US2404601A - Microbalance - Google Patents

Description

July 23, 1946. w SEYTER 2,404,601

MI CRO BALANCE Filed Ma '24, 1944 2 Sheets-Sheet 1 July 23, 1946. Y

W. C. SEYTER MI CRO BALANCE Filed May 24, 1944 2 Sheets-Sheet 2 29 U E I Patented July 23, 1946 MICROBALANCE William Christopher Seyter, Union City, N. J assignor to The Torsion Balance 00., New York, N. Y., a corporation of New York Application May 24, 1944, Serial No. 537,058

8 Claims. 1

My present invention relates to balances, and more particularly to micro balances and aims to provide certain improvements therein.

Among the objects of the present invention are (l) to provide a micro balance wherein the stirrup and the beam arrestment contacts are so adjusted that in releasing said arrestment means, the knife edges for supporting the stirrups will seat-before the central knife edge of the beam; (2) wherein lateral tilting of the stirrups is prevented when the pans supported by the stirrups are being loaded or unloaded; (3) wherein springs are'provided to insure lowering of the arrestment arms for both the beam and the stirrups when the lift rod controlling said arms is lowered; (4) wherein perfect placement of the rider on the beam will be obtained both endwise sidewise; (5) wherein index means are provided for facilitating such rider placement and the reading of the rider position on the beam; and (6) wherein the construction is less complicated and more easily adjusted in consonance with the extreme accuracy of the balance so that less time will be required for making adjustments.

The foregoing and other objects of my invention not specifically enumerated, I accomplish by the novel construction and cooperative arrangements of parts hereinafter described and illustrated in the accompanying drawings showing a preferred embodiment, and wherein:

Figure 1 is a front elevation of the upper portion of a micro balance embodying the novel features of my invention, parts thereof being broken away to better illustrate the construction, the enclosing case and the optical devices for reading the swings of the index being omitted.

Fig. 2 is a top plan view of the balance beam with the stirrups mounted thereon.

Fig. 3 is an end elevation of the balance beam as viewed from the left end thereof, with the stirrups held in arrested position.

Fig. 4 is a section taken substantially along the plane of the line 4-4 of Fig. 1.

Fig. 5 is a detail section taken along the plane of the line 55 of Fig. 4.

Figs. 6 and 7 are side elevations of modified forms of rider lifters.

Fig. 8 is a section taken along the plane of the line 8-8 of Fig. 7.

Referring to the drawings, let the reference character I0 indicate a vertical hollow column such as is usually mounted on the base of an enclosed balance. and guided Within the column fOr vertical reciprocation therein is a lift rod II which is usually operated by a thumb wheel (not shown) extending outwardly at the front of the case below the base thereof, the function of the lift rod being to move arrestment means for the beam and the stirrups into and out of operative position. Rigidly mounted on the top of the column is a block I2 having mounted in its top a central bearing consisting of an inset piece I3 of agate, boron carbide or other extremely hard material having a highly polished plane top sur face for supporting the central knife edge I4 of a balance beam I5. Secured to the block I2 are a pair of arms I6 in which are fixed aligned pivot pins I1 upon which are pivotally mounted 9. pair of oppositely disposed Y-shaped beam arrestment arms I8 and a pair of oppositely disposed Y-shaped stirrup arrestment arms I9 having fork-shaped end pieces I9. Preferably the axis of the pivot pins ll lie in the top plane surface of the bearing member I3. The balance beam I5, which may be of any desired form, carries adjacent each of its ends an upwardly-directed knife edge 20, and preferably the bearing edges of the knife edges I 4 and 20 all lie in a common plane. Adapted to be seatably supported upon the terminal knife edges 20 when the balance beam is supported on its central knife edge are a pair of stirrups 2! each comprising a rigidly depending cradle 22 which, in turn, dependingly supports a double hook-shaped member 23 through an intermediate link 23a. The hookshaped members 23 are adapted to support the bows 24 of balance pans (not shown).

The balance beam I5 is adapted to be held in arrested position, that is, with its central knife edge raised out of contact with the bearing I3 by arrestment means herein shown as consisting of a ball-shaped member 25 carried by an adjustable screw mounted adjacent one end of one of the beam arrestment arms I8 for cooperative engagement with a downwardly directed cupshaped member 26 carried by the beam, and by a pair of adjustable screws 21 carried by the other beam arrestment arm I8 for cooperative engagement with a transverse bar 28 carried by the beam. These beam arrestment means may be of a type well known in the art and more detailed description thereof is not thought necessary. The stirrup arrestment means consist of a pair of upwardly-extending adjustable screws 29. carried by each of the fork-shaped end pieces IS on the stirrup arrestment arms I9, the free end of one of said screws being adapted for cooperation with a downwardly-directed cupshaped element 30 carried by the stirrup and the free end of the other screw being adapted for cooperation with an inverted V-shaped groove member 3i carried by the stirrup. These stirrup arrestment means likewise are of a type well known in the art, and further description thereof is not thought necessary.

