US2815790A - Apparatus for making helical conveyor blades by edgewise bending and squeezing rolls - Google Patents

Description

Dec. 10, 1957 T. L. MAYRATH 2,815,790

APPARATUS FOR MAKING HELICAL. CONVEYOR BLADES BY EDGEWISE BENDING AND SQUEEZING ROLLS Filed June 3, 1955 ATTORNEY United States Patent APPARATUS FOR MAKING HELICAL CONVEYOR BLADES BY EDGEWISE BENDING AND SQUEEZ- ING ROLLS Thomas L. Mayrath, Dodge City, Kans.

Application June 3, 1955, Serial No. 512,970 3 Claims. (Cl. 153--2) This invention pertains to the making of helical shapes from flat strip stock, and particularly to the formation of helical conveyor blades from a continuous flat strip of metal or the like.

In the past, helical conveyor blades and similar helical elements have been successfully formed from a continuous strip of fiat stock by bending the flat strip in, or nearly in, its own plane, and thereafter axially stretching the spiral'thus formed to the desired degree for application to a central shaft. Much the same result has been accomplished by the passage of the flat strip between two squeeze rolls whose working surfaces contacting the strip across its width are not parallel. As a result of the non-parallelism of the two rolls, as the strip as squeezed by the rolls and one of its edges is squeezed or stretched more than is the other. Each of these methods of obtaining a spiral-from a strip of flat stock is satisfactory within certain limits. However, each is quite limited with respect to the degree of pitch that may be obtained thereby, due to the elastic limits of the material and hardening of the material due to so-called cold-working. If in either of these prior methods it is attempted to obtain a degree of bending or curvature that is greater than what has proved to be an inconveniently small magnitude, the material of the strip tends to crack and break. This is particularly true where the strip stock is of substaritial width, and where the outside diameter of the helix is considerably greater than the inside diameter.

The present invention overcomes the limits just mentioned, by applying alternate tension and compression loads to the strip in directions which are perpendicular to one another. Since in the production of helical members from flat stock, it is necessary to increase the effective length of one edge of the stock many times more than the effective length of the opposite edge, the problem of fracture and cold-working becomes apparent. In the case of forming a helix whose inside (shaft) diameter is to be 1", and whose outside diameter is to be 5", with a helical pitch of 5", the required final length of the outside edge of the strip (per foot of helix) will be 39.5", while the corresponding length of the inside edge will be 14.16. This amount of cold stretching will produce fracture cracks in most materials, even allowing for the fact that a part of the ratio of lengths is absorbed by incidental compression of the inner edge of the stock. The invention makes it feasible to accomplish such a helix, and even more strongly curved ones, without producing these fractures. Actual helices having outer-toinne'r length ratios of as much as 8 to 1 have been satisfactorily accomplished using the present invention, without the necessity for any heating of the strip itself.

In general, the improved method of the invention involves first continuously bending the metal strip in its own plane to an intermediate curvature, followed by the selective application of squeezing or compressional force to the outer edge of the curved strip, this compression being'di'rected across the thickness of the strip and hence at a right angle to the plane in which the original curva ture was produced. The degree of compression applied at this stage is such as to establish approximately the final desired outside diameter of the helix, but since the subsequent operation of bending this spiral in a transverse direction in order to form a helix of the desired final pitch will usually slightly further reduce the outside diameter, allowance is made for this factor in establishing the degree of compression. To carry out this process most conveniently at production rates, there is provided novel apparatus in which the strip of flat stock is subjected to the bending and squeezing processes, in turn, with subsequent lateral bending of the bent strip in order to form the helix. It is in the alternate bending and squeezing of the strip that the advantages of the invention are obtained, since it has been found that a strip of a suitable metallic material may be cold-formed into a spiral of relatively many more turns per unit length by this alternate bending and squeezing process, and to a smaller final radius, without exceeding the elastic limits thereof than can be obtained by merely bending or squeezing alone. When the desired degree of curvature is thus accomplished the spiral strip is finally bent in a direction transverse to the direction of previous bending in order to convert the spiral into the desired helix. The degree of transverse bending is controlled, both at the point of first bending the strip out of its own' plane and at a point spaced a suitable distance down along the helix that is thus formed, in order to fix the final pitch of the helix as desired.

Other objects and a clearer understanding of the in vention will be realized by referring to the following detailed description of a preferred form of the improved method and apparatus, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a side elevation view of a preferred apparatus for carrying out the invention, portions being broken away for clarity.

Fig. 2 is a view of the same apparatus from above, With parts in section.

