Abstract:
A universal tube clamp, having a head portion with an aperture formed therein with set screws to retain another object thereto, and a clamping portion. The clamping portion has an outer perimeter sidewall defining an opening with knurls formed on inside walls, a generally T-shaped slot with a vertical portion that extends from a bottom of the sidewall upwardly towards the head portion with ears formed on both sides of the slot, and a horizontal slot portion that extends horizontally through the sidewall above the two ears, and a bolt which forces the two ears together to reduce a diameter of the opening. The ear that the bolt head impinges on is narrower than the threaded ear, and the vertical portion of the T-shaped slot is wider at the bottom of the sidewall than at its top where it joins the horizontal slot portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to tube clamps and tube clamp assemblies for use in prosthetic limbs. More particularly, the invention relates to a universal tube clamp and tube clamp assembly that are smaller, lighter, less expensive to manufacture, and more reliable than currently available tube clamps and tube clamp assemblies 
         [0002]    Prosthetic limbs are attached to the residual limb or stump by a stump socket, which is a shell that closely conforms to the residual limb. Attached to the stump socket is a threaded socket adaptor which is adapted to engage with an intermediate connector, such a pyramid plug. Some pyramid plugs have a base region in the general shape of a segment of sphere from the top of which extends a four sided frustum with the wider end at the top thereof. One such pyramid plug is shown in  FIG. 23 . Pyramid plugs are widely used in constructing prosthetics, and the frustum(s) of the pyramid plugs are adapted to adjustably engage with adapters and clamps to assemble a prosthetics. 
         [0003]    Multi-prong laminating adaptors are also used in the prosthetic industry in the creation of laminated stump sockets. The laminated stump socket is fit over the residual limb or stump of the patient, and is configured to allow the prosthetic device to be attached thereto via connection with the laminating adaptor. 
         [0004]    Part of the skill of a prosthetist is in selecting the right combination of sizes, shapes, lengths and angles of the various components from different manufacturers in order to make a prosthetic that strong, reliable, and comfortable for a patient and that can be easily adjusted and stay in adjustment under regular and repeated use. Components that can be more easily and reliably used allow a prosthetist to do a better job with less time and improved patient satisfaction. For prosthetics that substitute for elongate limbs, such as the calves, thighs, etc., high strength tubes are commonly used with connectors at both ends. The tubes can be constructed out of material such as aluminum, steel, and composite materials such as carbon fiber, and the connectors, e.g., tube clamps and receivers, can be formed of high strength material such as aluminum, stainless steel, and titanium. While titanium is an ideal material for prosthetics since it is extremely strong and light, it is much more expensive than stainless steel and more difficult to machine. The tubes will come in a variety of diameters, wall thicknesses, materials, and lengths depending on the requirement, and the practitioner will cut the tube length to size to provide the needed length. Tube sizes which are commonly available to the industry include diameters of 22 mm, 25 mm, and 34 mm. The accepted “standard” size of a tube clamp is considered to be 30 mm. Depending on the manufacturer, the sizes and tolerances of the tubing can vary widely, so a tube from one manufacturer that is nominally 30 mm OD might be undersized by about 0.8 mm while a tube from another manufacturer may be oversized by about 0.8 mm. As a result, tube clamps and receivers are generally sized large to fix tube from different manufacturers. In order to provide for connection between tubes and other components of the prosthetic, the tube clamps and receivers are positioned on both ends of the tube. For speed and ease of assembly, tubes can be provided with a tube clamp or a receiver pre-affixed to one end of the tube. In prior art tube clamp assemblies, tubes of predetermined lengths, e.g., 20, 30, 40 cm, are provided with a receiver adhered to one end, e.g., such as by epoxy adhesive. The prosthetist will cut the second end of the tube to the required length and then attach a tube clamp to the second end of the tube. This second clamp is clamped on the second end of the tube by a screw that squeezes the tube clamp and secures it to the tube. Unfortunately, with repeated shock and possibly different coefficients of thermal expansion between the tube, which may be of one material, e.g., aluminum, and the tube clamps or receiver, which may be made of another material, e.g., stainless steel, aluminum alloy, titanium, for example, the adhesive bond between the first tube clamp or receiver and the tube can become compromised. If this occurs, the tube clamp or receiver can rotate relative to the tube, which will place the components out of alignment with each other. Moreover, with prior art clamps that are mechanically tightened with a screw, the second tube clamp can become loose on the tube and thereby allow rotation of the parts relative to each other, which is undesirable. 
