A polarized electromagnet.

TECHNICAL FIELD

The present invention is directed to a polarized electromagnet, and more particularly to an improvement on a polarized electromagnet with an axially movable core which extends through an excitation coil and which has pole plates at its opposite ends respectively located between magnetic gaps formed between the opposite poles of permanent magnet means for axial movement upon energization and deenergization of the excitation oil.

BACKGROUND ART

Such polarized electromagnet is well known in the art. For example, U.S. Pat. No. 4,509,026 discloses a general structure of the polarized electromagnet in which an axially movable core extends through an excitation coil with pole plates at the opposite ends of the core located in magnetic gaps formed between the opposed pole ends of inner and outer yoke means which are magnetized by permanent magnet means to opposite polarities. In this structure, the inner yoke means have its pole ends extending inwardly of the lateral ends of pole plates in abuttable relation therewith so that the pole plate comes into engagement with the adjacent pole end of the inner yoke means when attracted thereto. This means that each pole end of the inner yoke means is spaced axially from the adjacent pole plate being in the position magnetically repelled from the pole end by a distance exactly equal to the stroke required for the axial movement of the core. Thus, in order to move the pole plate towards the adjacent pole end of the inner yoke means by the energization of the coil it is always required to generate a magnetic force compensating for the magnetic resistance determined by that distance. In other words, the prior electromagnet has response sensitivity inherently and directly determined by that distance between the pole end of the inner yoke means and the adjacent pole plate in the position repelled away therefrom, and is therefore practically impossible to raise the response sensitivity without reducing that distance or the stroke of the core.

DISCLOSURE OF THE INVENTION

In view of the above problem, the present invention is contemplated to give improved response sensitivity to a polarized electromagnet without sacrificing its output stroke. The polarized electromagnet in accordance with the present invention comprises an excitation coil and an axially movable core extending through the excitation coil to be magnetically coupled therewith for movement between the two positions upon energization and deenergization of the excitation coil. The core has at its opposite ends pole plates extending transversely of the core axis and is magnetically coupled through the pole plates to inner and outer yoke means which are magnetized to opposite polarites by permanent magnet means. The outer yoke means extends parallel to the core in transversely spaced relation thereto and has at its opposite ends respective outer pole ends which are located axially outwardly of the adjacent pole plates of the core. The inner yoke means extends parallel to the core inwardly of the outer yoke means and is formed at its opposite ends respectively with inner pole ends which are cooperative with the adjacent ones of the outer pole ends to form therebetween respective magnetic gaps in which the corresponding ones of the pole plates are positioned, respectively. The electromagnet of the present invention is characterized in that at least one of the inner pole ends terminates in a pole tip which is positioned transversely outwardly of the adjacent pole plate and extends in the axial direction to a point where it overlies the adjacent pole plate when the latter is in a position of being magnetically attracted to the pole tip such that the inward face of the pole tip comes into direct facing relation to the lateral edge of the adjacent pole plate in the attracted position. With this provision that the inner pole end or the pole tip is allowed to extend over or even past the adjacent pole plate being in the attracted position, it is possible to reduce the gap between the pole tip and the adjacent pole plate in the other position away from that pole tip, therefore reducing the magnetic resistance therebetween without accompanying the reduction in the stroke of the core. Accordingly, the electromagnet can require a correspondingly reduced magnetic force for switching the core to its attracted position to the pole tip of the inner yoke means from the other position, providing an improved response sensitivity of the core movement to the energizing signal.

It is therefore a primary object of the present invention to provide a polarized electromagnet which is capable of increasing the response sensitivity to the energizing signal without sacrificing the stroke of the core.

In a preferred embodiment, one of the inner pole ends defines the pole tip while the other pole end extends transversely into the path of the adjacent pole plate to define thereat a pole flange which comes into contact with the adjacent pole plate when the latter is magnetically attracted to said pole flange such that the core is held stable at the position where the pole flange attracts the adjacent pole plate by the magnetic force of the permanent magnet means and is driven to move towards the other position upon the energization of the electromagnet. The core is spring biased toward the stable position for assuring the core to return to the attracted position upon the deenergization of the electromagnet.

It is therefore another object of the present invention to provide a polarized electromagnet of monostable type which retains the improved response sensitivity.

Included in the electromagnet is a guide which is made of non-magnetic material and is fixed to the inner and outer yoke means. The guide extends between the pole tip and the adjacent pole plate and is formed with a guide surface along which the lateral edge of the pole plate is guided as the core moves axially between the two axially spaced positions. Thus, the core is smoothly guided in its axial movement without causing any lateral fluctuations, which is therefore a further object of the present invention.

