Abstract:
A wheel suspension system for reducing or eliminating the shock associated with travelling over bumps and dents on a roadway on a wide variety of low speed wheeled transportation equipment. The system includes substantially vertically positioned swing arms connected between the wheel axle and frame of the wheeled transportation equipment. The swing arms cause a bump or a dent on the ground to feel as if travelling over smooth ramps and thereby eliminating the shock normally felt when travelling over the bumps or dents. The system does not utilize shock absorbing springs and is structurally simpler and more stable. Furthermore, the system keeps the gravity center of the frame of the wheeled transportation equipment at a similar level to that with no suspension system and also increases the wheel&#39;s ability to overcome large obstacles.

Description:
REFERENCE TO RELATED APPLICATIONS 
     Priority for this application is claimed from the U.S. provisional patent application Ser. No. 60/082,558, filed Apr. 21, 1998, entitled “Wheel Suspension for Small Wheels to Overcome Big Obstacle”. 
    
    
     BACKGROUND OF THE INVENTION 
     This application is also based on disclosure documents by the same inventor with disclosure document numbers: 429340,432511, 429131, 429131, 428843, 427754, 428048, in 1997; and 442273, 438665, 444981, 444459, 441661, 437590, 437273, 436836, 436693, 436206, 436035, 435779, 435671, 430641, 431767, 432317, 434741, 42997, 429722 in 1998. 
     1. Field of the Invention 
     This invention relates generally to wheel suspension systems, and more particularly to a wheel suspension system able to smooth movement of an object or load carried on wheels when travelling over obstructions on a surface being navigated. 
     2. Background of the Invention 
     Conventional wheel suspension systems greatly improve the function of the wheel, one of the oldest inventions, for travelling on non smooth surface, by smoothing out the momentum of the object the wheel carries, which the movement of the weight center of the wheel may not be smooth. The distance between the wheel and the object it carries is flexible so that when the wheel encounters as obstacle the distance between the wheel and object being carried thereby shrinks in order for the wheel to overcome the obstacle while keeping the momentum of the object relatively unchanged. This inevitably increases the gravity center of the object, which in certain situations (e.g., inline roller skate), is a big disadvantage. Also the shrinkable distance between the object and the wheel requires elastic material to connect the wheel and the object. This increases the complexity and cost, decreases the reliability and stability in some applications and introduces vibration to the object. 
     It is thus desirable to provide a fundamentally new wheel suspension mechanism. It is further desirable to provide a wheel suspension mechanism in which contrary to conventional suspension systems, the distance between the wheel and the object it carries will not shrink in the normal position. Thus, the gravity center of the object can be positioned as low as if no suspension system were used, and the object will have maximum stability. It is yet further desirable to provide a wheel suspension mechanism which does not require any form of elastic material (like spring etc), and therefore is simpler, more reliable and introduces no vibration to the object. It is still further desirable to provide a wheel suspension mechanism which overcomes the drawbacks of conventional suspension systems and could be applied to all sorts of low speed equipment such as, bicycles, trailers, scooters, skates, skate boards, roller skis, wheelchairs, baby strollers, carts, dollies etc. and some industrial applications. 
     SUMMARY OF THE INVENTION 
     This invention relates generally to wheel suspension system and, more particularly, to a wheel suspension system able to smooth movement of an object carried on wheels when travelling over obstructions on a surface being navigated. 
     A primary object of the present invention is to provide a wheel suspension mechanism which overcomes the drawbacks of conventional suspension systems and could be applied to all sorts of low speed equipment like bicycles, trailers, scooters, skates, skate boards, roller skis, wheelchairs, baby strollers, carts, dollies etc. and some industrial applications. 
     A further object of the present invention is to provide a wheel suspension mechanism in which, contrary to conventional suspension systems, the distance between the wheel and the object carried thereby does not shrink in the normal position, thus, the gravity center of the object can be positioned as if no suspension system were used, and the object will have maximum stability. 
     An even further object of the present invention is to provide a wheel suspension mechanism which does not require any form of elastic material (like spring, etc.), and therefore is simpler, more reliable and introduces no vibration to the object. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views. 
