US2820851A - Two-motion switch - Google Patents

Description

Jan. 21, 1958 K, w. GRAYBILL ETAL $820,851

TWO-MOTION swrrcn Filed Aug; 30, 1954 V 2 Sheets-Sheet 1 I INVENTORS mm w. GRAYBILL HANS useauscn Fl G. l

21, 958 K. w. GRAYBILLJETAL 2,820,351

TWO-MOTION SWITCH Filed Aug. 30, 1954 2 Sheets-Sheet 2 mvenronsk KENNETH w. GRAY-BILL HANS ssuesauscn ATTY.

, provided to control both I secondary movement of the switch wipers.

United States Patent" TWO-MOTION SWITCH Kenneth W. Graybill, Elmhurst, and Hans Sengebusch,

Ch cago, Ill., assignors to General Telephone Laboratones, Incorporated, a corporation of Delaware Application August 30, 1954, Serial No. 452,752 Claims. (Cl. 179-2752) The main object of the present invention is to provide automatic switches of simple structure having primary and secondary movements. They are more rapid and accurate 1n operation especially during the secondary movement as compared with the present day automatic switches.

One of the features of the invention relates to an im I proved drive mechanism with an improved driving unit for an automatic switch in which a single driving member is Another feature relates to a combination of an improved the primary movement and the a direct drive mechanism with an improved changeover mechanism for changing the direction of movement of the wipers.

'A further novel feature resides in an improved driving unit of modified form, which comprises a first and a second ratchet wheel secured respectively to a first and a second sprocket wheel actuated by two stepping pawls. Both sprocket wheels are in mesh with a series of equally 'spaced lugs of an associated main rack. The second sprocket wheel has a pre-determined shorter radius than the radius of the first sprocket wheel, so that the associated main rack is caused to travel a pre-determined distance per step in response to the rotation of the first sprocket wheel, whereas the second sprocket wheel, upon actuation, will cause the main rack to travel a pre-determined shorter distance per step, with the result of achieving a higher rate of stepping.

In most known automatic switches using a main rack to control both the primary and the secondary movement of the switch, the main rack always travels an equal predetermined distance in response to each actuation of the stepping pawl without discrimination as to either the primary or secondary movement. It "is well known in the art that the bank contacts which are accessible to the wipers are arranged in groups within a pre-determined space and the space between levels or groups of bank contacts is greater than the distance between adjacent :bank contacts within the same group. obvious that when the wipers move into the bank con- It is, therefore,

tacts by the secondary movement, the main rack is only required to travel a shorter distance per step than it would have been required to travel per step in the case of the vertical movement of the wipers during the primarymovement. According to the present invention, more rapid operation is obtained when the main rack takes shorter steps in its secondary movement as compared with the distance of each step that the main rack has to travel during the primary movement. This adjustment of distance correspondingly increases the speed of stepping and certainly would meet the demand of high speed stepping especially in view of the fact that the wipers have to travel over sixteen contacts during the secondary movement.

Another feature of this invention resides in'the improved ice holding and releasing mechanism including a release spider controllable by a latch bar and a changeover member in removing the holding detent and stepping pawl from the path of the teeth of the sprocket wheel and the ratchet wheel respectively.

Other objects and features of this invention will be brought out more clearly upon a perusal of the following specification and drawings in which:

Fig. 1 is a plan view of the switch provided with a single driving unit;

Fig. 2 is a front view of a stationary rack and the main rack having numerals thereon to indicate the position of wipers;

Fig. 3 is a plan view of a modified driving unit with two sprocket wheels, two ratchet wheels and two stepping pawls;

Fig. 4 is an enlarged view of a portion of the driving unit of Pig. 3 showing the series of equally spaced lugs of the main rack meshing with two sprocket wheels of dilferent radius.

Referring now briefly 'to Figs. 1 and 2, the apparatus comprises a driving unit D having a hub 1, a sprocket wheel 2, a ratchet wheel 3, a release spider 6, a detent 12, a driving member 13, a stepping pawl 14, a latch member 20, a latch bar 15, "a main rack 24, a main carriage 34, a wiper carriage 37, Wipers 38, wiper. rack 39, a stationary rack 32, a locking arm 28, a changeover magnet '51, a changeover member 52, stepping magnet 23, and a double gear unit 40.

