Manifold assembly for a gas range

A manifold tube is formed from a straight length of thin wall tube initially having a uniform circular cross section. A first segment of the tube is left in its initial circular cross section configuration. The first segment includes an inlet end of the tube. A second segment of the tube is flattened to form opposed flat wall portions spaced apart by a distance smaller than the diameter of the circular portion and separated by side walls spaced apart by a distance greater than the diameter. An inlet fitting is attached to the inlet end of the tube. A bend is formed in the first segment of the tube between the inlet end and the second segment. Burner valves and on oven control valve are secured with metal-to-metal contact to the flat wall portions in the second segment of the tube.

FIELD OF THE INVENTION
 The present invention relates to a gas distribution manifold assembly for a
 gas cooking range.
 DESCRIPTION OF THE PRIOR ART
 A typical gas range has at least one, and usually several, top burners and
 may also have an oven burner. A manifold assembly is used to distribute
 gas from a gas inlet to the burners through valves, including burner
 valves for the top burners and a thermostatic control valve for the oven
 burner.
 A manifold assembly of a type that was widely used in the past includes a
 round thick wall tube or pipe having a circular cross section. The wall of
 the tube or pipe is thick and strong enough to permit components of the
 assembly to be attached directly to the wall by threaded connections.
 Thus, an inlet end of the tube or pipe is threaded to mate with a gas
 supply fitting, and the other end of the tube or pipe is closed, for
 example by a cap or a plug threaded onto or into the pipe. Burner valves
 are attached directly to the wall of the tube or pipe, typically by
 threading a nipple of the valve body into a female threaded hole formed in
 the wall of the tube or pipe. Because of the configuration of a typical
 range, the tube or pipe may require at least one bend or elbow along its
 length.
 This type of manifold assembly is heavy and expensive due to its massive
 wall thickness and the number of parts and assembly operations required
 for its manufacture. To overcome these disadvantages, the modern trend is
 to make manifold assemblies using thin wall tubing instead of thick wall
 pipe or tube. Various approaches have been employed, but none has fully
 met the need for a manifold assembly that is low in cost and easy to
 assemble.
 One approach is to use a thin wall round tube having a circular cross
 section throughout its length. One advantage is that a round tube is low
 in cost. Another advantage is that a round tube can be easily formed with
 one or more bends using readily available numerically controlled
 equipment, and the bends can be relatively sharp, with a small radius of
 curvature. Thin wall round tubing has problems however. Thin wall tubing
 does not permit the direct attachment of threaded inlet fittings and caps
 to the ends of the tube because the material is not sufficiently thick and
 strong. Typically therefore the inlet end of the thin wall tube has a
 machined inlet fitting welded in place and the opposite end is closed by a
 welded in place plug or by pinching the tube wall. It is difficult to
 mount burner and thermostat oven control valves to a tube wall having a
 circular cross section. Because the tube wall is not thick enough to
 accept threaded nipples, the valves are attached by a fastener system, and
 it is difficult to fasten valve bodies to a circular surface. A saddle
 arrangement or other complex structure and/or difficult assembly operation
 is required to reliably mount valve bodies to a round thin wall tube.
 In an attempt to overcome problems with a tube having a circular cross
 section, tubes with flat walls have been employed. One known manifold
 assembly is made with a thin wall tube having a square cross section
 throughout its length. Another known manifold assembly uses a flattened
 thin wall tube with opposed curved side walls and opposed flat top and
 bottom walls through out its length. Flat walls have the advantage that it
 is easier to mount valves to a flat surface than to the curved surface of
 a round tube. However the flat wall tubes have other problems. It is
 difficult to form a bend in a square or flattened tube. Such a tube cannot
 be shaped into a sharp, small radius bend. In addition, such tubes can
 only be bent in limited ways. A bend in a plane that is not parallel or
 perpendicular to the flat tube wall is not practical. Finally, it is
 difficult to attach an inlet fitting or a cap or plug to the end of a thin
 wall tube having a non-circular cross section.
 U.S. Pat. No. 2,896,975 discloses a pipe manifold using a round pipe with a
 thick wall section strong enough to receive a threaded valve nipple. At
 locations where valves are to be attached, the pipe is deformed to
 reinforce the pipe. The deformed segments include flattened, angled side
 walls and a flat top wall.
