A peristalitic pump comprising a pump housing accommodating a hose. A hollow space surrounding the hose is provided between the outer wall of the hose and the pump housing. The ends of the hose are sealingly attached all around to corresponding supply and discharge ends of the pump housing. The pump housing is provided with connecting tubes for supplying a pressure medium to the hollow space and discharging the medium therefrom, in order to exert pressure at desired points of time on the outer wall of the hose. The hose has an elliptic cross-sectional form adjacent the supply end along a given trajectory. Starting from the supply end, which is circular in cross-section, the hose becomes gradually flatter and broader to give a minimal value and sequentially in the direction of the hose portion extending toward the discharge end become increasingly less flat and broad in the same manner until the circular cross-section is obtained. The hose has a constant wall thickness along the entire length between the supply end and the discharge end and a constant inner circumferential length of the cross-section.

BACKGROUND OF THE INVENTION 
A known peristaltic pump is described in U.S. Pat. No. 3,406,633. The known 
pump is based on the principle that the hose is squeezed by the medium 
supplied to the hollow space, so that the pumpable material present in the 
hose is urged from the hose. 
In order to ensure that the compression of the hose starts at the proper 
place, so that the pumpable material is forced in the proper direction, 
the hose in the known pump is designed in such a way that the wall 
thickness of the hose increases from the supply end to the discharge end. 
A drawback of this known pump is that the required hose is difficult to 
manufacture. Another drawback is that the hose in the known pump has 
already been squeezed considerably along the entire length before the hose 
walls contact each other at a point. Since the pumping action in the 
proper direction is not initiated until the hose has been entirely 
squeezed at least locally, the efficiency of the known pump is very low. 
Furthermore a separate check device is necessary in the known pump, which 
results in damage to particles present in the pumpable material. For 
example, where blood is pumped, the blood platelets could be damaged, 
which is highly undesirable. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide a peristaltic pump which can be 
manufactured in a simple manner and in which the hose is first entirely or 
substantially entirely squeezed in a predetermined place before the rest 
of the hose is squeezed. 
It is another object of the invention to provide a peristaltic pump 
comprising a special check device, the operation of which is based on the 
same principle as the operation of the pump proper, and which does not 
result in damage to the particles present in the pumpable material. 
SUMMARY OF THE INVENTION 
These and other objects of the present invention are achieved by a pump of 
the above described type wherein the hose adjacent the supply end has an 
elliptic cross-sectional shape over a portion thereof which, starting from 
the circular cross-section adjacent the supply end, becomes gradually 
flatter and wider to a given minimal value and subsequently, in the 
direction extending towards the discharge end of the hose portion, becomes 
increasingly less flat and broad until the cross-section again becomes 
circular.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The pump shown in FIG. 1 comprises a pump housing 1 which is cylindrical 
and may be made of metal, glass or a suitable synthetic plastic material. 
The pump housing is provided at the supply end with a mounting flange 2 
for a pump hose 3. A similar mounting flange 4 is present at the discharge 
end. 
A pump hose to be described is disposed in the pump housing and comprises 
annular end collars 5, which are clamped against the flanges of the pump 
housing by means of clamping rings 6. To this end the clamping rings may 
be attached by means of bolts against the end flanges of the pump housing. 
Naturally, other attachment methods are possible also. 
The hose 3 has a constant wall thickness and a constant cross-sectional 
circumference along its entire length. 
The pump housing comprises a connecting tube 7 for a line, not shown, for 
supplying at desired points in time a pressure medium to the hollow space 
8 between the pump housing and the outer wall of the hose. Said pressure 
medium may be a suitable gas or a suitable liquid. 
When a pressure medium is supplied via the connecting tube 7 to the space 
8, the hose is squeezed, so that the pumpable material present in the hose 
is forced out of the hose. If no special steps are taken, the hose will 
first be squeezed approximately midway in its length and equal amounts of 
pumpable material will be pressed to the supply end and the discharge end. 
