WO2006071622A1

WO2006071622A1 - Fixture for holding a tubular workpiece having a clamping assembly with a biased workpiece engaging member

Info

Publication number: WO2006071622A1
Application number: PCT/US2005/046068
Authority: WO
Inventors: Ronald L. Dick
Original assignee: Swagelok Company
Priority date: 2004-12-28
Filing date: 2005-12-20
Publication date: 2006-07-06

Abstract

The present invention relates to a fixture (10) for holding a workpiece comprising a supporting member (22) defining an aperture (24) for receiving the workpiece at least one clamping assembly (18) assembled with the supporting member (22), each clamping assembly (18) comprising a workpiece engaging member (12) for engagement with the workpiece engaging member (12) to bias the workpiece engaging member (12) into engagement with the workpiece and a mounting member that holds the workpiece engaging member (12) and the biasing member, the mounting member being assembled to the supporting member (22) such that the workpiece engagement member (12) extends at least partially radially inwards of the aperture (14). The invention relates also to a method for holding a workpiece in alignment during a welding operation with elastically biasing at least one contact point against the workpiece and moving the workpiece relative to the at least one contact point.

Description

FIXTURE FOR HOLDING A TUBULAR WORKPIECE HAVING A CLAMPING ASSEMBL WITH A BIASED WORKPIECE ENGAGING MEMBER

Field of the Invention

[0001] The invention is generally directed towards apparatuses and methods that provide for holding work pieces. More specifically, the invention is directed towards apparatuses and methods for holding work pieces to be welded.

Related Applications

[0002] The present application claims priority from United States provisional application serial number 60/639,480, entitled "Welding Fixture," filed on December 28, 2004. United States provisional application serial number 60/639,480 is incorporated herein by reference in its entirety.

Background of the Invention

[0003] Fittings are welded to conduits in a variety of applications. Most commonly fittings are welded to conduits in the assembly of flow systems. Fittings typically provide a transition from one conduit to another conduit and perform functions such as: redirecting flow in a flow path; reducing or increasing the size of the cross-sectional area of a flow path; splitting or combining flow paths; and inserting components, such as a valve, into a flow path. Fittings and conduits are often held by a fixture during the welding process. Fixtures often rigidly secure the fitting and the conduit and do not allow for adjustment of the positions of either the fitting or the conduit after the fixtures are tightened. One example of a fitting that is commonly welded to a conduit is a sanitary fitting.

[0004] Sanitary fittings are normally used in applications where cleanliness is important, such as in food, beverage, water, and dairy systems. For these types of systems, it is often necessary to clean the inside of piping or tubing that is inaccessible from outside the system. One typical method is to flush the piping or tubing with a cleansing solution. In order to increase the effectiveness of a cleansing solution, it is important that fittings connected to piping or tubing provide smooth internal surfaces at the connections. If an internal surface has edges or hidden surfaces it may be more difficult to clean that surface by flushing. [0005] The design and manufacturing of sanitary fittings provide for smooth internal surfaces at the connection of the fitting with piping or tubing, which allow for sanitary surfaces inside of food, beverage, water, dairy, and other such systems. However, the design and manufacturing of sanitary fittings also is driven by a need for low unit cost, which causes some inconsistency in the dimensions and characteristics of sanitary fittings. For example, there may be inconsistent diameters along the length of the fitting; straight lengths on either end of a fitting may not be long enough to allow for easy fixturing; and end faces of the fitting may not be square with respect to a longitudinal axis of the fitting. Due to the inconsistencies in dimensions and characteristics of fittings, manual welding is normally the preferred method of joining sanitary fittings to piping and tubing. Manual welding normally allows for manual manipulation of the alignment and position of fittings to account for any inconsistencies in sanitary fittings.

[0006] Normally, orbital welding produces a higher quality and more consistent weld than does manual welding. However, customary fixturing for orbital welding can make it difficult to weld sanitary fittings using orbital welding. Normally, orbital welding fixturing rigidly clamps onto the outer surface of a fitting. For sanitary fittings with inconsistent outer dimensions, this can lead to a fitting either being loose in a fixture or not being aligned properly when the fixture is tightened.

