US3512396A - Falling body viscosimeter - Google Patents

Description

May 19,1970 TS'UNEO OKAMOTO 3,512,396

FALLING BODY VISCOS IMETER Filed June 21, 1968 3 Sheets-Sheet 1- 4;: EEE

May 19, 19701 TSUNEO OKAMOTO 3,512,396

FALLING BODY VISCOSIMETER Filed June-21, 1968 s Sheets-Sheet 2 AS TO cc; NB I PC Dc TV R0 BM (3 v FP f 307 May 19,- 1970 TSUNEO OKAMQTO 3,512,396

FALLING BODY VISCOSIMETER 5 Sheets-Sheet 3 Filed June 21, 1968 United States Patent Int. Cl. G01n 11/12 U.S. C]. 7357 Claims ABSTRACT OF THE DISCLOSURE A falling body viscosimeter has falling body disposed in a tubular body, and the falling body is releasably engaged by a lifting member connected integrally to the lower end of a main shaft which is disposed in the tubular body for reciprocal axial movement therein. The tubular body is immersed in a fluid Whose viscosity is to be measured, and the lifting member is moved upwardly with the main shaft to a level at which the falling body remains submerged in the fluid, whereafter the lifting member is quickly lowered to its original position to cause the falling body to be released and drop freely through the fluid until it again engages the lifting member, the time interval for the falling body to drop freely being measured to determine the viscosity of the fluid.

The present invention relates to a falling body viscosimeter, and more particularly to such falling body viscosimeter which is so designed that the time interval for a falling body to freely drop a predetermined distance in a given fluid is measured and the viscosity of said fluid is determined by said time interval.

In the chemical industry it is frequently necessary during a production process to measure the viscosity of a fluid in a large and high temperature reactor from time to time. With conventional continuous-measuring type falling body viscosimeters, however, the viscosity of fluids, such as polymerized oils, or suspensions which tend to form a film on drying, cannot be measured accurately because the free dropping of the falling body cannot be obtained due to the friction between said fluids and a foreign substance such as the film of the fluid which is formed on a portion of said falling body which is above the fluid level, and is attached thereto. Further, the conventional falling body viscosimeters are not adapted to accurately measure or record the viscosities of non-Newtonian fluids, such as emulsions or thixotropic fluids because it has been impossible to reduce the viscosity measuring stress by reducing the weight of the falling body.

According to the present invention, the falling body is entirely submerged in the fluid to be measured and not permitted to be exposed above the fluid level at a portion throughout the period of the measuring operation, so that no foreign substances are allowed to attach on the surface of the falling body and accordingly no error occurs in the measurement result. Moreover, according to the present invention, the falling body can be made extremely light in weight no matter how long the falling body accommodating element may be extended as required by the place of use and therefore can be used with any fluids, including those mentioned above, for accurately measuring and recording the viscosities of said fluids.

The falling body viscosimeter according to the present invention comprises a viscosity measuring assembly including an electrically conductive tubular body adapted to be inserted vertically into a fluid and having at least one fluid passage hole at a portion to be dipped into said fluid, an electrically conductive main shaft disposed in said tubular body for axial movement therein from a low position to a high position, an electrically conductive lifting member secured to the lower end of said main shaft to be moved with said main shaft integrally therewith and an electrically conductive falling body disposed in said tubular body in engagement with said lifting member, said falling body being carried upwardly by said lifting member when the latter moves upwardly from a low position to a high position but being released from electrical and mechanical engagement with said lifting member when the latter drops quickly to the original low position and dropping freely through the sample fluid in said tubular body until it engages said lifting member again; means for sensing the moment when said lifting member begins to move downwardly from said high position to the original position with said main shaft and the engagement between it and said falling body is released; and means for sensing the moment when said falling body has completed its free dropping through the fluid, by an electrical change, such as capacitive or resistive change, between said main shaft and said tubular body.