Similar reference characters-are applied to similar parts in both the original audgmodifiedv form ofthe two motion se'lectiveswitch.

Turning now briefly to Figs. '3 and 4, the apparatus in modified form comprises a driving unit D having a first hub 1, a first sprocket wheel 2, a first ratchet wheel 3, a release spider 6, a detent 12, a driving member 13, a stepping pawl 14, a latch member 20, a latch bar 15, a second hub '1, a second sprocket wheel 2, a second ratchet wheel 3', a second stepping pawl 14', a main rack 24, spaced lugs 26, a main carriage 34, a wiper carriage 37, wipers 38, wiper rack 39, a stationary rack 32, a locking arm 28, a stepping magnet 23, a changeover magnet 51, a changeover member 52 and a gear unit 40.

The particular embodiment of the switch disclosed herein is capable of performing any of the well known functions of two motion switches, such as telephone-linefinders, selectors and connectors.

Referring now more particularly to Fig. l, the Wiper carriage 37, movably mounted on the main carriage 34, carries a plurality of wipers such as 38, to which, bank cont cts in rows (not shown) are accessible. A main rack 24 comprises a locking notch 27, a latch restoring pin 25 and a plurality of notches such as 26, with which the corresponding teeth 4 of the sprocket wheel 2 are meshing. A stationary rack 32 mounted adjacent to the main rack 24 has ten notches such as 33, each of which, as best shown in Fig. 2, corresponds to a particular row or level of its associated bank contacts (not shown). A locking arm 28 pivoted on a suitable point 35 of the main carriage 34 comprises a first projection 31 being adapted to register with the notch 27 of the main rack 24 for locking the main carriage 34 to the main rack 24. A second projection 30 on the locking arm 28 is so adapted as to be received by any one of the notches such spective teeth 4 and 26. A ratchet wheel 3 is secured to the sprocket wheel 2 and rotatable therewith and is actuated by a driving pawl 14 which is controllable by the stepping magnet 23 through the medium of a driving member 13. A release spider 6, rotatably mounted on the hub 1, and yet independent of the rotation of either the sprocket wheel 2 or the ratchet 3, comprises a first arm 7, a second arm 8, a third arm 9, a fourth arm 10, and a restoring spring 11 mounted thereon. A holding detent 12 cooperates with the teeth 4 on the sprocket wheel 1 2 to hold the switch in its operated position. A latch member 20 mounted near the spider 6 has a tail extension 19, a first notch 21 and a second notch 22. A latch bar 15 is pivotally mounted on a suitable point 50, which also represents a first extension of changeover member 52, whose second extension 53 appears in the form of dotted lines on the right side of the locking arm 28. A first extension 17 on the latch bar 15 engages the tail extension 19 of the latch member 20. A second extension 16 on the latch bar 15 is engaged by the latch restoring pin 25 on the main rack 24.

When the changeover magnet 51 is electrically energized by any suitable control circuit (not shown), the

armature 54 is attracted, moving arm 54 therewith and thereby moving the changeover member 52 to the right. It may be pointed out that a bent over portion 29 of locking arm 28 cooperates with the second extension 53 of the changeover member 52 for locking the main rack 24 in its normal position. The first actuation of the second extension 53 upon the energization' of the changeover magnet 51 removes the extension 53 to the right I from the path of the locking arm bent over portion 29,

