US3141846A

US3141846A - Load control unit for cyclical centrifugal installation

Info

Publication number: US3141846A
Application number: US185409A
Authority: US
Inventors: Jr Thomas R Laven
Original assignee: Western States Machine Co
Current assignee: Western States Machine Co
Priority date: 1962-04-05
Filing date: 1962-04-05
Publication date: 1964-07-21
Anticipated expiration: 1981-07-21

Description

July 21, 1964- T. R. LAVEN, JR

LOAD CONTROL UNIT FOR CYCLICAL CENTRIF'UGAL INSTALLATION Filed April 5, 1962 3 Sheets-Sheet 1 Minimum,

NNNNNN OR THOMAS R.LAVEN,JR.

AT %RNEY July 21, 1964 T. R. LAVEN, JR 3,141,346

LOAD CONTROL UNIT FOR CYCLICAL CENTRIFUGAL INSTALLATION Filed April 5, 1962 3 Sheets-Sheet 2 Fig.2 29

INVENTOR THOMAS R. LAVEN,JR.

Fig 4 031-42.

ORNEY y 21, 1964 T. R. LAVEN, JR 3,141,846

LOAD CONTROL. UNIT FOR CYCLICAL CENTRIFUGAL INSTALLATION Filed April 5, 1962 s Sheets-Sheet a Fig.3

INVENTOR THOMAS R. LAVEN, JR.

AT RNEY United States Patent Ofiiice 3,141,846 Patented July 21, 1964 3,141,846 LOAD CUN'IROL UNIT FOR CYCLICAL CENTRHFUGAL WSTALLATKON Thomas R. Laveu, in, Hamilton, Ohio, assignor to The Western States Machine Company, Hamilton, ()hio, a corporation of Utah Filed Apr. 5, 1962, Ser. No. 185,409 7 Claims. (Ql. 233-19) This invention relates to a new and improved loading control mechanism useful especially for regulating the introduction of charge material into heavy cyclical centrifugal machines of the types used, for example, in chemical industries or in the manufacture and refining of sugar.

More specifically, this invention relates to a mechanism for controlling the thickness of charges formed in a rotating basket of a centrifugal machine by material flowing through a loading device into the basket.

It is an object of the present invention to provide such a control mechanism which effectively controls the thickness of the charge wall formed in the basket, which is compact and relatively simple in construction and operation and occupies little of the space available at the curb of the centrifugal, and which may be easily installed on and removed from existing installations without disassembly of the installations.

It is a more specific object of the present invention to provide such a mechansim which is readily adjustable to vary the thickness of the charge wall to be obtained by its operation and which gives assurance that in every condition of the adjustment an attendant of the installation will have a direct visual indication of the charge thickness for which the mechanism is adjusted.

These and other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof and from the accompanying drawings in which:

FIG. 1 is a diagrammatic assembly view of a cyclical centrifugal installation provided with the loading control mechanism of the present invention;

FIG. 2 is a cross-sectional view of the loading control mechanism taken on line 22 of FIG. 1;

FIG. 3 is a schematic diagram of the loading control mechanism showing in dotted lines positions assumed by the principal operating parts thereof in a working position, in solid lines positions to which these parts are moved by a charge wall forming in the basket, and in chain lines positions which these parts assume in a rest position; and

FIG. 4 is a view partially in cross section of the loading control mechanism as it appears in a transitory position, between the above-mentioned working and rest positions, where the center lines of the principal operating parts are aligned.

Referring first to FIG. 1, the cyclical centrifugal installation shown therein includes a fixed curb structure 1, a portion of the cover 2 of which is broken away to reveal a centrifugal basket 3 mounted for rotation within the curb structure. A portion of the top 4 of the basket is in turn broken away to reveal the basket side wall 5 on which charge material, delivered to the rotating basket through a suitable loading device, such, for example, as the pipe 6, accumulates to form a charge wall as indicated at 7.

A loading valve indicated schematically at 8 controls the delivery of charge material through the pipe 6 into the basket. In the illustrated centrifugal installation, the valve 8 is solenoid actuated and when energized is opened, whereby to deliver charge material to the basket. When deenergized this valve is closed to prevent or terminate such delivery.

