Patent Publication Number: US-7714692-B2

Title: Thermal overload trip apparatus and method for adjusting trip sensitivity thereof

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a thermal overload trip apparatus which is applicable to an electrical device for protecting a motor and an electrical load device, such as a thermal overload relay or a manual motor starter, more particularly, to a thermal overload trip apparatus which is capable of efficiently adjusting a sensitivity thereof using an adjusting screw without adjusting an adjusting knob and a method for adjusting a trip sensitivity thereof. 
   2. Description of the Related Art 
   An overload protecting function, a basic function of a thermal overload trip apparatus, is implemented by performing a trip operation when an overload or overcurrent within a current range satisfying a pre-set condition for the trip operation is generated in an electric circuit. The current range may refer to a current range for the trip operation according to an IEC (International Electrotechnical Commission) standard specified as an international electrical standard. For example, a condition for the trip operation is that the trip operation should be performed within two hours when a current corresponding to 1.2 times of a rated current is conducted in a circuit and the trip operation should be performed more than two hours and within several hours when a current corresponding to 1.05 times of the rated current is conducted. 
   The thermal overload (overcurrent) trip apparatus generally includes a heater coil generating heat when an overcurrent is generated by being connected onto the circuit and positioned near the bimetals so as to provide a driving force for a trip operation by said bimetals being bent when the heater coil generates heat, so as to act as a driving actuator. One example of the thermal overload trip apparatus using the bimetals will be described with reference to  FIGS. 1 and 2 . 
     FIG. 1  is a diagram showing a configuration of a thermal overload trip apparatus in accordance with the related art, and  FIG. 2  is a diagram showing a relation between an adjusting cam and a trip sensitivity adjusting range in the thermal overload trip apparatus in accordance with the related art. 
   In  FIG. 1 , a reference numeral  1  designates bimetals. Here, three bimetals are provided so as to be connected onto each circuit of three-phase Alternating Current. Thus, the bimetals are bent by heat from a heater coil (not shown) generating heat when an overcurrent is generated, and accordingly provide a driving force for a trip operation. A reference numeral  2  designates a shifter mechanism. The shifter mechanism  2  is a means for transferring the driving force for the trip operation from the bimetals  1  and is movable in a horizontal direction on the drawing by contacting the bimetals  1  in right and left directions so as to receive the driving force caused by the bent bimetals  1 . In  FIG. 1 , a reference numeral  3  designates a trip mechanism. The trip mechanism is biased to be rotated in a direction of the trip operation by a spring (reference numeral not given). In  FIG. 1 , a reference numeral  4  designates a latch mechanism for releasing the trip mechanism  3  to be rotated in the direction of the trip operation or restricting the trip mechanism  3  not to be rotated in the direction of the trip operation. The latch mechanism  4  has one end portion installed to face a driving force transfer portion of the shifter mechanism  2  with each other so as to receive the driving force from the shifter mechanism  2 , another end portion disposed on a rotation locus of the trip mechanism  3  so as to restrict or release the trip mechanism  3 , and a middle portion therebetween supported by a rotation shaft (reference numeral not given) to be rotatable. A reference numeral  6  designates a contact point between the trip mechanism  3  and the latch mechanism  4  at the restriction position. In  FIG. 1 , at a position contacting one portion of the latch mechanism  4 , an adjusting knob mechanism  5  is disposed to be rotatable so as to displace the latch mechanism  4  to be closer or to be distant to/from the shifter mechanism  2  resulting from changes of a contact pressure while contacting the latch mechanism  4 . Here, the adjusting knob mechanism  5  includes a cam portion  9  having a varying radius of curvature of its outer circumstance, and an adjusting knob  10  coupled to the cam portion  9  or integrally extended from the cam portion  9  so as to rotate the cam portion  9 . In  FIG. 1 , a reference character y indicates a bending displacement (bending amount) of the bimetals and indicates a pre-set displacement amount (distance) of the bending bimetals  1  when a pre-set overcurrent is conducted in the circuit. And, a reference numeral Δy indicates an allowance for trip operation and indicates a pre-set gap between the shifter mechanism  2  and the latch mechanism  4  when the shifter mechanism  2  is displaced by the pre-set bending amount y of the bimetals  1  caused by generation of the pre-set overcurrent. The allowance for trip operation is adjustable by the adjusting knob mechanism  5 . 
