US2388755A - Hydraulic lift mechanism - Google Patents

Description

2 Sheets-Sheet 1 Nw., 11.3, 1945. sfB. MCLEOD HYDRAULIC LIFT MECHANISM Filed July 16, 1940 S. B. MCLEOD HYDRAULIC LIFT MECHANISM Nov. 13, 1945.

Filed July 16, 1940 2 Sheets-Sheet 2 WN wk Mum www d. ZH@ M f m5. mi m w Z 5MM Patented Nov. 13, 1945 UNITED sTATEs' PATENT oFFlcT-: :saam I' smarty* Intranets Mien.,eon onanermemm applicants .my 1s, me, seran No. 34am' sown. (cnet- 52) This invention relates to a hydraulic lift mechanism or system for raising and lowering or opensively, to the raising and lowering of so-called col lapsible tops for vehicle bodies of the convertible s type One of the objects of the present invention is to provide simplified mechanism of the foregoing character capable of easy application to or installation in a vehicle body, and one in which ample and easily controlled power is provided for the raising or lowering movement of the top.

Another object of the invention ls to provide improved mechanism of the foregoing character which is relatively compact and capable of installation in a relatively small space.

A further object of the invention is to provide an improved hydraulic lift mechanism including an operating cylinder and piston structure having a single piston rod, and means for compensating for the difference in volume or space within the cylinder at opposite sides of the piston, said means also compensating for volume changes of the fluid in the system due to the operating pressures and expansion or contraction of the fluid due to temperature variations and permitting manual actuation of the top without using the pump.

Another object of the invention is to provide an improved hydraulic lift mechanism or system having means which permits the system to be illled without the necessity of providing for the external bleeding thereof.

Another object of the invention is to provide improved hydraulic lift mechanism which may include an airtight and upper compensating reservoir and a fluid system connected therewith which together constitute a sealed unit.

Other objects and advantages of this invention electric motor, fluid pump, valve mechanism.

associated parts, embodying the present invention: and

Fig. 4 is a view similar to Fig'. 2, showing a modified form ofvalve mechanism embodying the presentinvention; and s Fis. 5 is a view similar to Fig. 4 showing the.'

valves in their neutral leaking position and also showing another modified form of valve unit embodying the present invention.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement ofparts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understoodthat the phraseology or terminology employed herein is Vfor the purpose of descnption and not of umsehen.

Referring now particularly to Fig. 1, there is shown one adaptation of the present invention. In the present instance the hydraulic lift mecha- 5 nism or system of the present invention is shownas installed in the rear deck compartment or space Il of a motor vehicle body of the convertible type in which the top is adapted to be raisedand lowlered to provide a closed or open body. Ihe mechanism shown may be mounted in any convenient location, such as upon the floor I I of the rear deck v compartment' or in a channel member of the ve- 4 hicle frame, parts thereof being located below and thus concealed by the floor.

In the present embodiment, the lift mechanism is attached or connected to the linkage or frame l member. such as the member I2 of the collapsible top for the vehicle body, and comprises a cylinder Il having a piston Il mounted upon a single piston rod Il which is preferably connected with the will appear in the following description and ap- '40 link u through the medium of a Substantially upended claims, reference being had to the accomshaped bracket member It. The lower end of the cylinder I3 is pivotally mounted for swinging movement at I'I to a base or bracket I8 mounted 5 upon the floor I I. By virtue of the presence of the piston rod IB, it will be understood that when the piston I4 is located at a point in the cylinder midway its opposite ends. the area I9 below the piston is somewhat greater than the area 2li above Fig; 2 is an enlarged sectional view of t e valve to the Piston.

mechanism of the present invention, taken substantially along the line -2-2 of Fig. 1,1ooking in the direction of the arrows; Fig. 3 is a perspective view of a somewhat modified arrangement of a power unit consisting of an The system includes an oil reservoir 2| and a pump 22 adapted to be driven or operated by means of an electric motor mounted within a. casing 23, there being, of course, oil lines or reservoir with the cylinder Il. Preferably the reservoir is above the valve unit as shown, to make for easier nlling. The motor 2l is of the reversible type capable of being driven in either a clockwise or a counterclockwise direction so that the pump 22 may likewise be driven in eitherv direction. 'I'he reservoir 2| communicates y througha pipe line or tube 24 with a compensating or shuttle valve vunit shown as a whole at 2li. see particularly Fig.` 2. 'I'he oil pump 22 is connected by means of a pipe line 28 to the left side of the valve 25 through the medium of a T-shaped coupling 21 to which is attached a .pipe line 28 which extends through a base plate 20 mounted on the door II and is connected to another pipe line ll which extends to and is tapped at li into the cap or upper end lla of the cylinder.