Summary of Invention

[0007] The present application relates to fixturing that allows work pieces to be held and properly aligned. For example, the disclosed fixture may be used to hold and properly align a sanitary fitting and a conduit. Such a fixture may be used to hold a work piece for any manner of operations, including for example, a welding operation.

[0008] One example embodiment of the invention is a fixture for holding a fitting for orbital welding the fitting to a conduit. The fixture comprises a work piece engaging member positioned for engagement with the fitting and a biasing member that biases the work piece engaging member into engagement with the fitting. The fixture may also comprise a mounting member which assembles to a supporting member of the fixture and holds the work piece engaging member and the biasing member, such that the work piece engaging member extends at least partially radially inward of an aperture in the supporting member that receives the work piece. The position of the work piece in the fixture may be adjusted by moving or positioning the work piece relative to the work piece engaging member. Brief Description of Drawings

[0009] Figure 1 is a perspective view of a fixture for use in an orbital welding process;

[0010] Figure 2 is a perspective view of a clamping assembly;

[0011] Figure 3A is a side view of the clamping assembly;

[0012] Figure 3B is a cross-sectional view of the clamping assembly;

[0013] Figure 3C is a front view of the clamping assembly;

[0014] Figure 4 is a perspective view of a fixture for holding a fitting during an orbital welding process;

[0015] Figure 5A is a front view of a fixture for use in an orbital welding process;

[0016] Figure 5B is a cross-section view of a fixture for use in an orbital welding process; and

[0017] Figure 6 is a side view of a fixture for use in an orbital welding process.

Detailed Description of Invention

[0018] While the described embodiments herein are presented in the context of a fixture for holding a work piece, such as a fitting, for welding to a second work piece, such as a conduit, those skilled in the art will readily appreciate that the present invention may be used in many different welding or fixturing applications, including but not limited in any manner to: manual welding; welding of one fitting to another fitting; welding of one conduit to another conduit; welding of a sanitary fitting to a conduit; and welding of any component that offers variable outer dimensions, short tangent lengths, or contact faces that are not square to the length of the fitting. These examples are intended to illustrate the broad application of the invention for fixtures that hold work pieces in alignment to perform operations such as welding. The specific design and operation of the apparatuses and methods selected provides no limitation on the present invention except as otherwise expressly noted herein.

[0019] The present invention is directed to a fixture for holding and aligning a work piece, for example, for aligning a fitting for welding the fitting to piping, tubing, or other such conduits. The fixture allows for manual manipulation of the fitting position to permit adjustments that may be needed to properly align the fitting to a conduit. A fitting may, for example, have an elbow and a short straight length, or tangent on one end that may make fixturing the fitting in a conventional fixture difficult. Additionally, other work piece conditions, such as irregularity in shape or imprecise outer diameter tolerances, may result in difficulty in clamping and aligning the work piece.

[0020] In the example provided in Figure 1, an embodiment of the invention includes a work piece engaging member 12 positioned to engage with a work piece 14, such as a fitting, and a biasing member 16 (shown in Figure 3B) to elastically bias the work piece engaging member 12 into engagement with the work piece 14. In the illustrated embodiment, the position of the work piece engaging member 12 is determined by the surface of the work piece 14 against which the work piece engaging member 12 engages.

[0021] Referring to Figures 2, 3A, and 3B, the illustrated work piece engaging member 12 and biasing member 16 are assembled within a housing or mounting member 20 to form a clamping assembly 18. In the illustrated embodiment, the work piece engaging member 12 is a plunger and the biasing member 16 is a mechanical coil spring. It will be appreciated that a work piece engaging member 12 may be any component that is capable of transferring force from the biasing member 16 to the work piece 14, such as a cam or lever (not shown), and the biasing member 16 may be any component that is capable of applying a force to the work piece engaging member 12 while allowing axial movement of the work piece engaging member 12 relative to the mounting member 20, such as a series of Belleville spring washers, as shown and described in co-pending United States non-provisional application serial number 10/893,459, entitled "Pipe Collets," filed on July 16, 2004, the application being incorporated herein by reference in its entirety.

