US2753405A - Rotary limit switch assembly - Google Patents

Description

y 3, 1956 P. H. DANLY ET AL 2,753,405

ROTARY LIMIT SWITCH ASSEMBLY Filed June 30, 1953 3 Sheets-Sheet l /0 fo 6 55 H 5 INVENTORS July 3, 1956 p, H. DANLY ET AL 2,753,405

ROTARY LIMIT SWITCH ASSEMBLY Filed June 30, 1953 3 Sheets-Sheet 2 INVENTORS PH/LO H. DAM/LY 8c l fls/L GEOQGEFF MLW United States Patent ROTARY LIMIT SWITCH ASSEMBLY Philo H. Danly, Hinsdale, and Vasil Georgefi, La Grange Park, Ill., assignors to Danly Machine Specialties, Inc., Chicago, 111., a corporation of Illinois Application June 30, 1953, Serial No. 365,107 8 Claims. (Cl. 200-17) Our invention relates to rotary limit switch assemblies and more particularly to an improved rotary limit switch assembly wherein the positions of the switches may be adjusted when the machine with which the assembly is used is in operation.

In modern automatic machines many operations must be performed in the proper timed sequence, and some means must be provided for initiating the various operations in predetermined phase relation with the cycle of the machine. A machine requiring such a variety of operations is a power press. Some of the operations which must be automatically performed are, for example, stopping the press at the top of the stroke, the operation of mechanical handling devices, initiation of the feeding and removal of material, the operation of die stops, the supplying of drawing compound to the stock and the operation of the locking device for the press cushion. The means used in the prior art to control these operations is a limit switch assembly. In these assemblies of the rotary type, a series of radially spaced cams arranged on a shaft connected to the press shaft actuate at the proper time each of a series of switches fixedly mounted on the assembly housing. To set up the press, the cams are arranged in the estimated proper angular relationship on the shaft, the press is started and the operations ensue in approximately the proper relation. However, only in an extremely rare case will the cams be properly positioned upon the first Setting. The sequence of operations after the first setting must be observed, the machine stopped and the cams readjusted. That is, the proper setup of the press can only be determined by a series of trial and error operations, for each of which operations the press must be stopped and restarted. To obviate this necessity for continual stopping and starting, it has been suggested that a linear limit switch assembly be used so that adjustment of the switch positions is possible while the press is in motion. In such an assembly a cam member actuated from the press is reciprocated along a line with simple harmonic motion, and a number of switches are adjustably arranged alongside the cam in the proper spaced relationship so as to be actuated at the proper times. It is well known, however, that in simple harmonic motion, the amplitude of motion is extremely small during certain intervals of the cycle. For example, between 3-00 to 30 degrees in the cycle and from 150 to 210 degrees, approximately, the amplitude of displacement is very small in comparison with the amplitude in other intervals of the cycle. Therefore, if switches are so arranged alongside a linearly reciprocating cam member and a large number of operations required during one of the intervals referred to above, a great number of switches must be crowded in a small space, since the cam moves only a small distance along the line in the interval. If the number of operations required in an interval of small amplitude of motion is great enough, it may well be physically impossible to mount enough switches in the interval. Furthermore, in presses in which limit switch assemblies are used to control the press operations during a working cycle, the stopping of the press is under the control of one of the limit switches. Therefore, in the event that the drive means of the assembly is arrested by the rupture or disengagement of its connection to the rotating press parts, the press wiL not be stopped by its limit switch but will continue to operate until stopped by the operator. During this continued period of operation there is great danger of injury to the operator and to the press and dies. We have invented an improved rotary limit switch assembly which permits adjustment of the switches relative to the cams while the press is in motion and provides equal space for switches in all intervals of the cycle, In addition we provide an improved rotary limit switch assembly including safety means for automatically stopping the press when the shaft of our rotary limit switch assembly is accidentally arrested during an operating cycle.

One object of our invention is to provide an improved rotary limit switch assembly wherein adjustment of the sequence of operations is possible while the press is in motion.

Another object of our invention is the provision of an improved rotary limit switch assembly wherein the results of any switch setting may be immediately observed and corrected.

Another object of our invention is the provision of an improved rotary limit switch assembly including means for automatically stopping the press when the drive means of the assembly is arrested.

Other and further objects of our invention will appear from the following description.