         [0005]    In the case of prior art titanium tube clamps, they are often formed by machining cylindrical stock. Due to the very high costs of titanium, designs that can reduce the amount of material required to form a tube clamp or receiver will result is great cost savings as well as weight savings, both of which are desirable. 
         [0006]    Accordingly, there is a need for improved tube clamps and tube clamp assemblies. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention is a tube clamps and tube clamp assemblies for use in prosthetic limbs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a typical prior art setup for a below the knee prosthetic. 
           [0009]      FIG. 2  is a perspective view of a prior art tube clamp. 
           [0010]      FIG. 3  is a bottom plan view of the prior art tube clamp of  FIG. 2 . 
           [0011]      FIG. 4  is a perspective view of a prior art receiver. 
           [0012]      FIG. 5  is a bottom plan view of the prior art receiver of  FIG. 4 . 
           [0013]      FIG. 6  is a perspective view of an exemplary embodiment of a tube clamp of the invention. 
           [0014]      FIG. 7  is a front view of the tube clamp of  FIG. 6 . 
           [0015]      FIG. 8  is a top plan view of the tube clamp of  FIG. 6 . 
           [0016]      FIG. 9  is a bottom plan view of the tube clamp of  FIG. 6  but with a screw. 
           [0017]      FIG. 10  is a cross-sectional view of the tube clamp of  FIG. 6  through view lines  10 - 10  of  FIG. 8 . 
           [0018]      FIG. 11  is a perspective view of an exemplary embodiment of a receiver of the invention which is adapted to be permanently attached to an end of a tube. 
           [0019]      FIG. 12  is a front view of the receiver of  FIG. 11 . 
           [0020]      FIG. 13  is a top plan view of the receiver of  FIG. 11 . 
           [0021]      FIG. 14  is a bottom plan view of the receiver of  FIG. 11 . 
           [0022]      FIG. 15  is a cross-sectional view of the receiver through view lines  15 - 15  of  FIG. 13 . 
           [0023]      FIG. 16  is a side view of a prior art tube clamp assembly with a prior art receiver of  FIG. 4  adhered to a first end of the tube and the prior art tube clamp of  FIG. 2  clamped to the second end of the tube. 
           [0024]      FIG. 17  is a cross-sectional view of the prior art receiver glued to the tube through view lines  17 - 17  of  FIG. 16 . 
           [0025]      FIG. 18  is a cross-sectional view of the prior art tube clamp clamped on the tube through view lines  18 - 18  of  FIG. 16 . 
           [0026]      FIG. 19  is a side view of the art tube clamp assembly of the invention with the exemplary receiver of  FIG. 11  fixed to a first end of the tube and the exemplary tube clamp of  FIG. 6  clamped to the second end of the tube. 
           [0027]      FIG. 20  is a cross-sectional view of the receiver fitted on the tube through view lines  20 - 20  of  FIG. 19 . 
           [0028]      FIG. 21  is a cross-sectional view of the exemplary tube clamp clamped on the tube through view lines  21 - 21  of  FIG. 19 . 
           [0029]      FIG. 22  is a perspective view of a prior art pyramid plug. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Turning first to  FIG. 1 , there is shown a perspective view of one typical setup for a below the knee prosthetic  10 . A residual limb or stump socket  12  fits onto the patient&#39;s residual limb (not shown). The stump socket  12  has a socket adaptor  14  at a lower end, and is adapted to engage with an intermediate connector, such a pyramid plug, as shown in  FIG. 22 , but not revealed in this view. The pyramid plug connects the socket adaptor  14  to a prior art receiver  16 , which is fitted on a first end  18  of a tube  20 . At the second end  22  of the tube  20  a prior art tube clamp  22  is attached. The tube clamp  22  is in turn connected to a prosthetic foot  26  via a connector  28 . 