In a modified version of the present invention, a polarized electromagnet of bistable type is shown in which each one of the inner pole ends defines the pole tip positioned laterally outwardly of the adjacent pole plate and extending in the axial direction to a point where it overlies the adjacent pole plate when the latter is magnetically attracted to the pole tip. The pole tips are spaced from the adjacent pole plates to form therebetween respective gaps with a magnetic resistance substantially equal to each other so that the core is rendered stable at either of the two axially spaced positions.

It is therefore a further object of the present invention to provide a polarized electromagnet of bistable type which retains the improved response sensitivity.

These and still other objects and advantages will become apparent from the following description of the preferred embodiment of the present invention when taken in conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

<ul id="ul0001" list-style="none"><li>FIG. 1 is a vertical section of a remotely controllable circuit breaker employing an improved polarized electromagnet in accordance with a preferred embodiment of the present invention;</li><li>FIG. 2 is a top view of the breaker;</li><li>FIG. 3 is an exploded perspective view of the breaker;</li><li>FIG. 4 is an exploded perspective view of the electromagnet;</li><li>FIG. 5 is a vertical section of the breaker showing a protecting cover for the electromagnet;</li><li>FIG. 6 is an exploded perspective view of an L-shaped actuator and a second contact arm employed in the breaker;</li><li>FIG. 7 is a partial view showing the mounting of an operation indicator in relation to the L-shaped actuator in the breaker;</li><li>FIGS. 8 and 9 are explanatory views respectively showing the operation of the electromagnet;</li><li>FIGS. 10 to 13 are respectively vertical sections illustrating various operating modes of the breaker;</li><li>FIG. 14 is a partial perspective view of an arc extinguishing chute and its associated portion of the breaker housing;</li><li>FIG. 15 is a partial front view illustrating an arc driving arrangement utilized in a modification of the breaker;</li><li>FIG. 16 is a front view illustrating the rigid connection between the plunger of the electromagnet and a joint for the second contact of the breaker;</li><li>FIG. 17 is a sectional view of the joint utilized in FIG. 16;</li><li>FIGS. 18 and 19 are respectively perspective views showing modifications of the joint utilized in FIG. 16;</li><li>FIGS. 20 to 22 are respectively schematic views showing modified structures of the electromagnet; and</li><li>FIGS. 23 and 24 are respectively schematic views showing an electromagnetic contactor utilizing the electromagnet of the present invention.</li></ul>

MODES FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 to 3, there is shown a remotely controllable circuit breaker which incorporates a polarized electromagnet in accordance with a preferred embodiment of the invention. The breaker comprises a housing <b>1</b> of electrically insulative material in which a manually operable switching mechanism <b>20</b> is provided to open and close a single set of first and second breaker contacts <b>11</b> and <b>12</b> by manipulation of a manual handle <b>22</b>.

The housing <b>1</b> includes a side cover <b>3</b> and is separated by a partition <b>4</b> into two compartments, one for receiving the switching mechanism <b>20</b> and the other for receiving a remotely controllable electromagnet switch <b>60</b> which is responsive to a remote control signal fed from a location remote from the breaker for opening the contacts, such remote control responsive contact opening operation overriding the manual switching operation to forcibly open the contacts <b>11</b> and <b>12</b>.

The switching mechanism <b>20</b> comprises a frame <b>21</b> pivotally supporting the manual handle <b>22</b> about a handle pivot <b>23</b> at the upper end and a first movable contact arm <b>31</b> about a pivot pin <b>33</b> at the right end of the frame <b>21</b>. The first movable contact arm <b>31</b> carries at its lower end the first contact <b>11</b> and is electrically connected to a line terminal <b>10</b> at the left end of the housing <b>1</b> by way of a braid <b>13</b>, the frame <b>21</b>, a bimetallic strip <b>50</b>, and a magnetic coil <b>51</b>. The second contact <b>12</b> is carried on the lower end of a second movable contact arm <b>32</b> extending vertically in generally parallel relation to the first contact arm <b>31</b> and electrically connected to a load terminal <b>14</b> at the right end of the housing <b>1</b> by way of a braid <b>15</b>. The first contact arm <b>31</b> is pivoted at the middle of its length by the pivot pin <b>33</b> and is connected at its upper end to the handle <b>22</b> by way of pivot links <b>35</b> and <b>37</b> so that it is movable between an OFF position and an ON position as the handle <b>22</b> is manipulated to pivot about the handle pivot <b>23</b>. The first contact arm <b>31</b> has its upper end connected to the pivot link <b>35</b> by a pivot pin <b>34</b>. In FIG. 1, the first contact arm <b>31</b> is shown in its ON position where it has the first contact <b>11</b> in contact with the second contact <b>21</b> and is held in this position against the bias of a compression spring <b>39</b> by the action of a toggle linkage formed by pivot connections at pins <b>23</b>, <b>36</b>, and <b>38</b>. The linkage connecting handle <b>22</b> and the first contact arm <b>31</b> in the present embodiment assures the contact closing in a delayed-make fashion and the contact opening in a quick-break fashion.

