CA1122081A - Bellows assembly and method of making the same - Google Patents

Abstract

BELLOWS ASSEMBLY AND METHOD OF MAKING THE SAME

Abstract A bellows assembly and method of making the assembly are disclosed. The assembly comprises a bellows head including thin walled flexible members which are joined to define an ex-pansible chamber. An anchor fitting attaches and communicates the bellows head to a capillary tube and an expansible fluid occupies the tube and chamber. A base supports the bellows head and capillary tube with the anchor fitting interconnecting the bellows head, tube and base. The anchor fitting is bonded to the diaphragm member and capillary tube and deformably engages the base plate to clamp the base plate to the bellows head.

Description

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The present invention relates to fluid operated ac-tuators and more particularly relates to expansible chamber bellows assemblies.
Thermostatic and pressure controls have employed thin walled metal bellows for operating actuated devices such as control switches, valves and the like. The bellows are typ-ically filled with a fluid and arle flexed in accordance with differential pressure forces acting on the bellows walls. One typical use of such bellows is in thermally responsive controls wherein the expansible chamber defined by the bellows communi-cates with a closed capillary tube and a vaporizable liquid is contained by the tube and bellows. An increase in temperature ~` at a location along the length of the capillary tube causes an increase in vapor pressure and the bellows chamber expands while a reduction in temperature at a location along the length of the capillary tube permits contraction of the bellows volume.
Expansion and contraction of the bellows actuates a switch or valve directly or through a suitable motion transmitting linkag~.
; In order for such controls to respond accurately and consistently to sensed pressure or temperature changes the bel-lows assembly must positively engage and remain accurately pos-itioned with respect to the actuated device. Accordingly, bel-lows heads have conventionally included structurally strong, rigid fittings for both anchoring the bellows head in place with~
respect to the associated control and for transmitting force from the bellows head to the switch, valve, or motion transmitt-ing linkage. At the same time the bellows chamber must be con-structed from easily flexible components in order for the control to be adequately sensitive to pressure or temperature changes.

One successful prior art bellows head included a pair of flexible sheet metal diaphragms hermetically brazed together 1. .~

