Abstract:
A swivel locking device for stroller wheel, comprising: a seat, a wheel bearing assembly, a locking pin, a biasing member, and an operating member. The seat and the wheel bearing assembly are coupled so as to rotate with respect to each other. The locking pin may move between a first position where the seat is coupled to suppress rotation between the seat and the wheel bearing assembly and a second position where the seat is decoupled to allow the rotation between the seat and the wheel bearing assembly. Normally, the biasing member biases the locking pin to the first position. The operating member moves between a locked position and a unlocked position. Movement of the operating member toward the locked position causes the locking pin to move toward the first position. The movement of operating member toward the unlocked position causes the locking pin to move toward the second position.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to swivel locking devices for stroller wheel, in particular to swivel locking devices for stroller wheel having a simple structure, easy to manipulate, and automatically orientatable. 
   2. Related Art 
   Strollers usually have wheels rotatably attached to the stem of the frame so as to freely rotate around the stem with respect to the frame by 360° in order to manipulate and change the traveling direction of the strollers conveniently. In addition, disposition of wheel swivel locking device between the stem of the frame and the wheels of the strollers is also known, such that the wheels may be switched from a state of being able to rotate around the stem into a state of being unable to rotate around the stem as needed and/or desired. For instance, U.S. Pat. No. 5,351,364 and U.S. Pat. No. 5,975,545 disclose examples of conventional swivel locking devices for stroller wheel. However, these conventional swivel locking devices are flawed in structural complexity, inconvenient manipulation, and incapability of automatic orientation. 
   SUMMARY OF THE INVENTION 
   Hence, an object of the present invention is to provide an swivel locking device for stroller wheel which has a simple structure and is easy to manipulate and automatically orientatable. 
   The swivel locking device for stroller wheel according to an embodiment of the present invention includes a seat, a wheel bearing assembly, a locking pin, a biasing member, and an operating member. The seat and the wheel bearing assembly are coupled so as to rotate with respect to each other. The locking pin is disposed on the wheel bearing assembly so as to move between a first position where the locking pin is coupled to the seat and the wheel bearing assembly is unable to rotate around the seat and a second position where the locking pin is decoupled to the seat to allow the rotation between the seat and the wheel bearing assembly. Normally, the biasing member biases the locking pin to the first position. The operating member is coupled to the wheel bearing assembly so as to move between a locked position and a unlocked position. The operating member is operatively coupled to the locking pin, such that movement of the operating member toward the locked position causes the locking pin to move toward the first position under biasing force of the biasing member, and the movement of the operating member toward the unlocked position causes the locking pin to move toward the second position against the biasing force of the biasing member. 
   Preferably, the locking pin includes: a first portion coupled to the biasing member in the wheel bearing assembly and capable of being coupled to the seat, and a second portion extending from the first portion to the outside of the wheel bearing assembly for being operatively coupled to the operating member. 
   Preferably, the second portion of the locking pin extends horizontally to the outside of the wheel bearing assembly, and the operating member abuts against the second portion of the locking pin. 
   Preferably, the operating member includes a horizontal portion to be coupled to the locking pin in the wheel bearing assembly. 
   Preferably, the locking pin includes a window, and the horizontal portion of the operating member passes through the window and the biasing member is disposed within the wheel bearing assembly between the operating member and the locking pin. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, a positioning slot is disposed in the seat. The locking pin is held on the first position by the partly locking pin inserted into the positioning slot, and the locking pin completely exits the positioning slot when the locking pin is on the second position. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, a bump is disposed on one of the operating member and the wheel bearing assembly, and a recess is disposed on the other one of the operating member and the wheel bearing assembly, when the bump is engaged with the recess, the locking pin is retained on the second position. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the wheel bearing assembly comprises a wheel bearing and a base coupled to the wheel bearing, the seat and the base are coupled so as to rotate with respect to each other, and the operating member is movably coupled to the base. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the wheel bearing assembly further includes a shock absorber disposed between the wheel bearing and the base. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, a trench for receiving the biasing member and partial locking pin has an opening near a front edge of the wheel bearing assembly, the opening is spaced communication in the front and the top side of the front edge. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, a cavity is formed on the base for receiving the seat, and a clasping mechanism is disposed in the cavity for restricting movement of the seat along an axis of the cavity. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the locking pin is coupled to the biasing member mounted within the trench. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the seat includes a mounting portion coupled to the wheel bearing assembly and a rim formed above the mounting portion, the rim includes two partitioning walls to define the positioning slot. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the operating member includes a pair of arms pivotably coupled to both sides of the wheel bearing assembly respectively, and a manipulating portion connected between the pair of arms so as to extend away from the wheel bearing assembly and operatively coupled to the locking pin. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, a pair of bumps are disposed on the pair of arms of the operating member and a pair of first recesses and a pair of second recesses are disposed on the wheel bearing assembly to selectively engage with the pair of bumps for holding the operating member in the first position and the second position respectively. 
