US 3566053 A
Description (OCR text may contain errors)
I United States Patent 13,566,053
 Inventor Ray A. Gause  References Cited L; Gragge, Tex. FOREIGN PATENTS i211 PP 8 7,33 264 762 6 1964 Netherlands 200 153 19  Filed May 23, 1969 i i 45] patented Feb. 23 1971 Primary Examn er Robert S. Macon  Assignee Gause Dynamics Corporation Assistant EmmmerH Hohausel' Housmn Tex. Attorney-Cushman, Darby & Cushman  ADAPTABLE REPAIRABLE AND SEALED MIT ABSTRACT: A limit switch or microswitch is described in SWITCH which the switch or switches and the actuating means are entirely housed in a sealed, waterproof and airtight assembly. 7Ch'ms2Drawmg Figs The switches are axially operable microswitches which are  [1.8. CI 200/47, sealed in a switch housing which may be threadably engaged 200/153 with the main assembly housing; thus facilitating easy replace-  Int. Cl H02j l/l6 ment of switches. The actuating means is a reciprocating  Field of Search 200/47, piston placed in a separate sealed housing member which also is in threaded engagement with the main assembly housing.
PATENIEU F B2319n 3; 566; 053
INVENTOR @flM RAY GAUSE AfToR ADAPTABLE REPAIRABLE AND SEALED LIMIT SWITCH This invention relates to a limit switch using axially operable microswitches which are actuated by a reciprocally operating piston or plunger means.
An object of this invention is to provide a novel switch assembly which will permit the replacement of the holder in which the switch or switches are mounted without requiring readjustment of the switch installation. In a preferred embodiment of this invention as described hereinbelow this object is realized by mounting the switch in a switch housing or holder which may be threadably engaged with a main assembly housing and in which the body of the switch housing or holder which may be threadably engaged with a main assembly housing and in which the body of the switch housing is manufactured so that there is little variance between the lengths of like switch housings of the same manufacture. Therefore, the switch housing can be removed and replaced with a like member without disturbing the basic installation or adjustment of the overall switch assembly.
Another object of this invention is to provide a novel switch assembly which comprises three main component assemblies, each of which are easily replaceable for maintenance purposes, and wherein the assembly is sealed so that detrimental environmental conditions will not be detrimental to the operation of the switch. Further, the sealed switch assembly constructed according to the principles of this invention permits installation in explosive environments because the small internal air volume and the sealed condition of the assembly will render internal and external explosions virtually impossible.
The foregoing and other objects and advantages of the invention will appear from the following description of a preferred embodiment illustrated in the accompanying drawings, wherein:
FIG. 1 is an expanded side cross-sectional view of a switch assembly constructed according to the principles of this invention showing the complete assembly as installed with a connector plug attached; and
FIG. 2 is a side elevation of the switch housing shown mounted in the main assembly housing in FIG. 1.
Referring to FIG. 1 the main assembly housing 1 is a hollow cylindrical member having sharp V-threads in each end. Microswitches 17 are shown mounted in .a switch housing 2 which is threadably engaged with the main assembly housing 1 and is shown as having a connector plug 19 connected thereto in engagement with wires 21 extending from the microswitches 17.
At this point, reference is made to FIG. 2 for a structural description of switch housing 2. FIG. 2 is an external side elevation of switch holder 2 with the switches 17 mounted therein and wires 21 extending vertically from switches. Retaining pins 16 are provided extending through the body of switch housing 2 to hold microswitches 17in place. A friction lock is provided on the threads of the body of switch housing 2 to hold it in place when threaded into assembly housing 1 and is especially useful when the switch is subjected to heavy vibrations. When switches 17 are inserted and pinned, by means of retaining pins 16, in housing 2 and contact wires 21 are soldered on to switches 17, the axial dimension of switch housing 2 from a flange 32, at the upper end of the switch housing, to end of the contact pin 30 is carefully checked. In manufacturing switch housings 2 this length dimension is maintained within 10.003 inches during fabrication and assembly. By maintaining such dimensional consistency between switch housings, replacement of switch housings without further adjustment is readily facilitated. Further, such replacement may be accomplished without disturbing the installation or adjustment of the main switch assembly.
