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Patent 1328890 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 1328890
(21) Application Number: 616238
(54) English Title: OSCILLATING AND LOCKING APPARATUS AND METHOD FOR VIBRATING TRAY WEIGHING SCALE
(54) French Title: ORGANE DE MISE EN OSCILLATION/VERROUILLAGE ET METHODE D'UTILISATION SUR BALANCE A PLATEAU VIBRANT
Status: Deemed expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 265/5
(51) International Patent Classification (IPC):
  • G01G 3/16 (2006.01)
(72) Inventors :
  • HUBBARD, DAVID W. (United States of America)
(73) Owners :
  • PITNEY BOWES INC. (United States of America)
(71) Applicants :
(74) Agent: MACRAE & CO.
(74) Associate agent:
(45) Issued: 1994-04-26
(22) Filed Date: 1989-01-06
Availability of licence: Yes
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
141,443 United States of America 1988-01-07

Abstracts

English Abstract


OSCILLATING AND LOCKING APPARATUS AND METHOD
FOR VIBRATING TRAY WEIGHT SCALE

Abstract of the Disclosure
Oscillating and alternatively locking apparatus and
method of determining the mass of an article by the shift of
the period of oscillation of a flexibly mounted platform. An
article whose mass is to be determined is placed upon the
platform. The platform is caused to oscillate and the period
of harmonic motion is calibrated. This period is compared
against the period of harmonic motion when there is no
article upon the platform, and the difference, or shift, in
frequency, allows a determination of the mass of the article.
A reversible motor is used to provide drive to a conveyor for
transporting mail pieces onto the tray and for causing
oscillation of the tray for purposes of weighing.


Claims

Note: Claims are shown in the official language in which they were submitted.




THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A weighing scale comprising:
a base;
an article supporting tray having a finger
projecting therefrom;
at least one flexible member connecting said tray to
said base;
a transducer operatively connected to said flexible
member;
an arm pivotally connected to said base and
engageable with said finger;
said arm being operative to move said finger thereby
causing said tray to oscillate and generate kinetic energy in
said one flexible member.
2. The weighing scale of claim 1 wherein said
finger has an abutment portion and said arm has a shoulder
that are engageable whereby when said arm is in a first
position said tray is locked.
3. The weighing scale of claim 2 wherein said one
flexible member has potential energy therein when said tray
is locked.
4. The weighing scale of claim 3 wherein upon said
arm being pivoted in a first direction said finger and said
arm are disengaged from one another, said finger is moved to
a second position and said potential energy in said one
flexible member is converted to kinetic energy thereby
causing said tray to oscillate.
5. The weighing scale of claim 4 wherein said arm
has an angular bearing surface adjacent said shoulder to
contact said finger and urge said finger toward said shoulder



21
to move said finger from said second position to said first
position as said arm is pivoted in a second pivotal
direction.
6. A scale comprising:
a frame;
a base;
at least one spring connecting said base to said
frame;
a shaft rotatably supported by said frame;
an article supporting tray;
at least one flexible member connecting said tray to
said base;
a transducer attached to said at least one flexible
member;
a motor supported by said frame;
a pulley disposed upon said shaft;
a belt providing drive between said motor and said
pulley;
a cam mounted on said shaft;
a link rotatably supported by said base and having a
cam follower in engagement with said cam; and
a finger depending from said tray and engageable
with said link, whereby upon rotation of said shaft said link
responds to said cam to interact with said finger to cause
oscillation of said tray.


Description

Note: Descriptions are shown in the official language in which they were submitted.


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This invention relates to weighi~g scales and, in
particular, weighing scales which oscillate the article
supporting tray. This application is a divisional
application of applicant's copending application Serial
No. 587,682 filed January 6, 1989.
~ s technology progresses, processes tend to proceed at a
faster pace. Most processes require the coordination of a
number of components, and the process can only proceed as
fast as the slowest component allows unle~s multiple like
components are used. There are certain processes in which
the weight of an article is required, but -to date no scale
has been available that provides accurate, fast weighing. By
accurate is meant the ability to weigh an object having a
weight of up to 32 ounces within l/32 of an ounce. By ~ast
is meant the ability to weigh a stream of conveyed articles
within less than one second per article. ~ process where
there is a need for fast weighing is in the processing of
mail. High speed systems have been developed whereby the
appropriate number of inserts, which number may vary from
envelope to envelope, are placed within an envelope. The
envelope is sealed and postage is printed on the envelope.
Before the postage can be printed, howevqr, it is necessary
that the weight of the mail piece be determined. Heretofore,
weighing devices for such mail processing systems have been
developed, but these generally have been rather slow.
Actually, many prior weighing devices combined a standard
scale with a mechanism that would stop the mail to allow
weighing to take place. In order to accommodate ~he output
of an inserter, multiple scales would be used with alternate
mail pieces diverted to such scales.
Mucll effort has been expended in trying to develop a
weighing scale that meets the heretofore enumerated goals.
One weighing scale that has been found highly successful in
this endeavor is described in co-pending patent application
entitled APPARATUS AND METHOD OF DETERMINING THE MASS OF AN
AR'rICLE BY MEASURING THE SHIFT IN THE PERIOD OF HARMONIC
MOTIOW, filed July 6, 1988 and having Serial No. 57l,282

