CA1103287A

CA1103287A - Method and apparatus for pneumatically charging a scale with flowable materials

Info

Publication number: CA1103287A
Application number: CA318,936A
Authority: CA
Inventors: Wolfgang Krambrock
Original assignee: Waeschle Maschinenfabrik GmbH
Current assignee: Waeschle Maschinenfabrik GmbH
Priority date: 1977-12-30
Filing date: 1979-01-02
Publication date: 1981-06-16
Also published as: LU80732A1; ZA787318B; GB2012438B; DE2759009A1; SE7812833L; JPS5497982A; FR2413297A1; IT1102447B; DK571278A; NL7812210A; GB2012438A; BE873130A; IT7831330A0

Abstract

ABSTRACT OF THE DISCLOSURE

A method and an apparatus for pneumatic conveying of flowable materials are disclosed. Flowable material is entrained in an air stream and conveyed into the con-tainer of a container-type scale. When the scale senses that the weight of admitted material is approaching the preset desired weight it causes a reduction in the ma-terial flow. This ligher flow then continues until the preset weight is reached, at which time the admission of material into the air stream is terminated. The air stream, however, continues to flow until all or substan-tially all material still present in the conduit at this time has been conveyed into the container to be weighed along with the remainder of the container contents.

Description

~ 3;2~

WITH FLOWABLE MATE~IALS

' BACKGROUND OF THE INVENTION

Field of the Invention The present invention relates to the pneumatic con-veying of flowable ma~erials.

More particularly, the invention relates to a method of pneumatically charging a scale with flowable materials to be weighed.

The invention also relates to an apparatus for cary-ing out the method, -The Prior Art Pneumatic conveying of flowable materials in e.g.

pulverulent form, is known. It is also known to pneumat-ically (i.e. by blowing or suction) charge a container-type sc~le with a mixture of several different flowable mater-iale; and to stop further charging automatically when a predetermined weight of the mixture is found to be present on the scale.

-2-1 ¦ To be economically feasible, this type of transporta-¦ tion requires that a maximum amount of flowable material ¦ be transported, using a minimum amount of air. Compliance l with this requirement, however, causes certain operating ¦ problems in that the transportation of the materials is not entirely uniform. That is to say, hilling and similar accumulation of the materials takes place in the con-veying conduit; when sufficient material has built up so l as no longer to be able to withstand the air flow, all ¦ the material of such an accumulation tends to yield at once and thus to enter the scale in a body. This means that if the conveying air happens to be switched off by the scale mechanism (due to sufficient weight being present l on the scale) at the moment such a body of accumu~lation ¦ material enters the scale, then the total amount of ma-¦ terial finally present in the scale will exceed the preset amount by the weight of this body of material.
Depending upon the conveying conduit diameter and the ef-l ficiency of the pneumatic system, this excess weight may ¦ amount to anywhere from about 100 grams to several kilo-grams.

If a mixture is to be fo~ in the scale from several different flowable materials, it is advisable to have the individual conveying conduits from the separate material sources (i.e. material containers) discharge into a single I
1 ¦ common conduit leading to the scale; this convergence can ¦ take place anywhere intermediate the containers and the ¦ scale. The single common conduit may extend horizontally ¦ and be flexible, thus reducing the chances of interference ¦ with the operation of the weighing system of the scale.

¦ However, this use of a single common conduit has ¦ the disadvantage that the several different materials flow ¦ through it in succession. Thus, when the scale determines ¦ that a sufficient quantity of a first material is present 1~ ¦ in it and switches off the pneumatic system, whatever ¦ residual amount of this irst material is still present ¦ will immediately drop to the floor of the conduit. When ¦ conveying is subsequently resumed for a second one of the ¦ materials of which the mixture is to be composed, then ¦ the residual amount of the first material will, of course, ¦ also be transported into the scale. It is clear that the I scale will then contain more of the first material than ¦ is intended.

¦ These problems have been recognized in the art and l proposals have been made in German patents Nos. 2,034,983 and 2,361,279, as well as in German Published Application ¦ (DY`-OS) 2,544,890, to overcome them. For various reasons, l however, these proposals fall short of providinq a fully ¦ satisfactory solution to the problems and further improve-¦ ments are desirable.

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¦ SUMMARY OF T~IE INVENTION
I

¦ Accordingly, it is an object of the present inven-¦ tion to provide such improve~lients.