Included in the switching mechanism <b>20</b> is a trip mechanism <b>40</b> which opens the contacts <b>11</b> and <b>12</b> upon occurrence of predetermined overload current conditions detected by the bimetallic strip <b>50</b> or by the magnetic coil <b>51</b> which are connected in series between the first contact arm <b>31</b> and the line terminal <b>10</b>. The trip mechanism <b>40</b> includes a latch lever <b>41</b> pivotally supported on the frame <b>21</b> and a cradle link <b>44</b> pivoted at its upper end to the handle 22 by the handle pivot <b>23</b>. The cradle link <b>44</b> has a slit <b>45</b> for guiding therealong the pin <b>38</b> connecting the pivot links <b>35</b> and <b>37</b>, and is therefore urged by the spring <b>39</b> in a clockwise direction in the figure about the handle pivot <b>23</b>. The cradle link <b>44</b> is kept latched at <b>46</b> by the end of the horizontal arm of the latch lever <b>41</b> and is held in the position against the bias of the spring <b>39</b>. The latch lever <b>41</b> is pivotable about a pin <b>42</b> and is urged by a torsion spring <b>43</b> in the counterclockwise direction as viewed in the figures. The vertical arm of the latch lever <b>41</b> extends along the bimetallic strip <b>50</b> in abuttable relation thereto.

When the bimetallic strip <b>50</b> sees an overcurrent, it is deflected toward the vertical arm of the latch lever <b>41</b> to force the same to pivot in the clockwise direction, thus unlatching the cradle link <b>44</b>. Upon this occurrence, the cradle link <b>44</b> is urged by the spring <b>39</b> to pivot in the counterclockwise direction to thereby pull the pin <b>38</b> retained in the slit <b>45</b> to the right, as seen in FIG. <b>11</b>, thus forcing the first contact arm <b>31</b> to pivot about the pin <b>33</b> from the ON position to the OFF position.

The magnetic coil <b>51</b> includes a release rod <b>52</b> which extends therethrough to be axially movable. As shown in FIG. 3, the release rod <b>52</b> comprises a movable core <b>53</b> biased by a spring <b>57</b> away from a fixed core <b>56</b> at one end of the coil <b>51</b> and has at its one end a catch <b>54</b> for engagement with the first contact arm <b>31</b>. The release rod <b>52</b> also includes a drive pin <b>55</b> extending through a fixed core <b>56</b> to be in abuttable against the lower end of the vertical arm of the latch lever <b>41</b>. Upon the occurrence of an extreme overcurrent flowing through the circuit, the magnetic coil <b>51</b> is magnetized to thereby attract the movable core <b>53</b> towards the fixed core <b>56</b>. At this time, the first contact arm <b>31</b> is pulled by the catch <b>54</b> of the movable core <b>53</b> to be forcibly disengaged from the second contact arm <b>32</b> for immediate contact separation. Also at the same time, the drive pin <b>55</b> is pushed by the movable core <b>53</b> to strike the lower end of latch lever <b>41</b>, thus pivoting the latch lever <b>41</b> to unlatch the cradle link <b>44</b>, after which the same tripping action is performed as initiated by the bimetallic strip <b>50</b> to keep the contacts opened until they are reset by the manipulation of the handle <b>22</b>. In this manner, the contact separation effected by directly pulling the first contact arm <b>31</b> always precedes the contact separation by the trip action and therefore assures an immediate contact separation for protecting the load circuit from an extreme overcurrent condition. It is noted at this point that the first contact arm <b>31</b> is connected to the release rod <b>52</b> at a point opposite of the pivot axis <b>33</b> from the upper effort point <b>34</b> receiving the forces from the handle <b>22</b> as well as from the trip mechanism <b>40</b>. With this structure, the release rod <b>52</b> can give an enough contact separation travel distance equivalent to that effected by the handle movement and the tripping action, yet allowing the magnetic coil <b>51</b> to be spaced from the effort point <b>35</b> along the length of the first contact arm <b>31</b> to such an extent as to accommodate within that length the parts or the portion of the switching mechanism <b>20</b>. Thus, the switching mechanism <b>20</b> including the magnetic coil <b>51</b> can be made in a compact arrangement while retaining the immediate and reliable contact separation by the magnetic coil <b>51</b>.