1 1 328890
the scale described in the co-pending application, as well as
others of its type require a fast, efficient method of
; feeding locking the various components when articles are
.~ being conveyed onto the tray of the scale and for releasing
and vibrating the tray during the weighing operation.
Specifically, the invention relates to a weighing
; scale comprising: a base; an article supporting tray
having a finger projecting therefrom; at least one
~1 flexible member connecting the tray to the base; a
¦ 10 transducer operatively connected to the flexible member;
an arm pivotally connected to the base and engageable
with the finger; the arm being operative to move the
finger thereby causing the tray to oscillate and generate
kinet~c energy n ~e one flexible member.




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Thus, a unique locking and oscillating device has been
conceived for a scale utilizing the principles of harmonic
vibration for the purposes of determining the weight of an
article. A flexibly mounted tray has a finger depending
therefrom that contacts an angled surface. In one occurrence
the tray is caused to oscillate. From -the frequency of the
oscillation the mass of an article on the tray can be
determined. ~fter the mass is determined the finger can be
engaged by a different part of the angled surface to lock the
-tray.

Brief Description of the Drawin~s
Fig. 1 is a perspective view o~ a scale that
incorporates the instant invention;
Fig. 2 is an exploded perspective view showing selected
parts oE the scale shown in Fig. l;
Fig. 3 is a cross-sectional longitudinal view of the
scale shown in Fig. 1;
Fig. 4 is a plan view taken along the lines 4-4 of Fig.
3;
Fig. 5 is an end view taken along the lines 5-5 in Fig.
4;
Fig. 6 is a cross-sectional view of a fle~ure member
that is part of the scale shown in Fig. 1:
Fig. 7 is a side eleva-tional view taken along the lines
7-7 of Fig. 4;
Fig. 8 is a side elevational view taken along the lines
8 8 of Fig. 4;
Fig. 9 is a side elevational view taken along the lines
9-9 of Fig. 4;
Fig. 10 is a side elevational view taken along the lines
10-10 of Fig. 4;
Fig. 11 is a block diagram of the circuitry employed
within the scale shown in Fig. 1;
Fig. 12 is a block diagram of the components of the
electronic controller shown in Fig. 11;

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; Figs. 13a-13b are graphs that show a single pulse
applied to the weighing device, a plot of the output
generated by a transducer as a result of the oscillation, and
a square wave form of the output, respectively; and
Fig. 14 is a flow chart describing the steps involved in
i measuring the mass of an article.

, Detailed Descri~etion of the InventlonWith reference to Fig. 1, a weighing scale that
incorporates the instant invention is shown generally at 12
and includes a housing 13 that is open at the top 14. The
components contained wi-thin the housing 13 are shown in Figs.
2-10, and, with reference to Fig. 2, include a frame 18 that
is attached to the floor of the housing and supports four
, uprights 16. To each upright 16 a leaf spring 20 is attached
3 15 by means of a cap 22 that is bolted to the upright with a
portion of the leaf spring therebetween. It will be noticed
that the leaf springs are formed at an angle and have a lower
portion that is adjacent to one of two laterally extending
plates 24. The angle of the leaf spring is preferably
between 5' and 15' relative to the ver-tical. The springs 20
are bolted to the plates 24 by a cap 26, the lower portion of
the springs being located between the caps 26 and the plates
24. In this way the two plates 24 are supported by the frame
18 through the springs 20 to be isolated therefrom.
Secured to each of the plates 24 are a pair of flexible
members 30 having a general parallelogram configuration, the
details of whose structure is shown in Fig. 6. Each flexible
member 30 has a pair of opposed sides 32. A transducer 33 is
secured to at least one of the sides 32 of one of the
flexible members 30. This transducer may be a device such as
a piezoelectric device such that a voltage is generated in
~ accordance with the bending of the transducer. The flexible
J:: members 30 have a pair of openings 34 at the bottom thereof
that receive bolts 36 that extend through the plates 24 to
7~ 35 thereby secure the flexible members to the plates. The
~ flexible members 30 also have an opening 38 at the top
t thereof that are in registration with openings 42 within a

