Electrical high current industrial oven or fryer compression connection

• US 4,831,240 A
• Filed: 10/08/1987
• Issued: 05/16/1989
• Est. Priority Date: 10/08/1987
• Status: Expired due to Term

• Current Assignee: Hester Industries Incorporated
• Original Assignee: Hester Industries Incorporated
• Inventors: Davis, Kenneth F.
• Primary Examiner(s): Walberg, Teresa J.
• Application Number:
  US07/105,676
• Time in Patent Office: 586 Days
• Field of Search: 219/539, 219/541, 439/819, 439/822, 174/94 R, 361/310, 338/332
• US Class Current: 219/539
• CPC Class Codes: H01R 4/06 Riveted connections by explosion H01R4/08
• CPC Class Codes: H01R 9/22 Bases, e.g. strip, block, panel for printed circuits H01R12/50

Abstract

Industrial electric ovens and fryers of the type used for cooking precooked foods such as meats prior to packaging of the food draw high currents which tend to melt internal electrical connections. An industrial heating device includes compression-type electrical connections which reliably carry high currents and are capable of withstanding high voltage levels without breaking down. Compression-type electrical connections are used instead of the screw-type connections of the prior art to insure that all electrical connections have reliable, relatively large current-carrying cross-sectional contact areas. The electrical connection matrix of the resulting industrial heating device has increased current-carrying capacity and is much more reliable and resistant to electrical failure.

Claims

1. An industrial heating device including:

a heating chamber;

a conductive strip connected to a power input terminal;

electrical heating element means operatively connected to said chamber for heating said chamber, said electrical heating element means having an electrical terminal directly contacting said conductive strip; and

connection forming means mechanically coupled to said strip and said heating element terminal for forming an electrical compression connection between said conductive strip and said heating element electrical terminal and for enhancing the flow of electrical current between said conductive strip and said contacting electrical terminal,

said connection forming means including;

a first annular compression washer means disposed in contact with said electrical terminal,

a second annular compression washer means disposed in contact with said strip, said strip and said electrical terminal contacting one another and being disposed between said first and second annular washers means, and

fastener means for biasing said first and second washers means together, said first and second washer means for creating an annular electrically conductive compression contact area between said strip and said contacting electrical terminal, substantially all of said electrical current flowing between said conductive strip and said contacting electrical terminal through said annular electrically conductive compression contact area.

2. A heating device as in claim 1 wherein:

said heating element terminal includes a flat conductive disk defining a hole therethrough;

said conductive strip defines a hole therethrough; and

said fastener means includes high tensile steel bolt means disposed through said disk hole and said strip hole for biasing said first and second annular washers means together.

3. A heating device as in claim 2 wherein said disk and strip comprise similar metals.

4. A heating device as in claim 2 wherein said fastener means includes a rivet having:

(a) an elongated cylindrical center portion disposed within said disk hole and strip hole, (b) a first enlarged portion means disposed on one end of said cylindrical center portion in contact with said first washer means for applying a first force to said conductive strip through said first washer means, and (c) a second enlarged portion means disposed on another end of said cylindrical center portion in contact with said second washer means for applying a second force opposing said first force to said disk through said second washer means.

5. A device as in claim 1 wherein:

said conductive strip has a first surface and a second surface opposing said first surface;

said electrical terminal has a first surface and a second surface opposing said first surface;

said first annular washer means is disposed in contact with electrical terminal first surface;

said second annular washer means is disposed in contact with said conductive strip first surface;

said conductive strip second surface is disposed directly in contact with said terminal second surface; and

said annular compression contact area formed by said fastener means is distributed evenly in a ring between said first and second annular washers at the contacting conductive strip second surface and terminal second surface.

