Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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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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
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; 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
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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
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~ , forming a rigid device supporting'member and assembling ~ ~
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~ 20 the member to the chamber device with the tubular portion
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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
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engaging the member and clamping the member,between the
' convolution and the dèvice wall
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Other features and advantages of the invention
will become apparent from the following detailed,description - '
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, 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
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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
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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
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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
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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
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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
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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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