         [0031]      FIG. 2  is a perspective view of a prior art tube clamp  24  and  FIG. 3  is a bottom plan view of the prior art tube clamp of  FIG. 2 . It has a frustum receiving head region  30 , and a clamping portion  32 . A slot  34  is formed through the sidewall  48  of the clamping portion  32  and extends between two ears  36 A and  36 B. A bolt  42  will pass through an enlarged hole  38  in ear  36 A and be threaded into ear  36 B which has a threaded hole  40 . At the frustum receiving head region  30  a bore  60  is formed therein, and four treaded holes  62  are formed through a perimeter  64  thereof. As best shown in  FIG. 18 , the threaded holes  62  are tilted downwardly, and are adapted to receive allen bolts  78  (shown in  FIG. 3 ) which will project into the bore  60  and are used to retain a frustum head of a pyramid plug  450  such as shown in  FIG. 22 . The frustum receiving head region  30  has a top end  66  at the entrance of the bore  60 . A cupped rim  68  is formed at the mouth of the bore  60  and narrows going into the bore  60 . The cupped rim  68  is adapted to act as a seat for a spheroidal base region  452  of the pyramid plug  450  and allows the pyramid plug  450  to be swiveled relative to the tube clamp  24 . As can be seen, the cupped rim  68  is fairly deep and extends from the top end  66  of the entrance of the bore  60  down to termination edge  70 , and provides for a great abundance of contact surface with the spheroidal base region  452  of the pyramid plug  450 . From the termination edge  70  the bore  60  widens downwardly to a bottom edge  72 , where a collar  74  is formed. The volume in the bore  60  between the termination edge  70  and the bottom edge  72  is generally frustum shaped, and is adapted to receive a four sided frustum plug  454  of the pyramid plug  450  In the clamping portion  32 , a central bore  44  is formed, having a smooth walled inside surface  76 . When the tube  24  is inserted in the central bore  44 , the end of the tube  24  will be prevented from traveling further inward by making contact with the collar  74 . 
         [0032]    As shown in  FIG. 3 , when tightened, the bolt  42  will cause the two ears  36 A and  36 B to be pulled together by virtue of the slot  34  and reduce the inner diameter “d” of the central bore  44  of the clamping portion  32 . In prior art designs, the tightening of the bolt  42  tends to squeeze the bottom end  46  of the lower clamping portion  32  more than an upper end of the clamping portion  32  near a terminating end  40  of the slot  34 . Thus, the majority of the reduction in diameter “d” of the central bore  44  occurs near the bottom end  46  of the clamping portion  32 . In prior art tube clamps  32 , the slot  32  is formed straight through the ears  36 A and  36 B and has the same width at the terminating end  48  as at the bottom end  46 . Thus, there are cases where the ears  36 A and  36 B will touch each other when clamped. The ears  36 A and  36 B are generally evenly sized and shaped with similar amounts of material formed above the sidewalls  48 . This large amount material of the ears  36 A and  36 B can make the sidewalls  48  in the region of the ears excessively rigid and can impede movement of the sidewalls, and thus interfere with reduction of the diameter “d” of the central bore  44  when the bolt  42  is tightened. Some additional shortcomings of the prior art design of tube clamp  24  are discussed further below. 
         [0033]      FIG. 4  is a perspective view and  FIG. 5  is a bottom plan view of a prior art receiver  16  which is similar to the prior art tube clamp  24  of  FIGS. 2 ,  3  and  18 , and like reference numerals are used to refer to both prior art component. The prior art receiver  16  has a frustum receiving head region  30 , and has a lower tube engagement portion  80  which has a central bore  82  At the frustum receiving head region  30  a bore  60  is formed therein, and four treaded holes  62  are formed through a perimeter  64  thereof. The threaded holes  62  are tilted downwardly, and are adapted to receive allen bolts (shown in  FIG. 3 ) which will project into the bore  60  and are used to retain a frustum head of a pyramid plug  450 , such as shown in  FIG. 22 . The frustum receiving head region  30  has a top end  66  at the entrance of the bore  60 . A cupped rim  68  is formed at the mouth of the bore  60  and narrows going into the bore  60 . The cupped rim  68  is adapted to act as a seat for a base region  452  of the pyramid plug  450  and allows the pyramid plug  450  to be swiveled relative to the receiver  16 . As can be seen, the cupped rim  68  is fairly deep and extends from the top end  66  of the entrance of the bore  60  down to termination edge  70 , and provides for a great abundance of contact surface with the base region  454  of the pyramid plug  450 . From the termination edge  70 , the bore  60  widens downwardly to a bottom edge  72 , where a collar  74  is formed. The volume in the bore  60  between the termination edge  70  and the bottom edge  72  is generally frustum shaped, and is adapted to receive the four sided frustum  454  of the pyramid plug  450 . The tube engaging portion  80  is below the collar  74  and is sized to slip over a tube  20  and be glued thereto as shown in  FIG. 16 . The inside surface  76  of the bore  82  is smooth walled as shown in  FIG. 17 . When the tube  20  is inserted in the bore  82 , the end of the tube  24  will be prevented from traveling further inward by making contact with the collar  74 . A key difference between the tube clamp and the receiver  16  is that it includes neither a slot nor ears that are tightened with a bolt. The prior art receiver  16  are adhered to a tube  20  by adhesive, such as epoxy, as shown in  FIG. 17 . An inner surface  76  of central bore  82  of receiver  16  is smooth, and generally the inner surface will be scuffed up and cleaned, e.g., with alcohol, as is the end of the tube to which the receiver  16  will be adhered. However, due to mismatches between the inner diameter “d” of the receiver, and the outer diameter “OD” of the tube  20 , a relatively large gap can exist which must be filled with adhesive  308  if a reliable bond is to be formed. As noted above, with time, temperature fluctuations, repeated shock and vibrations, the adhesive bond  308  between the inside surface  76  of the receiver  16  and the outside surface  302  of the tube  20  can give way, resulting in rotation of the receiver  16  and tube  20  relative to each other. 
