Abstract:
A method for roll packing foam mattress cores includes the step of providing a radially collapsible mandrel for winding up the foam material. Compression of the foam material is accomplished during the roll operation via a compression roller associated with the mandrel. After a sufficient amount of foam material has been rolled, the mandrel is collapsed to facilitate easy removal of the roll. In one embodiment of the invention, packing material is applied to a surface of the foam as it is rolled to prevent adhesion of successive layers in the roll.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention pertains to foam cores for mattresses, and more particularly to a method for packaging foam cores into rolls.  
           [0003]    2. Description of the Prior Art  
           [0004]    The use of foam cores in the manufacture of mattresses is known in the art. These foam-core mattresses may be made from a single foam material or multiple foam materials assembled together in layers. The foam cores are typically made from latex, urethane, or other suitable materials. Conventional fabrication of foam cores involves the production of a large block, or bun, of foam material which is subsequently cut to desired lengths and thicknesses. The cut-to-length cores are then shipped to mattress manufacturers for assembly into mattress products. Conventional methods of transporting the foam cores simply involves loading the cut lengths of foam onto a truck or van for delivery to the manufacturers. This method of transporting foam cores utilizes a significant amount of cargo space and, because of the compressible nature of the foam, is highly inefficient. Other components used in the manufacture of mattresses, such as batting and fabric cover materials, are typically shipped in roll form. to increase transportation efficiency. Likewise, it has been desired to roll pack foam core materials as well.  
           [0005]    Roll packing generally involves winding-up of a desired material to form a compact roll and then securing the roll to prevent uncoiling of the roll during handling. In the case of compressible materials such as foam or spring cores, it is often desired to compress the materials during the roll packing process to obtain a more dense and compact roll. Various devices have been used to achieve compression of the materials. U.S. Pat. No. 3,927,504 to Forrister discloses an apparatus for compressing and rolling resilient foamed sheet material without the use of a mandrel. Some roll packing systems further include a mandrel for facilitating the winding of the material. For example, U.S. Pat. No. 6,098,378 to Wyatt and U.S. Pat. No. 4,711,067 to Magni each disclose a mandrel comprising two semi-mandrels that, after winding, are axially separated from each other to remove the mandrel from the wound mattress core. U.S. Pat. No. 2,114,008 to Wunderlich discloses a spring packing machine having a radially collapsible arbor for use in roll packing spring assemblies.  
           [0006]    While the use of mandrels is generally known for facilitating winding of mattress cores, the roll packing of foam cores onto mandrels has heretofore been a problem because the foam material does not slide easily off of the mandrel after being rolled up. Difficulties in removing the foam from the mandrel are due to the material&#39;s high friction coefficient in combination with the high compression force against the mandrel that is created when the compressed foam is wound onto the mandrel. When a spring core is compressed onto a mandrel, the spring material has a natural tendency to want to expand in a direction radially outward from the mandrel. On the other hand, when a foam core is compressed onto a mandrel, the foam material has a natural tendency to want to expand in both radial directions, i.e., to expand radially outward from the mandrel and radially inward to the mandrel. As a result of the inward compressive force, the foam material essentially sticks to the mandrel. As a further result, attempting to withdraw the foam core from the mandrel may damage the foam surface or cause undesirable telescoping of the rolled foam as it is removed from the mandrel. There is thus a need for a means for efficiently packaging lengths of foam material into a roll without damaging the material or causing undesirable telescoping of the rolled foam.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a method for efficiently packaging a length of compressible foam material, such as latex, urethane, or other polymeric foam material, into a roll for efficient delivery to manufacturers or end users. To this end and in accordance with the present invention, an apparatus is provided having a mandrel which is radially collapsible to decrease an outer diameter of the mandrel, and having a compression roller associated with the mandrel for compressing in-fed foam material prior to winding onto the mandrel. An apparatus for roll packing foam materials according to the present invention is disclosed in U.S. patent application Ser. No. ______, entitled “Apparatus and Method for Roll Packing Compressible Materials,” filed on even date herewith, and incorporated by reference herein in its entirety. The collapsible mandrel is provided in the radially expanded position for winding a length of foam material into a roll, the mandrel is then collapsed, and the roll is then removed from the collapsed mandrel without damaging the foam material. The foam material is compressed as it is being wound onto the mandrel so that a compact and efficiently packaged roll of foam is produced for easy shipping and storing in a smaller space than conventionally supplied lengths of foam material, with the result that the foam has very little permanent compression set when it is finally unrolled. The spacing between the mandrel and the compression roller may be varied in order to adjust the amount of compression on the foam material passing between the mandrel and the compression roller.  
           [0008]    In one embodiment of the invention, a packing material dispenser holds a roll of packing material and dispenses it to a surface of the foam material as it is being wound onto the mandrel to prevent adhesion of subsequent sections of the rolled foam so that unpacking of the roll may be easily accomplished. The packing material may be paper, plastic, a fabric material, or other suitable material for packaging the foam into a roll and preventing adhesion of consecutive surfaces of the foam on the roll. In another embodiment of the invention, a feed table, upstream of the mandrel and compression roller, is used to support the infed foam material and direct it between the mandrel and compression roller for winding onto the mandrel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.  
