Patent Publication Number: US-2022232992-A1

Title: High tension coil spring structure for bed mattress having means for preventing friction noise

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priorities from Korean Patent Application Number 10-2013-113990 filed on Sep. 25, 2013, Korean Patent Application Number 10-2013-115999 filed on Sep. 30, 2013, claiming priority from Korean Patent Application Number 10-2013-113990 filed on Sep. 25, 2013, and Korean Patent Application Number 10-2013-136458 filed on Nov. 11, 2013, claiming priorities from Korean Patent Application Number 10-2013-113990 filed on Sep. 25, 2013 and Korean Patent Application Number 10-2013-115999 filed on Sep. 30, 2013, the entire contents of which are incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a high tension coil spring structure for a bed mattress having exposed wiring portions which are formed on coil springs and cooperate with spring bodies to absorb an external load, and more particularly, to a high tension coil spring structure for a bed mattress having means for preventing friction noise which can significantly increase the elasticity of exposed wiring portions as well as fundamentally preventing noise that is created by friction between the exposed wiring portions and surrounding wiring portions while the exposed wiring portions are being compressed. 
     Description of Related Art 
     In general, a bed mattress is an instrument for sleeping which provides a cushion or a buffering force using cushion members which are respectively stacked on the upper surface and the lower surface of a spring assembly. The spring assembly includes a plurality of coil springs which are provided between upper and lower frames inside the bed mattress and are regularly arranged in columns and rows and spaced apart from each other at preset distances. 
     In addition, “exposed wire springs” were developed, and have been used as means for enhancing the cushioning and buffering force of the bed mattress. The exposed wire springs include coil springs which are disposed in the top-bottom direction between the upper and lower edge members of the frame such that the coil springs protrude above the upper edge member. 
     For instance, as shown in  FIG. 1 a   , a spring assembly  1  includes upper and lower edge members  20  and  20 ′, coil springs  10  which are arranged in rows and columns R and C within the space between the upper edge member  20  and the lower edge member  20 ′, and helical coils  30  which are spirally engaged with the coil springs  10  in the direction of rows R. 
     In addition, as shown in  FIG. 1 b   , each of the coil springs  10  includes a body wiring portion  12  situated in a space between the upper edge member  20  and the lower edge member  20 ′, end wiring portions  14  provided on both ends of the body wiring portion  12  so as to be engaged with the upper and lower edge members  20  and  20 ′, and an exposed wiring portion  16  extending from one of the end wiring portions  14  so as to be exposed from the edge member  20 . 
     Here, in the case of attempting to set the spring assembly  1 , when the helical coils  30  are engaged in the state in which the coil springs  10  are set at preset distances from each other between the edge members  20  and  20 ′, the exposed wiring portions  16  are set such that they protrude above the upper edge member  20  or below the lower edge member  20 ′. 
     In addition, when the spring assembly  1  is applied to a bed mattress, the exposed wiring portions  16  absorb shock when a small load is applied in response to, for example, a user rolling over on the bed, and the body wiring portions  12  absorb the shock when a large load is applied from the user. 
     The coil springs  12  advantageously increase the comfort and convenience of the user since the exposed wiring portions  16  and the body wiring portions  12  properly distribute the shock-absorbing function in response to variations in the load applied to the bed mattress. However, the coil springs  12  have, at least, the following problems. 
     First, as shown in  FIG. 2 , in the process in which the coil spring  10  is compressed at the moment that the bed mattress is subjected to a load, a contact wiring portion  16 - 5  of the exposed wiring portion  16  abuts to the end wiring portion  14  which is positioned below while moving down. This consequently creates noise due to contact between the exposed wiring portion  16  and the end wiring portion  14 . 
     Second, when a large load is applied to the bed mattress, the exposed wiring portion  16  of the spring assembly is compressed, and concurrently, the body wiring portion  12  is compressed at high speed. Rapid compression of the exposed wiring portion  16  increases friction between the exposed wiring portion  16  and the end wiring portion  14 , thereby creating friction noise. 
