Abstract:
A spring assembly includes telescopically adjustable inner and outer members biased in an extension direction by a coil spring. A preload member is provided to apply a compression preload to the coil spring. The preload member can eliminate stickiness and the popping sound that are drawbacks of the prior art, and the fabric sleeve also provides general noise reduction when the spring assembly changes length.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit as a continuation-in-part of U.S. patent application Ser. No. 13/622,648 filed Sep. 19, 2012, which application is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure relates generally to mattresses and cushioning devices for home and/or hospital use, and more particularly to a telescoping spring assembly usable as a component of a mattress or cushioning device. 
       BACKGROUND OF THE INVENTION 
       [0003]    U.S. Pat. No. 6,996,865 to Sabin describes a mattress structure in which a support assembly comprises a support plate having an array of mounting holes each receiving a respective telescoping spring assembly. In U.S. Pat. No. 6,996,865, various embodiments of the spring assembly are identified by the reference numerals 20, 120, 220, 320, and 420. The various spring assembly embodiments are telescoping spring assemblies in the sense that each has an inner member arranged to be axially slidable within an outer tubular member, and a mechanical spring is arranged within the inner and outer members to bias the members in an extension direction. The Sabin patent teaches that it is desirable to preload the spring to control firmness. In order to achieve preload, Sabin discloses the use of a spacer (e.g., spacers 28, 128, and 228) engaging an end of the spring and one of the tubular members, wherein the spacer has an axial length chosen to provide a desired preload. The spring assemblies mounted on the support plate may have different preload characteristics achieved by using spacers of different lengths to vary the firmness of the mattress in different support zones. 
         [0004]    Efforts to commercialize the invention in U.S. Pat. No. 6,996,865 have been met with certain design challenges. A significant challenge has been the fact that the preload applied to the coil spring is transmitted to the inner and outer tubular members. Under this design, the inner and outer members are forced into a fully extended condition (absent external loading) and are prevented from separating by engagement of opposing shoulder surfaces on the external wall surface of the inner member and on the internal wall surface of the outer member. As a result, the frictional engagement between the shoulders of the inner and outer members causes the spring assembly to be “sticky” at times, and the spring assembly does not always react as intended when an external load is first applied. Moreover, after an external load is removed from a compressed spring assembly, the biasing force of the coil spring immediately pushes the outer member in the extension direction, and the ensuing engagement of opposing shoulder surfaces on the inner and outer members generates a popping sound that is disruptive to a person at rest. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention solves both of these challenges, and does so by eliminating the need for a spacer of special length in each spring assembly. 
         [0006]    The present invention is embodied by a spring assembly comprising a tubular outer member including a support end and an open receiving end opposite the support end, and a tubular inner member including an insertion end and a mounting end opposite the insertion end, wherein the insertion end of the inner member is received through the open receiving end of the outer member such that the outer member is telescopically movable relative to the inner member in a compression direction and an extension direction opposite from the compression direction. The spring assembly further comprises a coil spring arranged to bias the outer member in the extension direction relative to the inner member. In accordance with the present invention, the spring assembly comprises a fabric sleeve fitted about an inner diameter and an outer diameter of the coil spring, wherein the fabric sleeve is closed at its opposite ends to apply a compression preload to the coil spring. The fabric sleeve prevents transmission of the preload to the tubular members to eliminate the problems of stickiness and noise when the spring assembly changes length. 
         [0007]    The present invention may also be embodied as a spring assembly including a tubular outer member including a support end and an open receiving end opposite the support end. The assembly may also include an inner member, including an insertion end and a mounting end opposite the insertion end. The insertion end can be received by the outer member through the open receiving end of the outer member, the outer member being telescopically movable relative to the inner member in a compression direction and an extension direction opposite from the compression direction. A coil spring can be arranged to bias the outer member in the extension direction relative to the inner member. A first bumper insert may be arranged at a first end of the coil spring, and a second bumper insert may be arranged at a second end of the coil spring. A preload member can extend from the first bumper insert to the second bumper insert. The preload member may be configured to apply a compression preload to the coil spring. 
