US2903528A

US2903528A - Continuously adjustable limit switch

Info

Publication number: US2903528A
Application number: US725243A
Authority: US
Inventors: Edward H Kuhn
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1958-03-31
Filing date: 1958-03-31
Publication date: 1959-09-08
Anticipated expiration: 1976-09-08

Description

p 1959 E. H. KUHN 2,903,528

CONTINUOUSLY ADJUSTABLE LIMIT SWITCH Filed March 31, 1958 4 5 SheetS -Sheet 1 AT TORNEYS,

Sept. 8, 1959 E; H. KUHN 2,903,528

CONTINUOUSLY ADJUSTABLE LIMIT SWITCH Filed March 31, 1958 5 Sheets-Sheet 2 v VENTOR ED RD H. KUHN 5v sap/Z wit? ya ATTORNEYS Sept. 8, 1959 E. H. mm 2,903,528

CONTINUOUSLY ADJUSTABLE LIMIT SWITCH INVENTOR EDWARD H. KUHN BY I 5 g; 9

ATTORNEYS Sept. 8, 1959 E. H. KUHN 2,903,528

CONTINUOUSLY ADJUSTABLE LIMIT SWITCH Filed March 51, 1958 5 Sheets-Sheet s mml,

5 lNVENT OR 37 EDWARD l-LKUHN -1' I 4/ BY (Fm 541 a I w 4;

AT TORNEYS United States Patent 2,903,528 CONTINUOUSLY ADJUSTABLE LIMIT SWITCH Edward H. Kuhn, Whitefish Bay, Wis., assignor to Allen- .Bradley Company, Milwaukee, Wis, a corporation of Wisconsin Application March 31, 1958, Serial No. 725,243

12 Claims. (Cl. 200-38) This invention relates to adjustable continuously rotating multiple limit switches; and more particularly to such a switch used in connection with machines which have a repetitive cycle of operation, in which use this limit switch renders possible the opening and closing independent circui-ts at any desired angular position, and keeping these circuits open or closed for practically any desired angular travel.

Switches of that sort have a wide application in programming control and time-sequence operations. They are commonly used on power-presses and similar machinery, where a speed change, or even a complete stoppage or reversal, of a part or all of the machinery, is required at certain positions of the main drive.

Such a switch may well comprise a number of cams, mounted on and rotatable with a rotating shaft, the lobe or lobes of each cam'making contact, at various stages of rotation with an independent roller-type contact unit.

The angular position and angular size of each cam-lobe should lee-adjustable, or at least interchangeable, so as to render any given multiple switch adaptable to a large number of'alternative uses; but also, in any given use at least a degree of adjustability is essential to the greatest efiic-iency of the controlled machinery. The making of any such precision adjustment has heretofore required repeated stopping the machine, adjusting, and then star-tingup the machine again to check the results of the adjustment, especially when two or more operations are so closely interrelated that the adjusting of one throws out the correctness of the prior adjustment of the other.

Accordingly the principal objective of the present invention is to devise a rotating multiple limit switch, in which at least the time, and preferably also the duration, of each controlled operation, is readily adjustable While the machine is in motion.

A further objective is to devise such a switch which is readily adjustable from the outside, without opening the switch-box.

Other objects and advantages will appear in the description which follows. i

In the description, reference is made to the accompanying drawings, forming a part hereof, in which there are shown by way of illustration and not of limitation one certain specific form in which the machine of the present invention may be embodied.

In the drawings:

Fig. 1 is a plan view of the switch in its case, dimensions reduced to two-thirds.

Fig. 2 is a similar view to the same scale, with the shaft, and the mechanisms supported thereby, removed so as to expose the contact units and the adjusting wormpinionsJ Fig. 3 is a plan View of one cam-unit and its associated contact-unit, namely the second set of mechanism from the right in Fig. 1. Fig. 3 and all subsequent figures are to full scale. I

Fig. 4 is a front elevation of the same cam-unit, as seen from the line 4-4 in Fig. 5.