¦ More particularly, it is an object of the present ¦ invention to provide an improved pneumatic scale-charging ¦ method which avoids the prior-art disadvantages. ..

Still more specifica:Lly, it is an-object of the in- .
¦ vention to provide an improved method of the type under .
l discussion, wherein any danger of clogging of the pneumat-¦ ic conveying conduit or conduits is eliminated.

An additional object is to provide such a:method as mentioned above, wherein residual material:still-.present:
in the conveying conduit at the time-.the signal-is given for conveying to cease, is still forwarded.to the scale:::
so that it can be included in the weighing.procedure.: --A concomitant object of the-invention-is to provide an apparatus for carrying out the novel method. :
. .

Pursuant to these objects, and still:others which will become apparent hereafter, one aspect of.tlle invention re sides in a method comprising.the steps:of.advancing:a I
1 ¦ stream of pneumatic fluid in a conduit towards a con-¦ tainer which is to be charged to a predetermined extent, ¦ admitting flowable material at a high first rate into the ¦ conduit.for entrainment by ti~e stream, reducing the ad-¦ mission of flowable material to a lower second rate as charging of the container approaches the predetermined extent, terminating the admission of flowable material into the conduit when the predetermined extent is reached, I and continuing to advance the stream of pneumatic fluid ¦ towards the container at :Least until substantially all flowable material present in the conauit has been con-veyed into the container. -Another object resides in an apparatus comPrising ¦ supply means for supplying flowable material, a container lS ¦ to be charged with the flowable material to a predeterminedextent, conduit means connecting the supply means with the container, means for advancing in the conduit means a stream of pneumatic fluid towards the container, means for admitting flowable material from the supply means into the conduit means at a higher first rate until the charg-ing of said container approaches the predetermined extent, for thereafter reducing the admission of the flowable material to a lower second rate until the predetermined extent is reached, and for terminating the admission when 25- the predeterminedextent is reached, and means for continuing , ~

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~ 3ÇZ87 1 ¦ to advance the stream of pneumatic fluid until at least substantially all flowable material present in the conduit means has been conveyed into the container.

The novel features which are considered as character-istic for the invention a:re set forth in par-ticular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional ob~ects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

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i3~!37 s~Lr~[~ D~CRIPTIOi~ 0~' T~IE Dl~AWINGS
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~ i~3. 1 ix a dia~Jrclmmcltic illustration o one embodilnent of all apparatus accordirlg ~o the invelltion;
~ ig. 2a is a diclgrammatic view, showin~ a conduit junction suitable for use in the appaLatus of Fi~. l;
Fig. 2b is a view similar to Fig. 2a but showing a different conduit junction;
Fig. 3 is a diagrammatic view of still a further conduit junction;
Fig. 4 is a view analo~30us to Fig. 1 but illustrating another embodiment of tne apparatus;
Fig. 5 shows a further embodiment of the apparatus, in a view similar to that of Fig. 4;
Fig. 6 is a diagrammatic view, illustrating one embodiment of a closure for controlling the outlets from the respective flowable-material supply containers;
Fig. 7 is a view similar to Fig. G but showing a different embodiment;
Fi~. 8 is another view similar to Fig. 6, showing still a ~urther embodiment; and Figs. 9a and 9b on the same sheet as Fig. 6 are respectively a side view and an end view of still another closure embodiment.

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¦ DE:SCRIPTION OF TIIE rREF3~RRED E~lBOi~IMENTS

¦ The inventive method and apparatus will be jointly I described hereafter, with relerence to the several Figures ¦ of ~he drawings.

¦ A fixst embodiment is illustràted in Fig. 1 wherein ¦ reference numeral 1 designates the weighing container of ¦ a container-type scaie. Such scales are known (c.. the ¦ aforementioned German patents and published application) l and therefore require no detailed description. Reference 1~ ¦ numeral 2 designates a weight-recording device (also ¦ known), e.g. a dial, and reference numeral 3 a valve which ¦ opens and closes the outlet of the container 1.

l The scale is further provided or associated with a ¦ dust-separator ~known per se) in which dust is separated l from the conveying air. Container 1 has a rigid (i.e. not ~flexible) inlet nipple 5. Clean air from which dust has been removed in the separator 4j passes via an outlet nipple ~ and a flexible conduit 7 (e.g. a hose) to the suction side of a blower 9; an electromagnetic air shut-off valve 8 is interposed in the conduit 7 upstream of the ~lower 9.
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A plurality of supply containers 14, 15, 16 and 17 is ~ :
:~ . , 1, I

1 ¦ provided (there could be more or fewer), each holding a different flowable material. Thesc materials are to be mixed together in the container 1 and weighed, to produce a batch of material having a predetermined weight and con-taining predetermined weight-percentages of the individual materials. A flexible common conduit 10 communicates at one end with the nipple 5 of container 1; at its other end it communicates with a conduit junction 11 which in turn communicates with respective conduits 12, 13 and 14' leading to the containers 14-17. -Each conduit also com-municates with an air aspirating opening 18-20, respective- .
ly.

