Patent Publication Number: US-7708119-B2

Title: Brake device for pushcart

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 11/151,852 filed Jun. 13, 2005, which claims priority to and the benefit of Chinese Patent Application No. 2005-00015554 filed on Jan. 28, 2005, the disclosures of which are fully incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a brake device for a pushcart, and more particularly to a brake device that includes an operating portion, which can be operated to lock two wheels. 
     A conventional brake device includes two operating members that can be actuated to lock two aligned wheels. The use of two separate operating members results in a troublesome braking process. Such a brake device is disclosed in U.S. Pat. Nos. 4,479,566 and 5,368,133. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide a brake device for a pushcart, which includes a single operating portion that can be actuated to lock and unlock two aligned wheels. 
     According to this invention, a brake device for a pushcart includes a main movable member disposed movably within a main seat, an auxiliary movable member disposed movably within an auxiliary seat, and a connecting member interconnecting the main and auxiliary movable members. The main movable member is biased to an upper limit position, and is movable to a lower limit position so as to engage a main brake pin with a groove in a main pin-engaging member that is connected fixedly to one wheel. Hence, the connecting member moves the auxiliary movable member from a first position to a second position so as to engage an auxiliary brake pin with a groove in an auxiliary pin-engaging member that is connected fixedly to another wheel. As a result, the wheels are locked. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of this invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
         FIG. 1  is an assembled perspective view of the first preferred embodiment of a brake device for a pushcart according to this invention; 
         FIG. 2  is a fragmentary exploded perspective view of the first preferred embodiment, illustrating a structure for locking one wheel; 
         FIG. 3  is a fragmentary exploded perspective view of the first preferred embodiment, illustrating a structure for locking another wheel; 
         FIG. 4  is a fragmentary perspective view of a cam groove portion of a main movable member of the first preferred embodiment; 
         FIG. 5  is a side view of the cam groove portion of the main movable member of the first preferred embodiment; 
         FIG. 6  is a fragmentary schematic view of the first preferred embodiment, illustrating an upper limit position of the main movable member; 
         FIG. 7  is a fragmentary schematic view of the first preferred embodiment, illustrating a lower limit position of the main movable member; 
         FIG. 8  is an assembled perspective view of the second preferred embodiment of a brake device for a pushcart according to this invention; 
         FIG. 9  is a fragmentary schematic view of the second preferred embodiment, illustrating an upper limit position of a main movable member; 
         FIG. 10  is a fragmentary schematic view of the second preferred embodiment, illustrating a lower limit position of the main movable member; 
         FIG. 11  is a fragmentary perspective view of the second preferred embodiment, illustrating a structure for locking one wheel; 
         FIG. 12  is a fragmentary schematic view of the second preferred embodiment, illustrating a first position of an auxiliary movable member; and 
         FIG. 13  is a fragmentary schematic view of the second preferred embodiment, illustrating a second position of the auxiliary movable member. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Before the present invention is described in greater detail in connection with the preferred embodiments, it should be noted that similar elements and structures are designated by like reference numerals throughout the entire disclosure. 
     Referring to  FIG. 1 , the first preferred embodiment of a brake device according to this invention is mounted on a pushcart. The pushcart has a cart frame  1  and a pair of aligned first and second wheels  2 ,  2 ′. 
     Referring to  FIGS. 1 ,  2  and  3 , the brake device includes a hollow main seat  3 , a hollow auxiliary seat  4 , a main movable member  5 , an auxiliary movable member  6 , a main brake mechanism  7 , an auxiliary brake mechanism  7 ′, a main positioning unit  8 , an auxiliary positioning unit  8 ′ and a drive unit  9 . 
     The main and auxiliary seats  3 ,  4  are disposed fixedly on the cart frame  1 , and are located respectively in proximity to the first and second wheels  2 ,  2 ′. Each of the main and auxiliary movable members  5 ,  6  is formed with a vertical slide slot  51 ,  61 . Each of the main and auxiliary seats  3 ,  4  is configured as an upright tube, and includes a lower end wall  31 ,  41  and a fixed retaining pin  32 ,  42 . The retaining pins  32 ,  42  are received respectively and slidably within the slide slots  51 ,  61 . Therefore, the main and auxiliary movable members  5 ,  6  are retained respectively on the main and auxiliary seats  3 ,  4 . The main movable member  5  has an outer surface that is formed with a cam portion  52 . The cam portion  52  has a tapered lower end  521 . The auxiliary movable member  6  also has an outer surface that is formed with a cam portion  62 . The cam portion  62  also has a tapered lower end (not shown). 
