MEASURING INSTRUMENT FOR USE IN THE ADJUSTMENT OF THE CO2 PRESSURE IN DRAUGHT BEER SYSTEMS

INSTRUMENT DE MESURE POUR SERVIR AU REGLAGE DE LA PRESSION DE CO2 DANS LES SYSTEMES DE BIERE EN FUT

English Abstract

2062984 9011504 PCTABS00002
A manometer has incorporated therein a thermometer whose
indicator (15) moves along the manometer scale (13) so that the indicator
(15) indicates the ideal CO2 equilibrium pressure in the
draught beer keg under all temperature conditions. To compensate for
the system-constant pressure drop in the draught beer system which
occurs during dispensing, the indicator (15) of the thermometer
can be manually caused to indicate a corresponding increment to
the equilibrium pressure, so that under all temperature conditions
the thermometer indicator (15) is present at the point on the
manometer scale which corresponds to the desired CO2 pressure.
The correct CO2 pressure is then set by always causing the
manometer pointer (12) to point at the thermometer indicator (15).

Claims

WO 90/11504 PCT/DK90/00078
- 5 -
P a t e n t C l a i m s :
1. A measuring instrument for use in the adjustment of
the CO2 pressure in draught beer systems and comprising a
manometer and a thermometer (14), whose indicator (15) is
adapted to move along or in direct readable relationship
with the manometer scale (13), c h a r a c t e r i z e d
in that the indicator (15) of the thermometer is adapted
to indicate on the manometer scale (13) the temperature-
dependent pressure desired at any time.
2. A measuring instrument according to claim 1, c h a -
r a c t e r i z e d in that the thermometer is thus posi-
tioned as to be movable manually with respect to the mano-
meter.
3. A measuring instrument according to claim 1 or 2,
where the manometer has a pointer (12) movable along a
circular arc, c h a r a c t e r i z e d in that also the
thermometer (14) has a pointer (15) which is movable along
the same circular arc.

Description

WO90/11504 2 ~ PCT/DK90/00078
A measuring instrument for use in the adjustment of the
C2 pressure in draught beer systems
_____________________________________ ___ _____
The invention concerns a measuring instrument for use in
the adjustment of the CO2 pressure in draught beer sys-
tems. It is important for the quality of the dispensed
beer that its CO2 content is kept within certain limits.
Normally, CO2 is used as a propellant for dispensing of
- 10 draught beer, CO2 being supplied from a CO2 bottle through
a reduction valve which maintains a constant CO2 pressure
over the beer surface in the keg. This pressure is
measured on a conventional manometer.
The CO2 amount dissolved in the beer depends upon both the
C2 partial pressure on the beer surface and upon the tem.
. perature of the beer (cf. Dal~on's and Henry's laws).
, Since, usually the CO2 used has a purity of above 99.95%,
the CO2 manometer display is in practice equal to the CO2
partial pressure. The relation between the three quanti-
ties can be read on special, empirically determined dia-
grams. However, the process necessary for correct pressure
` adjustment on the basis of such a reading requires certain
technical knowledge so that the bartender operating the
draught beer system often finds it necessary to send for
an expert from outside to mak.e the adjustment, which is
both expensive and time-consuming.
:,
In draught beer systems, a pressure loss occurs from keg
: 30 to tap owing to the difference in height between these.
During dispensing, flow pressure loss moreover occurs in
the connection from keg to tap. These pressure losses are
individual constants for each individual draught beer sys-
tem.
.. . . . . . .
- . -. ,: -. ' : ,
' ' ' ' ~

