US3320375A - Continuously adjustable limit switch - Google Patents

Description

May 16, 1967 Filed Oct.

C. S. ALDRlCH ETAL CONTINUOUSLY ADJUSTABLE LIMIT //VOEX /4 I I 3 22"a, 2 0 22b 2 70 f' mm 75 H W {Slum um, I l

SWITCH 5 Sheets-Sheet 1 (a) EDGE OF OPEN WINDOW -(b) lVU/PMHL POSITION 0F HYDE X LINE JNVENTORS CHARLES S. ALDRICH BY LEON N. CANICK ATTORNEY May 16, 1967 Filed Oct.

C. S. ALDRICH ETAL CONTINUOUSLY ADJUSTABLE LIMIT SWITCH 5 $heets-$heet I N VE N TORS CHARLES S. ALDRICH BY LEON N. CANICK ATTORNEY y 16, 1%? 5. ALDRICH ETAL. 3,320,375

CONTINUOUSLY ADJUSTABLE LIMIT SWITCH sneetsesheet rs Filed Oct.

INVENTORS CHARLES S. ALDRICH LEON N. CANICK @MM m AT TQIEY United States Patent 3,320,375 CONTINUOUSLY ADJUSTABLE LIMIT SWITCH Charles S. Aldrich, 205 Hawthorne Road, Kings Park, N.Y. 11754, and Leon N. Canick, 6700 192nd St., Fresh Meadows, N.Y. 11365 Filed Oct. 5, 1965, Ser. No. 493,006 11 Claims. (Cl. ZOO-47) This invention relates to adjustable limit switches actuated by continuously rotating elements and more particularly, but not limited thereto, to improvements in limit switches of the type disclosed in US. Patent 3,060,286.

Adjustable limit switches of the prior art are generally complex and costly devices. In order to provide their stated function they include differential gearing arrangements, intricate cams, cam followers, etc. In many instances adjustability is limited to an arc of substantially less than 360. Of more importance is the fact that the adjustment angle is not precise and in many instances is just an approximate setting within a wide range. The device must then be reset to achieve the finer adjustment. Frequently, the readjustment must be done in several stages. While this is intended to give greater accuracy, it many times results in a compromise setting because of the increased handling.

By way of contrast to the prior art, the instant device is a high capacity, infinitely adjustable rotating shaft limit switch designed for controlling, programming, cycling and sequencing machine operations. It is calibrated and preset at the factory to an accurate reference point. The adjustment problems of 'the prior art devices are thereby eliminated. The purchaser need'then make only a simple external screw driver adjustment to set the on and olf points of the switch anywhere between 3 and 357. This may be done while the utilization apparatus is either rotating or stationary. The setting made at the factory is a known quantity as are the desired actuation points of the switch. Accordingly, only simple arithmetic is required to accurately reset the device to the users specific requirements. This need only be done once for each application. Switching positions and dwell angles are indicated precisely by high resolution dials calibrated and readable to better than 0.5". The dials are located adjacent to external adjusting screws, permitting even com plex control programs to be set up or changed solely by means of the dial indications.

This invention provides several improvements over the apparatus disclosed in our US. Patent 3,060,286, issued Oct. 23, 1962. The general functions and much of the structures of the present invention are similar to those disclosed in the aforementioned patent. Accordingly, many of the common elements will not be described in great detail.

A feature of the instant application is the provision of improved visual indication of the switching angles.

An additional feature in the present invention is the provision of means to control the overtravel of the leaf spring in the snap action switch.

It is also an object of the present invention to provide more conveniently placed switches so that the replacement thereof may be facilitated.

A feature of the present invention is the provision of a choice of housing configurations to meet many installation requirements. In addition, the instant invention permits the utilization of a variety of switch types.

It is an object of the present invention to provide means for resetting the calibrations that indicate the switching angles.

It is another object to provide means for externally setting the aforementioned calibrations.

Still another object of the invention is to provide a compound actuating lever for the switch.

A further object is to provide means for adjusting a portion of the compound lever from a point externally of the housing.

These and other features, objects and advantages of the invention will, in part, be pointed out with particularity and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawing, which forms an integral part thereof.

In the various figures of the drawing like reference characters designate like parts.

