US3472976A - Contact operating mechanism - Google Patents

Description

United States Patent 3,472,976 CONTACT OPERATING MECHANISM Charles A. Hunt, Wolcott, Conn., assignor to North American Rockwell Corporation, New York, N.Y., a corporation of Delaware Filed Dec. 1. 1967, Ser. No. 687,324 Int. Cl. H01h 7/08, 43/10 US. Cl. 200-38 16 Claims ABSTRACT OF THE DISCLOSURE Operating mechanism including a rotary cam means and contacts operated thereby, some having relatively rapid or short operating periods and others substantially longer periods. The cam is driven from a motor by intermittent drive mechanism to provide rapid cam movement during the switching times.

This invention relates to a timer having intermittent drive means to permit shorter and more positive switch actuation cycles than are possible with the same switch structure driven continuously. In particular, it relates to an interrupter timer of simple construction capable of generating very long and very short pulses at the same time.

In repeat cycle timers one of the limitations is the range of timing operations. A single cam can control the operation of a number of cam followers on which contacts are mounted but the operating cycle of all of the contacts has heretofore been required to be relatively similar. As an example, in the case of interrupter timers for telephone use, it is common to require that one set of contacts be closed for perhaps half a second or so only once in every four seconds while another set of contacts in the same timer must open and close once each second and still another set of contacts must close (or open) twice a second and remains closed (or open) for a very small fraction of a second, for example about .03 second. There is no difficulty in providing a relatively slow moving cam which will open and close a set of contacts once in every four seconds and there is no difficulty in providing a cam that will operate a set of contacts twice a second for even as small an interval as .03 second per operation. The difficulty comes in providing one cam that will perform both the slow operation and the rapid operation at the same time and will also provide a high degree of accuracy in the particular part of the cycle in which the individual contacts are actuated.

Heretofore the wide range of operation has required two separate cams one driven from the other at substantially different speeds. One of the cams turned rather rapidly and controlled the relatively high speed contacts while the other cam turned much more slowly and operated the low speed contacts.

In accordance with the present invention both low speed and high speed cams are mounted on a common cam shaft and are turned at the same rate of speed. A synchronous motor drives the cam shaft by way of a Geneva mechanism that rotates the cam shaft in a series of rapid jumps so timed with respect to the required timing of the contact openings and closings that the cam shaft is moving at a relatively high speed just prior to and gduring and for a short time after the contact openings and closings but at other times is stationary so that the average speed of the cam shaft is relatively low.

The contacts may be mounted on resilient blades held ;in an insulating support and extending alongside the operating surfaces of the cams. The contacts are divided into pairs and each pair includes at least one movable contact that engages, usually by a roller follower or some other ICE suitable follower, the operating surface of the cam. The blades are resiliently biased so that movement of the cam surface past the follower of the movable blade or blades causes the pair or pairs of contacts either to engage each other or to separate from each other, depending on the shape of the undulations on the cam surface.

One of the objects of the present invention is to provide a stable, accurate repeating timer having a relatively wide range of operating cycle speeds available simultaneously. Further objects will be apparent from the following specification together with the drawings in which:

FIG. 1 is a side view of a timer constructed according to the invention;

FIG. 2 is a typical timing diagram for the timer of FIG. 1; and

FIG. 3 is a cross-sectional view of the timer of FIG. 1.

FIG. 4 is a partial cross sectional view of a modified embodiment of the present invention.

The timer in FIG. 1 includes a motor 11 driving a pinion 12 meshed with a second pinion 13 and mounted on a plate 14. The plate 14 and a similar plate 16 serve as end plates for the timer and are connected by machine screws 17 and 18 and spaced apart by insulating members 19 and 21.

Between the end plates 14 and 16 is a shaft on which are mounted a Geneva gear 22, three cylindrical cams 23-25 and suitable spacing washers 26 and 27 at the ends to locate the cams and the Geneva gear properly. The Geneva gear meshes with a semi-cylindrical central member 28 on the pinion 13 and a pin 29 also located on the pinion 13 and eccentrically placed with respect to the axis of the pinion.

Three sets of contact blades are shown in FIG. 1, the first comprising a relatively movable blade 31 and a relatively stationary blade 32 which operate in conjunction with the cam 23 which, in this embodiment, is a relatively high speed cam. A second set of blades, comprising a movable blade 33 and a relatively fixed blade 34, is located adjacent the intermediate speed cam 24, and a third set of blades, comprising a movable blade 36 and a relatively fixed blade 37, is located adjacent the relatively low speed cam 25. All of the blades are firmly 'affixed at one end in slots in the insulating support 19 and an insulating wall 38 is provided between the relatively fixed blades and the movable blades.