     A main biasing member  53  is configured as a coiled compression spring, and is disposed between the main movable member  5  and the lower end wall  31  of the main seat  3 . Thus, the main movable member  5  is biased by the main biasing member  53  to move upwardly away from the lower end wall  31  of the main seat  3  toward an upper limit position shown in  FIG. 6 . 
     An auxiliary biasing member  63  is configured as a coiled compression spring, and is disposed between the auxiliary movable member  6  and the lower end wall  41  of the auxiliary seat  4 . Thus, the auxiliary movable member  6  is biased by the auxiliary biasing member  63  to move upwardly from the lower end wall  41  of the auxiliary seat  4  toward a first position corresponding to the upper limit position of the main movable member  5 . 
     The main movable member  5  has an operating portion  54  that projects from the main seat  3  and that can be pressed so that the main movable member  5  moves to a lower limit position shown in  FIG. 7 . The auxiliary movable member  6  is also movable downwardly to a second position corresponding to the lower limit position of the main movable member  5 . 
     The main brake mechanism  7  includes a main pin-engaging member  71 , a main brake pin  72  and a main resilient member  73 . The auxiliary brake mechanism  7 ′ is similar in construction to the main brake mechanism  7 , and includes an auxiliary pin-engaging member  71 , an auxiliary brake pin  72  and an auxiliary resilient member  73 . The main and auxiliary pin-engaging members  71  are connected respectively and fixedly to the first and second wheels  2 ,  2 ′. Each of the main and auxiliary pin-engaging members  71  is formed with a plurality of ribs  711  (see  FIG. 6 ) that extend radially and outwardly therefrom. Any adjacent two ribs  711  define a pin-engaging groove  712  therebetween. 
     Each of the main and auxiliary seats  3 ,  4  is formed with a wall unit  30 ,  40  that has a hole  301 ,  401 . The main and auxiliary brake pins  72  extend respectively through the holes  301 ,  401  in the main and auxiliary seats  3 ,  4 . The main and auxiliary brake pins  72  have heads  721  disposed respectively within the main and auxiliary seats  3 ,  4 . The main and auxiliary resilient members  73  are configured as coiled compression springs, and are sleeved respectively on the main and auxiliary brake pins  72 . The main resilient member  73  is disposed between the head  721  of the main brake pin  72  and the wall unit  30  of the main seat  3 . Similarly, the auxiliary resilient member  73  is also disposed between the head  721  of the auxiliary brake pin  72  and the wall unit  40  of the auxiliary seat  4 . As such, the head  721  of each of the main and auxiliary brake pins  72  is biased to move away from the corresponding wall unit  30 ,  40 . This results in disengagement of the main and auxiliary brake pins  72  from the grooves  712  in the main and auxiliary pin-engaging members  71 . 
     The main positioning unit  8  can hold the movable member  5  at the upper and lower limit positions. The auxiliary positioning unit  8 ′ can hold the auxiliary member  6  at the first and second positions. Because the main and auxiliary positioning units  8 ,  8 ′ are similar in construction, only the main positioning unit  8  is described in detail below. 
