Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a spring compensation mechanism for a swash-
plate drive. A known hot-gas reciprocating engine has at least three recipro-
cable piston-like members each having a driving rod which, via a sliding mem- ~`~
` ber, co-operates with a plate. The plate is provlded on a rotatably journalled
shaft in such a manner that the splate connot perform a rotation relative to
the shaft but can tilt about a tilting shaft extending transversely to the
centre line of the shaft. Means are also provided to tilt the plate.
Hot-gas reciprocating engines of the above-mentioned type are known
; from the United States Patent Specification 3,511,102. -~
In said known hot-gas reciprocating engine, a variation in the stroke
of the pistons co-operating with said plate is effected by tilting the plate
about the tilting shaft. This results in a variation of the supplied power
in engines and in a variation of the cooling capacity in refrigerators.
During operation of a hot-gas reciprocating engine, a torque always
acts on the plate which tries to rotate the plate to the position at right
angles to the shaft. The torque is directly proportional to the angle which
the plate encloses with the plane perpendicular to the shaft and is substan-
tially not dependent on the number of revolutions.
In controlling the power of these machines, the torque co-operates
or counteracts, dependent on the increase or decrease of the power.
In order to increase the power tha plate should be moved against
the torque. In order to be able to do this rapidly, much power is required
which, in certain circumstances, is not available. On the contrary, when .;
decreasing the power, with co-operating torque, there is excessive power.
The excessive power should be stored temporaril~ so that it can be used
afterwards.
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I~ is an object of the invention to provide a spring compensation
mechanism for a hot-gas reciprocating engille which can be controlled rapidly
and with little power.
Accordingly, the apparatus of the invention is a spring compensa-
tion mechanism for a swashplate drive, said drive including a drive shaft
mounted for rotation about its center line, a tilting shaft extending trans-
versely to the center line of the drive shaft, a swashplate tiltably mounted
about said tilting shaft and coupled to said drive shaft for rotation there-
with, a plurality of driving rods mounted for reciprocating movement r01ative
to said drive shaft, said drive rods being coupled to said swashplate such
that, the swashplate being tilted at an oblique angle with respect to the
drive shaft center line, driving force exerted by said rods against said
swashplate imparts rotational torque to said swashplate for rotating said
drive shaft, said force also tending to tilt said swashplate toward a position
perpendicular to said center line, and means for tilting said swashplate
about said tilting shaft, wherein said mechanism comprises a pair of
compensating rods, means for coupling one end of each of said rods to the
swash plate and for guiding said one ends for movement in a first direction
in response to tilting of said swash plate, the other ends of said rods being
guided for movement in a direction transverse to said first direction and a
spring coupled to said other ends and arranged to be resiliently stressed by
movement of said rod other ends in response to tilting of the swashplate, ~;
the spring constant and orientation of said spring being such ~hat stressing -
: of the spring produces a change in force proportional to the force change
caused by the tendency of said driving rods to tilt said swashplate toward
said perpendicular position.
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So in this manner, with downward controlJ a quantity of energy will
be stored in the spring mechanism, which energy can be used when increasing
the power to vary the position of the plate. As a result of this the control
can be carried out rapidl~ and with little power. The spring mechanism may
comprise both mechanic and gas spring constructions.
; The rod of the spring mechanism in this construction is in equilib-
rium of forces ~balanced) in any position. When the position varies, trans- ;
port of energy will take place from the spring which acts on one end of the
rod to the spring co-operating with the other end of the rod. The spring
which co-operates with one end of the rod has as it were a negative spring
characteristic. ;
In a favourable embodiment the spring mechanism comprises at least
one pair of identical rods which are pivotall~ coupled together and in which
the free ends of the two rods are straight-guided in the same direction, the
pivot being coupled to the plate and the two free ends being each coupled to
a spring, or conversely, the spring constant of the two springs together being
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substantially equal to the spring constant of the gas
forces acting on the plate via the piston-like members.
In a further embodiment the spring mechanism
comprises at least four identical rods which are pivo-
tally connected together and form a diamond of rods,
two opposite pivots being connected to the plate and
the two other pivots each co-operating with a spring.
A favourable embodiment of the hot-gas reci-
procating engine according to the invention is character-
ized in that two structural components are guided on the
shaft, so as to be slidable on said shaft, one of said
components being coupled to a point of the plate which
is present on one side of the tilting shaft, the other
component being coupled to a point of the plate which is
present on the other side of the tilting shaft, the two
structural components being coupled together by at least
two pivotally connected rods of equal length, a spring
acting on each of the pivots, the spring constant of
all the springs together being substantially equal to `~
the spring constant of the gas forces acting on the
plate via the pistons.
