Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M25/00—Catheters; Hollow probes
  • A61M25/01—Introducing, guiding, advancing, emplacing or holding catheters
  • A61M25/0105—Steering means as part of the catheter or advancing means; Markers for positioning
  • A61M25/0127—Magnetic means; Magnetic markers
• • 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
• • 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
  • H01H36/0033—Mountings; Housings; Connections

Definitions

• the present invention relates to a magnetic reed switch, and more particularly, but not by way of limitation, to a shielded magnetic reed switch which, when exposed to the magnetic flux of an approaching magnetic field source, does not actuate until the distance between the shielded magnetic reed switch and the approaching magnetic field source is less than or equal to a predetermined distance.
• the shielded magnetic reed switch provides a sensor which actuates and thereby provides an input to an electrical circuit to indicate the distance between the shielded magnetic reed switch and the approaching magnetic field source.
• Magnetic reed switches are well known in the art.
• a magnetic reed switch has associated with it a specific magnetic field strength (sometimes referred to herein as magnetic flux) required to actuate the reed switch.
• a very strong magnetic field e.g., a permanent magnet having at a magnetic field strength of at least 300 Gauss at a distance of 4 inches from the magnet's pole face
• a typical magnetic reed switch will actuate at a distance of 12-18 inches from the source of the very strong magnetic field.
• Progress in the area of magnetic reed switches has largely involved development of ever more sensitive reed switches, i.e., reed switches requiring low magnetic field strength (low magnetic flux) for actuation.
• the present invention provides a magnetic reed switch disposed within a ferrous metal housing, thereby requiring a stronger magnetic flux than would otherwise be required to actuate the unshielded magnetic reed switch. Based on the selection of the reed switch and the architecture of the ferrous metal housing, the shielded magnetic reed switch of the present invention remains unactuated in the presence of the magnetic field strength normally resulting in actuation of the unshielded magnetic reed switch.
• the present invention further provides a sensor for detecting the presence of an approaching magnetic field source at a predetermined distance.
• An object of the present invention is to provide a magnetic reed switch which, in the presence of a magnetic field source having sufficient magnetic flux to actuate the magnetic reed switch, remains unactuated until the magnetic field source is within a predetermined distance from the magnetic reed switch. It is another object of the present invention to provided a series of shielded magnetic reed switches which, when used together, indicate the progress of an approaching magnetic field source.
• FIG. 1 is an enlarged cross-sectional view of a shielded magnetic reed switch of the present invention.
• FIG.2 is an enlarged cross-sectional view of a second embodiment of a shielded magnetic reed switch of the present invention.
• FIG. 3 is an enlarged cross-sectional view of a third embodiment of a shielded magnetic reed switch of the present invention.
• FIG. 4 is a representation of the operation of applicants' invention.
• FIG. 5 is another representation of the operation of applicants' invention.
• FIGS. 1-3 shown therein are three embodiments of the shielded magnetic reed switch 10 of the present invention.
• a normally open magnetic reed switch 16 consisting of reeds 12, 14 sealed in a glass envelope 17, is disposed within a ferrous metal housing 30. Electrical leads 18, 20 are soldered to the portions of the reeds 12, 14, and heat shrink 22, 24 is applied as indicated.
• the magnetic reed switch 16 is then placed within the ferrous metal housing 30 and potting compound 36 holds the reed switch 16 and leads 18, 20 in position within the ferrous metal housing 30.
• a ferrous metal housing 30 having a diameter of about 0.125 inch, a tubular wall 32 thickness of about 0.0125 inches, and a thickened end portion 34 of about 0.125 inches at its maximum thickness results in closure of the magnetic reed switch 16 when the permanent magnet
• FIG. 2 shown therein is another embodiment of the shielded magnetic reed switch 10 of the present invention.
• the tubular wall 32A is about 0.0125 inches thick and the thickened end portion 34A of ferrous metal housing 30 is about 0.151 inches thick.
• the thickened end portion 34A is about 0.125 inches thick at its thickest point.
• FIG. 3 shown therein is another embodiment of the shielded magnetic reed switch 10 of the present invention.
• the tubular wall 32B is about 0.025 inches thick and the ferrous metal housing is about 0.151 inches thick.
