192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-03-31
2001-08-28
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
Reexamination Certificate
active
06279710
ABSTRACT:
This application is based on patent application Nos. 11-96942 and 11-288314 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic clutch in which a shaft rotatable about an axis thereof is electrically connected to an input-side rotary member such as a gear which is rotatably mounted onto the shaft.
Heretofore, an electromagnetic clutch of the above type has been constructed, for example, as shown in
FIG. 8
, which is a cross-sectional view of the electromagnetic clutch. The electromagnetic clutch shown in
FIG. 8
is generally used as a part operatively connected to a sheet feed mechanism of an image forming apparatus such as a copier. The electromagnetic clutch includes a field
51
of a blind-hole double-layered tubular structure having a tubular fitting portion
50
in the middle, a ring-like energizing coil
52
mounted on the fitting portion
50
in the field
51
, and a shaft
53
inserted in the field
51
to be rotatable about an axis thereof. A rotor
55
formed with a circumferentially extending slit (through hole)
54
is fixed on the shaft
53
near the energizing coil
52
.
A gear
56
is rotatably mounted onto the shaft
53
at a position opposing the energizing coil
52
with the rotor
55
interposed between the gear
56
and the energizing coil
52
. The gear
56
is rotatable when a rotating force from an external device is transmitted thereto. An armature
57
is mounted on the shaft
53
opposing to the gear
56
with a plate spring
58
interposed between the armature
57
and the gear
56
. Specifically, the armature
57
and the gear
56
are integrally assembled with the plate spring
58
in such a manner that the plate spring
58
is fixed to the armature
57
by swaging projections
59
which are integrally and circumferentially formed on a surface of the armature
57
with the plate spring
58
simultaneously mounted on the gear
56
by screws
60
at plural positions circumferentially.
Annular grooves
61
,
62
are formed in opposite ends of the shaft
53
. Fitting ring-like engaging pieces
63
,
64
respectively in the annular grooves
61
,
62
prevents the field
51
and the gear
56
from disengaging from the shaft
53
. Note that at least the field
51
, shaft
53
, rotor
55
, and armature
57
are made of a magnetized material such as ferrite metal.
In the above-constructed electromagnetic clutch, when the energizing coil
52
is excited, the armature
57
is magnetically attracted to the rotor
55
against a spring force of the plate spring
58
, and thus, a rotation of the gear
56
is transmitted to the rotor
55
to rotate the shaft
53
. On the other hand, when the energizing coil
52
is de-energized, the armature
57
springs away from the rotor
55
and returns to the original position opposing the gear
56
due to a restoration force of the plate spring
57
. Thereby, the rotation of the shaft
53
is suspended.
In the electromagnetic clutch shown in
FIG. 8
, assembling operations such as tightly fixing the plate spring
58
onto the armature
57
by swaging or the like and fixing the plate spring
58
on the gear
56
with screws are required, which makes the assembling operation complex and may result in raising the production cost of the electromagnetic clutch with a difficulty in reducing the size of the plate spring
58
. Further, it is highly likely that variation of a swaging force and a fixing force may occur at the swaging and fixing operation, which may resultantly vary the resilient performance of the plate spring
58
. In view of the above possibility, swaging/fixing operation should be carried out with caution, which may deteriorate the assembling efficiency.
Another arrangement of the electromagnetic clutch has been proposed (for example, in Japanese Examined Utility Model Publication No. 7-24666) as shown in
FIGS. 9A and 9B
.
FIG. 9A
is a partially sectional view illustrating a state that an armature is mounted on a gear, and
FIG. 9B
is a plan view of a spring used in this electromagnetic clutch.
As shown in
FIG. 9A
, the electromagnetic clutch is constructed in such a manner that an armature
57
′ is mounted on a gear
56
′ together with a ring-like spring
58
′ formed with a through hole
582
′ in the center thereof. As shown in
FIG. 9B
, the ring-like spring
58
′ is formed with radially inwardly protruding projections
581
′ along an inner circumference thereof at a certain interval. Each projection
581
′ is formed with a bent portion
583
′ at a lead end thereof. Placing the armature
57
′ along a fitting groove
562
′ formed in a circumference of the gear
56
′ near a through hole
561
′ of the gear
56
′ and press-fitting the armature
57
′ into the fitting groove
562
′ resiliently holds the armature
57
′ in the gear
56
′.
The electromagnetic clutch shown in
FIGS. 9A and 9B
(namely, the latter arrangement) can omit the swaging/fixing operation which has been required in the electromagnetic clutch shown in FIG.
8
and simplify the assembling operation to some extent which may contribute to lowering the production cost of the electromagnetic clutch to some extent. The latter arrangement may also be advantageous in improving assembling efficiency because merely press-fitting the ring-like spring
58
′ into the fitting groove
562
′ accomplishes mounting of the armature
57
′ onto the gear
56
′. However, the latter arrangement necessitates an additional step of forming the bent portion
583
′ at the lead end of the projection
581
′ after press-molding the ring-like spring
58
′. Further, the latter arrangement has a difficulty in producing a small-sized spring
58
′ due to the existence of the radially inwardly protruding projections
581
′, thereby likely to raise the production cost of the electromagnetic clutch as a whole.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide an electromagnetic clutch having a structure that enables to simplify the assembling operation of the electromagnetic clutch and to reduce the production cost thereof.
According to an aspect of this invention, an electromagnetic clutch comprises: a rotatable shaft; a field coil having an energizing coil mounted on the shaft; an output-side rotary member which is non-rotatably mounted on the shaft on a side opposing to the field coil; an input-side rotary member which is rotatably mounted on the shaft; a drive transmitting member rotatable together with the input-side rotary member for transmitting a drive power from the input-side rotary member to the output-side rotary member; and an elastic member for allowing the drive transmitting member to shift from the input-side rotary member side to the output-side rotary member side when the energizing coil is energized. The input-side rotary member includes a tubular part into which the shaft is inserted and a plurality of slip stopper projections formed at a lead end on an outer periphery of the tubular part circumferentially at a certain interval, and the drive transmitting member is formed with a through hole and a plurality of radially inwardly protruding projections at respective positions corresponding to spaces between the adjacent slip stopper projections, the drive transmitting member being held on the input-side rotary member in a state that the tubular part is fitted in the through hole of the drive transmitting member, and the elastic member in a ring shape resilient material having a radial thickness greater than a radial distance between an outer surface of the tubular part of the input-side rotary member and an innermost end of the projection of the drive transmitting member mounted on the tubular part, the elastic member being mounted on the tubular part between the slip stopper projections and the drive transmitting member.
In this arrangement, when the energizing
Bonck Rodney H.
Jordan and Hamburg LLP
Kyocera Mita Corporation
Rodriguez Saul
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