   Preferably, in the swivel locking devices according to the aforementioned embodiments, the swivel locking devices further include a stopping mechanism for preventing the operating member from outrunning the locked position while the operating member is pivoted upwardly relative to the wheel bearing assembly. 
   The swivel locking device for stroller wheel according to another embodiment of the present invention includes a seat, a wheel bearing assembly, a locking pin, a biasing member, and an operating member. The wheel bearing assembly is rotatably coupled to the seat. The locking pin is mounted on a trench of the wheel bearing assembly and movable between a first position where the locking pin is coupled to the seat and the wheel bearing assembly is unable to rotate relative to the seat and a second position where the locking pin is decoupled to the seat to allow the wheel bearing assembly rotate relative to the seat freely. The biasing member is mounted within the trench of the wheel bearing assembly and normally biases the locking pin to the first position. The operating member includes a pair of arms coupled to both sides of the wheel bearing assembly respectively, and a manipulating portion connected between the pair of arms. The manipulating portion has an horizontal portion. The biasing member is located between the locking pin and the horizontal portion. The operating member is pivoted relative to the wheel bearing assembly between a locked position where the locking pin is moved toward the first position and a unlocked position where the locking pin is moved toward the second position. 
   Preferably, the locking pin includes a window, and the horizontal portion of the operating member passes through the window and the biasing member is disposed within the wheel bearing assembly between the operating member and the locking pin. 
   To those skilled in the art, these and other objects, features, aspects, and advantages of the present invention will become apparent from the detailed descriptions of the preferred embodiments of the invention with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view showing the swivel locking device for stroller wheel connected between the stem and the wheels of a stroller according to a preferred embodiment of the present invention, wherein the swivel locking device is in a locked state. 
       FIG. 2  is a schematic view of the swivel locking device shown in  FIG. 1 . 
       FIG. 3  is an exploded view of the swivel locking device shown in  FIG. 2 . 
       FIG. 4  is a bottom view of a seat of the swivel locking device shown in  FIG. 3 . 
       FIG. 5  is a lateral sectional view of the swivel locking device shown in  FIG. 2 , wherein the swivel locking device is in an unlocked state. 
       FIG. 6  is a front sectional view of the swivel locking device shown in  FIG. 2 , wherein the swivel locking device is in the unlocked state. 
       FIG. 7  is a lateral sectional view of the swivel locking device shown in  FIG. 2 , wherein the swivel locking device is in the locked state. 
       FIG. 8  is a front sectional view of the swivel locking device shown in  FIG. 2 , wherein the swivel locking device is in the locked state. 
       FIG. 9  is a schematic view showing the swivel locking device for stroller wheels according to another preferred embodiment of the present invention, wherein the swivel locking device is in the locked state. 
       FIG. 10  is a schematic view of the swivel locking device shown in  FIG. 9 . 
       FIG. 11  is an exploded view of the swivel locking device shown in  FIG. 10 . 
       FIG. 12  is a back view of the locking pin, the operating member, and the biasing member of the swivel locking device shown in  FIG. 11 . 
       FIG. 13  is a lateral sectional view of the swivel locking device shown in  FIG. 10 , wherein the swivel locking device is in the locked state. 
       FIG. 14  is a lateral sectional view of the swivel locking device shown in  FIG. 10 , wherein the swivel locking device is in the unlocked state. 
       FIG. 15  is a lateral sectional view of the swivel locking device shown in  FIG. 10 , wherein the swivel locking device is switching from the unlocked state into the locked state. 
   

   DETAILED DESCRIPTION 
   Preferred embodiments of the present invention will be described in the following with reference to the accompanying drawings. 
   First Preferred Embodiment 
   First, referring to  FIG. 1 , an swivel locking device  14  for stroller wheel coupled between a stem  10  of a stroller frame (not shown) and a pair of wheels  18  according to the preferred embodiment of the present invention is shown. The stem  10  is fixedly coupled to the swivel locking device  14 , and the pair of wheels  18  are rotatably installed on an axle (not shown) fixedly passing through the swivel locking device  14 . The swivel locking device  14  is switched between a locked state and an unlocked state, such that when the swivel locking device  14  is in the unlocked state, the pair of wheels  18  may rotate around the stem  10  along with a portion of the swivel locking device  14 , and when the swivel locking device  14  is switched into the locked state from the unlocked state, the pair of wheels  18  are locked and prohibited from rotating around the stem  10 .  FIG. 1  shows the swivel locking device  14  in the locked state. 
   Since the stroller and the components thereof except the swivel locking device  14  according to the present invention are known in this field, the details thereof are omitted herein. In addition, it is apparent to those skilled in the art that the stroller can be of any kind, and the arrangement and amount of the stroller wheels are not limited to what shown here. 
   The structure of the swivel locking device  14  for stroller wheel according to a preferred embodiment of the present invention is described in detail below with reference to  FIGS. 2 to 8 . As clearly shown in  FIG. 3 , the swivel locking device  14  includes a wheel bearing assembly  20 , a seat  22 , an operating member  24 , a locking pin  26 , and a biasing member  28 . In this embodiment, the wheel bearing assembly  20  includes a wheel bearing  30 , a base  32  coupled to the wheel bearing  30 , and a shock absorber  34  disposed between the wheel bearing  30  and the base  32 . 
