DRAG CAP FOR A PLASMA ARC TORCH
A consumable component for use in a plasma arc torch is provided that includes a body having a distal end face and at least one extension disposed within the distal end face. The extension is configured to maintain a predetermined torch height above a workpiece during drag cutting operations, for either manual or automated plasma cutting operations.
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This application claims the benefit of provisional application Ser. No. 61/545,561, titled “Plasma Arc Torch With Improved Drag Cutting,” filed on Oct. 10, 2011, the contents of which are incorporated herein by reference in their entirety.
FIELDThe present disclosure relates to plasma arc torches and more specifically to consumables for use in drag cutting operations of the plasma arc torches.
BACKGROUNDThe statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Plasma arc torches, also known as electric arc torches, are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. In a typical plasma arc torch, the gas to be ionized is supplied to a distal end of the torch and flows past an electrode before exiting through an orifice in the tip, or nozzle, of the plasma arc torch. The electrode has a relatively negative potential and operates as a cathode. Conversely, the torch tip constitutes a relatively positive potential and operates as an anode during piloting. Further, the electrode is in a spaced relationship with the tip, thereby creating a gap, at the distal end of the torch. In operation, a pilot arc is created in the gap between the electrode and the tip, often referred to as the plasma arc chamber, wherein the pilot arc heats and ionizes the gas. The ionized gas is blown out of the torch and appears as a plasma stream that extends distally off the tip. As the distal end of the torch is moved to a position close to the workpiece, the arc jumps or transfers from the torch tip to the workpiece with the aid of a switching circuit activated by the power supply. Accordingly, the workpiece serves as the anode, and the plasma arc torch is operated in a “transferred arc” mode.
The plasma arc torch is generally maintained at a predetermined torch height during operation for optimum cut quality. For manual operation, a welder can adjust the torch height based on the arc voltage between the torch tip and the workpiece even for cutting a workpiece with varied height or thickness. For automated plasma arc torches controlled by robots, however, the torch height control becomes difficult or slow based on the arc voltage. Therefore, the robot-controlled plasma arc torches are generally pre-programmed with a fixed torch height. As such, the robot-controlled plasma arc torches can be used to cut limited types of workpieces, such as small workpieces which are more dimensionally stable during cutting or thicker workpieces which are less sensitive to height variations of the workpiece. The robot-controlled plasma arc troches are not suitable for cutting workpieces with height variations.
Moreover, using robotic-controlled plasma arc torches to cut large thin materials poses another challenge in that the large thin materials may have a dimensional tolerance that is greater than the torch height (in the range of 0.020 to 0.150 inches). In other words, the height variations in the workpiece may be greater than the torch height. The large thin materials may have deformed due to heat or residual stress generated during prior operations such as stamping. Without the ability to adjust the torch height during operation, the automated plasma arc torches would not achieve optimum cut quality or may be damaged by the workpiece.
SUMMARYIn one form of the present disclosure, a drag cap for use in a plasma arc torch is provided that comprises a body having a distal end face, and a plurality of balls disposed within the distal end face of the drag cap body.
In another form, a consumable component for use in a plasma arc torch is provided that comprises a body having a distal end face, and at least one extension disposed within the distal end face of the body. The extension is configured to maintain a predetermined torch height above a workpiece during drag cutting operations.
In still another form, a tip for use in a plasma arc torch is provided that comprises a body having a distal end face, and a plurality of balls disposed within the distal end face of the body.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. It should also be understood that various cross-hatching patterns used in the drawings are not intended to limit the specific materials that may be employed with the present disclosure. The cross-hatching patterns are merely exemplary of preferable materials or are used to distinguish between adjacent or mating components illustrated within the drawings for purposes of clarity.
Referring to
The torch head 12 is adjoined with a coolant supply tube 30, a plasma gas tube 32, a coolant return tube 34, and a secondary gas tube 35, wherein plasma gas and secondary gas are supplied to and cooling fluid is supplied to and returned from the plasma arc torch 10 during operation. A torch lead (not shown) is mounted to the proximal end of the torch head 12. A coolant tube 42 in fluid communication with the coolant supply tube 30 extends distally from the torch head 12 and is inserted into the consumable cartridge 16, which will be described in more detail below. The consumable cartridge 16 includes a locking ring 117 (shown in
Referring to
The tip 102 is electrically separated from the electrode 100 by the spacer 104, which results in a plasma chamber 172 being formed between the electrode 100 and the tip 102. The tip 102 further comprises a central orifice (or an exit orifice) 174, through which a plasma stream exits during operation of the plasma arc torch 10 as the plasma gas is ionized within the plasma chamber 172. The plasma gas enters the tip 102 through the gas passageway 173 of the spacer 104. The tip 102 defines a distal end surface 103.