The second contact arm <b>32</b> is connected through an L-shaped actuator <b>80</b> to the remotely controllable electromagnet switch <b>60</b> to be driven thereby to move between an operative position where the second contact <b>12</b> is engageable with the first contact <b>11</b> and an inoperative or disable position where the second contact <b>12</b> is inhibited from engaging with the first contact <b>11</b> irrespective of the condition of the manually switching mechanism <b>20</b>. The electromagnet switch <b>60</b> is activated in response to a remote control signal fed from a remote station through lines <b>17</b>. In the present embodiment, the electromagnet switch <b>60</b> is polarized electromagnet of monostable type which keeps the second contact <b>12</b> in the operative position of FIG. 1 in the deenergized condition and moves the second contact <b>12</b>, upon being energized, to the inoperative position to disable a load connected to the breaker.

The electromagnet switch <b>60</b> comprises, as best shown in FIGS. 1 and <b>4</b>, an excitation coil <b>61</b> wound around a bobbin <b>62</b>, an axially movable plunger core <b>63</b> extending through the bobbin <b>62</b>, paired inner yokes <b>64</b>, paired outer yokes <b>65</b>, and permanent magnets <b>66</b> each interposed between the inner and outer yokes <b>64</b> and <b>65</b> to magnetize them in the opposite polarity. The inner and outer yokes <b>64</b> and <b>65</b> define inner and outer pole ends <b>67</b> and <b>68</b> respectively at the upper and lower ends thereof, and extend outwardly of the excitation coil <b>61</b> in parallel with the axis thereof so as to form magnetic gaps between the adjacent inner and outer pole ends <b>67</b> and <b>68</b>. Provided respectively at the upper and lower ends of the plunger core <b>63</b> are pole plates <b>69</b> each located between the magnetic gap. The outer pole ends <b>68</b> at the upper and lower ends of the outer yoke <b>65</b> are bent at a right angle to form flanged pole ends to be abuttable with the corresponding one of the upper and lower pole plates <b>69</b>. The inner pole end <b>67</b> is bent at a right angle only at the upper end of the inner yoke <b>64</b> to form a flanged pole end for abutment with the upper pole plate <b>69</b>, while the inner pole end <b>67</b> at the lower end is spaced laterally outwardly from the pole plate <b>69</b> to form therebetween a constant air gap so that the plunger core <b>63</b> is stable at the position of FIG. 1 in which the upper and lower pole plates <b>69</b> are respectively in contact with the upper inner pole ends <b>67</b> and the lower outer pole ends <b>68</b> to complete the circuit of the magnetic flux emanating from the permanent magnets <b>66</b>.

When the excitation coil <b>61</b> is energized by the control signal of a given polarity, the plunger core <b>63</b> is magnetized in the direction opposing the magnetic flux by the permanent magnets <b>66</b> to be thereby driven to move axially upwardly. The upper end of the plunger core <b>63</b> is connected to the L-shaped actuator <b>80</b> carrying the second contact arm <b>32</b> so that upon energization of the electromagnet <b>60</b> the upward movement of the plunger core <b>63</b> is transmitted to the second contact arm <b>32</b> to move the same into the inoperative position for opening the breaker circuit. In this position, the pole plate <b>69</b> at the upper end of the plunger core <b>63</b> abuts through a residual plate <b>73</b> against the flanged outer pole ends <b>68</b> at the upper ends of the outer yokes <b>65</b>. Upon deenergization of the electromagnet <b>60</b>, the plunger core <b>63</b> moves downwardly back to its stable position by the help of a return spring <b>86</b> acting on the connection between the plunger core <b>63</b> and the actuator <b>80</b>, bringing the second contact arm <b>32</b> back into the operative position. The electromagnet switch <b>60</b> thus constructed is received within a cavity surrounded by the partition <b>4</b> with a joint <b>75</b> at the upper end of the plunger core <b>63</b> extending upwardly through the partition <b>4</b>.

The L-shaped actuator <b>80</b> is made of electrically insulative material with a horizontal member <b>81</b> and a vertical member <b>83</b>, and is mounted in the housing <b>1</b> outwardly of the partition <b>4</b> with its connection between the members <b>81</b> and <b>83</b> pivotally supported about a pivot post <b>5</b> integral with the housing <b>1</b>. The horizontal member <b>81</b> extends over the width dimension of the electromagnet switch <b>60</b> and is connected at its free end by an integral pin <b>82</b> to the joint <b>75</b> at the upper end of the plunger core <b>63</b>. The spring <b>86</b> biasing the plunger core <b>63</b> to its stable position is held between the end of the horizontal member <b>81</b> and the upper wall of the housing <b>1</b>. The vertical member <b>83</b> likewise extends over the length dimension of the electromagnet switch <b>60</b> and carries the second contact arm <b>32</b> for movement thereof between the operative and inoperative positions. As shown in FIG. 6, the upper half portion of the second contact arm <b>32</b> is held within a slit <b>84</b> of the vertical member <b>83</b> with its lengthwise center abutting against a fulcrum projection <b>85</b> in the slit <b>84</b> and with a compression spring <b>88</b> interposed beween the upper end of the second contact arm <b>32</b> and the vertical member <b>83</b>. Thus, the second contact arm <b>32</b> is allowed to pivot about the fulcrum projection <b>85</b> to a limited extent relative to the vertical member <b>83</b> against the bias of the spring <b>88</b>. This is contemplated to effect a rapid contact separation on the side of the second contact arm <b>32</b> in case of an extreme overcurrent flowing through the circuit. That is, the second contact arm <b>32</b> will be instantly driven to move away from the first contact arm <b>31</b> while the actuator <b>80</b> is kept stationary due to the electromagnetic repulsion forces acting between the first and second contact arms <b>31</b> and <b>32</b> extending in parallel relation to each other and seeing such extreme overcurrent, enabling prompt contact separation in advance of the contact separation by the tripping mechanism <b>40</b> for safely protecting the load. A stop <b>8</b> projects integrally from the housing <b>1</b> for abutment respectively with the fist and second contact arms <b>31</b> and <b>32</b> upwardly of the first and second contacts <b>11</b> and <b>12</b>.

