Method and apparatus for testing containers

[54] METHOD AND APPARATUS FOR TESTING CONTAINERS

[75] Inventors: Othmar Stieger, Kindhausen; Alfred Wenger, Neftenbach, both of Switzerland

[73] Assignee: Elpatronic AG, Zug, Switzerland
[21] Appl. No.: 132,792
[22] Filed: Oct. 7,1993

Related U.S. Application Data

[62] Division of Ser. No. 909,975, Jul. 7, 1992.

[30] Foreign Application Priority Data

Jul. 8, 1991 [CH] Switzerland 02022/91

Mar. 16, 1992 [CH] Switzerland 00846/92

[51] Int. CI.5 G01M 3/32

[52] U.S. a 73/49.2; 73/37

[58] Field of Search . 73/37, 49.2, 41

[56] References Cited

U.S. PATENT DOCUMENTS

2,592,984 4/1952 Walling 73/37

3,805,594 4/1974 Hayashi 73/49.2

3,834,429 9/1974 Schulz 73/45

4,459,843 7/1984 Durham 73/37

4,708,014 11/1987 Janitz 73/49.2

4,715,214 12/1987 Tueter et al 73/49.2

4,768,372 9/1988 Lehmann 73/49.2

4,837,707 6/1989 Giometti et al 73/49.2

FOREIGN PATENT DOCUMENTS

WO86/00701 1/1986 European Pat. Off. .

0217140 4/1987 European Pat. Off. .

0279120 8/1988 European Pat. Off. .

3108459 9/1982 Fed. Rep. of Germany .

The apparatus for checking the volume of bottles (1) comprises a head (2) adapted to be moved sealingly onto the bottle mouth (21), with a metering piston (7) which is displaceable in relation to the head (2) to be inserted into the bottle (1) and compress the air contained therein, and a pressure sensor (9) for measuring the excess pressure produced in the bottle. The measured volume (11) in the bottle is linked to a compensating volume (12) through a duct (10). The compensating volume is determined on the one hand by the constant starting height of the metering piston (7) and on the other hand by the variable displacement path length of the head (2). This ensures that the compression ratios are always the same for bottles of different heights, since differences of bottle height are compensated by a balancing piston (13) in the opposite direction, which alters the compensating volume (12) according to the sealing displacement path of the head (2) and thus always keeps the compressed measured volume exactly constant. The apparatus enables deviations in volume occurring in a series production process for plastic or glass bottles to be determined without the need to supply external air to the bottles. The measuring cycle is initiated by recording the pressure rise when the head (2) is placed upon the container (1).

2 Claims, 4 Drawing Sheets