   The wheel bearing  30  includes an axle receiving portion  36  extending laterally, a supporting portion  38  integrally extending forward and upward from the axle receiving portion  36 , and a base coupling portion  40  formed on the supporting portion  38  opposite to the axle receiving portion  36 . A traverse non-circular axle hole  42  is disposed on the axle receiving portion  36  for receiving the axle (not shown) coupled to the wheels  18 . The axle coupled to the wheels  18  may be fixedly or rotatably received in the axle hole  42 . The supporting portion  38  is preferably formed with a hollow portion  44  with an opening facing up for receiving the shock absorber  34 . The base coupling portion  40  includes a traverse base coupling hole  46  for receiving a coupler (not shown) to couple the wheel bearing  30  to the base  32 . 
   The base  32  includes a body  48 , a cylindrical seat coupling portion  50  extending upward from the top of the body  48 , and a wheel bearing receiving portion  52  extending backward from the body  48 . As preferably shown in  FIGS. 5 and 7 , the bottom of the body  48  and the interior of the wheel bearing receiving portion  52  are formed hollow and space communicated for receiving the partly wheel bearing  30  and the shock absorber  34 . Further, a pair of pivot holes  55  are disposed on sides in the vicinity of the rear of the wheel bearing receiving portion  52  for receiving a pivot pin (not shown) to pivotably couple the operating member  24  to the base  32 . 
   As will be further described, the body  48  of the base  32  includes an upright cylindrical cavity  51  extending from the seat coupling portion  50  into the body  48  for receiving a portion of the seat  22 . As preferably shown in  FIGS. 6 and 8 , a pair of hooked clasps  53  are disposed on the bottom of the cavity  51 , which become a portion of the clasping mechanism for restricting the movement of the seat  22  along the axis of the cavity  51  when being received in the cavity  51  of the body  48 . A vertical trench  54  is disposed in the front portion of the body  48  opposite to the wheel bearing receiving portion  52 . The vertical trench  54  is formed with a lower closed end at the body  48 , and has an opening disposed in the vicinity of the front edge  56  and is spaced communication in the front and the top side of the front edge  56 . Further, the body  48  has a pair of flanges  60  protruding from the top edges on both sides of the body  48 , a pair of first recesses  62  below and separate from the pair of flanges  60 , a pair of second recesses  64  below and separate from the pair of first recesses  62 , and a pair of wheel bearing coupling holes  66  disposed on the bottom of the body  48  below and separate from the pair of second recesses  64 . 
   The seat  22  includes a substantially cylindrical mounting portion  70 , a stem coupling portion  72  capable of fixedly coupling to the stem  10  of the stroller frame, and a rim  74  substantially in an oval shape when being viewed from above formed between the mounting portion  70  and the stem coupling portion  72 . A stem receiving hole  75  is disposed on the mounting portion  70  for receiving the end portion of the stem  10 . As preferably shown in  FIGS. 4 to 7 , the mounting portion  70  has a shape and a size capable of being received within the cavity  51  of the base  32 . The bottom of the mounting portion  70  includes a cylindrical clasping portion  76  protruding into the stem receiving hole  75  of the mounting portion  70 . The clasping portion  76  defines a clasping hole  78  allowing the pair of clasps  53  on the bottom of the cavity  51  in the base  32  to pass through. More specifically, the clasping portion  76  with the clasping hole  78  and the pair of hooked clasps  53  form a clasping mechanism for restricting the movement of the seat  22  along the axis of the cavity  51  when the seat  22  is installed in the cavity  51 . 
   As preferably shown in  FIGS. 4 to 7 , the rim  74  of the seat  22  forms a capping trench  80  which has an opening facing down corresponding to the cylindrical seat coupling portion  50  of the base  32 . The shapes and sizes of the coupling portion  50  and the capping trench  80  are designed such that when the seat  22  is installed in the cavity  51  of the base  32  while the coupling portion  50  is inserted into the capping trench  80 , the seat  22  and the base  32  may rotate around the axis of the cavity  51  with respect to each other. Further, as preferably shown in  FIGS. 4 and 7 , the rim  74  has a front portion  82  and a rear portion  88  opposite to the front portion  82 . The front portion  82  has a shape and a size that when the seat  22  is installed in the cavity  51  of the base  32  and rotates with respect to the base  32  such that the front portion  82  is right above the vertical trench  54 , the outer surface  84  of the front portion  82  is substantially even with the outer surfaces of the front edge  56  of the base  32  and the front walls  58  of the vertical trench  54 . Further, a positioning slot  86  communicating with the capping trench  80  and having an opening facing down is disposed on the front portion  82  of the rim  74 . The positioning slot  86  is defined by two partitioning walls  85  in the capping trench  80  and substantially extending backward from the inner surface of the front portion  82  of the rim  74 . The positioning slot  86  has a sectional profile and a size substantially corresponding to those of the vertical trench  54  of the base  32 . In addition, the position of the positioning slot  86  is designated so that only when the seat  22  is installed in the cavity  51  of the base  32  and rotates with respect to the base  32  such that the front portion  82  is right above the vertical trench  54 , the positioning slot  86  is exactly aligned and communicates with the vertical trench  54 . In other words, as long as the front portion  82  of the seat  22  is not above the vertical trench  54 , the positioning slot  86  is not aligned with the vertical trench  54 , and the top opening of the vertical trench  54  is at least partially closed by the bottom surface of the seat  22 . 
