US3727851A

US3727851A - Apparatus for winding insulation onto vessels

Info

Publication number: US3727851A
Application number: US00561833A
Authority: US
Inventors: J Beninati; P Duron; J Perry
Original assignee: Airco Inc
Current assignee: Airco Inc
Priority date: 1966-06-30
Filing date: 1966-06-30
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17

Abstract

Thermal insulation is applied circumferentially to a vessel by rotating the vessel about its longitudinal axis to cover the cylindrical suraace with one layer per each revolution. A series of carriages are simultaneously driven about the vessel on a track inclined slightly to the horizontal axial plane of the vessel to wrap insulating tapes in a substantially longitudinal direction to provide interlocked layers of thermal insulation over both the end areas and intermediate surface.

Description

United States Patent n 1 Beninati et al.

[ 1 Apr. 17,1973

[ APPARATUS FOR WINDING INSULATION oNTo VESSELS- [75] Inventors: John J. Beninati, Kenilworth, N..l.;

Paul P. Duron, Anaheim, Calif.; James L. Perry, Glen Ellyn, lll.

[73] Assignee: Airco, Inc., New York, NY.

[22] Filed: June 30, 1966 [21] App]. No.: 561,833

[52] US. Cl. ..242/7.23, l56/l86, 156/445 [51 Int. Cl. ..B65h 89/00 [58] Field of Search ..242/2, 3, 7, ll, 242/158; 156/169, l70, 186, 189, 425, 445;

[56] References Cited UNITED STATES PATENTS 3,140,058 '7/l964 Courtney ..242/2 3,255,976 6/ l 966 Mcde .242/7 3,276,936 10/1966 Uhlig et al 156/425 3,309,185 3/l967 Weber r r ..242/2 X 3,333,778 8/1967 Levenetz et al. I ..242/3 2,987,100 6/1961 Strickland et al ..242/7 X Primary ExaminerBilly S. Taylor v Attorney-Edmund W. Bopp and H. Hume Mathews 5 7 ABSTRACT Thermal insulation is applied circumferentially to a vessel by rotating the vessel about its longitudinal axis to cover the cylindrical suraace with one layer per each revolution. A series of carriages are simultaneously driven about the vessel on a track inclined slightly to the horizontal axial plane of the vessel to wrap insulating tapes in a substantially longitudinal direction to provide interlocked layers of thermal insulation over both the end areas and intermediate surface.

14 Claims, 12 Drawing Figures PATENTEDAPR 1 11m '3'. 727, 85 1 SHIN 2 0F 2 mvsmons T. JOHN J. BENINATI PAUL P. DURON JAMES L. PERRY ATTORNEY.

APPARATUS FOR WINDING INSULATION ONTO VESSELS This invention relates to methods and apparatus for applying heat insulation to a vessel, and more particularly to cryogenic vessels. The invention is more particularly concerned with the wrapping of layers of insu-.

lation around the vessel and with the apparatus by which the wrapping is applied.

In its broader aspects, it is an object of the invention to provide an improved method for wrapping heat insu lation over the outside, including the ends, of a vessel.

Another object is to wrap some insulating layers around the periphery of the vessel in a spiral and to wrap other insulating layers longitudinally around the vessel, and over the ends of the vessel, in a helical wrap that overlaps by various amounts influenced by rotation of the vessel about its longitudinal axis.

Another object is to wrap heat insulation of a vessel with mechanically controlled tension of the insulating material as it wraps; and this is an important advantage of the invention because the density of the insulation depends upon the tension with which it is wrapped, and the insulating effect of the insulation depends upon its density over the area to which it is applied. It may be said, therefore, that another object is to obtain more uniform insulating results.

Still another object is to apply heat insulation in suc cessive layers that are wrapped in circumferential and longitudinal directions with the latter extending over the ends on different sides of the centers of the ends so that the different layers which are interlocked cannot be dislodged from the vessel.