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tray 40. The tray 40 is attached to the flexible members 30
as by bolts 41 that are received within the openings 38 of
the fle~ible members. The tray 40 also has a longitudinally
extending opening 44 therein. The tray 40 is in the form of
an inverted dish with a honeycomb configuration shown
generally at 46 so as to provide light weight to the tray 40.
Four uprights 48 are attached to the two plates 24 and
mounted thereon is a base 50 having generally "T" shaped
members 52 with dependent portions 54 attached thereto. The
purpose of the T shaped members 52 and dependent portions is
to increase the weight of the base 50. With reEerence to
Figs. 3, two pairs of opposed brackets 60 are supported by
the base 50 and each pair of brackets supports a pin 52
-therebetween. An idler pulley 64 is rotatably mounted on
each of the pins 62. With reference to Figs. 3 and 5, a pair
of opposed brackets 66 are supported by the frame 18 and each
bracket has a bearing 68 therein that receives a shaft 70
that is thus supported by the opposed brackets. A pulley 72
is disposed upon the shaft 70, there being a one way bearing
74 between the pulley 72 and shaft 70 thereby allowing the
pulley to be free wheeling relative to the shaft when the
pull~y is rotated in one direction, i.e~ no drive will be
transmitted therebetween, but the shaft will be driven by the
pulley when the pulley is pulley driven in the opposite
direction. The pulley 72 has a sleeve portion 76 about which
another pulley 78 is mounted with a one way bearing 80
therebetween. The one way bearing 80 will be opposite in
terms of functional direction to that of the one way bearing
74 so that when the pulley rotates in the clockwise
direction, as seen in Fig. 3, the one way bearing 80 will
provide drive between the pulley 72 and pulley 78 but when
the pulley 72 is driven in the counter clockwise direction,
pulley 78 is free wheeling and no drive is transmitted
therebetween.
A bracket 82 mounts a reversible motor 84, there being a
pulley 86 secured to the output shaft 88 of the motor. A
belt 90 is trained about the pulleys 72,86 to provide drive
to the pulley 72.

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~ 1 328890
A stepped bracket 94 is mounted to the tray 40 and
supports a light 92. A photodetector 95 is located
immediately below the tray 40 there being an opening within
the tray for light to pass through. The detector is in
alignment with the light 92 so as to sense the presence of an
object therebetween. The bracket 94 supports a plurality of
shafts 96 to which paired arms 98 are attached, there being
pins 100 extending between and joining the paired arms, each
pin supporting a idler roller 102. A tension spring 104 is
supported by each of the shafts 96, the tension spring having
a first tang 106 that abuts the bracket 94 and a second tang
108 that is in engagement with the upper part of one of the
paired arms 98. With this construction, the arms 98 are
biased towards the tray 40. A pair of arcuat skis 110 are
located on each of the paired arms 98. A mail piece 112 in
the form of an envelope is shown in Fig. 3 in a position in
which its weight would be determined by the weighing scale
12.
With reference to Figs. 4 and 8, two pairs of stanchions
114 are located opposite one another in a paired relationship
and connected by a shaft 116 that is supported fixedly by
each pair of stations 114. Rotatably supported by each shaft
116 are a pair of generally L-shaped arms 118 that are joined
together by a connector 120. Secured to each connector 120
is a follower 122. The upper portions of the arms 124 are
rotatably supported by pins 126 that are received within a
pair of brackets 128. The brackets 128 are connected to one
another by shafts 130 that rotatably receive intermediate
rollers 132 and end rollers 134, the latter being slightly
larger. Each of the brackets 128 has an elongated slot 136
therein that receive the shaft 116 thereby allowing movement
of the brackets relative to the shaft. A pair of cams
138,140 are mounted on the shaft 70, one of the cams 140
being in engagement with the cam follower 122. A stanchion
141 having a longitudinal extending opening 142 therein
slidably receives a rod 144 within such opening. The rod 144
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1 3288qO
is in engagement with the cam 138 at one end, and a follower
122 of an arm 118 at its other end. A tension spring 146 is
secured to opposed pairs of arms 118 for the purpose of
urging the followers 122 against the cam 140 and rod 144,
respectively.
Referring now to Figs. 4 and 7, the frame 18 has mounted
, thereon an abutment 152. The shaft 70 fixedly supports a cam
154 that has a large diameter portion 156 and a small
diameter por-tion 158. Disposed about the shaft 70 is a
~ 10 spring 160 having one tang 162 that is received within an
j opening 164 of the cam, and another tang 166 that is received
within the opening 168 of the stanchion 66. The spring
rotates the cam 154 and the shaft 70 in the clockwise
direction as seen in Fig. 7 to thereby urge the cam portion
~ 15 156 against the abutment 152.
`~ With reference to Figs. 5 and 9, the scale 12 has amechanism 169 responsive to the shaft 70 for locking and
initiating oscillation that includes a cam 170 that has an
opening 171 therein with a first camed surface 172 and a
second camed surface 174, the cam 170 being mounted on the
¦ shaft 70 for rotation therewith. A support 176 is located on
the base 50 and a shaft 178 is attached to this support. A
generally V shaped link 180 is mounted about the shaft 178
with a friction bearing 179 located therebetwesn. The
function of the friction bearing is to create a resistance to
movement on the part of the link 180 so that force is
required to rotate the link about the shaft. The generally V
shaped link 180 has a first arm 182 and a second arm 184, the
`I latter having a cam follower 186 at the end thereof that is
received within the opening 171. The first arm 182, has a
projecting portion 188 that has an angular bearing surface
190 with a shoulder 192 at the end thereof. A finger 194
depends from the tray 40 and has a rectangular abutment
member 196 that is engageable with the projection 188 to lock
the tray 40 to the base 50. The rest position of the tray 40
as a result of the flexible members 30 is such that the
abutment portion would be located at a position midway of the
angular bearing surface 190.