   The stem coupling portion  72  of the seat  22  extends upward on the rear  88  of the rim  74 . The stem coupling portion  72  includes a hole  90  for receiving a securing member (not shown) to fixedly couple the stem  10  whose end portion is received in the receiving hole  75  of the seat  22 . 
   The locking pin  26  basically includes a first upright portion  92 , a horizontal portion  94  extending horizontally from the bottom of the first upright portion  92  substantially perpendicular to the first upright portion  92 , a second upright portion  96  extending downward from the middle of the horizontal portion  94  substantially perpendicular to the horizontal portion  94 , and a third upright portion  98  extending downward from the bottom of the first upright portion  92  substantially parallel to the second upright portion  96 . The first upright portion  92  has a sectional profile and a size substantially corresponding to the sectional profiles and the sizes of the vertical trench  54  of the base  32  and the positioning slot  86  of the seat  22 . A substantially upright bar  91  is disposed on the rear of the first upright portion  92  facing the coupling portion  50 . The bar  91  may be received in the trench formed between two substantially upright bar  57  in front of the coupling portion  50 . The third upright portion  98  has a sectional profile which size is smaller than that of the first upright portion  92 . 
   In this embodiment, the biasing member  28  is a spring. As preferably shown in  FIGS. 5 and 7 , the shape and size of the spring (biasing member)  28  is selected so as to be uprightly received in the vertical trench  54  of the base  32 . 
   In this embodiment, the operating member  24  is substantially U-shaped. The operating member  24  basically includes a pair of arms  100  extending in parallel with each other and a manipulating portion  102  connected between the pair of arms  100  on a pair of corresponding ends of the arms  100 . Each of the arms  100  includes a pivot hole  104  on the other end opposite to the manipulating portion  102  for receiving the pivot pin (not shown) in cooperation with the pivot holes  55  of the base  32 , so as to pivotally couple the operating member  24  to the base  32 . Each of the arms  100  includes stopping recesses  106  and bumps  108  below and separate from the stopping recesses  106  on the side facing the base  32  between the pivot hole  104  and the manipulating portion  102 . The stopping recesses  106  and the flanges  60  of the base  32  are formed to prevent the operating member  24  from moving upward, and the bumps  108  form an engaging mechanism along with the first recesses  62  and the second recesses  64  of the base  32  respectively for holding the operating member  24  with respect to the pivot position of the base  32 , as will be further described hereinafter. However, the shapes of the bumps  108 , the first recesses  62 , and the second recesses  64  are not limited herein. Also, the bumps  108  may be replaced with recesses while the first recesses  62  and the second recesses  64  may be replaced with bumps to form the engaging mechanism which holds the operating member  24  with respect to the pivot position of the base  32 . 
   As preferably shown in  FIG. 2 , the curve of the inner surface of the manipulating portion  102  of the operating member  24  matches those of the front edge  56  of the body  48  of the base  32  and the front walls  58  of the vertical trench  54 , such that when the operating member  24  is pivotably coupled to the base  32 , the manipulating portion  102  of the operating member  24  extends outward away from the base  32 . Further, as preferably shown in  FIGS. 5 and 7 , a recess  110  is disposed on the bottom of the manipulating portion  102 . The recess  110  abuts against the horizontal portion  94  of the locking pin  26  after the swivel locking device  14  is assembled. 
   The shock absorber  34  is made of a resilient material known in this field. The shock absorber  34  can be received in the hollow portion  44  in the supporting portion  38  of the wheel bearing  30 , the hollow portion on the bottom of the body  48  of the base  32 , and the hollow interior of the wheel bearing receiving portion  52  of the base  32 , so as to be disposed between the wheel bearing  30  and the base  32 . As preferably shown in  FIGS. 5 and 7 , after the swivel locking device  14  is assembled, a portion of the shock absorber  34  directly contacts the bottom of the mounting portion  70  of the seat  22  installed in the cavity  51  by the breach formed on the bottom of the cavity  51  of the base  32 , whereby providing shock absorbing effect. In addition, it is apparent to those skilled in the art that the type and/or shape of the shock absorber are not limited to what shown here. 
