HK1099358B - Tube assembly and method - Google Patents

Description

Tube assembly and method

Background

1. Field of the disclosure

The present invention relates generally to pipe couplings, and more particularly to coupling a flow measurement pipe to a base member.

2. Description of the related Art

The measurement and control of fluid flow is important in the process industry. Many manufacturing processes require very high precision and repeatability in fluid delivery, and therefore require accurate measurement and control of the mass flow rate of the process fluid. Various techniques are known for measuring mass flow. For example, mass flow measurement based on the coriolis force effect provides a direct measure of mass flow. In a typical coriolis force flow sensor, a flow sensor tube through which a fluid flow passes is vibrated. The tube is typically in the form of one or more loops. The shape of the loop is such that the vector of mass flow is directed in opposite directions at different parts of the loop. The loops in the tube may be, for example, "U", rectangular, triangular or "delta" shaped, or helical. In the case of a special straight tube, there are two simultaneous angular velocity vectors that coincide with anchor points in the tube, while the mass flow vector is in a single direction.

The angular velocity vector changes direction because the direction of rotation in the vibration system changes. As a result, the coriolis force acts in opposite directions at any given time, with the mass flow vector or angular velocity vector pointing in opposite directions. Since the angular velocity vector is constantly changing due to the vibration system, the coriolis force is also constantly changing. As a result, a dynamic twisting motion is applied on top of the tube oscillating motion. The magnitude of the twist is proportional to the mass flow rate at a particular angular velocity.

A thermal mass flow instrument measures flow by directing a small portion of the liquid flow through a flow sensor tube. Heating is applied in the middle of the sensor tube, which is provided with temperature sensors on either side of the heater. Each temperature sensor measures the fluid temperature at a respective location. The first temperature sensor measures temperature upstream of the heater. The second temperature sensor measures a temperature downstream of the heater and reflects a corresponding temperature of the fluid when heated by the heater. The difference in fluid temperature across the heater is proportional to the mass flow rate.

In such a flow measuring device. The flow sensor tube is typically located on the base member and is typically at or adjacent to the inlet or outlet end of the tube. In order to provide reliable operation, the connection of the pipes must be strong and sealed leak-free. Typically, the flow tube is brazed to the base member. Brazing forms a strong and sealed connection, but may have a relatively poor corrosion resistance compared to the material of the tube. Welding is the preferred method of attachment. However, known manufacturing processes and tolerances often make it difficult to obtain a satisfactory welded pipe joint, especially in low flow applications requiring extremely small flow sensor tubes.

The present invention addresses the disadvantages associated with the prior art.

Summary of the disclosure

In one aspect of the present disclosure, a flow sensor tube assembly includes a base member having generally opposed first and second faces. An aperture extends through the base member and an end of the flow sensor tube is received in the aperture. A filler material is disposed in the opening and around the flow sensor tube adjacent the first side of the base member to connect the tube to the base member. A groove may be formed in the first face of the base member around the aperture to form a projection adjacent the aperture to assist in the brazing operation. Adjacent the second side of the base member, the flow sensor tube is welded to the base member. In an exemplary embodiment, to obtain improved welding, a nipple (nipple) is defined by the second face of the base member to better match the thickness of the welded component. Additionally, a nipple may be formed around the flow sensor tube to eliminate a gap between the aperture and the flow sensor tube.

A second aperture may be provided for receiving the opposite end of the flow sensor tube. The end of the tube may be attached to the base member in the same manner as the first end, with a filler material disposed in the second opening and around the flow sensor tube adjacent the first side of the base member, and with the second end of the flow sensor tube welded to the base member adjacent the second side of the base member.

Also disclosed is a method of connecting a tube to a base member, including inserting an end of the tube into an aperture extending through the base member. A filler material is disposed in the aperture around the circumference of the tube adjacent the first side of the base member to connect the tube to the base member. Further, the tube is welded to the base member adjacent the second face of the base member. The second face of the base member may be formed on the tube to eliminate a gap between the aperture and the tube. In certain embodiments, the tapered nipple defined by the base member may be formed using a lash adjuster or swage (swege) to eliminate the gap between the bore and the tube.

Brief description of the drawings

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

fig. 1 is a block diagram showing the components of a mass flow measurement device.

Fig. 2 is an exploded perspective view of a tube assembly according to aspects of the present invention.

Fig. 3 is an assembled perspective view of the tube assembly shown in fig. 2.

Fig. 4 is a sectional view showing the components of the pipe assembly shown in fig. 2 and 3.

Fig. 5 is a bottom view of the base member of the tube assembly shown in fig. 2 and 3.

FIG. 6 is a cross-sectional view schematically illustrating lash adjusters and component parts of the tube assemblies disclosed herein.

