US2168209A - Spring counterbalance - Google Patents

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Aug. 1, 1939. I w HAUPT 2,168,209

SPRING COUNTERBALANCE Filed July 16, 1937 INVENTOR ZZZ BY f ATTORNEY Patented Aug. 1, 1939 2,168,209

UNITED STATES PATENT OFFICE SPRING COUNTERBALANCE Walter H. Haupt, Ludlow, Ky., assignor to The Kelley-Koett Manufacturing Company, Inc., Covington, Ky., a corporation of Ohio Application July 16, 1937, Serial No. 154,047 s Claims. (01. 248123) This invention relates to a counterbalancing plate I! and a lower end plate l8 between which system for 'X-ray apparatus, ultra-violet lamps, and into which are mounted a plurality of heliand the like. cal springs l9. If desired, only one spring may Among the objects of this invention is the probe used, but in the case where heavy weights have vision of such a system in which weights are subto be balanced, a plurality is recommended be- 5 stitutedby springs. Ordinarily a weight and a cause many small springs are cheaper than one spring are regarded as mechanical equivalents large one and by leaving ofi one or adding one and no invention is deemed to reside in their a closer approximation of the weight to the interchange. It has long been desired however, spring tension can be had. Failure of-one spring 10 to replace the heavy weights necessary to balance also will not allow the weight to fall if a plurality 10 heavy shockproof X-ray heads which contain of springs are used. transformers and oil and frequently weigh over a On bottom end plate l8, a second cable l3a, is hundred pounds. The problem is not merely to attached in a non-slidable manner by means of balance such a head at a given point on a 001- a central eye bolt 20 and then the cable continues umn or standard but to balance it statically at down the column, as will be explained. The up- 15 any point on the column While making the head D end p e which is Stationary during the easy to move and balance throughout the height counterbalancing operation, is adjustable for of the column. If such an arrangement is suce and consequent y for Spring tension by a cessful, the saving in weight can be utilized to vertical screw 2!. Turning a nut 22 which is make the column and base stifier and stronger. integral with the screw and located above cap 20 The ti saving in weight of course, need not I5 is sufiicient to accomplish the adjustment since be nullified by making the rest of the apparatus the screw is threaded in plate I! but unthreaded heavier. where it passed thru cap 15. A spring guide 23 is It is well known that helical springs do not also provided n t e co to p the Springs 251 require equal work to make them contract or from twisting when the tension is increased by 25 expand equal distances at all times. The more turnin nut the spring is already compressed, the greater the Inverted on the upper part of base I0 and relative amount of work necessary to make it within it is a pulley 24 of peculiar shape. It is still shorter. The more it is already stretched, so mounted as to be freely rotatable on an axle 30.: the greater the relative amount of work to make boss .25 which is attached rigidly to the inner 3 it stretch still further. If such a spring is used side of base II]. The upper end of the pulley is in a balancing arrangement to act upon a congrooved with sheaves, but'is generally cylindrical, stant weight, there will be more or less cable to but the lower end is grooved with sheaves of a take up, depending upon the leverage exerted by rapidly decreasing spiral form. The distance of 5; the weight. The means provided for taking up this spiral from its axis 25 is proportional to the 5 and paying out cable while changing the leverage increase in work performed as the springs I9 are thereupon are an essential part of my invention. stressed from minimum tension, at which they In the drawing, Fig. l is a vertical section of are when carriage I2 is at its uppermost posian X-ray standard showing the spring and take tion on the column, to a position of maximum up arrangement. tension which they occupy when carriage I2 is 40 Fig. 2 is a plan view of the top of the column as far down the column'as to be in contact with showing the pulley arrangement. shoulder 26 of base Ill. It is believed that a Fig. 3 is a cross section of the column taken sp r l f s h approximately Such q ckness along the line 3-3 of Fig. 1. is knownin mechanics as the fusee spiral al- 4 is a plan view of the spiral pulley as tho absolutely definite information on this point 45 seen from below. is not at hand. In the drawing, [0 is the base of the apparatus Another way o expressing this at on s t while II is the column. I2 is the X-ray head say that t product of e sp n tensi n times and carriage (shown only in part) to be balanced. the axial distance of the acting point on the spi- It encircles the column. A cable l3 extends from r l gr v i designed to be a on nt and efiec- 50 Y carriage l2 over a pulley l4 mounted obliquely tively equal to the product of the load being as shown in Fig. 2 on the top of the column, balanced times the radial distance of the effective which is a cap 15. radius on the cylindrical part of 24.

Within the column ll, there is a spring as- A third way of expressing this would be to say sembly l6, which is made up of an upper end that as the spring tension increases the pull of 5 the springs is applied closer to center and becomes less effective as rapidly as the pull increases so as to have a constant efiect. This constant eifect permits the load to be balanced at rest at any point on the column. When the pull of the springs I9 is greatest, its efiective lever arm on the pulley is least, therefore, no greater pull is exerted than when the lever arm is greater but the pulling force less.

The upper part of pulley 24 is cylindrical so that cable !3 may have a constant point of application. This cable comes down the column after leaving pulley l4, passes unattached thru the spring assembly and then turns toward pulley 24 after leaving a pulley 2'! at the base of the column. It is wrapped around the cylindrical portion of pulley 24 sufiiciently to allow full traverse of the carriage l2 on the column. Cable I3 is then anchored at its pulley end to a point on the cylindrical part of pulley 24, as shown in Fig. 4.