   Upon assembly of the swivel locking device  14 , the shock absorber  34  is first partially received in the hollow portion  44  of the supporting portion  38  of the wheel bearing  30 . Then, the base  32  covers the wheel bearing  30  containing the shock absorber  34 , such that the exposed portion of the shock absorber  34  from the wheel bearing  30  and a portion of the supporting portion  38  and the base coupling portion of the wheel bearing  30  are contained in the hollow interior of the wheel bearing receiving portion  52  of the base  32  and the hollow portion on the bottom of the body  48 . Then, a connecting member (not shown) passes through a wheel bearing coupling hole  66  disposed on a side of the body  48  of the base  32 , base coupling holes  46  disposed on the base coupling portion  40  of the wheel bearing  30 , and another wheel bearing coupling hole  66  disposed on another sided of the body  48  of the base  32  in this order, whereby coupling the wheel bearing  30  to the base  32 . 
   As preferably shown in  FIGS. 5 and 7 , the spring  28  is then uprightly received in the vertical trench  54  of the base  32 , such that the bottom of the spring  28  abuts against the lower closed end of the vertical trench  54  of the body  48  of the base  32 . The locking pin  26  is mounted above the spring  28  and is inserted into the vertical trench  54  such that the third upright portion  98  of the locking pin  26  is received in the winding of the spring  28 , the bottom of the first upright portion  92  and a portion of the bottom of the horizontal portion  94  abut against the top of the spring  28 , the horizontal portion  94  extends to the outside of the base  32  from an opening defined by the opposite front walls  58  of the vertical trench  54 , and the second upright portion  96  is substantially abutted against the front edge  56  of the base  32 . 
   The operating member  24  is then pivotably coupled to the base  32  by the pivot pin (not shown). More specifically, the pivot pin passes through one of the pivot holes  104  disposed on the arms  100  of the operating member  24 , then the pair of pivot holes  55  disposed on the wheel bearing receiving portion  52  of the base  32 , and finally the other pivot hole  104  disposed on the other arm  100  of the operating member  24 , whereby the operating member  24  is pivotably coupled to the base  32 . In addition, the front portion of the horizontal portion  94  of the locking pin  26  abuts against the recess  110  on the manipulating portion  102  of the operating member  24 . As a result, the downward pivot of the operating member  24  with respect to the base  32  may cause the locking pin  26  to move downward and compress the spring  28 , and the upward pivot of the operating member  24  with respect to the base  32  may remove the downward force applied on the locking pin  26 , such that the locking pin  26  is biased by the counterforce of the spring  28 . 
   Further, when the operating member  24  is pivotably coupled to the base  32  as preferably shown in  FIGS. 6 and 8 , the stopping recesses  106  and the bumps  108  are disposed on the arms  100  of the operating member  24  corresponding to the flanges  60 , the first recesses  62 , and the second recesses  64  disposed on the body  48  of the base  32 . The bumps  108  of the operating member  24  and the first recesses  62  of the base  32  are defined as a first engaging mechanism for providing an upper limit position of the operating member  24 . That is, the operating member  24  may pivot upward with respect to the base  32  until the bumps  108  of the operating member  24  engage with the first recesses  62  of the base  32  so that the first engaging mechanism holds the operating member  24  in the upper limit position as shown in  FIG. 8 . This upper limit position of the operating member  24  is defined as a locked position of the operating member  24 . When the operating member  24  is on the locked position, the swivel locking device  14  is in the locked state, such that the wheels  18  are locked and prohibited from rotating around the stem  10 , as will be further described hereinafter. Similarly, the bumps  108  of the operating member  24  and the second recesses  64  of the base  32  are defined as a second engaging mechanism for providing a lower limit position of the operating member  24 . That is, the operating member  24  may pivot downward with respect to the base  32  until the bumps  108  of the operating member  24  engage with the second recesses  64  of the base  32  so that the second engaging mechanism holds the operating member  24  on this lower limit position as shown in  FIG. 6 . This lower limit position of the operating member  24  is defined as an unlocked position of the operating member  24 . When the operating member  24  is on the unlocked position, the swivel locking device  14  is in the unlocked state, such that the wheels  18  are released to freely rotate around the stem  10 , as will be further described hereinafter. 
   Further, the stopping recesses  106  disposed on the arms  100  of the operating member  24  and the flanges  60  of the body  48  of the base  32  are defined as a stopping mechanism for preventing the operating member  24  from outrunning the locked position due to over-bias by the user. That is, as preferably shown in  FIG. 8 , when the operating member  24  pivots upward with respect to the base  32  until the bumps  108  of the operating member  24  engage with the first recesses  62  of the base  32 , the flanges  60  of the base  32  engage with the stopping recesses  106  of the operating member  24 , thereby the operating member  24  is prevented from continuing to pivot upward. 
