Background Art [2] In general, a triple action pressure switch detects three different pressures and controls turning on/off of two switches according to the detected pressure. An example of a conventional triple action pressure switch is disclosed in Japanese Patent Publication No. hei 7-114094.

[3] The structure and operation of the conventional triple action pressure switch are described with reference to FIGS. 1 and 2. FIG. 1 is a sectional view illustrating the structure of a conventional triple action pressure switch. FIG. 2 is a view showing the operational pressure feature of the conventional triple action pressure switch.

[4] Referring to FIG. 1, the conventional triple action pressure switch includes a housing 1 having a path for inputting a fluid pressure, a switch case 2 combined to the housing 1, a diaphragm 22 fixed between the housing 1 and the switch case 2, forming a seal, a first reversible plate 3 having an upper surface contacting a lower surface of the diaphragm 22, a first sliding member 4 having an upper surface that holds an outer circumferential portion of the first reversible plate 3, a circular protruding portion on a lower surface thereof, and a center hole formed at the center thereof, in which an outer circumference thereof slides on an inner wall portion of the switch case 2, a second reversible plate 5 having an upper surface contacting the circular protruding portion of the first sliding member 4 and a hole formed at the center portion thereof, a second sliding member 6 having an upper surface that holds an outer circumferential portion of the second reversible plate 5, a center shaft hole at the center thereof coaxially with the center hole of the first sliding member 4, and a central protruding portion hor- inntally protruding from the center shaft hole on a lower surface thereof, in which an outer circumference thereof slides on the inner wall portion of the switch case 2, a third reversible plate 7 having an inner circumferential portion coupled to an side surface of the central protruding portion and an outer circumferential portion held by a step portion of the inner wall of the switch case 2, a second working rod 24 having an upper end contacting the lower surface of the second reversible plate 5 and penetrating the center shaft hole of the second sliding member 6, a first working rod 23 having an upper end contacting the lower surface of the first reversible plate 3 and penetrating the center hole, the hole, and the inside of the second working rod 24, a first electric switch portion SW1 having a first mobile contact point coupled to a lower end of the first working rod 23 and a fixed contact point contacting and separated from the first mobile contact point, and a second electric switch portion SW2 having a second mobile contact point couple to a lower end of the second working rod 24 and a third mobile contact point contacting and separated from the second mobile contact point and coupled to the central protruding portion.

[5] Referring to FIG. 2, when a fluid pressure P + AP is applied to the third reversible L L plate 7, the third reversible plate 7 performs a snap action toward the electric switch portion and the second sliding member 6 moves toward the electric switch portion. The central protruding portion 25 of the second sliding member 6 presses a first switch lever 17 of the second electric switch portion SW2 to turn the second electric switch portion SW2 on.

[6] When the fluid pressure rises to reach P, the first reversible plate 3 performs a M snap action toward the electric switch portion. Then, the first working rod 23 moves toward the first electric switch portion SW1 and presses a switch lever 18 of the first electric switch portion SW1 to turn the first electric switch portion SW1 off.

[7] When the fluid pressure rises to reach P, the second reversible plate 5 performs a H snap action toward the switch portion. Then, the second working rod 24 presses a second switch lever 16 of the second electric switch portion SW2 to turn the second electric switch portion SW2 off.

[8] When the fluid pressure is lowered from P to P PAP, the second reversible plate H H H 5 is returned to its original shape. The second electric switch portion SW2 is turned on by a returning force of the second switch lever 16.

[9] When the fluid pressure is lowered to P PAP, the first reversible plate 3 is M M returned to its original shape. The first electric switch portion SW1 is turned on by a returning force of the switch lever 18.

[10] When the fluid pressure is lowered to P, the third reversible plate 7 is returned to L its original shape. The second electric switch portion SW2 is turned off by a returning force of the first switch lever 17.

[11] Since the conventional triple action pressure switch is widely used in places where a change in temperature is great, such as, in an air conditioner or an engine room of a car, the first working rod and the second working rod are manufactured of alumina ceramics which exhibits a small change in expansion/contraction according to the temperature.