An indicator <b>90</b> is mounted adjacent the actuator <b>80</b> to be pivotable together therewith beween two angled positions indicative of the operative and inoperative positions of the second contact arm <b>32</b>. The indicator <b>90</b> comprises a lever <b>91</b> extending in an overlying relation to the vertical member <b>83</b> of the actuator <b>80</b> and a display section <b>92</b> at the upper end of the lever <b>91</b>. The display section <b>92</b> may be provided with markings for the inoperative and operative positions of the second contact arm <b>32</b> which can be viewed through a window <b>6</b> in the upper wall of the housing <b>1</b>. As shown in FIG. 7, the lever <b>91</b> is pivoted at a pivot pin <b>7</b> spaced downwardly from the pivot axis <b>5</b> for the actuator <b>80</b> and is connected at its lower end <b>93</b> to the vertical member <b>83</b> of the actuator <b>80</b> in order to obtain a greater lever ratio for obtaining a sufficient amount of angular displacement of the display section <b>92</b> which is required for the changeover of the marking to be viewed through the window <b>6</b>.

As shown in FIGS. 4 and 5, a protective cover <b>100</b> of electrically and magnetically insulating material is provided to fit within the confines of the partition <b>4</b> over the electromagnet <b>60</b>, completely insulating the electromagnet <b>60</b> from the adjacently disposed second contact arm <b>32</b> and the load terminal <b>14</b>, and further from an arc drive member <b>116</b> extending along the outer vertical surface of the partition <b>4</b> in parallel with the second contact arm <b>32</b>, the details of the arc drive member <b>116</b> will be discussed hereinafter with regard to an arc extinction mechanism. Integrally extending upwardly from the protective cover <b>100</b> is a grooved flange <b>101</b> which extends beyond the partition <b>4</b> to be fitted within the upper wall of the housing <b>1</b> and the upper end wall of the partition <b>4</b> in an overlying relation to the horizontal member <b>81</b> of the L-shaped actuator <b>80</b>. It is within this grooved flange <b>101</b> that the braid <b>15</b> interconnecting the second contact arm <b>32</b> and the load terminal <b>14</b> is received so that it is also completely insulated from the electromagnet <b>60</b>.

Now referring to FIGS. 8 and 9, the electromagnet switch <b>60</b> will be discussed with its characterizing feature for improved response sensitivity to the control signal or reliable plunger movement upon the energization of the excitation coil <b>61</b>. The electromagnet is characterized in that the inner pole end <b>67</b> at the lower end of each inner yoke <b>64</b> extends straight to define thereat a pole tip that is laterally spaced from the vertical plane in which the lateral edge of the adjacent pole plate <b>69</b> travels as the plunger core <b>63</b> moves axially in response to the energization and deenergization of the excitation coil <b>61</b>. With this result, the pole tip <b>67</b> is permitted to extend over the lateral side of the adjacent pole plate <b>69</b> in its attracted position to the inner yokes <b>64</b> [FIG. 9] in order to reduce the gap or magnetic resistance between the pole tip <b>67</b> and the adjacent pole plate <b>69</b> in its attracted position to the outer yokes <b>65</b> [FIG. 10] while retaining a desired plunger stroke and without interference with the movement of the pole plate <b>69</b>. Consequently, when the excitation coil <b>61</b> is energized to produce in the magnetic circuit a magnetic flux 0̸₁ opposing the magnetic flux 0̸₂ by the permanent magnet <b>66</b>, the magnetic flux 0̸₁ will pass through thus reduced gap <b>X</b>, or reduced magnetic resistance between the pole tip <b>67</b> and the adjacent pole plate <b>69</b>, thereby increasing a magnetic attraction force acting on the plunger core <b>63</b> to move its axially upwardly to the position of FIG. 9 from the position of FIG. 10. In other words, the plunger core <b>63</b> can have an improved response sensitively to the energization of the excitation coil <b>61</b>, or the remote control signal.