In the drawing:

FIG. 1 is a side elevational view of a single stack unit drawn to a reduced scale;

FIG. 2 is a side elevational view of a multi-stack unit, also drawn to a reduced scale;

FIG. 3 is a side elevational view, partially in section of a two-stack limit switch incorporating the features of the present invention;

FIG. 4 is a sectional plan view taken along line 4-4 of FIG. 3;

FIG. 5 is a sectional elevation view of the calibration dial and gear assembly;

FIG. 5A is a partial plan view, on a reduced scale, taken along line 5A5A of FIG. 5;

FIG. 6 is a fragmentary sectional plan view illustrating access means for the calibrated drum dial;

FIG. 7 is an exploded fragmentary perspective view showing the principal elements of one of the novel features of this invention; and

FIG. 8 is a schematic illustration of the calibrating method.

Referring now to the drawings, FIG. 1 and FIG. 2 illustrate two possible alternative arrangements of the present invention. Therein is shown a single stack unit 10 (FIG. 1) and a multi-stack unit (FIG. 2) comprised of a plurality of ganged members 10. FIG. 2 fragmenta rily illustrates a cover member 12 that may also be included. A shaft 14, common to all the units in FIG. 2 and adapted to be coupled to a utilization device (not shown), extends outwardly from one end of the housing 16 and a switch or switches 18 are secured to the outside housing surface. Windows 20 formed in the housing expose a pair of calibrated drum scales 22a and 22b, which, in combination with adjusting screws 24a, 24b and locking screws 26a, 26b, respectively, provide visual indication of the switching angles.

For simplicity, only one of the many possible locations of the switch with respect to the calibrating window is shown, it being understood that several variations of the illustrated arrangement are possible. By way of example, the switches could be either on the left or right hand side of the housing and the shaft could extend from either end. Of course, the entire assembly could be supplied either with or without a cover member.

Also, instead of the panel type mounting end 28 illustrated in FIG. 1, hanger plates 30 (FIG. 2) for chassis mounting may be provided. In this case the switches could be located on top of the housing with the window on either the left or right hand side, or, alternatively, the switches may be positioned on top of the housing and the windows on either side. It is also within the scope of the present invention to provide two or more parallel arrays of multi-stack units having coupling means, such as a gear train, therebetween and a single output shaft common to all stacks.

A feature of the present invention is particularly apparent in FIG. 2. Therein it will be seen that the angular mounting of each switch with respect to the housing facilitates the removal or replacement of the switches when so desired. The axis of the switch mounting screws 32 are parallel to each other but are offset and not in line with one another. Therefore, the head of each screw is readily accessible.

For a clear understanding of still other improved structure comprising the present invention, a brief description of existing, patented structure would be helpful. Reference may be had to a showing of a two-stack unit in FIGS. 3, 4 and 5. Axial shaft 14 extends through the housing and is rotatably journalled in bearings 34 disposed in housing end plates 36. Posts 38a, 38b and 38c, which are very accurately located, join the spaced end plates and, in addition, perform an important function that will be fully in conjunction with the calibrating means used with the switching angle readout.

A wheel 40, made, for example, of nylon, Delrin, or other suitable material, is pivotally mounted, by means of a split clamp 42 and a bracket 43, on shaft 14 for rotation therewith. Positioned directly beneath the wheel is a pair of concentrically nesting inner and outer crown gears 44a and 44b, respectively. Pinions 46a and 46b (FIG. 4) secured to the inner ends of adjusting screws 24a and 24b, provide means for angularly adjusting the relationship of the gears to each other. Once the gears are properly located, screws 26a and 26b, each having a flange overlaying the flange of its respective adjusting screw, are utilized to lock the pinions in place in order to prevent inadvertent movement of the crown gears.

With particular referenceto FIG. 4 and FIG. 5, it will be seen that the crown gears are mounted in substantially the same manner as in the aforementioned patent. However, there are two areas of difference and these will now be explained. Plate 48 supports a hub member 50 which is disposed about shaft 14 and which also supports the crown gears. Inner crown gear 44a is secured to lower ring 52 by means of screws 54 while outer crown gear 44b is secured to upper ring 56 by means of screws 58. The gears and their respective rings are adapted to be independently rotated with respect to each other and with respect to the shaft.