The drag cap 112 is mounted around the tip 112 and the spacer 104 and defines a secondary gas chamber 167 between the drag cap 112 and the tip 112. The secondary gas chamber 167 allows a secondary gas to flow through to cool the tip 102 during operation. The drag cap 112 includes a plurality of extensions in the form of balls 184 at a distal end face 182 of the drag cap 112. The plurality of balls 184 contact a cutting surface 107 of a workpiece 105 to maintain a torch height H measured from the cutting surface 107 of the workpiece 105 to the distal end face 103 of the tip 102. It should be understood that although the extensions are shown and described in the form of balls, alternate geometries may be employed while remaining within the scope of the present disclosure.
Referring to
Referring to
More specifically, the plasma arc torch 202 includes a consumable cartridge 212 having a structure similar to that of
The torch height controller 204 in accordance with the first embodiment of the present disclosure includes a torch holder 220 surrounding the plasma arc torch 202, a movable part 222 fixedly coupled to the torch holder 220, and a fixed part 224 fixedly coupled to the robotic arm 206. The fixed part 224 defines a slot 226. The movable part 222 includes an insertion block 228 mating with the slot 226 and slidably received in the slot 226. While the slot 226 and the insertion block 228 are shown to have a substantially V or triangular shape, the slot 226 and the insertion block 228 may have different shapes and configurations without departing from the scope of the present disclosure. For example, the slot 226 and the insertion block 228 may have a rectangular shape, circular shape as long as the insertion block 228 can be slidably retained within the slot 226.
As clearly shown in
The constant low force is maintained to ensure that the drag cap 214 remains in contact with the workpiece 105 during operation. The balls 216 in the drag cap 214 facilitate smooth drag along the cutting surface 107 of the workpiece 105 during operation. For example, when the plasma arc torch 202 is moved to a part of the workpiece 105 that is slightly recessed (e.g., having a reduced height or thickness) from the cutting surface 107 of the workpiece 105 and thus the distance between the cutting surface 107 and the distal end face of the tip is increased, the compression spring 230 may push the plasma arc torch 202 distally against the workpiece 105 so that the predetermined torch height H is maintained. When the plasma arc torch 202 is moved to a part of the workpiece 105 that is slightly raised (e.g., having an increased height or thickness), the raised part of the workpiece 105 may apply a reaction force to the torch body 208 and the movable part 222 to overcome the biasing force of the compression spring 230, thereby moving the insertion block 228 proximally relative to the slot 226. The predetermined torch height H is thus maintained despite the uneven cutting surface 107 of the workpiece 105 without changing the height position of the robotic arm 206. Preferably, a short stroke of less than 1 inch of travel is provided to limit the mass of the assembly and its moment of inertia.
Referring to
The fixed part 310 includes a guide rail 312. The movable part 308 includes a mounting member 310 fixedly coupled to the torch holder 306 and a sliding block 314 slidably received in the guide rail 312. A compression coil spring 316 engages the sliding block 314 to provide a biasing force on the sliding block 314, which in turn biases the plasma arc torch 302 against the workpiece 105 to maintain a predetermined torch height. The torch height can be adjusted and maintained to the predetermined torch height by biasing the sliding block 314 against the compression coil spring 316.
Referring to
A robot arm connecting member 424 is disposed on the cylindrical housing 410 for connecting to the torch holder 408 to a robotic arm 426. The torch holder 408 is mounted around the torch body 404 in a way such that the plasma arc torch 402 is free to rotate within the cylindrical housing 410 to change the rotational position of the plasma arc torch 402 relative to the robotic arm 426. This configuration prevents the torch lead 406 from twisting.
During operation, the compression coil spring 420 may be further compressed in the proximal direction by the movable part 418 when the plasma arc torch 402 is moved to a raised portion of the workpiece 105. The workpiece 105 applies a reaction force to the torch body 404 to move the torch body 404 distally. The movable part 418, which is fixedly coupled to the torch body 404, overcomes the biasing force of the compression coil spring 420 and pushes the compression coil spring 420. As a result, the torch height is maintained despite the changed height of the workpiece 105. The biasing force of the compression coil spring 420 may be adjusted by changing the position of the retaining flange 420 relative to the cylindrical housing 410. The position of the retaining flange 420 relative to the cylindrical housing 410 is maintained through the engagement between the inner teethed surface 418 and the teethed outer surface 422.
Referring to
More specifically, the torch height controller 504 includes a distal flange 508, a proximal flange 510, an inner bearing 512, an outer bearing 514, and a compression spring 516. The distal flange 508 and the proximal flange 510 are fixedly coupled to the torch body 518. The inner bearing 512 is mounted around the torch body 518 of the plasma arc torch 502 and the outer bearing 514 is mounted around the inner bearing 512. The inner bearing 512 allows for translational movement of the plasma arc torch 502 relative to the inner bearing 512 along a longitudinal axis X of the plasma arc torch 502 and does not allow rotation of the plasma arc torch 502 relative to the inner bearing 512. The outer bearing 514 allows rotation of the inner bearing 512 relative to the outer bearing 514 and does not allow for translational movement of the inner bearing 512 relative to the outer bearing 514. The compression spring 516 is disposed between the inner bearing 512 and the proximal flange 510 to bias the inner bearing 512 and consequently the plasma arc torch 502 toward the cutting surface 107 of the workpiece 105. The distal flange 508 functions as a stop to limit the translational movement of the plasma arc torch 502.