For achieving a smooth movement of the pole plate <b>69</b> in relation to the pole tips <b>67</b> of the inner yokes <b>64</b>, the coil bobbin <b>62</b> is formed with a thin-walled guide segment <b>74</b> extending integrally from the lower flanged portion thereof into the clearance between the pole tip <b>67</b> and the lateral face of the adjacent pole plate <b>69</b>. The guide segment <b>74</b> defines on its inner surface a smoothly finished guide surface along which the lateral edge of the adjacent pole plate <b>69</b> will be guided as the plunger core <b>62</b> is driven to move axially.

Although the electromagnet <b>60</b> in the present invention is configured to be symmetrical with respect to the axis of the plunger core <b>63</b>, it is equally possible to arrange an inner yoke <b>64</b>, an outer yoke <b>65</b>, a permanent magnet <b>66</b>, and pole plates <b>69</b> on the one lateral side of the plunger core <b>63</b>, as shown in FIG. 20.

Further, the breaker of the present invention may utilize as a remote control switch means an electromagnet of bistable type, as shown in FIGS. 21 and 22, which holds the second contact at either of the inoperative and operative positions and switches the positions by receiving control signal of opposite polarities. In these modifications of FIGS. 21 and <b>22</b>, the same scheme is applied to increase response sensitivity of the plunger core <b>63B, 63C</b> to the energization of the excitation coil <b>61B, 61C</b>, by adopting the like arrangement that the inner yoke <b>64B, 64C</b> has its pole ends, or pole tips <b>67B</b>, <b>67C</b> offset laterally outwardly of the adjacent pole plate <b>69B</b>, <b>69C</b> to permit the inner pole ends to extend over the lateral side of the pole plates <b>69B, 69C</b> in their attracted position to the inner pole ends <b>67B, 67C</b>.

Mounted in the bottom of the breaker housing <b>1</b> is an arc extinction assembly which comprises an art chute <b>110</b>, an arc runner <b>115</b> extending along the inner bottom of the housing <b>1</b> in the contact separating direction and terminating in the bottom of the arc chute <b>110</b>, and the arc drive member <b>116</b> extending vertically along the partition <b>4</b> and connected at its lower end to the arc runner <b>115</b>. The arc runner <b>115</b> is integrally formed with the arc drive member <b>116</b> and is electrically connected therethrough to the second contact arm <b>32</b> at <b>117</b>. Once an arc is developed between the separating contacts <b>11</b> and <b>12</b> as seen in a rapid contact separation due to the overcurrent condition, one end of the arc is shifted from the second contact <b>12</b> onto the immediately adjacent portion of the arc runner <b>115</b> while the other end of the arc is on the first contact <b>11</b>. As the first contact <b>11</b> travels along a path to its OFF position, the arc proceeds with the one end thereof anchored on the arc runner <b>115</b> into the arc chute <b>110</b> where it comes into contact with a stack of spaced arc shearing plates <b>112</b> to be extinguished thereat. The stack of the arc shearing plates <b>112</b> are supported by a holder <b>113</b> and disposed between the ends of the arc runner <b>115</b> and a horizontal plate <b>25</b> on the frame <b>21</b> of the switching mechanism <b>20</b>.

When the arc is shifted to extend between the first contact <b>11</b> and the arc runner <b>115</b>, the arc current will flow through a U-shaped path composed of the first contact arm <b>31</b>, the arcing gap, the position of the arc runner <b>115</b> and the arc drive member <b>116</b> extending generally in parallel relation to the first contact arm <b>31</b>. Whereby electromagnetic repulsion forces are produced between the parallel conducting limbs of the U-shaped path and are concentrated on the arc to urge or drive it towards the arc chute <b>110</b> for rapid extinction of the arc. It is noted at this time that the arc drive member <b>116</b> constitutes the U-shaped arc current path instead of the second contact arm <b>32</b> upon the occurrence of the arc, keeping the second contact arm <b>32</b> free from the arc current and protecting the second contact <b>12</b> from being damaged by the arc. This is particularly advantageous in that the second contact arm <b>32</b> can be selected solely in view of its conductivity and without regard to arc resistivity, and that the arc drive member <b>116</b> and the arc runner <b>115</b> can be selected mainly in view of its arc resistivity. To this end, the second contact arm <b>32</b> is made from a copper or its alloy having a superior conductivity while the arc runner <b>115</b> and the arc drive member <b>116</b> are made of an iron or ferro alloy having good heat resistivity but relatively great electric resistance. With the use of such material having relatively great electric resistance for the arc runner <b>115</b> and arc drive member <b>116</b>, a considerable current limiting effect can be obtained upon the arc current flowing therethrough, thereby contributing to the extinction of the arc.