Fig. 3 is a front elevation of the final pitch-determining mechanism of the invention, showing the relationship of the other apparatus thereto, and partly in section on line 33 of Fig. 2.

In Figs. 1 and 2; the strip 10 of fiat stock such as steel is'sh'own entering between the spaced guide plates 12 and 14' which serve to restrain the strip 10 from buckling as a result of the bending forces to be applied. The guide plates 12 and 14 are so positioned with respect to each other that the spacing therebetween is just sufficient to allow the strip 10 to pass. Obviously, the guide plates may be made adjustable, or can be replaced as a unit in order to adapt the guideway to different widths and thicknesses of the strip material. Mounted upon and extending between the guide plates 12 and 14 are rollers 16 and 18 which bear against the upper edge of the strip 10 as it passes between the plates 12 and 14. Similarly mounted in the guides is a third roller 20 which bears against the lower edge of the strip 10. Roller 20 has spaced flanges (one is shown at 21) which bear against opposite faces of strip 10. The three rollers 16, 18 and 20 define the path of travel of the strip 10 between the guide plates 12 and 14. A fourth roller 22 is adjustably mounted by means of arm 23 with respect to the framework or pillar 24 upon which is fixedly mounted the guide assembly comprising the plates 12 and 14 and rollers 16, 18 and 20. Roller 22 is positioned in the plane of the strip 10 and at a position in the vertical plane which is below that of the upper edge of the strip in the guide. As the strip 10 is initially fed through the machine to begin the operation thereof, it is fed under the roller 22 in such manner that the upper edge of the strip bears against the roller'2 2, causingthe strip 10 to bend in its own plane.

3 This bend is the first of the three major operations performed upon the strip in the process of transforming it from a strip of flat stock to the spiral or helical configuration required.

After the strip has been subjected to the above described bending, it is fed between two squeeze rolls 26 and 28, having conical working faces and 32, respectively. Rolls 26 and 28 are journalled in rigid bearings 34 and 36, which bearings are mounted upon a common frame member of sufficient bulk and strength to support the rolls 26 and 28 during the operation of the machine. As may be seen in Fig. 2, the working faces 30 and 32 of rolls 26 and 28 are not parallel, as they contact strip 10, but are farther apart at their tips. Roll 28 is driven from motor shaft 38 by means of spur gears 40 and 42 in such direction that strip 10 is drawn in a downward direction by frictional engagement with the working face 32. Such frictional engagement is provided by the relative positioning of the working faces 30 and 32 which are adapted to squeeze the strip 10 as it passes between them. Clearly, both rolls 26 and 28 could be power driven if desired. The rolls 26 and 28 are adjustably mounted with respect to each other, and may be adjusted both as to the spacing and the angle between them by means such as the turnbuckles 44 and 46. It will be understood that one or both of the bearings 34 and 36 is adjustably mounted upon their common frame member. As was previously stated, the working faces 30 and 32 of the rolls 26 and 28 are not parallel as they contact strip 10, but are farther apart at the tips. As the strip 10 is caused to pass between the working faces 30 and 32 due to the rotation of rolls 26 and 28, a further bending takes place due to the relatively greater elongation of that edge of strip 10 which is farther from the tips of faces 30 and 32. This edge of strip 10 is the upper edge as the strip is fed between guide plates 12 and 14 and under roll 22, and is the outer peripheral edge of the strip after the bend is produced.

Subsequent to the squeezing step that is thus accomplished between the working surfaces of the squeeze rolls 26 and 28, the strip 10 is bent out of its own plane by reason of the action of the roller 48, as better shown in Fig. 3. Roller 48 is mounted for free rotation upon an arm 50 suitably supported as by pillar 24, and bears against the inner or shorter edge of the bent strip. As may be seen in Fig. 1, arm 50 is adjustably mounted on the pillar as by means of pivot bolt 52 and adjusting means comprising the threaded shaft 54, bracket 56 on pillar 24 and nut 58. The pivotal position of arm 50, and hence the position of the roller 48, determines the approximate pitch of the spiral to be produced, the precise final pitch being fixed by the positioning of the guide pin 60 which is fixedly mounted as on head 62 of a post 64. Post 64 is adjustably mounted with respect to framework pillar 24 by any suitable means, such as a threaded shaft and nut, whereby the longitudinal distance along the spiral between the pillar 24 and the post 64 may be varied. As may be seen in Fig. 3, the inner or shorter edge of the strip 10 bears on pin 60 at the head 62 and the positioning of the post 64 and its pin is such that an axial stretching of the helix is accomplished. Thus the combined action of the roller 48 and the pin 60 constitute the third major operation, namely that of forming a helix from the bent and squeezed flat strip.