The blades extend through the insulating support 19 and are attached to a printed circuit connector 41 to make connection with a set of contact blades 42 in a male plug that comprises the insulating member 21 and the contacts 42. The motor 11 also has connections 43 joined to the printed circuit connector 41 and from there to the blades 42.

In order to provide a specific illustration of the operation of the timer in FIG. 1 a typical timing diagram is shown in FIG. 2. The basic cycle of four seconds and, as may be seen, one timing signal 44 is to provide a pulse 46 once each four seconds and each of these pulses is to last for approximately one half-second. While the pulse 46 is shown with a negative polarity, it could just as well be a positive pulse since the polarity has no bearing on the present invention. The polarity would be determined by the way in which the contacts are connected to a battery or other power sup-ply or they may be determined by whether the undulations on the cam surface cause the contacts to move together or apart. Until the timer contacts are connected to a source of current, the pulses in the waveforms in FIG. 2 really represent relative movements of the contacts between open and closed positions. Thus, the pulses may be described as impulse connections, but it may be simpler to refer to them as current pulses. The pulse 46 is determined in timing and duration by the opening and closing of the contacts attached to the movable blade 36 and the relatively fixed blade 37 and these operations of the contacts 36 and 37 are controlled in turn by the convolutions on the operating surface of the cam 25.

A second timing signal 47 is made up of a series of pulses 48 having a repetition rate of one pulse per second and a duration of approximately one half-second per pulse. These pulses are formed by the contacts attached to the blades 33 and 34 controlled by the central cylindrical cam surface 24. While the pulses 48 have a repetition rate four times as high as the pulses 46, the ratio of these two rates is not very high, and earns operating at the same speed can produce them with little trouble. Moreover, the duration of each of the pulses 48 is relatively long and is also easily produced by the controlling cam 24.

A third pulse signal 51 is also shown in FIG. 2 and this signal comprises a series of short impulses 52 having a repetition rate twice as great as that of the pulses 48 and eight times as great as that of the pulses 46. In itself, the repetition rate is not extremely high, but difficulty in producing these arises because of their short duration. For the sake of simplicity it will be considered that the pulses 52 are produced when the contacts attached to the blades 31 and 32 are opened in response to the convolutions of the cam surface 23, but in actual fact the same difficulty arises when short pulses of duration comparable to the pulses 52 are formed by closing a pair of contacts. The critical feature is that the cam follower that is attached to the blade 31 must follow an undulation having a very narrow width, or angular dimension, in the surface of the cam 23 in order to produce a short pulse.

FIG. 3 is a cross-sectional view that shows the contact blades 31 and 32 and their relationship to the cam 23. As may be seen, the cam 23 is in the shape of a circular cylinder with relatively small sectors 53 removed from its periphery. The resilient blade 31 has at its free end a cam follower in the shape of a circular member 54 which rolls along the surface of the cam 23 and follows the undulations by virtue of the fact that the resilient blade 31 causes the follower 54 to press against the cam surface. As may be seen, the radius of curvature of each of the sectors 53 is not much greater than the radius of curvature of the follower 54 which means that as the cam 23 rotates the follower 54 makes a quick in-and-out movement as each of the undulations 53 sweeps past. While the undulations are shown as having more or less circular configuration, they could have a somewhat V- shaped configuration with more or less the same result. The exact configuration is determined by the necessary width to permit the cam follower 54 to enter the undulations and by the duration of the pulses that are to be produced by such motion of the cam follower. Another requirement is that the cam follower 54 move toward the center of the cam 23 far enough and fast enough to separate the movable contact 56 supported on the blade 31 from the relatively fixed contact 57 supported on the blade 32 as quickly as possible in order to minimize arcing between the contacts.

The undulations 53 on the surface of the cam 23 could extend outwardly instead of inwardly, but for the shortest possible pulses 52 the inwardly extending undulations, or depressions, are required. The reason for this is that an outwardly extending undulation must move entirely past the effective width of the cam follower 54 in order to complete one of the pulses 52. Just how great the effective width of the cam follower is is dependent upon how far the undulation extends outwardly. As may be seen, the cam follower 54 is a roller and its maximum effective width would be its diameter, but if the undulation only extended a short distance outwardly from the cylindrical surface of the cam 23, only a part of the cylindrical surface of the roller 54 would make contact with it and therefore the effective width of the cam follower would be less than the diameter of the roller.