   In the meantime, referring to  FIG. 2 , a configuration of the cam portion  9  included in the adjusting knob mechanism  5  in accordance with the related art will be described. 
   In  FIG. 2 , a reference character a indicates a cam adjustable range covering angles between a maximum trip operation insensitive adjusting position  12  and a maximum trip operation sensitive adjusting position  13 . However, since a manufacturer of the thermal overload trip apparatus in the related art has adjusted an initial position of the cam portion  9  such as an initially-set position for the cam portion  11  by rotating the adjusting knob  10  of  FIG. 1  during manufacturing, a range allowing a user to substantially adjust the rotation angle of the cam portion  9  is a substantially-adjustable range for the cam b. In  FIG. 2 , a reference character c indicates an initially-set adjusting range for the cam. 
   Operation of the thermal overload trip apparatus in accordance with the related art will be described. 
   First, the trip operation will be described. When the heater coil (not shown) generates heat by the overcurrent in the circuit, the bimetals  1  are bent and moved rightward on the drawing. Accordingly, the shifter mechanism  2  is moved rightward on  FIG. 1 , that is in a shifter mechanism operating direction  7  applied when the overcurrent is generated by a value obtained by adding the allowance for trip operation Δy to the bending amount y by the driving force of the bimetals  1  bent more than the value adding the allowance for trip operation Δy to the bending amount y, accordingly the latch mechanism  4  is pressed rightward and then rotated in a counterclockwise direction on the drawing. Then, the trip mechanism  3  restricted by the latch mechanism  4  is released and then rotated in the tripping direction, that is in the counterclockwise direction by an elastic force of a spring (reference numeral not given), and accordingly a succeeding switching mechanism (not shown) is operated into a trip (circuit-opening) position and then the circuit is tripped (broken), thereby protecting the circuit and a load device. 
   Next, a sensitivity adjusting operation for the trip operation will be described with reference to  FIGS. 1 and 2 . 
   Under a state that the initial position of the cam portion  9  is adjusted by a manufacturer such as the initially-set position for the cam portion  11  in  FIG. 2 , if the user rotates the cam portion  9  of  FIG. 1  in the counterclockwise direction, the latch mechanism  4  is rotated clockwise, centering the rotation shaft (reference numeral not given), that is in a trip operation sensitivity sensitive adjusting direction  8 , accordingly the allowance for trip operation Δy becomes narrow and the trip operation sensitivity of the device with respect to the overcurrent becomes more sensitive. 
   Since the thermal overload trip apparatus in accordance with the related art has a configuration that the trip operation sensitivity is adjusted only by the cam portion and the latch mechanism, it is difficult to precisely specify relative positions between the cam portion and the latch mechanism and a driving force transfer structure thereof and relative positions between the latch mechanism and the shifter mechanism and a driving force transfer structure thereof and to install the apparatus based on a standard. Thus, the thermal overload trip apparatus in accordance with the related art has a possibility to cause defects during manufacturing that there is no allowance for trip operation or the tripping operation is not performed even if the cam portion is rotated to the maximum sensitive position. 
   And, since the thermal overload trip apparatus in accordance with the related art has a structure requiring disassembling and re-adjusting the relative positions between the components and the driving force transfer structure thereof when the defectiveness occurs in the manufacturing processes, it may deteriorate productivity of manufacturing. 
   SUMMARY OF THE INVENTION 
   Therefore, the present invention is directed to providing a thermal overload trip apparatus which is capable of simply adjusting a trip operation sensitivity without disassembling and reassembling processes of components even if defectiveness occurs while adjusting the trip operation sensitivity. 