[12] However, although the alumina ceramics is thermally very stable, since it exhibits a low toughness. Thus, when an impact is applied during steps of releasing the triple action pressure switch or installing the triple action pressure switch at a necessary position, the triple action pressure switch manufactured of alumina ceramics is easily broken.

[13] In other words, the conventional triple action pressure switch has a structure to turn the switch on/off by sequentially disposing the three reversible plates sensing a medium pressure, a high pressure, and a low pressure in an inner space thereof. The conventional triple action pressure switch additionally includes the first working rod which turns a lower switch (SW1) on/off according to the medium pressure and the second working rod which turns an upper switch (SW2) on/off according to the high pressure. The first working rod is operated inside the second working rod.

[14] Thus, the first working rod has a length sufficient to reach the lower switch so that the length of the first working rod is extended too long so as to be easily damaged by an external impact. Also, the first working rod and the second working rod can be damaged by an unnecessary interaction therebetween.

[15] To solve the above problems, Japanese Utility Nbdel Publication No. hei 7-29731 discloses a structure to reduce an impact by manufacturing the second working rod using synthetic resin. However, when the second working rod is manufactured of synthetic resin, since durability is deteriorated, the second working rod is easily abraded. Also, since the synthetic resin has a thermal expansion rate greater than alumina ceramics, a stable operation is not guaranteed. Therefore, an improved triple action pressure switch to solve the above problems is needed.

Disclosure of Invention Technical Problem [16] To solve the above and other problems, the present invention provides a triple action pressure switch in which a low pressure sensing disc is disposed in the middle of three pressure sensing discs and a third pivot base is added so that a lower surface of the third pivot base directly turns a lower switch on/off.

[17] Also, the present invention provides a triple action pressure switch in which a guide pin directly turns an upper switch on/off.

[18] Also, the present invention provides a triple action pressure switch which dose not need the second working rod.

Technical Solution [19] According to an aspect of the present invention, there is provided a triple action pressure switch including a cap having a path thrash which a compressed fluid passes, a base coupled to the cap, a seal member fixed between the cap and the base, first and second switches capable of opening and closing, and a switch driving unit to change an open/closed state of the first and second switches according to the pressure of the fluid, wherein the switch driving unit comprises a first pressure sensing disc having an upper surface at a peripheral portion thereof contacting a lower surface of the seam member, a first pivot base having an upper surface holding the peripheral portion of the first pressure sensing disc, a center hole formed at a center thereof, a protruding rod extended from the center hole and a flat step encompassing an outer cir- cumference of the protruding rod which are formed at a lower surface thereof, and an outer circumference directly sliding on an inner wall of the base, a second pressure sensing disc having a rod hole thrash which an outer circumference of the protruding rod passes formed at a center thereof and an upper surface at a peripheral portion of the rod hole contacting the flat step, a second pivot base having an upper surface holding a peripheral portion of the second pressure sensing disc, a rod hole thrash which the protruding rod passing thrash the rod hole passes formed at a center thereof, and an outer circumference directly sliding on the inner wall of the base, a third pivot base having a protruding portion formed at both ends of an outer circumference of an upper surface thereof, an upper surface of an end portion of the protruding portion contacting a lower surface of the second pivot base, a space formed by the upper surface thereof, an inner side wall of the protruding portion, and the lower surface of the second pivot base, a circular protrusion protruding as a shaft around the center and a shoulder step encompassing the outer circumference of the circular protrusion which are formed at the lower surface thereof, and an outer circumference directly sliding on the inner wall of the base, a third pressure sensing disc having a circumference hole thrash which the circular protrusion passes and an upper surface around the circular hole contacting the shoulder step, and a guide pin having an upper end contacting the lower surface of the first pressure sensing disc and passing thrash the center hole of the first pivot base, wherein the end portion of the protruding rod and a lower end of the guide pin change an open/closed state of the first switch and the circular protrusion changes an open/closed state of the second switch.

