US1915725A - Laboratory burette holder - Google Patents

Description

June 27, 1933. E. H. FISHER LABORATORY BURE'ITE HOLDER Filed July 16, 1932 2 Sheets-Sheet .1

INVENTOR "UNITED :STATES Patented June 27, 1933 I nnwm n. menus, on. rrrrsnnnen, PENNSYLVANIA, Assrenon rojrrsirula scrnnrirro COMPANY, or PITTSBURGH, PENNSYLVANIA', A oonronnrron'orrnztNsYLvANrA LABORATORY BUREITE HOLDER.

Application filed July 16,

This invention relates to burette holders,

entire length ofthe-burette.

The holders or clamps heretofore used for;

supporting burettes have been subject to-va rious disadvantages. For example all. such holders, whether of the spring, clamp or other type, engagethe buretteinsuch a man.

her as to obscure a substantial portion Of'ltfi' scale divisions, which necessitates moving 'the burette in the holder to make readings in such obstructed regions. Some types ofthese holders also torman opaque backing over a substantial vertical height of the burette, thus cutting off the transmission of light through that portion. This-makes it di'flicult .to make accurate readings in and adjacent to such portions, since errors may arise from parallaxphenomenadue to dift'erences in the appearance of the meniscus under transmitted and under reflected light, as is the case where part of the burette is shut off from 80 transmitted light.

Moreover, the burette holders heretofore commercially available have not provided fully satisfactory supporting action. 'For ,instance they clamp the burette at asingle (point, so that theburette may tilt, thus causing errors in reading, or so that theburette v may slide upwardly and downwardly in-the support. Others may require heavy clamping action such as to endanger the burette,

4o while all clamp types are slow acting, re-

quiring that the jaws be 'opened'to'thefull width of the burette to insert or remove it,

and since the jaws are screw-actuated this 1s a tlme-consum ng and. ob ectionable operation- The holder provided by this invention Comprises a backing plate having at oneside verjtically spaced forwardly extending fixed finf & gers aligned: forf vertical contact with one {side ofa burette, and. an arm pivotally con 1 nected to the plateto move between the fixed 1932. Serial No. 622,837 I fingers. its extended end vthe pivoted t arm carries a pin,'and this arm is impelled contlnuously toward the fingers to'bringv its p111 into engagement with the side of a burette oppositethat engaged by the fixed fingers.

Thus'the burette is held between generally parallel .clamping fingers which positively engage opposite sides of the burette and do not obstruct the scale- Most suitably the pin contactstheadjacent' side of the burette at a point intermediate that which isengaged by the fingers, soas to eXert' an angularclamping thrust, and advantageouslythe movable arm is positioned rearwardly of theplate with its pin extending forwardly and generallyparallel -to the i'fingers; Preferablythe fixed fingersare positioned at the ends of vertically spaced fixed arms which pro ject laterally from the backing plate, and a pair of arms are pivotally connected to the rear of the plate and urged onetoward each finger to engagethe burette in the manner .just described. This construction permits transmission of light through substantially. theenti're scale, d i

The invention may be descr bed further jwith referenceto the accompanying drawings, of whioh Figs. '1 and Z'are a vertical rear elevation and a top planview, respectively, of oneembodiment; Figs. 3 and 41 views similar to Figs. ,1 and 2,;shofwing the preferred embodiment; and Fig. 5 a side view of the disassembled clamping arms of th holder .shown in Figs. 3 and 4:. V

The holder maybe constructed to support a single burette, lthoughpreferably both sides of the plate are constructed in the manv ner just explained for, supporting two burettes. Such an embodiment is shown in the drawings.

bent forwardly to form fingers?) which pr'eferably areoiiset, as shown in Fig. 2, to form a sort of cradle for one side-of a burette 4:, but without. obstructing its scale divisions. An arm 5 having a forwardly projecting pin :6 at one end ispivotally connectedat its other 7 I H The embodiment shown in Figs. 1 and. 2

end to the backing plate, for example by mounting the arm upon a stud 7 projecting rearwardly from plate 1. This permits arm 5 and pin 6 to move between arms 2 for contact with the burette, while leaving the front of the burette fully exposed. A spring 8 acting between the plate and movable arm urges the arm continuously toward one of the fingers.

In the use of this embodiment arm 5 is drawn upwardly against the tension of spring 8 to provide sufiicient space for insertion of burette 4 between the fixed fingers 3 and pin 6. Upon permitting arm 5 to move down wardly under the spring pressure pin 6 engages one side of the burette and thrusts it against fingers 8. It will be observed that 1n this embodiment the pin'acts between the fingers, and exerts an angular thrust. This is particularly advantageous, for secure clamping of the burette is thereby obtained with relatively light pressures, and the angular forces tend to prevent vertical slippage.

The holder may be supported in any desired manner. In the embodiment shown a stirrup 9v receives rod 10 of a ring stand, or the like, the holder being locked in any desired vertical position by a set screw 11, Fig. 2.