   It is another object of the present invention to provide a method for adjusting a trip sensitivity of a thermal overload trip apparatus which is capable of simply adjusting a trip operation sensitivity without disassembling and reassembling processes of components even if defectiveness occurs while adjusting the trip operation sensitivity. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a thermal overload trip apparatus, in the thermal overload trip apparatus having bimetals for providing mechanical displacement according to an overload on a circuit and a shifter mechanism for transferring the mechanical displacement of the bimetals as a driving force, the apparatus comprising: a trip mechanism driven to a trip position by the driving force from the shifter mechanism when the overload is generated in the circuit; a release lever mechanism having one portion rotatably installed to contact the shifter mechanism so as to receive the driving force from the shifter mechanism and another portion installed to contact the trip mechanism, so that the release lever mechanism press the trip mechanism and drive the trip mechanism to the trip position when there is the driving force from the shifter mechanism, or the release lever mechanism release the trip mechanism when there is no driving force from the shifter mechanism, when the overload is generated in the circuit; an adjusting lever having a portion for rotatably supporting the release lever mechanism so as to operate the release lever mechanism to be horizontally moved by the rotation; an adjusting knob having an upper surface provided with a setting groove and a lower portion provided with a cam portion so as to set a trip operation position according to a rated current; and a means connected to the adjusting lever to rotate the adjusting lever so as to independently adjust a sensitivity to the trip operation current regardless of manipulation of the adjusting knob. 
   Another aspect of the present invention is to provide a method for adjusting a trip sensitivity of a thermal overload trip apparatus, in the thermal overload trip apparatus comprising bimetals for providing a mechanical displacement according to an overload in a circuit, a shifter mechanism for transferring the mechanical displacement of the bimetals as a driving force, a trip mechanism reversed to a trip position by the driving force from the shifter mechanism when the overload is generated in the circuit, a release lever mechanism having one portion rotatably installed to contact the shifter mechanism so as to receive the driving force from the shifter mechanism and another portion installed to contact the trip mechanism, so that the release lever mechanism presses the trip mechanism and drive the trip mechanism to the trip position when there is the driving force from the shifter mechanism, or the release lever mechanism releases the trip mechanism when there is no driving force from the shifter mechanism, when the overload is generated in the circuit, an adjusting lever having a portion for rotatably supporting the release lever mechanism so as to operate the release lever mechanism to be horizontally moved by the rotation, an adjusting knob having an upper surface provided with a setting groove and a lower portion provided with a cam portion so as to set a trip operation position according to a rated current, and a means connected to the adjusting lever to rotate the adjusting lever so as to independently adjust sensitivity to the trip operation current regardless of manipulation of the adjusting knob, the method comprising: setting an initial position of the adjusting knob; assembling components forming the thermal overload trip apparatus; conducting a predetermined over current to the thermal overload trip apparatus assembled in the assembling step for a predetermined time; adjusting the adjusting screw by rotating the adjusting screw until a trip operation occurs under a state that the adjusting knob is maintained at the initially set position; and marking the rated current at a periphery of the adjusting knob. 
   The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain the principles of the invention. 
     In the drawings: 
       FIG. 1  is a diagram showing a configuration of a thermal overload trip apparatus in accordance with the related art; 
       FIG. 2  is a diagram showing a relation between an adjusting cam and a trip sensitivity adjusting range in the thermal overload trip apparatus in accordance with the related art; 
       FIG. 3  is a diagram showing a configuration of a thermal overload trip apparatus in accordance with the present invention; 
       FIG. 4  is a planar view partially showing a relation between an adjusting cam and an adjusting screw for adjusting a trip sensitivity range in the thermal overload trip apparatus in accordance with the present invention; 
       FIG. 5  is a flow chart showing a configuration of a method for adjusting a trip sensitivity of the thermal overload trip apparatus in accordance with the present invention; and 
       FIG. 6  is a planar view showing a graduation member installed at a periphery of an adjusting knob in the thermal overload trip apparatus in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Description will now be given in detail of the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     FIG. 3  is a diagram showing a configuration of a thermal overload trip apparatus in accordance with the present invention, and  FIG. 4  is a planar view partially showing a relation between an adjusting cam and an adjusting screw for adjusting a trip sensitivity range in the thermal overload trip apparatus in accordance with the present invention. 
   As shown in  FIGS. 3 and 4 , the thermal overload trip apparatus in accordance with the present invention includes bimetals  14 . The bimetals  14  serve to provide a driving force for trip operation by winding of a heater coil (not shown) generating heat when an overcurrent is generated and then being bent when the heater coil generates heat. Preferably, three bimetals  14  are disposed to be connected onto each circuit of three-phase Alternating Current. 