The loading control mechanism of the present invention, indicated generally as it), includes a housing 11 adapted to be supported on the cover 2 of the curb structure and a shaft 12 rotatably carried in the housing and extending downwardly therefrom. A charge feeler 13 is carried by and extends radially from the lower end of the shaft, and a radial lever 14 and radial stop member 15 are mounted on and movable with the shaft within the housing. A switch 16 is fixed to one wall of the housing and a fluid pressure cylinder 17 is fixed to another wall of the housing and has a piston rod 18 extending into the housing and connected therein to lever 14.

The cylinder 17 is preferably of the single acting spring return type containing the piston rod 18 extending through its forward end and containing a return spring 1.8a which continuously urges the piston rod toward its retracted position near the backward end of the cylinder. The cylinder is connected by a fluid pressure line 19 to a control valve indicated schematically at 2% A fluid supply line 21 connects the valve 2%) wth a source, not shown, of fluid under pressure, and the valve has a vent line or port 22 for releasing fluid pressure from the cylinder through line 19. The valve 20 is preferably solenoid actuated. When energized it connects line 19 to the supply line 21, to supply fluid under pressure to the cylinder to extend the piston rod, and when deenergized it exhausts pressure fluid from the cylinder and allows the piston rod to be retracted under the force of the return spring.

Conductors 23 and 24 provide an electrical circuit 25 which includes the valves 8 and 20, the switch 16, and a power source 26, so that when the switch is closed the valves 8 and 20 are energized and when the switch is open they are deenergized. A switch 24a permits the circuit 25 to be opened to inactivate the loading control mechanism whenever desired.

Referring now to FIG. 4, it will be seen that the housing 11 is box shaped and includes a top wall 27, a bottom wall 23 and side walls 29, 3t 31 and 32 (FIG. 2). The housing is releasably but fixedly secured to the curb cover 2 as by screws 33 extending through wall 28. Integral with the housing is a tubular structure 34 which extends downwardly from the housing into the basket through an opening 35 in the curb top, and which encloses and provides supporting bearings for the shaft 12.

The upper end of shaft 12 carries a head 36 disposed Within an opening 37 in the housing top wall 2'7. The shaft extends downwardly therefrom through the housing and through the tubular structure 34 in engagement with

bearing sleeves

38 and 39 at the top and bottom ends respectively, of that structure. The lower end of the shaft extends below sleeve 39 to its connection with the radial arm 13:: of the feeler 13, at a location intermediate the top and bottom walls of the basket.

The head 36 includes a pointer 40 (FIGS. 1 and 3) formed on the upper surface thereof so as to be visible at all times to an attendant of the installation. The pointer cooperates with a suitably calibrated scale 41 formed on the top wall 27 around the opening 37 therein to provide a visible indication to the attendant of the angular position of the charge feeler relative to the basket sidewall 5. The scale 41 preferably includes an ou or rest indicium and a plurality of numerical indicia.

The stop member 15 is fixed to and extends radially from a sleeve portion of the head 36 at a location below top wall 27 of the housing. The free end of this stop member coacts with a portion 31a of the housing side wall 31, which portion constitutes a fixed abutment limiting clockwise motion of the stop member, hence of the assembly of head 36, shaft 12 and feeler 13, to a limiting position thereof corresponding to the desired rest position of the feeler and the OUT location of the pointer 46.

Upper and

lower arms

42 and 43, which together constitute the radial lever 14, have sleeve portions which are received loosely on the shaft within the housing between the head 36 and the bottom wall 23. The

arms

42 and 43 are connected for rotation with shaft 12 by a bolt 44 which extends downwardly through an arcuate slot 45 (FIG. 1) formed in the head 36, into aligned and suitably threaded bores 46 in the arms.

As seen most fully in FIGS. 1 and 4, the arm 42 has a free end portion formed with a finger 48 and the arm 43 has a free end portion formed with a finger 47 below and spaced horizontally from the finger 48. A portion of the lower side of the arm 42 between the sleeve and free end portions thereof, and an oppositely facing portion of the upper side of the arm 43, are recessed so that the arms define a horizontally extending cavity 49 therebetween.

The fluid pressure cylinder 17, as shown most fully in FIG. 2, is fixed to the side wall 29 of the housing 12 and its piston rod 18 extends through a suitable opening in that wall and into the interior of the housing where it is connected to the

arms

42 and 43 by an elongated adapter nut 56 positioned in the cavity 49. The nut 50 has a longitudinally extending bore comprising a threaded portion 51 and a smooth portion 52, and a longitudinally extending slot 53 whcih passes vertically through the nut and traverses the smooth bore portion 52. The nut 56 is secured to the piston rod 18 by engagement of the threaded bore portion 51 with the threaded free end of the piston rod and is slidably mounted in the opening 49 by a pin 54 which extends through aligned radial slots 55 in the

arms

42 and 43 and through the slot 53 in the adapter nut.

