U.S. patent number 3,721,209 [Application Number 05/187,405] was granted by the patent office on 1973-03-20 for developing unit for electrostatic copying apparatus.
Invention is credited to Karl Hartwig, Gunter Maurischat, Gunter Schnall, Roland Szostak, Jurgen Vossnacke.
United States Patent |
3,721,209 |
Szostak , et al. |
March 20, 1973 |
DEVELOPING UNIT FOR ELECTROSTATIC COPYING APPARATUS
Abstract
An electrostatic copying apparatus wherein a driven xerographic
surface which carries electrostatic latent images receives
developer material from the buckets of a conveyor which is normally
driven in a first direction but can be driven in a second direction
to thereby retract the foremost filled bucket away from a dumping
position. The conveyor is driven by a reversible electric motor
which is automatically started in reverse in response to
deenergization of a relay and is automatically arrested after a
predetermined interval of operation in reverse to thus insure that
the contents of filled buckets on the conveyor are unlikely to
spill into the copying apparatus when a carriage which supports the
conveyor and a magazine for developer material is moved to and from
a retracted position. The circuit of the motor is opened by a
switch which is held in closed position by a power train between
the conveyor and the motor when the conveyor is driven in the first
direction. The switch is caused to open in response to such
operation of the power train that the conveyor is driven in the
second direction.
Inventors: |
Szostak; Roland (Grunwald,
DT), Hartwig; Karl (Unterhaching, DT),
Maurischat; Gunter (Munich, DT), Schnall; Gunter
(Munich, DT), Vossnacke; Jurgen (Pullach,
DT) |
Family
ID: |
5784641 |
Appl.
No.: |
05/187,405 |
Filed: |
October 7, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Oct 9, 1970 [DT] |
|
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P 20 49 650.8 |
|
Current U.S.
Class: |
399/53; 118/636;
222/DIG.1 |
Current CPC
Class: |
G03G
15/0896 (20130101); Y10S 222/01 (20130101) |
Current International
Class: |
G03G
15/08 (20060101); B05c 011/00 (); G03g
013/00 () |
Field of
Search: |
;118/2,3,4,6,7,8,636,637,DIG.24 ;222/DIG.1,76,63 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stein; Mervin
Assistant Examiner: Millstein; Leo
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims:
1. In an electrostatic copying apparatus, a combination comprising
a driven xerographic surface; a developing unit including a
support, a source of flowable developer material provided on said
support, conveyor means mounted on said support and actuatable to
move in a first direction and to thereby deliver developer material
from said source to said surface and in a second direction at least
substantially counter to said first direction, and reversible drive
means for said conveyor means; and control means for said drive
means comprising a reversing device including a member movable
automatically upon leaving a first position in which said drive
means is operated to move said conveyor means in said first
direction to assume a second position in which said drive means is
operated to move said conveyor means in said second direction, and
arresting means for terminating the operation of said drive means
with a predetermined delay following the movement of said member of
said reversing device to said second position thereof.
2. A combination as defined in claim 1, wherein said support is
movable with reference to said xerographic surface to and from an
operative position in which the developer material delivered by
said conveyor means can reach successive increments of said
surface.
3. A combination as defined in claim 1, wherein said conveyor means
comprises an endless flexible element having a plurality of
receptacles arranged to discharge developer material onto said
xerographic surface when said drive means moves said flexible
element in said first direction.
4. A combination as defined in claim 3, wherein said predetermined
delay is such that a receptacle which is about to discharge
developer material is moved to a material retaining position in
response to movement of said flexible element in said second
direction.
5. A combination as defined in claim 1, wherein said drive means
comprises a portion which moves in one direction when said drive
means moves said conveyor means in said first direction and in
another direction when said drive means moves said conveyor means
in said second direction, said arresting means comprising follower
means which is engaged by said portion of said drive means and
arrests said drive means in response to movement of said portion of
said drive means in said other direction.
6. A combination as defined in claim 5, wherein said drive means
comprises a reversible prime mover and a power train connecting
said prime mover with said conveyor means, said portion of said
drive means forming part of said power train.
7. A combination as defined in claim 6, wherein said portion of
said drive means comprises a plurality of entraining elements for
said follower means.
8. A combination as defined in claim 1, wherein said drive means
comprises a reversible electric motor and said reversing device
comprises a two-way electric switch in circuit with said motor,
said switch having first and second fixed contacts and a movable
contact which respectively engages said first and second contacts
when said motor is respectively operated to move said conveyor
means in said first and second directions.