   Then, the mounting portion  70  of the seat  22  is inserted into the cavity  51  of the base  32  and the coupling portion  50  of the base  32  being inserted into the capping trench  80  of the seat  22 , until the hooked clasps  53  formed on the bottom of the cavity  51  pass through the clasping hole  78  formed on the bottom of the mounting portion  70  to clasp the clasping portion  76 . Thus, the seat  22  is mounted on the base  32  such that the seat  22  and the base  32  may rotate around the axis of the cavity  51  with respect to each other but the movement of the seat  22  along the axis of the cavity  51  is restricted. During assembly of the seat  22 , the operating member  24  may pivot downward to the unlocked position so as to overcome the biasing force of the spring  28  to bias the locking pin  26 , whereby preventing the first upright portion  92  of the locking pin  26  from interfering the assembly of the seat  22 . Alternatively, the front portion  82  of the rim  74  of the seat  22  may be ensured to be right above the vertical trench  54  of the base  32  during assembly of the seat  22 , so that the positioning slot  86  with an opening facing down disposed on the front portion  82  is exactly aligned and communicates the vertical trench  54 . As a result, the first upright portion  92  of the locking pin  26  on the spring  28  in the vertical trench  54  may be smoothly inserted into the positioning slot  86  during the assembly of the seat  22  without any interference. 
   After completion of the assembly of the swivel locking device  14  as mentioned above, the end of the stem  10  may be inserted into the stem receiving hole  75  of the seat  22 , and a securing member (not shown) may pass through the hole  90  of the stem coupling portion  72  of the seat  22  and a corresponding hole (not shown) formed on the stem  10 , thereby the stem  10  is fixedly coupled to the seat  22 . Finally, the wheels  18  may be rotatably installed on the axle fixedly passing through the axle hole  42  of the axle receiving portion  36  of the wheel bearing  30 . 
   Hereinafter, the operation of the swivel locking device  14  according to a preferred embodiment of the present invention is described in detail mainly with reference to  FIGS. 5 to 8 .  FIGS. 7 and 8  show the swivel locking device  14  in the locked state. When the swivel locking device  14  is in the locked state, as shown in  FIG. 8 , the operating member  24  is held on the locked position by the first engaging mechanism formed by the bumps  108  of the operating member  24  along with the first recesses  62  of the base  32  and the stopping mechanism formed by the stopping recesses  106  of the operating member  24  along with the flanges  60  of the base  32 . Also, when the swivel locking device  14  is in the locked state, as shown in  FIG. 7 , the locking pin  26  is biased to a first position by the spring  28 . More specifically, when the locking pin  26  is on the first position as shown in  FIG. 7 , the horizontal portion  94  of the locking pin  26  extending from the vertical trench  54  to the outside of the base  32  abuts against the recess  110  on the bottom of the manipulating portion  102  of the operating member  24  held on the locked position, and the top of the first upright portion  92  of the locking pin  26  enters the positioning slot  86  of the rim  74  of the seat  22  and the swivel locking device  14  is retained on the locked state. As the locking pin  26  extends from the vertical trench  54  of the base  32  into the positioning slot  86  of the seat  22 , since the movement of the locking pin  26  on the first position is restricted by the two partitioning walls  85  in the capping trench  80  of the seat  22 , the locking pin  26  prevents the seat  22  and the base  32  from rotating with respect to each other, and the seat  22  and the wheel bearing assembly  20  including the base  32 , the shock absorber  34 , and the wheel bearing  30  are thus prevented from rotating with respect to each other. As a result, the wheels  18  coupled to the wheel bearing assembly  20  are locked and prohibited from freely rotating around the seat  22  and the stem  10  fixedly coupled to the seat  22 . 
   When a user desires the wheels  18  to be unlocked so as to freely rotate around the stem  10 , the user may apply a downward force to the upper surface of the manipulating portion  102  of the operating member  24  held on the locked position by hand or foot, so as to overcome the holding force of the first engaging mechanism, such that the operating member  24  may pivot downward with respect to the base  32 . Since the horizontal portion  94  of the locking pin  26  on the first position abuts against the recess  110  of the operating member  24  on the locked position as described above, the downward pivot of the operating member  24  with respect to the base  32  may apply a downward pressure on the horizontal portion  94  of the locking pin  26 , whereby the upward biasing force of the spring  28  may be overcome to bring down the locking pin  26  and compress the spring  28 . The operating member  24  may pivot downward until the bumps  108  of the operating member  24  engage with the second recesses  64  of the base  32 . Meanwhile, the second engaging mechanism formed by the bumps  108  and the second recesses  64  as described above may hold the operating member  24  on this lower limit position, i.e., the unlocked position of the operating member  24 , as shown in  FIG. 6 . When the operating member  24  is held on the unlocked position by the second engaging mechanism as shown in  FIG. 5 , the locking pin  26  has been biased by the operating member  24  and is on the second position separate from the seat  22 . More specifically, when the locking pin  26  is on the second position separate from the seat  22 , as shown in  FIG. 5 , the locking pin  26  may compress the spring  28  under the horizontal portion  94  abutting against the recess  110  of the operating member  24 , and the first upright portion  92  of the locking pin  26  is completely in the vertical trench  54 . That is, the locking pin  26  completely exits the positioning slot  86  of the rim  74  of the seat  22  and is completely separate from the seat  22 . Therefore, the seat  22  and the base  32  may rotate with respect to each other, and whereby the seat  22  and the wheel bearing assembly  20  including the base  32 , the shock absorber  34 , and the wheel bearing  30  may freely rotate with respect to each other. As a result, the wheels  18  may freely rotate around the stem  10  with respect to the stroller frame along with the wheel bearing assembly  20 . 