     FIG. 1 is a front view of a front wheel axle fixed to two string arms of the wheel suspension system of the present invention; 
     FIG. 2 is a front view of a wheel axle of a bicycle fixed to the two string arms of the wheel suspension system of the present invention; 
     FIG. 3 is a side view of a wheel axle of a bicycle fixed to the two string arms of the wheel suspension system of the present invention; 
     FIG. 4 is a side view of a front wheel of a bicycle without the wheel suspension system of the present invention approaching a bump; 
     FIG. 5 is a side view of the front wheel of a bicycle without the wheel suspension system of the present invention from FIG. 4 meeting the bump; 
     FIG. 6 is a side view of the front wheel of a bicycle without the wheel suspension system of the present invention from FIG. 4 rolling over the bump; 
     FIG. 7 is a side view of a front wheel of a bicycle with the wheel suspension system of the present invention approaching a bump; 
     FIG. 8 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 7 touching the bump; 
     FIG. 9 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 7 showing movement of the swing arms when meeting the bump; 
     FIG. 10 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 7 rolling over the bump; 
     FIG. 11 is a side view of a front wheel of a bicycle with the wheel suspension system of the present invention approaching a dent; 
     FIG. 12 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 11 showing movement of the swing arms when touching an edge of the dent; 
     FIG. 13 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 11 showing movement of the swing arms when touching a bottom of the dent; 
     FIG. 14 is a side view of the front wheel of a bicycle with the wheel suspension system of the present invention from FIG. 11 showing the swing arms returning to the normal position after passing the dent; 
     FIG. 15 is a side view of a wheel connected to the wheel suspension system of the present invention in a load free situation; 
     FIG. 16 is a side view of a wheel connected to the wheel suspension system of the present invention under a load and moving at a constant speed; 
     FIG. 17 is a side view of a wheel connected to the wheel suspension system of the present invention under a load, moving at a constant speed and with increased torque in the spring; 
     FIG. 18 is a side view of a wheel connected to the wheel suspension system of the present invention with a forward spring hooker; 
     FIG. 19 is a side view of a wheel connected to the wheel suspension system of the present invention with a backward spring hooker; 
     FIG. 20 is a perspective view of the wheel suspension system of the present invention with increased torque in the spring; 
     FIG. 21 is a front view of the wheel suspension system of the present invention shown in FIG. 20; 
     FIG. 22 is a side view of the wheel suspension system of the present invention shown in FIG. 20 connected to a wheel of a bicycle; 
     FIG. 23 is a side view of the wheel suspension system of the present invention connected to a front wheel of a bicycle allowing increased forward and backward movement for the wheel; 
     FIG. 24 is a side view of a scooter equipped with the wheel suspension system of the present invention; 
     FIG. 25 is a front view of the scooter of FIG. 24 equipped with the wheel suspension system of the present invention; 
     FIG. 26 is a back view of the scooter of FIG. 24 equipped with the wheel suspension system of the present invention; 
     FIG. 27 is a side view of a bicycle wheel connected to the wheel suspension system of the present invention wherein the swing arms are telescopic shock absorbers; 
     FIG. 28 is a side view of a bicycle wheel connected to the wheel suspension system of the present invention stopping upon contacting a bump with the fork continuing to swing; 
     FIG. 29 illustrates a front view of the wheel suspension system of the present invention connected to small wheels; 
     FIG. 30 is a side view of the wheel connected to the wheel suspension system of the present invention shown in FIG. 29; 
     FIG. 31 is a side view of the wheel connected to the wheel suspension system of the present invention of FIG. 29 showing rotation around the joint upon contact with a bump; 
     FIG. 32 is a side view of an inline skate having the wheel suspension system of the present invention connected to a front wheel thereof; 
     FIG. 33 is a front view of an inline skate as seen from FIG. 32 having the wheel suspension system of the present invention connected to a front wheel thereof; 
     FIG. 34 is a front view of an inline skate having the wheel suspension system of the present invention connected to each wheel thereof; 
     FIG. 35 is a side view of an inline skate as seen from FIG. 34 having the wheel suspension system of the present invention connected to each wheel thereof; 
     FIG. 36 is a front cross-sectional view of an inline skate having the wheel suspension system of the present invention; 
     FIG. 37 is a front cross-sectional view of an inline skate having an alternate embodiment of the wheel suspension system of the present invention connected thereto; 
     FIG. 38 is a front cross-sectional view of an inline skate having compact form of the wheel suspension system of the present invention connected thereto; 
