Abstract:
A rotary paddle level switch has a housing, a driving unit, two switches, a resilient member, a clutch, a transmission shaft, and a propeller. A resilient clip of the clutch holds a non-circular actuation section of the transmission shaft. When the driving unit drives the clutch to rotate, the transmission shaft and the propeller are driven by the clutch. When the propeller is rapidly rotated by suddenly exerting an excessively large external force thereon, as the resilient clip holds the transmission shaft by elastic force, the fast rotating transmission shaft removes itself from the holding of the resilient clip and is rotated without driving the resilient clip to rotate, thereby avoiding the transmission of the external force and damage to the driving unit. As the clutch just needs a clutch stand and a resilient clip to achieve the foregoing function, the level switch is structurally simple and relatively inexpensive.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a level switch, and more particularly to a rotary paddle level switch applied to detect material level of warehouse. 
     2. Description of the Related Art 
     Level switches are applicable to material management of warehouse, and serve to monitor the availability of material in warehouse or to detect the level of material stored in warehouse. The material in a warehouse may be any kind of material with a constant specific weight, such as, animal feed, grain, peanut, malt, clay, sand, limestone, rock, sawdust, lumber, metal, rubber, resin, plastic pellet, regrinding plastic, coal, cast material, and the like. Level switches can be classified as rotary paddle level switches, vibrating fork level switches, and capacitive level switches according to design concepts of the level switches. 
     A conventional rotary paddle level switch has a housing, a driving unit, a first switch, a second switch, a torque spring, a transmission shaft, and a propeller. The driving unit is pivotally mounted inside the housing, and has a pressing rod mounted away an axial direction and extending in an eccentric direction. The two switches are mounted inside the housing. One end of the torque spring abuts against an inner wall of the housing, and the other end of the torque spring pushes against the pressing rod such that the pressing rod abuts against the first switch. The transmission shaft is driven by the driving unit, and protrudes beyond the housing. The propeller is mounted on an external end of the transmission shaft. 
     When the conventional rotary paddle level switch is mounted in a warehouse and is operated, the driving unit drives the transmission shaft to rotate the propeller. When the level of a stored material rises up to reach the propeller, the propeller and the transmission shaft stop rotating because of the resistance caused by the material, and the driving unit compresses the torque spring to reversely rotate the transmission shaft. The pressing rod of the driving unit then departs from the first switch and abuts against the second switch instead. The driving unit stops rotating the transmission shaft after the pressing rod no longer abuts against the first switch. The second switch signals that the material has been accumulated to a designated level after being abutted, so as to achieve the objective of monitoring the level of a material stored in a warehouse. 
     However, the conventional rotary paddle level switch has the following shortcomings. 
     Firstly, during the course of dropping a material in a warehouse, the material may hit the propeller from a specific angle to abruptly rotate the propeller at a high speed. Rotating at a high speed, the parts of the driving unit, such as transmission gears, are prone to damage. A clutch is therefore mounted between the transmission shaft and the driving unit. When the propeller and the transmission shaft are subject to an excessively large external force, the clutch disconnects the transmission shaft from the driving unit to prevent the driving unit from being damaged. However, the conventional clutch is structurally complicated, and the production cost of the clutch is relatively high. 
     Secondly, when the propeller hits the accumulated material and generates a resistance force, the resistance force generates a torque that is indirectly exerted on the torque spring. However, the sensitivity and accuracy of the torque spring are not as satisfactory as expected, early or late deactivation of the driving unit. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a rotary paddle level switch being structurally simple and less costly. 
     To achieve the foregoing objective, the A rotary paddle level switch has a housing, a circuit board, a first switch, a second switch, a resilient member, a clutch, and a propeller. 
     The circuit board is mounted inside the housing. 
     The driving unit is rotatably mounted inside the housing, is electrically connected to the circuit board, and has a pressing member and an output member. The pressing member and the output member are not co-axial. The pressing member is mounted on a bottom of the driving unit. The output member is rotatably mounted in the driving unit and protrudes downwards. 
     The first switch is mounted inside the housing and is electrically connected to the circuit board. 
     The second switch is mounted inside the housing, is electrically connected to the circuit board, and is spaced apart from the first switch by a gap. 
     The resilient member is mounted inside the housing, and pulls the driving unit for the pressing member of the driving unit to abut against the first switch. 