   In  FIG. 3 , a reference numeral  15  designates a shifter mechanism for transferring a mechanical displacement of the bimetals  14  as a driving force. The shifter mechanism  15  includes upper and lower shifter plates (reference numeral not given) movable in a horizontal direction by pressure caused by bending the bimetals  14 , and a rotation lever (reference numeral not given) rotatably supported by the upper and lower shifter plates so as to be rotated in a clockwise direction when the upper shifter plate is moved rightward and the lower shifter plate is moved leftward and to be rotated in a counterclockwise direction when the upper shifter plate is moved leftward and the lower shifter plate is moved rightward. 
   In  FIG. 3 , a reference numeral  17  designates a trip device driven to a trip position by the driving force from the shifter mechanism  15  when the overload is generated in the circuit. The trip device  17  includes a long leaf spring, a short leaf spring having a length half of the long leaf spring and having one end portion fixed with one end portion of the long leaf spring, and a coil spring having both end portions respectively supported by the long leaf spring and the short leaf spring. Accordingly, when a load is applied to the long leaf spring and the short leaf spring more than a pre-determined load, a free end portion of the long leaf spring is reversed to rise above a horizon from a state lower than the horizon. Here, the coil spring is bent. When the load applied to the trip device  17  is removed, the coil spring returns to the original state from the bent state. Accordingly, the long leaf spring is reversed to the state that the free end portion thereof is lower than the horizon. 
   Though it is not shown, one side of the reversing trip mechanism  17 , particularly, the free end portion of the long leaf spring is connected with interlock to a switching mechanism for breaking the circuit through a trip operation, and accordingly the free end portion of the long leaf spring is reversed to be higher than the horizon, thereby performing the trip operation. 
   In  FIG. 3 , a release lever mechanism having one portion rotatably installed at a position contacting the shifter mechanism  15  so as to receive the driving force from the shifter mechanism  15  and another portion installed to contact the trip mechanism  17  is provided. The release lever mechanism, when an overload is generated in the circuit, is operated to drive the trip mechanism  17  to the trip position by pressing the trip mechanism  17  when there is the driving force from the shifter mechanism  15 , while releases the trip mechanism  17  when there is no driving force from the shifter mechanism  15 . 
   In  FIG. 3 , an adjusting lever  19  having a portion rotatably supporting the release lever mechanism is provided to operate the release lever mechanism to be horizontally moved by rotation. 
   The release lever mechanism includes a release lever  16  having one end rotatably supported by the adjusting lever  19  and another end contacting the trip mechanism  17 , and a driving force transfer plate  21  having one end fixed to the release lever  16  and another end contacting the shifter mechanism  15  (more particularly, the rotation lever of the shifter mechanism  15 ). A reference numeral  22  is a fixing mechanism for fixing the driving force transfer plate  21  to the release lever  16 . Particularly, the fixing mechanism  22  may include a protrusion protruded from the release lever  16 , a fixing plate fitted into the protrusion, and fixing screws for fixing the driving force transfer plate  21  to the fixing plate. 
   The adjusting lever  19  is rotatable in a clockwise or counterclockwise direction centering a rotation shaft (reference numeral not given) coupled to a lower portion thereof. And, the adjusting lever  19  is provided with a portion rotatably supporting the release lever  16 . The portion includes a supporting portion  19   a  extended from the upper portion thereof in a horizontal direction and a rotation shaft portion  19   a - 1  independently connected to the supporting portion  19   a  or integrated with the supporting portion  19   a.    
   The thermal overload trip apparatus in accordance with the present invention has a configuration to set a sensitivity degree for the overload (overcurrent) in the circuit to perform the trip operation and adjust the sensitivity degree. As the configuration for rotatingly adjusting and setting a position for the trip operation according to a rated current, the configuration includes an adjusting knob  18  having an upper surface provided with a setting groove  18   b  and a lower portion provided with a cam portion  18   a , and a means connected to the adjusting lever  19  so as to rotate the adjusting lever  19  and independently adjust a sensitivity to trip operation current regardless of manipulation of the adjusting knob  18 . 