For enhancing to shift the one end of the arc to the arc runner <b>115</b>, a pilot extension <b>118</b> extends from the lower end of the second contact arm <b>32</b> in close proximity to the arc runner <b>115</b>. For the same purpose, the connection between the arc runner <b>115</b> and the arc drive member <b>116</b> may be bent toward the lower end of the second contact arm <b>32</b>, as seen in FIG. 15, a modification of the present embodiment. In this modification, a vertical segment <b>119</b> is formed in the connection between the arc runner <b>115</b> and the arc drive member <b>116</b> to extend in a position closer to the first contact arm <b>31</b> than the substantial portion of the arc driver member <b>116</b>. Thus, the vertical segment <b>119</b> acts to exert the electromagnetic force for urging the arc towards the arc chute <b>110</b>, in addition to that it serves as a barrier for blowing back an arc gas towards the arc chute <b>110</b>.

For receiving the arc chute <b>110</b>, there is formed in the lower portion of the housing <b>1</b> a chamber <b>120</b> which opens in the direction of the first and second contacts <b>11</b> and <b>12</b> and which is confined at its rear by a vertical rib <b>121</b>, at its bottom by a horizontal rib <b>122</b>, and at its opposite sides respectively by the housing <b>1</b> and the side cover <b>3</b>. These ribs <b>121</b> and <b>122</b> are integral with the housing <b>1</b>. The arc chute <b>110</b> is disposed in the chamber <b>120</b> with the rear wall of the holder <b>113</b> in spaced relation to the vertical rib <b>121</b> so as to form therebetween a space <b>123</b>. As shown in FIG. 14, it is through this space <b>123</b> that escape ports <b>114</b> in the rear wall of the holder <b>113</b> communicate with an exhaust port <b>125</b> formed in the bottom wall of the housing <b>1</b> downwardly of the horizontal rib <b>122</b> for exhausting a volume of ionized gases produced by the arc reacting with its environments including the arc shearing plates <b>112</b>. As seen in the figure, the side wall or the side cover <b>3</b> is notched to form on the rear portion of the side face of the arc chute <b>110</b> an additional space <b>124</b> which communicates rearwardly with the space <b>123</b> and downwardly with the exhaust port <b>125</b>. Thus, the arc gas rushing out through the escape ports <b>114</b> can be routed through the spaces <b>124</b> and <b>125</b> along several flow courses as indicated by arrows in the figure toward the exhaust port <b>125</b> to be finally discharged outwardly of the housing <b>1</b>. It is noted at this point that the vertical section of the partition <b>4</b> surrounding the electromagnet switch <b>60</b> acts as a barrier preventing the entry of the arc gas into the electromagnet <b>60</b> as well as to blow back the arc gas toward the arc chute <b>110</b> for expelling it through the escape ports <b>114</b>.

FIG. 16 shows the connection of the plunger core <b>63</b> of the electromagnet <b>60</b> and the joint <b>75</b> utilized to couple the plunger core <b>63</b> to the horizontal member <b>81</b> of the L-shaped actuator <b>80</b>. The joint <b>75</b> is made of a plastic material and comprises a square ring <b>76</b> and a tab <b>77</b> extending from the opposite sides of the ring <b>76</b>, as shown in FIGS. 4 and 16, for pivotal connection by the pin <b>82</b> to the actuator <b>80</b>. The ring <b>76</b> fits around a center stud <b>71</b> projecting from the upper end of the plunger core <b>63</b> with the upper pole plate <b>69</b> held between the ring <b>76</b> and a shouldered stop <b>72</b> on the upper end of the plunger core <b>63</b>. After placing the ring <b>76</b> in position, the upper end of the stud <b>71</b> is struck at spaced points <b>S</b> by a suitable jig so as to partially deform the portion outwardly of the points <b>S</b> into engagement with a bevelled brim <b>78</b> formed around the inner periphery of the ring <b>76</b>, thus rigidly connecting the joint <b>75</b> to the upper end of the plunger core <b>63</b> at the same time of connecting the pole plate <b>69</b> thereto.

As shown in FIGS. 18 and 19, other types of joints <b>130A</b> and <b>130B</b> may be utilized instead of the joint <b>75</b>. Each of the joint <b>130A</b> and <b>130B</b> comprises a base <b>131A</b>, <b>131B</b> with a pair of upward tabs <b>134A</b>, <b>134B</b> on the opposite sides thereof. The base <b>131A</b>, <b>131B</b> has in its center an aperture <b>132A</b>, <b>132B</b> with a beveled brim <b>133A</b>, <b>133B</b> around the upper edge thereof so that the upper end of the like plunger core extending through the aperture <b>132A</b>, <b>132B</b> can be partially deformed for engagement with the bevelled brim <b>133A</b>, <b>133B</b> in the like manner as described in the above. The tabs <b>134A</b> and <b>134B</b> are formed respectively with bearing holes <b>135A</b> and bearing grooves <b>135B</b> for pivotal connection to the horizontal member of the L-shaped actuator by means of a pin.