[20] According to another aspect of the present invention, there is provided a triple action pressure switch including a cap having a path through which a compressed fluid passes, a base coupled to the cap, a seal member fixed between the cap and the base, first and second switches capable of opening and closing, and a switch driving unit to change an open/closed state of the first and second switches according to the pressure of the fluid, wherein the switch driving unit comprises, a first pressure sensing disc having an upper surface at a peripheral portion thereof contacting a lower surface of the seam member, a first pivot base having an upper surface holding the peripheral portion of the first pressure sensing disc, a center hole formed at a center thereof, a protruding rod extended from the center hole and a flat step encompassing an outer cir- cumference of the protruding rod which are formed at a lower surface thereof, and an outer circumference directly sliding on an inner wall of the base, a second pressure sensing disc having a rod hole through which an outer circumference of the protruding rod passes formed at a center thereof and an upper surface at a peripheral portion of the rod hole contacting the flat step, a second pivot base having an upper surface holding a peripheral portion of the second pressure sensing disc, a rod hole through which the protruding rod passing through the rod hole passes formed at a center thereof, a protruding portion formed at both ends of an outer circumference of a lower surface thereof, and an outer circumference directly sliding on the inner wall of the base, a third pivot base having an upper surface of an end portion of the protruding portion contacting an upper surface thereof, a space formed by the upper surface thereof, an inner side wall of the protruding portion, and the lower surface of the second pivot base, a circular protrusion protruding as a shaft around the center and a shoulder step encompassing the outer circumference of the circular protrusion which are formed at the lower surface thereof, and an outer circumference directly sliding on the inner wall of the base, a third pressure sensing disc having a circumference hole through which the circular protrusion passes and an upper surface around the circular hole contacting the shoulder step, and a guide pin having an upper end contacting the lower surface of the first pressure sensing disc and passing through the center hole of the first pivot base, wherein the end portion of the protruding rod and a lower end of the guide pin change an open/closed state of the first switch and the circular protrusion changes an open/closed state of the second switch.

[21] The first switch is disposed in the space and has a low pressure contact point open/ closed to the end portion of the protruding rod and a high pressure contact point contacting/separated from the low pressure contact point and open/closed to the lower end of the guide pin.

[22] The second switch is disposed under the third pressure sensing disc and has a mobile contact point open/closed to the circular protrusion and a fixed contact point contacting/separated from the mobile contact point.

[23] The seal member comprises a seal film to make the path and the first pressure sensing unit in a seal state and an O-ring to make the cap and the base in a seal state.

[24] Each of the first pressing sensing disc, the second pressure sensing disc, and the third pressure sensing disc has a dish shape having one protruding surface, and has a hysteresis characteristic so that the protruding surface is reversed when a pressure exceeding a predetermined value is applied to the protruding surface, and the protruding surface is returned to the original state when a pressure less than the pre- determined value is applied.

[25] The first pressure sensing disc detects a high pressure cut-off pressure P and P H H ? AP and performs a reversing action, the second pressure sensing disc detects a low H pressure cut-off pressure P and P +AP and performs a reversing action, and the third L L L pressure sensing disc detects a medium pressure cut-off pressure P and P ? AP and M MM performs a reversing action.

Advantageous Effects [26] As described above, the triple action pressure switch according to the present invention has the following effects.

[27] First, since the guide pin can open/close the upper switch and accordingly the length of the guide pin is reduced as much as the interval of the switches, compared to the conventional technology, the possibility of the guide pin being damaged by an external impact is reduced and linearity is improved. Thus, the triple action pressure switch can operate stably.

[28] Second, since the disc detecting a low pressure is disposed in the middle of the three pressure sensing discs [29] and a third pivot base is added so that a lower surface of the third pivot base directly opens/closes the lower switch according to the reversion of the third pressure sensing disc, [30] the second working rod is not needed so that the conventional problem that the working rod is damaged by the interaction between the first and second working rods can be solved.

