Multi value capacitor

[0001] This application claims priority from U.S. Provisional Patent Application Ser. No. 60/667,791 filed on Apr. 1, 2005, and U.S. Provisional Patent Application Ser. No. 60/601,048 filed on Aug. 12, 2004, both of which are incorporated herein in their entirety.

[0002] This invention relates to a multi value capacitor for an electric motor. More particularly, the invention relates to a multi value capacitor that can be configured by a repair technician in the field to have one of a number of capacitance values to accommodate the circumstance required to maintain or repair a particular electric motor being serviced.

[0003] A distributor for electric motors currently carries several motor run capacitors of different values that must be stocked to fill the service chain. Service technicians and distributors must stock capacitors of different values even though only a few values are high volume.

[0004] A motor run capacitor consists of several parts: a steel or aluminum can with insulator/connections on the top and with a capacitor element inside. Oil or paraffin filling acts as a moisture barrier and an electrical insulator for the capacitor element. The capacitor element consisting of two foil layers separated by an insulator (paper, Mylar, or other very thin insulating material). The foil(s) and insulating material are made in the form of a long sandwich 2 or 3 inches high and several 10's of feet long. The sandwich is rolled to form a cylindrical shaped capacitor element that has electrical connections to each of the 2 foils. The rolled capacitor element is typically 1 inch in diameter and 2 or 3 inches long. The rolled capacitor element is placed into the can and connected through two terminals on the outside of the can.

[0005] Dual capacitors are made with a similar construction, but one of the foil layers is separated to form two capacitor elements. An additional lead wire is connected to the third foil. A dual capacitor with asymmetrical capacitance values can be configured to create a three value capacitor by connecting the first element, the second element, or both elements in parallel.

[0006] Because a good portion of the cost of a motor run capacitor is in the case, winding the element, packaging, and general handling, a single capacitor that can be configured to provide different values offers cost advantages over stocking multiple capacitors of different values.

[0007] The multi value motor capacitor of the present invention is constructed in a single can having a core with three capacitor elements. The capacitor elements are designed to provide capacitance values that, when connected in various combinations, provide all of the popular capacitance values. Therefore one SKU part number will cover the majority of motor capacitor applications.

[0008] For example, the capacitance values for the capacitor elements for the multi value capacitor of the present invention could be 2.5 μF, 5.0 μF, and 10.0 μF. The multi value capacitor would cost less than the sum of the individual capacitors due to the common components.

[0009] The following table shows the seven capacitance values that can be derived from the multi value capacitor having capacitor elements of 2.5 μF, 5.0 μF, and 10.0 μF.

[0010]

	TABLE 1
	Equivalent	Core values
	Capacitor	2.5	5	10
	2.5	X
	5		X
	7.5	X	X
	10			X
	12.5	X		X
	15		X	X
	17.5	X	X	X

[0011] As demonstrated above the multi value capacitor replicates seven popular values while being only slightly larger than a standard dual 5/10 capacitor. The capacitor has a simple two terminal hook up and looks similar to existing round or oval capacitors.

[0012] In one embodiment of the invention, the field programming is accomplished by a dial switch mechanism, which when turned provides contact connections between and among the various capacitor elements in accordance with the values in Table 1 above. The dial switch mechanism includes a rotating contact that engages multiple cam contacts to connect the capacitor elements in different combinations to create multiple capacitance values. In another embodiment of the present invention, inserting or removing screws at the top of the capacitor accomplishes field programming. The screws interconnect the capacitor elements in accordance with the values in Table 1 above.

[0028] Turning to FIG. 1, the multi value capacitor 10 of the present invention comprises a can 12 with a top cover 14. A common terminal 22 and a switched terminal 24 are mounted on the top cover 14 of the can 12. A dial switch mechanism 28 is also mounted on top cover 14 of the can 12. The dial switch mechanism 28 includes a pointer 34 mounted on the top cover 14 and a dial cover 30 with indices 32 printed thereon. The pointer 34 and the indices 32 indicate the value of the capacitance selected by rotating the dial switch mechanism 28.

[0029] FIG. 2 shows schematically the construction of the multi value capacitor 10. The multi value capacitor 10 includes a 10.0 μF capacitor element 46 and a dual 2.5 μF and 5.0 μF capacitor element 48 (although three separate capacitor elements could be employed). The capacitor elements 46 and 48 are connected to the common terminal 22, by means of a common lead wire 50. The 10.0 μF element 46 is connected to the dial switch mechanism 28 by 10.0 μF lead wire 52. The separate sections of the of 2.5 μF and 5.0 μF element 48 are connected to the of dial switch mechanism 28 by means of a 5.0 μg lead wire 54 and a 2.5 μF lead wire 56. The dial switch mechanism 28 is connected to the switched terminal 24 by means of a switched lead wire 58.

[0030] In order to provide multiple values of capacitance at the terminals 22 and 24, the dial switch mechanism 28 connects the capacitor elements 46 and 48 in the combinations shown in Table 1 above to provide the seven values of capacitance.