Fig. 7 and 8 are cross-sectional views of the tube assembly showing exemplary tube positions relative to the base member.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Detailed description of the invention

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Fig. 1 illustrates, in principle, the components of a mass flow sensor based on the coriolis effect. For simplicity, portions of the present disclosure are shown as applied to coriolis mass flow measurement devices, however, the present disclosure is applicable to other devices requiring a secure, fluid-tight tube connection. For example, it would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure to apply the concepts of this disclosure to other flow measurement devices, such as thermal mass flow measurement devices.

The coriolis mass flow sensor 10 shown in fig. 1 includes a flow sensor tube 12 provided with a drive device 14 positioned relative thereto to vibrate the tube 12. The pick-off 16 is positioned relative to the tube 10 to measure the twist in the tube 10 due to coriolis forces. The two ends of the flow sensor tube 10 are connected to a base member in a base housing 18 which may contain the inlet and outlet connections of the device. The exemplary flow sensor tube 10 shown in FIG. 1 is generally U-shaped, but other shapes may be used, such as triangular, rectangular, helical, or straight.

FIG. 2 is an exploded perspective view of an exemplary flow sensor tube assembly 100 in accordance with aspects of the present invention. The sensor tube assembly 100 includes a base member 110 and a flow sensor tube 112. The base member 110 has an aperture 114 extending therethrough for receiving both ends of the flow sensor tube 112. Typically, one end of the flow sensor tube 112 is an inlet and the opposite end is an outlet, such that a fluid flow is established in the flow sensor tube 112 to measure the flow rate. Fig. 3 shows the flow sensor tube assembly 100 with both ends of the flow sensor tube 112 received in the openings 114.

Fig. 4 is a cross-sectional view showing both ends of the flow tube 112 received in the openings 114 of the base member 110. A filler material 120 is disposed in the opening 114 and around the flow sensor tube 112 adjacent a first side (top side as viewed in fig. 4) of the base member 110 to attach the tube 112 to the base member. In the exemplary embodiment, a low temperature alloy material is used to facilitate a brazed connection adjacent the top surface of base member 110. Silver-copper alloys are suitable filler materials for the braze joint. In other embodiments, solder or an adhesive, such as epoxy, is used as the filler material to attach the flow sensor tube 112 adjacent the first side of the base member 110.

The flow sensor tube 112 is also connected to the base member 110 by a second connection 122 at a second face (the bottom face shown in fig. 4), where the tube 112 is welded to the base member 110. The dual contact connection of the flow sensor 112 to the base member 110 provides a secure, leak-free connection. The welded connection 122 provides a fluid seal while the brazed joint 120 provides a structural connection.

In the exemplary embodiment, aperture 114 has two segments 114a and 114b that define a first diameter and a second diameter, respectively. The diameter of the first section 114a is greater than the second diameter 114b such that a radial gap is formed around the tube 112 to provide clearance for the filler material 120. In some embodiments using a brazing filler material, the brazed connection is achieved using induction heating because it provides sufficient localized heat and does not damage the tubes 112. To facilitate the brazing process, the top surface of the base member 110 defines an annular groove 150 to form a boss 152 that allows placement of an induction heating tool for brazing attachment.

In welding, it is necessary to match the thicknesses of the two parts to be welded. The base member 110 is generally much thicker than the tube 112, especially in low flow applications where very thin tubes are used. To more closely match the thickness of the plate to the thickness of the base member 110 attached to the wall of the tube 112, a nipple 130 is formed at the bottom of the base member 110. Fig. 5 is a bottom perspective view of the base member 110, showing the nipple 130 defined by the base member 110.

In the exemplary flow tube assembly, the base member is about 0.330 inches thick, while the flow sensor tube 112 has a wall thickness of about 0.001 inches. In the exemplary embodiment, the end of nipple 130 is tapered to approximately 0.001 inches (similar to the thickness of the pipe wall) where it is welded.

In addition to matching the thickness of the parts to be welded, it is also preferable to reduce the gap between the parts to about 10% of the thickness of the parts. Manufacturing tolerances between the second segment 114b and the diameter of the tube 112 make it difficult to form the required intimate contact between the flow sensor tube 112 and the base member 110 to achieve a consistent weld and fluid tight joint. In the exemplary embodiment cited above, where the tube 112 has a wall thickness of 0.001 inch, then a tolerable gap of 0.0001 inch is allowable. However, a typical tolerance for the outer diameter of the flow sensor tube 112 is 0.0002 inches, which may result in an unacceptable 0.0004 inch gap.

