US1514800A - Automatic switch - Google Patents

Description

Nov. 11 1924' M. SKENDER AUTOMATIC SWITCH Filed Sept. '7. 1923 3 Sheets-Sheet. l

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Nov. 11 1924- M. SKENDER AUTOMATIC SWITCH Filed Sept. '7. 1923 3 Sheets-Sheet 2 Wt'nesses:

Nov. 11 1924.

M. SKENDER AUTOMATIC SWITCH Filed Sept. 7. 1923 3 Sheets-Sheet 3 17am): W. M07452 Jen/are,

Patented Nov. 11, 1924.

MICHAEL SKENDER, OF IPITTSBURGH, PENNSYLVANIA.

AUTOMATIC SWITCH.

Application filed September To all whom it may concern:

Be it known that I, MICHAEL SKENDER, a citizen of the United States, and resident of East End, Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented" certain new and useful Improvements in "Automatic Switches, of which the following is a specification.

This invention relates to switches, and more particularly to automatic limit and reversing switches, and has for one of its objects the rovision .of a switch of this class adapted to prevent the over-running of hoistin cranes and the like.

Anot er object is to provide .a switch which will be normally held in position to normally complete the field circuit to the motor in the dlrection of operation and will, when tipped automatically, break this circuit and make areverse field circuit.

A further object is to provide means for holding the switch in reverse position after it has been tripped, until the controller is moved to off or neutral position.

A still further object is to provide a switch of the class described having the novel construction, combination and desi of parts hereinafter described and illustrated in the accompanying drawings.

In the drawings, Figure 1 is a top plan of a switch constructed in accordance with my invention, the cover being removed for clearness.

Figure 2 is a front side elevation.

Figure 3 is an end elevation showing counterweight operating mechanism.

Figure 4 is an end elevation taken opposite Figure 3.

Figure 5' is a rear side elevation in combination with a wiring diagram.

Referring more particularly to the drawings, the letter A designates-the supporting structure of the switch as a whole, which supports the switch parts and is composed of a ba'se2, end walls 3 and 3" and back wall 4. Preferably when in use a housing or cover (not shown) will be provided to enclose the supporting structure and working parts of the switch.

A pair of dividing wallsor artitions 5 and 6, secured to the base and back wall 2 and 4, respectively, serve to divide the s ace between the end, walls 3 and 3' into t ree separate working chambers.

Upper and lower contacts 7 and 8 are 7, 1923. Serial No. 661,462.

mounted on the back wall between the end wall 3 and dividing wall 5, and other upper and lower contacts 9 and 10 are mounted on the back wall between the dividing walls 5 and 6.

A shaft 11 is journaled in suitable bearings in the end walls 3 and 3, and the portion of the shaft extending from the dividing wall 6 to the end wall 3 is provided with an insulated sleeve covering 12.

A pair of contact arms 14 and 15, secured on the sleeve covered portion of the shaft 11, are connected by flexible connecting strips 14 and 15 to binding posts 14 and 15*, respectively, and arranged to contact with either the upper contacts 7 and 9 or lower contacts 8 and 10, according to the position of the shaft 11.

A solenoid core 16 is mounted in the space between the wall 6 and end wall 3" and isadapted to be energized when the shaft is rotated clockwise so as to cause the arms 14 and 15 to contact with the contacts 8 and 10, and a solenoid plunger 17 is secured on the shaft 11 so that it will be attracted b the energized core 16 and hold the sha t in position.

A lever arm 19 is secured intermediate its ends at 20 to the end of the shaft 11 which projects through the end wall 3 and a counterweight 21 is rigidly secured to one end of the lever while its other end has a slightly heavier counterweight 22 suspended therefrom by a cable 23. The counterweight 22 is provided with a cable arm 24 having an aperture therein through which one of the hoisting cables of a crane is passed as designated by the numeral 25. The cable 25 is provided with a stop block 26 adapted to engage the counterweight 22 and lift the same as the load is lifted beyond its safe limit, or predetermined point.

