Patent Publication Number: US-2016221630-A1

Title: Double-Acting Safety Skewer

Description:
The subject of this invention relates to the bicycle industry. More specifically, the disclosed invention teaches a novel hub mounting skewer that compensates for the presence of the mandatory safety tabs on the frame forks of a bicycle. Advantageously, the present invention may be used on both front and rear hubs, as well as on a wide variety of contemporary human powered vehicles including bicycles, both fixed gear and variable cog types, recumbent cycles, and tandems. 
     BACKGROUND OF THE INVENTION 
     Chain driven bicycles have existed for many years. These human powered vehicles come in many forms, for example the classic sitting upright bicycle, recumbent sitting reclined bicycle, tandems, fixed gear, BMX and so on. Each of these is driven by a cog and chain means. Generally the chain receives power input from a peddle crank that has a rotational motive force exerted upon it from a rider&#39;s legs. The force is transferred by the chain to the driven wheel via a geared chain-ring/cog combination, for example, wherein the cog is in turn mechanically linked to a hub. The hub is attached to the drive wheel by means of spokes or solid inserts such as in the so-called disk wheels. The drive wheel may be located at the front or the rear of the human powered vehicle. In this way linear force from a rider&#39;s legs is transformed to rotational force applied to the driven wheel and then to the road surface. A second, non-drive wheel is generally present at the end of the vehicle opposite the driven wheel. 
     From time to time the wheels of a bicycle must be detached from the bicycle frame, for example, to change a flat tire or to replace a worn part. There exist many contemporary methods for attaching a wheel to the bicycle frame. One method uses a solid axle threaded on both ends, generally found in the BMX type bicycle. Once the axle ends have been located correctly in the frame lugs, the nuts are tightened to fix the wheel in place. A second method uses a hollow axle through which a rod, referred to in the art as a skewer, is run. One end of the skewer has a lever and the other end an adjustable nut. Once the wheel is in the correct position in the lugs of the bicycle frame the lever is operated which results in a clamping force to fix the wheel in place. This latter method represents the majority of wheel mounting techniques in use today. 
     While these methods are functional, they suffer from a common flaw. In both cases the rider must perform multiple steps to remove the wheel from the bicycle frame to perform service. In the first case, a wrench or pair of wrenches must be used to loosen both nuts, then the nuts run out away from the frame lugs prior to removing the wheel. In the case of the lever operated skewer, once the tension on the skewer rod has been released by operating the lever, the nut on the opposite side from the lever must be loosened further, or run out in order to clear the frame lugs to allow removal of the wheel for service. In all cases the nut(s) on the apparatus must be operated sufficiently to clear the safety tabs mandated by regulatory policy. These tabs, so called lawyer tabs, are in place to prevent a wheel from slipping out of the frame lugs if the mounting apparatus has inadvertently become loosened, for example by road vibration or improper installation. 
     Once the wheel is clear, maintenance can occur. But the same problems exist in reverse upon remounting of the wheel. For the case of the solid axle, the wheel must be inserted into the frame lugs, then each of the nuts run in to fix the wheel in place, then a wrench or pair of wrenches must be applied to both nuts to firmly secure the wheel in place. For the case of the lever operated skewer, the wheel must be located in the frame lugs, then the nut run in to the approximate position required to engage the lever, then the rider must operate the lever to see if the nut is in the correct position. This process must be repeated several times in order to ensure proper capture of the hub in the bicycle frame with the appropriate clamping force. As can be seen, both of these methods require numerous steps and are very inefficient. 
     What would be desirable is a method for mounting/dismounting a bicycle wheel that eliminates the need for the user to deal with nuts or inefficient lever mechanisms. The apparatus of the present invention provides an improved wheel mounting/dismounting method that accomplishes this as well as eliminating other problems related to the prior art methods discussed above. 
     SUMMARY OF THE INVENTION 
     The present invention teaches a novel double-acting skewer that provides sufficient safety tab clearance with a single lever motion without the need to manipulate any other component of the mounting apparatus. Once the apparatus of the present invention has been mounted and adjusted to a specific frame, the wheel may be mounted and dismounted using only the clamping lever. More importantly, once adjusted properly, the clamping force is repeatable and the clamping lever returns to the same location consistently. 
     The apparatus of the present invention is comprised of three main components: a skewer rod, a clamping nut and a double-acting cam-and-lever mechanism. The clamping nut and skewer rod are of the contemporary type, with the significant difference that the skewer rod is threaded on both ends in order to provide a wide range of adjustment to accommodate a similarly wide range in frame lug separation. 
