Apparatus for measuring moisture content of grain or the like

Abstract: Apparatus for use in measuring the moisture content of grain comprises a grinding mechanism (C) for grinding grain, a chamber (M) disposed to receive ground grain directly from the grinding mechanism, and a piston or ram (D) movable into chamber (M) to compress the ground grain therein. Electrical contacts (F) are so disposed in chamber (M) or the ram (D) as to be in contact with the mass of compressed ground grain at predetermined locations on said mass and the moisture content of the material is determined on the basis of the electrical resistance, between contacts (F) provided by said mass of compressed ground grain.

Description: THIS INVENTION relates to improved apparatus for the preparation of a material before moisture-content measurement using an electrical moisture meter. One method of measuring moisture content in materials such as grain and other particulates electrically, is to measure the conductance or capacitance of the material. An established procedure for preparing a sample of the material before the measurement can be made is to grind (pulverize) the material into a uniform particle size and then as a separate step, to place or compress the ground material in good contact with a set of electrodes connected with an instrument for measuring capacitance or conductance. The above procedure can be cumbersome and can lead to errors as there is the possibility of a change of moisture content during grinding and during subsequent transfer of the ground material to the measuring electrodes. Other procedures where the grain is mashed and compressed between two plates lead to difficulties at different moisture contents and different sample sizes. British Patent Specification No. 885306 discloses apparatus for measuring the moisture content of grain and which comprises a body, a grinding mechanism in the body comprising an outer grinding ring fixed in the body and a central grinding wheel rotatable within the grinding ring. The body provides a chamber below the grinding mechanism to receive, directly from the grinding mechanism, grain ground by the grinding mechanism. A piston is carried on the underside of the central grinding wheel. The central grinding wheel is rotatable by means of a flat-sided spindle received within a slot extending diametrally across a driving shaft extending axially from a knob rotatable at an upper end of the body. The central grinding wheel is rotatable with respect to but is fixed axially relative to a hollow screw, screw-threadedly engaged in an insert carried in the housing. Locating pins carried at the ends of the divided driving spindle can engage in keyways provided in the interior of the screw when the knob is pulled axially into an extended position so that the rotation of the knob then causes the central grinding wheel and with it the piston to be advanced into the chamber to compress the ground material against electrodes used in sensing the electrical resistance of the ground compressed material, to determine moisture content. U.S. Patent Specification No. 3293907 discloses testing apparatus for cyclically determining the moisture content of grain and in which apparatus for grinding grain, compressing the ground grain and testing the electrical-resistance of the ground grain is rotated continuously within a casing having an inlet opening for grain at an upper part thereof and a discharge opening for tested samples adjacent a bottom thereof. During rotation of the mechanism, an inlet of the rotating apparatus comes into register with the inlet opening in the casing to receive a charge of grain to be ground then, as the apparatus rotates, the charge of grain is ground, returned to an inlet neck section of the rotating mechanism after the radially outer end of that section has been closed by a first transversely sliding gate, the charge of the ground grain then being held captive in that inlet neck section by dosing a second transversely sliding gate disposed radially inwardly of the first. The charge of ground grain, thus held captive in the neck section between the transversely sliding gates, is subsequently compressed, during continued rotation of the apparatus, by radial movement of the radially outer part of the neck section, carrying the first gate, towards the radially inner part of the neck section carried by the radially inner part of the neck section. This radial movement is occasioned by engagement of the radially outer part with a cam within the housing. The electrical resistance of the sample is then tested, the gates withdrawn and the tested sample expelled through the discharge opening. It is an object of the present invention to provide an improved apparatus for use in measuring moisture content by the above-noted method. According to the invention there is provided apparatus for use in measuring the moisture content of grain or other particulate material, comprising a body (A), a grinding mechanism (C) in the body for grinding grain or other particulate material, a chamber (M) provided by the body and disposed to receive, directly from the grinding mechanism, ground grain or other material ground by the grinding mechanism, a piston or ram (D) movable into said chamber (M) to compress the ground material therein, and electrical contacts so disposed in said chamber or on said ram as to be in contact with the mass of compressed ground material, resulting from such movement into the chamber, at predetermined locations on said mass, whereby the moisture content of the material can be determined on the basis of the electrical resistance, between said electrodes, provided by said mass of compressed ground material, said grinding mechanism and said ram or piston being operable selectively by a common input member (H) characterised in that said grinding mechanism (C) comprises a fixed grinding disc, stationary