In Figure 5 a diagram of the circuits made by the switch, when controlling a series wound motor, is shown. The numerals 27 and 28 designate the positive and negative feed wires, respectively, 29 designates the controller and 30 and 31 designate the motor field and armature, respectively.

Assuming that a load is to be raised, the controller 29 is moved to the proper position which will cause a circuit to be made from the plus line 27 through the binding post 14, connection 14 and arm 14 to contact 7, thence through wire 33 to the motor field 30, through the field 30, thence through troller 29, wire 37 to armature 31, through the armature to wire 36, through controller 29 to wire 28 on other side of line.

When the load is raised to its upper limit, the stop block 26 will engage the cable arm 24 and raise counterweight 22, thus permitting the counterweight 21 to rock the shaft 11 clockwise, breaking the contact between the arms 14 and 15 and the respective contacts 7 and 9 making contact immediately with the contacts 8 and 10, respectively, which will cause a reverse flow of current through the motor field 30 and thereby cause the motor to rotate in the reverse direction and lower the load, which movement Will continue until the circuit is broken by the operator moving the controller 30. i

I When the arms 14 and 15 have made contact with the contacts 8 and 10 the following circuit will be made, from positive wire '27, post 14 connection 14, arm 14, contact 8, to wire 40 to coil or solenoid core 16, through core 16 to Wire 41, thence through a resistance 42, to wire 43, wire 34, to the motor field 30, through the field 30 to wire 33 to contact 7, thence through a connecting wire 44 to contact 10, then through arm 15, connection 15, and post 15*, to w'ire35, through controller 29 to wire 37 to armature 31, through the armature to wire 36,through controller 29 to wire 28 on other side of line. It will be readily understood that the above circuit will cause the reverse energization of the field 30 and reverse rotation of the motor.

By including the resistance 42 in the reverse motor circuit the energization of the motor will be weakened so that the reverse rotation of the motor caused by the operation of this switch will be slower than when a direct circuit is made in the usual manner through the controller.

In operation, when the crane or other hoisting apparatus is raising a load, if the operator neglects to stop the motor before the stop block 26 engages the counterweight 22, the switch will operate to automatically break the forward or lifting circuit to the motor field and immediately make the reverse circuit above described, which will serve to stop the forward or hoisting movement of the motor and cause it to operate in the reverse direction to lower the load, although such lowering will be considerably slower due to the resistance 42.

The downward movement of the load will attract the operators attention, and he will then move the controller to neutral position and break all circuits through the controller, thus stopping the operation of the motor and de-energizin the solenoid coil 16. When the coil 16 1s (lo-energized the counterweight 22 will cause the shaft 11 to rotate in a counterclockwise direction, providing the load has moved downward a suflic-ient distance for the stop 26 to release the counterweight 22, thus causing the arms 14 and 15 to again engage the contacts 7 and '9. If the load has not been lowered a sufiicient distance for the stop to release the counterweight 22, the switch arms 14 and 15 will remain in contact with the contacts 8 and 10, and it will be impossible for the operator to raise the load by completing a forward circuit to the field 30, since such circuit will be transposed into a reverse circuit by the switch and cause the motor to rotate in a reverse direction soas to lower the load.

It will also be noted that once the/switch arms 14 and 15 have engaged the contacts 8 and 10 to make a reverse circuit to the field 30,theywill remain in thisposition due to the action of the solenoid until the circuit is broken by the controller 29, regardless of the position of the counterwei hts, thus preventing a continuous reversal of direction and the up and down movement of the load as would be caused if the counterweights alone controlled the position of the switch arms.

I claim 1. A limit and reversing switch comprising a body portion, a shaft mounted forrotation in said body portion, counterweights for rotating said shaft, an insulated sleeve on said shaft, a plurality of double acting contact jfingers secured on said shaft, rigid contacts on said body portion adapted to be engaged by said contact fingers, and means for holding said contact fingers in reversing position after said switch has acted to automatically make the reverse circuit until the circuit through said switch is broken.

