US841161A - Counterbalance. - Google Patents

Description

No. 841,161. PATENTED JAN. 15, 1907. W. LEWIS.

COUNTERBALANCE.

APPLICATION FILED SEPT.20,1904.

4 SHEETSSHEET 1.

WITNESSES: 1 INVENTOR v m [Mr/1e THE NORRIS PETERS co., wnsmuamn, 04 c.

PATENTED JAN. 15, 1907.

W. LEWIS. OOUNTBRBALANGE. APPLIGATION FILED SEPT,20,1904.

4 SHEETS-SHEET 2.

Jay. 2.

IN 'ENTOR Qua/162 B 611' Attorney,

} WITNESSES:

0., WASHINGTDN. ma

PATENTED JAN. 15, 1907.

W. LEWIS. UOUNTBRBALANCE. APPLICATION FILED EPT. 20.1904.

4 SHEETSSHEET 4.

WITNESSES: (5 aw IN VE NTOF By /11'1' Altar/1c UNITED STATES,

PATENT OFFICE.

VVILFRED LEVIS, OF PHILADELPHIA, PENNSYLVANIA.

' COUNTERBALANCE.

Specification of Letters Patent.

Patented Jan. 15, 1907.

Application filed September 20,1904- Serial No. 225.278.

To all whom it may concern:

Be it known that I, WILFRED LEwIs, a citizen of the United States, and a resident of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a certain new and useful Improvement, in Counterbalances, of which thefollowing is a specification.

' This invention relates to a counterbalance that may be used in many or all classes of machinery, and especially in those classes of machinery wherein the weight or bulk of an ordinary counterbalance is objectionable.

The most common form of counterbalance is the Weightedlever; but'this form is not practicable in all cases, and various arrangements of springs have been resorted to in or-; der to counteract the effect of a weight or Such force acting in any given direction.

spring-counterbalances, however, are objec-- tionable in that the resistance offered thereby is variable and increases with the compression or expansion of the spring, and they for that reason are merely approximate coonterbalances.

The primary object of this invention is to avoid the defects of and the objections to previouscounterbalances and to provide by means of springs a uniform force acting in any given direction to counteract a uniform force orweight acting in the opposite direction.

' Another object is so to adjust the springs that they may be used to exert more or less force, as may be desired, at the beginning or the end of the travel through which they are intended to act, and other objects, as will hereinafter appear.

To the ends thereof the invention consists of features of construction, arrangements, and combinations of devices hereinafter described, and more particularly pointed out in the appended claims.

Several embodiments of the invention are illustrated in the accompanying drawings, forming part hereof, in which Figure 1 is a vertical sectional view of an apparatus in which the invention is embodied. Fig. 2 is a like view of a modified arrangement. Fig. 3 is a diagram illustrating the principle of the invention. Fig. 4 is a plan, partly in section, on the plane indicated in Fig. 5 by the line 4 4 of another modification. Fig. 5 is an end view of the last-mentioned modification. Fig. 6 is a vertical sectional view on the plane indicated in Fig. 5 by the line 6 6. Fig. 7 is'a side elevation, and Fig. 8 is a vertical sectional view on the plane indicated in Fig. 5 by the line 8 8.

Referring to the drawings, the referencenumeral 1 marks a frame which is attached to the. guides or standards 2, and it is remarked that these guides 2 may form part of the framework of the machine in which the counterbalance is to be used.

The reference 3 denotes a cross-head which is slidable along the guides 2 and is provided witha platform, carrier, or table 25, on which may rest or to which may be secured the weight, load, or part which is to be counterbalanced, and 9 marks helical springs surrounding the guides or standards 2. The springs may be designed very accurately for the duty to be performed, or their tension may be varied, if desired, in any known or suitable manner.