The vessel includes apparatus for applying heat insulation in accordance with the method of this invention; and to drive mechanism and tension control means for the apparatus. I

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part thereof, in which like reference characters indicate corresponding parts in all the views;

FIG. I is a diagrammatic side elevation of apparatus for applying heat insulation to a vessel in accordance with this invention;

FIG. 2 is a top plan view of the apparatus shown in FIG. 1;

FIG. 3 is an end view, on a reduced scale and partly broken away, of the apparatus shown in FIGS. 1 and 2 and with the means for applying a circumferential wrap of insulation to the vessel;

FIGS. 4 and 5 are enlarged, fragmentary, sectional views taken on the lines 4l-6 and 55, respectively, of FIG. 1;

FIG. 6 is a greatly enlarged detail view taken on the section line 6-6 of FIG. 5;

FIG. 7 is a diagram showing the manner in which the tape is applied to each end of the vessel;

FIGS. 2-11 are diagrammatic views showing suc cessive steps of the application of the circumferential spiral insulation and the longitudinally extending helical insulation; and

FIG. 12 is a greatly enlarged, fragmentary, sectional view showing the insulation after application to the outside of a vessel.

The drawing shows a cryogenic vessel 16 which is closed by ends l8 and 2%. There is a shaft 22 extending from the center of the end 18 and a shaft 24 extending from the center of the end 20. These

shafts

22 and 24 can be rigidly connected with the vessel in various ways and are preferably connected with the vessel by having the ends of the vessel made with center openings or sockets for receiving the shafts 22 and 241.

The shaft 22 rotates in bearing means 26 at the top of a pedestal 28; and the shaft 24l rotates in bearing means 36 at the top of a pedestal 32. At least one of the

shafts

22 and 24 has thrust bearings (not shown) for preventing endwise movement of the vessel 16. There is a sprocket 36 secured to the shaft 22 and this sprocket is rotated by a chain 38 which passes around another sprocket 40 on the output shaft of a speed reducer 412 which is driven by a motor 44.

The motor 24 receives its power from a power line 46 and the motor is equipped with any suitable conventional speed control device 3-3 for regulating the speed at which the vessel 116 rotates. In practice, the speed reducer 62 is also constructed so that it is capable of varying the speed of rotation of the sprocket 40 to obtain accurate control of the rotary speed of the vessel 16.

There is a frame or guide 52 which extends around the vessel 116. This guide 52 has a bracket 54 on each side with a stud 56 extending into a bearing 58 at the top of a pedestal 66. The bearings 5% are in alignment and the guide 52 can rock about a transverse center line which is close to the transverse center line through I the mid point of the longitudinal axis of the vessel 16. The guide 52 is rocked on this transverse axis into the angular position shown in FIG. I which locates one end of the guide 52 above the shaft 22 and the other end below the shaft 24. The reason for this arrangement will be apparent in the description of the manner of applying the insulation lengthwise of the vessel 116.

In order to hold the guide 52 in its selected angular position, there is a pedestal 62 connected to a bracket 64, on the frame 52, by a vertically adjustable connector 66. There is another pedestal 7% connected with a bracket d0 of the guide 52 by an adjustable connector 82.

The guide 52 is made up of sections. For example, referring to FIG. 2, there is a straight section 52a with flanges 86 at its opposite ends. Then there is a short section 5212 with similar flanges by which the sections are connected together. The next section of the guide 52 is a curved section 52c with the same kind of flanges 86; and this curved section connects with a straight section 52d which is located above the shaft 22. In similar fashion the guide 52 is of symmetrical construction on both sides around its entire extent. The brackets which support the guide 52 are preferably located at connections between sections so that the flanges 86 can be used for connecting the guide 52 with the brackets. It will be understood that the

pedestals

28, 32, 60, 62 and 76, or at least most of them, are movable so as to accommodate vessels of different diameter and different length. When the apparatus is to be used with a vessel of greater diameter, longer sections 52d are inserted into the guide 52. This makes the guide 52 wider. When the vessel is longer, the length of the guide 52 can be increased by using longer straight sections or more straight sections such as the section 52a.

Such changes in the length of the frame also change the angle at which it is located in order to have the frame pass over the shaft 22 and under the shaft 24 at locations close to these shafts and, therefore, close to the centers of the ends of the vessel. The longer the vessel, the more nearly the guide 52 approaches a horizontal position. I

There are carriages 90 which are supported by the guide 52. The construction by which these carriages are supported from the guide will be described in connection with FIG. 5. For the present, it is sufficient to understand that the carriage 90 runs along the guide 52 and that it carries tape holders 92 which support reels of tape 94 which wrap around the vessel 16 as the carriage 90 travels along the guide 52 and as the vessel 16 rotates about its longitudinal axis. These reels of tape 94 are moved around the vessel in the plane of the guide 52.

