This invention relates generally to mechanisms for guiding a rope being wound onto or unwound from a drum, and more particularly to a rope guide for guiding a rope being wound onto or unwound from a helical groove formed in the peripheral surface of the drum of a hoist, such as a wire, air, or electric hoist, and to a hoist provided with such a rope guide.

BRIEF DESCRIPTION OF THE PRIOR ART

A known rope guide for an electric hoist having a drum with a helical groove on it's peripheral surface has a threaded nut with a thread profile having the same profile and pitch as the helical groove of the drum of the hoist. The nut consists of three steel segments or shells filled internally with a lining which are joined together with the exception of the adjacent ends of the first and third segments which are connected together by a cleat provided with a slot through which the rope passes into the rope guide. The slot serves to guide the rope as it is wound onto or unwound from the drum. One end of the nut has an internal peripheral groove which receives a spring pressing member. The spring pressing member is tightly pressed against two adjacent turns of rope lying in the grooves of the hoisting drum. The rope-guiding slot is located between the nut thread and the spring pressing member and is positioned to coincide exactly with the drum groove. When the hoisting drum rotates, the nut does not rotate about it's axis, but is moved along the drum axis, pushing the spring pressing member with it. The spring pressing member rotates with the drum, and since it is pushed axially under the action of the nut, jumps over the adjacent turns of rope.

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The above type of rope guide is expensive to manufacture, and the machining of the internal thread in the nut segments is particularly costly. It has considerable dead weight, which decreases the capacity of the hoist. The efficiency of the hoist is reduced by the high sliding friction force, which is the sum of three forces due to; friction between the steel drum and nut thread, friction between the spring pressing member and the nut, and friction between the rope and spring pressing member when it moves axially along the drum. This type of rope guide also has a short service life due to the large radial dimension of the rope guide, and due to the side walls of the rope-guiding slot in the nut, through which the rope passes, being perpendicular to the drum axis. Because of these two factors, when the loaded rope deviates from a substantially vertical direction from the drum axis, a large bending moment acts on the radially outer edge of the slot, which can result in breakage of the nut sectors, or rapid wear of the slot and/or the rope. Finally, the large axial length of the rope guide (about 5 pitch length of the drum groove) requires that the hoisting drum is considerably longer than necessary to provide a given height of the load elevation.

Other rope guides and material handling arrangements are shown in; U.S. Patent 4,634,078 to Kaufmann et al, U.S. Patent 3,226,090 to Sauerbey, U.S. Patent 2,926,867 to Nardone, U.S. Patent 1,973,446 to Rosenquist, U.S. Patent 1,782,446 to Lang. UK Patent Application 2 061 861 to Storer, German Patent Offenlegungsschrift 1 756 614, and Norweigan Patent 108 153, also show various rope guides. However, none teach the combination of features working together as a whole in accordance with the present invention.

My German Patent Offenlegungsschrift 27 32 108 discloses a rope guide which utilizes steel shells that are filled internally with a lining made of plastics material ("Kunststoffmaterial") . Each of the linings is provided with seatings ("Sitzflachen") , for barrel-shaped rollers and

seatings for balls. The barrel-shaped rollers and balls rotate in their respective seatings formed in the plastic linings. Thus, the rollers and balls rotate in mating recesses or seatings in the plastic lining. One-half of the circumference of each ball and roller is pressed into contact with the mating plastic seating surface. It has been found that this arrangement results in a relatively large surface area which is subjected to sliding friction and impedes smooth rotation which causes loose loops to form in the rope as it is wound and unwound from the drum.

Thus, there exists a need for a lightweight, durable rope guide mechanism with a high efficiency, low cost, and short axial length.

