US1236485A - Safety-limit switch. - Google Patents

Description

F. A. BUNDLE. SAFETY LIMIT SWITCH.

APPLICATION FILED DEC. 27| 1915.

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SAFETY-LIMIT SWITCH.

Specication of Letters Patent.

Patented Aug. 14, 1917.

Application led December 27, 1915. Serial No. 68,834.

To all whom t may concern.' y

Be it known that I, FRED A. RUNDLE, a citizen of the United States, residing at Harvey, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Safety-Limit Switches, of which the following is a specification.

This invention is a safety limit switch applicable in general to machines of all kinds, but especially to hoisting mechanisms such as traveling cranes for cutting oil the electric current when the mechanism has reached the safetylimit in its path of travel in a given direction.

The object of the invention is to provide a device of this kind which can be operated by the moving mechanism without said moving mechanism coming to a too abrupt stop and one which automatically closes itself whenever the moving mechanism ofthe machine reverses its direction of motion and recedes from the danger position at whichit opened the switch.

The invention consists in a device which is capable of carrying out these objects, which can be easily and cheaply made and installed, which is satisfactory in operation and in one having the special features and details of construction hereafter more fully set forth.

In the drawings,

Figure 1 is a side,

Fig. 2 an end, and

Fig 3 a plan view of mechanism illustrating this invention in its preferred form.

The particular embodiment of' the machine here illustrated is applied to a lifting mechanism such as a traveling crane having a main frame 10. Rigidly attached to this frame 10 by any suitable means, such as the bolts 12, is a bracket 14, preferably overhanging the frame as shown, so that a Fig. 1.

jarod orshaft 18 provided with an elon gated n' slot 20 in which limit screw 22 lo depending llug bearing 16 integral with it may clear the frame, as clearly appears in Slidable through this bearing is cated in the bearing 16 enters to permit longitudinal movement of the rod 18 Yup and down between full line and dotted line position of Fig. 1 without it being possible to remove the rod 18 in either direction from the bearing 16 except, of course, by removing the bolt 22. On the lower end of rod 18 is a plate 24 adapted to be engaged by the pulleys 26 journaled in block 28 at 30. To

this block 28 is attached the usual load liftmg hook (not shown). Over the pulleys 26 passes the lifting rope or chain 29 Whose mlddle traverses equalizing pulley 31 mounted on frame 1() in the ordinary manner.

When the power lifting mechanism has raised the block 28 to the position of Fig. 1, the pulleys 26 strike the lower end of shaft 18 and plate 24 and any further movement of the pulleys 26 upward movesshaft 18 upward unt1l it finally reaches the dotted line `position of Fig. 1. When the block 28 and pulleys 26 begin to move downward, the weight of rod or shaft 18 carries it downward from the dotted line position until it finally reaches the full line position of Fig. 1. In Aother words, the rod or shaft 18 1s movable upward by the load during a certain period in the path of travel' of the load and it returns to normal position whenever the load is not in that portion of its path of travel.

Suitably located at one side of the central axis of the rod or shaft 18 and on the bracket 14 is a horizontal pivot or shaft 32 carrying a movable lever 34 adapted to swing in a vertical plane which includes the axis of shaft 18- and to normally lie in a position across the end of said shaft as clearly appears in Figs. 1 and 3. In fact, a lug or stop 36 is provided so that it cannot move entirely out of the path of travel of rod or shaft 18, as fully appears in the ydotted line position of Fig. 1. This lever 34 is, as clearly appears in Fig. 3, made' with an aperture 38 lying in the plane of the rod or shaft 18 of such a size and shape that, as clearly appears in dotted lines'of Fig. 1, the rod 18 may pass through and beyond lever 34, leaving said lever leaning against the rod the result being that as rod 18 is moved downward, gravity Will move lever 34 downward as soon as the upper end of rod 18 clears the notch 38. In the particular form of mechanism here illustrated, the aperture 38, as clearly appears in Figs. 2 and 3, takes the form of. an opening between the bifurcated ends 34a and 34b of the lever 34. The bifurcation of the lever is such as to permit rod 18 to be straddled by lever 34 interme- .latter are, of course, provided with suitable electric wires 50.