I associated contact-unit, as seen from the line 55 2 Fig. 5 is a side elevation of the same cam-unit and in Figs. 1, 4, and 10.

Fig. 6 is a vertical section of the same cam-unit, seen from the line 6-6 in Figs. 4 and 10.

Fig. 7 is a vertical section of the same cam-unit, seen from the line 77 in Figs. 4 and 10.

Fig. 8 is a vertical section of the same cam unit, seen from the line 88 in Figs. 4 and 10.

Fig. 9 is a side elevation of the same cam-unit, as seen from the line 99 in Figs. 4 and 10.

Fig. 10 is a vertical section of the same cam-unit, as seen from the line 10-10 in Figs. 5 and 7.

Throughout the description, the same reference-numeral is applied to the same member or to similar members.

Turning to Fig. 1, with some reference to Fig. 5, it will be seen that 21 is a switch-box, having a cover 22. Secured to the bottom of the box 21 in any appropriate manner, as by large-screws 23, is a main frame 24. In the side of the box there may be an appropriate orifice 26 for the entry of conduits.

A shaft 27 extends across the box, and is journaled in appropriate bearings such as 28, attached to frame 241 Keyed to shaft 27, there are a plurality (six, as shown) of cam-units 31, the elements of which will be analyzed later herein. These units are held against lengthwise motion on the shaft, between split retaining ring 32 in a circumferential groove on the'shaft, adjacent the righthand bearing 28, and a spacer 33 and nut 34 on a threaded portion'of the shaft, adjacent the left-hand bearing 28.

Further details as to the shaft, except as mentioned hereinafter, need not be given as they form no part of the invention.

Turn now to Fig. 2 which shows the contents of the box with the shaft and cam-units removed. And also refer to Fig. 5.

Supported on channel-like sub-frame 36, which is appropriately secured to main-frame 24, there are a plurality (six, as shown) of roller-type contact-units 37, each of which is associated with one of cam-units 31. The contact-units shown are normally-closed break-circuit electric switches; but it should be understood that other electrical types and other than electrical types of contact units could be used without departing from the spirit of the present invention. For example, but not limitation, normallyopen make-circuit switches, could be used; or fluid-pressure circuits, controlled by contact opening or closing valves.

The type of contact-unit 37 shown will be discussed in some, but not much, detail hereinafter.

Supported on channel-shaped sub-frame 38, which is appropriately secured to main-frame 24, are a plurality of worm-pinions 39, each of which (for adjusting pur poses, as will be explained hereinafter) is associated with one of cam-units 31. Each worm-pinion is integral with a shaft 41, and terminates in an adjusting-head 42. The functioning of the worm-pinions and further details of their mounting will be given hereinafter.

The details of a typical cam-unit 31 will now be discussed, with particular reference to Figs. 3 to 10. This cam-unit is essentially a set of planetary (i.e., simple epicycle) gearing, consisting of (see Fig. 7) a sun pinion 43 as the driving member; a plurality of planet pinions 44, whose bearings 45 are journaled on axles 46 projecting from a spider 47, which serves as the arm of the system and is the stationary member; and an internal ring gear 48 as the driven member.

The sun pinion 43 has an elongated hub 49, which extends through the entire cam-unit and contacts the units on each side of it, or the retaining-ring 32 or the spacer 33, as the case may be.

All the sun pinions 43 are keyed to shaft 27 by a long key 54) which extends the length of all of them through key-ways 51 in each of them and long keyway 52 in shaft 27.

Spider 47 has a bearing 53 which is journaled on one end of hub 49 of sun pinion 43. On the periphery of spider 47 is cut a worm gear 54, to engage worm pinion 39. Some of the teeth of worm gear 54 are cut away to receive the ends of indicating plate support 56 which is attached thereto, as by screws 57. On the face of this support is attached indicating plate 58, as by screws 59. This plate is calibrated as will be explained hereinafter. The worm-gear teeth underneath indicating plate support 56 serve no useful purpose, but it is simpler to cut teeth on the entire periphery of spider 47 than to cut them only where needed.