Description of Drawings [31] FIG. 1 is a vertical sectional view illustrating the structure of the conventional triple action pressure switch; [32] FIG. 2 is a view illustrating an operating pressure characteristic of the triple action pressure switch of FIG. 1; [33] FIG. 3 is an exploded perspective view illustrating a triple action pressure switch according to an embodiment of the present invention; [34] FIG. 4 is a plan view of the triple action pressure switch of FIG. 3; [35] FIG. 5 is a vertical sectional view taken along line A-A to show the structure of the triple action pressure switch of FIG. 4; [36] FIG. 6 is a vertical sectional view taken along line B-B to show the structure of the triple action pressure switch of FIG. 4; [37] FIG. 7 is a view illustrating an operating pressure characteristic of the triple action pressure switch of FIG. 4; [38] FIG. 8 is a vertical sectional view illustrating a triple action pressure switch according to another embodiment of the present invention; [39] FIG. 9 is a view illustrating an operating pressure characteristic of the triple action pressure switch of FIG. 8; [40] FIG. 10 is an exploded perspective view illustrating a triple action pressure switch according to yet another embodiment of the present invention; [41] FIG. 11 is a vertical sectional view taken along line A-A to show the structure of the triple action pressure switch of FIG. 10; and [42] FIG. 12 is a vertical sectional view taken along line B-B to show the structure of the triple action pressure switch of FIG. 10.

Best Mode [43] Referring to FIGS. 3,4, 5, and 6, a triple action pressure switch 100 according to an embodiment of the present invention includes a cap 102 having a path thrash which a compressed fluid passes, a base 104 coupled to the cap 102, seal means fixed between the cap 102 and the base 104, first and second switches SW1 and SW2 capable of opening and closing, and a switch driving unit to change an open/closed state of the first and second switches SW1 and SW2 according to the pressure of the fluid.

[44] The cap 102 and the base 104 are coupled to each other, thus constituting a main body of the triple action pressure switch 100. The first and second switches SW1 and SW2 and the switch driving unit are disposed in an inner space in the base 104. The switch driving unit is installed to be able to change the open/closed state of the switches SW1 and SW2 three times according to the pressure applied thrash the path.

[45] The seal means can be formed of a seal film 108 and an O-ring 106. The seal film 108 makes the path of the cap 102 and the first pressure sensing disc 110 in a seal state so that the fluid does not flow into the base 104 where the switch driving unit and the switches SW1 and SW2 operate, but is transferred to the switch driving unit thrash the first pressure sensing disc 110. The O-ring 106 makes the cap 102 and the base 104 in a seal state and can be formed of polyimide resin.

[46] The switch driving unit is a characteristic feature of the triple action pressure switch according to the present embodiment.

[47] In the conventional triple action pressure switch, the switches are open/closed by the three reversible plates detecting a medium pressure, a high pressure, and a low pressure which are sequentially disposed in the inner space. Since the first working rod to open/close the upper switch according to the medium pressure and the second working rod to open/close the lower switch according to the high pressure are separately provided, the working rods can be easily damaged by an external impact and an interaction therebetween.

[48] However, in the triple action pressure switch according to the present embodiment of the present invention, since the disc detecting a lower pressure is disposed in the middle of the three pressure sensing discs, a third pivot base is added, and the lower surface of the third pivot base can directly open/close the lower switch, the guide pin (the first working rod of the conventional technology) can directly open/close the upper switch so that the second working rod is not needed.

[49] Thus, according to the triple action pressure switch according to the present embodiment of the present invention, the length of the guide pin is reduced as much as the interval between the switches so that the possibility of the guide pin being damaged by an external impact is reduced and linearity is improved. Thus, the triple action pressure switch operates stably.

[50] Also, according to the triple action pressure switch according to the present embodiment of the present invention, the problem that the working rod is damaged by the interaction between the first and second working rods can be solved.

[51] The switch driving unit will now be described below.

[52] The switch driving unit may include the first pressure sensing disc 110, a first pivot base 120, a second pressure sensing disc 112, a second pivot base 130, a third pivot base 140, a third pressure sensing disc 116, and a guide pin 190.

