DEVELOPER SHUT-OFF APPARATUS

APPAREIL D'ARRET DE REVELATEUR

English Abstract

DEVELOPER SHUT-OFF APPARATUS
ABSTRACT OF DISCLOSURE
A developer sump is communicated to a magnetic trans-
port means through a developer outlet at the lower end of the
sump. During development function, magnetic developer flows
from the sump through the outlet to the magnetic transport
means. A magnetic gate is normally located away from the out-
let during the development function and is arranged to be swung
into a position adjacent to the opening to magnetically stop
the flow of developer through the outlet when it is desired
to purge the development system.

Claims

WHAT IS CLAIMED IS:
1. In a development system: A surface capable
of having a developable image thereon, a developer sump,
said sump having ferromagnetic developer therein, magnetic
means for presenting said developer to said surface, a
developer outlet at the lowermost portion of said sump, said
developer flowing through said outlet to said means for
presenting said developer to said surface, and magnetic gate
means for selectively either magnetically blocking the entire
flow of developer through said outlet or for allowing flow
of developer through said outlet.
2. The structure as recited in Claim 1 wherein
said magnetic gate means comprises a permanent magnet, means
for moving said magnet into a closed position adjacent said
outlet to block the entire flow of developer through said
outlet and for moving said magnet away from said outlet to
an open position to allow flow of developer through said
outlet.
3. The structure as recited in Claim 2 further
comprising means mounting said magnet for pivotal movement
between said open and closed positions.
4. The structure as recited in Claim 3 wherein
said surface is a photoconductive surface and said developer
comprises toner particles and ferromagnetic carrier particles.
5. The structure as recited in Claim 4 wherein
said magnetic means comprises rotatable rollers of non-magnetic
material each surrounding a magnetic member.
- 6 -

Description

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This invention relates to a magnetic brush development
system with a simple and effective means for purging the system
of developer material.
In accordance with this invention there is provided,
in a development system: a surface capable of having a developable
image thereon, a developer sump, said sump having ferromagnetic
developer therein, magnetic means for presenting said developer
to said surface, a developer outlet at the lowermost portion of
said sump, said developer flowing through said outlet to said
means for presenting said developer to said surface, and magnetic
gate means for selectively either magnetically blocking the entire
flow of developer through said outlet or for allowing flow of
developer through said outlet.
This invention will become more apparent from the
following description with reference to the drawings wherein:
Figure 1 is a cross-sectional view of a development
system illustrating a magnetic gate in open position; and
Figure 2 is a partial view of Figure 1 showing the
magnetic gate in closed position.
Referring to Figure 1, there is illustrated a
rotatable drum 10 having a photoconductive surface thereon
and a developer housing 12 located adjacent to the drum. The
photoconductive surface is adapted to receive an electrostatic
latent image thereon. The developer housing includes a developer
sump 13 having a quantity of developer 14 therein. The developer
14 comprises toner particles and ferromagnetic carrier particles.
The triboelectric characteristics of these particles are such
that the toner particles will be triboelectrically attracted to
the carrier particles and the charge on the toner particles will
be opposite to the charge of the latent image. A plurality of
"magnetic brush" rollers 15 are rotatably mounted on the side

