US3009523A - Rigidly mounted spring counterforce - Google Patents

Description

Nov.'2l, 1961 s. WILLIAMS 2 RIGIDLY MOUNTED SPRING COUNTERFORCE Filed Oct. 24, 1956 4 Sheets-Sheet 1 INVENTOR.

LAWRENCE 5. W/LL/AMS A rro/qw 7 rs Nov. 21, 1961 1.. s. WILLIAMS 3,009,523

RIGIDLY MOUNTED SPRING COUNTERFORCE Filed Oct. 24, 1956 4 Sheets-Sheet 2 INVENTOR.

LAWRENCE 5. W/LL/AMS ORNE Y Nov. 21, 1961 1.. s. WILLIAMS 3,009,523

RIGIDLY MOUNTED SPRING COUNTERFORCE Filed Oct. 24, 1956 4 Sheets-Sheet 3 )f [3401 UL INVENTOR.

L A l V/PEA/CE S IMLL/A M5 wwgu ATTOR/V Kg Nov. 21, 1961 s. WILLIAMS 3,009,523

RIGIDLY MOUNTED SPRING COUNTERFORCE Filed Oct. 24, 1956 4 Sheets-Sheet 4 INVENTOR.

Al l RE/VCE 5. W/LL/AMS AHORNE S 3,009,523 RIGIDLY MOUNTED SPRING COUNTERFORCE Lawrence S. Williams, Toledo, Ohio, assignor, by mesne assignments, to Toledo I Scale Corporation, Toledo, Ohio, a corporation of Ohio Filed Oct. 24, 1956, Ser. No. 618,050

3 Claims. (Cl. 177-168) I k This invention relates to weighing scales and in particular to improved means for rigidly mounting and for adjusting load counterbalancing elements of the spring counterforce type.

Weighing scales that employ springs for offsetting a load usually employ pivotal connections for supporting the, springs and for connecting the springs to the load supporting mechanisms. 'I hese pivotal connections, while they reduce or eliminate the transmission of bending moments to the springs, introduce a number of connections where slight dimensional changes are apt to take place during the use of the scales. Such slight dimensional changes are especially serious in projected indication Weighing scales, an example of which isshown in U.S. Patent No. 2,723,113 issued on November 8, 1955,

to D. A. Meeker and to I. M. Sherman, in which the.

improved means for rigidly rnounting and for adjusting load counterbalancing elements are especiallyv useful. In such projected indication scales, indications ofiloads are projected from a chart that moves according to the elongation of one or more load counterbalancing springs and that has indicia which are so small that slight dimensional changes in the spring connections'show up as large errors in the projected indications.

The principal object of this invention is to provide an improved clampable connection for a spring counterforce which functions to immovably anchor an end of the spring.

Another object of the invention is to provide. a flatsided helical spring counterforce and clampable connections therefor in lieu of pivotal connections.

A further object of the invention isto' provide, in a weighing scale, improved means for making Zeroand tare adjustments. I I i Other objects and advantages of the invention will be apparent from the following description, the accompanyv ing drawings and the appendedclaims. 7

According to the invention, a weighing scale comprising a frameand a lever pivotally mountedin the frame is provided with load counterbalancing means rigidly connected to'r the frame by an'improved, clainpable connection and a bell crank that" may be rocked for zero and tare adjustments and to the leverbyanother and similar improved 'clampable connection.

3,009,523 Patented Nov. 21, 1 961 FIGURE VII is a plan view which is similar to FIG- URE IV of a modification of the device shown in FIG- URE IV. I v

FIGURE VIII is a vertical sectional view taken along the line VIIl-VIII of FIGURE VII.

FIGURE IX is an exploded view of thedevice shown in FIGURE vn. I FIGURE X is a plan view which is similar to FIGURE IV of another modification of the device shown in FIG- URE IV. I 7 FIGURE XI is a vertical sectional view taken the line XI-XI of FIGURE X.

FIGURE XII is an enlarged plan view which is similar to FIGURE IV of still another modification of the device along shown in FIGURE IV.

1 on a load placed .upon a load receiver 1 is transmitted to a pivotally mounted lever 2 fulcrumed on ball bearings 3 in a frame cf the weighing scale. The ball bearing mountings for the lever 2 is shown in detail and is claimed in the applicants copending application Serial No. 434,759

' which was filed on June 7, i954. The mounting for the lever 2 includes a'p-air of studs 5, only one of which is shown, fixedly attached to the lever and engaging the races of the ball bearings 3 mounted within cup-shaped housings 6 that are clamped in V-Lgrooves .7 of pedestals 8 of the frame 4. The bearing'housings 6 are clamped in position in the V -grooves 7 by straps) fitting over the housings and held in place by screws 10. f

The load forces acting on the lever 2, are transmitted to load counterbalancing means including a helical spring 11 rigidly connected to the lever 2 and to the frame 4 which spring preferably is a flat-sided spring that is generally rectangular in cross section. Instead of the single I [spring counterfo'rcell, several "Springs may be ii sed'in hereinbefc're referred to application Serial No. 434,759.