The present invention is a significant improvement over the prior art in general, and these patents in particular. The present invention overcomes the above described problems by utilizing rollers mounted on axles, and disc-shaped drum engaging elements mounted on axles which roll in the helical rope groove in the drum, rather than balls. These structural features eliminate the plastic lining and seating arrangement and results in significantly improved operation because the interior surface of the rollers are engaged with the axles only at the point of tangency and there is no frictional engagement on the circumference of the rollers.

SUMMARY OF THE INVENTION The present invention relates to a rope guide for guiding a rope being wound onto or unwound from the drum of a hoist, comprising a sectored rolling bearing ring made of U- shaped steel shells adapted to surround the drum and turns of rope wound thereon, one of the sectors being provided with a slot for entry of the rope into the guide and each sector having welded U-shaped steel shells facing inwardly towards the peripheral surface of the drum, a plurality of axles fixed in said inwardly-facing U-shaped steel shells of the

sectors, each of which axles receives a respective rope- engaging member which is rotatable on its axle and rolls over the peripheral surface of two and three adjacent turns of the rope, and a drum engaging member which is rotatable on its axle and rolls over the groove of the drum, whereby, in use of the guide, said rope engaging members and drum-engaging members by their axles form a roll bearing, urged inwardly into engagement with the rope and with the drum.

In a preferred embodiment of the rope guide in accordance with the invention, the rope-engaging members are barrel-shaped rollers and double-barrel shaped rollers, and the drum-engaging members are disc-shaped rollers. In the case of a rope guide for a hoist having a hoisting drum provided with a helical groove for the reception of the hoisting rope, rope-engaging members in the form of barrel and double-barrel-shaped rollers and drum-engaging members in the form of disc-shaped rollers are mounted on axles which are inclined to the drum axis at an angle substantially equal to the helix angle of the drum groove.

Preferably, each of the sectors comprises a shell made of sheet steel, and each of the shells has internally mounted U-shaped steel shells for receiving the rope-engaging members, and U-shaped steel shells for receiving the drum- engaging members. In the sector which is provided with a slot for the entry of a rope into the guide, the slot preferably has side walls which converge in the radially- inward direction. This slotted sector may be made in two parts which can be assembled and dismantled readily to facilitate feeding of the rope into the guide.

Compared with the previously known rope guides described above, the advantages of a rope guide in accordance with the present invention and having the preferred features mentioned above are as follows.

It is cheaper to manufacture, since the sectors do not have internal screw threads. A greater hoisting distance can be provided by a drum of the same length, due to the

guide having a shorter axial length, which allows manufacturing of shorter drums and using a shorter rope in one and the same load elevation, due to the guide having a shorter axial length. Since the rope-engaging members rely on rolling friction rather than sliding friction, the overall efficiency of a hoist employing the guide is higher. Furthermore, both the rope guide and the rope employed therewith have a longer service life, due to the fact that the converging walls of the rope entry slot allow the rope to deviate from a direction perpendicular to the drum axis without imparting an excessive bending moment on the guide.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevation of one embodiment of a rope guide in accordance with the present invention.

Fig. 2 is an end elevation of the rope guide as seen in the direction of the arrow A in Fig. 1.

Figs. 3 to 6 are cross section views at an enlarged scale, taken along the lines 3-3, 4-4, 5-5, and 6-6, of Fig. 2.

Figs. 7A and 7B taken together is a schematic illustration of the circumference of the hoist drum depicted in a flat plane with the roller members of the circular guide of Fig. 2 superposed over the helical groove of the drum.

Figs. 8A and 8B taken together is a schematic illustration of the circumference of the hoist drum depicted in a flat plane similar to Figs. 7A and 7B, but showing modified roller members of the circular guide superposed over the helical groove of the drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings by numerals of reference, the rope guide shown in the drawings is intend for use on the drum of an electric hoist. In Figs. 1 and 2, the hoist drum is not shown. In Figs. 3 to 6 of the drawings, the helical groove 8 in the periphery of the drum and the rope 9 which is wound into the groove are shown in broken line, but the drum

is not shown. Figs. 7A and 7B illustrate the circumference of the hoist drum depicted in a flat plane with the roller members of the circular guide of Fig. 2 superposed over the helical groove of the drum. Figs. 8A and 8B also illustrate the circumference of the hoist drum depicted in a flat plane similar to Figs. 7A and 7B, but showing modified roller members of the circular guide superposed over the helical groove of the drum.

