US 3865326 A
A core plug for insertion into a bore defined by relatively soft material to maintain the shape of the bore. The core plug has a cylindrical wooden body and a plurality of resilient, wire members extending circumferentially about the body. The wire members are formed with a point projecting radially out from the body which dig into the soft material to prevent the plug from readily moving out of the bore after being inserted into it. The wire members are mounted by their ends in a shallow groove encircling the body in a manner allowing them to bend to be nearly completely hidden in the groove.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Beaudoin CORE PLUG FOREIGN PATENTS OR APPLICATIONS 640,479 5/1962 Canada 242/686 1 Feb. 11', 1975 Primary Examiner-Edward J. McCarthy  ABSTRACT A core plug for insertion into a bore defined by relatively soft material to maintain the shape of the bore. The core plug has a cylindrical wooden body and a plurality of resilient, wire members extending circumferentially about the body. The wire members are formed with a point projecting radially out from the body which dig into the soft material to prevent the plug from readily moving out of the bore after being inserted into it. The wire members are mounted by their ends in a shallow groove encircling the body in a manner allowing them to bend to be nearly completely hidden in the groove.
7 Claims, 4 Drawing Figures cons PLUG This invention is directed towards a core plug.
The invention is more particularly directed towards an improved core plug of the type inserted into the hollow core of rolls of newsprint paper or rolls of other similar material.
Newsprint paper rolls are normally provided with a hollow core or tube made of cardboard or other soft paper-like material. The tube is used in mounting the roll for unwinding. The ends of the tube are normally protected against damage during shipping of the roll by means of plugs which are pushed in the ends of the tube. The plugs are usually made of wood to keep the cost of the plugs low. The wood, however, is not always dry and the plugs may shrink as the wood dries. The tubes themselves are also made to high inside diameter tolerances. Thus, the plugs often do not have a proper press fit in the tube and this can cause the plugs to pop out of the tube and become lodged between wrapping paper extending over the ends of the rolls and the paper roll itself. When the paper rolls are piled one on top of another, with their ends facing, a plug popped out of a tube in a lower roll can, under the weight of the top rolls, be pressed into the edge of the newsprint paper causing considerable damage.
To overcome this problem, plugs have been made with resilient holding means which hold a plug in a tube, even if the plug shrinks, and to compensate for variations of the inside diameter of tubes of a given nominal inside diameter. A plug with resilient holding means, suitable for small tubes, is shown in my U.S. Pat. No. 2,985,292, issued May 23, 1966. A plug with resilient holding means suitable for large tubes is shown in my U.S. Pat. No. 3,115,969, issued Dec. 31, 1963. Both of these known plugs, however, do not grip the tube as securely as required. The plugs can still occasionally pop out; the resilient holding members act by compression; their protruding intermediate portion are pressed radially inwardly of the plug. This causes their anchored ends to loosen within the plug material, whereby the members have less resiliency and no longer firmly grip the tube. Because of the loosening tendency, the plugs cannot always be satisfactorily reused. In U.S. Pat. No. 3,115,969, a tool must be used to rotate the plug, it must be screwed into the tube.
It is the purpose of the present invention to provide an improved core plug which grips the tube in a more positive manner to maintain the plug in position. It is another purpose of the present invention to provide a core plug which has more positively mounted resilient holding means. It is also a further purpose of the present invention to provide an improved core plug of the above type which can, if desired, be made to be readily reusable.
The invention is particularly directed towards a core plug adapted to be inserted into a cylindrical bore, defined by relatively soft material. The plug has a cylindrical body and a plurality of elongate, spaced-apart, resilient holding members extending about the body intermediate its ends. Each member is attached by its ends to the body and has a point intermediate its ends projecting radially outwardly from the body to cooperate with the soft material to hold the plug in the bore. The ends of each member lie in a plane which is substantially perpendicular to the longitudinal axis of the body.
Each plug preferably has a shallow circumferential groove extending about the body with the ends of the members being mounted at or adjacent the base of the groove.
In one embodiment, the groove has a radially extending shoulder and an angled surface extending down to the base of the shoulder, as seen in cross-section.
In another embodiment, the groove can have a shallow V-shape, as seen in cross-section.
The invention will now be described in detail having reference to the accompanying drawings, wherein:
FIG. 1 is an elevation view in partial cross-section of a newsprint paper roll having three plugs according to the present invention;
FIG. 2 is a detailed end view showing a plug inserted in the end of a core tube;
FIG. 3 is a cross-sectional view of the plug and core tube taken along line 33, in FIG. 2; and
FIG. 4 is a detailed end view showing another embodiment of a plug inserted in the end of a core tube.
FIG. 1 shows a newsprint roll 1 having plugs 3 of the present invention inserted into the ends of the core tube 7, about which the paper is wound. The core tube is made of cardboard or other suitable soft material. The plugs 3 prevent the ends 5 of the core tube 7 from being damaged, thus allowing proper mounting of the roll 1 in a printing plant.
The core plugs 5 comprise a cylindrical body 9 having length somewhat equal to its diameter. A central hole 11 extends axially through the cylindrical body. This hole permits the insertion of a tool into the core tube through the plug which tool is used to withdraw the plug from the tube after it has served its purpose.
