The present invention relates to dial assemblies for use with magnetically driven gauges and, in particular, a magnetically biased reed switch for indicating a certain liquid level.
Magnetically driven gauges are commonly utilized in measuring the liquid level of liquified compressed gases such as LP gas. These types of gauges are commonly employed in pressure vessels. The gauge assembly typically has two parts, one being a float assembly and the other being a dial assembly. The float assembly generally comprises a float which moves in response to changes in liquid level. The float assembly has a gauge head for attaching to the vessel. As the float moves in response to changes in liquid levels, the tank magnet of the float assembly rotates corresponding to changes in the float position. The gauge head seals the float assembly from the outside environment. The separate dial assembly is used in connection with the float assembly. The dial assembly is mounted on the outside of the gauge head and positioned such that it is operatively adjacent to the tank magnet. The dial assembly typically has a back with a pivot pin, and a dial magnet which is rotatable about the pivot pin. When the dial assembly is mounted on the gauge head, it is positioned such that the tank magnet and dial magnet are magnetically coupled. Thus, as the tank magnet rotates it will cause a corresponding rotation of the dial magnet. The dial magnet can include a pointer either as a part of the magnet or as a separate piece. The pointer can then be used in combination with indicia on the dial face to provide a visual indication of the liquid level in the tank to the user.
One disadvantage of these gauges is that the tank may be located where the dial is not conveniently observed by the operator. To address that disadvantage, dial assemblies have been used which include a resistive element in order to provide a continuous and instantaneous transmission of a signal representing the tank level to a location remote from the tank that is more easily viewed by the user. Such a dial assembly is illustrated in U.S. Pat. No. 4,987,400. These dial assemblies have a disadvantage in that they are costly to construct and require circuitry to match the output with the remote gauge.
There has been a continuing need for a low cost remote indicator of the fluid level in such a vessel. In many applications, it is not necessary to have a readily visible indication of liquid level available to the operator. What is desirable, however, is an indication of low liquid level so that the operator may refuel before exhausting the fuel supply. The present invention provides a dial assembly which may be used with existing float assemblies to provide a remote indication that the fuel is low and refueling is appropriate. The present invention has the advantage of being easy to construct, requires little sophisticated circuitry to implement and can be retrofitted on many existing float assemblies.
In one aspect, the present invention relates to the dial assembly for use in a magnetically driven gauge. The assembly includes a first member which has a pivot pin extending therefrom, a dial magnet which is rotatable about the pivot pin, and a reed switch assembly positioned operatively adjacent to the dial magnet. The second member is provided to cooperate with the first member to form a housing for the dial magnet. The reed switch assembly includes a reed switch, a bias magnet, and electrical leads to the reed switch. In addition, the reed switch assembly may be integral with the dial assembly or may be a separate unit which is attachable to the housing of the dial assembly. The bias magnet functions to hold the two reeds of the reed switch in contact, thereby allowing the reed switch to form an electrical path. The reed switch assembly and the dial magnet are positioned operatively adjacent to one another. In operation, when the reed switch is in a first orientation (for example, the closed orientation where the reeds are in contact), the poles of the dial magnet are also in a first orientation. Preferably, the poles of the dial magnet are on opposite sides of the pivot pin and rotate about the pivot pin. In the first orientation, which may be the reed switch closed orientation, the dial magnet can be rotated through an arc in which the reed switch will remain closed. Any position on this arc would be a first orientation position of the dial magnet. The reed switch is held in a second orientation (an open switch where the reeds are not in contact) when the dial magnet is in a second orientation. The second orientation of the dial magnet would be any position in the arc of rotation of the dial magnet in which the reed switch remains open. Thus, the invention allows one pole of the dial magnet to pass by the reed switch without causing the reed switch to open, and to cause the reed switch to open when the other pole of the dial magnet passes by the reed switch. Thus, the invention allows for a construction of the dial assembly having a reed switch assembly wherein the dial magnet can rotate more than 180° but only cause the reed switch to change orientation when only one of the dial magnet poles pass nearby. Passage of the other poles of the dial magnet does not cause the reed switch to change orientation.
