ffi SB

NBSIR 75-722

Closure Testing Equipment

Instruction Manual

Malcolm S. Morse

Product Engineering Division

Center for Consumer Product Technology

Institute for Applied Technology

October 1 975

Final Report

Prepared for Consumer Product Safety Commission

Washington, D. C. 20016

NBSIR 75-722

CLOSURE TESTING EQUIPMENT

INSTRUCTION MANUAL

Malcolm S. Morse

Product Engineering Division

Center for Consumer Product Technology

Institute for Applied Technology

October 1 975

Final Report

Prepared for Consumer Product Safety Commission

Washington, D. C. 20016

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy An cker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

TABLE OF CONTENTS

Page

1.0 INTRODUCTION 1

2.0 OPERATING INSTRUCTIONS 2 2.0.0 General 2 2.0.1 Units and Conversion Factors 2 2.1.0 Physical and Electrical Specifications 2 2.2.0 Initial Setup 4 2.3.0 Calibration Procedure . 5 2.4.0 Operation of Individual Units 7

3.0 CLOSURE TEST PROCEDURES 9

3.0.0 Closure Operating Characteristics 9 3.2.0 Measurement Techniques 10

3.3.0 Measurement Value Criteria .... 11

3.4.0 Environmental Considerations 12

3.5.0 Specific Test Procedures 12

4.0 MAINTENANCE INSTRUCTIONS 14

4.1.0 Theory of Operation 14

4.2.0 Maintenance 17

4.3.0 Repair and Trouble Shooting 18

APPENDIX

Parts List 19

FIGURES

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Overall View of Closure Testing Equipment

Closure Operating Forces

Pry and Shell Forces

List of Safety Closure Types

Overall View of Special Units

Electronic Unit - Rear View

Electronic Unit - Interior View

Amplifier Unit

Block Diagram of Equipment

1.0 INTRODUCTION

The NBS Closure Testing Equipment is designed to make accurate

measurements of the critical characteristics of the "Childproof" closures

required by the Poisoning Prevention Packaging Act of 1971. In general,

these characteristics are defined as the forces necessary to open these

closures, either in the manner by which the closure was designed to be

opened, or in an undesired manner.

The general design philosophy for this equipment is to use normal

manual manipulation of the closure and container to the greatest extent

consistent with accurate measurement. This philosophy originated when an investigation of the problem indicated that this approach would give

results consistent with actual field use and would tend to show up

deficiencies not apparent if the closure were tested with automated

equipment

Because it is not possible to define all possible types of childproof

closures by a set of physical requirements, the assumption is made that all

childproof closures which have passed the "Protocol" test are satisfactory

if they conform in all critical respects to the samples originally tested.

The "Protocol" test, however, does not provide any physically measurable

dimensions, forces, tolerances, or limits which can be used to insure that

future closures of the same nominal design conform to those tested. This

lack of definitive measurements is due to the fact that at the time the Act

was passed these measurable quantities were not known for any closures, and

suitable measuring equipment was not available to measure and define these

quantities

Because of the lack of standards, the measurement procedures given

here should be regarded only as preliminary and tentative. These

procedures have been designed to measure what are assumed to be the

critical quantities, but only further and extensive testing can provide

assurance of the validity of these assumptions. In addition, the problem

of setting limits for the measured quantities is still to be resolved.

"Protocol" test as defined in section 1700.20 of Chapter II Subchapter E of Title 16 of the regulations of the U.S. Consumer Product Safety

Commission.
2.0 OPERATING INSTRUCTIONS

2.0.0 General

The NBS Closure Testing Equipment consists of three main units: the

Electronic Unit, the Force-Torque Table, and an X-Y Recorder. An overall

view of the equipment is shown as figure 1. In addition two specialized

units are provided. The first of these is for making bite and squeeze

measurements (Bite and Squeeze Unit) and the second is for making pry

measurements (Pry and Shell Unit).

The equipment basically provides three independent force measuring

channels which can be used simultaneously or in any combination. The force

or torque being measured by each channel is displayed on a calibrated

digital panel meter, and may also be simultaneously recorded on the X-Y

recorder. However, since the X-Y recorder has only two recording channels,

only two quantities may be recorded simultaneously although three may be

measured and displayed. The X-Y recorder may also be used to record the

output of one force channel continuously against time. To further increase

the versatility of the equipment, a peak-reading circuit is provided which

may be used to hold the highest reading occurring on a force channel during

a given interval.

2.0.1 Units and Conversion Factors

The equip lent is calibrated in newtons and in newton-meters as the

force and torque units, respectively. The newton is the unit of force used

in the International System. In terras of older units, a newton is

equivalent to 0.102 kilogram-force and a newton-meter is equivalent to

0.102 me ter-kilogram- force or 0.738 foot-pound-force.

2.1.0 Physical and electrical specifications

The detailed physical and electrical characteristics of the equipment

are tabulated below.

