05/009829

12/14/1971

02/09/1970

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242/613.500

242/609

B65D85/66; B65H75/18; B65H19/00; B65D85/67

206/59R,59F,58,52,654 242/68.6 287/2 285/397,109

Dixson Jr., William T.

This is a continuation-in-part of copending application Ser. No. 817,875 filed Apr. 21, 1969 now abandoned.

What is claimed is

1. An end cap for protecting hollow paper cores comprising a hollow cylindrical molded plastic body portion having an outwardly extending external flange portion about one edge thereof, a plurality of axially extending circumferentially displaced splines distributed about and extending along the outer surface of said body portion and a plurality of toothlike projections superimposed upon said splines, said toothlike projections having definite, though rounded, upper corners and being of less height than the splines on which they are superimposed.

2. An end cap according to claim 1 wherein said body portion has a slight taper and wherein said splines and toothlike projections follow said taper.

3. An end cap according to claim 1 wherein said toothlike projections are free of sharp corners.

4. An end cap according to claim 1 wherein said toothlike projections are of teardrop configuration.

5. An end cap according to claim 1 wherein the height of the toothlike projections is related to the plastic material of which they are formed such that they may be withdrawn from an undercut mold without being sheared by the mold upon withdrawal therefrom.

6. An end cap according to claim 1 wherein said body portion is formed with a plurality of radially extending internal reinforcing vanes which terminate at an inner surface of said body portion in alignment with said splines.

7. An end cap according to claim 1 wherein said flange and body portions are joined by a curved connecting region and wherein said body portion includes radially extending internal reinforcing vanes which terminate at an inner surface of said body portion and extend along said inner surface to a location along said curved connecting region.

8. In combination a hollow tubular core of paperlike material and at least one plastic end cap forced into an end of said core, said end cap having a hollow cylindrical body portion and axially extending splines distributed thereabout and forming an interference fit at displaced locations about said core and a plurality of toothlike projections superimposed on said splines and penetrating into the inner surface of said core, said toothlike projections having definite, though rounded, upper corners and being of less height than the splines on which they are superimposed.

9. A combination according to claim 8 wherein the inner surface of said paper core surrounds each toothlike projection and is free of gouges in the region of said projections.

10. A double-end cap for protecting hollow paper cores comprising an integral unitary molded plastic structure having a pair of coaxially arranged cylindrical inner and outer walls separated by a plurality of radially and axially extending ribs and an outer flange extending out from and around the outer cylindrical wall midway along the length thereof.

11. A double-end cap according to claim 10 and further including a central flange wall extending from the inner to the outer cylindrical wall, midway along the length thereof.

12. A double-end cap according to claim 10 and further including a plurality of axially extending splines distributed about the outer surface of said outer cylindrical wall on both sides of said outer flange.

13. A double-end cap according to claim 11 wherein the ribs on one side of said central flange wall are rotationally offset and thereby mutually staggered with respect to the ribs on the opposite side of said central flange wall.

14. A double-end cap according to claim 12 wherein said splines are aligned with said ribs.

This invention relates to end caps for protecting the ends of hollow paper cores and more particularly it concerns novel arrangements which enable inexpensively manufactured end caps to be maintained securely in place when pushed into the ends of paper cores.

End caps, otherwise known as core plugs, are used to protect the ends of hollow paper cores about which plastic or other sheet material is wound for storage or shipment. The end caps, which are usually made of metal or plastic, comprise a cylindrical plug portion which fits closely into the ends of the paper cores, and an outwardly extending external flange portion about the outer edge of the cylindrical portion which covers and protects the end of the core.

Both end caps and the cores which they protect must be capable of being produced very inexpensively since they are essentially disposable items. The cores are usually made of heavy paper or paperboard in tubular form; and the end caps are either drawn from sheet metal or molded from plastic.

One of the most common difficulties encountered with end caps and cores of previous construction is that of maintaining the end caps tightly in place during shipment. Often, the end caps would fall out without being noticed. Then when the core is set down or dropped, its unprotected end is damaged; and in many cases the material wound about the core is also damaged.

It has been difficult to provide end caps which would always stay in place in the cores because the cores, being made of paper, cannot be held to a close internal diameter tolerance. Thus, while an end cap may fit tightly into one core, it will slip out of another. One technique employed in the past to overcome this situation has been to provide axially extending ribs or splines on the outer surface of the body portion of the end cap which inserts into the paper core. These splines are of sufficient height to fit tightly even into the largest core diameter; and in the case of smaller core diameters the core will deform or partially flatten between the splines, thus allowing them to enter tightly into the core. This technique, however, is not entirely satisfactory for it depends upon the resiliency of the core, that is, its tendency to return to rounded condition which is relied upon to maintain sufficient pressure against the splines to hold the end cap tightly in place. In actual practice, the core simply loses its resiliency and eventually the end cap slips out of place.