so that the main rack 24 is now free to move upward. The latch bar 15 has a normal, an off-normal and a release position, which will bedwelt upon in a later paragraph. When the latch bar 15 is positioned normal, the second extension 16 on the latch bar 15 is engaged by the latch restoring pin 25 on the main rack 24 in such a manner as to hold the latch bar 15 in a position as shown in Fig. 1 to prevent the engagement of the latch bar notch 18 with the second arm 8 of the release spider 6 when magnet 51 is first energized. In the event the changeover member 52 is first actuated to the right, the latch bar 15 is locked-in its normal position, and is, therefore, unable to rotate the release spider 6, as the notch 18 passes under arm 8 without engaging it. Also the extension 17 on latch bar 15 holds the latch member 20 in engagement as it slides downward along extension 19 thereof. Upon the actuation of the stepping magnet '23, while magnet 51 is held energized, the driving pawl 14 is actuated to rotate ratchet wheel 3 and sprocket wheel 2 so as to advance the main rack 24 together w1th the main carriage 34 and the wiper carriage 37 to a position opposite a selected level of the associated bank contacts. As soon as the main rack is raised one step, the pm 25 moves away from extension 16 so that latch bar 15 is raised by its spring 15' to cause extension 17 to disengage extension 19 and to bring notch 18 up on a level with arm 8. Upon the deenergization of the changeover magnet 51, the changeover member 52 is released to thereby push the second extension 53 to the left against edge of bent over portion 29 of the locking arm 28 to insert the second projection 30 thereof into one of the notches 33 of the stationary rack 32 corresponding to the selected bank level so as to lock the main carriage 34 to said stationary rack 32 at such a level and prevent further vertical movement thereof. The reoperation of the stepping magnet 23 again actuates the driving pawl 14 to step the ratchet wheel 3 and sprocket wheel 2, and, in turn, the main rack 24 to, in this case, move the wiper carriage 37 and the wipers 38 to the right into the selected level of the associated bank contacrs through the cooperation of wiper rack 39 and double gear unit 40.

Turning now to the releasing operation, as already pointed out, the latch bar 15 pivotally mounted on the first extension 50 of changeover member 52 is now in its off-normal position. When magnet 51 is now operated, the bar 15 is moved to the right and engages the second arm 8 of spider 6. When pin 25 moved upward and latch bar 15 also moved upward the first extension 17 on the latch bar 15 moves away from the tail extension 19 of the latch member 20 to permit later upward movement thereof. When the latch bar 15 is positioned normal, the second extension 16 on the latch bar 15 engages the latch restoring pin 25 -on"the main rack 24, so as to disable the latch bar notch 18v with a view to preventing the engagement of the latch bar notch 18 with the second arm 8 of the release spider G in case the changeover member is first actuated to the right. The latch bar 15 will, however, take its off-normal position as above described as soon as the latch restoring ,pin 25 is advanced with the main rack 24 from their normal positions in response to the rotation of sprocket Wheel 2 controllable by the actuation of the stepping pawl 14 on the ratchet wheel 3. A second actuation of the changeover magnet 51 will move the latch bar 15 from its offnormal position to its release position, and the latch bar notch 18 is caused to rotate the second spider arm 8 I clockwise. The third spider arm 9 thus moves from the first latch member notch 21 into notch 22, where it is held in place during the release period and latch member 26 moves clockwise under the influence of spring 55 as it is no longer held by extension 17. In the'meantime, the fourth arm 10 removes the detent 12 from thepath of the sprocket teeth 4 and the first arm 7 removes the stepping pawl 14 from the path of the ratchet teeth; 5. When extension 53 moves to the right the locking arm 28 is no longer held in its left hand position, and spring 36 is free to later move it to the right. The sprocket wheel 2 is now free to rotate counterclockwise, and the tension on the restoring springs 41 and 42, responsive to the rotation of the spider arms 7, 8, 9 and 10, cooperate to restore the wiper carriage 37 to its left hand position by the downward movement of rack 24 and to align the locking notch 27 on the main rack 24 with the first projection 31 of the locking arm 28. In response to this alignment, the locking arm biased by the efiects of the restoring spring 36 immediately locks the first projection 31 into the locking notch 27 of the main rack 24 and thereby move the second projection 30 of the locking arm 28 out of engagement from the combed notch 33 of the stationary rack 32. After this locking and unlocking op eration, the main carriage 34 is again locked with the main rack 24 and the restoring spring 42 is therefore efiective to restore the main rack 24 together with the main carriage 24 and the wiper carriage 37 to normal.

