US 2520402 A
Description (OCR text may contain errors)
Aug. 29, 1950 P. R. HIRSH 2,520,402
WIRE-WRAPPING MACHINE Filed Aug. 18, 1944 4 Sheets-Sheet 1 a2 FIG-1.
M6? Km Aug. 29, 1950 P. R. HIRSH 2,520,402
WIRE-WRAPPING MACHINE Filed Aug. 18, 1944 4 Sheets-Sheet 2 dTTOZR YEY g- 29, 1950 I P. R. HIRSH 2,520,402
WIRE-WRAPPING MACHINE Filed Aug. 18, 1944 4 Sheets-Sheet 5 INVEN TOR. P/l/Z/R A.
Wei/(w Patented Aug. 29, 1950 UNITED STATES PATENT OFFICE WIRE-WRAPPING MACHINE Application August 18, 1944, Serial No. 550,122
11 Claims. 1
This invention relates to the construction of tanks, standpipes, large diameter pipes and like structures and more particularly to machines for applying tensioned windings about such structures.
Among the objects of the invention is to eifect economies in the construction of tanks and other objects made from material such as concrete which, except for externally applied reinforcing, Would have a low bursting strength.
Another object of the invention is to provide a wire wrapping machine capable of governing tension in a wire during a winding operation so as to enable maximum utilization of the strength of a given wire, and the application of a predetermined tension whereby selection of a suitable wire may be made in the interest of avoiding such waste of material as would otherwise result by the employment of a wire having strength greater than required and by applying the wire under an unknown tension. Another object of the invention is to provide a Wire wrapping machine capable of wrapping wire uniformly under a predetermined amount of tension so as to enable utilization of the well known principle of prestressin-g for the purpose of economy in reinforcing steel and improved functioning of the structure.
The machine of the present invention is capable of exerting any desired tension in a wire and of maintaining such tension during a wire winding operation in which the Wire is laid about an object, such as a tank, standpipe, or large diameter pipe. The wire winding and stressing machine is caused to travel over the surface of an object by cooperating mechanisms which traverse the machine about the object and at the same time advance it longitudinally of the axis of the object. The travel of the machine circumferentially of the object and longitudinally of the object is subject to control so that the speed of application of the wire and the pitch of the wire being applied are capable of variation with respect to each other whereby different requirements of construction may be readily met. The machine is capable of use for the construction and reinforcing of tanks and other containers designed for containing liquids and materials having diiferent static heads and containers having different heights. Other uses of the invention will be apparent from the herein contained description of a form of machine; for example, a tensioned wrapping can be applied thereby about solid objects, such as concrete columns and piles.
Further and other objects of the present in vention will be hereinafter set forth in the accompanying specification and claims and demonstrated by the drawings which show by way of illustration a preferred embodiment and'the principle of my invention and what I now consider the best mode in which I have contemplated applying that principle. Other embodiments of the invention employing the same principle may be used and structural changes made as desired by those skilled in the art within the spirit of the appended claims and without departing from the present invention.
' Referring to the drawings,
Fig. 1 illustrates a front elevation of part of a machine embodying the principle of the invention;
Fig. 2 is a side elevation of the machine shown in Fig. 1 with its associated wire winding carriage in working position;
Fig. 3 is a top view of the machine shown in Fig. 2;
Fig. 4 is a front elevation of the wire Winding carriage;
Fig. 5 is a horizontal sectional view of mechanism for changing the position of a guide sheave;
Fig. 6 is a section on line 6-6 of Fig. 5;
Fig. 7 is a schematic view illustrating the manner in which the wire and tension-applying cable is trained over sheaves; and
Figs. 8 and 9 are detail views of a wire clamp.
While the machine is suitable for applying Wire about tanks, standpipes, large diameter pipes and other objects designed for various uses, and having walls of different strengths apart from the reinforcing provided by a tensioned winding, a particularly useful application of the invention is for affording economies in the construction of objects wherein the wall has but little tensional strength, such as, for example, a wall made of concrete or mortar and having as an integral part thereof but little or no steel reinforcing. Such objects may be molded or cast in place wholly by the employment of concrete, or they may be built up by the application of mortar by projecting devices. After the wall has been constructed, the wall is placed under compressive stress by the application of a tensioned wire winding against its exterior surface. The amount of compression in the material of a wall for maintaining the wall under compressive stress when the tank is filled, is predetermined, and the winding is applied under such tensional stress as will meet this condition. Consequently, it is important that the exact amount of pro-stressing required is determined. It also is a matter of considerable im- .5 portance that the maximum strength of available wire be made use of in order that the cost of materials are maintained at a minimum. In order that these objectives be attained, it is of ultimate importance that a machine be able to maintain the wire required tensional strength to meet the specifications of a particular job.
