Swaged Wire Rope And Method Of Manufacture

Abstract

An improved swaged wire rope is produced by winding in a predetermined manner a plurality of strands about a flexible core of greater diameter than that of said strands and swaging the so formed wire rope construction until a smooth, void-free exterior surface of the rope is obtained. The new swaged wire rope is particularly suitable for operations where abrasion, shock loading and general rope abuse are prevalent.

Description

This invention relates to a novel swaged wire rope and to the method of producing same.

It is already known to produce various types of swaged wire rope. For example, U.S. Pat. No. 3,457,718 issued July, 29, 1969 to John C. Otto et al, discloses one method of manufacturing high density wire rope by swaging a rope structure wherein each strand comprises a plurality of wires stranded about a soft, pliant core of plastic or the like. Such ropes, however, would have limited utility as they cannot be used for operations which impart to the rope a great deal of abuse, such as logging main lines, demolition ball cables, towing cables and the like. This is, of course, due to the fact that they comprise a plurality of soft, pliant cores of plastic or similar material which will not withstand such abuse.

Another example is disclosed in U.S. Pat. No. 3,130,536 issued on Apr. 28, 1964 to Vincent C. J. Peterson et al. According to this patent, compacted wire rope is produced by swaging each strand separately and then helically wrapping the strands about a core to form the wire rope. There are several disadvantages to such construction. The first is due to the fact that such wire rope is not produced as an integral unit in a single swaging operation, but every strand must be swaged separately. Thus, the swaging of each strand must be carefully controlled to produce a final rope of uniform strength and configuration. It is much more difficult and expensive to swage each element separately and then put them together, rather than swaging the wire rope in one single operation. The other important disadvantage is that the swaged strands are simply wrapped around the core and thus the core does not participate, so to say, in the swaging process. The core remains undeformed and in exactly the same shape as originally used. This results in a non unitary construction which may provide failures of the rope during abusive applications. It will also be appreciated that good integral wrapping of the strands around the core is extremely difficult to achieve in such circumstances, since each strand has flattened slippery faces which may result in irregular lays and slippages of the strand on the core during the wrapping operation.

All these limitations and disadvantages are overcome or substantially reduced by the present invention.

Thus, the principal object of the present invention is to provide a novel swaged wire rope which will have an integral, compacted construction and a smooth, void-free exterior surface and which will have an excellent resistance to general abuse.

Another object of this invention is to provide a simple, efficient and inexpensive method of manufacturing such swaged wire rope.

Other objects and advantages of the invention will be apparent from the following more detailed description thereof.

Generally, there is provided in accordance with this invention a swaged wire rope of integral construction having a flexible central core supporting a plurality of strands wound around said core, said core being of a larger diameter than that of the surrounding strands and said strands being wound around said core with a lay such that there remains about 1-1.5 percent gap between the strands before swaging, and there is a reduction in diameter of the rope of about 8 to 16 percent produced by swaging the entire rope construction, sufficient to fill completely the gaps between the strands and provide a smooth, void-free exterior surface.

A preferred swaged wire rope of this invention comprises a flexible core formed of a plurality of low carbon steel stranded wires having a tensile strength of between 50,000 and 100,000 psi whereas the surrounding strands are formed of high carbon steel wires having a tensile strength of between 200,000 and 300,000 psi. A particularly preferred flexible core is formed of a soft steel 19 wire seale center 9/9/1 construction and has a tensile strength of between 60,000 and 80,000 psi whereas the particularly preferred strands wound around such center would each be formed of 26 wires of hard steel having a tensile strength of between 250,000 and 270,000 psi.

When the strands are wound around the core, the preferred gap left between the strands before swaging is of about 1 percent and the preferred reduction in diameter of the rope due to swaging is of about 10-12 percent.

The number of strands surrounding the core may, of course, vary depending on the desired final rope construction. Thus, when a six stranded rope is made, the preferred reduction in diameter due to swaging will be between about 10 and 15 percent. On the other hand, when an eight stranded rope is made, i.e., eight strands are wound around the core, the reduction produced by swaging will preferably be between about 9 and 12 percent. With even higher number of strands, the reduction will be proportionally lower.

The method of manufacturing the novel swaged wire rope according to this invention generally comprises winding a plurality of strands, of the type described above, about a flexible core of greater diameter than that of said strands, the winding being carried out with a lay factor of between 5 and 6 and in such a manner that there remains a gap of about 1-1.5 percent between the strands surrounding said core, and swaging the so formed wire rope construction up to a total reduction in diameter between 8 and 16 percent, whereby the gaps between said strands are completely filled and a smooth, void-free exterior surface of the rope is obtained.

