GB2096227A - Method and apparatus for silo construction - Google Patents

Abstract

The bed of a truck, supports a circular helical guide 7 of a diameter substantially greater than the width of the truck bed. A coil of sheet metal within the guide, supplies a continuous strip to the guide. The top and bottom edges of the strip are bent to form edges which are interlocked by pressure rollers as the strip feeds around the guide. A power saw mounted on arm 20 levels the top edge of the first convolution and also the bottom of the last convolution. A crane (25) on the truck bed lowers a cover (27) onto the tower after the starting convolution is complete and level. The crane lifts the completed tower from off the track and sets it on a prepared foundation (F) alongside the truck. <IMAGE>

Description

SPECIFICATION Method and apparatus for silo construction This invention relates to a method and apparatus for silo construction, and more particularly to formation and erection of silos and similar storage buildings, especially for the rapid on-site formation and erection of such buildings.

A typical silo is a cylindrical structure of the order of about twenty feet (6 meters) in diameter and sixty feet (18 meters) in height with a generally conical roof section having a hatch through which material to be stored is discharged into the structure. Its size, and particularly the diameter, makes impractical prefabrication of the structure at a central plant and its subsequent transportation to the place of use.

Silos have heretofore been constructed in various ways, including a process wherein a continuous strip of metal is unrolled from a coil and moved through an apparatus that converts it into a vertical helix by the successive forming of each convolution below the preceding one and continuously joining the lower edge of the preceding convolution to the upper edge of the one being formed, the height and structure continuously increasing from the bottom upward as the forming of each convolution progressively takes shape. When the desired height has been reached, the bottom is cut off in a horizontal plane to set the silo level on the prepared foundation.

Generally one of two procedures is used in this operation. In one, erection of the structure is effected directly above a previously prepared foundation. This involves the location of the required apparatus and machinery partly on and partly adjacent the prepared base and its subsequent removal, including cutting an opening through the silo for the removal of internal parts of the equipment from inside the silo after the operation is finished.The second, which is practical only when a group of silos are to be simultaneously constructed in one area, requires the placement of several prepared foundations within a fixed radius, the placement of the forming apparatus at some location in the area within a given radius of all of the foundations, and the installation of an immense crane capable of lifting each silo as it is completed from the forming apparatus and placing it on one of the prepared foundations, all of which must be within the slewing and luffing capacity of the crane. This obviously is an impractical procedure where only one or two silos are to be erected or where existing structures do not permit the grouping of all of the units within the operating radius of the crane.

The present invention is particularly concerned with forming and erecting a silo wherein a coil of strip metal is formed into a helical shell of a diameter too large for over the road transportation and wherein there is required the use of an inclined circular track of a diameter at least as large as the diameter of the helical shell.

The present invention in one aspect provides a method of forming and erecting a silo, comprising: (a) transporting a circular track in sections to the site where the silo is to be placed, assembling the track on a flat bed truck intermediate the ends of the truck with outrigged section at each side of the truck supported on outrigger track supports level with the bed of the truck and above ground level; (b) transferring a roll of strip metal mounted on the truck bed into a cylindrical helix by moving it edgewise up and around an inclined circular track and progressively joining the upper edge of the strip metal as it is shaped by the inclined circular track into an added convolution to the lower edge of the completed convolution immediately above it;; (c) severing the cylindrical helix when it has reached a selected height by cutting it in a horizontal plane at a level above the level at which the progressive joining of the said edges is effected, whereby the edges of helix above and below the plane of cutting are joined through a completed convolution and the lower edge of the kerf is sufficiently level and complete to provide the start of the next cylindrical helix; and (d) lowering the completed cylindrical helix after severing is completed onto a prepared base.

The method of the invention is carried out in apparatus which includes a helical track with a lower starting end, having a diameter at least equal to the diameter of the helical shell and of a circular extent of at least one complete convolution of the shell.

