Rotary joint with axial compensation

A rotary joint for introducing or removing a heat exchanging medium, such as steam, from a rotary dryer drum characterized by its ability to accommodate significant axial expansion or contraction with respect to the axis of drum rotation. A rod supported housing includes an axially displaceable nipple having an end engaging an annular seal ring associated with a drum journal mounted wear plate. Axial movement between the wear plate and joint housing is accommodated by relative movement between the housing and nipple, and preferably, springs axially bias the nipple into engagement with a self-aligning seal ring to maintain a fluid tight connection under all thermal and pressure conditions.

BACKGROUND OF THE INVENTION 
Rotary heat exchanging drums are widely used in the paper, fabric and web 
making industries. A plurality of heat exchanging drums sequentially 
contact the web engaging the drum's periphery to transfer heat between the 
drum and web. In many instances, steam is introduced into the drums 
through a rotary joint and condenses upon the drum shell inner wall and 
the condensate is removed through the same or another rotary joint. In 
some web forming operations cool water may be introduced into the drum to 
cool the web being processed. 
A heat exchanging drum will be subjected to a wide range of temperatures. 
During start up the drum may be cold, i.e. at room temperature. 
Pressurized steam is introduced into the drum through the rotary joint, 
and it is important that the seals of the rotary joint be effective under 
all temperature conditions to provide a fluid tight seal regardless of the 
temperature of the joint or drum. Due to the thermal expansion and 
contraction of the drum, which may be significant, the axial dimension of 
the drum, and its associated supporting shafts and journals, will 
significantly vary under the different temperatures to which the drum is 
exposed. As the rotary joint is mounted at the end of the drum journal the 
axial dimensional variation of the drum journal often negatively affects 
the effectiveness of the rotary joint seals as the joint seals often 
utilize axial forces and pressures to produce sealing. Hence, under "cold" 
conditions the rotary joint seal surfaces may not be as effective as under 
"hot" operating conditions unless thermal compensating constructions are 
utilized, and under hot operating conditions axial expansion may produce 
excessive seal pressures. 
While it is known to design rotary joints for drum type heat exchangers 
having thermal seal compensating features, known thermal compensating 
designs are relatively limited in the degree of axial compensation that 
may be accommodated, and a need exists for a rotary joint capable of 
effectively functioning under a wide range of thermal conditions. 
It is an object of the invention to provide a rotary joint for use with 
rotary drum type heat exchangers which is capable of accommodating large 
axial dimensional variations due to thermal expansion and contraction. 
Another object of the invention is to provide a rotary joint for rotary 
heat exchangers wherein a combination of axial and radial seals are 
utilized to provide effective fluid tight sealing under a wide range of 
temperatures. 
An additional object of the invention is to provide a rotary joint capable 
of accommodating significant axial dimensional variations which is 
self-aligning with respect to the heat exchanger drum axis of rotation and 
is capable of maintaining a fluid tight connection even though 
eccentricities exist between the axes of the rotating heat exchanging drum 
and the rotary joint housing. 
Yet another object of the invention is to provide a rotary joint capable of 
effectively operating under a wide range of thermal conditions and the 
joint sealing structure remains effective throughout the operating range 
of the joint. 
In the practice of the invention a mounting flange is concentrically 
mounted upon the end of the journal of a rotating heat exchanger drum or 
the like. A wear plate is, in turn, mounted upon the flange, and the wear 
plate includes a seal surface concentric with the central passage which 
extends through the wear plate and the mounting flange. 
The rotary joint housing is supported upon rods in a conventional manner, 
and the housing includes a cylindrical chamber substantially coaxially 
related to the axis of drum rotation. A generally cylindrical nipple is 
axially displaceable within the housing chamber and an end cap mounted 
upon an end of the housing includes seals which interconnect the housing 
and nipple in a fluid tight manner, yet permit the nipple to be axially 
displaced with respect to the housing and chamber. 
The exterior end of the nipple abuts against an annular seal ring which 
engages the wear plate seal surface, and keying means interposed between 
the housing end cap and nipple cause the nipple to be rotatably fixed with 
respect to the housing. 