[53] Each of the first, second, and third pressure sensing discs 110,112, and 116 has a dish shape having one protruding surface and a hysteresis characteristic so that, when a pressure exceeding a predetermined value is applied in the protruding direction, the protruding portion thereof is reversed and, when a pressure lower than the pre- determined value is applied, the protruding portion thereof is reversed back to the original state.

[54] The first pressure sensing disc 110 detects a high pressure cut-off pressure P and H P ? AP and performs a reversing action. The second pressure sensing disc 112 detects H H a low pressure cut-off pressure P and P +AP and performs a reversing action. The L L L third pressure sensing disc 116 detects a medium pressure cut-off pressure P and P M M ? AP and performs a reversing action.

M [55] The first pressure sensing disc 110 has a peripheral portion whose upper surface contacts a lower surface of the sealing member 108. An outer circumference of the peripheral portion is held by an upper surface of the first pivot base 120. The first pressure sensing disc 110 performs a reversing action by detecting high pressure cut- off pressures P and P PAP.

H H H [56] An outer circumferential wall is formed on the upper surface of the first pivot base 120 and a center hole 122 is formed at the center thereof. A protruding rod 124 extending from the center hole 122 and a flat step 126 encompassing an outer cir- cumference of the protruding rod 124 are formed on a lower surface of the first pivot base 120. The outer circumference of the first pivot base 120 directly slides on an inner wall of the base 104. The outer circumferential wall of the upper surface of the first pivot base 120 holds the peripheral portion of the first pressure sensing disc 110. The first pivot base 120 transfers the pressure of a fluid passing through the first pressure sensing disc 110 to the second pressure sensing disc 112 through the flat step 126. Si- rrultaneously, when the second pressure sensing disc 112 is reversed, the first pivot base 110 moves downward as much as a displacement due to the reversion of the second pressure sensing disc 112 so that the pressure is transferred to a low pressure operator 152 of a first switch SW1 by means of an end portion of the protruding rod 124.

[57] The second pressure sensing disc 112 has a rod hole 113 formed at the center thereof through which an outer circumference of the protruding rod 124 passes. An upper surface 114 of the second pressure sensing disc 112 around the rod hole 113 is disposed to contact the flat step 126. An outer circumference of the peripheral portion of the second pressure sensing disc 112 is held by an upper surface of the second pivot base 130. The second pressure sensing disc 112 is disposed in the middle of the three pressure sensing discs 110,112, and 116 which sense pressure and detects low pressure cut-off pressures P and P +AP to perform a reversing action.

L L L [58] An outer circumferential wall is formed on the upper surface of the second pivot base 130. A rod hole 132 is formed at the center of the second pivot base 130 thrash which the protruding rod 124 penetrating the rod hole 113 passes. The outer cir- cumference of the second pivot base 130 directly slides on the inner wall of the base 104 The outer circumferential wall of the upper surface of the second pivot base 130 holds the peripheral portion of the second pressure sensing disc 112.

[59] The third pivot base 140 has a protruding portion 146 protruding upward from both ends of an outer circumference thereof. A circular protrusion 142 protrudes downward from the center of a lower surface of the third pivot base 140 and a shoulder step 144 is formed to encompass an outer circumference of the circular protrusion 142. The outer circumference of the third pivot base 140 directly slides on the inner wall of the base 104. An end portion 148 of the protruding portion 146 is disposed to contact the lower surface of the second pivot base 130. The upper surface of the third pivot base 140, an inner side wall 147 of the protruding portion 146, and the lower surface of the second pivot base 130 form a space where the first switch SW1 is installed.

[60] The three pivot base 140 transfers the pressure of a fluid passing thrash the first pressure sensing disc 110, the first pivot base 120, and the second pivot base 130 to the third pressure sensing disc 116 via the shoulder step 144, and sirn. iltaneously, moves downward as much as a displacement due to the reversion when the third pressure sensing disc 116 is reversed. Thus, the pressure is transferred to a mobile operator 172 of the second switch SW2 via the circular protrusion 142.

