US3524599A - Mortar and pestle for grinding and mixing - Google Patents

Description

Aug. 18, 1970 s. JOACHIM'GUNTER HEILENZ 3,

MORTAR AND PESTLE FOR GRINDING AND MIXING Filed April 25, 1967 s Sheets-Sheet 1 Inventor SGA9FPIL8CZ 1753i 6777" 6072i? Hea 28722,

5 wz'jph aa 'wzavzawa Aug. 18, 1970 s. JOACHIMTGUNTER HEILENZ 3, ,599

' MORTAR AND PESTLEYFOR, GRINDING AND MIXING Filed April 25, 196'? 3 Sheets-Sheet 2 Inventor Q7 unfek H 61 26722 gage Aug. 18, 1970 s. JOACHIMGUNTERHEILENZ 3,524,599

I MORTAR AND PESTLE FOR GRINDING AND MIXING Filed April 25, 1 967 5 Sheets-Sheet 3 Inventor filegfizlad, JoacLLm flZ Hei'Zevzz v Aftys United States Patent 59, 37 Int. Cl. B02c 19/08, 2/06 US. Cl. 241-199 13 Claims ABSTRACT OF THE DISCLOSURE A grinding and mixing appliance comprising a mechanically driven generally cylindrical pestle mounted to rotate eccentrically in a mortar supported rotably on a table, said pestle having a cut away lower face such that the pestle rotates in a cavity in said mortar to engage the entire surface thereof once during each revolution.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to apparatus for grinding and mixing materials for use in producing spectrochemical or other samples which are required to be ground or mixed homogeneously.

Description of the prior art In the production of spectrochemical samples, the substance to be analysed and buffering substances must be mixed with a carrier substance normally graphite. If quantitative determinations are to be carried out, standard additions of elements to be determined and reference elements must also be included in the mixture. Such samples or specimens thus represent multicomponent mixtures of solids. The carrier substance is the principal ingredient of the specimens. The proportions of the other ingredients of the mixture mostly differ by several powers of ten. It is extremely difficult at present to accomplish the homogeneity of the mixture which is absolutely necessary in a mixture of this kind for reliable analysis. Mixing in a mortar operated manually has hitherto proved to be the most satisfactory method and although the homogeneity required can always be thus obtained, a very long time, e.g. half-an-hour, must be expended on preparation of an adequately homogeneous specimen, which frequently renders it impossible to perform extensive series of experiments, also owing to the mental strain on the person preparing the specimen. In the case of a hand mortar moreover, which is open at the top, there is a risk of contaminating the material to be ground with environmental agents, and the possibility of absorption of atmospheric humidity.

The main object of the present invention is to provide a grinding and mixing appliance operating according to the mortar principle, in which the aforesaid difficulties are eliminated or at least minimised and by which spectrochemical specimens may be prepared within a short time and without expenditure of onerous manual labour.

SUMMARY According to the present invention there is provided a grinding and mixing appliance for use in the preparation of spectrochemical or other samples to be ground or milled or mixed homogenously, comprising a mechanically driven and preferably electromotively driven pestle which is cylindrical along at least a part of its periphery and which rotates about an axis eccentrical with respect to its cylindrical peripheral surface, said pestle engaging 3,524,599 Patented Aug. 18, 1970 eccentrically in a rotatable and essentially hollow cylindrical mortar in such manner that it comes into at least contact with the side of the mortar once in each revolution.

The powder to be mixed is simultaneously milled fine and mixed in the mixing appliance. The milling action is engendered by the impingement of the pestle as it moves eccentrically of the axis of the mortar in engagement with the side of the mortar. This contact is only of short duration, occurring once during each revolution of the pestle, so that other powder particles are brought into the milling area in each rotation, thereby creating a very good mixing action. Very satisfactorily homogenised specimens, which can be prepared to the same degree of homogeneity in a hand mortar within half-an-hour at the shortest, are obtained within a short time, e.g. within 1 to 3 minutes, as a result of the rapid motion of the pestle.

The pestle preferably largely fills the cavity of the mortar, e.g. to the extent that the volume of the pestle preferably amounts to 4.7 cm. for a mortar cavity of 6.2 cm A hollow space of 1.5 cm. would be left in this case, which is adequate, because only small quantities of the samples are required. The narrow cavity also has the advantage that the mixing action is particularly intensive, since no dead areas can be formed within the cavity, in which the powder cakes and escapes the mixing action. Greater or smaller sample volumes may be processed by appropriate enlargement or reduction of the mortar cavity and pestle volume.

