Traction Device

Abstract

The self-reeving tractive device is usable as a hoist, capstan or winch. The drum rotates within a housing having a helical groove on the inside cooperating with the drum to confine the (wire) rope to the groove. A pinch roller projects through the housing to squeeze or hold the rope against the drum. When the rope end is introduced through an opening at one end of the drum, the roller grips the rope in cooperation with the drum to force the rope to feed into the groove. With each complete wrap on the drum, the roller again grips the rope so it is continually forced along the groove. The rope leaves the drum at the other end of the drum and passes through an opening in the housing. Another roller, spring pressed, acts on the rope to keep tension on the tail to prevent relaxing of the rope with consequent loss of frictional engagement with the drum. For practical purposes, the drum is totally enclosed and the risk of getting "caught" in the wraps is minimal.

Description

BACKGROUND OF THE INVENTION

In traction devices of the general type disclosed herein, the matter of winding wire rope on the drum has been somewhat of a problem and has frequently been a rather complex affair permitting mistakes to be made and frequently allowing the rope to spring from the drum if tension was relieved. This, in turn, gave rise to the possibility of overwraps and the like, all impairing efficient use of the equipment. Furthermore, the rope was exposed so as to give rise to the risk of getting clothing or one's hand caught in the rope.

SUMMARY OF THE INVENTION

This invention is directed to simplification of the reeving of a traction device and to provision of a traction device which maintains the rope wound on the drum in proper position whether or not tension is maintained on the working line. Furthermore, the present arrangement is virtually snag proof in that the rope on the drum is, for all practical purposes, totally enclosed.

By providing an internal helical groove in the housing surrounding the drum and forcing the rope to follow the groove so that it is wrapped around and fed along the drum, the arrangement becomes self-reeving. A pinch roller cooperating with the drum and having the same surface speed as the drum acts to force the rope into the groove and keep it properly tensioned on the drum. A tailing roller applies a final pinch to the tail preventing that end from going slack and permitting the slack to feed back through the rope so as to lose the grip on the drum.

In the past various drums have been proposed having grooves in the drum surface. This does not accomplish what is accomplished here by way of self-reeving.

Since the rope is confined between the drum and the groove and there is obviously friction between the rope and the groove, the power to turn the drum is greater than in an ordinary winch arrangement. This is considered more than offset by the simple foolproof operation permitted by this design.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly exploded, perspective view with parts broken away to show the manner in which the wire rope is wrapped on the drum.

FIG. 2 is a longitudinal, horizontal section through the housing with the drum and pinch roller not sectioned.

FIG. 3 is a vertical cross section through the traction device at the end from which the rope exits.

FIG. 4 is a vertical section through the traction device at the end of which the rope is fed to be wrapped on the drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The traction drive drum 10 is contained within housing 12 including cylindrical section 14 and end plates 16,18. The drum is journaled in the end plates in bearings 20,22 and is driven by the motor (electric, hydraulic or, for that matter, a hand drive) through shaft 26. Gear 28 on shaft 26 drives gear 30 on jackshaft 32. The pinch roller 34 is fixed on the jackshaft and the roller assembly is journaled in bearings 36,38 in the housing end plates 16,18. The mean radius of gear 28 corresponds to the drum radius plus approximately half the thickness of wire rope 48. The mean radius of gear 30 corresponds to the radius of pinch roller 34 plus half the rope diameter and thus, due to the gear drive, the roller and drum will rotate at the same peripheral speed to smoothly pick up and drive the rope between the drum and roller. Theoretically, the roller would not have to be driven but it is deemed advantageous to drive both the drum and roller so as to maximize the force applied to the wire rope. The housing is extended by means of a further housing member 40 to enclose the motor and gearing. The drum can be provided with longitudinal striations 42 or have a roughened surface to increase the grip of the drum on the wire rope.

The inside of the cylindrical portion 14 of housing 12 is provided with a helical groove 44 which starts in alignment with the aperture in rope guide 46. When the rope is inserted through the guide, the end is picked up between the rotating drum and the pinch roller and forced into the helical groove and thus is wrapped on and fed along the drum. After each complete revolution the end will again pass between the pinch roller and drum to be re-engaged thereby so the drive force is maintained on the rope to force it through the helical groove. Close to the end of the helical groove, the housing is apertured to permit the tailing roller 50 to engage the rope and hold it firmly against the drum by reason of compressed spring 54 acting on the plunger 52 supporting the tailing roller. The end of the rope then is automatically fed through the aperture 56 and leaves the traction device. With tension on rope 48 in the direction of the arrow in FIGS. 1, 3, and 4, there could be, notwithstanding the action of the pinch roller, some tendency for the line to slip on the drum but with the roller 50 acting on the line at the tail, this tendency is eliminated and a considerable load can be carried on the line due to the frictional engagement of the wraps on the drum.

The action of the tailing roller is interesting. The spring force is applied through the roller to the rope on a line which would fall below the center of the drum in FIG. 3. This develops a force component tangential to the drum pointing towards the tail . . . . . i.e., resisting run-out of the line. The tailing force thus obtained is adequate to resist pulling line from the drum. This tailing force would not be obtained if the roller applied the spring force radially.

This construction provides automatic reeving of the rope while preventing overriding of the wraps. The rope is fully enclosed to reduce danger of getting one's hand or clothing caught. The proper number of wraps must be used, thus insuring safe operating conditions.

The pinch roller is made of resilient urethane which will give an effective spring loading to the engagement of the roller on the rope. Deformation of the roller also obtains a good "grip" on the rope strands. If desired, the pinch roller could be spring loaded but this is not considered necessary.

Claims

I claim:

1. A traction device comprising:

a drum having a generally cylindrical surface,

means for rotating the drum in either direction,

a generally cylindrical housing enclosing the drum and having an internal helical groove positioned close enough to the drum so as to engage and confine therein a rope wound directly on said drum surface whereby the rope must follow the groove and is, therefore, forced axially over said surface,

an aperture in one end of the housing in alignment with the corresponding end of the helical groove to permit rope to be entered into the groove and fed around the drum following the groove,

an aperture in the other end of the housing in alignment with the other end of the helical groove to permit egress of the rope from the housing.

2. A device according to claim 1 including a pinch roller projecting through the housing and fixed in position close enough to the drum so as to grip the rope between the pinch roller and the drum.

3. A device according to claim 2 in which the pinch roller axis is parallel to the axis of the drum and has an axial length generally corresponding to that of the drum whereby the pinch roller engages the rope along the length of the drum.

4. A device according to claim 3 including means driving the pinch roller at the same peripheral speed as the drum.

5. A device according to claim 2 including a roller projecting through the housing in proximity to the point where the rope egresses from the housing to engage the rope adjacent the point of egress and hold it firmly against the drum.

6. A device according to claim 5 including means driving the pinch roller at the same peripheral speed as the drum.

7. A device according to claim 6 in which the pinch roller axis is parallel to the axis of the drum and has an axial length generally corresponding to that of the drum whereby the pinch roller engages the rope along the length of the drum.