The operation of the apparatus of the invention is now obvious. As the flat strip 10 is fed into the machine, it enters the passage between the guide plates 12 and 14 and is subjected to a bending action in its own plane by reason of the relative positioning of the rollers 16, 18, 20 and 22. The degree of bending accomplished at this first bend is controlled by the positioning of the roller 22.

A second or squeezing stage is accomplished when the strip 10 passes between the non-parallel strip-contacting portions of working faces 30 and 32 of rolls 26 and 28. Power is supplied to the roll or rolls in such rotational sense that the strip 10 is drawn down between the rolls,

The degree of bending accomplished at this second or squeezing stage is controlled by the angle between the rolls 26 and 28. If, for instance, a greater bend is desired, the angle between the roll axes is decreased and the nonparallelism of the working surfaces 30 and 32 is thus increased, increasing the difference in the relative magnitude of squeezing to which the opposite lateral edges of the strip 10 are subjected. An increase in the angle between rolls 26 and 28 would have the opposite result. If it were to be found also desirable to compress the strip 16 generally, in addition to differentially between the edges, the rolls 26 and 28 may be moved bodily closer together. Also, the squeeze rolls may be moved with respect to each other with or without changing the angle therebetween, in order that strips of different thicknesses may be accommodated.

As a third step and final step, the strip is bent in a direction transverse to the plane of bending by the roller 48, which bears against the inner or shorter edge of the strip. There is thus formed a spiral helix, the pitch of which is approximately that of the finished product. The final pitch is accurately determined by the positioning of a guide post 64 which carries the head 62 and pin 60. The inner edge of the spiral formed by the strip 10 is made to bear against the pin 60, so positioned along the helix as to determine finally the pitch initially approximated by the position and angulation of roller 48. The inside and outside diameters of the finished spiral are indicated by the legends ID and OD in Fig.3.

It will be seen from the above that the helix produced is especially well suited for conveyors of the screw type in which the helix is secured about a central shaft, as by welding the turns to such shaft. The reduction in thickness of the ribbon stock is entirely at the outer edge, so that the thickness of the finished helical ribbon increases as one proceeds from the outer edge toward the helical axis. This not only maintains adequate stock at the center for fastening purposes, but for the usual case in which the conveyor flight in operation is embedded in the material being conveyed, provides a good distribution of material radially of the flight to resist the reaction moments produced by the conveying operation. The design, from this radial viewpoint, approaches the constant-strength beam of tapered thickness.

While the process has been described in detail in connection with a particular apparatus for carrying it out, and which apparatus is itself possessed of novel advantages, it is clear that the process can also be carried out without special machinery. Thus, the initial bending can be accomplished by hand if desired, and the differential squeezing by a hammering operation rather than by continuous compression. The lateral deflection of the turns need not be continuous, but can be introduced from time to time as the final desired curvature is approached, to establish the desired pitch. Apparatus can readily be envisioned which would substitute hammering or other compressional forces for the rolling operation, although the latter is presently believed to present commercial advantages. The feeding drive need not be applied at the squeeze rolls, but the strip could be fed by subsidiary driving means of known type.

Since the ribbon or strip must be bent edgewise to produce the desired flat helical turns, it will be understood that the term in its own plane" as used herein refers to the plane perpendicular to the thickness dimension of the original strip stock. The invention is not intended to be limited to the details described above and shown in the drawings, which are given by way of example of the best way known for practising the invention, except as such limitations may be required by the terms of the appended claims.

What is claimed is:

1. Apparatus for forming a helix from flat metallic strip stock, comprising bending rolls for guiding the strip into a curved shape in its own plane, a pair of squeezing rolls for receiving the curved strip therebetween and for diflerentially squeezing the outer curved edge to increase the curvature, and means for directing the strip leaving said rolls laterally of the central plane of said rolls to form a helical shape.

2. Apparatus in accordance with claim 1, including means for driving at least one of said squeezing rolls to effect feeding of the strip.

3. Apparatus in accordance with claim 1, in which said squeezing rolls have conical facing surfaces so disposed as to approach one another closer at the position between their surfaces occupied by the outer curved edge of the entering strip.

References Cited in the file of this patent UNITED STATES PATENTS Evans Sept. 10, 1878 Reinnan Aug. 24, 1886 Zimmermann Jan. 19, 1926 Gredell Dec. 10, 1929 Dorndorf Sept. 9, 1930 Bundy Feb. 7, 1933 Pickard Dec. 12, 1933 Nigro Nov. 20, 1934 Fulson Nov. 11, 1941 Stikeleather Apr. 17, 1945

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