   The means includes an adjusting screw  20  connected to the adjusting lever  19  by a screw so as to rotate the adjusting lever  19  and adjust the sensitivity to trip operation current by independently adjusting a rotation angle of the release lever mechanism by the adjusting lever  19  regardless of manipulation of the adjusting knob  18 . The adjusting screw  20  is a screw having a head portion provided with a manipulating groove to which a screw driver is connected and a body portion provided with a screw thread. An end portion of the body portion opposite to the head portion is installed to contact the cam portion  18   a  of the adjusting knob  18 . 
   As shown in  FIG. 4 , upon rotatingly adjusting the adjusting knob  18  to the set adjusting groove  18   b  by connecting with a tool such as the screw driver, the end portion of the body portion of the adjusting screw  20  comes into contact with the cam portion  18   a  provided with a cam surface having a changing radius of an outer circumference of itself. Accordingly, the adjusting screw  20  is displaced in the horizontal direction according to the variation of the radius of the cam surface. That is, when the adjusting screw  20  contacts a portion of the cam portion  18   a  having a small radius of the cam surface, the adjusting screw  20  is moved leftward in  FIG. 3 . Accordingly, the adjusting lever  19  is rotated in the counterclockwise direction. When the adjusting screw  20  contacts a portion of the cam portion  18   a  having a large radius of the cam surface, the adjusting screw  20  is moved rightward in  FIG. 3 . Accordingly, the adjusting lever  19  is rotated in the clockwise direction. When the adjusting lever  19  is rotated in the counterclockwise direction, the driving force transfer plate  21  is rotated in the counterclockwise direction through the release lever  16  interposed therebetween thus to be distant from the shifter mechanism  15 . Accordingly, the trip operation set current is increased and the trip operation sensitivity decreases. When the adjusting lever  19  is rotated in the clockwise direction, the driving force transfer plate  21  is rotated in the clockwise direction through the release lever  16  interposed therebetween thus to be closer to the shifter mechanism  15 . Accordingly, the trip operation set current is decreased and the trip operation sensitivity increases. 
   The thermal overload trip apparatus in accordance with the present invention includes the adjusting screw  20  as a means for independently adjusting the sensitivity to the trip operation current regardless of manipulation of the adjusting knob  18 . When the adjusting screw  20  is rotated in the clockwise direction by the screw driver, the adjusting screw  20  is rotated at its original position, but the upper portion of the adjusting lever  19  coupled to the adjusting screw  20  by a screw is horizontally moved rightward along the screw thread of the adjusting screw  20  in  FIG. 3 . Accordingly, the adjusting lever  19  is rotated in the clockwise direction centering a rotation shaft (reference numeral not given) at the lower portion thereof. When the adjusting screw  20  is rotated in the counterclockwise direction by the screw driver, the adjusting screw  20  is rotated at its original position, but the upper portion of the adjusting lever  19  coupled to the adjusting screw  20  by a screw is horizontally moved leftward along the screw thread of the adjusting screw  20  in  FIG. 3 . Accordingly, the adjusting lever  19  is rotated in the counterclockwise direction centering the rotation shaft (reference numeral not given) at the lower portion thereof. When the adjusting lever  19  is rotated in the counterclockwise direction, the driving force transfer plate  21  is rotated in the counterclockwise direction through the release lever  16  interposed therebetween thus to be distant from the shifter mechanism  15 . Accordingly, the trip operation set current is increased and the trip operation sensitivity decreases. When the adjusting lever  19  is rotated in the clockwise direction, the driving force transfer plate  21  is rotated in the clockwise direction through the release lever  16  interposed therebetween thus to be closer to the shifter mechanism  15 . Accordingly, the trip operation set current is decreased and the trip operation sensitivity increases. Accordingly, it is capable of independently setting and adjusting the trip operation current by the adjusting screw  20  regardless of manipulation of the adjusting knob  18  in accordance with the present invention. 
   In the meantime, when the bimetals  14  are bent rightward in  FIG. 3  resulting from that the overcurrent in the circuit, an upper shifter of the shifter mechanism  15  is moved rightward and a lower shifter thereof remains at its original position, accordingly the rotation lever is rotated in the clockwise direction and thus the lower portion of the driving force transfer plate  21  is pressed. Accordingly, the driving force transfer plate  21  is rotated in the counterclockwise direction and then the release lever  16  connected to the upper portion of the driving force transfer plate  21  is rotated in the counterclockwise direction centering the rotation shaft portion  19   a - 1 . Accordingly, the trip mechanism  17  is pressed by the end portion of the release lever  16 . At a moment that the trip mechanism  17  is pressed to be rotated more than a trip operation initiation rotation angle X 0 , the trip mechanism  17  is driven. Accordingly, the free end portion of the long leaf spring is moved up over the horizon. Thus, the switching mechanism (not shown) connected to the free end portion of the long leaf spring is operated to the trip position and then the circuit is broken, thereby protecting the circuit and the load device from the overcurrent. 