At this juncture, the latch restoring pin 25 also restores to normal in engagement with extension 16 and moves the latch bar 15 back to its normal position to in turn cause extension 17 to engage extension 19 to move latch member 20 back to normal. The restoring spring 11 restores the third spider arm 9 from the second latch member notch 22 to the first latch member notch 21 and thereby causes all the spider arms together with the detent 12 and pawl 14 to be restored to their respective normal positions.

Turning now to Figs. 3 and 4, the two motion selective switch in modified form comprises a driving unit D similar to that of Fig. 1 having a first hub 1 mounted on a base with a first sprocket wheel 2 and a first ratchet wheel 3 rotatably secured thereon. A release spider 6 is also rotatably mounted on huh I but is neither biased by the rotation of the sprocket wheel 2 nor afiected by the ratchet wheel 3. The primary movement of the switch wipers is controlled by the first set of wheels such as ratchet wheel 3 and sprocket 2, which are rotated by a first stepping .pawl 14. The secondary movement of the switch wipers is controlled by a second ratchet wheel 3 and a second sprocket wheel 2', both of which are rotatably mounted on a second hub 1' and rotated by a second stepping pawl 14'. A series of equally spaced lugs 26',.as best seen in Fig. 4, secured to the main rack 24' are meshing with both sprocket wheels 2 and 2'. However, the radius of the second sprocket wheel 2 is a predetermined amount aborter than that of the first sprocket wheel 2, so that during the secondary movement, the main rack 24' is caused to travel a pre-determined shorter distance per step than that of the primary movement. A holding detent 12 cooperates with the teeth 4 of the first sprocket wheel 2 in order to hold the same as well as rack 24' in its operated position. A stepping magnet 23 is provided to operate a driving member 13, which has a first pawl 14 and a second pawl v14 as already pointed out. A changeover member 52 is actuated by the changeover magnet 51. Spring means .RI and :R2 are mounted on the changeover member 52 for positioning the driving member 13 so that the first pawl 14 is opera- .tively associated with the first ratchet wheel 3, and the second pawl 14 is disassociated from the second ratchet wheel 3 upon the first operation of the changeover magnet 51.

It may be pointed out here that Fig. '1 shows that the main ,rack 24 rises .175 inches for each step. This .175 inches isthe minimum vertical movement that will allow for proper wiper clearance in the vertical plane.

The distance of wiper movement into the bank horivrontally as shown in Fig. 1 is only .098 inch or more specifically one tooth of a 32 pitch gear. And since the main rack 24 also rises .175 inch per step during the secondary movement, it is necessary to use a double gear between the two racks, as also shown in Fig. 1.

:Returning now to Fig. 3, it would, therefore, be of a great advantage, if after the changeover magnet 51 has fallen back, that is, during the secondary movement, the main rack 24 could be made to take shorter steps, 0.98 inches, as caused by the shorter circumference of the second sprocket wheel 2' as stated above. This would not only permit the double gear between the two racks of Fig. 1 to be replaced with a single gear as shown in Fig. 3, but would also enable fast stepping as explained in the beginning of the specification.