     FIG. 39 is front cross-sectional view of an inline skate having an alternate embodiment of the wheel suspension system of the present invention connected thereto; 
     FIG. 40 is a side view of the wheel suspension system of the present invention connected to a wheel through an intermediate frame; 
     FIG. 41 is a front view of the wheel suspension system of the present invention connected to a wheel through an intermediate frame as seen in FIG. 40; 
     FIG. 42 is a side view of a wheel set suspended by the wheel suspension system of the present invention; 
     FIG. 43 is a front view of a wheel set shown in FIG. 42 suspended by the wheel suspension system of the present invention; 
     FIG. 44 is a side view of a skate shoe suspended by the wheel suspension system of the present invention with pivot joints connected between the wheel set; 
     FIG. 45 is a side view of a skate shoe suspended by the wheel suspension system of the present invention as shown in FIG. 44 with increased torque on the spring; 
     FIG. 46 is a side view of the wheel suspension system of the present invention connected between sets of two wheels of an in line skate; 
     FIG. 47 is a front view of the wheel suspension system of the present invention connected between sets of two wheels of an in line skate; 
     FIG. 48 is a side view of the wheel suspension system of the present invention connected between sets of two wheels of an in line skate with increased torque in the spring; 
     FIG. 49 is a side view of a wheel set of an in line skate including the wheel suspension system of the present invention equipped with a cable swing arm; 
     FIG. 50 is a back view of an in line skate including the wheel suspension system of the present invention equipped with a cable swing arm; 
     FIG. 51 is a side view of a whole skate including the wheel suspension system of the present invention equipped with a cable swing arm; 
     FIG. 52 is a side view of wheels of an in line skate including the wheel suspension system of the present invention and having a cable ring for hooking two hookers; 
     FIG. 53 is a front view of wheels of an in line skate shown in FIG. 52 including the wheel suspension system of the present invention and having a cable ring for hooking two hookers; 
     FIG. 54 is a side view of an in line skate including the wheel suspension system of the present invention connected to the front of the wheel set and conventional suspension on the back of the wheel set; 
     FIG. 55 is a side view of a hand truck including the wheel suspension system of the present invention; 
     FIG. 56 is a rear view of the hand truck shown in FIG. 55 including the wheel suspension system of the present invention; 
     FIG. 57 is a side view of a cart including the wheel suspension system of the present invention; 
     FIG. 58 is a rear view of the cart shown in FIG. 57 including the wheel suspension system of the present invention; 
     FIG. 59 is a rear view of wheels of a baby stroller including the wheel suspension system of the present invention; 
     FIG. 60 is a side view of a frame of the baby stroller including the wheel suspension system of the present invention for multi-direction wheels; 
     FIG. 61 is a side view of a frame of the baby stroller including the wheel suspension system of the present invention for single direction wheels; 
     FIG. 62 is a perspective view of double wheels of the baby stroller including the wheel suspension system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, FIGS. 1 through 62 illustrate the wheel suspension system of the present invention indicated generally by the numeral  10 . 
     It is better to use an example to explain the basic mechanism behind the wheel suspension system  10  of the present invention. In the following subsections, a bicycle  12  having a front wheel  5  is used as a simple model to define this new suspension system  10  and study the physics behind it. 
     1.1 The Concept of Tangential Suspension (TS) 
     FIGS. 1-3 are different views of TS  10  of the present invention applied to the front wheel  5  of a bicycle. FIG. 1 shows that the front wheel axle  2  can be fixed to the two swing arms  1 . Extending from each of the two swing arms  1  is a joint  3 . 
     FIG. 2 is the font view of the front wheel  5  of the bicycle  12  equipped with TS  10 . Note that the two swing arms  1  are pivotally connected to the front fork  4  of the bicycle frame  14  via the joints  3  on the ends of each swing arm  2 . The joints  3  are positioned below the wheel axle  2  because of the weight of the frame  14 . The wheel  5  pivots about the axle  2 . FIG. 3 is the side view of the same embodiment. Note that the swing arms  1  extend perpendicular to the ground  8  and the joints  16  between the wheel  5  and the swing arms  1  are above the joints  3  between the front fork  4  and the swing arms  1 . (This swing arm  1  position is defined as the NORMAL POSITION). In real world design, joints  3  should be more delicate in order to achieve torsional rigidity. The swing arms  1  should be able to rotate around joints  3  in both the forward and backward direction for at most 90 degrees. (More than that could be harmful and should be restricted). 