So in this manner a mechanical coupling is
obtained between the spring mechanism and the plate, -
which coupling can give good satisfaction when the
centrifugal forces do not play too large a part.
In a further favourable embodiment, the plate
is coupled to the spring mechanism via one or more
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liquid columns.
The great advantage of such a hydraulic coupl-
ing is that the spring mechanism can he arranged sepa~
rately from the driving mechanism.
In a further favourable embodiment of the engine
according to the invention, each of the said springs on
its side remote from the spring mechanism is supported
by an element wh$ch can be moved in the direction of
the spring, means being present to move the spring mecha-
nism and plate connected thereto by a displacement of
each of the said elements, the spring constant of all
the springs together differlng slightly from the spring
constant of the gas forces acting on the plate via the
pistons. By a displacement of the said elements, a move~
ment of the spring mechanism and the plate coupled there- .'.'!
to takes place.
According to a further embodiment, the movable
elements may be constituted by pistons which limit a
space to which liquid can be supplied or from which liquid
can be removed. In this manner the engine can be con-
trolled hydraulically.
In a further embodiment the relevant liquid
spaces furthermore comprise a narrow liquid outlet aper-
ture. As a result of this, in the stationary condition,
the plate can nevertheless be moved again to its posi-
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tion at right angles to the shaft, due to the occurring
gas ~orces.
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The invention will now be described in greater
detail with reference to the drawing, in which
Flg. 1 is a diagrammatic cross-sectional view
of a hot-gas engine having a so-called l'swash-plate"
driving mechanism.
Fig. 2 shows diagrammatically an example of a
compensation mechanism, and
Fig. 3 shows diagrammatically another embodi-
ment in which the compensation mechanism is also com-
bined with a displacement mechanism.
The hot-gas engine shown in Fig. 1 comprises
a number, at least three, of double acting pistons 1
which reciprocate in cylinders 2. Below each of the said
pistons there is a cold compression space 3 while above
each of the pistons there is a hot expansion space 4.
A number of units each comprising a cooler 5
and a regenerator 6 are arranged between the cylinders 2.
Each of the said units communicates on the
cooler side with one cold space 3 in one of the cylin-
ders 2 and communicates on the regenerator side with a
warm space 4 in another cylinder 2 via a heater 7. In
this manner a double-acting hot-gas engine is obtained
which is described in detail in Dutch Patent Specifica-
; tion 65813, so that further explanation need not be
given.
Each of the pistons 1 comprises a driving rod
8 which co-operates with a plate 10 via sliding members 9.
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The plate 10 is connected to a shaft 11 in such manner that it can-
not rotate relative to the shaft 11 but can tilt about a tilting shaft 12.
In order to cause the plate 13 to move about the tilting shaft, the
plate is pivotally connected to a pair of pistons 14-15 at the area 13 on one
side of the tilting shaft and to a pair of pistons 17-18 on the other side of
the tilting shaft at the area 16.
The pistons 14 and 18 which are present on one side of the plate ld
limit a space 19, while the pistons 15-17 present on the other side of the
plate lO limit a space 20.
The spaces 19 and 20 can be made to communicate, via a duct 21, with .
- a device which is not shown and with which liquid can be supplied to or
removed from the relevant spaces.
During operation of hot-gas engines a gaseous working medium under
high pressure is present in the spaces 3 and 4 and the communicatlons there-
between, which medium reciprocates between the cold and warm spaces as a
result of the movements of the pistons.
The gas forces exerted on the pistons are transferred to the plate
10 via the driving rods 8 and the sliding members 9. Said forces exert on
the plate 10
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a torque ~Jhich tries to force the plate lO to a position
normal to the shaft, Said torque varies substantially
linearly with the angleo~and is zero when~ = 0 and is
maximum when ~= max, for example 22.
In order to control the supplied power of the
engine, either the plate 10 must be moved against the
torque or with the torque. In one case this will cost
power, whereas in the other case an excess of power is
available.
It is the object of the invention to provide
a solution in that sense that the plate 10 is balanced
in any position, so at any angle ~, so that the move-
ment neither in one direction nor in the other direction
costs power or provides an excess of power.
This has been achieved by connecting the pair
of pistons 14-15 to a structural component 22 which is
slidably connected to the shaft 11~ while piston pair ;~
17-18 is connected to a structural component 23 which
is also guided on the shaft 11 so as to be slidable.
The structural components 22 and 23 are coupled
together by one or more pairs of rods 24-25 which are
pivotally coupled together at point 26.
Each of the pivots 26 is connected to a spring
27 which bears at its other end against a dish spring
23 which is rigidly secured to the shaft 11.