The release spider 6 comprises first, second, third and fourth arms. The locking arm 28 is pivotally mounted on a suitable point 35 of the main carriage 34 for locking the main rack 24' in its normal position as in Fig. 1. The main carriage 34 is substantially the same as shown in Fig. l. The latch'member 20 has a tail extension 19 and a first notch 21 and a second notch 22. The latch bar 15 is pivotally mounted on the changeover member 52 and comprises a notch 18 and two extensions 17 and 16. The first extension 17 of latch bar 15 is engaged on tail extension 19 of latch member 20. The second extension 16 of latch bar 15 cooperates with a restoring pin 25 on the main rack 24 to hold the latch bar 15 in its normal position as shown in Fig. 3 so as to disable the engagement of the driving notch 18 with second spider arm 8, when the changeover member 52 is first actuated. However, the first actuation of the changeover member 52 removes the extension 53 thereof out of the path of the bent over portion 29 of locking arm 28 so as to permit upward movement of the main rack 24' and by moving springs R2 and A1 renders pawl 14 effective. It should be borne in mindthat the latch bar 15 is locked in its normal position by pin 25 and is, therefore, unable to rotate the release spider 6, when magnet 51 is first energized, since the notch 18 moves to the right under arm ,8 without engaging it. Also the extension 17 on latch bar 15 holds the latch member 20 in position, as extension 17 slides along extension 19 of latch member 20. The actuation of the stepping magnet 23 will then actuate the .first pawl. .14 :to step the .first ratchet wheel 3 and sprocket wheel .2 .in order to advance the main rack 24 .andmain carriage 34 into alignment witha selected level, as in Fig. 1 the wiper .carriage 37 is held from longitudinal movement by a .springsuchas 41. As soon as the main rack is raised one stepthe pin 25moves away from extension .16 so that latch bar 15 is raised by its spring 15' to cause extension 17 to disengage extension '19 and to bring notch (18 up on a level with arm 8.

.The changeover member 52.is restored by a first restoration of the changeover magnet 51 to cause spring means R1, R2 to disassociate the .first pawl 14 .from operative engagement with :the first ratchet wheel 3 and also to position the second ,pawl 14 (for operative engagement with the second ratchet wheel 3. The restoration of the changeover member .52 also causes extension 53 to engage locking arm 28 and move it .to the left so that projection 30engages one of the notches 33 .in the stationary rack 32 to prevent .further upward'movement of carriage 34and therefore cause further upwardmovement of 24 to move the wiper carriage to the right bymeans of-gear 4D and the teeth on mainrack 24'. The stepping magnet again actuates the driving member .13'and, this time, the second pawl .14 is urged to step the second ratchet 3', thus rotating the second sprocketwheel 2', which in turn advances the main rack 24' to a selected position.

.At this juncture, the restoring pin 25 and the main rack .24 are .no longer positioned on their normal positions. Under this condition, .upon the first restoration of the changeover member 52, the latch bar 15 immediately moves to its off-normal position, since extension 16 is not any more engaged with restoring pin 25, as explained above. A second actuation of the changeover magnet .51 moves the latch bar .15 from its off-normalposition to its release position by directing the latch bar notch 18 to engage the second spider arm 8 and thereby rotate all the other spider arms. As a consequence, the third spider arm 9 moves from the first latch member notch 21 to the second latch member notch 22; the fourth arm 10 thereby removes the detent 12 .from the path of the teeth 4 of the first sprocket wheel 2; the first arm 7 there by moves to a release position to prevent the first pawl 14 from restoring to its operative engagement with the first ratchet wheel 3. The second actuation of the changeover member 52 moves spring means R1 to cause the disassociation of the second pawl -14'.from the second ratchet wheel 3' and also causes the first pawl 14 to engage the first spider arm 7 in its release position. Since the removal of the detent 12 from the path of the teeth 4 of the sprocket wheel 2 and the respective disassociation of both pawls 14 and 14 from ratchet wheels 3 and 3 have been completed, the restoring spring (not shown) on the main rack 24, therefore, cooperate with the restoring spring (not shown) on wiperrack 39 to restore the wiper carriage and main rack 24' to normal. The latch restoring pin 25 also restores to normal into engagement with extension 16 and moves the latch bar 15 back to its normal position. The restoring springs 55 and 11 thus cooperate to restore the third spider arm 9 from the second latch member notch 22 back to the first latch member notch 21 and thereby cause all the spider arms together with the detent 12 and pawls 14 and 14' to be restored to their respective normal position as shown in Fig. 3.

The present embodiment is the preferred embodiment but it is to be understood that the changes can be made in the present embodiment by one skilled in the art without departing from the spirit and scope of this invention.

Having described the invention, what is considered to be new and is desired to have protected by Letters Patent will be set forth in the following claims.