An assembled machine is illustrated in the drawings. This includes a traverse control support or frame it (Fig. 1), an elevating platform or elevator H and wire winding mechanism I2 (Figs. 2 and 3). The machine is shown in an operating position opposite a tank 3. The illustrated tank may be any other kind of vertically standing object about which a tensioned wrapping is to be applied.
The support It! is in the form of a skeleton box-like tower which is made up of structural steel members including four main columns of which the front pair 14 and I5 are shown in Fig. 1. The two columns at the back of the frame are similar to the front pair. The front and back pairs of these columns are connected, respectively, by head-beams l6 and ll and by foot-beams l8 and I9. Head-beams l6 and I! are connected at their ends by channel irons 2b and 2!, and similar structural elements connect the foot-beams l8 and 59. Columns 14 and i5 are cross-braced by a suitable number of structural elements 22, 23 and 24, but the vertical expanse between head-beam ii and the foot-beam at the back of the tower is open to provide for the vertical travel of elevating platform l l. The construction Of support lil thusfar described is extended to the left and right (Fig. l) by frames 25, 26, made up from structural elements which are rigidly secured to the main columns and thus constitute parts of the support. Sets of cross-braces 2i and 28, (Fig. 2) and other suitable connecting members 29, provide lateral rigidity to the support;
The support is provided with a pair of bolster blocks 38, M, which carry bearings for pairs of truck wheels 32, 33,-respective1y. Each bolster the wall of the tank.
During a wire winding operation the support or tower travels on the rails around the tank and causes the wire winding mechanism to wrap Wire around the tank. The drive for traversing the complete machine may consist of a source of motive power mounted anywhere on the machine. A convenient location for the driving motor is shown at $2 (Fig. 3) at the lower part of the supporting tower. It is suflicient to provide power for driving one wheel of each of the pairs of truck wheels 32 and 33. Shaft 43 for one of the truck wheels 33 is driven from a val"- able speed transmission M, (Figs. 1, 2 and 3) through the intermediary of a pair of bevel gears 45, vertical shaft 35 and a pair of bevel gears 41, one of which is keyed to truck wheel shaft 43. The bevel gears receive their drive from the output shaft of variable speed transmission transmission M, which is in turn driven from motor 42 through a chain or belt and sprocket connection 48.
The power drive to one of truck wheels is obtained from vertical shaft 35 through a chain and sprocket connection 5i), including a sprocket wheel 5! on vertical shaft 34. A pair of bevel gears 52 transmit the rotation of vertical shaft 34 to shaft 53 by which one of the wheels of the pair of truck wheels 32 is driven. It is apparent that the speed of travel of the supporting tower about the tank may be regulated by changing the adjustment of the variable speed If the motor for traversing the machine about the tank is mounted on the elevating platform l l, or on the wire winding mechanism l2, and is arranged to drive the rollers I M and l 15 of the wire winding mechanism which bear against the exterior of the tank as described hereinafter, then the driving connections from motor 42 to the truck wheels 32 and 33 may be dispensed with, if desired. Should two traversing drives be used, the motors for each drive preferably would be synchronized so that each would exert the same driving influence for traversing the machine.
The elevating platform H includes a pair of stringers 55, 56, which are connected at their ends by I-bearns 5?, 58, to form a rectangular frame (Figs. 1 and 2). The I-beams extend beyond stringer 56 in cantilever fashion for supporting the winding mechanism carriage opposite the tank wall, as illustrated in Fig. 2. The I- beams carry rails 59, [iii which provide support for guiding the wire winding mechanism so that the same may determine its own position with respect to the supporting tower and platform. The platform may be boarded over with planks 6| for the convenience of the operator. The end of the platform remote from the tank is provided with a counterweight 62 for counterbalancing the eccentric weight of the wire winding mechanism.