   When the user desires the wheels  18  to be locked so as not to freely rotate around the stem  10 , the user may apply an upward force to the lower surface of the manipulating portion  102  of the operating member  24  held on the unlocked position by hand or foot, so as to overcome the holding force of the second engaging mechanism, such that the operating member  24  may pivot upward with respect to the base  32 . Because as shown in  FIG. 5 , the horizontal portion  94  of the locking pin  26  on the second position abuts against the recess  110  on the bottom of the operating member  24  on the unlocked position, the upward pivot of the operating member  24  with respect to the base  32  may release the force applied on the horizontal portion  94  of the locking pin  26  by the operating member  24 . Therefore, once the operating member  24  pivots upward and leaves the locked position, the locking pin  26  on the second position is spontaneously biased by the spring  28  under the counterforce of the compressed spring  28  and separate from the second position. The operating member  24  may, as described above, pivot upward until being held on the locked position as shown in  FIGS. 7 and 8 . However, even the operating member  24  has been held on the locked position, if the front portion  82  of the seat  22  is not on the top of the vertical trench  54  of the base  32 , the positioning slot  86  of the seat  22  is not exactly aligned and communicates with the vertical trench  54 . Therefore, the top of the first upright portion  92  of the locking pin  26  is unable to enter the positioning slot  86  and is blocked by the bottom surface of the front portion  82  of the seat  22 , whereby the spring  28  is still compressed by the locking pin  26 . Meanwhile, if the seat  22  rotates with respect to the base  32  such that the front portion  82  of the seat  22  is on the top of the vertical trench  54  of the base  32 , whereby the positioning slot  86  of the seat  22  is exactly aligned and communicates with the vertical trench  54 , since the bottom surface of the seat  22  no longer blocks the top of the first upright portion  92  of the locking pin  26 , the locking pin  26  is spontaneously biased by the spring  28  under the counterforce of the compressed spring  28 , the top of the first upright portion  92  of the locking pin  26  therefore enters the positioning slot  86  of the seat  22 , causing the locking pin  26  to move to the first position automatically where the seat  22  is coupled as shown in  FIG. 7 . This automatic swivel locking effect may conveniently lock the wheels  18 , such that the wheels  18  are prevented from freely rotate around the stem  10 . 
   Second Preferred Embodiment 
   Referring to  FIG. 9 , which shows an swivel locking device  314  for stroller wheel coupled between a pair of wheels  318  according to another preferred embodiment of the present invention. Since the swivel locking device  314  is assembled with the stem and the wheels  318  in the same manner used for the swivel locking device  14  in the first preferred embodiment of the present invention, the descriptions thereof are omitted herein. In addition, the swivel locking device  314  shown in  FIG. 9  is in the locked state. 
   The structure of the swivel locking device  314  for stroller wheel according to another preferred embodiment of the present invention will be described in detail with reference to  FIGS. 10 to 15 . As clearly shown in  FIG. 11 , the swivel locking device  314  basically includes a wheel bearing assembly  320 , a seat  322 , an operating member  324 , a locking pin  326 , and a biasing member  328 . In this embodiment, the wheel bearing assembly  320  basically includes a wheel bearing  330 , a base  332  coupled to the wheel bearing  330 , and a shock absorber  334  disposed between the wheel bearing  330  and the base  332 . 
   Since the wheel bearing  330 , the shock absorber  334 , and the seat  322  in this embodiment are similar to those in the first preferred embodiment of the present invention, the descriptions thereof are omitted herein. Also, the base  332  in this embodiment is similar to the base  32  in the first preferred embodiment of the present invention, except that the base  332  in this embodiment does not include the flanges  60  of the base  32  in the first preferred embodiment. 
   An upright portion  396  is extended downward from the bottom of the manipulating portion  402  of the operating member  324 , and is substantially abutted against the front edge of the base  332 . As preferably shown in  FIG. 12 , the rear of the upright portion  396  of the operating member  324  includes a horizontal portion  403  extending backward, and the top of the horizontal portion  403  includes a stud  405  to be received in the hollow portion of the biasing member  328 , whereby the biasing member  328  is held. The arms  400  of the operating member  324  includes bumps  408  on the side facing the base  332  for selectively engaging with the first recesses  362  and the second recesses  364  of the base  332 . However, the shapes of the bumps  408 , the first recesses  362 , and the second recesses  364  are not limited herein. Also, the bumps  408  may be replaced with recesses while the first recesses  362  and the second recesses  364  may be replaced with bumps to achieve the purpose of holding the operating member  324 . 