1. Electronic~Unit

Physical characteristics:

35 cm long x 25 cm high x 28 cm deep

Weight: 6.83 kg

Electrical characteristics:

Line voltage 117 Vrms +10% 57-63 Hz

D C Output voltage to auxiliary force measuring units:

10.0 volts +0.2% (3 0.050A

2
Signal input voltage range: 0 +100 mV

Signal voltage output to X-Y Recorder: 0 to +20mV

Sweep voltage output to X-Y Recorder: 0 to +10V

2. Force-Torque Table

Physical characteristics:

25.5 cm long x 21.0 cm high x 25.5 cm deep

Weight: 8.65 kg

Electrical Characteristics: Input voltage: 10 Vdc +0.2%

from Electronic Unit

Output signal voltage: 0 to 100 mV

3. X-Y Recorder

Physical characteristics:

44 cm long x 14 cm high x 27 cm deep

Weight: 9 kg

Electrical Characteristics

Power requirements: 115 Vrras +10% 50 Hz to 400 Hz, 40W

Signal Input voltage range: Maximum inout +200V peak

differential, +500V peak common mode

to ground

Input impedance: greater than 1 megohm

Sensitivity: 0.5 raV/cm to 5000 mV/cm

4. Bite and Squeeze Unit

Physical characteristics:

18 cm long x 6.5 cm high x 2.5 cm deep

Weight: 0.412 kg

Electrical Characteristics: Input voltage: 10. 0 Vdc +2%

from Electronic Unit

Output signal 0-+l00mV

5. Pry and Shell Unit

Physical characteristics:

3
30 cm long x 3.1 cm high x 2.5 cm deep

Weight: 0.272 kg

Electrical Characteristic Input voltage: 10.0 Vdc +2%

Electronic Unit

Output signal: 0 - +l00mV

2.2.0 Initial Setup

2.2.1 Connections

The equipment is prepared for operation by connecting the Electronic

Unit and the X-Y Recorder to a suitable ac power source ana making the

interconnections between the Electronic Unit, X-Y Recorder, Force-Torque

Table and the Specialized Units if used (see figure 1). For maximum

accuracy an initial warmup time of 30 minutes should be allowed. The

equipment may be left on continuously.

2.2.2 Zeroing

Each of the three signal channels of the Electronic Unit as well as

the two channels of the X-Y recorder is provided with a separate zeroing

control. After initial warmup thes-i controls should be set to their

desired initial positions as follows:

a. X-Y Recorder. Each of the three indicators of the

Electronic Unit has located directly beneath it an Indicator Range Switch incorporating a zero position. When

this switch is set on the zero position the input to

the digital indicator is shorted, providing a noninal

zero output voltage as indicated on the panel indicators.

This also provides a nominal zero output to the X-Y

Recorder, since the outputs to the recorder are identical

with the voltages indicated by the digital indicator

units. Therefore, in order to zero the X-Y Recorder

the channel switches on the Electronic Unit should

first be set to zero. This will give a nominal zero output to the recorder when the Recorder output switches

are set to the appropriate channel. The X-Y Recorder may now

be set to the appropriate zero position by means of its individual zero controls. (Before carrying out this procedure,

the Operating Instructions section of the manufacturer's

Instruction Manual for the X-Y recorder should be read

careful ly .

b. Electronic Unit. After initial warm up, and with the

Indicator Range Switches set to the Zero position as specified above, the readings on the digital indicators

4
should be close to zero. (Small deviations from zero under these conditions are compensated for in the

measurement procedure and need not be corrected.) If

the zero readings under these conditions exceed one or two

in the last digit, reference should be made to the maintenance

section of this manual.

c« Force-Torque Table. After the initial zeroing procedure described above is carried out, the Force and

Torque Range Controls on the Electronic Unit should

be set to the range to be used in the measurements and

the Force-Torque channels should be zeroed, using

the individual zeroing controls mounted on the ForceTorque Table. (The Force-Torque Table must be

connected to socket 2 of the Electronic Unit for

this procedure). During this procedure, as during

any procedures where a test result recording is not

required, the Recorder Output Switches on the

Electronic Unit should be set to the Zero position.

d. Specialized Units (Bite and Squeeze Unit, Pry and Shell

Unit). The third or Special signal channel on the Electronic

Unit (Socket 1) is for use /ith either of the Specialized Units.

It should be zeroed with the appropriate specialized unit connected

to socket 1 on the Electronic Unit and with the Special Channel

Range Switch set to the range to be used. Under these

conditions this channel is zeroed using the Special

Unit zero control mounted on the front panel of the

Electronic Unit. Care should be taken to prevent the

accidental application of force to the specialized

units during the zeroing procedure.

2.3.0 Calibration Procedure

2.3.1 X-Y Recorder Calibration

In operating the Closure Testing Equipment it will normally

be desirable to record the outputs of the various • force channels,

since more information can be obtained from the detailed re- cording of any test than can be obtained from isolated indicator

readings. The flexibility of the equipment is such that the re- corder scale can be varied over wide limits and can be readily

calibrated for any desired scale factor in either newtons or newtonmeters. This is done by the following procedure:

1. Estimate, either by experience or trial, the maximum

force or torque which will be encountered in the

testing procedure.

5
2. With the help of the table below chose a suitable

range scale for the channels to be recorded.

Table A

Channel Rang o Max. PermissibleLoading

Output Voltage

(Approximate)

Force

Force

Torque

Torque

Special

Special

1000 newtons

200 newtons

2.0 newtonmeters

0*2 newtonmeters

10.0 (x 10)

1.0 (x 1.0)

1200 newtons

1200 newtons

3.0 newtonmeters

3.0 newtonmeters

See rating on Unit

See rating on Unit

0.1 mV/N

0.1 raV/N

10 mV/Nm

10 mV/Nm

See calibration

on Unit

See Calibration

on Unit

3. From the output in mV/N (mV/Nm if from a torque channel) and the maximum expected force (torque)

calculate the maximum expected voltage output from the

Electronic Unit.

4. Using the X-Y Recorder on its calibrated range, select

the scale factor in mV/cm which will give the maximum

usable deflection of the recorder.

As an alternative procedure a steady force equivalent

to the maximum expected during testing may be applied

(after zeroing) to the channel which is to be recorded,

and its value may be read on the digital indicators.

