DE2826511A1 - AUTOMATIC PRECISION SCALE - Google Patents

Description

LEINWEBER & ZIMMERMANN

PATENT LAWYERS

Dipl.-Ing. H. Leinweber (1930-7 «) Dipl.-Ing. Heinz Zimmermann Dipl.-Ing. A. Gf. v. Wengersky

Roaental 7 ■ D-βΟΟΟ Munich

2. Ascent (Kustermann-Passage) Telephone (089) 2603989 Telex 528191 lepatd Telegr. Addr. Leinpat Munich

June 16, 197ΰ

Under sign g / lCr / C

3-450, B-431, ^ -452

Pitney-Bowes, Inc. Stamford, Connecticut 06904 U.S.A. Automatic precision balance

The invention relates to an improvement in a precision balance, and more particularly to an improved one liquid point display converter for determining the state of equilibrium the scales.

With precision balances, it is of the utmost importance to equip each element of the balance with a given minimum error. Of all the elements of the balance, none is more important than the part that determines when the balance is exactly in equilibrium. The invention disclosed balance automatically belongs to a new type of working precision balances and the invention relates to a W _a traders for these new scale that is both accurate and sensitive.

-2-

000862/077 *

ORIGINAL INSPECTED

The difficulty with all voting devices is that they are often influenced by other forces, v / ie chafing effects and inaccuracies in cutting edges or other swivel components.

The zero point display transducer according to the invention is designed so that it is essentially different from the aforementioned Influences is free and is therefore more sensitive and more accurate than similar devices according to the prior art.

Most of the precision balances in use now operate on the principle of balancing a load-induced moment and observation of the weights or moments necessary to achieve the desired balance conditions are created. In this regard, the balance according to the invention works no differently than anything that has been done before is used in practice in this area.

As is also well known, a sensitive balance such as a precision balance requires an analytical balance usually careful adjustments to bring the balance into equilibrium, where these careful adjustments are not only tedious but also time-consuming.

The invention aims to eliminate the task of the operator in performing this Scale settings. The invention relieves the operator of the trouble of observing the display of the balance Make the necessary settings and wait for the display of the balance to come to a standstill in order to display a weight value obtain.

The balance according to the invention has a means for the settings previously required by the operator to be carried out automatically.

To create an accurate and sensitive precision balance, the loading weight must move longitudinally of the balance beam accomplished with a minimum of 'frictional force will. Because the frictional force comes from the normal force exerted on the balance beam by the load weight depends, the solution "was devised to store the loading weight in a rolling motion on the balance beam.

This solution was for the elimination of friction effects ten sufficient, but created the difficulty of a backlash in the lead screw connection. .Different In other words, some force in the lead screw connection was still necessary for an accurate coupling between the loading weight and the lead screw drive. The invention was considered adjustable Coupling device for the aforementioned connection conceived, which a predetermined force or a predetermined .Aprint can deliver.

The invention relates to a single point display converter for a precision or analytical balance. The precision balance according to the invention has a balance beam, which in response to a known weight, which is displaceable along the balance beam, in a first direction pivoted around a base. The balance beam swivels in Responding to an unknown weight acting on the balance beam in a second opposite direction. The unknown weight is the weight to be determined by the scales.

-X-

The zero point display converter according to the invention determines when the balance beam is in a position of equilibrium. "The transducer comprises a first and a second strip, each of which carries the beam. Each of the strips is compared to a third strip supporting the beam relatively thin. Since these first and second strips are thin, they set the balance beam when deflecting little or no resistance. These strips are also relatively stiff along an axial path, so that they effectively bear the full weight of the balance beam.

The third strip is relatively thick with respect to the first and second strips and in an axial, the weight bearing direction relatively soft. Four strain gauges are on the third strip for scanning the pivoting of the balance beam attached. They are in a conventional Wheatstone bridge circuit arranged. The sign of the output voltage of this circuit determines the pivoting direction of the balance beam and its size is proportional to the angle through which the balance beam is pivoted.] The invention relates to ane automatic precision balance. The balance includes an axle shaft which is caused to rotate when a The load to be weighed is placed on a shell that is attached to the axle shaft and carries the load. A movable known one Weight movably supported by the axle shaft is increased in response to the load caused by the load to be weighed Movement caused to move on the axle shaft. The movement of the known weight exercises an opposite one or compensating moment on the axle shaft.