The mortar is preferably rotatably arranged so that it is entrained by the contact with the pestle. To keep the speed of revolution of the mortar within limits (e.g. approximately 40 rpm), the rotation may be braked by a brake such as a friction brake. The rotata bility of the mortar has the advantage of little wear, since the contact between the pestle and mortar always occurs at a different point, so that the whole mortar wall is affected.

Although the passive rotation of the mortar, as herein described, is adequate, the mortar is preferably provided with its own rotary drive, the direction of rotation preferably being the same as the direction of rotation of the pestle. The drive usually comprises an electric motor connected to the pestle and/or mortar through a reduction gear.

In one preferred construction the lower end face of the pestle is cut off obliquely, preferably by an oblique or chamfer area, which merges into an area at right angles to the axis of the pestle along the line of a diameter. An edge is formed at the transition to the area at right angles to the axis from this oblique area, which scrapes the material of the sample off the bottom of the mortar, the pestle being close to the bottom of the mortar e.g. approximately 0.1 mm. from the bottom.

Alternatively the end face of the pestle may have a step, which preferably extends along a diameter. The step may have a height of 1 mm. for example. The edge formed thereby performs an impact action on the material at the bottom of the mortar and acts as a scraper preventing caking of material on the bottom.

A roof-like cross-section may be ground on the pestle, which interrupts the cylindrical milling surface, the edge thus formed carrying out an impact action on the material to be comminuted.

In another construction the mortar is arranged in a tiltable fastening whereby a shaking action is created which prevents the powder caking-on at any point and mixing is engendered.

In another embodiment, the mortar is situated on a horizontally displaceable working table or platform and is immobilisable in optional positions. The immobilisation may for example be effected by a set screw which engages in a stationary tapped hole. The table or platform is preferably displaceable in a horizontal direction against the force of a spring, so that it can yield when an unexpected resistance, e.g. in the form of a coarse grain, is present in the mortar. A table-mounted pedestal drill may for example be employed for driving the pestle. The top of the mortar is preferably covered.

The mortar and/or pestle are most satisfactorily made of hard material, e.g. high-grade stone (agate, corundum), Widia, or boron carbide. This choice of material is to be recommended especially if other material could be ground off and could thereby damage the specimens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order that the invention may be more fully understood some embodiments in accordance therewith will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a cross-section through a mixing appliance;

FIG. 2 is a plan view of the mixing appliance with the driving motor being omitted;

FIG. 3 is a perspective view of another form of mixing appliance;

FIG. 4 is a side elevation of the appliance of FIG. 3;

FIG. 5 is a plan View of the mortar-bearing table or platform of the construction in FIGS. 3 and 4, the table being drawn to substantially larger scale;

FIG. 6 is a cross-section along line VIVI in FIG. 5; and,

FIG. 7 is a cross-section along line VII-VII in FIG. 5.

Referring to FIGS. 1 and 2 the appliance is mounted on a stand which comprises a base 1 and an upright 2. The upper side 3 of the base 1 is machined precisely fiat and acts as a bearer for a tiltable mounting 4. This tiltable mounting has two surfaces 5 and 6 which converge in the manner of a roof. A kind of bearing edge or fin 7 is present at the line of intersection of these areas 5 and 6, about which the mounting 4 can tilt.

A ball bearing 8 is inset with its outer race in the mounting 4. In the inner race or ring 9 of the ball bearing '8 is an outer mortar portion 10, in which a mortar 11, preferably of gem stone, e.g. agate, is secured by a pin 11a. The mortar cavity 12 has a substantially cylindrical shape. The cylindrical space is outwardly tapered in funnel shape at 13.

The grinding or milling element 14 of a pestle engages in the mortar cavity 12. This grinding element is cylindrical and substantially fills the cavity 12 of the mortar. The lower end face of the pestle consists of an area 16 at right angles to the axis 15 of the pestle and of an area 17 extending obliquely thereto. The two areas 16 and 17 intersect along an edge 18.

The pestle shank 19 is secured in a chuck 20 of a tablemounted drill by a sleeve 22 having an eccentrical bore 23. The sleeve 22 is secured on the shank 19 by a set screw 24. At the upper extremity of the shank 19 is an abutment screw 25 which may be secured on the shank by locknuts 26. The screw 25 bears against an axial stop 26 of the clamping jaws of the chuck 20.