When the falling body viscosimeter of the present invention is used for measuring the viscosity of a fluid in which air bubbles are present, said viscosimeter is, in addition to the elements described above, further provided with means for retaining the falling body at the highest position in the tubular body for a period of time along with the main shaft and the lifting member, and means for lowering said falling body from the highest position to a high fixed position slightly below said highest position along with said main shaft and said lifting member.

A preferred embodiment of the present invention will be described hereafter with reference to the accompanying drawings, wherein:

FIG. 1 is a diagramatical cross sectional view of a fluid viscosity measuring assembly of the falling body viscosimeter according to the present invention, wherein a falling body is accommodated;

FIG. 2 is a perspective view of the falling body disengaged from a lifting member;

FIG. 2a is a perspective view of another embodiment of falling body;

FIG. 3a is a main circuit diagram of the electric relay circuit used in the present invention;

FIGS. 3b-3d are diagrams of circuits associated with said main circuit;

FIG. 4 is an example of the high frequency oscillatertype relay circuit used in the present invention;

FIG. 5 is a perspective view of another form of the falling body;

FIG. 6 is a perspective view of a guide member to be mounted on the falling body; and

FIG. 7 is a fragmentary cross sectional view of another form of the viscosity measuring assembly.

FIG. 1 shows the structure of a viscosity measuring assembly which is generally indicated by numeral 1. This assembly is inserted into a fluid to be measured perpendicularly to the surface AA' of said fluid.

A tubular body 101 has a fluid inlet opening 102 at its bottom end with a check valve 102B disposed therein, and fluid outlet openings 103 at an intermediate portion thereof. The inner wall surface 101A of that portion of the tubular body 101 above a spacer 107 to be described later, is finished smooth to constitute a pneumatic cylinder, in which a piston 108 is slidably disposed. The

portion of the tubular body 101 below a spacer 114, to be described later, has a precisely finished inner surface 101B and constitutes a measuring cylinder having a falling body 106 slidably disposed therein. A main shaft 104 is disposed in the tubular body 101 which extends axially in said tubular body and has a lifting member 105 fixedly secured to the lower end thereof. The fluid inlet opening 102 may be omitted by either making the fluid outlet openings 103 large or suitably selecting the positions of said fluid outlet openings.

The lifting member 105, as shown in FIG. 2, is preferably composed of a circular plate 201 fixedly connected at its center to the lower end of the main shaft 104 at right angles thereto and a thin ring plate 202 which is formed therein with a gap 202A and connected integrally with said circular plate 201 by means of a plurality of parallel rods 203, with the center thereof located on the axis of the main shaft 104, said gap in the ring plate being of a size suflicient to provide for the passage of a supporting rod 208 of the exchangeable falling body 106 therethrough. However, the structure of the lifting member 105 is not necessarily limited only to the one shown in FIG. 2 but, for instance, the top ends of the rods 203 may be bent and fixed to the lower end of the main shaft 104 by eliminating the circular plate 201, or the gap 202A may be eliminated where the arrangement is such that an engaging disc 206 of the falling body 106 is threadably connected to the supporting rod 208. Still alternatively the thin ring plate 202 may be combined with the circular plate 201 by means, instead of the plurality of rods 203, of a suitably perforated single tube which is coaxial with the main shaft 104 and slightly smaller in inner diameter than the outer diameter of the ring plate 202.

The falling body 106 is preferably composed of a cupshaped bottomed cylinder 207, the supporting rod 208 extending upright from the center of the bottom plate 209 of said bottomed cylinder and a thin disc 206 is connected to the top end of said supporting rod at right angles thereto. Alternatively, as shown in FIG. 2a the falling body may be composed of a solid cylinder 207', a rod 208 extending upright from the center of the top surface of said solid cylinder and the thin disc 206 connected to the top end of said rod 208 at right angles thereto. When the supporting rod 208 of the falling body 106 is located at the center of the lifting member 105 by passing it through the gap 202A in the ring plate 202, the thin disc 206 is supported by the peripheral edge of a concentric hole 202B in said ring plate, the diameter of which hole is smaller than the diameter of said thin disc, and the outer peripheral surface of the cylinder 207 is located adjacent to the precisely finished inner surface 101B of the tubular body 101. As seen in FIG. 2, the cylinder 207 is provided therein with a cylindrical cavity whose inner diameter is larger than the outer diameter of the ring plate 202 so that said ring plate 202 may be received in said cylindrical cavity without contacting the peripheral wall of the same. Such an arrangement is advantageous, not only in reducing the weight of the falling body but also in shortening the height of the falling body 106.

