Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention pertains to a clutch with new and improved coolant
flow control means to provide no coolant flow when the clutch is disengaged
and to provide coolant flow during clutch engagement.
The clutch disclosed herein may be used in a jet engine start system
and is used to transmit variable power in the starting cycle depending upon
a control pressure applied to the clutch for controlling the degree of
engagement of the clutch plates. This mode of operation involved slippage
which creates heat due to friction and, therefore, the clutch is constructed
to have a substantial flow of coolant through the clutch. An initial step
in the cyle is to start certain components by driving of a motor from an
accumulator and it has been found that a time delay in operation is caused
by coolant flow through the clutch which provides too much drag torque. In
order to reduce the drag torque, the invention disclosed herein provides for
shutting off the coolant flow during the initial step of the cycle when the
clutch engagement control pressure is of a relatively low value and
initiating coolant flow when the control pressure is at a higher value.
It is known in the prior art to have clutches with coolant flow and
with the flow of the coolant controlled by means responsive to a control
pressure for controlling clutch engagement. The prior art does not show a
structure of the type disclosed herein wherein components are structurally
related to provide the desired results with a minimum number of parts and
with minimal additon of weight which is of particular importance in
structure associated with aircraft.
SUMMARY OF THE INVENTION
A primary feature of the invention is to provide a clutch with
coolant flow control means by the addition of a control valve and actuating
structure therefor within the inner clutch drum of the clutch to block
coolant flow through the inner clutch drum to a surrounding clutch chamber
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until such time as a control pressure reaches a value to shift the control
valve and permit coolant flow to the clutch chamber.
An object of the invention is to provide a clutch with coolant flow
control means wherein the clutch structure includes an inner clutch drum
with a surrounding clutch chamber having interengageable clutch members with
means responsive to a control pressure of a predetermined value to cause
driving engagement of the clutch members, the inner clutch drum having a
central hollow section defining a flow path including at least one passage
extending from the central hollow section to said clutch chamber and a
control valve positioned within the central hollow section to be in said
flow path and normally urged to a position to block said connecting passage,
and means responsive to said control pressure for moving said control valve
away from said position to open the connecting passage and provide coolant
flow to the clutch chamber.
Still another object of the invention is to provide a clutch as
defined in the preceding paragraph wherein the control valve comprises a
valve member having longitudinally extending passages therethrough to have
coolant positioned at both ends of the valve member for balancing forces
thereon and a piston within the inner clutch drum coaxially positioned with
said valve member and mechanically linked to the valve member and subject to
control pressure whereby control pressure acting on the piston causes
movement of the piston and valve member to have a control pressure of a
certain value move the valve member to a position whereby coolant flows to
the clutch chamber.
BRIEF DESCRIPTION OF THE DRAWING
The Figure is a central vertical section of the clutch.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The clutch structure includes an inner clutch drum, indicated
generally at 10, and an outer clutch drum, indicated generally at 11, which
are concentrically arranged and with the outer clutch drum 11 being mounted
for rotation relative to the inner clutch drum by a pair of bearings 15 and
16. The inner clutch drum 10 is driven from a drive train including an
input gear 17 secured thereto and the clutch output is from a gear 18
integral with the outer clutch drum 11. A generally annular space between
the inner and outer clutch drum defines a clutch chamber with a series of
interfitted clutch members in the form of clutch plates 20 positioned within
the chamber. Alternate clutch plates 20 are attached to the inn clutch
drum 10 by fitting on keys 21 extending longitudinally of the inner clutch
drum and the remaining clutch plates Z0 are fitted to keys 22 carried on the
inner surface of the outer clutch drum 11.
The engagement of the clutch plates 20 is under the control of a
piston 25 which is slidably mounted on a central tubular hollow section 26
of the inner clutch drum. The piston 25 may move to the right, as viewed in
the Figure, to engage an end plate 27 which is keyed to the inner clutch
drum keys 21 to compress the clutch plates. A control pressure for clutch
engagement is delivered through an opening 30 in the tubular section 26,
with flow passages 31 delivering control pressure into a chamber defined by
a housing 32 in which the piston 25 moves and which is sealed thereto by an
0-ring. The clutch plates are disengaged by a disengagement spring 35
surrounding the central tubular section 26 and acting on the piston 25 in a
direction to move the piston toward the left when he control pressure is
reduced. The flow of coolant for cooling the clutch plates 20 is through an
inlet 40 at one end of the central tubular section of the inner clutch drum
and through radial passages 41 in the wall of the section. The foregoing
structure is generally known in the art.
A sleeve 45 is fitted within the hollow interior of the inner clutch
drum and defines a pair of chambers 46 and 47 with a connecting passage 51.
The chamber 47 has a series of radial passages 50 adjacent one end thereof
for directing coolant flow from the chamber 47 to the clutch chamber with
flow through the radial passages 41. A control valve having a valve member
44
55 is located within the chamber 47 and urged to the position shown by a
spring 48 whereby the valve member blocks the radial passages 50 to prevent
coolant flow from the inlet 40 to the clutch chamber.
The chamber 46 has an actuating member in the form of a piston 60
movable therein and subject to control pressure by means of a passage 61
which connects with the previously mentioned opening 30. The actuator
piston 60 and the valve member 55 are mechanically interconnected by a rod
62 disposed in the passage 51 whereby control pressure acting on the piston
60 controls the position of the valve member 55 subject to the force of the
spring 48.
When the control pressure is of a relatively low value, the force
generated thereby on the piston 60 is not sufficient to overcome the force
of the spring 48 and the valve member 55 remains in the position shown.
Thus, there is no coolant flow to the clutch chamber and no drag torque
resulting from the coolant flow. When the control pressure increases to a
value sufficient to overcome the force of the spring 48, the piston 60 and
the valve member 55 move to the right to have the valve member uncover the
radial passages 50 whereby coolant can flow to the clutch chamber. This
coolant flow is through a series of longitudinally-extending passages 65 in
zo the valve member 55. These passages permit coolant to always be present at
both sides of the valve member to equalize the forces on the valve member
from pressure of the coolant. Once the valve member is shifted tothe right
to open the radial passages 50, coolant flows through the passages 65 of the
valve member and through the radial passages 50 to the clutch chamber.
Subsequently, when the control pressure drops to a value sufficient to let
the spring 48 move the valve member back to the position shown in the
Figure, the coolant flow is cut off from the clutch chamber. The chamber 46
has ports 69 to permit connection of the chamber behind the piston 60 to
case pressure. The outer clutch drum 11 has a plurality of openings 70 in
the wall thereof to permit coolant to leave the clutch chamber.
In operation of the system using the clutch disclosed herein, clutch
control pressure is low during acceleration of a starter turbine and, thus,
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coolant flow is not deliv~red to the clutch chamber to avoid drag torque.
When the starter turbine reaches operating speed and the clutch is to
operate, the control pressure increases and the loading of the spring 48 is
overcome to shift the valve member 55 and permit coolant flow to the clutch
chamber.
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