         [0034]      FIG. 6  is a perspective view and  FIG. 7  is a front view of an exemplary embodiment of a universal tube clamp  100  of the invention.  FIG. 8  is a top plan view of the tube clamp of  FIG. 6 , and  FIG. 9  is a bottom plan view of the tube clamp of  FIG. 6 .  FIG. 10  is a cross-sectional view of the tube clamp of  FIG. 6  through view lines  10 - 10  of  FIG. 8 . The universal tube clamp  100  of the invention has a frustum receiving head portion  102 , and a clamping portion  104  located below the head region  102 . A generally T-shaped slot  106  is formed through a sidewall  108  of the clamping portion  104  and has a vertical slot section  106 V that extends between two ears  110 A and  110 B and a horizontal slot section  106 H that connects to an upper end  112  of the vertical section  106 V. The vertical slot section  106 V is preferably wider at its bottom  114  than at its top  112 . A bolt  116  or other compression member (shown in  FIG. 9 ) will pass through an enlarged hole  118  in ear  110 A and be threaded into a threaded hole  120  in ear  110 B. When the bolt  116  is tightened, it will cause the two ears  110 A and  110 B to be effectively moved together in the area of the slot  106 V and thereby reduce an internal diameter “d” of the clamping portion  104 . 
         [0035]    In prior art tube clamps designs, such as shown in  FIGS. 2 and 3 , the ears  36 A and  36 B are generally evenly sized and shaped with similar amounts of material formed above the sidewalls  48 , the sidewalls  48  in the region of the ears  36 A and  36 B can be excessively rigid and can impede, movement of the sidewalls, and thus interfere with reduction of the diameter “d” of the central bore  44  when the bolt  42  is tightened. Thus, tightening of the bolt  42  tends to squeeze just the bottom end  46  of the lower clamping portion  32  more than an upper end of the clamping portion  32  near the terminating end  49  of the slot  34 . Moreover, in prior art tube clamps  32  shown in  FIGS. 2 and 3 , the slot  32  is formed straight through the ears  36 A and  36 B and has the same width at the terminating end  49  as at the bottom end  46 . As noted above, the tolerances of tubes and tube clamps from different manufacturers often widely vary, and therefore, tube clamps are often oversized in their inner diameter and fit loosely on the ends of tubes. When this occurs, the prosthetist must tightened the bolt excessively, and there are cases where inner surfaces of the ears  36 A and  36 B will touch each other and prevent further tightening. Thus, in prior art designs, the majority of the reduction in diameter “d” of the central bore  44  occurs near the bottom end  46  of the clamping portion  32  and the area of contact between the tube clamp  24  on a tube  20  is minimum. 