-5- eoö8S2 / 0779

in which an equilibrium detector determines that the two opposite noments are the same, the movement becomes of the known weight. The movement begins ri8o for the weight of the load to be weighed.

The axle shaft is preferably in the form of a lead screw and the known weight is screwed onto it. The guide screw is driven to rotate by a motor and in this way moves the known weight on the guide screw. A coding disk attached to the guide screw by operation measures the rotation of the guide screw and thus measures the movement of the known weight. TDi e invention relates to an improvement in an automatic precision balance. A coupling device for adjusting the contact pressure between a guide screw and an elastic weight provides an accurate and sensitive operation of the balance. The coupling device comprises a frame that carries a weight member in rolling motion. A rotatable lead screw is rotatably supported in the tt _a hmen and extends through the weight member. A leaf spring having a helically threaded portion at one end is engaged by the helical thread with the lead screw, while at the other end it is attached to the weight member. When the lead screw is driven to rotate, the screw threaded part advances on the lead screw, thereby causing the leaf spring to move the weight member.

-6- $ 09882/0778

-Jf-

Further details, advantages and features of the invention emerge from the following description and the drawing, to which express reference is made for all details not described in the text. It shows:

.Fig. 1 is a scheraatiscue side view of the invention Precision balance,

Fig. 2 is a functional block diagram of the in Fig. 1 shown precision balance,

Fig. 3 is a perspective view of the precision balance shown in Fig. 1,

Fig. 4 is a side view of the precision balance shown in Fig. 3,

FIG. 5 is a perspective view of one of FIG. shown liullpoint display converter and

Figure 6 is a cutaway perspective view of a load weight and lead screw construction to eliminate idle, as shown in the precision balance of FIG.

In Figs. 1, 3 and 4 are schematiscue and constructive Views of the precision forecast according to the invention shown. The balance consists of a base and frame part 10 on which a bendable load-bearing structure 11

attached if.t. DU lasttrrgenae xuDustruktion 11 can from be of the type of a pn & rwide LlaUfc construction or can be a bendable ü-eienLaiordnung etc., ü, ine Sonr.Ie 12 is on the movable wall 14 of the bendable load-bearing Construction 11 is attached (.Fig. 1) and wira susangled (Pieilrichtung 13) »if a load weighing below 30 is placed on them.

A rotatable axle shaft 15 extends horizontally through an opening 16 in the bend-deflectable wall 14. A web part 17 is attached to the wall 14 and extends from there. In this way, when the shell 12 is deflected (arrow direction 13), the actuatable axle shaft 15 is pivoted in a counterclockwise direction, as shown by the arrow direction 1y. A riulipunktsanzeigewnndler, indicated generally by arrow 20 and detailed in .Fig. 5, it tests the equilibrium t-deviation suffered by the axle shaft 15 from the horizontal plane. This equilibrium test converter 20 generates a signal which is fed to a rotor 21. The notor 21 is attached to the axle shaft 15 and rotates the axle shaft Vj in response to the imbalance signal sent from the transducer 20.

The axle shaft 15 has at least one section, which is provided with a thread int. In other words, the axle shaft 15 can be viewed as a guide screw. When the .guide screw (axle shaft (15)) rotates, becomes a displaceable weight 22, which is placed on the axle shaft 15 by a thread, on the axle shaft

15 moves forward. "The axle shaft 15 is in this way in urelmnr; set and the weight 22 is moved in such a way that the axle shaft 15 is placed in a horizontal position of equilibrium will. In other words, the weight 22 is moved forward along the axle shaft 15 in the direction 23 by a pivoting movement to cause the axle shaft 15 clockwise. The weight 22 is moved forward until the transducer 20 senses an equilibrium position and the motor 21 simultaneously receives a signal from the transducer 20 to stop the axle shaft 15 in rotation.