The second cable, l3a runs from the eyebolt 29 around the pulley 28 at the base of the column, thence to and about the spiral portion of pulley 24. At the top point of the spiral it is anchored as Fig. 4 shows. The arrangement is such that cable l3a reaches the apex of the spiral and spring assembly 16 is stretched to its greatest tension when carriage I2 is at its lowermost point.

To operate my counterbalancing system it is merely necessary to lift or depress carriage l2 slightly and to cease applying force when the carriage has attained the desired position. Downward motion of the carriage pulls end plate I8 down by exerting a pull on cable l3 wrapped on pulley 24, causing the pulley to rotate and Wrap up the cable with a continuously decreasing lever arm. The action may be likened to that of a bicycle going up hill, the drive sprocket continually decreasing in size as the hill grows steeperso that the effort required to turn the pedals stays constant. Lifting the carriage merely reverses the process.

I claim as my invention- 1. In an apparatus comprising a column and a carriage to be counterbalanced on said column and a base supporting said column and carriage, a plurality of helical springs vertically arranged inside the column, a pair of end plates to which the ends of said springs are attached, the lower part of the assembly being movable, a combination pulley comprising a spirally grooved portion and a coaxial cylindrical portion, said pulley being rotatably mounted on the base, a cable connecting the lower end of the spring assembly with the spiral groove of the said pulley and a second cable connecting the carriage to the cylindrical part of said pulley, the spiral grooves on the face of the pulley being adapted to guide the second cable so as to keep the counterbalancing force of the spring assembly exerted upon the carriage through said first cable, a constant.

2. In an apparatus comprisng a column and a carriage to be counterbalanced on said column, a hollow base supporting said column and carriage, a plurality of helical springs vertically arranged within said column, a pair of end plates to which said springs are attached, the lower part of the assembly being vertically movable within the column, screw means for vertically adjusting the height of the upper one of said plates, a combination pulley comprising a spirally grooved portion and a coaxial cylindrical portion, said pulley being rotatably mounted on the base, a cable connecting the lower end of the spring assembly with the spiral groove of the said pulley and a second cable connecting the carriage to the cylindrical part of said pulley, the spiral grooves on the face of the pulley being adapted to guide the second cable so as to keep the counterbalancing force of the spring assembly exerted upon the carriage through said first cable, a constant.

3. An apparatus according to claim 2 in which the construction of the spiral pulley is such that as the tension of the springs increase, the effective lever arm of the cable on the pulley, by which the pull of the springs is exerted, becomes less in the same proportion.

4. In an X-ray standard or the like, a base, a column arising from said base, a carriage movable on said column, a plurality of helical springs within saidcolumn, end plates to which said springs are anchored, the lower part of the assembly being vertically movable within the column, means for holding rigid the upper one of said end plates, a pulley at the top of said column, pair of pulleys at the bottom of said column, a spiral pulley in said base, a cylindrical portion on said pulley, a cable extending from the said carriage over the first pulley unattachedly down said column, around one of said lower pulleys thence to and about the cylindrical.

part of said spiral pulley, where it is fastened, a second cable attached to and extending about said spiral pulley back to the other of the pulleys at the base of said column and thence to the lower end plate where it is tightly fastened.

5. An apparatus according to claim 4 in which the spiral pulley has grooves which run in a fusee spiral. v

6. In an X-ray apparatus or the like, a hollow base, a column arising therefrom, a carriage movable on said column, a plurality of helical springs vertically arranged within said column, a pair of end plates to which the ends of said springs are attached, the lower part of the assembly being vertically movable within the column, a cap on said column, a screw running thru.

said cap and the upper one of said end plates, a pulley mounted on said cap, a pair of pulleys at the base of said column, an inverted spiral pulley rotatably mounted Within the base, said pulley having a cylindrical section, and a cable extending from said carriage over said first pulley down the column, around one of said pulleys at the base of said column, then to and about the cylindrical section of said spiral pulley, a second cable extending about a spiral path on said pulley thence around the second of the pulleys at the base of said column'and finally being attache to the lower one of said end plates.

'7. An apparatus according to claim 6 in which. the spiral path of said spiral pulley is at such distances from the axis of rotation of said pulley that the product of the spring tension times the axial distance of the acting point on the spiral is a constant eilectively equal to the product of the load being balanced times the radial distance of the effective radius on the cylindrical part of said pulley.

8. In a counterweight balancing device, a vertical column, a carriage movable along said column, a pulley having combined cylindrical and spirally grooved co-axial portions, acable joining said pulley and carriageso as to effect a rotary movement of the said pulley as a 'conse-.

quence of the movement of the carriage caused by a pull on the cable which is joined to the cylindrical portion of said pulley, a helical spring assembly within said column, said assembly comprising an upper rigidly held plate, a lower vertically movable plate and a plurality of helical springs each attached by one of its ends to one of said plates, a second cable joining the lower one of said plates with the spiral portion of said pulley, the proportions of the pulley cable and spring being such in relation to each other that when the spring assembly is stretched to its maximum by reason of a position of said carriage, the lever arm of the second cable on the pulley, tending to produce rotation thereof, is at 5 its maximum.

WALTER H. HAUPT.

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