     Referring to  FIGS. 2 ,  4  and  5 , the main positioning unit  8  includes a cam groove portion  81  and a resilient lock pin  82 . The lock pin  82  has a mounting end  821  mounted to an inner surface of the main seat  3 , and an L-shaped insert end  822  engaging the cam groove portion  81 . The cam groove portion  81  is formed on an outer surface of the main movable member  5 , and has a V-shaped projection  811 , and first, second, third and fourth slanting surfaces  812 ,  813 ,  814 ,  815 . The V-shaped projection  811  defines a groove  816  for engaging the lock pin  82 . The first, second, third and fourth slanting surfaces  812 ,  813 ,  814 ,  815  are disposed around the V-shaped projection  811 . Any two adjacent ones of the first, second, third and fourth slanting surfaces  812 ,  813 ,  814 ,  815  are interconnected by an inclined guiding surface  817  in a known manner so as to constitute a stepped annular groove structure around the V-shaped projection  811 . Thus, the insert end  822  of the lock pin  82  is guided to move around the V-shaped projection  811  in a predetermined direction shown by the arrows in  FIG. 5  along a path defined by the first, fourth, second and third slanting surfaces  812 ,  815 ,  813 ,  814 . When the insert end  822  of the lock pin  82  is disposed at the first slanting surface  812 , the main movable member  5  is locked at the upper limit position. When the operating portion  54  of the main movable member  5  is pressed to move the insert end  822  of the lock pin  82  onto the second slanting surface  813  via the fourth slanting surface  815 , the main movable member  5  is locked at the lower limit position. Subsequently, when the operating portion  54  of the main movable member  5  is again pressed, the insert end  822  of the lock pin  82  moves from the second slanting surface  813  onto the first slanting surface  812  via the third slanting surface  814 . 
     The drive unit  9  includes an outer tube  91 , a cable-guiding member  92 , and a connecting member  93  that is configured as a cable. The outer tube  91  is disposed between the main and auxiliary movable members  5 ,  6 , and has opposite first and second ends  911 ,  912 . The cable-guiding member  92  is disposed fixedly on an upper end of the main seat  3 . The connecting member  93  extends through the outer tube  91 , and has a driving end  931  projecting from the first end  911  of the outer tube  91 , and a driven end  932  projecting from the second end  912  of the outer tube  91 . The driving end  931  extends though the cable-guiding member  92  and the upper end of the main seat  3 , and is fastened to the cam portion  52  of the main movable member  5  at a position under the cable-guiding member  92 . Thus, when the main movable member  5  moves downwardly, the driving end  931  of the connecting member  93  is pulled downwardly away from the first end  911  of the outer tube  91 . The driven end  932  extends through the lower end wall  41  of the auxiliary seat  4 , and is fastened to a lower end of the auxiliary movable member  6 . Thus, when the driven end  932  of the connecting member  93  moves toward the second end  912  of the outer tube  91 , the auxiliary movable member  6  moves downwardly within the auxiliary seat  4 . 
     As such, when the main movable member  5  moves downwardly from the upper limit position to the lower limit position, the auxiliary movable member  6  moves downwardly from the first position to the second position. 
     When the main movable member  5  is disposed at the upper limit position, the head  721  of the main brake pin  72  is biased by the main resilient member  73  to press against the outer surface of the main movable member  5  at a position below the cam portion  52 , as shown in  FIG. 6 . As such, the main brake pin  72  is disengaged from the grooves  712  in the main pin-engaging member  71 . When the main movable member  5  is in the upper limit position, slack is provided in the connecting member  93 , and the auxiliary movable member  6  is biased by the auxiliary biasing member  63  to its upper limit position (i.e., the first position), as described above. Thus, the auxiliary brake pin  72  is also disengaged from the grooves  712  in the auxiliary pin-engaging member  71 . As a result, rotation of the first and second wheels  2 ,  2 ′ is allowed. 
     When the main movable member  5  is pressed to the lower limit position, the main brake pin  72  presses against the cam portion  52  of the main movable member  5 . Thus, the cam portion  52  moves the main brake pin  72  to engage one of the grooves  712  in the main pin-engaging member  71 . At the same time, corresponding movement of the connecting member  93  effects movement the auxiliary movable member  6  to the second position so as to engage the auxiliary brake pin  72  with one of the grooves  712  in the auxiliary pin-engaging member  71 . As a result, the first and second wheels  2 ,  2 ′ are locked, and the main movable member  5  and the auxiliary movable member  6  are held respectively at the lower limit position and the second position. 
     Subsequently, when the main movable member  5  is pressed once again, the main positioning unit  8  cooperates with the main biasing member  53  to move the main movable member  5  back to the upper limit position. On the other hand, the auxiliary positioning unit  8 ′ cooperates with the auxiliary biasing member  63  to move the auxiliary movable member  6  back to the first position. 
       FIGS. 8 ,  9 ,  10  and  11  show the second preferred embodiment of a brake device according to this invention. The structural and operational aspects of the second preferred embodiment different from those of the first preferred embodiment are described in the succeeding paragraphs. 