As in our prior patent, the gears are each provided with arcuate slots of similar dimension, the overall length of the combined slots being varied by rotation of one or both of the gears. In addition, a closure member 60 is also provided to overlay the web portions of the gears. However, the present apparatus is substantially larger than that disclosed in the aforesaid patent and therefore the thin sheet metal stop member described in the patent cannot be relied on. Accordingly, a single, downwardly depending pin 62 is press fit into the central web portion of the outer gear 44b and a pair of upwardly extending pins 64, spaced approximately 180 apart, are press fit into the ring integral with the inner gear 44a.

The function of the closure member and pins is therefore the same as in our previous patent, although structure more suitable to the size of the device is provided.

Referring now to FIG. 5A, it will be noted that closure member 60 overlays the central portion of the crown gears. When the effective slot opening is near the zero angle or closed position, closure member 60 serves to cover the other slot opening which results. Closure member 60 has a bent down tab 65 which is positioned between the steps in the gear webs. The tab serves to properly position the closure member to close off the false slot but does not function as a stop since a large torque can be put on the gears during the adjustment procedure. Since switches 18 may be of the single-pole, double-throw type, the actual adjusting switching angle available is to 360".

Another feature of this invention is illustrated in FIG. and FIG. 6. Scales 22a and 22b are each provided with a set screw 66 that normally holds the scales in a fixed, predetermined position with respect to the crown gears. However, when calibrating the instrument, the angular position of each scale may be varied to reflect the switch actuating angles. The arcuate length of window 20 is very accurately fabricated whereby, in cooperation with accurately positioned posts 38a and 38b and a reference line 68 provided on the rear window surface, the instrument may be calibrated. The window is normally held in place by screws 70, the removal of which permits the window to slide between the extreme positions of abutment from posts 38a and 38b. A recess 72 (FIG. 6) is formed in the front surface of the window so that the window may be moved with the aid of a screwdriver or other such tool. 1

The calibration of each scale is utilized to indicate either the actuating or deactuating angle of its associated switch. For ease of reading and to avoid confusion, the scales are color coded. By way of example, a gold scale would refer to the open circuit condition of the switch while the silver scale would refer to the closed circuit condition of the switch. FIG. 1 illustrates a suitable plate 74 marked with the switching angle data.

The apparatus is calibrated with respect to a master in the following manner, reference fbeing had to FIG. 6:

(a) By using external screws 24a and 24b to rotate the crown gears, set screws 66 are brought into the area behind window 20.

(b) Screws are removed from the housing.

(c) Window 20 is moved to the left until it abuts posts 38b. It should be noted that the arcuate length of window 20 is such that when it is in the retracted position the right band edge of the window remains exposed within the opening. This exposed edge then substitutes for index line 68. The edge does not simulate the exact position of line 68. It actually creates a new position. But this new position being identical in a multi-stack unit is just as effective for calibration purposes.

(d) Set screw 66 is then loosened.

(e) By inserting a screw driver into set screw 66, the scale is held in place and the proper pinion is used to rotate a crown gear to the precise position where the switch is either opened or closed. The set screw is then tightened and the procedure is repeated with the other scale. At this time the length of the slot in which wheel 40 rides has been established in relation to the readings on the dials.

(f) Once again the crown gears are rotated by their respective pinions until the desired switching angle falls underneath reference line 68. Thus, as shown in FIG. 1, the switch may be energized at 200 and de-energized at The establishment of the slot length made in paragraph (e) is arbitrary to the extent that it determines only the duration of a particular switch condition. However, the second setting of the scales as described in this paragraph is of importance where two or more switches have a finite timed relationship with each other.

Since the limit switch is composed of a number of sections, each operated from a common shaft, it is necessary that they be phased to operate in unison. Since there are minor manufacturing differences between components in each section and since the overtravel adjustment of the switches may differ in each case and, further, since there may be differences in the actuation in the individual snap action switch, it is necessary to phase the apparatus after assembly. This is done by opening of the windows 20 to provide access to the dial rings. The first switch is then adjusted for actuation and its dial ring 22a moved so that some arbitrary number, which for convenience may be 0, is indexed for a reference line which again may be the edge of window 20. The switch is then deactivated by turning of screw 24b. The calibrated scale 22b is also turned to, say 180, and then locked in place with the set screw. It is to be noted that the important thing is that the switches all be phased together and it is not important whether a particular line or edge of the window is used as the reference.