     The double-acting cam-and-lever mechanism is a sub-assembly further comprised of a cam housing, a cam housing cap, a cam actuator, a double-acting cam and a clamping lever. The double-acting cam is permanently attached to the clamping lever such that when the clamping lever is rotated the double-acting cam follows the same rotational movement. The double-acting cam is located within a sliding cam actuator such that when rotational movement occurs by the double-acting cam [hereinafter dacam] the sliding cam actuator moves laterally in response. 
     In turn, the sliding cam actuator is permanently attached to a first end of a skewer rod via threads on that first end. As the sliding cam actuator moves laterally in response to the rotation of the dacam, the skewer rod follows. The second end of the skewer rod has a threaded section that is mated to a clamping nut. As the skewer rod moves in response to the sliding cam actuator, a clamping force is either applied or removed depending on the direction of the skewer rod travel. The length of the travel of the skewer rod is such that a gap sufficient to clear the safety tabs on a bicycle frame is created, allowing the wheel to be dropped out without further intervention by the rider. 
     Of importance is that the apparatus of the present invention has both a very repeatable gap and a very repeatable clamping force, thus once the apparatus has been properly fitted to a specific bicycle frame, it may be removed and replaced repeatedly without any need for adjustment of the various components. Due to the double action of the cam, even if the clamping lever should become accidentally displaced, the wheel will remain mounted. This is due to the fact that upon initial operation of the clamping lever only a portion of the dismounting gap is created. It is the second, or double action of the clamping lever that provides the gap needed. As well as the advantages discussed above, other advantages of the present invention are discussed below in conjunction with the drawings and figures attached. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 : is an example of a prior art lever operated skewer apparatus. 
         FIG. 2 : is an exploded isometric view of the improved fixed gap skewer apparatus of the present invention. 
         FIG. 3 : is a detailed exploded isometric view of the double-acting-cam of the improved fixed gap skewer apparatus of the present invention. 
         FIG. 4A : is an isometric view of the double-acting cam of the improved fixed gap skewer apparatus present invention. 
         FIG. 4B : is a cross-sectional view of the double-acting cam of the improved fixed gap skewer apparatus present invention. 
         FIG. 5A : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention in the in-use state. 
         FIG. 5B : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention in the clamping pressure partially released state. 
         FIG. 5C : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention in the clamping pressure fully released state. 
         FIG. 5D : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention in the clamping pressure released safety state. 
         FIG. 5E : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention with the clamping pressure fully released and removal gap created state. 
         FIG. 5F : shows a cross-sectional view of the improved fixed gap skewer apparatus of the present invention in the locked open state. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As described briefly above, the improved fixed gap skewer apparatus of the present invention provides a number of advantages over the prior art, including importantly both safety and efficiency. To best understand the advances made by the present invention it is important to understand the prior art methods used. Note that while the method of using a pair of clamping nuts and a solid axle is still in use, particularly on BMX and fixed gear bicycles, it will not be discussed in detail since those skilled in the art will recognize the rudimentary characteristics of this method. 
     Looking at  FIG. 1  the most commonly used contemporary wheel mounting apparatus is shown. A bicycle wheel hub  14 , in this case a non-driven wheel, has a number of spokes  16  radiating from the hub flanges. These spokes attach to a rim (not shown for clarity) upon which is mounted a tire. Note that while a non-driven wheel is shown, the same theory applies to driven wheels as well, and moreover, to wheels that use discs or tri-spoke configurations. The salient point is that a hub is attached to a rim in some manner, forming a wheel that needs to be mounted to the frame of a bicycle. Note also that while the term “bicycle” is used throughout, the principles discussed herein apply to a plurality of human powered vehicles including recumbent cycles, tandems, unicycles, fixed gear bicycles, and certain types of amputee vehicles such as wheel chairs and hand operated racing chairs. 
     The wheel formed by hub  14  and spokes  16  have a skewer assembly comprised of clamping nut  19 , skewer rod  20 , and lever sub-assembly  21 . When in use the lever  23  is in position A. A cam internal to the lever sub-assembly  21  applies a pulling force on the skewer rod  20  such that when in position A the wheel is firmly mounted in the lugs  18 A and  18 B of the frame forks  12 A and  12 B. It will be recognized by those of skill in the art that the internal cam of lever sub-assembly  21 , while not discussed here in detail, is of the single acting type common in the industry. 
     Still looking at  FIG. 1 , each of the frame forks  12 A and  12 B have associated with them a safety tab  17 A and  17 B respectively. These safety tabs  17 A and  17 B, referred to contemporarily as lawyer tabs, are proscribed by law in order to insure that the wheel remains mounted—albeit loosely—to the frame of the bicycle if the lever  23  inadvertently becomes loosened. These tabs protrude outward from the frame lugs at a distance of approximately 0.1 inch preventing the wheel from completely dismounting during operation, for example from vibration as a result of traversing a rough road surface. 
