US2254910A - Safety hoist - Google Patents

Description

atenfted Sept. 2, 194i ai" r I,'erica SAFETY HOIST .lohn W. Richards, Davenport, Iowa, and CyrilV.

.Tcndream Rock Island, Ill.

Application December 17, 1938, Serial No. 246,296

7fClaims. (Cl. 2511-175) mechanism for use with hoists to support the '1 f load on the hoist in cases of breakage of the hoist cable.

Under the present system of daily inspection of hoisting apparatus in large factories, including inspection of the hoisting cable, it would be expected that instances of cable breakage would be extremely rare. Surprisingly, the -fact is that -cable breakage is quite common. This is due to a number of causes, one of which is the fact that the men pull the hoist hook to the load so that the cable is out of line with the cable channel on the hoist drum, and the cable will then jump into the adjacent turn of the channel. When load is placed on such a misplaced cable, breakage often occurs. -Failure is also caused by a number of other factors.

It is accordingly an object of our invention to provide a hoist which involves an auxiliary cable to support the load in case of failure of the main cable, and operative only in case of breakage of the main cable. A further object is to provide a safety device which may be employed with .a conventional hoist to support the load in case of hoist failure. A yet further object is to provide a safety device of the above character which, when a new cable is inserted for a broken hoist cable, releases automatically upon operation of the hoist.

Other objects and advantages will be apparent from a consideration of the following description taken in conjunction with the accompanying drawing in which:

Fig. l is an elevation of a hoist provided with the safety mechanism of the present invention;

Fig. 2 is a section of the safetymechanismy substantially on the line 2-2 inFig. l; and

Fig. 3 is a section substantially on the line 3-3 in Fig. 2.

The particularhoist shown is of the type involving a traveling carriage. It kshould initially be understood that the specic hoist ldisclosed is employed for exemplication only and that this invention is applicable to anyhoist having a load-supporting cable, chain, or the like, even including the hoists involved in `so-called building elevators. For purposes of brevity in this description, the term hoist `is applied to any hoist involving a load-supporting cable, and

ber of the character of a rope, stranded cable, chain, or the like. y

The hoist shown involves a set of wheels 4 pivotally ,mounted in the-hoist frame plates 5, which-wheelsare `po'sitiroried to roll on flanges of the .beam 6. A shaft l `carried by the plates 5 rotatably supports the hoist drum 8 upon which cable 9 is arranged to be wound. This support il is secured tothe cable 9. Thus, as shown, the support Il may -comprise a block in which i sheave `lili is pivoted, the support being secured to thecableby having the cable pass-ed around the sheave.

-A casing I-li is secured as by the bolts l5 be,- tween the plates 5, and is provided therein with a drum i6 which is keyed to shaft il. A gear 8, alsovkeyed to shaft Il, meshes with a gear i9 rotatably mounted on stub shaft 2K0 fixed in the casing. A helical spring 42l has its inner end secured non-rotatably with respect `to the casing as lby beingrsecured to the stub shaft, and

has its outer end secured to a pin 22 on the gear I9. Y

A cable 23 which is anchored on the drum I6 extendsthroughY an opening-Min the lower portion of the casing l5. The cable 23 is in supporting engagement with the support Il as-by having a hook 2,5 provided at the terminus4 of the cable, which hook interconnects with the link. The cable 23 is wound on the drum in such a ldirection that, when the cable'is pulled,

to actuate the lock into operative position and the term cable. is applied to any flexible memprevent unwinding of the drum. AThe lock may comprise a ratchet-2S for rotation nunison with drum i6 and a -pawl 2l pivotally mounted on thepin28 and DQSiton-ed to engage ratchet A2li and prevent unwndng of the drum against the action of the Winding spring. -Spring 29 is in engagement with the pawl .and with the casing and is arranged to bias the pawl into engagement with theratchet. yHolding rod 30 is pivoted at one end to the pawl and extends through the casing into engagement with the hoist cable, the cable, through the rod 3S, holding. the `pawl out of engagement with t'he ratchet. As shown, `the rod 36 is provided with a bifurcated yend for receivingthe `cable which tends to move the rod axially.

In operation with thehoist assembled as above described, the block may vloeraised or lowered byturning hoist drum ..8 by conventional structure not shown. The spring 29 is of such strength that the weight of the block and of the cable 9 is suicient that the cable holds the pawl out of engagement with the ratchet by pressing against the rod 30. As the block is lowered, the cable 23 is unwound from the drum I6 against the action of the spring 2l, which spring is of a strength sufficient to lift the cable 23 but insufficient to lift also the block. When the hoist is raised, the spring 2|, through the gears I8 and I9 and the shaft I1, rotates the drum I6 to raise the cable 23 in accordance with movement of the block.

