US2300954A - Electric step switch - Google Patents

Description

Ncv. 3, 1942. A. J. M MA'STER ELECTRIC STEP SWITCH Filed Dec. 16, 1957 4 Sheets-Sheet l fizz/612567":

' Jjyo aai'ez" A. J. MCMASTER 2,300,954 ELECTRIC ssrsr SWITCH 7 Filed Dec. 16, 1937 4 Sheets-Sheet 2 Nov. 3, 1942.

W w Z wwwm il fi NOV. 3, 1942. McMAsTER' ELECTRIC STEP SWITCH Filed Dec. 16, 1937 4 Sheets-Sheet 3 Nov. 3, 1942.

A. J. M MAsTER nmzcmzc STEP swmcn Filed Dec. 16, 1937 4 Sheets-Sheet 4 Patented Nov. 3, 1942 ELECTRIC STEP SWITCH Archie J. McMaster, Highland Park, Ill., assignor to G-M Laboratories,"lnc., Chicago, 111., a corporation of Illinois Application December 16, 1937, Serial No. 180,058

Claims. (Cl. 172-126) The present invention relates generally to step switches operated by electric magnets, and relates more particularly to reciprocating magnetic motors adapted to operate such switches.

An indexing switch commonly includes a set of electric contactors which are adapted to be stepped or indexed together from one'position to the next through a series of positions. The contactors are adapted to engage a separate set of stationary contacts in each of their several indexed positions and so can establish a different set of circuit connections in each position. The contactors may be driven by a reciprocating magnet through a pawl, ratchet and detent mechanism. Such a switch indexes or steps from position to position when its operating magnet is intermittently energized, and such a switch will self cycle or step through a number of positions automatically if it is equipped with switch contacts for controlling its own operating magnet.

Objects of the present invention include the provision of an improved self cycling indexing switch, which is slow, deliberate and steady in action, which is quiet in operation, which operates easily and gently so as to subject its working parts to a minimum of wear, tear and 'operating strain, and which operates at an even and substantially constant speed over a wide range of operating voltages applied to its magnet coil. These and other objects and advantages of my present invention will become apparent from the following description of a specific embodiment of the invention. While this particular description serves by way of example to illustrate the manner in which the invention may be used and practiced, the invention is not limited to the particular details of construction of any embodiment or example. In the drawmgs:

Figs. 1 and 2 are respectively a general elevation and a general plan view of a self cycling indexing switch embodying my present invention, the operating parts thereof being illustrated in a rest position, or unoperated position, of the switch;

Fig. 3 is a partially broken away elevation of a view similar to Fig. 1 but showing a different part of the mechanism. Specifically Fig. 3 in a section taken along the line 33 of Fig. 2;

Fig. 4 is a right end elevation, partly'in section, of the switch as seen in Figs. 1 and 3;

Fig. 5 is a partial right side elevation of Fig. 4, and therefore is a partial rear view of Figs. 1 and 3;

Figs. 6, 7 and 8 illustrate the mechanism shown in Fig. 1 in a series of successive operated positions; and

Figs. 9, 10 and 11 similarly illustrate the mechanism shown in Fig. 3 in a series of successive operated positions corresponding to the operated positions of Figs. 6, '7 and 8.

In Figs. 1 and 2 a stationary circular plate l2 of insulating material carries a series of concentric contact rings I4 and also a number of individual rivet-like contact buttons IE spaced uniformally on a series of concentric circles so as to lie also in radial rows. A rotatable contact arm l8 of insulating material carries a series of five individual contact assemblies 20 for engaging the individual contact rings l4, andcarries also a second group of five individual contact assemblies 22 for engaging the individual contact buttons l6.

The contactor assemblies 20 and 22 are of a construction shown and claimed in my co-p'ending application Ser. No. 125,689 filed February 15, 1937.