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Referring now to Figs. 5 and 10, a locking mechanism 198
is provided for locking the tray 10 during the periods when
objects to be weighed are transported onto the tray and
releasing the tray 40 during oscillation. A lambda (upper
case) shaped stanchion 200 is supported by the frame 18 and
has a pin 202 extending therefrom. A generally Z shaped link
204 is rotatably supported by the pin 202 and has a first leg
206, and a second leg 207, the latter having an opening 208
therein. A post 210 is supported by the frame 18 and a
tension spring 212 extends from the opening 208 to the post
210 to urge the arm link 204 in a counter clockwise
direction. A Eirst leaf spring 214, preferably made of
stainless stèel is supported by and extends from the
stanchion 200 towards and is in spaced relationship with the
second leg 206. A finger 216 depends from the base 50 and
supports a second leaf spring 218 that extends intermediate
the first leaf spring 214 and the stanchion 200 so as to lock
the base 50 as a result of the force applied by the leg 206
resulting from the biasing effect of the spring 212. Mounted
on the shaft 70 is a cam 220 for rotation therewith. This
cam 220 engages the link 204 as the shaft 70 rotates to
overcome the effect of the spring 212 and urge the link in a
clockwise direction and disengage the leg 206 from the leaf
spring 214, thereby unlocking the base 50 from the frame 18.
Referring now to Fig. 11, a controller 221, the details
of which are shown in Fig. 12, is in communication with a
computer 222 that has a switch 224 for connecting the scale
with line power and a display 226 where the weight of an
object that is determined by the scale will be shown. The
electronic controller 221 is in electrical communication with
the photosensor 95, the drive motor 84 and the piezoelectric
33.
The components of the electronic controller 130 are
shown in Fig. 12 and include a band pass filter 228 that
receives the output from the piezoelectric transducer 33 and
is connected to a zero crossing detector 230. The band pass
filter 228 eliminates high frequency electrical noise and low
frequency mechanical noise from the signal received ~rom the




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s
~ piezoelectric transducer 33. In electrical connection with
s, the band pass filter 228 is the zero crossing detector 230
which converts the signal received from the band pass filter
to a square wave. The zero crossing detector 230 is in
electrical connection with an edge detector 232 that detects
the edge of each square wave produced by the zero crossing
, detector. The edge detector 232 is in electrical connection
with a flip-flop 234 that receives an input from a AND gate
236. The AND gate 236 is in connection with the computer 222
and a counter 238 that has input from a clock 240 and the
edge detector 232. A one shot vibrator 241 is in connection
with a flip-flop 242 and with the photosensor 95. The flip-
~ flop 242 is in communication with the computer 222. Thus, as
¦ a mail piece 112 is sensed by the photosensor 33, the one
shot vibrator 241 will send a pulse to the flip-flop 242
which in turn will communicate to the computer 222 the
presence oP a mail piece. Alternatively, after a mail piece
112 is conveyed away from the tray 40 to no longer be sensed
by the photosensor 33, the one shot 241 will again pulse the
flip-flop 242 to signal the computer 222.
! In operation, power is supplied to the scale 12 by
enabling the switch 224 located on the computer 222.
Although the switch is shown on the computer 222, it is
apparent that this is not critical in any convenient means
may be used for providing power to the scale 12. With power
supplied to the system, the motor 84 will be caused to drive
in a clockwise direction thereby rotating the pulley 72
through the belt 90. With rotation of the pulley 72, the
pulley 78 will be rotated due to the presence of the one way
bearing 80. The pulley 78 is driven in a clockwise direction
as seen in Fig. 3 thereby driving the belt 148. With the
belt 148 being driven, the pulley 64 and the drive rollers
134 will also be driven. The smaller rollers 132 act as
support for the belt 148 as it moves within the opening 44 of
the tray 40.



