GB2171194A

GB2171194A - A fume hood

Info

Publication number: GB2171194A
Application number: GB08528371A
Authority: GB
Inventors: Tatsumi Morikawa; Yoshio Osawa; Takao Kawakami; Naoki Yoshida
Original assignee: Yamato Scientific Co Ltd
Current assignee: Yamato Scientific Co Ltd
Priority date: 1982-10-16
Filing date: 1985-11-18
Publication date: 1986-08-20
Also published as: GB2171194B; GB8528371D0; DE3336630A1; GB8326594D0; GB2129928A; GB2169701B; GB2129928B; GB8528370D0; GB2169701A

Abstract

An exhaust duct 3, which is to discharge outside the room in which the fume hood 1 is installed, exhausts air from the work space in the hood, so that air is drawn into the hood from the room. A unit 7 measures the air speed in the exhaust duct 3. The volume of the room is input on a control panel 35. An arithmetic unit computes the degree of ventilation of the room from the volume input on the control panel 35 and the output of the air speed measuring unit 7, and the result is displayed as an air change number on a digital display 37. <IMAGE>

Description

1 GB 2 171 194 A 1

SPECIFICATION

A fume hood The present invention relates to a fume hood having an apparatus for measuring the quantity of air flow.

An object of a fume hood is to protect an experimenter from noxious fumes generated during experiment. Its important function is to exhaust noxious fumes generated within the fume hood.

In general, the exhaust capability of a fume hood is represented by the inlet velocity of ambient air flowing through an opening in the front face. That is to say, the quantity of air flow exhausted can be generalized as follows:

Quantity of air flow exhausted in one minute (m'lminute) = Area of opening in the front face (M2) X inlet air flow velocity (m/second) x 60.

The inlet air flow velocity depends upon the conditions of an experiment carried out in the fume hood including kinds and amounts of gases generated during the experiment.

For assuring the safety of a fume hood, therefore, it is necessary to confirm the operation condition of the fume hood, i.e., whether the inlet air velocity on the front face is suitable or not. Confirmation of this operation condition can be conducted by measuring the quantity of airflow discharged from the exhaust duct of the fume hood.

For the purpose of measuring the quantity of the 95 discharged airflow, it is conceivable to install an air flow velocity sensor.

Brief description of the drawing 35 Figure 1 is a front elevational view of one embodi- 100 ment of the fume hood according to the present invention. Figure 2 is a lateral sectional view of the embodiment of Figure 1.

Detailed description of preferred embodiment

Figure 1 and Figure 2 are respectively a front view and a lateral sectional view of a fume hood 1. A glass door 11 is provided on a front opening 9 and an exhaust duct 3 is provided on the upper part of the fume hood 1. The glass door 11 is supported by wire 13 at its upper left and right portions. The glass door 11 may be arbitrarily moved upward or downward by winding up or down the wire 13 via pulleyes 15.

And the opening area within the front opening 115 section 9 may be adjusted by moving the glass door 11 upward or downward. The wire 13 is wound around a worm (not illustrated) in a front glass opening detector 16 via a weight 14, wherein the detector 16 detects the opening degree of the glass door based upon the rotation direction and rotation amount of the worm.

Provided within the fume hood 1 are an exhaust aperture 17 which is in communication with the above-described exhaust duct 3, and a by-pass air flow path 19. The exhaust aperture 17 is provided on an upper wall 21. The by-pass air path 19 is defined by a rear wall 23 of the fume hood 1 and a buffleplate 25 depending from the rear end of the upper wail 21.

Provided on the exhaust duct 3 are a blower (not illustrated) and a by-pass section 5 which is positioned on the suction side of the exhaust blower at a right angle in relation to the side wall of the exhaust duct 3 and in communication with the ambient air.

As shown in Figure 3 and Figure 4, the by-pass section 5 is composed of a suction section 27 for drawing the ambient air and an fitting section 33 to be inserted to a through hole 31 which is provided on a cylindrical wall 29 of the exhaust duct 3. The diameter D of the suction section 27 is made to be larger than the diameter d of the fitting section 27 so that the velocity of the ambient air drawn by the suction section 27 may be decreased.