         [0036]    In contrast with the prior art design of tube clamps, the tube clamp  100  of the invention provides for a much more effective clamping action by virtue of the generally T-shaped slot  106  formed through the sidewall  108 . Firstly, by providing a vertical slot section  106 V that is preferably wider at its bottom  114  than at its top  112 , greater reduction in the inner diameter “d” of the tube clamp  100  can take place before there is contact of the inner sides of the ears  110 A and  110 B of the slot  106 . Moreover, the horizontal slot section  106 H allows the areas of the clamping portion  104  below the horizontal slot section  106 H to be displaced more readily, even areas that are further up on the clamping portion  104 , and with less force and thus there can be greater reduction in the internal diameter “d”. Lastly, by providing ear  110 A having a smaller profile and with less material merging with the sidewall  108 , the portion of the sidewall in the area of the ear  110 A is less rigid and moves more when the bolt  116  is tightened into the threaded hole  120  in ear  110 B. If desired, ear  110 B can also be made to have less bulk so that that area of the sidewall  108  on the opposition side of the vertical slot section  106 V will also be displaced more readily. 
         [0037]    At the frustum receiving head region  102  a central bore  130  is formed therein, and four treaded holes  132  are formed through a perimeter  134  thereof. As best shown in  FIG. 10 , the threaded holes  132  are tilted downwardly, and are adapted to receive allen bolts (not shown) which will project into the bore  130  and are used to retain a frustum head  454  of a pyramid plug  450 , such as shown in  FIG. 21 . The frustum receiving head region  102  has a top end  136  at the mouth of the central bore  130 . A cupped rim  138  is formed at the mouth of the central bore  130  and narrows going into the central bore  130 . The cupped rim  138  is adapted to act as a seat for a base region  452  of the pyramid plug  450 , and allows the pyramid plug  450  to be swiveled relative to the tube clamp  100 . As can be seen, unlike the cupped rim  68  of the prior art tube clamp  24  of  FIG. 2 , the cupped rim  138  of the invention does not extend to the perimeter  134  of the frustum receiving head region  102 , but instead stops short and thus there is a relatively large flat top end  136 . The cupped rim  138  extends from an edge  140  on the top end  136  of the mouth of the central bore  130  down to termination edge  142  inside the central bore  130 , and provides for adequate contact surface with the base region  452  of the pyramid plug  450 . From the termination edge  142  of the cupped rim  138 , the central bore  130  widens downwardly to a bottom edge  144 , where a collar  146  is formed. The volume in the bore  130  between the termination edge  142  and the bottom edge  144  is generally frustum shaped, and is adapted to receive the four sided frustum  454  of the pyramid plug  450 . Unlike the tube clamp  24  of the prior art, an inside surface  148  of a bore  150  of the clamping portion  104  has knurls  152  formed thereon. These knurls  152  are preferably formed vertically oriented on the inside surface  148  of the sidewall  108 . As shown in  FIG. 10 , the knurls  152  are formed on the lower portion of the inside wall  148  below the horizontal slot portion  106 H. Using the example of the setup shown in  FIG. 1 , when the clamping portion  104  is clamped on the tube  20 , the tube  24  will be prevented from traveling further inward into the bore  150  by making contact with the collar  146 , and the knurls  152  will mechanically “bite into” the outer surface of the tube  20 , and help prevent the tube  20  from being rotated relative to the universal tube clamp  100 . 
         [0038]    Industry standards for the tube clamp I.D finish is between 32μ-64μ. A fixed, non-rotating position of the tube clamp and pylon relies on the tight tolerance between the I.D tube clamp and O.D pylon. There is minimal friction between the tube clamp I.D and pylon O.D due to the high surface finish of the pylon O.D (Aluminum and Carbon) and the standard I.D finish of the tube clamp. Rotating eventually occurs due to this discrepancy. The knurls in the TiMed tube clamp penetrates the surface of Aluminum and/or Carbon tubes; thus, preventing rotation. 