Between the front and back pairs of columns of the tower, opposite column I4 and column [5, respectively, there is a vertically extending guide rail 63 and a similar vertical guide rail 64 (Fig. 3). These two vertical guide rails are secured to the tower and extend from its foot to its headbeams. Guide rail 63 is engaged on opposite sides by a pair of rollers or guide blocks 65 which are carried by the elevating platform H. A similar pair of .rollers or guide blocks 66 engage opposite sides of vertical guide rail 64.
The platform ii is supported, and its rising and lowering movements are controlled, by pairs of chains at each end of the platform. Chain H3, at the right side of Fig. 1, has its ends connected to stringer at H Its companion chain '52, at the same side of the tower, has its ends connected to stringer 56 at is (Fig. 2).
The upper extent of sprocket chain 10 passes over a single sprocket 13, and the lower extent of the chain passes over another single sprocket 14. Chain Ill also is engaged by idler sprockets 75, 16 and a driven sprocket l! on countershaft 78. It will thus be seen that rotation of the countershaft 18 in either direction will cause the right end of stringer (Fig. 1) to rise or lower, as the case may be.
A similar arrangement of idler and driven sprockets is provided for engaging the companion sprocket chain 12 to enable corresponding movements of the right end of stringer 56 through operation of countershaft '18. As shown in Fig. 2, upper and lower single sprockets 19, 80,
idler sprockets 8|, 82 and driven sprocket 88 are mounted in the frame for guiding and actuating sprocket chain I2. Driven sprockets I1 and 83 are carried by countershaft I8 which has a driving sprocket and chain connection 84. This driving sprocket and chain connection 84 is driven from a speed reducer 85.
Speed reducer 85 is directly connected to the power shaft 86 of variable speed transmission 44 so that its driving effect on the countershaft is directly proportional to the speed of motor 42 which is directly connected to shaft 86. Since the drive for the traverse of the tower about a tank is derived through the power output shaft 81 of the variable speed transmission 44, it is apparent that flexibility is provided for varying the rate of travel of the machine about the tank with respect to the elevating rate of the wire winding mechanism and its platform II. By varying the rate of circumferential travel of the machine with respect to the elevating rate of the platform, the resultant direction of the movement of the wire winding mechanism over the surface of the tank can be controlled whereby the pitch of the wire wrapping may be varied at will.
The left end of the platform (Fig. l) is supported, and its rising and lowering movements are controlled through a pair of similarly mounted chains, one of which is shown at 88 in Fig.1. These chains are operable together and at the same rate as chains I and I2 during vertical travel of the platform. Chain 88 is connected to the left end of stringer 55 at 89 (Fig. 1). Its upper end is trained over a double sprocket 90 and its lower end is trained over a single sprock- Double sprocket 90 is engaged by an endless chain 92 which engages the single sprocket 93 and is driven thereby. Sprocket 93 is driven through gears 94, 95, the latter of which is keyed to the same shaft to which sprocket I3 is keyed. It is thus apparent that the two ends of stringer 55 will be caused to rise and lower at the same time and at the same rate, the drive for chain 88 being derived through chain 82 and chain 10 from the countershaft I8. A chain companion to chain 88 is attached to the left end of stringer 56 and it is operated simultaneously therewith from countershaft I8 through chain and sprocket connections located at the back of the tower which:
are similar to those described for operating chain 88. It is thus apparent that similar elevating and depressing movements are simultaneously imparted to both ends of platform II.
For lowering the platform, the drive between the power shaft 86 and the output power shaft '81 of the variable speed transmission 44 can be discontinued and the motor 42 driven in the reverse direction, or a reverse gear mechanism may be interposed between the motor and variable speed mechanism shaft 86.
Wire winding mechanism The wire winding mechanism carriage includes a box frame having a lower rectangular frame I00 and an upper rectangular frame IOI connected together by a number of standards such as I02, I03 (Fig. 2). The upper and lower rectangular frames and the standards may be formed from structural elements such as channel irons or angle irons and as illustrated in the drawings. The box frame is mounted upon and fastened to a supporting rectangular frame I05 (Figs. 2 and 4). Brackets I08, I01 areattached to the frame and carry bearings for roller shafts I08, I09. Shaft I08 has at its ends rollers H0 and III and shaft I09 also has at its ends similar rollers, one of which is shown at II3 (Fig. 2) The left hand rollers (Fig. 1) bear upon rail 58 and rollers II I and H3 bear upon rail 50. These rails rest, respectively, upon beams 51 and 58 of the platform so that the carriage may be moved horizontally to and from the tower and float between the tower and the tank during a wire winding operation. I
For providing a wheeled contact between the carriage and the tank as the machine travels about the tank there are provided two pairs of rollers H4, H5, mounted, respectively, on vertical shafts H6, H1 (Figs. 3 and 4). The shafts are attached to bearings supported by the box frame of the carriage. I
The function of the wire winding mechanism is to enable the winding of a wire under tension about a tank, standpipe or a large diameter pipe. A number of sheaves are provided for guiding the wire during a winding operation and for cooperation with a tensioning device designed for maintaining the wire under a predetermined tension as it is being applied to the object. While the arrangement of the sheaves may be changed so as to enable the winding of wire in either direction about an object, I find it convenient to describe the wire winding mechanism as arranged for applying a wire in a clockwise direction as seen from above.