The preferred lay factor is about 5.7 and the preferred gap between the strands is about 1 percent prior to swaging.

At first glance, it may appear that the applicants have simply taken a ready made wire rope and compacted it by a swager. This is not at all the case. As a matter of interest, the applicants originally tried such approach of simply taking a wire rope from the finished stock and swaging the same to some degree. This procedure has not produced the desired result, i.e., the desired increase in the life of the rope and resistance to general abuse. The fact is that when a finished rope is swaged to a reduction in diameter of let us say 10 percent, there occurs substantial deformation of the metal strands, and since in normal ropes there is almost no gap between the strands, such swaging is accompanied by substantial nicking and damaging of the individual strands, thus adversely affecting the tensile strength and ductility of the final rope.

Further tests and research revealed, however, that by providing a central core which would be more flexible than the surrounding strands which it supports, and which would be larger in diameter than said strands, and by winding the strands around said core in such a manner that there remains about 1-1.5 percent gap between said strands, there is produced a greatly improved integral wire rope when such construction is swaged to achieve a reduction in diameter of between about 8 and 16 percent. These parameters have been achieved after a great deal of testing and experimentation and it is believed that they are essential to provide the extraordinary improvements in performance produced by the new swaged rope.

By way of explanation, it is believed that when these conditions are met, the swaging of the rope will not result in an undesirable nicking and deformation of the individual strands within the rope, but rather the deformed strands will fill the spaces left by the gaps between them and to some extent will project into the more flexible and larger core provided in the middle, thus forming a smooth and tight overall construction of the wire rope.

The method of producing such swaged wire ropes is also essentially novel. According to this method, the strands are wound about the larger and more flexible core with a lay factor of between 5 and 6 and in such a manner that there remains a gap between the strands of about 1-1.5 percent. Then, the so formed rope is swaged up to a total reduction of between 8 and 16 percent, sufficient to fill completely the gaps between the strands and provide a smooth, void-free exterior surface.

It is well known to the man of the art that the lay factor of the rope is the number which must be multiplied by the diameter of the rope to give the lay of the rope. In normal non-swaged ropes the lay factor is generally between 6 and 7. For example, 6.28 is a lay factor used for many standard ropes.

It has been found, however, that such lay factors of 6-7, when used before swaging, are not satisfactory for the swaged wire rope of the present invention since after swaging they result in lays which are too long and produce wire ropes which are insufficiently flexible and which do not have a good smooth surface. On the other hand, it has also been found that when the lay factor is too small and the lay is therefore too short, one cannot get the reduction in diameter which is desired and which results in the greatly improved life and resistance to general abuse. Maintaining a proper lay in the production of the novel swaged wire rope is therefore an important feature of this invention.

The swaging operation as such is generally known and it consists in deforming the wire rope by a succession of rapid hammer blows until a desired reduction in diameter is achieved. There are many swaging machines known in the art and it is not necessary to describe them in detail. One such machine, which is suitable for the purposes of the present invention, is described and claimed in U.S. Pat. No. 3,149,509 of Albert H. Oquist et al, issued Sept. 22, 1964.

The invention will now be further described with reference to the appended drawings in which:

FIG. 1 is a general schematic plan-view illustration of a preferred method according to the present invention for producing the novel swaged wire rope;

FIG. 2 is a side view illustrating the novel swaged wire rope of the present invention as it is produced;

FIG. 3 is an end view illustrating the same wire rope;

FIG. 4 is another side view drawn from a photograph and showing the novel tight and smooth swaged wire rope construction of this invention; and

FIG. 5 is an enlarged cross-section view drawn from a photograph and clearly showing the cross-section of the novel swaged wire rope.

As illustrated in FIG. 1, the swaged wire rope of the present invention is produced in a simple, efficient and continuous operation. Thus, core 10 is unwound from core pay-off 11 and is forwarded through a middle guiding tube 12. Rope strands 14a, 14b, 14c, 14d, 14e and 14f are unwound from stand pay-offs 15a, 15b, 15c, 15d, 15e and 15f respectively and forwarded through guides 16 and guide sheaves 17 in six positions around tube 12 within which passes the core. It should be noted that FIG. 1 is a plan view of the arrangement and consequently some of the pay-off rolls are seen only partially and some of the strands must be assumed to pass one over the other.

Then, the core 10 as well as the strands 14 pass through a guide plate 18 and the strands are suitably wound around the core within die 19 by means of a rotating preforming head 20. As already mentioned previously, the winding is carried out with a lay factor of about 5-6 and in such a manner as to leave a gap of about 1-1.5 percent between the strands. These adjustments can easily be carried out by men of the art.