[61] The third pressure sensing disc 116 has a circular hole 117 formed at the center thereof thrash which the circular protrusion 142 passes. An upper surface 118 of the third pressure sensing disc 116 around the circular hole 117 contacts the shoulder step 144. The outer circumference of the peripheral portion of the third pressure sensing disc 116 is directly held by a disc receiving portion 105 formed on the inner wall of the base 104. The third pressure sensing disc 116 detects the medium pressure P and P M M ? AP to perform an reversing action.

M [62] The upper end of the guide pin 190 contacts the lower surface of the first pressure sensing disc 110 and penetrates the center hole 122 of the first pivot base 120. The guide pin 190 transfers a reversing force of the first pressure sensing disc 110 to a high pressure operator 162 of the first switch SW1 thrash a lower end portion thereof.

[63] The first switch SW1 is disposed in a space formed by the third pivot base 140 and includes a low pressure operator 152 driven by an end portion of the protruding rod 124, a low pressure contact point 154 coupled to a leading end portion of the low pressure operator 152, a high pressure operator 162 driven by a lower end of the guide pin 190, and a high pressure contact point 164 coupled to a leading end portion of the high pressure operator 162 and contacting and separated from the low pressure contact point 154.

[64] The low pressure operator 152 and the high pressure operator 162 can be made of leaf springs having a predetermined elasticity. The low pressure operator 152 has a pin hole 153 formed at the center thereof thrash which the guide pin 190 passes. A protruding rod contact portion 155 is formed at around the pin hole 153. The low pressure operator 152 is disposed above the high pressure operator 162 parallel thereto so that the low pressure contact point 154 and the high pressure contact point 164 are installed to face each other.

[65] The first switch SW1 may further include a low pressure port 150 and a high pressure port 160 coupled to the low pressure operator 152 and the high pressure operator 162 to fix the low pressure operator 152 and the high pressure operator 162 inside the base 104. The low pressure port 150 and the high pressure port 160 can contact an electric circuit (not shown) outside the triple action pressure switch 100.

[66] The second switch SW2 is disposed under the third pressure sensing disc 116 and includes a mobile operator 172 driven by the circular protrusion 142, a mobile contact point 174 coupled to a leading end portion of the mobile operator 172, and a fixed contact point 182 contacting and separated from the mobile contact point 174. The mobile operator 172 is disposed above the fixed contact point 182 so that the mobile contact point 174 and the fixed contact point 182 are installed to face each other.

[67] The second switch SW2 may further include a mobile port 170 and a fixed port 180 which fix the mobile operator 172 and the fixed contact point 182 inside the base 104. The mobile port 170 and the fixed contact port 180 can be connected to the electric circuit (not shown) outside the triple action pressure switch 100.

[68] The first, second, and third pressure sensing discs 110,112, and 116 constituting the switch driving unit is operated as follows.

[69] When the pressure of a fluid is below P, the protruding portion of the first H pressure sensing disc 110 protrudes upward. However, when a pressure over P is H applied, the protruding portion is reversed to protrude downward due to a reversing action. A displacement due to the reversing action of the first pressure sensing disc 110 presses the guide pin 190 downward. Accordingly, the lower end of the guide pin 190 presses the high pressure operator 162 of the first switch SW1 so that the high pressure contact point 164 is separated from the low pressure contact point 154. Thus, the first switch SW1 is in an open state, that is, electrically disconnected.

[70] When the pressure of a fluid is below P +AP, the protruding portion of the second L L pressure sensing disc 112 protrudes upward. However, when a pressure over P +AP is L L applied, the protruding portion is reversed to protrude downward due to a reversing action. A displacement due to the reversing action of the second pressure sensing disc 112 makes the first pivot base 120 slide downward. Accordingly, the lower end of the protruding rod 124 presses the low pressure operator 152 of the first switch SW1 so that the low pressure contact point 154 contacts the high pressure contact point 164.

Thus, the first switch SW1 is in a closed state, that is, electrically connected.

[71] When the pressure of a fluid reaches a high pressure and then is lowered to the pressure P, the second pressure sensing disc 112 is reversed to the original state so as L to push the first pivot base 120 upward. Accordingly, the protruding rod 124 no longer presses the low pressure operator 152 of the first switch SW1 so that the first switch SW1 returns to the open state.