After establishing the proper length dimension, a potting compound, indicated as 20 in FIG. 1, is inserted around wires 21 over switches 17. The entire switch housing assembly LII shown in FIG. 2 after construction in the foregoing manner may then be threadably inserted into the main assembly housing 1 with a sealing or potting compound 15, see FIG. 1, installed in the mating area between housing 1 and the flange 32 of switch housing 2. Dual switches 17 are provided in this preferred embodiment in order to provide a backup capability in the event of a switch failure, but it must be noted that the principles of this invention are not limited in their application to a dual switch construction. Either switch may be selected to have a sufficient current capacity to perform the required function, and the size of wire used for wires 21 may be selected to carry current up to the maximum current capacity of the switch. As is conventional, the microswitches may contain a center tap and may be wired for normally open or normally closed circuit functions permitting a variety of wiring configurations. Preferably the microswitches 17 are metal encapsulated for maximum protection of the plastic switch body as well as providing environmental protection. The standard microswitch body may be modified by adding a metal shield and rubber diaphragm to yield the aforementioned environmental and assembly protection.
Referring back to FIG. 1, a piston housing 4 is threadably engaged with the end of assembly housing 1 opposite the end in which switch housing 2 is inserted. Piston housing 4 is hollow through the central portion thereof to allow the mounting therein of a piston member 5. Piston 5 is adapted to travel longitudinally through the axis of piston housing 4 in the direction of contact pins 30. A piston guide 7, substantially cylindrical in shape s inserted in the opening through piston housing 4 between the inner surface of that opening and piston 5. 0- rings 12 and 13 provide sealing between the guide 7 and piston housing 4 and the guide 7 and piston 5, respectively. A slipper seal 11 preferably made of a self-lubricating material is provided and held pressurably against piston 5 also to facilitate motion of piston 5. A retaining ring 9 is placed over piston guide 7 to hold the assembly in place. A compression spring 18 in contact with piston guide 7 and a boss on piston 5 biases the piston away from switch contacts 30. A second piston guide 6 is mounted in the end of piston housing 4 away from the remainder of the assembly in the same manner as was piston guide 7. Another set of O-rings l2 and 13 provide the necessary sealing of the areas between the piston housing and the piston guide and the piston guide and the piston, respectively. Outside piston guide 6 is held in place by a-guide plate 8 and a retaining ring 9.
After the entire piston housing assembly is inserted into the main assembly housing 1, a potting compound 14 seals the interface between the piston housing 4 and assembly housing I. The mating threads on the piston housing 4 may also have a friction insert 10 to insure against vibrations which may tend to loosen the thread joint. A button 3 is mounted on top of piston 5 in order to facilitate contact of the piston with contact pins 30 of switches 17.
In operation any force imparted to the exposed end of piston 5 will tend to move it in the direction of contact pin 30 of the switches 17. The actuating force, which may be provided by a variety of means, such as hell cranks, cams or solenoids, must be sufficient to overcome the compressive force of spring 18. It is to be noted that spring 18 may be selected to meet any of a variety of individual load requirements. Piston 5 will easily slide through slipper seals 11 which act as well to enhance the sealing effect of O-rings 13 which provide a compressive force behind the slipper seal 11. The O-rings 12 on the outside surfaces of piston guide 6 and 7, respectively, act to prevent moisture from entering the switch cavity. The presence of piston guides 6 and 7 insures that the motion of piston 5 will be only axial thereby preventing jamming or binding. The travel of piston 5 is unimpeded until the actuator button 3 makes contact with contact pins 30. From this point of initial contact switch 17 actuation requires only 0.03 inches of travel of piston 5. Any additional travel of piston 5 will then bottom-out on the piston housing 4. Any additional travel required could be handled by a standard microswitch over travel arm installed to actuate piston 5. As is apparent from the drawing, switches 17 are actuated simultaneously.