The outlets of the containers.14-17.communicate with the conduits 12, 13, 14' via respective electromagnetically.
controlled valves 21-24,(which are.to.be.described. .
later), and upstream of these valves, i.e. between the .
same and the respective air-aspirating openings 18-20, the .
.conduits have interposed in them the illustrated electro- --magnetically controlled air flow valves:25-27, respective-ly.

. The operation of this embodiment is as.follows: - -Let it be assumed that the program-control.for the -scale (known per se and not forming part of:the invention~

~1 -10- l '' ~

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I
1 ¦ calls for a predetermine`d amount by weight of the material ¦ in container 16, the valves 21-24 and 25, 27 are closed ¦ and the valve 26 is opened. Thereafter, the valve 23 is fu _ ¦ ly opened so that a maximum flow of material (heavy 5 ¦ flow) is aspirated into the conduit 13 and travels from l there via conduit 10 to container 1. When the scale ¦ registèrs the presence in container 1 of an amount of material from container 16 which is roughly equivalent to the required predetermined amount, it produces a 1 signal which substantially (but not fully) ~closes the valve 26, so that now only a much reduced flow (fine flow) of material can pass to the container 1. When the scale thereafter registers the presence of the predetermined amount of material in the container 1, the valve 23 is then 1 completely closed. However, valve 26 continues to remain open and air is drawn through it and the conduits 13, 10 until all residual material contained in these conduits has been aspirated into the container 1. Tests have shown that the amount (by weight) of such residual material is 2 for all intents and purposes constant from one time to the next, so that it is a simple matter to make allowance for its weight by correspondingly reducing the weight level at which the scale, respectively the device 2, issues the signal which causes the valve 23 to fully close. This 2 means that exceeding of the preselected quantity can be reliably avoided, independently of the lenqth of the con-duits 13 and 10 (and, of course, correspondingly the condui s 12, 14' and 10).

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1 ¦ The same operation applies correspondingly when ma-terial is to be withdrawn from the containers 14 and 17.

Similarly, if different amounts of different ma-terials are to be withdrawn via one and the same conduit (e.g. from containers 14, 15 via conduit 12), the same operation applies; i.e. the conduits (e.g. 12 and 10) are always emptied completely of all material before additional material is admitted into them. This is of particular importance when two containers having different materials communicate with a single conduit ~e.g. 12), since it reliably avoids mixing of the materials in the conduit.

Furthermore, the total removal of material from the conduits prior to admission of another material, assures that the dan~er of clogging on initiation of the admission of another material is avoided; such a danger would other-wise result from the presence of material which was not previously fully removed from the conduits.

A particular advantage of the embodiment in Fig. 1 is that the conduits 12, 13 and 14' can be united and discharge into the junction 11, very soon after the con-tainers 14-17, so that only a single flexihle conduit 10 need connect them with the container 1. It is important, in this connection, that immediately upstream of the - ; - !
. . ~ . . ~ ' ' , ' '~ ' ~ $'~
1 ¦ junction 11 each of the conduits 12, 13, 14' has a ver~ic-al leg, since this assures that no material aecumulations ean take place in the junction 11.

Various different types of junctions can be used, some of these being illustrated in Figs. 2a, 2b and 3.
Fig. 2a shows a junction 11 corresponding to the one in Fig. 1, on an enlarged sciale; the conduits 12, 13, 14' feed into a funnel-shaped member leading to the conduit 10.

10 ; ~ The junetion 11' in Fig. ~ has a vertieal part of a eenter eonduit merge with inelined parts of two outer eonduits, so that the three openings of these eonduits togetherbound a spase whi~h in turn so~nunieates with an outlet leading to the eonduit 10.

In Fig. 3 one of the eonduits leads direetlv towards the eonduit 10 (not shown) and the other eonduits open into this one conduit from the side and at a downwardly inelined angle. The junetion 11" in this Figure is therefore arranged in series.