Another technique employed to ensure that end caps will remain securely in place in the ends of hollow cores is to form toothlike projections about the outer surface of the body portion of the end cap. These projections are designed to dig into the inner surface of the paper core in the manner of a barb and hold the end cap in place. This arrangement is not altogether satisfactory for in many cases the projections will simply cut longitudinal grooves into the paper core and will not, therefore, be capable of hooking into the material of the core. Another difficulty with the toothed projection arrangement is that separate operations are required to form the projections; and this adds considerably to the cost of the finished product.

The present invention overcomes these above-described difficulties of the prior art.

According to the present invention, there is provided a novel end cap construction formed of injection molded plastic material having a cylindrical body portion and an outwardly extending flangelike projection at one end thereof. A plurality of axially extending ribs are formed about the body portion and a series of small toothlike projections are formed along the upper surface of the ribs.

A novel cooperation is achieved between the ribs and the toothlike projections in the end cap of the present invention. The toothlike projections are made quite small, i.e., less than the height of the ribs. This permits them to be formed in a simple injection molding device without need for special operations or special operations which the severe undercuts of large toothlike formations would require. In addition, the ribs themselves permit a close fit between the end cap and a paper core; and the small teeth on top of the ribs may be forced into the core to provide barblike holding action without the cutting of grooves which larger teeth produce.

According to a further aspect of the present invention there is provided a novel double-end cap construction for use between adjacent axially aligned cores. This novel double-end cap construction is specially arranged to permit fabrication in a single simple injection molding operation. The novel double-end cap of the present invention involves a pair of coaxially arranged cylindrical walls held in position by means of axially and radially extending ribs, and an outer flange extending about the outer surface of the outer cylindrical wall midway along its length. This arrangement permits molding dies to operate in an axial direction from opposite ends to produce a complete integral structure in one operation. Moreover, this arrangement permits the incorporation of a central flange wall extending from the inner to the outer cylindrical walls, for strengthening purposes, at a location substantially coplanar with the outer flange.

Various further and more specific objects, features and advantages of the invention will appear from the description given below, taken in connection with the accompanying drawings, illustrating by way of example preferred forms of the invention.

In the drawings:

FIG. 1 is a perspective view illustrating a fully loaded paper core into which an end cap according to the present invention is inserted;

FIG. 2 is an enlarged exploded view illustrating one end of the hollow paper core of FIG. 1 and end cap associated therewith;

FIG. 3 is an enlarged end view of the end cap shown in FIG. 2;

FIG. 4 is an opposite end view of the end cap shown in FIG. 2;

FIG. 5 is an enlarged section view taken along line 5--5 of FIG. 3;

FIG. 6 is an enlarged fragmentary portion of the end cap shown in FIG. 5 inserted into the paper core;

FIG. 7 is a further enlarged fragmentary view illustrating the interaction between a toothlike projection on the end cap of FIG. 6 and the corresponding region of the hollow paper core;

FIG. 8 is an enlarged fragmentary section view taken along line 8--8 of FIG. 6.

FIG. 9 is an exploded view of a multiple core and double end cap assembly forming another embodiment of the present invention;

FIG. 10 is an enlarged end view of the double-end cap of FIG. 9; and

FIG. 11 is a section view taken along line 11--11 of FIG. 10.

As shown in FIG. 1, an elongated hollow paper core 10 has wound thereon an elongated sheet or film 12, of paper, plastic or other material to be packaged for shipment or storage. An injection molded plastic end cap 14 is provided at each end of the core 10. These end caps serve to protect the core 10 and the material 12 during storage or shipment. Thus, the end caps 14 act to absorb initial impact shocks whenever the core is dropped on one end.

In addition, the plastic end caps are provided with a central opening 16, through which a mounting shaft may be extended for mounting the entire assembly while the sheet material 12 is being withdrawn therefrom.

Turning now to FIG. 2, it will be seen that the end cap 14 comprises a cylindrical body portion 18 and a flange portion 20, which extends outwardly from one end of the cylindrical body portion 18. An inner cylindrical wall 22, defining the central opening 16, is arranged coaxially within the cylindrical body portion 18, and is supported therein by means of a plurality of radially extending vanes 24.

A plurality of axially extending external splines 26 are formed on the outer surface of the body portion 18, and a series of small toothlike projections 28 are formed along the upper surface of the splines 26. As can be seen in FIG. 2, the plastic end cap 14 is configured such that its body portion 18, including the splines 26 and the toothlike projections 28, can be inserted into the interior of the hollow paper core 10 from the end thereof. In this arrangement, the flange portion 20 of the plastic end cap 14 abuts the end of the paper core 10. As can be seen in FIG. 2, the splines 26 are arranged in alignment with the vanes 24. The advantages resulting from this arrangement will be discussed more fully hereinafter.