The springs 27 are constructed so that together
they show a spring characteristic which is equal to the
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characteristic oE the forces exertecl on the structural
components 22 and 23 by the piston pairs 14-15 ancl
17-18.
In this manner a compensation mechanism is
obtained in ~hich upon moving the plate 10 to its posi-
tion at right angles to the shaft, the structural com- -
ponents 22 and 23 move towards each other which involves
that the springs 27 are compressed so that the energy
originating from the plate 10 is stored in said springs.
The energy stored in the springs 27 may afterwards be
used again upon moving the plate 10 in the opposite ~ ;~
direction.
The compensation mechanism may be compared with
a diamond in the corners of which four identical springs
engage. It can be proved theoretically that such a dia-
mond is balanced in any position.
This means that the hydraulic liquid which
upon moving is supplied to or withdrawn from the spaces
20~ 19 via duct 21, need substantially not supply any
movement work ~not couhting friction)~ so that the hot-
gas engine can hence be controlled very rapidly.
Instead of a hydraulic system for moving the
plate, mechanical means may also be used for this pur-
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pose~ if desired? Due to the direct coupling of the -
piston pairs 14-15 and 17-18 with the compensation me
chanism, the latter must necessarily also rotate with ;`~
the shaft 11. At high numbers of revolution, such large
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centrifugal ~orces may occur as a result~ th~t the
compensation effect is adversely influenced. In order
to avoid this, a hydraulic coupling may be provided
between the plates 10 and the compensation mechanism.
In this case a compensation mechanism as is
shown in Fig. 2 may be used. This comprises a diamond
of four pivotally connected rods 24~25. Two opposite
corners 26 of said diamond are each connected to a
spring 27. The two other corners each comprise a piston
30 which limits a space 31 in a cylinder 32. Each of the
spaces 31 communicates with the duct 21 via a pipe 33.
For moving the~plate, a ~separate hydraulic system or
mechanical means may be used. -
The construction is proportioned so that the
characteristic of the springs corresponds at least sub-
stantially with the variation of the forces exerted by
the pistons 30 when said pistons move.
When moving the plAte 10, the volume of the
spaces 20 and 19 will vary. This means that the liquid
column between the spaces and the pistons 30 moves so
that the pistons 30 experience a displacement. When the
plate 10 assumes a more inclined position, the pistons
30 will move apart and, conversely3 when moving to the
position normal to the shaft, the~pistons move towards
each other. The forces exerted by the pistons 30 vary
proportionally with the variation of the angle ~5. By
; giving the springs 27 a characteristic which corresponds
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to the forces characteristic, the rod diamond 24~ 25 is
balanced in any position. This means that for displacing
; the diamond and plate 10 connected thereto substantially
no forces are necessary so that the displacement can be
carried out very rapidly. The displacement should be car-
ried out hydraulically or mechanically with a separate
mechanism.
Fig, 3 shows diagrammatically another embodiment
in which the compensation mechanism is also combined with
-la displacement mechanism.
The compensation mechanism comprises the same
components as that of Fig. 2. The only difference in
this case is that the springs 27 are connected to pis-
tons 33 which bound a space 34 in a cylinder 35. Further-
more,~the spring characteristic of the springs 27 has
now been chosen to be slighly different from the forces
characteristic exerted~by the pistons 30. ;
When due to the supply of liquid via ducts 36
the pistons 33 are move~, the prestress of-the springs
27 varieS thereby and the rod diamond 24~ 25 is unbalanced,
As a result of this the pistons 30 will be displaced
until a new equilibrium state is reached.
In order to ensure that with stationary engine `~
the gas forces can force the plate 10 to its position ~ ;
normal to the shaft, each of the cylinders 35 has a
narrow aperture 38 through which liquid can leak away
so that in the stationary condition the liquid can flow -~
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away from the spaces 34. This means that the pistons 33
are moved apart as a result of which unbalance of the
cliamond rod occurs. In order to restore this, the pis-
tons 30 move towards each other so that the plate 10
moves to its position normal to the shaft.
From the above it will be obvious that the
above-described invention provides a hot-gas engine
having a movable swash-plate driving mechanism of which
the plate is coupled to a compensation mechanism which
exerts on the plate a torque which is equally large as,
is opposite to and vaies in the same manner with the
position of the plate as the torque exerted on the plate
by the gas forces. This compensation mechanism balances
the plate in any position so that the displacement
can be carried out without work and hence very rapidly.
In the embodiments the springs are shown as
being real mechanical springs; it will be obvious, how-
ever, that the springs may also be formed by gas springs,
i.e. a piston supported by a gas buffer. ~;~
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