The invention in another aspect provides apparatus for forming and erecting a silo, comprising: (a) a tractor trailer truck the trailer of which has a bed longer than the diameter of a helical track secured thereon but narrower than the said diameter; (b) two diametrically opposed sections of the helical track secured to the truck bed and extending across the bed and separated a distance from each other the full diameter of the completed helical track of which they constitute a part;; (c) outrigger track support means at each side of the truck bed when the apparatus is in use for erecting a silo arranged to stabilize the truck bed against transverse tilting, helical track support sections detachably joined to the track sections on the truck bed and supported by the outrigger track support means, the said helical track sections, when in place, complementing those on the bed to form the required helical track; (d) a turntable secured to the truck bed in the area between the said two track sections fixed to the truck bed arranged to rotatably hold a coil of strip metal positioned one end up on the turntable; (e) peeler means for unwinding strip metal from the turntable and guiding it edgewise;; (f) a starting track section on the truck bed arranged to receive the lower edge of the strip emerging from the peeler means and guide the strip in an involute path to the lower starting end of the helical track: (g) power-driven means arranged to drive the strip around the helical track and to join by a pressure rolled seam the upper edge of the oncoming strip to the lower edge of the convolution immediately above; and (h) cut-off means fixed on the truck bed within the area of the circular track arranged to cut the formed helix completely in two in a horizontal plane above the level of the said power-driven means for joining the upper edge of the oncoming strip.

The present invention thus provides a method and apparatus wherein the apparatus, including all power-driven machinery, is permanently mounted on a flat bed truck, except that there are outriggers removably attached to each side of the truck bed that provides support for complementary sections of the helical guide or track up which the metal strip moves edgewise as it is formed into each successive convolution. The bed of the truck may also support a crane which transfers the finished structure from the forming apparatus on the truck bed to a permanent foundation on which it will subsequently stand.

The invention thus provides a method and apparatus by which a truck of over-the-road dimensions may be driven alongside a previously prepared foundation for the silo, the metal formed into a helical cylinder with the upper edge of each successive convolution progressively sealed to the lower edge of the previous convolution and with the top and bottom edges of the cy!inder levelled off and a cover applied, after which the silo is then lowered from the truck onto the permanent foundation. The invention may be advantageously used for the erection of only one or of several silos in the area.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is an illustrative view showing the start of the operation of constructing a silo, following the levelling off of the top edge of the first convolution after the completion of the second convolution; Figure 2 is a plan view of a portion of a truck bed with outriggers in place at each side of the truck and showing diagrammatically several power-driven units permanently carried on the truck bed other than a crane; Figure 2A is a detailed perspective view showing the type of roller used in providing the helical track for the lower edge of the sheet while bending the sheet into cylindrical shape; Figure 3 is a view similar to Figure 1 showing the operation of transferring the silo from the truck to a foundation on which it will be secured;; Figure 4 is a detailed view showing in vertical section one form of continuous seam which may be used to connect the edges of the convolutions; Figure 5 illustrates one manner of levelling off the top and bottom convolutions of the cylindrical tower; and Figure 6 shows an alternative manner of levelling off the top and bottom convolutions of the cylindrical tower.

Referring first to Figures 1 to 3, a flat bed truck 2 of acceptable width for over the road travel, that is a width of about eight feet, is articulated with a tractor 3 in a conventional tractor-trailer rig.

Intermediate the ends of the truck at each side of the bed are a pair of spaced extensible and retractable or hinged outrigger support arms 4 with hydraulic jacks 5 at their outer ends, and generally similar stabilizing supports 6 with hydraulic jacks are desirably located at each side of the truck bed near the rear end.

In the drawing the tractor trailer unit is illustrated in position alongside a prepared concrete foundation F, with the outrigger and stabilizing supports extended and the jacks projected into contact with the earth with the bed generally level.

There is a helical track support, designated generally as 7, fixed to the bed of the truck with its centre on or close to the longitudinal centre line of the truck bed. It has fixed sections, two diametrically opposed ones of which, 7a and 7b, extend across and are anchored to the truck bed.

Two other opposed segments, 7c and 7d, are outrigger sections supported on the outrigger support arms 4, one segment being at one side of the truck bed and the other at the opposite side.

