US1522896A - Limit switch - Google Patents

Limit switch Download PDF

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Publication number
US1522896A
US1522896A US656320A US65632023A US1522896A US 1522896 A US1522896 A US 1522896A US 656320 A US656320 A US 656320A US 65632023 A US65632023 A US 65632023A US 1522896 A US1522896 A US 1522896A
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Prior art keywords
switch
carriage
screw
arm
casing
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US656320A
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Mckay Heubert
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Mckay Heubert
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    • GPHYSICS
    • G04HOROLOGY
    • G04FTIME-INTERVAL MEASURING
    • G04F3/00Apparatus which can be set and started to measure-off predetermined or adjustably-fixed time intervals with driving mechanisms, e.g. dosimeter with clockwork
    • G04F3/06Apparatus which can be set and started to measure-off predetermined or adjustably-fixed time intervals with driving mechanisms, e.g. dosimeter with clockwork with electric driving mechanisms

Description

Ian. 3, 1925.
H. M KAY LIMIT SWITCH Filed Aug. 8, 1923 Hewwem 2 Patented Jan. 13, 1925.
UNETE fiTATE HEUBERT MCKAY, OF SEATTLE, VIASHINGTON.
LIMIT SWITCH. i
Application filed. August 8, 1923. Serial No. 656,320.
To all whom it may concern:
Be it known that I, HEUBERT MCKAY, a citizen of the United States of America, and resident of the city of Seattle, in the county of King and State of Washington, have invented certain new and useful Improvements in Limit Switches, of which the following is a specification.
My invention relates to a limit stop and is particularly designed for use in connection with the engine or motor which is employed to operate pumps or like apparatus which it is desired to operate for a considerable period and then stop.
It is an object of my invention to provide such a limit switch which can be set at will for operation of the engine or motor through a given period of time, and which will then automatically break the controlling circuit to stop the operation of the motor or engine, thus to obviate the necessity of the operator being present or leaving other duties to manually stop its operation.
A further object is the provision of a simple and conveniently operated switch of this type.
A further object is the provision of means in such a switch which will prevent damage to the mechanism in case the switch fails to break the circuit or stop the operation of the engine or motor.
' A further object is the provision of a switch of this sort and mechanism for controlling the same whereby the switch may readily be disconnected from the automatic mechanism to permit manual operation thereof, and further, a mounting for the switch which will permit such disconnection and which will maintain the switch in accessible position and shielded against short circuiting or damage from oil or grease which is necessarily associated with the automatic mechanism.
Other objects, and especially those re lating to structural details, may be ascertained from a study of the accompanying drawings, in which my invention is shown in its present preferred form, and of the present specification and the claims terminating the same. 1
My invention comprises those novel parts which are shown in the accompanying drawings, described in the specification, and particularly defined by the claims terminating the same.
Figure 1 is a plan View of my mechanism, the casing enclosing the same being shown in section and certain parts above the line of section being omitted.
Figures 2 and 3 are transverse sections through the automatic limiting mechanism, showing parts respectively in operative and inoperative positions.
As stated above, I intend my device to be used for such purposes as for controlling the operation of a pump on a farm, wherein it is desired to operate the pump for perhaps three hours and then to stop its operation. The pump in such case might be operated by an internal combustion engine, including an ignition circuit, or by an electric motor. In either case the switch meme here 2 and 20 may be included either in the main circuit of the engine or motor or in a control circuit. The manner of connection of these switch members is unimportant. I have shown a pulley 10, which is connected to rotate a screw 1 through suitable speed reduction means. The pulley 10 is intended to be connected in some suitable manner to be driven by the motor or engine which drives the pump, in the illustration given above. Thus it will be seen that so long as the motor or engine driving the pump is. operative, the screw 1 will rotate, and as the switch members 2 and are in the control circuit of the motor or engine, it follows that the screw 1 will rotate solong as the switch members 2 and 20 are in contact.
The exact drive connection between the pulley 10 and the screw 1 is immaterial, although I prefer that it should include pulleys 11 and 12 connected by a belt 13. By this means, or its equivalent, it is possible to vary the speed ratio between the pulley 10 and the screw 1 to accommodate a given limit switch mechanism to engines or motors of different speeds. This is done by varying the relative diameters of the pulleys 11 and 12.
The speed reduction gearing and the screw 1 which it drives, are preferably enclosed within a casing 3 upon which fits a cover 31. Within this casing 8 I mount a carriage 4 which is movable towards and from the screw 1 and is provided with threads 41 which are complemental to and engageable with the threads of the screw 1. Such movement of the carriage towards and from the screw may be secured in a variety of ways. For this purpose I have shown a ,pin" 47.
the carriage at reachesthe end of its'normal travel the spring 24-will pull upon the switch guide rod42, j ournaled in the casing 3 upon eccentric bearings 43. By rotating the rod 42 upon these eccentric bearings 43, as by means of a handle 4%, thecarriage t is reciprocated.
I have shown a handle connected to the carriage 4 and projecting through a slot 34 in the casing 3. A bar 4E6-secured to the carriage within the casing is visible through anenlargementt? of the-slot 3st and may he graduated in proper units, as of time, corresponding to the rate of travel of the carriage 4: when its threads are engaged with the screw. 1. The carriage t can thus be set at'any position lengthwise of the screw 1 whenits threads all are disengaged therefrom by means of the handlef tti, and the length of time which will be requi: ed to advance the carriage to the'end otits normal travel, by means 0t rotation of the screw 1', can be determined by-ret'erence to the gageorscale bar 46, visible through the enlarged index opening 35.
