Safety device for hoisting mechanisms.

Application filed July 10,1905. Serial No. 268,924.

To all whom It may concern:

Be it known that we, John M. Rohlfing and Peter D. Horton, citizens of the United States, residing at Alliance, in the county of Stark and State of Ohio, have invented certain.new and useful Improvements in Safety Devices for Hoisting Mechanisms, of which the following is a specification.

The invention to be hereinafter described relates to safety devices for hoisting mechanism, and more particularly to means for preventing overwinding of the hoist chains or cables, the object being to provide means for controlling or stopping the main hoistmotor when the hoisting limit has been reached, thus preventing injury to the apparatus and possible danger to the workmen that would necessarily result from overwinding of the main hoist chains or cables.

With the above generally-stated objects in view the present invention consists of a winding-drum having means to be engaged by the hoist chain or cable when the limit of hoist has been reached and devices actuated by such means for controlling or stopping the main hoist-motor; and the invention further consists of the parts and combinations, to be hereinafter described, and definitely pointed out in the claims.

As one embodiment of the present invention we have selected for illustration and description a form of electric traveling crane, wherein a trolley carrying the winding-drum is mounted to travel upon overhead tracks or supports and wherein also the drum may be actuated by any desirable form of electric motor; but we desire it to be distinctly understood that we do not regard the invention as circumscribed by such details or the character of motor employed, or the fact that the motor be mechanical or electric, or whether the controlling devices be in the form of an electric switch or merely mechanical connections to the prime mover, whereby the latter may be controlled or' stopped when the hoist limit has been reached. All such detailed substitutions are within the selective province of the mechanic skilled in this art, and any such variations may be made within the sphere of the present invention, as will be well understood. Therefore in the following description and claims when the term “motor” is employed it is to be understood as unrestricted to either an electric or mechanical motor unless the context is such as to require the one or the other.

In the drawings, which illustrate one of the many forms the invention may assume, Figure 1 is an enlarged detail view showing a winding-drum, parts being broken away and 6o others in section, and also portions of a trolley-frame or drum-support. Fig. 2 is a detail cross-section on line 2 2, Fig. 1, showing one form of switch and electric circuits that may be employed. Fig. 3 is a diagrammatic 65 view of an electric circuit or wiring that may be used in connection with an electric motor. Fig. 4 is a similar view showing the position of the switch in making the short circuit. Fig. 5 is a diagrammatic view of a simple 70 form of short-circuiting device to throw out the circuit-breaker, as will hereinafter appear.

Referring to the drawings, A represents a winding-drum of any usual or preferred char- 75 acter and which may be actuated from any suitable source of power fully understood by those skilled in the art. In the present embodiment of the invention the drum A, as shown on Figs. 3 and 4, is illustrated as driven 80 from an electric motor. As the drum A is rotated one way or the other by the motor it winds upon itself or unwinds the hoist chain or cable B, such chain or cable being preferably wound upon the drum progressively 85 from its ends inward toward the center and resting in suitable grooves b of the drum.

Mounted upon the winding-drum A, preferably, though not necessarily, within a recessed portion A', is the mechanism for actu- 90 ating the switch or other device and which for identification may be referred to as the “controller-trip.” This mechanism comprises a rocking lever a, having its fulcrum between its ends, as shown, and bearing upon an end 95 of the rocking lever a is the trip-pin V, which has a cylindrical portion b², adapted to slide in a suitable bushing or guideway b³ and being limited in its outward sliding movement bymeans of a collar b^l. The trip-pin b' has at its 100 outer end a seat δ⁵, adapted to receive the hoist chain or cable B as the latter is wound about the drum and reaches the limit of hoist.

Mounted in an adjacent portion of the recess A⁷ of the drum is the trip-pawl c, having 105 a pin c' extending downward through a suitable bushing or guideway c². At its lower end the pin d is preferably screw-threaded and supplied with a nut c³, between which and the bottom of the bushing or guideway c³ no is interposed the expansible spring c⁴. Obviously the expansive force of the spring c⁴

813,451 may be readily adjusted by means of the nut c³ so that the normal action thereof is to depress the trip-pawl c, lower the left-hand end of the rocking lever a, and maintain the trippin b' raised, with its seated end b⁵ projected beyond the surface of the drum A.