2. A limit and reversing switch comprising a body portion, a shaft mounted in said body portion, means for automatically operating said shaft, a plurality of contact fingers on said shaft,'contact elements on said body portion adapted to be engaged by said contact fingers to complete the clrcuits through said switch, said shaft being adapted to be automatically rotated to disengage said fingers from some of said contacts and engage said fingers with other of said contacts to break the forward circuit and make a reverse circuit, and means for holding said fingers in reverse contact after said switch has acted to make the reverse circuit until the circuit through said switch is broken. r

3. A limit and reversing switch compris ing a body portion, a shaft mounted in said body portion, means for automatically operating said shaft, a plurality of contact fingers on said shaft, contact elements on said body portion adapted to be engaged by said contact fingers to complete the circuits through said switch, said shaft being adapted to be automatically rotated to disengage said fingers from some of said contacts and engage said fingers with other of said contacts to break the forward circuit and make a reverse circuit, a solenoid core arm secured to said shaft, and a solenoid coil adapted to be energized when the reverse circuit is made through said switch, said energized coil being adapted to attract and hold said core arm, thereby preventing the rotation of said shaft.

4. The combination with a hoisting cable, a motor for furnishing the power to operate said cable, and a controller for making and breaking the circuit to said motor, of means independent of said controller and operable automatically when said cable reaches a predetermined point in its hoisting travel for breaking the forward circuit to said motor and making a reversing circuit, said means being adapted to maintain said reversing circuit until said controller is moved to off or neutral position.

5. The combination with a hoisting cable, a motor for furnishing the power to operate said cable, and a controller for making and breaking the circuit to said motor, of a combined limit and reversing switch through which the circuit from said controller to said motor is made, said switch being normally in position to complete a forward or hoisting circuit to said motor and being adapted to be automatically operated by said cable at a predetermined point in the hoisting travel of said cable to break said forward circuit and complete a reverse circuit to said motor, means normally tending to return said switch to position to make said forward circuit, and means for preventing said return operation until said controller has been moved to neutral or off position.

6. The combination with a hoisting cable. a motor for furnishing the power to operate said cable, and a controller for making and breaking the circuit to said motor, of a combined limit and reversing switch through which the circuit from said controller to said motor is made, said switch comprising a pair of double acting contactin fingers, a plurality of contacts for sai fingers, means for normally holding said fingers in engagement with some of said contacts to close the forward circuit from said controller to said motor, meahs for automatically tripping said fingers to disen age them from said contacts and engage t em with other of said contacts when said hoisting cable reaches a predetermined position, thereby breaking said forward circuit and making a reverse circuit to said motor without operating said controller, and electrically operated means energized by said reverse circuit adapted to hold said switch in reverse position regardless of the position of said tripping means until said controllcr is moved to neutral or off position.

7. The combination with a hoisting cable. of a motor control comprising a motor having the usual armature and field, a source of electric energy, a controller for making and breaking the usual circuits to said motor armature and field, and an automatic limit and reversing switch connected in the motorfield circuit between said controller and said field, said switch being provided with a pair of double contact fingers, a pair of forward and a pair of reversing contacts for said fingers, means for normally holding said fingers in engagement with said forward contacts so as to complete a forward circuit from said controller to said field, means for automatically tripping said fingers to disengage said fingers from said forward contacts and engage them with said reversing contacts, thereby breaking said forward circuit and making a reverse circuit to said field, a solenoid core 'arm connected with said fingers, a solenoid coil connected in the reverse field circuit and adapted to attract and hold said core arm, thereby preventing the return of said fingers to their normal position until said controller is moved to off position to open the circuits through said switch.

In testimony whereof I have hereunto set my hand.

MICHAEL SKENDER.

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