According to my present invention, the arrestment and the seating of the beam and the arrestment and seating of the stirrups are made to take place in a time sequential order, that is to say, when the arrestment means are released, the stirrups will first simultaneously seat upon the terminal knife edges of the beam and at a short interval thereafter the central knife edge of the beam will seat upon its bearing 53. This sequential timed seating of the stirrups andthe beam is accomplished by employing the separate and independently operable beam arrestment arms I3 and stirrup arrestment arms 19 and by causing said arms to move at different rates by operation of the lift rod ll. This sequential timed movement is brought about by connecting the lift rod I I to the arrestment arms l8 and l through adjustable connecting rods 32 and 33, respectively, one end of each of said rods 32 being pivotally connected to a depending lug lta on one of the arrestment arms is and one end of each of said rods 33 being pivotally connected to a depending lug Ifia on one of the arrestment arms l9, and locating the pivotal connections 34 between the rods 33 and the stirrup arrestment arms it at a somewhat shorter distance from the pivotal mounting of said arms with the axis of the pins l7 than the pivotal connections 35 between the rods 32 and the beam arrestment arms l8. In view of the disposition of the free ends of the arms l8 above the arms l9, the latter have openings 19b therein through which the lugs i811 extend and are movable. To transmit the motion of the lift rod l i to the respective arrestment arms I3 and I9 through the rods 82 and 33, the other ends of said rods are pivotally mounted to a horizontalar-m 36 of a cross-shaped member 31 which is rigidly secured to the lift rod H by screws 38 or equivalent means. Inasmuch as the lift rod 1 l is mounted to move within the column If] and the arm 36 must move therewith, the column is formed with laterally aligned slots 39 to permit of such movement. To insure against any sticking or lagging in the movement of the arrestment arms when the lift rod is lowered, I provide pairs of springs All for bearing upon the stirrup arrestment arms l9 and pairs of springs M for bearing upon the beam arrestment arms I B. These springs may be of any desired form and may be mounted in any convenient manner, and are herein shown as leaf-springs suitably bent and rigidly secured to the top of the column by fastening screws 42.

In the loading and the unloading of the pans of the conventional analytical or chemical balance there is always danger of causing a lateral tilting of the stirrups, so that when they are brought down into seating engagement upon the terminal knife edges of the balance beam, such tilted stirrups will introduce an error in the weighing operation because of the change in the effective lengths of the balance beam arms between the central knife edge support and the offset supports of the stirrup-s, To overcome this source of error, which, if inherent in micro balances, would. constitute a major error, I provide means wherein such lateral tilting of the stirrups is prevented when the pans are being loaded and unloaded. This I accomplish by supplementing the conventional stirrup arrestment means 29, 3B and to said fins.

My present invention also contemplates the provision cit means whereby perfect placement of the rider on the beam will be obtained, both endwise and sidewise, and wherein means are provided for facilitating such rider placement and the reading of the rider position on the beam. To accomplish this I provide a rider carrier 55 which is mounted for movement, both longitudinally and ver ically of the beam. in any approved manner. herein shown, the rider carrier 45 is fixedly mounted on a carrier rod :26 which is guided along space rods to move parallel to the beam, said carrier rod also being rotatable about its Mounted on said rider carrier is a vertically--disposed tubular guiding member :18 within which is vertically and nomrotatably movable a plunger which, at its lower end, carries a rider lifter 58. Vertical movement is imparted to the plunger through a connecting arm 5i, one end of which is fixedly mounted on the carrier rod 46 and the opposite end of which is forked and straddles the ends of a projecting .pin 52 mounted on the plunger as and extending through vertical slots 53 in the tubular guiding member 48.

The rider lifter 5%] comprises a pair of spaced arms 5d, the free ends of which have reentrant portions 55, the free ends of which, in turn, are formed with notched aligned rider-supporting seats 5%. The rider lifter is intended for cooperation with a rider 5'5 which is in the form of a straight piece of wire of circular cross-section, the leng n of said rider being such as to extend across and project a slight distance on either side of the beam so as to be supportable in the seats fill of the rider lifter when raised above the beam and to be seated on the beam when the rider lifter is moved below the top of the beam. In this connection it will be obvious that the transverse distance between the reentrant ends of the rider arms is slightly greater than the depth of the beam. so that in the vertical movement of said rider lifter the arms will straddle the beam. The top of the balance beam is preferably transversely notched, as indicated at 58. to accommodate the rider, each notch indicating a predetermined weight when the rider is mounted therein. For facilitating the placement of the rider in any particular notch, the rider lifter is preferably formed with an index pointer 59;: for aiding in indexing the notch on the beam with the rider when supported by the rider carrier. It will be observed, however, that when the rider lifter has deposited the rider in a particular notch, that the arms of the rider would ordinarily obscure the rider from the view of the analyst, and to remedy this condition the rider arm facing the front of the balance case may be formed of transparent material such as Lucite or the like. The indexing and placement of the rider on the beam may be further expedited by the use of a magnifying lens 59 adjustably carried by the rider carrier 45 on an arm ii extending therefrom.

