Sanitary steam injection heater

A skeletonized piston assembly in which a tube forms a piston shank and an enlarged thin disc has a peripheral edge which provides the piston skirt. A guide disc is spaced from the other disc and guides movement of the piston. Quick release fittings and a removable helical flight assembly adapt the heater for sanitary applications and easy clean-out.

BACKGROUND OF THE INVENTION 
The invention relates to a steam injection heater of the type disclosed in 
U.S. Pat. No. 2,455,498 and U.S. Pat. No. 3,984,504. These heaters are 
desirably provided with a steam regulating piston as disclosed in these 
patents. When using the heater to heat slurries with solids with large 
particle sizes, the solids can enter the space between the piston skirt 
and cooperating chamber wall to interfere with smooth operation of the 
piston. The heaters illustrated in the foregoing patents also are not 
specifically designed for sanitary heating applications. The components 
cannot be readily disassembled for cleaning purposes. 
SUMMARY OF THE INVENTION 
The invention provides a steam regulating piston which is less susceptible 
to interference from particles and a sanitary construction. The piston 
employs an annular disc secured at the end of a tube for the operative 
element of the piston, with the peripheral surface of the disc forming the 
piston skirt. The thin skirt with a small axial or longitudinal extend 
minimizes retention of large particles in the space between the piston and 
chamber wall. It also renders the heater particularly appropriate for 
processing food slurries which contain semi-solids. The piston is guided 
for rectilinear movement by a guide disc which is secured to the tube 
remote from the piston disc. The guide disc does not fully occupy the 
cross-section of the steam chamber and this permits pass-through of 
solids. The guide disc prevents tumbling of the piston and does contact 
the chamber wall at one or more points to guide the piston. The piston 
tube also serves as a locator and connector for the coil spring which 
biases the piston to a closed position. 
Other features of the invention which make the heater particularly suitable 
for sanitary heating applications include a separable helical flight 
assembly which contains multiple ribbons which are located proximate the 
inside periphery of the cylindrical casing of the heater. The flight 
assembly interrupts laminar flow of the slurry to insure uniform heating 
as disclosed in the foregoing patents. The ribbons extend in a helical 
path between two washer-shaped discs which serve as connectors to connect 
the individual ribbons or flights. The separable helical flight assembly 
enables easy removal for cleaning. Other clean-out features include easy 
piston removal in which the steam injection tube is provided with a spring 
abutment or stop which is held in place by a pin which can be removed to 
release and remove the piston, spring and spring abutment. The sanitary 
heater is also adapted to use quick clamp fittings or sanitary threaded 
parts to facilitate rapid sanitary clean-out and disassembly. 
Further objects, features and advantages of the invention will become 
apparent from the disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Although the disclosure hereof is detailed and exact to enable those 
skilled in the art to practice the invention, the physical embodiments 
herein disclosed merely exemplify the invention which may be embodied in 
other specific structure. The scope of the invention is defined in the 
claims appended hereto. 
FIG. 1 discloses a steam injection tube 10 which can be of the type 
illustrated in U.S. Pat No. 3,984,504 or U.S. Pat. No. 2,455,498, the 
entire disclosures of which are incorporated herein by reference. The 
steam injector tube 10 is contained in the interior of a larger diameter 
casing or housing such as 12, as illustrated in FIG. 3. The steam 
injection tube 10 has an inlet 11 and foraminous or perforated cylindrical 
wall 13 to allow escape of steam to intermix with the slurry being heated, 
which moves continuously in the annular space between the casing 12 and 
the injection heater tube 10 between the casing inlet 11 and outlet (not 
shown in FIG. 1). 
The steam injection tube includes a skeletonized piston assembly 14 for the 
purposes disclosed in U.S. Pat. No. 2,455,498 which acts to restrict the 
length of the injector tube which is being employed to discharge steam and 
a hence the number of orifices that are involved in steam injection. The 
piston moves as the spring expands or contracts due to increased or 
decreased pressure on the piston. This maintains a pressure differential 
and avoids a pressure equilibrium between the fluids outside the steam 
injector tube and the steam in the tube which can cause alternating surges 
of steam and pressure which can produce shock vibration, hammering and 
noise. 