     The main seat  3  includes an integral horizontal tube  33  that has a proximate end  331  proximate to the main seat  3 , and a distal end  332  distal from the main seat  3 . The horizontal tube  33  is formed with an inner flange  333  and an outer flange  334  that extend respectively, radially and inwardly from the proximate end  331  and the distal end  332 . 
     The main brake pin  72  extends through the horizontal tube  33 , and has an engaging end  722  that is movable to engage one of the grooves  712  in the main pin-engaging member  71 , and a mounting end  723  that is opposite to the engaging end  722  and that has a cam follower  724 . The cam portion  52  of the main movable member  5  is disposed between the cam follower  724  and the horizontal tube  33 . The main brake pin  72  is provided with a fixed outward flange  74  that extends radially and outwardly therefrom and that is disposed between the inner and outer flanges  333 ,  334  of the horizontal tube  33 . The cam follower  724  of the main brake pin  72  is movable to engage the cam portion  52  of the main movable member  5 . The cam portion  52  of the main movable member  5  has a wide lower portion  522  and a narrow upper portion  523 . 
     The main resilient member  73  is configured as a coiled compression spring, and is sleeved on the main brake pin  72  between the inner flange  333  of the horizontal tube  33  and the outward flange  74  of the main brake pin  72 . Therefore, the main brake pin  72  is biased toward the main pin-engaging member  71 . 
     The auxiliary seat  4  has an upper end wall  43 . The auxiliary biasing member  63  is disposed between the auxiliary movable member  6  and the upper end wall  43  of the auxiliary seat  4 . As such, the auxiliary movable member  6  is biased to move downwardly away from the upper end wall  43  of the auxiliary seat  4  to the first position (i.e., its lower limit position). 
     The cable-guiding member  92  is formed integrally with the main seat  3 . The connecting member  93  is connected to the main movable member  5  in the same manner as in the first preferred embodiment. The drive unit  9  further includes another cable-guiding member  92 ′ formed integrally with the auxiliary seat  4  and connected to the auxiliary movable member  6  in the same manner in which the connecting member  93  is connected to the main movable member  5 . As such, downward movement of the main movable member  5  within the main seat  3  results in upward movement of the auxiliary movable member  6  within the auxiliary seat  4 . 
     When the main movable member  5  is disposed at the upper limit position shown in  FIG. 9 , the cam follower  724  of the main brake pin  72  engages the wide lower portion  522  of the main movable member  5  so that the main brake pin  72  is disengaged from the grooves  712  in the main pin-engaging member  71 . At this time, the auxiliary movable member  6  is biased by the auxiliary biasing member  63  downwardly to the first position shown in  FIG. 12 . In the first position, the cam follower  724  of the auxiliary brake pin  72  engages a wide upper portion  622  of the cam portion  62  of the auxiliary movable member  6 . As such, the auxiliary brake pin  72  is disengaged from the grooves  712  in the auxiliary pin-engaging member  71 . As a result, rotation of the first and second wheels  2 ,  2 ′ is allowed. 
     When the operating portion  54  of the main movable member  5  is pressed so that the main movable member  5  moves to the lower limit position shown in  FIG. 10 , the cam follower  724  of the main brake pin  72  engages the narrow upper portion  523  of the cam portion  52  of the main movable member  5 . Hence, the main brake pin  72  is biased by the main resilient member  73  to engage one of the grooves  712  in the main pin-engaging member  71 . At the same time, the connecting member  93  moves said auxiliary movable member  6  upwardly to the second position shown in  FIG. 13 . In the second position, the cam follower  724  of the auxiliary brake pin  72  engages a narrow lower portion  623  of the cam portion  62  of the auxiliary movable member  6 . Hence, the auxiliary brake pin  72  is biased by the auxiliary resilient member  73  to engage one of the grooves  712  in the auxiliary pin-engaging member  71 . As a result, the first and second wheels  2 ,  2 ′ are locked. 
     In this embodiment, the main positioning unit  8  (see  FIG. 2 ) is preserved, and the auxiliary positioning unit  8 ′ (see  FIG. 3 ) is omitted. 
     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.