Provided in the suction section 27 of the by-pass section 5 is an airflow velocity sensor 7 such as a hot-wire anemometer for detecting the by-pass air flow velocity Vs of the ambient air which has been drawn by the suction section 27. The by-pass airflow velocity Vs of the by-pass section 5 thus detected by the airflow velocity sensor 7 becomes large as the airflow velocity in the exhaust duct is increased. The correlation between them yields the airflow velocity in the exhaust duct, which in turn provides the discharged airflow. In this case, with the by-pass secton being tailored removable, it is possible to select an arbitrary diameter of the suction section in the by-pass section, whereby it is possible to establish the optimum measurement range of the air flow velocity sensor in correspondence with the wide-range measurement of an exhaust airflow rate.

By using this fume hood, not only the exhaust of air contained in the fume hood but also the ventilation of air contained in the room housing that fume hood become possible. At this time, it is important for the health of a person working in the room to know the ventilation effectiveness in that room. An arithmetic unit 28 computes the airflow exhausted from the exhaust duct 3 and the inlet air flow velocity of the ambient air flowing through the opening of the glass door using the opening degree of the glass door which has been detected bythe glass opening detector 16. The exhaust airflow and the inlet airflow velocity thus computed are displayed on a digital display 37 provided on a control panel 35.

The operation will now be described.

Gases generated within the fume hood 1 are exhausted from the exhaust duct 3 through the exhaust aperture 17 and the by-pass air path 19 by the ambient air flowing into the hood through the front opening 9 with an appropriate inlet air flow velocity. Atthis time, gases having small specific gravities flow into the exhaust duct 3 through the exhaust aperture 17, and gases having large specific gravities flow into the exhaust duct 3 through the by-pass air path 19.

By the exhaust airfrom the exhaust duct 3, the ambient air is drawn into the exhaust duct 3 from the by-pass section 5.

The by-pass air f low velocity Vs of the ambient air when drawn into this by-pass section 5 is detected by the air f low velocity sensor 7. The arithmetic unit also has a function of computing the degree of ventilation in the room wherein the fume hood is placed. That is to say, when the volume of the installation room (or symbols each representing a 2 GB 2 171 194 A 2 rankwhereto thevolume belongs) is inputed through the control panel, the aritmetic unit 28 outputs the degree of ventilation based upon the volume of the installation room and the exhaust airflow, the degree of ventilation being displayed on the digital display 37. In this case, the degree of ventilation is represented by the number of ventilation works, i.e., the number of replacements of the air within the installation room per hour whereto the amount of ventilation corresponds.

Claims

1. A fume hood including a hood for forming an experimental work space and an exhaust duct for coupling said hood with the outside of the installation room and effecting a forced exhaust work, exhaust from said hood being conducted and ventilation of the installation room being conducted through said hood, said fume hood comprising: a sensor for detecting an airspeed within said exhaust duct; a control panel for input of the volume of installa- tion room, an arithmetic unitfor outputing the degree of ventilation based on the volume input on said control panel and the air speed of the exhaust air flow detected by said sensor, a display means for digitally displaying the number of ventilation works on the basis of the degree of ventilation output by said arithmetic unit.

2. An apparatus for measuring and displaying the front inlet air speed of a fume hood comprising; an air speed measuring unitfor measuring the exhaust speed of said fume hood; an opening degree measuring unit for measuring the opening degree of a front door; an arithmetic unit for computing the speed of air flowing into said fume hood depending upon the opening degree of said front door by using outputs of said airspeed measuring unit and said opening degree measuring unit; and an air speed display unit for displaying the result computed by said arithmetic unit.

3. A fume hood comprising; a hood for forming an experimental work space, an exhaust duct for coupling said hood with the outside of the installation room and effecting a forced exhaust work by a blower, a by-pass section which is provided on said exhaust duct and which is in communication with the ambient air, and an air speed sensor placed in said by-pass section for detecting a by-pass air speed of the ambient air which is sucked into said exhaust duct through said by-pass section.

Amendments to the claims have been filed, and have the following effect:(a) Claims 1 to 3 above have been deleted or textually amended. (b) New ortextually amended claims have been filed as follows:- 1. A fume hood comprising: a hood forming an experimental work space; an exhaust duct for exhausting the air in the work space, whereby air is drawn into the hood from the room in which the fume hood is installed, the duct discharging outside the room, in use of the fume hood; means for measuring the air speed in the exhaust duct; a control panel for input of the volume of the room; an arithmetic unit for outputting the degree of ventila- tion based on the volume input on the control panel and the output of the air speed measuring means; and display means for digitally displaying the air change number on the basis of the degree of ventilation output bythe arithmetic unit.

Printed in the U K for HMSO, D8818935, 6186,7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.