On the other hand, in the case of the depression-type undulations 53 shown in the drawing it is not necessary for the cam 23 to move the entire undulation past the roller. What actually takes place is that as the undulation approaches the cam follower 54 and the cam follower starts down into the depression, there is sufficient resilience in the relatively fixed blade 32 to permit the contact 57 to follow and remain in engagement with the movable contact 56 for a while. At some point the barrier 33 halts any further movement of the blade 32 and the contacts 56 and 57 separate due to the motion of the follower 54 farther down into the depression 53 as the cam 23 continues to rotate. Because of the fact that the depression 53 has normally about the same radius of curvature as the follower 54, particularly on the entrance side of the depression, which is the side that the follower 54 traverses as it enters the depression, the movement of the follower 54 more or less radially inwardly toward the axis of the cam shaft 16 is quite rapid and the contacts 56 and 57 are separated sharply. However, due to the narrowness, or small included angle, of the depression 53, the follower 54 almost immediately is subjected to outward pressure by the exit side of the depression 53, and the contact 56 is thereby thrust rapidly back into engagement with the contact 57 before the follower leaves the depression. The time that the contacts 56 and 57 are separated from each other is thus much less than the time required for the cam 23 to rotate sufficiently to cause an entire depression 53 to pass across the cam follower 54.

The Geneva wheel 22 shown in FIG. 3 has sixteen cusps 58 separated by sixteen radial slots 59, whereas the pinion 13 has only a single pin 29 to engage each of the slots 59. Thus, the wheel 22 rotates once for each sixteen revolutions of the pinion 13, which means that the average speed of the wheel 22 is the average speed of the pinion. However, because of the fact that the wheel moves only during the time that the pin 29 engages one of the slots 59 and remains stationary when the semi-cylindrical member 28 engages the concave portion of one of the cusps 58, the instantaneous speed of the wheel 22 reaches a relatively high maximum value.

To be specific, if the wheel 22 rotates in a series of sixteen steps per revolution, the included angle between each pair of steps is 225, and if the wheel must complete one revolution every four seconds the average speed 1s 15 r.p.m., broken up into two hundred and forty steps per minute. Each step is accomplished when the pinion 13 rotates approximately one-fourth of a revolution; during the remainder of each revolution of the pinion the pin 29 is not engaged with any of the slots 59. Since the pinion rotates sixteen times as fast as the wheel 22, the speed of the pinion is 240 r.p.m., or one revolution in one-fourth of a second. Since each step of the wheel 22 is accomplished in about one-fourth of a revolution of the pinion 13, the wheel 22 moves one step in about .0625 second. Moreover, this motion is not uniform but smoothly builds up to a peak and then smoothly reduces to zero. Therefore, most of the motion of the wheel 22 takes place in approximately .06 second per step, which is about 2% of the time required for a complete revolution. This means that the entire undulation 53 moves past the follower 54 in .06 second, but since the actual transfer of the movable contact 56 from one of its limiting positions in which it is in engagement with the relatively fixed contact 57, to the other limiting position in which it is not in engagement with the relatively fixed contact takes place in only a fraction of the total time required for one of the depressions 53 to move completely past the follower 54, it is possible to produce a pulse 52 having a much shorter duration than the .06 second just mentioned. In fact pulses are produced having a duration of .03 second or less, which is less than 1% pf the total time required for the cam 23 to make one revolution.

It should be understood that the pulses 52 are produced by making a relatively large movement of the movable contact 57. Pulses of approximately the same length could be produced by actuators of the type known heretofore only if those actuators restricted the movement of the movable contact to a small value. This, in turn, would restrict the permissible voltage differences between the contacts 56 and 57 and in addition would render the timing of the pulses erratic. With the intermittent motion of the present invention, the timing of the pulses can be made quite accurate both in the sense of the duration of the pulses and in the sense of the timing between pulses. In addition, the relatively long and rapid movement of the movable contact 57 reduces the chance of arcing between the contacts 56 and 57 and greatly increases the life of the contacts. In order to obtain good connection between the contacts it is preferable that they be renewed, and intact of cylindrical shape with the axis of the contact 56 substantially perpendicular to the axis of the contact 57.

In the embodiment shown, the cam 23 has eight undulations 53, which merely means that a pulse 52 is produced only on every other step of the intermittent motion of the Geneva wheel 22. The important consideration is that each of the depressions 53 is angularly positioned on the cam 23 with respect to the position of one of the slots 59 in the Geneva wheel 22 so that the depression 53 moves entirely past the follower 54 during the time that the pin 29 is in engagement With one of the Slots 59.