The contactor assemblies 20 and 22 ride over the left face of the disc 22 as seen in Fig; 4', and electrical connections to the separate con-' tact rings l4 and contact buttons I6 are made by wires l5 and I! at the right side of the disc [2 as seen in Fig. 4. An aperture IS in the disc I2 under the rings I4 permits the wires I 5 to be soldered directly to the under surfaces of the rings l4 from the back face of the disc l2 (the right surface as seen in Fig. 4). l

As may be seen in the partial sectional view of Fig. 4, the insulating contact disc I2 is bolted to a stud or shaft 24 which in turn is bolted to a formed sheet metal frame 26 so that the disc I2 is thereby non-rotatably secured to the frame 26. The contact arm I8, as is shown in Figv 2, is carried by a formed metal bracket 28. This bracket 28 and a peripherally notched disc 36, together with a reinforcing washer 32, are riveted to a bushing 34 which turns on the stud or shaft 24. The bracket 28, and therefore the contact arm I8, is securely held in non-rotatable relation with the notched disc 30 by means of a blind rivet (not shown) partially punched in the bracket 28 and seated in a perforation (also not shown) in the disc 30. Also rotatably mounted on the stud or shaft 24 is a bushing 36, shown best in Fig. 4, which carries a lever 38. The lever 38 is shown best in Fig. 3. It carries a pawl 40 which is held resiliently in engagement with the peripheral notches of the driving disc 3!! by a spring 42. A detent 44, smilar in construction to the pawl 48 is mounted on the frame 28 and is held resiliently in engagement with the peripheral notches of the disc 38 by a spring 46. The lever 38 is adapted to be oscillated on the shaft 24 to drive the disc 39 and the contact arm l8 therewith in a direction counterclockwise as viewed in Figs. 1 and 3. The lever 38 and pawl 4!! drive the disc 30 as the lever 38 swings towards the left as viewed in Figs. 1 and 3, and the detent 44 prevents retrograde motion of the disc 30 while the lever 38 is returning towards the right. A driving spring 48 is provided for moving the lever 38 in the direction which drives the disc 30, and a magnet that is designated generally by the reference numeral 50 serves to cook the spring.

An over-drive stop 52 serves to register disc 38 accurately and to stop it in the proper position. This stop is so placed that the driving pawl 48 stops against it, and in so stopping becomes firm- 1y wedged in engagement with the peripheral notches of the disc 30. This arrangement positively prevents forward motion of the disc 38 while the pawl 40 is resting against its overdrive stop 52. A lever stop 54 stops the lever 38 itself and all of the moving parts directly connected thereto, such as for example, the armature of the magnet 58. Both of the stops 52 and 54 are adjustable, and the stop 52 should be so adjusted with respect to the position of the stop 54 that the stop 54 takes the blow imparted by the weight of the lever 38 and its directly connected parts, so that the overdrive stop 52 stops only the pawl 40, the disc 30, and the latters connected contact arm l8. This adjustment is obtained by permitting a slight lost motion or back lash in the disc 30 when the lever 33 rests firmly against stop 54.

The magnet 58 is shown in detail in Fig. 3. It includes a steel frame consisting of a cylindrical shell 56 and two end plates 58, a magnetic core 60 and an energizing coil 82. The windings of the coil 62 are insulated from the steel frame by layers of insulating material 64. The core 60 slides in a brass tube 66 which is closed with a plug 68 so that the core or plunger 88 is subjected to an air cushion dash-pot action or snubbing action. A screw is adjustable to open and close an opening 12 in the plug 68 to adjust the degree of air leakage which relieves or reduces the dash pot or cushioning action,

When either alternating or direct current is passed through the windings of the coil 62 of the magnet 50, the magnet exerts a pull on its core 60 to draw the core into the coil. This pull, of course, diminishes to zero as the left end of the core 80 (as viewed in Fig. 3) comes into the position in which it is flush with the outer surface of the left one of the two steel end plates 58. The link 14 connecting the core 50 with the lever 38 is of such length that the core 58 lies approximately in the position of zero pull just described, when the pawl 4!] clicks over from one notch of the disc 38 to the next as the lever 38 is cooked, that is, as the lever 38 is moved towards the left by the magnet 58 as viewed in Fig. 3. No positive stop other than the magnet 58 itself is provided for limiting the motion of the lever 38 towards the left. Accordingly sufficient space is left in the left end of the tube 85 to permit the core 68 to move towards the left considerably beyond its position of zero pull. It will move beyond that position only when carried there by its own momentum and the momentum of the lever 38 attached thereto.

