US2797878A

US2797878A - Apparatus for applying a tensioned wire wrapping to concrete articles

Info

Publication number: US2797878A
Application number: US374308A
Authority: US
Inventors: Jr John M Crom
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-08-14
Filing date: 1953-08-14
Publication date: 1957-07-02
Anticipated expiration: 1974-07-02

Description

y 957 J. M. CROM, JR 2,797,878

APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING TO CONCRETE ARTICLES Filed Aug. 14, 1955 5 Sheets-Sheet l Movemen/ Fig INVENTOR y 2, 1957 J. M. CROM, JR 2,797,878

APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING TO CONCRETE ARTICLES Filed Aug. 14, 1955 5 Sheets-Sheet 2 //vv,5- r09 Movemenf July 2, 1957 J.M.CROM,JR APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING TO CONCRETE ARTICLES 5 Sheets-Sheet 5 Filed Aug. 14, 1953 IN VE N TOR July 2, 1957 J. M. CROM, JR 2,797,878 APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING TO CONCRETE ARTICLES Filed Aug. 14, 1953 5 Sheets-Sheet 4 Movemenf y 957 J. M. CROM, JR 2,797,878

APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING TO CC-NCRETE ARTICLES 5 SheetsSheet 5 Filed Aug. 14, 1953 X i n x I ,1, i7 {ii 1 D/recfion of W/hd/hg F lg. /3

INVENTOR United States Patent Ofiice 2,797,878 Patented July '2, 1957 APPARATUS FOR APPLYING A TENSIONED WIRE WRAPPING T CQNCRETE ARTICLES John M. Crorn, In, Falls Church, Va.

Application August 14, 1953, Serial No. 374,308

8 Claims. (Cl. 242-7) This invention is concerned with an apparatus for winding with tensioned wire in the interest of prestressing large immovable or unwieldy structures such as tanks, silos, or the like having a circular, square, or any other geometrical cross-section. It is also adaptable for winding other stationary structures such as beams in the longitudinal direction. The invention is particularly concerned with the wire tensioning arrangement and the driving traction means.

This invention provides certain improvements over my pending application Serial No. 289,063, filed May 21, 1952, now Patent No. 2,749,054, issued June 5, 1956. In this prior application a method was disclosed for Wrapping a tank with wire in the furtherance of the well known principle of prestressing for the purpose of economy in reinforcing steel and improved functioning of the structure, whereby tension was produced in the wire with expenditure of relatively little power by providing a reciprocity of action between pay-out of wire from a vehicle and movement of the vehicle around the tank, such as to pay out wire at a lesser speed than the linear forward movement of the vehicle around the tank. This was accomplished by means of a pay-out element mounted on the vehicle, meshing at the established speed ratio with a heavy roller chain in frictional, non-slipping contact around the circumference of the tank wall. The pay-out element was characterized as a rotatable device preventing slippage of wire around it, but discharging wire in proportion to its rotation. In the present invention elements of the same general type are used, also in a manner which will realize the same relatively low power expenditure, but which will eliminate the need for the heavy and costly roller chain while retaining uniformity and control in the degree of tensioning.

The basic tensioning means of the new invention consists of three principal elements located on the vehicle circumrotating about the tank or other structure. In operation the vehicle lays down a relatively loose wire as a temporary wrapping in traveling around the tank. The wire is returned again to the vehicle one or more turns later after it has acquired sufiicient frictional resistance through contact with the tank wall to prevent any slipping back to the point on the vehicle where it is being laid down. On being returned to the vehicle, the wire is carried around the first of the elements for tensioning. The latter, a take-up element, is similar in characteristics to the element described in application Serial No. 289,063, now Patent No. 2,749,054, allowing a non-slippage discharge of wire in accordance with its rotation. The third element, a pay-out element, is also similar in its construction, and is connected for reciprocity of rotation with the first element. The connection between the two is such that the pay-out element will let out wire onto the tank as the permanent winding at a slower rate than it is picked up by the take-up element. The intermediate element is a device for absorbing the stretch in the wire continually developing as the wire is tensioned. This second element can be a suspended or floating sheave around which the intermediate portion of wire is looped. The sheave must be counterbalanced by a weight or other force su'fficient to keep slack out of the wire loop and to give the small back tension that may be necessary in the prevention of slippage around the take-up and payout elements. Tension in the wire is developed in accordance to the ditference in rates of take-up and payout of the wire by separate elements-on the vehicle itself in contradistinction to my referred-to earlier invention, which had no take-up element, the structure itself serving as the interconnected means of take-up.

A primary object of the invention is to provide a simple and improved means for applying tension to wire being wound on stationary structures, whereby the tens'ioning means is not dependent of engagement on the wire by reducing orifices, weights or beam balanced winches, brakes, =or-other resistances, all commonly known to the art.

Another object of the invention is to give improvement in the winding of tank structures over my prior invention, application Serial No. 289,063, now Patent No. "2,749,054, by permitting use of the wire itself as the means for securing frictional contact with the structure, thus eliminating the heavy and expensive roller chain required in my prior invention.