Using the variable calibration controls of the X-Y

Recorder, the sensitivity of the X-Y recorder may be

set to give the maximum deflection desired, and the

calibration factor may be obtained (in N/cra or

Nm/cra) by dividing the indicated force by

the number of centimeters of deflection produced. For

the force channel a convenient method of producing a known force is to use a known weight.

6
2.3.2 Equipment Calibration

The equipment calibration may be checked conveniently by

applying known forces to the channels, most conveniently by means

of known weights, and checking the reading of the digital indicators.

Any departure of the equipment from calibration by more than 10%

calls for maintenance.

2.4.0 Operation of Individual Units

2.4.1 Electronic Unit

The Electronic Unit is always used with either the Force-Torque

Table or one of the specialized units or with both together. Operation of

the range and zeroing controls has already been covered by the zeroing and

calibration instructions given above. The instructions below will cover

the operation of two other features of the Electronic Unit, the Sweep

Circuit and the Peak Reading Circuit.

2.4.1.1 Sweep Circuit

The Sweep Circuit is controlled by the Sweep Control Switch,

located to the right of the Reading Mode Switch on the bottom of the front

panel of the Electronic Unit (see figure 1). Te purpose of this circuit

is to move the pen of the X—Y recorder slowly along one axis, so that a variable voltage derived from the Force Torque or Special channels and

applied to the other axis will be recorded against time. The voltage

output of the sweep circuit rises slowly from zero to 10 volts when the

sweep control switch is set to the Sweep positions. The Hold position on

the Sweep Control Switch interrupts the sweep voltage and maintains it at

that value, and the Reset position restores the voltage to zero. The Sweep

Circuit givrs a comparatively slow sweep from zero to 10 volts. (This slow

sweep may be increased over a very wide range by changing the sensitivity

setting of the X-Y recorder.) The recorder selection switches on the

Electronic Unit are used to apply the sweep voltage to the desired recorder

axis.

2.4.1.2 Peak Reading Circuit

The peak reading circuit provides a convenient method of making

readings when only a maximum force reading is needed, as for shelling and

stripping tests. Peak readings are also useful when the recorder is not

being used and the presence of transient peak values is suspected. The

peak reading circuit can be switched into any one of the three channels of

the Electronic Unit. When it is switched into a channel the digital meter

will read and hold the highest force (or torque) encountered between

consecutive depressions of the peak reading reset button. The peak reading

circuits cannot be used on a channel which is being recorded, since their

use will distort the reading. Since there is some "droop" in the peak

reading circuits, the highest reading obtained should be noted. In using

7
the peak reading circuit the polarity selector switch should first be set

to the expected reading polarity. It should be noted that use of the peak

reading circuits causes a reversal of the sign of the readings on the

digital indicators.

2.4.2 Force-Torque Table

The Force-Torque Table is designed to measure vertical forces (both

upward and downward) exerted on containers mounted on it, and also to

measure torques both clockwise and counterclockwise exerted on these

containers. A wide range of forces (0-1000N) and torques (0-lONra) can be

accurately measured. Since a force exerted on a closure is equivalent to

force exerted on the container, the practical effect is to measure closure

forces.

Operation of the force-torque table involves clamping a containerclosure combination into the universal clamp, being careful to insure that

it is centered, and exerting force on the closure. These forces will then

be displayed on the digital indicators of the Electronic Unit and may be

recorded, if desired, on the recorder. Forces necessary to replace the

closure may also be displayed and recorded in the same manner. Since most

childproof closures require either push, pull, or twist forces, or a combination to remove them, the operation of the closure while clamped in

the force-torque table will provide a measurement of the characteristics o the closure from the point of view of its operation.

For example, certain closures will operate only if they are turned

with a certain torque while being pulled, or pushed, with a certain force.

Such measurements of simultaneous forces are difficult or impossible with

other types of equipment, which cannot measure the required quantities

simultaneously

2. A. 3 Specialized Units

All of the specialized units plug into socket 1 of the Electronic

Unit and their readings are displayed on the "Special" digital indicator.

The readings can also be recorded on the X-Y Recorder.

2.4.4 Specialized Units: The Bite and Squeeze Unit

This unit is designed to exert a calibrated squeeze force on a closure, similar to that exerted by a finger squeeze or a bite. After

being plugged into the special channel this unit is first zeroed. It is

then tightened onto the closure until the desired result is reached

(desired torque on the closure as shown on the torque channel, for example

or desired or specified pressure) and is then used to rotate or otherwise

manipulate the closure.

8
2.4.5 Specialized Unit: Pry and Shelling Unit

This unit (see figure 3), is designed to produce a calibrated pry or shelling force. The method of use of the instrument is shown x n figure 3.

Calibration of this unit is in terms of torque. When it is used for

prying, the force involved may be derived from the length of the radius

a nn

2.4.6 Specialized Units: Squeeze Unit

The squeeze unit was designed to measure the force exerted by a person between his thumb and opposed fingers. It is not directly

applicable to closure measurements but extends the usefulness of the

equipment into human factors measurement.

2.4.7 X-Y Recorder

The X-Y recorder is placed in operation by setting the control

switch to the "on" position and setting the recorder output switches on the

Electronics unit to give the desired display. During actual operation of

the recorder the control switch should be in the "pen down" position, and

at all other times when the recorder power is on it should be in the "pen

up" position. Before making any actual test recordings the X-Y recorder

should be calibrated as outlined above.

Further details of the operation of the X-Y recorder are given in

the manufacturer's instruction book which is provided with the equipment.