9. A combination as defined in claim 8, wherein said control means
further comprises relay means actuatable to assume first and second
conditions and to thereby respectively effect a movement of said
movable contact into engagement with said first and second fixed
contacts.
10. A combination as defined in claim 9, wherein said reversing
device further comprises means for permanently biasing said movable
contact into engagement with said second fixed contact.
11. A combination as defined in claim 1, wherein said drive means
comprises a prime mover and a power train connecting said prime
mover with said conveyor means, said power train including a
portion arranged to move in one direction during movement of said
conveyor means in said first direction and in another direction
during movement of said conveyor means in said second direction,
said arresting means comprising a microswitch and a follower
extending into the path of movement of said portion of said power
train and arranged to maintain said microswitch in a first
condition in which the microswitch permits the operation of said
prime mover during movement of said portion of said power train in
said one direction and to cause said microswitch to assume a second
condition with said predetermined delay following the start of
movement of said portion of said power train in said other
direction whereby said microswitch effects a termination of
operation of said prime mover.
Description
BACKGROUND OF THE INVENTION
The present invention relates to improvements in electrostatic
copying apparatus, and more particularly to improvements in that
unit or component of an electrostatic copying apparatus which
supplies flowable developer material to a driven xerographic
surface to thereby convert electrostatic latent images on such
surface into powder images.
It was already proposed to mount various parts of the developing
unit in an electrostatic copying apparatus on a carriage or another
suitable support which is movable with reference to the driven
xerographic surface to and from an operative position. The parts of
the developing unit include a source of developer material (such
material preferably consists of electroscopic toner particles which
are mixed with a suitable granular carrier) and a conveyor which
delivers developer material from the source to the driven
xerographic surface whereby the thus delivered toner converts
electrostatic latent images on the xerographic surface into powder
images which are thereupon transferred onto a sheet or web of paper
or other transfer material and are fused to such transfer material
to obtain permanent copies of the originals.
The conveyor of the developing unit is preferably (but not
necessarily) a bucket type conveyor wherein an endless flexible
element carries a series of fixedly mounted or pivotable
receptacles in the form of buckets which remove developer material
from the source and discharge their contents onto the driven
xerographic surface at a transfer station. In accordance with a
prior proposal, the bucket type conveyor is driven by a reversible
motor which can be actuated to change the direction of movement of
the conveyor prior to transport of the carriage from its operative
position. Such movement of the bucket type conveyor in reverse is
intended to prevent one or more filled buckets which dwell at or
immediately upstream of the transfer station from discharging their
contents into the copying apparatus during movement of the carriage
from its operative position. Unnecessary dumping of developer
material results in contamination of the copying apparatus as well
as in losses in toner particles and carrier granules. In accordance
with he aforementioned prior proposal, the motor for the bucket
type conveyor must be reversed by hand, and such manipulation can
also result in unlatching of the carriage so that the latter is
free to move or to be moved from its operative position. The
operation of the motor in reverse (i.e., in a direction to move the
buckets of the conveyor in a direction which is necessary to
prevent the foremost filled bucket or buckets from discharging
their contents during movement of the carriage from its operative
position) is terminated with a delay which is normally selected by
the attendant. It was found that such mode of controlling the
operation of drive means for the conveyor is not sufficiently
reliable because the foremost receptacle or receptacles are still
likely to discharge their contents in response to movement of the
carriage from its operative position, for example, if an attendant
forgets to start the motor in reverse or if the operation in
reverse is not terminated prior to movement of the carriage from
its operative position.
SUMMARY OF THE INVENTION
An object of the invention is to provide an electrostatic copying
apparatus with a novel and improved developing unit wherein the
conveyor which serves to deliver developer material from a source
to the driven xerographic surface is less likely to unnecessarily
spill developer material prior to and during transport of the
developing unit from its operative position than in presently known
copying apparatus.
Another object of the invention is to provide an electrostatic
copying apparatus with a novel and improved control system which is
capable of automatically reversing the direction of movement of the
conveyor for developer material when the movement of the conveyor
in the normal or forward direction is terminated and which insures
that the movement of the conveyor in reverse is terminated with a
delay which is necessary to insure that the conveyor is least
likely to unnecessarily spill developer material onto the
xerographic surface and/or onto or into other parts of the copying
apparatus.
A further object of the invention is to provide a control system
which embodies the above outlined features and which can be
incorporated in presently known electrostatic copying apparatus
without necessitating extensive changes in the construction and/or
mounting of the developing unit.