Another object of the invention is to provide a means giving other improvement in the winding of tank structures over my prior invention, application Serial No. 289,063, now Patent No. 2,749,054, by permitting winding of wire at considerable distances above or below the vehicle without introducing a horizontal force couple tending to tip the machine. In the prior invention the location of the traction roller chain was for all practical considerations fixed at the level of the vehicle body. Winding-out the wire at any apprecibale distances above or below the machine necessary in some phases of tank winding, introduced difficulties requiring ballasting of the vehicle to keep it riding level. In the present invention the temporary wire wrapping for traction and the wire in final position can be maintained at the same elevation giving inherent stability to the vehicle, and permitting a very small and lightweight vehicle construction.

Another object is to provide a means for continuously winding a wire under tension that will require relatively little power as contrasted with many earlier methods where the wire was continuously pulled against a reducing orifice, brake, or other resistance means.

Another object is to provide a means for controlling the tension in a wire being continuously wound on a structure by engaging the wire through elements of a tensioning means from a loose, temporary wrapping around the structure, whereby a fixed ratio of speeds correspondingto the desired degree of tension is established in the elements for taking up wire of the temporary wrapping and for paying it out again to the structure as the permanent winding.

Another object is to provide a means for controlling the tension in a wire being continuously wound on a structure, which is not dependent on adjusting within close limits the speed ratios of the elements for take-up and pay-out from the temporary loose wrapping, but which is dependent on providing speed ratios tending to overtension the wire with relief to the desired degree of tension being attained by slipping through an interconnecting clutch.

Another object is to provide a means of tensioning wire continuously around a cylindrical tank structure with motive power being provided through the wheels of an overhead carriage which rides the top of the wall and supports the tensioning vehicle.

Another object is to provide a means of tensioning wire continuously around a structure while introducing the driving power into the wire itself by engagement of a rotatable wheel on the wire of the temporary wrapping at least one wrap ahead of the point of take-up by the tensioning mechanism.

Another object is to provide a means of tensioning wire continuously around structures of any cross-sectional shape, such as square tanks or beams in the longitudinal direction by employing a contact wheel assembly which bears against the side of the structure on a vertical line contact enabling passage around corners, and which guides wire to and from the structure being wound as required by the tensioning mechanism.

Another object is to provide a means of tensioning wire continuously around any structure of any crosssectional shape, which can be of a varying dimension, such as a pipe having a low pitch taper down which the Wire will not slide.

These and other features of the invention will be best understood and appreciated from the following description of preferred embodiments thereof selected for purposes of illustration and shown in the accompanying drawings in which,

Figure 1 is a front elevation of a wire wrapping vehicle supported by an overhead carriage applying tensioned wire to a tank structure in accordance with the method of this invention.

Figure 2 is a plan view of the vehicle of Figure 1 in traverse around the tank structure.

Figure 3 is an elevation directed toward the leading end of the overhead carriage of Figure 1, showing method of drive.

Figure 4 is a diagrammatic representation of the paths taken by the wire in Figure l and of the force relationships in the wire.

Figure 5 is a View of an alternative arrangement of a pay-out and take-up element interconnected by a clutch, in partial section so as to show the interior construction.

Figure 6 is an alternative arrangement in plan View of a wire wrapping vehicle applying tensioned wire to a tank structure, with the drive being by engagement with the wire through one of the wheels of a contact wheel assembly.

Figure 7 is a front elevation of Figure 6.

, Figure 8 is a diagrammatic representation of the paths taken by the wire in Figures 6 and 7.

Figure 9 is' a front elevation of a vehicle adapted for winding tensioned wire on beams, and illustrating a modification of a contact wheel assembly from that shown in Figures 6 and 7.

Figure 10 is a sectional plan of the vehicle taken along line 1010 of Figure 9.

Figure 11 is an elevation directed toward the trailing end of the removed detail of the contact wheel assembly.

Figure 12 is a diagrammatic representation of the paths taken by the wire in Figures 9, 10, and 11.

Figure 13 is a plan view of a further embodiment of 'the invention showing a tapered pipe section in rotation taking up a tensioned Wrapping.

Figure 14 shows the tapered pipe of Figure 13 in crosssection with the elements of the tensioning means in side view. a

Common to any embodiment of the invention are several requisites. First there must be an article to be wound with tensioned wire and machine elements exterior to the article to eifect the winding. There must be, a relative movement between the two for placing the wire, either by rotation of the article with the machine elements being fixed or by orbital movement of the machine elements around the article. As will be shown herein, the orbital path of the machine elements around the article does not have to be circular, it being necessary only that it conform to the cross-sectional shape of the article.

Second there must be a source of wire, usually from a roll of wire on a swift, that is loosely applied as a temporary wrapping around the article through relative movement between the article and the machine elements. There must be enough turns of Wire in the temporary wrapping combined with the slight back tension present at the source that will offer frictional resistance against slippage at the point of application from the source.

In effect a continuous, non-slipping, relatively untensioned supply of wire is being provided through the temporary wrapping that bears the same path length around the article that the tensioned wire will finally occupy.

Third there must be a tensioning means among the machine elements continuously acting to shorten this supply of non-slipping, untensioned wire which is fed through it, with attending tension being a function of the shortening.

The novelties being claimed are in the means for shortening the Wire supply of the temporary wrapping, and in the means for driving the tensioning means and other machine elements relative to the article.