 U.S. Pat. No. 5,979,430 discloses a manifold having tube portions of square
 cross section. The ends of the square tube are deformed outwardly by a
 mandrel to an enlarged diameter round shape that can accept round plugs to
 seal the tube ends. In addition, prior to the present invention,
 Harper-Wyman Company has made and sold Harper 7060 and 7062 Series
 manifold assemblies using square thin wall tube.
 SUMMARY OF THE INVENTION
 A principal object of the present invention is to provide an improved
 manifold assembly for a gas range that performs well and is inexpensive to
 manufacture. Other objects are to provide an improved manifold assembly
 having a thin wall tube to which valves can be attached without using
 saddles or the like; to provide an improved manifold assembly having a
 tube that can be formed with sharp bends in any plane and that can include
 compound bends; to provide an improved manifold assembly which can accept
 a simple round inlet fitting; to provide an improved end closure for the
 tube of a manifold assembly; to provide an improved thin wall tube
 structure for use in a gas range manifold assembly; to provide an improved
 method for making a manifold assembly and manifold tube; and to provide a
 manifold assembly overcoming disadvantages of known manifold assemblies.
 In brief, in accordance with the invention there is provided a manifold
 assembly for a gas range. A thin wall metal tube forms an elongated gas
 conduit having an inlet end and a closed end. At least one valve is
 mounted on the conduit for controlling the flow of gas from the conduit.
 The tube has a first segment along its length, the first segment having a
 circular cross section with a diameter. The tube has a second segment
 along its length, the second segment having a non-circular cross section
 with opposed first and second wall portions alternating with opposed third
 and fourth wall portions. The first and second wall portions are flat and
 parallel to one another and are spaced apart by a distance less than the
 diameter of the first segment. The third and fourth wall portions are
 spaced apart by a distance larger than the diameter of the first segment.
 The valve is mounted to the second segment of the tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Having reference now to the drawings and initially to FIG. 1, there is
 illustrated a manifold assembly generally designated as 20 and constructed
 in accordance with the principles of the present invention. The manifold
 assembly 20 is used in a gas cooking range (not shown) to distribute gas
 from a gas supply to four top burners and an oven burner. The principles
 of the invention can be applied to manifold assemblies for gas cooking
 ranges of other configurations, including for example ranges with a
 different number of top burners and ranges without an oven burner. In
 general, the manifold assembly 20 includes a manifold tube 22 having an
 inlet end 24 and a closed end 26. For controlling the supply of gas to the
 range top and oven burners, the manifold assembly 20 includes four burner
 valves 28 and a thermostatic oven control valve 30.
 The manifold assembly 20 is configured for use in a range having a rear
 entry gas supply and front panel mounted controls. As a result the
 manifold tube 22 has a bend 32 interconnecting a front tube portion 34 and
 a rearwardly extending tube portion 36. An inlet fitting 38 is attached to
 the inlet end 24 of the manifold tube 22. To support the manifold assembly
 20 in a gas range, it includes a pair of forward mounting brackets 40 and
 an inlet section mounting bracket 42.
 In accordance with the invention, the manifold tube 22 has segments with
 different cross sections. A first segment 44 has a uniform circular cross
 section throughout its length, as seen in FIG. 2. A second segment 46 has
 a uniform non-circular cross section throughout its length, as seen in
 FIG. 3. The circular segment 44 extends from the inlet end 24 of the
 manifold tube along the entire rearwardly extending portion 36 and along
 the entire bend 32 to the front tube portion 34. The non-circular segment
 46 constitutes nearly all of the front tube portion 34. The circular and
 non-circular segments 44 and 46 are joined by a short transition region 48
 near the upstream end of the front tube portion 34. Bracket 42 and inlet
 fitting 38 are mounted to the circular segment 44, while the valves 28 and
 30 as well as the brackets 40 are mounted to the non-circular segment 46.
 The manifold tube 22 is made from a straight length of thin wall metal
 round tube 50 seen in broken and full lines in FIG. 6. A sequence of steps
 in the method of making the tube 22 from the tube 50 is described with
 reference to FIGS. 4-7. In a preferred embodiment of the invention, the
 tube 50 is an aluminized steel tube having an outer diameter of about
 three-quarters of an inch, and having a uniform twenty gauge wall
 thickness of about 0.034 inch throughout its length. The term "thin wall"
 means a tube wall thickness less than 0.10 inch that is not sufficiently
 thick and strong for the direct attachment of valves and the like with
 threaded connections. Initially the tube 50 is straight and has a uniform
 wall thickness and a uniform circular cross section throughout its length.