Hub 61 serves as a hub for ring gear 48 and for the cams to be hereinafter described, and (with spider 47) constitutes a gear-case, which should be filled with appriate lubricant. Through its bearing 62, hub 61 is journaled on the opposite end of hub 49 of sun pinion 43 from the end on which spider 47 is journaled.

Ring gear 48 is secured to hub 61 by two pins 63. See Figs. 7 and 10.

In each cam-unit there are one or more cams, secured to the face of hub 61. Preferably there are two such cams, 64 and 66, each having two diametrically opposite identical cam-lobes 67. The cams can be obtained with lobes of various different angular extent, so as to obtain roughly any desired minimum duration of operation of the contact-units. Preferably, but not necessarily, the lobes of cam 66 are identical to those of cam 64; but there is the following difference between the two cams of any pair. Compare cam 64 of Fig. 6 with cam 66 of Fig. 5, both of which cams are secured to the face of hub 61 by the three bolts 68, screwed into threaded holes 70 in said hub (see Fig. 10). But in cam 64 of Fig. 6, these bolts pass through smooth holes 69, thus holding cam 64 fixedly oriented with respect to hub 61; whereas in cam 66 of Fig. 5, these bolts pass through arcuate slots 71, which permit adjusting cam 66 angularly with respect to hub 61 and hence with respect to cam 64, thus increasing the combined effective angular extent of lobes 67. In Fig. the full-line showing of the lobes represents the lobes 67 of both cams in coincidence, as shown in Fig. 4, thus producing the minimum combined extent; whereas, the dotted-line showing in Fig. 5, represents lobes 67 of cam 66 angularly retarded slightly, with respect to the lobes of cam 64, thus increasing the combined angular extent of each pair of lobes. The two cams, when secured together, can be regarded as a single cam.

The elements of each cam-unit are secured together by the presence at each face of the unit (see Figs. 3, 4, 5, and of a washer 72, held by a split retainingring 73 in a circumferential groove in hub 49 of sun pinion 43.

Contactunit 37 will now be briefly described with particular reference to Figs. 3 and 5. The description will not go into details inasmuch as the details of this unit do not form a part of the present invention.

74 represents the dielectric base of this unit, which base is secured to sub-frame 36 in any convenient manner. Pivoted on this base, as at 76, is a rocker-arm consisting of two parts rigidly connected together. Upper part 77 is dielectric, lower part 78 preferably metallic. A roller 79 is journaled in the lower part. On the base 74 are two electric terminals 81, each electrically connected to one of two fixed contacts 82.

A bridge 83, carried by the upper part 77 of the rockerarm normally constitutes a closed circuit between contacts 82, when the rocker-arm is pivoted under the in fluence of spring 84, except whenever the rocker-arm is pivoted in the opposite direction by the pressure of a camlobe 67 on roller 79.

The mounting of worm-pinions 39 will now be detailed. By reference to Fig. 5, it will be seen that shaft 41 extends loosely through holes in sub-frame 38, and through metallic washer 86 and rubber washer 87; and that adjusting head 42 projects very loosely through hole 88 in the front of box 21.

Split retaining rings 89, 91, and 92 fit in respective circumferential grooves in shaft 41. The grooves for rings 89 and 91 are sufficiently near together so that these rings place spring washer 93 under compression; thus the friction of ring 89 and spring washer 93 render it difficult for Worm pinion 39 to turn, thus cumulating with the natural tendency of a worm pinion to resist turning under the influence of its worm gear; thus any adjustment effected by the worm gearing tends to remain adjusted. Spring washer 94 is primarily to hold

washers

86 and 87 in place; to the extent that it may reduce the friction of ring 89, it serves to increase the friction of spring washer 93.

There is a window 96 in the cover 22 of the box. See Fig. 5 The glass or other transparent pane of this window has a scored index line 97 directly above the axis of main shaft 27. This line extends transversely across all of the indicating plates 58. Its position and extent is shown in Fig. 1.