A compression spring 56 is disposed within the smooth bore portion 52 and extends into the slot 53 so as to hear at its opposite ends against the piston rod 18 and the pin 54, respectively. The spring 56 thus continuously biases the pin, and thereby the

arms

42 and 43, head 36, shaft 12, and charge feeler 13, in a counterclockwise direction, as viewed in FIG. 1.

The switch 16, as seen in FIG. 4, is fixed to the side wall 30 of the housing 12 and has a head portion 57 extending through a suitable opening in that wall, upon which portion a switch arm 58 is swingable within the housing about a horizontal axis. The switch arm has a position indicated by solid lines in FIG. 3, at which the switch 16 is open, and a position indicated by dotted lines in FIG. 3, at which the switch 16 is closed. The switch arm carries on its free end a roller 59 which is disposed in the path of and adapted to be selectively engaged by the

fingers

47 and 48 on the

arms

42 and 43, whereby to move the switch arm between its aforesaid positions.

The positions of the various operating elements of the loading control mechanism when the mechanism is at rest are shown in chain lines in FIG. 3. The switch 16 is then closed, so that the valves 8 and 20 are deenergized and the piston rod of cylinder 17 is retracted; the stop member 15 is in engagement with the abutment 31a; the charge feeler 13 is in its out or rest position away from the basket side wall and the pointer 40 indicates this latter fact by its position opposite the out indiciurn on the scale 41.

To actuate the mechanism, an electrical signal is supplied to the valve 20, as by the closing of a switch 60 (FIG. 1) in an auxiliary circuit 61 connected to the valve. The valve 26 is energized upon receipt of this of this signal so that fluid under pressure is supplied through the lines 21 and 19, and the piston rod in the cylinder is thus extended. Extension of the piston rod rotates the assembly of the shaft, charge feeler, lever, and stop arm from the chain line or rest position thereof to the dotted line or working position thereof. The distance of travel of the lever arm 14 in the course of movement of said assembly to said working position is substantially the same in every operation of the mechanism, being fixed by the permitted travel of the piston 18 in the cylinder 17. Such travel is stopped at the point where further forward movement or extension of the piston is blocked by the spring 18a compressed between the head of the piston and the forward end of the cylinder 17. Accordingly, in each operation of the mechanism the arm 14 is brought to a relatively fixed location in space which lies at a fixed angular distance from its rest position and has a fixed relationship to the location of the side wall 5 of the centrifugal basket.

When said assembly reaches said working position, the stop arm 15 is spaced away from the abutment 31a; the charge feeler is in its working position relative to the basket side wall, i.e., the position at which a charge wall building up in the basket is to start the valve closing movement of the feeler; and the pointer indicates the exact distance of the feeler from the basket wall by its position opposite one of the numerical indicia on the scale 41. In the course of the movement of the assembly to its working position, the finger 47 on the arm 43 engages the switch roller 59 and moves the switch arm 58 to its dotted line or closed position. Closing of the switch 16 closes the circuit 25 to the valves 8 and 29, thereby opening the valve 8 to commence delivery of charge material into the basket through the pipe 6, and thereby holding the valve 20 energized. Thus, the electrical signal from the circuit 61 which initiates the loading cycle need only be of a duration sufficient to cause full extension of the piston rod in cylinder 17.

As the charge material enters the rotating basket, it forms an annular charge wall 7 of progressively increasing thickness on the side wall 5 of the basket. As the charge wall reaches the thickness indicated by the dotted lines of FIG. 3, it engages the charge feeler and begins to move the assembly of the charge feeler, shaft, lever, and stop arm inward from the working position toward the rest position. This inward movement is permitted, even though the cylinder 17 is still extended due to the continued energization of the valve 26, by the movability of the pin 54 on the

arms

42 and 43 in the slot 53 in the adapter nut 50 on the end of the piston rod. Such movement, however, is resisted by the compression of the spring 56 between the pin 54- and the piston rod 18, which compression is readily predetermined and set so as to provide any desired force in resistance to the inward feeler movement. During this charge-induced movement of the assembly, the finger 43 on the arm 42 engages the roller 59 on the switch arm 58 and moves the switch from its closed or dotted line position of FIG. 3 toward its open or solid line position. The switch reaches its open position as the charge wall forming in the basket reaches its desired final thickness, as indicated by the solid line at the inside of the charge wall in FIG. 3. The position of the assembly at the instant the switch is opened is shown by the solid lines of FIG. 3.