         [0039]      FIG. 11  is a perspective view and  FIG. 12  is a front view of an exemplary embodiment of a receiver  200  of the invention which is adapted to be permanently attached to an end of a tube, as shown in  FIG. 19 .  FIG. 13  is a top plan view and  FIG. 14  is a bottom plan view of the receiver  200 .  FIG. 15  is a cross-sectional view of the receiver  200  through view lines  15 - 15  of  FIG. 13 . The receiver  200  of the invention has a frustum receiving head portion  202 , and a lower tube engaging portion  204  located below the head region  202 . At the frustum receiving head region  202  a central bore  206  is formed therein, and four treaded holes  208  are formed through a perimeter  210  thereof. As best shown in  FIG. 15 , the threaded holes  208  are tilted downwardly and are adapted to receive allen bolts  240  which will project into the bore  206  and are used to retain a frustum head  454  of a pyramid plug  450  such as shown in  FIG. 22 . The frustum receiving head region  202  has a top end  212  at the mouth of the central bore  206 . A cupped rim  214  is formed at the mouth of the central bore  206  and narrows going into the central bore  206 . The cupped rim  214  is adapted to act as a seat for a spheroidal base region  452  of the pyramid plug  450  and allows the pyramid plug  450  to be swiveled relative to the receiver  200 . As can be seen, unlike the cupped rim  68  of the prior art receiver clamp  24  of  FIG. 2 , the cupped rim  214  of the invention does not extend to the perimeter  210  of the frustum receiving head region  202 , but instead stops short and thus there is a relatively large flat top end  212 . The cupped rim  214  extends from an edge  216  on the top end  212  of the mouth of the central bore  206  down to termination edge  218  inside the central bore  206 , and provides for adequate contact surface with the spheroidal base region  452  of the pyramid plug  450  From the termination edge  218  of the cupped rim  214 , the central bore  206  widens downwardly to a bottom edge  220 , where a collar  222  is formed. The volume in the bore  206  between the termination edge  218  and the bottom edge  220  is generally frustum shaped, and is adapted to receive the four sided frustum plug  454  of the pyramid plug  450 . Unlike the prior art receiver  16  of  FIG. 4 , in the receiver  200  the inside surface  224  of the bore  226  of the tube receiving portion  204  has knurls  230  formed thereon. These knurls  230  are preferably vertically oriented on the inside surface  224  of the sidewall  232 . 
         [0040]      FIG. 16  is a side view of a prior art tube clamp assembly  300  with a prior art receiver  16  of  FIG. 4  adhered to an outside surface  302  of the tube  20  at a first end  304 , and the prior art tube clamp  24  of  FIG. 2  clamped to a second end  306  of the tube  20 . 
         [0041]      FIG. 17  is a cross-sectional view of the prior art receiver  16  glued to the tube  20  through view lines  17 - 17  of  FIG. 16  with the end  24  of the tube  20  seated against the collar  74 . As can be seen, adhesive  308  will be fill the space between the inside surface  76  of the sidewall  80  of receiver  16  and the outside surface  302  of tube  20 . As previously noted, receivers and tubes of different manufacturers can vary widely in tolerances, and accordingly, the space between the sidewall  80  of receiver  16  and the outside of tube  20  can range from narrow to wide. As noted above, the tube can be made of materials including steel, aluminum, carbon fiber composite, and the receiver can be made of a different material, such as stainless steel, titanium, aluminum, and the receiver  16  and tube  20  can therefore have different coefficients of thermal expansion. Moreover, the adhesive joint is often subject to repeated stress and shock. As a result, the adhesive joint can fail. 
         [0042]      FIG. 18  is a cross-sectional view of the prior art tube clamp  24  clamped onto an outer surface  302  of the tube  20  through view lines  18 - 18  of  FIG. 16 . Before the bolt (not shown) is tightened through the ears  36 A and  36 B (only ear  46 B being shown), a gap  310  is present between the outer surface  302  of the tube  20  and the smooth walled inside surface  76  of the clamping portion  32 . With the second end  306  of the tube  24  inserted in the central bore  44 , the second end  306  of the tube  24  will be prevented from traveling further inward by making contact with the collar  74 . When bolt (not shown) is tightened through the ears  36 A and  36 B (only ear  36 B being shown), the gap  310  present between the outer surface  302  of the tube  20  and the smooth walled inside surface  76  of the clamping portion  32  will squeeze the bottom end  46  of the clamping portion  32  more than an upper end of the clamping portion  32  near a terminating end of the slot  34  (as shown in  FIGS. 2 and 3 ). Thus, the majority of the reduction in diameter “d” of the central bore  44  occurs near the bottom end  46  of the clamping portion  32 , and there is little if no surface contact between the outer surface  302  of the tube  20  and the smooth walled inside surface  76  of the clamping portion  32  except near a bottom of the clamping portion. Since the clamping portion  32  has a smooth walled inside surface  76 , there is little bite between the clamping portion  32  and the tube  20 . Lastly, as previously discussed with reference to  FIGS. 2 and 3 , tube clamps and tubes of different manufacturers can vary widely in tolerances, and accordingly, the space  310  between the sidewall  48  of tube clamp  24  and the outside surface  302  of tube  20  can range from narrow to wide so sometimes if the tube clamp  24  has central bore  44  with an oversized diameter d and the tube  20  has a smaller than average outer diameter, the width of the slot  34  is too narrow and the ears  36 A and  36 B contact before the tube clamp  24  can be sufficiently tightened on the outer surface  302  of the tube  20 , and as a result, the tube clamp  24  and tube  20  can rotate relative to each other. 