For uniformity in assembling the cam-units on shaft 27, the following is recommended. See Figs. 6 and 7. It makes no particular difference just where on the periphcry of ring-gear 48 or its hub 61, pins 63 which hold those two elements together, are located; except that it is advisable that each be adjacent the base of a tooth. Furthermore, before the holes for pins 63 are drilled, ring-gear 48 should be so oriented with respect to hub 61 that each of bolt-holes 70 in that hub is opposite a tooth of that gear.

Sun pinion 43 is assembled on spider 47 and locked to it by washer 72 and split retaining ring 73. Then planet pinions 44 are added, and sun pinion 43 is turned so that its key-way 51 is pointed directly toward the zero of indicating plate 58, which is the position of the keyway shown in Fig. 7. This constitutes the first sub-assembly.

The second sub-assembly consists of cam-hub 61, with earns 64 and 66 secured to it by bolts 68. It will be noted from Figs. 5 and 6 that one of these bolts is opposite the leading edge of one of cam-lobes 67.

The second sub-assembly is then placed on the first sub-assembly, and so oriented that this bolt is degrees counter-clockwise from the zero of the indicating plate. This is because the roller 79 of the contact-unit happens to be so located that, with this orientation the contacts will open when Zero of the scale is up. See Fig. 5.

The two sub-assemblies are then secured together by washer 72 and split retaining ring 73.

The thus completed cam-units can then be strung on and keyed to main shaft 27, and the whole placed in the box, with the several worm-pinions 39 in engagement with the respective worm-gears 54. Whereupon each camunit can be adjusted to its proper relative time in the cycle, by turning respective adjusting head 42.

Certain proportions will now be discussed.

As built, sun-pinion 43 has 30 teeth, and internal ringgear 48 has 60 teeth. Thus with spider 47 held locked, at full turn of the sun-pinion clockwise (as seen in Figs. 5, 6, 7, and 8) will rotate the ring-gear (and hence the cam) a one-half turn counterclockwise. In view of this, each cam has two diametrically located cam-lobes 67, so that these tWo lobes will function at exactly the corresponding point of time in each of the alternate cycles of main shaft 27.

When the sun-pinion is held stationary, and the spider is adjusted one-third of a turn clockwise, the ring-gear (and hence the cam) will be adjusted one-half a turn clockwise: i.e., one full cycle, thus retarding the occurrence of the cam-action one full rotation of the shaft. To

indicate this, the indicating plate extends for 120 degrees and graduates this 120 degrees as 360 degrees.

The assumption of stopping the sun-pinion is merely for the purpose of simplifying the computation, a wellknown expedient in connection with planetary transinissions. The result would be the same, if the adjustment in question were made while shaft 27 was in motion.

If a 1 to 3 ratio of sun-pinion to ring-gear were employed, the cams should have three equally spaced lobes, and the indicating plate should extend 90 degrees graduated as 360. And so on for ratios of 1 to any higher integer. Thus for a ratio of 1 to N, there would be N equally spaced lobes, and the indicating plate should extend 360/ (N +1) degrees, graduated as 360. N must be an integer, for the cycle to repeat. N equals 2, as in the device as shown, is highly preferable.

Not only can the duration of the operative contact of each of the two cam-lobes of a given cam-unit with its associated contact-unit be altered at will by the substitution of cams having lobes of a greater or lesser angular spread, and not only can this duration be further and more finely altered (while the controlled machine is quiet) by slightly altering the relative angular position of the two cams of the unit (as already explained), but also the same or further adjustment can be effected, while the machine is in motion, by utilizing the following expedient.

Control the operation in qumtion by two cam-units and two associated contact-units, with their cam-lobes overlapping; that is to say, the cam-lobe of the lead unit comes into contact, and then before it disconnects, the cam-lobe of the follower unit comes into contact. The time of the operation is adjusted by manipulation of the worm-pinion of the lead unit; and then the duration of the operation is adjusted by manipulation of the wormpinion of the follower unit. If the contact-units are normally-closed break units, they are wired in series. If normally-open make units, they are wired in parallel.