     Third, when a load is applied to the bed mattress, the exposed wiring portion abuts to the end wiring portion while being compressed, whereby the elasticity of the exposed wiring portion is limited. Accordingly, solutions for preventing stress due to friction noise between the exposed wiring portions  16  and the end wiring portions  14  while the bed mattress is being used and for increasing the longevity of the coil spring are urgently required. 
     As shown in  FIG. 3A , an approach was proposed in a coil spring (Korean Patent No. 10-0717543, U.S. Pat. No. 7,677,541 B2) that was previously invented by the applicant. This coil spring includes a body spring  10  and an exposure wire spring  20 , in which a connection end portion  24  which connects the exposure wire spring  20  to the body spring  10  has a contact-preventing end  30 . 
     Although the coil spring shown in  FIG. 3A  prevents frictional noise between the body spring  10  and the exposure wire spring  20  using the contact-preventing end  30  to a certain extent, the coil spring fails to completely prevent frictional noise since the exposure wire spring  20  comes into contact with the body spring  10  when the range in which the exposed wire spring  20  moves downward exceeds the height of the contact-preventing end  30 . 
     In addition, although the coil spring shown in  FIG. 3A  is focused on the contact-preventing end  30  which prevents frictional noise, there is a drawback in that the amount of elasticity with which the exposure wire spring  20  moves upward and downward is limited since the exposure wire spring  20  has a small number of turns. 
     In addition, as shown in  FIG. 3B , an approach was proposed in a coil spring (Korean Patent No. 10-0717545, U.S. Pat. No. 8,109,490) that was previously invented by the applicant. This coil spring including a body spring  10  and an exposure wire spring  20 , in which a connection end portion  24  which connects the exposure wire spring  20  to the body spring  10  has contact-preventing/rigidity-reinforcing ends  30  and  32 , thereby preventing frictional noise between the body spring  10  and the exposure wire spring  20 . 
     Although the coil spring shown in  FIG. 3B  prevents frictional noise between the body spring  10  and the exposure wire spring  20  using the contact-preventing/rigidity-reinforcing ends  30  and  32  to a certain extent, the coil spring fails to completely prevent frictional noise since the exposure wire spring  20  comes into contact with the body spring  10  when the range in which the exposed wire spring  20  moves downward exceeds the height of the contact-preventing/rigidity-reinforcing ends  30  and  32 . 
     In addition, although the coil spring shown in  FIG. 3B  is focused on the contact-preventing/rigidity-reinforcing ends  30  and  32  which prevent frictional noise, there is a drawback in that the amount of elasticity with which the exposure wire spring  20  moves upward and downward is limited since the exposure wire spring  20  has a small number of turns. 
     Furthermore, as shown in  FIG. 3C , an approach was proposed in a coil spring (Korean Patent No. 10-0820579) that was previously invented by the applicant. This coil spring including a body portion  115   a  and an exposed wiring portion  115   b . An uppermost wiring portion  30  formed on the body portion  115   a  has concave portions  60  and  70  which absorb the return load of the body portion  115   a , thereby preventing frictional noise between the body portion  115   a  and the exposed wiring portion  115   b.    
     Although the coil spring shown in  FIG. 3C  prevents frictional noise between the body portion  115   a  and the exposed wiring portion  115   b  using the concave portions  60  and  70  to a certain extent, the coil spring fails to completely prevent frictional noise since the exposed wiring portion  115   b  comes into contact with the body portion  115   a  when the range in which the exposed wiring portion  115   b  moves downward exceeds the height of the concave portions  60  and  70 . 
     In addition, although the coil spring shown in  FIG. 3C  is focused on the concave portions  60  and  70  which prevent frictional noise, there is a drawback in that the amount of elasticity with which the exposed wiring portion  115   b  moves upward and downward is limited since the exposed wiring portion  115   b  has a small number of turns. 
     The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention provide a ‘high tension coil spring structure for a bed mattress having means for preventing friction noise which can significantly increase the elasticity of an exposed wiring portion which protrudes upward or downward from a spring assembly while fundamentally preventing noise that is created by friction between the exposed wiring portion and a surrounding wiring portion while the exposed wiring portion is being compressed. 