The rope guide includes three arcuate sectors comprising sheet steel shells IA, IB and IC, into the interior of each is welded U-shaped shells 2A, 2B, 2C, 7A, and 7B, respectively, made of steel. Each of the U-shaped shells 2A, 2B, 2C, 7A and 7B is provided with holes for axles 6, 22, 24 and 25 on which rotate diεc rollers 4c, barrel rollers 3, disc rollers 4b, and double-barrel rollers 5, respectively, made of steel. The axes of rotation of all rollers are disposed at an angle substantially equal to the helix angle of the drum groove 8.

The shells IA and IB are of one piece construction, but the shell IC is made in two parts 7A and 7B connected together by screws 20. When assembled together, the two parts 7A and 7B define a slot 23 in the shell IC through which the rope 9 enters the guide, the side walls of the slot converging in the radially-inward direction (see Figs. 3 and 4) , the inclined angle between these side walls being approximately 60°. The slot 23 is inclined to the side faces of the shell IC at an angle OCequal to the helix angle of the groove 8 (Fig. 1) .

The pair of shells IA and IB, and the pair of shells IA and IC are connected together by a steel connection member 18 secured to one of the shells of the pair by screws 19 and welded to the other shell of the pair, as can be seen in Fig. 2, The shells IB and IC are joined by means of a U-shaped cleat 13 having the free ends of its limbs secure, for example welded or screwed, to the shell IC. A catch 21 secured to the end of the shell IB lying adjacent to the

shell IC slides between, and is guided by, the limbs of the U-shaped cleat 13 and limits the amount by which the adjacent ends of the shells IB and IC can separate from one another.

Adjacent ends of the shells IB and IC are urged towards one another by pair of helical springs 10 (only one of which can be seen, and is shown in broken lines, in Fig. 2) . One end of each spring 10 is anchored to the shell IB and the other end of each spring is anchored to a screw- threaded rod 11 mounted in a cleat 14 secured to the shell IC. The position of each rod 11 in the cleat 14 is adjustable by means of threaded nuts 12. By suitably adjusting the nuts 12, the drum-engaging disc rollers 4b and 4c are located in the groove 8, and the barrel rollers 3 and double-barrel rollers 5 of all three shells IA, IB and IC are pressed on the rope 9 so that the friction force resisting sliding between the rope 9 and the groove 8 is greater than the total frictional force resisting rotation of the barrel and double-barrel rollers 3 and 5 on their axles. The sliding friction force between the rope 9 and groove 8 arises from the pressing of the barrel and double-barrel rollers 3 and 5 against the rope 9 and the pull in the rope due to the load, the dead weight of the rope and the weight of the hook or other attachment device connected to the rope.

Figs. 7A and 7B illustrate the circumference of the hoist drum depicted in a flat plane with the roller members of the circular guide superposed over the helical groove 8 of the drum. The slot 23 in the shell through which the rope 9 enters is shown in broken line.

As shown in Figs. 3, 7A and 7B, the barrel-rollers 3 have a disc-shaped portion received between adjacent turns of rope 9 and inwardly curved surfaces on each outer side of the disc-shaped portion which roll on the outer peripheral surfaces of two adjacent turns of rope 9. As shown in Figs. 5, 7A and 7B, the double-barrel rollers 5 have a first inwardly curved portion which rolls on the outer peripheral surface of a first turn of rope 9, a disc-shaped portion at

each outer end of the first inwardly curved portion received between second and third turns of rope at each side of the first turn of rope, and inwardly curved surfaces on each outer side of each disc-shaped portion which roll on the outer peripheral surfaces of the second and third turns of rope.