The distance from the initial starting position from which the weight moved is a corn for dos Weight of the load placed on the tray 12. This distance can be determined by the number of revolutions which the axle shaft 15 has been measured by the rotor 11 will. For this purpose are the axle shaft 15 and the Hotor.21 operatively connected to an axle shaft encoder 25. This encoder 25 measures the number of revolutions the axle shaft. This measurement is then fed to a counter and converted into a weight display value. Of the Encoders used for this purpose can be of the type disclosed by Disc Instruments, Inc., Costa Mesa, California; Model EC80 Rotaswitch.

Figure 2 shows a block diagram of the operation of the precision balance system. When an unknown weight on the shell 12 is placed on top of it, causing the weight 30 a pivoting movement of the axle shaft 15 on the weighing pan, with the result that the transducer 20 detects an imbalance. The converter 20 operates the motor 21, which the

309882/0779

jC-UbG (.axle shaft) 15 set in rotation. Uie axle shaft previous year areht in order aas known counterweight 22 vorwärt i.zubewegen what verursacat pivotal movement of the axle shaft M in an opposite "not clothes to that of dei.i - sampled .. Ciicilor 20 imbalance L-It gc auGzugleicho :: ..

Finally, if irt a position of equilibrium reached i.iiüt aor u-oüierer 2-j which Gresamtsaül of revolutions dor .t'ünrungsschraube Vj and iiiart this information eincu ..iiiiler (uiiiv / andiungseinheit) to 2o to this x-iecsung in a to convert immediate G-ev / ichtsanseigev / eri.

For this uir.wGnaiui: _c :. The necessary calculation is v / ohi- and contains a sucLetion of the coments around the e 1i>, ie the: known u-ev / icht 22 multiplied by the distance that it has covered longer than the axles 15 equals the unknown Ü -weight ~ j> ö multiplied by dc-Li given distance, in which there is vosi kieschwenkpukt the ACi ₁ EWGlIe 15 attacks. The solution to this moment equilibrium is given by the weight of the unknown weight 30.

In the .tlg ·. 3, 4 and 6 is the movable weight 22 and the axle shaft 15 shown in detail. the Axle shaft 15 is here part of a pivotable assembly 75, which side arms 31 and 32 having an elongated Form box-like frames. The assembly or the "Took 75 contains a crosspiece 34, each transverse with arms 31 and 32 are connected. Axle 15 is rotatably mounted within this frame, which can be seen at the bearing point 35, which is on the in Pig. 3 and 4 shown Crosspiece 34 is shown. The axle shaft 15 and the swiveling tiahmen is a unitary assembly and

- «jur is durcii stripes; lo and 37 of the banal; 20 swivel-mounted, as will be explained in detail below, her ttahme-n i; jt attached to a ^ iock 40, v / which in turn wedges the otroiie-u ;; o and 3Ϊ between blocks 3o una "-JJ ( siene i'ig. 5).

In order to enable fine adjustment of the precision balance, it is necessary to switch off the friction and empty space between the guide screw (Achcv / elle Vj) and aem overweight 22. For this purpose, the weight 22 is designed so that it is supported primarily by friction. The weight 22 is designed in a box-like iorm, as from I ¹ Ig. j and ο can be seen. The weight itself carries three wheels 41, 42 and 43, which carry the weight 22 as shown for full movement on the arms 31 and 32. Ug 31 and 32, the OB desired weight bear the arms 22, occurs at the Ptthrungoschraubenverbindung zwisehen your weight and the axle shaft PY very little tteibung on. 'Therefore, the axle shaft 15 can move the weight 22 very precisely and precisely.

Among other things, however, a predetermined value is still required to prevent backlash, an arrangement is provided to load the guide screw with a given or predetermined value, iine leaf spring 44 is each attached to bearing parts Ab and 46, as in .Fig. 6 shown iai. The bearing parts 43 and are screwed onto the guide screw 15, and the leaf spring 44 is connected to the weight 22 via an axle shaft 4b which is mounted inside the weight 22.