Preferred embodiments of the inventionare illustrated I in theaccornpanying drawing 7 v. I I p H g fl aw s e a i FIGURESI is a side elevational view of a weighing scale, with parts broken away. and parts. shown .in section incorporatingthe improved means for rigidly mount ing and for'ad justing load counterbalancing elements.

FI GUREII is an enlarged elevational view of-the bell crank and the mounting therefor as seen from a position along'the line II I"I of FIGURE I looking in the direc I tionin'dicated by the-arrows.

\ The extension of the spring 11, which is proportional 'to the load on the scale, permits the spring supported end 'ofthe lever 2 to drop a distance proportional to the load and this movement is transmitted through linkage, which is not shown since it forms no part of the present invention but which may be like that illustrated in the hereinbefo'rereferred to US. Patent No. 2,723,113, to move a chart through equal increments, for equal increments of load onthe'scale. Images ofweight, price and'com p'uted fvaliie indicia are project'e d' from the chart onto a downwardly tilted display screen 12 by means of an optical system, the chart and the optical system being shown in detail in said US. Patent No. 2,723,113. The chart and the connection between the chart and the lever 2 are enclosed in a housing 13 erected on the rear portion of the frame 4.

The upper end of the spring 11 is rigidly connected to a threaded rod 14 attached at its upper end to a trunnion 15, having horizontally extending pins 16, only one of which is shown, which rest in V-shaped bearing surfaces 17 of bifurcated portion 1-8 of a bell crank 19, the threaded rod 14 being rockable about the axes of the pins 16. The bifurcated portion 18- of the bell crank 19 and its bearing surfaces 17 are shown in detail in FIGURES II and III. The bell crank 19 is rockable about the axes of cone pointed screws 20 which are threaded through the ears 21 of a bracket 22 fixedly mounted on a shelf-like part of the frame 4, the screws 20 cooperating with conical depressions in the bell crank and being held against turning by lock nuts 23 which are so adjusted that the bell crank is free to rock yet is mounted with a minium of play.

The bell crank 19 may be rocked either by turning a tare knob 24 which is located exteriorly of the housing 13 on the end of a sleeve-like screw 25 that is threaded through the bracket 22 to move an end of a second screw 26 threaded within the sleeve-like screw toward or away from the lower arm of the bell crank or the bell crank may be rocked by directly turning the second screw 26 and holding the sleeve-like screw 25 stationary. Force provided by the spring counterforce 11 always urges the bell crank 19 against the end of the second screw 26 and the pins 16 against the bearing surfaces 17 of the bifurcated portion 18 of the bell crank. When the sleevelike screw 25 is turned by the tare knob 24, the second screw 26 always turns with it as one because the second screw 26 is threaded through the inside of a coil 27 which is threaded in turn into a threaded part 28 of the sleevelike screw 25. Threading the second screw 26 through the coil 27 provides a very tight connection entirely free of play. However, the screw 26 can be turned relative to the screw 25 by holding the knob 24 with one hand 7 and by turning the screw 26 by means of a screw driver, the kerf 29 of the screw 26 being about flush with the outer surface of the tare knob 24. i

In order that the tare weight of a container placed upon the load receiver 1 may be offset, the tare knob is turned clockwise to move a stop pin 30 on the screw 25 away from a second pin 31 on the bracket 22 and to advance the end of the screw 26 toward the bell crank 19 until zero weight is indicated on the screen 12. This rocks the bell crank 19 clockwise as viewed in FIGURE I about the axes of the cone pointed screws 20 and lifts the spring supported end of the lever 2 and the parts operating in unison therewith upward a distance equal to the distance which the end of the lever 2 moved downward under the influence of the tare weight of the container on the load receiver 1. Zero adjustment is made by holding the tare knob 24 stationary and turning the screw 26 to rock the bell crank 19 and position the spring counterforce 11 and the spring supported end of the lever 2 along with the parts operating inunison therewith. There, thus, is provided first means, i.e., the sleeve-like screw 25fand its knob 24, for rocking the bell crank 19 to position the load counterbalancing means, i.e, the spring counterforce 11, for tare adjustment, and second means, i.e., the screw 26,0perable independently of the first means, for rocking the bell crank to position the load counterbalancing means for zero adjustment.

Irioperation, the zero adjustment is made by holding the" tare knob 24 stationary and turning the screws 26 until zero weight indication is displayed on the screen .12 when no load is upon the load receiver 1. A container to be filled is then placed upon the load receiver 1 and the tare knob is turneduntilQzero weight indication isv displayed again on the screen 12. After the container is filled, the weight of ;the net load in the container is indicated on the display screen 12.