Associated with the carriage l are means for controlling the position of the switch members 2 and 20: I have shown the switch member 20 as mounted upon the cover 31. and the.member 2 as carried upon a bell crank arm 21 pivotedat 23 uponthe cover 31. 1 One arm'of the lever '21 extends within the casing 3 where it is engageable with a pin'4c7carried by the carriage 4,. The length ofthis pin 47 is so proportioned relative to the position otthe'bell-cranlclever 21 and the screw 1 that when the'carriage 4 reaches the end of its normal travel upon the screw 1, theswitchfarm'21 willpass beyond the end of'the'pin 47. A spring 2e may be secured to an arm-25 secured upon the shaft 23' whiclrcarriesith'e switch arm 21, and anchored'atrrts other end to the cover 31 or'to the casing "8/ By this means the switch members 2 and 20 tend constantly to be separated but may. 'be held closed against the tendency of the spring 24 by means of the Itwill be evidenflthen that when arm, and the latter, being unsupported then "by the Pilit'l, will permit the switch members 2 and 20to' be separated, thus to break the controlling circuitot the motor or engine.
I have shown the end of the screw 1 re- "duced, as shown at This plies beyond the normal end of travel otthe carriage 4. If it should happen that the-switch'members 2'and' 20' should not be separated when the carriage reaches the end of its normal travel, or if' for some other reason the motor or engine-should"fail to-stop, its continued operation would carry the carriage l beyondthe-end of the screw l to the cut-away -por-. tion 15. lvhile the screw would continue to rotate, it would not then produce any th'ereto' and engageable'therewith, means for further movement of the carriage 4t and the mechanism consequently would not be damaged.
It is believed-that; it will be obvious from the above description how the carriage 4, by disengagement trom the screw 1, may be adjusted lengthwise thereof and set to operate tor agiven period of time, and how at the end of that period of time the switch members 2 and 20 will be separated to stop theoperation of the motor or switch. I will, therefore, not go into further detail regard ing the-operation ot the device.
.Vhat I claim as iny invention is: 7
l. A limit switch comprising, in combination with a pair of switch members normally tending to be separated, a screw rotatable while said'switch is closed, a carriage havcarriage tor-holding said switch members closed until the carriage reaches the end" of its normal travel, andmeansfor moving saidca -riage atwill towards the screw to engage its threads therewith, or awaytrom the screw to permit adjustment of the position of the carriage lengthwise of the screw.
3. In combination with a pair of switch members normally tending'to be separated, a screw rotatable while said switch is closed, a carriage having threads complemental thereto and engagealole therewith, meansl upon said carriage for holding said switch members closed until the] carriage-reaches the end of its normal travel, a rod guiding said carriage for movement lengthwise ot the screw and eccentric bearings tor said: guide rod, whereby the carriage may be moved at will'towards the screwto permit manual movement of the carriage lengthwise of the screw. J
4. In combination with'a pair-of switch members norm ally tending to be. separated, a switch arm carryingone of said members, a screw rotatable' 'whiles aid switch is closed, a carriage movable towards and from the screw and having threads] complementat moving said carriage towards'or away from thescrew to engage its threads therewith or disengage them: therefrom, respectively, and a pin movable with said carriage and engageable bysaid-switch arm, andf'of a length to support the latter until the carriage reaches the end of its normal travel.
5. In combination with a pair of switch members normally tending to be separated, a screw rotatable while said switch is closed, limit means including a threaded member engageable with said screw for retaining said switch members closed, and operable through said screw to release the switch members after a predetermined period of operation, and the threads of said screw being cut away at a point beyond the position of the threaded member at the normal releasing position.
6. In combination with a casing and a removable cover therefor, a switch arm pivotally mounted upon said cover a pair of complemental switch members, one upon said arm and the other upon said cover, means within said casing having a bearing engagement with said switch arm, and operable to permit separation 01' the switch members following a predetermined period of operation, said means and the switch arm being disengageable upon removal of said cover.
7. In combination with a casing, a switch arm supported from and movable relative to said casing, and projecting therethrough, a pair of. complemental switch members, one upon the outer portion of said arm and the other upon the outside of said casing, means tending to move said switch arm to separate said switch members, and means within said casing engageable with the inner end of said arm to maintain said switch members in contact, and operable to permit separation of said switch members following a predetern'iined period of operation.
8. A device as in claim 7 including a removable cover for the casing, the switch arm and its associated parts being mounted on said cover and the arm projecting therethrough, said means engaging the inner end of the switch arm being fixed within the easing, and being disengageable from said arm to permit separation of the switch members upon removal of the cover.
9. In combination with a control arm normally tending to move to an inoperative or stop position, a screw rotatable while said arm remains in operative position, a carriage having threads complemental to the screw and engageable therewith, and means upon said carriage for holding said arm in operative position until the carriage reaches the end of its normal travel, said means and the arm being thereupon disengageable to permit movement of the arm to normal inoperative position.
Signed at Seattle, King county, VVashington, this 31st day of July, 1923 HEUBERT MoKAY.
US656320A 1923-08-08 1923-08-08 Limit switch Expired - Lifetime US1522896A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3037097A (en) * 1955-10-21 1962-05-29 Borg Warner Sequential controller
US3529104A (en) * 1968-04-19 1970-09-15 Plessey Airborne Corp Limit switch operating mechanism for actuators

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3037097A (en) * 1955-10-21 1962-05-29 Borg Warner Sequential controller
US3529104A (en) * 1968-04-19 1970-09-15 Plessey Airborne Corp Limit switch operating mechanism for actuators

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