A pipe line il extends'from the pump 22 to a T-coupling ll, similar to coupling 21, and is tapped into the right side of the valve 2l. Another pipe line Il extends from the T-coupling through an opening in the floor plate 29 and is connected to a pipe line It which is tapped into or connected at Il to the lower cap member or closure ilb oi' the cylinder.

The instrument panel l of the vehicle supports an electric switch 40 controlled by a pull rod Il. This switch is electrically connected by wiring or cable 42 to av solenoid Il mounted upon the motor casing.

As described above, my improved hydraulic lii't mechanism or system includes means for connection to a frame member or linkage at one side only oi' a collapsible top. It will be understood that if it is desirable to connect the hydraulic mechanism to a similar frame member or linkage at tbe opposite side of the top. an additional cylinder llt is provided. The construction of the cylinder I". its piston, piston rod, mounting means and the means for attaching the piston rod to the linkage of the top is similar to that above described. As shown in Fig..1, the pipe line 28 extends through an upright supporting bracket It and is connected to a transversely extending pipe line 4l which passes through brackets 41 and member and to the floor respectively, and is connected to a pipe line 49 which extends to and is connected with the upper end of the cylinder Ill. The pipe line 2B from the opposite end or side of the valve structure 2l has a branch connection through the bracket 4l with a transversely extending pipeline l0, which pipe line extends through bracket 41 and plate 4l and is connected with a pipe line Il which is tapped into the lower end or head Ilb of the cylinder by means oi' a tap or connection 52. It will be understood that all or portions oi' the pipe line referred to may be in the form oi' ilexible hose or conduit, thus permitting freedom of movement oi' the cylinders Il and |30. Thus, when the motor 22 and pump 22 are driven in a clockwise direction, oil passes under pressure through the lines 28, 2l and III t0 the upper end of the cylinder Il and at the same time through the lines 4l and I! to the upper end of the cylinder |30. 'I'he pressure of the oil or other iluid in the system when V.the motor and pump are being driven in a clockwise direction forces the pistons in the respective cylinders I3 and |30 downwardly to move the links or top frame members or bows downwardly toward the floor Ii to collapse the top (not shown).

Referring now particularly t0 Fis. 2, and with high pressure being applied to the chambersl above the pistons in the cylinders Il and |20, the parts of the compensating or shuttle valve unit 25 are in the positions shown in this figure.

The valve structure 2l has a body portion 00 which, as shown merely by way of example, is of substantially T-shape having a transverse port or passageway 8| and a connecting longitudinal passageway 82. It will be understood, however, that the body portion may be of any desired shape. Valve seats l2 and I4 are formed in the body at opposite ends of the passageway or valve bore 62. 'I'he body is hollowed out at its opposite longitudinal end portions to provide sockets o r chambers Il and 88. These chambers are internally threaded at 05a and a to receive and support threaded coupling nuts 6l and Il. Pipe lines 2| and Il are connected with the couplings Il and 8l, respectively.

The shuttle valve assembly for each of the chambers It and I6 and the passageway l2 is identical. As shown, the assembly at the lei't of Fig. 2 comprises a poppet or disk valve Il mounted upon a stem 10 and held against an abutment by spring 14. The valve l2 has one or more openings or passages tta therethrough. The valve stem is supported in position by means of a compression spring 1I whose inner end engages the head on stem 'It and also engages the central portion of the valve Il. The outer end of spring 1i seats against the inner face of member Il and is maintained in position by means of a series of fingers or projections 12 on said member. l

The stem 10 also carries a relatively smaller disk valve or excess pressure relief valve 'Il which is normally urged toward the poppet valve Il to close the openings or ports "a in the valve Il 40 by means of a compression coil spring 1l, having Il attached to a body frame its outer end seated against the valve 'Il and its inner end against a washer 1t adjustably held in position by a nut 16.

