US 3359786 A
Description (OCR text may contain errors)
Dec. 26, 1967 G. VON ALFTHAN 3,359,736
METHOD OF AND APPARATUS FOR DETERMINING THE SHI-VES CONTENT IN A FIBER SUSPENSION Filed April 6, 1965 iii 33: 5:5 5:5
INVENTOR GEOPG voN ALFTHAN BY ATTORNEY United States Patent 3,359,786 METHOD OF AND APPARATUS FOR DETERMIN- ING THE SHIVES CONTENT IN A FIBER SUS- PENSION Georg von Alfthan, Helsinki, Finland, assignor to Osakeyhtio Keskuslaboratorio Centrallaboratorium Aktiebolag, a corporation of Finland Filed Apr. 6, 1965, Ser. No. 446,063 Claims. (Cl. 73-61) ABSTRACT OF THE DISCLOSURE A known amount of the fiber suspension, such as wood fibers suspended in water, is fed through a slit having a predetermined size such that shives or fiber bundles above a predetermined maximum size are caught by the slit, whereby to decrease the rate of liquid flow through the slit. The decrease in flow through the slit, which is a measure of the shive or fiber bundle content, is determined. A preferred manner of making such determination is to rinse the slit as soon as it has been clogged to a predetermined extent, and registering the number of rinsings of the slit for a known amount of suspension; the result gives a measure of the content of shives or fiber bundles in the suspension.
It is of great importance that the shives content in a fiber suspension intended for paper manufacture is as low as possible. Thus it is important to check the shives con tent by means of suitable methods of determination. The methods used up to now are rather tedious and timeconsuming. No method is known for continuous determination of the shives content. The object of the present invention is therefore to effect a means for rapid determination of the content of shives or fiber bundles with a minimum amount of work.
The main characteristics of the means according to this invention are that a known amount of the suspension is fed through a slit which, at least to its main features, consists of two oblique walls, preferably forming an acute angle, the dimensions of the slit being such that shives or fiber bundles above a certain maximum size are caught by the slit diminishing the rate of liquid flow, and that the decrease in flow through the slit is determined as a measure of the content of shives or fiber bundles.
A suitable way of determination is to rinse the slit as soon as a predetermined extent of clogging has been reached, and the number of rinsings per the known amount of suspension is registered as a measure of the content of shives or fiber bundles. According to one of the modifications of the invention, a fiber suspension of given concentration is fed continuously through the slit, and the rinsing frequency is recorded as a measure of the content of shives or fiber bundles.
The invention also includes an apparatus for application of the means described, the apparatus being characterized by a number of devices for the purpose of feeding a known amount of suspension through a slit which, at least to its main features, consists of two oblique walls, preferably forming an acute angle, the dimensions of the slit being such that shives or fiber bundles above a certain maximum size are caught by the slit, diminislring the rate of liquid flow, and by devices for registration of the decrease in flow through the slit.
The invention is described in more detail in the following with reference to the annexed drawing schematically showing an embodiment of an apparatus for the determination of the content of shives or fiber bundles in a fiber suspension.
3,359,786 Patented Dec. 26, 1967 In the drawing 1 designates a pulp tank from which a pipe 2 provided with a valve 3 leads to an overflow tank 4 which is provided with a water inlet having a valve 5. A pipe 6 leads from the overflow tank 4 to the upper portion of a glass tube 7. The glass tube 7 is provided with a conically widening lower portion 8 the inside of which is ground. Inside the conical portion 8 there is provided a body 9 concentric with the conical portion 8. In the embodiment shown the body 9 is formed as a spherical segment. Between the body 9 and the conical portion 8 there is formed a narrow slit 10 which is dimensioned such that a diluted pulp suspension may flow unimpededly past the body 9 while larger particles, for instance shives, are caught by the slit. The tube 7 is freely suspended from an adjusting knob 11 by means of which the height position of the tube can be adjusted in relation to the body 9 for regulating the Width of the slit 10. The adjusting knob 11 is preferably provided with a pointer 12 which together with a corresponding scale 26 directly indicates the width of the slit 10. The usable range of the slit is for example between 0.15 and 0.60
The spherical body 9 is supported by a pneumatic cylinder 13 which is connected by a pipe 14 provided with an air valve 15 and a pressure reducing valve 16 to a pressure air source (not shown). A branch line 17 leads from the pipe 14 to the pulp tank 1. The air valve 15 is a two-way valve having three ports. In the first of its two positions the valve 15 connects the source of compressed air to cylinder 13 through two of its ports which are then in communication, the third port, which is connected to the atmosphere, then being closed. In the second of its two positions the valve 15 closes the port thereof which is connected to the source of compressed air, and connects the cylinder 13 to the atmosphere.
In the upper portion of tube 7, above the mouth of pipe 6, there is provided a contact 18 forming part of an electrical circuit 19. The circuit 19 also includes a relay 20 commanding an operating device 21 of the valve 15 and a pulse counter device 22. The circuit 19 may further include a recorder 23 and an alarm device 24 both connected to the counter device 22.
Below the tube 7 a vessel 25 is provided for the collecting and removal of pulp suspension flowing through the slit 10.