6. An industrial heating device including:

a heating chamber;

a conductive strip connected to a power input terminal;

electrical heating element means operatively connected to said chamber for heating said chamber, said electrical heating element means terminating in an electrical terminal, said electrical terminal directly contacting said conductive strip; and

connection forming means mechanically coupled to said strip and said heating element electrical terminal for providing an electrical current pathway between said conductive strip and said heating element electrical terminal, wherein;

said heating element electrical terminal including an integral press-formed contact portion defining a substantially planar first contact surface;

said strip terminating in a further press-formed contact portion defining a substantially planar further contact surface in direct contact under compression with said first contact surface; and

said connection forming means including an exothermic weld maintaining said compression contact between said first and further contact surfaces such that substantially all electrical current flowing between said conductive strip and said heating element electrical terminal flows directly between said first contact surface and said further contact surface.

7. A heating device as in claim 6 wherein said heating element contact portion and said strip contact portion comprise dissimilar metals.

8. In an industrial oven of a type including a heating chamber and a matrix of heating elements operatively connected thereto for heating said chamber, said matrix including:

a power input terminal connected to at least one phase of a multi-phase external power source;

a conductive strip connected to said power input terminal, said strip defining plural holes therethrough;

plural tubular electrical heating elements connected to said conductive strip, each heating element at least partially disposed within said chamber, each heating element including a cylindrical post terminating in a substantially planar electrical terminal pad integrally formed with said cylindrical post, said terminal pad directly contacting said conductive strip, said pad including means defining a hole therethrough aligned in registry with an associated one of said conductive strip plural holes; and

plural electrical connection forming means mechanically coupled to said electrical terminal pads and said conductive strip for forming electrical current pathways between said conductive strip and said corresponding plural electrical terminal pads, each said plural electrical connection forming means including;

a first non-planar compression washer disposed in contact with said heating element electrical terminal pad, said first washer having a hole therethrough, said first washer hole aligned with said electrical terminal pad hole,

a second non-planar compression washer disposed on said conductive strip, said second washer having a hole therethrough, said second washer hole aligned with one of said holes in said conductive strip, and

a rivet having first and second heads connected together by a center body portion, said body portion disposed through said aligned first washer hole, said electrical terminal pad hole, said conductive strip hole and said second washer hole, said rivet exerting compression forces forming an annular electrical contact compression region at the contact between said heating element electrical terminal pad and said conductive strip, said first and second non-planar washers insuring that the compression forces exerted by said rivet heads are distributed evenly to establish said annular electrical contact region, substantially all electrical current flowing between said terminal pad and said conductive strip flowing through said annular contact region directly between said terminal pad and said conductive strip, substantially none of said electrical current flowing between said terminal pad and said conductive strip flowing through said rivet center body portion.

9. An industrial oven including:

means defining a heating chamber for cooking food; and

a heating element matrix for heating said chamber, said matrix including;

an electrically conductive power input terminal,

plural electrical heating elements operatively connected to said chamber, each heating element having at least one electrical terminal,

plural substantially planar electrically conductive strip conductor means connecting said heater element electrical terminals to said power input terminal, each strip conductor means connecting a single associated heater element terminal to said power input terminal, said plural strip conductor means being arranged in a stack and directly contacting adjacent ones of said plural strip conductor means in said stack, and

clamping means for forming electrically conductive compression regions between contacting strip conductor means adjacent in said stack and for forming a further compression region between said power input terminal and at least one of said strip conductor means, substantially all electrical current flowing between said power input terminal and said plural heating elements flowing through said compression regions.

10. An oven as in claim 9 wherein said clamping means includes:

first and second plates opposing one another, said stack disposed between said plates; and

biasing means for biasing said plates toward one another, said biasing means including a compression spring having a first end disposed on said first plate and a second end disposed on said second plate.

11. An oven as in claim 9 wherein:

said clamping means includes first and second plates opposing one another, said stack disposed between said plates, said first and second plates each define a slot therethrough; and

said biasing means comprises a compression spring including a flat elongated center portion having first and second ends, a first hairpin portion connected to said center portion first end, a second hairpin portion connected to said center portion second end, and first and second distal end portions, said first distal end portion being connected to said center portion first end by said first hairpin portion, said second distal end portion being connected to said center portion by said second hairpin portion, said first distal end portion being engaged with said first plate slot, said second distal end portion being engaged with said second plate slot.