[0022] As shown in Figure 1, the clamping assembly 18 can be coupled to one or more supporting members 22, proximate to the work piece 14, to allow the work piece engaging member 12 to engage the work piece 14. Figure 4 shows a fixture 10 without a work piece 14. In this exemplary embodiment, the fixture 10 includes two supporting members 22, and four clamping assemblies 18; however, it should be noted that the invention may include a different number of supporting members or clamping assemblies. The supporting members 22 may be semicircular plates with semicircular cut-outs. When the supporting members 22 are placed in communication with one another, the cutouts form an aperture 24 through which a work piece 14 can be accommodated. This exemplary arrangement may further include a holder 8 for holding the supporting members 22 together. The holder 8 may include two halves 8A, 8B held together by a hinge or hinge mechanism 7 and may be releasably connected in an engaged or closed position by a releasable latch or lock fixture 9, as shown in Figure 1. Alternatively, the supporting member 22 may be a single body defining an aperture for receiving the work piece (not shown). In the illustrated embodiment, the clamping assemblies 18 are coupled to the supporting members 22 such that the work piece engaging members 12 are biased towards the center of the aperture 24 and may extend radially inward of the aperture. In the illustrated example the aperture 24 is circular to accommodate a cylindrical work piece. The aperture 24 could take on any geometric shape necessary to accommodate any type of work piece. For example, the aperture 24 could take on a rectangular or oval shape to accommodate a non-cylindrical work piece. As the aperture 24 may be defined by supporting member surfaces that are clearance surfaces (i.e., they do not contact the work piece when the work piece is clamped), the precise shape, dimensions, and tolerances of the aperture 24 may not be critical, making the fixture assembly more cost-effective (as precise tolerances are unnecessary) and adaptable to accommodate work pieces of varying dimensions.

[0023] When a work piece is placed through the aperture 24, as shown in Figures 5A and 5B (in cross-section) the work piece engaging members 12 apply a force to the work piece 14. The clamping assemblies 18 are positioned so that, prior to placing a work piece 14 into the fixture 10, the tips 12' of the work piece engaging members 12 extend into the aperture 24 so that there is an interference between the tips of the work piece engaging member 12 and the outer surface of the work piece 14. When the work piece 14 is placed in the aperture 24, the work piece engaging members 12 are displaced away from the center of the aperture 24 and towards corresponding biasing members 16. The biasing member 16 reacts by compressing and exerting a force onto the work piece engaging member 12. This force causes contact to be maintained between the work piece engaging member 12 and the work piece 14. This contact results in the work piece engaging members 12 placing a force on the work piece 14. In the exemplary embodiment, the work piece 14 is held by the fixture, but the work piece engaging members allow the position of the work piece 14 to be adjusted or moved. This adjustment or movement is possible because when the work piece engaging members 12 are in contact with the work piece 14 the biasing members 16 are not completely compressed. When a work piece 14 is manually manipulated to alter the positioning or alignment of the work piece 14 some of the work piece engaging members 12 may be displaced or retracted further into corresponding mounting members 20 and some of the work piece engaging members 12 may be displaced or extended further out of the corresponding mounting members 20. The biasing members 16 are normally in a state of partial compression where a force is exerted on the work piece engaging member 12 and greater compression is possible. Therefore, when a work piece 14 is fixtured, the ability for the work piece engaging members 12 to be displaced either further into the mounting member 20 or further out of the mounting member 20 allows for the movement needed to position and align a work piece 14.