3.0 CLOSURE TEST PROCEDURES

3.1.0 Closure Operating Characteristics

Almost all of the closures which this equipment is designed to test are intended to be opened by hand by normal adults. At the same time, they are designed to be proof against opening by children up to the age of five

years. While the "childproof" feature of the closures may not depend

directly on the ability of the adult to exert a greater force than a child,

it is still true that for almost all closures there is some correlation

between the childproof feature and the forces necessary to open the

closure.

For example, one commonly used closure must be manually rotated to a specific position, urhere it can be removed by an upwardly exerted force.

The childproof feature is not directly dependent on the inability of the

child to rotate the closure, but the force required to make this rotation

is important for two reasons.

First, if the force is too great, the normal user will be unable to

rotate the cap, and thus it will be ineffective as a reusable closure.

9
Second, if the force required to make this rotation is too small,

the cap will rotate almost at random in response to very small forces, and

in this case the security of the cap will be less than normal. Thus, for

the closure to function normally, the rotation force must lie between two

limits, even though these limits may be widely spaced. In general, such

limits can be established for all operating forces for all types of

childproof closures.

3.2.0 Measurement Techniques

The closure testing equipment is designed to measure, as closely as practicable, the characteristics of the closures as they are operated by

consumers in actual use. While the closures are the items of principal

interest, the actual measurements are made on the combination of the

closure and its accompanying container. It should be noted that in some cases variations in the container dimensions, finish, etc. may

substantially affect the closure operating characteristics. In making

tests on the closures, normal operation by the consumer should always be

kept in mind, and handling of the closure should reproduce consumer

handling whenever this will not interfere with measurement accuracy.

Testing should be designed to bring out variables which will be encountered

in actual use, rather than to eliminate such variables in the interests of

more consistent, but less representative, measurements.

For example, if in measuring the turning torque of a cap type of

closure, the cap is held in a holding fixture or jig, the measured results

will be considerably more uniform than if the cap is held in the fingers.

This is because the jig will eliminate the warming of the cap by the

fingers and will modify the unequal pressure distribution of the finger

grasp. However, results obtained using the jig will not be representative

of the results obtained by the consumer in actual use, while the use of the

natural finger grasp will duplicate actual conditions.

3.2.1 Use of the Force-Torque Table

Most closure measurements will be made with a closure-container

combination clamped onto the Force-Torque Table. In making these

measurements, it should be remembered that here the Force-Torque table is

substituting for one of the two hands normally used to open a closurecontainer combination, so that the forces being measured by the ForceTorque Table are the forces exerted on the closure by the other hand. Care

should be taken to see that the hand operating the closure does not exert

any force directly on the container itself, since this will result in

incorrect readings. The Force-Torque Table is designed to measure vertical

force in either the up or down direction (Push or Pull) as well as twisting

forces (torque) in either clockwise or counterclockwise directions.

In measuring push or pull forces on the closures with the ForceTorque Table, it will be necessary to compensate for the weight of the

10
container, which can be conveniently done by means of the Force Zero

control. Also, if pull forces exceeding the weight of the Force-Torque

Table are to be measured, it will be necessary to fasten the Table to a suitable fixed support.

3.2.2 Pry and Shelling Tests

In addition to the operation of the closures in their intended

manner, experience has shown that children attempt to open some closures by

banging, prying, or biting them in an unorthodox manner. This is

especially true of the two-piece overcap type of design, where the child

may so distort the cap as to destroy the normal child-proof feature. For

this type of cap, and for other caps subject to similar unorthodox opening

attempts, it is necessary to measure not only the forces necessary to open

the cap in the normal manner, but also to measure any unorthodox forces

that may open the cap or distort it so that it is no longer child-proof.

Tests to measure such forces are known as pry or shelling tests, since in

the common two-piece overcap type of closure the common method of attack is

to attempt to pry off or "shell" the overcap.

Tests to measure the prying or shelling force required to destroy

the childproof feature are commonly made with the Pry and Shell Unit, which

is shown in figure 3.

3.2.3 Bite and Squeeze Tests

Some childproof containers are designed to be opened by utilizing a combination of forces which include applying a squeeze force to some particular point or general region. In this case it is, of course

necessary to measure the force required for this operation. For this

purpose the Bite and Squeeze Unit shown in figure 5 is provided and may be

used to apply and measure squeeze forces.

In addition to the use of a desired squeeze force to operate a childproof closure in its normal manner, it has been found that children

may attempt to open containers by biting or squeezing even when such a method of opening is not desired or contemplated by the manufacturer. The

ability of a child to so open a closure constitutes a failure. It may

therefore be desirable to measure squeeze forces necessary to open (or

destroy the childproof feature) of containers not designed for such

opening, and this may also be done with the Bite and Squeeze Unit.

3.3.0 Measurement Value Criteria

In measuring the forces necessary to open a childproof closure, and

in establishing exact criteria for recording measurement values it will be

necessary for the investigator to make a judgement or to establish criteria

based on the normal operation of the closure. For example, in measuring

the characteristics of a push and turn closure, it is possible to apply and

measure a very large range of push forces on the closure. In general,

11
there will be a range of push forces which will be insufficient to operate

the closure, and a range of push forces which will be more than sufficient

to operate the closure. The desired value, the critical value of force, is

the value which is just sufficient to operate the closure. This value

will be marked by an abrupt change in the torque necessary to rotate the

closure, and it is this change in torque which enables the operator to

determine the critical value (minimum operating value) of the push force.

In other types of closures other criteria will be necessary to determine

the critical forces which are desired. Depending on the types of closures

these criteria may be a force change, a torque change, or a change in some visual characteristic. In all cases, the selection of the criterion should

be based on the normal operation of the closure.