   In the meantime, a method for adjusting a trip sensitivity of the thermal overload trip apparatus in accordance with the present invention will be described with reference to  FIGS. 5 and 6 . 
     FIG. 5  is a flow chart showing a configuration of the method for adjusting the trip sensitivity of the thermal overload trip apparatus in accordance with the present invention, and  FIG. 6  is a planar view showing a graduation member installed at a periphery of the adjusting knob in the thermal overload trip apparatus in accordance with the present invention. 
   The method for adjusting the trip sensitivity (hereafter, referred to as an adjusting method) of the thermal overload trip apparatus in accordance with the present invention may include: setting an initial position of the adjusting knob  18  (ST 1 ); assembling components forming the thermal overload trip apparatus (ST 2 ); conducting a predetermined overcurrent to the thermal overload trip apparatus assembled in the assembling step (ST 2 ) during a predetermined time (ST 3 ); adjusting the adjusting screw  20  by rotating the adjusting screw  20  until tripping occurs under a state that the adjusting knob  18  remains at its initially set position (ST 4 ). 
   More particularly, the setting step (ST 1 ) for the initial position of the adjusting knob is implemented by determining the initially-set position (that is, initial rotation angle) of the adjusting knob  18 , according to the trip operation current performing the trip operation, to a predetermined position (angle). 
   The assembling step (ST 2 ) is implemented by forming an assembly of the thermal overload trip apparatus by assembling the bimetals  14 , the shifter mechanism  15 , the trip mechanism  17 , the release lever mechanism  16 , the adjusting lever  19 , the adjusting knob  18 , the adjusting screw  20  and the like, components of the thermal overload trip apparatus in accordance with the present invention. 
   The overcurrent conducting step (ST 3 ) is implemented by conducting the pre-determined overcurrent (trip operation current), having a predetermined increase value with respect to a rated current (e.g., 5A, 10A, 15A), to the thermal overload trip apparatus of the present invention during an allowable conducting time (e.g., 2 hours) specified in an international electrical standard or an international electrical safety standard. In other words, the step is to conduct a predetermined value of a test current during a predetermined allowable conducting time. 
   The adjusting screw adjusting step (ST 4 ) is implemented by arbitrarily generating the trip operation by rotatingly adjusting the adjusting screw  20  thus to adjust the trip sensitivity under a state that the adjusting knob  18  remains at the initially-set position (initial rotation angle). Here, at a moment that the trip operation occurs, the adjusting of the trip sensitivity is completed. 
   The adjusting method of the thermal overload trip apparatus in accordance with the present invention further comprises a step of marking the rated current at a periphery of the adjusting knob (ST 5 ). 
   The rated current marking step (ST 5 ) is implemented by marking an additional rated current at the periphery of the adjusting knob under a state that the adjusting of the trip sensitivity is completed. In detail, in the rated current marking step (ST 5 ) according to one embodiment, the rated current may be directly marked at the periphery of the adjusting knob  18 . 
   Also, in the rated current marking step (ST 5 ) according to another embodiment, the rated current (e.g., 5A, 10A, 15A) may be marked on a graduation member  18   c  installed at the periphery of the adjusting knob  18 . 
   Therefore, according to the thermal overload trip apparatus and a method for adjusting the trip sensitivity thereof of the present invention, it is not required to disassemble and reassemble the components even if inferiority occurs while adjusting the trip operation sensitivity. Accordingly, the simplicity of simply adjusting the trip operation sensitivity is assured. 
   Further, the thermal overload trip apparatus in accordance with the present invention includes the means for independently adjusting the sensitivity to the trip operation current regardless of the cam portion, accordingly it is possible to adjust the sensitivity to the trip operation current without rotation of the adjusting knob. 
   The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
   As the present inventive features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.