US3360173A - Web guidance device - Google Patents

Description

Dec. 26, 1967 J. w. MILLER 3,360,173

WEB GUIDANCE DEVICE Filed Jan. 4, 1965 FIG. 5

INVENTOR. JOHN W. MILLER BY 2 Z Agent United States Patent 3,360,173 WEB GUIDANCE DEVICE John W. Miller, Smyrna, Ga., assignor to Lockheed Aircraft Corporation, Burbank, Calif. Filed Jan. 4, 1965, Ser. No. 422,963 2 Claims. (Cl. 226-196) This invention relates in general to a device for guiding a moving web and in particular to a device for guiding a web during wind or rewind operations so that the deviation of the web from its nominal course of travel is minimized or prevented.

Many thin web-like materials are contained on spools or reels so that the material can conveniently be stored or contained for utilization at a desired time. Examples of this may be found in the manufacture or use of paper, textiles, and any other substance which is characterized by being relatively thin and flexible and which may conveniently be stored in rolled or spooled form during at least a part of its cycle of manufacture and utilization.

Web-like materials used, for example, in recording and similar applications may be withdrawn from and rewound onto their supply spool many times. An example of such a material is found in the recording paper frequently used in oscillographic recorders. Once exposed and developed this paper, which may be for example twelve inches in width, must be unwound from its supply spool to a sufficient extent to permit scrutiny of a desired portion of the information recorded thereon. Frequently, the paper will be mounted in suitable readout or viewing apparatus including a supply spool holder and a take-up spool holder. Either or both of these spool holders are motorized to permit rapid unwinding and/or rewinding of the paper whereby relatively rapid access to any portion of the paper contained on the supply spool may be had.

One problem occurring with the use of such apparatus is that of guiding the paper so that it will flow evenly onto the unwind or rewind spool. Such spools generally are of two types: the first including a pair of disc-like side members to support and protect the paper on the spool, and the second consisting merely of a hub onto which the paper is wound. With the former type of spool, a lateral shift in the paper being wound onto the spool may cause the paper to become torn or otherwise damaged through interference with one of the disc-like side members. While this danger is not present with the spool of the latter type, such lateral deviation results in a spool of paper having an effective width in excess of the reel width of the paper, and further having relatively vulnerable edges which are subject to tearing and fraying. Furthermore, an unevenly wound spool of paper, when next unwound for observation or other use, cannot be received upon the take-up spool without lateral displacement of this spool. Further lateral shift of the paper upon unwinding and subsequent rewinding usually only compounds the extent of lateral shift of the paper as seen on the rewound spool.

Several techniques for guiding paper or similar weblike materials are known to the prior art. One such technique involves the use of photoelectric apparatus to detect lateral deviation of the web from its nominal path. Suitable electronic circuitry connected to the photoelectric apparatus drives electric motors or other devices to compensate for the lateral shift of the web. In addition to requiring numerous complex and expensive components, this technique suffers the added disadvantage of being relatively unreliable for high speed operation because of the delay time necessarily involved in the requisite feedback loop.

Another technique involves the use of a Web-like medium having prepunched holes along one or both sides thereof which register on mating gears or pins in the web 3,360,173 Patented Dec. 26, 1967 drive train or in idler members. This has the obvious disadvantage of requiring a prepunched web-like medium, a circumstance which is not always possible or acceptable. The presence of the prepunched holes in the web also renders the web more susceptible to tearing, especially at high web speeds.

Another technique does not involve the use of any apparatus to insure uniform winding but merely consists of trimming away the edges of the unevenly wound paper as contained upon a spool. This solution requires the apparatus necessary to perform the trimming, and necessarily results in a quantity of scrap resulting from the trimming operation. Additionally, with many rewinds and attendant trimming operations, a substantial portion of the width of the web would eventually be trimmed away.

Still another technique involves the use of V-shaped brackets cupped around the edges of the web. Although some edge guiding can be accomplished in this manner, this technique suffers the practical limitation that too much tension applied to an edge can cause tearing of the edge or of the entire web. In particular, it has been found that a paper web can be forced very little in this manner.

It has been learned that web guidance can be accomplis-hed simply and easily and without resort to complex more saddle-like devices each of which is formed and dimensioned to provide a restoring force to the web in opposition to lateral deviation of the web from its nominal path. The intensity of this restoring force is substantially exponentially proportional to the extent of deviation of the web and is directed to the under side of a portion of the width of the web that has been displaced by the device from the nominal plane in which the web is traveling.