In the operation of the device, assume that A the parts are in the .positionof full lines in Fig. 1 .with the switch 40-46 closed, and that the load carrying block 28 is movingupward from the full. line position toward the dotted line, position. As the distance from pivot`32 to the center line of rod -18 vis less than the distance from saidv pivot 'to2 I the switch contacts '4Q-46v it will .beA

seen that it only'. takes a very slightmovement of the4 rod l-uplward to elevate lever 34 sufficiently to separate-.contacts 40 from contacts 46, -thus cutting off the cuient which propels the motorwhich is raising the block 28. If the momentum 0f the' load in moving upward is suiiicient to ca the block 28 beyond the point which thus opens the switch, block 28 and consequently the load is free to move upward until rod 18 vreaches the dotted line position of Fig. 1.

But in all positions after the switch has been opened, the lever 34 continues to bear.

against the rod 18 and is ready to, under the action of gravity, return .to normal position, thus insuring the supplying of .power current through the contacts 40-46 to the powerl operating mechanism just as soon as the load recedes from the danger position which caused the switch to open. It will thus be seen that the switch device o ens quickly and sharply as soon as the limit of safe movement of the load has been reached and that it .automatically closes as soon as 'the load recedes from the danger position.

By providing the notch or recess 38 in lever 34 it is possible to place the rod 18 close to pivot 32 of lever 34 thus securing a quick action of the switch, as heretoforeI described, and yet have the lever 34 always leanagainst the rod 18 at a sufficient angle so that gravity has a owerful iniiuence on the lever 34 to close t e switch in the manner described.

Spring 60 is provided for two purposes; to check the final movement of rod 18 and load following it as it reaches its upper position, thus avoiding injury to the trolley,

and 'to start the rod downward against any possible friction as soon as the load begins to move downward.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

. 1. In a device of the class described, an apertured operating lever and a reci rocatable member movable toward and rom said lever so located that in a portion of its path of travel it engages said lever to move it and during the remainder of its path of travel passes through the aperture in said lever but does not operate said lever.

2. In a device of the class described, an apertured operating lever so located that it it is movable in one direction by gravity, and a member reciprocatable toward said lever to first move it a given distance contrary to gravity and then pass through the aperture in the lever leaving the vlever supy ported byvsaid reciprocatable member, for the-purposes set forth.

3. In `mechanism of the class described,

--the combination with two opposite switch points to be connected anddisconnected, an

apertured levermember carryin at one end one of said'switch points and pivoted at its other end, and a reciprocatable member opei'atable by the machine controlled by the switch engaging said lever so* that as-said member is reciprocated in one directionit first moves said lever to open said switch and then passes through the aperture in the lever, for the purposes set forth.

4. Ina device of the class described, the combination with a suitable frame carrying a switch point, a member movably attached to the frame and carrying a second switch contact enga eable with the rst one, and a second mova le` member reciprocatable with reference to the frame but in a different -dii.

rection from the direction of movement of the first mentioned movable member adapted to, in moving, engagesaid rst mentioned movable member for a suiiicient length of time to separate said switch contact and thereafter, in its movement, move through an aperture in said first mentioned movable member, for the purposes set forth.

5, In a device of the class described, a bifurcated operating lever so located that it is movable in one direction by gravity, and a member reciprocatable toward said member `from the 'direction of movement of the first mentioned movable member adapted to, in moving, engage said first mentioned member for a suiicient length of time to operate said switch contacts and thereafter in its movement move through the bifurcation in the first mentioned movable member, for the purposes set forth.

7. A device of the class described, in combination with a fixed support and a pair of switch points, an operating lever pivoted to the support, bifurcated at its free end, switch points upon the respective bifurcated end parts of the lever engageable in one position with the switch points upon the fixed support, a reciprocatable member movable through the fixed support toward and from said lever so located that in a portion of its path of travel it engages said lever to move it to separate the switch points, and during the remainder of its path of travel passes between the bifurcated ends of the lever, said ends bein so proportioned that in this position the ever straddles the movable lever.

In witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

FRED A. RUNDLE.

Witnesses:

DWIGHT B. CHEEVER, SELINA E. HIGGINS.

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