When the switch 16 opens, the valve 8 is deenergized to terminate delivery of charge material to the basket, so that the charge wall formed in the basket will have a predetermined desired thickness. Opening of the switch 16 also deenergizes the valve 20, thereby exhausting pressure fluid from the cylinder and allowing the return spring therein to move the assembly to the rest or chain line position of the feeler, determined by engagement of the stop member against the abutment 31a, where the feeler is held safely away from the range of gyratory movements of the basket and its contents at high speed. During its movement from closed to open position the switch roller 59 follows an arcuate path in which it drops below and becomes disengaged from the finger 48 so as no longer to impede movement of that finger as the assembly moves from its solid line to its chain line or rest position.

The loading control mechanism is thus operative to produce a final charge wall thickness which is determined by the distance of the charge feeler from the wall of the basket in the working position of the feeler. To adjust the wall thickness to be produced by operation of the mechanism, the assembly is first moved to its extreme counterclockwise position by an actuation of valve to extend fully the piston rod in the cylinder. The bolt 44 is then loosened and the assembly of the shaft, stop member, and charge feeler is moved angularly relative to the lever 14 (i.e., arms 42 and 43) to a position where the numerical indicium opposite the pointer corresponds to the desired final wall thickness. The bolt is then tightened to set the mechanism in its adjusted position.

It will be seen that the angular adjustment of the shaft, head 36, and the feeler, which is effected in order to vary the working position of the feeler, occurs without any change of the relative positions of the cylinder 17, piston 18, adapter nut 50, lever 14 and switch 16. As the adjustment is made, the bolt 44 moves angularly in the arcuate slot 45 formed in the head 36. Accordingly, when the bolt is re-tightened in adjusted position, the working position of the feeler and the position of the pointer are changed, but the positional relationships of the parts which operate the switch 16 to open and close the loading valve remain unchanged. The pointer, therefore, will always indicate the charge thickness to be obtained, when the piston rod in the cylinder is extended to open the loading valve.

Further, the rest position to which the assembly will be moved following such adjustment will be the same for all conditions of adjustment since the stop member 15, being moved with the shaft and charge feeler during their adjustment relative to the lever 14, is always at an angular distance from the fixed abutment 31a corresponding to the angular distance of the feeler from its rest position.

It will of course be apparent that the fluid and electric circuitry of the illustrated embodiment is merely exemplary and may take other forms consistent with the invention. For example, a fluid pressure cylinder may be used to control the operation of the valve 8, in which event a solenoid actuated valve such as indicated at 2t) may be used to control the delivery of pressure fluid both to the loading control cylinder 17 and to the above mentioned valve operating cylinder.

Although a preferred embodiment of the invention has been shown and described in detail, it is to be understood that the new features of the invention may be utilized in other ways and are not restricted to the embodiment shown except as required by a fair construction of the appended claims.

I claim:

1. In a centrifugal installation including a centrifugal basket and a loading valve controlling the delivery of charge material into the basket, a loading control unit for controlling the thickness of charges of said material formed in the basket, comprising:

a charge feeler movable within the basket between a rest position away from the location of a charge therein and a working position where the feeler will be engaged and returned toward rest position by a charge wall forming in the basket,

an angularly movable support carrying said feeler,

actuating means for said loading valve,

an actuating element carried by said support and operative, at a fixed location in space, in response to return movement from working position of the assembly of said feeler, said support and said actuating element, to cause said actuating means to close the loading valve,

operating means for turning said assembly from rest position to working position,

means operative upon every such turning of said assembly to stop the assembly at a working position wherein said actuating element is at a fixed location in space lying at a fixed angular distance beyond the first mentioned fixed location so that in every loading operation a movement of the assembly by the charge wall through a return are of definite length will move said actuating means to effect closing of the loading valve,

means rendered operative upon the last-mentioned movement of said actuating means to move said assembly to rest position through a further return are,

means releasably and resettably interconnecting said support and said actuating element for adjustment of the angular position of said support and said feeler relative to said actuating element whereby the distance of the feeler from the basket wall at said working position, and thereby the charge thickness at which the loading valve will be closed, is variable at will,

a stop member carried by said support,

and an abutment fixed in the path of said stop member at a desired limit of the return movement of said assembly, whereby the feeler and the support are confined to the same rest position upon every return movement thereof irrespective of the position of adjustment thereof relative to said actuating element.