One embodiment of these novelties is apparent in Figures 1, 2, and 3, wherein a Wire wrapping vehicle 1 supported and driven from an overhead carriage 2, is illustrated in the process of applying a tensioned Wrapping of wire 3 to a concrete tank 7. The source of wire is a roll 4 turning off swift 5, and passing through a series of rollers 6 to create some slight back tension. Experience has shown that the back tension need be no more than about one twenty-fifth of the applied tension in the final wrapping 3, this usually being sufiicient to keep the wire snugly in position around the tank and Without circumferential slipping going as far back as the source 4. The series of rollers 6 provide a convenient means of obtaining the needed back tension, but other means, such as a brake block or a die, work equally well. The Wire then passes onto the tank 7 to form the temporary wrapping 8. The temporary wrapping 8 has a suflicient number of turns, usually no more than two or three being required, to create a friction path forestalling slippage at source 4 from the force differential between the fully tensioned wire of the permanent wrapping 3 and the relatively loose wire of the source 4. The vehicle 1 advances around the tank 7 taking up the wire of the temporary wrapping 8 by the element 9 through guide means 10. Guide means 10 is a freely rolling caster serving to align and direct the horizontal wire entering from the tank 7 into a path vertically downward as required by the location of the wheel of the take-up element 9. An I-beam 11 supports the guide means 10, as well as vehicle wheels 12 through bracket 13. The wire is carried around the wheel of take-up element 9, passing therefrom over free turning sheave 14 to form a loop 15, from whence it goes around the wheel of pay-out element 16. A second guiding means 17, similar to first means 10, transmits the wire from the wheel of pay-out element 16 into the final ten sioned wrapping 3 on the tank 7.

Elements for take-up 9 and pay-out 16 are similarly constructed wheels characterized by tapered faces. Wire, when wrapped several times around wheels of this con struction, will not freely slip, although one end is under considerable tension, provided the other end has some measure of counter-tension. It can be shown by a recognized formula well known to the art that the frictional capacity around the wheel for two and a half turns of wire is 25, this figure representing the ratio in the tensions of the tight wire to the loose wire that can be supported without slippage for a coetficient of friction value of 0.205 for steel on steel. When the taper is correctly designed, such a wheel will continuously handle tensioned wire, each turn progressively sliding down the taper as the wheel rotates. The downward slide presents a slight amount of circumferential creep. This must be allowed for in considering a wheel diameter that will give a certain relative amount of take-up or pay-out. Hence this a relativelyconstant pull on sheave 14.

reases '3 type of wheel has ability to controllablycheckslippage of wire therearound, although not preventing slippage altogether. Other types of wheels can be substituted that have means for preventing slippage, such as wedges or fingers that are cam actuated to bear forcefully on the wire during its passage aroundthe wheel.

The wheels of the'take-up and pay-out

elements

9 and 16 are interconnected. In Figure 2 the interconnection isby integral construction of the wheels, which are free to roll as one through bearings on-shaft 18, cantilevered from support post 19. If the wheels were differently situated, the interconnection might bethrough gearing or sprockets and chain. In one situation to be described, the interconnection is by means of 'a clutch. Movement of one wheel produces movement in the other wheel, thus giving reciprocity of rotation. The hookup between wheels is such that any rotationwill produce wire take-up by one wheel and pay-out by the other, the relative amount being in relation to wheel diameters and-ratio of turning speeds through the interconnection.

Figures 1 and 2 show the wheel of the'take-up element 9 to be larger than the wheel of thepay-out element 16. Hence for the integral construction of the interconnection illustrated, it follows that the rate of'taking up wire from the temporary wrapping 8 by virtue of traversing vehicle 1 around tank 7, is greater than the rate at which wire is being paid out into the final'wrapping 3. Inasmuch as the path lengths for the wire around the tank are the same before and after engagement by the elements of the vehicle 1, it is to be concluded that the wire-must be stretching by the difference in take-up and pay-out in order that this requirement may be satisfied. As the take-up element 9 is picking up wire faster than pay-out element 16 is letting it out, wire is therefore accumulating between

elements

9 and 16, and hence'it follows that the stretch must appear at locations other than intermediatelyto the

elements

9 and 16. Further the total stretch must equal the total accumulation between

elements

9 and 16. The stretching results in tension being produced in the wire approximately in proportion to the stretch.

InFigure 1 a free rolling sheave 14 is provided to control the loop of wire 15 forming as a result of wire accumulating between elements 9 and'16. In effect sheave 14- is absorbing stretch being produced in the wire around tank 7 by action of the tensioning means,

elements

9 and 16. Sheave 14 is given upward pull by cable 21), spooling from drum 21 located on the overhead carriage 2. An A frame 22 mounting on the top of overhead carriage 2 and being braced by cables 23 running to a post not shown situated at the center of the tank 7, supports the drum 21 anda motor 24. The latter drives the drum 21, imparting Due to sway of vehicle 1 that may occur during-travel, adjustment of the sheave 14 upward or downward may be necessary. Motor 24, therefore, should have constant torque characteristics and should allow overhauling in reverse to release any excess pull. It should be able to endure continuing stall. Many air and hydraulic motors have these characteristics. In an alternative arrangement a weight could be substituted for motor 24. Here cable 2t would have been directed upward over a pulley on the A frame 22 to a weight acting to give pull on the cable 20. Relatively little force need be exerted on sheave 14, it being necessary only that the weight of sheave 14 be supported and slack eliminated in the wire loop 15, such as to prevent wire slippage around

elements

9 and 16. Referring back to the example cited for the frictional capacity of the wheels of

elements

9 and 16, wherebythe tension ratios of the tight were to the loose wire around the wheels needed to be noless than 25 to 1, it would 'then be necessary to provide a force on sheave 14110 more thana'oout one twelfth-the tension to be-expected in the "final wrapping 3. This force could "be reduced still furcal 6 ther by providing more turns of wire around the wheels of

elements

9 and 16.