There are a plurality of carriages 90 and they are preferably spaced at equal distances along the length of the guide 52. Each carriage 90 is connected to the next adjacent carriage along the guide 52 by a connector bar 96 (FIG. 4) which serves to move every carriage as a unit with the successive carriages. The connector bars 96 are pivotally connected with the carriages 90 and thus the carriages 90 and the connector bars 92 form an articulated structure capable of passing around the curves of the guide 52. It is necessary that the clearance between the guide 52 and all portions of the vessel 16 be sufficient to permit passage of the carriages 90 and the reels of tape 94 which are the parts projecting furthest from the guide 52.

The carriages 90 are driven by a carriage drive unit 100 located along the guide 52 at one side and only one side of the guide 52. This carriage drive unit has a motor 102 (FIG. 1) which operates a driving gear 104 through a chain and sprocket connection 106 and a speed reducer 108. The driven gear 104 meshes with another gear 110 which drives an endless belt that will be explained in connection with FIG. 4. For the present it is sufficient to understand that lugs on the endless belt engage successive carriages 90 to move the carriage along the guide 52 for a distance equal to the length of the endless belt; and by the time that a carriage has travelled this distance, another lug on the endless belt will come into position to contact with the next successive carriage. Thus the endless belt of the carriage drive unit 100 must be at least as long, in the direction of travel of the carriages, as the distance between corresponding portions of successive carriages. Only three carriages 90 are shown in the drawing (FIG. 2) in order to have the illustration clearer but the course followed by the carriages and the presence of the other carriages is indicated by the dotted line 114.

The motors 42 and 102 (FIG. 1) receive power from the same power line 46, and the speed of these motors, and the gear reductions in the speed reducers 42 and 108 are correlated so that the tape holders 92 of the carriages 90 apply a layer of tape over the entire length of the vessel 16, and around the ends of the vessel and for the full circumference of the vessel for each complete revolution of the vessel 16 about its longitudinal axis. The actual speed of movement of the carriages 90 along the guide 52 as compared with the angular speed of rotation of the vessel 16 about its longitudinal axis depends upon a number of different factors. One of these is the width of the tape carried by the holders 46; another is the amount of overlap, if any, of the tape at the mid region of the vessel; and still another is the total number of tape reels 94 from which tape is being withdrawn in applying a layer to the vessel 16.

FIG. 3 shows the vessel 16 rotating in a clockwise direction about its longitudinal axis; and shows a sheet 120 of insulating material being wrapped around the circumference of the vessel 16. This sheet 120 unwraps from a reel 122 supported on suitable bearings (not shown) and the sheet passes across guide rolls 124 which serve to prevent the sheet from sagging lengthwise as it moves toward the vessel 16. The sheet of insulation 120 cannot be shown on the vessel 16 in FIG. 2 without covering of the structure which needs to be illustrated but the longitudinal extent of the sheet 120 is indicated in FIG. 2 by showing one of the guide rolls 124 and a portion of the sheet 120 which is broken away before it extends over the frame 52.

FIG. 2 shows two of the tapes 94a and 94b which are wrapped on the vessel 16 from the tape holders 92 of the carriage 90. The vessel 16 rotates in the direction indicated by the arrow 130 in FIG. 2.

FIGS. 4 and 5 show a section of the guide 52. This section consists of four angles 132 connected at their ends to a flange 134. There is a similar flange in each end of the angles 132. These flanges are connected by bolts 136 to corresponding flanges of the next guide sections. The carriage 90 includes wheels 140 which run on horizontal faces of the angles 132. Ordinarily the wheel 140 which is nearest to the tape holder 92 contacts with the angle 132 below it and the corresponding wheels 140 on the side of the carriage remote from the tape holders contact with the angle 132 above it.

Carriage has other wheels 142 which contact with vertical surfaces of the angles 132. Thus the wheels I40 and 142 prevent displacement of the carriage 90 in all directions except lengthwise of the guide 52. There are openings 146 in the flanges 134 for the passage of the rollers and 142 through the flanges to the angles of the next section of the guide 52.