[0024] As shown in the clamping assembly 18 exemplary embodiment of Figures 3 A,

3B, and 3C, the mounting member 20 may include a housing 20' that can be mounted to the support member using mounting holes 25, and fasteners (not shown). The housing 20' may be provided with a generally cylindrical bore 19 in which the biasing member 16 (in this embodiment, a coil spring) and work piece engaging member 12 may be received, allowing the work piece engaging member 12 and biasing member 16 to move axially, while limiting the lateral movement of the work piece engaging member 12 and biasing member 16. Additionally, the work piece engaging member 12 may be provided with a slight taper from its base to its tip, and the bore 19 may be provided with a corresponding inward taper toward its opening, such that the base of the work piece engaging member 12 has an interference fit with the upper portion of the bore 19. This interference fit may prevent the work piece engaging member from being pushed out of the housing 20' by the biasing member 16 before the work piece 14 has been placed in the fixture 10. It should be noted that it may be desirable to avoid positioning the clamping assembly 18 such that the work piece engaging member 12 is retracted so far into the bore 19 that a gap is created between the work piece engaging member 12 and the side wall of the bore 19, which would allow the work piece engaging member to move laterally in the housing 20', and potentially affect the alignment of the work piece engaging member 12 against the work piece 14.

[0025] Also, the directions and magnitudes of the forces applied to the work piece 14 by each of the corresponding work piece engaging members 12 may allow for alignment or positioning of the work piece 14 with respect to the fixture without manipulation or adjustment of the fixture itself. As shown in Figures 1, 4, and 5, the clamping assemblies 18 may be positioned at 90° intervals around the supporting members 22, with the work piece engaging members 12 directed inward of, and normal to, the aperture 24. This arrangement illustrates one possible embodiment in which the gripping forces exerted on the work piece engaging member 12 act in opposite directions to each other, thereby counteracting each other. Additionally, it may be preferable to utilize biasing members 16 which provide relatively consistent output forces across a range of displacement or compression, such that a less compressed biasing member 16, or extended work piece engaging member 12, will provide a gripping force sufficient to counteract an opposing force from a more compressed biasing member 16, or retracted work piece engaging member 12, so as to allow secure alignment in many different positions and orientations of the work piece 14. [0026] Further, the clamping assembly 18 of an exemplary embodiment may be adapted to allow for adjustment of a full range of motion of the work piece engaging member 12 and the biasing member 16; that is, permitting adjustment of both a fully extended position of the work piece engaging member 12 and a fully retracted position of the work piece engaging member 12. For example, as shown in Figure 3B, the housing 20' may be provided with a threaded port 21 and threaded adjusting member 23. The adjusting member 23 may be advanced or retracted to adjust the positions of the work piece engaging member 12 and the biasing member 16. When the adjusting member 23 is advanced, the work piece engaging member 12 and the biasing member 16 are pushed further toward the aperture 24 (as shown in Figure 3C), to either engage the work piece 14 (if a gap is present between the work piece 14 and the work piece engaging member 12) or provide increased force on the work piece 14 to grip the work piece 14 more securely or to counteract an opposing force on the work piece 14 by one of the other clamping assemblies 18. When the adjusting member 23 is retracted, the work piece engaging member 12 and the biasing member 16 are drawn further into the mounting member 20 and away from the aperture 24, to accommodate a larger work piece 14, or to reduce the force applied to the work piece 14. In the exemplary embodiment of Figures 3A, 3B, and 3C, the adjusting member 23 provides the bore 19 in which the work piece engaging member 12 and biasing member 16 are received. Alternatively, the bore may be defined by the housing, and a set screw may be installed at a threaded base of the bore to push the work piece engaging member and biasing member toward the aperture or allow the work piece engaging member and biasing member to be drawn away from the aperture (not shown). Other means of adjusting the range of motion of the work piece engaging member 12 and biasing member 16 may be provided, such as the use of any type of adjustable shoulder or stopper within the mounting member to restrict or extend the travel of the work piece engaging member 12 and/or biasing member 16, or the inclusion of additional biasing members (such as extra springs).

[0027] Additionally, further adjustability and adaptability of the fixture may be provided by allowing the clamping assemblies 18 to be positionable on the supporting members 22, either radially toward or away from the aperture 24, rotationally around the circumference of the aperture 24, or angularly with respect to the intersecting edge of the aperture 24. By providing a wide range of mounting positions for the clamping assemblies 18 on the supporting members 22, through the use of, for example, mating mounting holes and threaded fasteners (not shown), the fixture may be adapted to accommodate work pieces of many different shapes, sizes, and tolerances. Such means for attaching and positioning the clamping assemblies on the supporting members may also provide greater adaptability by allowing for replacement of worn clamping assemblies, retrofitting the fixture with clamping assemblies of different sizes, materials, output forces, and contact surfaces, or using the fixture with a different number of clamping assemblies as needed to properly secure and align the work piece.

