Rope hoist with an emergency braking arrangement
A cable hoist having an emergency braking arrangement comprising a dual toothed wheel assembly driven via a cable drum of the hoist. One of two toothed wheels of the toothed wheel assembly is sensed by a sensing lever of an anchor and an opposite end of the anchor interacts with a ratchet wheel of the toothed wheel assembly. As soon as an over speed occurs, the anchor engages in the ratchet wheel and causes a rotary movement of a carrier on which the anchor is mounted. This rotary motion is used to trigger a mechanical braking arrangement coupled to the cable drum.
1. A cable hoist comprising:
a rotatably supported cable drum;
a drive for rotating the cable drum;
a braking arrangement for braking rotary movement of the cable drum, said braking arrangement including a triggering mechanism and a control device;
said control device including a toothed wheel assembly supported on an axle rotatably driven by rotation of the cable drum, said tooth wheel assembly including a driving wheel having radial extensions and a ratchet wheel having teeth;
an anchor carrier support on said axle for pivotal movement;
an anchor supported on said anchor carrier having a pawl at one end for interacting with the ratchet wheel and a sensing member at an opposite end for interacting with the driving wheel; and
a clutch assembly arranged between the anchor carrier and the triggering mechanism for transmitting a pivoting notion of the anchor carrier to the triggering mechanism.
2. The cable hoist of claim 1 in which said driving wheel has a polygonal outside circumferential form.
3. The cable hoist of claim 1 in which said clinch assembly is a slip friction clutch assembly operatively arranged between said driving wheel and said cable drum.
4. The cable hoist of claim 1 including a belt assembly for driving the driving wheel, said belt assembly comprising a pulley non-rotatably coupled to the cable drum and a belt for driving the driving wheel as an incident to rotation of the pulley.
5. The cable hoist of claim 4 in which said belt assembly rotates the driving wheel at a greater rotational speed than the rotational speed of the cable drum.
6. The cable hoist of claim 4 , including a belt tensioning arrangement associated with the belt.
7. The cable hoist of claim 1 in which said anchor has an associated spring that biases the anchor in a position in which the pawl of the anchor is out of engagement with the ratchet wheel.
8. The cable hoist of claim 7 in which said spring and anchor interact such that during rotation of the cable drum the anchor follows a contour of the driving wheel without over lifting.
9. The cable hoist of claim 1 in which said sensing member includes a sensing roller rotatably supported on the anchor.
10. The cable hoist of claim 1 in which during rotational speed of the cable drum, the anchor remains in engagement with the driving wheel.
11. The cable hoist of claim 1 in which the clutch assembly includes a Bowden cable.
12. The cable hoist of claim 1 in which the braking arrangement includes a brake drum non-rotatably coupled to the cable drum, and said brake drum including at least one brake shoe.
13. The cable hoist of claim 12 in which the braking arrangement includes a detent device for locking the at least one brake shoe in place.