-11-

809582/0 779

-YES-

uie nf-welie can be threatened by a screw over.sheher head inserted into a slot 49 in order to put the leaf spring 44 under tension, and this tension loads a? . one wün ^ cl-tc-n or vor- ^ c Gbeneix ^ xü-'i over ede .bearing 4r- and 4c. ine ^ ^ leniiniiiuttcr n.it iü.e:.:. NIFC "C £ iraubs yü holds the axle shaft 46 in its Cteilun ^ · strong to maintain the predetermined voltage on the leaf spring 44 Somi ^ is apparent dcu awar the Krait of G-ev / ichtf 22 τοη the .L ' ^! Ühruiigsschrc "iUDen connections in aen iicreruLgen 43 and 4b is removed, however a certain iä-ax v / ie which is fed to avoid a backlash by means of the ultrasonic spring 44 su.

This is the coupling of the load weight to the i'führungE. screw ki.nn not only in a precision balance vervienduii ;; find, but according to the invention is gcns generally a device for coupling a load is provided, which has a UaIiKien as well as a rolling one movement on the lialiraen 7 !? stored weight L. part 22, one rotatable guide £ .screw 15, which rotates in room 7b is mounted and sicii through the weight part 22 through extends and a leaf spring 44, which is on a land with a 'file 45, 4υ having a screw thread is provided if.t, where the one screw thread on v / ei sender filing through the screw thread with the screw thread 15 in Mngriff is and the leaf spring 44 with his other and is attached to the u-weight part 22.

In iig. 5 is explained in detail by converter 20, As mentioned above, the pivotable is assumed to be 75 each Strips j) 6 and 37 attached and this is how that is Weight of the swiveling tiahmeus 75 through these strips

-12-S 0 5 8 BT / ff 77 9

fL

carry. The stripes Jo una 37 and yourseiup each one for himself! £ UF.ge slit liahines 35 attached and carried through it, which by an extension 57, a dIocIc ■ jb and a viandunf; b4 is rigidly attached to your sub-frame 10. From this it can be seen that the strips 36 and 37 account for the main part of the weight of the pivotable assembly 7 !? wear, this load-bearing suspension being directly traceable back to the frame 10 ic-t.

The strips % and 37 are designed to be very thin compared to the central strip 70 of the transducer 20. This enables the pivotable assembly 75 to pivot very easily because the strips 36 and 37 represent a very low bending resistance for this assembly.

The middle strip 70 iit relatively the same; Designed to be somewhat resistant to deflection of the pivotable frame 75 and connected to an L-shaped web 54, which is flexibly suspended by pairs of .uU-ttfedern 71 and 72. The ulattfedern 71 and 72 are anchored with a crossbar 80 , which is attached to the slit frame 33 on its side. The strip 70 is connected at its other end to the pivotable base group 75 by means of the block 40.

It can thus be seen that the middle strip 70 yields to both bending and tensile stresses, while it is resistant to bending itself.

The thinner strips 36 and 37 are stiff or rigid against tensile stress or axial load, while the thicker middle stripe relatively soft and

-13-

is resilient to tensile stress or axial load.

In this way the two outer strips 3b and 37 are while they make up most of the weight of the carry pivotable assembly 75, firmly and completely resilient, against the pivoting moments of assembly 75.

On the other hand, the middle strip 70 is compliant for bending moments caused by the assembly 75 and almost completely compliant to the tensile or axial load created by assembly 75.

On the back of the strip 70 are four strain gauges 90, 90a, 91 and 91a attached. These gauge elements each feel the. . Swivel movement of assembly 75 in both clockwise and counterclockwise directions.

or Tension Meter The accuracy of the strain gauges / 90, yOa, 91 and 91a

for scanning a pivoting of the assembly 75 is due to the structural arrangement of the strips 36, 37 and very much increased. These elements are represented by the The loads and stresses caused by the weight of the assembly 75 are not distorted, since this load is caught by the strips 36 and 37. These Keßelemente 90, 90a, 91 and 91a are also from because of the flexible suspension bridge with the leaf springs 71 and 72 Turning errors free. The strain gauges, which are electrically located in a Wheatstone bridge are, however, sensitive to the homents of the assembly 75.