The invention is embodied in an electrostatic copying apparatus
which comprises a driven preferably drum-shaped xerographic
surface, a developing unit including a support which is preferably
movable to and from an operative position with reference to the
xerographic surface, a source of flowable solid developer material
provided on the support, conveyor means mounted on the support and
actuatable to move in a first direction to thereby deliver
developer material from the source to the xerographic surface and
in a second direction at least substantially counter to the first
direction, and reversible drive means which is preferably mounted
on the support and can move the conveyor means in the first or
second direction, and novel control means for the drive means. The
control means comprises a reversing device (e.g., a device
including a two-way electric switch which is controlled by a relay)
a portion of which is movable between a first position in which the
drive means is operated to move the conveyor means in the first
direction and a second position in which the drive means is
operated to move the conveyor means in the second direction, and
arresting means for terminating the operation of the drive means
with a predetermined delay following the movement of the movable
portion of the reversing device to its second position. The
arrangement is preferably such that the movable portion of the
reversing device automatically assumes its second position when it
is caused to leave the first position so that the reversal in
direction of movement of the conveyor means from the first to the
second direction and the termination of movement in the second
direction take place in automatic response to movement of the
movable portion of the reversing device from its first
position.
If the conveyor means comprises a bucket type conveyor, the
movement in the second direction is terminated with such a delay
that the foremost filled bucket is invariably caused to assume a
position in which its contents cannot be spilled or dumped when the
xerographic surface is arrested and/or when the support for the
source and conveyor means is moved from and thereupon to its
operative position with reference to the xerographic surface.
The novel features which are considered as characteristic of the
invention are set forth in particular in the appended claims. The
improved copying apparatus itself, however, both as to its
construction and its mode of operation, together with additional
features and advantages thereof, will be best understood upon
perusal of the following detailed description of certain specific
embodiments with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary schematic partly elevational and partly
sectional view of an electrostatic copying apparatus having a
developing unit which embodies the invention; and
FIG. 2 is an enlarged elevational view of a detail in a modified
developing unit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, there is shown a portion of an
electrostatic copying apparatus (also called xerographic developer
apparatus) which comprises a frame or housing 1 supporting the
shaft 2 of a drum-shaped xerographic surface 3 (hereinafter called
drum). The periphery of the drum 3 is provided with a layer of
photoconductive insulating material on a conductive backing, and
this drum travels repeatedly past a series of xerographic
processing stations in a manner well known from the art of
electrostatic copying apparatus. FIG. 1 merely shows the developing
station for a novel developing unit which is controlled by a novel
control system. The drum 3 is assumed to rotate in a
counterclockwise direction, as viewed in FIG. 1, and its
photoconductive layer is assumed to be provided with an
electrostatic latent image prior to travel past the developing
station so that the latent image can be converted into a powder
image which is thereupon transferred onto a sheet or web of paper
or other transfer material and is fused to such transfer
material.
The developing unit comprises a support 7 here shown as a carriage
which is provided with wheels 4, 5 serving to travel along one or
more guide rails 6 provided therefor on the frame 1 so that the
carriage 7 can move with reference to the drum 3 to and from the
illustrated operative position in which two idler rollers 8, 9 of
the carriage abut against the periphery of the drum 3. The carriage
7 is normally held in the illustrated operative operative position
by a spring-biased retaining member or latch 50 which can be moved
in the direction indicated by the arrow to thereby allow retraction
of the carriage 7 from its operative position by way of a handle
10. The direction in which the carriage 7 is movable from the
illustrated operative position is indicated by an arrow A.
The carriage 7 supports a magazine, hopper or an analogous source
14 of flowable solid developer material 14a. This material consists
of electroscopic pulverulent toner mixed with a suitable granular
carrier. The size and color of toner particles depend on the
intended purpose; such particles normally consist of an
electroscopic resin and a colorant such as an organic or inorganic
pigment or dye. The carrier granules attract toner to their
surfaces.