2. A centrifugal installation according to claim 1, said loading control unit further comprising:

a pointer carried by said support and held in fixed angular relation thereto during any adjustment aforesaid so that the angular relation of said pointer to said actuating element is varied by such adjustment,

and a fixed scale adjacent to said pointer,

said pointer and said scale being disposed so as to be visible to an attendant, whereby the positions of the feeler relative to the basket wall will be correctly indicated to the attendant in all conditions of said adjustment.

3. In a centrifugal installation including a centrifugal basket and a loading valve controlling the delivery of charge material into the basket, a loading control unit for controlling the thickness of charges of said material formed in the basket, comprising:

an angularly movable support member carrying said feeler,

actuating means for said loading valve,

an actuating element carried by said support and operative, in response to a predetermined amount of return movement from working position of the assembly of said feeler, said support and said actuating element, to cause said actuating means to close the loading valve,

and an operating member connected to said support member for turning said assembly from rest position to working position,

one of said members having a spring received in a slot formed therein and the other carrying a pin extending through said slot and movable therein against the resistance of said spring through a distance corresponding to said predetermined amount so that the gate closing return movement of the charge feeler under the force of the charge wall forming in the basket is resisted by the predetermined force of said spring.

4. In a centrifugal installation including a centrifugal basket and a loading valve controlling the delivery of charge material into the basket, a loading control unit for controlling the thickness of charges of said material formed in the basket, comprising:

an angularly movable support carrying said feeler,

actuating means for said loading valve including a switch movable between valve opening and valve closing positions,

an arm carried by and turnable with said support and engageable with said switch,

said arm being operative in response to return movement from Working position of the assembly of said feeler, said support and said arm to move said switch to valve closing position, whereby to close said valve,

a single acting spring return fluid pressure cylinder comprising a piston rod connected to said arm and operable upon full extention of said rod by fluid admitted under pressure to the cylinder to turn said assembly from rest position to working position,

means operative in response to movement of said switch to valve closing position to exhaust pressure fluid from said cylinder whereby said rod is retracted by the return spring of the cylinder and said assembly is returned to rest position,

means releasably and resettably interconnecting said support and said arm for adjustment of the angular position of said support and said feeler relative to said arm whereby the distance of the feeler from the basket Wall at said working position, and there by the charge thickness at which the loading valve will be closed, is variable at will,

a stop member carried by said support,

and an abutment fixed in the path of said stop member at a desired limit of the return movement of said assembly, whereby the feeler and the support are confined to the same rest position upon every return movement thereof irrespective of the position of adjustment thereof relative to said arm.

5. In a centrifugal installation including a centrifugal basket and a loading valve controlling the delivery of charge material into the basket, a loading control unit for controlling the thickness of charges of said material formed in the basket, comprising:

an angularly movable support carrying said feeler,

actuating means for said loading valve,

means movable with said support and operative in response to a predetermined amount of return movement from working position of the assembly of said feeler, said support and said movable means to cause said actuating means to close the loading valve,

an arm member carried by and turnable with said support, a

an operating member connected to said arm member for turning said assembly from rest position to a working position where said arm member is at a fixed location in space,

one of said members having a spring received in a slot formed therein and the other carrying a pin extending through said slot and movable therein against the resistance of said spring through a distance corresponding to said predetermined amount so that the aforesaid return movement of the charge feeler under the force of the charge wall forming in the basket is resisted by the predetermined force of said spring,

and means releasably and resettably interconnecting said support and said arm member for adjustment of the angular position of said support and feeler relative to said arm member whereby the distance of the feeler from the basket wall at said working position is variable at will without aifecting the position of said pin in said slot so that the charge feeler may undergo said predetermined amount of return movement to close the loading valve from any of its adjusted working positions.