In general our invention contemplates the provision of a housing having a shaft rotatably mounted therein, a plurality of cams mounted on the shaft and means for clamping said cams to the shaft in predetermined angular relationship. A number of switches corresponding to the number of operations it is desired to perform are provided for cooperation with respective cams. Mounting means mount the cams for limited movement with respect to the housing and locking means lock the switches in the positions to which they have been moved. In addition we provide an embodiment including stop means for automatically stopping the press when the shaft of the switch assembly is arrested.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

Figure l is a perspective view of our improved rotary limit switch assembly showing the general arrangement of parts.

Figure 2 is a sectional view of the erally along the line 2-2 of Figure larged scale.

Figure 3 is a sectional view along the line 3-3 of Figure 2.

Figure 4 is a fragmentary sectional view of another assembly taken gen- 1, drawn on an enof the assembly taken embodiment of our invention.

Figure 5 is a sectional view with a part broken away taken along the line 5-5 of Figure 4.

More particularly, referring now to the drawings, we provide a housing generally indicated at 10 and having top and bottom members 11 and sides 13 in which is rotatably mounted a shaft 12. One end of shaft 12 is mounted for rotation in a bearing 14 provided in one of the sides 13 of housing 10 and the other end of shaft 12 is supported in ball bearings 16 mounted in the other side of housing 11). Bearing 16 is mounted in a bearing housing 18 and retained therein by an annular plate 20 fixed to the bearing cap by screws 22, and bearing housing 18 C) is secured to a housing by suitable means such as screws 19. A shock absorbing washer 24 is provided between the lip of housing 18 and the side of housing 10. Shaft 12 has an enlarged central portion 25 which may be of any desired cross-sectional shape but is preferably in the form of a square having rounded corners, as can readily be seen in Figure 3. It is desirable that this portion 25 be of any such noncircular configuration in order that the friction between portion 25 and the members mounted thereon may be a minimum, and a generally square section has been shown. One end of shaft 12 is provided with a keyway 23 by means of which it is coupled to the press drive so as to be rotated in phase therewith.

On the noncircular portion 25 of shaft 12 we mount a series of annular bushings 26, and between each pair of these bushings we arrange a pair of cam members 28 having circular openings therein to permit mounting them on the shaft. Each bushing 26 mounts a pair of switch-supporting arms 30 and an annular spacer 32. It will be noted that each pair of arms 30 is se arated by a washer 34, and washers 36 are disposed between each pair of cams 28. In addition, alternate cams are spaced from the adjacent bushings by washers 38. We provide shaft 12 with threaded portions 40 and 42 at the ends of portion 25. An internally threaded sleeve or nut 44 is threaded on portion 40 and an internally recessed nut 46 is threaded on portion 42. A spring 48 is disposed in the recess 50 of nut 46 and bears on a washer 52 which in turn engages one of the bushings 26.

When We tighten nut 46 by means of a tool inserted in recess 54, the force exerted is transmitted through washer 52 and bushing 26 to the cams and so forth through all the bushings and cams to sleeve 44. Thus the cams are clamped between sleeve 44, the intervening bushings 26 and nut 46, and are thus rigidly held with respect to shaft 12 and constrained to rotate therewith. When we desire to adjust the cams, we loosen nut 46 sufliciently to unclamp the cams. The spring 48 then frictionally holds the cams in position. The arms 30 are free to rotate with respect to shaft 12, since they are not subjected to clamping pressure, being mounted on the bushings 26, while cams 28 rotate with the shaft.

On the ends of the levers 30 we mount switches, generally indicated at 56. As shown in the drawings, only certain of the arms 30 may have switches mounted thereon. The number of switches depends upon the number of operations we desire to control. The switches are held on the levers by means of screws 58 pasing through arms 30 and into the switch housings 60.

The switch housings 60 are made of insulating material and provided with a pair of recesses 62 for the reception of a pair of spring-urged plungers 64 and 66. Plunger 64 may, for example, operate to close the switch and plunger 66 to open the switch. Another opening 68 is provided in the housings to receive cam member 70, which is mounted on a shaft 72 extending through member 70 and into a bushing 74 provided in a hole 76 adjacent the end of arm 30. The opposite end of shaft 72 has a reduced portion 78 extending outside housing 60 and on which We fixedly mount an actuating arm 80 by means of a nut 82. On the other end of the arm 80 we mount a roller 84 for engagement with the cam 28 corresponding to the supporting arm 30 on which the respective switch is mounted. Roller 84 is carried by a bushing 86 surrounding a pin 88 having an enlarged portion 90 on one end for retaining the roller and a reduced portion 92 on the other end, by means of which it is fixed on arm 80 by a nut 94.