The material used for sealing or potting compounds 14, and will render the bottom and top joints of the switch assembly completely waterproof, and such compounds are available which will withstand temperatures of up'to 800 F. The only possible leakage of air or liquids would have to be around and past the two O-rings l2 and 13 and the slipper seals 11 on each of the piston guides 6 and 7', and any such leakage is negligible. If desired, the entire assembly may be made of corrosion resistant material to facilitate use in any environment. For use on aircraft where weight is a critical factor, switch housing 2 and assembly housing 1 may be fabricated from aluminum with the remainder of the parts being of the same construction as described herein above.
To install a switch assembly constructed according to the principles of this invention assembly housing 1 need only be inserted in a dulled hole, e.g. five-eighths inches in diameter, and jam nuts 31 used to secure it therein. Jam nuts 31 may be used as well to provide slight adjustments of the assembly, as when a new switch housing 2 is installed.
The preferred embodiment of my invention described hereinabove is only exemplary, and it will be apparent to those skilled in the art that modifications in the elements or their structural arrangement may be made within the scope of the appended claims.
l. A microswitch assembly comprising a hollow cylindrical housing member, a microswitch housing threadably engaged into said assembly housing at one end thereof, first sealing means interposed between said assembly housing and said microswitch housing preventing fluid communication between the interior of said assembly housing and the exterior thereof, at least one microswitch having an axially operable contact pin, said microswitch being contained in a sealed manner within said microswitch housing with said contact pin extending from said microswitch housing into the interior of said assembly housing, a piston housing threadably engaged into said assembly housing at the other end thereof, second sealing means interposed between said assembly housing and said piston housing preventing fluid communication between the interior of said assembly housing and the exterior thereof, piston means mounted in said piston housing for axial motion therein and adapted at an end thereof interior of said assembly housing to abut and actuate said contact pin at the end of the axial travel of said piston mean s into said assembly housing, and third sealing means interposed between said piston means and said piston housing preventing fluid communication between the interior of said assembly housing and the exterior thereof while allowing axial motion of said piston means in said piston housing.
2. The microswitch assembly defined in claim I wherein two microswitches are contained and sealed in said microswitch housing in a side-by-side relationship, one of said microswitches being adapted to operate in case of failure of the other of said microswitches.
3. The microswitch assembly defined in claim 1 having in addition a compression spring means biasing said piston means in a direction away from said contact pin of said switch and wherein said spring means is removable for easy replacement with another spring having different compressibility, thereby easily adapting said assembly to different uses.
4. The microswitch assembly defined in claim 1 wherein said microswitch housing comprises a threaded outerbody adapted to be threadably engaged with said assembly housing and wherein said microswitch is sealed in said microswitch housing by a potting compound.
5. The microswitch assembly defined in claim 1 wherein said piston housing is a hollow, substantially cylindrical member and said piston means comprises substantially solid shaft disposed at the center of said housing for reciprocal motion axially therethrough.
6. The microswitch assembly defined in claim 5 having In addition first and second cylindrical piston guide means placed radially outwardly of said piston means and radially inwardly of the interior surface of said piston housing for preventing eccentric motion of said piston means, one of said guide means being placed on in an end of said piston housing adjacent the interior of said assembly housing and the other of said guide means being placed in an end of said piston housing away from said assembly housing and wherein said third sealing means comprises sealing rings interposed between each of said guide means and said piston means and sealing rings inter posed between each of said guide means and the interior surface of said piston housing.
7. The microswitch assembly defined in claim 6 wherein slipper seals are provided between said sealing rings which are between said piston guides and said piston in such a manner that said sealing rings exert a compressive force on said slipper seals.