In Fig. 'I I have illustrated the course of the wire through the winding and tensioning mechanism. The wire II 3 is supplied from. a spool I I9 which is mounted upon a bracket I20 on the carriage. The bracket has a spindle about which the spool may rotate as the wire is drawn from it. In threading the'wire through the Wire winding mechanism it is drawn over sheave I2I and then passes around the object one or more times and then passes over sheave I22 at the other end of the winding mechanism (Fig. 7). The one or more turns about the object are in advance of the final turns of wire which remain on the object as a permanent part of its construction. In many cases one turn of the wire will suflice but more can be made in order to assure frictional resistance between spool H8 and the portion of the wire I23 which comes to the winding mechanism after it encircles the object.
After passing over sheave I22 the wire passes successively over sheaves I24 and I25, each of which is free to rotate on a fixed shaft. The wire then passes over fioating sheave I26 and sheaves I21, I28, and I29, which are free to rotate. Shafts of sheaves I2I, I22, I24, I25, I27, I28 and I29 are carried upon brackets extending from structural elements of the carriage. Theseseven sheaves are idlers for changing the direction of the wire. The positions of sheave I22 and of sheaves I2I and I29 are adjustable for purposes hereinafter described.
Upon leaving sheave I28 the wire passes over sheave I29 and its end is anchored at I30, which is the starting point for the permanent winding. This ordinarily would be located at the lowest point of an object to which wire reinforcing is to be applied, as shown in Fig. 2. The anchor is a fixed member solidly attached to the exterior of the object. Tension is applied to the wire by the application of force to the floating sheave I 26.
When the machine is first threaded, sheave I26 is at its most right-hand position, justto the left of sheave I25 (Fig. 7), and a loop of the wire is engaged-thereby; The loop is intermediate :separ'ated windings;the-temporary advance wind- .ing and the final permanent winding. Force is iapplied-to sheave I26 through a cable I3I which is attached to a yoke I32. 2 ended from a trolley I33 which carries the yoke and shaft upon which sheave I26 is mounted, the arms of the yoke serving to support the end of the shaft at either side of the sheave. Trolley I33 is provided with a pair of rollers which bear upon the flanges of an H-shaped beamstructure I34. Beam structure I34 is fixed to and is carried by the wire winding carriage and itserves tosupportthe wire tensioning mechanism I35 (Figs. 7, 3 and '4). Upon the left end ofbeam structure I34 there is mounted a freely rotatable guide sheave I38 over which cable I3I Thewiretensioning mechanism illustrated comprises a weighing beam I pivotally mounted at HI :and carrying at its free end awinch I42 which is'driven bymotor I43. The cable attached to yoke I32 and passing over sheave 538 extends to winch I42 to whichit is attached. In the operation of the wiretensioning device, the weighing beam I40 .floats betweencontacts I and I46 which operate-a limit switch 'i i'i by which the operation of the'motor is controlled. The weighing beam 140 maintains cable I3I in tension and the amount of tension can be varied by changing the load applied on the weighing beam. As the wire is wound about the object, it is extended in length as the result of the tension applied thereto through sheave I26 and this extension is taken up ,by the permissible movement of sheave I26 between sheave I25 and sheave I33 at the end of beam structure I34. In travelling from its extreme right-hand position to its extreme lefthand position, as shown in Fig. 7, cable I 3I is being taken up by winch I42 under the operation of the motor I43, which is started when contact I45 operates switch I I! as the weighing beam drops. The operation of the motor is discontinued when weighing beam I40 rises sufficiently to cause contact I46 to operate switch I41 and break the motor connection.