         [0008]    In another embodiment, the present invention is embodied as a method of making a spring assembly. A tubular outer member including a support end and an open receiving end opposite the support end can be provided. An inner member including an insertion end and a mounting end opposite the insertion end can be provided. A coil spring may be arranged to bias the outer member in the extension direction relative to the inner member. A first bumper insert may be arranged at a first end of the coil spring. A second bumper insert may be arranged at a second end of the coil spring. A preload member can be arranged to extend from the first bumper insert to the second bumper insert. The preload member can be configured to apply a compression preload to the coil spring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING VIEWS 
         [0009]    Features and advantages of embodiment(s) of the present disclosure will become apparent by reference to the following detailed description and drawings, in which: 
           [0010]      FIG. 1  is a perspective view of a telescoping spring assembly formed in accordance with an embodiment of the present invention; 
           [0011]      FIG. 2  is an exploded view of the telescoping spring assembly shown in  FIG. 1 ; 
           [0012]      FIG. 3  is an exploded view of a support cap subassembly of the spring assembly shown in  FIG. 1 ; 
           [0013]      FIG. 4  is an end view of the support cap subassembly shown in  FIG. 3 ; 
           [0014]      FIG. 5  is an exploded view of a mounting subassembly of the spring assembly shown in  FIG. 1 ; 
           [0015]      FIG. 6  is an end view of the mounting subassembly shown in  FIG. 5 ; 
           [0016]      FIG. 7  is an end view of a coil spring of the telescoping spring assembly, wherein the coil spring is enclosed in a fabric sleeve; 
           [0017]      FIG. 8  is a perspective view of a preload member; and 
           [0018]      FIG. 9  is an end view of the preload member of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    A telescoping spring assembly formed in accordance with the present invention is shown in  FIG. 1  and identified generally by reference numeral  10 . Spring assembly  10  comprises a tubular inner member including an insertion end and a mounting end opposite the insertion end. The mounting end is characterized by a fitting  13  for insertion into a corresponding mounting hole of a plate (not shown), whereby an array of closely spaced spring assemblies  10  may be formed to provide the core of a mattress as taught by the aforementioned U.S. Pat. No. 6,996,865, the entire disclosure of which is incorporated herein by reference. Spring assembly  10  also comprises a tubular outer member  14  including a support end  15  and an open receiving end opposite the support end. As may be seen in  FIG. 1 , the insertion end of inner member  12  is received by outer member  14  through the open receiving end of the outer member. As may be understood, outer member  14  is telescopically movable relative to inner member  12  in a compression direction to shorten the overall length of spring assembly  10 , and in an extension direction opposite from the compression direction to extend the overall length of the spring assembly. 
         [0020]    Reference is made now to  FIG. 2 . Spring assembly  10  further comprises a coil spring  16  arranged to bias outer member  14  in the extension direction relative to inner member  12 . In the embodiment shown, one end of coil spring  16  bears against a bumper insert  18  disposed at the insertion end of inner member  12 , and an opposite end of coil spring  16  bears against another bumper insert  20  disposed in outer member  14  axially adjacent to support end  15 . 
         [0021]      FIGS. 3 and 4  show outer member  14  and bumper insert  20  in further detail. As may be seen, outer member  14  includes a plurality axially extending ribs  24  spaced at regular angular intervals about an internal wall of the outer member adjacent the open receiving end of the outer member. In the embodiment shown, bumper insert  20  includes a generally rigid plastic insert on which an elastically deformable bumper piece  26  is mounted to face inner member  12 , and a bumper spring  28  is disposed on the opposite side of bumper insert  20  to engage support end  15  of outer member  14 . Bumper spring  28  may be chosen to have greater stiffness than coil spring  16 .  FIGS. 5 and 6  show inner member  12  and bumper insert  18  in further detail. Inner member  12  includes a circumferential shoulder  30  around an external wall of the inner member adjacent the insertion end of the inner member. In the embodiment shown, bumper insert  18  includes a generally rigid plastic having a lip  32  sized to engage the insertion end of inner member  12  such that bumper insert  18  remains located at the insertion end of inner member  12 . An elastically deformable bumper piece  34  is mounted on bumper insert  18  to face bumper insert  20 . A bumper spring  36  is disposed on the same side of bumper insert  18  so that it also faces bumper insert  20 . Bumper spring  36  may be chosen to have greater stiffness than coil spring  16 . The bumper inserts  18  and  20 , and the bumper springs  36  and  28 , provide stiffer cushioning as spring assembly  10  approaches a fully compressed condition to prevent “bottoming out” under very heavy external loads. 