         [0010]    [0010]FIG. 1A is a schematic illustration of an apparatus for use in practicing one embodiment of the method of the present invention and illustrates the step of directing foam material between the mandrel and compression roller.  
         [0011]    [0011]FIG. 1B shows the apparatus of FIG. 1A and illustrates the step of winding foam material onto the mandrel.  
         [0012]    [0012]FIG. 1C shows the apparatus of FIG. 1B and illustrates the step of collapsing the mandrel.  
         [0013]    [0013]FIG. 2 is a flow chart depicting the steps involved in roll packing foam cores according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]    The present invention provides a method for roll packing foam mattress cores onto a mandrel wherein the wound, compressed core can be easily removed from the mandrel by radially collapsing the mandrel. The method of the present invention, which overcomes the difficulties presented by the nature of foam materials, as discussed above, may be best explained in connection with the figures herein.  
         [0015]    With reference to FIGS.  1 A- 1 C, there is shown an illustration of an apparatus  10  for roll packing compressible foam material  12 , in accordance with one embodiment of the present invention. The apparatus  10  includes an elongated mandrel  14  for receiving infed foam material  12  and winding the foam  12  into a roll  16  as the mandrel  14  is turned about its rotational axis  18 . The mandrel  14  is constructed to be radially collapsible, whereby the outer diameter  20   a  of the mandrel  14  may be reduced. A compression roller  22  is located proximate the mandrel  14  and has a rotational axis  24  substantially parallel to the rotational axis  18  of the mandrel  14 . The relative positions of the mandrel  14  and the compression roller  22  may be adjusted to either increase or decrease the spacing  26  between their respective outer surfaces. The spacing  26  between the mandrel  14  and compression roller  22  determines the amount of compression to be applied to the infed length of foam material  12 . A feed table  28  may be located upstream of the mandrel  14  and compression roller  22 . The feed table  28  supports a length of foam material  12  and directs the foam material  12  between the mandrel  14  and the compression roller  22  as the foam  12  is being wound upon the mandrel  14 . A packing material dispenser  30  is located upstream of the mandrel  14  and compression roller  22  and contains a roll of packing material  32 . The packing material  32  is applied to a first surface  34  of the infed foam material  12  as it passes between the mandrel  14  and the compression roller  22  and thus forms a barrier layer  36  between successive layers  38  of the foam material  12  as it is wound upon the mandrel  14 . The packing material  32  may be paper, plastic, a fabric material, or other packing material suitable for preventing adhesion of successive layers of foam material. The apparatus  10  may further include one or more feed rollers  40  associated with the packing material dispenser  30  for controlling the dispensing and application of packing material  32  to the first surface  34  of the foam  12  as it is fed between the mandrel  14  and compression roller  22 . In an alternative embodiment, not shown, the packing material dispenser  30  and feed rollers  40  may be positioned above the foam  12  so as to feed the packing material  32  to second surface  35  of the infed material before it contacts the mandrel  14 .  
         [0016]    As more fully shown in FIG. 1B, mandrel  14  is rotated such that foam  12  is drawn between the compression roller  22  and the mandrel  14  and is thereby compressed while being wound onto the mandrel  14 . The position of compression roller  22  may be continuously adjusted as the roll thickness increases to provide the desired degree of compression of the foam material  12 . When a desired quantity of foam material  12  has been wound onto the mandrel  14 , the mandrel  14  is stopped. The roll  16  may then be banded or strapped to retain the roll shape. Thereafter, mandrel  14  is collapsed such that the outer diameter  20   b  of the mandrel  14  is less than the inner diameter  42  of the roll  16  of foam material  12  as more fully shown in FIG. 1C. The banded roll  16  may then be easily removed from the mandrel  14  for further processing or shipment to a manufacturer or end user. Because the mandrel  14  is radially collapsed prior to removing the roll  16 , the foam material  12  is not damaged as it is slid off the mandrel  14 . Furthermore, it has been discovered that the foam material surprisingly exhibits very little compression set after it is finally unrolled to its free state. Measurements taken from a latex foam core roll packed according to the method of the present invention exhibited permanent compression set when unrolled of less than about 3% after having remained rolled for one month.  
         [0017]    [0017]FIG. 2 depicts the general steps involved in roll packing compressible foam materials according to one embodiment of the present invention. In particular, in step  50 , the spacing between a mandrel and a compression roller is set to obtain a desired compression for a given infed foam material. In step  60 , a length of foam material and backing material are positioned at the infeed side between the mandrel and the compression roller. In step  70 , the foam material is fed through the mandrel and compression roller and secured to the mandrel. In step  80 , the foam material is wound upon the mandrel while additional foam is continuously fed and compressed between the compression roller and the mandrel, and as the packing material is continuously applied to a first side of the in-fed foam. In step  90 , the position of the compression roller may be periodically or continuously adjusted, as necessary, to accommodate the continuously increasing size of the roll of compressed foam material. When a desired quantity of foam has been wound upon the mandrel, rotation of the mandrel is stopped, as in step  100 , and the roll is banded, as in step  110 , to secure the foam material in the rolled and compressed state. In step  120 , the mandrel is collapsed to permit removal in step  130  of the roll from the mandrel.  
         [0018]    While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of applicant&#39;s general inventive concept.