Referring to
More specifically, the consumable cartridge 602 includes a cartridge body 106, a spacer 104 received within the cartridge body 106, an anode member 108 secured to the cartridge body 106, a baffle 110 surrounding the anode member 108, and a shield cap 114 surrounding the baffle 110. The spacer 104, the cartridge body 106, the anode member 108, the baffle 110 and the shield cap 114 are similar to those described in connection with
The electrode 604 includes a hollow housing portion 620 disposed inside the cartridge body 106 and an elongated portion 622 extending distally from the hollow housing portion 620. An emissive insert 624 is disposed at a distal end 626 of the elongated portion 622.
The tip 606 includes a proximal portion 628 and a distal portion 630. An annular flange 632 is disposed proximate the proximal portion 628. A spring receiving space 632 is defined by the tip support housing 608, the proximal portion 628 and the annular flange 630 of the tip 606. The distal portion 630 has a rounded shape to facilitate dragging contact with the surface 107 of the workpiece 105. An exit orifice 640 is formed in the distal portion 630 of the tip 606. The tip 606 is separated from the electrode 608. The distal end face of the electrode 608 and the rounded portion 630 of the tip 606 have a clearance C and define a plasma chamber 650 therebetween.
The tip support housing 612 includes a distal cylindrical portion 642 for receiving the proximal portion 628 of the tip 606. A stop 644 is disposed inside the tip support housing 612 to limit the translational movement of the tip 606 in the distal direction. The coil spring 616 is received within the spring receiving space 632 to bias the tip 606 against the cutting surface 107 of the workpiece 105. The insulator 116 is disposed between the tip support housing 608 and the secondary cap 614 to provide electrical insulation therebetween.
In the present embodiment, the tip 606, not the secondary cap 614 is in contact with the workpiece 107 during operation. The distance between the distal end face of the electrode 604 and the exit orifice 640 of the tip 606 can be varied by the coil spring 616. The tip 606 is spring-loaded and can have translation movement along a longitudinal direction of the plasma arc torch 600 to adjust the distance between distal end face of the electrode 604 and the exit orifice 640 of the tip 606.
While only the tip 606 is shown to be spring-loaded, it is understood and appreciated that the electrode 604, the spacer 104 and the secondary cap 614 can be configured to be spring-loaded to maintain the tip-to-electrode clearances within the plasma chamber 650.
Referring now to
As shown, the tip 700 includes a distal end face 702 and a plurality of extensions, in the form of balls 704, disposed therein. As set forth above in connection with the drag cap, the balls 704 protrude from the distal end face 702 a distance that equates to a predetermined torch height above a workpiece during drag cutting operations. The balls 704 take on the characteristics and alternate forms as with the drag cap balls 184, such as being rotatable in one form, or being made of ceramic or steel, among other materials and other alternate embodiments. Accordingly, these forms as set forth in detail above shall be construed to be included within the scope of the tip balls 704.
Referring to
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
Claims
1. A drag cap for use in a plasma arc torch comprising:
- a body having a distal end face; and
- a plurality of balls disposed within the distal end face of the drag cap body.
2. The drag cap according to claim 1 comprising three balls.
3. The drag cap according to claim 1, wherein the balls are rotatable.
4. The drag cap according to claim 1, wherein the balls are a ceramic material.
5. The drag cap according to claim 1, wherein the balls are a steel material.
6. The drag cap according to claim 1, wherein the body defines a hollow cone shape.
7. A consumable component for use in a plasma arc torch comprising:
- a body having a distal end face; and
- at least one extension disposed within the distal end face of the body, the extension configured to maintain a predetermined torch height above a workpiece during drag cutting operations.
8. The consumable component according to claim 7, wherein the consumable component is a tip.
9. The consumable component according to claim 7, wherein the consumable component is a drag cap.
10. The consumable component according to claim 7 comprising a plurality of extensions.
11. The consumable component according to claim 10, wherein the plurality of extensions are balls.
12. The consumable component according to claim 11 comprising three balls.
13. The consumable component according to claim 11, wherein the balls are rotatable.
14. The consumable component according to claim 7, wherein the extension is a ceramic material.
15. The consumable component according to claim 7, wherein the extension is a steel material.
16. A tip for use in a plasma arc torch comprising:
- a body having a distal end face; and
- a plurality of balls disposed within the distal end face of the body.
17. The tip according to claim 16 comprising three balls.
18. The tip according to claim 16, wherein the balls are rotatable.
19. The tip according to claim 16, wherein the balls are a ceramic material.
20. The tip according to claim 16, wherein the balls are a steel material.
Type: Application
Filed: Oct 10, 2012
Publication Date: Apr 11, 2013
Applicant: Thermal Dynamics Corporation (West Lebanon, NH)
Inventor: Thermal Dynamics Corporation (West Lebanon, NH)
Application Number: 13/649,009
International Classification: B23K 10/00 (20060101);