It is desirable for the hose to be entirely squeezed adjacent the supply 
end, so that substantially all of the pumpable material is pressed to the 
dicharge end. To ensure that the hose will be entirely squeezed first 
adjacent the supply end, the hose according to the invention has a portion 
8 adjacent the supply end which has a special shape. This shape is 
obtained without weakening the hose. 
Furthermore, this shaped is chosen in such a way that, during squeezing, 
only very small tensile stresses will occur in the hose material. 
To this end, the cross-section of the hose, seen from the supply end in the 
direction of the discharge end, is first circular, then elliptic. The 
elliptic form becomes increasingly flatter as far as the place indicated 
at 10, and progressively becomes less flat until beyond specially shaped 
portion 9, the hose again has a circular cross-section. This is further 
indicated in FIGS. 4a-4d which show respectively cross-sections A-D of the 
hose shown in FIGS. 2 and 3. 
In this manner there is formed a "weak spot" where the hose closes first 
when a pressure medium is supplied to the hollow space 8. This "weak 
spot", however is a weak spot only in the sense that at the "weak spot", 
the resistance against squeezing is slight. The "weak spot", however, is 
not a weak spot in the hose, since the wall thickness of the hose at that 
location is not reduced. 
Since the inner cross-sectional circumference of the hose is constant, only 
slight tensile stresses occur in the hose wall during squeezing of the 
hose adjacent the "weak spot", so that long life is ensured. Furthermore, 
this feature minimizes the impediment to the flow of material through the 
hose resulting from the weak spot. 
A hose having a cross-sectional configuration as described above can be 
formed in a simple manner on a correspondingly formed core and can be 
seamless. A seamless hose enhances proper operation of the pump. Because 
the cross-section of the hose has a constant inner circumference, the core 
can easily be drawn from the hose formed thereon. 
According to a further feature of the invention there is provided at the 
discharge end of the hose a specially formed hose portion 11 functioning 
as a check device. 
This portion 11 can be integral with the hose 3, as shown in FIG. 3, but 
can also comprise a separate hose portion which links up with the 
discharge end of the hose 3. 
In both cases the portion 11 is disposed in a separate housing portion 12 
comprising a supply tube 13 for supplying pressure medium to a hollow 
space 14 between the housing portion 12 and the hose portion 11. 
The hose portion 11, as shown in FIGS. 2 and 3, can have the same shape as 
the portion 9 of the hose 3, but can also have a cross-section 
corresponding to the cross-section of the line to be connected to the 
pump. 
As with the rest of hose 3, the wall thickness of the hose portion 11 is 
uniform along the entire length and the cross-sectional circumference is 
constant. 
When the hose portion 11 is integral with the hose 3, it is necessary to 
apply a collar to the hose at the transition between the hose 3 and the 
hose portion 11, to actuate separately pump hose 3 and the hose portion 
11. The collar is clamped between corresponding flanges formed in the pump 
housing 1 and the housing portion 12. 
When the hose portion 11 is not integral with the hose 3, the hose portion 
11 is provided at both ends with collars of its own that are adapted to be 
clamped. 
The operation of the pump shown in FIGS. 2 and 3 is as follows. As soon as 
the hose 3 is filled with the pumpable material, a pressure medium is 
supplied to the hollow space 8 via the connecting tube 7. The hose 3 is 
thereby first squeezed at 10, so that subsequent squeezing of the rest of 
the hose is initiated. This squeezing takes place gradually from the 
portion 10 towards the discharge end of the hose. As a result the pumpable 
material is pressed via the portion 11, which is open at that moment and 
functioning as a check device, to a delivery line (not shown) connected to 
the free end of the portion 11. 
As soon as the hose 3 is entirely squeezed, the pressure medium is supplied 
to the hollow space 14, so that the portion 11 is squeezed as well. 
Immediately thereafter the pressure medium is discharged from the hollow 
space 8, so that the hose 3 assumes its original shape and refills with 
the pumpable material. The hose 3 is then squeezed again, at least at the 
weak spot. The weak spot is squeezed entirely or substantially entirely, 
so that the portion 11 is opened. Finally, the pressure medium is 
discharged from the hollow space 14 and the above described cycle starts 
again. 