Thereafter, the obtained rope passes through capstan 21 and is then swaged by swager 22 up to a total reduction in diameter of between 8 and 16 percent.

Finally, the resulting swaged wire rope 23 is wound on a take-off 24.

This operation is efficient and economical and has proved effective at speeds up to and exceeding 20 feet per minute. It should be noted also that a light lubrication is called for at the stranding operation. As far as the actual swaging operation is concerned, it was found that a better swaged finish is obtained on surfaces which have no lubrication at all. This, however, is not-suitable for most wire rope applications and consequently the applicants prefer to apply a very light coating of lubricant to the strands. In some cases, it may be sufficient to lubricate the rope after it exits from the swager, however, in such circumstances, the lubricant usually does not sufficiently penetrate the swaged rope.

The obtained swaged wire rope 23 is illustrated in FIGS. 2, 3, 4 and 5. From FIG. 2 it will be seen that the various strands 25 are in tight contact with each other and the wires forming these strands have been flattened to exhibit smooth, flat and generally uniform faces 26. The black edge sections 27 represent the remainder of the lubricant on the rope as it exits from swager 22. The final smooth and tight aspect of the rope is particularly well illustrated by the photograph-like drawing of FIG. 4.

FIG. 3 shows an end or section view of a six stranded swaged rope 23 on a black background. It will be noted that in this particular case, the core 28 is a soft steel 19-wire seale center having a combination of wires 9/9/1. Its diameter is slightly greater than that of the surrounding strands 25 which, in this case, consist of a 26-wire strand construction made of hard steel. Strands 25 are flattened so as to touch each other tightly on each side and to project somewhat into the softer core 28 at the bottom, forming a particularly tight and unitary combination as this is especially well shown in the enlarged drawing of FIG. 5, where the rope end is shown surrounded by an annular holding member.

The invention will now be further illustrated by means of the following non limitative examples:

EXAMPLE 1

A swaged wire rope of 1/2 inch diameter has been produced in accordance with the present invention. For this purpose a 9/16 inch diameter six stranded wire rope was first made using a rope lay factor of 5.7 and leaving a gap between the strands of about 1 percent. A 19 wire seale warrington strand core having a diameter slightly greater than that of the strands was used for this purpose. This core was made of soft steel (or low carbon steel) having a tensile strength of 80,000-100,000 psi. The surrounding strands were 26 wire strands of regular construction and were made of hard steel (or high carbon steel) having a tensile strength of 250,000-270,000 psi. The rope was then swaged to 1/2 inch in diameter, which represents a reduction of about 11 percent.

This rope was used for log skidder main lines and was compared with a standard six stranded non-swaged rope of 9/16 inch diameter in which the strands also consisted of 26 wires each and were made of the same type of high carbon steel. The results are summarized below:

Type of Rope Diameter Inches Breaking Strength (Lbs) Cost $ Average Rope Life ______________________________________ Standard Rope (High Strength) 9/16 33,500 34.10 4,000 trees Swaged Rope according to this invention 1/2 32,000 34.10 10,000 trees ______________________________________

Other results measured on same or similar ropes both of six stranded construction and of eight stranded construction have clearly demonstrated that the swaged wire rope of the present invention gives a minimum of 50 percent increase in rope life for log skidder main line applications over standard ropes of similar strength and cost.

EXAMPLE 2

A six stranded swaged wire rope of 1 inch diameter was produced in accordance with the present invention again using low carbon steel for the core strand and high carbon steel for the surrounding strands. The initial diameter of the rope (prior to swaging) was 11/8 inch and it was reduced to 1 inch by swaging, which is a reduction of about 12 percent. This wire rope was used for a back-hoe in-haul and compared with standard non-swaged rope used for the same purpose. The results were as follows:

Type of Rope Diameter Inches Construction Breaking Strength (Lbs) Cost Average Life ______________________________________ Standard Rope 1 6.times.25 Langs lay 89,600 $77.00 2.3 days Swaged Rope according to this invention 1 6.times.26 123,000 $104.50 18 days ______________________________________

This result was obtained from a machine digging in exceptionally hard ground, producing a shorter than normal life. The 18 days rope life is an average of 12 ropes used to date.

It will be appreciated that although the cost of the swaged rope of the present invention is about one-third higher than that of the standard rope for this application, its average life is almost 8 times longer.