The mortar 11 is held in the outer or lower mortar portion 10 by a sleeve-shaped element 27 screwed on a thread 70 of the lower mortar portion 10. The element 27 has an internal conical bore 28 into which is inset a conical part 29 the conicity of which is slightly smaller than the conicity of the sleeve, thereby ensuring dust-proof closure, since the lower extremity of the part 29 bears or seats in the hollow cone. This part 29 is firmly pressed against the side of the conical bore 28 by a screw cap 30 which engages in a thread 31 of the sleeve-shaped element 27. Central bores 32 and 33 are formed in the parts 29 and 30 for traversing by the pestle shank 19. The components 27, 29 and 30 are preferably of Perspex (registered trademark).

It is apparent from FIG. 2 in particular that the mounting 4 is held in a fork-shaped part 34 uided with a median guide bar or the like 60- of T-shaped cross-section. In this way, the part 34 is displaceable and immobilisable in any position by the clamping screw 36 having a tommy bar 37. Retaining bars or gibs 35a and 35b are provided made of synthetic material. The fork-shaped part 34 is pressed against the base by this securing screw 36 (see FIG. 1). The element 38 which is secured by a screw 39 to the foot 1 of the stand and bears with a foot 40 against the contact surface 41, e.g. a surface of the table, acts as a bearing element for the fork 34.

A conically shaped rubber buffer 43 is secured to the fork-shaped part by a pin 42. This buffer bears against the outer side of the mounting 4. Inserts or attachments 61 of metal are disposed on the mounting 4, of synthetic material, to reduce wear at the points of contact with the fork 34. The mounting moreover has an extension 44 with an elongated hole 45 which is traversed by a guide bolt 46 for a compression coil spring 47. A nut 48 within the base or foot 1 secures the bolt 46 to the foot 1. At the top, the compression coil spring 47 bears against a head 49 of the guide bolt 46, and at the bottom against a washer 50 covering the elongated hole 45.

A brake 51 is also fitted on the foot 1 of the stand (see FIG. 2). This comprises a brake shoe 52 on which is a braking facing or lining 53, and an adjusting device for the brake shoe, comprising a screwbolt 54 and a nut 55. The bolt 54 is passed through a hole of the pin 56 with a clearance. A compression spring 54 presses the brake shoe against the motar holder or socket 10. The pestle may have an upper flange-like projection acting as a dust fiinger.

This mixing appliance operates as follows:

Initially the pestle 14 is retracted from the motar. The cover is removed. The specimen to be mixed is now placed in the mortar 11, after which the pestle is inserted and the cover or cap is screwed on again at the same time. The precise correct depth of penetration of the pestle into the mortar is assured by abutment of the upper extremity of the shank of the pestle. The lower surface 16 of the pestle is concomitantly spaced approximately 0.1 mm. from the bottom of the motar. Setting is possible by the longitudinal displaceability of the table-mounted drill on the upright or column 2 of the stand. The motor is now switched on, thereby setting the pestle in rotation. Since the pestle runs eccentrically to the mortar 11 (e.g. eccentricity of 0.7 mm.), it comes close to the side of the mortar during each revolution, thereby crushing the powder present between the pestle and the side of the mortar. During contact with the side of the mortar, the pestle tends to entrain the mortar by friction, which is possible by virtue of the rotatable mounting of the lower mortar portion 10. The entrainment occurs for a short period only, since the contact between the pestle and mortar equally subsists for a short time only. If the mortar were to speed up (the speed of revolution of the mortar is normally approximately 40 r.p.m. for a speed of revolution of the pestle of 1100 r.p.m.), the motion may be braked by the braking device 51 to 56.

The correct position of the pestle relative to the mortar may be set by displacement of the fork 34. The fork 34 is then clamped fast in the correct setting position. The entire mounting of the mortar is tilted slightly about the tilting edge 7 during each impingement of the pestle on the side of the mortar. The return spring 47 and the rubber buffer 43 provide a return force which thrusts the mortar mounting back into a median position. A shaking motion of the magnitude desired may be obtained by appropriate adjustment of the return spring 47 thus preventing the powder sticking to the side of the mortar. Sticking to the bottom is prevented by the edge 18 situated on the lower end face of the pestle. Since the absolutely dry material to be mixed may not absorb any moisture as it is processing, the mixing space is heated to approximately 30 C. above the ambient temperature by a weak infra-red lamp (not shown) which is turned towards the lower mortar portion 10.