The tape holder 92 has a fixed bottom flange 150 from which the reel of tape 94 is supported. There is preferably a washer 152 on top of the flange 150 for holding the reel of tape 94 out of contact with the stationary flange 150. The tape holder 92 has an upper portion 154 which is connected to the rest of the tape holder by a hinge 156 so that the upper portion 154 can swing upward away from the flange 150 to permit the inserting of new tapes in the tape holder.

Each reel of tape 94 is wound on a hub 160 that fits over an axle 162. This axle is shown as a bolt in FIG. 5 and is preferably screwed into the flange 150 and is then locked by a nut 158. The construction of the hub 60 is preferably that shown in FIG. 6 which provides lost motion and spring means for maintaining the tension on the tape. There is an outer hub 160a surrounding an inner hub 160b. There are recesses 166 in the inner hub 160b. Each of these recesses 166 has a substantial angular extent and there are preferably three such recesses at equal angular spacing around the hub. The outer hub 160a has lugs 170 which extend into the 'one end of the recesses 166 and thus take up the lost motion in one direction.

The springs 172 are on the side of the lugs 170 which causes the springs 172 to yield and be partially compressed when tape is being pulled from the reel of tape 94 which is wrapped on the outer hub 160a. Rotation of the hub 160 is opposed by a brake 176 which is compressed against the fixed axle 162 by a screw 178 threaded into an opening in the inner hub 160b. This screw 178 is tightened up to maintain sufficient friction so that whenever the pull on the tape relaxes, the springs 172 will move the outer hub 160a backwards and wind some tape back on the reels 94.

The time when this rewinding is necessary for tension control is when the carriage approaches the end of the vessel and starts around the curve to pass across an end of the vessel. During this passage around the corner of the vessel there may be some accumulation of slack in the tape, unless some expedient for reversing the direction of movement of the tape reel 94 is employed as shown in FIG. 6. The reason for such an accumula tion of slack is that the reels of tape are moving closer to the vessel as they travel around the corner of the vessel and are moving closer at a rate which is sometimes faster than the rate at which tape is wrapping on the vessel, the exact correlation being dependent upon the shape of the vessel being wrapped.

Various other expedients can be used for maintaining tension on the tape at all times and for wrapping tape back on the reel when the tension relaxes, and the construction shown in FIG. 6 is merely representative of such means insofar as the broader aspects of the invention are concerned. Also, it will be understood that the brake for resisting unwinding of the tape reels 94 canv take many different forms and can be a softer friction washer at the location of the washer 152 (FIG. 5) and the corresponding washer 152' at the top of the reel. When these washers are employed as friction washers they should be constructed so as to exert their friction on the inner hub 1611b (FIG. 6) and not on the outer hub 160a if such a lost motion connection is employed.

The means for propelling the carriage 90 along the guide 52 is shown in FIG. 4 and a portion of the construction is shown at the lower part of FIG. 5. There are wheels, preferably sprocket wheels 162 on axles 164 which are supported by a frame 186 connected at oppositc ends to the flanges 134 at the ends of the guide sections that includes the carriage drive unit 100. A belt, preferably a chain or link belt 191) passes around the sprocket wheels 184. This is an endless belt and it has a plurality of dogs 192 connected to it at equally spaced intervals. In the drawing there are two such dogs 192. The straight runs of the belt 190 extend generally parallel to the direction of the guide 52, and the run which is closest to the angles 132 on which the carriage runs, is in such a position that the dog 192 on this run projects upwardly between the lower angles 132 and contacts with a downwardly extending portion 194 of the carriage 90, as shown in FIGS. 4 and 5.

One of the sprocket wheels 184 is driven from the gears 104 and 110 (FIG. 1) and this drives the belt 190 (FIG. 4) continuously and at uniform speed. Whenever the dog 192 in contact with the carriage has moved the carriage close to the end of the run of the belt 190, the next dog 192 has moved into position to engage the next carriage so that there is always one dog in position to keep the carriage assembly moving along the guide 52.

FIG. 7 shows the way in which the tape wraps over the end 20 of the vessel 6. One tape 94c is indicated in dot and dash lines and this tape passes across the head or end 20 substantially tangent to the shaft 24. The portions of the tape 94c which are behind subsequent tapes are dotted in FIG. 7.