 The cross section of the tube 50 as initially supplied is the same as the
 cross section seen in FIG. 2. Round thin wall tube of this type has the
 advantage that it is inexpensive.
 The first step in the method of manufacturing the manifold assembly 20, as
 indicated in FIG. 4, is to bend the straight tube 50 and thus create the
 bend 32 separating the front and rearwardly extending tube portions 34 and
 36. The initial, straight shape is seen in broken lines in FIG. 4 and the
 shape after forming the bend 32 is seen in full lines. Widely available
 numerically controlled equipment can be used to form the bend 32. Because
 the bending operation is performed on round tube, the bend can be
 relatively sharp. In a preferred embodiment of the invention the radius of
 curvature of the bend 32 is about one and one-half inches relative to the
 centerline of the tube 50. Although a single ninety degree bend is
 illustrated, single or compound bends of any desired angle can be made to
 tailor the manifold tube 22 and assembly 20 to any specific range
 application. Because a round tube can be bent in any plane, great
 flexibility in design is possible.
 After the bending operation, although the configuration of the tube is
 changed, the tube retains a substantially circular cross section and a
 substantially uniform wall thickness throughout its length, with only
 minor variations at the bend 32 resulting from deformation during the
 bending operation. Thus at this point in the manufacturing process, the
 entire tube length retains essentially the cross section seen in FIG. 2.
 The next step in forming the tube 22 is to flatten the cross section of
 that part of the tube 50 other than the circular section 44, specifically
 including the non-circular segment 46 and the end portion that is to
 become the closed end 26. Tooling for forming the non-circular cross
 section seen in FIGS. 4 and 5. An elongated mandrel 52 is inserted into
 the front tube portion 34 and the tube and mandrel 52 are placed between a
 tool 54 having a recess 56 and a mating tool 58. The mandrel 52 and the
 tools 54 and 58 extend throughout the entire axial length of the part of
 the tube 50 that is to be provided with the non-circular cross section of
 FIG. 3.
 As seen by comparing FIGS. 4 and 5, when the tools 54 and 58 are closed
 together over the tube 50 and the mandrel 52, the tube is deformed so that
 it no longer has a circular cross section, but instead has a non-circular
 cross section as seen in FIG. 3. This non-circular cross section includes
 a pair of opposed, parallel, flat tube wall portions 60 and 62 separated
 by opposed, curved wall portions 64 and 66. It is preferred that the
 curved portions 64 and 66 are undeformed, radially outwardly displaced
 sections of the initial round cross section of the tube 50. In the
 resulting cross sectional shape, the flat portions 60 and 62 are spaced
 apart by a distance smaller than the diameter of the original circular
 cross sectional shape and the curved portions 64 and 66 are separated by a
 distance larger than the diameter of the original circular cross sectional
 shape. If desired, the upper flat portion 60 may be wider than the lower
 flat portion 62 to provide a larger area for mounting of the valves 28 and
 30.
 The next step in manufacturing the manifold tube 22 is to provide circular
 holes 68 and square holes 70 for mounting of the burner valves 28, holes
 72 for mounting the oven control valve 30 and a hole 74 for admitting gas
 to the oven control valve 30. The holes 68, 70, 72 and 74 are preferably
 made by punching through the wall of the tube 22 with punches of
 corresponding size and shape. The holes 70, the hole 74 and two holes 72
 are made in the upper flat wall portion 60. The holes 68 and the remaining
 two holes 72 are made in the lower flat wall portion 62. A mandrel can be
 inserted into the tube to support the tube during the punching operations.
 It is preferred that the holes 68 are made before the holes 70 to reduce
 the possibility of the removed material remaining in the tube. FIG. 7
 illustrates the manifold tube 22 at this stage of manufacture with the
 non-circular cross section formed and with the holes 68-74 formed in the
 tube wall portions 60 and 62.
 After the manifold tube 22 is formed and punched as seen in FIG. 7, the
 closed end 26 is formed. Before closing the end of the tube 22, a short
 end segment is returned from the non-circular cross section shape seen in
 FIG. 3 to the circular cross section shape seen in FIG. 2. Preferably this
 is done by closing a mating pair of circular clamps over the end portion
 of the tube 22. After the circular end segment is prepared, the tube wall
 material at the end of the tube is shaped into a flat, radial end wall 26.