3.4.0 Environmental Considerations

3.4.1 Temperature

Most closures are temperature sensitive, and for this reason the

ambient temperature of the test is quite significant. Closures may also

undergo gradual dimensional distortion or "creep", the exact amount

depending on time, temperature and pressure conditions. For this reason

the temperature of the closures and their containers should be known and

reproducible. Also, handling the closure may change its temperature and

hence its critical characteristics.

3.4.2 Humidity

Some closures may be sensitive to humidity as well as to

temperature. For this reason, tests should be conducted under known

humidity conditions. It may be anticipated that if a closure is senitive

to humidity there will probably be a lag effect, so that the effect of

exposure to a particular humidity will persist for an appreciable time

after the humidity is changed.

3.4.3 Operating Interval

Because many of the materials used in closures are subject to the

phenomenon of "cold flow" or "memory" the operating characteristics of the

closure may depend on the time interval between operations, and this factor

itself may well vary with ambient temperature. Where this phenomenon

exists it may have a very substantial effect on the operating

characteristics of the closure. Conceivably a closure might be acceptable

if tested at intervals of an hour and might not be acceptable if tested at

operating intervals of five minutes or of a day. Where this phenomenon is

encountered a careful evaluation of the way in which it will affect the

closure operating characteristics must be made. Test procedures must then

be designed to take this into account.

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3.5.0 Specific Test Procedures

3.5.1 Test Procedures for Specific Closures

Specific test procedures should be written for each model of

closure, based on experience with that model, and keeping in mind the

operating principles (with especial emphasis on the factors which are basic

to the childproof feature) and the methods, if any, which could be used to

defeat the childproof feature. All procedures, in addition to specifying

the critical measurements and parameters and the methods of measurement,

should call for recording the manufacturer's type, mold number, material,

environmental conditions, storage time, and type of contents. Where it is

suspected that the contents may influence operation of the closure, testing

should be performed on samples which contain materials in the condition and

of the type normally found in such container-closure combinations.

3.5.2 Types and Test Methods

While the writing of test procedures for each closure type (closurecontainer combination) is beyond the scope of this report, general

principles applicable to some of the container types which have been

studied are discussed below.

3.5.3 Motions and Forces

A number of generalized childproof closure types together with the

forces which are applied to operate them, are illustrated in the

accompanying sketch (figure 2) and are further defined in figure 4 by type

and sub-type. Suggested generalized test procedures are also listed. It

should be realized that this list is by no means complete.

As can be seen from the figures, the closures can be classified

according to the general type of closure and the childproof feature. Many

require two coordinated motions, or the application of two coordinated

forces, but others do not. To a large extent, it is this diversity that

introduces the major testing problems. Test methods must be directed to

the measurements of the normal forces required to operate these closures,

as well as the forces necessary to defeat the childproof feature. The

three basic forces applicable to the designs illustrated are push or pull,

turn, and squeeze.

3.5.4 Two Independent Motion Closures

A widely used class of closures is known as Two Independent Motion

closures. These closures may be either thread or lug types, and their

operation in general involves an overcap and an inner cap. In the

unoperated condition the outer cap spins freely, and the inner cap seals

the container. Operation is achieved by either pulling or pushing the

13
outer cap so that it locks into the inner cap and is able to turn it.

Critical characteristics are the force necessary to engage the outer cap

with the inner cap and the torque necessary to turn the outer cap after

engagement in order to open the combination. Recorder plots of vertical

force against torque have proven to be very useful in evaluating the

characteristics of this type of closure.

3.5.5 Turn and Lift Snap Caps

A common type of closure is the "turn and lift" snap cap. These

caps are molded of a flexible material and snap over a projecting lip on

the closure. They are operated by turning the cap until some feature is

properly aligned, at which time an upward or downward force can be applied

to remove the cap. Critical forces are the force required to rotate the

cap to its aligned position and the upward force required to remove it.

For some styles a critical force might be the force required to remove the

cap when it is in its unaligned position, or the force required to remove

it in an undesired fashion. The recorder can be used to record the torque

and the force in both cases.

3.5.6 Squeeze and Turn Caps

The squeeze and turn type requires squeezing the sides of the cap in

order to turn and remove it. Testing requires measuring the squeeze force

necessary to turn the cap as well as the torque necessary for a given

squeeze. This measurement is made using the Bite and Squeeze unit in

connection with the Force-Torque table. The Bite and Squeeze unit is

applied to the cap and tightened to apply the squeeze force in the desired

place on the cap. The squeeze unit is tightened while squeezing the cap

and watching the torque indicator. When the torque reading increases

sharply, the squeeze force is becoming effective, and its reading should be

noted at the point where the inner cap just begins to rotate, or at the

highest point previous to rotation. Recorder plots of squeeze force

against torque are useful in this type of measurement.

4.0 MAINTENANCE INSTRUCTIONS

4.1.0 Theory of Operation

4.1.1 General Considerations

The NBS Closure Testing Equipment is an assembly of units for

measuring and recording the forces involved in the removal and replacement

of closures on containers, specifically child resistant containers. The

equipment uses strain gages mounted on cantilever beams to transform the

mechanical forces involved into accurately proportional electrical signals,

which are then amplified, displayed, and recorded by the remainder of the

14
equipment. Both mechanical and electronic considerations are involved in

the maintenance and repair of the equipment.