Apart from serving as a support to the screw-threaded rods 11, the cleat 14 also serves as a stop member counter¬ acting a clockwise torque (as viewed in Fig. 2) imparted to the rope guide by the rope 9, the cleat 14 being arranged to bear against an abutment 15, which may be a stationary portion of the housing of the electric hoist. Another cleat 16, secured by the screws 20 to the end of the shell IC lying adjacent the shell IA, serves as a stop member counteracting a counter-clockwise torque (as viewed in Fig. 2) imparted to the rope guide by the rope, the cleat 16 being arranged to bear against an abutment 15A, which again may be a stationary portion of the housing of the electric hoist.

The cleat 16 may also serve to actuate one or more limit switches controlling the electric hoist. The numeral 17 designates the actuating arm of such a limit switch.

Figs. 8A and 8B illustrate the circumference of the hoist drum depicted in a flat plane similar to Figs. 7A and 7B, but showing modified roller members of the circular guide superposed over the helical groove 8 of the drum. The slot 23 in the shell through which the rope 9 enters is shown in broken line. In this modification, a drum-engaging disc roller 30 is received in the groove 8, and a rope-engaging concave barrel roller 31 having an inwardly curved concave central portion with disc-shaped ends is received over a groove 8 and rolls on the outer peripheral surface of a turn of rope 9. Also in this modification, the separate drum- engaging disc rollers 4B and 4C, and the rope engaging barrel rollers 3, and double-barrel rollers 5 are replaced by unitary rollers. A number of single-disc barrel rollers 32, and double-disc barrel rollers 33 are mounted on axles secured to the outer shells.

The single-disc barrel rollers 32 have an outer drum- engaging roller at one end which is received in a drum groove 8 and axially spaced inwardly curved rope-engaging surfaces with disc-shaped portions between the curved surfaces. The disc-shaped portions are received between adjacent turns of rope 9 and the inwardly curved surfaces roll on the outer peripheral surfaces of adjacent turns of rope. The double- disc barrel rollers 33 have a pair of drum-engaging rollers at one outer end which are received in two adjacent drum grooves 8 and axially spaced inwardly curved rope-engaging surfaces with disc-shaped portions between the curved surfaces. The disc-shaped portions are received between adjacent turns of rope and the inwardly curved surfaces roll on the outer peripheral surfaces of adjacent turns of rope.

OPERATION In use of the above-described rope guide, the barrel rollers 3 and double-barrel rollers 5, or the single-disc barrel rollers 32 and double-disc barrel rollers 33, rotating on their axles in the U-shaped shells 7A, 2A and 2B, roll along the peripheral surface of the rope 9, press the rope 9 into the drum groove 8 as the drum of the hoist rotates. The pressure exerted on the rope by the rollers 3 and 5, or 32 and 33 can be adjusted by adjusting the tension of the springs 10. As winding or unwinding of the rope proceeds, the rope guide is driven axially along the drum mostly by engagement of the barrel and double-barrel rollers 3 and 5 or the single-disc triple-barrel rollers 32 and double-disc double-barrel rollers, with the rope, and additionally by engagement of the disc rollers 4B and 4C or drum engaging disc portions of the single-disc barrel rollers 32 and double-disc barrel rollers 33, in the helical groove 8, so that the slot 23 is always aligned with the underlying portion of the groove 8. As previously mentioned, the side walls of the slot 23 converge in the radially-inward direction, and due to this, the rope 9 can deviate by up to

30° from a direction perpendicular to the drum axis without imparting an excessive bending moment on the shell IC. From Fig. 2 it will be seen that double-barrel rollers 5 are provided adjacent each end of the shell IC so that the rope 9 is engaged by a double-barrel roller 5 (or the concave rope engaging portions of the unitary rollers 32 and 33) immediately before it emerges from the slot 23.