US3118027A

US3118027A - Electrical switch including viscously damped timing device

Info

Publication number: US3118027A
Application number: US172912A
Authority: US
Inventors: Robert L Boyles
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-02-13
Filing date: 1962-02-13
Publication date: 1964-01-14
Anticipated expiration: 1981-01-14

Description

Jan. 14, 1964 R. BOYLES 3,118,027

ELECTRICAL SWITCH INCLUDING VISCOUSLY DAMPED TIMING DEVICE Filed Feb. 15, 1962 F 2 M W F gzm' Faber t L I B gg/es,

United States Patent 3,118,027 ELECTRHCAL SWITCH ENCLUDHNG VESCOUSELY DAMPED Till ENG DEVKCE IL. lioyles, Wayland, Mass, assignor to General Electric Qompany, a corporation of New York Fiied Feb. 13;, 1962, Ser. No. 172,912 9 tClaims. (Cl. filth-T94) This invention relates to timing apparatus for measuring the lapse of a predetermined time interval and more specifically to timing devices of the type employing a viscous substance to damp or control the rotation of a timing member.

Generally speaking, a viscously damped timing device is a mechanism in which the speed of a moving body, usually rotating, is controlled by immersing the body in a high viscosity fluid. Although timers operating on this basic principle are known in the prior art, there is always a need to reduce the cost of such timers and improve their reliability in view of the ever-increasing usage of timing devices. One of the more important uses of a timer is to control the operation of an electrical switch.

Accordingly, it is a primary object of the invention to provide an improved viscously damped timer having a minimum number of parts and thus being very reliable and relatively inexpensive to fabricate.

It is another object of the invention to provide a low cost, viscously damped timing device which is uniquely combined with an electrical switch to control the operation of the switch.

The invention in one of its broader aspects includes a housing rotatably mounted around and partially supported by a support member mounted on a shaft extending through a wall of the housing. A second shaft is connected to the housing and is rotatably supported in a fixed support. A spring is connected to urge the housing to rotate in one direction. The rotating housing may be used as a timing member by positioning a high viscosity fluid within the housing in contact with the support memher to retard or damp the rotation of the housing around the support member. By proper selection of the spring strength and the viscous fluid, as well as other parameters of the mechanism, an accurate timing device is obtained.

As another aspect of the invention, the rotating housing may be employed to operate an electrical switch.

Further features, objects and advantages will be a parent with reference to the following drawings in which:

FIG. 1 is a side elevation of the timing device of the invention with an outer support casing partially cut away to provide a view of the interior;

FIG. 2 is another side elevation of the timing device of the invention being rotated 99 from the view of FIG. 1 and with the support casing partially cut away;

FIG. 3 is a transverse sectional view along the line 3 3 of P16. 1;

FIG. 4 is a plan view of the housing of the timing device with the housing cover removed and showing the gear means positioned within the housing; and

HG. 5 is a side elevation of the assembled housing of the invention shown in cr'osssection.

Referring now to the drawings and first particularly to FIGS. 1 and 2, the timing device of the invention may be seen as including an outer support casing it}, which been given a cup shape and is shown in inverted position. The casing it may be made of any suitable material, but is preferably made of a material which is light in weight yet sufficiently rigid to withstand the stresses to which the casing will be subjected. The integral end 12 of the casing it forms one support plate, while the opposite end of the casing has a radially extending flange 14- to which is attached, by riveting or other suitable means, a second support plate 16, which is preferably made of an electric insulating material for supporting switch contacts that will be hereinafter described.