We provide curved top and bottom members 11 of housing 10 with a series of spaced slots 98 in which we mount locking means, generally indicated at 96. Each of the locking means includes a cylindrical locking pin 100, one end of which is of a reduced diameter and adapted to be inserted in the recess 102 of a switch housing 60. Portions 104 of pins 100 are laterally reduced in the di-:

rection of the width of slots 98 but not in the direction of the length of slots 98 so that pins ride along the slots but are prevented from rotating in the slots. Pointers 106 and knurled locking nuts 108 are mounted on cylindrical threaded portions 110 extending above portion 104. When the pins 100 are drawn up into the clamped position, no pull is exerted on the switch housing since the pins 100 slide relative to recesses 102. In addition, we have arranged the parts so that pin 100 will not extend all the way within the recess 102 when the locking nut 108 is clamped to the housing. Enough space is left so that pin 100 may drop further into the recess 102 when the locking nut 108 is loosened. The pointers 106 are provided for cooperation with appropriate scales on housing 10 so that we may record the relative ositions of the locking means and associated switches in a particular operation.

We arrange certain of the switches at the top of the housing and certain others at the bottom thereof. Generally alternate switches are at the top and bottom of the housing, an arrangement dictated by space considerations. We can arrange the cams, of course, in any desired angular relationship. Leads 112 extend from the switches to the outside apparatus through an appropriately insulated opening 114 and are of sufficient length to per mit adjustment of the position of the switch lever with which they are associated.

In the embodiment of our invention illustrated in Figures 4 and 5 we have provided a simplified arrangement of parts and a safety means for stopping the press in the event that the shaft of the limit switch assembly is arrested by the rupture or disengagement of its connection to the rotating press parts. In this form we mount a shaft having an enlarged central portion 122 of a noncircular configuration within the housing 10. The right-hand end of this shaft is mounted in a bearing (not shown) similar to bearing 14 described in connection with the embodiment illustrated in Figures 1 and 2. The left-hand end of shaft 120 is mounted in ball bearing 124. A collar 126 having an annular flange 128 on its inner periphery is fixed to housing 10 by any appropriate means such as screws 130 and surrounds and seats the outer race 132 of bearing 124. A nut 134 is threaded on shaft 120 and bears on the inner race 136 of bearing 124 through a washer 138 to hold the inner race in position against bushing 139 on the shaft. A bearing cap 140 covers nut 134 and is fixed to collar 128 by any suitable means such as screws 142. Cap 140 holds outer race 132 against flange 128.

We arrange a plurality of annular bushings 144 along the enlarged portion 122 of shaft 120. Between each pair of bushings 144, we dispose a cam 146 having a circular opening 148 surrounding portion 122 of shaft 120. Each bushing 144 carries a switch-supporting arm 150. A nut or collar 152 is threaded on shaft 120 at the left-hand end of portion 122 as viewed in Figure 4. Clamping means similar to that described in connection with the embodiment illustrated in Figures 1 and 2 is provided at the right-hand end of portion 122 to clamp the cams and arms in the selected relative positions around shaft 120.

Each of the arms is provided at a point intermediate its length with a pair of spaced lateral projections 154 on which we mount a limit switch 156 having an actuating button 158 by any suitable means such as screws 160. Leads 159 and 161 provide electrical connections for the switch.

An arm 162 is pivotally mounted on a pin 164 carried by the arm 150. Each of the arms 162 has a roller 166 rotatably carried by a pin 168 on the end of the arm 162 opposite pin 164. A recess 170 in each of the arms 162 houses a spring 172 which bears with one end on one of the projections 154. Spring 172 urges arm 162 in a clockwise direction as viewed in Figure 5. A stop 173 on supporting arm 150 limits the movement of actuating arm 162 in this direction. We also provide each of the arms 162 with a projection 174 for engagement with 'actuating button 158 of the associated limit switch 156. Each of the rollers 166 is so disposed as to be engaged by one of the cams 146 at some point in a cycle of operation of the switch. When a roller is engaged by a cam, the respective arm 162 is rotated in a counterclockwise direction as viewed in Figure 5 to engage its associated switch actuating button 158. The arrangement of parts is such that springs 170 urge arms 162 to a position where they bear against stops 173 and projections 174 will not actuate switch operating buttons 158 when the associated roller 166 is not engaged by its respective cam.

