Abstract:
A wear-premonitory carbon brush holder includes a holder body and a premonitory circuit. A carbon brush that is received in the holder body is reciprocately moveable in the holder body along a predetermined path. The premonitory circuit has a sensing unit mounted on the holder body for activating the premonitory circuit to generate a predetermined action or a warning signal when the carbon brush moves in the holder body to a predetermined position.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to carbon brushes for use in motors, and more particularly to a wear-premonitory carbon brush holder.  
         [0003]     2. Description of the Related Art  
         [0004]     As shown in  FIG. 1 , a conventional carbon brush holder  1  includes a holder body  11  for accommodating a spring A and a carbon brush B. The spring A has an end contacting against an internal end of the holder body  11  and the other end contacting against an end of the carbon brush B; meanwhile, the carbon brush B is pushed by the spring A to contact against the rotor C of the motor and then transfers the electric current to the rotor C to drive the rotor C to rotate.  
         [0005]     Because the friction generated between the carbon brush B and the rotor C wears the carbon brush B, the carbon brush B needs the resilience generated by the spring A to keep contacting against the rotor C. However, the resilience of the spring A will be gradually reduced when the spring A is self-extended along with the wear of the carbon brush B. When the carbon brush B is worn to a certain degree, the spring A fails to provide sufficient resilience to enable the carbon brush B to keep contacting against the rotor C, such that a gap will be formed between the carbon brush B and the rotor C to incur imperfect contact therebetween to further generate arc sparks. Thus, when the motor mounted with the carbon brush holder  1  is operated, the operator has to frequently check the wear degree of the carbon brush B and replace the carbon brush B when the carbon brush B is worn to a certain degree.  
         [0006]     As shown in  FIG. 2 , another conventional carbon brush holder  2  is different from the aforementioned carbon brush holder  1  by that the spring D is a constant-force spring that generates balanced constant resilience to avoid the generation of the aforementioned arc sparks; however, the operator still has to frequently check the wear degree of the carbon brush  2 .  
       SUMMARY OF THE INVENTION  
       [0007]     The primary objective of the present invention is to provide a carbon brush holder that premonishes the operator to replace the carbon brush when the carbon brush is worn to a certain degree, and thereby it is unnecessary to frequently check whether the carbon brush is worn out and needs to be replaced.  
         [0008]     The foregoing objective of the present invention is attained by the wear-premonitory carbon brush holder that is composed of a holder body and a premonitory circuit. A carbon brush is received in the holder body and slidably reciprocates along a predetermined path. The premonitory circuit has a sensing unit mounted on the holder body for activating the premonitory circuit to generate a predetermined action or a warning signal when the carbon brush moves to a predetermined position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic view of a conventional carbon brush working with a rotor of a motor;  
         [0010]      FIG. 2  is a schematic view of another conventional carbon brush working with a rotor of a motor;  
         [0011]      FIG. 3  is a sectional view of a first preferred embodiment of the present invention, showing that a tongue is away from a spring;  
         [0012]      FIG. 4  is another sectional view of the first preferred embodiment of the present invention, showing that the tongue contacts the spring;  
         [0013]      FIG. 5  is a sectional view of a second preferred embodiment of the present invention;  
         [0014]      FIG. 6  is a sectional view of a third preferred embodiment of the present invention;  
         [0015]      FIG. 7  is a sectional view of a fourth preferred embodiment of the present invention;  
         [0016]      FIG. 8  is a top view of a fifth preferred embodiment of the present invention;  
         [0017]      FIG. 9  is a sectional view of the fifth preferred embodiment of the present invention, showing that a carbon brush contacts the tongue;  
         [0018]      FIG. 10  similar to  FIG. 9  shows that the tongue is away from the carbon brush;  
         [0019]      FIG. 11  is a front sectional view of a sixth preferred embodiment of the present invention;  
         [0020]      FIG. 12  is a right sectional view of the sixth preferred embodiment of the present invention, showing that an actuating bar is oppressed;  
         [0021]      FIG. 13  is another right sectional view of the sixth preferred embodiment of the present invention, showing that the actuating bar is not exerted by a force; and  
         [0022]      FIG. 14  is a sectional view of a seventh preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Referring to  FIG. 3 , a carbon brush holder  3  constructed according to a first preferred embodiment of the present invention is composed of a holder body  20  and a premonitory circuit  30 .  