-14-309882 / 0779

Because of the unique design of the transducer 20 and the weight 22 it can be seen that a very sensitive automatic precision balance was created which achieves the aforementioned objects of the invention.

-15-

8ÜSö8Z7 QY 7 9

Claims (1)

Claims Precision balance; with a balance beam, which is pivoted around a base in response to a bc-k & nntes weight that is different along the balance beam, in a first direction and in a second opposite direction in response to an unknown weight acting on the balance beam pivoted uniian u ullpunktsanzeigewandler for detecting a state of equilibrium of the balance beam, characterized in that the inllpunktsanzeigewandler has a first (36) and second (37) strips, each of which is connected to the base (10) and carries the balance beam, each of the strips proportionally is thin so that it offers little resistance to the balance beam when it deflects, while each of the strips in an axial seal is relatively stiff to support the weight of the balance beam, so that a third strip (70) is provided through the base ( 10) is carried, and carries the balance beam, the third strip (70) with respect to the ers th (36) and second (37) strips is relatively thick, while it is relatively soft in an axial direction bearing the weight of the balance beam, and that a "strain gauge device (90, 90a, 91, 91a) on the third strip (70) is attached to detect a pivoting of the balance beam from an equilibrium position, the strain gauge device being relatively unaffected by changes in the weight acting on the third strip (70) in an axial, weight-bearing direction. -16- ORIGINAL INSPECTED 2. Precision balance according to claim 1, characterized by Dadurdi, that the third strip (70) is arranged between the first (3b) and the second (37) strip. 3. Precision balance according to claim 1, characterized in that the strain gauge device has four strain gauges ^{arranged on the third strip (70), the four strain gauges being electrically arranged in a wheatstone 1} shy bridge. 4. Precision v / aage according to claim 1, characterized in that the third strip (70) through an intermediate switched on the uasis (10) and the third strip (70) Leaf spring carrier (71, 72) is carried. b. Precision balance according to Claim 4, characterized in that the spring support contains a pair of leaf springs (71, 72) arranged essentially in parallel. 6. Automatic precision balance, in particular according to claim 1, characterized by a base (10), a load-bearing one Structure (11) carried by the base (10) and in response to a load placed thereon (30) movable i & t, a rotatable i'guide screw (15), the not actuated with the load-bearing construction (11) connected i & t and carries a movable loading weight (22) screwed thereon, the lead screw (15) is pivotably mounted on this base and in response to a movement of both the load-bearing construction (11) or the load weight (22) is pivotable, and the movement of the load-bearing structure (11) -17-Ö09882 / 0 ?? Ö Guide screw (15) in an opposite notch pivoted than the one made by the aewegunp; of Load & weight (22) caused an actuation associated with the screw cap (15) " (21) to drive the guide screw (15) in the Sinai one Twist around the load weight (22) on the guide screw (15) movably move one of the isapis (10) carried balance detector (20) to detect when the lead screw (15) is affected by the weight (22) is pivoted into a state of equilibrium, the loading weight (22) being a sufficient distance the lead screw (15) is advanced to the pivoting movement to compensate, which by the load-bearing construction (11) on the guide screw (15) as a result of the placing of a weight (30) on the load-bearing structure (11) is caused and a heating device (25, 26) which is actuated with the (15) is connected to the turns of the guide screw (15), the measurement of the revolutions being a hatred for the weight of the load (30). 7. Automatic precision balance according to claim 6, characterized in that the balance detector (20) by a flexible connecting strip connected between the base (10) and the guide screw (15) 070) is carried, the flexible connecting strip undergoes a bend when the lead screw (15) a Pivoting experiences, whereby the balance detector a bending stress in the flexible. Connecting strip (70) detected and therefore the achievement of an equilibrium pivoting state can grasp by the guide screw (15). -18- 809882/07? " δ. Automatic precision balance according to claim 7, characterized in that the equilibrium detector is one Deünungtiaesservorrichtung (90, 90a, 91, 91a) which is mounted on the flexible connecting strip (70). 