I spring which is'shown in FIGURE V, load upon the spring Means are provided in the form of clamps or calibrators 32 which function to rigidly connect or immovably anchor the spring counterforce 11 to the lever 2 and to the rod 14. Each of the calibrators 32 includes a block or first member 33, a cooperating clamp or second member 34, and a clamp screw 35, an end of the spring 11 being clamped between the block and the clamp which is held in place by means of the clamp screw. The calibrators 32 are adjustably fixed one to the spring supported end of the lever 2 and one to the lower end of the rod 14 by means of connections which extend through vertical holes 36 in the blocks 33. Each of the blocks 33 has a clamping surface 37 which is curved to fit a flat side of an end of the spring 11 and each of the clamps 34 has a clamping surface 38which is relieved relative to a clamped part of an end of the spring 11 to provide two gripping points on the end of the spring. The relieved part of the clamp 34 is indicated at 39 in FIGURES IV and V and is an important feature of the calibrator construction, since its use insures that there is no possibility for the end of the spring to shift in the calibrator during operation of the weighing scale. The two gripping points are shown at 40 in FIGURE IV.

The improved spring counterforce and the supports therefor precisely position each of the elements contributing to the indication of load so that the uncertaintly of load indication is reduced. Rigidly mounting the ends of the weighing spring according to the invention so'that there is no possibility for the spring to shift in its mountings during operation removes practically all of the erratic error of the scale and also the back weighing error, i.e., the difierence between the indication of load when the load is increased as against the indication of the same load as the load is being decreased.

Considering the generally rectangular section of the depending on its direction puts the upper or the lower surface of the spring in tension and the other surface in compression which tension and compression forces extend along the spring into that part of the spring which is clamped between the block 33 and the clamp 34. These forces are overcome by the friction of the calibrator on the spring so that no relativemovement between the spring and the calibrator occurs. If the clamping force of the calibrator should happen to be less than the shear force exerted on the loaded spring at a take off or gripping point 40, the spring would shift at such point relative to the calibrator. When the load upon such a shiftable spring is reduced, the chances are strong that the spring will not return to its orginal location because of the friction in the calibrator. Such a condition produces the erratic error and the back weighing error hereinbefore mentioned. Such possibility of shifting is eliminated by relieving the clamp 34 as indicated at 39. This concen trates the force exerted by the clamp screw 35 at the two gripping points 40 instead of allowing the force provided by the screw to be greatly divided and distributed along the clamping surfaces 37 and 38 of the block and of the clamp and insuresv that the clamping forceof the calibrator 32 on the spring 11 is always much greater than the shear force on the'spring at its take off point from the calibrator.

Since it is usually impossible to wind springs to have a certain load carrying capacity at a certain extension, the calibrators 32 also function to vary selectively the location of the gripping points 40 on the spring..{ [his is accomplished by loos-enin-g the clamp screws 35; by loosening the connections between the blocks 33 and the lever relative to the spring to lengthen its effective or. usable length and thereby increase its deflection fora given .unit of load placed upon theload receiver 1. Conversely, if the spring is too weak such that the spring extension is too great for the correct indication of load, one or the other or both of the calibrators can be turned relative to the spring to shorten its effective or usable length and thus reduce its extension for a given load applied to the load receiver 1. v t

A modification of the calibrators 32 is shown in FIG- URES VII-IX. Reference numerals in FIGURES VII- IX which are similar to those in FIGURES -IV-VI identify parts which are similar in structure and in function to those illustrated in FIGURES IV-VI. The only difference between the calibrator 32 (FIGURES IV-VI) and the calibrator 32a (FIGURES VI I-IX) is that, whereas in the calibrator 32 the clamping surface 37 of the block 33 is curved to fit a fiat side of an end of the spring 11, in the calibrator 32a, the clamping surface 38a of the clamp 34a is curved to fit a fiat side of the end of the spring and, whereas in the calibrator 32 the clamping surface 38 of the clamp 34 is relieved relative to a clamped part of an end of the spring, in the calibrator 32a the clamping surface 37a of the block 33a is relieved relative to a clamped part of an end of the spring, i.e., a more or less reversal of parts. This causes the gripping points 40a to be at'the clamping surface 37a of the block 33a instead of at theclamping surface of the clamp as are the gripping points 40 and the relieved part 39a to be between' the block 33a and the spring 11as shown in FIG- URES VII and VIII instead of between the clamp and the spring as shown at 39 in FIGURE V.