     2.2 The Physics Behind TS 
     FIGS. 4-6 show how a bicycle front wheel  5  without any suspension system overcomes an obstacle  18  on a surface of the ground  8 . The curve, labeled with the numeral  20 , on top of FIG. 6 shows the trajectory of the frame  14  with respect to time in the whole procedure. Note that there is a corner  22  in the curve, which means the momentum (the time derivative of the trajectory) has a jump when the wheel  5  touches the bump  18 . Therefore there is a shock acting on the frame  14  to cause the jump of momentum. As can be seen from FIGS. 4 and 5, the arrow  24  on top of FIG.  4  and the arrow  26  on top of FIG. 5 indicate the trajectory of the frame  14  prior to and up until contact of the wheel  5  with the bump  18 . As the wheel  5  is traveling on flat ground  8  until contacting the bump  18 , the trajectory of the wheel  5  is parallel to the around  18 . 
     FIGS. 7-10 shows how the TS  10  eliminates the shock which occurs in wheeled objects not containing the TS  10 . 
     FIG. 7 shows that the bicycle front wheel  5  with TS  10  connected thereto is moving towards a bump  18 . The arrow  28  on the top of FIG. 7 shows the trajectory of the frame  14 . FIG. 8 shows the moment of the bicycle  12  when the wheel  5  touches the bump  18 . Note that point A is where the wheel  5  contacts the ground  8  and point B is where the wheel  5  touches the bump  18 . The arrow labeled with the numeral  30  located on top of FIG. 8 indicates the trajectory of the frame  14  of the bicycle  12  prior to contacting the bump  18 . 
     FIG. 9 shows that, because the wheel is very light compared to the frame  14  and a rider positioned on the frame and riding the bicycle  12 , the wheel  5  stops while the frame  14  keeps moving forward and upward smoothly under the restricting of the swing arms  1 . The curve  32  on top of FIG. 9 shows the trajectory of the wheel  5  with respect to time. When the swing arm  1  swings to the position so that it points toward B, as shown in FIG. 9, (let&#39;s call this moment the CRITICAL MOMENT, and the angle between the line passing A and the wheel center  34  and the line passing B and the wheel center  36  the CRITICAL ANGLE  38 ), the force of the swing arm  1  acting on the wheel axle  40  will start to move the wheel  5  again over the bump  18 , as shown in FIG.  10 . The curve  42  on top of  10  shows the trajectory of the frame  14  in the whole procedure. Unlike the curve  20  in FIG. 6, this curve  42  is continuously differentiable. i.e., tangentially connected, therefore there is no shock acting on the frame  14  during the whole procedure. Notice that the direction change of the momentum in the curve  20  in FIG. 6 just before and after the corner  22  is as large as that in FIG. 9 at the beginning and the end of the concave up curve  42 . This tells us that TS  10  wouldn&#39;t cause “overshooting” theoretically. In the real world, the direction chance of the momentum in the curve  20  in FIG. 6 should be larger because the shock causes larger energy losses. That is why the rider will feel much smoother and slicker with TS  10  on a non smooth road. 
     FIGS. 11-14 show how the TS  10  reduces shocks from a dent. 44  (It totally eliminates shocks in this case in a low speed). 
     FIG. 11 shows the wheel  5  with TS  10  connected thereto moving toward the dent  44 . An arrow labeled with the numeral  46  indicates the trajectory of the wheel  5 . FIG. 12 shows that when the wheel  5  touches the edge A of the dent  44 , it (and the frame) will rotate downward around A until it touches the bottom B, as shown in FIG.  13 . Then the wheel  5  will stop while the frame  14  keeps on moving around the wheel axle under the restriction of the swing arms  1 . An arrow labeled with the numeral  48  above FIG. 12 indicates the trajectory of the wheel  5  as is begins to roll over the dent  44 . An arrow labeled with the numeral  50  above FIG. 13 indicates the trajectory of the wheel  5  as is completes rolling over the dent  44 . As can be seen when comparing the arrow  48  to the arrow  50 , the arrow  50  drops a longer distance indicating the wheel  5  has passed completely over the dent  44 . FIG. 14 shows that when the swing arm  1  moves to the normal position, the wheel  5  will start moving again along with the frame  14 . Note that the curve labeled with the numeral  52  on top of FIG. 14 shows the trajectory of the frame  14  and wheel  5  through the whole procedure of travelling over the dent  44 , which is continuously differentiable and therefore no shock (in lower speed) is felt by a rider. 