 Preferably the end wall 26 is formed by rotating the tube 22 around the
 axis of the front portion 34 and displacing the tube wall material
 radially inwardly in a metal spinning operation. To assure a gas tight
 seal at the center of the end wall 26, a central region 76 is welded to
 puddle molten material which hardens in a gas impervious body. As best
 seen in FIGS. 8 and 9, when the reshaping and closing of the end segment
 is completed, the end portion of the tube 22 includes a short round
 segment 78, preferably not longer than about one inch, having a circular
 cross section as well as a transition portion 80 separating the round
 segment 78 from the non-circular segment 46.
 The inlet fitting 38 is used to connect the manifold assembly 20 to a
 threaded fitting communicating with a gas supply. The fitting 38 as seen
 in FIG. 10 includes a threaded nipple portion 82, a sleeve 84 that is
 received in the end of the tube 22, and a flange 86 that abuts the end of
 the tube 22. Because the inlet end of the tube is part of the circular
 segment 44 and has a circular cross section (FIG. 2) the sleeve 84 has a
 simple circular cross section and the fitting 38 is an inexpensive
 machined part. The fitting is welded to the end of the tube 22 and the
 resulting weld bead 88 holds the fitting 38 securely in place and provides
 a gas tight seal.
 The brackets 40 and 42 are used to support the manifold assembly 20 in a
 range. As seen in FIGS. 1 and 11, bracket 40 is a stamped and formed sheet
 metal part having a tube receiving section 90 shaped to received the
 non-circular cross section of the non-circular segment 46 of the tube 22.
 An integral strap portion 92 partly severed from the main body is
 initially formed into the position seen in broken lines in FIG. 11. When
 the section 90 is in place on the tube 22, the strap portion 92 is moved
 to the position seen in full lines in FIG. 11 and is attached to a base
 portion 94 of the bracket. Although various fastening methods could be
 used, it is preferred that the strap 92 and base 94 are joined by a
 TOX.RTM. formed connection 95 made with "rivetless rivet" apparatus
 available from TOX.RTM. Pressotechnik L.L.C., 730 Racquet Club Drive,
 Addison, Ill. 60101. Capturing the non-circular section 46 of the tube 22
 between the section 90 and strap 92 firmly anchors the bracket 40 in
 place. The bracket 40 includes a leg portion 96 and a mounting flange
 portion 98 positioned to be connected to a mounting point in a range in
 which the manifold assembly 20 is to be supported.
 As seen in FIGS. 1 and 12, bracket 42 is also a stamped and formed sheet
 metal part having a tube receiving section 100 shaped to received the
 circular cross section of the circular segment 44 of the tube 22. An
 integral strap portion 102 partly severed from the main body is initially
 formed into the position seen in broken lines in FIG. 12. When the section
 100 is in place on the tube 22, the strap portion 102 is moved to the
 position seen in full lines in FIG. 12 and is attached to a base portion
 104 of the bracket. Although various fastening methods could be used, it
 is preferred that the strap 102 and base 104 are joined by a TOX.RTM.
 formed connection 106 made with "rivetless rivet" apparatus available from
 TOX.RTM. Pressotechnik L.L.C., 730 Racquet Club Drive, Addison, Ill.
 60101. Capturing the tube 22 between the section 100 and strap 102 firmly
 anchors the bracket 42 in place. The bracket 42 includes an extending
 mounting leg portion 108 positioned to be connected to a mounting point in
 a range in which the manifold assembly 20 is to be supported. A pair of
 gussets 110 provide strength at the intersection of the base portion 104
 and the tube receiving section 100.
 FIGS. 13 and 14 illustrate an alternative mounting bracket 112 that can be
 used to support the inlet section of the manifold tube 22. The bracket 112
 includes a tube receiving section 114 having a semi-circular shape that
 receives the circular cross section of the circular segment 44 of the tube
 22. The semi-circular tube receiving section 114 is placed over the inlet
 end of the tube 22 abutting against the flange 86 of the inlet fitting 38
 before the inlet fitting is welded in place. When the fitting 38 is welded
 into place, the weld bead 88 performs an additional function of attaching
 the semi-circular section 114 of the mounting bracket 112 to the tube 22.