It is unnecessary to dwell at length upon the operation of the cams 24 and 25 since these cams produce relatively long pulses similar to pulses that have been produced heretofore in other actuator mechanisms. However, the intermittent motion of the Geneva wheel 22 should be correlated with undulations on the surfaces of the cams 24 and 25 to obtain the same precision of timing as is obtained for the pulses 52. The undulations on the surfaces of the cams 24 and 25 should also be shaped to provide the rapid contact separation described in connection with the contacts 56 and 57 for such rapid separation even in the case of contacts producing long pulses is quite beneficial in permitting the longest possible contact life.

FIG. 3 also shows a second set of fixed and movable contacts 56a and 57a which correspond exactly to the contacts 56 and 57 and are similarly supported and controlled. The contacts 56a and 57a may be used in parallel with the contacts 56 and 57 or, more usually, to divide the total load with contacts 56 and 57, although not connected directly electrically in parallel. Because of the similarity with the contacts 56 and 57, the operation of the contacts 56a and 57a: need not be described in detail.

FIG. 4 shows a modified form in which the movable contact 157 and the relatively fixed contact 156 are arranged to engage each other for short impulse periods of time rather than to be separated from each other. This merely requires that the contact 156 be located on the side of the contact 157 toward the cam 23 and that the blade 132 supporting the relatively fixed contact 156 be positioned by a barrier 138 facing in the opposite direction from the barrier 38 of FIG. 3, but serving to provide the necessary restraint for the blade 132.

While this invention has been described in specific terms it will be understood by those skilled in the art that modifications may be made without departing from the true scope of the invention as defined by the following claims.

What is claimed is:

1. An interrupter timer comprising: a motor; a cam shaft comprising first and second cylindrical cam surfaces; a Geneva pinion connected to said motor to be rotated thereby; a Geneva wheel actuated by said pinion to rotate intermittently and connected to said cam shaft to rotate said cam shaft intermittently in intervals of high rotational speed compared to the average rotational speed of said cam shaft; first and second cam followers engaging said first and second cams, respectively; first and second movable contacts connected to said first and second cam followers, respectively; first and second relatively stationary contacts engageable by said first and second movable contacts, respectively, as said followers are actuated by said cams, said first cam actuating said first follower more rapidly than said second cam actuates said second follower, said Geneva wheel being oriented with respect to said first cam to actuate said first cam follower during the time when said pinion is rotating said Geneva wheel.

2. The timer of claim 1 in which said Geneva wheel is rigidly attached to said cam shaft.

3. The timer of claim 1 in which said first follower has a predetermined arcuate dimension with respect to said first cam surface and said first cam surface has an undulation with a predetermined radial dimension and a predetermined included angle to cause said first movable cam to move into and out of contact with said first relatively stationary contact as said first cam surface moves said undulation past said first cam follower during an interval of said intermittent motion, the duration of connection between said first movable contact and said first relatively stationary contact being less than the minimum duration of engagement possible with said first cam and first cam follower if said first cam rotated continuously at the same average speed.

4. The timer of claim 1 in which said first follower has a cylindrically shaped follower surface engaging said cam surface, and said follower surface has a predetermined arcuate dimension with respect to said first cam surface and said first cam surface is an external cylindrical surface and has a depression with a concave surface to receive said follower, the said depression having a predetermined radial dimension on said cam surface and a predetermined included angle to cause said first movable cam to move out of and into contact with said first relatively stationary contact as said first cam surface moves said depression past said first cam follower during an interval of said intermittent motion, the duration of connection between said first movable contact and said first relatively stationary contact being less than the minimum duration of engagement possible with said first cam and first cam follower if said first cam rotated continuously at the same average speed.

5. The timer of claim 1 in which said first cam surface has an undulation, and said first cam follower causes said first movable contact to engage said first relatively stationary contact as said undulation moves past said first cam follower, the instantaneous rotational speed of said cam shaft while said undulation is moving past said first cam follower and the angular width of said undulation being such that said first movable contact engages said first relatively stationary contact for a period of time less than approximately 5% of the total time required for said cam shaft to make one revolution.

6. The timer of claim 5 in which the instantaneous rotational speed of said cam shaft and the angular width of said undulation are such that said first movable contact engages said first relatively stationary contact for a period of time less than approximately 1% of the total time required for said cam shaft to make one revolution.

7. The timer of claim 1 in which said undulation is a depression in said cam surface.

-8. The timer of claim 1 in which said first camsurface comprises a plurality of undulations to cause said first movable contact to engage said first relatively fixed contact a corresponding number of times each revolution of said cam shaft to produce a series of impulse connections each having a first duration, and said second cam surface has at least one undulation to cause said second movable contact to engage said second relatively fixed contact at least once each revolution of said cam shaft for a predetermined time to produce an impulse connection having a second duration, the repetition rate of impulse connections of said first movable and fixed contacts being at least four times as great as the repetition rate of impulse connections of said second movable and fixed contacts and said second duration being at least ten times as great as said first duration.