For a better understanding of the forces existing throughout the system, a diagrammatic representation of the path taken by the wire in its passage onto the tank as a wrapping in final tension is presented in Figure 4. All wheels of the diagram are on bearings, including the integral wheel combination of the take-up and pay-out elements, and therefore the torques from wire tensions are in balance about any wheel. Assuming the force, W, to be negligible in its action, it follows that there is this relation between tension forces, T1 and T2: T1/T2 equals RZ/Rl. It is therefore seen that considerable tension must exist in the wire just ahead of the take-up element 9, inasmuch as R and R1 differ only slightly. This being the case, it means that the wire being engaged by the take-up element 9 has'been prestretched. The takeup element must, therefore, handle an elongated supply of wire coming from temporary wrapping 8, the stretch having developed in advance of the vehicle rather than behind the pay-out element 16. Accordingly the wheel of take-up element 9 must be even largerwith respect to the wheel-of pay-out element 16 than would be the case if untensioned wire were coming to the take-up element. Calculation has shown that the theoretical ratio of R1 to R2 that will produce the desired tension in the wire of permanent wrapping 3 equals very nearly (1+s) where s is the unit strain in the wire when under the desired tension. In a typical case, tensioning a No. 8 steel wire (0.162 inch diameter) to 2900 lbs. load will result in a strain in the range of 0.005. The theoretical ratio between wheel sizes of take-up and pay-out elements is then 1.01. The wire immediately ahead of the take-up element would have a theoretical tension of 2871 lbs. For all practical purposes there is counterbalance in the tensions of the wire between points immediately ahead of take-up element 9 and behind the pay-out element 16.

Note that in rotation of the take-up and pay-out elements of Figure 4, power must be interchanged between the latter elements, because of the interconnection. Inasmuch as the tensions of wire in each element very nearly counterbalance each other, the interchange of power therebetween tends to be counteractive, requiring the addition of very little power to effect drive.

Referring again to Figure 1, vehicle 1 in combination with a tensioning means such as described above or any of equivalent character giving substantial counterbalance in the tensions of wire at points before and after engagement by the tensioning means, is pulled around tank 7 by the overhead carriage 2 through support cables 25. Overhead carriage 2 is powered by a motor 26, giving drive to wheel 27 through sprockets and chain 28. The weight of vehicle 1, in combination with a slight lag behind the overhead carriage 2, evidenced by the inclination of support cables 25, creates sufficient horizontal force component to overcome the sum of the relatively light drags still remaining from a counterbalancing tensioning means, from friction, and from back tension at rollers 6.

Overhead carriage 2 has two

end sections

29 and 30, which are made up of welded tube members.

End sections

29 and 30 are assembled in conformity with the curvature of tank 7, being connected by means of clamps 31 to other tubular members that serve as spacers 32 and cross-braces (the latter not shown) to give a rigid construction. The whole is tied back by cables 33 to a post (not shown) at the center of tank 7. The overhead carriage 2 is usually equipped with a means (not shown) that engages the ends of supporting cables 25, running down over sheaves 34-, in order that vehicle 1 can be lifted progressively to give spacing in the wire wrappings.

Advantage is gained by having the counterbalancing wires entering and leaving the vehicle at the same elevation through guide means 10 and '17. In this manner no force couples are introduced which would tend to unbalance or tilt the vehicle, these being prevalent in some other winding machines known to the art. The I-beams 11 supporting guide means and 17 can bearranged to allow adjustment vertically, thus controlling the elevation of the wire placement. It may be desirable also to provide a second pair of guide means 10 and 17 attaching to the bottom of I-beams 11, in order that wire may be Wound below the level of the vehicle.

In some instances it may prove difficult to establish the exact ratio in the wheel sizes of take-up and pay-out elements that will give the desired tension. This may be overcome by providing a greater ratio in wheel sizes tending to overtension the wire, and providing an arrangement such as is illustrated in Figure 5, to afford relief. Here illustrated is an interconnecting clutch means replacing the integrally constructed wheels of take-up and pay-out

elements

9 and 16 as shown in Figures 1 and 2.

A torque can now be established at which the pay-out wheel 39 will slip relative to the take-up wheel 38, by adjusting the air pressure going to sac 35. Air sac 35 is attached to and extends completely around an inner rim 36 on the wheel of pay-out element 39. Air pressure forces sac 35 into frictional engagement with the internal drum surface on the wheel of take-up element 38. Wheels of

elements

38 and 39 have individual bearings 37 running on shaft 18. If the tension in the wire becomes excessive, countertorques are developed on the clutched

wheel combination

38 and 39, to produce relative slipping between the wheels. Such slippage shortens the loop of wire accumulating between

elements

38 and 39, thus relieving the tension to normal.