Positioned within the casing 10 is a housing 18 having connected thereto a set shaft 26, which extends through the support plate 12 and is rotatably supported within the plate. The shaft 2t may be provided with a knob 21 or other suitable means by which set shaft 20 may be manually rotated. A dial (not shown) with suitable indicia thereon may be placed beneath the knob 21 to indicate the period of time for which the shaft is set. The housing 18 is adapted to receive a support member such as a gear 22 mounted on one end of shaft 24, which extends through a housing cover 26 and is supported by support plate 16. As can be seen in FIG. 5, the housing 18 has formed therein an internal socket 28 adapted to serve as a bearing for the reduced end portion 30 of the shaft 24 so that the gear 22 and housing 18 are rotatably supported with respect to each other. The housing cover 2.6 may be attached to the housing by a plurality of

bolts

32, 34, 36, and 33, as seen in FIG. 3, or other suitable means. The gear 22 may serve as a sun gear by including a pair of pinion or

planet gears

41 and 42 mounted on stub shafts 41 and 4-3, respectively, which are rotatably supported within the casing 18 and its cover 26 to mesh with the sun gear 22. The relationship of the gears may be readily seen by reference to FIGS. 4 and 5. The housing 18 and cover 26 in effect form a gear box for the sun and planet gears.

Referring to FIGS. 1 and 4, it may be seen that the lower end 44 of gear shaft 24 has a reduced diameter so that a shoulder 45 is formed at the point where the diameter changes. This shoulder serves as a bearing surface between the shaft 24 and the plate 16. The shaft is secured in this position, wherein the shoulder 45 abuts the plate 16 by a plain washer 46 backed by a friction washer 47. The washer 47 has a plurality of inwardly extending radial fingers which frictionally engage the shaft end 44 when the washer is forced onto the shaft. This arrangement serves as an inexpensive friction clutch to resist relative rotation between the shaft 24 and the casing support plate 16.

A torsion spring 48 positioned around the set shaft 2%) between the housing 18 and the support plate 12 may be employed to provide the power for the timing device. One end 5% of the spring 48 is restrained by a peg 52 extending downwardly from the support plate 12, as may be seen in FIGS. 1 and 3. The opposite end 54 of the spring 48 is restrained by the lug 56 which extends upwardly from the top surface of the housing 18. With the spring 43 connected as described and as shown in FIGS. 1 and 3, it will be apparent that the spring 43 will tend to urge the set shaft 26} and the housing 18 to a home position wherein there is the least tension on the spring. If the set shaft 20 is rotated by means of knob 21 in a clockwise direction, as viewed in FIG. 3, it will be necessary to overcome the resistance of the spring 48. Upon releasing the shaft 2%, the spring 8 will rotate the shaft and the housing 18 carrying planet gears 4d and 42 in a counterclockwise direction around sun gear 22 back to the original home position. it can be seen from FIG. 3 that the peg 52 is positioned approximately the same radial distance from the shaft 2% as the lug 56. Consequently, the rotation of the housing is limited as the lug 56 moves into engagement with the peg 52. Further, it can be seen that with the arrangement shown, the housing 18 can only be moved slightly less than one revolution in a clockwise direction by the shaft 25) due to the fact that the lug 56 would again engage the peg 52. However, it should be understood that similar spring arrangements may be employed whereby the amount of rotation could 3 be increased without departing from the scope of the invcntion.

The torque produced by the spring 48 and transmitted by planet gears and 42 to sun gear 22 is not sufi'icient to overcome the resistance of the friction clutch arrangement so that when the housing is returning to its be e or position of least restraint, the housing 18 will rotate around the gear 2?. and shaft 2 which will not rotate with respect to support plate to by virtue of the friction clutch. When the shaft 2 is rotated in a clockwise direction and then released, it will, if not further restrained, snap back to its original position very rapidly since the frictional resistance between the components revolving around the gear and

shaft arrangement

22 and 24 is very slight when compared to the torque of the spring 4%. in order to practically utilize the housing 18 as a timing member, it is necessary to reduce its speed of rotation caused by the spring 43. For this purpose, the housing 18 is filled with a fiuid having a high viscosity so that the layer of such fluid between the teeth of sun gear 22 and planet gears 4i) and 42 and between the surfaces of the gears and the surrounding housing is and cover 26 will retard the relative rotation of the components. The high viscosity fluid resists the shearing forces which arise when two closely spaced components are immersed in a liquid and rotated relative to each other. There are a variety of high viscosity fluids which may be located within the housing to dampen the movement; the choice depends upon the application for the timer. It has been found that a silicone gel is particularly well suited as a damping liquid.