• the thickened end portion 34B is about 0.125 inches thick at its thickest point.
• FIGS. 1-3 the ferrous metal housing 30 is annealed to a full soft condition to maximize magnetic permeability.
• FIGS. 4 and 5 the operation of the shielded magnetic reed switch 10 (much enlarged) in the presence of a magnetic field associated with a permanent magnet M is illustrated.
• a distance D in FIGS. 4 and 5 defines the distance between the shielded magnetic reed switch 10 and the pole face P of permanent magnet M (about 3.5 to 5. 0 inches) at which closure of the magnetic reed switch 16 occurs.
• the permanent magnet M is positioned out of range of the distance D at which closure of the magnetic reed switch 16 (see FIGS. 1-3) is desired.
• the ferrous metal housing 30 At distances exceeding D (i.e., distances greater than about 5 inches and within the 12-18 inches at which an unshielded magnetic reed switch 16 would normally close) the ferrous metal housing 30 (see FIGS. 1 -3) absorbs the magnetic flux produced by the permanent magnet M and prevents the magnetic reed switch 16 from closing.
• the magnetic reed switch 16 connected to a generic electrical circuit by electrical leads 18, 20 remains open.
• the permanent magnet M is positioned within the distance D at which the shielded magnetic reed switch 10 closes.
• the magnetic reed switch 16 connected to the generic electrical circuit by electrical leads 18, 20 is now closed.
• the shielded magnetic reed switch 10 While the operation of the shielded magnetic reed switch 10 is illustrated in conjunction with a permanent magnet M, it will be understood by one skilled in the art that the shielded magnetic reed switch 10 of the present invention operates as illustrated with any magnetic field source (i.e., with either a permanent magnet or an electromagnet). It will be understood by one skilled in the art that the ferrous metal housing 30 acts as a magnetic shield to prevent the reeds 12, 14 from closing prematurely and, further, that the structure of the ferrous metal housing 30, including the thickness of the tubular wall 32, 32A, 32B and the thickness of the thickened end portion 34, 34A, 34B determine the distance D from the magnetic field source (e.g., the permanent magnet
• a relatively thinner tubular wall 32, 32A, 32B will result in closure of the magnetic reed switch 16 at a relatively greater operating distance D.
• a relatively thinner thickened end portion 34, 34A, 34B will also result in closure of the magnetic reed switch 16 at a relatively greater operating distance D.
• Selection of the magnetic reed switch 16 also affects the operating distance D.
• a magnetic reed switch 16 having relatively more flexible reeds results in closure of the magnetic reed switch 16 at a relatively greater operating distance D, whereas a magnetic reed switch 16 having relatively stiffer reeds effectively reduces the distance D at which the magnetic reed switch 16 closes.
• the present invention is for apparatus involving a magnetic reed switch disposed within a ferrous housing, so that the shielded magnetic reed switch actuates at a predetermined distance from an approaching magnetic field source. In the absence of the ferrous housing, the magnetic reed switch will actuate at a distance greater than the predetermined distance. While applicants' invention is illustrated herein as being a normally open magnetic reed switch 16 disposed within a ferrous metal housing 30, it will be understood to one skilled in the art that reed switches can be either normally open or normally closed.
• a single-pole, single-throw (SPST), normally-open magnetic reed switch (also referred to by those skilled in the art as a Form "A” reed switch) is illustrated herein.
• SPST single-pole, single-throw
• SPDT normally-closed magnetic reed switches
• SPDT single- pole, double-throw
• C break-before-make reed switches

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biophysics (AREA)
• Pulmonology (AREA)
• Engineering & Computer Science (AREA)
• Anesthesiology (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Hematology (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Switches That Are Operated By Magnetic Or Electric Fields (AREA)

Applications Claiming Priority (5)

Publications (2)

Family

ID=26978890

Family Applications (1)

Country Status (6)

Families Citing this family (2)

Family Cites Families (5)

• 2000
  • 2000-04-05 JP JP2000619240A patent/JP2003526181A/ja active Pending
  • 2000-04-05 WO PCT/US2000/008997 patent/WO2000070914A2/en not_active Ceased
  • 2000-04-05 EP EP00920144A patent/EP1579729A2/de not_active Withdrawn
  • 2000-04-05 CA CA002371495A patent/CA2371495A1/en not_active Abandoned
  • 2000-04-05 AU AU40726/00A patent/AU4072600A/en not_active Abandoned
  • 2000-04-05 MX MXPA01011922A patent/MXPA01011922A/es unknown

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