     In an aspect of the present invention, provided is a high tension coil spring structure for a bed mattress that includes: body wiring portions which are disposed regularly at preset distances from each other in the space between an upper edge member and a lower edge member, upper and lower end wiring portions which are provided on both ends of the body wiring portions and set within the range in which the upper and lower edge members are disposed; upper and lower exposed wiring portions which extend from at least one of the upper and lower end wiring portions so as to be exposed from the upper or lower edge members; diameter-increasing portions which are provided on at least one of the upper and lower end wiring portions and define spaces in which upper and lower exposure start wiring portions of the upper and lower exposed wiring portions move upward and downward while the coil spring structure is being compressed; and means for preventing friction noise which are provided on at least one of the upper and lower end wiring portions. The means for preventing friction noise include rigid support ends which are provided on at least one of the body wiring portion and the upper and lower exposed wiring portions, and absorb shock by absorbing a compressive load applied from the upper and lower exposed wiring portions. The diameter-increasing portions provide spaces in which upper and lower exposure start wiring portions move upward and downward while the coil spring structure is being compressed, thereby preventing frictional noise between the upper and lower end wiring portions and the upper and lower exposure start wiring portions. When a compressive load is applied to the coil spring structure, a plurality of wiring portions formed in the upper and lower exposed wiring portions move upward and downward along the side walls of the rigid support ends, thereby increasing elasticity. 
     As set forth above, the present invention has at least the following effects. 
     First, since the coil spring structure is provided with the diameter-increasing portion which forms a path along which the exposed wiring portion moves upward and downward, it is possible to consequently remove friction that is created due to contact between the exposed wiring portion and the end wiring portion while the exposed wiring portion is being compressed, thereby fundamentally preventing noise. 
     Second, since the coil spring structure is provided with the diameter-increasing portion which forms a path along which the exposed wiring portion moves upward and downward, the exposed wiring portion and the body wiring portion move only upward and downward without being displaced or deformed in the lateral direction, thereby increasing longevity. 
     Third, in the state where friction noise between the exposed wiring portion and the end wiring portion of the coil spring is prevented, the exposed wiring portions are provided with a plurality of wiring portions such that the wiring portions form a spring layer separate from the spring body. Consequently, small and large loads applied to the bed mattress are discriminated and suitable amounts of buffering force are provided, and at the same time, the elasticity of the upper and lower exposed wiring portions is significantly enhanced, thereby improving the quality of a product. 
     Fourth, the process of foaming the exposed wiring portion, which was proposed in Korean Patent No. 444347 (U.S. Pat. No. 6,983,503) as means for preventing friction noise in the coil spring, becomes unnecessary. It is possible to preclude equipment which seals the exposed wiring portion and the sealing process as well as reducing the price for purchasing that equipment and the cost for the process, thereby improving productivity. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from, or are set forth in greater detail in the accompanying drawings, which are incorporated herein, and in the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  and  FIG. 1B  are views showing the assembled state of a spring assembly of the related art, in which  FIG. 1A  is a perspective view showing the assembled state of the spring assembly, and  FIG. 1B  is a cross-sectional view showing the assembled state of the spring assembly; 
         FIG. 2  is a cross-sectional view illustrating creation of noise from the coil spring of the related art; 
         FIG. 3A ,  FIG. 3B  and  FIG. 3C  are cross-sectional views of coil springs for preventing frictional noise that were previously invented by the applicant; 
         FIG. 4A ,  FIG. 4B ,  FIG. 4C  and  FIG. 4D  are views showing the engaged state of a spring assembly according to the present invention, in which  FIG. 4A  is a cross-sectional view showing the engaged state of the spring assembly, and  FIG. 4B  to  FIG. 4D  are perspective views showing the engaged state of the spring assembly; 