         [0022]    Airflow into and out of spring assembly  10  during telescoping volume changes is allowed by passages through the mounting end of inner member  12  and the support end of outer member  14 , however these passages are not visible in the drawing views. Such airflow is also allowed by passages  38  through bumper inserts  18  and  20 , and by gaps  40  between ribs  24  in outer member  14 . 
         [0023]    Axial separation of outer member  14  and inner member  12  may be prevented unless an intentionally large separation force is applied. In the embodiment shown, axial separation is prevented by engagement of circumferential shoulder  30  with the ends of ribs  24  closest to support end  15 . However, as will be understood from the description below, when coil spring  16  is properly preloaded, outer member  14  freely floats on the coil spring such that the ends of ribs  24  are slightly spaced from engagement with shoulder  30  to avoid the sticking problem mentioned in the background section. 
         [0024]    In accordance with the present invention, spring assembly  10  additionally comprises a fabric sleeve  22  fitted about an inner diameter and an outer diameter of coil spring  16 , wherein fabric sleeve  22  is closed at its opposite ends to apply a compression preload to coil spring  16 . The compression preload applied to spring  16  decreases the length of the spring enough so that the ends of ribs  24  on outer member  14  do not engage shoulder  30  on inner member  12 . For example, the compression preload may be chosen to provide a distance of about one-eighth of an inch between the ends of ribs  24  and shoulder  30  when spring assembly  10  is at rest and free of external loading. 
         [0025]    Fabric sleeve  22  may be formed about coil spring  16  in a variety of ways. In one way, the sleeve begins as two separate generally rectangular sheets of non-stretch fabric, one to fit about the outer diameter of coil spring  16  and the other to fit about the inner diameter of coil spring  16 . If coil spring  16  is a variable stiffness coil spring wherein the inner and outer diameters vary along the axial length of the spring, then the outer sheet must fit around the largest outer diameter and the inner sheet must fit within the smallest inner diameter. Each sheet is folded over onto itself and a lengthwise seam is formed along overlapping portions of the sheet to provide a generally tubular sleeve portion of appropriate diameter depending upon whether the sleeve portion is internal or external. The external and internal sleeve portions are then arranged around the outer diameter and inner diameter of coil spring  16 , respectively a first circumferential seam may then be made near one end of coil spring  16  to secure the external sleeve portion to the internal sleeve portion. A preload is applied to coil spring  16  by compressing the coil spring to a predetermined axial length, and then a second circumferential seam is made near the second end of the compressed coil spring to secure the external sleeve portion to the internal sleeve portion, thereby confining the coil spring in a preloaded condition. 
         [0026]    In another way of fitting fabric sleeve  22  to coil spring  16 , the fabric sleeve begins as a single generally rectangular sheet of non-stretch fabric in excess of two times the intended length of preloaded coil spring  16 . The single sheet is folded over onto itself and a lengthwise seam is formed along overlapping portions of the sheet to provide an elongated tubular sleeve portion of appropriate diameter to fit about the outer diameter of coil spring  16 . The coil spring is inserted into the elongated tubular sleeve portion and the sleeve is inverted (turned inside-out) and fed through the interior of the coil spring. As a result, one end of the spring will be confined against the folded sleeve, and the other end of the spring will be near an open end where the two unconnected ends of the fabric sleeve are aligned with one another. A preload is applied to coil spring  16  by compressing the coil spring to a predetermined axial length, and then a circumferential seam is made to attach the aligned ends of the fabric sleeve to one another, thereby closing the open end to confine the coil spring in a preloaded condition. 
         [0027]    Those skilled in the art will understand that seams may be formed by sewing or by ultrasonic welding, and that the amount of excess fabric material needed to form sleeve  22  may depend on the seam technology used. 
         [0028]    At least two fabrics have been found particularly suitable for use in forming fabric sleeve  22 . The first is Sparmont 900 needle punched fabric, which is recommended for coil springs with spring rates of two pounds per inch or less. The second is SW400 sonic welded fabric, which is recommended for coil springs with spring rates from two to four pounds per inch. Both fabrics are supplied by NuTex Concepts located at 2424 Norwood Street, Lenoir, N.C. 28645. Of course, other fabrics may be used. 