.20 The embodiment in Fig. 4 is almost identically the same as in Fig. 1 and like referenee numerals designate ~ 7 1 ¦ li~e components. The difference is that the valves 25-27 are replaced by valves 28-30 which are interposed be-~,c~ tween the conduits 12, 13, -~3a-and the junction 11. Their function is, of course, the same as that of valves 25-27 and it will be understood that one of the valves 28-30 (i.e. the one in the conduit through which material is to be conveyed) will be open while the others are closed, for as long as the conveying operation takes.

The embodiment in Fig. 5 is again substantially the same as in Fig. 1, except that here the valves 25-27 are replaced by a remote-controllable multi-way valve 31 (known per se) having e.g. a magnet M and corresponding in its function to the valves 28-30 of Fig. 4.

The outflow of material from the containers 14-17 must be positively controlled to avoid operating difficul-ties. This is done by means of the valves 21-24. Several types of specific valve constructions suitable for this purpose are described with reference to Figs. 6-9.

The valve shown in Fig. 6 (and those in Figs. 7-9) co,responds to any one of the valves 21-24. It comprises a tubular valve element 32 which is slidable in the con-veying conduit with which the respective container (frag-mentarily sh ) communicates. ~lso locate~ in the same ' ' ' ~ 3~8~
1 ¦ conduit (but small enough not to fully block the same) is _ I a pneumatic cylinder and piston unit 33 whose piston is inked with the valve member 32 via the illustrated elast-l ic link~ge. The operation Gf the unit 33 is controlled by ¦ means of a commercially available (not illustrated) elec-tromagnetic valve of the three-port four-position, three-port five-position, four-port four-position or four-port five-position type, which admits compressed air to the l unit 33 depending upon the valve position. The unit 33 10 ¦ in turn moves the valve member 32 between the operating positions I (l~heavy flow"), II ("light flow'l) and III t"val~ e closed"~. The cylinder of unit 33 may carry switches 34, 35, 36 which detect the position of the piston (they could also e.g. be on the valve member 32 itself) and produce signals which are supplied to the program control device;
however, this is Xnown per se and requires no detailed description. The switches may be mounted on the cylinder by e.g. tension straps (similar to hose clamps) so that they can be moved lengthwise of the cylinder, to thereby vary their position and correspondingly vary the cross-sectional area of the container outlet exposed by the valve member 32 in its different positions (this of course varies the stream of conveyed material~. The seals acting be-tween the container and the valve member 32 (when the same is in closed position) to prevent escape of material into the conduit, are known per se and therefore not illustrated.

I ~ 7 1 1 The embodiment of the clos~lre in Fig. 7 is analogous to that in Fig. 6, except that here the tubular valve member 32 is replaced with a plate-shaped valve member 37 l which is pressed by a sprin~y element 38 against a seal-¦ ing surface 39. The pneumatic cylinder-and-piston unit is here located ou~side the conduit and the piston rod extends slidably but in sealed condition through the wall of the conduit. The operation and control is the l same as in Fig. 6.

The embodiment in Fig. 8 uses a pneumatically operated flap valve 40 which can again assume the three previously described operating positions I, II and III.
It is pivoted to these positions by a pneumatic cylinder-and-piston unit 41 to which it is linked by the illustrat-ed linkage. In particular, the width to whlch the con-tainer outlet is opened in the positions I and II can be steplessly adjusted in this embodiment by making use of the adjusting mechanism shown, namely a push-rod 43 one end of which is provided with a bolt or the like which can be slid in the illustrated slot 4~ to di~ferent position~
and there arrested. This will vary the degree to which flaF 4O expose~ the outlet of the container when in the positions I and II, A precise adjustment of the light is e~ected through conveniently positioning a ring 44 on the pi~ton rod of unit 41. Therearter ring 44 is blocked ;~
on the pi'ston rod by screw (not shown) or similar means.
In po~ition I ing 44 cooperate~ with a .
~ .

~ ~ 32~7 1 ¦ order to lock pneumatically operated latch unit 45 in ¦ the pi~ton rod in this posltion. Sig-¦ nals to the program control and indicative of whether ¦ the flap 40 is in position I, II or III, can be produced ¦ by mechanically actuated c:on~ercially available limit ¦ switches cooperating with e.g. pushrod 43.