in the body, and a rotatable grinding disc, said common input member comprising a hub and a manually operable handle (H) secured to the hub, said hub providing the driving connection between the handle and the rotatable grinding disc, said piston or ram (D) being carried by a shaft (T) extending along the rotary axis of the handle within a hollow barrel mounted coaxially within the hub, the barrel being coupled with a cap arranged coaxially within said hub, said hollow barrel forming an output member of said clutch, and wherein (a) the shaft (T) is screw-threadedly engaged in said hollow barrel and is axially slidable in, but it non-rotatable with respect to, a central guide member fixed with respect to said body, or (b) the shaft is guided for axial movement in said barrel but is non-rotatable therein and the shaft is screw-threadedly engaged in said central guide member; whereby rotation of said barrel within said body causes axial movement of said shaft (T) and thus of said piston (D) relative to said chamber (M), and wherein said barrel can be selectively rotationally coupled with said handle and hub or decoupled therefrom, by means of a slide (G) slidable along said handle (H) inwardly towards the rotary axis of the handle, or outwardly away from said rotary axis, respectively to extend into a diametral slot provided across the top of said cap and to be removed from said slot, and thus respectively to couple the handle with said cap and decouple the handle from said cap. An embodiment of the invention is described below by way of example with reference to the accompanying drawings, wherein:- FIGURE 1 is a view in vertical section of an apparatus embodying the invention in one position thereof, FIGURE 2 is a view similar to Figure 1 but showing the apparatus in another position thereof, and FIGURE 3 is a perspective view of the apparatus of Figures 1 and 2, in conjunction with apparatus for sensing electrical resistance and displaying moisture content values calculated therefrom. The apparatus shown in the drawings is intended for use in measurement of the moisture content of grain. The apparatus consists of the main body (A) affording a grain hopper (B). In use of the apparatus, grain introduced via the hopper is ground between the discs (C) formed with sharp blades or teeth, one of the discs being stationary in the body (A) and the other being coupled to a manually rotatable handle for rotation therewith. The handle (H) carries a slide (G) operable to couple the handle with, and decouple the handle from, a piston mechanism described below. With the slide (G) in the position shown in Figure 1, the piston mechanism (T, D) is de-coupled from the handle and is unaffected by turning action of the handle. With the slide (G) in the position shown in Figure 1, when the handle (H) is turned, the movable disc (C) rotates with respect to the fixed disc (C) and grain from the hopper is ground between the discs (C) and the ground grain falls into a measuring chamber (M) provided below the discs (C). When the chamber (M) is sufficiently full of grain, the slide (G) is placed as shown in Figure 2, it extends into a diametral slot provided across the top of a cap arranged co-axially within a hub secured to handle (H) and which provides the driving connection between the handle (H) and the rotatable grinding disc (C). The cap forms an input member of a slipping clutch which includes an output member in the form of a hollow internally screw-threaded barrel mounted within the hub coaxially with respect to the latter, in such a way that the hub can rotate around the hollow barrel when permitted to do so by the slipping clutch. The slipping clutch incorporates a friction ring or serrated ring which is non-rotatable with respect to the cap and is urged by the compression spring (S) surrounding the barrel into engagement with a friction ring or serrated ring carried by, or provided by the upper end of the barrel, so that the cap will slip relative to the barrel when the torque exerted by the cap on the barrel exceeds a predetermined value. Located within the hollow barrel is an externally screw-threaded shaft (T) extending along the rotary axis of the handle and screw-threadedly engaged with the interior of the hollow barrel. The shaft (T) is slidable longitudinally with respect to discs (C) and housing (A) whilst being restrained from rotation with respect thereto, for example by longitudinal grooves (not shown) along the shaft (T) cooperating with splines (not shown) in a central guide member fixed within the fixed disc (C). Alternatively, of course, the hollow barrel and shaft (T) may have cooperating splines and grooves preventing relative rotation between the barrel and the shaft (T) and the shaft (T) may be screw-threadedly engaged with an internal screw thread in such central guide member. In either case the result is then when the shaft (T) is coupled directly to the handle (H) via the slipping clutch, when the handle (H) is turned, the shaft (T) is screwed downwards until such time as the slipping clutch mechanism allows the handle to slip without any further downward motion of shaft (T). A piston (D) is carried at the lower end of shaft (T) within chamber (M) and is dimensioned to be a close sliding fit in a cylindrical lower part of chamber (M). The bottom of chamber (M) is provided by a plate (F) of insulating material carrying spaced electrodes which are exposed to the chamber (M) and are connected with terminals (not shown) for connection with an electrical measuring instrument (I). In operation, with the apparatus in the position shown in Figure 1, a measured amount of grain is poured into the hopper (B). The handle (H) is now turned clockwise, effectively grinding the grain between the plates (C). The ground grain falls into the measuring chamber (M). When all the grain has been ground through, the slide (G) is now pushed towards the