The wrapping operation of Figure 1 is started by threading the wire from source 4 around rollers, tank, and wheels in the described sequence, and anchoring the wire end by means of a bolt to the wall of tank 7. The wire is threaded snugly, leaving a loop 15 as small as possible around sheave 14. Motor 24 is activated to place loop 15 under tension. The wire 3 is then tensioned by advancing the vehicle around the tank. When a roll of wire 4 has been exhausted, it has been found convenient to attach the beginning end of a new roll to the tail end of the old roll, using line splices well known to the art. The splice should be behind the rollers 6, as it is not adapted to travel through the rollers. Winding is then continued until the splice arrives at the guide means It), whereupon the wire is permanently clamped to the tank wall behind guide means 17. The tension may then be relieved in the wire through the various rollers and wheels on the vehicle. The splice can generally be worked through the latter impediments, when the wire is untensioned. Once the splice has arrived back of guide means 17, the placement of tensioned wire may be resumed.

An alternative method for driving a wire tensioning vehicle around a tank or other structure is illustrated in Figures 6 and 7. Here shown is a vehicle 40 traveling around a structure 41. Wire is supplied from a source 42, the wire then being pulled through an orifice 43 to create the relatively slight back tension for the reason detailed in the embodiment of Figures 1 and 2. The orifice here replaces the series of rollers 6 of Figures 1 and 2. The wire is guided into temporary wrapping 50 on structure 41 by means of free rolling wheel 44, it being one of a number of coaxial wheels constituting a contact wheel assembly 45. It is to be noted here that the wire from the source can be guided directly to the structure through means other than a wheel of a contact wheel assembly without impairing greatly the efiicient action of the contact wheel assembly in traveling around corners, such as in Figure 9. However it is generally convenient to have guidance around one of the wheels of the contact wheel assembly.

Driving wheel 46, one of the wheels in the assembly 45, picks up the Wire of the temporary wrapping 50 around the structure 41 one or two convulutions back from the source 42. vThe wheel 46 powered by motor 47 tractionally carries the wire around it, thus pulling vehicle around the structure, and causing wire to flow around all of the free turning wire wheels of the assembly 4-5 and the sheave of stretch absorbing means 48. Wheel 46 has a tapered face, and is similar in characteristics to the wheels of take-up and pay-out

elements

9 and 16 of Figures 1 and 2. The wheel 46, therefore, has capabilities of continuously exerting pull on the wire in advance of it, without noticeable slippage, while discharging it rearwardly onto the structure 41 as a continuation of temporary wrapping 50 at considerably less tension. After another turn, usually only one being required, around structure 41, the wire is again picked up by the vehicle 40 and engaged by other wheels of the contact wheel assembly 45, this time starting with the wheel of the takeup element 49. The wire of the temporary wrapping 50 passes in almost non-slipping contact several turns around the wheel of take-up element 49, finally emerging to form loop 51 being controlled and directed by the free rolling sheave 48. A force from cable 52 on the sheave 48 keeps the loop 51 free of slack and provides sufiicient back tension to prevent wire slippage around

wheel elements

49 and 53, in the same manner as was described in the embodiment illustrated in Figures 1 and 2. The wire of loop 51 is carried a number of turns around the wheel of pay-out element 53, also a member of contact wheel assembly 45, which deposits it in place on structure 41 as the final tensioned wrapping 54.

Figure 8 is a simplified diagram of the course taken by the wire around the wheels of the contact wheel assembly as it is taken from source 42, until it is laid down as the final tensioned wrapping 54. The wire is shown originating from source 42 at A, from Where it passes over wheel 44 to start the temporary wrapping at B. The wire continues one or more turns around structure 41 from B until it arrives at C from where it is engaged by driving wheel 46, being tractionally carried around wheel 46 in one turn to be deposited at D. The wire continues from D in another turn around structure 41 arriving at E, from whence it is tractionally taken up in several turns by element 49, thence passing over sheave 48, and being paid out tractionally in several turns by element 53 into the final tensioned wrapping 54 at F.

The cable 52 originates from a means (not shown) supported by an outrigger (not shown) mounting to the front of vehicle 40. This means consists of a drum and motor equivalent to those described and shown on Figures 1 and 3. Supporting mean for vehicle 40 are not shown, this depending on the rigging of the particular application. Wheels 56 keep the vehicle frame 57 from coming into contact with structure 41. Free rolling wheels take the radial load of the tensioned Wires on the other wheels of the contact wheel assembly 45, as well as keeping the same other wheels from touching the surface of structure 41.

Wheels of take-up and pay-out

elements

49 and 53 are again integrally constructed for reciprocity of rotation, with wheels of element 49 being larger than the wheel of 53, such that the desired degree of tension is introduced into the final wrapping 54. If desired, the alternate arrangement of the clutch of Figure 5 could have been incorporated.

