Patent Document

BACKGROUND 
     (a) Technical Field 
     The present invention relates to a cart caster that is installed on each of the edges of a bottom surface of a manned and unmanned cart to carry a product through a rolling motion, and more particularly, to a cart caster that is automatically converted into a fixed or rotating caster according to a forward/backward traveling direction of a cart to ensure safe travel and thereby easily carry a product and improve work conditions. 
     (b) Background Art 
     In general, the cart caster is installed on each of the edges of a bottom surface of a manned and unmanned cart to carry a heavy product to a destination through a rolling motion. Conventionally, the caster is installed at the bottom surface so that an operator directly push the cart to transport. Recently a power cart having an electric power means to transport and an unmanned cart automatically transporting along rails installed at the floor are used. 
     Along with the development of the cart, the caster that is installed at the bottom surface of the cart has also been continuously developed. For example, a fixed type caster which enables the cart to move forward/backward only by simple rolling motion by being attached to the bottom surface of the cart was used in the past, a rotary caster which makes the change of the direction of the cart easy is used recently. In case of the caster configuration mounted with four casters consisted of two fore wheels and two rear wheels, the swivel type is used for the fore wheel and the fixed type is used for the rear wheel for easy change of the direction and safe travel. If the rotary casters are used for both of the fore wheel and the rear wheel, the caster may deviate from the right passage or the product may be dropped because a severe shaking may occur while rolling the cart. Thus, such caster combination is not used except special cases. 
     In addition, if the swivel type is used for the caster corresponding to the fore wheel and the fixed type is used for the caster corresponding to the rear wheel, the safe travel is secured while moving forward. However, when the cart is moving backward in that configuration, the caster corresponding to the fore wheel becomes the fixed type and the caster corresponding to the rear wheel becomes the swivel type. In this case, the change of the direction is accomplished by the rotation of the rear wheel, and the safe travel is not secured. Thus, for safe travel, the user needs to turn the cart around so that the rotary caster is always positioned at the position of the fore wheel. Of course, if the space around the working place is sufficiently large so that the cart can be turned around and travelled, then there will not be significant problems. However, if it is difficult to turn the cart around, there can be problems in the travel. 
     Therefore, a caster which can be converted into the fixed type and the swivel type was developed. The typical one for this caster is the Korea published laid-open utility 20-1998-053584. 
     Referring to this publication, it consists of a swivel plate and a fixed plate and has a fixing bolt, so that it can be used as the fixed type or swivel type caster by coupling or separating the fixing bolt if necessary. After installing this caster to the cart, when moving forward, the fixing bolt is separated from the caster corresponding to the fore wheel so as to construct the swivel type and the fixing bolt is coupled to the caster corresponding to the rear wheel so as to construct the fixed type, and when moving backward, to the contrary, the fixing bolt is separated from the caster corresponding to the rear wheel and the fixing bolt is coupled to the caster corresponding to the fore wheel, then the safe travel will be possible. However, there is a disadvantage that such operation should be manually carried out by the operator so that great inconveniences occur. 
     SUMMARY OF THE DISCLOSURE 
     The present invention has been made in an effort to solve the above-described problems and an object of the present invention is to provide a cart caster which can be automatically converted into a fixed caster or rotating caster according to the forward/backward movement of the cart so as to ensure safe travel in order to easily carry a product and improve work conditions. 
     The present invention to accomplish the above mentioned object comprises: a fixing plate configured to be fixedly installed at a bottom surface of the cart, wherein a coupling section is formed at a middle of a bottom surface of the fixing plate and a coupling recess is formed at one side of the coupling section; a bracket having a coupling shaft configured to rotationally couple to the coupling section formed at the fixing plate, the coupling shaft being formed at an upper surface thereof, and having an inserting hole positioned at the same vertical line as the coupling recess, the inserting hole being formed at one side thereof; a wheel eccentrically mounted to a lower side of inside of the bracket so as to perform a rolling motion; and a swiveling conversion unit comprising: a swiveling plate installed at an upper side of the inside of the bracket with a rotating shaft so as to be able to perform a seesaw motion; a fixing pin installed at one end side of the swiveling plate and configured to be inserted in the coupling recess of the fixing plate by upwardly penetrating the inserting hole of the bracket so as to restrain a swivel of the fixing plate and the bracket; and a rotating member installed at an other end side of the swiveling plate, wherein the rotating member is raised or lowered according to a rotation direction of the wheel by being closely contacted to the wheel so as to lower or raise the fixing pin installed at the one end side so that the fixing pin is separated from the coupling recess of the fixing plate so as to make the bracket to be able to swivel or the fixing pin is coupled to the coupling recess so as to make the bracket to be fixed. 