Accordingly, it is an object of this invention to provide an improved web guidance device.

Another object of this invention is to provide a web guidance device that is simple in construction and effective in operation.

A further object of this invention is to provide a web guidance device that does not endanger the web.

Still another object of this invention is to provide a web guidance device that is capable of functioning on webs lacking guide perforations or other special preparation.

Yet another object of this invention is to provide a Web guidance technique that permits the web to be rewound an indefinite number of times.

A still further object of this invention is to provide a Web guidance device having virtually instantaneous response to lateral deviation from the nominal path of the web.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

FIGURE 1 illustrates a perspective view of an embodiment of the invention;

FIGURE 2 shows a section view of the embodiment taken along line 22 of FIGURE 1; and

FIGURE 3 shows a section view of the embodiment taken along line 3-3 of FIGURE 2.

Stated generally, this embodiment of the invention coinprises a saddle-like member having a concave curve looking in the direction of web travel and a convex curve looking perpendicularly to the direction of web travel.

More particularly, with respect to the embodiment of the invention shown in the drawing, there is seen in FIGURE 1 thereof a web guide member indicated generally at 10. This member may, by way of example, be

3 unitary in construction and includes side portions 11 and end portions 12. The top portion 13 of this member, across which the web to be guided is drawn, is shaped in a compound curve somewhat akin to the shape of a horse saddle.

As seen in the section views of FIGURES 2 and 3, top portion 13 comprises a generally concave shaped curve looking in the direction of web travel and further comprises a generally convex shaped surface looking in the direction transversely to the direction of web travel. More specifically, the shape of portion 13 looking in the direction of web travel, as shown in FIGURE 2, includes a central portion 14 having a relatively small amount of concavity and end portions 15 and 16 having a relatively large amount of concavity.

The convex surface of the guide member as seen in the direction transverse to the direction of web travel may, by way of example, define circumferential segments of constant radius as seen in section at 17 in FIGURE 3. The convex surface may be so positioned and dimensioned that the leading and trailing edges of contact of the web with the surface are approximately tangent to the web, and the aforesaid radius of the circumferential segments may be defined by the point of intersection of lines perpendicular to these tangents. The width of the guide member as seen in FIGURE 3 depends upon such factors as the degree. of change in direction imparted to the web by the guide member and the stiffness and thickness of the web undergoing guidance.

In the operation of this web guidance device, the web to be guided is passed over the member in such a way that the web, when following its nominal or desired path of travel, will be substantially centered with respect to the central portion 14 of the member. For example, good results have been obtained with placement of the guide member adjacent the spool onto which the web is being wound, so that the web is drawn over the member immediately prior to being wound onto the spool. Where bidirectional web travel exists, a guide member preferably should be disposed adjacent each spool to provide guidance for the web as it enters that particular spool.

When the web being drawn across the guide member is substantially centered in the central portion 14 of the member, the lateral forces exerted on the web from the concave shape of the member are equal in magnitude and opposite in direction. If the web tends to shift laterally, however, the leading web edge in the direction of lateral shift will encounter one of end portions or 16, andthis end portion will exert a restoring force on the web tending to oppose the lateral shift of the web. Because of the increasing concavity of end portions 15 and 16, the magnitude of the restoring force applied to the web is approximately exponentially dependent upon the extent of deviation of the web from the central portion, and this restoring force is applied not to the edge of the web but to a substantial portion of the under side of the web whereby there is avoided the danger of damage to the web encountered with conventional edge guidance techniques.

Sufiicient tension should be applied to the web to enable an effective amount of restoring force to be applied to the web by the guide member. Tensioning of the web can be achieved through any suitable procedure such as the use of idler rollers and/ or drag-braking of the spool or reel from which the web is being supplied during a particular operation.

The web guide member may be made of any suitable material such as wood, plastic, metal, Micarta, nylon, or the like. A smooth, slick surface on top portion 13 is desirable to minimize friction between the web and the surface.