EXAMPLE 3

A swaged wire rope 7/8 inch in diameter was produced in accordance with the present invention, with materials of the same type as in Examples 1 and 2. It was compared with a standard non-swaged wire rope 1 inch in diameter when used as a demolition ball hoist line. The following results were obtained:

Type of Rope Diameter Inches Construction Breaking Strength (Lbs) Cost $ Rope Life ______________________________________ Standard Rope 1 6.times.25 Regular 89,600 $77.00 1 week Swaged Rope according to this invention 7/8 6.times.25 94,000 $84.80 5 weeks to date and still in service ______________________________________

This test was carried out at the Asbestos Mines in the province of Quebec where fine blasting of the ore is unacceptable and additional fragmentation of the ore is achieved through the use of a 4 ton demolition ball on a 25 ton mobile crane unit. It will be noted that although the cost of the swaged rope of the present invention is slightly higher, its life is over five times longer than that of standard ropes now used for such purposes.

In addition to the above non limitative examples, many tests have been made with various swaged ropes produced in accordance with this invention. Such ropes have been used as chokers, as grapple loading system ropes, as grapple yarding system ropes, as skidder main lines and are presently tried for purposes such as pile driving ropes, shovel hoist ropes, boom suspension ropes, trawl warps, elevator compensating ropes, pulp log conveyor ropes, and the like. The present reports indicate that the swaged ropes of the present invention when compared with standard ropes used for the similar applications result in double rope life fairly consistently and often result in outperforming the standard ropes five to one and more. This surprising increase in the rope life for applications where abrasion, bad winding, shock loading and general rope abuse are prevalent was certainly not expected and should be found of major advantage to the wire rope industry.

It should be noted that the illustrated and exemplified embodiments discussed above are in no way limitative and that many modifications can be effected by men familiar with the art without departing from the spirit of the present invention and the scope of the following claims. Thus, various types of cores and strands can be used and the materials from which these cores and strands are made can vary extensively, depending on the final application and ultimate use of the wire rope. In the process of producing the rope, various steps and conditions can be changed and adapted as required for each individual case or application. Thus, the invention is not limited to the specifically disclosed embodiments but rather encompasses various changes and modifications that could easily be carried out by men familiar with this art.

Claims

We claim:

1. Swaged wire rope of integral construction having a flexible central core supporting a plurality of strands wound around said core, said core being of a larger diameter than that of the surrounding strands and said strands being wound around said core with a lay such that there remains about 1-1.5 percent gap between the strands before swaging, and there is a reduction in diameter of the rope of about 8 to 16 percent produced by swaging the entire rope construction, sufficient to fill completely the gaps between the strands and provide a smooth, void-free exterior surface.

2. Swaged wire rope according to claim 1, wherein said flexible core is formed of a plurality of low carbon steel stranded wires having a tensile strength of between 50,000 and 100,000 psi, and said surrounding strands are formed of high carbon steel wires having a tensile strength of between 200,000 and 300,000 psi.

3. Swaged wire rope according to claim 1, wherein said flexible core is formed of a soft steel 19 wire seale center 9/9/1 construction having a tensile strength of between 60,000 and 80,000 psi and said surrounding strands are each formed of 26 wires of hard steel having a tensile strength of between 250,000 and 270,000 psi.

4. Swaged wire rope according to claim 1, wherein said gap between the strands is about 1 percent before swaging and there is a reduction in diameter of the rope due to swaging of about 10-12 percent.

5. Swaged wire rope according to claim 1, having six strands surrounding the core and having a reduction in diameter produced by swaging of between about 10 and 15 percent.

6. Swaged wire rope according to claim 1, having eight strands surrounding the core and having a reduction in diameter produced by swaging of between about 9 and 12 percent.

7. Method of manufacturing swaged wire rope which comprises winding a plurality of strands about a flexible core of great diameter than that of said strands, the winding being carried out with a lay factor of between 5 and 6 and in such a manner that there remains a gap of about 1-1.5 percent between the strands surrounding said core, and swaging the so formed wire rope construction up to a total reduction in diameter between 8 and 16 percent, whereby the gaps between said strands are completely filled and a smooth, void-free exterior surface of the rope is obtained.

8. Method according to claim 7, wherein said strands are wound around said core with a lay factor of about 5.7 and with a gap between the strands of about 1 percent prior to swaging.

9. Method according to claim 7, for the manufacture of a six-stranded rope, wherein six strands are wound around said core and the wire rope is swaged up to a total reduction in diameter of between about 10 and 15 percent.

10. Method according to claim 7, for the manufacture of an eight-stranded rope, wherein eight strands are wound around said core and the wire rope is swaged up to a total reduction in diameter of between about 9 and 12 percent.