Sealing assembly for sealing an opening in a plate through which a shaft extends

An arrangement for sealing an opening in a plate (1) through which a shaft extends, the plate separating the "wet" and the "dry" zones of a packing machine from each other. In packing machines great demands are made on the tightness and durability of such shaft bushings, especially against strong washing agents, and the sealing assembly in accordance with the invention, therefore, has a flexible connection with the plate (1) and two O-rings (9,10), which are partly enclosed by two halves of a sealing assembly. Thereby, the O-rings are protected during washing as well as during operation. This design also produces a good sealing effect even when the shaft moves a little in radial direction during operation.

FIELD OF THE INVENTION 
The present invention relates to an arrangement for the sealing an opening 
in a plate through which a shaft extends. 
BACKGROUND OF THE INVENTION 
Shaft bushings in plates (e.g. walls, guard-plates or the like) can be 
sealed in various manners in order to prevent contaminations or liquid 
from passing along the shaft. In cases of axially movable, reciprocating 
shafts flexible bellows of rubber or plastics are generally used, which 
are connected in a liquid-tight manner on the one hand to the shaft, on 
the other hand to the plate along the edge of the hole through which the 
shaft extends. In cases of shafts with large axial movements seals of very 
high flexibility are required, not only in the longitudinal direction of 
the shaft but also radially, since shafts of this type during maneuvering 
frequently move a little in a lateral direction. Therefore, in this type 
of shaft bushing rubber bellows and the like occasionally cannot be used. 
Within certain technical fields, e.g. in machines for the packaging of 
liquid foodstuffs, the packing machine is divided into a "wet" and a "dry" 
zone. In the wet zone filling of the packing containers takes place along 
with a part of the forming work and closing of the packing containers. It 
must be possible to clean the wet zone with strong washing agents and to 
flush it with water and possibly steam. The dry zone comprises the driving 
and lubricating system of the machine which must be completely separated 
from the wet zone. Between the two zones, which are separated from one 
another by means of a frame plate of stainless steel, run shafts with 
axial as well as rotational movement. The sealing of these shafts has to 
be done very carefully, on the one hand because of the handling of 
delicate food substances (milk etc.) which on no account must be allowed 
to take up the flavor of, or be contaminated by, the driving system of the 
machine, on the other hand because of the use of harsh cleaning and 
sterilizing agents which must not be permitted to enter into the dry zone 
of the machine. 
OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
It is an object of the present invention to provide a flexible arrangement 
for the sealing an opening in a plate through which a shaft extends this 
arrangement being designed so that it is especially suitable for use in 
packing machines, and more particularly for the sealing of shafts which, 
performing primarily an axial, but also a radial, reciprocating movement, 
pass through a plate which divides wet and dry zones of the machine. 
It is a further object of the present invention to provide a shaft seal of 
the abovementioned type, this shaft seal being of such a design that it 
provides good resistance to the harsh operating conditions which exist in 
a packing machine and is not affected either by cleaning agents, oil or by 
high temperatures. 
It is a further object of the present invention to provide a shaft seal of 
the abovementioned type which is resistant to wear, is simple and reliable 
as well as low in cost. 
These and other objects have been achieved in accordance with the invention 
in that an arrangement of the type described in the introduction has been 
given the characteristic, that it comprises an assembly surrounding the 
shaft in a slidable manner, which has two halves facing each other which 
via intermediate flexible sealing material rest against the plate in an 
area surrounding the shaft. 
Preferred embodiments of the arrangement in accordance with the invention 
have been given the characteristics which are evident from the subsidiary 
claims. 
By designing the arrangement in accordance with the invention as a two-part 
assembly where axial movement of the shaft is made possible by a slide 
bearing tightly surrounding the shaft, and the radial movement of the 
shaft is taken up via the flexible sealing rings, an arrangement of the 
required flexibility is obtained which does not include any accessible 
rubber or plastic components which may be damaged by the sometimes 
aggressive environment in a packing machine. The design of the arrangement 
brings with it also great durability in respect of high temperatures and 
wear, and the parts which eventually do wear out can be exchanged at low 
cost, since they constitute standard components.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
In a packing machine (not shown), which e.g. may be of the type which is 
described in Swedish Pat. No. 361857, a "wet" and a "dry" zone exist which 
are separated from each other by means of a substantially horizontally 
placed plate 1 of stainless steel. Above the plate 1 is the wet zone of 
the machine, that is to say the part of the packing machine where the 
packing containers are formed from more or less prepared packing material 
by folding, forming and sealing, and are filled with the desired contents 
and closed. In this zone very high demands are made on cleanliness and 
hygiene, and the wet zone is washed, therefore, frequently with strong 
washing agent, e.g. caustic soda, and is flushed with water or steam. 