In the disclosed embodiment a single fitting is mounted upon the housing in 
communication with the chamber to permit a heat exchanging medium to be 
introduced into the chamber, or removed therefrom, and the axially 
moveable relationship between the housing and nipple permits extensive 
axial displacement between the nipple and housing to occur without 
adversely affecting the efficiency of the rotary joint seals. 
Preferably, a plurality of compression springs interposed between the 
housing and nipple bias the nipple toward the wear plate and seal ring to 
insure engagement between the nipple, seal ring and wear plate under all 
conditions. 
The components of a rotary joint in accord with the invention are 
relatively simple in configuration permitting economical construction and 
assembly, and a rotary joint constructed in accord with the inventive 
concepts may be installed by those having average skill in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A rotary joint in accord with the invention is generally indicated at 10, 
and the joint 10 is associated with the end of a rotary drum journal 12. 
The journal 12 constitutes a shaft supporting a heat exchanging drum such 
as commonly used in paper mills, not shown, and the journal includes a 
radial flat end face 14 which is countersunk at 16 concentric to the 
journal axis of rotation. 
A flange 18 is of a generally flat configuration and includes a cylindrical 
axial extension 20 which is received within the journal countersink 16. 
Five bolt recesses and holes 22 are circumferentially spaced about the 
axis of the flange 18 and bolts 24 received within holes 22 firmly mount 
the flange 18 upon the end of the journal 12 in a concentric manner by 
means of the journal threaded holes 26 receiving the bolts 24. 
The flange 18 includes a central bore 28 coaxially aligned and 
communicating with the drum journal bore 30, FIG. 1. Also, the flange 18 
includes an outer radial face 32 which is concentrically countersunk at 
34. 
A wear plate 36 is mounted against the flange face 32 and includes a 
coaxial bore 38 communicating with bores 28 and 30, and the wear plate 
includes a cylindrical extension 40 closely received within the flange 
countersink 34. A plurality of countersunk bolt holes 42 are defined in 
the wear plate for receiving the bolts 44 which are threadedly received 
within threaded holes 45 formed in the flange 18, and in this manner the 
wear plate 36 is firmly connected to the flange 18 in a concentric manner. 
The wear plate 36 includes a seal surface 46 concentric to the bore 38, and 
adjacent thereto. The seal surface 46 constitutes a concave spherical 
segment surface for cooperation with a complementary seal ring surface as 
later described. 
The wear plate also includes an annular axially extending skirt 48 which 
defines an annular recess 50. 
The rotary joint housing is indicated at 52 and is of a generally 
cylindrical configuration having an internal cylindrical bore 54, a radial 
flat outer end 56 and a radial flat inner end 58. The bore 54, 
intermediate the housing ends, defines a cylindrical chamber 60. 
The housing 52 includes radially extending yokes 62 having axial holes 64 
defined adjacent the yoke ends for slidably receiving the support rods 66. 
At their outer ends, the rods 66 are threaded for receiving the adjustable 
mounting nuts 68 and spacer 70, and the rods 66, at their inner ends, are 
supported upon brackets 72, FIG. 4, fixed upon stationary support 
structure located adjacent the drum journal. The rods 66, in association 
with the yokes 62, is of the conventional type often employed with rotary 
joints for drum type heat exchangers. 
An annular end cap 74 is mounted upon the inner housing end 58 by a 
plurality of bolts 76 threaded into the housing. The end cap includes a 
cylindrical bore 78 and grooves defined in the end cap receive the 
elastomer 0-rings 80 for establishing a sealed relationship with the 
nipple received within the end cap, as later described. 
A plurality of axially extending threaded holes 82 are defined in the end 
cap and each receives a smooth walled cylindrical pin 84 which extends in 
an axial direction toward the wear plate 36. 
A generally cylindrical nipple 86 is slidably received within the housing 
52 and housing chamber 60. The nipple 86 includes an internal bore 88 
extending therethrough, and the nipple exterior cylindrical surface 90 is 
closely received within the end cap bore 78 in an axially slidable manner. 
The seal rings 80 engage the nipple surface 90 in a fluid tight sealed 
manner. 