FIGS. 23 and 24 show an electromagnetic contactor as another application in which the electromagnet of the present invention is utilized. The parts of the electromagnet are designated by the like numerals with the suffix of <b>A</b> for an easy reference purpose. The contactor is of a normally closed switch and includes, in addition to the electromagnet <b>60A</b>, an actuator <b>140</b> extending in the axial direction of the plunger core <b>63A</b> and connected at its one end thereto. A contact arm <b>141</b> in the form of a spring leaf extends through the actuator <b>140</b> in perpendicular relation thereto and has first contacts <b>142</b> on its opposite ends for contact with second contacts <b>143</b> on individual fixed conductors <b>144</b>. In the deenergized condition of the electromagnet <b>60A</b> [FIG. 24], the contact arm <b>141</b> receives a retaining force from the end of the actuator <b>140</b> through a spring <b>145</b> to keep the contacts closed with a suitable contact pressure given by the spring <b>145</b>. Upon energization of the electromagnet <b>60A</b>, the actuator <b>140</b> is driven by the plunger core <b>63A</b> to move the contact arm <b>141</b> at <b>148</b> in the direction of separating the contacts <b>142</b> and <b>143</b> [FIG. 23]. A return spring <b>149</b> is provided to act on the end of the actuator <b>140</b> in its contact separating position for assisting the plunger core <b>63A</b> to move back to its stable position of FIG. 24.

The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

LIST OF REFERENCE NUMERALS

<ul id="ul0002" list-style="none"><li>1 housing</li><li>3 side cover</li><li>4 partition</li><li>5 pivot post</li><li>6 window</li><li>7 pivot pin</li><li>8 stop</li><li>10 line terminal</li><li>11 first contact</li><li>12 second contact</li><li>13 braid</li><li>14 load terminal</li><li>15 braid</li><li>17 line</li><li>20 switching mechanism</li><li>21 frame</li><li>22 handle</li><li>23 handle pivot</li><li>25 horizontal plate</li><li>31 first contact arm</li><li>32 second contact arm</li><li>33 pivot pin</li><li>34 pivot pin</li><li>35 pivot link</li><li>36 pin</li><li>37 pivot link</li><li>38 pin</li><li>39 compression spring</li><li>40 trip mechanism</li><li>41 latch lever</li><li>42 pin</li><li>43 torsion spring</li><li>44 cradle link</li><li>45 slit</li><li>46 latch end</li><li>50 bimetallic strip</li><li>51 magnetic coil</li><li>52 release rod</li><li>53 movable core</li><li>54 catch</li><li>55 drive pin</li><li>56 fixed core</li><li>57 spring</li><li>60 electromagnet switch</li><li>61 excitation coil</li><li>62 coil bobbin</li><li>63 plunger core</li><li>64 inner yoke</li><li>65 outer yoke</li><li>66 permanent magnet</li><li>67 inner pole end</li><li>68 outer pole end</li><li>69 pole plate</li><li>71 center stud</li><li>72 shoulder stop</li><li>73 residual plate</li><li>74 guide segment</li><li>75 joint</li><li>76 ring</li><li>77 tab</li><li>78 beveled brim</li><li>80 L-shaped actuator</li><li>81 horizontal member</li><li>82 pin</li><li>83 vertical member</li><li>84 slit</li><li>85 fulcrum projection</li><li>86 return spring</li><li>88 compression spring</li><li>90 indicator</li><li>91 lever</li><li>92 display section</li><li>100 protective cover</li><li>101 grooved flange</li><li>110 arc chute</li><li>112 arc shearing plate</li><li>113 holder</li><li>114 escape ports</li><li>115 arc runner</li><li>116 arc drive member</li><li>117 connection</li><li>118 pilot extension</li><li>119 vertical segment</li><li>120 chamber</li><li>121 vertical rib</li><li>122 horizontal rib</li><li>123 space</li><li>124 additional space</li><li>125 exhaust port</li><li>130A joint</li><li>130B joint</li><li>131A base</li><li>131B base</li><li>132A aperture</li><li>132B aperture</li><li>133A beveled brim</li><li>133B beveled brim</li><li>134A tab</li><li>134B tab</li><li>135A hole</li><li>135B groove</li><li>140 actuator</li><li>141 contact arm</li><li>142 first contact</li><li>143 second contact</li><li>144 contact carrier</li><li>145 spring</li><li>149 return spring</li></ul>