Underneath the plate 1 is the "dry" zone of the machine where the driving 
system of the machine is located with electric motors, shafts and cams 
which are lubricated by means of a comprehensive lubricating system. This 
zone must not be reached by cleaning agent or contents, since in such a 
case the lubricating system as well as the electrical components might be 
damaged. Similarly it is of greatest importance, of course, that 
lubricating oil or contaminations from the dry zone cannot reach the wet 
zone of the packing machine, since the foodstuff products handled here in 
such a case might be contaminated or take up the flavor of e.g. the 
lubricating oil. 
Through the plate 1 pass a number of shafts, substantially vertically, 
these shafts being required for the transmission of movement from the 
driving system of the machine to the different units for forming, sealing 
and filling which are located in the wet zone of the machine (these 
components are not described in more detail since they are not directly 
connected to this invention, but reference is made to the Swedish patent 
mentioned earlier which provides a detailed description of a packing 
machine of the type in which the arrangement according to invention 
advantageously can be used). 
One of the shafts which pass through the plate 1 is indicated in the FIGURE 
by the reference designation 2. The shaft 2 extends vertically through the 
plate 1 and has an axially reciprocating movement. The shaft 2 extends 
through a circular hole in the plate 1 and is sealed off with the help of 
a sealing assembly 3 in accordance with the invention. The sealing 
assembly consists of an upper part or sealing member 4 and a lower part or 
sealing member 5 which are manufactured from a corrosion-resistant 
material (stainless steel) and are held together by means of a number of 
fixing devices 6 in the form of screws which are threaded into the upper 
sealing member 4 of the sealing assembly 3 and pass through freerunning 
holes in the lower sealing member 5. The two assembly parts 4,5 have 
recesses on their inner end surface which face each other in the form of 
concentric slots 7,8 wherein are located O-rings 9 and 10 respectively. 
With the help of the fixing devices 6 the two sealing members 4,5 of the 
sealing assembly are pressed in direction towards each other so that the 
two O-rings 9,10 (but not the assembly parts 4,5) will rest against the 
upper and lower surface respectively of the plate 1 in an area enclosing 
the shaft along the edge of the hole in the plate provided for the passage 
of the shaft. 
In the central part of the sealing assembly 3 is a concentric hole for the 
shaft 2 wherein is located a slide bearing 11. The slide bearing, which 
may be manufactured from any suitable bearing material known in itself, is 
supported by the upper part 4 of the sealing assembly 3 which extends down 
below the plane of the plate 1 in a corresponding recess in the lower part 
5 of the sealing assembly 3. The part of the hole for the shaft 2 which is 
located in the lower part 5 of the sealing assembly has a slightly larger 
diameter than the shaft 2 and lack a slide bearing, so that the shaft 2 
can pass freely without contact with the lower part 5. 
The design described of the arrangement in accordance with the invention 
makes it possible for the shaft 2 to perform its reciprocating, axial 
movement only by gliding axially in the glide bearing 11 without the 
sealing assembly 3 otherwise being affected. However, if, as is frequently 
the case, the axial movement is combined with a certain radial movement 
the sealing assembly 3 may be displaced in lateral direction without the 
sealing contact between the flexible O-rings 9,10 and the two sides of the 
plate 1 being lost, since the uppr and the lower sealing members 4,5 are 
screwed together only until the O-rings 9,10 rest against the two sides of 
the plate 1. Thus there is no direct contact between either the upper or 
the lower half and the plate 1, but each part 4,5 has a clearance of 
approx. 0.5-1 mm to the plate. This clearance, which is delimited by the 
mutual contact between the central portions of the two sealing members 
4,5, ensures that the movement of the sealing assembly 3 in lateral 
direction is limited only by the flexibility of the O-rings. 
For a number of reasons, the sealing assembly 3 in accordance with the 
invention is very suitable for being used in packing machines. The upper 
side of the assembly, that is to say the side facing towards the "wet" 
zone of the packing machine, is wholly smooth and lacks screwholes, 
grooves or the like which may collect dirt and are difficult to clean. The 
assembly is very durable in respect to the demanding environment in a 
packing machine, since the more sensitive parts of the assembly, that is 
to say the two O-rings, rest well-protected between the two assembly parts 
4,5 manufactured from stainless steel. Thanks to their placing the O-rings 
are protected from being sprayed directly with cleaning agent or steam, as 
well as from oil spatter, and they possess therefore a long service life. 
When they have to be exchanged all the same the substitution, thanks to 
the simple design of the assembly, can be done in a simple manner and at 
low cost, since the O-rings are standard components. The slide bearing of 
the sealing assembly, which also may be of a standard type, likewise has 
long durability since the design of the assembly and the flexible setting 
in the plate 1 brings with it a certain inclination of the shaft 2 without 
the wear being increased appreciably. 
An arrangement in accordance with the invention has proved in practical 
tests to function well and the combination of "floating" manner of fixing 
and durable material give a very well sealing function over a long time. 
While this invention has been illustrated and described in accordance with 
a preferred embodiment, it is recognized that variations and changes may 
be made and equivalents employed herein without departing from the 
invention as set forth in the claims.