As noted in the description for the embodiment of the invention in Figures 1 and 2, the tensions in the wire at either side of the tensioning means are substantially counterbalancing. If the drive wheel 46 were immediately in front of the tensioning means (for example at E in Figure 8), an additional load would be introduced to the wire equal to the force required to overcome the sum of any ditferential in the tensions of the wire through the tensioning means, the frictional resistance of the various wheels, the back tension on the wire from the orifice 43 at the start of the temporary wrapping, and possibly the resistance introduced from the vehicle supporting means not shown. The sum of these forces would be in all likelihood enough to break the wire or at the least to subject it to severe yielding. A law of friction well known to the art provides that the tensions of a wrapping around a structure diminish rapidly from the tight side of the wrapping going back to the loose side in accordance with an exponential relation. Accordingly the tension in the wrapping generally about one turn or less forward of the tensioning means has been so reduced that the sum of the resistance forces enumerated above can be superimposed on the normal tension existing at that point, without overloading the wire to a dangerous degree. Thus we have a drive means acting on the wire at a point in advance of a tensioning means, thelatter subjecting the wire to substantially counterbalancing tensions immediately before and after the tensioning means as illustrated in Figures 6 and 7. Such a drive means would work equally well in combination with tensioning means revealed by earlier patent art producing counterbalance in the tensions of wire fore and aft of the tensioning means employing a weight or force exerted on a loop in the wire between the temporary and the final wrapping.

The contact wheel assembly 45 illustrated in Figures 6 and 7 can operate in tensioning wire on structures having other than circular cross-sections, provided the diameters of all the wheels transmitting wire under tension are in close proximity with the structure, i. e. being very nearly as large as wheels 55 which freely roll against the structure 41, and which also are members of the contact wheel assembly 45. However the mechanics of winding tensioned wire on a non-circular structure can be better understood by referring to Figures 9, l0, and 11. Here a vehicle 64 is illustrated in the process of winding tensioned wire 65, on a horizontally situated beam 58. In this particular embodiment of the invention there is also a source of wire 71, a back tensioning means 72, a temporary wrapping 73, and a contact wheel assembly 59, having one wheel 60 rolling against the beam 53. The one wheel 60 is all that is required in this instance to keep the other wheels of the assembly 59 from touching the surface of the beam. This can be appreciated when it is considered that the overall axial length of the assembly 59 has been exaggerated for reasons of clarity in the illustration and also that vehicle 64 is sturdily enough supported by casters 61 so that the axis of assembly 59 remains very nearly perpendicular. The take-up and pay-out elements 69 and 7d are removed from the contact wheel assembly 59 in this embodiment. They are, however, connected for reciprocity of rotation at l to l reverse ratios through a speed reversing gear box 66 and keyed shafts 67 and 63. As in the other embodiments described, the wheel of take-up element 69 is larger than the Wheel of pay-out element '76. Again

elements

69 and 70 are constructed with tapered faces designed to controllably check slippage of wire therearound. Hence wire istractionally taken up from temporary wrapping 73 faster than it is tractionally paid out as the final tensioned wrapping 65, thus having creation of tension.

Figure 12 is a diagrammatic illustration of the course taken by the wire in passing from the source 71 until placed as the final tensioned winding 65 around beam 58. This simplifies understanding of the paths taken by the wire in passing around the various wheels of Figures 9, 10, and 11. As in the earlier embodiment represented by Figures 6 and 7, the driving means for vehicle 64 is through forcible rotation of a driving wheel 74 situated in the contact wheel assembly 59. Driving wheel 74 is of tapered face construction, thus being able to tractionally carry around it the wire of temporary wrapping 73, in rotation by motor 75 through keying to shaft 76. Driving wheel 74 is shown picking up the wire of temporary wrapping 73 at L on Figure 12, the wire at this point being a one or more turn continuation around beam 58 from K, with further continuation over guide sheave 98 to the source 71 at J. The wire is tractionally carried around wheel 74 in one turn and returned to the beam at M, where it continues one turn around beam 58, to be picked up again by guide wheel 77 at N. The wire is guided by wheel 77 to the wheel of take-up element 69, around which it is carried several times, finally coming oif above and passing around stretch absorbing sheave 78. From sheave 78 the wire is carried downward and several turns around wheel of pay-out element 70, discharging to guide wheel 79, which transmits the wire into final position on beam 58 at 0.

Guide wheels

77 and 79 are members of contact wheel assembly 59. They are shown to be integrally joinedtogether, freely rolling as one on shaft 76. Inasmuch as wire must be taken up faster than it is paid out, it is desirable that wheel 77 be larger than wheel 79 by the same ratio that wheel of take-up element 69 is larger than wheel of pay-out element 70. Otherwise there would be power losses in slippage around wheel 77. When the size ratios of

wheels

77 and 79 are correctly designed, they can be considered as additional frictional surface of the take-up and pay-out elements. If desired,

wheels

77 and 79 can be individual, each rolling independently on its own bearing. Their relative sizes would not be important in this case.

Vehicle 64 is supported by casters 61, which roll on the ground or other suitable supporting structures. Wheels 80 on the inside of vehicle 64 keep the horseshoe frame 97 of the vehicle from coming into contact with any part of beam 58. It can be seen from Figure 9 that as vehicle 64 reaches the rounded end of beam 58, contact wheel assembly 59 will remain in contact with beam 58 through wheel 60, by virtue of inward force components from various tensioned wires going around other wheels of assembly 59. Centrifugal force swings vehicle 64 around the end of beam 58 in following contact wheel assembly 59 as it rolls around the beam end until wheels 80 can again come into play against the side of beam 58. All wheels of the contact wheel assembly 59 picking up or laying down wire are advantageously provided of a size very nearly equal to wheel 60 so that wire will not have to be unduly lifted, and thus stretched as contact wheel assembly 59 rolls around the beam end. The invention is not limited to structures having broadly rounded corners, but will apply also to corners that are sharp.