     In order for a rider to remove the wheel from the bicycle, for example, to fix a flat tire, the lever  23  must first be moved approximately 180 degrees from position A to position B to release the clamping pressure. Once the clamping pressure has been released, the lever  23  must be turned counter-clockwise in direction C a number of times [while holding the clamping nut  19 ] to create the gap G needed to allow the wheel to clear the safety tabs  17 A and  17 B. Depending on the specific bicycle configuration, the rider may be required to turn the lever up to six or more times. 
     Supposing now that the tire has been repaired and that the wheel is ready to be remounted, the rider places the wheel in the frame lugs  18 A and  18 B, then turns the lever  23  a number of times clockwise to re-clamp the wheel into the frame. Unfortunately, since the number of turns completed to dismount the wheel is random, and since the cam in the lever sub-assembly  21  is only single acting, it may take several attempts to re-achieve the proper setting for the skewer assembly. Additionally, even if the rider manages to get the number of turns correct on the first try, there is no guarantee that the lever  23  will return to the proper orientation without having to mess about with the clamping nut  19 . Returning to the proper orientation is important since it is highly undesirable to have the lever interfere with other bicycle components or with an adjacent bicycle, for example, in a race. In all, the trial-and-error method of remounting a wheel is highly inefficient and leaves a lot to be desired. 
       FIG. 2  shows an apparatus  100  according to the present invention that solves the shortfalls of the prior art methods discussed. As with prior art methods, a clamping nut  80  in tandem with a skewer rod  60  is used to provide the clamping force needed under the influence of a cam located within a cam housing assembly  50 . While the clamping nut  80  used here is a MemoryNut™ from Liberty Wheel Systems, LLC, Folsom, Calif., it will be recognized by those of skill in the art that any suitable clamping nut could be used without departing from the spirit of the invention. For example, but not meant as a limitation, a stainless steel or titanium nut could be used. 
     As discussed in detail below in conjunction with  FIG. 3 , a cam located within cam housing  50  is double acting, providing an improvement in both safety and efficiency. Of note is that the lever associated with the cam housing  50  need only be operated once. There is no need to first release the clamping pressure then rotate the lever to create the requisite gap to clear the safety tabs. Instead, the double-acting cam (dacam) located within cam housing  50  first releases the pressure in a first opening motion and then creates the requisite gap on a second, continuous opening motion. This double action is a significant advance in the art. 
     Referring now to  FIG. 3 , the cam housing assembly  50  is shown in detail in an isometric view. A cam housing shell  52  has a hole  53  in one side through which the dacam  70  is inserted. In a preferred embodiment of the present invention the cam shell housing  52  is made from aluminum; however, it will be recognized by those of skill in the art that other materials, for example titanium, could be used without departing from the spirit of the invention. A lever  51  has an interference fit about a hexagonal stub  71  on the end of the dacam  70 . Once in place, a retaining pin  54  ensures that the lever  51  and dacam  70  do not slip out of the cam housing shell  52 . 
     In a preferred embodiment of the present invention the lever  51  is made from aluminum; however, it will be recognized by those of skill in the art that other materials, for example titanium, could be used without departing from the spirit of the invention. Dacam  70  of the current invention is made from hardened steel, for example heat treated B4A2 stock. This harder material is used to ensure that the lever  51  and skewer rod  60  do not wear the surface of the cam or the hexagonal stub  71 . Skewer rod  60  is made from stainless steel. 
     Also inside the cam shell housing  52  is a cam actuator  58 . The cam actuator  58  has a cavity  55  through which dacam  70  may be inserted. When properly assembled, as lever  51  is rotated, dacam  70  also rotates inside the cam actuator cavity  55  causing the cam actuator  58  to move in a lateral direction in response to the rotational motion of lever  51 . In a preferred embodiment of the present invention the cam actuator  58  is made from steel; however, it will be recognized by those of skill in the art that other materials, for example heat treated aluminum, could be used without departing from the spirit of the invention. 
     The apparatus of the present invention is completed when release spring  56  is fitted about the collar of cam actuator  58  and cam housing cap  59  is threadably attached to cam shell housing  52 . Skewer rod  60  passes through a hole  57  in cam housing cap  59  and threadably attaches to cam actuator  58 . As cam actuator  58  moves laterally in response to a rotational movement of lever  51  skewer rod  60  and cam housing shell  52  move laterally with respect to each other ultimately creating a gap sufficient to allow a bicycle wheel to clear the safety tabs on a bicycle frame as explained in detail in conjunction with  FIG. 5A through 5F  below. 