When a wire winding operation has proceeded to such an extent that sheave I26 has reached the end of its travel, it becomes necessary to stop the Winding operation so as to place sheave I26 'atits starting position just to the left of sheave .-I25.
The operation of the machine is discontinued for this purpose and wire H8 is temporarily clamped to the frame of the carriage by clamps I50, 151 which are secured to brackets I52 and I53, respectively. By these clamping means, the wire permanently wound about the object and which comes to the carriage over sheave I29, and the portion of the wire which comes to the carriage over sheave I22 can be held without loss of tension so that the opera- .tion of the wire tensioning device I35 may be temporarily discontinued. Upon effecting this clamping, and the release of tension in cable I3I, sheave I26 can be moved to its starting position at the left of sheave I25, a section of wire of by compression thereupon and frictionally engages bothends.
This yoke is susand rollers H4 and H5.
:After the wire has been spliced, the operating tension may be reapplied to the wire lay exertin the proper amount of pull on cable I3I by causing operation of the tension applying mechanism I35. Thereafter the clamping effect of clamps I50 and I5I on the spliced wire is removedand the machine is ready for continuing the winding operation under the same conditions of tension that prevailed before making the splice. When the supply of wire from spool H9 is exhausted,
the empty spool may bereplaced by a filled spool and its wire spliced to the end of the wire temporarily encircling the tank between sheaves -'I2I and I22.
Clamp I50 also may be used temporarily as a brake on the wire when the machine is being set up to provide sufficient frictional hold on the object by the wrapping between spool H9 and sheave I22 to resist the load'to be applied b the tensioning mechanism.
Guide sheaves I2I, I29 and I22 maybe mounted on permanently positioned shafts but I sprefer to mount them on supports which will permit their positions to be adjusted vertically :to enable the wire winding machine to start wrapping an object at its bottom and to endxthe wrapping at its top. As shown in the drawings, particularly in Figs. 2 and l, the positions of these sheaves are close to the lower part of the carriage and in this position the beginning .of
.the wrapping can start at the bottom of the object, as shown in .Fig. 2. Except for the last turns at the top of theobject, these sheaves'may remain, if desired, in the positions illustrated in the drawings, but in order to complete the winding-of the object at its 'top end, provision is made for moving the sheaves to the upper portion of the carriage. This is desirable because the exterior of the object laterally sup- ;mamtained taut while at the same time it is I ports the carriage by reason of the pressure exerted by the tensioned wire on the carriage Sheaves I2I and I29 are supported and moved similarly to sheave I22 and it will suffice to explain the operating and supportng structure for the latter sheave.
Sheave I22, Figs. 3, 4, 5, 6 and 7, is supported on a stud shaft I56 which is carried by a slide I51. Parallel rails I58 and I59 are provided for guiding the slide. The slides are fastened to a plate IIiI which is secured to the carriage. The slide has fastened to it the ends of an endless chain I62 which passes over sprocket wheels I63, I64 carried by plate I6I. Sprocket wheel I63 is keyed to .a shaft carrying a worm wheel I65 which is engaged by a worm I56. The shaft of worm I66 is connected to a shaft I61 having hand wheels I68, I69 which are readily accessible to an operator. The mechanism for adjusting the position of the sheaves I2I and I29 along guide rails I70, "I at the other end of the carriage is arranged and constructed similarly to that for adjusting the position of sheave I22, and its worm wheel shaft is similarly connected to hand wheel shaft I61. The worm gears and worms are of the self-locking type whereby the sheaves are held in any set position. a It is apparent from the description .of operation of the mechanism for changing the positions of sheaves I2I, I22 and I29 that the spacing of the wrappings of wire about the ob- .ject can be changed independently of any change in the elevaton of platform II. This may be accomplished under manual control by .9 having an operator gradually lift the sheaves by turning one of the hand wheels I68, I69 as the tower is traversing about the object. The upper limit of movement of the sheaves, with respect to the carriage, need be sufficient only to permit winding to a point just above the uppermost rollers H4, H by which the carriage is supported against the object under the influence of the tensioned wrapping.
When the last turn of Wire has been laid against the object, the machine is stopped and the wire is securely fastened to an anchor fixed to the object. When the wire is secured, the tension on the wire is released and the end of the wire beyond the anchor is cut.
If it should be considered desirable, turns of wire about the object may be occasionally anchored to members fixed in the wall of the object, but this practice is not deemed indispensable because the present invention enables the tensioning of wire about an object within desired limits which are carefully computed beforehand and therefore are known to be below the maximum breaking strength of the wire.
