BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a magnetic guide for magnetically guiding a remote device, and more particularly, but not by way of limitation, to a ferrous metal follower which moves in response to movement of a magnetically coupled leader magnet and a shielded magnetic reed switch which actuates at the point at which a magnetic coupling is established between the ferrous metal follower and the leader magnet. In another embodiment, a follower magnet is used instead of a ferrous metal follower to further enhance the magnetic coupling. In another embodiment, the shielded magnetic reed switch provides a sensor which actuates and thereby provides an input to an electrical circuit to indicate establishment of the magnetic coupling.
2. Background Art 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. In the presence of a very strong permanent magnetic having 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 pole face. 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.
Likewise, the use of magnets to manipulate ferrous materials is well known in the art. Over the years, a variety of children's toys have used magnets to manipulate such diverse items as simulated ice skaters (magnets underneath a simulated ice ring, ferrous metal follower or follower magnets attached to the feet of toy skaters) and simulated dancers (magnets underneath a simulated dance floor, ferrous metal followers or follower magnets attached to the feet of toy dancers).
Until now, no one has developed a magnetic reed switch for use in combination with a ferrous metal follower which is moved and otherwise manipulated by a leader magnet, so that the magnetic reed switch actuates at a predetermined distance commensurate with establishment of a magnetic coupling between the ferrous metal follower and the leader magnet.
3. Disclosure of the Invention The present invention provides a ferrous metal follower guided by a leader magnet. The ferrous metal follower is positioned adjacent to a magnetic reed switch disposed within a ferrous metal housing. 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 leader magnet until the distance between the shielded magnetic reed switch and the leader magnet matches the distance for formation of a magnetic coupling between the ferrous metal follower and the leader magnet. The present invention further provides a sensor for indicating a predetermined distance between the ferrous metal follower and the leader magnet at which a magnetic coupling is established.
An object of the present invention is to provide a magnetic guide, wherein a ferrous metal follower (or a follower magnet) is positioned adjacent to a magnetic reed switch which, in the presence of a leader magnet 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 at which predetermined distance a magnetic coupling is established between the leader magnet and the ferrous metal follower.
It is another object of the present invention to provide a shielded magnetic reed switch for use with a leader magnet and a ferrous metal follower, which shielded magnetic reed switch indicates a predetermined distance between the magnetic reed switch and the leader magnet by actuating when the approaching leader magnet is within the predetermined distance.
4. Brief Description of the Drawings FIG. 1 is an enlarged cross-sectionai view of a ferrous metal follower and a shielded magnetic reed switch for use with a leader magnet according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a second embodiment of a shielded magnetic reed switch and ferrous metal follower for use with a leader magnet according to the present invention.
FIG. 3 is an enlarged cross-sectional view of a third embodiment of a shielded magnetic reed switch and ferrous metal follower for use with a leader magnet according to the present invention.
FIG. 4 is a representation of applicants'invention showing the operation of a leader magnet in conjunction with the ferrous metal follower and shielded magnetic reed switches of FIGS. 1-3.
FIG. 5 is another representation of applicants'invention showing the operation of a leader magnet in conjunction with the ferrous metal follower and shielded magnetic reed switches of FIGS. 1-3.
FIG. 6 is an enlarged cross-sectional view of a shielded magnetic reed switch and a follower magnet for use with a leader magnet according to the present invention.
FIG. 7 is an enlarged cross-sectional view of a second embodiment of a shielded magnetic reed switch and a follower magnet for use with a leader magnet according to the present invention.
FIG. 8 is an enlarged cross-sectional view of a third embodiment of a shielded magnetic reed switch and a follower magnet for use with a leader magnet according to the present invention.
FIG. 9 is a representation of applicants'invention showing the operation of a leader magnet in conjunction with a follower magnet and the shielded magnetic reed switches of FIGS. 6-8.
FIG. 10 is another representation of applicants'invention showing the operation of a leader magnet in conjunction with the follower magnet and the shielded magnetic reed switches of FIGS. 6-8.
FIG. 11 shows applicants'shielded magnetic reed switch of FIG. 6 and a follower magnet secured within a flexible plastic tube.
5. Best Mode for Carrying Out the Invention In the following description of the invention, like numerals and characters designate like elements throughout the figures of the drawings.
Referring now to FIGS. 1-3, shown therein are three embodiments of the shielded magnetic reed switch 10 and a ferrous metal follower 38. A remote device R is indicated by dashed lines. In FIG. 1, 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.
Positioned adjacent the shielded magnetic reed switch is a ferrous metal follower 38. It will be understood to one skilled in the art that the method of attachment of the shielded magnetic reed switch 10 and the ferrous metal follower 38 to the remote device R is not critical to applicants'invention. For example, the shielded magnetic reed switch 10 and the ferrous metal follower 38 can be jointly encapsulated and incorporated into the body of the remote device R. Although crude in design, the shielded magnetic red switch 10 and the ferrous metal follower 38 may also be fastened to the remote device R by means of a suitable adhesive.