The valve assembly at the right of Fig. 2 comprises parts corresponding to those of the valve assembly at the left of this figure, namely, a disk valve 12 having one or more holes or openings 'la therethrough. The valve is mounted upon a stem l0' and is supported in position by a compression spring Il whose outer end engages and grips the head on stern I0 and also engages the central portion of the valve 1l. The inner end of the spring ll seats against the inner face of member 8l and is maintalned'in position by means of a series of fingers or projections l2 on said member.

The stem l0 also carries a relatively smaller excess pressure relief disk valve which, as shown herein, is held against the poppet valve 'Il to close the openings 'lla formed therein, by means of a compression coil spring Il having its outer end seated against the valve Il and its inner end against a washer l5 adjustably held in position upon the stem Il by a nut Il.

'I'he filling and bleeding of the system may be accomplished substantially as follows:

The system is illled through the reservoir 2| by pouring fluid into the reservoir and running the pump 22 in one direction thereby sucking the fluid from the reservoir until the piston I 4 of cylinder I3 has reached the end of its stroke and no more iluid can be added. The pump is then operated in the opposite direction and the reservoir is filled as necessary and fluid sucked from opposite direction several times until all of the air is completely forced out through the relief poppet valves 19 and 93. v

The operationv of the mechanism heretofore de'. scribed is substantially as follows:

The pull rod 4I on the instrument panel is actuated to operate the electric switch 49 and the solenoid 43 to run the motor and drive the pump 22 in a counterclockwise direction. When the pump isv thus driven or run in a counter-clockwise direction, the fluid is drawn from the upper end of the cylinder I3 and forced into 'the lower end thereof. However, as the volume or capacity ol the upper end of the cylinder is less than that of the lower end due to the presence therein of the piston rod l5, a suction is-created in line 2B opening the poppet valve or flapper 69 and allowing fluid to be drawn from the reservoir 2il past valve il into' the line 29 and hence to the lower end of the cylinder to compensate for this difference; The ilapper or poppet valve 19, of course, is closed under the influence of its spring 8i and the pump pressure in coupling 34. When the line pressure of the lower end builds up to a predetermined high pressure, the relief poppet tt starts'to open gradually until at any predetermined pressure such, for example, as 125 pounds per square inch,'it hasopened suiilciently to by-pass enough iluid through the holes 19a in the dapper 19 on the .pressure side of the pump. around the open flapper or poppet valve 99, to the suction side of the pump 22 so that no further pressure can be built up and the line pressure will remain constant and never exceed thepredeterminerivv pressure setting.

When the pump 22 is operated in aciockwise direction the fluid is' drawn from the lower end of the cylinder I2 and forced into the upper end thereof. However, as the volume or capacity of the upper end of the-cylinder is less than that of the lower end due to displacement by the piston rod, an excess or surplus of fluid is left in the'lower endof the cylinder as the piston I4 starts to move downward under the pressure of the fluid builtup in line 26. The iiapper valve 69 remains closed under .thisV pressure. This excess fiuid in thelower end of the cylinder is then put under compression by the movement downward of ,the 'piston I4 and pressure is also built up in the lower end causing the 'iiapper valve 19 to also' remain 'closed as aresult of thepressure appliedlto the -uppr endv and the consequent movement of-thepiston. These pressures both increase'until-relief poppet 13 starts to open according to its vpredetermined setting and allows this excess oilto by-p'ass through holes 69a in "the'apper valve 99 and into the 'reservoir 2i. When allof this excess fluid hasl byi-passed into the' reservoir, then line 9i `becomes the suction sidel of the pump and the by-pass at pop otr pressure (125 pounds per square inch) is as before, from the line 26 at the pressure side through holes 99a inthe poppet valve or iiapper 69 around the" open ilapper 19 to the line 3B at the suction side. Thus Figure 2 shows this condition after this excess liquid has been by-passed into the reservoir, and reliefl valve 13 remains open and the relative suction in coupling .34 has opened valve 19. Thus in this form of the invention with .the main valves independent, the relief valves 13 and 8l are essential to the operation, as it will be apparent that the piston could not move if they were not present and there were no substantial leakage.

i The foregoing description relates to the operation of the device in connection with a single cylinder I3. It will be understood' that when a second cylinder, namely, the cylinder |30, is employed, the interconnecting lines 46, 50, etc., as described above, function with their associated lines 26, 93, etc., and in connection with cylinder I3 to actuate the pistons in both cylinders sivmultaneously.