Turning now to FIG. 3, it will be seen that the vanes 24 are exposed at the flange end of the end cap 14. These vanes extend from the end of the inner cylindrical wall 22, which is within the cylindrical body portion 18, to the beginning of the flange portion 20. As shown in FIG. 4, there is provided an annular wall 30 which covers the opposite end of the vanes 24, and which extends between the cylindrical body portion 18 and the inner cylindrical wall 22. As shown in FIG. 5, one end of the inner cylindrical wall 22 is coplanar with the corresponding end of the cylindrical body portion 18 and the annular wall 30. The vanes 24, as stated above, merge with the outer end of the cylindrical body portion 18 precisely where it meets the flange portion 20. Actually, the cylindrical body portion 18 and the flange portion 20 are joined by a radius 32; and it is at an intermediate region of this radius that the vanes 24 join with the cylindrical body portion 18. It will be appreciated that with this arrangement the vanes 24, in addition to supporting the inner cylindrical wall 22 with respect to the cylindrical body portion 18, further serve to reinforce the flange portion 20, thereby enabling it to withstand the shocks and stresses which occur when a mallet is used to drive the end cap 14 into the core 10, or when the core 10 is dropped on one end.

As shown in FIG. 5, the cylindrical body portion 18 is slightly tapered so that it may wedge into the hollow paper core 10. In addition, the splines 26 follow the slight taper of the cylindrical body portion 18. Each spline 26 is provided with three of the toothlike projections 28. These projections are displaced axially along each spline and are also dimensioned to follow the general taper of the spline and body portion.

As can be seen in FIG. 5, an interference fit is provided between the splines 26 and the hollow paper core 10. The core, however, can accommodate this interference fit by flattening somewhat in the regions between the splines 26 and the hollow paper core 10, will depend upon the particular internal diameter of the paper core. This may vary from core to core because of the relatively loose manufacturing tolerances associated with such items; or it may change from time to time for an individual core due to the shrinkage and expansion characteristics of the paper from which the core is made. It is important that the plastic end cap 14 be securely maintained in place in spite of these core diameter variations.

Turning now to FIG. 6, it will be seen that when the plastic end cap 14 is fully in place, the splines 26 force outwardly on the inner surface of the hollow paper core 10 thereby providing a wedging action which helps to hold the end cap in place. As shown in FIGS. 6, 7 and 8, the toothlike projections 28, which extend upwardly from the tops of the splines 26, individually penetrate further into the surface of the hollow paper core 10. The projections 28 are generally teardropped in shape and have a definite upper, though rounded, corner 29. In addition, the projections 28 are considerably smaller in height than the splines 26. This permits the projections to push upwardly and outwardly at concentrated locations within the hollow paper core but at the same time it prevents them from forming permanent longitudinal gouges or channels along the inner surface of the core when the end cap 14 is forced into place. Thus, as can be seen in FIGS. 6 and 7, the material of the paper core is merely pushed aside by the projections 28, and thereafter settles back around behind each of the individual projections 28 to provide surfaces against which the projections may perform a barblike holding action to prevent the end cap from slipping out from the core.

It will be appreciated from the above that the toothlike projections 28 cooperate with the splines 26 in that the splines serve to accommodate the diameter variation encountered in the paper core 10, while the small toothlike projections 28 operate to hold the end cap securely in place by penetrating into the hollow paper core at displaced locations. Moreover, because the toothlike projections 28 are not required to accommodate core diameter variations (this being handled by the splines on which the projections are superimposed), the projections 28 can be made large enough to provide a barblike holding action without at the same time being so large as to cause gouging of the core which would defeat the barb action.

The plastic end cap 14, as indicated above, is made of injection molded plastic. The use of this material in conjunction with the particular design of the splines 26 and the toothlike projections 28, permits a rapid and very economical method of manufacture. It is known that injection molded plastics possess a certain "memory" characteristic by which they may be molded in a die which is undercut to a certain extent; and when they are retracted from the die they will squeeze in so as to permit such retraction and thereafter they will assume the shape which they possessed when they were being formed in the die itself. Thus, so long as the undercuts to be formed (i.e., those which form the toothlike projections 28), are not too severe it is possible to form these projections or undercuts in a simple die structure without the need for special composite multiple action die arrangements. Of course, since projections of this nature involve undercuts, they could not be formed on drawn metal objects without separate forming operations.