     2.3 Rolling Resistance Compensated Tangential Suspension (CTS) and Rolling Resistance Super Compensated Tangential Suspension (SCTS) 
     Because the swing arm  1  should be in normal position just before hitting a bump  18  in order to eliminate the shock, it is better to introduce a torque to act on the swing arm from the frame  14  around the joint  3  (i.e., the joint between the swing arm and the frame) should be introduced. Thus, when the wheel with TS  10  is rolling on a smooth level and flat surface  8 , the torque is just enough to balance the torque caused by the rolling resistance so that the swing arm  1  will stay in a normal position. TS  10  with torque to achieve the above purpose is defined as Compensated Tangential Suspension (CTS). 
     FIGS. 15 and 16 show a wheel with CTS in different situations. FIG. 15 shows the wheel  5  in a load free situation. In this example, the torque is achieved by a pulling spring  6 . Note that the swinging arm  1  leans forward because of the torque. 
     FIG. 16 shows the same embodiment under a load  54  and moving with constant speed V indicated by the arrow labeled with the numeral  56  on a smooth level and flat surface  8 , 
     Note that because of the load  54  and rolling resistance, the swing arm  1  stays in the normal position prepared for an upcoming bump  18  or dent  44 . The torque should be adjustable according to the load  54  applied to the wheel  5  in order to achieve CTS because the rolling resistance depends on the weight of the load  54  and the bearing resistance coefficient. 
     If we increase the torque on CTS slightly we get Super Compensated Tangential Suspension (SCTS). 
     FIG. 17 shows the same embodiment as in FIGS. 15 and 16 under the load  54  and moving with constant speed V as indicated by the arrow labeled  56  on a smooth level and flat surface  8 . Note that because the spring  6  is stronger than in CTS, even with the load  54  and rolling resistance, the swing arm  1  can&#39;t stay in normal position. Instead, it leans forward a little bit. The advantage of SCTS is that because the wheel has a little upward freedom (as shown in FIG.  17 ), it has the properties of conventional suspension systems when dealing with tiny road noise. When the obstacle on the road is larger than the wheel&#39;s upward freedom, the properties of TS start to take effect. 
     3 Applications to Individual Wheels 
     FIG. 18 is an example of applying CTS  10  to the front wheel  5  of a bicycle  12 . Note that the front fork  4  contains a forward spring hooker  7 . The pulling spring  6  connecting the wheel axle  2  and the hooker  7  provides the torque to achieve CTS. You can see that under the load indicated by the arrow labeled  54  and moving with constant speed V indicated by the arrow labeled with the numeral  56  on a flat surface  8 , the swing arm  1  is in the normal position. 
     FIG. 19 is another example of applying CTS to the front wheel  5  of a bicycle  12 . Note the swing arm  1  contains a backward spring hooker  7 . The pulling spring  6  connecting the hooker  7  and the fork  4  provides the CTS torque. The difference between the two examples is that the rate of change of the torque with respect to the rotation of the swing arm  1  is different when the swing arm  1  is in normal position. In other words, the sensitivity to the road noise is different for the two examples. 
     FIGS. 20-22 provide an example of applying SCTS to the front wheel  5  of a bicycle  10 . 
     FIG. 23 is another example of applying CTS to the front wheel  5  of a bicycle  12 . Note that the torque is given by another positioning of spring means  6 . This positioning allows the wheel  5  to have more freedom swinging forward and backward. 
     FIG. 24 is the side view of a scooter  58  equipped with TS  10 . 
     FIG. 26 is the front view of the same embodiment of the scooter  58  equipped with TS  10 . 
     FIG. 25 is the rear view of the same embodiment of the scooter  58  equipped with TS  10 . 
     FIG. 27 is another variation of TS  10  applied to the front wheel  5  of a bicycle  10 . This figure shows a side view of the wheel the other side being symmetrical thereto. Note that the wheel axle  2  is connected to the front fork  4  via swing arms  1 . The swing arms  1  are telescopic shock absorbers or other variable length means which enable the swing arm I to extend and contract (of course the swing arm  1  is rigid to prevent bending in order to make sure the wheel  5  is laterally rigid). FIG. 27 is the situation when the wheel  5  just hits a bump  18 . 