The undersurface of the thin engaging disc 206 and the upper surface of the ring plate 202 are finished smooth. During the measuring operation, the falling body 106 and the lifting member 105 engage each other only at said surfaces and no contact is made between the connecting rods 203 and the thin engaging disc 206, between the supporting rod 208 and the ring plate 202, and between the ring plate 202 and the bottom wall of the cylinder 209.

In this case, the electrical contact between the engaging disc 206 and the ring plate 202 may be improved and an electrical change between the main shaft 104 including member 105 and the tubular body 101 may be provided more positively at the moment of contact of said disc with said plate, by providing on one of the confronting smooth surfaces of said disc or said plate a plurality of projections of the same height or by recessing slightly the portion of the underside of disc 206 at the peripheral edge thereof.

The main shaft 104 may be moved up and down, for example, by the following mechanism. Namely, the fixed spacer 107 is provided in the tubular body 101 with a packing 107A, consisting of a rubber O-ring, sealably disposed between it and the main shaft 104, and a piston 108 provided with a packing 108A is integrally mounted on the main shaft at a location spaced above said spacer 107, so as to form a pressure chamber 101C therebetween. At the lower portion of the pressure chamber 101C there is provided an inlet port 109 through which a pressure fluid is introduced into said pressure chamber. The pressure fluid inlet port 109 is in communication with a pressure source (not shown) through a three-way change-over valve 109A and a conduit 109B. The threeway change-over valve 109A is provided with an electromagnet AQ and is operative in such a manner that when the electromagnet AQ is energized, the pressure fluid is fed into the pressure chamber 101C from the pressure source through the conduit 109B, three-way change-over valve 109A and inlet port 109, while when the electromagnet AQ is deenergized, the pressure fluid in the pressure chamber 1010 is discharged through an outlet port 109C of the three-way change-over valve 109A. Another fixed spacer 110 is provided in the upper portion of the tubular body 101. This fixed spacer 110 has an air passage hole 110A bored therethrough. The portion of the main shaft 104 extending above the spacer 110 is provided with a fixed collar 104A which is adapted to abut against the spacer 110 for thereby stopping the downward movement of the main shaft. Between the underside of the spacer 110 and a plate secured to the main shaft there isprovided a compression coiled spring 111 having its ends anchored therebetween. In a central hole of a spacer 112 at the top end of the tubular body is disposed a pin 112B projecting downwardly into the interior of said tubular body. When a pressure is built up in the pressure chamber 101C upon energization of the electromagnet AQ, the piston 108 is urged upwardly against the spring 111, so that the main shaft 104 is moved upwardly accordingly and pushes the pin 112B upward actuating a limit switch TP which will be more fully described hereinafter. Upon actuating the limit switch TP, the electromagnet AQ is deenergized, so that the three-way changeover valve 109A is shifted into a position in which the inlet 109B is closed and the exhaust 109C is opened. As a result, the pressure in the pressure chamber 101C is reduced and the main shaft 104 moves quickly downwardly with the lifting member under the bias of the spring 111 and its own weight, until the collar 104A abuts against the spacer 110. Namely, the main shaft 104 with the collar 104A makes a reciprocal movement moving a distance defined by the pin 112B and the spacer 110. Therefore, the moving distance of the main shaft 104 can be selected optionally and the moving distance of falling body conforms to the moving distance of the main shaft.

As the lifting member 105 moves quickly downwardly, the ring plate 202 is disengaged from the undersurface of the disc 206 and returns to the original position before the falling body 106 does, so that the falling body 106 is set free from the lifting member 105 and begins to drop freely in the sample fluid. During the gravitational dropping movement of the falling body, the fluid below the falling body is displaced to above said falling body through a gap between the outer surface of the falling body and the inner surface 101B of the tubular body 101, and at the same time a capacitor C shown in FIG. 3d, is charged.