In a preferred embodiment of the present invention, the first member of the dial assembly forms a base. Extending from the first member is the pivot pin. Rotatably mounted about the pivot pin is a dial magnet. The dial magnet may either include a pointer as part of the magnet or be attached to a pointer assembly. Mounted between the pointer and the first member is a dial face bearing indicia of liquid level. A second member forms a cover over the dial magnet and pointer. The cover may include as an integral part, the reed switch assembly. In another preferred embodiment, the cover may define a receptacle for receiving a reed switch assembly. In one embodiment, the cover may include a receptacle into which the reed switch assembly can be received. The reed switch can be held in position by friction fit, mechanical means, or by adhesive. Alternatively, the cover can provide a projection onto which the reed switch may be mounted by friction fit, mechanical means, or adhesive.
A more complete understanding of the invention can be had by referring to the following detailed description, together with the accompanying drawings wherein:
Referring now to the drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, there is illustrated in
Dial assembly 10 has a back member 50. Extending from back member 50 is pivot pin 52. Rotatably mounted on pivot pin 52 is dial magnet 54, either as part of dial magnet 54 or as a separate attachment is pointer 56. Also attached to the back, is dial face 58 which is marked with indicia indicating various tank levels. Attached to back member 50 is cover member 60. Cover member 60 defines a receptacle 62 to receive reed switch assembly 64. In one embodiment, the reed switch assembly 64 can be an integral part of the cover member 60. Alternatively, it can be a separate unit which is attached to cover member 60. The pivot pin can be attached to cover member rather than to the member back.
Referring now to
The reed switch and bias magnet can extend across the full diameter of the dial magnet or only a portion of the dial magnet. When the north and south poles of each magnet are properly oriented to each other, the reed switch is held closed by the magnetic field. Thus, even though one magnetic pole passes under the reed switch, the reed switch will not be activated because the two magnets will not be properly aligned so as to open the reed switch.
It will be appreciated that there will be some hysteresis such that the reed switch will be open when the desired magnetic pole of dial magnet 54 travels through a certain arc. In other words, on each side of the alignment of the appropriate poles, the switch will remain open within a certain radial arc of travel of the pole on the dial magnet. The hysteresis can be used such that the dial magnet and reed switch can be positioned such so the reed switch remains open between the opening point on the arc and the empty stop. Referring to
A number of factors can affect the opening and closing of the reed switch and the length of the arc over which the switch will remain open. These factors include the shape of each magnet, the strength of each magnet, and the distance of each magnet from the reed switch. Each of these variables can be selected to affect the desired opening of the reed switch and to some extent the length of the arc over which the reed switch will remain open. The present invention can be used with well known dial magnets as shown in U.S. Pat. No. 4,987,400 or with shaped style magnets as shown in Published U.S. application Ser. No. 20020088278, Liquid Level gauge with Removable Hall Device.
The leads 70 and 72 from the reed switch assembly are hooked to an appropriate circuit. This circuit can be constructed so that an indicator light will be illuminated when the contacts of the reed switch are in the open (non contact) positions. As is known in the art the circuit can be constructed such that the light would be illuminated when the reed switch was normally opened or illuminated when the reed switch was normally closed as desired.
In a preferred embodiment of the present invention illustrated in
Thus, the present invention provides an assembly in which the reed switch will be in a closed position when one pole of the dial magnet is in a first orientation on each side of said pole. The reed switch remains closed as the dial magnet travels outside said first orientation.
Although several embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it is understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications or substitution of parts and elements without departing from the invention.
Applicant claims priority to provisional application Ser. No. 60/465,839 filed Apr. 25, 2003, entitled “Dail Assembly with Magnetically Biased Reed Switch”.
Number | Name | Date | Kind |
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3806851 | McCormick | Apr 1974 | A |
3859651 | Thomas, Jr. | Jan 1975 | A |
4567763 | Schiffbauer | Feb 1986 | A |
4943791 | Holce et al. | Jul 1990 | A |
4987400 | Fekete | Jan 1991 | A |
5438869 | Mueller et al. | Aug 1995 | A |
6089086 | Swindler et al. | Jul 2000 | A |
6479981 | Schweitzer, Jr. et al. | Nov 2002 | B2 |
20020088278 | Ross, Jr. | Jul 2002 | A1 |
Number | Date | Country | |
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20040212468 A1 | Oct 2004 | US |
Number | Date | Country | |
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60465839 | Apr 2003 | US |