         FIG. 5A  and  FIG. 5B  are first conceptual views showing a process in which an upper exposed wiring portion of a coil spring according to the present invention is compressed, upper and lower end wiring portions of the coil spring having the shape of a round spring, in which  FIG. 5A  is a cross-sectional view showing the process in which the coil spring is compressed, and  FIG. 5B  is a perspective view showing the process in which the coil spring is compressed; 
         FIG. 6A  and  FIG. 6B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of a round spring and a rigid support end is formed in a body wiring portion, in which  FIG. 6A  is a cross-sectional view showing first to fifth embodiments of the coil spring, and  FIG. 6B  is a perspective view showing the showing first to fifth embodiments of the coil spring; 
         FIG. 7A  and  FIG. 7B  are second conceptual views showing a process in which an upper exposed wiring portion of a coil spring according to the present invention is compressed, upper and lower end wiring portions of the coil spring having the shape of an offset spring, in which  FIG. 7A  is a cross-sectional view showing the process in which the coil spring is compressed, and  FIG. 7B  is a perspective view showing the process in which the coil spring is compressed; 
         FIG. 8A  and  FIG. 8B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of an offset spring and a rigid support end is formed in a body wiring portion, in which  FIG. 8A  is a cross-sectional view showing sixth to tenth embodiments of the coil spring, and  FIG. 8B  is a perspective view showing the showing sixth to tenth embodiments of the coil spring; 
         FIG. 9A  and  FIG. 9B  are third conceptual views showing a process in which an upper exposed wiring portion of a coil spring according to the present invention is compressed, upper and lower end wiring portions of the coil spring having the shape of a round-offset spring, in which  FIG. 9A  is a cross-sectional view showing the process in which the coil spring is compressed, and  FIG. 9B  is a perspective view showing the process in which the coil spring is compressed; 
         FIG. 10A  and  FIG. 10B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of a round-offset spring and a rigid support end is formed in a body wiring portion, in which  FIG. 10A  is a cross-sectional view showing eleventh to fifteenth embodiments of the coil spring,  FIG. 10B  is a perspective view showing the showing the eleventh to fifteenth embodiments of the coil spring; 
         FIG. 10C  is a perspective view showing coil springs according to the present invention, in one of which a coil end of a lower end wiring portion forms a linear free end B which is opened without being engaged with a wiring portion, and in another one of which a coil end of an upper exposed wiring portion forms a linear free end B which is opened without being engaged with a wiring portion; 
         FIG. 11A ,  FIG. 11B  and  FIG. 11C  are perspective views showing coil springs according to the present invention in each of which a handcuff portion C is formed on a coil end of a lower end wiring portion so as to engage with a wiring portion, in which  FIG. 11A  is a perspective view showing the coil spring in which the number of turns of the exposed wiring portion is 4,  FIG. 11B  is a perspective view showing the coil spring in which the number of turns of the exposed wiring portion is 5, and,  FIG. 11C  is a perspective view showing the coil spring in which the number of turns of the exposed wiring portion is 6; 
         FIG. 12A  and  FIG. 12B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of a round spring and a rigid support end is formed in at least one of upper and lower exposed wiring portions, in which  FIG. 12A  is a cross-sectional view showing sixteenth to nineteenth embodiments of the coil spring,  FIG. 12B  is a perspective view showing the showing the sixteenth to nineteenth embodiments of the coil spring; 
         FIG. 13A  and  FIG. 13B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of an offset spring and a rigid support end is formed in at least one of upper and lower exposed wiring portions, in which  FIG. 13A  is a cross-sectional view showing twentieth to twenty third embodiments of the coil spring,  FIG. 13B  is a perspective view showing the showing the twentieth to twenty third embodiments of the coil spring; and 
         FIG. 14A  and  FIG. 14B  are views showing a coil spring according to the present invention in which upper and lower end wiring portions have the shape of a round-offset spring and a rigid support end is formed in at least one of upper and lower exposed wiring portions, in which  FIG. 14A  is a cross-sectional view showing twenty fourth to twenty seventh embodiments of the coil spring,  FIG. 14B  is a perspective view showing the showing the twenty fourth to twenty seventh embodiments of the coil spring. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. 