Throughout the discription, to facilitate understanding, a certain direction of rotation of shaft 27 has been assumed, namely clockwise as seen in Figs. 5, 7, and 8; but it should be understood will operate satisfactorily with the direction of rotation reversed.

Many departures, in addition to those already mentioned, may be made from the details shown and described herein, without departing from the spirit of the present invention. For example, but not limitation: There could be more or less than two planet pinions; the contact-unit could be any sort of a contact-unit actuable by a cam, even to the extent of including a fluidpressure valve instead of electric contacts; spur gearing could be substituted for the worm gearing; any one of three elements (sun-pinion, ring gear, and planet-pinion spider) could be the driving member of the planetary transmission, any one of the remaining two could be the driven member, and the third could be the adjustably stationary member, although the choice selected in the present invention gives the best ratios; the cams could be geared to the driven member, instead of coaxial therewith; the adjusting means could be controlled automatically, by the condition of the work, instead of manually; the teeth of the adjusting gear could all be left on, and the indexing plate be otherwise located, even to the extent of locating it on or with respect to the shaft of the adjusting pinion; etc.; etc.

Now that one embodiment of the invention has been shown and described, and several departures therefrom have been suggested, it is to be understood that the invention is not to be limited to the specific form or arrangement of parts herein shown and described.

What is claimed is:

1. In an adjustable continuously-rotatable multiple limit-switch, the combination of: a base; a plurality of oam-actu-able contact-units mounted on the base; a plurality of cam-units, to actuate the respective contact-units;

and a drive-shaft, journaled on the base, for driving the cam-units in unison; wherein each cam-unit includes: a planetary transmission (comprising a sun-pinion, a ringgear, a planet-pinion spider, and at least one planetpinion), substantially identical as to all cam-units; a rotary cam to which the ring-gear is drivingly connected and which is adapted to periodically press upon and thus actuate the contact-unit, and an adjusting gear which is drivingly connected to the spider and normally holds the spider against rotation; and wherein the drive shaft is drivingly connected to all the sun-pinions; and wherein there is journaled on the base and drivingly engaging each adjusting gear, a pinion for angularly adjusting said gear so as to advance or retard the orientation of the respective cam with relation to the other cams, and for holding said gear fixed in adjusted position; and means for manually turning said pinion to perform such adjustment.

2. In an adjustable continuously-rotatable multiple limit-switch, the combination of: a base; a drive-shaft, journaled on the base; a plurality of cam-actuable contact-units mounted on the base; and, with respect to each of said contact-units, the following: a rotary cam, journally supported by the base, and adapted to periodically press upon and thus actuate the contact unit; a planetary transmission (comprising a sun-pinion, a ring-gear, a planet-pinion spider, and at least one planet-pinion) substantially identical as to all cam-units, journally supported by the base, the ring gear being drivingly connected to the cam, and the sunapinion being connected to the drive-shaft to be driven thereby in unison with the other sun-pinions; an adjusting gear, drivingly connected to the spider and normally holding the spider against rotation; and, journaled on the base and drivingly engaging said adjusting gear, a pinion for angularly adjusting said gear so as to advance or retard the orientation of the respective cam with relation to the other cams, and for holding said gear fixed in adjusted position; and means for manually turning said pinion to perform such adjustment.

3. In a cam-unit, for use in an adjustable continuouslyrotatable limit-switch, to actuate a contact-unit therein, which switch includes a main shaft, the combination of: a sun-pinion, having an elongated cylindrical hub, and adapted to be drivably attached to the shaft; journaled on said hub at one side of said sun-pinion, a spider, having at least one stub axle, and a peripheral gear, adapted to engage an adjusting pinion; journaled on each such stub axle, a planet-pinion engaging the sun-pinion; an internal ring-gear, coaxial with the sun-pinion, and surrounding and engaging the planet-pinions; journaled on the sun-pinions hub at the other side of the sun-pinion, a hub for the ring-gear rigidly attached thereto, and constituting with the spider a gear-case for the sun and planet pinions and the ring-gear, adapted to contain appropriate lubricant; a rotary cam, rigidly attached to the ring-gears hub, and adapted to periodically press upon and thus actuate the contact-unit; and means secured to each end of the sun-pinions hub to confine the other recited elements between them.

