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

Abstract: 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).

Description: A measuring instrument for use in the adjustment of the C0 2 pressure in draught beer systems The invention concerns a measuring instrument for use in the adjustment of the C0 2 pressure in draught beer sys¬ tems. It is important for the quality of the dispensed beer that its C0 2 content is kept within certain limits. Normally, C0 2 is used as a propellant for dispensing of draught beer, C0 2 being supplied from a C0 2 bottle through a reduction valve which maintains a constant C0 2 pressure over the beer surface in the keg. This pressure is measured on a conventional manometer. The C0 2 amount dissolved in the beer depends upon both the C0 2 partial pressure on the beer surface and upon the tem¬ perature of the beer (cf. Dalton's and Henry's laws). Since, usually the C0 2 used has a purity of above 99.95%, the C0 2 manometer display is in practice equal to the C0 2 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 make the adjustment, which is both expensive and time-consuming. In draught beer systems, a pressure loss occurs from keg 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. 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 C0 2 in balance with C0 2 dissolved in the beer, and only very slowly (i.e. within 2-3 weeks) will it increase the C0 2 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 C0 2 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 CO- pressure in the keg so that the beer maintains the desired C0 2 content irrespec¬ tive of temperature variations in the keg. This object is achieved in that the measuring instrument is constructed as stated in the characterizing portion of claim 1. Since the relation between pressure and tempera¬ ture in equilibrium at a specific, desired C0 2 content is substantially linear in the actual regions (typically about 10-30°C and about 0.1-2.5 bars), the pressure, with 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 to be caused to point at the indicator of the thermometer. A particularly 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. 1 and 2 show an embodiment of the measuring instrument of the invention, seen from the side and from the front, respectively. Fig. 3 shows the relation between C0 2 pressure and tempe¬ rature for a given C0 2 concentration in the beer. In the drawing 10 is a cylindrical instrument casing with a connection piece 11 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 face of the thermometer cas- ing and a compensation scale 18 on the cylinder face of the casing 10 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 scale 18 can suitably be calibrated in pressure units for direct adjustment of the compensation pressure as an in¬ crement to the equilibrium pressure from the C0 2 content of the beer. Fig. 3 shows the dashed curve A C0 2 equilibrium pressure over the surface of the beer as a function of the tempera¬ ture of the beer with a specific, desired C0 2 concentra¬ tion in the beer. In the temperature range 10-30°C 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 C0 2 pressure on the manometer scale 13. Then, the bartender just has to adjust the C0 2 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.

Claims: P a t e n t C l a i m s : 1. A measuring instrument for use in the adjustment of the C0 2 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. A measuring instrument for use in the adjustment of the C0 2 pressure in draught beer systems ABSTRACT A manometer has incorporated therein a thermometer whose indicator (15) moves along the manometer scale (13) so that the indicator (15) indicates the ideal C0 2 equi¬ librium pressure in the draught beer keg under all tempe- rature 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 C0 2 pres- sure. The correct C0 2 pressure is then set by always causing the manometer pointer (12) to point at the thermometer indica¬ tor (15). Fig. 2.

Inventors: RASMUSSEN JAN NOERAGER, RASMUSSEN, JAN, NOERAGER
Applicants: CARLSBERG AS
Application year: 1990
Main classification: G01L19
IPC codes: G01L19