The operation of the apparatus shown is as follows:
The width of the slit 10 is adjusted to the desired value by turning the adjustment knob 11. The height of the overflow tank ,4 above the tube 7 is adjusted so that the water level in the tube 7 is in equilibrium at a level mark at the upper end of the tube. A sample of pulp, for example 20 g., is transferred to the pulp tank 1 and diluted to a desired concentration. The pulp is kept moving by means of a stream of air through the branch line 17. The valve 15 is in its first position, so that cylinder 13 is held in elevated position by compressed air supplied to it by pipe 14. The pulp valve 3 is opened, and the pulp flows through the pipe 2 to the overflow tank 4 where it meets a stream of water and is further diluted. The pulp is flowing in this diluted condition to the tube 7. The diluted pulp suspension flows unimpededly past the spherical body 9 through the slit 10. If the pulp, however, contains particles, such as shives, that are thicker than the width of the slit 10, these are caught by the slit. As a atmosphere. The air will then leave the cylinder 13 supporting the spherical body 9, and the body 9 falls down so that the slit 10 is widened. All the shives caught by the slit 10 are then rinsed away by the flow of suspension through the slit 10. The rinsing time is, by adjustment of the air pressure by means of the pressure reducing valve 16, regulated in such a way that the liquid level sinks back to the initial equilibrium level. Upon actuation, the relay 20 also gives a pulse to the counter 22. The described procedure is repeated until the entire pulp quantity has flowed through the apparatus. The number of rinsings indicated by the counter 22 serves as a measure of the shive content of the pulp.
Instead of the batchwise operation described above, the apparatus may also be run continuously. In that case a pulp suspension having a known concentration is continuously fed through the tube 7 and slit 10, the operation being otherwise as above. The number of rinsings per a selected time unit is recorded by the recorder 23 and serves as a measure of the shive content of the pulp. The alarm device 24 is arranged to operate when a certain allowable shive content is exceeded.
The invention is not restricted to the embodiment shown and described, which is intended for purposes of illustration only. Thus for example, the tube 7 may as well be arranged to rise for rising of the slit 10, the body 9 being stationary. The shape of the body 9 may also differ from that shown in the drawing. Further, it is also possible to use a linear slit which then is defined between two plane walls arranged at an angle with respect to each other, one of said walls being adjustable for rinsing of the slit and regulating the width thereof.
1. A method for the determination of the shive content of pulps, comprising forming a liquid suspension of a selected amount of pulp, causing said suspension to flow along a restricted path including a slit, dimensioning said slit to allow fibers to pass but to retain particles exceeding a pre-selected size, detecting a pre-selected decrease of flow through said slit caused by its partial clogging by retained particles, momentarily widening said slit for rinsing it of said retained particles upon detecting said decrease of flow, and registering the number of rinsings per said amount of pulp as 'a measure of the shive content of said pulp.
2. A method for the determination of the shive content of pulps, comprising causing a liquid suspension of pulp to flow continuously at a selected rate of flow along a restricted path including a slit, dimensioning said slit to allow fibers to pass but to retain particles exceeding a pre-selected size, detecting a pre-selected decrease of flow through said slit caused by its partial clogging by retained particles, momentarily widening said slit for rinsing it of said retained particles each time said decrease of flow has been detected, and registering the number of rinsings per time unit as a measure of the shive content of said pulp.
3. An apparatus for the determination of the shive content of pulps, comprising means providing a restricted path including a slit having a length dimension considerably exceeding its width dimension, said slit being dimensioned to allow fibers to pass but to retain particles exceeding a preselected size, means for passing a liquid suspension of pulp at a selected rate of flow along said path through said slit, means for momentarily widening said slit, means responsive to a pre-selected decrease of flow through said slit caused by retained particles and controlling said means for the widening of said slit, and registering means responsive to said flow responsive means.
4. An apparatus as in claim 3, said restricted path comprising a vertical tube having a. conically widening lower portion and a body inserted in said lower position concentrically therewith, said tube and said body defining together an annular slit.
5. An apparatus as in claim 4, the portion of said body facing the direction of fiow through said tube being spherical.
6. An apparatus for the determination of the shive content of pulps, comprising a vertical tube having a conically widening lower portion, a body in and concentric with said lower portion, said body and said lower portion forming together an annular slit having such a width that pulp fibers may pass while larger particles are retained by the slit, means for feeding a liquid suspension of pulp in a downward direction through said tube and said slit at such a rate that the suspension flow in said tube will attain an equilibrium level at a substantial height above said slit, means for momentarily displacing said tube and said body with respect to each other in a slit widening direction, an electrical circuit including circuit closing means located in said tube at a selected height above said equilibrium level and responsive to a rising of the liquid level in said tube caused "by particles retained in said slit, relay means responsive to said circuit closing means and controlling said tube and body displacing means, and pulse counter means responsive to said relay means.
7. An apparatus as in claim 6, said tube and body displacing means comprising a pneumatic cylinder supporting said body and slidable between an upper slit forming position and a lower slit widening position, said cylinder being connected to a pressure air source through a valve, said valve being controlled by said relay means.
8. An apparatus as in claim 7, said valve being regulated to retain said body in a slit widening position for a period of time sufiicient to allow the liquid level in said tube to return to said equilibrium position.
9. An apparatus as in claim 8, the portion of said body facing the direction of flow through said tube being spherical.
10. An apparatus as in claim 9, said electrical circuit further including recording means and alarm means actuated by said pulse counter means.
References Cited UNITED STATES PATENTS 2,346,746 4/ 1944 Green 73-63 3,222,916 12/ 196-5 Davis. 3,276,248 10/1966 Cyr 736l DAVID SCHONBERG, Primary Examiner,