As the vessel 16 rotates clockwise in FIG. 7, the next tape 94d is applied and this tape is also substantially tangent to the shaft 24 and therefore has percent overlap with the tape 94c adjacent to the center of the end 20 but somewhat less overlap as the tapes approach the circumference of the vessel. This tape 94 is shown in dash lines where it is visible and is dotted where it is behind the subsequently applied tape.

With further rotation of the vessel in a clockwise direction, the tape 94:2 is applied. This tape, shown in full lines, is also substantially tangent to the shaft 24 adjacent the center of the end 20 and has 100 percent overlap with the other tapes 94c and 94d. The overlap increases, as in the other cases, as the tape 24e extends toward the circumference of the vessel 16. The region at which the tapes have 100 percent overlap travels around the end 20 in a counterclockwise direction as the vessel rotates clockwise but the insulation is much thicker over the end 20 because of the substantial overlap at these end regions. However, the additional overlap of the insulating tapes at the ends of the vessel compensate for the fact that the only insulation over the ends of the vessel is that obtained from the tapes which are wound longitudinally around the vessel. The sheet insulation (FIGS. 2 and 3) does not extend over the ends 18 and 21).

FIGS. 8-11 are diagrammatic views showing the way the insulation is applied as the vessel 16 rotates. In FIG. 8 the sheet insulation 120 has been wrapped around 90 of the vessel 16, and the carriages for applying the tapes longitudinally around the vessel are then started. During the next 90 of rotation of the vessel 16, the tapes 94 are applied over 90 above the horizontal guide on which the tape carriages run on one side and 90 below the horizontal guide on which the carriages run on the other side. This results in the fact that the rotation is clockwise.

FIG. 10 shows the insulation after another 90 of rotation from the FIG. 9 position. Tape insulation 94 has now been applied around the entire circumference of the vessel 16 and the sheet insulation 120 is located under the tape 94 for one-half of the circumference and is then located above the tape 94 for the next 90 of the circumference.

As the vessel 16 completes one revolution, as shown in FIG. 11, there is a layer of sheet insulation 1211 extending around the entire circumference of the vessel.

This has the tape insulation 94 under the sheet 120 for the second half of the revolution and the sheet insulation 120 is directly against the outside of the vessel 16 for the other half of the first revolution. Tape continues to be applied over the sheet insulation 120 and thus the insulation is built up with alternating layers of sheet insulation 120 and tape insulation 94 as shown in FIG. 4. The sheet insulation 120 forms a continuous spiral and is thus interlocked with the successive groups of convolutions of the insulating tape 94 which is wound longitudinally about the vessel 16.

The number of insulation layers applied to the vessel depends upon the quality of the sheet and tape and upon the total heat insulation desired for the use for which the vessel is intended. The invention permits very large numbers of insulation layers to be built up around the vessel with minimum expense in labor. Thicknesses in the drawing are exaggerated for clearer illustration.

The preferred embodiments of the invention have been illustrated and described. Terms of orientation are, of course, relative. Changes and modifications can be made, and some features can be used in different combinations without departing from the invention as defined in the claims.

I claim:

1. Apparatus for applying wrapping material to a vessel including in combination bearing means for supporting a vessel for rotation about a longitudinal axis, means for wrapping material around the vessel in a generally circumferential direction as the vessel rotates about said axis, and means for simultaneously wrapping other material around the vessel generally length-wise thereof comprising a carriage movable along a course in a plane that is at an angle to said axis and that intersects said axis, a guide along which the carriage moves, the guide extending along the sides of the vessel and across both ends of said vessel, means for rotating the vessel about said axis, and means for moving the carriage along the guide in timed relation with the speed of rotation of the vessel about said axis, said simultaneous wrapping causing said circumferential and length-wise wrappings to interlock.

2. The apparatus described in claim 1 characterized by said other material being in tape form in a tape holder on the carriage and from which tape is unwound to wrap generally lengthwise around the vessel, and a connection between the tape holder and the carriage and on which the tape holder rotates as the tape is wrapped on the vessel, and means resisting the movement of the tape so as to maintain a predetermined tension on the tape as it is wrapped on the vessel.

3. The apparatus described in claim 2 characterized by the means resisting movement of the tape being a part of the connection between the tape holder and the carriage, and said connection having lost motion between the means resisting movement of the tape and the tape that is wrapping on the vessel, the pull of the vessel on the tape as it wraps being sufficient in normal operation to take up the lost motion in one direction, and resilient means in the lost motion connection that takes up the lost motion in the opposite direction when the tension on the tape drops below a given minimum, the said resilient means exerting force in a direction to rewind the tape on the tape holder and thus prevent any accumulation of slack in the tape.