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walls of the developer housing 12 and are located contiguous
to the photoconductive surface 10. The rollers 15 are con-
structed of non-magnetic material and each surround a station-
ary permanent magnet 16. The magnets 16 are arranged to
effect a magnetic field for attracting the developer onto the
rollers 15 and to present toner particles to a latent image
carried by the photoconductive surface. A pair of "magnetic
transport" rollers 18, constructed of non-magnetic material, are
rotatably mounted to the side walls of the developer housing
below the magnetic brush rollers 15. A plurality of magnets 20
are located within each roller 18 and are so positioned to set
up a magnetic field for attracting the magnetic developer onto
the transport rollers to transport the same to the magnetic
brush rollers 15.
The developer sump 13 comprises a front wall 24
separating the sump from the rollers 15 and 18, a rear sloping
wall 26 and an upper wall 28 each of which are of non-magnetic
material. A developer outlet 32 is located at the lowermost
portion of the developer sump 13 for allowing developer to
flow from the sump to the transport rollers 18. Affixed to
the upper wall 28 is a toner dispenser 34 having toner particles
36 therein which are periodically dispensed into the developer
sump 13 by a rotatable foam roller 38. A pair of spaced
flanges 40 (only one shown) extend from the rear wall 26 of the
sump 13 and a shaft 42 is rotatably mounted thereon. A magnetic
gate 44 is provided and comprises a plate 46 fixedly secured at
one end to the shaft 42. A permanent magnetic bar 48 is secured
to the other end of the plate and extends across the entire width
of the outlet 32. A hand lever 49 is rigidly secured to the
shaft 42 and may be engaged by an operator's hand or be operated

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by a remotely controlled linkage for causing rotation of
the shaft 42 and thereby the magnetic gate 44 from an open
position shown in Figure 1 to a closed position shown in Figure
2 whereby the permanent magnet 48 engages the rear wall 26
of the sump adjacent to the outlet 32 to magnetically block
the entire flow of developer through the outlet 32. Obviously,
rotation of the lever in the opposite direction will reopen
the magnetic gate. Detents may be employed for holding the
lever 49 in a gate open or closed position.
A chute 50 is located between the uppermost magnetic
brush roller 15 and a residual developer opening 52 in the
upper wall 28 of the developer sump 13 to direct residual de-
veloper material from the uppermost roll 15 into the sump 13.
A passive cross mixer 54 is located immediately below the
residual developer opening 52 and the toner dispenser 34 to
receive the residual developer and fresh toner thereon and
effect mixing thereof prior to discharging the same into the
lower end of the developer sump 13.
In operation, an electrostatic latent image is
formed on the photoconductive surface 10 in the customary
manner as the drum rotates past an imaging station (not shown).
The magnetic gate 44 is in the open position as shown in Figure 1
which allows the developer to flow from the sump13 through the
outlet 32 to the magnetic transport rollers 18. The developer
is carried by the magnetic transport rollers 18 to the magnetic
brush rollers 15 whereby the toner particles in the developer
material are presented to the latent image to develop the same
as the latent image on the photoconductive surface is brought
therepast. The developed image is then transferred to a copy
sheet by well-known methods. Residual developer is carried to

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the uppermost magnetic brush roller 15 whereby upon movement
of the developer out of the magnetic field of the magnet
surrounded by such roller the developer is allowed to drop
by gravity down the chute 50 to the residual developer opening
52 onto the cross mixer 54. Fresh toner 36 is dispensed onto
the cross mixer 54 by the foam roller 38 to be mixed with t~e
residual developer and the developer is discharged from the
cross mixer to the lower end of the sump 13. This process
continues through each development function.
It is customary to move the developer housing 12
away from the photoconductor drum 10 in order to repair
elements on the developer housing or for replacing the photo-
conductor drum. Before doing this, it is most desirable to
purge the system of developer to prevent developer from con-
taminating the rest of the machine. To do this, the lever
49 is manually engaged to rotate the shaft 42 and thereby
the magnetic gate 44 into its closed position which is up
against the rear wall 26 adjacent to the outlet 32 as shown
in Figure 2. The ferromagnetic developer particles are
trapped within the magnetic field of the magnet 48 and thereby
blocks the outlet 32 to stop further flow of the developer
material from the sump to the transport rollers 18. Con-
tinued rotation of the transport rollers 18 and the magnetic
brush rollers 15 delivers the developer within that portion
of the developer housing to the uppermost roller 15 whereby
it is discharged from the uppermost roller 15 onto the
chute 50 and back into the developer sump 13 thereby purging
the system of developer. After the system is purged, the
developer housing 12 may be moved away from the photoconductor
10 with little chance of developer material contaminating the
machine.