The cross-head 3 and the carrier i in the instance shown in Figs. 1 and 2 are moved downward against the resistance of said .springs 9 by means of a lever com rising an operating-arm 6, a shaft 4, to wh'ic the arm 6 is fast and which shaft is ournaled in a lug depending from the frame 1, an arm 5, fast on said shaft 4, a crank-pin or wrist 7 on the said arm 5, and a rod 8, which rests and slides in bearings on-the cross-head 3 and with which the crank-pin 7 is pivotally connected directly in the construction shown in Fig. 1 and indirectly in the construction shown in Fig. 2. A helical spring 10, surrounding the rod 8 and abutting against a part of the cross-head 3 and against a collar 26 on the rod 8, tends to move the rod and the pin 7 transversely of the apparatus. The parts are by preference so proportioned and arranged that the crank-arm 5 stands vertical, or nearly so, when the cross-head is in its upper position against the stops or frame 1, since this arrangement prevents any downward motion of the table t, as the same is loaded or weighted, until the lever 6 is operated. As the lever 6 is swung upward and to the left in Fig. 1 the cross-head and. the

parts or weight supported thereby are moved downward against the resistance of the springs 9 and 10 until the time the crank-pin 7 reaches the horizontal through the axis of the shaft 4. Thereafter the spring 10 acts to move the table or carrier downwardly. With the springs 9 arranged to counterbalance exactly the weight or load when the crank 7 is on said line of centers the carrier will be held in that position, the spring exerting no moment either waythat is to say, the spring-rod 8 opposes and then assists the continued motion of the cross-head 3, according to the positions of the crank 7 with relation- Fig. 2 represents a more practical coi' struc- .to convenience.

tion in which absolute perfection. is sacrificed In both cases, however, the operation is substantially the samaand in. Fig. 2 it is only the angularity of the l nk 11. that vitiates'the result. The principle of the invention is perfectly embodied in the construction illustrated. in Fig. 1, and to this construction the explanatory diagram Fig. 3 will be seen to apply.

Referring to Fig. 3. the reference-letter C denotes the crank-shaft; P and P, the crankpin in intermedi ate positions. Now it will be seen as the crank-pin moves in the circle A P P that the springs. 9 will be compressed, for any point P at the angle (X to the vertical line A B, by an amount represented by C P vers. 0!, represented on the diagram by the distance 0 P. At the same time the spring 10 will be compressed by an amount represented by P M .or C P sina, If both springs 9 and 10 are fully extended when the crankpin is at the point A. and begin to be compressed as the crank-pin moves through the angle a then A M equal to P 0 represents the compression of the springs 9 and A 0 equal to P M. represents the compression of the spring 10. When the crank-pin reaches the point D in'a line normal to the line A B at the center of motion of the crank-pin, both springs will have the same compression, A C or C P, equal to the radius of the crank, and in this position the elastic force of each spring should be equal to the weight of the cross-head 3 and the parts or load supported thereby or acting thereon. When this is the case, the cross-head will be in perfect equilibrium in any position for a part turn of the crank, as a reference to Fig. 3 will easily demonstrate. Tn this mid position the crank-pin at the point D- the spring 10 has no effect, and the spring system exactly counteracts the weight. At any inter1nediate position P the spring 10 exerts a force represented by P M, and this force acting at the distanceM C above the center C produces the moment P M x M C, and this moment is counteracted by the equal and opposite moment represented by the force M C acting at the distance P M or N- C, or P N at the distance 1 1M. The sum of the forces P N and P O equals N O or P, the radius of the crank. and this is truefor any position whatever. Forexample, when the crank pin moves to the position P"thespring9 :ex' erts the upward force P 0 and the s ring 10 the downward force P N.v The agebraic' sum of these forces is N as in the previous position P. Frictlon aside, the counterbalmade to takethe place of a weighted lever. in the construction shown in 2 the per rection of the counterbalance isto a slightcxtent affected by the angularity of the link '1'] a .75 ance is therefore a perfect one and 'can'be; 7

but as the length of this link is increased the discrepancy diminishes.