For a permanent magnet M having a magnetic flux field of about 350 Gauss at a distance of 4 inches from the pole face P (see FIGS. 4 and 5), 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 M is within 3.5 to 5.0 inches of the magnetic reed switch 16 the adjacent ferrous metal follower 38. In the absence of the ferrous metal housing 30, the reeds 12,14 of the magnetic reed switch 16 close at a distance of about 12-18 inches between the pole face P of the permanent magnet M and the magnetic reed switch 16, a distance well beyond the distance at which a magnetic coupling is created between the ferrous metal follower 38 and the permanent magnet M.
In the present invention, the permanent magnet M is also referred to as the leader magnet M. Once a magnetic coupling is created between the ferrous metal follower 38 and the leader magnet M, the ferrous metal follower 38 (and any remote device R attached to the ferrous metal follower) moves in response to movements of the leader magnet M.
Referring now to FIG. 2, shown therein is another embodiment of the shielded magnetic reed switch 10 and the ferrous metal follower 38 of the present invention. In FIG. 2, 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.
Referring now to FIG. 3, shown therein is another embodiment of the shielded magnetic reed switch 10 and the ferrous metal follower 38 of the present invention. In FIG. 3, 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.
In FIGS. 1-3, the ferrous metal housing 30 is annealed to a full soft condition to maximize magnetic permeability.
In FIGS. 4 and 5, the operation of the shielded magnetic reed switch 10 (much enlarged), the ferrous metal follower 38, and the leader 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 leader magnet M (about 3.5 to 5.0 inches) at which closure of the magnetic reed switch 16 occurs.
Referring now to FIG. 4, the leader 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 (more specifically, the distance at which a magnetic coupling between the ferrous metal follower 38 and the leader magnet M is established). 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 leader 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.
Referring now to FIG. 5, the leader magnet M is positioned within the distance D at which a magnetic coupling is established and 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.
Referring now to FIGS. 6-8, shown therein are three embodiments of the shielded magnetic reed switch 10 and a follower magnet 40 attached to a remote device R. In FIGS. 6-8, the structure is like that of FIGS. 1-3, respectfully, except for the substitution of a follower magnet 40 (FIGS. 6-8) for the ferrous metal follower 38 (FIGS.
1-3). The magnetic coupling established between the follower magnet 40 (FIGS. 6-8) and the leader magnet M is stronger than the magnetic coupling established between the ferrous metal follower 38 (FIGS. 1-3) and the leader magnet M, thereby providing a more positive magnetic guide.
It will be understood by one skilled in the art that the ferrous metal housing 30 can also perform double duty as the ferrous metal follower. The size and shape of the ferrous metal follower is a design choice based on the size of the remote device R and the resistance to be encountered in its manipulation.
In FIGS. 9 and 10, the operation of the shielded magnetic reed switch 10 (much enlarged), the follower magnet 40, and the leader magnet M is illustrated. A distance D in FIGS. 9 and 10 defines the distance between the shielded magnetic reed switch 10 and the pole face P of leader magnet M (about 3.5 to 5.0 inches) at which closure of the magnetic reed switch 16 occurs.
Referring now to FIG. 9, the leader magnet M is positioned out of range of the distance D at which closure of the magnetic reed switch 16 (see FIGS. 6-8) is desired (wherein the distance D corresponds to the distance at which a magnetic coupling between the follower magnet 40 and the leader magnet M is established). 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. 6-8) absorbs the magnetic flux produced by the leader 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.
Referring now to FIG. 10, the leader magnet M is positioned within the distance D at which a magnetic coupling is established and 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.
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).
Referring now to FIG. 11, the shielded magnetic reed switch 10 and the follower magnet 40 of FIG. 6 are enclose in a flexible plastic tube 42. The plastic tube 42 includes a slight bulge 44 and an opening 46 through which the follower magnet 40 may be inserted. An opening 48 in the flexible plastic tube 42 is available for attachment to the remote device R to be guided by applicants'invention.
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 leader magnet M) at which the shielded magnetic reed switch 10 closes. 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.
It will be further understood by one skilled in the art that 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. Single-pole, single-throw (SPST), normally-closed magnetic reed switches (also referred to by those skilled in the art as Form"B"reed switches), single-pole, double- throw (SPDT), break-before-make reed switches (also referred to by those skilled in the art as Form"C"reed switches), and single-pole, double-throw, make-before-break reed switches (also referred to by those skilled in the art as Form"D"reed switches) are known in the art and suitable for use in lieu of the magnetic reed switch 16 of FIGS. 1-3 and 6-8. Whether Form A, Form B, Form C, or Form D, each type of switch can be shielded in accordance with the present invention as taught herein.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and many modifications and variations are possible in light of the above teaching. The embodiments were chosen in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best use the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
6. Industrial Applicability The magnetic guide of the present invention includes a sensor which indicates the establishment of a magnetic coupling between the leader magnet and the follower magnet. The sensor provides an affirmative indication to the user that the manipulation of the leader will result in a corresponding movement of the follower magnet and any device attached thereto.
It will be understood by one skilled in the art that the magnetic guide of the present invention can be used to guide copper wires through hollow walls, manipulate fiber optic cameras in close environments such as plastic pipes, and, more generally, to create a magnetic guidance path by creating a traction force between the leader magnet and the follower magnet. In each instance, the sensor of the present invention actuates when the leader magnet is in the traction position with respect to the follower magnet.