By way of example, an end cap for protecting hollow cores having a nominal 3-inch inner diameter has an outer body portion diameter which tapers inwardly at an angle of about 2° from a maximum diameter of 3.030 inches to a minimum diameter of 2.980 inches. This end cap has eight equally spaced splines approximately 0.017 inches in height. The toothlike projections themselves extend 0.005 to 0.010 inches above the splines. The outer surface contours of the projections are rounded and free of sharp corners.

Also as indicated previously, the splines 26 are arranged in alignment with the vanes 24. This arrangement ensures that the end cap will be most solidly reinforced radially at those locations where the splines 26 and the toothlike projections 28 engage the hollow paper core 10. Thus, any deformation which occurs will take place in the core 10 and not in the end cap 14. A further feature of the cooperative arrangement between the vanes 24 and the splines 26 lies in the fact that the plastic material is concentrated most heavily in the region of the toothlike projections 28. This concentration of plastic material results in a slower cooling of the material following the injection molding process. Because the material cools more slowly in this region, the toothlike projections 28 are not fully hardened at the time the end cap 14 is removed from the injection molding die in which it is formed. Thus, the projections 28 are less likely to be sheared off and form sharp corners as the end cap 14 is removed from the die. Instead, the toothlike projections merely deform to a certain degree during removal and thereafter they reassume their initial configuration.

FIGS. 9-11 show another embodiment of the present invention which is used for the packaging of several core rolls in stacked or aligned arrangement.

As seen in FIG. 9 there is provided a double-end cap 40 which extends into and forms a connection between two axially aligned cores 42 on which rolls 44 of sheet material are wound. The cores 42 are of the same construction as the core 10 of FIG. 1.

The overall configuration of the double-end cap 40 resembles two of the single-end caps 14 glued together back to back. The present construction however avoids the necessity of separate fabrication and assembly of different elements. Instead, with the present construction a double-end cap suitable for interconnecting two axially aligned cores may be completely fabricated in a single molding operation.

The construction of the double-end cap 40 is best seen in FIGS. 10 and 11. As there shown the double end cap comprises inner and outer cylindrical walls 46 and 48 maintained in coaxial alignment by means of a central annular flange wall 50 and a plurality of axially and radially extending ribs 52. The inner wall 47 has a central opening 53 therethrough which may accommodate an axle or other supporting shaft (not shown). The annular flange wall 50 is positioned approximately half way along the axial length of the inner and outer cylindrical walls 46 and 48. The ribs 52 extend radially from the inner cylindrical wall 46 to the outer cylindrical wall 48, and axially from the opposite sides of the annular flange wall 50.

It will be noted that the radial ribs 52 on one side of the annular wall 50 are staggered with respect to the ribs 52 on the opposite side of the wall 50. This arrangement has been found to provide better flow of plastic material during the molding operation than is obtained where the ribs on the opposite sides of the wall 50 ate aligned. The staggered rib arrangement also avoids the buildup of a large concentrated mass of plastic in one region. Such a large concentration of plastic is undesirable in the molding operation since the plastic material in such regions would cool more slowly than the adjacent plastic material and thus may give rise to dimensional distortion of the finished product.

An outer flange 54 extends around the outside of the outer cylindrical wall 48 approximately midway along its length. As shown in FIG. 11, the outer flange 54 is located in generally coplanar relationship with the flange wall 50.

The outer cylindrical wall 48 is tapered slightly on opposite sides of the outer flange 54, and axially extending splines 56 are distributed about the outer surface of the wall 48. Preferably, for purposes of strength, these splines are aligned with the corresponding ribs 52.

The double-end cap 40 is used as shown in FIG. 9. The portions of the outer cylindrical wall 48 on opposite sides of the outer flange 54 extend respectively into the ends of two adjacent cores 42 thereby holding them in alignment. The diameter of the outer cylindrical wall 48 and the height of the splines 56 are chosen to ensure a snug fit into each core. It is not usually necessary however to provide special means to prevent slipping out of the double-end cap 50 for it will be held in place by the adjacent rolls 44 themselves. Thus in such instances the protrusions described in connection with the preceding embodiments may be dispensed with.

It will be appreciated that the particular construction of the double-end cap 50 makes possible complete fabrication by injection molding of plastic in a single operation. The mold dies may approach from opposite directions to form the radially and axially extending ribs 52 and the portions of the inner and outer cylindrical walls 46 and 48 on opposite sides of the annular flange wall 50 and the outer flange 54. There are no undercuts, reverse bends or overhangs which would require complex or multiple die operations. The entire forming operation is thus completed in one action and none of the assembly or other complex fabrication procedures such as are required in prior art arrangements are needed with the present construction.

It will be appreciated that the end cap configurations of the present invention ensure a secure and reliable fit with hollow paper cores which are subject to internal diameter variations. At the same time, the end caps of the present invention are easily and economically manufactured.