The abutting ends of the several sections are flanged and bolted together at 8 for removal of the outrigger sections for storage on the truck bed when the assembly is moving over the road from one place to another so that the width of the load may then be within legal limits, that is the width of the truck bed itself.

Typically the frame 7 describes a circle of about 20 feet (6 meters) in diameter and its top surface defines one convolution of a helix, the pitch of which approximates the width of the sheet metal strip s from which the shell of the silo is formed. The actual track comprises a succession of closely spaced peripherally grooved rollers 9, each on a mounting structure 10 welded or bolted to the top flange of the track support 7 (see Figure 2A).

There is a turntable 11 mounted on the bed of the truck within the circular confines of the circular track support being remote from track support section 7a with its axis of rotation tilted slightly away from the central axis of the circular track so that, as a coil of metal 1 3 set on the turntable unwinds, its bottom edge will extend a slight incline upwardiy toward the starting or lower end of the helical track. Typically the coil of metal may be of the order of five feet (152 cm) in diameter and forty inches (roughly one meter) high.

Adjacent to the turntable and the coil there is a set of guide or peeler rolls 14 followed by edge forming rolls 15 of a well-known type arranged to shape both the top and bottom edges of the strip s in such manner that they will subsequently interfit when the top edge of the strip is brought into contact with the lower edge of the strip forming the previously completed convolution of the cylindrical helix into which the strip is progressively formed. Both the peeler and edge forming roll units are of known construction.

From the edging rolls the strip moves in a somewhat involute curved path up an inclined starting track 16 on the truck bed up the helical track until its upper edge moves into interfitting engagement with its own lower edge where that lower edge has progressed to around 3600 upwardly and around the inclined circular or helical track formed by the circular frame and its succession of guide rolls.

Following the interfitting of the two edges, they move in continuous progression between a power driven seam rolling and driving roll unit 17 having outer and inner roll elements 17' and 17", respectively, which shape the interfitting strip edges into a closed seam and which also drive the strip up and around the helical track, of course rotating the previously formed structure as it does so.

In Figure 4 there is shown one form of rolled seam that may result where the lower edge A of the strip forms an outwardly offset inwardly turned hook B into which is locked an inwardly offset outwardly turned hook B' at the top edge A' of the newly forming lower convolution. Sealing material comprised of plastic strips may be embodied in the seam as indicated at C and C'.

This type of seam is known in the art and has been used in the manufacture of helical sheet metal pipe.

The seam closing rolls, being power driven and engaging as they do the interlocked edges with great pressure in their bight, also supply the driving force which, as indicated above, rotates the helix as it forms and moves it up the inclined circular track of guide rollers by engagement with which the strip, which receives its intitial curvature on the starting track, is guided to complete circular helical turns.

With the completion of the first convolution and the start of the second, it is apparent that the top edge of the structure will then be inclined through a complete circle, making it necessary to level the top by cutting away the top to be of even height above the level of the bed of the truck. For this purpose there is a horizontally swinging friction saw unit 20.

The saw unit comprises a post 21, fixed to the truck bed at the centre of the circular track support, having a radially adjustable horizontally extending arm 22 rotatable through 3600 about the vertical axis of the post. At the outer end of withe arm there is a motor driven saw, preferably a high-speed friction saw 23. The saw is at an elevation where it will swing about the post at the proper level to square off the top of the first convolution, which is at the level of the junction where the first full circle or convolution ends and the second one begins, or at least desirably not above that level in order to reduce waste.

In making the cutt off, the saw is moved radially outward until it cuts through the metal shells and then is moved horizontally in an arc of perhaps ten inches or a foot (25-30 cm) when a T-shaped spacer 24 is inserted in the kerf (see Figure 5). The stem is inserted in the kerf and has a thickness equal to the vertical width of the kerf so that it keeps the kerf open and the weight off the saw and keeps the tower vertical while the cross head of the spacer helps keep the metal wall above the kerf in line with the uncut shell below the kerf.