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.~ ' at their outer peripheries, each having a central opening in which respective force transmitting and anchoring fittings ~ere mounted. The fi~tings were attached to the respective diaphragm members b~ brazed joints. The anchor fitting was constructed to be secured to a rigid base plate by a staking operation.
The base plate was in ~urn rigidly attached to the control hous-ing.
The fittings were machined from rod-stock (frequently brass) and the bxazing operation was usually accomplished by fixturing all of the components of the bellows head together and passing them through a brazing furnace, or the like, in order to bond the assembly components together.
The production costs of these bellows heads were relatively high for a number of reasons in addition to those attributable to costs of materials. The number of brazed joints - between components of the assemblies was relatively great whlch tended to increase the chances for "leaky" malfunctioning bellows ;~ being produced Because the anchor fitting had to be seated in an opening in the associated diaphragm member the diaphragm -members of each bellows had to be separatel~ stocked and handled during production. Because the diaphragm members were ~ormed from thin sheets of metal, any operation Which would tend to ~
- alter the stress conditions o~ the diaphragm material would also tend to change the diapXragm spring rate and thereby alter the . , .
response of the diaphragm~to sensed temperature or pressure changes. The stamping operation for producing the diaphragm member openings was such an operation.
The present invention provides a new and improved bellows assembly and method of making the same wherein the bel-lows assembly construction is substantially simplified and thecost of its manufacture reduced appreciably compared to the prior .
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~1~2C~81 According to the present invention there is provided a bellows assembly having a bellows head including a thln walled flexible member defining at least part of an expansible chamber and having an aperture therein, a tube communicating with the chamher via the aperture, a rigid base member supporting the bello~ls head and extending along the flexible member, the base member defining an opening aligned with the aperture, and a fitting interconn~ecting the flexible member, the tube and the base mem~er. The fitting includes a thin walled tubular body surrounding the tube and extending through the base member opening, a flange disposed between the base member and the flexible member, ~` the flange being bonded to the flexible member about the aperture so that the aperture is aligned with the tubular body, an outwardly upset fitting body portion engaged with the base member to clamp the base member and the bellows unit together, and bonding means for securing the tube in the body member.
In a specific embodiment of the invention, the `
fitting flange is resistance welded to its associated `- bellows diaphragm so that the confronting bellows diaphragm and fitting flange have a weld joint extending continuously~
about the fitting hody opening.` With the diaphragm member ;~
so attached to the anahor itting the portion of the diaphragm extending across the fitting opening is supported and isolated from stress patterns in the remainder of the diaphragm member, and vice versa. Accordingly a :~:
; simple piercing tool can be thrust through the diaphragm ;~ 30 member into the tubular itting body section without any danger of bending or excessive tearing of the diaphra~m member radially beyond the weld joint. Moreover the .. :
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piercin~ can be acco~plished without materially changing the stress conditions of the diaphragm ~ortion radially outwardly from the flanae, i.e. the "spring rate" of the diaphra~m is unaffected.
This feature of the invention permits use of identical diaphràgm memhers adjacent the base plate and at the extension side of the bel:Lows head by eliminating the need for producing the bellows chamber opening hy a stamping operation as well as eliminating tooling associated with the stamping operation. Any necessity for separately producinq, handling and stocking bellows diaphragm members which differ from each other only by virtue of having a ~ - stamped bellows chamber opening is also precluded.
;, According to another aspect of the present ~ invention there is provided a method of making a bellows .~
assembly which includes the steps of forming a flexible wall expansible chamber device having a relatively rigid tubular portion projecting from a wall thereof, and , . ~ :
~ , forming a rigid device supporting'member and assembling ~ ~
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~ 20 the member to the chamber device with the tubular portion :- :
projecting freely, through'an opening in the supporting member. ~The tubular portion is deformed to yieldably `~; bulge the portion wall outward beyond at least part of ~' the supporting member,opening, and the bulged wall portion is collapsed to define an ~outwardiy extending convolution ~ ~ .
engaging the member and clamping the member,between the ' convolution and the dèvice wall ~ ~ .
Other features and advantages of the invention will become apparent from the following detailed,description - ' .
, 30 of a preferred embodiment made with reference to'the accompanying drawings.
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FIGURE 1 is a schematic view of a control unit embodying the present invention with parts shown in cross~section, FIGURE 2 iS a flow chart showing manu~acturing steps undertaken in producing bellows assemblies forming part of the control unit of FIGURE l;
FIGURE 3 iS a cross sectional vie~ illustrating the diaphragm assembly at one stage of manufacture;
FIGURE 4 iS a cross sectional view illustrating another stage in the bellows assembly formation;
: FIGURE 5 iS a view seen approximately from the plane indicated by the line 5-5 of FIGURE ~;
FIGURE 6 is a cross sectional view of a bellows hea~ subassembly during a welding operation;
FIGURES 7-10 are fragmentary cross sectional views.
of stages in the assembIy of the bellows head to a ~ -supporting base; and - : ~

~ .o _ ~ . - 4a -Bl FIGURE 11 is a view seen approximately from the plane indicated by the line 11-11 of FIGURE 9.
FIGURE 1 of the drawings schematically illustrates a control unit 10 embodying the present invention c~nnected for controlling operation of a suitable control device 11 in response to sensed temperature. The control unit 10 comprises a control housing, or frame, 12 which rigidly supports a control switch 13 and bellows assembly 14, the latter being e~fective to operate the control switch via an actuating linkage 15 (schematically illustrated). The controlled device can be formed by any suit-able electrically operated component and for the purpose of this description may be considered to be an electric motor for driving a refrigerant compressor drive motor which is energized by the control unit 10 in response to a given sensed temperature level and de-energized in response to the control unit sensing a pre-determined lower temperature.
The bellows assembly 14 is formed by a bellows head 16, a capillary tube 18 (attached to and communicating with the bellows head), and a supporting base member 20 supporting the bellows head and capillary tube and rigidly supported by the control unit housing 12. The bellows head 16 is preferably a capsule type bellows which expands in response to increases in sensed temperature along the length of the capillary tube and contracts when the temperature along the capillary tube is re duced. Expansion and contraction of the bellows head actuates the control switch 13 via the linkage 15 to control energization of the device 11. The locations of the control switch and bel-lows assembly relative to the control housing 12 are accurately established and maintained and together with the geometry o~
the linkage 15 govern the temperature levels at which the device 11 is energized and de-energized.