     Preferably, the rotating member comprises: a support plate coupled to the other end side of the swiveling plate with a hinge shaft so as to be rotatable, wherein a slot is formed at one side of the support plate and an auxiliary wheel is installed at lower end of the support plate with a one-way bearing so as to be rotated in only one direction according to the rotation direction of the wheel by being closely contacted to the outer surface of the wheel, a support pin coupled to one side of the swiveling plate and coupled to the slot of the support plate so as to limit the rotation radius of the support plate, and an elastic member installed at the swiveling plate to provide an elastic force so as to lower downwardly the support plate so that the auxiliary wheel provided at the lower end of the support plate is closely contacted to the wheel. 
     According to the present invention, since the cart caster is automatically converted into a fixed or rotating caster by an operation of a swiveling conversion unit including an auxiliary wheel that is closely contacted to a wheel according to the forward/backward movement of the cart so as to rotate in only one direction and a fixing pin inserted into a coupling hole of a fixing plate, the present invention has an effect that safe travel may be ensured in order to easily carry a product and improve work conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a cart caster according to a preferred embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the cart caster according to a preferred embodiment of the present invention; 
         FIG. 3  is a perspective view showing a fixing plate according to a preferred embodiment of the present invention turned upside down; 
         FIG. 4( a )  is an enlarged perspective view of the cart caster according to a preferred embodiment of the present invention,  FIG. 4( b )  is a partly exploded perspective view, and  FIG. 4( c )  is a sectional view along a line A-A of (a) showing coupling relation; 
         FIG. 5  is a sectional view along a line B-B of  FIG. 1  showing coupling relation of the fixed and rotating caster according to a preferred embodiment of the present invention; 
         FIGS. 6( a ) to 6( c )  are perspective views showing operation relations of the cart caster according to a preferred embodiment of the present invention; and 
         FIGS. 7( a ) and 7( b )  are schematic side views showing conditions of use of the cart caster according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The cart caster according to the present invention will be described below in detail with reference to the accompanying drawings. 
     Before describing, it should be mentioned that the terminologies or the words used in the present specification and the claims should not be interpreted by limiting to the usual or dictionary-defined meanings but should be interpreted according to the meanings and the concepts appropriate to the technical thoughts of the present invention based on the principle that the inventor can appropriately define the concept of terminologies to best describe his invention. 
     Therefore, it should be understood that since an embodiment described in the present specification and the structures shown in the drawings are only the most preferred embodiment of the present invention and do not represent all technical thoughts of the present invention, there can be various equivalents and changes which can substitute the technical thoughts at the time of the present application. 
       FIG. 1  is a perspective view of a cart caster according to a preferred embodiment of the present invention,  FIG. 2  is an exploded perspective view of the cart caster according to a preferred embodiment of the present invention, and  FIG. 3  is a perspective view showing a fixing plate according to a preferred embodiment of the present invention turned upside down. 
     Referring to  FIGS. 1 and 2 , the cart caster  10  of the present invention includes a fixing plate  100 , a bracket  200 , a wheel  300 , and a swiveling conversion unit  400 . 
     First, the fixing plate  100  is fixedly installed at a lower surface, that is, a bottom surface of the cart and is formed in a form of sheet as shown in  FIG. 3 , and a coupling section  110  is formed at the middle of the bottom surface thereof and a coupling recess  120  is formed at one side of the coupling section  110 . Of course, bolt holes and the like not denoted with reference number are formed at edge portion of the fixing plate  100  for coupling to the cart. In addition, a bearing  130  is provided at inner circumference surface of the coupling section  110  for smooth rotation when it is coupled to a coupling shaft  210  of the bracket  200  which will be described later. 
     Next, the bracket  200  has a shape opened forward/backward and to lower side, and the coupling shaft  210  configured to rotationally couple to the coupling section  110  formed at the fixing plate  100  is formed at an upper surface of the bracket, and an inserting hole  220  is formed at one side, and the inserting hole  220  is formed to be positioned at the same vertical line as the coupling recess  120  formed at the fixing plate  100 . In addition, first and second penetration holes  230 ,  240  are formed at a lower side and an upper side of both side walls of the bracket  200 , and the second penetration hole  240  is not formed at an identical vertical line as the first penetration hole  230  but eccentrically formed. 