     FIG. 28 shows that the wheel stops while the fork  4  swings or continues forward until it reaches the critical moment. Note that the swing arm  1  is pulled to extend a greater distance at this point in the movement of the wheel over the bump  18  than at the point of movement shown in FIG. 27 but still extends a distance less than the wheel radius. Using a variable swing arm  1  in TS  10  not only eliminates the shock when encountering a bump  18  in the roadway  8  and but also reduces the direction change of the momentum therefore the rider will feel smoother than on pure TS  10 . 
     TS  10  is also ideal for small wheels to over come large obstacles smoothly. FIG. 29 is a front view along the moving direction of the wheel  5 . The wheel rotates around a moving axle  2  which can rotate around the joints  3  with the frame  4 . Note that joint  3  is in a lower position than joint  2 . The moving axle  2  also connects the frame  4  with pulling springs  6  in order to stay in the normal position as shown in FIG. 29 for on or off level ground situations. FIG. 30 is a side view of the same embodiment shown in FIG.  29 . Assume the ground  8  is flat, the joint  2  is almost vertically above joint  3  in the normal position. FIG. 31 is a similar view to that of FIG. 30, showing the wheel  5  encountering an obstacle. In this case the momentum of the frame  4  causes the joint  3  to rotate around joint  2  which smoohtly changes the directing of the momentum of the frame  4  upward as shown in the picture. When the swing arm  1  swings to the critical angle it will pull the wheel  5  to roll over obstacles  18 . 
     FIGS. 32-33 are, respectively, a side view and front view of an inline skate  60  with CTS  10  applied only to the front wheel  62  to reduce shock to improve ability of overcoming obstacles while having the most economic structure. Note that the swing arms  1  are fixed to the axle  2  of the front wheel  62  at one end, and are pivotally connected to the frame  64  via joints  3  at the other end. The pushing spring  66  add a certain amount of torque to the swing arm  1  to offset the rolling resistance on smooth surface  8  in order to satisfy the requirement of CTS  10 . Also notice that one can open a “window”  68  on each side of the frame  4  to allow the swing arms  1  to swing on the same surfaces the frames are on. Because this consideration is trivial, I am not going to draw a another picture for it and just want to point out that CTS  10  can be used without sacrificing old goodness. Conventional springs can also be applied to the rear part of the skate set to take advantage of the larger space above the wheel set there. 
     FIGS. 34 and 35 show different views of an inline skate set  60  equipped with independent CTS  10  for each wheel  70 . Because CTS  10  can keep the gravity center of the frame  64  as low a s if no suspension system were used, therefore is ideal for the skate  60 . 
     FIG. 35 shows the side view of the skate set  60 . Note that the skate set  60  is supposed to be under load and moving at a constant speed on a flat surface  8 . The spring means  6  should be adjusted so that in the above situation the swing arm  1  will be close to the normal position (i.e., perpendicular to the ground) in order to satisfy the requirement of CTS  10 . There are all sorts of way to add certain torque to the swing arm  1  to compensate the rolling resistance on a flat surface  8 . The spring  6  shown in the picture is just one example. FIG. 34 is the rear view of the same embodiment. Note that the swing arm  1  is fixed to the wheel axle  2  (around which the wheel  70  can rotate), but is pivotally connected to the frame  64  on its other end at a lower position. 
     By adjusting the strength of the spring  6  one may easily achieve independent SCTS  10  or a mixture of independent CTS and SCTS. 
     FIG. 39 is the cross-section of a wheel  5  equipped with TS in a most compact way. Let&#39;s call it a TS Wheel. The only difference from conventional wheels is that the axle  2  extends through the core ecentrically (while the outer part of the wheel  5  is supposed to be able to rotate around the core), and the axle  2  itself is supposed to be pivotally connected to the frame  72 . (or it itself pivotally go through the core of the wheel  5 ). The TS wheel can be applied to all sorts of moving equipment to eliminate shocks. 
     FIGS. 40 and 41 are different views of a single wheel  5  equipped with TS through an intermediate frame  72 . The intermediate frame  72  allows more freedom to choose the positioning of joints  3  and the length of the swing arms  1 . 