The inner end 13 of the body 9 has a bevelled edge 15 to more easily allow the plug to be inserted into the core tube. The outer end 17 of the body has a flange 19 which co-operates with the end 5 of the core tube to stop the core plug from being pushed right into the core tube.
The core plug is provided with a plurality of resilient holding means 21. The resilient holding means 21 preferably comprise a plurality of elongated members 23 which extend around the circumference of the cylindrical body spaced apart from each other and lying in a plane perpendicular to the longitudinal axis of the core plug. The wire members 23 have a point 25 intermediate their ends 27, 29 which digs into the soft core tube material to hold the plug in the core tube. The wire members 23 are attached to the body by inserting the ends 27, 29 into the body, preferably by stapling. The points 25 extend radially outwardly away from the body. The ends 27, 29 of each wire member 23 lie in a plane which is substantially perpendicular to the longitudinal axis of the core plug. This prevents the members from being readily loosened when the plug is pushed into the tube, since the plug holding force applied on the point 25 of member 23 acts perpendicular to a line joining the anchor points at ends 27, 29. Thus, the holding force is equally distributed at ends 27, 29. The members 23, being resilient, bend towards the end of the tube when the plug is inserted in the tube. Bending occurs in a direction perpendicular to the normal plane of member 23. Thus, no forces act on the anchor points 27, 29 in the normal plane of the members 23 and said anchor points do not become loosened. The points 25 act in a manner similar to a fish hook, make entry easy but with drawal difficult.
To provide greater adjustability in the plug, permitting it to be used with a greater variation in side between the plug and the core tube than normal, a groove 31 is be provided extending circumferentially about the plug. In one embodiment, shown in FIG. 2, the groove 31 is formed by a slightly sloping surface 33 extending down towards the front of the plug, and terminating at the base of the groove defined by a vertical shoulder 35. The resilient members 23 are mounted in the base of the groove 31 adjacent to the shoulder 35. The groove provides room to receive the bent resilient members if the fit between the plug and the core tube is tight. The surface 33 has a width substantially equal to the distance the point 25 extends out from the body, thus providing sufficient space in the groove to receive almost all of the member, if bent, while still having the point project above the body surface. The shoulder 35, bearing against the lower part of the members 23, makes it more difficult to remove the plugs.
In another embodiment of the invention, as shown in FIG. 4, the members 23 can be mounted in the base of a shallow V-shaped groove 41 which encircles the body of the plug. The members 23 are similar to those previously described. The shallow, V-shaped groove 42 has two slightly angled surfaces 43, 45 extending down towards one another and meeting to form the base 47 of the groove. The members 23 are mounted in the base 47. This plug differs from the previously described plug in that it can be reused if desired. It will be noted that clearance for the members 23 is provided adjacent the front end of the plug by surface 45, so that they can be bent over and down into this space when the plug is being withdrawn from the tube. When the plug is reused, the wire members will bend over from their position adjacent the leading surface 45 of the shallow groove to a position adjacent the trailing surface 43 but still extending above the cylindrical surface of the body where they again act as a fish hook to securely hold the plug within the tube.
lfdesired, the plugs 3 can be made without the flange 19 at one end 17 permitting the plug to be inserted right into the centre of the tube if more support for the tube is necessary. Such a plug 3', without a flange, is shown in FIG. I of the drawings.
The plug body is preferably made from suitable hardwood. The resilient members are preferably made from suitable metal wire material.
The plugs of the invention can be used in tubes varying as much as three-sixteenths inch in their nominal internal diameters.
The plugs of the invention can be used in rolls of wound soft material having no core tube with the resilient members 23 gripping directly into the soft mate rial. As examples, the plugs'can be used for rolls of linoleums, aluminum foil, newsprint paper. waxed paper. wrapping paper, all types of coated papers and sheet material used in the building industry. In all cases, the plug is effectively locked in position.
What I claim is:
l. A plug adapted to be inserted into a cylindrical bore defined by relatively soft material, the plug comprising a cylindrical body, and a plurality of elongate, spaced-apart, resilient holding members extending about the body intermediate the ends of the body, each member attached by its ends to the body, and having a point intermediate its ends projecting radially outwardly from the body, to co-operate with the soft material to hold the plug in the bore, the ends of each member lying in a plane which is substantially perpendicular to the longitudinal axis of the body and a shallow groove extending eircumferentially about the body intermediate the ends of the body, the ends of the holding members being attached to the body at or adjacent the base of the groove.
2. A plug as claimed in claim I, wherein the groove, as seen in cross-section, has a radially extending shoulder adjacent the end of the plug which is to be inserted into the bore first, and a surface angling down to the bottom of the shoulder.
3. A plug as claimed in claim 2, wherein the groove surface has a width substantially equal to the distance each point of each member projects from the body.
4. A plug as claimed in claim 1, wherein the groove, as seen in cross-section, is of a shallow V-shape.
5. A plug as claimed in claim 4, wherein the two surfaces of the V-shaped groove each have a width substantially equal to the distance each point of each member projects from the body.
6. A plug as claimed in claim 1, including a flange at the end of the plug opposite the end first inserted into the bore to limit movement of the plug into the bore.
7. A plug as claimed in claim I, wherein the body is made of wood and the holding members are made of wire.