In operation, the set shaft 20 is manually rotated in a clockwise direction the desired amount. The high viscosity silicone gel will cause the sun gear 22 to rotate with the housing and the friction clutch will not prevent the shaft 2 5 from rotating within the support plate 16 due to the fact that the resistive force of the friction clutch can be easily overcome by manual torque applied to the set shaft 20. Upon releasing the set shaft, the housing 18 and shaft 2% will be urged to their original position by the spring 48. The silicone gel will resist relative rotation between the housing and sun gear 22 so that the sun gear is also urged to rotate. The torsional force introduced by the spring 2-8 is relatively low, however, and is not sufficient to overcome the frictional force of the friction clutch so that the shaft 2d held in a permanent position with respect to support plate As a result, the housing 13 and planet gears it) and revolve slowly about sun gear 22 until lug 56 engages the stop peg 52. Thus, a uniquely arranged timing device capable of measuring a time interval is obtained.

The speed of rotation may, of course, be varied by varying the parameters of the components involved. Some of such parameters are the torsional strength of spring 43, the degree of rotation permitted set shaft 20, the viscosity of the retarding fluid employed, and the internal clearance between the sun and planet gears and the surrounding housing. Regarding the latter parameters, it should be noted that sun gear 22 is formed with an upper recess 57 and a lower recess 53, as seen in FIG. 5, to increase the fluid capacity of the housing 1%.

One of the prime advantages of the timing device as shown and described is its simplicity, employing a minimum number of parts while yet being rugged and reliable. It should be appreciated that the timing device in its simplest form comprises a housing, filled with high viscosity fluid, rotating about a member securely mounted on a fixed shaft. That is, while the device is performing its timing function, the shaft 24 is in a fixed stationary position. The clutch arrangement employed in the device provides a unique but simple means by which the timing device can be reset.

The timer of the invention may be employed to control or operate any variety of external components, and is particularly suited to operate an electrical switch. In

fit

l accordance with another aspect of the invention, a switch has been uniquely combined with the tin: r hcretof ore described. Referring to FIGS. 1 and 2, a pair of diametrically spaced switch terminals and as are shown depending froin the insulating support plate 16 where they are supported by a pair of rivets 6d and 65, respectively, or by other suitable means. Both rivets extend through the support plate, rivet 64 forming an internal co ct and rivet 66 having attached thereto a flexible contact arm 63. The arm, which may be formed in a single stamping operation, extends around both sides of shaft 24 to form a closed loop, as seen in HS. 2. On the free end of the contact arm as, there is provided a contact '70 which engages contact 64 when the switch is closed. in the arrangement shown, the contact arm 63 is flexed so that the switch is normally closed; that is, the contact 7'9 normally engages the contact 64 if other means do not intervene to open or separate the contacts.

The intervening or opening action may be actuated by the timing element of the invention which is the rotating housing and cover combination is and 26. This is accomplished by providing the contact arm 68, FIGS. 1 and 2, with an upwardly extending '72 having mounted thereon a permanent magnet 7% and by providing an armature 76, made of iron or other magnetic material, attached to the lower surface of cover The magnet 74- and armature 76 are positioned the same distance from the rotational axis of the timer so that as the housing and cover assembly 13, 26 rotates after the timer has been set, the armature '76 will gradually move toward the permanent magnet '74. As the armature 76 approaches the magnet 74, the magnet mounted on the flexible arm 68 is attracted to the fixed armature to thereby quickly and positively snap open or separate the contacts 64 and '79. The switch components are angularly positioned so that the magnet 74 is attracted to the armature 76 just as the lug 56 moves into engagement with the peg 5.2 which is the end of the timing cycle. The prevention of further counterclockwise rotation prevents the contacts from being damaged. When the timer is once more set, the armature '76? is moved away from the magnet "/4, and the flexible contact arm 68 quickly and positively snaps the contact 79 into engagement with the contact 64- once more closing the switch. To restrain the closing action of the contact arm 66, an insulating stop peg '73 extending upwardly from the insulating support plate 16 may be provided to interrupt the inertial force of the magnet 74 caused by the movement of the contact arm in the switch closing action.