What is claimed is:

.1. In a driving unit for an automatic switch, a hub, a sprocket wheel rotatably mounted on said "hub, a ratchet wheelsecured to said sprocket wheel and rotatable therewithy a' release spide'r rotatably mounted on said hub independent of the rotation of said sprocket and ratchet wheels, said spider having a normal and a release position, a main rack meshing with the teeth on said sprocket wheel, a main carriage and a secondary carriage movably associated with said rack, a holding detent normally engaging the teeth of said sprocket wheel to hold the same in its operated position, a driving pawl for rotating said ratchet and sprocket wheels,a stepping magnet for operating said pawl, a changeover magnet, locking means for locking said-main rack in its normal position, a changeover member operated by a first actuation of said changeover magnet for operating said locking means to permit movement of said rack, actuation of said stepping magnet operating said pawl to rotate said ratchet and sprocket wheels to advance said main rack for moving said main carriage in one direction, deenergization of said changeover magnet releasing said changeover member to thereby cause said locking means to be effective for locking said main carriage in said advanc'edposition, reoperation of said stepping magnet again actuating said pawl to rotate said ratchet and sprocket wheels to move said secondary carriage in another direction, a latch bar operated in response to a second actuation of said changeover magnet for rotating said spider from its normal position to its release position, means on said spider in its release position for disengaging said detent from the teeth of said sprocket wheel and for disassociating said pawl from the teeth of said ratchet wheel, a main rack restoring means efiective in response to said disengagement of said detent and said disassociation of said pawl for restoring said main rack to its normal position, and means including said latch bar effective in response to the restoration of said main rack to normal for restoring said spider to its normal position.

2. In a driving unit for an automatic switch, a first hub, a first sprocket wheel rotatably mounted on said hub, a first ratchet wheel secured to said first sprocket wheel and rotatable therewith; a release spider having a normal and a release position rotatably mounted on said first hub independent of the rotation of said first sprocket and ratchet wheels; a second hub, a second sprocket wheel rotatably mounted on said second hub, a second ratchet wheel secured to said second sprocket wheel and rotatable therewith; a series of equally spaced lugs on a main rack meshing with the teeth on said first and second sprocket wheels; a main carriage and a secondary carriage movably associated with said main rack; a holding detent cooperating with. the teeth on said first sprocket wheel to I hold the same in its operated position; a driving member having a normal position; a first pawl on said driving member for rotating said first ratchet and sprocket wheels; at second pawl on said driving member for rotating said second ratchet and sprocket wheels; a stepping magnet for operating said driving member; a changeover magnet; a changeover member actuated by said changeover magnet; spring means mounted on said changeover member for positioning said driving member so that said first pawl is operatively associated with said first ratchet wheel while said second pawl is disassociated from said second ratchet wheel upon operation of said changeover magnet; locking means for locking said main rack in its normal position; said changeover member operated by a first actuation of said changeover magnet for operating said lock-ing means to permit movement of said rack, 21 first actuation of said stepping magnet operating said first pawl to rotate said first ratchet and sprocket wheels to advance said main rack to move said main carriage in one direction; said changeover member restored by a first restoration of said changeover magnet to cause said spring means to disassociate said first pawl from operative engagement with said first ratchet wheel and to position said second pawl for operative engagement with said second ratchet wheel; said stepping magnet again actuating said driving member and said second pawl to step said second ratchet and sprocket wheels to again advance actuation of said changeover magnet for rotating said spider from its normal position to its release position,

means on said spider in its release position for disengaging said detent from the teeth of said first sprocket wheel and for positioning said first pawl away from operative e11 gagement with said first ratchet wheel; said spring means on said changeover member efiective in response to said second actuation of said changeover member for moving said driving means to hold said first pawl against said spider means and for disassociation of said second pawl for said second ratchet wheel; a main rack restoring means effective in response to said disassociation of both said pawls from said first and second ratchet wheels respectively as well as said disengagement of said detent from the path of the teeth of said first sprocket wheel for restoring said main rack to normal; and means including said latch bar efiective in response to the restoration of said main rack to normal for restoring said spider, detent, and driving member to their respective normal position.