As is best shown in Figs. 1, 2 and 4, a snap switch is provided for controlling the current sup plied to the coil of the solenoid magnet 58. This snap switch is adapted to be operated by the movement of the lever 38 itself. The snap switch includes contacts I6 and a snap mechanism for operating the contacts. That mechanism includes a snap follower 18 and a spring 80. The spring is stretched between the follower l8 and a bracket 82 carried on the lever 38. This bracket 82 and the lever 38 serve as the actuator member of the snap mechanism.

The snap follower 18 consists of a loop of wire, the specific shape of which is best seen in Fig. 4. It is pivotally supported at an axis 84, by the plate or frame 26 and a bracket carried thereon. The loop 18 rotates in this pivotal support between two adjustable eccentric stops, 88 and 90.

In its normal position, shown in Fig. 1, the follower I5 is held against the stop 88 by the tension of the spring 88. As the lever 38 moves toward the left as viewed in Fig. l, the point of support of the spring 83 on the bracket 82 also moves towards the left so that the line of action of the spring 88 is made to sweep through the axis 84 of the follower 78. That is, the pull on the follower 18 is taken over the dead center position of the follower. As the line of action of the spring 80 swings to the left of the axis 84, the direction in which the spring 88 tends to rotate the follower 13 reverses so that the follower I8 is urged toward the left. Thereupon, the spring 80 rives the follower 18 with a quick snap motion from its stop 98 its stop 88. As it comes into position against the stop 88, the snap follower 78 opens the contacts 15, and then lying against the stop 88, the follower holds the contacts in their open position. When the lever 38 moves again towards the right to its normal position against the stop 54, the spring 88 causes its line of action 84 again to sweep across the axis 84 of the follower I8 to snap the follower back into its normal position against the stop 98. When the follower I8 is in its normal position against the stop 90, the contacts 16 close under the force of the inherent tension of the cantilever blades on which they are supported.

The contacts 16 are connected in series with the winding of the solenoid magnet 50 as is shown in Fig. 1. A condenser 92 is connected across the contacts 16 to reduce sparking at the contacts '16 when they are opened to interrupt the electric circuit. The use of the condenser in this manner for spark suppression is well known in the art and forms no part of my present invention.

When completely assembled the mechanism is adjusted for proper operation as follows: Inasmuch as no adjustment is provided for the position of the detent 44, that detent determines the rest position or indexed position of the notched disc 3|]. First the overdrive stop 52 is adjusted to stop the counterclockwise motion (as viewed in Fig. 3) of the notched disc 30 when that disc has rotated counterclockwise only slightly beyond the position in which it permits the detent 44 to snap into a new notch. The overdrive stop 52 determines the limit of the forward or counterclockwise motion of the disc 38. Next the lever stop 54 is adjusted to take the impact of the lever 38 so as to prevent the momentum of the lever 38 from driving against the overdrive stop 52. When the stop 54 is properly adjusted, the lever 38 may be held against the stop 54 and the notched disc 30 will exhibit a slight play about the pawl 48 in that it may oscillate slightly stopping against the pawl 48 in both the forward and backward directions. The detent 44 should be held away from the notched disc while the play at the pawl 40 is being tested. This second adjustment may slightly shorten th stroke of the lever 38, and therefore th operation of the detent 44 must be checked again and if necessary the stops 52 and 54 should beslightly readjusted before further adjustments of the mechanism are made.