     As shown in  FIG. 4A  to  FIG. 14B , the present invention provides a high tension coil spring structure for a bed mattress having means for preventing friction noise. The high tension coil spring structure includes body wiring portions  12  which are disposed regularly at preset distances from each other in the space between an upper edge member  20  and a lower edge member  20 ′, upper and lower end wiring portions  14  and  14 ′ which are provided on both ends of the body wiring portions  12  and set within the range in which the upper and lower edge members  20  and  20 ′ are disposed, upper and lower exposed wiring portions  16  and  16 ′ which extend from at least one of the upper and lower end wiring portions  14  and  14 ′ so as to be exposed from the upper or lower edge members  20  or  20 ′, diameter-increasing portions A which are provided on at least one of the upper and lower end wiring portions  14  and  14 ′ and define spaces in which upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′ of the upper and lower exposed wiring portions  16  and  16 ′ move upward and downward while the coil spring structure is being compressed, and means for preventing friction noise which are provided on at least one of the upper and lower end wiring portions  14  and  14 ′. The means for preventing friction noise include rigid support ends  18  which are provided on at least one of the body wiring portion  12  and the upper and lower exposed wiring portions  16  and  16 ′, and absorb shock by absorbing a compressive load applied from the upper and lower exposed wiring portions  16  and  16 ′. Since the diameter-increasing portions A provide spaces in which upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′ move upward and downward while the coil spring structure is being compressed, frictional noise between the upper and lower end wiring portions  14  and  14 ′ and the upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′ is prevented. When a compressive load is applied to the coil spring structure, a plurality of wiring portions formed in the upper and lower exposed wiring portions  16  and  16 ′ move upward and downward along the side walls of the rigid support ends  18 , thereby increasing elasticity. 
     Here, since the upper and lower edge members  20  and  20 ′ and the helical coils  30  are well-known in the art, they will be described using the same reference numerals and signs as in  FIG. 1A ,  FIG. 1B  and  FIG. 2 . Disclosure will be limited to coil springs  10  which are sequentially disposed between the upper and lower edge members  20  and  20 ′. 
     In addition, the coil springs  10  can be implemented as round coil springs, as shown in  FIG. 5A ,  FIG. 5B ,  FIG. 6A  and  FIG. 6B , offset coil springs, as shown in  FIG. 7A ,  FIG. 7B ,  FIG. 8A  and  FIG. 8B , or round-offset coil springs, as shown in  FIG. 9A ,  FIG. 9B ,  FIG. 10A ,  FIG. 10B  and  FIG. 10C , depending on the shape of the upper and lower end wiring portions  14  and  14 ′ and the structure of the wiring portions. 
     In addition, when the coil springs  10  are implemented as the round coil springs, the upper exposed wiring portions  16  can be configured as shown in part (a) of  FIG. 6A  and  FIG. 6B  (first embodiment), the lower exposed wiring portions  16 ′ can be configured as shown in part (b) of  FIG. 6A  and  FIG. 6B  (second embodiment), or both the upper exposed wiring portions  16  and the lower exposed wiring portions  16 ′ can be configured as shown in parts (c) to (e) of  FIG. 6A  and  FIG. 6B  (third to fifth embodiments). 
     Furthermore, when the coil springs  10  are implemented as the offset coil springs, the upper exposed wiring portions  16  can be configured as shown in part (a) of  FIG. 8A  and  FIG. 8B  (sixth embodiment), the lower exposed wiring portions  16 ′ can be configured as shown in part (b) of  FIG. 8A  and  FIG. 8B  (seventh embodiment), or both the upper exposed wiring portions  16  and the lower exposed wiring portions  16 ′ can be configured as shown in parts (c) to (e) of  FIG. 8A  and  FIG. 8B  (eighth to tenth embodiments). 
     In addition, when the coil springs  10  are implemented as the round-offset coil springs, the upper exposed wiring portions  16  can be configured as shown in part (a) of  FIG. 10A  and  FIG. 10B  (eleventh embodiment), the lower exposed wiring portions  16 ′ can be configured as shown in part (b) of  FIG. 10A  and  FIG. 10B  (twelfth embodiment), or both the upper exposed wiring portions  16  and the lower exposed wiring portions  16 ′ can be configured as shown in parts (c) to (e) of  FIG. 10A  and  FIG. 10B  (thirteenth to fifteenth embodiments). 