[0028] The tip 12' of the work piece engaging member 12 of an exemplary embodiment of the invention is hemispherical in shape, as evident in Figures 2, 3A, and 3B. While any of a wide range of sizes and shapes of work piece engaging members may be used, it is noted that the use of a work piece engaging member 12 having a relatively small contact surface area for engagement with the work piece 14 at a discrete contact point may facilitate easier alignment of the work piece. When fϊxturing a work piece with an irregular outer surface or a short tangent length available to be gripped, the use of a larger contact surface between the work piece engaging member 12 and the work piece 14 may result in uneven contact between the engaging surfaces, which can cause the work piece to become skewed or tilted in the fixture, resulting in a misalignment with the conduit or other work piece to which the work piece 14 is to be welded. An additional advantage of using a work piece engaging member 12 with a hemispherical (or similarly contoured) tip 12' is that a discrete contact point may still be provided even if the work piece 14 contacts the tip 12' at a different position or angle. It should also be noted that it may be desirable to position or adapt the clamping assembly 18 such that the minimum amount of force required to hold the work piece 14 in place is applied by the work piece engaging member 12 to the work piece 14, to minimize marks or indentations in the work piece 14 and the work piece engaging member 12.

[0029] While the work piece engaging member 12, biasing member 16, and mounting member 20 of an exemplary embodiment are constructed in stainless steel, any of a number of materials may be used for these components, with consideration given to the material's pertinent properties, such as, for example, heat resistance and electrical conductivity. [0030] Figure 6 illustrates a second work piece, such as a conduit 26, secured by fixturing. The conduit 26 may be cylindrical with a more uniform outer diameter and may therefore be secured by a more conventional fixturing collet 28 (shown in cross-section in Figure 5B). Similar to the supporting members 22, the collet members 28A, 28B forming the collet 28 in this example illustration are semicircular plates with semicircular cutouts. When the collet members 28A, 28B are placed in communication, the cutouts form an aperture 29 to accommodate and secure the conduit 26. Unlike the exemplary supporting members 22 used with the work piece 14 in the illustrated embodiment, the collet 28 may be dimensioned to prevent any substantial movement of the conduit 26 with respect to the collet 28 and secure the conduit 26 in a more rigid manner. The collet 28 may be one of any number of clamping or fixturing devices as known in the field, and may be assembled into a collet assembly 13, which may include hinging and latching mechanisms similar to those of the fixture 10. [0031] Once the work piece 14 is held by the work piece engaging members 12 and the conduit 26 is secured in the collet 28, the work piece 14 and the conduit 26 can be placed in communication, as shown in Figures 5B and 6, and can be welded together. The movement allowed by the work piece engaging members 12 and the biasing members 16 allows the position of the work piece 14, with respect to the conduit 26, to be manually manipulated to properly align the work piece 14 with the conduit 26. Proper alignment can entail placing the work piece 14 and conduit 26 into communication, adjusting the work piece 14 so that the end face is flush with the end face of the conduit 26, or rotation of work piece 14 for proper rotational alignment with the conduit 26. Once alignment is achieved, the work piece 14 and the conduit 26 can be welded together. The welding process can be orbital welding, for example, accomplished by an orbital weld head 30. A space to accommodate a weld head or other instrument may be provided by assembling a spacer 11 between the fixture 10 and the collet assembly 13.

[0032] In another embodiment the collets 28 that rigidly secure the conduit 26 are replaced by the above described supporting members 22 and clamping assemblies 18 to hold the conduit 26, or any other work piece to which the work piece 14 is to be welded. This embodiment allows adjustment of both the work piece 14 and the conduit 26. This arrangement may allow for larger inconsistencies in the dimensions and characteristics of the conduit 26 to be accounted for in aligning of the conduit 26 to the work piece 14 prior to welding.