         [0043]      FIG. 19  is a side view of the art tube clamp assembly  400  of the invention with the exemplary receiver  200  of  FIG. 11  secured to an outside surface  302  of the tube  20  at a first end  304 , and the exemplary tube clamp  100  of  FIG. 6  clamped to the second end  306  of the tube  20 . 
         [0044]      FIG. 20  is a cross-sectional view of the receiver  200  of  FIG. 11  fitted on the tube  20  through view lines  20 - 20  of  FIG. 19 . The knurls  230  extend inwardly from inner walls  224  having a nominal diameter “d” and are sized proportioned to be provide a smaller inner diameter than expected outer diameter of tubes  20  of various manufacturers. In practice, the receiver  200  will be compressed or pounded onto the end  304  of the tube  20 , and the knurls  230  will mechanically form furrows or gashes in the outer surface  302  of the tube  20 , and help prevent the tube  20  from being rotated relative to the receiver  200 , even in cases where the outer diameter of the tube is smaller than expected. The knurls  230  can have a variety of cross-sections shapes including but not limited to v-shaped points, rectangles, trapezoids. While the knurls  230  are showed continuous spaced inside the central bore but only at a lower end thereof, they can extend further up the central bore is desired. 
         [0045]      FIG. 21  is a cross-sectional view of the exemplary tube clamp  100  clamped on the tube  20  through view lines  21 - 21  of  FIG. 19 . Before the bolt (not shown) is tightened through the ears  110 A and  110 B (only ear  110 B being shown), a gap  402  is present between the outer surface  302  of the tube  20  and the knurled walled inside surface  148  of the clamping portion  104 . With the second end  306  of the tube  24  inserted in the central bore  150  (see  FIG. 9 ), the second end  306  of the tube  24  will be prevented from traveling further inward by making contact with the collar  74 . When bolt (not shown) is tightened through the ears  110 A and  110 B (only ear  110 B being shown), the gap  310  present between the outer surface  302  of the tube  20  and the knurls  152  on the inside surface  148  of the clamping portion  104  will move inwardly regions of the clamping portion below the horizontal slot section  106 H, and thus resulting in both a greater reduction in diameter “d” of the central bore  150  over more of the sidewall  108  compared to the prior art tube clamp  24 , so that there will be greater contact between the outer surface  302  of the tube  20  and the knurls  152  on the inside surface  148  of the clamping portion  104 . Moreover, by virtue of the vertical slot section  106 H being wider at its bottom  114  than at its top  112 , there can be greater movement of the sidewalls  108  compared to the prior art tube clamp  32 . When the tube clamp is tightened, the knurls  152  will mechanically “bite into” the outer surface  302  of the tube  20 , and help prevent the tube  20  from being rotated relative to the universal tube clamp  100 . Before the bolt (not shown) is tightened through the ears  110 A and  110 B (only ear  110 B being shown), a gap  402  is present between the outer surface  302  of the tube  20  and the knurled walled inside surface  148  of the clamping portion  104 . 
         [0046]    Referring to  FIGS. 16 and 19 , as can be seen by comparing the relative lengths of the prior art receiver  16  with the receiver  200  of the invention, and the prior art tube clamp  24  with the universal tube clamp  100  of the invention, the receiver  200  and the universal tube clamp  100  of the invention are substantially shorter in length than the prior art receiver  16  and prior art tube clamp  24 , respectively. In cases were expensive material is used to manufacturer these components, e.g., titanium, this reduction in length (about 23%) results in less material be used, which substantially reduces material costs and weight of the finished product, while decreasing likelihood of failure. 
         [0047]      FIG. 22  is a perspective view of a prior art pyramid plug  450  having a spheroidal base region  452  with a four sided frustum plug  454  extending from a top and bottom thereof. 
         [0048]    Having thus described the exemplary embodiments of the present invention, it should be understood by those skilled in the art that the above disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. The presently disclosed embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.