What is claimed is:
1. A machine for applying wire about a tank or like stationary object, comprising a structure having a vertical height at least as high as an object about which a wire is to be wrapped, a track for guiding said structure about said object, means including wheels supporting said structure on said track, a wire-wrapping mechanism, means carried by said structure of elevating said wire-wrapping mechanism, and means for advancing said structure over said track, said lastnamed means including a motor and connections from said motor to said wheels for driving said wheels to propel said wire-winding mechanism by advancement of said structure.
2. A machine for applying wire about a tank or like stationary object, comprising a structure having a vertical height at least as high as an object about which a wire is to be wrapped, a track for guiding said structure about said object, means including Wheels supporting said structure on said track, an elevator, means carried by said structure for guiding said elevator for vertical travel, means for actuating said elevator along said guiding means, and means for actuating said structure over its track, said lastnamed means including a motor and connections from said motor to said Wheels for driving said wheels to propel said elevator about said object by movement of said structure over said track.
3. A machine for applying a wire about a tank or like stationary object, comprising a structure adapted to travel in a path concentric to the object, an elevator carried thereby, means on said structure for guiding said elevator opposite the surface of said object, a track carried by said elevator and extending normal to the surface of the object, a carriage mounted on said track, a wire-wrapping mechanism on said carriage, and rollers carried by said carriage for engaging the surface of said object during a wire winding operation.
4. In a machine for wrapping a wire about an object, the combination comprising a carriage having sheaves adapted to engage a loop of wire with reaches which extend between the sheaves and opposite sides of an object, means including a cable attached to one of said sheaves whereby tension may be applied to said loop of wire, guide sheaves for said reaches of wire, adjustable supports on said carriage for said guide sheaves, and
actuatable means for changing the positions of said adjustable supports on said carriage while tension is maintained in said wire whereby the locations of said reaches of wire may be changed 5 with respect to said carriage,
5. In a machine for wrapping a wire about an object, the combination comprising a carriage having sheaves adapted to engage a loop of wire with ,reaches which extend between the sheaves and opposite sides of an object, all of said sheaves being idlers providing for the free running thereover of said wire and the training of said wire through said carriage, a platform, means having connection withsaid platform and said. carriage for enabling movement of the carriage laterally of itself, rollers on said carriage for providing support for the carriage against an object to be wrapped with wire' and travel of the carriage over the surface of said object, the axes of said rollers being at substantially right angles to the permissible direction of movement of said care riage on said means, and means separate from said sheaves and said Wire for causing said carriage to travel on said rollers during a wire-wrapping operation, said last-named means being operatively connected to said platform to move said platform and said carriage in a direction perpendicular to the axes of said rollers and about said object. t
.6, In a machine for wrapping a wire about an object, the combination comprising a carriage adapted for relative movement with respect to the surface of a bodyto be wrapped with wire, means carried by said carriage for engaging a loop of wire having reaches which constitute extensions from separated windings of the line about theob 'ect said means including an idler sheave engaging said loop of Wire, said loop of wire and reaches being an intermediate portion of a wire wrapped about said object, means for exerting force on saidsheave for applying tension to saidloop of wire, tension-applying means, carried by said carriage and attached to said force-exerting means, rollers carried by said carfrom separated windings about the object, said loopof Wire and; continuations constituting an intermediate portion of a 'wire Wrapped about 0 said object, means carried by said carriage for applying: tension in said loop of wire, means cooperating with said carriage and bearing against the surface of said object for wholly supporting said carriage during a wire-wrapping operation,
5 and means separatefrom said tension-applying meansand, said wire to; traverse said carriage over the surface 1 of said object during a wirewrapping operation, said last-named means being driven independently of the tension in said loop of wire.
8. A machine for applying a wire about a tank or like stationary object, comprising a structure adapted to travel in a path concentric to a tank, an elevator mounted on said structure, means for moving and guiding said elevator vertically in rewrapping mechanism including sheaves for engaging a loop of wire formed by continuations Certificate of Correction Patent No. 2,520,402 August 29, 1950 PHILIP HIRSH It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:
Column 8, line 74, for elevaton read elevation; column 9, line 33, for the Word of read for;
and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.
Signed and sealed this 14th day of November, A. D. 1950.
THOMAS F. MURPHY,
Assistant Commissioner of Patents.