12. An oven as in claim 9 wherein:

said oven further includes;

a housing having first and second wall portions defining a slot therebetween, and

further plural strip conductor means being arranged in a further stack, said first-mentioned and further stacks being disposed in said slot; and

said clamping means also forms compression connections between adjacent strip conductor means in said further stack and forms a compression connection between said power input terminal and at least one of said strip conductor means of said further stack.

13. An oven as in claim 12 wherein said clamping means engages with said housing first and second wall portions.

14. An oven as in claim 12 wherein said first and second plates each define slots therethrough, and said biasing means engages with said first plate slot and second plate slot.

16. An oven as in claim 14 further including a mica separator disposed between said second plate and said first and second stacks.

15. An industrial oven including:

means defining a heating chamber;

a housing having first and second wall portions defining a slot therebetween; and

a heating element matrix for heating said chamber, said matrix including;

a power input terminal;

plural electrical heating elements operatively connected to said chamber, each heating element having at least one electrical terminal,

plural strip conductor means connecting said heater element electrical terminals to said power input terminal, each strip conductor means connecting a single associated heater element terminal to said power input terminal, said plural strip conductor means being arranged in a stack,

further plural strip conductor means being arranged in a further stack, said first-mentioned and further stacks being disposed in said slot; and

clamping means for forming compression connections between strip conductor means adjacent in said stack and for forming a compression connection between said power input terminal and at least one of said strip conductor means,

said clamping means also forming compression connections between adjacent strip conductor means in said further stack and forming a compression connection between said power input terminal and at least one of said strip conductor means of said further stack,

said clamping means including;

a first conductive plate defining a shoulder portion disposed in said slot between said first-mentioned and further stacks and engaged with said housing first wall portion;

a second conductive plate defining a shoulder portion disposed in said slot between said first-mentioned and further stacks and engaged with said housing second wall portion; and

biasing means connected to said first and second plates for forming electrical compression connections between said first plate and said first-mentioned and further stacks.

17. In an industrial oven of a type including a heating chamber and a matrix of heating elements operatively connected thereto for heating said chamber, said matrix including:

a power input terminal connected to at least one phase of a multi-phase external power source;

a conductive strip connected to said power input terminal, said strip defining a hole therethrough;

a tubular electrical heating element connected to said conductive strip, said heating element at least partially disposed within said chamber, said heating element including a cylindrical post terminating in a substantially planar electrical terminal pad integrally formed with said cylindrical post, said terminal pad directly contacting said conductive strip, said pad including means defining a hole therethrough aligned in registry with said conductive strip hole; and

electrical connection forming/maintaining means mechanically coupled to said electrical terminal pad and said conductive strip for providing a reliable path for enhancing the flow of electrical current directly between said conductive strip and said electrical terminal pad and for preventing arcing and oxidation from occurring along said path between said conductive strip and said terminal pad, said electrical connection forming/maintaining means including;

a first non-planar compression washer disposed in contact with said heating element electrical terminal pad, said first washer having a hole therethrough, said first washer hole aligned with said electrical terminal pad hole,

a second non-planar compression washer disposed on said conductive strip, said second washer having hole therethrough, said second washer hole aligned with said hole in said conductive strip, and

a fastener having first and second heads connected together by a center body portion, said body portion disposed through said aligned first washer hole, said electrical terminal pad hole, said conductive strip hole and said second washer hole, said fastener in combination with said first and second non-planar washers exerting an evenly distributed compression force biasing said heating element electrical terminal pad towards said conductive strip, said compression force forming an annular electrical contact compression region at the contact between said heating element electrical terminal pad and said conductive strip, said first and second non-planar washers distributing the compression force exerted by said first and second fastener heads evenly to establish said annular electrical contact region surrounding said fastener body but spaced away from and concentric with said fastener body.