[72] When the pressure of a fluid is below P, the protruding portion of the third M pressure sensing disc 116 protrudes upward. However, when a pressure over P is M applied, the protruding portion is reversed to protrude downward due to a reversing action. The displacement due to the reversing action of the third pressure sensing disc 116 makes the third pivot base 140 slide downward. Accordingly, the circular protrusion 142 presses the mobile operator 172 of the first switch SW1 so that the mobile contact point 174 contacts the fixed contact point 182. Thus, the second switch SW2 is in an open state, that is, electrically disconnected.

[73] When the pressure of a fluid is lowered to the pressure P PAP, the third pressure M M sensing disc 116 is reversed to the original state so as to push the third pivot base 140 upward. Accordingly, the circular protrusion 142 no longer presses the mobile operator 172 of the second switch SW2 so that the second switch SW2 returns to the open state.

[74] The operation of the triple action pressure switch having the above structure is described below with reference to FIG. 7. Here, in the following description, it is assumed that the pressure of a fluid applied to the switch driving unit of the triple action pressure switch according to the present embodiment gradually increases to reach the high pressure P and gradually decreases under the set low pressure P.

H L [75] First, when the pressure of a fluid, P +AP is applied to the first pressure sensing L L disc 110, a load is applied to the upper surface 114 of the second pressure sensing disc 112 through the flat step 126 of the first pivot base 120. Then, the second pressure sensing disc 112 is reversed downward by the load and the first pivot base 120 slides down. As the protruding rod 124 of the first pivot base 120 presses the low pressure operator 152 of the first switch SW1, the low pressure contact point 154 contacts the high pressure contact point 164 so that the first switch SW1 is in a closed state, that is, electrically connected.

[76] Here, the guide pin 190 disposed in the center hole 122 of the fist pivot base 120 does not move downward by the movement of the first pivot base 120.

[77] When the pressure of a fluid increases to the pressure P, the load is applied to the M upper surface 118 of the third pressure sensing disc 116 through the first pressure sensing disc 110, the first pivot base 120, the second pivot base 130, the third pivot base 140, and the should step 144 of the third pivot base 140. Then, the third pressure sensing disc 116 is reversed downward by the load and the third pivot base 140 slides down. As the circular protrusion 142 of the third pivot base 140 presses the mobile operator 172 of the second switch SW2, the mobile contact point 174 contacts the fixed contact point 182 so that the second switch SW2 is in a closed state, that is, electrically connected.

[78] When the pressure of a fluid increases further to the pressure P, the first pressure H sensing disc 110 is reversed. A reversing force due to the reversion of the first pressure sensing disc 110 is transferred to the guide pin 190 of which the upper end contacts the center portion of the lower portion of the first pressure sensing disc 110. The lower end of the moved guide pin 190 presses the high pressure operator 162 of the first switch SW1 so that the high pressure contact point 164 is separated from the low pressure contact point 154. Thus, the first switch SW1 is in an open state, that is, electrically disconnected.

[79] When the pressure of a fluid is lowered from P to P PAP, the first pressure H H H sensing disc 110 is reversed to the original state so that a force transferred to the guide pin 190 is decreased. The guide pin 190 is moved upward by an elastic force of the high pressure operator 162 of the first switch SW1. Accordingly, the high pressure contact point 164 contacts the low pressure contact point 154 so that the first switch SW1 is in a closed state, that is, electrically connected.

[80] When the pressure of a fluid is lowered to P PAP, the third pressure sensing disc M M 116 is reversed to the original state so as to push the third pivot base 140 upward.

Then, the circular protrusion 142 no longer presses the mobile operator 172 of the second switch SW2 so that the mobile contact point 174 is separated from the fixed contact point 182 by the elastic force of the mobile operator 172 of the second switch SW2 Accordingly, the second switch SW2 is in an open state, that is, electrically dis- connected.

[81] When the pressure of a fluid is lowered further to P, the second pressure sensing L disc 112 is reversed to the original state so as to push the first pivot base 120 upward.

