US2657590A - Double dog detent for two-motion switches - Google Patents

Description

Nov. 3, 1953 R. L. HUFFMAN DOUBLE DOG DETENT FOR TWO-MOTION SWITCHES 2 Sheets-Sheet 1 Filed May 3,1949

INVENTOR. I ROBERT L. Hl JFFMAN M ATTORNEY Nov. 3, 1953 HUFFMAN 2,657,590

DOUBLE DOGDETENT FOR TWO-MOTION SWITCHES Filed May 5, 1949 2 Sheets-Sheet 2 INVENTOR. ROBERT L. HUFFMAN ATTORNEY Patented Nov. 3, 1953 DOUBLE DOG DETENT FOR TWO-MOTION SWITCHES Robert L. Huffman, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application May 3, 1949, Serial No. 91,096

1 Claim.

This invention relates in general to selective switching mechanism and more particularly to two-motion selective switching mechanism and still more particularly to two motion selective switching mechanism for use in automatic telephone systems.

More specifically, the invention relates to the provision of a new and improved means for enabling the Switch-shaft in a switch of the Strowger type to reach a predetermined position and be held in such a position until released. Basically such a switch is shown in a patent to Keith and Erickson, No. 815,321.

One of the objects of the invention is to provide a new and improved double dog to assure accurate operation in a switch of the above char acter enabling the speed of the switch to be greatly increased.

Another object is to correct a condition known as stuttering which developed in the conventionally double-dogged switch when the release time of the actuating magnets is stepped up.

Still another object of the invention is to pro vide a double dog which has detents with differ ent moments of inertia so that the inertia of one may be overcome without affecting the other.

A still further object of the invention is to provide a flexible rotary detent in a double dog which can quickly spring into adjacent ratchet teeth without the delay of the conventional type which occurs while the double dog restoring spring is overcoming the inertia of the double dogs mass.

And still another object of this invention, while providing the other features mentioned above, is to provide a flexible rotary detent for a double dog which will not readily become out of adjustment thereby throwing off other detailed adjustments.

These and other objects and features will be pointed out and explained fully hereinafter in the specification, reference being had to the accompanying drawings, Figures 1 to 5, inclusive, in which:

Fig. 1 is a left perspective view of a switching mechanism of the Strowger type with bank contacts and bank wipers left off.

Fig. 2 is a right perspective view of Figure 1 above.

Fig. 3 is a plan view of the members immediately co-operating in the rotation of the switch shaft.

Fig. 4 is an end view of the double dog with its mounting pin.

Fig. 5 is a front View of the double dog also with its mounting pin.

The conventional double dog has been used in switches of the Strowger type for a numper of years but has limited the speed at which such a switch could operate for reasons which will immediately hereinafter be discussed.

It has been known for some time, altho not visible to the naked eye, that the conventional double dog bounced two or three or more times each time it moved into engagement with a ratchet tooth on the switch shaft. A maximum rate of operation was generally conceded to be limited to a speed whereby the actuating pawl initiating rotary motion to the switch shaft would be allowed to remain operated at its full stroke holding the shaft in its predetermined position sufficiently long before releasing for the double dog to settle down and engage the adjacent ratchet tooth to secure the switch shaft in the attained predetermined position. This holding time at the full stroke during rotary motion obviously slows operation of the switch by a length of time equal to the amount of the time lost in one holding operation multiplied by the number of rotary steps necessary to reach the ultimate predetermined position. No method to remove this speed limitation was forthcoming over a period of greater than forty years. As soon as the operating speed of the switch was increased beyond the critical speed described hereinbefore by decreasing the release time of the rotary actuating means, the rotary pawl would complete its stroke and begin its return before the double dog rotary detent had stopped bouncing. The shaft would rotate back to the preceding step having been deprived of the locking function of the rotary detent which must, if at all, occur while the rotary actuating pawl is at its full stroke. This cycle would then be repeated over and over creating what was dubbed a stuttering effect. With no corrective means forthcoming the industry accepted this limited speed of operation as the maximum attainable.

