US2558517A

US2558517A - Adjustable limit switch means

Info

Publication number: US2558517A
Application number: US652767A
Authority: US
Inventors: Handelman Philip
Original assignee: Reliance Steel Products Co
Current assignee: Reliance Steel Products Co
Priority date: 1946-03-07
Filing date: 1946-03-07
Publication date: 1951-06-26
Anticipated expiration: 1968-06-26

Description

June 26, 1951 P. HANDELMAN 2,553,517

ADJUSTABLE LIMIT SWITCH MEANS Filed March 7, 1946 4 Sheets-Sheet l INVENTOR hL'Zip flandelman a} ,4

' ATTORNEYS June 26, 1951 Filed March 7, 1946 P. HANDELMAN ADJUSTABLE LIMIT SWITCH MEANS 4 Sheets-Sheet 2 Philip flandelman INVENTOR ATTORNEYS June 26, 1951 P. HANDELMAN ADJUSTABLE LIMIT SWITCH'MEANS' 4 Sheets-Sheet 3 Filed March 7, 1946 Fig INVENTOR P72 ilip Handelman ,WM ATTORNEYS P. HANDELMAN 2,558 517 ADJUSTABLE LIMiT SWITCH MEANS June 26, 1951 4 She'ets-Shet 4 Filed March '7, 1946 INVENTQR [it Handelmcuz ATTORNEYS Patented June 26, 1951 UNITED STATES PATENT OFFICE ADJUSTABLE LIMIT SWITCH MEANS Philip Handelman, Pittsburgh, Pa., assignor to Reliance Steel Products Company, McKeesport, Pa., a corporation of Pennsylvania Application March 7, 1946, Serial No. 652,767

3 Claims. 1

This invention pertains to an adjustable limit switch means and, more particularly, to means which can be readily adjusted so as to control the opening or closing of limit switches and thereby limit the travel of a controlled object such as an open hearth damper type reversing valve or any other object whose travel is to be controlled.

In many industrial operations such as, for example, in open hearth furnace operations, it may be desirable to operate a valve, which controls the egress of waste gases to the stack, or in other words, controls the stack draft for certain periods of time. This is accomplished by varying the lift of a valve thusdiminishing and increasing the valve opening. These valves are usually operated by electric motors controlled by suitable pushbuttons. One pushbutton is operated to open the valve and the other to close it. In attempting to uniformly control the degree of opening solely by pushbutton, the matter of judgement on the part of the operator plays an important part and in many cases of misjudgement of an inexperienced operator, unsatisfactory operation of the furnace may be obtained thus causing a considerable loss of fuel and the possible spoiling of the material in the furnace.

An object of my invention, therefore, is to provide a novel adjustable limit switch means that will cause automatic limit switching and thereby avoid the above-named disadvantages inherent in many presently known control sys terns for controlling valves in furnaces and the like.

A further object of my invention is to provide a limit switch means including a pair of rotatable clutch members, one of which members is coupled to and is driven by an object Whose motion is to be controlled, and wherein switching means are operated upon predetermined rotary movement of such member.

A more specific object of my invention is to provide a uniform, foolproof device which can be easily adjusted so as to secure different limits of movement of an element to be controlled, such as a motor actuated valve or the like.

Other objects and advantages will become apparent from a study of the following specification taken with the accompanying drawings in which:

Figure l is a top plan view of an adjustable limit switch means embodying the principles of my invention;

Figure 2 is a cross-sectional view taken along line II-II of Figure 1;

Figure 3 is a cross-sectional view taken along line III-III of Figure 2;

Figure 4 is a front elevational View of the device shown in Figure 1, and

Figure 5 is an enlarged front elevational view of the dials shown in Figures 1, 2 and 4.

Referring more particularly to Figures 1 and 2, numeral 2 denotes a supporting structure carrying a fixed sleeve 3 having a longitudinal bore. A hollow shaft or sleeve 4 has a portion of reduced diameter which extends through sleeve 3 and forms a telescopic fit therewith, or more strictly speaking, forms a telescopic fit with a hollow sleeve I therebetween. A drum 5 is keyed to the shaft 3 and has a cable 20 wound therearound, one end of the cable being fastened to main cable drum at (Figure 2) and one end being fastened to small counterweight 2|. A main cable IE0 is Wound around the main cable drum and one end of the cable is connected to an object whose motion is to be controlled, such as, for example, a valve 22 (see Figures 2 and 4) so that when the valve is being opened, the drum is driven or rotated in one direction and when the valve is being closed, the drum 5 is driven or rotated in the opposite direction by the small counterweight 2|. Main cable Hill, in this case, also has a counterweight lill attached to its free end so that the movement of the valve will be always resisted by the weight.

Adjacent to the periphery of drum 5 is integrally secured a cam or finger 6. The end face of the sleeve is knurled or serrated at 7. An end plate or switch actuator carrier 8 has a face which is also knurled or serrated and which is adapted to engage the knurled surface I to form a friction clutch. Plate 8 is keyed to an operating shaft [2. Plate 8 has an integral arm ID to which is rigidly fastened a cam or finger H. The operating shaft it which slidably and rotatably passes through an adjusting nut 15, compression spring I4, sleeve 21 to which it is keyed and through handle l3 to which it is keyed where operating shaft i2 ends. The compression helical spring M has one end which bears against the adjusting nut l5 which is screwed into hollow shaft 4 and the other end bears against the shoulder l6 of a sleeve 21, thereby tending to urge the shaft [2 toward the left, as viewed in Figure 2, to hold the knurled surfaces in frictional contact so that the arm It] will be driven by and revolve with the drum. After the adjusting nut is screwed so as to obtain the desired tension on spring [4, it may be locked in place by pin [8.