Each of the arms 150 has a lateral flange 176 at its end. Locking means, generally indicated by reference character 178, are mounted in the slots 98 in the curved top and bottom members 11 of housing 10. The locking pins 180 of the assembly are adapted to be inserted in corresponding holes 182 in flanges 176 and have reduced portions 184' which ride in the slots 98 and prevent rotation of pins 180. A knurled nut 186 and lock nut 188 are threaded on a shank 190 extending outwardly from reduced portion 184 of each of the locking means 178. Suitable covers 192, supported on hinges 194 fixed to housing by screws 196, may be provided and held in the closed position by screws 198 carried by a flange 200 on the housing.

We key a collar 202 to shaft 120 at a point to the left of nut 152 as viewed in Figure 4 by means of a key 204. A spur gear 206 is attached to flange 208 of collar 202 by suitable means such as bolts 210. Gear 206 drives a pinion 212 on the end of a coupling sleeve 214 fixed to the shaft 216 of a zero speed switch 220, of a type well known in the art, by means such as a set screw 215. Zero speed switch 220 is carried by a housing 222 fixed to the housing 10 by suitable means such as screws 224. An enclosure 226 mounted on the housing 10 by rivets 228 may be provided to isolate gearing 206, 212 from the remainder of the switch assembly.

While we have shown the switches of our assembly supported on arms carried by the assembly shaft, it will be understood that the switches could be mounted in the slots 98 and actuated by their respective cams with out the necessity of using any supporting arms. We prefer, however, to employ such supporting arms to hold the switches securely in the positions in which they have been locked.

In operation, in the form of our invention shown in Figures l to 3, we first assemble our device in the manner shown with a suitable number of switches Within the housing and loosen nut 46 by means of a tool inserted in recess 54 to permit movement of cams 28 against friction exerted by spring 48. Switch supporting arms are best positioned initially in the center of slots 98 and clamped in position. We then dispose cams 28 in approximately the correct angular positions and tighten nut 46 so that it clamps the cams in the positions to which they have been moved. We start the press and observe the sequence of operations; invariably, adjustments must be made. To make adjustments, we loosen nuts 108 to permit movement of their associated switch and arm along a slot 98. When the proper positions have been reached, we again tighten the nut. The correct positions are determined during the time the adjustment is being made by observation of the press operation. When all necessary adjustments have been made, the press will be operating properly and all functions will be performed in the desired sequence. That is, the cams 28 rotate and engage rollers 84 to rock actuating arms 80 and rotate cam members 70 in the proper direction to actuate either plunger 64 or 66 to start or stop the equipment being controlled. It should be noted that we make all adjustments without the necessity of stopping the press.

The operation of the embodiment illustrated in Figures 4 and 5 is similar to that of the form shown in Figures 1 and 2. Locking means 178, carrying their associated arms 150 and switches 156, are moved to the centers of slots 98 and locked. Cams 146 are moved to approximately the correct relative positions and clamped in place by the clamping means. The press is started and any necessary adjustments made by again moving locking means 178 and their associated switches along the slots 98. As is the case in the form illustrated in Figures 1 and 2, these last adjustments can be made without stopping the press. When the switches have been set, the cams 146 rotate and engage their respective rollers 166 to rotate arms 162 so that projections 174 actuate their corresponding switch operating buttons 158 to perform the desired operations in the proper sequence.

In the event that the control shaft leading to shaft breaks or shaft 120 for any reason ceases to rotate during a press cycle, spur gear 206 will no longer rotate pinion 212 and shaft 216 of the zero speed switch 220 will stop. As is well known in the art, while shaft 216 of zero speed switch 220 continues to rotate, the zero switch will be closed. However, when the shaft 216 stops, the switch will open. We have arranged our device so that the opening of switch 220 will actuate the press control to stop the press. Therefore, if for any reason shaft 120 stops rotating, the press will be stopped.