The radial rows of contacts l6 on th contact disc l2 are brought into register with the moving contacts 22 by rotating the contact disc I2 on the stud 24. The disc I2 is clamped in position by a threaded nut and is held against rotation by a lock washer interposed between the face of the disc I2 and the shoulder of the stud 24.

Next the eccentric stop 98 (Figs. 1 and 6) of the snap mechanism is adjusted. The armature 68 and lever 38 are moved by hand towards the left into the position in which they are shown in Fig. 9. In this position the lever 38 has moved somewhat beyond the point at which the pawl 48 snaps into a new notch. While the lever 38 is held in this position the eccentric stop 90 (see Figs. 1 and 6) is rotated so as to move the snap follower 18 towards the left into the position in which it is shown in full lines in Fig. 6. In this position of the apparatus, the line of action of the spring 88 passes through the pivotal axis 84 of the snap follower 18 so that the follower 18 is on the verge of snapping to the left into the position 18a as shown in dotted lines in Fig. 6. Next the lever 38 is returned towards the right into the position shown in Fig. 11. In this position the lever 38 is still somewhat removed from its stop 54 and the detent 44 has ridden up onto thetip of a tooth of the notched wheel 38. With the lever 38 in this position, the eccentric stop 88 (Fig. 8) is adjusted to move the snap follower 18 towards th left until it is in the position shown in full lines in Fig. 8. In this position of the apparatus, the snap follower 18 is on the verge of snapping to the right into the position 18b shown in dotted lines in Fig. 8.

Next the mounting position of the contact assembly is adjusted by sliding the bracket 11 under the heads of its mounting screws (see Figs. 1 and 7) until thecontact assembly is in such position that the snap follower 18, when it lies against the eccentric stop 88 (Fig. '7) engages the vertex of the angular bend at the right hand end of the blade 19. With the blade 19 so adjusted the spring tension of the contact blades can exert little or no force, other than friction, which will either retard or aid the motion of the snap follower 18 away from its stop 88. Next the two upper blades which support the contact buttons 18 are bent into such an adjustment that they engage each other firmly when the snap follower l8 lies against the stop 98 (normal position) leaving the blade 19 free, and such that the contacts 18 separate a considerable distance when the snap follower 18 moves into position against the stop 88 to lift the tension spring I9.

Finally the air leak screw 18 (See Fig. 3) is adjusted to provide the best value of air leakage from the dash pot. It will be apparent that some leakage can occur around the core 60 itself by the passage of air through the clearance space between th solenoid core 60 and the brass tube 86 in which it slides. During the adjustment of the screw 18 the switch is operated from a power supply of the maximum voltage on which the switch is intended to operate. When the power is applied to the two connecting wires 9| and 93, the switch will operate automatically and continuously, indexing its moving contacts 22 from on radial row of contacts l8 to th next each time that the armature and lever 38 reciprocate. Inasmuch as the lever has no stop to limit its motion towards the left, if the air leakage from the dash pot space is too great, the armature 68 will drive against the plug 68 (Fig. 3). The force of the armature 68 repeatedly striking against th plug 68 creates considerable noise and also imposes severe operating strains upon the mechanism. Whil the apparatus is operating on the highest voltage for which it is intended, the screw 10 is turned in to partially cover the opening 12, until the switch quiets down. The quieting will indicate that the solenoid'armature or plunger 60 has ceased to strike against the plug 88.

When so adjusted the switch will operate quietly and reliably at any voltage between the maximum voltag forwhich it is adjusted and the minimum voltage which will supply sufficient current to the winding of the magnet 58 to cook the driving spring 48. Furthermore the speed of operation will change very little with the voltage applied to the coil.