Regardless of manufacturing tolerances, to achieve intimate contact, after the tube 112 is inserted into the bore 114, the base member 110 may be shaped so as to eliminate a gap between the tube 112 and the second section 114b of the bore 114. As shown in fig. 4, a portion of the second section 114b of the aperture 114 is within the nipple 130. In the exemplary embodiment, a lash adjuster or swage 140 is pressed against nipple 130 under a controlled force to close any gap between opening 114 and flow sensor tube 112. FIG. 6 schematically illustrates a swaging process that forms base member 110 around tube 112 in an exemplary tube assembly. Fig. 6 shows the base member 110 inverted so that the nipple 130 formed by the bottom surface of the base member 110 is facing upward as shown. In the illustrated embodiment, the nipple 130 is generally conical, forming a taper of approximately 62. The lash adjuster 140 has a taper 142 of about 60 deg. which, when an external force is applied to the lash adjuster 140 to swage the bore 114 about the tube 112, the taper 142 interferes with the nipple 130, thereby eliminating any gap therebetween.

Fig. 7 and 8 show some different tube positions/weld geometries. In fig. 7, the tube 114 is positioned such that one end of the tube 114 is substantially flush with the nipple 130. In this case, welding is performed orthogonal to the base member 110. In fig. 8, the tube 114 extends from the base member 110. In this case, welding is performed while being inclined at a certain angle.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the scope of protection herein is as set forth in the claims appended hereto.

Claims (19)

1. A flow sensor tube assembly comprising:

a base member having opposing first and second faces;

a first nipple defined by a second face of the base member;

an aperture extending through the base member and the first nipple;

a flow sensor tube having one end received in the aperture;

a filler material disposed in the aperture and around the flow sensor tube adjacent the first face of the base member; and

the flow sensor tube is welded to the first nipple, the end of the first nipple having a thickness approximately equal to the wall thickness of the flow sensor tube.

2. The flow sensor tube assembly of claim 1, wherein the bore has first and second sections defining first and second diameters, respectively, the first diameter being greater than the second diameter.

3. The flow sensor tube assembly of claim 2, wherein the filler material is disposed in the first section of the aperture and around the flow sensor tube.

4. The flow sensor tube assembly of claim 2, wherein the second section of the bore is at least partially in the first nipple.

5. The flow sensor tube assembly of claim 1, wherein the first nipple defined by the second face of the base member is swaged around the flow sensor tube adjacent the aperture to eliminate a gap between the aperture and the flow sensor tube.

6. The flow sensor tube assembly of claim 1, wherein the first nipple is formed around the flow sensor tube so as to eliminate a gap between the aperture and the flow sensor tube.

7. The flow sensor tube assembly of claim 1, wherein a portion of the flow sensor tube extends from the second face of the base member.

8. The flow sensor tube assembly of claim 1, further comprising:

a second aperture extending through the base member and a second nipple defined by a second face of the base member;

a second end of the flow sensor tube received in the second aperture;

a filler material disposed in the second aperture adjacent the first face of the base member and surrounding the flow sensor tube; and

the second end of the flow sensor tube is welded to the second nipple.

9. The flow sensor tube assembly of claim 1, further comprising a groove defined in the first face of the base member surrounding the aperture, thereby forming a boss adjacent the aperture and between the groove and the aperture.

10. The flow sensor tube assembly of claim 1, wherein the filler material comprises a brazing material.

11. The flow sensor tube assembly of claim 1, wherein the filler material comprises solder.

12. The flow sensor tube assembly of claim 1, wherein the filler material comprises an epoxy.

13. A method of connecting a tube to a base member, the method comprising:

inserting an end of the tube into a first aperture extending through the base member from a first face of the base member to a second face of the base member, wherein the end of the tube is inserted from the first face to the second face and is in a first nipple defined by and extending from the second face of the base member, wherein a thickness of an end of the first nipple is approximately equal to a tube wall thickness of the tube;

disposing a filler material in the aperture and around the tube adjacent the first face of the base member; and

welding the tube to the first nipple.

14. The method of claim 13, wherein the first bore has first and second sections defining first and second diameters, respectively, the first diameter being greater than the second diameter, wherein disposing the filler material comprises disposing the filler material in the first section of the first bore and around the tube.

15. The method of claim 13, further comprising, prior to welding, swaging the first nipple defined by the second face of the base member on the tube.

16. The method of claim 15, wherein the swaging comprises swaging the first nipple on the tube with a lash adjuster or swage.

17. The method of claim 13, wherein the tube is inserted into the first aperture such that a portion of the tube extends from the first nipple defined by the second face of the base member.

18. The method of claim 13, further comprising:

inserting a second end of the tube into a second aperture extending through the base member from the first face to the second face and through a second nipple; wherein the second nipple is defined by and extends from a second face of the base member, the second end of the tube being in the second nipple, wherein;

disposing a filler material in the second aperture and around the second end of the tube adjacent the first face of the base member; and

welding the second end of the tube to the second nipple.

19. The method of claim 13, wherein the filler material comprises a brazing material, the method further comprising inductively heating the brazing material in the first bore.