It will be noted in the constructions illus trated in Figs. 1' and 2 that the cross-head. 3 is brought to bear against the frame 1 whenthe crank-pin Tis a little off the line of cen ters, in which case it may be desirable to have the cross-head excessively counterweighted in v i order to hold it firmly'against the frame 1. This can be effected easily by givingithe.

spring 10 a longer compression than is repre sented by the radius of the crank. For ex' ample, in Fig. 3 the vertical line A B may represent the base from which compressions of the spring-10 are .to'be n1easured. A-little cxcessof compression. when the crank-pin is- 1 Y near the line of centers adds very much'tothe I supporting power: of the'devicey'but adds i very little to the effort required on thehandlever 6 to overcome it. The arrangement,

therefore, is very flexible in its application. 7 p The cross head 3 can be made to stay up or to stay down, according to'the stilfness or adjustment of the springs 9 and 10. In the spring 10 acts on the link 11, and it is,

always the effect of this spring at the point =7 that is to be considered.- If the point of'c'onnection between the spring rod Sand the'link i 1 1 be made adjustable lengthwise of thelirlr, the effective strength of the spring-rod may be varied or adjusted. It is obviousthat the construction and operation of the springs '9 and 10 may be varied from that shown'in.

Figs. 1;- and 2 without departing from this i.n'- r r1 act upon the crank5 to produce the sameefvention. For example, (the springs 9 might feet. as they do by direct action-against the cross-head 3 or another crank-shaft, andanif other set of springs might be added to assist the crank-shaft and springs shownin Figs. 1 and2.-

When

the'talo'le t istoo large'to be easily squared by the cross-head 3 and guides 2, a,

pair of shafts with cranks and links con-. nected. to foursquaring-points may beadv'antageously employed, as shown in Figs. 4 to 8, inclusive. frame 1 is fixed to standards orguides' 2* near their bottom, and the carrier ortable tis connected with rock-shafts journaled on In this arrangement the 'eration of the shafts 4*;

the frame 1 by the cranks 5 and links 11 and the table or carrier t slides on the guides 2 The shafts 4 are compelled to move together in unison by any suitable means, as by geared segments or by themeans shown in. the drawings and next to be described. Each shaft 4 has two pulleys or disks 14 15 fast thereto to turn therewith, and said disks 14 15 are connected in pairs by straps or ribbons 16', which connect opposite sides of the disks '14 15, so that one or the other of said straps or ribbons 16 is under tension during the op- This arrangement of ribbons is preferred to toothed gearing on account of its compactness and adaptability to varying center distances. The cranks 5 are thereby moved in reverse directions and the side thrust of the links 11 is balanced one by the other. The ends of the straps 16 are clamped between blocks 17 and the disks 14 15, said blocks being set into the disks and held in place by screws 18. The disks 14 are splined or otherwise attached to the shafts 4, while the disks 15 are adjustably connected. with said shafts 4*, preferably as follows: The disks 14 have lugs'or pins 19 on their sides next to the disks 15, and the disks. 15 have swiveled pins 20 thereon next to the disks 14. Screws 21 pass through the lugss19 and engage with threaded holes in the pins 20, the preferred arrangement being such that each. screw pulls or is under tension and not compression in tightening the straps 16, as this avoids a swivel connection between the screws 21 and the lugs 19. 22 is a stoparm fast on a shaft 4 and which coacts with the frame 1 to limit the motion ofthe table t toward the frame 1 while one of the shafts 4 has an arm or lever 6 whereby it may be operated, and the other shaft 4 has an extension 23 thereon for arresting the arm or lever 6 as the links 11 and the cranks 5* are in line with each other or are a little past or short of the lines of centers. At one side of the apparatus the cranks 5 are extended at 24 beyond the shafts 4 and wrists 25 on the arms 24 are connected by a compressionspring 10 and telescoping rods 8, which are pivotally connected to the cranks 25 and which have disk-abutments 26 thereon for the spring 10 At the other side of the apparatus the cranks 5 are extended at right angles at 2'7 28 to form. bell-levers, and the arms 27 28 are arranged to have detachable crank-pins 29 connected thereto, as by screwthreading the pins and holes in the cranks. The pins 29 have reduced ends-on which cross arms or bars 31 are pivoted, the bars being held in place by washers and pins 33. The ends of the arms 31 are perforated, and the ends of a coiled spring 9 engage with the said perforations. The tension of the spring 9 may be varied by engaging one end thereof more or less with the corresponding crossarm 31 before engaging the other end thereof with the other cross-arm '31. It is remarked alsothat the tension of the springs 9 and 10 may be made adjustable, if desired, and that the crank- pins 25 and 27 may be set in adjustable cranks to control the effective stiffness of these springs. -VVith the parts arranged as shown in Figs. 4 to S, inclusive, the springs counterbalance the table or carrier t and a given weight or load thereon, so that the operation of moving the lever 6 until the stop 22 strikes the frame 1 and back until the lever 6 -is arrested by the stop 23 requires a minimum of effort. It will be seen that the springs 9 and 1O as thus arranged on cranks at right angles are equivalent in effect to the springs 9 and 10 shown in Figs. 1 and 2 and that the principle upon which all of the forms of the invention shown is based is illustrated in the diagram Fig. 3 of the drawings.