It is to be understood that the reservoir 2i is used only as a compensatory and also a reserve supply reservoir. This reservoir' compensates for the diil'erence in volume between the upper end of the cylinder (or cylinders) rand the lower end thereof due to the presence of and therefore volume or space occupied by, the piston rod i5.

In other words, Without the reservoir 2i, the volume of oil in the lower end of the cylindei` would all have to be forced into the smaller space or volume at the upper end of the cylinder. This, of course, would be impossible and the result would be a locking or binding of the oil pump and the piston at 'some point in the stroke. Moreover, due to lthe'space occupied by the piston it, there is not sufficient oil in the upper end of the cylinder I9 to completely fill the lower end thereof. However, the reservoir 2li also provides means for compensating for volume changes of the oil due to the operating pressure and to the expansion or contraction of said oil due to any temperature variation. In addition, the compensating reservoir permits filling of the system Without "the necessity of external bleeding, that is, the

pressure balance valve, through the medium of the reservoir, is self-bleeding when the system is filled.

By virtue of the factthat the Vreservoir 2i is merely a compensating reservoir for the slight changes in volume, and because of the fact that a slight vacuum or a few pounds of pressure in the reservoir would make nodifference to the operation of,r the system, due to the presence of the pressure balance valve, the reservoir can be made airtight and thusthe whole fluid system becomes a wholly sealed unit Referring now particularly to Fig. 3 of. the drawings, there is shown a somewhat modified and preferred arrangement of the power unit constituting the present invention. In this form of the invention the electric motor and the gear pump 9| for the fluid are arranged in tandem and preferably in-a horizontal plane. The valve unit duit bands, straps, or members 96 and 91 conncct the source of power to the solenoids and to the electric motor. The switch 40, shown in Fig. l, is connected with'the solenoids 93 and 94 through the medium of the wires or cables 42, seen also in Fig. l.

` In other respects, the present arrangement of power unit is similar to that of Fig. 1. there being a pipe line 2l leading to the upper oil or other fluid reservoir 2|. Pipe lines 2t and 3i, corresponding to similar lines shown in Fig. 1, leail nism embodying the present invention and installation, mounting, and service are easier, and the cost is reduced.

The valve mechanism shown in Fig. 4 is substantially like that of Fig. 2 except that the poppet or disk-like valves 69 and 'Il are controlled or actuated by mechanical means as well as by fluid pressure in the system. That is to say, when one poppet is' held against its seat by fluid pressure. the other poppet is held'off its seat mechanically. With the parts yin the positions shownin Fig. 4. fluid pressure in the system is holdirig the valve 68 on its seat BI whereas the valve 19 is simultaneously held oif its seat Il by mechanical means. As shown herein, merely by way of example, thevalve stems 10 and Il have inward opposed extensions 10a and 80a, respectively, which project inwardly beyond the inner faces of the spring adjusting nuts 'It and Il and abut or engage one another. Thus, the valve stem 10, 10a mechanically holds the valve 'i9 oif its seat. With the parts in the reverse position or toward the left of Fig. 4, with the valve 'l0 against its seat 64, the valve stem portions 'I Ila. 80a will mechanically maintain the valve 09 unseated or oil its seat 63. As will be seen from Fig. 4, and since the two valve stems 'l0 and 80 are long enough to hold one valve off its seat when the other is closed, it will be apparent that when the valve unit itself (the two valves 8l and 19 and their stems 1li and 80) is held in its normal or inoperative central position by the identical light centering springs Il and 8l, the valves will be slightly oil their seats and will thus permit la small by-pass leakage through the valve bore.

This feature is valuable since it permits a direct manual operation of the top when the pump is inoperative, as when the electric I'notor cannot be turned on or the like. For example, if the electric motor is energized through the ignition switch, the top can be raised ii' the owner is away with the ignition key.