         [0024]     The holder body  20  includes a base  21  and a copper barrel  22  in which an elongated receiving slot  23  that has an opening is provided. A spring A and a carbon brush B are accommodated in the receiving slot  23  through the opening. The holder body  20  has a through hole  24  running through the inner and outer walls of the copper barrel  22 .  
         [0025]     The premonitory circuit  30  includes a sensing unit  31  and an alarm indicator  32 , which is embodied as a warning lamp in this preferred embodiment. The sensing unit  31  is formed of an insulated plug  33  and an electrically conductive member which is embodied as a copper springy tongue  34  in this embodiment. The insulated plug  33  is securely disposed in the through hole  24  of the copper barrel  22 . The springy tongue  34  is inserted into a midsection of the insulated plug  33  and has a free end extending into the receiving slot  23  and the other end electrically connected with the alarm indicator  32  of the premonitory circuit  30  by wire. When the carbon brush B is worn to a certain degree, the spring A that is self-extended due to the wear of the carbon brush B contacts the free end of the springy tongue  34  as shown in  FIG. 4 .  
         [0026]     Referring to  FIG. 4 , when an end of the carbon brush B keeps contacting against a surface of a rotor E of a motor to be worn, the spring A resiliently extends forwards to keep the worn end of the carbon brush B contacting against the surface of the rotor E. When the spring A resiliently extends further for a length to contact the springy tongue  34 , the electric current flows through the connection between the spring A and the springy tongue  34  to electrically conduct the premonitory circuit  30  to further activate the alarm indicator  32  to function.  
         [0027]     When the carbon brush B is worn for a predetermined length, the premonitory circuit  30  generates a predetermined action or transmits a warning signal to prompt the operator to replace the worn carbon brush B, such that the operator will not have to frequently check the wear degree of the carbon brush B and decide whether the carbon brush B needs to be replaced. Hence, the present invention saves lots of time of checking for the operator to avoid the carbon brush B from being worn-out that causes sudden stop of the motor to further incur abnormal operation.  
         [0028]     The sensing unit of the premonitory circuit and the warning signal can be any alternatives that alert the operator to replace the carbon brush when the carbon brush is worn to a certain degree.  
         [0029]     Referring to  FIG. 5 , the carbon holder  4  constructed according to a second preferred embodiment of the present invention is shown different from the aforementioned first preferred embodiment by that the premonitory circuit  30  further includes a normally open switch loop  35  and a warning unit (not shown), which can be embodied as a buzzer, an alarm indicator, and so on, in addition to the sensing unit  31 . When the carbon brush B is worn to a certain degree, the spring A extends to contact the springy tongue  34  to be electrically connected with the switch loop  35  to further activate the warning unit to function.  
         [0030]     Referring to  FIG. 6 , the carbon holder  5  constructed according to a third preferred embodiment of the present invention is different from the second preferred embodiment by that the premonitory circuit  40  further includes a sensing unit  41  having an insulated plug  43 , a first tongue  44  and a second tongue  45  in addition to the normally open switch loop  42  and the warning unit (not shown). The first and second tongues  44  and  45  are inserted inside the insulated plug  43  and parallel spaced apart from each other for a predetermined distance. The first and second tongues  44  and  45  each have a free end extending into the receiving slot  23  of the holder body  20  to be at a position which the spring A can contact while the spring A extends, and other end connected with the premonitory circuit  40 . Thus, the two tongues  44  and  45  contact each other to electrically conduct the switch loop  42  to activate the warning unit to function.  
         [0031]     When the carbon brush B is worn to enable the spring A to extend to a predetermined position, the spring A contacts and pushes the first tongue  44  to bend, then the first tongue  44  contacts the second tongue  45  to enable the switch loop  42  of the premonitory circuit  40  to be electrically conducted, and further the warning unit transmits a warning signal or action.  