The bellows head 16 is formed by thin resilient sheet metal diaphragm members 24, 26, an extension point fitting 28 5.

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carried by the diaphragm member 24 for engagement with the actuat-ing linkage 15, and an anchor fitting 30 for attaching the dia-phragm member 26 to the base member 20 and the capillary tube 18. The diaphragm members 24, 26 are substantially the same, each being formed by a circular body having a central generally circular, planar section 34, a series of circumferential cor-rugations extending about the central body section 34 and a outwardly extending peripheral flange 38. The diaphragm flanges 38 are bonded together by a weld bead 40 which extends contin-uously about the members to establish a hermetic chamber 42within the bellows head. The chamber 42 is communicable with the capillary tube 18 via a central opening 44 which is formed in the diaphragm member 26. In the preferred embodiment the - diaphragm members are formed from stainless steel sheet material which is only a few thousandths of an inch thick.
The capillary 18 is a relatively thin walled copper alloy tube having an open end section 50 received by the anchor fitting, a remote hermetically closed end 52 and a body section 54 which is illustrated in broken lines as forming a helix.
The chamber 42 and capillary tube 18 contain a vaporizable fluid o~ any suitable or conventional type which causes expansion of the bellows head in response to sensed temperature increases along the extent of the capillary and contraction of the bellows head when tempera~ures along the capillary are reduced.
The extension point fitting 28 is formed from a drawn cup-like sheet steel member which is inverted on the diaphragm member 24 and has a planar end surace 28a engaging the linkage 15 and a circumferential flange 28b by which the extension point fitting is bonded to the diaphragm member central section 34.
In the preferred and illustrated embodiment of the invention the diaphragm member 24 and extension point fitting 28 are con-nected by a resistance welded joint and the diaphragm member central section 34 is imperforate.
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The anchor fitting 30 is formed by an open ended drawn sheet steel member which defines a thin walled tubular body 45 extending from the diaphragm membler 26 through the supporting base 20 and a circumferential gen~erally planar flange 46 by which the anchor fitting 30 is attached to the diaphragm member central section. The anchor fitting 30 defines a through opening 47 communicating with the central diaphgram opening 44, an outwardly bulged crimp 48 in the body 45 for rigidly clamping the support-ing base member and bellows head together, and a flared end section 49 through which the capillary tube is received.
The base member 20 is formed by a stamped structurally strong sheet metal plate defining a central generally circular land 60 supporting the bellows head 16 and a mounting opening 62 through which the anchor fitting 30 extends. In the preferred embodiment the mounting opening 62 is non-circular, or polygonal, and defines relieved sections 64 which coact with the anchor fitting body to effectiveIy key the anchor fitting to the base member and prevent rotation of the bellows head relative to the linkage 15 and the control body.
FIGURE 2 shows, in abrievated schematic form, a pro-cedure by which the bellows assembly 14 is fabricated. The A bellows head is assembled in a series of operations followed by assembly of the bellows head 16, capillary tube 18 and the ; supporting base 20.
The bellows head 16 is assembled by welding the dia- ~ -phragm members to the respective extension point and anchor fittings and then to each other. After the extension point and anchor fittings are initially drawn they are copper plated and fed to nests which receive and support the respective fittings and diaphragm members during their joining. Referring to FIGURE

3 a nest 70 (illustrated in part) supports an anchor fitting 7.
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30 with its flange 46 oriented upwardly and its body 45 extending downwardly through a centering opening in the nest. A diaphragm member 26 is disposed in the nest over the fitting 30 with the nest 70 engaging the diaphragm about its periphery to center it with respect to the fitting.
The fitting and diaphragm are resistance welded to-gether in the nest 70 at a welding station illustrated schemat-ically by FIGURE 3. The flange 46 is formed with a narrow con-tinuous circumferentially extending bead 46a contacting the diaphragm 26~ A resistance welding power supply 72 is connected across the fitting 30 and diaphragm 26n When welding current flows through the juncture of the bead 46a and the diaphragm the fitting and diaphragm materials are rapidly fused together :~ , continuously about the flange 46 so that the anchor fitting and `~ diaphragm are hermetically joined.
The resistance welding equipment is schematically -~ illustrated and may be of any suitable type. The welding equip-ment is preferably constructed so that one welding electrode is reciprocally movable into welding position (as illustrated) when the nest 70 is moved to the welding station. After the weld~
is formed the electrode is withdrawn to enable the nest to move to another work station.
Assembly of the extension point fitting 28 to the diaphragm 24 is accomplished substantially the same as described in reference to FIGURE 3 and therefore is not further illustrated or described.
When the diaphragm 26 and anchor fitting 30 are joined, the nest 70 is advanced to a piercing station where the aperture 44 is formed. Referring to FIGURE 4 the nest 70 is located in the piercing station so that a piercing tool 80 is aligned with the anchor fitting through the opening 47. The preferred pierc-ing tool 80 is a cylindrical rod having a circularly tapered - . .