4. In an adjustable continuously-rotatable multiple limit switch, the combination of: a base; a plurality of cam-actuable contact-units mounted on the base; a plurality of cam-units, to actuate the respective contact-units; and a drive-shaft, journaled on the base, for driving the cam-units in unison; wherein each cam-unit includes: a planetary transmission (comprising the following elements: a sun-pinion, a ring-gear, a planet pinion spider, and at least one planet-pinion), substantially identical as to all cam units; a rotary cam to which one of the first three planetary elements is drivingly connected and which is adapted to periodically contact and thus actuate the contact-unit, and an adjusting gear which is drivingly connected to another of the first three planetary elements and normally holds said element against rotation; and wherein the drive shaft is drivingly connected to all of another of the first three planetary elements; and wherein there is journaled on the base and drivingly engaging each adjusting gear, a pinion for angularly adjusting said gear so as to advance or retard the orientation of the respective cam with relation to the other cams, and for holding said gear fixed in adjusted position; and means for manually turning said pinion to perform such adjustment.

5. An adjustable continuously-rotatable multiple limitswitch according to claim 1, wherein each cam is so connected to the corresponding ring-gear as to rotate therewith, and wherein each sun-pinion is so connected to the shaft as to rotate therewith; and wherein the gear ratio of each ring-gear to the corresponding sun-pinion is an integer.

6. An adjustable continuously rotatable multiple limitswitch according to claim 5, wherein the cam surface of each cam is divided into N identical configurations, where N is the integer.

7. An adjustable continuously-rotatable multiple limitswitch according to claim 6, wherein there is an armate indexing plate carried rigidly by each spider, and an index fixed with respect to the base, the plate being so graduated that each angular unit of extent of plate is occupied by N+1 angular units of graduation.

8. An adjustable continuously-rotatable multiple limitswitch according to claim 7, wherein the integer is 2.

9. In a cam-unit, for use in an adjustable continuously rotatable limit-switch, to actuate a contact-unit therein, which switch includes a main-shaft, the combination of: a planetary transmission (comprising a sun-pinion, a ringgear, a planet-pinion spider, and at least one planetpinion), said sun-pinion being adapted to be drivably connected to said shaft; a rotary cam to which the ringgear is drivingly connected and which is adapted to periodically press upon and thus actuate the contact-unit; and an adjusting gear, drivingly connected to the spider, and adapted to drivably engage an adjusting pinion; and wherein the cam is so connected to the ring-gear as to rotate therewith, and wherein the sun pinion is. adapted to be so connected to the shaft as to rotate therewith; and wherein the gear-ratio of the ring-gear to the sun pinion is an integer.

10. An adjustable continuously rotatable multiple limitswitch according to claim 9, wherein the cam surface of each cam is divided into N identical configurations, where N is the integer.

11. An adjustable continuously-rotatable multiple limitswitch according to claim 10, wherein there is an arcuate indexing plate carried rigidly by the spider and adapted to be read by a fixed index, this plate being so graduated that each angular unit of extent of plate is occupied by N +1 angular units of graduation.

12. An adjustable continuously-rotatable multiple limitswitch according to claim 11, wherein the integer is 2.

References Cited in the file of this patent UNITED STATES PATENTS 1,684,064 Miller Sept. 11, 1928 1,724,714 Kersten Aug. 13, 1929 2,450,311 Strunk et a1 Sept. 28, 1948 2,528,344 Davis Oct. 31, 1950 2,554,545 Winder May 29, 1951 2,852,957 Breit-ensen Sept. 23, 1958