     Next, the wheel  300  is eccentrically mounted to a lower side of inside of the bracket  200  using a support shaft  310  inserted to the second penetration hole  240  so as to perform a rolling motion, and is a kind of wheel being widely used. 
     Finally, the swiveling conversion unit  400  is installed to be positioned at an upper side of the inside of the bracket  200 , that is, the upper side of the wheel  300  mounted at the bracket  200 , so as to be automatically operated to come into a condition in which the bracket  200  and the fixing plate  100  swivel or come into a condition in which they are fixed according to the rotation direction of the wheel  300 , wherein the swiveling conversion unit comprises a swiveling plate  410  installed at the bracket  200  with a rotating shaft  412  coupled to the first penetration hole  230  of the bracket  200  so as to be able to perform a seesaw motion, a fixing pin  420  installed at one end side of the swiveling plate  410 , and a rotating member  430  installed at the other end side of the swiveling plate  410 . A detailed structure and operation relation of the swiveling conversion unit  400  will be reviewed again below. 
       FIG. 4( a )  is an enlarged perspective view of the cart caster according to a preferred embodiment of the present invention,  FIG. 4( b )  is a partly exploded perspective view, and  FIG. 4( c )  is a sectional view along a line A-A of (a) showing coupling relation. 
     Referring to the drawings, the swiveling conversion unit  400  comprises the swiveling plate  410 , the fixing pin  420  and the rotating member  430  as reviewed above. 
     First, the swiveling plate  410  is mounted at the first penetration hole  230  of the bracket  200  not shown in these drawings with the rotating shaft  412  so as to be able to perform the seesaw motion. 
     Next, the fixing pin  420  is installed at one end side, that is, rear end of the swiveling plate  410  so as to be protruded upward, and is configured to be inserted into the coupling recess  120  of the fixing plate  100  by being protruded upward through the inserting hole  220  of the bracket  200  not shown in these drawings. The coupling relation thereof will be reviewed below. 
     Next, the rotating member  430  is installed at the other end side, that is, forward end of the swiveling plate  410  and comprises a support plate  432 , a support pin  437  and an elastic member  438 , wherein a support plate  432  is coupled to the other end side of the swiveling plate  410  with a hinge shaft  433  so as to be rotatable, and a slot  434  is formed at one side of the support plate, and an auxiliary wheel  435  is installed at lower end of the support plate with a one-way bearing so as to be rotated in only one direction according to the rotation direction of the wheel  300  by being closely contacted to the outer surface of the wheel  300  not shown in these drawings, wherein the support pin  437  is coupled to one side of the swiveling plate  410  and is coupled to the slot  434  of the support plate  432  so as to limit the rotation radius of the support plate  432 , and wherein one end of the elastic member  438  is installed at one side of the swiveling plate  410  and its other end is extended to the support plate  432  and provides an elastic force so as to lower downwardly the support plate  432  so that the auxiliary wheel  435  provided at the lower end of the support plate is closely contacted to the wheel  300  not shown in these drawings and to push upwardly the fixing pin  420  positioned at the opposite side. 
     The one-way bearing  436  for mounting the auxiliary wheel  435  is also referred to as a one-way clutch and is constructed to rotate in only one direction, clockwise or counterclockwise. The one-way bearing is being widely used and the description thereof will be omitted. 
     The support pin  432  is inserted into the slot  434  formed at the support plate  432 , and is to limit the rotation range of the support plate  432  rotationally coupled with the hinge shaft  433 . The support plate  432  can rotate clockwise or counterclockwise with the hinge shaft  433  as a center of rotation. 
     The cart caster of the present invention is configured and operated as follows. 
       FIG. 5  is a sectional view along a line B-B of  FIG. 1  showing coupling relation of the cart caster according to a preferred embodiment of the present invention, and  FIGS. 6( a ) to 6( c )  are perspective views showing operation relations of the cart caster according to a preferred embodiment of the present invention. 
     First, referring to  FIG. 5 , the coupling shaft  210  of the bracket  200  is inserted and coupled to the coupling section  110  formed at the bottom surface of the fixing plate  100 , and the wheel  300  is eccentrically mounted below the bracket  200  via the support shaft  310 . The inserting hole  220  formed at one side of the bracket  200  and the coupling recess  120  formed at one side of the bottom side of the fixing plate  100  are positioned at a same vertical line. In addition, the swiveling conversion unit  400  is installed at inner upper side of the bracket  200 . That is, the swiveling plate  410  of the swiveling conversion unit  400  is coupled to the bracket  200  with the rotating shaft  412  so as to be able to perform a seesaw motion, and the fixing pin  420  installed at one end side of the swiveling plate  410  upwardly penetrates the inserting hole  220  of the bracket  200  and is inserted into the coupling recess  120 . The fixing plate  100  and the bracket  200  cannot swivel in this condition. 