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1 328890
It will be noted that as the belt 148^is being driven,
the shaft 70 is static. This results from the presence of
the one way bearing 74 which allows the shaft 70 to remain
free wheeling within the rotating pulley 72 when the latter
is driven in the clockwise direction. With the shaft 70
being static, the tray 40 is locked to the base 50 because of
the locking oscillating mechanism 169 and the base 50 is
locked to the frame 18 because of the locking mechanism 198.
When a mail piece 112 is to be weighed, it is placed upon the
tray 40 at the location of the belt 44 and conveyed between
~he belt and the idler rollers 102. Because of the biasing
action of the springs 104 upon the arms 98, the rollers 102
will engage a mail piece 112 and urge it against the belt 148
until such time as the mail piece envelope 112 comes between
the light 92 and photosensor 95. Upon this occurring, the
photosensor 95 will send a signal to the computer 222
indicating the presence of the envelope 112. Upon this
occurring, the computer 222 will cause the electronic
controller to reverse the angular rotation of the drive motor
84 from clockwise to counter clockwise. This counter
rotation will be for only a 180 rotation of the motor output
shaft 86.
With the motor 84 rotating in the reverse direction
180, the drive to the belt 148 will be terminated and the
sha~t 70 will be rotated 180. This results from the pulley
72 being rotated in the opposite direction 180 thereby ~
allowing the pulley 78 to be free wheeling due to the `
presence of the one way bearing 80. Meanwhile, the one way
bearing 74 will transmit drive from the pulley 72 to the
shaft 70. With such rotation of the shaft, the spring 1~0
will be overcome and the cams 138,140, the cam 154 and the
cam 170 will also be rotated hal~ a revolution.
With reference to Fig. 8, Fig. 8A shows the posture of
the brackets 128 and the rollers 132,134 that are supported
thereby when the motor 84 is continuously driving in a
clockwise direction. This is the posture in which a mail
piece 112 will be transported across the tray 40 by the belt
148. As the motor 88 rotates in an opposite counter




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1 3288~0
clockwise direction half a revolution, the cams 138 and 140
are rotated by the shaft 70 so as to assume the position
shown in Fig. 8B. In this posture the cams 138,140 are
rotated so that their sur~aces are driven away from
engagement with the rod 144. With this occurring, the
tension spring 146 will pull upon the opposed paired arms 118
towards one another to thereby urge one of the cam followers
122 against the cam surEace 140 and the other cam follower
122 against the rod 44. With this occurring, the rod 144
will move to maintain engagement with the cam 138, to the
left as seen in Fig. 8, and the arms 118 will be rotated in
unison with the shaft 116 with the opening 136 thereby
causing the bracket 128 to move downwardly. The presence of
the elongated slot 136 in the arms bracket 128 provides the
space required for such movement. As the bracket 128 is
pulled down by the action of the arms 114, it carries
therewith the belt 148 and the accompanying rollers 132,134
out of the opening 44 of the tray. With reference to Figs. 3
and 5, upon this occurring, the springs 90 will urge the arms
98 downwardly thereby urging the rollers 102 against the mail
piece 112 and the skis 110 against the mail piece at the
location of the tray 40. When in the drive condition, the
belt 148 was located within the slot 44, the rollers 102
engaged the mail piece so as to cooperate with the drive
thereof and the skis 110 were at a location slightly above
the envelope. With the belt 148 removed f rom the opening 44,
the rollers 102 will engage the mail piece at the location of
the opening, the skis 110 will hold the mail piece against
the tray 40. In this way, the mail piece 112 is held firmly
against the tray 40 during oscillation of the tray as will be
de.scribed hereinafter so that an accurate weight can be made.
Obviously, if the envelope experiences any movement during
oscillation, an inaccurate weighing would not be obtained.
With reference to Fig. 10, upon rotation of the shaft
70, the cam 220 will be rotated in the counter clockwise
direction and engage the link 204. This will cause the link
204 to be rotated about the pin 202 in a clockwise direction
thereby disengaging the first leg 206 from the leaf springs
214,218 and unlocking -the base 40 from the frame 18.