As will be apparent, the valve umts shown in Figs. 1 and 4 and having two valve rods, one for each end of the valve bore, will permit individual adjustment or removal and insertion of the two valves and their stems. If desired, a single common valve stem maybe employed for both of the valves 89 and 10, which if used, would supplant abutting separate valve stems 10, 10a and 80, 80a. In that event, a single spring between the relief poppets 1l and 83 would take the place of the separate springs 14 and I4. It will be understood that if a single valve stem were used, it would be of .the proper length so that when one of the poppet valves was seated, the other valve would be oil.' its seat and here also there will be the by-pass leakage in inoperative position to permit direct manual operation of the top and consequently of the direct connected piston motor. As will be apparent, both here and in the form of Fig. 4, thev centering springs will aid in holding the valves slightly of! their seats to permit slow manual operation since the valves will not be closed until there is an appreciable pressure side valve. v

This single valve stem form of the valve unit is shown in Fig. 5, which is identical with and has; referencev 'characters similar to, Fig. 4, except for the single spring 14 for the relief valves, thc single valve stem 10', and the omission -of parts 1l, il, and separate abutting stem parts Na and Ita. It will also be seen that Fig. 5 shows both the valves Bl and 'Il held oif their seats` in their neutral leaking position.

When the valve mechanism of Fig. 4 is employed, the filling and bleeding oi' the system would be accomplished substantially as follows:

The system is filled through the reservoir 2| by pouring fluid into thelreservoir and runninz the pump 22 in one direction thereby sucking fluidA from the reservoir until the piston i4 has reached the end of its stroke and no more fluid can be added. The pump 22 is then run in the opposite direction with the reservoir kept full and the oil or other fluid is sucked from the reservoir and other end of the cylinder I3 until the piston has reached the end 'of its stroke in the opposite direction.

. Bleeding m'ay be accomplished in two ways in the present System.

The pump is `first operated several times, iirs't in one direction and then in the other direction. When the pressure poppet or napper valve closes, the other poppet is mechanically held open by the contacting stems 'Illa and 30a so that the supply side vof the valve mechanism or line is always open to the reservoir 2| and to atmosphere. Accordingly, any air in the system is free toescape from the side not under pressure during the operation of the unit and the movement of the piston.

Additional bleeding is accomplished through the relief poppets 13 and Il which open gradually under pressure and allow the air to be forced out.

'I'he operation of the system when embodying the valve mechanism of Fig. 4 or of the common valve stem form is substantially as follows:

When the pump 22 is run or operated in a.v

'counterclockwise direction, the fluid is drawn from the upper end of the cylinder I3 and forced into the lower end thereof. Thus pressure in line I5 closesthe poppet valve I8 and'l opens valve 88 as the flow increases. The reservoir is then mechanically placed in communication with the upper end of the cylinder line so that the needed extra fluid due to the piston rod `displacement in theupper end of the cylinder direction the fluid is drawn from the lower end of the cylinder I3 and forced into the upper end thereof. Thus pressure in line 28 similarly closes the poppet or iiapper valve 69 and opens the valve or i'iapper 10. The reservoir 2| is then mechanically communicated with the lower end of the cylinder line so that the excess iiuid in the bottom of the cylinder Il, due to the displacement of the piston rod in the upper end of the cylinder. is free to ilow into the reservoir during the operation of the unit and the movement of the piston I4. l

The relief poppet 13 functions in exactly same manner as in Fig. 2.

' 'I'hus it will be apparent that in these other the forms of the invention, in which the main valves 69 and 19 are not independent but interact so that when one isclosed it holds the other oif its seat, the relief valves 'I3 and 83, While not essential to operation as in the rst form, are highly desirable to not only limit excess pressures in the motor, as from thick oil on Va cold morning and to permit the use of an excess powered electric motor and pump, but, more important, to provide a safety feature whereby the rat of motion' of the convertible top and particularly the force pushing it are limited so that it is not dangerous (as to children) and, in fact, may be stopped by hand if the switch cannot be reached. Obviously, these advantages may also be realized in the first form.

It is to be understood that the operation is the same as above described when two cylinders I3 and |30 are employed.

It will be understood that the hydraulic power system embodying the present invention can, of course, be operated from any convenient form of power other than the electric motor described herein. If the source of power could not convenientlybe reversed, a valve could be installed in the pressure and suction lines in the vicinity of the pump 22 to reverse the flow of fluid in these lines by means of a moving plunger instead of by means of reversing the pump itself.