Then, the protruding rod 124 no longer presses the low pressure operator 152 of the first switch SW1 so that the low pressure contact point 154 is separated from the high pressure contact point 164 by the elastic force of the low pressure operator 152 of the first switch SW1. Thus, the first switch SW1 is in an open state, that is, electrically dis- connected.

[82] As described above, the triple action pressure switch can be operated in three phases by using the hysteresis characteristic of the pressure sensing disc of the switch driving unit and the elastic force of the operator of the switch.

Mode for Invention [83] FIG. 8 is a vertical sectional view illustrating a triple action pressure switch according to another embodiment of the present invention. FIG. 9 is a view illustrating an operating pressure characteristic of the triple action pressure switch of FIG. 8.

[84] Referring to FIGS. 8 and 9, in the second switch SW2, the mobile operator 172 is disposed under the fixed contact point 182 and the mobile contact point 174 and the fixed contact point 182 are in contact with each other. When the pressure of a fluid exceeds P, the second switch is in an open (off) state. When the pressure of a fluid is M lowered to P PAP, the second switch SW2 is in a closed (on) state. The other M M structure and operation are the same as those described with reference to FIGS. 3,4, 5, and 6.

[85] FIG. 10 is an exploded perspective view illustrating a triple action pressure switch according to yet another embodiment of the present invention. FIG. 11 is a vertical sectional view taken along line A-A to show the structure of the triple action pressure switch of FIG. 10. FIG. 12 is a vertical sectional view taken along line B-B to show the structure of the triple action pressure switch of FIG. 10.

[86] Referring to FIGS. 10,11, and 12, in the triple action pressure switch according to yet another embodiment of the present invention, a second pivot base 230 has an outer circumferential wall formed on an upper surface thereof. A rod hole 232 thrash which the protruding rod 124 passing thrash the rod hole 113 passes is formed at the center of the second pivot base 230. A protruding portion 234 is formed at both ends of the outer circumference of a lower surface of the second pivot base 230. The outer cir- cumference of the second pivot base 230 directly slides on the inner wall of the base 104. An outer circumferential wall of the upper surface of the second pivot base 230 holds the peripheral portion of the second pressure sensing disc 112.

[87] Also, a third pivot base 240 has an upper surface which contacts an end portion of the protruding portion 234 of the second pivot base 230. A circular protrusion 242 protruding as a shaft at the center of the third pivot base 240 and a shoulder step 244 encompassing an outer circumference of the circular protrusion 242 are formed on a lower surface of the third pivot base 240. The outer circumference of the third pivot base 240 directly slide on the inner wall of the base 104. The upper surface of the third pivot base 140 contacts the end portion of the protruding portion 234 while the upper surface, the inner side wall 236 of the protruding portion 234, and the lower surface of the second pivot base 230 form a space where the first switch SW1 is installed.

[88] The third pivot base 240 transfers the pressure of a fluid passing through the first pressure sensing disc 110, the first pivot base 120, and the second pivot base 230 to the third pressure sensing disc 116 via the shoulder step 244. Sirn. iltaneously, when the third pressure sensing disc 116 is reversed, the third pivot base 240 is moved downward as much as a placement due to the reversion and transfers the pressure to the mobile operator 172 of the second switch SW2 via the circular protrusion 242.

[89] The other structure and operation are the same as those of the triple action pressure switch described with reference to FIGS. 3,4, 5,6, and 7.

[90] Also, in the triple action pressure switch according to yet another embodiment of the present invention, as shown in FIGS. 8 and 9, the mobile operator 172 of the second switch SW2 is disposed under the fixed contact point 182 and the mobile contact point 174 and the fixed contact point 182 are in contact with each other.

Industrial Applicability [91] As described above, in the triple action pressure switch according the present invention, since three different pressures are detected and the on/off state of the two switches are controlled according to the detected pressure, the pressure of coolant in room air conditioners or car air conditioners or various hydraulic pressures of a brake or oil pump for a car are detected so that external apparatuses can be operated according to the detected pressure.