     The transmission shaft is mounted in the housing, has an actuation section formed on a top end of the transmission shaft, and has a non-circular section. A bottom end of the transmission shaft protrudes downward beyond the housing. 
     The clutch is mounted inside the housing, is connected between the driving unit and the transmission shaft, is driven by the driving unit to rotate, and has a clutch stand and a resilient clip. 
     The clutch stand is non-relatively rotationally coupled to the output member of the driving unit, and sleeves the actuation section of the transmission shaft. 
     The resilient clip is mounted inside the clutch stand, clips the actuation section of the transmission shaft, and is selectively opened by the actuation section. 
     The propeller is mounted on the transmission shaft, and is located outside the housing. 
     The present invention is advantageous in that the resilient clip of the clutch holds the non-circular actuation section of the transmission shaft and the clutch is rotatable with the transmission shaft and the propeller when the driving unit drives the clutch to rotate during a regular operating condition, and the transmission removes itself from the holding of resilient clip and is rotated alone without driving the resilient clip to rotate when the propeller is suddenly subject to an excessively large external force and all of a sudden the external force drives the transmission shaft to rapidly rotate, so as to avoid the transmission of the external force and damage to the driving unit. The clutch only has a clutch stand and a resilient clip to achieve the foregoing effectiveness, and is therefore structurally simple and relatively cost-effective. 
     Additionally, the resilient member is a tension spring, which has higher sensitivity and torque accuracy. Accordingly, the resilient spring allows the driving unit to accurately resist the torque and moves the pressing member at a right timing. The rotary paddle level switch further has a light-emitting unit connected to the housing and electrically connected to the circuit board. When a material is accumulated up to a designated level, the second switch is triggered, and the light-emitting unit simultaneously emits light to be visible to users. 
     Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rotary paddle level switch; 
         FIG. 2  is a partially exploded perspective view of the rotary paddle level switch in  FIG. 1 ; 
         FIG. 3  is another partially exploded perspective view of the rotary paddle level switch in  FIG. 1 ; 
         FIG. 4  is a partially enlarged perspective view of a mounting desk and a driving unit in  FIG. 2  assembled together; 
         FIG. 5  is a side view in partial section of the rotary paddle level switch in  FIG. 1 ; 
         FIG. 6  is a partially enlarged perspective view of a clutch and the driving unit in  FIG. 2 ; 
         FIG. 7  is an enlarged exploded view of the clutch in  FIG. 6 ; 
         FIG. 8  is an operational top view in partial section of the clutch in  FIG. 7 ; 
         FIG. 9  is an operational top view of the driving unit in  FIG. 6 ; 
         FIG. 10  is another operational top view of the driving unit in  FIG. 6 ; and 
         FIG. 11  is another operational top view in partial section of the clutch in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 to 3 , a rotary paddle level switch in accordance with the present invention has a housing  10 , a circuit board  14 , a driving unit  20 , a first switch  31 , a second switch  32 , a resilient member  40 , a light-emitting unit  50 , a clutch  60 , a transmission shaft  70 , and a propeller  80 . 
     With reference to  FIGS. 2 to 5 , the housing  10  has a bottom base  11 , a top cover  12 , a support board  13 , and a mounting desk  15 . The bottom base  11  and the top cover  12  are combined to define a chamber therein. The top cover  12  has a light-transmitting portion  121  mounted on a top of the top cover  12 . The support board  13  is securely mounted inside the bottom base  11 , and has a first track hole  131 . The first track hole  131  is formed through the support board  13 , and is a round hole. The mounting desk  15  is mounted on a top of the support board  13 , and has an insertion hole  151  and at least one wire track  152 ,  153 . The insertion hole  151  is formed in a top surface of the mounting desk  15 . The at least one wire track  152 ,  153  is formed on the top surface and a side surface of the mounting desk  15 . 
     The circuit board  14  is mounted inside the housing  10 , is mounted on a bottom of the support board  13 , and a second track hole  141 . The second track hole  141  is formed through the support board  13 , and is a curved hole. The second track hole  141  is located underneath the first track hole  131  of the support board  13 . 
