US2681184A - Wire tension control - Google Patents

Description

June 15, 1954 c. THOMAS WIRE TENSION CONTROL Filed April 1'7, 1953 INVENTOR Lewzls 6. 1120mm" $2M 9 laz /MW ATTORNEYS 3 3 Q m m a w 4 w w O. Y w w m m: mm Qw O P m mm: mm

Patented June 15, 1954 UNHTED STATS tTET OFFICE 7 Claims.

This invention relates to wire tension control devices, and particularly, to an apparatus for maintaining uniform tension in a wire or the like being fed to a wrapping machine. It is desirable to wrap many tubular objects, such as a concrete pipe, thin-walled tubing and the like, with wire under tension to thereby prestress the tubular structure and render it able to withstand great internal pressures without fracture. The apparatus of the present invention, however, may be employed to tension wire being fed to and utilized by any other mechanism or apparatus.

In. general, the apparatus consists of a pulley or sheave engageable with a run of the wire being fed to the wrapping machine and tension applying means arranged to constantly urge the pulley in a direction to apply tension to the wire and to maintain a uniform tension therein. The pulley is mounted on a carriage or carrier to which a cable is attached, either directly or by means of a traveling pulley, and which cable is placed under tension by having its other end held in fixed position and by having a weight suspended. from an intermediate portion of the cable. The magnitude of the weight determines the pull of the cable on the pulley and, therefore, the tension applied to the wire.

Since the rate of feed of wire may vary or its extent of elongation may vary as the process proceeds, the weight may rise or fall and the carriage or carrier may move through an impractically large range of movement. Too large a range of movement would necessitate an unusually large and bulky apparatus. The present invention is concerned with means for regulating the range of movement of the tensioning weight and consists of a winch to which the stationarily held end of the cable is attached and which winch is under control of the weight. If the weights rise beyond a predetermined limit, the winch is actuated to unwind cable therefrom and. thus lower the weights to the desired level without, in any way, changing or even momentarily disturbing the tension applied to the wire. Likewise, if the weights drop below a predetermined lower limit, control means are actuated to wind more cable on the winch and thus raise the weights to the desired level.

It has been heretofore proposed to regulate the tension in a wire being fed to a machine by I means of a weight. The prior art devices, however, engage the traveling wire directly by the weighted pulley and regulate the rate of feed of the wire to keep the weight within the desired range of vertical movement. Such arrangements Cll are subject to many disadvantages, since the control of the rate of feed must be exercised with extreme accuracy and at frequent intervals.

The present invention is not concerned with regulation of the rate of feed or" the wire being tensioned, but exercises control only on the length of the secondary cable supporting the tensioning weight.

It is, therefore, an object of this invention to provide a simple arrangement of weights to impose uniform tension on a traveling wire.

It is a further object of this invention to provide a device for tensioning a traveling wire and which is free of adverse effects occasioned by vibrations caused by the traveling wire or the feed motor therefor.

It is a further object of this invention to provide a wire tensioning device wherein the tension may be regulated a desired amount without the necessity of performing any complicated calculations.

It is a still further object of this invention to provide a wire tensioning device of unusually simple and economical construction.

Further objects and advantages will be readily apparent to those skilled in the art as the description proceeds in connection with the accompanying drawings, wherein:

Fig. 1 is a schematic side elevational view of an apparatus embodying the present invention; and

Fig. 2 is an enlarged sectional view taken on the line 2-2 of Fig. 1.

The apparatus shown in the drawings schematically illustrates a machine for wrapping wire under tension about a cylindrical concrete pipe 2, by way of example. It is to be understood that the wire being tensioned may be utilized by any other suitable machine within the scope of the present invention. The concrete pipe 2 may be supported for rotation about its longitudinal axis in any conventional manner and caused to rotate about that axis to wrap a tensioned wire r about its outer surface. Further means (not shown) may be provided for moving the pipe 2 longitudinally of its axis as wrapping proceeds, to maintain that portion of the pipe being wrapped always in line with the path of advance of tensioned Wire 5. Such means are conventional and need not be described further.

Wire 1 is supplied by a suitable reel 6 or other source of supply and is fed therefrom (such as by controlling rotation of the reel 6) at a rate corresponding to the rate of rotation of the pipe 2. Preferably, the wire is fed from reel 6 at a somewhat lesser rate than it is wrapped on pipe 2 since placing the wire under tension increases its length somewhat.