[0031] With referenced to FIGS. 3 and 6-14, the dial switch mechanism 28 includes a dial shaft 40, a dial cover 30, a dial detent 36, a detent spring 38, a rotating contact 42 or central contacting member, a 10.0 μF cam contact 62, a 5.0 μF cam contact 64, and a 2.5 μF cam contact 66. As best shown in FIG. 7, the 10.0 μF lead wire 52 is connected to a 10.0 μF terminal 53. Likewise, the 5.0 μF lead wire 54 is connected to a 5.0 μF terminal 55, the 2.5 μF lead wire 56 is connected to a 2.5 μF terminal 57, and the common lead wire 50 is connected to a common terminal 51. The terminals 51, 53, 55, and 57 are mounted on insulating mounting strip 60. The terminals 53, 55, and 57 are connected to the 10.0 μF cam contact 62, the 5.0 μF cam contact 64, and the 2.5 μF cam contact 66, respectively.

[0032] In FIG. 3, the top cover 14 has been removed from the can 12 in order to expose the dial detent 36 connected to one end of the dial shaft 40. The dial cover 30 is mounted on the dial detent 36 so that manual rotation of the of dial cover 30, rotates the dial detent 36 and the dial shaft 40. The rotating contact 42 is connected to the dial shaft 40 and rotates with the dial shaft 40 as the dial detent 36 is manually turned by means of the dial cover 30. The detent spring 38 restrains the rotation of the dial shaft 40 in one of eight rotational positions. FIGS. 6 and 7 illustrate the detail of the dial switch mechanism 28, particularly the relationship between the rotating contact 42 and the cam contacts 62, 64, and 66.

[0033] The rotating contact 42 is illustrated in FIGS. 9a-9g. The 2.5 μF cam contact 66 is shown in FIGS. 10a-10e, the 5.0 μF cam contact 64 is shown in FIGS. 11a-11e, and the 10.0 μF cam contact 62 is shown in FIGS. 12a-12e. The rotating contact 42 (FIGS. 9a-9g) has three contacts, the outside wiper contact 43 which engages the 2.5 μF cam contact 66, the middle wiper contact 44 which engages the 5.0 μF cam contact 64, and the inside wiper contact 45 which engages the 10.0 μF cam contact 62. As shown in FIGS. 10a-10e, the 2.5 μF cam contact 66 has four raised portions 68-71 and four alternating depressed portions 73-76. As shown in FIGS. 11a-11e, the 5.0 μF cam contact 64 has two raised portions 78 and 79 and two alternating depressed portions 81 and 82. As shown in FIGS. 12a-12e, the 10.0 μF cam contact 62 has one raised portion 84 and one alternating depressed portion 85.

[0034] Returning to FIG. 6, rotation of the dial shaft 40 causes the rotating contact 42 with its three wiper contacts 43, 44, and 45 to engage the raised portions of the cam contacts 62, 64, and 66 in various combinations for each of the eight positions defined by the dial detent 36. For example, in the position shown in FIG. 6, the wiper contact 43 of the rotating contact 42 engages the raised portion 71 of the 2.5 μF cam contact 66. The other wiper contacts 44 and 45 of the rotating contact 42 are aligned with depressed portions of the 5.0 μF cam contact 64 and of the 10.0 μF cam contact 62. Therefore, only the 2.5 μF capacitor element is connected through the shaft 40 to the switched lead wire 58 and thereby to the output terminal 24. Thus the multi value capacitor 10 has a value of 2.5 μF when the dial switch mechanism 28 is in the position shown in FIG. 6.

[0035] When the dial shaft 40 rotates clockwise to the next position established by the dial detent 36, the rotating contact 42 disengages the 2.5 μF cam contact 66 and engages the 5.0 μF cam contact 64. Consequently the value of the capacitor 10 is 5.0 μF. When the dial shaft 40 rotates clockwise to the next position established by the dial detent 36, the rotating contact 42 engages the 2.5 μF cam contact 66 and also engages the 5.0 μF cam contact 64. Consequently the value of the capacitor 10 is 7.5 μF. When the dial shaft 40 rotates clockwise to the next position established by the dial detent 36, the rotating contact 42 disengages the 2.5 μF cam contact 66, disengages the 5.0 μF cam contact 64, and engages only the 10.0 μF cam contact 66. Consequently the value of the capacitor 10 is 10.0 μF. Each further rotation of the dial shaft 40 connects the capacitor elements 46, 48 in accordance with Table 1 above. In the last rotational position (one position counter-clockwise from the position shown in FIG. 6), the rotating contact 42 aligns with the depressed portions of each of the cam contacts 62, 64, and 66 and the capacitance value is 0 μF.

[0036] Another embodiment of the present invention is illustrated in FIG. 15, wherein the dial switch mechanism 28 is replaced with multiple screws 80, 82, 84 that are able to engage the central contacting member to connect the switched terminal 24 with the various capacitor elements 46, 48. That is, inserting or removing the screws 80, 82, 84 at the top of the can 12 accomplishes field programming. The screws 80, 82, 84 interconnect the capacitor elements 46, 48 in accordance with the values in Table 1 above.

[0037] While this invention has been described with reference to preferred embodiments thereof, it is to be understood that variations and modifications can be affected within the spirit and scope of the invention as described herein and as described in the appended claims.