   A substantially upright bar  391  is disposed on the rear of the locking pin  326  facing the base  332 , and the bar  391  may be received in a trench  354  between two substantially upright bars  357 . As preferably shown in  FIG. 12 , the locking pin  326  has a window  393 . The window  393  extends downward from vicinity of the middle of the locking pin  326  to the bottom of the locking pin  326  and forms an accommodation space for receiving the biasing member  328 . As preferably shown in  FIGS. 13 to 15 , the horizontal portion  403  of the operating member  324  passes through the window  393  of the locking pin  326 , such that the operating member  324  is operatively coupled to the locking pin  326 . The biasing member  328  is disposed within the vertical trench of the wheel bearing assembly  320  and between the operating member  324  and the locking pin  326 . The top end of the biasing member  328  is abutted against a closed end of the accommodation space of the locking pin  326  where is near the top wall of the window. Further, as shown in  FIGS. 13 and 14 , the uncompressed height of the biasing member  328  is designed such that when the bumps  408  of the operating member  324  engage with the first recesses  362  of the base  332 , the locking pin  326  is biased by the biasing member such that the top of the locking pin  326  enters the positioning slot  386  formed in the seat  322 , and when the bumps  408  of the operating member  324  engage with the second recesses  364  of the base  332 , the biasing member  328  may have a most suitable height so that the locking pin  326  may completely exit the positioning slot  386  formed in the seat  322 . 
   Next, the operation of the swivel locking device  314  according to the second preferred embodiment of the present invention will be described with reference to  FIGS. 13 to 15  and it is similar to the first preferred embodiment. 
     FIG. 13  shows the swivel locking device  314  in the locked state. When the swivel locking device  314  is in the locked state, the bumps  408  disposed on the operating member  324  may engage with the first recesses  362  of the base  332  to hold the operating member  324  on the locked position, and the locking pin  326  is biased by the biasing member  328 , such that the top of the locking pin  326  enters the positioning slot  386  formed in the seat  322 . Similar to the seat used in the first preferred embodiment of the present invention, since there are also two identical partitioning walls (not shown) in the seat  322  used herein for limiting the movement of the locking pin  326 , when the top of the locking pin  326  is in the positioning slot  386 , the locking pin  326  prevents the seat  322  and the base  332  from rotating with respect to each other, thereby preventing the seat  322  and the wheel bearing assembly  320  including the base  332 , the shock absorber  334 , and the wheel bearing  330  from rotating with respect to each other. As a result, the wheels  318  coupled to the wheel bearing assembly  320  are locked and unable to freely rotate around the seat  322  and the stem fixedly coupled to the seat  322  (not shown). 
     FIG. 14  shows the swivel locking device  314  in the unlocked state. When the user desires the wheels  318  to be unlocked so as to freely rotate around the stem, the user may bias the manipulating portion  402  of the operating member  324  held on the locked position, such that the operating member  324  may pivot downward with respect to the base  332 , whereby the bumps  408  of the operating member  324  engage with the second recesses  364  of the base  332 , i.e., the unlocked position of the operating member  324 . Because the locking pin  326  is supported by the biasing member  328 , and the biasing member  328  is held by a stud  405  disposed on the operating member  324 , when the operating member  324  pivots downward to the unlocked position, the biasing member  328  and the locking pin  326  may be caused to move downward, and the locking pin  326  may completely exit the positioning slot  386  formed in the seat  322 . As a result, the seat  322  and the base  332  may rotate with respect to each other, whereby the seat  322  and the wheel bearing assembly  320  including the base  332 , the shock absorber  334 , and the wheel bearing  330  may rotate with respect to each other. Therefore, the wheels  318  may freely rotate around the stem with respect to the stroller frame along with the wheel bearing assembly  320 . 
   When the user desires the wheels  318  to be locked so as not to freely rotate around the stem, the user may bias the manipulating portion  402  of the operating member  324  held on the unlocked position, such that the operating member  324  may pivot upward with respect to the base  332  to the locked position. However, as shown in  FIG. 15 , even the operating member  324  has been held on the locked position, if the seat  322  does not rotate with respect to the base  332  to a proper position where the top of the locking pin  326  is not aligned with the positioning slot  386  formed in the seat  322 , the top of the locking pin  326  may be blocked by the bottom surface of the rim  374  of the seat  322 , whereby the biasing member  328  is compressed. In the meantime, if the seat  322  rotates with respect to the base  332  to a proper position where the top of the locking pin  326  is aligned with the positioning slot  386 , since the bottom surface of the rim  374  of the seat  322  no longer blocks the top of the locking pin  326 , the locking pin  326  may be immediately biased by the compressed biasing member  328 , such that the top of the locking pin  326  enters the positioning slot  386  and the base  332  is automatically locked relative to the seat  322  as shown in  FIG. 13 . This automatic swivel locking effect may conveniently lock the wheels  318  so that the wheels  318  are prevented from freely rotating around the stem. 
   Although a few embodiments are given for detailed descriptions of the present invention, it is apparent to those skilled in the art that various change and modification are possible without departing from the spirit and the scope define by the claims of the present invention. In addition, the descriptions of the embodiments are for explanation but not for limitation of the scope defined by the claims and the equivalents of the present invention.