     FIG. 40 is the side view of the embodiment. Note that the joints between the intermediate frame  72  and the swing arms  1  are positioned at different height to allow more freedom of the swing arm  1  rotation in one direction. The swing arms  1  should be pivotally connected to the frame  72  on their other ends and the connection should satisfy the requirements of TS and allow the swing arms  1  to move parallel to one another. 
     FIG. 41 is the rear view of the same embodiment. Note that the swing arms  1  on the left side and on the right side are positioned non-symmetrically. This is for anti-torsional, anti-lateral force considerations. There is a lot of freedom in positioning the swing arms  1  through an intermediate frame. 
     FIG. 37 is another variation of TS. In this embodiment, the frame  4  pivotally connects the swing arm  1  via bearing  3  only on one side of the wheel  5  for structural simplicity. 
     FIG. 36 is the most common form of TS. 
     FIG. 38 is the TS wheel defined previously, the most compact form of TS. In this embodiment, the core  1  of the wheel  5  also serves as the swing arm  1 . And the wheel axle  2  (which is fixed to the frame  4 ) ecentrically go through the core via rotatable bearing  3 . 
     4 Applications to a Set of Connected Wheels 
     When applying the idea of TS to inline skates  60 , we can put the whole wheel set  70  into suspension. FIG. 42 is the side view of the wheel set  70 . The pivot joints  2  go between the gap of the wheels  70 . The swing arms  1  are connected to the main frame (not shown) of the skate  60  by the pivot joints  3 . 
     FIG. 43 is a rear view of the wheel set. From this view one can see clearly that the joints  3  pivotally connect to the main frame  4 . There are also springs  6  connecting the wheel set  70  and the main frame  4  in order to restore the normal position of the swing arm  1  when riding on a rough road. 
     FIG. 44 is the side view of the whole skate shoe  60  equipped with the TS suspension system. The pivot joints  3  between the wheel set and the main frame  4  are blocked by the frame  64 , and therefore are shown by the dotted lines. 
     The advantages of the TS suspension are fully explored when applied to inline skates  60  because it enables the skate shoe to remain positioned in a conventional low profile position. 
     FIG. 45 is the side view of the inline skate unit  60  equipped with the SCTS. Note that the spring  6  connecting the wheel set  70  and the frame  64  pulls forward in order to satisfy the SCTS requirement. 
     FIGS. 46-48 are different views of another application of SCTS to inline roller  60 . In this embodiment, the pivot joint  2  between the wheel set  70  and the swing arm  1  is located higher to enable the swing arm  1  to have a length which is equal to the wheel radius (note that if the length of the swing arm  1  is greater than the radius of the wheel  5 , then at the critical moment, the gravity center of the frame  64  will have already been raised to a distance greater than the height of the bump  18 , causing “overshooting”). The pulling string  6  (metal or plastic) is easily replaced by a pulling string having a different strength, i.e. either stronger or weaker, in order to achieve either SCTS or STS respectively. 
     TS, CTS, or SCTS can also be easily applied to truck type roller skates, roller skateboards, roller skis and other recreational or transportation equipment. They can be used for the whole wheel set or can be used individually for each wheel or a subset of the wheel set to achieve different effects. 
     FIGS. 49-51 are different views of an inline skate unit  60  equipped with CTS using cable swing arm  1 . 
     FIG. 49 is the side view of the wheel set  70  with the swing cables  1  attached at the front and the rear part. The length of the swing cables  1  should are preferably substantially equal. They can be positioned symmetrically or non-symmetrically on both sides of the wheel set  70  as long as the projections of their movements onto the wheel set surface are all parallel to each other. The surface of the wheel set  70  should be flat and smooth in order to run through the frame  64  freely. 
     FIG. 51 is the side view of the whole inline skate unit  60 . 
     FIG. 50 in the rear view of the same embodiment. Note that the frame  64  keeps the wheel set  70  standing by surface contact and a connection with the swing cables  1 . Therefore the inner surface on the frame  64  must be also very smooth, and the frame  64  should be laterally rigid. Also notice that the swing cables  1  have a certain inclination. The inclination helps stabilize the wheel set  70  when running and also helps the frame  64  to stand lateral force in a powerful stride. 
     FIGS. 52-53 are two views of another variation of TS as applied to the inline skate  60 . 