Experiments were made by applicant toward lightening the mass of the double dog so that it could respond more quickly by having its inertia overcome more readily by the double dog restoring spring. However, this did not prove practical since the lighter metals would not hold shape under the pounding. The inventor then conceived the idea of substituting a light, but strong hard steel spring member for the rotary detent. Such a member, being light in mass could have its inertia over-come more readily and if tensioned in addition, could overcome its own inertia due to its stored up potential energy.

Experiments along this line of reasoning brought out ramifications in the use of such a spring member. Springs bent into a right angle detent as well as springs bent at obtuse angles were tested. However, under actual operating conditions determined by life tests, springs with a sharp bend therein of any angle rapidly lost their tension. Since the variation in tension of the rotary detent would cause other members of the switch to become out of adjustment, use of a bent spring member would be impractical, for its employment would require either frequent replacement or equally frequent complete readjustment of the switch, either of which is commercially unfeasible. Finally, a straight tension spring and bracket member to properly position the spring in relation to the rotary teeth was devised. The practicality of a, straight spring rotary detent was proven beyond a doubt when it was life tested, operating successfully in over a million operations at an increased switch operating speed without recurrence of the stuttering condition nor with appreciable variation in adjustment.

Referring again to the drawings, the new and improved double dog will now be described in detail.

The double dog 1, shown in Figures 4 and 5 has as the major portion of its mass a continuous member of metal stamped out of cold rolled steel and variously bent to form a vertical detent 2, to engage the horizontal circular or vertical ratchet teeth H, a back stop member 3, an elongated ear 6 having a stud l, and two parallel horizontally bent ears 8 having axially aligned holes bored therein for mounting purposes. Fixedly attached. to this continuous member is a tri-plane bracket member 4, side 4a being the side affixed. This aiiixation may be any standard means, preferably a spot weld. Side 4?] of the bracket member is in a vertical plane which intersects a vertical plane including the axis of the cores of the rotary magnets at an angle of 45, in addition to which the bracket has two tapped holes side by side. Adjustably attached to side 4b of the bracket member is a light straight steel spring member 5 of slight mass which at one end is mounted by means of two threaded bolts 9, thru the two holes near one end of spring member 5 into the tapped holes in side 4b of the bracket member. The spring is then tensioned so that it rests snugly against backstop 3 and positioned so that the other end is parallel to the crests of rotary ratchet teeth 12 while its length is such that when the vertical detent 2 is engaging a vertical ratchet tooth H, the spring member 5 may upon rotation of shaft l engage and hold the radial surface of a rotary ratchet tooth. The rotary detent is therefore comprised of three members, backstop 3 integral with the vertical detent 2; bracket member 4 and rotary detent spring 5. By the manner in which the various pieces are assembled the 00mm pleted double dog comprises a vertical detent and a rotary detent rigidly attached together.

The double dog as detailed above is mounted to frame it by a pin M thru the axially aligned holes in ears 3, pin M having a shoulder l and held in place by clamp 16.

When the switch is at rest or normal, the detents of the double dog are held out of engagement with their associated ratchet teeth by a release link spring I'i engaging stud 1 by means of a slot cut into the release link for that purpose.

Upon the first vertical motion imparted to shaft II] by energization of vertical magnets l8 thru the medium of a vertical armature I9 and pawl 20, a hook 2| on the vertical armature l9 lifts release link spring ll off of stud I. At this time double dog restoring spring 22 attached at one end to frame l3 and tensioned against vertical detent 2 of double dog I forces vertical detent 2 into engagement with a vertical tooth I.

The vertical detent 2 will successively be forced out of the vertical tooth upon the next energization of the vertical magnets It but urged into the next tooth by the double dog restoring spring, this cycle repeated until a predetermined vertical level is reached. The vertical detent 2 by a combination of the inertia due to the mass of the double dog and the force exerted by the double dog restoring spring thereon will then continue to engage and hold the vertical tooth at the level reached during subsequent rotary motion.