     The swiveling member  430  is installed at the other end side of the swiveling plate  410 . That is, the supporting plate  432  of the rotating member  430  is rotationally coupled to the swiveling plate  410  with the hinge shaft  433 . However, the rotation range of the supporting plate  432  is restricted by the supporting pin  437  coupled to the slot  434  formed at one side. The auxiliary wheel  435  is mounted at the bottom part of the supporting plate  432 , and is installed with the one-way bearing  436  so as to be rotatable in only one direction. For example, the auxiliary wheel  435  is constructed to be able to rotate clockwise but not able to rotate counterclockwise. 
     In addition, the elastic member  438  provided at one side of the swiveling plate  410  is mounted so as to provide the elastic force on the upper side of the supporting plate  432  mounted with the auxiliary wheel  435  so that the auxiliary wheel  435  is always closely contacted to the wheel  300 . 
     The caster of the present invention is operated as in  FIG. 6 . 
     That is, as shown in  FIG. 6( a ) , when the fixing plate  100  is advanced in the arrow direction while the wheel  300  is abutted against the ground, the wheel  300  is rotated counterclockwise and starts rolling motion. In addition, as described before, the auxiliary wheel  435  of the rotating member  430  closely contacted to the wheel  300  rotates clockwise while maintaining a condition of being able to rotate clockwise and being closely contacted to the wheel  300 . In this condition, the caster becomes a fixed type which cannot be swiveled because the bracket  200  is connected to the fixing plate  100  with the fixing pin  420 . 
     As shown in  FIG. 6( b ) , when the caster  10  which was advancing is moved backward in the arrow direction, the wheel  300  is rotated clockwise, and the auxiliary wheel  435  closely attached contacted to this wheel should be rotated counterclockwise.—But, it cannot be rotated counterclockwise due to the one-way bearing  436 . Although the auxiliary wheel  435  cannot be rotated, since it is closely contacted to the rotating wheel  300  due to the elastic member  438  and the supporting plate  432  mounted with the auxiliary wheel  435  is rotationally provided to the swiveling plate  410  with the hinge shaft  433 , the supporting plate  432  is rotated counterclockwise with the hinge shaft  433  as the center of rotation due to the friction of the auxiliary wheel  435  and gradually rises. Due to this rising of the supporting plate  432 , the swiveling plate  410  is rotated clockwise around the rotating shaft  412  so as to make the fixing pin  420  to be lowered and separated from the coupling recess  120  of the fixing plate  100 . Since the slot  434  is formed at the supporting plate  432  and the supporting pin  437  is inserted into this slot  434 , the rotation range of the supporting plate  432  is limited to the length of the slot  434  and the length of the slot  434  is formed to such an extent that the fixing pin  420  installed at the swiveling plate  410  can be separated from the coupling recess  120  of the fixing plate  100 . 
     In this way, when the fixing pin  420  is separated from the coupling recess  120  of the fixing plate  100 , the bracket  200  becomes a swivel type. In this condition, if further traveled as shown in  FIG. 6( c ) , the wheel  300  eccentrically mounted to the bracket  200  is rotated together with the bracket  200  and the auxiliary wheel  435  is positioned at the fore end in the direction of travel. If the change of direction is accomplished in this way, the fixing pin  420  is positioned at the side opposite to coupling recess  120  formed at the fixing plate  100 . That is, since the fixing pin  420  cannot connect the bracket  200  and the fixing plate  100  but abuts the bottom surface of the fixing plate  100 , it provides the swivel caster in which the bracket  200  swivels. In addition, the auxiliary wheel  435  closely contacted to the wheel  300  due to the change of the direction of the bracket  200  is rotated counterclockwise which is opposite direction to the initially shown in  FIG. 6( a ) . 
     If the fixing plate  100  of the caster is moved again in the advancing direction as in  FIG. 6( a ) , the change of the direction is accomplished to the condition of  FIG. 6( a )  due to the wheel  300  eccentrically mounted to the bracket  200  and the auxiliary wheel  435  which was raised due to the elastic member  438  is also lowered to make the fixing pin  420  provided at the other end side to be raised and inserted in the coupling recess  120  of the fixing plate  100 . 