In order to make the switch completely and safely insulated, it is desirable to make the housing 18 and cover 26 of non-conducting material such as nylon or the like. Further, although the high viscosity fluid is located within the housing, there is always a possibility of some leakage. Consequently, it is desirable that a dielectric high viscosity fluid be employed within the housing, so that there would be no interference with the operation of the switch in the event leakage should occur.

While a particular embodiment of this invention has been illustrated and described, modifications thereof will occur to those skilled in the art. Accordingly, it should be understood that this invention is not limited to the particular arrangement disclosed, and it is intended in the appended claims to cover all modifications which do not depart from the spirit and scope of the invention.

Having thus described the invention, what is claimed is:

l. A viscously damped timing device comprising a sup port, a housing, a member positioned within said housing, a first shaft fixed to said member and extending through said housing, said member and said first shaft being maintained by said support, means for preventing rotation of said first shaft, a second shaft fixed to said housing and extending outwardly therefrom for rotatably mounting said housing with res ect to said first shaft, power means for rotating said housing in one direction, manual means for rotating said housing in the opposite direction from an initial position to a selected position, and a viscous material within said housing in contact with said member to retard the rotation of said housing by said power means for establishing a controlled time interval during which the housing returns to said initial position from said selected position, said time interval being proportional to the distance through which said housing rotates.

2. A viscously damped timing device comprising first and second supports, a housing positioned between said supports, a shaft fixed to said housing and rotatably mounted in said first support, gear means rotatably mounted within said housing, a shaft fixed to said gear means extending through sai' housing and supported by said second support, clutch means securing the gear means shaft to said second support, power means for urging said housing in one direction, said power means providing a rotationai force which is less than the resistive force of said clutch means so that said gear means shaft is held stationary while said housing rotates around the gear means, and a viscous Iiuid located within said housing surrounding said gear means to retard the rotation of said housing around said gear means by said power means for estabiishing a controlled time interval, said interval being proportional to the distance through which said housing rotates.

3. The timing device of claim 2 in which said gear means includes a sun gear mounted on said gear means shaft and at least one planet gear rotatabiy mounted within said housing and engaged with said sun gear.

4. A viscously damped timing device comprising a support casing, a housing, a set shaft fixed to said housing and extending through said support casing to be rotatably supported thereby, gear means rotatabiy mounted within said housing, a shaft connected to said gear means exten through said housing and supported by said support casing, friction clutch means securing said gear mean shaft to said support casing to resist rotation of said gear means shaft, a torsion spring surrounding said set shaft and positioned bet 'een said housing and said support casing, said spring having one end connected to said support casing and the opposite end to said housing, said spring providing a torque on said set shaft and housing which is less than the resistive torque of said friction clutch so that said gear means shaft remains stationary while said housing rotates around the gear means, and a viscous material located within said housing surrounding said gear means to retard the rotation of said housing by said power means providing a timing means for establishing a controlled time interval, said interval being aroportional to the number of radians through which said housing rotates.

5. The timing device of claim 4 including manual means to set said timing device by rotating said set shaft against the urging of said spring and said friction clutch.