In case of failure of hoist cable 9, the rod 30 is allowed to move by the spring 29, which allows the pawl 21 to move into the path of the ratchet 2S. The drum It is thereby prevented by being locked from turning, and the cable 23 supports the load. A new cable may be substituted for the cable 9 and, when the hoist is Wound up sufficiently to take the load `on the new cable instead of on auxiliary cable 23, the new cable presses the rod 30 to unlocked position.

It Should be understood that our invention is not limited to the form of the invention disclosed in the drawing, .but that considerable latitude in the embodiment is possible within the scope hereof.

Having now described our invention, claim:

l. A safety device, for use with hoists which employ a lifting cable and a load-supporting device, comprising a drum mounted for rotation, a safety cable adapted to be wound on and unwound from said drum upon rotation thereof, said safety cable being free from any driving connection with the winding mechanism for the lifting cable and arranged to be secured to the supporting device of the hoist, spring means tending to rotate said drum in a direction to wind up the safety cable, the torque on said drum caused by said spring means being sufficient to wind up said safety cable but insufficient to lift said supporting device, whereby, when no load is attached to the supporting device, it may be lowered against the action of the spring means to the load, and means responsive to breakage of the hoist cable for preventing rotation of said safety drum in lowering direction.

2. A safety device, for use with hoists which employ a hoist cable and a load-supporting device, comprising a drum mounted for rotation, a safety cable adapted to be wound on and unwound from said drum upon rotation thereof, and safety cable being arranged to be secured to the supporting device of the hoist, means independent of the hoist operating means tending to rotate said drum in a direction to wind up the safety cable and allowing unwinding upon lowering of the supporting device, locking means to lock said drum against rotation when the load is unsupported by the hoist cable whereby to prevent dropping of the load, and means normally bearing against the hoist cable for actuating the locking means into nonlocking position when the hoist cable is unbroken.

3. A hoist comprising a hoist cable, a hoist drum'upon which the hoist cable is wound and unwound upon rotation of the hoist drum, supporting means secured on said hoist cable for attachment to a load and for movement with said cable, a safety drum rotatably mounted on an axis fixed with respect to the axis of the hoist drum, a safety cable arranged to be Wound upon and unwound from said safety drum, said supporting means being connected to said safety cable, spring means operatively connected to said safety drum tending to rotate said safety drum in a direction to wind up the safety cable, the torque on the drum caused by said spring means being sucient to wind up the safety cable but insuiiicient to lift said supporting device, whereby, when no load is attached to the supporting means, it may be lowered against the action of the spring means to a load, and means associated with the safety drum and hoist cable and responsive to breakage of said hoist cable to prevent rotation of said safety drum in lowering direction.

4. A hoist comprising a hoist cable, a hoist drum upon which the hoist cable is wound and from which it is unwound upon rotation of the hoist drum, a supporting device to which the hoist cable is secured, a safety cable connected thereto, a safety drum upon which said safety cable is wound and unwound upon rotation of the safety drum, spring means connected operatively to and acting to rotate the safety drum and keep the safety cable taut, the tension on said safety cable produced by the spring means being insuflicient to lift said supporting device, whereby, when no load is attached to the s'up- Y porting device, it may be lowered against the action of the spring means to the load, and means responsive to breakage of the hoist cable for preventing rotation of the safety drum and thereby preventing dropping of the load, the load acting, when being lowered, to rotate the safety drum and tighten the spring means, and the spring means acting to wind the safety cable on the safety drum when the tension on the safety cable is reduced by raising the load.

5. A mechanism of the character described comprising, in combination, a hoisting drum, a hoisting cable connected thereto and to a load to be lifted, a second drum connected to the hoisting drum by common supporting means, a second cable connected thereto and to said load, a ratchet rigidly connected to the second drum and rotating therewith, a latch for preventing rotation of said ratchet, actuating means for said latch directly connected to said latch and normally engaging the hoisting cable when the load is supported thereby and holding the latch out of engagement with the ratchet, actuating means for the latch to cause it to engage the ratchet and prevent retrograde rotation of the second drum if the first cable fails to support the load, and means connected to the second drum and operative to cause the second drum to rotate when the load is being lifted whereby to insure that the second cable will not be permitted to become slack.

6. A structure as dened by claim 5 in which said operative means comprises a spring, the tension of which is increased when the load is lowered, and a multiplying gearing connecting the spring and the second drum for causing a greater take-up of cable on the second drum for a given expansion of the spring than if the force of the A rotatably mounted in said frame, a hoist cable having one end anchored to said frame and the other end secured to said drum to be wound thereon, a load-supporting device secured to said cable and movable therealong between the an-` chored end and the drum, a safety drum robearing against the hoist cable between the anchored end and the supporting device; normally permittingrotation of said safety drum whenjza load is supported by the hoist cable and movable With said stop means when the latter is moved into operative position upon breakage of said hoist cable.

JOHN W. RICHARDS.

CYRIL V. TONDREAU.

Images