 The bracket 112 includes an extending mounting leg 116 positioned to be
 connected to a mounting point in a range in which the manifold assembly 20
 is to be supported.
 FIG. 15 illustrates the mounting of a burner valve 28 to the manifold tube
 22. The burner valve 28 has a valve body 118 with a mounting stem 120
 extending through the opening 70 in the flat tube wall 60. The outer shape
 of the stem 120 is square and matches the square shape of the opening 70
 to provide a keyed, anti-rotational fit. A screw 122 is received through
 the opening 72 in the wall 62 and threads into the stem 120.
 The distance between a shoulder 124 on the body 118 and the tip of the stem
 120 is equal to or very slightly smaller than the distance between the
 upper surfaces of the walls 60 and 62. When the screw 122 is tightened, a
 cap 126 of the screw bottoms out against the tube wall, capturing the wall
 62 between the cap 126 and the stem 120 and the shoulder 124 bottoms out
 against the upper surface of the wall 60. These contact regions provide
 metal-to-metal contact as the screw 122 is threaded into the stem 120 and
 reaches its fully tightened position. At this point, an abrupt increase of
 tightening torque is encountered and is easily detected as an indication
 of full tightening of the screw 122. The rigid metal-to-metal contact
 between the screw cap 126 and the tip of the stem 120 through the wall 60
 prevents over tightening which could otherwise deform the tube 22 by
 moving the walls 60 and 62 toward one another.
 A pair of seals 128 and 130 are captured in recesses in the shoulder 124
 and cap 126 respectively. The seals are compressed and captured when screw
 122 is tightened to prevent leakage of gas from the manifold assembly.
 Capturing of the seals 128 and 130 prevents creep of the seal material due
 to temperature and/or pressure. Gas is admitted to the burner valve 28
 through a radial passage 132 in the stem 120 and a passage 134 extending
 upward into the valve body 118. As seen in FIG. 1, each burner valve 28
 includes a fitting 136 for connection to a conduit supplying gas to a top
 burner and an operating stem 138 intended to be rotated by a knob (not
 shown) for turning an internal valve member and controlling the admission
 of gas from the passage 134 to the fitting 136.
 FIG. 16 illustrates the attachment of the thermostat oven control valve 30
 to the non-circular segment 46 of the manifold tube 22. The control valve
 30 includes a valve body 140 having a flat face 142 overlying the top
 surface of the flat tubing wall portion 60. A pair of screws 144 extend
 through the aligned openings 72 in the walls 62 and 60 and are threaded
 into the valve body 140. Shoulders 146 on shank portions 148 of the
 fasteners 144 engage with metal-to-metal contact against seats 150 on the
 face 142 when the fasteners 144 are fully tightened. Seals 152 are
 captured in cavities under cap flanges 154 of the fasteners 144, and
 another seal gasket 156 is sandwiched between the flat face 142 and the
 tubing flat wall portion 60. Gas is admitted to the control valve 30
 through the opening 74 and a passage 158 in the valve body 140. As seen in
 FIG. 1, the oven control valve includes an outlet fitting 160 for
 supplying gas to a conduit extending to a range oven burner. An oven pilot
 burner is supplied with gas through a pilot fitting 162. A conduit 164
 extends to a temperature sensor located in the range oven for returning a
 temperature feedback signal to the control valve 30. An operating stem 166
 can be rotated by a knob (not shown) to operate an internal assembly to
 admit gas to the outlet fitting 160 and to control the gas flow to
 maintain a selected oven temperature.
 The distance between the shoulders 146 and the cap flanges 154 of the
 screws 144 is equal to or very slightly smaller than the distance between
 the outer surfaces of the walls 60 and 62 minus the compressed thickness
 of the gasket 156. When the screws 144 are tightened, the metal-to-metal
 contact between the shoulders 146 and seats 150 results in an abrupt
 increase in torque that is easily detected and provides an indication of
 completion of the assembly. The rigid metal to metal contact prevents over
 tightening which could otherwise deform the tube 22 by moving the walls 60
 and 62 toward one another or which could otherwise result in over
 compression of the seal gasket 156.
 While the present invention has been described with reference to the
 details of the embodiments of the invention shown in the drawing, these
 details are not intended to limit the scope of the invention as claimed in
 the appended claims.