After placing the spacer in the kerf, cutting is continued through another increment of arc, after which another spacer is inserted and this process is repeated until the entire circle has been cut. In addition to or in lieu of using the spacer, and after the initial top cut, the kerf may cut in a discontinuous manner, as illustrated in Figure 6, such that narrow connecting portions 24a hold the partially severed section in place until the circle with such uncut connections has been completed and the the uncut connections may be cut away as the final step, at which time the crane hereinafter referred to may hold the upper section of the structure vertical and keep it from lowering as the connecting portions are cut away.

At the rear end of the truck bed there is an extensible slewing and luffing crane 25 and there is an electric generator, indicated by the enclosure 26, for powering the various mechanisms and operating the crane. This, like the crane, is of a conventional construction. The slewing operation of the crane may be effected by rotating the crane at its base 25a on the truck bed and the luffing by essending or retracting the boom and/or increasing or decreasing the angle of the boom and its separately adjustable top section 25b.

After the top edge of the shell has been levelled oft as above described, a prefabricated top cover 27 is swung by the crane into position ove the shell, lowered to fit over the edge which has just been levelled on the shell and bolted or otherwise joined to the top edge of the shell by conventional means.

The cover, after being swung in place, remains attached by means of its central lifting eye 28 to a crane hook 29 which is swivelled in a pully block 30 of the crane. After the roof is attached, the formation of the shell may continue by rotating the shell as successive convolutions are progressively formed. By having the crane hook attached to the cover as the operation proceeds, the structure may be steadied against strong wind that might otherwise overstress the metal where the joint between the edges is in the process of being closed.

After the shell has reached the required height, the rotation of the shell, peeler, edge former.

etc., is stopped and the level cut-off saw is again operated as before to provide a level bottom edge to the shell, and in so doing forms a level starting edge for the next shell. The crane, still hooked to the eye of the cover, is then operated as shown in Figure 3 to swing the structure from the forming apparatus on the truck bed and lower it onto the foundation F to be anchored thereon in any preferred or conventional manner known to the art, such as welding or bolting.

It will be seen that by constructing the structure on an elevated platform provided by the flat bed truck, workmen can exit and enter the interior of the structure for operating the cut off by stopping under the outriggers. Also, if in the operation of building a second or third silo the first roll of metal is exhausted, the operation can be stopped and a standby roll of metal placed on the turntable and its leading edge advanced through the peeler, straightener, and edge formers to meet the trailing end of the preceding roll. Thereupon, the ends may be joined by welding or seaming and the process continued as before. Access to the interior of the structure for this operation is important. Electric lighting inside the structure during construction may be supplied from the generator 26.

The term "silo" as used herein shall mean vertical cylindrical structures commonly used for storage of materials of various kinds.

In this specification the terms "helical track" and "inclined circular track" are used interchangeably to mean the same thing.

Claims (13)

Claims

1. A method of forming and erecting a silo, comprising: (a) transporting a circular track in sections to the site where the silo is to be placed, assembling the track on a flat bed truck intermediate the ends of the truck with outrigged sections at each side of the truck supported on outrigger track supports level with the bed of the truck and above ground level; (b) transferring a roll of strip metal mounted on the truck bed into a cylindrical helix by moving it edge-wise up and around an inclined circular track and progressively joining the upper edge of the strip metal as it is shaped by the inclined circular track into an added convolution to the lower edge of the completed convolution immediately above it;; (c) severing the cylindrical helix when it has reached a selected height by cutting it in a horizontal plane at a level above the level at which the progressive joining of the said edges is effected, whereby the edges of the helix above and below the plane of cutting are joined through a completed convolution and the lower edge of the kerf is sufficiently level and complete to provide the start of the next cylindrical helix; and (d) lowering the completed cylindrical helix after severing is completed onto a prepared base.

2. A method as claimed in Claim 1, wherein the forming of the cylindrical helix is interrupted after at least one convolution has been completed and severing of the helix is effected by severing means to provide a level upper edge on the cylindrical helix, and wherein a cover is affixed to the said level upper edge prior to completion of the helix.