       FIG. 4  provides the details of the geometry of dacam  70 . As will be understood through an analysis of  FIGS. 5A through 5F  below, the dacam  70  is key to the operation of the improved fixed gap skewer apparatus of the present invention. In  FIG. 4A  the dacam  70  is shown in an isometric view with a section line S 1 -S 1  looking towards the end of the dacam opposite the hexagonal stub  71 . As can be seen, dacam  70  is comprised of three parts: a hexagonal section  71 , two narrow cylindrical sections  74  and a double-acting cam section  72 . The double-acting cam section  72  is double acting in that its profile is comprised of a plurality of radii. Taken together the plurality of radii act to both lock the wheel in place for use and provide the requisite gap for dismounting without the need to manipulate the clamping nut [ 80  in  FIG. 2 ] or the lever [ 51  in  FIG. 2 ]. 
     The hexagonal section  71  of dacam  70  is used as a mounting pin for the lever [ 51  in  FIG. 2 ]. The two narrow cylindrical sections  74  function both to locate the dacam  70  inside the cam housing [ 52  of  FIG. 3 ] and to provide a rotational bearing surface about which the lever can turn. Finally, the double-acting cam section  72  of dacam  70  provides the surface against which a first end of a skewer rod [ 80  in  FIG. 2 ] operates. 
     Turning to  FIG. 4B , a cross sectional view of the dacam  70  is shown. The narrow cylindrical section  74  (one of two) is shown with its center at the intersection of vertical centerline V CL  and horizontal centerline H CL . This is the rotation point for the dacam  70 . A double-acting cam section  72  is offset from the center point of the narrow cylindrical section  74 . The offset creates locking ridge  76  used to lock the apparatus in the closed, or in-use position. Major radius R 1  is the primary lobe of dacam  70  providing the lateral movement required to create the gap required to bypass the safety tabs on a bicycle frame. In a preferred embodiment, major radius R 1  is 0.137 inches. Minor radii R 2  and R 3  are required to compensate for the offset allowing the dacam  70  to rotate inside the cam actuator [ 58  of  FIG. 3 ]. In a preferred embodiment of the present invention, minor radii R 2  and R 3  are 0.04 inches. The flat surface  78  of dacam  70  is used to allow the rounded tip of the skewer rod [ 60  in  FIG. 3 ] to slide and eventually seat against the locking ridge  76 . In combination the major radius  72 , the flat surface  78  and the locking ridge  76  function as both the force to needed to keep a wheel mounted in the frame of a bicycle and to create the required gap for removal, thus the dacam  70  is double-acting. 
     Turning now to  FIGS. 5A through 5F  the operational details of the present invention are discussed. Beginning with  FIG. 5A , the apparatus of the present invention  50  is shown in the in-use, or mounted position. Lever  51  has been moved to the locked closed, or wheel mounted orientation. In the mounted position clamping nut  80  is hard against frame fork  18 B, thus no gap exists between the two. 
     Note that while the lever  51  is shown in a vertical orientation, it is not mandatory that the locked closed position be vertical. Pragmatically, the lever  51  could be in any orientation and is shown in the vertical only because, as a matter of practice, most riders prefer this orientation. Note also that the lever  51  is shown in dotted lines in order to more clearly illustrate the internal details of the present invention. 
     In the locked closed position dacam  70  has been wedged between the inner surface of the cam actuator  58  and the tapered tip of skewer rod  60 . In obtaining this position a release spring  56  has been completely decompressed such that only a minimal lateral force exists on the face of the cam actuator  58 . The cam actuator  58  is free to slide laterally inside cam housing  52 . The cam actuator  58  and the release spring  56  are held in place by cam housing cap  59 . To begin the dismounting operation the rider will rotate the lever  51  in direction indicated by the arrow A. 
     In  FIG. 5B  the rider has moved the lever  51  further in a counter-clockwise direction indicated by arrow B. Dacam  70  has moved away from the locked position and skewer rod  60  is moving along the flat surface of dacam  70 . Cam actuator  58  has begun a lateral movement towards the frame of the bicycle which releases pressure between clamping nut  80  and frame lug  18 B. At the same time a small distance D 1  has formed between the cam actuator and the inside of the cam shell  52  causing release spring  56  to compress slightly. Note that while the cam actuator has moved distance D 1 , the clamping nut  80  also moves a similar distance G 1  due to the fact that the cam actuator and the skewer rod  80  are threadably connected, thus they move in concert. At this time the wheel may be loose, but the spring loaded cam housing shell  52  and cam in combination with the safety tabs prevent the wheel from being dismounted from the bicycle frame. 