The carriage 7 further supports a bucket type conveyor 13 which
serves to deliver developer material 14a from the source 14 to the
periphery of the drum 3 at a transfer station 51 which is shown as
being adjacent to the idler roller 8. The conveyor 13 comprises one
or more endless flexible chains or belts 13a which are trained over
sprocket wheels or pulleys 11, 12 and carry a series of equidistant
receptacles in the form of buckets 13b. Successive buckets 13b are
filled with developer material 14a at the lower end turn of the
conveyor 13 (i.e., in the region of the sprocket wheel or pulley
12) and their contents are discharged onto the peripheral surface
of the drum 3 at the upper end turn of the conveyor 13, i.e., at
the transfer station 51. A dispenser 15 for toner particles is
mounted on the carriage 7 above the upwardly travelling stretch of
the chain or belt 13a to discharge toner into successive
receptacles 13b whereby the toner particles are attracted to the
carrier granules. The lower end portion of the dispenser 15
accommodates a rotary brush 16 which discharges accurately metered
quantities of toner through one or more outlet orifices 15a whereby
the stream or streams of toner particles descend onto successive
batches of developer material 14a in the upwardly moving filled
receptacles 13b. The purpose of the dispenser 15 is to guarantee a
satisfactory toner concentration (i.e., a desirable ratio of toner
particles to carrier) which is best suited to insure acceptable
quality of developed images on the transfer material. If there is a
deficiency of toner in the developer material which is being
transported toward the transfer station 51, the areas of the
electrostatic latent image will be unable to attract sufficient
toner to fully develop the powder image. If there is an excess of
toner particles in the filled receptacles 13b, the image areas will
become overly dark because toner particles are likely to adhere to
non-image areas.
The developing unit of the copying apparatus shown in FIG. 1
further comprises a drive means for the conveyor 13. Such drive
means comprises a prime mover M, here shown as a reversible
electric motor which is preferably mounted on the carriage 7, and a
power train 17 which connects the output shaft 52 of the motor M
with the shaft for the sprocket wheel or pulley 12. The electric
circuit of the motor M comprises two power leads 28, 33 connected
with a plug 53 which is automatically coupled to an outlet 54
constituting a source of A-C current when the carriage 7 assumes
the operative position of FIG. 1. The plug 53 is disconnected from
the outlet 54 in response to movement of the carriage 7 in the
direction indicated by the arrow A.
The power train 17 comprises a portion 18 (here shown as an endless
flexible belt or chain) which is movable in a first direction
(arrow B) to thereby drive the chain or belt 13a of the conveyor 13
in a first or forward direction (arrow D) so that the receptacles
13b travel from the source 14, below the outlet or outlets 15a of
the dispenser 15, and toward the transfer station 51 where their
contents are caused to cascade over the peripheral surface of the
driven drum 3. The belt or chain 18 is further movable in a second
direction (arrow E) to thereby drive the chain or belt 13a of the
conveyor 13 in a direction indicated by the arrow F. During
movement of the chain or belt 13a in the direction of arrow F, a
filled receptacle 13b which is located at or immediately upstream
of the transfer station 51 is moved rearwardly (i.e., downwardly as
indicated by the arrow F) so that it safely retains its contents
during movement of the carriage 7 in and thereupon counter to the
direction indicated by the arrow A. This reduces the likelihood of
contamination of the copying apparatus with developer material and
unnecessary losses in toner particles and carrier granules during
movement of the carriage 7 to and from an inoperative or retracted
position in which the source 14 and dispenser 15 are readily
accessible for refilling with developer material 14a and toner
particles.
The control system for the drive means of the developing unit
comprises a reversing device 55 for the electric motor M and an
arresting device 56 which automatically terminates (with a
predetermined delay) the operation of the motor M in reverse,
namely, such operation of the motor M that the belt or chain 18 of
the power train 17 is driven in the direction indicated by the
arrow E. The arresting device 56 includes an electric switch having
a movable contact 20 which is pivotable at 19 and a fixed contact
21 which is engaged by the movable contact 20 when the belt or
chain 18 of the power train 17 is driven in the direction indicated
by the arrow B. The movable contact 20 of the arresting device 56
constitutes a follower which extends into the path of movement of
the righthand stretch of the chain or belt 18 and is urged against
the fixed contact 21 when the belt or chain 18 moves in the
direction indicated by the arrow B. When the direction of movement
of the chain or belt 18 is reversed so that the latter moves in the
direction indicated by the arrow E, a certain interval of time
elapses before the movable contact or follower 20 is caused to
assume the illustrated position in which the switch 20, 21 is open
and the motor M is disconnected from the current source 54.