It is observed that various modifications of the above described pump are 
possible. 
For instance, the cross-section of the check device 11 can correspond to 
the cross-section of the delivery line to be coupled to the pump. Such an 
embodiment is diagrammatically shown in FIGS. 5, 6 and 7f-7h. FIGS. 5 and 
6 diagrammatically show the discharge portion of a pump according to the 
invention similar to FIGS. 2 and 3. Corresponding portions are indicated 
by the same reference numerals provided with an accent. Various 
cross-sections F-H of the check device 11 are shown in FIGS. 7f-7h. The 
dimensions of the cross-sections are smaller than the dimensions of the 
corresponding cross-sections of FIGS. 2 and 3. 
In order to obtain a smooth transition between the pump hose 3 and the 
check device 11, there is formed in the check device 11 a conical portion 
15 having a circular cross-section throughout. This conical portion 15 can 
be supported by and attached to a correspondingly formed flange 16 in the 
housing portion 12. 
Furthermore, it is possible to fill the hollow space 14 or 14' once with a 
pre-compressed gas under a given pressure. This pre-compression should be 
such that the portion 11 or 11' is normally squeezed, but opens as soon as 
pressure is exerted by the hose 3 on the pumpable material, so that the 
pumpable material is forced to the portion 11 or 11'. 
Separate control of the pressure in the hollow space 14 or 14' via the 
supply and discharge of the pressure medium is not necessary in that case. 
Although the figures show the check device 11 or 11' as being connected to 
the pump hose 3, it is also possible to apply the check device around the 
discharge end of the pump hose. The check device in this case will have a 
configuration similar to the configuration of check device 11 shown in 
FIGS. 2 and 3 and check device 11' shown in FIGS. 5 and 6. This 
configuration is necessary to ensure that the end portion of the hose 3 
which is to be squeezed by the check device is squeezed in the same 
direction as the rest of the hose 3. 
Such an embodiment is diagrammatically shown in FIG. 8. A hose-like check 
device 20 is disposed in a housing 21 having a larger diameter than the 
housing 1 and surrounds the discharge end of the pump hose 3. Although 
check device 20 has a configuration similar to that of check device 11, it 
has a larger minimum cross-section than check device 11, in order to apply 
check device 20 around the hose 3. The check device 20 is attached to 
flanges formed in the housing 21 in the same manner as hose portions 11 
and 11' are respectively attached to flanges formed in housing portions 12 
and 12', while a hollow space 22 is provided between check device 20 and 
housing 21 to which a pressure medium can be supplied. 
According to a further embodiment of the invention, as shown in FIG. 9, at 
least the hollow space 8 is filled at least partly with a liquid of such a 
specific weight that buoyancy of the liquid compensates for the weight of 
the hose 3 as well as the weight of the pumpable material present in the 
hose. As a result the pump hose can have an unlimited length without its 
sagging, which could impede optimal operation of the pump. Another 
advantage of supplying a liquid in the hollow space is that little 
pressure need be supplied to squeeze the hose. Consequently, the pump can 
be operated more quickly, so that a larger capacity is obtained without 
varying the dimensions of the pump. At the same time less pressurized gas 
is required, so that the efficiency of the pump is improved. 
Preferably, liquid glycerol is used. Liquid glycerol has a specific weight 
of 1.2 and its use is allowed to be used in the food industry. 
It is observed that the modifications described in the original U.S. patent 
application 167,354, now U.S. Pat. No. 4,424,009, which have as their 
object to prevent the wall portions adjoining each other in the squeezed 
condition of the pump hose from adhering to each other, or to promote 
rapid opening of the pump hose, can also be used in the above described 
pump. 
Such modifications, as well as the modifications shown in FIGS. 4, 5 and 11 
of U.S. Pat. No. 4,424,009 or the modification wherein an additional hose 
is provided in the pump hose, are deemed to fall within the scope of the 
invention.