     The diameter-increasing portions A can be applied to any type of the coil springs  10  which are used in the field of bed mattresses in place of the round coil springs, the offset coil springs, or the round-offset coil springs, and this structure, of course, belongs to the scope of the present invention. 
     In addition, each of the coil springs  10  includes the body wiring portion  12 , the upper and lower end wiring portions  14  and  14 ′, the upper and lower exposed wiring portions  16  and  16 ′ and the rigid support ends  18 . In particular, the diameter-increasing portion A is provided on at least one of the upper and lower end wiring portions  14  and  14 ′. 
     The body wiring portion  12  refers to the wiring portion which forms the main body of the coil spring  10  to support the entire load applied to the coil spring  10 . The body wiring portion  12  is interposed in the vertical direction in the space between the upper and lower edge members  20  and  20 ′ in order to absorb the weight of a user. The body wiring portion  12  can have a variety of shapes including the shape of a double-headed drum. 
     In addition, the upper and lower end wiring portions  14  and  14 ′ refer to the wiring portions which are respectively formed on the upper and lower ends of the body wiring portions  12  so as to extend in the horizontal direction and are positioned within the range in which the upper and lower edge members  20  and  20 ′ are disposed. The upper and lower end wiring portions  14  and  14 ′ are butted to the upper and lower edge members  20 , and are fixed using fixing pins or helical coils. 
     Here, the upper and lower end wiring portions  14  and  14 ′ can be formed at an angle of incline that deviates from the horizontal state, depending on the angle of incline of the upper and lower exposed wiring portions  16  and  16 ′, and this structure also belongs to the scope of the present invention. 
     Although the wiring portions are formed at a slightly inclined angle, the upper and lower end wiring portions  14  and  14 ′ can be horizontally set when they are butted to and engaged with the upper and lower edge members  20  and  20 ′ using the helical coils  30 . 
     In addition, the lower end wiring portion  14 ′ may form a linear free end B on the coil end thereof which is opened without being engaged with the wiring portion, as shown in  FIG. 10C , or a handcuff portion C on the coil end thereof which is engaged with the wiring portion, as shown in  FIG. 11A ,  FIG. 11B  and  FIG. 11C . 
     In addition, as shown in  FIG. 11A  to  FIG. 11C , it is preferred that the upper and lower end wiring portions  14  and  14 ′ have a round, offset or round-offset shape. In particular, one or two convex portions D which increase the inner diameter of the wiring portion may be formed on the upper and/or lower end wiring portions  14  and  14 ′, and this belongs to the scope of the present invention. 
     Although it is, of course, possible to make the upper and dower end wiring portions  14  and  14 ′ having the same shape, the upper and lower end wiring portions having different shapes also belong to the scope of the present invention. 
     In addition, the upper and lower exposed wiring portions  16  and  16 ′ refer to the wiring portions which extend from the upper end wiring portions  14  and/or the lower end wiring portions  14 ′ and cooperate with the body wiring portions  12  in order to absorb a load applied to the bed mattress. The upper and lower exposed wiring portions  16  and  16 ′ are wound such that their diameter is smaller than the diameter of the body wiring portions  12 . 
     In this case, the body wiring portions  12  absorb shock in response to a large load applied to the bed mattress, whereas the upper and lower exposed wiring portions  16  and  16 ′ absorb shock in response to a smaller load applied to the bed mattress. 
     Here, the upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′ formed on the upper and lower exposed wiring portions  16  and  16 ′ refer to the portions of the upper and lower exposed wiring portions  16  and  16 ′ which are positioned close to the upper and lower end wiring portions  14  and  14 ′. 
     Although the number of turns of the upper and lower exposed wiring portions  16  and  16 ′ is preferably 3 to 6, as shown in  FIG. 11A  to  FIG. 11C , in order to induce high tension to the coil springs  10 , the number of turns greater than 6 also belongs to the scope of the present invention. 