The aforementioned reversing device 55 comprises a two-way electric
switch which is connected in series with the switch 20, 21 of the
arresting device 56. The switch of the reversing device 55
comprises a movable member or contact 27 which can engage a first
fixed contact 27a or a second fixed contact 27b. A helical spring
42 normally biases the movable contact 27 to one of its two
positions, for example, toward engagement with the fixed contact
27b. The contact 27 can be moved into engagement with the fixed
contact 27a in response to energization of a relay 36 which is
connected to a source 57 of electrical energy (e.g., 24 volts) by
conductors 38, 39 and 40. A switch 41 (which may constitute the
master switch of the copying apparatus or is mechanically connected
with such master switch) must be closed in order to energize the
relay 36 and to thereby maintain the movable contact 27 in the
illustrated position in which the motor M operates in a forward
direction to drive the chain or belt 18 of the power train 17 in
the direction indicated by the arrow B. The reference characters
29, 30, 31, 32, 34, 35, 37 denote conductors which connect the
switches 20, 21 and 27, 27a, 27b with each other and with the power
leads 28, 33.
THE OPERATION
In order to start the chain or belt 13a of the conveyor 13 in the
direction indicated by the arrow D, the attendant must move the
carriage 7 to the illustrated operative position (in which the
idler rollers 8, 9 engage the periphery of the driven drum 3 and
the plug 53 is operatively connected with the current source 54)
and the switch 41 must be closed to energize the relay 36 and to
thus maintain the movable member or contact 27 of the reversing
device 55 in engagement with the fixed contact 27 a. The circuit of
the motor M is then completed by way of the power lead 28,
conductor 29, contacts 27, 27a, conductors 37, 35, 34 and power
lead 33. The motor M drives the chain or belt 13a of the conveyor
13 in the direction indicated by the arrow D, i.e., the chain or
belt 18 of the power train 17 is driven in the direction indicated
by the arrow B. The right-hand stretch of the chain or belt 18
closes the switch of the arresting device 56 by causing the movable
contact 20 to pivot at 19 in a counterclockwise direction, as
viewed in FIG. 1, and to engage the fixed contact 21. Such closing
of the switch 20, 21 has no effect on the operation of the motor M,
as long as the movable contact 27 engages the fixed contact 27a of
the two-way switch of the reversing device 55. The receptacles 13b
of the conveyor 13 draw developer material 14a from the source 14
and transport such material (arrow D) below the outlet or outlets
15a of the dispenser 15 to enrich the developer material with toner
particles. The receptacles 13b are caused to discharge batches of
developer material at the transfer station 51 whereby such material
converts the electrostatic latent image on the drum 3 into a powder
image.
If the switch 41 is opened on purpose by an attendant or
automatically, for example, in response to a signal which is
produced by a detector of the copying apparatus, the relay 36
becomes deenergized and the spring 42 automatically moves the
contact 27 into engagement with the fixed contact 27b. The
operation of the motor M is thereby reversed in a fully automatic
way because the motor circuit is completed by way of the power lead
33, conductors 34, 32, 31, contacts 21, 20 of the switch of the
arresting device 56, conductor 30, contacts 27b, 27 of the switch
of the reversing device 55, conductor 29 and power lead 28. The
output shaft 52 of the motor M drives the power train 17 in such a
way that the chains or belts 18, 13a respectively travel in the
directions indicated by arrows E and F. Thus, the foremost filled
receptacle 13b is moved downwardly and away from the transfer
station 51 and the righthand stretch of the chain or belt 18 moves
the contact 20 away from the contact 21 so that the motor M comes
to a complete stop at a time when the filled receptacles 13b of the
chain or belt 13a are held in positions in which they are unlikely
to spill their contents due to eventual shaking during movement of
the carriage 7 from and back toward the operative position shown in
FIG. 1.
The motor M is immediately started in a forward direction, so that
the chain or belt 13a is driven in the direction indicated by arrow
D, when the relay 36 is energized on closing of the switch 41
because the operation of the motor M in a forward direction is not
affected by the position of the movable contact 20 in the arresting
device 56. When the motor M drives the chain or belt 18 in the
direction indicated by the arrow B, the movable contact or follower
20 automatically returns into and is held in engagement with the
fixed contact 21 so that the arresting device 56 is ready to
interrupt the operation of the motor M with a desired delay as soon
as the spring 42 is free to move the contact 27 into engagement
with the fixed contact 27b.
FIG. 2 illustrates certain portions of the drive means and control
means in a modified developing unit. The reference character 118
denotes an endless flexible belt which forms part of a power train
corresponding to the power train 17 shown in FIG. 1. When the motor
M (not shown) which drives the power train including the belt 118
is operated in a forward direction, the belt 118 travels in the
direction indicated by the arrow C. This belt is provided with a
row of projections or teeth 118a which serve as entraining means
for a pivotable follower or trip 120 forming part of a modified
arresting device for the reversible prime mover of the drive which
includes the belt 118. The arresting device further includes a
microswitch 43 which is connected in the circuit of the prime mover
by conductors 30, 31 corresponding to the similarly referenced
conductors shown in FIG. 1. The microswitch 43 is closed and
completes the circuit of the prime mover for operation in reverse
when the belt 118 travels in the direction indicated by the arrow
C. The entraining projections 118a then cause the follower 120 to
move back and forth between the positions S1 and S2 in which the
microswitch 43 is closed. A spring (not specifically shown) urges
the follower 120 in a counterclockwise direction, as viewed in FIG.