The exterior end of the nipple 86 constitutes a flat radial face 92, and a 
radially extending shoulder 94 is defined upon the nipple of a diameter as 
to be readily received within the wear plate recess 50 as will be apparent 
from FIGS. 1 and 2. 
The nipple shoulder 94 is provided with a plurality of smooth axial holes 
96 for slidably receiving the pins 84, and each of the pins 84 is 
circumscribed by a compression spring 98 which is interposed between the 
end cap 74 and the nipple shoulder 94 biasing the nipple 86 toward the 
wear plate 36. 
An annular seal ring 100 is interposed between the wear plate 36 and the 
nipple end 92. Preferably, the seal ring 100 is formed of a long wearing 
sealing material such as antimony, and the seal ring includes a 
cylindrical bore 102 coaxially aligned with the bores 28, 30, 38 and 88. 
The seal ring face 104 is of a convex spherical segment configuration 
complementary to the wear plate surface 46, and the seal ring face 106 is 
flat and radial for accomplishing a fluid tight sealed relationship with 
the nipple 86. 
The fluid medium passing through the joint 10 communicates with the housing 
chamber 60 by means of the fitting 108 attached to the housing end 56. The 
fitting 108 includes a bore 110 communicating with the conduit connection 
112 which may be in the form of a soldered connection, or may consist of 
threads for receiving a pipe, or may merely constitute a countersink 
whereby a conduit flange may be connected thereto, not shown. The fitting 
face 114 is attached to the housing face 56 by bolts 116, and it will be 
appreciated that the open end 56 of the housing 52 constitutes a port for 
the housing which communicates with the fitting 108 which, in effect, 
closes the end of the housing chamber 60. 
In use, the rotary joint apparatus will be assembled as described above, 
and as illustrated in the drawings. The housing 52 will be axially 
adjusted relative to the end of the drum journal, and the flange 18, by 
means of the support rods 66 and the nuts 68. The adjustment will be 
generally similar to that shown in FIG. 1 wherein the nipple 86 will be 
partially received within the housing chamber 60, the springs 98 will be 
biasing the nipple end 92 into engagement with the seal ring face 106 and 
maintain the seal ring face 104 in a sealing relationship with the wear 
plate seal surface 46. The relationship shown in FIG. 1 may be considered 
a "cold" condition, and the introduction of a heat exchanging medium into 
housing 52 through fitting 108 will cause the pressurized medium to enter 
the nipple bore 88 and pass through the seal ring, wear plate, flange and 
drum journal bores into the heat exchanger drum, not shown. Of course, the 
rotary joint of the invention may also be received to remove condensate 
from the heat exchanger drum, and under such conditions the operation of 
the joint is identical as when functioning as a steam supply joint, for 
instance. 
As the heat exchanger drum heats, and axially expands, the drum journal end 
14 will move to the left, FIG. 2, axially displacing the flange 18, wear 
plate 36, seal ring 100 and nipple 86. This expansion retracts the nipple 
86 into the housing chamber 60 as illustrated in FIG. 2, compressing the 
springs 98, and the ends of the pins 84 will remain enclosed within the 
wear plate recess 50. 
It will be appreciated that the above described rotary joint structure 
permits significant axial displacement between the drum journal and the 
rotary joint housing 52 without adversely affecting the fluid tight sealed 
relationship therebetween. The relative rotation between the rotary joint 
and the drum journal occurs at seal ring 100, and the fact that surfaces 
46 and 104 are of a spherical segment configuration permits the seal ring 
to be self-aligning with respect to any eccentricities that may exist 
between the journal axis of rotation and the axis of the rotary joint. 
This self-aligning feature of the seal ring 100 is effective at all 
relative axial positions between the nipple 86 and the housing 52. 
The use of the springs 98 assures that the nipple will always be engaging 
the seal ring 100. However, it is to be appreciated that, under most 
conditions, an internal pressure exists within the housing chamber 60 
which will tend to bias the nipple toward the seal ring 100, and the 
primary purpose of the springs 98 is to assure a fluid tight relationship 
between the nipple, seal ring and wear plate under cold or low pressure 
conditions. 
It is appreciated that various modifications to the inventive concepts may 
be apparent to those skilled in the art without departing from the spirit 
and scope of the invention.