Thus it will be seen that we have accomplished the objects of our invention. We have provided an improved rotary limit switch assembly wherein the results of the initial setting can be immediately observed and corrected without the'necessity of stopping the press. The trial and error system of setting up a press has been eliminated. Only one setting up of the cams is necessary, and adjustments of the switches can be made to achieve the desired operation without stopping the press even once. In addition, we have provided safety means for automatically stopping the press in the event that the shaft of the rotary limit switch for any reason is arrested so that the press is not stopped by the proper limit switch.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is therefore to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. A rotary limit switch assembly comprising in combination a housing, a shaft rotatably mounted therein, a plurality of cams, means mounting said cams on said shaft for continuous adjustment of the circumferential position thereof on the shaft, means for clamping said cams to said shaft in predetermined angular relationship for rotation therewith, a plurality of switches, means for adjustably mounting the switches on said shaft for movement with respect to the housing when said cams are clamped and locking means for locking respective switches in the desired positions with relation to said housing, said clamping means being releasable to permit adjustment of the circumferential position of said cams while mounted on said shaft.

2. A rotary limit switch assembly as in claim 1 in which each of said switch mounting means comprises a bushing carried by the shaft and a supporting arm mounted on said bushing.

3. A rotary limit switch assembly as in claim 1 wherein said shaft is provided with threaded portions adjacent its ends and said clamping means includes a plurality of bushings mounted on said shaft intermediate the threaded portions and arranged so as to bear against said cams, a sleeve threadably mounted on one of said threaded portions, a nut mounted on the other of said threaded portions, the construction being such as to exert clamping pressure on said cams through the medium of said bushings when the nut is tightened. a. v

4. A rotary limit switch assembly as in claim 1 .in which said shaft is provided with threaded portions, adjacent itsends and saidclamping means includes atplurality of bushings mounted on said shaft intermediate the threaded portions and arranged so as to bear against said earns, a sleeve threadably mounted on one of said threaded portions, a recessed nut mounted on the other of said threaded portions and a spring disposed in the recess of said nut so as to exert frictional pressure on said cams through the medium of said bushings.

5. A rotary limit switch assembly :as in claim 1 in which said housing includes curved top and bottom .members provided with spaced slots and said locking means includesmernbers slidably mounted in said slots and means for locking said slidable members in the desired position in said slots.

'6. A rotary limit switch assembly as in claim 1 wherein said switch mounting means includes a plurality of supporting arms mounted on said shaft and said locking means includes members adjustably mounted on said housing, the arrangement of parts being such that pairs of said arms alternate with pairs of said cams along the shaft, and said adjustably mounted members are alternately mounted on the top and bottom of said housing.

7. A rotary limit switch assembly for use with a .machine tool including in combination a housing, a shaft rotatably mounted therein, a plurality of .cams, means mounting said cams on said shaft for continuous adjustment of the circumferential position thereof on the shaft, means for clamping said cams to said shaft in predetermined angular relationship for rotation therewith, a plurality of switches, means for adjustably mounting the switches on said shaft for movement withrespect to the housing when said cams are clamped, locking means for locking respective switches in the desired position with relation to the housing and stop means operable to stop said tool when said shaft is arrested, said clamping means being releasable to permit adjustment of the circumferential position of said cams while mounted on said shaft.

8. A rotary limit switch assembly for use with a machine ttool including in combination a housing, a shaft rotatably mounted in the housing, a plurality of cams, means mounting said cams on the shaft for continuous adjustment of the circumferential position thereof on the shaft, means for clamping said cams to said shaft in predetermined angular relationship for rotation therewith, a plurality of switches, means for adjustably mounting the switches on said shaft for movement with respect to the housing when said cams are clamped, locking means for locking respective switches in the desired position with respect to said housing, a zero speed switch and means for driving said zero speed switch from said shaft whereby said zero speed switch will stop the machine tool when said shaft is arrested, said clamping means being releasable to permit adjustment of the circumferential position of said cams while mounted on said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,169,039 Defandorf et al. Aug. 8, 1939 2,202,698 Latta May 28, 1940 2,273,963 Jereczek Feb. 24, 1942 2,636,949 Hunter Apr. 28, 1953

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