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1 328~90
Referring now to Figs. 5 and 9, when the tray 40 is in
the posture assumed when the motor is rotating in a clock~ise
- direction, the cam 170 is in the position as shown in Fig.
~, 9A. In this position, the tray 40 is locked to the base 50
by the presence of the arm 182 engaging the finger 194. More
specifically, the shoulder 192 will receive the abutment
member 196 and hold it firmly. It will be recalled that the
spring 160 urges the opening 171 against the cam follower 186
to rotate the link 180 in a clockwise direction. As the
- 10 shaft 70 is rotated a half revolution by the motor 84, the
cam 170 begins to rotate in the counter clockwise direction
as shown in Fig. 9A and the cam follower 186 will ~ollow the
first surface 172 until such time as it comes to the end o~
the opening whereupon the arm 182 will be rotated about the
shaft l78 in the counter clockwise direction, thereby
releasing the finger 194. More specifically, the rectangular
, abutment member 196 will lose engagement with the shoulder
¦ 190 thereby causing the tray 140 to oscillate as a result o~
; the tray 40 seeking its rest position. After a weighing has
taken place, and the shaft 70 is rotated to its original
position, as a result of the motor rotating the pulley 76
clockwise to release the shaft and the spring 160 rotating
the shaft 70 half a revolution clockwise. The cam follower
! 186 Will now follow the contoured surface 174 to thereby urge
the arm 182 into a clockwise direction. With this occurring,
the rectangular portion 196 will slide along the angle
portion 188 thereby urging the tray 140 to the right as shown
in Fig. 9 and away from its rest position until such time as
the abutment member 196 once more is cradled into the
shoulder 190. In this position of the tray 40, the flexure
members 32 are flexed slightly to apply a force on the tray
to the left as seen in Fig. 9 so that the tray will oscillate
upon being released by the locking and oscillating member 169 ::~
as just described.
With the tray 40 oscillation created as described
hereto~ore, the ~lexure members 30 will be flexed and a
voltage will be generated by the piezoelectric transducer 33.
This voltage plotted relative to time will produce a

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1 328~qO
sinusoidal curve as shown in Fig. 13a. It will be noted that
the flexure members 32 have a parallelogram configuration
with the arms 32 parallel to one another. This is
advantageous over having a single flexure member for the
reason that when such a flexure member bends, it experiences
a displacement that is non-linear relative to the stress in
the transducer. This results with a frequency that is
amplitude dependent. This is a disadvantage because using an
amplitude dependent frequency to determine weight cannot be
controlled very well. With the flexure member 30 having
parallel arms 32, as shown in Fig. 6, the top of the flexure
member, as well as the tray 40, moves generally parallel so
that it does not exert a torque on the tray. The tray 40
does move to a somewhat lower position when the flexure
members 30 bend, but this is not a particular problem. With
a single flexure member, there is a slight bend of the tray.
This slight bend contributes to spring constant of the scale
and since the tray is not a good elastic material, there is a
deterioration of the ability to determine the weight of an
object or the tray.
Upon oscillation of the tray, the transducer 33 will
send the single as indicated in Fig. 13 and the weight will
be determined.
~fter the shaEt 70 has been rotated a half revolution by
the motor as described, the tray 40 is unlocked for the base
50 and the base is unlocked for the frame 18. the plates 24
are suspendingly supported by the leaf springs 20 to the
frame to thereby isolate the base from vibrations experience
by the base. Angular leaf springs have been found to be
advantageous because they inhibit lateral movement of the
base 50 while still providing the required isolation.
The manner of determining weight will now be describedO
With the tray 40 having no mail piece 112 thereon, the motor
84 is actuated to drive the belt 90 half a revolution in the
reverse direction. This causes the first arm 18~ to
disengage from the finger 194 to occasion oscillation of the
tray 40 as described previously with the reference to Fig. 9.


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~ ` I 328890
The tray 40 will oscillate in the same horizontal direction
as the mail pieces 112 are to be conveyed, i.e,, in the plane
o~ the tray, left and right as seen in Fig. 3. This is
preferable otherwise the mail pieces 112 may tend to bounce.
As the flexible member 30 with the transducer 33 thereon is
flexed and continues to oscillate, the transducer will output
an alternating voltage that will have a frequency depending
upon the mass of the tray 40 and anything secured thereto.
It will be noted that the tray 40 has the idler rollers 102
and the mechanisms for supporting the idler rollers attached
thereto and is part of the mass that influences the
frequency. As the tray 40 oscillates, its oscillation is
measured by the transducer 33 as an output voltage as shown
in Fig. 13. When the tray 40 is first oscillated, the
sinusoidal curve is not symmetric and at least one cycle is
required before a uniform curve is obtained. Consequently, a
delay is required before measurements can be taken, this
delay being programmed into the computer 222 and is
approximately 0.024 secs. ~fter the delay, the frequency, or
period, of ~ero crossings is determined by the electronic
controller 221. After the frequency of zero crossings is
determined, an article such as an envelope or mail piece 112
is placed upon the tray 40. This is accomplished by first
supplying power to the motor 84 and other components by
closing the switch 222. Therea~ter a mail piece 112 is
placed upon the tray 40 by any standard mail piece conveying
means until it is received within the nip of the belt 112,
and the first idler roller 102~ The mail piece 112 will then
be driven onto the tray 40 by action of the belt 112 and
rollers 102 and will be sensed by the photosensor 95. Upon
the mail piece 112 being sensed, the drive motor 84 will be
rotated half a revolution in the opposite direction and the
brackets 128 lowered, as described previously with reference
to Fig~ 8, thereby lowering the belt 148 below the plane of
the tray 40. As the brackets 128 are pulled down ~rom the
tray 40, the belt 148 becomes disengaged from the mail piece
112 that is located upon the tray 40. In this state the tray
40 will have a new mass, which now includes the mass of the