3. A method as claimed in Claim 2, wherein a slewing and luffing crane on the truck bed outside the area of the track has the free end of its boom attached to the cover through a pivotable connection which steadies the cylindrical helix against tilting or leaning as the cylindrical helix increases to its ultimate height and, while so attached, moves the severed completed cylindrical helix from over the track and sets it on the prepared site.

4. A method as claimed in any of Claims 1 to 3, wherein the severing of the helix when it has attained the selected height is effected by progressively sawing a kerf through the cylindrical wall at the selected height and by advancing the kerf in increments while providing support at intervals between the severed edges against the kerf closing.

5. A method as claimed in any of Claims 1 to 3, wherein the severing of the helix when it has attained the selected height is effected by progressively sawing a kerf through the cylindrical wall and at intervals inserting spacers between the upper and lower edges of the resulting kerf to hold the kerf open and prevent the saw becoming jammed.

6. A method as claimed in any of Claims 1 to 5, wherein the severing of the cylindrical helix is effected by a workman on the truck bed manipulating a radially and circularly movable saw supported at a fixed elevation inside the cylinder, the workman acquiring access to the interior of the shell at one of two sides of the bed by entering under and through an outrigged section of the circular inclined track.

7. A method according to Claim 1 of forming and erecting a silo, substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

8. Apparatus for forming and erecting a silo, comprising: (a) a tractor trailer truck the trailer of which has a bed longer than the diameter of a helical track secured thereon but narrower than the said diameter; (b) two diametrically opposed sections of the helical track secured to the truck bed and extending across the bed and separated a distance from each other the full diameter of the completed helical track of which they constitute a part; (c) outrigger track support means at each side of the truck bed when the apparatus is in use for erecting a silo arranged to stabilize the truck bed against transverse tilting, helical track support sections detachably joined to the track sections on the truck bed and supported by the outrigger track support means, the said helical track sections, when in place, complementing those on the bed to form the required helical track;; (d) a turntable secured to the truck bed in the area between the said two track sections fixed to the truck bed arranged to rotatably hold a coil of strip metal positioned one end up on the turntable; (e) peeler means for unwinding strip metal from the turntable and guiding it edgewise; (f) a starting track section on the truck bed arranged to receive the lower edge of the strip emerging from the peeler means and guide the strip in an involute path to the lower starting end of the helical track; (g) power-driven means arranged to drive the strip around the helical track and to join by a pressure rolled seam the upper edge of the oncoming strip to the lower edge of the convolution immediately above; and (h) cut-off means fixed on the truck bed within the area of the circular track arranged to cut the formed helix completely in two in a horizontal plane above the level of said power-driven means for joining the upper edge of the oncoming strip.

9. Apparatus as claimed in Claim 8, wherein the said power-driven means for joining the edges by roll seaming also constitutes means for forcing the metal strip up and around the said helical track while also rotating all previously formed convolutions of the cylindrical helix.

10. Apparatus as claimed in Claim 8 or 9, further comprising edge turning means between the peeler means and the said power-driven means for turning the upper edge of the strip into a complementray shape for interfitting with the lower edge of the preceding convolution and for shaping the lower edge of the strip for subsequently interfitting with the upper edge of the succeeding convolution.

11. Apparatus as claimed in any of Claims 8 to 10 wherein the said cut-off means comprises a stand fixed to the truck bed at the centre of a diameter of the helical track, a radially extensible arm arranged to swing in a horizontal plane a full circle about the central axis of the stand and the centre of the track, and a power-driven saw wheel at the outer end of the said arm.

12. Apparatus as claimed in any of Claims 8 to 1 1, further comprising a luffing and slewing crane mounted on the truck outside the circular track and centered on the longitudinal axis of the bed arranged to steady the cylindrical shell during the manufacture thereof and during the cut-off operation and for moving and lowering it onto a foundation adjacent the truck after it has been cut off

1 3. Apparatus according to Claim 8 for forming and erecting a silo, substantially as herein described with reference to, and as shown in, Figures 1 to 3 of the accompanying drawings.