9. Contact actuating means comprising: first and secand contacts; a cam; means connecting said first contact to said cam to be controlled by said cam to be moved between first and second positions, said first contact engaging said second contact in one of said positions and being separated from said second contact in the other of and position; an undulation on said cam to move said first contact from said first position to said second position and back to said first position; drive means to move said cam rapidly during a first interval of time when said undulation is in position to control said first contact and to hold said cam substantially stationary immediately preceding and following said first interval of time when said undulation is not in position to control said first contact, said drive means comprising a motor, a pinion connected to said motor to be driven thereby, and an intermittent motion wheel engageable with said pinion to be driven thereby in a series of rapid partial rotations each followed by an interval of non-rotation, said intermittent motion wheel being connected to said cam to move said cam rapidly only when said intermittent motion wheel rotates.

It). The contact actuating means of claim 9 in which said second contact is a relatively stationary contact and said means connecting said first contact to said cam comprises a resilient mounting means for said first contact and a cam follower engaging said cam, said resilient mounting means pressing said cam follower against said cam.

11. The contact actuating means of claim 10 in which said intermittent motion wheel is a Geneva wheel having a plurality of cusps and said pinion is a Geneva pinion.

12. The contact actuating means of claim 11 in which said Geneva wheel comprises a plurality of substantially radial slots and said pinion comprises an axially extending pin to engage said slots to drive said Geneva wheel in each of said partial rotations at an instantaneous speed at least substantially ten times the average speed of rotation of said Geneva wheel for a full revolution.

13. The contact actuating means of claim 11 in which said undulation, one of said slots in said Geneva wheel, and said means connecting said first contact to said cam are relatively oriented so that said first contact moves from said first position to said second position and back to said first position while said pin on said pinion is in engagement with said one of said slots.

14. The contact actuating means of claim 13 in which said cam has a cylindrical cam surface, and said undulation comprises a depression in said cam surface and said cam follower surface is in contact with said cam surface over a smaller arc of said cam surface than the total included are of said depression.

15. The contact actuating means of claim 14 in which said first contact has a cylindrical surface facing said contact and with an axis in one direction and said second contact has a cylindrical surface facing said first contact and with an axis substantially perpendicular to the axis of the surface of said first contact.

16. An interrupter timer comprising a motor having a predetermined synchronous speed; a Geneva pinion connected to said motor to be rotated thereby; a Geneva wheel engaging said pinion and actuated thereby to rotate intermittently, said wheel having a plurality of cusps; a single cam shaft attached to said wheel to be driven thereby and comprising a plurality of cylindrical cam surfaces, a first one of said cam surfaces having a plurality of indentations spaced around its periphery; a first cam follower engaging said first cam surface to be controlled thereby; resilient means attached to said cam follower to press said follower against said first cam surface and into said indentations as said cam shaft rotates whereby said movable contact moves between a first end position corresponding to contact between said first cam follower and a radially outward portion of said first cam surface and a second end position corresponding to contact between said first cam follower and the bottom of one of said indentations; a first movable contact connected to said cam follower to be moved thereby; a first relatively fixed contact to be engaged by said first movable contact when said cam follower is at one of its end positions, said first cam causing said first movable contact to engage and disengage said first relatively fixed contact a plurality of times, equal to the number of said depressions, each revolution of said cam shaft, the duration of time for said first movable contact to move said first position into one of said depressions and back out to said first position being less than approximately 2% of the total time required for said cam shaft to make one revolution; a second cam surface on said cam shaft; a second cam follower engaging said second cam surface to be controlled thereby; a second movable contact attached to said second cam follower to move therewith; and a second relatively fixed contact engageable with said second movable contact, said second cam surface having at least one area of its periphery extending out from the axis of said cam shaft a predetermined distance and at least a second area radially closer to said axis of said cam shaft, the included angle of said area having a substantially greater included angle than the included angleof each of said depressions of said first cam surface.

References Cited UNITED STATES PATENTS 2,253,183 8/1941 Le Count. 2,791,648 5/ 1957 Maloney. 3,188,504 6/1965 Anderson. 3,250,864 5/ 1966 Bleibtreu et al. 3,358,277 12/1967 Selig 200--38 3,373,252 3/1968 Davin 20038 HERMAN O. JONES, Primary Examiner

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