The apparatus for maintaining wire 4 under uniform tension comprises a suitable fixed framework 8 provided with a trackway H} on which a carriage I2 is mounted for movement. Although shown in the drawings as a mere slide, the carriage [2 may be provided with rollers engaging trackway It. The carriage I2 has a roller or pulley i4 journalled thereon at l6 and around which wire 4 is trained. It will be obvious that wire 4 may progress from reel 6 to pipe 2 and merely causing rotation of pulley l4. Any force applied to carriage l2 urging it to the left will maintain wire 4 under corresponding tension. The tension in each run of wire 4 will be onehalf the force applied to carriage I 2.

The frame 8 also anchors one end i 8 of a cable 26. The cable 20 is trained about a second pulley 22 journalled on carriage I2 and extends over an idler pulley 24 journalled in bearing block 25 and downwardly into a pit or other suitable space 28. Within the space 26 the cable 26 is trained over a traveling pulley 28 then upwardly over a second idler pulley 36 journalled on framework 32. Also mounted on the framework 32 is a power driven winch 34 having a drum 36 about which the end of cable 20 is wound. A suitable motor 38 may be arranged to drive the winch drum 36 in either direction. The change of direction of rotation of winch drum 36 may be effected by clutches and gearing, but preferably motor 38 is a reversible electric motor.

The traveling pulley 28 in the pit or space 26 is journalled to a yoke 40 having a rod 42 extending downwardly therefrom and terminating in a head 44 underlying and supporting a platform 46. The platform 45 may have upwardly extending rods 48 fixed thereto (see also Fig. 2) adjacent the corners of the platform. A plurality of weight elements 56 are provided with openings near their ends corresponding to the spacing between rods 48 whereby the weight elements may be threaded on the rods 48 to be held in position thereby on platform 46. Weight elements 50 may be added or removed at will, to vary the tension of cable 2n and consequently the tension applied to wire 4.

It will be noted that weights 56 are suspended from cable 26 by means of a traveling pulley 28 and thus the tension in each run of cable 29 is one-half the total value of the weights 50 plus the platform and its associated structure. The cable 20, having its end 58 anchored to frame 8 and passing over a traveling pulley on carriage [2, will apply a force to the carriage i 2 equal to twice the tension in cable 25. In other words, the force applied to the carriage I2 is exactly equal to the weight suspended from cable 20 (ignoring friction). As stated previously, the tension applied to wire 4 is one-half the force applied to carriage l2. It will, therefore, be obvious that the tension in wire 4 may be readily and rapidly adjusted by adding or removing weights B in an amount equal to twice the desired change of tension in wire 4.

While the carriage i2 has been described as being supported by and guided along trackway I B, it will be apparent that in many installations the track 16 can be eliminated. In such case the carriage 12 will be suspended and held above the ground or other surface by the tension in wire 4 and cable 20.

Preferably the trackway It! is provided with at least one stop member 52 positioned to be engaged by an end of carriage 12 to prevent unwanted movement of carriage I2 beyond that stop position and consequent damage to control member 58, to be described. Likewise, bearing block 25 prevents too great movement of carriage [2 to the left and thus prevents damage to control member 56.

The weights 50 are so positioned on platform 46 that an edge 54 of the platform extends laterally outwardly beyond the weights. A pair of control members 56 and 58 are mounted on the side walls of the pit or space 26 and each is provided with a plunger or the like 6!} arranged in the path of movement of the edge 54 of platform 46. The upper control member 58 is positioned to be engaged by the platform 46 at about the time carriage l2 approaches stop 52 and the lower control member 56 is positioned to be engaged by platform at about the time carriage 12 reaches the leftmost limit of its travel on trackway Hi. In the position shown in Fig. 1, platform 46 is slightly below control member 58 and plunger 60 of control member 53 is just free of contact with platform 46. Assuming that under these conditions wire 4 is being continually fed to and wrapped on pipe 2, platform 46 and weights will maintain uniform tension in the wire without vertical movement. If for any reason the rate of feed of wire 4 slows down or an enlarged portion of wire is being tensioned so that its elongation is lessened, the platform 46 will rise slightly as a result of movement of carriage E2 to the right. Assuming that platform 46 rises sufiiciently to actuate plunger 60 of control member 56, a circuit consisting of suitable wiring in duct 52 is closed by a switch controlled by plunger 66 and energizes motor 36 to rotate winch drum 36 in a direction to unwind some of cable 26 from the drum. Such unwinding of cable 20 will increase the length of the cable between idler pulleys 24 and 36 and thus lower the platform 46 to again release plunger 66 and de-energize motor 38. At that time the weight is hanging free and performing its intended function.