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'.` ' , '' . , : :


'',S"' ~ '

~ 1 328890
mail piece 112. It will be appreciated that the mail piece
112 will be held securely upon the -tray 40 because the
rollers 102 will be lowered slightly into the opening 44 and
the skis 110 will press the mail piece 112 against the tray
as a resul-t of the biasing action of the springs 104 so the
mail piece and tray 40 will move as a unit.
With the mail piece 112 on the tray 40 in its weighing
position, i.e., under the rollers 102, the locking and
oscillating mechanism 1~9 will once more be enabled causing
the tray 40 to oscillate, as described previously, in the
same horizontal plane and direction as the mail piece 112 is
transported. This oscillation will be sensed by the
transducer 92 and the period of oscillation will be measured
as described previously. From this, one will be able to
determine the mass of the mail piece 112 located upon the
tray 40 in accordance with the formula:

ME = Cl (T2 - To2) + C2 ~T2 _ ~o2)2, (1)

where ME is the mail piece 112 mass, To is the period of
oscillation with no mail piece and T is the period with the
mail piece present upon the tray 40. To~ Cl and C2 are
constants which depend on the mass of the base 50, and the
mass of the tray 40 as well as on the spring constants of the
isolation springs 20 and the flexible supports 30. These
constants are determined empirically in a calibration
procedure in which the periods are determined for at least
two different masses as well as for the empty scale. In the
limit that the base 50 is substantially heavier than the mass
of the tray 40 plus the mass of the mail pieces 112, the
constant C1 is given by the formula:

30Cl - K / (4~2), (2)

where K is the spring constant of the flexible supports 30.
In the same limit To is given by the formula:


- 15 -

.: :
,., . .
,.~ .
... .
,,. ,, . - .

- 1 328890

To2 - ~4~2) Mp/K~ (3)

where Mp is the tray 40 mass.

When a spring is attached to two isolated masses m and M, its
period of oscillation is
T2 = 4 ~ ~ / X. (4)
where ~ is the reduced mass:
~ = m M / (m + M). (5)
In the limit where M is much larger than m, the reduced
mass is less than and close to the value of m. Equation (4)
can be solved for m in terms of T. In the scale 12, the base
50 mass M is much larger than m, the combined tray 40 and
mail piece 112 mass however, due to the accuracy required,
the difference between ~ and m must be taken into accountO
This is done by combining equations 4 and 5.
There are other corrections to the period due to the
fact that the system is damped slightly and due to the fact
that the base 50 is attached to the frame 18 through the
isolation springs 20. The system is further complicated by
the fact that the attempt to determine the period is done
through measurements of the first few periods of oscillation. ~-
During this time, some initial transients due to the initial
pulse are occurring. As a result, it can be said that the
mass is a non-linear function of the period squared with the
leading non-linearity given by equations 4 and 5. It has
been observed empirically that the non-linearity can be
approximated by a parabola represented by equation 1.
The mass is determined by the circuitry shown in Figs.
11 and 12. The computer 222, which may be any of a number of
standard commercially available computers such as a Compaq
Model 286 PC, is in communication with the electronic
controller 221. The transducer 33 will output a voltage that
is filtered by the band pass filter 228 and applied to the
zero crossing detector 230 which is basically an operational
amplifier that saturates at five volts to output a square
wave as shown in Fig. 13b. The duration of the square wave
yields the time between zero crossings which is determined by

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~: : , . . , : :

. . . . . .

1 328~90

the edge detector 232. The edge detector 232 outputs a pulse
when each edge of the square waves is detected, which of
course, represents zero crossings. These outputs are sent to
the counter 238 that counts the clock cycles between zero
crossings and sends count signals to the AND gate 236. The
flip-Elop will then send zero crossing signals to the
computer 222. ~ased upon this count, the computer ~22 will
then compute the mass of the mail piece 112 through an
algorithm that allows computation by application of the above
formulas. This computed mass is then shown on the display
226 or sent to a postage setting device of a postage meter
such as a Model 6500 postage meter available from Pitney
¦ Bowes Inc.
Upon completion of weighing, the computer will disable
the motor 48 thereby providing no power to the belt 90. With
¦ this occurring, with reEerence to Figs. 4, 5 and 7, the
spring 160, which is overcome during the half revolution
drive of the motor 84 will act upon the cam 154 to rotate the
shaft in a counter clockwise direction as shown in fig. 7.
With the rotation of the shaft in a counter clockwise
direction, the cams 138,140 will rotate it so as to act upon
one pair of arms 114 and the rod 144 will push against the
arms 114,115 to rotate them about the shafts 116 thereby
lifting the brackets 1~8 and causing the belt 148 to be
inserted once more into the opening 44 of the tray 40.
With this same rotation of the shaft 70 caused by the
spring 160, the cam 170 will rotate and thereby cause the
link 180 to be rotated in a clockwise direction as seen in
Fig. 9. ~s this occurs, the rectalinear abutment member 96
of the finger 194 slides upon the incline portion of the
projection 188 thereby urging the tray 140 to -the right as
shown in Fig. 9. This continues until the rectangular
abutment portion 196 falls into the shoulder 190 and is
secured thereby. In this position, the tray 140 i5 slightly
to the right relative to its neutral position so that the
flex members 30 are under tension. In this way, when the
link 180 is lifted, oscillation will occur as described
previously.