4. The apparatus described in claim 1 characterized bY there being a plurality of carriages movable along the guide, connectors joining each carriage with the next carriage ahead of and behind it on said guide, the connectors being angularly movable with respect to the carriages so that the assembly of carriages and connectors can pass around parts of the guide where the direction of the guide changes.

5. The apparatus described in claim 4 characterized by the connectors being bars pivotally joined to their respective carriages, and means for driving one of the carriages directly and the rest of the assembly by motion transmitted through said bars.

6. The apparatus described in claim 5 characterized by the means for driving one of the carriages being an endless belt that reverses its direction of travel by passing around wheels at spaced locations along a run of the guide, one run of the belt being close to said run of the guide and movable in a direction generally parallel to the run of the guide, and abutments on the belt in position to engage elements of successive carriages to propel said carriages along the guide, said run of the belt being at least as long as the minimum spacing of any of the carriages from the next adjacent carriages.

7. Apparatus for wrapping a three-dimensional object including means for supporting said object for rotation about a longitudinal axis, means for applying wrapping material around the object in a generally longitudinal direction as the object rotates about said axis, and other means operating in timed relationship with said first means for simultaneously wrapping other wrapping material around the object generally transversely to said first mentioned wrapping so that said wrappings interlock, said applying means comprises a material distributing carriage movable along guide means arranged in a plane that is at an angle to said axis and that intersects said axis, said guide means extending around said object so that said plane intersects said object.

8. The apparatus described in claim 7 in which the wrapping material is insulation.

9. The apparatus described in claim 7 in which said applying means includes tensioning means for maintaining a predetermined tension on said wrapping material as said carriage moves around said object.

10. Apparatus for applying wrapping to a vessel comprising shaft means at each end of said vessel, bearing means for supporting each of said shaft means for rotation of said vessel about a substantially horizontal axis, means for wrapping material around the vessel in a general circumferential direction as the vessel rotates about said axis, and means for simultaneously wrapping other material around the vessel generally lengthwise thereof comprising material distribution means passing over one of said shaft means at one end of said vessel and below the other of said shaft means at the other end of said vessel, means for rotating the vessel about said axis, said simultaneous wrapping causing said circumferential and lengthwise wrappings to interlock.

11. Apparatus as defined in claim 10 wherein the material distribution means comprises a pair of closely spaced reels mounted on a movable carriage, the reels being spaced apart a predetermined distance on said carriage to simultaneously apply a pair of tapes of material to the vessel in overlapping relationship in such a manner that a trailing edge of one tape in the pair is overlapped by a leading edge of the adjacent tape in the pair.

12. Apparatus for applying material to a large threedimensional form comprising means for supporting said form and for rotating said form about an axis of rotation, means for applying material around the form in a generally axial direction as the form rotates about said axis, and other means operating in timed relationship with said first means for simultaneously applying material around the form generally transversely to said first mentioned material so that said materials interlock, said first applying means including a portion extending around said form in a continuous closed path.

13. Apparatus as defined in claim 12 wherein said portion extending around the form is a guide means composed of interconnected sections capable of easy assembly and disassembly whereby sections of desired shape and length may be assembled to accommodatethe form being wrapped with material.

14. Apparatus as defined in claim 13 including means for pivotally mounting said guide .means about an axis lying in a plane at right angles to said axis of rotation.

Claims

12. Apparatus for applying material to a large three-dimensional form comprising means for supporting said form and for rotating said form about an axis of rotation, means for applying material around the form in a generally axial direction as the form rotates about said axis, and other means operating in timed relationship with said first means for simultaneously applying material around the form generally transversely to said first mentioned material so that said materials interlock, said first applying means including a portion extending around said form in a continuous closed path.

13. Apparatus as defined in claim 12 wherein said portion extending around the form is a guide means composed of interconnected sections capable of easy assembly and disassembly whereby sections of desired shape and length may be assembled to accommodate the form being wrapped with material.

14. Apparatus as defined in claim 13 including means for pivotally mounting said guide means about an axis lying in a plane at right angles to said axis of rotation.