By manually grasping handle [3 and moving it to the right as viewed in Figure 2, the clutch face of plate 8 is moved away from the knurled surface so as to allow arm In to be rotated relative to drum 5 by the mere turning of handle 13. After handle I3 is turned so that plate 8 is rotated to the desired angular position with respect to shaft 4, the handle is released, thereby allowing Spring [4 to cause the clutch surfaces to re-engage.

As will appear more clearly in Figures 1 and 4, two limit switches L and L are associated with the device. Limit switch L is operated by cam B on the drum 5, which cam engages a roller 23 forming part of the movable member of limit switch L and which when contacted with cam 6 trips the switch and opens the motor circuit when the valve reaches its closed position. The switch L is operated by the cam H on the rotating adjustable arm which cam serves to engage roller 24 secured to the movable element of limit switch L? and which serves to break the motor circuit when the valve is raised to a predetermined extent.

Suitable dials

25 and 26 are disposed on the front of the device and which indicate the zero or closed position of the valve and the setting at which arm H will engage the switch L to limit the opening movement of the valve. On large valves, the to indicate the number of inches that the valve opens.

The legends appearing on Figure 5 denote the various positions at which the valve starts to lift, or begins to open, or is fully open.

In operation, it may be assumed that the inner dial 26 is set at zero and that the outer dial 25 is set at zero when the valve is closed. In this position, cams or fingers H and 6 would be at the same relative position with no angular separation therebetween. Assume that the valve is to be opened 30 inches. The handle I3 is depressed and turned in a counter-clockwise direction along the inner calibration to the position 30 and then released. The cam or finger I I would then be angularly displaced from the cam or finger 6 a distance equal to the angular separation between the zero and numeral 36 positions. Similarly, if it is desired to operate the valve so as to cause greater or less opening thereof, handle i3 is depressed and turned an angular distance corresponding with the desired degree of opening of the valve.

Any well-known electric motor circuit controlled by pushbuttons, for example, for driving valve stem 22 in either direction, may be used, hence, illustration of such circuit is deemed unnecessary. Suffice to say that when the pushbutton is operated, the cam 6 will move away from switch L while cam II, turning with the drum, will also be carried around. Because it is angularly offset with respect to cam B, it will start to move toward its switch L When the valve opens 30 inches or to any other degree, depending upon the relative preset positioning of ials may be calibrated in inches shaft 4 and plate 8, the drum 5 will rotate to a position where cam ll contacts switch L to open the motor circuit and stop the raising of the valve. Upon pushing the valve-closing pushbutton, the drum 5 will rotate in the opposite direction until cam 6 operates the switch L at the closing position. The closing position is always the same, hence cam 6 is definitely fixed in its position with respect to drum 5, but arm I0 is angularly adjustable with respect to it.

It should be noted that while the above-described device, for purposes of illustration, is shown as being associated with a valve stem, it will be apparent to those skilled in the art that objects other than valves or valve stems may cause rotation of the drum so that movement of other such objects in one direction 01' an opposite direction may be similarly controlled by the limit switches. The limit switching means described above is particularly suitable for controlling the movements of objects traveling through appreciable distances.

Thus it will be seen that I have provided an efficient, compact and easily adjustable limit switch means for adjustably controlling or limiting the movement of valves and other similar objects. While I have illustrated and described a specific embodiment of my invention, it will be understood that this is merely by way of illustration and that various changes and modifications may be made within the contemplation of my invention and within the scope of the following claims.

I claim:

1. In an adjustable limit switch operating device, the arrangement including a cylindrical rotatable member having an axially extending bore, an adjusting nut received in said bore and having a threaded connection with said rotatable member, a first clutch element secured to an end surface of said rotatable member and at a right angle to the longitudinal axis of the bore, a rotatable shaft extending through said bore and adjusting nut and slidable axially therein, a second clutch element secured to one end of the shaft, a handle rigidly secured to the shaft, a sleeve providing a shoulder fixedly surrounding a portion of the length of the shaft and receivable in the bore, a helical spring within the bore and surrounding the shaft between the shoulder and the nut for biasing the second clutch element into engagement with the first clutch element whereby axial movement of the shaft by manipulation of the handle will compress said spring and separate the clutch elements.

2. In an adjustable limit switch operating device, the arrangement including a cylindrical rotatable member having an axially extending bore, an adjusting nut in said bore and having a threaded connection with said rotatable member, a first clutch face forming a part of the said rotatable member adjacent the bore, a rotatable and axially movable shaft extending through said bore and adjusting nut, a second clutch face secured to the shaft and facing the first clutch face, an annular shoulder fixed around the shaft, a helical spring around the shaft and extending between the shoulder and the nut for biasing the clutch faces into engagement with each other.

3. A device of the class described including a rotatable member having a centrally disposed axially extending bore, a serrated portion at the end face of the member and around the bore, a rotatable shaft extending through the bore and 5. slidable therein, a switch actuator element secured to one end of the shaft and having a serrated surface oppositely disposed relative to the serrated portion, a shoulder on said shaft, an adjusting nut having a threaded connection to said member at one end of the bore, said nut having an opening through which said shaft extends and in which it is rotatable and axially slidable, the end of the nut and the end of the shoulder defining the ends of an annular space between the shaft and the bore, a helical spring in said space and bearing against the shoulder and against the nut, said spring serving to urge the serrated portion and the serrated face into clutching engagement, and when said shaft is moved axially against the spring the serrated portion and the serrated face will be separated.

PHILIP HANDELMAN.

REFERENCES on'Efi The following references are of record in the file of this patent:

UNITED STATES PATENTS