     As described above, it can be seen that the caster  10  of the present invention can be automatically converted from the fixed type to the swivel type according to the direction of travel of the wheel  300 , and such caster is installed to the cart as follows. 
       FIGS. 7( a ) and 7( b )  are schematic side views showing conditions of use of the cart caster according to a preferred embodiment of the present invention. 
     First, referring to  FIG. 7( a ) , the caster  10  of the present invention is installed at the bottom surface of the cart  500  with the fixing plate  100  so as to construct the fore wheel and the rear wheel. When the caster  10  corresponding to the fore wheel is attached, the caster  10  is attached in the condition in which the fixing pin  420  of the swiveling conversion unit  400  upwardly protruded through the bracket  200  is not inserted into the coupling recess  120  by rotating the fixing plate  100  and by making the coupling recess  120  formed at the fixing plate  100  to be positioned at the front side, and when the caster  10  corresponding to the rear wheel is attached, it is attached under the condition in which the fixing pin  420  is inserted into the coupling recess  120  of the fixing plate  100 . That is, when the casters  10  are attached for the first time, the caster  10  corresponding to the fore wheel is attached in a swivel type, and the caster  10  corresponding to the rear wheel is attached in a fixed type. 
     In this condition, if the cart  500  is moved forward in the arrow direction, the wheels  300  corresponding to the fore wheel and the rear wheel are rotated counterclockwise so as to move the cart  500 . Since the auxiliary wheel  435  of the swiveling conversion unit  400  closely contacted to this wheel  300  is rotated clockwise while being closely contacted as reviewed above and the fixing pin  420  of the caster  10  corresponding to the fore wheel is separated from the coupling recess  120  of the fixing plate  100 . The bracket  200  and the fixing plate  100  are moved by the rolling motion of the wheel  300  in a swivel type in which the change of direction can be made easily. To the contrary, since the fixing pin  420  of the caster  10  corresponding to the rear wheel is inserted into the coupling recess  120  of the fixing plate  100 , the bracket  200  and the wheel  300  are moved by the rolling motion of the wheel  300  while being fixed. 
     In that condition, if the cart  500  is moved rearward as in  FIG. 7( b ) , since the caster  10  corresponding to the fore wheel is swivel type, it is naturally converted in its direction due to the wheel  300  eccentrically mounted, and the fixing pin  420  is inserted into the coupling recess  120  formed at the fixing plate  100  so as to be automatically changed to fixed type. To the contrary, in case of the caster  10  corresponding to the rear wheel, the auxiliary wheel  435  closely contacted due to the change of the rotation direction of the wheel  300  under the fixed type condition is raised by the frictional force so as to separate the fixing pin  420  from the coupling recess  120  of the fixing plate  100 , and the bracket  200  is converted in its direction due to the eccentrically mounted wheel  300  so that the fixing pin  420  is positioned at the side opposite to the coupling recess  120  and is automatically changed to the swivel type. That is, if the cart  500  is moved rearward, the rear wheel acts as the fore wheel and the fore wheel acts as the rear wheel. 
     As described above, in the caster  10  of the present invention attached at the bottom side of the cart  500 , since the caster  10  positioned at the front side of the travel direction is automatically converted to the swivel type and the caster  10  positioned at the rear side of the travel direction is automatically converted to the fixed type according to the travel direction of the cart  500 , the safety of the transportation at the time of forward/backward motion of the cart  500  is secured. In addition, the convenience of the use is considerably improved since the conversion to the fixed type and the swivel type is automatically accomplished. 
     In the meantime, since the cart  500  is widely known, it is briefly shown. However, it should be appreciated that it includes all carts for transporting articles such as the unmanned carrier, manned cart, etc. 
     The above content has described the characteristics and the technical advantages of the present invention more or less widely to help understand the claims of the present invention well. It should be appreciated by those skilled in the art that the described concepts and particular embodiments of the present invention can be immediately used as a basis for a design of other structures or a change to carry out objects similar to that of the present invention. 
     In addition, it should be appreciated by those skilled in the art that the described concepts and embodiments of the present invention can be a basis for amending to or designing other structure to carry out same objects as the present invention, and such amendments and the changed equivalent structure made by those skilled in the art can have various alternatives, substitutions and modifications within the spirit and scope of the invention as defined by the appended claims.

Technology Category: 7