An unobjectionably homogenous mixture is obtained within 2 to 3 minutes for a speed of revolution of the pestle of approximately 1100 r.p.m. To empty themortar it is extracted from its socket 10. A small flexible rod (not shown) is guided in the central bore a of the portion 10 for removal of the mortar, by which the mortar 11 is pressed out of the portion 10 (after unscrewing the parts 27, 29 and 30 as well as raising the pestle). To this end, the part 27 must be unscrewed beforehand. from the mortar portion 10. The pestle can then be drawn out of the mortar. The mortar may now be taken out ofits portion 10 and emptied, and may thereafter be cleaned and prepared for further use.

The appliance has been described in respect as used,

for the preparation of spectrochemical samples or specimens but it can be used for other substances to be mixed homogenously, for example in pharmacology, analysis by X-ray fluorescence, or in biochemistry.

Referring to FIGS. 3 to 7 this appliance has a box 80 acting as a base on which is a working table or platform 81 bearing the mounting for the mortar and the corresponding capping device described with reference to FIG. 1. The driving motor 82 for the pestle is vertically displaceable on a stand 83. The bar 83 is rigidly joined to the box 80. The motor 82 is fastened on a holder 84 which may be displaced along the bar 83 by a manual crank 85. To this end, a rack or toothed bar (not shown) is arranged on the bar 83, meshing with a pinion driven by the hand crank 85. A device 86 for fine adjustment of the vertical position of the driving motor 82 is also mounted on the holder. A lamp 95 is disposed on the bar 83 to illuminate the working table and the mortar.

The switching devices are in the lower portion of the appliance. Four control keys 88 to 91, a knob 92 for the main switch, a control knob 93 for setting the speed of revolution of the pestle and another control knob 94 for setting the speed of revolution of the mortar, are disposed on the front panel 87.

A hot air generator is provided in the box so that an outflow of the hot or warm air passes through a top pipe 140 through an orifice directed towards the mortar mounting 119.

The working table 81 is shown in greater detail in FIGS. 5 to 7. This table is secured on the top covering panel 96 of the box 80 and comprises a bearing portion 97 firmly connected to the plate 96, and a portion 98 displaceable relative thereto. The bearing portion 97 has a bottom frame 99 on which are fastened four ball sleeves 100 to 103 in which round rods 104 and 105 are slidably mounted.

Carrying elements 106 fastened to the table plate 107 are clamped fast on the rods 104, 105. In this way, the table plate 107 is mounted longitudinally displaceable, the longitudinal displacement being easily effected by the fit in the ball sleeves 100 to 103.

A part 108 is fastened on the base frame 99 and having a tapped hole 109 in which a bolt 110 is screwed. This bolt is connected by a spring 111 to an adjusting knob 112 which bears a setting scale 113. Thus when the adjusting knob 112 is turned, the table plate 107 is displaced together with. the parts fastened to it, since the rotation of the knob 112 is transmitted by the spring 111 to the screw bolt 110 screwed on its tapped hole 109.

A securing ring 114 is disposed on the table plate 107 which is covered by a sheet 139 of stainless steel. Within this securing ring is a cup 115 of synthetic material, which corresponds to the cup 4 of the construction described with reference to FIGS. 1 and 2. The cup 115 is pivoted within the ring 114, screws 116 acting as pivot pins. Within the cup 115 is a centering ring 117 which acts as an outer centering system for a double or twin row ball bearing 118. The mortar socket 119 is arranged 6 in the inner race or ring of the ball bearing 118, corresponding to the socket 10 of FIGS. 1 and 2. In this case too, the mortar 120 is co-rotatorily secured by a pin 121.

A lever 122 is pivotably mounted at 123 on the underside of the table plate 107. A tension spring 125 acts at 124 on the front extremity of the lever, its other extremity being hooked at 126 to the cup 115. A threaded spindle 128 acts at 127 on the other arm of the lever 122, a knurled nut 129 being screwed on its extremity projecting laterally over the table.