The main shaft 104, universal joint 1043 which may be used when the main shaft is long, spring 111, lifting member 105, falling body 106 and tubular body 101 are made from electrically conductive materials, such as stainless steel, bronze and aluminum, whereas the spacers 112, 110, 107, 114, piston 108 and packing 108A are made from electrically insulating materials, such as synthetic resins, rubber, leather, plastics, and ceramics. Therefore, it will be understood that the main shaft 104 is electrically connected to the spring 111 and electrically insulated from the tubular body 101.

A connecting wire 110B, electrically connected with spring 111 serves to electrically connect the main shaft 104- with the input terminal 401 (FIG. 4) of a high frequency oscillator-type relay circuit 113 via the spring 111. The tubular body 101 is connected to the ground terminal 416 (FIG. 4) of the relay circuit 113. During the free dropping of the falling body in the sample fluid, the spring 111, main shaft 104 and lifting member 105 constitute a unitary electric conductor and an electric capacity is produced between said unitary electric condutor and the tubular body 101. When the falling body 106 is again brought into contact with the lifting member 105 upon free dropping, it is electrically integrated with said unitary electric conductor and an electric capacity is further produced between the resultant unitary electric conductor and the tubular body. Since in this position the outer surface 207 and the bottom 209 of the falling body are located closely to the inner surface 1013 of the cylinder portion at the lower end of tubular body, the electric capacity increases drastically when the falling body is electrically integrated with the lifting member. The relay circuit 113 is energized by this increase in electric capacity and thereby the charging operation of the integrating capacitor C is stopped.

The above-desribed assembly 1, containing the falling body therein, is immersed in the fluid at least to the level of the line AA' during the viscosity measuring operation. Namely, the falling body 106 is maintained submerged in the sample fluid entirely throughout the period of measuring operation and thus even the disc 206- will not be dried outside of the fluid.

By introducing a purge gas into the tubular body through a gas inlet port 119 and discharging the same from sample fluid discharge holes 103 along with the fluid, after passing it through a small aperture 114A in the spacer 114, a smooth measuring operation can be obtained over a lengthly period of time.

Next, the operation of the Viscosimeter will be explained with reference to the circuit diagram. -In FIGS. 1, 3a, 3b, 3c, 3d and 4, the blocks indicated by characters AS, TV, etc. represent relays and small letters of these characters represent contacts operated by said respective relays. Resistors, capacitors and transistors are represented by the international symbols respectively. Reference numerals 301 and 301A represent the input terminals of the amplifier of a balancing potentiometertype automatic recorder (not shown) and 311 (FIG. 30) represents an excitation coil for a pen driving balancing motor used in said recorder (not shown). Reference symbol RD represents a Zener diode.

When a contact st is closed which is adapted to be closed only for a short period of time periodically, the relay AS is energized, whereby a contact as (FIG. 3b) is closed energizing the excitation coil AQ and therefore the three-way change-over valve 109A (FIG. 1) is actuated permitting the pressure fluid to flow into the pressure chamber 101C in the tubular body 101 through the inlet port 109B. Consequently, the piston 108 is moved upwardly causing an upward movement of the main shaft 104 and the lifting member 105, whereby the falling body 106 is moved upwardly with them. The sample fluid is sucked into the cylinder portion 101B of the tubular body through a strainer 102A and the inlet 102. while forcing the check valve 102B upwardly, and the sample fluid above the falling body 106 is discharged through the discharge openings 103. The top end of the main shaft 104 abuts against the undersurface of the spacer 112 pushing the pin 112B upwardly, whereby the contact tp of the limit switch TP is closed with the result that the relay TV is set and relay AS reset. The electromagnet ,AAQ is deenergized and the pressure fluid in the pressure chamber 101C is discharged through the exhaust 109C, so that the main shaft 104 moves quickly downwardly under the bias of the spring 111 and its own weight. A capacitor Cq is charged during the period wherein a contact W is closed, so that when the limit switch TP is reset as the main shaft 104 begins to move downwardly, the contact W is reset and the relay TQ is actuated momentarily by the discharge of the capacitor Cq, setting the relay CG.