hub, in the direction of the arrow in Figure 1, into the position shown in Figure 2, in which the slide, via the slipping clutch, directly couples the handle and the piston mechanism. Turning the handle (H) clockwise screws the shaft (T) and piston (D) downwards to compress the ground grain in chamber (M). The amount of compression of the grain is regulated by the force exerted by piston (D) which in turn is regulated by the action of the slipping clutch. The sample is now prepared ready for measurement with instrument (I). Figure 3 is a perspective view showing the grinder/compressor mounted on an electrical measuring instrument, which may be arranged to measure the electrical resistance or capacitance between the electrodes referred to and to derive from the measurement thus made a moisture content figure which may be displayed on a display provided on the instrument, for example, as illustrated, a digital LED or LCD display. The grinding and sample-compressing apparatus may be permanently secured to the instrument (I) or may be readily detachable therefrom and re-attachable thereto, for example by means of a bayonet or screw fitting, for example for ease of cleaning. By way of example, the plate (F) with the electrodes may be permanently secured to the instrument (I) but removably inserted within the lower end of chamber (M), so that after a measurement has been made the body (A), including the peripheral wall of chamber (M) and an integral external flange at the lower end of that wall can be separated from the instrument (I) and plate (F), allowing the chamber (M) to be emptied and cleaned before the grinding and compressing apparatus is re-attached to the instrument (I). It will be understood that after a grain sample has been ground and tested as described above, the handle (H) is rotated anti-clockwise to raise the shaft (T) and piston (D) until the shaft (T) and piston (D) are in the position shown in Figure 1, after which continued turning of the handle anti-clockwise will simply cause the clutch to slip. Thereafter the slide (G) is slid outwards along the handle, to the position shown in Figure 1, thereby decoupling the piston from the handle. An advantage of the system described with reference to the drawings is that the grain is contained within the confines of the grinder/compressor from its raw state to its ground and compressed state and during resistance or capacitance measurement hence diminishing the chances of moisture and temperature change during grinding/transferring/compressing of the sample.

Claims: Apparatus for use in measuring the moisture content of grain or other particulate material, comprising a body (A), a grinding mechanism (C) in the body for grinding grain or other particulate material, a chamber (M) provided by the body and disposed to receive, directly from the grinding mechanism, ground grain or other material ground by the grinding mechanism, a piston or ram (D) movable into said chamber (M) to compress the ground material therein, and electrical contacts so disposed in said chamber or on said ram as to be in contact with the mass of compressed ground material, resulting from such movement into the chamber, at predetermined locations on said mass, whereby the moisture content of the material can be determined on the basis of the electrical resistance, between said electrodes, provided by said mass of compressed ground material, said grinding mechanism and said ram or piston being operable selectively by a common input member (H) characterised in that said grinding mechanism (C) comprises a fixed grinding disc, stationary in the body, and a rotatable grinding disc, said common input member comprising a hub and a manually operable handle (H) secured to the hub, said hub providing the driving connection between the handle and the rotatable grinding disc, said piston or ram (D) being carried by a shaft (T) extending along the rotary axis of the handle within a hollow barrel mounted coaxially within the hub, the barrel being coupled with a cap arranged coaxially within said hub, said hollow barrel forming an output member of said clutch, and wherein (a) the shaft (T) is screw-threadedly engaged in said hollow barrel and is axially slidable in, but it non-rotatable with respect to, a central guide member fixed with respect to said body, or (b) the shaft is guided for axial movement in said barrel but is non-rotatable therein and the shaft is screw-threadedly engaged in said central guide member; whereby rotation of said barrel within said body causes axial movement of said shaft (T) and thus of said piston (D) relative to said chamber (M), and wherein said barrel can be selectively rotationally coupled with said handle and hub or decoupled therefrom, by means of a slide (G) slidable along said handle (H) inwardly towards the rotary axis of the handle, or outwardly away from said rotary axis, respectively to extend into a diametral slot provided across the top of said cap and to be removed from said slot, and thus respectively to couple the handle with said cap and decouple the handle from said cap. Apparatus according to claim 1 wherein said cap is coupled with said barrel by way of a slipping clutch within said hub, arranged to allow the cap to slip relative to the barrel when the torque exerted by the cap on the barrel exceeds a predetermined value. Apparatus according to claim 2 wherein said slipping clutch comprises a first friction ring or serrated ring which is non-rotatable with respect to the cap, a second friction ring or serrated ring carried by or provided by the upper end of the barrel and a compression spring surrounding the barrel and acting to urge said first friction ring into engagement with the second friction ring.

Inventors: DADACHANJI FALI MINOCHER, DADACHANJI, FALI MINOCHER
Applicants: PROTIMETER PLC
Application year: 1995
Main classification: G01N27
IPC codes: G01N33, G01N27