Gravimetric moisture-determination instrument with an air duct for cooling

Abstract

A measuring instrument ( 1 ) for gravimetric moisture determination consists of an instrument housing ( 2 ), a balance ( 3 ) installed in the instrument housing, and a radiant heater ( 8 ). The moisture content of a sample on a tray placed on the tray carrier ( 5 ) is determined by measuring the weight loss of the sample while it is being dried under the heater. The instrument is equipped with means for conducting an air stream generated by a fan ( 12 ) through the space between the sample tray carrier ( 5 ) and the weighing cell ( 21 ). The air-conducting means include an air duct that can be at least partially released from the instrument housing for cleaning.

What is claimed is:  
     
         1 . A measuring instrument for gravimetrically determining a moisture content of a sample, comprising an instrument housing, a balance with a weighing cell installed in the instrument housing, a tray carrier mounted on the weighing cell to hold a sample on a sample tray, a source of radiant heat arranged above the sample tray, and means for conducting a stream of air between the sample tray and the weighing cell, said means comprising an air duct; said radiant heat drying the sample and thereby causing the latter to lose weight; the balance being operable to monitor said weight loss and to therefrom determine the moisture content of the sample; wherein the means for conducting the air stream are configured to allow at least a part of the air duct to be released from the instrument housing for the purpose of cleaning the air duct.  
     
     
         2 . The measuring instrument of    claim 1   , wherein the air duct comprises an upper shell mounted on top of the instrument housing and closing off the air duct from above; wherein the measuring instrument comprises means for fastening the upper shell to the instrument housing; and wherein said means for fastening are releasable, thereby allowing the upper shell to be removed from the instrument housing.  
     
     
         3 . The measuring instrument of    claim 1   , wherein the air duct comprises an upper shell mounted on top of the instrument housing and closing off the air duct from above; wherein the upper shell is hinged to a rear portion of the instrument housing, thereby allowing the upper shell to be tilted about a horizontal axis.  
     
     
         4 . The measuring instrument of    claim 1   , wherein the air duct comprises an upper shell mounted on top of the instrument housing and closing off the air duct from above; wherein the upper shell is slidably mounted so that it can be pulled off in a forward direction.  
     
     
         5 . The measuring instrument of    claim 1   , wherein the air duct comprises a single-piece air duct unit, wherein the measuring instrument comprises means for fastening the single-piece air duct unit to the instrument housing, and wherein said means for fastening are releasable, thereby allowing the single-piece air duct unit to be removed from the instrument housing.  
     
     
         6 . The measuring instrument of    claim 1   , wherein the air duct has a U-shaped profile, closing off the instrument housing from above as well as laterally.  
     
     
         7 . The measuring instrument of    claim 1   , wherein the air duct has at least one branch channel running near an electronic portion of the measuring instrument and serving to cool said electronic portion.