6. In a cyclical centrifugal installation including a basket rotatable within a fixed curb, a loading valve for delivering charge material into the basket, and operating means for said loading valve, a loading control unit comprising:

a housing adapted to be supported on said curb,

a shaft rotatably carried in said housing to extend downwardly therefrom into said basket,

a charge feeler carried by and extending radially from said shaft and movable within the basket between a rest position away from the location of a charge therein and a working position where the feeler will be engaged and returned toward rest position by a charge wall forming in the basket,

a sleeve on and movable with said shaft,

a head fixed to said shaft above said sleeve and received in an opening in the top of said housing so that its angular position relative to the housing is always visible to an attendant to indicate to him the position of the feeler relative to the basket wall,

a radial arm on said sleeve within said housing,

a single acting spring return fluid pressure cylinder fixed to said housing and having a piston rod extending into said housing and connected therein to said arm,

the connection between said arm and said rod including a member continuously biasing the assembly of said arm, said shaft, and said feeler toward working position but being yieldable when said rod is fixed in position to allow said feeler to undergo the aforesaid return movement,

a supply line connected to said cylinder for supplying pressure fluid thereto to extend said rod against the resistance of the return spring of the cylinder and thereby rotate said assembly from rest to working position,

a switch within said housing moved by said arm upon rotation of the assembly to working position to cause said operating means to open the loading valve, and moved by said arm upon the aforesaid return movement of said feeler to cause said operating means to close the loading valve,

a control valve movable in response to said return movement to exhaust pressure fluid from said cylinder whereby said rod is retracted by said return spring and said feeler is thereby returned to rest position from the position to which it is moved by the charge wall,

means securing said sleeve for movement with said shaft but releasably and resettably relative thereto for adjustment of the angular position of said shaft and said feeler relative to said arm whereby to vary at will the distance of the feeler from the basket wall at said working position and thereby the thickness at which the loading valve will be closed,

and a radial member moved with said assembly to engage an abutment on said housing at a desired limit of the return movement of said assembly whereby to confine the feeler and shaft to the same rest 9 position upon every return movement thereof irrespective of the position of adjustment thereof relative to said arm.

7. A centrifugal installation according to claim 6, said head having an arcuate slot therein and said securing means comprising a fastening element extending through said slot and engaging said sleeve, said fastening element being releasable to permit adjustment of the angular position of said head and said shaft, relative to said element and the aforesaid radial arm, within the limits of said slot.

References Cited in the file of this patent UNITED STATES PATENTS 1,906,767 Roberts May 2, 1933 1,921,446 Andrews et al. Aug. 8, 1933 2,037,655 Roberts Apr. 14, 1936 10 Neuman Aug. 17, 1937 Neuman Aug. 31, 1943 Cox May 12, 1953 Tompkin June 23, 1953 Hertrich Dec. 20, 1955 Masson Feb. 4, 1958 Lepoutre et al May 23, 1961 Huser Dec. 5, 1961 McPhee et a1. Feb. 6, 1962 Smith et a1. July 17, 1962 FOREIGN PATENTS Belgium Dec. 31, 1952 (Corresponding US. 2,727,630, Dec. 20, 1955) Italy Apr. 24, 1959 France Sept. 26, 1932

Claims

1. IN A CENTRIFUGAL INSTALLATION INCLUDING A CENTRIFUGAL BASKET AND A LOADING VALVE CONTROLLING THE DELIVERY OF CHARGE MATERIAL INTO THE BASKET, A LOADING CONTROL UNIT FOR CONTROLLING THE THICKNESS OF CHARGES OF SAID MATERIAL FORMED IN THE BASKET, COMPRISING: A CHARGE FEELER MOVABLE WITHIN THE BASKET BETWEEN A REST POSITION AWAY FROM THE LOCATION OF A CHARGE THEREIN AND A WORKING POSITION WHERE THE FEELER WILL BE ENGAGED AND RETURNED TOWARD REST POSITION BY A CHARGE WALL FORMING IN THE BASKET, AN ANGULARLY MOVABLE SUPPORT CARRYING SAID FEELER, ACTUATING MEANS FOR SAID LOADING VALVE, AN ACTUATING ELEMENT CARRIED BY SAID SUPPORT AND OPERATIVE, AT A FIXED LOCATION IN SPACE, IN RESPONSE TO RETURN MOVEMENT FROM WORKING POSITION OF THE ASSEMBLY OF SAID FEELER, SAID SUPPORT AND SAID ACTUATING ELEMENT, TO CAUSE SAID ACTUATING MEANS TO CLOSE THE LOADING VALVE, OPERATING MEANS FOR TURNING SAID ASSEMBLY FROM REST POSITION TO WORKING POSITION,