A contact cg (FIG. 3d) is closed at this point for charging the integrating capacitor C and the charging of the capacitor C continues throughout the period of free dropping of the falling body in the sample fluid.

-A contact fv of the relay FV (FIG. 4) is held open 'during the free dropping of falling body but is closed at the moment when the falling body contacts the lifting member, and thus the relay FF is actuated by a charging current flowing through a capacitor Cf. The relay CG is reset by the action of a contact jp and the contact eg (FIG. 3d) is opened to interrupt charging of the capacitor C Thus, it will be appreciated that the voltage of the capacitor C is in proportion to the duration of free dropping of the falling body 106. By the action of the contact fp the relay NB is set and contact nb closed connecting the input terminal 301 of the amplifier of a recorder (not shown) to the capacitor C Also by the contact of fb and nb, the relay BM is energized for closing the contact bm (FIG. 3a) through a transistor Tr with a time delay as determined by the time constant relative to a resistor Ra and capacitor Cm, and the excitation coil 311 is also energized, so that the pen of the recorder (not shown) is driven to record the viscosity of the sample fluid which is determined by the voltage of capacitor C that is, the duration of free dropping of the falling body. A transistor Tr is energized with a time delay as determined by the time constant relative to a resistor Rb and a capacitor Cb, so that the transistor Tr is deenergized and the relay BM is reset for opening the contact bm These time constants are so selected as to provide a time for the recording pen to move and record the voltage of the capacitor C When the contact bm is opened and the balancing motor is deenergized, the recording pen is retained in its position motionlessly and thus a cycle of recording operation is completed.

Before the set of relay TV after said recording operation, the charge of capacitor C is discharged through resistor Rd and contact dc (FIG. 3d).

In the embodiment described above, use is made of the high frequency oscillator-type relay circuit 113 to detect the terminal point of the free dropping of falling body 10 6. This circuit is of a known type wherein a relay is actuated by making use of a change in electric capacitance, and an embodiment thereof is shown in FIG. 4. As shown, the circuit is composed of an oscillator circuit having two resonance circuits and a dc. amplifier circuit, the input terminal 401 being connected to the main shaft 104 and the grounding terminal 416 to the tubular body 101. Consequently, the capacitance of the capacitor 403 involves the capacitance between the main shaft 104 and the tubular body 101. During the free dropping of the falling body 106 in the sample fluid, the frequency of the resonance circuit, comprising an inductance 402 and a capacitor 403, coincides with the frequency of the resonance circuit 404 on the collector side of a transistor 409, and an adjustment is made such that the emitter current of the transistor 409 becomes extremely small. The capacitance 403, in the resonance circuit on the side of the input terminal 401, is increased and accordingly the emitter current is increased at a moment when the 7 falling body 106 is brought into contact with the ring plate 202 of the lifting member 105 at its disc 206. This increase of current is amplified by transistors 410 and 411, and actuates the relay FV, shown in FIG. 3, which operates the contact fv.

Periodically closing contact st may be the contact of a known timer, e.g. the contact of a motor timer.

In the embodiment described above, the duration of free dropping of the falling body is measured by integrating the charge of the capacitor C and measuring the voltage of said charge. Alternatively, the duration of free dropping, that is, the viscosity of the sample fluid, may be measured by supplying air into a tank of fixed capacity from an air source of a predetermined pressure through a throttle valve provided on said tank, during the free dropping of the falling body, and measuring a pressure in the tank. Still alternatively, the viscosity of the sample fluid may be measured by supplyin a pulse to a pulse counter from a constant pulse generator, during the free dropping of the falling body, and measuring the pulse number by suitable means.

