Apparatus for the pulsed dispensation of very small amounts of liquid, especially hydrogen peroxide
BACKGROUND 
     The invention concerns an apparatus for the pulsed dispensing of very small amounts of liquid under the control of a measuring apparatus (amounts, for example, of 0.1 to 1 cm 3 ), especially for use in sterilizing apparatus operating with hydrogen peroxide, especially for milk containers. 
     In the sterilizing of milk containers consisting of plastic coated cardboard, a very small amount of hydrogen peroxide is injected into the container. In a one-liter container, the standard amount is about 0.3 cm 3 , whereas in a half-liter container it is about 0.2 cm 3 . If too small an amount of hydrogen peroxide is injected, complete sterilization is no longer assured; if, however, too great an amount of hydrogen peroxide is injected, not only is the excess wasted, but also it has a negative influence on the milk. The need for trouble-free sterilization of containers therefore involves the precise metering of the amount of liquid to be injected in each container. This ncessitates a constant control of the amount of liquid. 
     It has already been attempted to achieve this control with a flow meter. In practice, however, it has been found that, where a pulsing dispensation of very small amounts of liquid is involved, a flow meter does not permit sufficiently precise measurements. 
     THE INVENTION 
     The invention is addressed to the problem of creating an apparatus for the pulsed dispensation of very small amounts under the control of a measuring instrument, which will be simple in construction and will permit the uninterrupted dispensing of the liquid. 
     This problem is solved in accordance with the invention by the fact that the measuring instrument has a measuring vessel which can be filled with a relatively larger amount of liquid (10 cm 3 , for example), whose outlet is connected to a means for the ejection of the small amount of liquid, and whose cross section is adapted to the small amount of liquid to be controlled such that a sensing apparatus having an upper and a lower sensing means responds with the accuracy of about one to five small amounts of liquid, the sensing apparatus activating, for the time of the removal of liquid from the measuring vessel, a counter which receives counting pulses from a pulse generator triggered by the ejecting means or, in the case of an ejecting means delivering a constant ejection quantity per unit of time, from a pulse generator supplying time pulses. 
     According to a first alternative construction, the measuring vessel can be filled with the liquid from the reservoir through a valve controlled by the sensing apparatus, the feeding of liquid to the measuring instrument being switchable from the reservoir to the measuring vessel. 
     According to a second alternative construction, the measuring vessel can be filled with liquid from a reservoir situated lower than the measuring vessel through a pump controlled by the sensing apparatus, and the delivery of liquid to the ejecting means being switchable from the reservoir to the measuring vessel by shutting off the pump. 
     According to a further development, a computer is connected to the counter and divides the amount of liquid taken from the measuring vessel by the total number of counting pulses. The output signal corresponds to the liquid consumption per container or per unit of time, as the case may be. The output signal of the computer can be delivered to a comparator for a maximum value and a comparator for a minimum value, which give a warning signal when the prescribed value is exceeded or is not reached. 
     With the apparatus of the invention, the amount of liquid dispensed by each ejection can be determined accurately in a simple manner, without the need for interrupting the pulsed dispensing of the liquid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further explained with the aid of a drawing wherein: 
     FIG. 1 is a schematic of one embodiment of the present invention; and 
     FIG. 2 is a schematic of another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A reservoir 1 is filled with hydrogen peroxide as sterilant. Hydrogen peroxide passes from the reservoir 1 through an open valve 2 to an ejecting member 3 which feeds very small amounts of liquid pulse-wise to a nozzle (D). The ejecting member 3 is combined with a pulse generator 4 which delivers a pulse to a pulse shaper 5 for each very small amount of liquid ejected. 
     When the valve 2 is open, hydrogen peroxide also passes into a measuring vessel 6. With the measuring vessel 6 there is associated a sensing system having an upper sensing means 7 and a lower sensing means 8. The sensing means 7 and 8 respond to the liquid level in the measuring vessel 6, namely to the float 9. The float 9 can be eliminated if the sensing means 7 and 8 are in the form of level detectors. 
     The sensing system 7-8 controls the valve 2 and a counter 11 through a start-stop system 10 according to the liquid level in the measuring vessel 6. This is accomplished in the following manner: with valve 2 open, when hydrogen peroxide passes through the ejecting member 3 to the nozzle D and also to the measuring vessel 6, the sensing means 7 sends a signal to the start-stop system 10 as soon as the float 9 reaches the level of this sensing means. The start-stop system 10 in turn at this instant gives a switching signal to valve 2; this valve is closed, so that no more liquid is taken from the reservoir 1. The liquid for the nozzle now comes exclusively from the measuring vessel 6. Simultaneously with the switching signal, the start-stop system, however, also gives a start signal to the counter 11 which is thereby opened to the counting pulses which come from the pulse generator 4 through the pulse shaper 5. As soon as the float 9 has dropped to the level of the sensing means 8, this sensing means gives a signal to the start-stop system 10. This in turn gives a switching signal to the valve 2 which opens, so that the measuring vessel 6 is refilled and the liquid for the nozzle is taken from the reservoir 1. Simultaneously with the switching signal, a stop signal also goes to the counter 11, which is closed to the counting pulses which come from the pulse generator 4 through the pulse former 5. 
     The counted number of pulses then enters into a computer 12 which divides the known amount of liquid between the levels of sensing means 7 and sensing means 8 by the number of counted plates. In this manner the computer output gives the amount of liquid dispensed per ejection and also per container. This value is delivered to the indicator means 13 and to comparators 14 and 15 for maximum and minimum value. As long as the value in computer 12 is in the tolerance range between the maximum and minimum set values, the comparators 14 and 15 emit no output signal. In such a case no readjustment of the ejection amount needs to be undertaken. 
     As soon as the float 9, upon the filling of the measuring vessel 6, reaches the level of the upper sensing means 7, the action described is repeated. It is apparent that, prior to the next count, the counter 11 has to be reset. This can be accomplished simultaneously with the delivery of the count to the computer 12. 
     In a variant embodiment of the invention (FIG. 2), the reservoir 1 is disposed underneath the measuring vessel 6. The liquid must thus be pumped upward. Instead of the valve 2, a pump 16 is installed. As long as the pump 16 is turned on, the measuring vessel 6 will fill. The pump 16 is shut off by the sensing means 7 through the start-stop system 10 when the upper liquid level is reached; it is turned on by the sensing means 8 when the lower level is reached. Otherwise, this embodiment is equal in construction and operation to the first embodiment. 
     It will be appreciated that the instant specification and claims are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.