Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H36/00—Switches actuated by change of magnetic field or of electric field, e.g. by change of relative position of magnet and switch, by shielding
  • H01H36/0006—Permanent magnet actuating reed switches
  • H01H36/0013—Permanent magnet actuating reed switches characterised by the co-operation between reed switch and permanent magnet; Magnetic circuits
  • H01H36/002—Actuation by moving ferromagnetic material, switch and magnet being fixed

Definitions

• the invention concerns a pressure switch, especially a hood switch, according to the introduction to claim 1.
• a second object of the pressure switch according to the invention is that it should be capable of being employed, e.g. in cars for retrofitting of alarms without height adaptation.
• a further object is to provide a pressure switch which can be placed in doors or window frames when installing house alarms.
• Fig. 1 illustrates the pressure switch according to the present invention.
• Fig. 2 illustrates how the pressure switch in fig. 1 is installed on a base.
• Fig. 3 illustrates the pressure switch in fig. 1 in the contact position and with the contact arm 4 fully open.
• Fig. 4 indicates the angular movement of the switch arm in a closed switch.
• Fig. 5 illustrates the pressure switch in fig. 1 in an open position and with the switch arm fully down.
• Fig. 6 illustrates the cable output from the switch in fig. 1.
• Fig. 7 illustrates the installation of the switch arm in the switch housing.
• Fig. 8 illustrates the location of a magnet in the switch housing.
• Fig. 9 illustrates schematically several pressure switches according to the present invention installed in an alarm circuit.
• Fig. 1 illustrates the pressure switch according to the invention with an exploded view of the components.
• the switch comprises a plastic housing 1 on to the side of which there is moulded a reed relay 2 in the section 8 on the side of the plastic housing and with a watertight cable outlet, thus preventing corrosion damage to the cables and contact legs. Ordinarily this is a major problem when using hood switches in cars due to road salting in winter, which results in the deposition of salt solution in the engine compartment.
• the switch is mounted on to a base with a self-tapping screw 7 which penetrates the housing 1.
• a permanent magnet 3 In a recess 9 in the switch housing 1 there is provided a permanent magnet 3.
• a steel switch arm 4 is mounted on the housing 1 in such a manner that it can cover the section of the housing 1 which does not include the section 8 at the side.
• the switch arm 4 pivots about a shaft 5 mounted in the housing 1 and is raised to the open position by a stainless steel spring 6 mounted on the shaft 5.
• the central section of the switch arm 4 on the side is provided with a downwardly projecting lug or section 10 which, when the switch arm 4 is located in the lowered position and in contact with the switch housing 1, enters a longitudinal slot 1 1 between the recess 9 and the section 8 which contains the reed relay 2.
• the polar axis of the permanent magnet 3 is substantially parallel to the switch arm's pivotal plane and thereby the section 10.
• the section 10 shields the reed relay 2 from the magnetic field of the permanent magnet 3 and the contact is broken.
• the switch arm 4 with the downwardly projecting section 10 is designed in such a manner that a rather small angular downward movement of the switch arm 4 will cause the switch to be opened.
• FIG. 2 The installation of the pressure switch according to the invention on a base is illustrated in more detail in fig. 2. It is secured by connecting the housing 1 to a self-tapping screw 7 and is quite simply mounted with a screwdriver.
• Fig. 3 shows the switch according to the invention in the closed position and with the contact arm raised. It will be seen that the downwardly projecting section 10 no longer provides a shield from the magnetic field.
• the switch arm 4 has been moved from the position illustrated by a dotted line to the position illustrated by a solid line. The switch is now open, but from the last position the downwardly projecting section 10 on the switch arm will block the magnetic field and keep the reed relay 2 open.
• Fig. 3 shows the switch according to the invention in the closed position and with the contact arm raised. It will be seen that the downwardly projecting section 10 no longer provides a shield from the magnetic field.
• the switch arm 4 has been moved from the position illustrated by a dotted line to the position illustrated by a solid line. The switch is now open, but
• FIG. 5 illustrates the switch according to the invention with the switch arm 4 fully down and resting on the housing 1 in such a manner that the switch is still located in the open position. It will be seen that the height of the switch in this position can be exceptionally low. The pressure switch is open over a great part of the switch arm's 4 angular movement from its contact with the housing 1, and this means that the switch 1 can be mounted even in a location where there is a substantial clearance between, e.g. hood and base.
• fig. 6 it can be seen how the wires 2a from the reed relay 2 (not shown) moulded into the switch housing 1 are passed in a watertight fashion out of the switch housing 1.
• Fig. 7 illustrates as shown in fig.
• Fig. 8 illustrates the switch housing 1 with the permanent magnet 3 removed.
• Fig. 8b illustrates how the permanent magnet is inserted from beneath into the recess on the switch housing 1 and is locked there by a snap device 13 which forms an integral part of the housing 1.
• fig. 9 shows how the pressure switch according to the invention can form part of an alarm circuit either in a car or in a house alarm.
• house alarms it is a very simple matter to adapt the switch according to the invention for use in door openings and window frames.
• a number of switches S can then be mounted in series.
• the switch according to the invention can be equipped with a small resistor R in parallel over the reed relay. If the alarm cable is now cut at some point between the switches or between the switches and an alarm central monitor, the resistance value detected and set in the central monitor according to the number of switches no longer applies and shows that the alarm circuit has been tampered with.
• the pressure switch according to the invention is mounted on the surface of a base, has a very low height when the switch arm 4 is located in abutment with the housing, and permits a large angular movement of the switch arm 4 before the relay is closed, a highly advantageous and flexible installation solution is obtained, especially when used as a hood switch in a car.
• the pressure switch according to the invention is particularly suited to being mounted close against a steel plate or another material which is influenced by magnetism, without the switch's function being affected.
• the pressure switch according to the invention as it is designed, is sabotage and tamper-proof and in general is particularly well suited to use as an hood switch or alarm switch in cars.

Landscapes

• Switch Cases, Indication, And Locking (AREA)
• Emergency Alarm Devices (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=19897952

Family Applications (1)

Country Status (3)

Cited By (2)

Citations (4)

• 1995
  • 1995-02-21 NO NO950657A patent/NO950657L/no unknown
• 1996
  • 1996-02-20 WO PCT/NO1996/000039 patent/WO1996026527A1/en active Application Filing
  • 1996-02-20 AU AU48517/96A patent/AU4851796A/en not_active Abandoned

Patent Citations (4)

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