Where the sample fluid is electrically conductive and the resistivity thereof is higher than those of the materials of the tubular body and main shaft, etc., a detecting circuit utilizing electric resistance change may be used as a means to detect the terminal point of free dropping of the falling body. In this case, the connecting wire 110B is connected to an electrode terminal of a conventional electrode-type water level detecting circuit with, variable sensitivity and the tubular body 101 to the opposed terminal of the circuit. The fluid resistance of the gap between the outer surface 207 and the undersurface 209 of the bottom wall of falling body, and the inner surface 101B of the cylinder portion of the tubular body, is much smaller than the fluid resistance between the lifting member-carrying main shaft 104- and the inner surface 1013 of the tubular body, since the gap between the former is small and the areas thereof are large. By detecting the moment when the resistance across both of the aforesaid terminals makes an abrupt change, the terminal point of free dropping of the falling body can be detected.

If a mechanical vibration is given to the present assembly during the measuring operation, the free dropping falling body is displaced out of the axis of the tubular body to irregularly contact the inner surface 101B of the cylinder portion of said tubular body, whereby the free dropping of the falling body is hampered and a fluctuation occurs in the measured values of viscosity.

In order to avoid such undesirable phenomenon, prismshaped projections 210 are formed on the outer surface 207 of the falling body as shown in FIG. 5. These projections 210 are provided at least at three locations on the outer peripheral surface of the falling body uniformly. By so doing, it is possible to prevent the outer surface of the falling bodyfrom directly contacting the inner surface 101B of the cylinder portion of tubular body during the free dropping of said falling body, and thereby avoid the fluctuation of measured values. The same effect may be obtained by attaching a guide disc 211, having radial projections 210 along the peripheral edge thereof as shown in FIG. 6, to the bottom end of the falling body 106 by means, for example, of a screw, instead of providing the projections 210 on the outer surface of said falling body.

in use of the viscosity measuring assembly described above for measuring the viscosity of a reaction fluid in the production process, for example, of a polyester resin, which contains a large amount of bubbles therein, a sample fluid entering the cylinder portion of the tubular body through the inlet hole 102 inevitably contains bubbles therein. The presence of such bubbles in the sample fluid is detrimental to accurate measurement of the viscosity because the bubbles passing through the gap between the outer surface 201- of the falling body and the inner surface 101B of the cylinder portion of tubular body interfere with the free dropping of said falling body, making it impossible to obtain the correct viscosity. Such a problem can be eliminated in the following manner. Namely, wh n bubbles are present in a sample fluid introduced into the cylinder portion of tubular body, the falling body lifted to the highest position is retained thereat for a while so as to permit the bubbles to rise through the fluid to be accumulated in a space below said falling body, and then the falling body is lowered from the highest position to a fixed starting position therebelow, whereupon the bubbles collected below the falling body are removed therefrom upwardly through the gap between the falling body and the tubular body. The falling body is thereafter set free for free droppin from the starting position to the original lower position through the sample fluid which has already been cleared of bubbles. in the manner described, the viscosity of the sample fluid can be measured accurately, without being subjected to the undesirable eflect of bubbles.

FIG. 7 shows another embodiment of the present invention, with a portion omitted, which is substantially the same as the preceding embodiment. In FIG. 7, there are shown means for elevating the main shaft and means for retaining the main shaft at the highest position and at the fixed starting position therebelow. According to this embodiment, the three-way change-over valve 109A, connected to the pressure gas conduit 109 open at a lower portion of the pressure chamber 101C, is connected at the other end to another three-way change-over valve 109E through the conduit 1098. A conduit 109D extending from the change-over valve 1001 is connected to a constant pressure source 1096, while another conduit 109E is connected to another constant pressure source 109E which is lower in pressure than said constant pressure source 109G. The changeover valve 109F is operative in such a manner that the conduits 109D and 109B are open in the energized state of an excitation coil AR, while the conduits 109E and 109B are opened in the deenergized state of said excitation coil AR. On the other hand, the change-over valve 109A is operative such that the conduits 109B and 109 are opened in the energized state of the excitation coil AQ, to provide for passage of a pressure fluid through said change-over valve from either one of the pressure fluid sources 109G and 109H, Whereas the conduit 109C and 109 are opened in the deenergized state of the excitation coil AQ.