A further embodiment of the invention is shown in Figs. 3 to 5, in which backing plate 1a is provided at each side with arcuately extending fixed vertically spaced arms 2a each of which is provided with a forwardly extending oifset finger 3a adapted, as in the preceding embodiment, to engage one side of a burette la. This form embodies two movable arms 5a and 5b projecting laterally from behind plate 1 and provided adjacent their outer ends with forwardly projecting p insfia. These arms are pivotally mounted at their inner ends upon a common stud a, and they are urged apart toward the adjacent fingers by a coil spring 8a whose ends are engaged in studs 15 formed on the arms. As in the preceding embodiment the burette is gripped between fingers 3a and pins 6a. The projecting ends 16 of arms 5a and 5bserve as a convenient gripping means for drawing the arms together against the tension of spring 8a.

Advantageously the holder is provided with means for limiting inward travel of the movable arms, so that each arm may be uniformly positioned with respect to the fingers 3a and the burette each time a burette is inserted in the holder. In the embodiment shown the arms are provided with projections 17 which contact with a stop 18 formed on the rear of the backing plat-e. This permits each arm to move midway of the fixed arms and fingers, so that when arms 5a and 5b are released they will assume substantially the same relative positions with respect to fingers 3a and the burette. As before, the pins 6a preferably act between the fingers, so that each time a burette is placed in the holder it is positively gripped by uniformly applied thrust of the movable arms.

Thus the invention provides burette hold ers which positively support and position the burettes, and which prevent vertical sliding and angular movements of the burette. In both embodiments the entire scale is free to unobstructed view at all times, and by making the arms narrow only relatively short vertical heights of the burette are cut off from transmission of light. The device is exceptionally quick acting, as willbe understood from the description and drawings, and is much more rapid and easy to use than the clamp type holders now in use. If desired,

and as is common practice, the burette-engagtion may be practiced'otherwise'than as specifically illustrated and described.

I claim: p

1. A clear-vision quick-acting burette holder comprising a backing plate having at one side a pair of laterally ext-ending vertically spaced fixed arms provided at their outer ends with forwardly projecting vertically aligned fingers for contact with one side of a burette, a pair of movable arms positioned rearwardly of the plate and pivotally connected at one end thereto to move toward and from each other and said fingers, each of said movable arms beingprovided at its extended end with a forwardly projecting pin positioned to cooperate with said fingers for; holding a burette therebetween, and a spring" acting between said movable arms continuously urging them apart toward the adjacent fingers, said fingers engaging one side ofa vertically positioned burette and said spring. acting on the movable arms urging said pins into engagement with the opposite side of the burette to thereby support the burette positlvely and with its graduations substantially unobstructed. i r I 2. A clear-vision quick-acting burette holder comprising a backing plate having at one side a pair of laterally extending vertically spaced fixed arms provided at their outer ends with forwardly projecting verti-e;

gle pivot pin at a point intermediate said- A fixed arms to move toward and from each other and said fingers, each o fsaidmov able arms being provided at its extended end with a forwardly projecting pin positioned to cooperate with said fingers for holding a burette therebetween, and a spring acting between said movable arms continuously urging them apart toward the adjacent fingers,

-' said fingers engaging one side of a vertically holder comprising a backing plate having' at one side a pair of laterally extending vertically spaced fixed arms provided at their outer ends with forwardly projecting vertically aligned fingers offset to receive one side of a burette, apair of movable'arms positioned rearwardly of said plate and pivotally connected at one end to the plate substantially midway between said fixed arms to move toward and'from each other and said pins, each of said movable arms being provided adjacent its extended end with a forwardly projecting pin positioned to cooperate with said fingers for holding a burette therebetween, and a spring acting between said movable arms continuously urging them apart toward. the adjacent fingers, said fingers engaging one side of a vertically positioned burette and said spring acting on the movable we arms urging said pins intojangular. engagement with the'opposite'side of the, burette at points intermediate the fingers to thereby support the burette positively and with its graduations substantially unobstructed. I

4. A clear-vision quick-acting burette holderrcomprising a backing plate having at one side a pair of laterally extending vertically spaced fixed arms provided at their outer ends withvertically aligned fingers for contact with a burette, a pair of movable arms disposed rearwardly of the plate and pivotally connected at one end thereto substantially midway of said fixed arms to swing 7 toward and from each other and said pins, means for restrictmg said movable arms 1n moving toward each other to a point midway between the fixed arms, each of said movable arms being provided adjacent its extended end with a forwardly projecting pin positioned to cooperate withsaid fingers for holding a burette therebetween, and a spring acting between said movable arms continu:

ously urging them apart toward the adjacent fingers, said fingers engaging one side of a vertically positioned burette and said spring acting on the movable arms urging said pins into angular engagement with the, opposite a side of the burette at points intermediate the fingers to thereby support the burette positively and with its graduations substan' tially unobstructed. I Intestimony whereof, I sign my name.

EDWIN H. FISHER.

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