I claim:

l. In a hydraulic lift mechanism for raising or lowering a convertible automobile top or the like, in combination, a reversible electric motor,

a liquid pump rotated in either direction thereby, a double acting cylinder and piston motor to raise or lower said top and having a piston rod at one end only so that unequal volumes are displaced at the two ends of the cylinder, two conduits connected to carry liquid from opposite sides of the pump to opposite sides of the piston,

a compensating and replenishing valve unit comprising means defining a valve bore connected between said conduits, a liquid reservoir connected to the intermediate portion of said bore and forming a sealed system with said conduits, the pump, the valve, and the cylinder, said bore having at each end a valve seat and a cooperatf ing valve member to be selectively seated by liquid ilow from the pump outlet, rod means between said valve members and having a length slightly greater than the spacing between said valve seats, and centering spring means normally or in inoperative position holding said two valve members slightly off their seats to permit manual lifting of the top and consequent actuation of the piston. A

2. In a convertible automobile top mechanism, a wholly sealed hydraulic actuating mechanism comprising a double acting piston motor having only asingle piston rod, a reversible liquid pump, a reversible electric motor driving said pump, conduits between said pump and motor to operate it in either direction, a liquid reservoir, and a shuttle valve unit including movable valve means actuated automatically and only by the liquid flow and pressures for selectively connecting said reservoir to the then low pressure conduit for operation of the top and motor by liquid now through said by-pass leakage passage, and said movable valve means including, as va part thereof and moving and cooperating therewith, resiliently biased excess pressure relief valve means to limit the pressure in either4 end of said piston motor in either direction of its travel by venting it`to the other end of the cylinder and to the reservoir to thus permit the use of an excess powered electric motor and pump with safety to careless passengers.

3. In a mechanism for convertible automobile tops or the like, a hydraulic actuating system comprising a double acting piston motor having a single piston rod to directly raise or lower said top. a reversible electric motor, a liquid pump means connected to operate said-motor, a reversing electric switch as the sole control for said electric motor and pump. a compensating shuttle valve unit operated automatically and only by the pressures due to liquid flow and connected across said pump connections, a liquid reservoir positioned above said valve unit and connected to said valve unit to be selectively communicated with the then low pressure side of the pump durlng pump operation, said shuttle valve unit including resilient valve centering means and cooperating means to provide upon non-operation of the pump means a by-pass leakage through said valve unit in its centered inoperative position to permit direct and slow manual actuation of the top and its motor piston.

4. In a mechanism for convertible automobile tops or the like, an hydraulic actuating system comprising a double acting piston motor having a sin'gle piston rod to directly raise or lower the top, reversible liquid pump means connected to operate said motor, a liquid reservoir, and a motor Volume change compensating shuttle valve unit comprising means den'ning a valve bore connected across the pump liquid connections, a connection from the reservoir to the intermediate portion of said bore, an outwardly facing valve seat at each end of said bore, a pair of coaxial and normally abutting valve rods in said bore, each carrying at its Outer end a disk valve mount ed thereon to be movable back and forth thereeither direction of piston motion, said valve unit v with and to be selectively closed against the valve seat only by the pressure from the then high pressure side of the pump so that it acts directly on its valve rod and through the abutting valve rods to push the other disk valve toward open position and to lift it off its seat, the length of said abutting rods and the spacing between said disk valves being greater than the distance between said valve seats, so that when said rods andl their valves are centered both valves are off their seats to provide a through or by-pass leakage passageand a centering spring in each end of the valve bore acting-aaginst each disk valve to automatically return them to and normally hold them in centered positions 01T their seats during non-operation of said pump means or low rates of liquid flow and pressures to thus permit slow manual operation of said top and said piston motor by liquid flow through said by-pass leakage passage.

5. In a raisable or lowerable automobile convertible top mechanism or the like, an hydraulic mechanism comprising a double acting piston motor having only a single piston rod, a reversible ilow liquid pump, a reversible electric motor driving said pump. conduits between said pump and motor to operate it in either direction in accordance with the direction of rotation o! said electric motor, a compensating liquid reservoir, and a compensating valve unit for selectively connecting said reservoir to the then low pressure conduit for either direction of piston motion to compensate for the difference in volumes due to the single piston rod, said unit including two independent and unconnected oppositely acting valves resiliently biased to their closed positions and r1o

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