a vertical axis, raised and lowered about a horizontal axis and moved toward and away from the vehicle, control circuitry connecting the control mechnism in the workmans platform to the control assembly and serving to electrically insulate the control mechanism from the control assembly, the control circuitry connecting the control mechanism to the control assembly including a transmitter mounted adjacent the outer end of the boom assembly and a receiver mounted adjacent the remainder of the workmans lift. p

4. An aerial lift as in claim 3 wherein the transmitter and receiver are mounted on the exterior of the boom structure.

5. In an aerial lift, a self-propelled vehicle, a workmans lift mounted on the vehicle and having a boom structure with a workmans platform secured to the outer end, the boom structure having portions formed of insulating material for insulating the workmans platform from the remainder of the lift, a control mechanism mounted on the workmans platform, a control assembly mounted adjacent the workmans lift, motive means connected to the control assembly for operating the workmans lift so that the outer end of the boom structure and the workmans platform secured thereto can be rotated cases about a vertical axis, raised and lowered about a horizontal axis and moved toward and away from the vehicle, control circuitry connecting the control mechanism in the workmans platform to the control assembly and serving to electrically insulate the control mechanism from the control assembly, the control mechanism having a plurality of switches, the means connecting the control mechanism to the control assembly including a plurality of lamps, a power supply, circuitry connecting the power supply to the lamps through the switches in the control mechanism so that the lamps are selectively energized upon operation of the control mechanism, a light transmitting member having good insulating qualities associated with each of the lamps so that the light from the lamp will be transmitted by the light transmitting member, a photosensitive element associated with each of the light transmitting members and adapted to receive light transmitted by the same, and circuitry connecting the photosensitive elements to the control assembly.

6. In an aerial lift, a self-propelled vehicle, a workmans lift mounted on the vehicle and having a boom structure with a workmans platform secured to its outer end, the boom structure having its outer extremity formed of insulating material for insulating the workmans platform from the remainder of the lift, a control mechanism mounted on the workmans platform and having a plurality of electrical circuits, a control assembly mounted on the lift, .motive means connected to the control assembly and operated by the control assembly for operating the workmans lift so that the outer end of the boom structure and the workmans platform secured thereto can be rotated about a vertical axis, raised and lowered about a horizontal axis and moved toward and away from the vehicle, means connecting the control mechanism to the control assembly so that the control'assembly will be operated in accordance with the conditioning of the switches in the control mechanism, saidlast named means having good insulating qualities serving to electrically insulate the control mechanism from the control assembly, said control means including a power supply mounted adjacent the outer end of the boom structure, a transmitter mounted adjacent the outer end of the boom structure, circuitry connecting the power supply through the control mechanism to the transmitter so that the transmitter is operated in accordance with the positioning of the control mechanism, a receiver mounted adjacent the remainder of the workmans lift, the transmitter and the receiver being insulated from each other, and circuitry connecting the receiver to the control assembly.

7. An aerial lift as in claim 6 wherein the transmitter is an ultrasonic transmitter and wherein the receiver is an ultrasonic receiver.

8. An aerial lift as in claim 6 wherein the transmitter is a light emitting transmitter and wherein the receiver is a light receiving receiver.

9. An aerial lift as in claim 8 wherein the means connecting the control mechanism to the control assembly includes a plurality of light transmitting members.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. IN AN AERIAL LIFT, A SELF-PROPELLED VEHICLE, A WORKMAN''S LIFT MOUNTED ON THE VEHICLE AND HAVING A BOOM STRUCTURE WITH A WORKMAN''S PLATFORM SECURED TO ITS OUTER END, THE BOOM STRUCTURE HAVING ITS OUTER EXTREMITY FORMED OF INSULATING MATERIAL FOR INSULATING THE WORKMAN''S PLATFORM FROM THE REMAINDER OF THE LIFT, A POWER SUPPLY MOUNTED ADJACENT THE OUTER END OF SAID BOOM STRUCTURE AND INSULATED FROM THE REMAINDER OF THE BOOM STRUCTURE, A CONTROL MECHANISM MOUNTED ON THE WORKMAN''S PLATFORM AND HAVING A PLURALITY OF ELECTRICAL SWITCHES CONNECTED TO SAID POWER SUPPLY, A CONTROL ASSEMBLY MOUNTED ON THE LIFT, MOTIVE MEANS CONNECTED TO THE CONTROL ASSEMBLY AND OPERATED BY THE CONTROL ASSEMBLY FOR OPERATING THE WORKMAN''S LIFT SO THAT THE OUTER END OF THE BOOM STRUCTURE AND THE WORKMAN''S PLATFORM CAN BE ROTATED ABOUT A VERTICAL AXIS, RAISED AND LOWERED ABOUT A HORIZONTAL AXIS AND MOVED TOWARD AND AWAY FROM THE VEHICLE, AND MEANS CONNECTING THE CONTROL MECHANISM TO THE CONTROL ASSEMBLY SO THAT THE CONTROL ASSEMBLY WILL BE OPERATED IN ACCORDANCE WITH THE CONDITIONING OF THE SWITCHES IN THE CONTROL MECHANISM AND HAVING GOOD INSULATING QUALITIES SERVING TO ELECTRICALLY INSULATE THE CONTROL MECHANISM FROM THE CONTROL ASSEMBLY.