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end forming a sharp point. The ~ool 80 is advanced into the diaphragm central section where it easily pierces the diaphragm material. When the tool 30 is withdrawn a pentagonal aperture remains in the diaphragm (See FIGJRE 5).
Because the diaphragm is welded to the anchor fitting about the flange 46 the piercing operation does not affect the stress in the diaphragm radially beyond the anchor fitting flange 46. Accordingly the formation of the aperture 44 in the dia-phragm member 26 does not alter the spring rate of the diaphragm.
Moreover the polygonal shape of the aperture 44 serves to prevent the capillary tube end 50 from extending into the chamber ~.
The bellows head assembly is completed by hermetically joining the diaphragm members along their peripheral flanges 38. Referring now to FIGURE 6 the welded diaphragms and fittings are separately transported to a laser beam welding apparatus where they are situated in mating nests 82, 84 and welded to-gether by use of a laser 86. The nest are constructed from a metal whi~h is an efficient heat conductor have circumferential projecting rims between which the diaphragm flanges 38 are clamp-ed and are rotatable. The nests are rotatably driven by a suit-able drive mechanism to rotate the engaged diaphragms relative to the laser beam. The engaged flanges 38 are thus moved through the laser beam which melts and fuses the diaphragm flanges.
The heat conductive nest material carries heat away from the weld joint to chill it. After slightly more than 360 degrees of rotation the laser beam is discontinued and the welded bellows head is removed from the nests 82, 84.
The assembled bellows head is then attached to the supporting base member 20. -n accordance with the present in-vention and as illustrated by FIGURES 7 and 8 the bellows head ,' Z~38~L

assembly is placed in a supporting nest 90 (only a part of which is shown) with the anchor fitting body 45 extending upwardly.
The base member is disposed on the bellows head assembly with the anchor fitting body extending loosely through the base member mounting opening 62. The nest 90 is moved to a work station illustrated in FIGURES 7 and 8 at which the anchor body is upset by a forming tool 92 to clamp the base member and bellows assembly together. The tool 92 defines a cylindrical cavity 94 conforming to the cylindrical shape of the undeformed fitting body 45.
- 10 The cavity 94 defines an internal end face 94a which engages the projecting end of the fitting body as the tool advances and an external annular end face 96 surrounding the cavity 94 for crimping the fitting body against the base member.
As the tool 92 advances, the projecting end of the anchor fitting body is closely surrounded and supported by the tool cavity wall 94. When the end face 94a engages the project-ing end of the anchor fitting body the anchor fitting bod~ sec-- tion between the tool 92 and the base member bulges outwardly as illustrated by the broken lines in FIGURE 7. The outwardly ~- 20 bulging body section expands into the supporting base opening 62. Part of the bulged section expands into the relieved opening sections 64 so that the support base and bellows head assembly : are fixed against relative rotation by the key-like interengage-: ment between anchor fitting and supporting base.
'~ ~s the tool 92 continues to advance toward the support base its external end face 96 engages the bulged section of the anchor fitting body and crimps the bulged section against the support base (See FIGURE 8). The compressive force exerted by the tool 92 on the bellows head assembly assures that the central sections of the bellows diaphragms are engaged with each other due to flexure of the diaphragm members and therefore that the 10 .