     With reference to  FIGS. 3 to 6 , the driving unit  20  is rotatably mounted between the support board  13  and the mounting desk  15 , and has multiple electric wires  24 , an output member  21 , a pressing member  22 , and multiple spring holes  23 . The electric wires  24  are connected with the driving unit  20 , and are connected to the circuit board  14  through the support board  13  as shown in  FIGS. 4 and 5 . The output member  21  is rotatably mounted in the driving unit  20  and protrudes downwards. The output member  21  is mounted through the support board  13  and the circuit board  14 . The driving unit  20  is mounted on the support board  13  with the output member  21  rotatably mounted through the support board  13 . The output member  21  has a stop surface  211  formed in a side of the output member  21 . The pressing member  22  and the output member  21  are not co-axial. The pressing member  22  is mounted on the bottom of the driving unit  20 , is mounted through the first track hole  131  of the support board  13  and the second track hole  141  of the circuit board  14 , and is movable within the first track hole  131  and the second track hole  141 . The spring holes  23  are formed in a top of the driving unit  20 , are aligned in a line with each adjacent two of the spring holes  23  spaced apart from each other by a gap. In the present embodiment, the driving unit is a motor. 
     With reference to  FIGS. 3 ,  5  and  6 , the first switch  31  and the second switch  32  are mounted on a bottom of the circuit board  14 , are spaced apart from each other by a gap, and are electrically connected to the circuit board  14 . The first switch  31  and the second switch  32  respectively have a first actuation part  311  and a second actuation part  321 . The first actuation part  311  and the second actuation part  321  are respectively mounted on a side of the first switch  31  and a side of the second switch  32  that face each other. When the first actuation part  311  and the second actuation part  321  are pressed, the first switch  31  and the second switch  32  are turned on. In the present embodiment, the first switch  31  and the second switch  32  are double pole double throw (DPDT) switch. Depending on requirements, the first switch  31  and the second switch  32  may also be optical switch, micro switch, Hall sensor, inductive sensor, and the like. 
     With reference to  FIGS. 2 to 4 , the resilient member  40  is mounted inside the housing  10 , and is connected between the mounting desk  15  and the driving unit  20 . One end of the resilient member  40  is inserted into the insertion hole  151  of the mounting desk  15 , and the other end of the resilient member  40  is inserted into one of the spring holes  23  on the driving unit  20 , such that the resilient member  40  can pull the driving unit  20  mounted on the support board  13  to abut against the first actuation part  311  of the first switch  31  so as to turn on the first switch  31 . The spring holes  23  on the driving unit  20  are provided for the resilient member  40  to be selectively inserted therein according to a desired pulling force of the resilient member  40  for pulling the driving unit  20 . In the present embodiment, the resilient member  40  is a tension spring. Given the high sensitivity and torque accuracy, the tension spring can accurately resist torque and move the pressing member at a right time. 
     With reference to  FIGS. 2 to 5 , the light-emitting unit  50  is centrally mounted on the top surface of the mounting desk  15 , and is located underneath the light-transmitting portion  121  of the top cover. The light-emitting unit  50  has multiple electric wires  51  sequentially mounted through the at least one wire track  152 ,  153  on the top surface and the side surface of the mounting desk  15 , and the support board  13 , and connected to the circuit board  14 . The light-emitting unit  50  is connected to the second switch  32  through the electric wires  51  and the circuit board  14 . Given the at least one wire track  152 ,  153  mounted through the mounting desk  15 , the electric wires  51  can be effectively fixed without moving around. 
     With reference to  FIGS. 2 , and  5  to  8 , the clutch  60  is mounted in the bottom base  11  of the housing  10 , is connected with the driving unit  20 , and is driven by the driving unit  20  to rotate. The clutch  60  has a connection member  61 , a threaded member  62 , a clutch stand  63 , and a resilient clip  64 . The connection member  61  completely sleeves the output member  21  of the driving unit  20 . The threaded member  62  is mounted in the connection member  61  through a screw engagement and abuts against the stop surface  211  of the output member  21  such that the output member  21  can drive the connection member  61  to rotate therewith. The clutch stand  63  partially sleeves the connection member  61 , and has a transmission recess  632 , a limit hole  633 , and a clip opening  631 . The transmission recess  632  is formed in a bottom surface of the clutch stand  63 . The limit hole  633  is formed through an edge portion of the clutch stand  63 , and takes the form of an elongated hole. The clip opening  631  is formed through the edge portion of the clutch stand  63  and an inner wall of the transmission recess  632 , and communicates with the limit hole  633  and the transmission recess  632 . The resilient clip  64  is made by bending a metal wire, is inserted in the transmission recess  632  through the clip opening  631 , and has a curved portion  641 , two clipping portions  642 , and two limiting portions  643 . The curved portion  641  is arc-shaped. The two clipping portions  642  respectively extend from two ends of the curved portion  641 , and are parallel to each other. The two limiting portions  643  respectively perpendicularly extend from two outer ends of the clipping portions  642 , are parallel to each other, and are inserted into the limit hole  633  to prevent the resilient clip  64  from being easily slipped out of the edge portion of the clutch stand  63 . 