9. Automatic precision balance according to claim 6, characterized in that the Keß device contains a coding disk (25) and a detector (26) for measuring the revolution of the .b ^: guide screw (15), the revolutions of the .guide screw (15) being an i- iai are the weight of the load (30). 10. Automatic precision balance in particular still Claim 6, characterized by a base (1ö), a load bearing ivonautruction (11) carried by the base (10) and in response to an applied thereto to be weighed load (30) is movable, a pivotable axle shaft (15) which is actuated with the load-bearing Lvonstruktion (11) eats connected and a movable load weight (22) carries thereon, the axle shaft (15) is pivotally mounted on the base (10) and in response to movement of either the load-bearing structure (11) or the loading weight (22) is pivotable and the movement of the load-bearing structure (11) the Axle shaft pivoted in a direction opposite to that caused by the movement of the loading weight (22) caused, a drive means (21) which is operatively connected to the loading weight (22) to to move the loading weight (22) movably on the axle shaft (15), a balance detector (20) carried by the base (10) to detect when the axle shaft (15) is through the loading weight (22) is welded into an equilibrium position is, the loading weight (22) by a sufficient 60Θ882 / 0779 _ ₁₉ _ Giieade distance along the axle shaft (13) moved itt, around the durco the placing of a weight (50) on the load-bearing structure (11) by the lastträger.de Construction (11) swiveling exerted on the axle shaft (15) balance and one with the ^ eiastungGgewi ' ht (22) operatively connected iueiJ device (2 ^, 26) to measure the movement of the load weight (22), the movement of the load weight (22) being a hatred for the weight of the load (30). 11.Automati see precision balance according to claim 10, characterized in that the balance detector (20) of one between the uasis (10) and the axle shaft (15) switched flexible connecting strips (70) carried is, the flexible connecting strip undergoes a bend when the axle shaft (15) pivots undergoes bending stress in the flexible connecting strip (70) by the equilibrium detector detected and therefore the achievement of an equilibrium pivot state can grasp through the axle shaft (15). 12. Automatic precision balance according to claim 11, characterized in that the balance detector is a has strain gauge device (90, 90a, 91, 91a) mounted on the flexible connecting strip (70). 13 · Precision balance in particular according to claim 1, with a balance beam that can be displaced along a pivotable balance beam movable loading weight, characterized in that the combination of loading weight and Balance beam contains a frame (75), v / elcher for a pivotable movement in the response to locomotion of the jjeiF'stungsweightes (22) on the frame (75) is built that the loading weight (22) is geoaut for a rolling movement on the frame (75) that a rotatable guide screw (15) on the frame (75) is rotatably mounted and operatively connected to the loading weight (22) to dss loading weight (22) along the broach (75), the frame (75) taking substantially the entire weight of the byast bearing weight (22) and that a device (44) provided i.st, which is the Deiastung \ s weight (22) in actuating contact with the rotatable guide screw (15) sets. 14. Precision balance according to claim 13, characterized in that that the device for adjusting the loading weight (22) includes a leaf spring (44) which is connected to the loading weight (22) at one end and a screw-threaded bearing device (45) (46) connected to its other end has, which is rotationally with the .Fueil screw (15) in engagement stent, wherein the bearing device (45, 46) for a locomotion on the guide screw (15) is caused when the. Lead screw (15) to a Rotation is driven, causing the leaf spring (44) to move the loading weight (22) on the frame (75) offset. -21-Ö098Ö2 / 077Ö 15. Precision balance according to claim 14, characterized in that that the load weight (22) is box-like Has shape. 16. Precision balance according to claim 14, characterized in that the device (44) for setting the an adjusting device (4ö, 49, 50, 51) for setting the set pressure of the device (44) for setting the weight of the load, such as that the bearing device (45, 46) and the guide screw (15) in contact with each other with a predetermined force are brought. 809802/0770