Another modification of the improved calibrator is shown in FIGURES X and XI. The principal difference between the calibrator 32b shown in FIGURES X and XI and the calibrators shown in FIGURES I-IX is that the calibrator 3212 has no clamping surface which is re lieved relative to a clamped part of an end of a spring. However, if the calibrator 32b is'carefully made and properly lubricated and tightened the clamped section of the spring is forced down and out into such intimate contact with the calibrator, which is carefully formed to fit The calibrator 32b includes a block or first member 33b, a cooperating clamp or second member 34b, and a clamp screw'35b, an end of the spring 11 being clamped between the block and the clamp which is held'in place by means of the clamp screw. An initial turn on each end of the spring 1 1 is open for attachment of the calibrator clamps; The calibrator 32b is adjustably connected to the threaded lower end of the rod 14 by means of a pair of nuts 41 which urge the block 33b and the clamp 34b toward each other, the blockand the clamp being separated by a spacer 42. Another one of the calibrators 32b is adjustably connected in a similar man ner to the spring supported end of the lever 2.

The block 33b is grooved to fit the bottom of an end section of the spring 11 (FIGURE XI) and has a clamping surface 37b which is curvedto fit afiat sideof an end of the spring 11. When the calibrator is lubricated and when the clamp screw 35]) is tightened, the clamp 34b forces the clamped section of the spring down and out into intimate contact with the grooved part and with a p the curved clamping surface 37b of the block 33b.

i The block 33c is grooved to fit the bottom of an end section of the spring 11 (FIGURE XIII), has a clamp surface37c which is curved to fit a flat side of an end of the spring 11, and carries a shouldered stud 44 upon which the clamp 34c bears. When the calibrator is lubricated and when the clamp screws 35c are tightened, the clamp 34c forces the clamped section of the spring down and out into intimate contact with the grooved part and with the curved clamping surface 37c of th block 330.

The improved spring counterforce and the several embodimen-ts of the improved supports therefor eliminate all of the pivotal connections that are commonly associated with weighing springs'and therefore precisely positions each of the elements contributing to the projected indication of load so that the uncertainty of indication (weight,

price, and computed value) is materially reduced. The improved bell crank structure for selectively positioning the spring counterforce provides convenient means for making zero and tare adjustments.

Various modifications in the attachment of the spring counterforce to its mountings and in the mechanism for adjustably supporting the spring may be made without departing from the spririt and scope of the invention.

Still another modification of the improved calibrator is shown in FIGURES X11 and XIII. The calibrator 32c includes a block or first member 3-30, a'cooperating clamp or second member 340, and a pair of clamp screws 35c,

' an end of the spring ll being clamped between the block and the clamp which is held in place by means of the An initial' turn. on each end of the 1 clamp screws 35c. spring 11 is open for attachment of the calibrator clamps; The block 33c is adjustably connected to the threaded lower end of the rod 14 by means of a pair of nuts 43.

Another one of the calibrators 326 is adjustably connected in a similar manner to the spring supported end of the lever 2.

Having described the invention, I claim:

1. A weighing scale, comprising in combination, a frame, a bell crank pivotally mounted on the frame, a lever pivotally mounted in the frame, a load counterbalancing spring operatively connected between the bell crank and the lever, means for rocking the bell crank comprising an externally and internally threaded sleeve-like screw threaded in the frame, a second screw threaded within the sleeve-like screw and mean for so connecting the screws that they turn as one from an index position to position the spring for an adjustment, one of the screws, when the other screw is held in the index position against turning, being operable independently of such other screw for rocking the bell crank to position the spring for an additional adjustment, and a pairof cooperable stop members one carried by the frame and one carried the bell crank, a second screw threaded within the sleevelike screw, the spring constantlyurging the other arm of the bell crank against an end of a screw, and means for so connecting the screws that they turn as one from an index position to position the spring for an adjustment,

.one of the screws, when the other screw is held in the balancing spring operatively connected between an arm of the bell crank and the lever, means for rocking the bell' crank comprising an externally and, internally threaded sleeve-likescrew threaded in the frame adjacent the bell crank, a coil threaded within the sleeve-like screw I and a second screw threaded inside the coil, the spring constantly urging the other arm of the bell crank against an end of the second screw, said coil providing such a tight connection that the screws turn as one from an index position without play to position the spring for a tare adjustment, the second screw, when-the sleeve-like screw is held in the index position against turning, being operable independently of the sleeve-like screw or rocking I the bell crank to position the spring for a zero adjustment, and a pair of cooperable stop members one carried by the frame and one carried by the sleeve-like screw for defining the index position,

References Cited in the file of this patent V UNITED STATES PATENTS 8 Cayo May 13, 1930 Walker Apr. 3, 1934 Farwell et a1 'Mar. 12, 1940 Stimpson et a1. Feb. 16, 1943 Thorsson ....-Nov. 13, 1945 Williams Mar. 17, 1953 Karp et a1. Nov. 10, 1953 Knobel Jan. 18, 1955 Williams Q Aug. 13, 1957 FOREIGN PATENTS Great Britain Jan. 8, '1900

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