     The transmission shaft  70  is mounted in the bottom base  11  of the housing  10  and is connected with the clutch  60 , and has an actuation section  71 . The actuation section  71  is formed on a top end of the transmission shaft  70 , and has a non-circular section. In the present embodiment, the actuation section  71  has two abutment surfaces  711 . The two abutment surfaces  711  are radially and oppositely formed in a periphery of the actuation section  71 . The actuation section  71  is mounted through the transmission recess  632  of the clutch stand  63  of the clutch  60 , and the two abutment surfaces  711  of the actuation section  71  are respectively held by the two clipping portions  642  of the resilient clip  64 . A bottom end of the transmission shaft  70  protrudes downward beyond the housing  10 . 
     With reference to  FIGS. 1 and 2 , the propeller  80  is mounted on the bottom end of the transmission shaft  70 , and is located beyond the housing  10 . 
     When in use, the rotary paddle level switch is fixed in a warehouse, and is electrically connected to a control system. 
     With reference to  FIGS. 2 ,  8 , and  9 , when the level of a material stored in the warehouse has not reached the propeller  80  of the rotary paddle level switch, the output portion  21  of the driving unit  20  drives the connection member  61  of the clutch  60  to rotate, the connection member  61  drives the clutch stand  63 , the clutch stand  63  drives the resilient clip  64  mounted inside the clutch stand  63  to rotate, and the resilient clip  64  drives the transmission shaft  70  held by the resilient clip  64  and the propeller  80  mounted on the bottom end of the transmission shaft  70  to simultaneously rotate. 
     When the material is piled up and blocks the rotation of the propeller  80 , the material becomes a resistance preventing the propeller  80  and the transmission shaft  80  from rotating. The higher the level of the stored material and the larger the resulting contact area with the propeller  80 , the more the resistance force is. Finally, the transmission shaft  70  is unable to rotate as a result of the escalating resistance force. With reference to  FIGS. 6 ,  8  and  10 , due to the increasing resistance force, the transmission shaft  70  is still held by the resilient clip  64  and fails to be removed from the resilient clip  64  because of the clipping force of the resilient clip  64 . Hence, the transmission shaft  70 , the clutch  60 , and the output member  21  of the driving unit  20  are motionless. Meanwhile, as the driving unit  20  is still in a turn-on condition, the output member  21  of the driving unit  20  must rotate in a direction opposite to the rotation direction of the driving unit  20  and further drives the pressing member  22  to rotate from the first switch  31  to abut against the second actuation part  321  of the second switch  32  so that the driving unit  20  is turned off and a signal is transmitted to the control system to inform that the level of the material has reached a designated height. With reference to  FIGS. 1 ,  2 , and  6 , when the second actuation part  321  of the second switch is turned on, the light-emitting unit  50  can be also turned on. The light emitted from the light-emitting unit  50  penetrates through the light-transmitting portion of the housing  10  to be visible to users. 
     The foregoing description associates with regular operation of the rotary paddle level switch. With reference to  FIGS. 1 ,  2  and  11 , when the material hits the propeller  80  at a particular angle and the propeller  80  together with the transmission shaft  70  suddenly rotate at a high speed, the sudden high rotation speed of the transmission shaft  70  will be released from the holding of the resilient clip  64  so that the transmission shaft  70  is rotated alone without driving the resilient clip  64  to rotate. Accordingly, the sudden high speed will not be transmitted to the driving unit  20  and damage the driving unit  20  to fulfill the purpose of providing the clutch  60 . 
     To achieve the foregoing effectiveness with just the clutch stand  63  and the resilient clip  64 , the clutch  60  is advantageous in simple structure and inexpensive cost. 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.