In Figs. 6, 7 and 8 I have illustrated alternative forms of rider lifters whereby indexing of a notch on the beam for placement of the rider therein and for reading such position of the rider on the beam can be accomplished. In each of the modifications the rider lifter comprises a pair of spaced reversely L-shaped arms 52 adapted in the ver tical movement thereof to straddle the beam. In Fig. 6 the horizontal arms of the Us are each formed with a rider-supporting seat 63, and the arm facing the front of the balance is also provided with an index 64. In Figs. 7 and 8 the ridersupporting seats are formed at the ends of reentrant lips 55 on the horizontal arms of the Us, and the arm facing the front of th balance is formed with indexes 66 and 61, the former being for the purpose of indexing the notch on the beam for placement of the rider, and the index 61 bein for assisting in reading the position of the rider when deposited on the beam.

The balance construction hereinbefore described, it will be understood, is intended to be housed within an enclosing case (not shown), and in view of the extreme accuracy of the balance such enclosing case may be provided with optical means for facilitating the reading of the graduations on an index member (not shown) carried by the depending movable pointer 68 carried by the beam l5, and counterbalanced to adjust the center of gravity of the beam by the adjustable nut 69.

In use the balance may be operated or manipulated in precisely the same manner as conventional analytical and micro balances, the fundamental distinctions between the present invention and prior balance constructions residing (1), in the timed sequential order in Which the stirrups are seated on the terminal knife edges of the beam and the central knife edge is thereafter seated on its bearing upon release of the respective arrestment arms; (2) wherein the lateral tilting of the stirrups is prevented when the pans supported by the stirrups are being loaded and unloaded; and (3) wherein perfect placement of the rider on the beam is facilitated, as is also the reading of the position of the rider on the beam.

While in the foregoing description I have explained the preferred embodiment of my invention, it is to be understood, however, that I do not wish to be limited to the precise details of construction disclosed since these may be varied within the range of engineering skil1 without departing from the spirit of my invention as defined in the appended claims.

What I claim is:

1. A balance comprising a column, a lift rod guided by said column, a balance beam having a central seatable knife edge and terminal knife edges, stirrups seatable on said terminal knife edges, beam arrestment arms, stirrup arrestment arms, and adjustable means connecting said lift rod with the respective arrestment arms for moving them sequentially, to first simultaneously seat the stirrups and to thereafter seat the central knife edge of the beam.

2, A balance comprising a column, a lift rod guided by said column, balance beam having a central seatable knife edge and terminal knife edges, stirrups seatable on said terminal knife edges, beam arresting arms, stirrup arresting arms, and rods of adjustable length connecting said lift rod with said arms for independently moving said arms subsequentially, to first simultaneously seat the stirrups and to thereafter seat the central knife edge of the beam.

3. A balance comprising a column, a lift rod guided by said column, a balance beam having a central seatable knife edge and terminal knife edges, stirrups seatable on said terminal knife edges, independently movable arms pivotally mounted on a common axis for arrestment of the beam and the stirrups, and rods of adjustable length connecting said lift rod with said arms, the connection of the rods with the stirrup arrestment arms being at a shorter distance from the pivotal mounting of said arms than the connecon of the rods with the beam arrestment arms for moving their respective arrestment arms sequentialiy, to first simultaneously seat the stirrups and to thereafter seat the central knife edge of the beam.

4. A balance comprising a balance beam having terminal knife edges, stirrups seatable on said knife edges, means for arrestment of the stirrups comprising arrestment levers and cooperating means on said levers and on the stirrups and means for preventing lateral tilting of the stirrups as the pans are being loaded and unloaded, said last mentioned means comprising supplemental cooperating means on the arrestment lever and on the stirrups.

5. A balance comprising a balance beam having terminal knife edges, stirrups seatable on said knife edges, means for arrestment of the stirrups comprising arrestment levers and means on said levers and the stirrups, and means for preventing lateral tilting of the stirrups as the pans are being loaded and unloaded, said last mentioned means comprising a pair of adjustable screws extending upwardly on each arrestment lever flanking and supplemental to the means for arrestment of the stirrups, said screws being adapted for engagement with laterally extending contact fins on the stirrups.

6. A balance according to claim 5 wherein the ends of the adjustable screws are closely spaced but normally in non-supporting relation to the contact fins on the stirrup.

7. A balance comprising a balance beam having a seatable central knife edge and terminal knife edges, stirrups seatable on said terminal knife edges, pivotally mounted independently movable arms for arrestment of the beam and the stirrups, means for operatively releasing said arrestment arms to permit the seating of the respective knife edges in timed sequential order, and spring means acting on said arrestment arms to insure their independent releasing movement upon operation of the releasing means.

8. A balance comprising a column, a lift rod guided by said column, a balance beam having a seatable central knife edge and terminal knife edges, stirrups seatable on said terminal knife edges, pivotally mounted independently movable arms for arrestment of the beam and the stirrups, means connecting the lift rod with the arrestment arms, means for operatively releasing said arrestment arms by operation of the lift rod to permit the seating of the respective knife edges in timed sequential order and spring means mounted on the column and bearing on said arrestment arms to insure their independent releasing movement upon operation of the lift rod.

WILLIAM CHRISTOPHER SEYTER.

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