[0033] In holding a work piece in alignment for a welding operation in a manner contemplated by an embodiment of the present invention, a contact surface is provided to engage the work piece. The contact surface may be elastically biased against the work piece, thereby allowing the work piece to be moved relative to the contact surface. Additionally, the entire range of motion of the contact surface may be adjusted, to accommodate different sizes of work pieces or different gripping forces on the work piece.

[0034] While various aspects of the invention are described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects may be realized in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub- combinations are intended to be within the scope of the present invention. Still further, while various alternative embodiments as to the various aspects and features of the invention, such as alternative materials, structures, configurations, methods, devices, software, hardware, control logic and so on may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the aspects, concepts or features of the invention into additional embodiments within the scope of the present invention even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the invention may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present invention however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated.

Claims

Having described the invention, it is now claimed:

1. A fixture for holding a work piece to be welded, the fixture comprising:

a supporting member defining an aperture for receiving the work piece; and

at least one clamping assembly assembled with the supporting member, each clamping assembly comprising:

a work piece engaging member positioned for engagement with the work piece;

a biasing member assembled with the work piece engaging member to bias the work piece engaging member into engagement with the work piece; and

a mounting member that holds the work piece engaging member and the biasing member, the mounting member being assembled to the supporting member such that the work piece engaging member extends at least partially radially inward of the aperture.

2. The fixture of claim 1, wherein the work piece engaging member comprises a hemispherical tip.

3. The fixture of claim 1, wherein the biasing member comprises a coil spring.

4. The fixture of claim 1, wherein the work piece engaging member and the biasing member are positionable with respect to the mounting member.

5. The fixture of claim 4, wherein the clamping assembly further comprises an adjusting member adapted to position of the work piece engaging member and the biasing member with respect to the mounting member.

6. The fixture of claim 1, wherein the mounting member is positionable with respect to the supporting member.

7. The fixture of claim 1, wherein the clamping assembly is adapted to provide engagement between the work piece engaging member and the work piece when the biasing member is in a partially retracted condition.

8. The fixture of claim 1, comprising two supporting members adapted to be held together in a coaxial relationship to define the aperture.

9. The fixture of claim 8, further comprising a holder for holding the supporting members together in a coaxial relationship.

10. The fixture of claim 1, wherein the work piece engaging member is adapted to extend and retract in a direction normal to the aperture.

11. The fixture of claim 1 , comprising a plurality of clamping assemblies.

12. The fixture of claim 11, wherein first clamping assemblies is adapted to apply a first clamping force on the work piece and a second clamping assembly is adapted to apply a second clamping force on the work piece.

13. The fixture of claim 12, wherein the second clamping force is directed to counteract the first clamping force.

14. The fixture of claim 1, comprising four clamping assemblies.

15. The fixture of claim 14, wherein the four clamping assemblies are positioned at approximately 90° intervals around the aperture.

16. The fixture of claim 14, wherein the four clamping assemblies are adapted to exert first, second, third, and fourth clamping forces on the work piece when the work piece is positioned in the aperture.

17. The fixture of claim 14, wherein the four clamping assemblies are adapted to allow adjustable positioning of the work piece with respect to the aperture without manipulating the fixture.

18. A fixture for holding a work piece to be welded, the fixture comprising:

a supporting member defining an aperture for receiving the work piece;

a work piece engaging member positioned for engagement with the work piece, wherein the work piece engaging member includes a hemispherical tip; and

a biasing member assembled with the work piece engaging member to bias the work piece engaging member into engagement with the work piece.

19. The fixture of claim 19, wherein the fixture is adapted to allow an entire range of motion of the work piece engaging member to be adjustable.

20. A method for holding a work piece in alignment for a welding operation, comprising:

receiving the work piece;

providing at least one discrete contact point for engaging the work piece;

elastically biasing the at least one contact point against the work piece;

moving the work piece relative to the at least one contact point.