A universal joint shaft 130, driving the mortar, has a lower part 131 coupled to the output shaft of a gear 141 in the box 80 and driven by an electric motor. The gear 141 is suspended from uprights 142, 142 fastened on the underside of the table plate 107. On the gearbox is a flange 144, on which an electric motor 143 is screwed. On the motor spindle is a worm 145 meshing with a worm gear 146 to which a universal joint shaft 130 is connected. The intermediary element 132 of the universal joint shaft is coupled to theadjacent shaft sections by joint pins 133, 134. The upper shaft section 135 is inserted into a bore 136 of the mortar socket 119 and is held co-rotatorily therein by a key 137.

The appliance of FIGS. 3 to 7 operates in similar manner to that in FIGS. 1 and 2, so that its function is not further described. By contrast to the construction of FIGS. 1 and 2, the mortar is positively driven. Control of the speed of revolution is possible in the range from 0 to 50 r.p.m., whereas the speed of revolution of the pestle may be controlled in the range from 0 to 2,000 r.p.m. The position of the pestle relative to the mortar may be adjusted by turning the adjusting screw 112, during which the table 98 is displaced. During great resistance in the material to be ground, e.g. in the case of coarse granulation, the table may be displaced slightly by stretching or shortening the spring 111, thus preventing inadmissibly large forces on the pestle. The loading of the spring 125 may be changed by the knurled nut 129,

thereby increasing or reducing the torque about the pins 116, thus making allowance for the greater inertial forces engendered at higher speed of revolution of the pestle. The tilting motion of the mortar may however be prevented by locking the cup by a screw 138, e.g. for the purpose of comminuting coarse material to be milled or ground.

I claim:

1. A grinding and mixing device operating in accordance with the mortar principle for the production of spectrochemical or other samples to be ground or mixed homogenously, comprising a driven pestle which is cylindn'cal at leastover a part of its periphery and which rotates around an axis which is eccentric in relation to its cylindrical peripheral surface, and which engages eccentrically with a rotatable mortar which is essentially a hollow and cylindrical member, in such a manner that it will touch the wall of the mortar at least approximately once in every revolution.

2. An appliance according to claim 1 wherein said pestle largely fills said mortar cavity.

3. An appliance according to claim 1 wherein said mortar is rotatably mounted and said pestle is disposed to contact said mortar to impart a rotary movement thereto.

4. An appliance according to claim 1 wherein the lower face of saidpestle is recesser by an oblique cut off lower end face, said recess merging into the remainder of said pestle along a diameter thereof.

5. An appliance according to claim 1 wherein said mortar is housed in a housing tiltable about'a single axis at right angles to said mortar axis.

6. An appliance according to claim 1, a spring disposed to urge said mortar mounting towards a base and a rubber buffer is provided disposed in a fork on the opposite side of said mortar mounting and presses against said mounting, said fork being displaceable transversely 7 of said pestle and mortar axes, and means provided to immobilise said fork.

7. An appliance according to claim 1 wherein, said mortar being mounted on a working table secured on rods guided in ball sleeves on said base and horizontally displaceable on said rods by a spring.

8. An appliance according to claim 1 wherein a base is provided comprising a box, a table on said box pivotally supporting a cup forming a rotatable mounting for said mortar, and said mortar driving means being mounted in said box and connected to said mortar by a universal joint shaft.

9. An appliance according to claim 1 wherein said pestle has a shank engaged in a rotatable chuck to rotate eccentrically with respect to said chuck axis of rotation.

10. An appliance according to claim 1 wherein the upper portion of said mortar is closed by a cover, and said mortar is mounted in a rotatable lower mortar portion, said cover having a bore through which said pestle is rotatably disposed.

11. An appliance according to claim 1 wherein said pestle has an upper dust flinging flange-like projection.

12. Grinding and mixing devices according to claim 1, in which a brake device is provided to stop the rotation 8 of the said mortar rotating in the same angular direction as said pestle.

13 Device according to claim 1, in which the mortar is closed on top by means of a screw cover which consists of a casing-shaped body with a conical bore, with a cover insert fitting into said bore and in which a screw coupling is provided for the cover pressing down firmly, and bores for the passage of the pestle shaft provided in the cover insert and in the cover screw coupling.

References Cited UNITED STATES PATENTS 340,271 4/1886 Abele 241 199 482,330 9/1892 Acers 241-205 15 2,161,998 6/1939 Chott 241 199X 2,579,239 12/1951 Lippmann 241 215 2,856,135 10/1958 Applegate 24l199 LESTER M. SWINGLE, Primary Examiner D. G. KELLY, Assistant Examiner US. Cl. X.R. 241-212, 285

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