In the top portion of the tubular body 101 is disposed a fixed case 112C with a movable plate 112E in which a compression coil spring 112D is accommodated. The movable plate 112E is urged against the lower end of the fixed case 1120 under the bias of the spring 112D but is not permitted to move off said case.

When the pressure gas is fed into the pressure chamber 101C from the source 109G at a regulated pressure, upon energization of the excitation coils AR and AQ, the lifting member-carrying main shaft 104 is moved upwardly while lifting the falling body 106, and pushes the springbiased movable plate 112E at its top end. The upward movement of the main shaft 104 and accordingly the upward movement of the lifting member and falling body, is stopped when the upwardly acting gas pressure is balanced with the weights of said three members and the total of the downward biasing forces of the springs 112D and 111, and thus the falling body 106 is retained in its highest position. The bubbles present in the sample fluid, sucked into the cylinder portion of tubular body, rise through said sample fluid and are accumulated in a space below the falling body, while said falling body is retained in the highest position.

Then, the excitation coil AR only is deenergized, whereupon the conduit 109D, communicating with the pressure gas source 1096, is closed and a pressure gas is fed into the pressure chamber 1010 from the pressure gas source 109H which is lower in pressure than said pressure gas source 109G. When the pressure in the pressure chamber 101C becomes equal to the pressure of the pressure gas source 109H, the gas pressure urging the piston 108 upwardly becomes lower than before and thus the top end of the main shaft 104 is moved downwardly to a position where the movable plate 112E rests on the lower edge of the case 1120, under the weights of said three members and the biasing forces of springs 112D and 111. Namely, the main shaft 104 is lowered from the highest position to the fixed starting position, causing the downward movement of the lifting member 105, and therefore the falling body moves gravitationally downwardly. During the downward movement of the falling body 106, the bubbles collected below the falling body are expelled through the gap between the outer surface 207 of falling body and the inner surface 101B of tubular body, and no bubbles are present in the sample fluid below the falling body 106.

After the falling body 106 has reached the fixed starting position and again the plate 206 of falling body is engaged with the plate 202 of the lifting member, the excitation coil AQ is deenergized, whereupon the gas in the pressure chamber 1010 is discharged through the conduit 109C, and the main shaft and lifting member quickly drop to the original position under the bias of the spring 111 as in the preceding embodiment. Therefore, the falling body 106 is set free for free dropping through the sample fluid in the manner described previously. By measuring the duration of the free dropping of falling body to its original position from the fixed starting position, the viscosity of the sample fluid can be measured without undergoing the detrimental effect of bubbles.

The excitation coils AQ and AR can be energized by the use of an ordinary motor timer. Charging of the capacitor C is commenced at the moment the relay FV is reset in the deenergized state of the excitation coils AQ and AR, and the charging is interrupted at the moment said relay FV is set. With such arrangement, it is possible to charge the capacitor C with a voltage in proportion to the duration of free dropping of the falling body from the fixed starting position to the original position.

What is claimed is:

1. A falling body viscosimeter comprising a viscosity measuring assembly including an electrically conductive tubular body adapted to be inserted vertically into a fluid and having at least one fluid passage hole at a portion to be immersed in said fluid, an electrically conductive main shaft disposed in said tubular body for movement along the axis of said tubular body from a low position to a high position, an electrically conductive lifting member fixed and electrically connected to the lower end of said main shaft to be moved integrally with said main shaft, and an electrically conductive falling body disposed in said tubular body and mechanically engaged and electrically connected to said lifting member, said falling body being carried upwardly by said lifting member when the lifting member moves upwardly from a low position to a high position but is set free from mechanical engagement and electrical connection with said lifting member when said lifting member drops more quickly than said falling body to the original low position, said falling body dropping freely through the sample fluid in said tubular body until it mechanically and electrically engages said lifting member again; means for sensing the moment when said lifting member begins to move downwardly from said high position to said low position along with said main shaft and the mechanical engagement between the lifting member and said falling body is released; and means for sensing the moment when said falling body has completed its free dropping through the fluid and contacts said lifting member, by an electrical change between said main shaft and said tubular body which occurs upon contact by said falling body and lifting member.