         [0029]    As will be understood, the use of fabric sleeve  22  in accordance with the present invention provides important benefits. Fabric sleeve  22  maintains the preload on coil spring  16  so that engagement between inner member  12  and outer member  14  is not necessary for this task. In this way, the problem of “stickiness” is solved, and the popping sound when the spring assembly returns to its extended position is eliminated. Moreover, preload can be determined by selecting a coil spring  16  having a spring rate and free length such that the coil spring provides a desired preload when compressed by fabric sleeve  22  to a predetermined, known length. The spring rate of coil spring  16  may be a variable spring rate to provide lesser firmness during initial compression of spring assembly  10  under external loading, followed by somewhat greater firmness as the spring assembly compresses further. The performance of each spring assembly can be individualized without the need for spacers of different lengths as taught by the prior art. Also, the fabric sleeve helps to dampen and absorb acoustic energy to provide quieter spring assembly performance apart from elimination of the popping sound mentioned above. 
         [0030]    As generally described above, the fabric sleeve  22  can serve as a “preload member” to apply a compression preload to coil spring  16 . However, a compression preload may be applied with other types of “preload members” that do not include a fabric sleeve fitted about the coil spring  16 . For example,  FIGS. 8 and 9  show another example of a preload member  50 .  FIG. 8  is a perspective view of a preload member.  FIG. 9  is an end view of the preload member of  FIG. 8 . 
         [0031]    The preload member  50  may extend from bumper insert  18  to bumper insert  20 , and include a length  52  and ends  54 . The length may be made of a flexible material, such as a woven nylon or fabric material. The ends  54  can be made of a more rigid material, such as plastic. It is contemplated, however, that the preload member  50  can be made uniformly of a single material. 
         [0032]    The preload member  50  may be located inside the diameter of coil spring  16 , for example, along approximately a center axis  16 A of the coil spring  16 . It is possible, for example, that the preload member  50  only extend along approximately center axis  16 A of the coil spring. In other words, it is possible that the preload member  50  is embodied as a single strand of material that extends between the bumper inserts  18 ,  20 . In one embodiment, the preload member  50  extends through the airflow passages  38  of the bumper inserts  18 ,  20 . The ends  54  may be protruded relative to the length  52  of the preload member  50  so as to prevent the ends  54  from sliding through the airflow passages  38 . 
         [0033]    The preload member  50  can be shorter (e.g. have a length) that is less than the length of the coil spring because the preload member  50  may rest within a portion of the bumper insets  18 ,  20  that extend into the coil spring  16 . Although the ends  54  are depicted as being located at an outer, opposite side of the bumper inserts  18 ,  20  relative to the length  52  of the preload member  50 . However, it is contemplated that the preload member  50  may be glued or otherwise affixed to an inner side of the bumper inserts  18 ,  20 . 
         [0034]    Unlike the fabric sleeve  22 , which can provide a compression preload by itself, preload member  50  cooperates with bumper inserts  18 ,  20  to apply a compression preload to the coil spring  16 . Furthermore, it is possible that the preload member  50  not touch the coil spring  16  in a rest state. However, in both instances (i.e. in using a preload member  50  or a fabric sleeve  22 ), the member applying the preload can generally extend between bumper insert  18  and bumper insert  20 . The preload member  50  may also have efficiencies over the fabric sleeve  22  such as being easier to produce, faster to install in a spring assembly  10 , and use less material. 
         [0035]    While the invention has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the invention to the particular forms set forth. The invention is intended to cover such alternatives, modifications and equivalents of the described embodiment as may be included within the spirit and scope of the invention. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           10  Spring assembly 
           12  Inner member 
           13  Mount fitting on inner member 
           14  Outer member 
           15  Support end of outer member 
           16  Coil spring 
           16 A Center axis of coil spring 
           18  Bumper insert of inner member 
           20  Bumper insert of outer member 
           22  Fabric sleeve 
           24  Ribs along internal wall of outer member 
           26  Bumper piece on bumper insert of outer member 
           28  Bumper spring on bumper insert of outer member 
           30  Circumferential shoulder of inner member 
           32  Lip on bumper insert of inner member 
           34  Bumper piece on bumper insert of inner member 
           36  Bumper spring on bumper insert of inner member 
           38  Airflow passages 
           40  Gaps between ribs 
           50  Second embodiment of a preload member 
           52  Length of second embodiment of a preload member 
           54  Ends of second embodiment of a preload member