From the construction thus far described it will be noted that the parts of this controller-trip normally rest with the trip-pawl c retracted by means of the spring c⁴ and the trip-pin V projected, so that should the winding-drum be rotated to the hoist limit the chain or cable B will wind about the drum until it reaches the projecting end of the trippin, whereupon it will force the trip-pin b' inward against the action of the spring c⁴, and simultaneously therewith the trip-pawl c will be projected. Obviously should an arm, linger, or rod be placed in position to be struck by the trip - pawl c when the latter is thus projected and the drum revolved and should such arm, finger, or rod be connected to the prime or hoist motor the latter can be controlled and stopped, and thus overwinding, with its liability of breakage and danger, be avoided.

In devising means to cooperate with the trip-pawl substantially in the manner outlined we have employed as a convenient actuating means for the hoist an electric motor, although, of course, the invention is not restricted thereto, and we provide a stopping means for such motor in the form of a limitswitch, one type of which is shown in Fig. 2, wherein D is a lever pivoted to the switchboard D' at d, Figs. 1 and 2, said lever being preferably adjustable in length by means of the binding-screw or thumb-nut d' and the slotted overlapping parts of the lever-arm, and said switchboard being suitably supported in proximity to the drum A by means of suitable brackets D², which may be secured to a trolley-frame D³. The switchboard D' has the contacts e e! e² e³ in connection with the field-circuit, as shown, and contacts e⁴, e⁵, and of the main circuit. Pivoted at e⁴ and e⁵ are the parallel knife-contacts E and E', connected to each other and to the lever D by means of the adjustable insulating-strip E², so that the trip-pawl c by engagement with the lower end of lever D and rotation of the drum throws the switch from one position to another, short-circuiting the armature, and thereby throwing the circuit-breaker· and stopping the motor.

Referring to Figs. 3 and 4 for a more detailed view of the wiring and circuits employed in connection with a form of limitswitch, it is noted that F represents the triplever pivoted at/and connected at its upper end by the strip F³ to the two parallel knifecontacts F' F², whereby as the trip-lever F is swung by means of the trip-pawl c the said knife-contacts are moved from the position indicated in Fig. 3 where, the armature is in circuit, as shown by the arrows, to the position indicated in Fig. 4, where the armature is short-circuited, and the circuit-breaker actuated, as indicated by the arrows in said Fig. 4. Said Figs. 3 and 4 illustrate the 70 switch in a slightly different form from what is shown in Fig. 2; but the action of the two is substantially the same, 4 4 representing the fields, 5 the armature, 6 the switch or trolley, 7 the controller, suitably located, as 75 in the cage of the crane, and 8 the circuitbreaker.

As further showing the variations that may be made in the form and embodiment of the present invention, Fig. 5 indicates dia- 80 grammatically a main line and circuit-breaker terminating in the contacts m m', disposed in proximity with the trip-pawl of the drum. In this modification it is simply necessary, as shown in Fig. 5, to form the head of the trip- 85 pawl of insulating material c¹⁰ and on top of the same secure a metal or like contact c¹¹, which when the trip-pawl is projected in the manner already described will wipe over the two contacts m m' and short-circuit the sys- 90 tern, thereby throwing out the circuit-breaker, which maybe located in the cage of the crane.

While we have shown the winding-drum A applied to an electric crane and carried by the framing of the trolley, it is to be understood 95 that the invention is not restricted as to these matters, the only essential being that the controller - trip carried by the drum shall have disposed near it, wherever its location, the instrumentalities for acting upon the motor 100 to stop the same when the limit of hoist has been reached, or, on the other hand, when the limit in either direction has been reached. While we have also described several forms of electric circuits in connection with an electric 105 motor for actuating the drum and a particular form of switch for stopping the motor, yet it is to be understood that our invention is not limited to these particulars, as instead of the forms of electric circuits indicated other no forms might be employed. Indeed, as hereinbefore pointed out, an electric circuit and motor are not at all essential, this form of the invention being selected merely as a matter of illustration. 115