2. A falling body viscosimeter as claimed in claim 1, wherein said falling body comprises a solid cylinder, a

rod extending axially from the center of the top surface of said solid cylinder, and a thin plate fixed to the top end of said rod, and a washer-like plate provided at the lower end of said lifting member for engagement and electrical contact with said thin plate.

3. A falling body viscosimeter as claimed in claim 1, wherein said falling body comprises a cup-shaped cylinder with a bottom, a rod extending axially from the center of the bottom of said cylinder and a thin plate fixed to said rod, and a washer-like plate provided at the lower end of said lifting member for engagement and electrical contact with said thin plate.

4. A falling body viscosimeter as claimed in claim 1, wherein said falling body is provided with radial projections on the outer peripheral surface thereof so as to prevent said outer peripheral surface from directly contacting the inner surface of said tubular body, said projections being arranged at substantially equal angular intervals.

5. A falling body viscosimeter as claimed in claim 1, wherein said falling body has a guide disc secured to the bottom end thereof, said guide disc being provided with radial projections along the peripheral edge thereof.

6. A falling body viscosimeter comprising a viscosity measuring assembly including an electrically conductive tubular body adapted to be inserted vertically into a fluid and having at least one fluid passage hole at a portion to be immersed in said fluid, an electrically conductive main shaft disposed in said tubular body for movement along the axis of said tubular body from a low position to a highest position, an electrically conductive lifting member fixed and electrically connected to the lower end of said main shaft to be moved integrally with said main shaft, and an electrically conductive falling body disposed in said tubular body and mechanically engaged and electrically connected to said lifting member, said falling body dropping freely through said sample fluid in said tubular body upon being set free from the electrical and mechanical engagement with said lifting member when the'latter drops more quickly than said falling body but being otherwise engaged by said lifting member during the rest of the time; means for lifting said falling body along with the lifting member and main shaft from the original low position to the highest position in the tubular body and retaining the same thereat for a period of time; means for lowering said falling body along with the lifting member from said highest position to a fixed starting position therebelow; means for quickly dropping said main shaft and said lifting member to said original low position and thereby causing said falling body to drop freely from said fixed starting position to said low position; means for sensing the moment when said falling body is disengaged from the lifting member and starts to drop freely from the fixed starting position; and means for sensing the moment when said falling body has completed its free dropping, by an electrical change between said main shaft and said tubular body which occurs upon contact of said falling body and lifting member.

7. A falling body viscosimeter as claimed in claim 6, wherein said falling body comprises a solid cylinder, a rod extending axially from the center of the top surface of said solid cylinder, and a thin plate fixed to the top end of said rod, and a washer-like plate provided at the lower end of said lifting member for engagement and electrical contact with said thin plate.

8. A falling body viscosimeter as claimed in claim 6, wherein said falling body comprises a cup-shaped cylinder with a bottom, a rod extending axially from the center of the bottom of said cylinder and a thin plate fixed to said rod, and a washer-like plate provided at the lower end of said lifting member for engagement and electrical contact with said thin plate.

9. A falling body viscosimeter as claimed in claim 6, wherein said falling body is provided with radial projections on the outer peripheral surface thereof so as to 1 1 12 prevent said outer peripheral surface from directly con- References Cited tacting the inner surface of said tubular body, said pro- UNITED STATES PATENTS jeCtlOIlS being arranged at substantially equal angular interva1s 2,491,389 12/1949 Norcross 73-7 10. A falling body viscosirneter as claimed in claim 6, 5 2778220 71/1957 Kuhlmann et wherein said falling body has a guide disc secured to the bottom end thereof, said guide disc being provided with CLEMENT SWISHER Pnmary Exammer radial projections along the peripheral edge thereof. J. W. ROSKOS, Assistant Examiner

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