     Instead of using a single cable hooking two hookers, e.g. joints  2  and  3 , a cable ring  1  is used. All the advantages of the cable swing arm are preserved, and in addition, the swing cable  1  can be ½ as thin as in the single cable and fastening the cable is easily performed by simply hooking the cable ring  1  to the two corresponding cable hookers  2  and  3 . Note that the pairs of hookers  2  and  3  connecting the same cable  1  should be of equal radius in order to keep the distance between them unchanged and eliminate abrasions and friction between the cable  1  and the hookers  2  and  3  during swinging. The distance between each pair of hookers is preferably no more than the radius of the wheel  5  in order to avoid “over shooting”. Also notice that the skate shoes are not in the graph. They can be attached to the top of the frame  64  in the conventional way. The wheel set  70  is preferably able to slide freely within the frame  64  therefore the surface of the wheel set  70  should be smooth. The hookers  2  and  3  also act as spacers in the gap between the wheel set  70  and the frame  64 , therefore the sliding surfaces between them should be smooth (not that for each pair of hookers, the upper hooker is part of the wheel set  70  and the lower hooker is part of the frame  64 .) 
     FIG. 54 is the side view of an inline skate unit  60  equipped with the so called Mixed Tangential Suspension (MTS). TS is applied at the front part of the wheel set  70  where there is no room for the wheel set  70  to bounce up, and conventional suspension is applied to the rear part of the wheel set  70  where there is room for the wheel set to bounce up. Note that the weight bearing spring  10  is compression type. The connection at the rear part is to restrict the side movement of the frame  64  (or the shoe) relative to the wheel set, while allowing freedom in other directions like up and down, back and forth. It is only used for describing the freedom, it is neither unique nor optimal. For example, one may use a single “C” shape leaf spring to replace both the spring  74  and the rear connection, or use surface contraction arrangement to replace the spring  6 . The weight bearing spring  10  must act directly above the axle  2  of the rear wheel or close to it, or behind it in order for the TS at the front to work as it is supposed (otherwise overshooting will occur at the front TS). The advantage of MTS is that it has kept all the properties of TS for all the wheels  5  in the wheel set  70 , and also provides the added advantage of conventional suspension for the rear  3  wheels. These combined advantages can also be achieved without MTS by a more independent combination of TS and conventional suspensions. For example, one may apply independent TS to the front wheel, and apply independent conventional suspension for the rest of the wheels or introduce a buffer at the heel part of the skate. 
     5 Applications to Coaxle Wheels 
     TS (CTS or SCTS) can also be applied to coaxial wheels. FIGS. 55-58 show the application of TS to utility carts to improve their ability of overcoming bumps and curbs. 
     FIG. 55 is the side view of a work cart with TS. As can be seen, the swing arm  1  is connected a wheel (not shown) at a first end thereof by a joint  2  and to the junction of the frame  4  with the base  76  at a second end thereof by a second joint  3 . 
     FIG. 56 is the rear view of the same embodiment. Note that the swing arms  1  and the axle  2  are rigidly connected to each other while the axle or joint  3  pivotally connects the frame  4  and the swing arms  1  to the wheels  5 . 
     FIG. 57 is the side view of a cart with TS. 
     FIG. 58 is the rear view of the same embodiment. In addition to improving the cart&#39;s ability to roll over curbs and reduce the shock associated therewith, the TS also makes the cart more stable than conventional suspension systems which introduce the vertical movement of the frame. Therefore, in this case, TS is ideal for carts carrying heavy loads, electronic equipment, street merchandise, etc. 
     FIG. 59 is a rear view of TS applied to the wheels of a baby stroller. Note that the “V” shape axle pivotally extends through three bearings (or simply, holes)  78 ,  80  and  82 , two at the wheel centers  78  and  82  and one at the frame  80 . 
     FIG. 60 is the side view of the frame  4  in the embodiment of FIG. 59, for a stroller having multi-direction wheels. 
     FIG. 61 is the side view of the frame  4  in the embodiment of FIG. 59, for a stroller having single-direction wheels. TS eliminates the shocks from the twin wheels when they encounter bumps or dents as described above with respect to bicycles, rollerblades and carts. 
     FIG. 62 is another variation of the TS applied to baby strollers with twin wheels. Note that the wheel axle  12  is fixed with the twin wheels. The swing arm  1  pivotally connects to the wheel axle  84  via bearing  2  on one ends and pivotally connects to the frame  4  via bearing  3  on the other end. Also notice that the frame is formed in the shape of an “O” in order to provide space for the movement of the wheel axle  84 .