Contact wheel assembly 59 is illustrated as having a bracket 81, supporting the drive motor 75, and the speed reversing gear box 66, these parts being shown removed from the vehicle 64 in Figure 11. The bracket 81 is attached to male dovetail 82. It is usually convenient to provide a means (not shown) for elevating dovetail 82 and thus contact wheel assembly 59.

Instead of driving the vehicle 64 through engagement of the wire of the ternoorarv wrapping 73 by the drive wheel 74, the drive might have been along more conventional lines. whereby one or more of the su porting wheels (equivalent to caster 61) would be powered in traction to the ground.

The stretch absorbing sheave 78 is supported by the A-frame 96, which mounts a motor 62 and drum 63. These are equivalent to the corresponding components of Figure 1.

A scheme for winding tapered articles is illustrated in Figures 13 and 14. The embodiment of the invention as shown is that for a tapered pipe section 83 being rotated. The article could just as well have been a stationary tank or beam structure having a taper or other varying cross-sectional area, while still being applicable to the principles to be described for the tapered pipe section 83 picking up a tensioned wrapping in rotation.

The tapered pipe section 83 is horizontally situated, being supported by

axial shafts

84 and 85 at each end. These shafts are connected to centering

flanges

86 and 87. The

shafts

84 and 85 are in bearings (not shown). One of the

shafts

84 and 85 is connected to a power source (not shown) for rotating the pipe section 83,

.The tensioning means

comprisiugelements

88, 89, and 90 is generally best mounted on a carriage (not shown) designed to traverse in a direction parallel to the axis of the pipe section 83. The traverse of thecarriage is best tied in with the rotation of the pipe section, in order that spacing of the wire wraps on the pipe section 83 can be controlled.

Wire from a source (not shown) is introduced through a back tensioning orifice 91, of the same type and characteristics used in Figures 6 and 7. The orifice 91 is mountable on the traversing carriage along with the tensioning means. The wire is taken up in a temporary wrapping of several turns by the pipe section 83 in rotation, so as to develop traction in accordance with the principles already set forth.

The wire of the temporary wrapping leaves pipe section 83 at point X to be taken up by the wheel of take-up element 88, which tractionally carries the wire several turns around itself finally discharging it to an equalizing element. The latter corresponds to the stretch absorbing element of the earlier embodiments of the invention, and consists of a free rolling sheave 90, which is held back through a force on cable 92, similar in character to the force described earlier in connection with the stretch absorbing element. There is also the similar weight or motor for providing the force on cable 92. Sheave 93 keeps cable 92 in alignment. Sheave 93 also is attached to the traversingcarriage (not shown).

From around sheave 90 the wire is brought to the wheel of the pay-out element 89. Pay-out element 89 tractionally carries the wire in several turns, finally paying it out from whence it is taken up by the rotating pipe section 83 as the final tensioned winding at point Y.

The wheels of take-up element 88 and pay-out element 89 are again integrally constructed for reciprocity of rotation. They are fixed to horizontal shaft 94, mounting to the traversing carriage (not shown) by bearings (not shown).

It should be observed that in applying a continuous wrapping of wire under the arrangement of Figures 13 and 14, wire is taken up along the taper at point X, and paid out again up the taper at point Y. The instantaneous path lengths of the wire around the pipe section 83 differ at points Y and X, this difierence varying as the difference in diameters at these points. In this case the path length is longer around the pipe for the paid-out wire than it is for the taken-up wire. We have indicated earlier the relationship of the element diameters in winding cylindrical structures. Accordingly with the above taper the relationship of the wheel diameters of take-up element 88 to pay-out element 89 must be less than the corresponding relationship in cylindrical winding, so as to compensate for the increased path length of the paid-out wire, in order that the wire be stretched the correct amount for the desired degree of tension.

By winding down the taper with the arrangement shown in Figures 13 and 14, it will be noted that the accumulation of wire in the loop 95 between

elements

88 and 89 will be less than for corresponding conditions in winding a cylindrical pipe. The reverse is true, if winding proceeds up the taper.

It can be seen that under certain conditions of taper and location of elements, the pay-out rate might conceivably have to be greater than the take-up rate. In this event the wire making up the difierence. must be drawn from the loop 95 being controlled by the sheave 99 of the equalizing element. 7

Frequently the taper on a pipe section or other structure might be discontinuous or vary in its slope. Here it is best to provide a ratio in the sizes of the take-up and pay-out elements of a maximum .for the expected range of conditions so that the wire will tend to be overstressed. The stress in the wire would then be relieved to the correct degree of tension by controlled slippage through a means, such as the clutch of Figure Thus, varying the pitch of the taper, would have no efiect on the tension of the wire.

Although this invention has been shown in specific embodiments, it is nevertheless understood that various changes and modifications obvious to one skilled in the art may be made without departing from the spirit and scope of this invention.