Rotary motion is imparted to the shaft 10 upon energization of rotary magnets 23 thru the medium of rotary armature 24 and pawl 25 engaging rotary teeth !2 and rotating shaft Ill one radial step.

As the first rotary motion occurs stationary dog 26 which has been riding in slot 21 slides under an adjacent circular tooth ll.

Simultaneousl as rotary motion is imparted in the manner described above, rotary detent spring member is forced away from its back stop 3 as the flank of the first rotary tooth slides along the interior surface of spring 5 toward the free end thereof. At a point just as the rotary pawl reaches its full stroke, the end of rotary detent spring member 5 slides over the crest of the tooth and under its own tension is driven into the adjacent valley between the teeth where it engages the radial surface of the tooth and holds it securely before the rotary pawl its return stroke even where release time of the rotary magnet has been appreciably decreased. Because of the light mass of the rotary detent spring and the positioning of its back stop member bounce is for all intents and purposes eliminated, and the light spring detent moves into engagement faster. This cycle is repeated until a predetermined number of rotary steps is reached. Each time the rotary detent spring will engage the next tooth just as the pawl reaches its full stroke, insuring accurate operation at greatly increased speed. Further, because of the large difference in mass between the heavy rolled steel portion of the double dog l as compared to the light mass of the rotary detent spring member 5, and because of the greatly increased speeds at which the rotary stepping is accomplished, the greater moment of inertia of the double dog is not overcome before the rotary detent spring secures a tooth, whereby the vertical detent remains stationary and engaged with a vertical tooth all during the rotary stepping; and further, because the vertical detents inertia is not overcome, no additional force need be exerted by the double dog restoring spring as it would be if the vertical detent were being pressed outward against it during rotary stepping. It is apparent then that the rotary detent spring member is securing the rotary teeth under its own tension and independent of the double dog restoring spring; and likewise vertical detent 2 of the double dog is not perceptibly moved outward from a vertical tooth H during rotary motion.

Release is accomplished when the release magnet 28 is energized causing release armature 29 thru pin 30 to strike ear 6 of the double dog, forcing ear 6 inward and rotating detents 2 and 5 of the double dog on pin 1 out of engagement with teeth H and I2.

The shaft, now resting on stationary dog 26 rotates clockwise under compulsion of helical spring 31 until stationary dog 26 falls into slot 21 whereupon gravity carries shaft l0 downward until it comes to rest at its normal position.

Having described the invention and its operation in detail, what I claim and desire to be protected by issuance of Letters Patent is:

The combination with a switch shaft having vertical selecting and release movements and rotary selecting and release movements and having a first series of teeth extending around the shaft and a second series of teeth extending lengthwise thereof, of a vertical detent for engaging said first teeth to hold said shaft in its vertical selecting positions, a rotary detent comprising a straight flexible spring secured rigidly to said vertical detent at one end of said spring and engaging said second teeth at the other end thereof to hold said shaft in its rotary selecting positions, a backstop for said spring detent integral with said vertical detent and positioned between said ends of said spring detent, said spring being tensioned against said teeth at said one end and against said backstop intermediate said ends,

said spring detent being movably flexed by said second teeth during rotary selecting movement of said shaft, said vertical detent being substantially independent of any flexing movement of the spring detent, and shaft release means for moving said vertical detent away from engagement with said first teeth, said backstop moving with said vertical detent to thereby remove said rotary detent from engagement with said rotary teeth whereby said rotary detent is movable with said vertical detent as a unit by means of the backstop when the vertical detent is removed from engagement with said first teeth to thereby release said shaft.

ROBERT L. HUFFMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 815,321 Keith et a1 Mar. 13, 1906 1,275,016 Goodrum Aug. 6, 1918 1,290,507 Carroll Jan. 7, 1919 1,675,311 Sengebusch June 26, 1928 1,772,798 Carlson Aug. 12, 1930 1,818,690 Carlson Aug. 11, 1931 2,410,432 Drake Nov. 5, 1946 FOREIGN PATENTS Number Country Date 205,062 Great Britain May 8, 1924

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