In accordance with the invention, the piston assembly 14 includes a tubular 
member 16 and an annular disc or head disc 18 located at one end thereof, 
with the disc 18 having a peripheral surface 20 which acts as a piston 
skirt and a planar surface 22 which forms the head surface of the piston. 
An intermediate guide disc 24 functions as an abutment for one end 26 of 
spring 43 and also cooperates with the disc 18 to guide the piston for 
rectilinear travel in the interior 28 of the steam injector tube 10. The 
other end of spring 43 can be restrained by an abutment 27 or cup (not 
shown) held in place by bolts. The disc 24 can have one or more relieved 
portions or non-concentric surfaces such as the corner 30 which permits 
pass-through of solids in the gap 32 between the inner surface of the 
injector tube and the periphery of the disc. Other configurations of the 
guide disc can be employed. The disc 24 desirably occupies less 
cross-sectional area than the disc 18. The pass-through of solids prevents 
interference with free movement of the piston in response to variations in 
steam pressure. The piston tube end 41 serves as a locator and support for 
the end of biasing spring 43 which urges the piston to the FIG. 1 
position. 
The minimal axial extent of the peripheral surface 20 minimizes the 
retention possibilities of solid particles between the piston skirt and 
wall as compared with a full length piston skirt. 
FIG. 3 illustrates a steam injector heater which is particularly adapted 
for sanitary applications because of easy clean-out capabilities and 
includes quick disconnect couplings 40 at each end, sanitary threads at 
42, 44 and 46 for quick disconnect and other clean-out features presently 
described. The casing 12 is shown with the steam tube in an inverted 
position as compared with the steam injector tube in FIG. 1. The heater 
(FIG. 3) can be employed in either vertical position or horizontally. It 
includes a steam injector tube 60 with a steam inlet 62 and a foraminous 
cylindrical wall 64. A foraminous diffusion screen as illustrated in U.S. 
Pat. No. 3,983,504 and designated 50 in the drawings of that patent can be 
employed for the purposes therein described. 
The heater of FIG. 3 also includes a slurry inlet 66 and a heated slurry 
outlet 68. The piston 18 illustrated in FIG. 1 can be employed, or a 
cup-shaped piston as illustrated in the above noted patents could be used. 
However, the piston 18 is particularly suitable for sanitary applications 
which would involve slurries with semi-solids or solids contained therein. 
The steam injector tube 60 is provided with a quickly removable piston 
abutment in the form of a grid 71 held in place by a pin which holds the 
spring under tension against the piston. In the disclosed construction, 
the pin 70 extends through a transverse aperture in the injection tube. 
The pin and grid are easily removed to disassemble the spring and piston. 
FIG. 4 illustrates the helical flight assembly 80 of FIG. 3 which includes 
two end plates 82 and 84 in spaced relationship with a plurality of 
helically arranged ribbon flight 86 which are interconnected by the 
plates. As illustrated, three ribbons are employed. The helical flights 86 
are located in close proximity to the interior surface 88 of the casing 12 
to cause turbulence and intermixing of the slurry being heated to avoid 
localized heating adjacent the injection tube which could cause scaling. 
Turbulent flow as opposed to laminar flow also provides uniform cooking of 
the slurry. The helical flight assembly is easily disassembled from the 
casing for cleaning purposes. 
The heater shown in FIG. 3 can be made of stainless steel parts with 
sanitary fittings. It can be used in the pulp and paper industry, the drug 
and cosmetic industry and generally for semi-solid aqueous products. In 
the food industry it can be used with various food products, including 
dairy products. 
Other modifications, such as substitution of a solid rod for tube 16 are 
within the purview of the invention.