I claim:

1. Apparatus for wrapping tensioned wire around an article comprising a vehicle adapted to beplaced in rolling contact with an article, means mounted on said vehicle for holding a source of wire to be payed out, means mounted on said vehicle for taking wire from its source and temporarily wrapping it around the article, a take-up drum and a pay-out drum each mounted for rotation on said vehicle, means mechanically connecting said drums for rotation ,in common, the relationship of said drums and said means mechanically connecting same being such that when rotated in common the peripheral speed of said takeup drum is greater than the peripheral speed of said payout drum, floating means to hold wire passing from said take-up drum to said pay-out drum in the form of a loop, means to bias said floating means to maintain slight tension on the wire loop and to take up elongation of the wire resulting from pay-out by said pay-out drum being less than take-up by said take-up drum, and means to impart relative movement between said vehicle and the article whereby the wire of the temporary wrapping is picked up and passed to said take-up drum and passed via said floating means to said pay-out drum from whence it is laid around the article as a permanent tensioned wrapping.

2. Apparatus as defined in claim 1 wherein said means mechanically connecting said drums includes a clutch for relieving overtension. a

3. Apparatus as defined in claim 1 wherein said means to impart relative movement between said vehicle and the article includes a self-propelled overhead carriage adapted to ride on the article and drag the vehicle thereover.

4. Apparatus as defined in claim 1 wherein said means to impart relative movement between said vehicle and the .article includes a contact wheel mounted on said vehicle engaging the article in a rolling contact, a pulley wheel coaxially mounted with said contact wheel on said vehicle for engaging wire wrapped on the article, and a motor op- :eratively connected to drive said pulley wheel whereby said vehicle is pulled around said article.

5. Apparatus for wrapping tensioned wire around an article comprising means holding a source of wire to be payed out as a temporary wrapping on the article, a takenp drum and a pay-out drum each mounted for rotation, means mechanically connecting said drums for rotation in common, the relationship of said drums and said means mechanically connecting same being such that when rotated in common the peripheral speed of said take-up drum is greater than the peripheral speed of said pay-out drum, floating means to hold wire passing from said takeup drum to said pay-out drum in the form of a loop, means to bias said floating means to maintain slight tension on the wire loop and to take up elongation of the wire resulting from pay-out by said pay-out drum being less than take-up by said take-up drum, and means to impart relative movement between the surface of the article and said drums whereby the wire of the temporary Wrapping is picked up and passed to said take-up drum and passed via said floating means to said pay-out drum .from whence it is laid on the article as a permanent tensioned wrapping.

6. Apparatus for wrapping tensioned wire around an article comprising means holding a source of wire to be payed out as a temporary wrapping on the article, a take-up drum and a pay-out drum each mounted for rotation, means including clutch means mechanically connecting said drums for rotation in common, the relationship of said drums and said means mechanically connecting same being such that when rotated in common the peripheral speed of said take-up drum is greater than the peripheral speed of said pay-out drum, floating means to hold wire passing from said take-up drum to said pay-out drum in the form of a loop, means to bias said floating means to maintain slight tension on the wire loop and to take up elongation of the wire resulting from pay-out by said pay-out drum being less than take-up by said take-up drum, and means to impart relative movement between the surface of the article and said drums whereby the wire of the temporary wrapping is picked up and passed to said take-up drum and passed via said floating means to said pay-out drum from whence it is laid on the article as a permanent tensioned wrapping.

7. Apparatus for wrapping tensioned wire around an article comprising means holding a source of wire to be payed out as a temporary wrapping on the article, a take-up drum and a pay-out drum each mounted for rotation, means mechanically connecting said drums for rotation in common, the relationship of said drums and said means mechanically connecting same being such that when rotated in common the peripheral speed of said take-up drum is greater than the peripheral speed of said pay-out drum, floating means to hold wire passing from said take-up drum to said pay-out drum in the form of a loop, means to bias said floating means to maintain slight tension on the wire loop and to take up elongation of the wire resulting from pay-out by said pay-out drum being less than take-up by said take-up drum, and means to impart relative movement between the surface of the article and said drums including a self-propelled carriage whereby the wire of the temporary wrapping is picked up and passed to said take-up drum and passed via said floating means to said pay-out drum from whence it is laid on the article as a permanent tensioned wrapping.

8. Apparatus for wrapping tensioned wire around an article comprising means holding a source of wire to be payed out as a temporary wrapping on the article, a take-up drum and a pay-out drum each mounted for rotation, means mechanically connecting said drums for rotation in common, the relationship of said drums and said means mechanically connecting same being such that when rotated in common the peripheral speed of said take-up drum is greater than the peripheral speed of said pay-out drum, floating means to hold wire passing from said take-up drum to said pay-out drum in the form of a loop, means to bias said floating means to maintain slight tension on the wire loop and to take up elongation of the wire resulting from pay-out by said pay-out drum being less than take-up by said take-up drum, and means to impart relative movement between the surface of the article and said drums including a contact wheel mounted on said vehicle, a pulley wheel coaxially mounted therewith for engaging wire and a motor operatively connected to drive said pulley wheel whereby the wire of the temporary wrapping is picked up and passed to said take-up drum and passed via said floating means to said pay-out drum from whence it is laid on the article as a permanent tensioned wrapping.

References Cited in the file of this patent UNITED STATES PATENTS 2,370,780 Crom Mar. 6, 1945 2,375,921 Hirsh May 15, 1945 2,520,402 Hirsh Aug. 29, 1950 2,520,403 Hirsh Aug. 29, 1950