It sometimes happens that the carrier t is to be loaded or weighted while the apparatus stands as in Fig. 4 and is to be moved when the apparatus has been inverted from that position. In such case the pins 29 are shifted to the arms 28, the spring 9 being connected with the said pins 29, as above mentioned. Thus by shifting the crank-pins one hundred and eighty degrees the appara tus can be rolled over through the same angle, and the counterbalance becomes equally effective in the new position.

The counterbalance herein shown has been used in practice in connection with moldmaking machines.

The gist of the. invention consists of two springs or two spring systems acting at right angles to each other on a crank or cranks to support a given load in any position of that crank or cranks. Two parallel springs or spring systems on cranks at right angles to each other are mechanically equivalent to the above, and the multiplication of springs and cranks to produce the same result comes within the spirit of my invention and the scope of my claims. I do not, therefore,

limit myself to the arrangements 'shownin the drawings and above described.

What I claim as new, and desire to secure by Letters Patent of the United States, is"

1. In a spring-counterbalance, a crank sustaining a load acting in a given direction, and a spring acting in the opposite direction, combined with a spring acting upon said crank normal to said direction, whereby the moments of the two springs acting to turn the crank can be made exactly equal and op- 'posite to the moment of the load upon the crank in all positions of the crank.

2. In a spring-counterbalance, the combination of a movable part, a plurality of springs for moving said part, and means whereby certain of said springs first resist and then assist the progressive motion of said part in one direction while the remainder of said springs continually resist said motion.

In a spring-counterbalance, the combination of a guided carrier, a plurality of springs for moving said. table or carrier, and means whereby certain of said springs first resist and then assist the progressive motion plurality of springs for moving the same, certain of said springs abutting against said carrier or a part connected thereto, and crank connection between certain of said springs and the fixed framework.

5. In a spring-counterbalance, the eombination of a framework, a carrier mov able and guided thereon, a plurality of springs for moving, said carrier, and crank connection between certain oi: said springs and the said framework. I

6; In a spring-counterbalance, the combination of a framework, a carrier movable thereon, a plurality of springs for moving said carrier, and crank connection between certain of said. springs and one of said framework and table elements.

7. In a spring counterbalance, the combination of a framework, a part movable relatively thereto, a spring resistance for resisting progressive motion. of said part in one direction, and crank-and-spring connection be tween said movable part and said framework.

8. In. a spring-counterbalance, the combination of a framework, a carrier movable thereon, a spring resistance for resisting progressive motion of said'carrier, a spring-r0 on said carrier, and acrank on the fixed framework connected with said springrod.

9. In a spring-counterbalance, the combi nationof a framework, a carrier movable thereon, a springresistanoe for resisting progressive motion of said carrier in one direction, a spring-rod on said carrier, and a crank on which said rod isv pivoted.

10. In a spring-counterbalance, crank mechanism for sustaining a load or uniform force acting in a given direction, combined .with springs arranged some to act on said crank. mechanism or the load in the opposite direction, and the remainder toact upon said crank mechanism normal to said direction,

Signed at Philadelphia, in the county of Philadelphia and State of Pennsylvania, this 15th day of August,- A. D. 1904. v

' WILFRED LEWIS. Witnesses:

IVIUMFOIRD, K. M.. MORGAN,

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