From the foregoing, it will be seen that there has been disclosed and described a web guidance device of simplified design and enhanced effectiveness. The guidance device contains no moving parts and applies to the web a restoring force that is approximately exponentially proportional to the extent of lateral shift of the web. This restoring force is applied to the web with substantially no loss of time due to feedback circuits, linkages, or the like. The guidance device disclosed and shown herein has been successfully used both to maintain the position of a web and to correct the position of a web that had been improperly or erratically wound onto a spool. Successful use of this guidance device has been observed with web speeds of 600 feet per minute, with no indication that successful web guidance could not be achieved with this device at higher speeds. Use of this device is not limited to paper webs but could be successfully employed with webs of textile, plastics, and the like.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

1. A web guidance device comprising: a stationary body member having a contoured surface across which a web to be guided may be drawn; said contoured surface as seen in a direction of web travel having a central portion providing subjacent support to a web drawn over said contoured surface; said contoured surface further having an end portion disposed on each side of said central portion so that said contoured surface comprises an effectively unitary surface made up of said central portion and both of said end portions, each of said end portions being contoured to displace the web from the nominal plane of travel thereof to enable the application to the displaced portion of the web through the face thereof in contact with said contoured surface of a force tending to laterally displace the web toward said central portion when the web deviates laterally therefrom; a cross section of said central portion as viewed in a direction of web travel defines a contoured surface line being nearly flat with a relatively small amount of concavity, the degree of concavity gradually increasing as a function of distance from the center of the nominal path of web travel; and a cross section of each of said end portions as viewed in a direction of web travel defines a contoured surface line having a relatively great amount of concavity, the degree of concavity increasing in an approximately exponential manner as a function of distance from the center of the nominal path of web travel.

2. A web guidance device comprising: a stationary body member having a contoured surface across which a Web to be guided may be drawn; said contoured surface as seen in a. direction of web travel having a central portion providing subjacent support to a web drawn over said contoured surface; said contoured surface further having an end portion disposed on each side of said central portion so that said contoured surface comprises an effectively unitary surface made up of said central portion and both of said end portions, each of said end portions being contoured to displace the web from the nominal plane of travel thereof to enable the application to the displaced portion of the web through the face thereof in contact with said contoured surface of a force tending to laterally displace the web toward said central portion when the web deviates laterally therefrom; a cross section of said central portion as viewed in a web' travel direction defines a first contoured surface line being nearly flat with a relatively small amount of concavity, the degree of concavity gradually increasing as a function of distance from the center of the nominal path of web travel; the width of said central portion is substantially equivalent to the width of a web to be guided by said device; a cross section of said body member taken at any point along the width thereof as viewed in a direction transverse to a web travel direction defines a convex contoured surface line; a cross section of each of said end portions as viewed in a Web travel direction defines a second contoured surface line having tangential contact with an end of said first contoured surface line and being an extension thereof outwardly from the center of the nominal path of web travel; each of said second contoured surfaces extends outwardly in the same direction from said tangential contact so that said second concave contoured surface lines have a substantially greater degree of concavity than said first contoured surface line; and each of said second contoured surfaces retaining said concave surface line configuration throughout the entire extent thereof and terminating at a location substantially higher than said central portion, said cross section as viewed in a web travel direction being symmetrical about a line extending through the center of the nominal path of web travel perpendicularly thereto.

References Cited UNITED STATES PATENTS 2,336,278 12/1943 Mihalyi 24276 X 3,143,270 8/1964 Cohen 226196 FOREIGN PATENTS 986,846 4/1951 France.

M. HENSON WOOD, JR., Primary Examiner. J. N. ERLICH, Assistant Examiner.

Claims (1)

1. A WEB GUIDANCE DEVICE COMPRISING: A STATIONARY BODY MEMBER HAVING A CONTOURED SURFACE ACROSS WHICH A WEB TO BE GUIDED MAY BE DRAWN; SAID CONTOURED SURFACE AS SEEN IN A DIRECTION OF WEB TRAVEL HAVING A CENTRAL PORTION PROVIDING SUBJACENT SUPPORT TO A WEB DRAWN OVER SAID CONTOURED SURFACE; SAID CONTOURED SURFACE FURTHER HAVING AN END PORTION DISPOSED ON EACH SIDE OF SAID CENTRAL PORTION SO THAT SAID CONTOURED SURFACE COMPRISES AND EFFECTIVE UNITARY SURFACE MADE UP OF SAID CENTRAL PORTION AND BOTH OF SAID END PORTIONS, EACH OF SAID END PORTIONS BEING CONTOURED TO DISPLACE THE WEB FROM THE NOMINAL PLANE OF TRAVEL THEREOF TO ENABLE THE APPLICATION TO THE DISPLACED PORTION OF THE WEB THROUGH THE FACE THEREOF IN CONTACT WITH SAID CONTOURED SURFACE OF A FORCE TENDING TO LATERALLY DISPLACE THE WEB TOWARD SAID CENTRAL

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