The winch drum 36 is thus a mere holding means or reaction member for cable 26 but is capable of being manipulated to change the length of the loop of cable 29 extending downwardly between idler pulleys 24 and 36. Other mechanisms could be employed for accomplishing the same function. For instance, the leftmost end of cable 20 could be anchored to a member movable along framework 32 and that member could be caused to move to the right or left in response to actuation of control members or 58.

The control member 56 is arranged in the motor circuit to energize the motor for rotation in a reverse direction from that described above, if and when the weights 56 and the platform 46 descend far enough to engage the plunger E6 of control member 5'5 and the result will be lifting of platform 46 to clear the control member 56 and again stop motor 38.

From the above description it will be apparent that applicant has devised an apparatus for maintaining uniform tension in a traveling wire and which will maintain that tension uniform without the necessity of constant adjustment even upon rather large variations in the rate of feed of the wire or variations in its degree of elongation.

The arrangement described for limiting the range of vertical movement of the weight not only reduces the overall size of the apparatus, but also insures accurate control of the tension in wire t. If the weight were permitted to descend in space 26 an unlimited distance, a substantial weight of cable (between pulleys 2d and 30) would add to the effective weight of the tensioning arrangement. By limiting the range of movement of platform is, the variation in the weight of cable 253 between pulleys 24 and 3B can be held to an inconsequential value.

While a single specific embodiment of the invention has been shown and described, it is to be understood that many modifications may be resorted to without departing from the invention as defined in the appended claims.

I claim:

1. Wire tension control apparatus comprising, a trackway, a carriage movable along said trackway, a pulley journalled on said carriage and adapted to engage an intermediate portion of a wire to be tensioned, a cable connected to said carriage and arranged to pull said carriage along said trackway in a wire tensioning direction, the other end of said cable being wound on a winch drum, reversible drive means arranged to drive said winch drum in either direction, spaced idler pulleys between said carriage and winch drum, said cable being trained over said idler pulleys and looped downwardly therebetween, a vertically movable Weight supported by said loop, vertically spaced control means arranged in the path of movement of said Weight, the uppermost control means causing said drive means to rotate said winch drum in a cable-unwinding direction when said weight engages said control means, and the lower control means, when engaged by said weight, causing said winch drum to rotate in a cable-winding direction.

2. Wire tension control apparatus as defined in claim 1 wherein said cable is trained over a second pulley journalled on said carriage, the end of said cable being anchored to a stationary structure.

3. Wire tension control apparatus as defined in claim 1 wherein said weight comprises, a platform, a pulley riding on said downwardly looped cable, said pulley being journalled to and supporting said platform, and a plurality of individually removable weight elements on said platform.

4. Wire tension control apparatus as defined in claim 3 wherein said weight elements are positioned inwardly of an edge of said platform and wherein said vertically spaced control means are positioned in the path of movement of said edge.

5. Wire tension control apparatus as defined in claim 1 wherein said drive means comprises a reversible electric motor and wherein said control means comprise motor control switches adapted to, respectively, energize said motor for rotation in dilierent directions.

6. Wire tension control apparatus comprising, means having a pulley journalled thereon adapted to engage an intermediate portion of a wire to be tensioned, a cable connected to said means and arranged to pull said means in a wire tensioning direction, said cable being also connected to a holding apparatus comprising a cable take-up and let-out device spaced from said means, the portion of said cable between said carriage and holding means being trained over guide means to form a downwardly extending loop of said cable, a weight suspended from said loop and being freely movable along said cable whereby to tension said cable and urge said means in a wire tensioning direction, and means responsive to vertical movement of said weight beyond upper or lower predetermined limits to actuate said take-up and let-out device to, respectively, increase or decrease the length of cable in said loop whereby to maintain said weight at all times within the range defined by said limits.

7. Wire tension control apparatus as defined in claim 6 wherein said weight includes removable weight elements whereby the tension applied to said wire may be readily adjusted.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,412,509 Johnstone Dec. 10, 1946 2,635,825 Stanford Apr. 21, 1953

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