     Looking at  FIG. 5C , the rider has moved the lever  51  further in a counter-clockwise direction as indicated by arrow C to the point where the minor radius [R 2  in  FIG. 4B ] of the dacam  70  is just about to move past the tapered end of skewer rod  60 . Note that the skewer rod  60  has a tapered end to allow the dacam  70  to easily pass without sticking or binding. At this point in the dismounting process the release spring  56  remains fully compressed, and the cam actuator  58  has reached its widest distance D 2 . At this point the gap G 2  between the clamping nut  80  and the frame lug  18 B is sufficient to allow the wheel to clear the safety tabs and drop away from the frame of the bicycle. 
     Referring now to  FIG. 5D , the rider has continued to move the lever  51  in direction D until the tip of the skewer rod  60  has just slipped past the minor radius of dacam  70 . As the skewer rod  60  is urged along the face of the major radius [R 1  of  FIG. 4B ] of dacam  70  the distance D 3  between the cam actuator  58  and the inner wall of the cam housing and the gap G 3  between the clamping nut  80  and the frame lug  18 B remain constant. 
     In  FIG. 5E  lever  51  has been moved in the direction of arrow E such that the major radius of dacam  70  [R 1  in  FIG. 4B ] is keeping a constant gap G 3  between the clamping nut  80  and the frame lug  18 B by the force applied to skewer rod  60 . In this state, a gap of at least 0.21 [or 0.105 inches on either side of the apparatus] inches has been created which is sufficient to clear the safety tabs on the fork of a bicycle frame. At this point in time the release spring  56  is fully compressed between the cam actuator  58  and the cam housing cap  59  and the distance D 3  between the cam actuator  58  and the cam housing  52  remains the same. This is the state of the apparatus just prior to being locked into the open position. 
       FIG. 5F  shows the locked open state of the apparatus. Here the lever  51  has been moved in the direction of arrow F until the lever  51  is approximately vertical. Dacam  70  has been wedged between the inner surface of cam actuator  58  and the tip of skewer rod  60  such that the tip of skewer rod  60  maintains the gap G 3  between the clamping nut  80  and the frame lug  18 B and the distance D 3  between the cam actuator  58  and the inner wall of the cam housing  52 . Release spring  56  remains fully compressed. In this state the wheel will drop free of the bicycle frame since the gap G 3  is sufficient to clear the safety tabs without further manipulation of the clamping nut  80  or the lever  51 . 
     Still referring to  FIG. 5F , remounting the wheel uses the reverse process just described above in conjunction with  FIGS. 5A through 5F . It is worthy of note that when the rider places the wheel back in the frame lugs and releases the lever  51  from the locked state, the release spring  56  urges the cam actuator  58  towards the closed end of cam shell  52 , causing the gaps G 3  and D 3  to close to the gaps G 2  and D 2  of  FIG. 5C . In this state the wheel will no longer drop out of the frame lugs, assisting the rider in the remounting process, improving further the efficiency of the present invention. It will be understood that continuing the closing motion of the lever  51  will cause the wheel to once again be properly mounted in the frame lugs of the bicycle, for example  12 A and  12 B of  FIG. 1 . Of importance is the fact that no manipulation of the clamping nut is required since the double acting cam provided the requisite clearance to remove/replace the wheel. This makes the present invention far superior to contemporary skewer apparatuses. 
     One advantage of the present invention is that a wheel on a bicycle may be removed from the frame lugs without the need to be concerned about clearing the safety tabs. The apparatus of the present invention is able to do this through the use of a double-acting cam that creates a gap sufficient to clear the safety tabs without the need to manipulate the clamping nut or the release lever. 
     A second advantage of the present invention is that once the apparatus has been properly installed, the captive nut used to create the clamping pressure no longer needs to be manipulated. This means that each time the wheel is removed and replaced all that need be done is operate the lever of the apparatus. When reinstalling the wheel to the bicycle the lever will repeatedly apply the proper clamping force without the need to readjust the clamping nut. 
     A third advantage of the present invention is that is has a spring loaded intermediate state that ensures that, even if the lever is inadvertently opened, the wheel will remain located in the lugs of the bicycle frame. A second motion of the lever of the apparatus is used to lock the improved skewer open in order to drop the wheel away from the frame of the bicycle. 
     A fourth advantage of the present invention is that it may be used for both front and rear mounting skewers. This is so since the double-acting cam mechanism that creates the required gap is contained entirely in the lever housing.