Reference may be had to FIG. 8 wherein a multistack unit is shown in relation to a master dial and a master index. After calibration to the edge of the window, as described above, the window is closed. When readings are taken to the actual index line 68, the readings will be off by an amount a-b. This, however, is merely a scale shif By moving a master index to position b, all switches would read correctly.

All switches in the gang now actuate and deaotuate at the same point of rotation of the shaft. Normally, a pulley or gear will be mounted on shaft 14. When the device is installed in the utilization apparatus normally the installer will keep the pulley or gear in a loosened condition on shaft 14 and move the drive belt, etc., to a point corresponding to the actuation point of the first section and then lock the pulley on to the shaft 14. This will now assure that the first switch is phased relative to the apparatus.

Still another feature of this invention is shown in FIGS. 3, 4 and 7. The mechanical life of a snap action switch is usually the function of the life of the thin leaf springs inside the switch. When the plunger pin of a snap action switch is depressed to a fully bottomed position, as in most devices using switches of this type, the internal leaf springs are excessively stressed and the life of the switch is shortened. The present invention provides means that may be externally manipulated so that the leaf spring does not bottom. The life of the spring is thereby greatly extended.

Compound bracket 76 is comprised of a first section 78 having an end 80 disposed about shaft 14. Compression spirng 82 urges end 80 into engagement with bushing 83 which, in turn, is urged against bracket 43 whereby pivoting of the bracket when wheel 40 enters or leaves the arcuate slot in crown gears is reflected in a deflection of first section 78. The opposite end of first section 78 is in the form of a plate 84 having a pair of spaced tabs or ears 86 and a transverse pin 88 extending through the tabs. The pin is secured in the housing wall by set screw 90 (FIG. 3).

The second section 92 of the compound bracket 76 is a stepped plate 94 having a pair of spaced tabs 96 loosely mounted on transverse pin 88. The opposite end of the second section is arranged to adjustably bear against the contact button of the switch. Torsion spring 98 is also disposed about pin 88 and has one end bearing against plate portion 84 of the first section and its opposite end bearing against the area of plate 94 between tabs 96. Finally a stud 100 is threadably supported in second section 92 such that its headed end is disposed proximate an aperture 102 in the housing while its opposite end bears against plate portion 84. Plug 104 (FIG. 3) is threadably removable from aperture 102 so that the stud may be externally manipulated.

It is evident from the foregoing description that rotation of stud 100 will change the angular relationship between the first and second sections of the compound bracket. Accordingly, torsion spring 98 will maintain the free end of the second section at a precisely predetermined position. In actual practice when the switch is installed on the unit the stud is adjusted so that the switch is just actuated plus approximately one-eighth turn of the stud beyond this point. This results in a nonbottoming switch and greatly extends the life of the switch.

It will be seen then that the various features, advantages and objectives of the present invention, as enumerated above, have all been incorporated in a rugged and efiicient device. Improved visual indication of the actuation points of conveniently mounted switches have also been provided. In addition, externally manipulatable means have been incorporated to extend the life of the switch.

There has been disclosed heretofore the best embodiments of the invention presently contemplated and it is to be understood that various changes and modifications tion thereof rotatably journaled in the housing, first and second cam means disposed in the housing, cam follower means carried by and rotatable ,with the shaft, means to independently vary the angular relationship between each of the cams and the shaft and a pivotally mounted, internal switch-actuating lever responsive to the movement of the cam follower means, first and second scale means coupled to the first and second cam means, respectively, and means to vary the relative position of a said scale means and the respective cam means, said first and second scale means having indicia thereon that are in juxtaposition with each other, said scale means and indicia being visible from the outside of the housing whereby the position of the indicia of said first and second scale means is indicative of the position of the first and second cam means.

2. The combination in accordance with claim 1 wherein the means to vary the angular position of the first and second cams are first and second gears, respectively, and externally movable first and second pinions, respectively, in meshing engagement with the gears, said scale means comprising first and second rings adjustably secured to the first and second gears.

3. The combination in accordance with claim 2 including a screw threadably disposed in each of said rings to the first and second gears, respectively.

4. The combination in accordance with claim 2 including a screw threadably disposed in each of said rings and adapted to bear against the'respective gear, said screws being adapted to restrain said rings against angular movement with respect to the gears.