WO90/115~4 2 ~ ~ % ~ 8 ~ - 2 - PCT/DK90100078
The instrument of the invention is used for adjusting the
temperature-compensated drive pressure in the keg to com-
pensate for the mentioned system-constant pressure losses
This compensation pressure is thus an increment to the
equilibrium pressure of Co2 in balance with CO2 dissolved
in the beer, and only very slowly (i.e. within 2-3 weeks)
will it increase the CO2 content in the beer noticeably.
US 2 239 221 discloses a measuring instrument of the pre-
sent type, but which for the present use requires adjust-
ment according to a specific numerical value on the scale
with consequent possibilities of error.
US 3 815 417 and US 4 638 671 describe instruments which
do not allow adjustment of the CO2 pressure in draught
beer systems with the same ease as the present invention.
The object of the invention is to provide a measuring in-
strument of the present type, which makes it easy for the
unskilled person to adjust the CO2 pressure in the keg so
that the beer maintains the desired CO2 content irrespec-
tive of temperature variations in the keg.
.:
This ob;ect is achieved in that the measuring instrument
is constructed as stated in the characterizing portion of
claim l. Since the relation between pressure and tempera-
ture in equilibrium at a specific, desired CO2 content is
substantially linear in the actual regions (typically
about 10-30C and about 0.1-2.5 bars), the pressure, with
30 this structure, is just to be adjusted so that the mano- ;
meter pointer constantly assumes a specific position with
respect to the temperature indicator.
The embodiment defined in claim 2 entails that the thermo-
meter can be placed in such a position with respect to the
manometer that, during adjustment, its pointer is simply
. . - ~: . . . :
. ~ , . . .
- , :. :. - ,, . ' :. . :: '.:

WO90/11~04 2~ g~ PCT/DK90/00078
:
-- 3 --
to be caused to point at the indicator of the thermometer.
A particula~ly simple and practical embodiment of the
measuring instrument is defined in claim 3.
The invention will be explained more fully below with re-
ference to the drawing, in which figs. l and 2 show an
embodiment of the measuring instrument of the invention,
seen from the side and from the front, respectively.
1 0
Fig. 3 shows the relation between CO2 pressure and tempe-
rature for a given C~2 concentration in the beer.
In the drawing lO is a cylindrical instrument casing with
a connection piece ll through which a manometer with a
pointer 12 and a circular arc-shaped scale 13 contained in
the casing can be connected with the measuring point.
The rear side of the casing rotatably mounts, in a manner
not shown in detail, a thermometer 14 with a pointer 15,
which can rotate about the same axis as the manometer
pointer 12 and is visible through a circular arc-shaped
slot 16, which is inwardly defined by the manometer scale
13. A mark 17 on the cylinder ~ace of the thermometer cas-
ing and a compensation scale 18 on the cylinder face ofthe casing lO make it possible to adjust and to read the
positions of the two measuring means with respect to each
other.
The purpose of the adjustment is to provide for compensa-
tion for pressure losses occurring during dispensing in
the draught beer system from keg to tap. This pressure
drop depends i.a. upon pipe length and difference in
height between keg and tap and is thus a system-constant,
which is set once and for all for the individual draught
; beer systems when the system is mounted. The compensation
:-
' ,; ' ' , . , ~ ' ' '
::

WO90/11504 PCT/DK90/00078
2 ~
scale 18 can suitably be calibrated in pressure units fordirect adjustment of the compensation pressure as an in-
crement to the equilibrium pressure from the CO2 content
of the beer.
Fig. 3 shows the dashed curve A CO2 equilibrium pressure
over the surface of the beer as a function of the tempera-
- ture of the beer with a specific, desired CO2 concentra-
tion in the beer. In the temperature range 10-30C the re-
lation can for practical purposes be approximated the
solid straight line B. Therefore, a linearly operating
thermometer may be used in practice.
.! :
The thermometer 14 is so constructed that its pointer 15
moves along the manometer scale 13 in case of temperature
changes with a relation between temperature and position `
on the manometer scale 13 as in fig. 3 with an increment ;
of the set compensation pressure.
.. . .
In a draught beer system where the compensation pressure
is set once on the measuring instrument, the thermometer
pointer 15 will always indicate the ideal CO2 pressure on ~`
, the manometer scale 13. Then, the bartender just has to
adjust the CO2 pressure by adjusting the reduction valve
so that the manometer pointer 12 will point at the ther-
mometer pointer 15. This is a simple process which re-
quires no form of skills or insight.
The invention is not restricted to the special embodiment
shown and described, since the constructive details can be
amended in several ways. This applies e.g. to the struc-
ture and the relative position of the two indicator
scales.
.,
; 35
:
,, ~.

Representative Drawing