An overall block diagram of the equipment is shown as figure 9. It

should be noted that the equipment can be divided into two groups, one group containing the primarily electronic items, i.e. the Electronic Unit

and the X-Y Recorder; and the other group containing the Force-Torque

Table, the Squeeze and Bite Unit, and the Pry and Shell Unit and the

Squeeze Unit. This second group is primarily electromechanical in nature.

4.1.2 Electronic Unit

The function of the Electronic Unit is to receive, process and

display the signals generated by the force transducers of the Force-Torque

Table and the specialized units. These signals are amplified and displayed

on the digital indicators of the Electronic Unit and made available for

recording by the X-Y Recorder. As snown in the block, diagram, the

Electronic Unit is composed of several sub-units, as follows:

a. Amplifier-Power Supply Units

b. Indicator Units

c« Sweep Unit

d. Peak. Reading Unit

e. Power Supply Units

These sub-units, together with their interconnecting wiring, switches, etc.

make up the Electronic Unit. The detailed functioning or each of these

sub-units is considered below.

a. Amplifier-Power Supply Units. The Amplifier-Power Supply

Units, A-l, A-2, and A-3 may be conveniently considered

as two separate sections, the power

supply section and the amplifier section. The circuit

diagram of these units is shown as figure 11. The

power supply section is composed of a rainaturized, highly

isolated power supply operating from the 117-volt line.

The output of this supply is regulated at 10.0 volts and

is used as the supply voltage to the strain gage bridges.

Two highly precise, low temperature coefficient 350 ohm

resistors serve as the inactive arras of the strain gage

bridge, and connect to the zeroing potentiometer (1.15

ohms) mounted on the front panel of the Electronic Unit.

(These resistors are used only in the "Special" channel

position). Two filter capacitors are used to bypass the

power supply output.

15
The amplifier section uses an encapsulated instrumentation

amplifier to amplify the strain gage output signal to

give a calibrated reading on the digital indicators

and the recorder output. Details of this instrumentation

amplifier are given in the parts list. Supply voltages

are derived from an external plus and minus 15-volt power

supply. Input protection and output stabilising

resistors and capacitors are incorporated in the circuit.

The gain of the amplifier is set by an adjustable gain resistor

which is mounted on the front panel of the Electronic

Unit and is selected by the range switch for the particular

amplifier unit.

b. Indicator Units. The digital indicator units are each 3-1/2

digit panel meters which are fed from the output of the

amplifier section through the Peak Reading Unit switch and a range

switch which provides for a short position and also selects

the appropriate decimal point as well as the gain resistor.

Basic sensitivity of the meters is 199.9 mV, full scale.

Reading rate is set at approximately 10 readings per second.

Details of these indicator units are given in the parts

list. The operating power for these units is derived from

a 5.0 volt, 3.0 ampere power supply.

c. Sweep Unit. The sweep unit functions to provide a ramp

voltage to one axis of the X-Y Recorder when it is

desired to move the recorder steadily along one axis while

recording a variable on the other axis. Its circuit diagram is shown as figure 13. A panel mounted function

control switch provides three settings: (1) Off (reset),

(2) Hold, and (3) Sweep. The sweep circuit is a standard

operational amplifier linear integrating circuit, using

an FET operational amplifier and a polystyrene integrating

capacitor. Integrating current is fed from the negative supply

through a high resistance. The output voltage is limited

to 10 volts.

d. Peak Reading Unit. The Peak Reading Unit may be switched

into any of the three signal channels (Force, Torque, or Special) by means of its front panel control switch, and

functions to preserve the digital panel meter reading of

the highest meter reading occurring during a selected

time interval. This circuit is primarily intended for use when making tests where the recorder is not to be used

and the main quantity of interest is a peak force or torque. The peak reading circuit is reset after the peak

reading is noted and will then function to preserve the

next peak reading occurring in the circuit.

16
The circuit diagram of this unit is shown as figure 12.

The circuit consists of two FET operational amplifiers in an overall feedback, configuration, with a peak, catching

diode and reset feature. Power required is supplied by

the plus and minus 15 volt power supply unit (see below).

e„ Power Supply Units. The dc power required by the

Electronic Unit is supplied by two unit power supplies

One of these supplies 5 volts at 3 amperes, and the

other supplies plus and minus 15 volts at 50 milliamperes.

Details of these power supplies are given in the Parts List.

4.1.3 X-Y Recorder

The X-Y Recorder provided as part of this equipment is a commercial item modified to make variable gain settings

reproducible (though not linear). Recordings are made with re- placeable pens on sheets of 8-1/2 x 11" graph paper. Wide range gain

and zero controls provide a high degree of flexibility. However, care must be taken to observe the calibration changes resulting when

any of the scale factors are changed. Full details of this unit

are given in the accompanying instruction book.

4.1.4 Force-Torque Table

The Fcrce-Torque Table is a table whose motion

is restrained by the two cantilever beams which give the force

measurements. The electrical circuit of the Force-Torque Table is

shown as figure 14. The strain gages are cemented to the cantilever

beams and transform the forces exerted on the beams to changes in

electrical resistance.

4.1.5 Bite and Squeeze Unit and Pry and Shell Unit

These are force measuring devices using the same cantilever

beam method of force measurement as is used in the Force-Torque

Table. Their circuit diagram is shown in figure 14, and the circuitry

differs from that of the Force-Torque Table only in that the zeroing

controls and reference bridge arm resistors are mounted in the

Electronic Unit.

4.2.0 Maintenance

4.2.1 Electronic Unit

The Electronic Unit does not require maintenance.

17
4.2.2 X-Y Recorder

The maintenance of the X-Y Recorder is covered by the

separate manual supplied with it.