     In addition, as shown in  FIG. 11A  to  FIG. 11C , it is preferred that the upper and lower exposed wiring portions  16  and  16 ′ have a round shape. The upper and lower exposed wiring portions may also have an offset shape or a round-offset shape. The upper and lower exposed wiring portions  16  and  16 ′ may have one or two convex portions D which increase the inner diameter of the wiring portions without departing from the scope of the present invention. 
     Of course, as shown in  FIG. 100  and  FIG. 12B , it is preferred that the linear free end B be formed on the coil end of at least one of the upper and lower exposed wiring portions  16  and  16 ′. In particular, the handcuff portion C may be formed in place of the linear free end B without departing from the scope of the present invention. 
     The diameter-increasing portions A are configured so as to increase the inner diameter of the upper and lower end wiring portions  14  and  14 ′, thereby defining spaces through which the upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′ can move upward and downward while fundamentally preventing frictional noise. It is preferred that the diameter-increasing portions A be provided by increasing the inner diameter of the upper and lower end wiring portions  14  and  14 ′ so as to be greater than the outer diameter of the upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′. 
     In addition, as shown in  FIG. 12A ,  FIG. 12B ,  FIG. 13A ,  FIG. 13B ,  FIG. 14A  and  FIG. 14B , when the upper and lower exposed wiring portions  16  and  16 ′ are provided with the rigid support ends  18 , it is preferred that the inner diameter of the upper and lower end wiring portions  14  and  14 ′ having the diameter-increasing portion A be greater than the outer diameter of the body wiring portion  12  in order to introduce the upper and lower exposed wiring portions  16  and  16 ′ to move upward and downward along the outer circumference of the body wiring portion  12 . 
     In addition, the wiring of the upper and lower end wiring portions  14  and  14 ′ can be formed so as to be inclined at a preset angle with respect to the horizontal surface in the process in which the diameter-increasing portions A are formed. Consequently, there is no contact between the upper and lower end wiring portions  14  and  14 ′ and the upper and lower exposure start wiring portions  16 - 5  and  16 - 5 ′, thereby preventing friction noise. This structure belongs to the scope of the present invention. 
     Furthermore, although the shape of the diameter-increasing portions A may correspond to the shape of the upper and lower end wiring portions  14  and  14 ′, it is preferred that the diameter-increasing portions A can have a round shape considering the structural characteristics of the coil springs  1 . 
     In addition, the rigid support ends  18  are provided on at least one of the body wiring portions  12  and the upper and lower exposed wiring portions  16  and  16 ′ so as to absorb a compressive load. When a small load is applied to the bed mattress, the rigid support ends  18  absorb the compressive load using the upper and lower exposed wiring portions  16  and  16 ′. In contrast, when a large load is applied to the bed mattress, the upper and lower exposed wiring portions  16  and  16 ′ absorb most of the load, and the body wiring portions  12  absorb the remaining load, thereby preventing frictional noise while significantly increasing elasticity. 
     As shown in parts (a) and (b) of  FIG. 6A  and  FIG. 6B , parts (a) and (b) of  FIG. 8A  and  FIG. 8B , and parts (a) and (b) of  FIG. 10A  and  FIG. 10B , one rigid support end  18  can be provided on the upper or lower portion of each of the body wiring portions  12 . In addition, as shown in part (e) of FIG.  6 A and  FIG. 6B , part (e) of  FIG. 8A  and  FIG. 8B , and part (e) of  FIG. 10A  and  FIG. 10B , the rigid support ends  18  can also be respectively provided between the upper end wiring portions  14  and the lower end wiring portions  14 ′. 
     As shown in parts (c) and (d) of  FIG. 6A  and  FIG. 6B , parts (c) and (d) of  FIG. 8A  and  FIG. 8B , and parts (c) and (d) of  FIG. 10A  and  FIG. 10B , a plurality of rigid support ends  18  can also be provided on each of the body wiring portions  12  such that the rigid support ends  18  are spaced apart predetermined distances from each other. This structure, of course, belongs to the technical scope of the present invention. 