6. A viscously damped timing device as defined in claim 1 including a pair of electrical contacts mounted in insulated relationship on said support, a movable contact arm attached to one of said contacts and adapted to be moved into and out of engagement with the other of said contacts, a permanent magnet mounted on said movable contact arm, an armature mounted on said timing member and adapted to move said contact arm by magnetically attracting said magnet when mo ed near the magnet, said armature and said magnet being arranged so that said armature is moved near said magnet at the end of said timed interval to separate said contacts.

7. A viscously damped timing device as defined in claim 2, a pair of eiectricai switch contacts mounted in insulated relationship on said second support plate, a movable contact arm attached to one of said contacts and adapted to be moved into and out of engagement with the other of said contacts, and means controlled by said housing for actuating said movable contact arm at the end or said time interval to control the operation of said switch contacts.

8. The timing device of claim 7 wherein said contact arm normally engages said other contact, and said actuating means comprises a permanent magnet mounted on the movable end of said contact arm and an armature mounted on said housing and adapted to move said contact arm by magnetically attracting said permanent magnet when in red near the magnet, said armature and said magnet being arranged so that said armature is moved near said magnet at the end of said timed interval to separate said contacts.

9. A viscousiy damped timing device comprising a support casing having a plurality of walls, a housing positioned within said casing, a shaft fixed to said housing and rotatably supported in said casing, 21 member rotatably mounted within said housing, a shaft fixed to said member, said member shaft having a reduced portion extending through a wall of said casing so th t the portion of said shaft adjacent the reduced portion forms a shoulder which abuts the surrounding casing wall, a washer frictionaily positioned on said reduced portion to secure said shoulder in engagement with said casing so that said shoulder and said washer form a "friction clutch about said member shaft, power means for urging said housing in one direction, said power means providing a ional force which is less than the reistive force of said friction clutch so that said member shaft is held stationary while sai housing rotates about said member, and a viscous material located within said housing in contact with said member to retard the rotation of said housing around said member so that a controlled time interval is obtained.

References Cited in the file of this patent UNITED STATES PATENTS 2,205,329 Wohlenhaus June 18, 1940 2,234,437 Kistler Mar. 11, 1941 2,604,163 Exline luly 22, 1952 2,693,231 Morganson Nov. 2, 1954 2,743,628 Scharaffa iay 1, 1956 2,744,972 Davis May 8, 1956 2,759,173 Hartzell ct al Aug. 14, 1956 2,946,902 Hagen iuly 26, 1960

Claims

1. A VISCOUSLY DAMPED TIMING DEVICE COMPRISING A SUPPORT, A HOUSING, A MEMBER POSITIONED WITHIN SAID HOUSING, A FIRST SHAFT FIXED TO SAID MEMBER AND EXTENDING THROUGH SAID HOUSING, SAID MEMBER AND SAID FIRST SHAFT BEING MAINTAINED BY SAID SUPPORT, MEANS FOR PREVENTING ROTATION OF SAID FIRST SHAFT, A SECOND SHAFT FIXED TO SAID HOUSING AND EXTENDING OUTWARDLY THEREFROM FOR ROTATABLY MOUNTING SAID HOUSING WITH RESPECT TO SAID FIRST SHAFT, POWER MEANS FOR ROTATING SAID HOUSING IN ONE DIRECTION, MANUAL MEANS FOR ROTATING SAID HOUSING IN THE OPPOSITE DIRECTION FROM AN INITIAL POSITION TO A SELECTED POSITION, AND A VISCOUS MATERIAL WITHIN SAID HOUSING IN CONTACT WITH SAID MEMBER TO RETARD THE ROTATION OF SAID HOUSING BY SAID POWER MEANS FOR ESTABLISHING A CONTROLLED TIME INTERVAL DURING WHICH THE HOUSING RETURNS TO SAID INITIAL POSITION FROM SAID SELECTED POSITION, SAID TIME INTERVAL BEING PROPORTIONAL TO THE DISTANCE THROUGH WHICH SAID HOUSING ROTATES.