         [0032]     Referring to  FIG. 7 , the carbon holder  6  constructed according to a fourth preferred embodiment of the present invention is characterized in that the premonitory circuit  50  includes a sensing unit  51  having a first tongue  53  and a second tongue  54  and an insulated plug  55 , a normally close switch loop  52  and a warning unit (not shown). The free ends of the first and second tongues  53  and  54  are slightly set to contact each other without bearing a force. In addition, the first tongue  53  is positioned close to the opening of the holder body  20  more than the second tongue  54  does, and the length that the first tongue  53  extends into the receiving slot  23  is longer than the second tongue  54 . When the carbon brush B is worn to enable the spring A to extend for a predetermined length, the first tongue  53  is contacted by the spring A to be pushed to further disengage from the second tongue  54 , such that the switch loop  52  is off to activate the warning unit to transmit a warning signal.  
         [0033]     Referring to  FIGS. 8-10 , the carbon brush holder  7  constructed according to a fifth preferred embodiment of the present invention is characterized in that the premonitory circuit  60  includes a sensing unit  61  having a tongue  63  and an insulated plug  64 , a normally close switch loop  62  and a warning unit (not shown). The tongue  63  is inserted inside the insulated plug  64  that is mounted on the holder body  20  and has a free end extending to the receiving slot  23  to keep contacting the carbon brush B. When the tongue  63  disengages from the carbon brush B, the normally close switch loop  62  is off to activate the warning unit.  
         [0034]     Referring to  FIGS. 11-13 , the carbon brush holder  8  constructed according to a sixth preferred embodiment of the present invention is composed of a holder body  70  and a premonitory circuit  80 .  
         [0035]     The holder body  70  includes a receiving slot  71  and a through hole  72 . The receiving slot  71  has an opening at a top end thereof for accommodating a constant-force spring D and a carbon brush B. The through hole  72  is positioned on the holder body  70  away from the opening of the receiving slot  71  and runs through the holder body for communication between inside and outside of the holder body  70 .  
         [0036]     The premonitory circuit  80  includes a resilient switch  81 , a normally open switch loop (not shown), and a warning unit (not shown). The resilient switch  81  is composed of a shell  83 , a spring  84 , and an actuating bar  85 . Each of the shell  83  and the actuating bar  85  is provided with a conductive piece  86 . When the actuating bar  85  is not exerted by any of forces, the spring  84  pushes the actuating bar  85  to enable the two conductive pieces  86  to contact each other. When the actuating bar  85  is exerted by a force, the actuating bar  85  is driven to moves towards inside of the shell  83  to compress the spring  84  to isolate the two conductive pieces  86 , as shown in  FIG. 12 . The resilient switch  81  is mounted inside the through hole  72  of the holder body  70 . Normally, the actuating bar  85  is pushed by the carbon brush B at an end thereof to move towards inside the shell  93  to compress the spring  84 , as sown in  FIG. 12 . The switch loop is designed being electrically conducted by the contact of the two conductive pieces  87  to further activate the warning unit.  
         [0037]     When the carbon brush B is worn to be pushed outwards by the constant-force spring D to disengage from the actuating bar  85 , the spring  84  pushes the actuating bar  85  to move towards the carbon brush B to enable the conductive piece  86  of the actuating bar  85  to contact the conductive piece  86  of the shell  83 , as shown in  FIG. 13 , and the switch loop is electrically conducted to activate the warning unit to transmit a warning signal.  
         [0038]     Referring to  FIG. 14 , the carbon brush holder  9  constructed according to a seventh preferred embodiment of the present invention is different from the aforementioned preferred embodiments by that the sensing unit  90  is composed of an infrared transmitter and an infrared receiver. The carbon brush B interrupts the communication between the infrared transmitter and the infrared receiver in a normal condition. When the carbon brush B is worn for a predetermined length, the carbon brush B moves away to remove the interruption of the communication and then the receiver can receive the signal transmitted from the transmitter, thereby activating the premonitory circuit  92  to transmit the warning signal.  
         [0039]     Furthermore, the sensing unit of the present invention can alternatively be other sensors, such as a sensor that detects the difference of colors or materials.