4.2.3 Force-Torque Table

The electrical portion of the Force-Torque Table should

require no maintenance. The bearings which insure free movement

of the platform should be kept clean and lubricated. In dusty

or adverse environments this unit should be kept covered when not

in use. Freedom of movement of the platform should be checked at

regular intervals, the length of which will depend on environmental

conditions, and if any excessive friction develops the bearings

should be cleaned and lubricated.

4.2.4 Bite and Squeeze Unit and Pry and Shell Unit

The remarks made above apply to these units as well.

4.3 Repair and Trouble Shooting

4.3.1 Electronic Unit

Normal electronic trouble shooting procedures apply to this

unit. Most problems are likely to be encountered either with socket

connections or from the failure of one of the electronic units.

The modular construction of the unit should assist in isolating

such problems.

18
APPENDIX

Parts List*

Ae Major Units

E-l Electronic Unit NBS Manufacture (Ref. Fig. 9)

Consists of Chassis Assembly plus sub-units (Ref. Fig. 10) as follows:

A-10, A-ll, A-12 Amplifier Sub-Units. NBS Manufacture

(Ref. Fig. 11) See parts list below.

1-1, 1-2, 1-3 Indicator Sub-Units. Newport Laborato-ies,

Inc. Model 253-01 3-1/2 Digit Panel Meter Model 253-02,

199.0 nV full scale, high input impedance, 10 per second

read rate, 300 volt overdrive, power supply 5.0V at 2.5 watts.

PR-10 Peak Reading Sub-Unit. NBS Manufacture (Ref. Fig. 12)

See parts list below.

PS-1 Power Supply Sub-Unit. Semi-Conduc tor Circuits, Inc.

Model 2.15.50, Regulated plus and minus 15 volts, at 50 nA

dc output, input 117V 60 Hz.

PS-2 Power Supply Sub-Unit. Power-Tec Div. of Airtronics,

Inc. Model 2B5-3, output 5.0 volts, dc regulated, at 3. OA,

input 117V 60 Hz.

SW-10 Sweep Unit. NBS Manufacture (Ref. Fig. 13)

See parts list below.

B-l Bite and Squeeze Unit. NBS Manufacture (Ref. Fig. 14)

See parts list below.

F-l Force-Torque Table. NBS Manufacture (Ref. Fig. 14)

See parts list below.

P-l Pry and Shell Unit. NBS Manufacture (Ref. Fig. 14)

See parts list below.

R-l X-Y Recorder Unit. MFE Corp., Model 715 "Plotamatic" flat

bed, 11" x 17" X-Y recorder. Power input 117V 60 Hz.

See separate manual.

* Precise identification of some parts as to manufacture has been made in

order that an exact replacement can be obtained in the event of failure.

Such identification in no way implies superiority to equivalent

components nor unique effectiveness over other possible choices.

19
B. Assembly and Sub-Units

E-l Chassis Assembly

F-l, F-2 Power line fuses, Type 3AG, 1.5 amperes

PL-1, Pilot light, 5.0V, LED type

R-l Special Channel Zeroing Resistor, 10 turn potentiometer, 1.15 ohms

Amphenol Type 205

R-2 Gain Control Resistor, 16.0k, 1% metal film, T.C. less than

10 ppm/deg C, 1/4 watt

R-3 Gain Control Resistor, Same as R-2 except 2.15k

R-4 Gain Control Resistor, Same as R-2 except 63.5k

R-5 Gain Control Resistor, Same as R-2 except 104k

R-6 Gain Control Resistor, Same as R-2 except 19.5k

R-7 • Gain Control Resistor, Same as R-2 except 19.5k

R-8, R-9, R-10, R-ll Decimal Point Resistors, carbon, 5.1k,

10% 1/4 watt

R-12, R-14, R-16 Gain Control Trimmer Resistors, lk metal film

25 turns, T.C. 10 ppm typical, Vishay Resistor Products

Style 1201P

R-13, R-15, R-17 Same as R-12 except 10k

SW-1 Range Selector Switch, Force, three pole, three position

rotary, ceramic, miniature

SW-2 Range Selector Switch, Torque, Same as SW-102

SW-3 Range Selector Switch, special, Same as SW-102

SW-4 Power Switch, single pole, single throw, toggle, miniature

SW-5 Recorder Channel Selector Switch, single pole, five

position rotary switch

20
A-10 Amplifier Sub-Unit

A-201 Instrunentation Amplifier, type AM-200C, Datel Systems

Incorporated. High input impedance, high CMRR, low drift, power

supply plus and minus 14 to 19 V at 7mA.

C-201, C-202 Power Supply filter capacitors. Electrolytic,

25 microfarad at 15 volts, miniature.

C-203 Output filter capacitor. 1.0 microfarad polystyrene or polycarbonate film, 80 volts dc

C-204, C-205 Power Supply filter capacitors for Instrumentation

Amplifier. Electrolytic, 25 microfarad at 25 volts, miniature.

PS-201 Bridge Power Supply. Output 10 V at 100 mA, input 117 V

60 Hz, miniaturized, output highly isolated. Acopian Corp. type 10E12

R-201, R-202 Bridge Balancing Resistors. 350.00 ohms 0.01%

temp, coefficient less than 1 ppm/deg C. Vishay Resistor Products type S-102

R-203, R-204 Amplifier Input protection resistors. 10k, 1/4 W

±0% carbon

R-205 Amplifier Trimming Resistor. 10k, Metal Film, 25 turns,

T.Cc 10 ppm, Vishay Resistor Products Style 1201P.