¦ Finally, Figs. 9 and 9a show an embodiment in ¦ which a tubular valve member 46 is located in the conduit ¦ beneath the container outlet and has an inlet opening ¦ 48. It is coupled with a pneumatic cylinder-and-piston I unit 47 via a link 49 which is connected to the piston rod ¦ and (through a slot 50 in the wall of the conduit) to ¦ the valve member 46. Operation of the unit 47 thus turns . I the valve member 46 between a fully closed position in ¦ which its opening 48 is out of registry with the container ¦ outlet, a fully open position in which opening 48 regis-¦ ters completely with the container outlet, and an inter-mediate position in which opening 48 registers partially l with the container outlet. Operation of unit 47 can be l controlled by a tnot illustrated) four-port three-position valve. Again, limit switches (not shown) can indicate the positions of valve member 46.

I While the invention has been illustrated and described ¦ as embodied in the context of weighing material mixtures, ¦ it :s not intended to be limited to the details shown, , I
1 ¦ since various modifications and structural changes may be made without departing in any way from the spirit of ¦ the present invention.

l Without further analysis, the foregoiny will so fully ¦ reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications withoùt omitting features that, from the standpoint of prior art, fairly constitute essential char-acteristics of the generic or specific aspe,cts of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of pneumatically charging a container of a scale with flowable material, comprising the steps of advancing a stream of pneumatic fluid in a conduit towards a container which is to be charged to a predetermined extent; admitting flowable material at a high first rate into said conduit for entrainment by said stream; reducing the admission of flowable material to a lower second rate as charging of the container approaches said predetermined extent; terminating the admission of flowable material into the conduit when said predetermined extent is reached; and continuing to advance said stream of pneumatic fluid towards said container at least until substantially all flowable material present in the conduit has been conveyed into said container.

2. A method as defined in claim 1, wherein the flowable material is admitted into said conduit from an outlet of a supply vessel, and the steps of reducing and terminating respectively comprise partly and complete-ly blocking said outlet.

3. A method as defined in claim 1; and further comprising repeating the preceding steps with a different flowable material.

4. In an apparatus for pneumatically charging a container of a scale with flowable material, a combination comprising supply means for supplying flowable material; a container to be charged with the flowable material to a predetermined extent; conduit means connecting said supply means with said container; means for advancing in said conduit means a stream of pneumatic fluid towards said container; means for admitting flowable material from said supply means into said conduit means at a higher first rate until the charging of said container approaches said predetermined extent, for thereafter reducing the admission of the flowable material to a lower second rate until the predetermined extent is reached, and for terminating the admission when said predetermined extent is reached; and means for terminating the advance of said stream of pneumatic fluid only after at least substantially all flowable material present in the conduit means has been conveyed into said container.

5. A combination as defined in claim 4, said conduit means comprising a main conduit communicating with said container and a plurality of feed conduits each communicating with said main conduit, and said sup-ply means comprising a plurality of different supply vessels each having an outlet communicating with one of said feed conduits.

6. A combination as defined in claim 5, said admitting means comprising a plurality of material ad-mitting valves, one of each for said outlets and each having a valve member movable between a valve closing position in which the respective outlet is blocked, a valve opening position in which the outlet is fully unblocked, and an intermediate position in which the outlet opening is partly unblocked.

7. A combination as defined in claim 5, said conduit means further including a juncture member via which said feed conduits jointly communicate with said main conduit.

8. A combination as defined in claim 7, said juncture member being a multiple-way valve.

9. A combination as defined in claim 7; and further comprising a blocking valve interposed in each of said feed conduits upstream of said juncture member.

10. A combination as defined in claim 6, said valve member being a tubular member slidable in said conduit relative to the respective outlet between said closing, opening and intermediate positions.

11. A combination as defined in claim 6, said valve member being a plate member slidable in said conduit relative to the respective outlet between said closing, opening and intermediate positions.

12. A combination as defined in claim 6, said valve member being a pivoted flap member pivotable in said conduit relative to the respective outlet between said closing, opening and intermediate positions.

13. A combination as defined in claim 6, said valve member being an open-ended tubular member turnably received in said conduit and having a circumferential wall provided with an aperture, said tubular member being turn-able relative to the respective outlet between said posi-tions in which said aperture is respectively out of regis-try with said outlet, in full registry with said outlet and in partial registry with said outlet.

14. A combination as defined in claim 6, each of said valves further comprising pneumatic means for moving the respective valve member between said positions thereof.