2, toward the position S3 in which the microswitch 43 is open and
arrests the prime mover (i.e., the microswitch terminates the
operation of the prime mover in reverse). The spring is free to
move the follower or trip 120 to the position S3 when the direction
of movement of the belt 118 is reversed (see the arrow G), i.e.,
when the belt 118 is driven in a direction corresponding to the
direction indicated by the arrow E shown in FIG. 1. The entraining
projections 118a then assist the aforementioned spring in moving
the follower 120 to the position S3 to thus open the microswitch 43
and to terminate the operation of the prime mover in reverse at a
time when all of the filled receptacles 13b of the conveyor 13 (not
shown in FIG. 2) dwell in positions in which they are unlikely or
less likely to discharge developer material during movement of the
carriage from and back to its operative position. The microswitch
43 may be any commercially available microswitch which is capable
of opening an electric circuit in response to movement of the
follower 120 to or close to the position S3 shown in FIG. 2. The
belt 118 can be a commercially available toothed belt with a row of
teeth which constitute the entraining projections 118a. The
distance between the projections 118a and the pivot axis of the
follower 120 is selected in such a way that the tip of the follower
120 rides over successive projections 118a when the follower
assumes the position S1. These projections 118a are preferably
capable of moving the follower 120 to the position S3 in automatic
response to a change in the direction of movement of the belt 118
from that indicated by the arrow C to that which is indicated by
arrow G. The normally very short delay with which the microswitch
43 opens in response to travel of the belt 118 in the direction
indicated by the arrow G suffices to move the foremost filled
receptacle 13b from the transfer station 51 so that such receptacle
(as well as each filled receptacle behind it) is either incapable
or less likely to discharge developer material onto the drum 3
and/or into the copying apparatus when the carriage 7 is being
moved along the guide rail or rails 6.
An important advantage of the improved developing unit is that the
attendant need not be concerned with the rearward transport of the
conveyor 13 because such rearward transport takes place in
automatic response to termination of forward transport of the chain
or belt 13a. Thus, all the operator (or an automatic detector) has
to do is to terminate the forward operation of the motor M by
deenergizing the relay 36; the control system then takes over and
first causes the motor M to drive the conveyor 13 in reverse (due
to the provision of spring 42 which moves the contact 27 into
engagement with the contact 27b as soon as the relay 36 is
deenergized) and thereupon arrests the motor M with requisite delay
(on opening of the switch in the arresting device) so that the
uncontrolled discharge of developer material is either impossible
or highly unlikely in spite of such mounting of the carriage 7 that
it can move to and from an operative position, a movement which
normally brings about some shaking of the receptacles 13b in the
conveyor 13. As a rule, the motor M will be arrested by the
arresting device 56 of FIG. 1 or the arresting device including the
microswitch 43 of FIG. 2 before the operator can unlatch the
retaining device 50 so that the carriage 7 is free to move in the
direction indicated by the arrow A.
It is further clear that the improved developing unit is
susceptible of many additional modifications. For example, the
follower 20 or 120 can be constructed and mounted in such a way
that it is held in frictional engagement with the belt 18 or 118 or
another movable portion of the power train between the motor M and
the conveyor 13. The structure which is shown in FIGS. 1 and 2 is
preferred at this time because its reliability is not dependent on
such variable factors as the coefficient of friction of the
material of the movable portion of the power train and/or the
coefficient of friction of the material of the follower in the
arresting device. It is further clear that the follower 20 or 120
can be arranged to receive motion from the flexible element 13a of
the conveyor 13 or from a gear, pulley or other movable part of the
power train.
The motor M can be any one of a number of commercially available
reversible-polarity electric motors, e.g., a conventional tandem
motor which can drive its output shaft 52 in two directions,
depending on the manner in which it is connected with the energy
source.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without
omitting features which fairly constitute essential characteristics
of the generic and specific aspects of our contribution to the art
and, therefore, such adaptations should and are intended to be
comprehended within the meaning and range of equivalence of the
claims.
* * * * *