3. In a driving unit for an automatic switch, a first sprocket wheel, a first ratchet wheel secured to said first sprocket wheel, a second sprocket wheel, a second ratchet wheel secured to said second sprocket wheel, a driving member having a first pawl for rotating said first ratchet and sprocket wheels, a second pawl in said driving mernher for rotating said second ratchet and sprocket wheels, a stepping magnet for operating said driving member, a changeover magnet, changeover means responsive to a first actuation of said changeover magnet for positioning said driving member to move said first pawl into opera= tive relationship with said first ratchet wheel and to move said second pawl from operative relationship with said second ratchet wheel, a main rack operatively coupled to said sprocket wheels, a main carriage and a secondary carriage movably associated with said rack; a first actuation of said stepping magnet operating said driving member to cause said first pawl to rotate said first ratchet and sprocket wheels to advance said main rack to move said main carriage in one direction, said changeover means responsive to the restoration of said changeover magnet for positioning said driving member to move said second pawl into operative relationship with said second ratchet wheel and to disengage said first pawl from operative relationship with said first ratchet wheel, a second actuation of said stepping magnet operating said driving member to cause said second pawl to rotate said second ratchet and sprocket wheels to again advance said rack to move said secondary carriage in another direction, holding means including said pawls for holding said main rack in its advanced positions, a release spider operated responsive to a second actuation of said changeover magnet for disabling said holding means and for positioning said driving means to operatively disable both said pawls, and means responsive to the operation of said release spider for restoring said main rack from its advanced positions.

4. In a driving unit as claimed in claim 3, wherein said second sprocket wheel has a predetermined shorter diameter than the diameter of said first sprocket wheel whereby said main rack travels a predetermined lesser distance in response to rotation of said second ratchet wheel than it does in response to rotation of said first ratchet wheel for corresponding actuation of said driving means.

5. In a driving unit for an automatic switch, a first sprocket wheel, a first ratchet wheel secured to said first sprocket wheel; a second sprocket wheel having a predetermined shorter diameter than the diameter of said first sprocket wheel, a second ratchet wheel secured to said second sprocket wheel, a driving member having a first pawl for rotating said first ratchet and sprocket wheels, 8.

second pawl on said driving member for rotating said second ratchet and sprocket wheels, a stepping magnet for operating said driving member, a changeover magnet, changeover means responsive to a first actuation of said changeover magnet for positioning said driving member to move said first pawl into operative relationship with said first ratchet wheel and to disengage said second pawl from operative relationship with said second ratchet wheel, a main rack operatively associated with said sprocket wheels, main carriage and a secondary carriage movably associated with said rack, a first actuation of said stepping magnet operating said driving member to cause said first pawl to rotate said first ratchet and sprocket wheels to advance said main rack a predetermined distance for each actuation of said first pawl so as to move said main carriage in one direction, said changeover means responsive to the restoration of said changeover magnet for positioning said driving member to move said second pawl into operative relationship with said second ratchet Wheel and to disengage said first pawl from operative relationship with said first ratchet wheel, a second actuation of said stepping magnet operating said driving member to cause said second pawl to rotate said second ratchet and sprocket Wheels to advance said main rack a predetermined shorter distance for each actuation of said second pawl so as to move said secondary carriage in another direction.

6. In a driving unit as claimed in claim 5, holding means including said pawls for holding said main rack in its advanced positions, a release spider operated in response to a second actuation of said changeover magnet for disabling said holding means and for d-isassociating said pawls from their associated ratchet wheels, and means responsive to the operation of said release spider for restoring said main rack from its advanced positions.

7. In a driving mechanism for an automatic switch, a movable main rack, 21 wiper carriage mounted on said rack and movable in one direction with and in another direction relative to said rack, a series of teeth on said rack, a pair of gears meshing with said teeth, means for moving said gears independently first to move said rack in large steps by means of one gear and then in shorter steps by means of the other gear, and means for first causing said rack to move said carriage therewith when moved in said large steps and for then causing said carriage to be moved relative to the rack when the rack is moved in said shorter steps.