5. In a switch actuating apparatus of the type including a hollow, apertured housing, an axial shaft having at least a portion thereof, rotatably journaled in the housing, first and second cam means disposed in the housing, cam follower means secured to and rotatable with the shaft, means to independently vary the angular relationship between each of the cams and the shaft and pivotally mounted switch-actuating means responsive to the movement of the cam follower means, that improvement therein which comprises a compound switch actuating lever having a first section loosely mounted on the shaft and a second section pivotally coupled to said first section, a portion of said second section being in abutting engagement with the switch, and adjustment means adapted to vary the position of said second section with respect to the switch.

6. The apparatus in accordance with claim 5 including biasing means maintaining said second section in an adjusted position.

'7. The apparatus in accordance with claim 5 wherein said adjustment means comprises a screw threadably disposed in said second section and arranged to bear against a portion of said first section.

8. The apparatus in accordance with claim 5 wherein said adjustment means are positioned proximate an aperture in the housing whereby said adjustment means are accessible from a point outside of the housing.

9. Actuating means adapted to be coupled to a utilization'device having a cyclical mode of operation, said actuating means comprising:

(a) at least one hollow housing having an aperture in the wall thereof;

(b) an axially disposed shaft having a portion thereof rotatably journaled in said housing;

(c) cam follower means secured to and rotatable with said shaft;

(d) first and second cam means disposed in said housing in the path of said follower means, said cam means being arranged to deflect said follower means;

(e) cam adjustment means carried by said housing,

said adjustment means comprising first and second gears integral with said first and second cam means respectively and first and second externally rotatable pinions in meshing engagement with said first and second gears, said pinions being arranged to vary to U to said first and second gears, respectively, said first and second scale means having indicia thereon that are visible from the outside of said housing, whereby the position of the indicia of said first and second scale means is indicative of the position of the said cam means; and

the angular position of said first and second cam (i) locking means for securing the position of a said means with respect to each other and with respect scale means relative to a said respective gear. to said shaft; 10. The apparatus in accordance with claim 9 includ- (f) at least one switch secured to an external portion 10 ing means to vary the position of said second section of said housing, said switch being disposed in coverof said lever with respect to the switch. ing relationship to the aperture in said housing; 11. The apparaus in accordance with claim 9 includ- (g) a switch actuating lever pivotally mounted in said ing a stud threadably disposed in said second section housing and responsive to the movement of said f land in abutment with said first section, said stud being lower means, Saidlevef eXteHding through the housing 15 adapted to vary the position of said second section of aperture and being adapted to abut the switch, said id 1ever i h respect to th it h actuating lever comprising first and second sections hingedly and resiliently connected to each other, said first section being disposed on said shaft and responsive to the movement of said cam follower 20 References Cited by the Examiner UNITED STATES PATENTS means, said second section being in opposition to 2,574,841 11/1951 Powell the aperture in said housing to abuttingly engage 2,921,151 1/1960 Krill 200-38 said switch, said second section being responsive 30601286 10/1962 Aldrich et 200-453-1974 3,227,821 1/1966 Hauser ZOO-153.19 X

to the movement of said first section whereby deflection of said cam follower by said cam means will sequentially actuate and deactuate said switch. (h) first and second scale means releasably coupled BERNARD A. GILHEANY, Primary Examiner.

H. E. SPRINGBORIN, Assistant Examiner.

Claims (1)

1. 5. IN A SWITCH ACTUATING APPARATUS OF THE TYPE INCLUDING A HOLLOW, APERTURED HOUSING, AN AXIAL SHAFT HAVING AT LEAST A PORTION THEREOF, ROTATABLY JOURNALED IN THE HOUSING, FIRST AND SECOND CAM MEANS DISPOSED IN THE HOUSING, CAM FOLLOWER MEANS SECURED TO AND ROTATABLE WITH THE SHAFT, MEANS TO INDEPENDENTLY VARY THE ANGULAR RELATIONSHIP BETWEEN EACH OF THE CAMS AND THE SHAFT AND PIVOTALLY MOUNTED SWITCH-ACTUATING MEANS RESPONSIVE TO THE MOVEMENT OF THE CAM FOLLOWER MEANS, THAT IMPROVEMENT THEREIN WHICH COMPRISES A COMPOUND SWITCH ACTUATING LEVER HAVING A FIRST SECTION LOOSELY MOUNTED ON THE SHAFT AND A SECOND SECTION PIVOTALLY COUPLED TO SAID FIRST

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