Expandable core-shafts

#Previously expandable shafts for releasably gripping the inside diameter of the cores for winding webs, which shafts contained radially extending rams operated by fluid pressure, often failed because they were unable to: (a) seal statically, (b) prevent leakage when sliding seals were used, (c) prevent rupture when rubber inflatable bags were used, and/or (d) control the stability of the pressuring fluid.

#Radially extending rams from such shafts to grip the inside of the cores of rolls of web, not only had to continuously grip radially outwardly but also were under large rapid varying stresses tangential to the shafts due to the torques and vibrations of the roll of web when changing its speed of rotation as in starting, accelerating, driving, braking, and stopping. This caused side wear in the piston rams or plungers, making annular seals between the relatively sliding parts, including O-rings, substantially useless, particularly at higher pressures, because of their leakage and/or seepage.

#In a closed hydraulic liquid system of this type, less than 0.1% loss of fluid can prevent the maintenance of an operable pressure. The stability of the hydraulic liquid also is critical, since expansion or contraction from heat or cold changes the volume enough, respectively, either: to activate the rams, or to reduce the volume of the liquid below the capacity of the system so that pressurizing is impossible.

#The above mentioned and other features, objects and advantages and a manner of obtaining them are described more specifically below by reference to embodiments of this invention shown in the accompanying drawings wherein:

#FIG. I is a perspective view of one end of an hydraulically expandable core-shaft according to one embodiment of this invention showing a part of a core and one of the leaves thereon broken away, and a wrench engaged for turning the sleeve for operating the piston of the master cylinder adjacent one end bearing of the shaft;

#FIG. II is a side elevation of another embodiment of a self-contained core-shaft similar to and reduced in size to that shown in FIG. I, with parts broken away to show the radially extendable gripping ram buttons in longitudinally staggered configuration and in direct contact with the core without segmental leaves, and with the master cylinder shown outside the bearing on one end of the shaft, instead of inside as shown in FIG. I; and with a pressure maintaining and limiting means at the other end of the shaft.

#In FIG. I there is shown one end of an hydraulically expandable coreshaft 20 according to one embodiment of this invention having an end bearing portion 22 of lesser diameter than the main shaft 20 adjacent which is provided a master cylinder 50 showing its outwardly knurled operating sleeve 24 and its adjacent locking ring or nut 26 having a radially inwardly extending hole 27 for engagement of the trunnion grip end of the wrench W shown in engagement in a corresponding hole 25 in the periphery of the sleeve 24. The outer cylindrical surface 28 of the shaft 20 is shown surrounded by segmental sleeves, shells or leaves 30, the outer surfaces of which may be roughened, coated, or plated, as desired, to frictionally engage the inside diameter of a core C which may be made of a fibrous material and used for the wrapping thereon paper, plastic films, metal foils, fabric, or the like type webs. The longitudinal segmental leaves 30 are herein shown to be divided into 120.degree. arcuate segments (shown more clearly in FIG. X), and are herein shown to be provided with recessed holes 32 into which screws 34 fit for removably anchoring the leaves 30 to guide and/or gripping rams or pistons 40 and/or 40', as more specifically shown in FIGS. III and XI and described in more detail below. Also shown in FIG. I is one of the radially extendable gripping rams or pistons 80 which pushes outwardly against the inside of the leaves 30 or directly against the inside of the core C (as shown in FIGS. II, IV and VIII) as being a means for expanding the circumference of the mandrel shaft 20. Different embodiments of these gripping rams or pistons will be described later in connection with FIGS. IV, VII, VIII and IX below.

#FIG. II shows another embodiment of a core-shaft 20' of this invention in which the master cylinder 50 and its locking ring or nut 26 are provided outside the bearing 22' instead of inside thereof as shown in FIG. I. At the other end of the shaft 20' is shown a pressure limiting and maintaining means 141 for the self-contained hydraulic system in the coreshaft of this invention, which means 141 will be described in more detail in the following Master Cylinders section. Furthermore this embodiment does not disclose the leaves 30 or their guides 40 as shown in FIG. I, but instead shows the radially outwardly extending rams or pistons 80 directly in contact with the inside diameter of a core C upon which the web is to be wound.

#In FIG. III there is shown one embodiment of how the guide piston 40 for the leaves 30 are anchored into the body of the shafts 20, through a threaded hole 41 that radially extends inwardly from the outer surface 28 of the shaft 20. This hole 41 has a larger diameter than the outer end of the guide piston 40, which piston has a flanged inner end 42 substantially the same diameter as the hole 41. Threaded into the outer end of the hole 41 is a holding nut 43 for compressing a helical spring 44 between it and the flange 42 for normally urging the leaves 30 into their retracted, or smaller core-shaft diameter, positions. The combination guide and extendable piston or plunger embodiment 40' will be described in more detail later in combination with the embodiment shown for the larger diameter core-shafts in FIGS. IX, X and XI.