8. A driving mechanism as claimed in claim 7 in which there is a sin le operating magnet having means for scccessively moving said gears, and a single changeover magnet for causing the operating magnet to change over from one to the other gear and also for subsequently releasing the switch.

9. A two motion selective switch comprising a main carriage; a wiper carriage movably mounted on said main carriage and having a plurality of wipers; a main rack having gear teeth, bank contacts arranged in levels accessible to said wipers; a hub; a sprocket wheel rotatably mounted on said hub and meshing with the teeth of said main rack; a ratchet wheel secured to said sprocket wheel and rotatable therewith; a release spider rotatably mounted on said hub independent of the rotation of said sprocket and ratchet wheels having a plurality of arms; a holding detent cooperating with the teeth on said sprocket wheel to hold the same in its operated position; a driving pawl for rotating said ratchet wheel and said sprocket wheel; a stepping magnet for operating said driving pawl; a changeover magnet; a changeover member actuated in response to the operation of said changeover magnet,

main rack together with said main carriage and said wiper carriage to a position opposite a selected level of said bank contacts; deenergization of said changeover magnet releasing said changeover member to thereby cause said locking means to be effective for locking said main carriage in a position corresponding to said selected bank level; reoperation of said stepping magnet again actuating said pawl to step said ratchet and sprocket wheels to move said wiper carriage to thereby move said wipers into said bank contacts of the selected level, a latch bar pivotally mounted on said changeover member and having a normal, an off-normal and a release position; means for locking said latch bar in its normal position upon the first actuation of said changeover magnet, means for thereafter moving said latch bar to said ofi-normal position, means responsive to said second actuation of said changeover magnet for moving said latch bar to its release position to thereby cause one of said spider arms to separate said detent from said sprocket wheel and another spider arm to separate said pawl from said ratchet wheel for thereby restoring said main rack to normal.

10. In a driving unit for an automatic switch, a hub, a first sprocket wheel rotatably mounted on said hub, a first ratchet wheel secured to said first sprocket wheel and rotatable therewith, a release spider rotatably mounted on said hub independent of the rotation of said first sprocket and ratchet wheels and having a plurality of arms, a restoring spring for said release spider; a second hub, a second sprocket wheel rotatably mounted on said second hub, a second ratchet wheel secured to said second sprocket wheel and rotatable therewith; a series of equally spaced lugs on a main rack meshing with the teeth on said first and second sprocket wheels; a holding detent cooperating with the teeth on said first sprocket wheel to hold the same in its operated position; a driving member having a first pawl for rotating said first ratchet and sprocket wheels; a second pawl on said driving member for rotating said second ratchet and sprocket wheels; a stepping magnet for operating said driving member, a changeover magnet; a changeover member actuated by said changeover magnet; spring means mounted on said changeover member for positioning said driving member so that said first pawl is operatively associated with said first ratchet wheel while said second pawl is disassociated from said second ratchet wheel upon the first operation of said changeover magnet; means for locking said main rack in its normal position, first actuation of said changeover member removing said locking means from said rack to permit movement thereof; actuation of said stepping magnet actuating said first pawl to step said first ratchet and sprocket wheels to advance said main rack, said changeover member restored by a first restoration of said changeover magnet to cause said spring means to disassociate said first pawl from operative engagement with said first ratchet wheel and to position said second pawl for operative engagement with said second ratchet wheel; said stepping magnet again actuating said driving member and in this case, said second pawl to step said second ratchet and sprocket wheels and, in turn, said main rack into a selected position, means responsive to a second actuation of said changeover magnet for causing one of said spider arms to move said detent from the path of the teeth of said first sprocket wheel and to cause another spider arm to prevent said first pawl from restoring to its operative engagement with said first ratchet wheel, whereby said main rack is permitted to restore to normal.

References Cited in the file of this patent UNITED STATES PATENTS 1,375,230 Reynolds Apr. 19, 1921 1,725,044 Aldendorf Aug. 30, 1929 2,607,856 Sengebusch Aug. 19, 1952 2,673,247 Sengebusch Mar. 23, 1954

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