- 17 -

:y ~ -




,~'~` '' ,.

1 328890
~nother activity that is taking place at this time
results from the action of the cam 220 upon the link 204. As
the shaft 70 is rotated in the counter clockwise direction,
the cam is rotated so that it loses engagement with the link
204. With this occurring, the tension spring 222 causes the
link 204 to pivot about the pin 202 in a counter clockwise
direction and the first leg 206 will press the leaf springs
212,218 between it and the vertically extending portion of
the stanchion 200. With this occurring, the base 50 becomes
loc~ed once more to the frame.
All of the movements described heretofore are in
response to the presence of the one way bearing 74 that
allows the shaft to be uneffected by drive of the pulley 72
when the motor is rotated in a first direction, but allows
drive of the shaft 70 when the pulley is driven in the
opposite direction so that the cams 138,140,170 and 220 are
driven thereby. In addition, one way bearing 80 allows the
pulley 78 to be rotated by the pulley 72 when the latter is
driven in the first direction, but provides for free wheeling
of the pulley 78 when the pulley 72 is driven in the second
rotational direction. The final element in the design is the
presence of the spring 160 that will return the shaft, and
all its components, to the original position after the motor
is disabled.
The flow chart of Fig. 14 describes the overall
operation of the weighing scale 12. Mail pieces are conveyed
250 across the tray 40 and the electronic system is
initialized 252. The display is set up 254 and an inquiry
made whether the first mail piece has passed 260. If the
first mail piece has passed, the system waits for the
envelope to reach a proper position 252. Upon the envelope
reaching its proper position, a reverse command signal is
sent to the motor controller 264. The system waits for the
motor to drive half a revolution and the motor is shut down
268. At this point the start time is stored 270, which is
followed by delay 272. The counters are clear 274 and,
again, followed by a delay 276. The zero crossings are
cleared 278 and an inquiry made if the crossings are ready

- 18 -



,, :

-
,,.:: . . ,
., ~ ` ' `~ ' ' . ~ , :

1 ~28~qO
280. If yes, the crossing ready bit is cleared 282, and the
zero crossing is enabled 284. An inquiry is made as to
whether this is the last zero crossing 286, if not, the
sequence of crossing ready is repeated, but if so, the weight
of the envelope is determined. After the weight of the
envelope is determined, the motor is start to run the
envelopes once more, and the results displayed 298. The mail
piece sensor is reset 300, an inquiry is made is whether this
is the last mail piece. If it is not the last mail piece,
then the process of weighing is repeated once more.
Using the method described above, one is able to obtain
quite accurate determinations of the mass of articles placed
upon the tray 40. The accuracy is better than 1/32 of an
ounce for mail pieces up to 32 ounces. Not only does one
obtain an extremely accurate measurement of the mass, but it
can be done in a rapid fashion. It has been found that a
single mail piece 112 in a stream of mail pieces can be
transported onto the tray ~0, stopped, weighed and ejected in
about 325 milliseconds. Overlapping entry of the next mail
piece 112 simultaneously with ejection of the preceding one
provides for weighing at the rate of 184 mail pieces per
minute. This represents a significant advance in the
weighing of articles in terms of cost, performance and
simplicity of electronics over prior weighing devices.
~, ,




-- 19 --




" ~

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 1994-04-26
(22) Filed 1989-01-06
(45) Issued 1994-04-26
Deemed Expired 2000-04-26

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Registration of a document - section 124 $0.00 1989-03-09
Application Fee $0.00 1991-11-27
Maintenance Fee - Patent - Old Act 2 1996-04-26 $100.00 1996-03-19
Maintenance Fee - Patent - Old Act 3 1997-04-28 $100.00 1997-03-19
Maintenance Fee - Patent - Old Act 4 1998-04-27 $100.00 1998-04-08
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
PITNEY BOWES INC.
Past Owners on Record
HUBBARD, DAVID W.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Description 1994-09-03 19 1,072
Drawings 1994-09-03 10 418
Claims 1994-09-03 2 77
Abstract 1994-09-03 1 32
Cover Page 1994-09-03 1 60
Representative Drawing 2002-05-08 1 15
PCT Correspondence 1994-01-19 1 19
Fees 1997-03-19 1 48
Fees 1996-03-19 1 45