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anchor fitting flange 46 is urged against the support base.
Thus, when the bulged section of the body 15 is crimped, as illustrated by FIGURE ~, the support base is tightly clamped between the crimped fitting body section and the flange 46.
The clamping between the fitting body and the base member fixes the spatial relationship between these components so that when the base is fixed to the control body the control will be readily calibrated and operate reliably.
The bellows assembly undergoes additional forming operations preparatory to the capillary tube being attached.
The nest 90 is moved to a work station at which the anchor fitting body projecting end is necked down to produce an inside diameter just slightly greater than the capillary tube diameter (See ` FIGURE 9). This operation is accomplished with a suitably tool lO0 which is forced onto the fitting body to deform it and then - retracted.
At a succeeding work station the projecting tip end ~ of the fitting body is flared radially outwardly~by a male tool 102 which is thrust into the fitting body.
The capillary tubing is then inserted into the anchor fitting body and a suitable brazing material is placed in the flared fitting body end. The capillary tube end 50 engages the diaphragm member 26 preventing the tube end from entering the chamber 42.
The capillary tube brazing material and anchor fitting are subjected to a source of high temperature flame, or a high temperature furnace atmosphere, which melts the brazing material to hermetically bond the capillary tube to the anchor fitting.
The temperature responsive fluid is then introduced into the capillary tube and chamber 42 after which the capillary tube end 52 is sealed closed.

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As indicated previously, the bellows assembly is fixed to the control unit housing 12 so that the bellows head support location is rigidly fixed. The supporting base is generally fixed to the housing by a staking operation after which the control is calibrated.
While only a single embodiment of the invention is illustrated and described in detail the present invention is not to be considered limited to the precise construction and methods of construction disclosed. Various modifications, adaptations and uses of the invention will become apparent to those skilled in the fields to which the invention relates and the intention is to cover all such modifications, adaptations and uses which come within the scope or spirit of the attached c1aims.

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Claims (9)

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A bellows assembly comprising:
(a) a bellows head including a thin walled flexible member defining at least part of an expansible chamber and having an aperture therein;
(b) a tube communicating with the chamber via said aperture;
(c) a rigid base member supporting said bellows head and extending along said flexible member, said base member de-fining an opening aligned with said aperture; and (d) a fitting interconnecting said flexible member, tube and base member comprising:
(i) a thin walled tubular body surrounding said tube and extending through said base member opening:
(ii) a flange disposed between said base member and said flexible member, said flange bonded to said flexible member about said aperture so that said ap-erture is aligned with said tubular body;
(iii) an outwardly upset fitting body portion engaged with said base member to clamp said base member and said bellows unit together; and (e) bonding means for securing said tube in said body member.

2. The bellows assembly claimed in claim 1 wherein the aperture in said base member is of polygonal shape and said fitting body wall is upset to engage at least part of said poly-gonal aperture and lock said bellows assembly against rotation relative to said base member.

3. The bellows assembly claimed in claim 1 wherein said outwardly upset fitting body portion is crimped into en-gagement with said base member.

4. The bellows assembly claimed in claim 3 wherein said fitting flange engages said base member on an opposite side from said crimped body portions.

5. The bellows assembly claimed in claim 1 wherein said flexible member is formed by a thin metal diaphragm, and further including a second diaphragm member, said first and second diaphragm members bonded together along their circumfer-ences.

6. A method of making a bellows assembly comprising:
(a) forming a flexible wall expansible chamber device having a relatively rigid tubular portion projecting from a wall thereof;
(b) forming a rigid device supporting member and assembling the member to the chamber device with the tubular portion projecting freely through an opening in the supporting member;
(c) deforming the tubular portion to yieldably bulge the portion wall outwardly beyond at least part of the supporting member opening; and, (d) collapsing the bulged wall portion to define an outwardly extending convolution engaging the member and clamping the member between the convolution and the device wall.

7. The method claimed in claim 6 wherein forming the flexible wall chamber includes forming a flexible metal diaphragm member, bonding a fitting defining said tubular portion to said diaphragm member and piercing said diaphragm member at a location surrounded by the bond between said fitting and said diaphragm member.

8. The method claimed in claim 6 wherein forming a flexible wall chamber includes forming a fitting defined by a relatively rigid tubular body portion having an outwardly ex-tending relatively rigid flange at one end, forming a flexible diaphragm member and bonding said relatively rigid flange to said diaphragm member at a location spaced from the diaphragm periphery.

9. The method claimed in claim 8 wherein forming said rigid device supporting member includes forming a noncircular opening in said supporting member and deforming said tubular portion includes bulging said wall into tight engagement with said opening to fix said tubular portion against rotation rela-tive to said supporting member.