     It is, of course, possible that the rigid support ends  18  be formed on the upper and lower exposed wiring portions  16  and  16 ′, as shown in  FIG. 12A  and  FIG. 12B  (sixteenth to nineteenth embodiments),  FIG. 13A  and  FIG. 13B  (twentieth to twenty third embodiments) and  FIG. 14A  and  FIG. 14B  (twenty fourth to twenty seventh embodiments). This structure, of course, belongs to the technical scope of the present invention. 
     In addition, it is preferred that the rigid support ends  18  be provided at a right or acute angle with respect to the upper and lower end wiring portions  14  and  14 ′ or the horizontal surface. 
     A description will be given below of the operation of the present invention. 
     First, since the process of fabricating the spring assembly  1  and the process of fabricating a bed mattress to which the spring assembly  1  is applied are well known in the art, descriptions thereof will be omitted. Disclosure will be limited to the structure of the coil springs  10  that prevents frictional noise and increases elasticity. 
     In particular, the operating structure will be described on assumption that the coil springs  10  having the structure of the present invention is applied to the bed mattress. 
     As shown in part (a) of  FIG. 5A  and  FIG. 5B , part (a) of  FIG. 7A  and  FIG. 7B  and part (a) of  FIG. 9A  and  FIG. 9B , if no load is applied to the bed mattress to which the coil spring  10  is applied, the upper exposed wiring portion  16  is set such that it protrudes above the upper edge member  20  and stays at that position. 
     In contrast, as shown in part (b) of  FIG. 5A  and  FIG. 5B , part (b) of  FIG. 7A  and  FIG. 7B  and part (b) of  FIG. 9A  and  FIG. 9B , when a small load from the user is applied to the bed mattress to which the coil spring  10  is applied, the upper exposed wiring portion  16  is depressed downward to the amount corresponding to the compressive load, thereby absorbing the compressive load. 
     In particular, as shown in part (c) of  FIG. 5A  and FIG.  5 B, part (c) of  FIG. 7A  and  FIG. 7B  and part (c) of  FIG. 9A  and  FIG. 9B , when a large load is applied to the bed mattress to which the coil spring  10  is applied, the upper exposure start wiring portions  16 - 5  of the upper exposed wiring portion  16  moves downward through the diameter-increasing portion A, thereby absorbing the compressive load. 
     In addition, as shown in parts (d) and (e) of  FIG. 5A  and  FIG. 5B , parts (d) and (e) of  FIG. 7A  and  FIG. 7B  and parts (d) and (e) of  FIG. 9A  and  FIG. 9B , when a stronger load is applied to the bed mattress to which the coil spring  10  is applied, the upper exposure start wiring portion  16 - 5  of the upper exposed wiring portion  16  moves further downward through the diameter-increasing portion A such that the range in which the upper exposed wiring portion  16  moves upward and downward is maximized, thereby maximizing the shock-absorbing efficiency. 
     Since the diameter-increasing portion A of the upper end wiring portion  14  defines the space where the upper exposure start wiring portion  16 - 5  can move upward and downward, the upper exposure start wiring portion  16 - 5  does not come into contact with the upper end wiring portion  14  while moving upward and downward. 
     At this time, when a strong load is applied to the bed mattress, due to the rigid support end  18  of the coil spring  10 , the upper and lower exposed wiring portions  16  and  16 ′ absorb most of the load and the body wiring portion  12  absorbs the remaining load, thereby preventing frictional noise and significantly increases elasticity. 
     Accordingly, when a strong load is applied to the bed mattress to which the coil spring  10  is applied, the diameter-increasing portion A of the upper end wiring portion prevents friction noise between the upper end wiring portion  14  and the other portions of the coil spring  10  and significantly increases the elasticity of the exposed wiring portions  16  and  16 ′ which are formed as a plurality of wiring portions, thereby increasing the longevity of a product and improving the quality of the product. 
     The foregoing descriptions of the specific exemplary embodiments of the present invention have been presented for the purposes of illustration with reference to the accompanying drawings. A person having ordinary skill in the art will appreciate that various modifications and alternatives are possible without departing from the scope of the present invention that shall be defined by the Claims appended hereto and their equivalents.