Both the dash pot restraint imposed upon the operation of the solenoid armature, and the snap acting control switch'which includes the snap follower 18, help to provide the constant speed of operation of this switch. An appreciable share of the total time consumed by a cycle of operation or oscillation of the lever 38 consists in the time required for the operation of the snap follower 18. This time is practically independent of the voltage which may be applied to the winding of the solenoid coil. The lever 38 undoubtedly moves somewhat faster when a high voltage is applied to the solenoil coil, but under such conditions, the lever 38 moves a greater distance towards the left and therefore while it moves faster it must move through a greater distance. This circumstance aids in keeping the total time for each oscillation substantially constant over wide ranges of voltage.

The snap switch by itself improves the reliability of operation and makes certain that each stroke of the solenoid will be a full stroke. The dash pot provides a cushion stop for the plunger, reduces noise and eases operating strains. The two together cooperate to drive the indexing switch quietly, reliably and at a substantially constant speed over a wide range of operating voltages.

It will be apparent that the present invention is not limited to the specific form or construction herein shown and described but that it is capable of various modifications. Accordingly the invention is to be limited only within the scope of the appended claims.

I claim:

1. In an indexing mechanism, a member to be indexed repeatedly in one direction, ratchet teeth on said member spaced in accordance with the indexing steps to be made by said member, a pawl for engaging said teeth to drive said member, a spring for driving said pawl in one direction to drive said member, means for limiting the driven motion of said pawl, said means including a stop for simultaneously stopping the spring-driven motions of said pawl and said member, an electromagnet for driving said pawl in the other direction to cook said spring, contacts operated by said magnet for controlling the energizing of the magnet to deenergize the magnet when the spring is cocked, said pawl being free to move in said other direction beyond its cocked position, a stop for preventing said pawl from moving far enough beyond said cocked position in said other direction to pick up an extra ratchet tooth on said member, and a dash pot for retarding th spring cocking motion of said pawl and for stopping it after said magnet is deenergized but before said pawl encounters a positive stop in said other direction.

2. The combination of claim 1 wherein there is included a spring snap mechanism operated by said magnet for operating said contacts, said snap mechanism including a snap follower and an actuator therefor such that said actuator moves to bias the snap follower and said snap follower responds by executing a sudden snap motion after the actuator reaches a certain position, said snap follower snapping between two extreme positions and lying normally in one of said extreme positions, said snap mechanism and said contacts thereof being so constructed and arranged that they operate to deenergize said magnet only when said snap follower lies substantially in its other extreme position.

3. In combination in a reciprocating electric magnetic motor, a reciprocable driven member biased to a normal position, an electromagnet for driving said driven member out of its normal position, a snap switch operated by said driven member, said snap switch including a spring driven snap follower and a link connecting said follower to said driven member to be actuated thereby, said follower and link including a spring for driving said follower, said snap follower having a normal extreme position and another extreme position, said switch including contacts operated by said follower for controlling the energizing of said magnet and so constructed and arranged that they deenergize said magnet only when said snap follower lies substantially in said other extreme position, said device being so constructed and arranged that said driven member is free to move in its magnet driven direction beyond its position at which said snap switch first tends to operate.

4. In combination in a reciprocating electromagnetic motor, a reciprocable driven member biased to a normal extreme position thereof, stops for defining said normal extreme position and also an opposite extreme position for said driven member, an electromagnet for driving said member out of said normal position towards said opposite position, and control means for said electromagnet operated by said driven member for controlling the energization of said magnet, said control means comprising a spring snap mechanism including a snap follower actuated by said driven member and adjusted to snap from a first to a second extreme snap position when said driven member is in substantially said normal position, and from said second to said first snap position when said driven member is intermediate its two extreme positions and substantially out of its said opposite extreme position, and comprising also spring closed electric contacts at said first snap position actuated to open position by said snap follower but only when said snap follower is substantially in said first extreme snap position, and circuit connections connecting said contacts in series with said magnet for controlling the electric energizing circuit thereof.

5. The combination of claim 4, wherein there is included a dash pot for opposing the magnet driven motion of said driven member.

ARCHIE J. MCMASTER.

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