> R-206 Amplifier Trimming Resistor. Metal film type, temp, coefficient

less than 10 ppm/deg C, 1/4 watt, selected with R-205 set to 5000 ohns

R-207 Output stabilizing resistor. 10 ohms, 1/4 watt, 10% carbon

R-208 Output stabilizing resistor 20k, 1/4 watt, 10% carbon

PR-10 Peak Reading Sub-Unit

A-301 Operational Amplifier, general purpose type, FET input.

Analog Devices, Inc. type 40J

A-302 Same as A-201

C-301 Integration Capacitor, 2.0 microfarad, 50 volts dc, polycarbonate

film, Cornell-Dublier type.WCR05WZ or equal

D-301, D-302 Blocking Diodes, Fairchild 1N3333

R-301 Summing Resistor, precision metal film 10k, 1/4 watt, 1%

R-302 Grounding Resistor, 2k, 10% carbon 1/4 watt

21
R-303 Feedback Resistor, 10k, 1% precision metal film 10k, 1/4 watt

R-304, R-305 Trimmer Resistor, lk metal film 25-turn, 10 ppm/deg C,

Vishay Resistor Products style 1201P

SW-301 Selector switch, rotary, 6 poles, 4 positions

SW-302 Polarity Switch, SPDT, dry circuit type (gold plated contacts)

SW-303 Reset Switch, pushbutton, N.O. dry circuit type (gold plated

contac ts)

ST-10 Sweep Unit

A-401 Operational Amplifier, Same as A-301

C-401 Integrating Capacitor, 10 microfarad at 200 volts, polystyrene

film.

R-401 Integrating Resistor: 50 megohms, 1/2 watt, 5%

R-403 Stabilizing Resistor 2k, 10% 1/4 watt, carbon

R-404 Output Divider Resistor, 1.2 k 10% 1/4 watt, carbon

R-406 Trimming Resistor, same as R304

SW-401 Sweep Selector Switch, DPDT, center off, dry circuit

(gold contacts) miniature, Alcoswitch model MTA-106F

F-l Force-Torque Table

R-501 Force Zeroing Potentiometer. Same as R-l

R-502 Torque Zeroing Potentiometer. Same as R-501

R-503 Bridge Balancing Resistor, 350.00 ohms, 0.01% Same as R-201

R-504 Bridge Balancing Resistor. Same as R-503

R-505 Bridge Balancing Resistt r. Same as R-503

R-506 Bridge Balancing Resistor. Same as R-503

SR-501 Strain Gage, 350 ohms, 1/16" temp, coefficient 13 ppm/deg C.

Gage factor 2.1, Micro-Measurements type CKA-13-062 VW-350

SR-502 SR-503, SR-504. Strain gage, same as SR-501

22
B-l Bite and Squeeze Unit

SR-601, SR-602 Strain Gage, same as SR-501

P-l Pry and Shell Unit

SR-701, SR-702 Strain Gage, same as SR-501

USC0MM-N8S-DC 23


Closure Operating Forces

Figure 2.

i

a. Push and Twist b. Pull and Twist

I

d. Center Push e. Pull tab

/

f. Squeeze and Lift

Q

Center Push

Edge Lift

/

h. Hold and Turn

Figure 4. List of Safety Closure Types

Type Subtype Symbol

Threaded cap Random push and twist A-l

Threaded cap Random pull and twist A

Threaded cap Localized push and twist A

Threaded cap Localized pull and twist A

Threaded cap Random squeeze and twist A

Threaded cap Localized squeeze and twist A

Threaded cap Key device A

Threaded cap Two hand twist A

Lug cap Random push and twist B-l

Lug cap Random pull and twist B-2

Lug cap Localized push and twist B-3

Lug cap Localized pull and twist B-4

Lug cap Random squeeze and twist B-5

Lug cap Localized squeeze and twist B-6

Lug cap Ring position B-7

Snap cap Alignment and pull C-l

Snap cap Alignment and push C-2

Snap cap Center push C-3

Snap cap Spot push C-4

Snap cap Center push and edge lift C-5

Snap cap Hinged tap and lift C-6

Snap cap Squeeze and lift C-7

Aerosol overcap Squeeze and lift D-l

Aerosol overcap Hold and lift D-2

Aerosol overcap Hold and turn D-3

Aerosol cap Turn and orient D-4

Aerosol cap Sequential push D-5

Aerosol cap Finger insert D-6

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U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. pubLk ation ok repor r no. MBSIR 75-722

2. Ciov't Accession

No.

3. Recipient's Accession No.

4. TITLIf AND SUBTITLE

Closure Testing Eouipment

Instruction Manual

5. Publication Date October 1975

6. Performing Organization Code

7. AUTHOR(S)

Malcolm S. Morse

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATICINAI RIIRFAII (IF CT AN DAPD^

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City. State*, ZIP)

Consumer Product Safety Commission

5^01 West bard Ave.

Bethesda, Maryland 20016

13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

T5. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less {actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

The MBS Closure Testing Equipment is designed to make accurate

measurerrents of the critical parameters of the "childproof"

closures required by the Poisoning Prevention Packaging Act of

1971. In general, these parameters are defined as the forces

necessary to open these closures, either in the manner by which

the closure was designed to be opened, or in an undesired manner.

This manual discusses the design and construction of the testing instrument and gives detailed instructions for its operation.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Bottle caps; child protection; .closure testing; containers

medicine bottles; poison packaging

18. AVAILABILITY [X Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

I For Official Distribution. Do Not Release to NTIS

UNCL ASSIFIED 42

Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20 )02. SD Cat. No. ( M

20. SK( URITY CLASS

(THIS PAGE)

22. Price

Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED 4.00

USCOMM.DC 29042-P74