US 2998730 A
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Description (OCR text may contain errors)
3 J 0 2 P? 1 ms SEARCH m P 5, 1961 NsM. RASKHODOFF ETAL 2,998,730
ADJUSTABLE SLIT Filed Aug. 50, 1960 '3 m.
32 3e 37 33 3s 43 5| I8 /////%W//////// 7 23 |(O 29 SI/ 24 I3/ 20 I2 2| 15 22 INVENTORQ NICHOLAS M. RASKHODOFF ARTHUR G. LOWELL BY 1%.! -M g/sd ATTORNEY United States Fatent O 2,998,730 ADJUSTABLE SLIT Nicholas M. Raskhodofi, Cheverly, Md., and Arthur G. Lowell, Washington, D.'C.; said Lowell assignor to the United States of America as represented by the Secretary of the Navy Filed Aug. 30, 1960, Ser. No. 53,018 3 (Claims. (Cl. 74-89) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention is directed to an optical slit device and more particularly to the drive mechanism for an adjustable optical slit device.
Heretofore optical slits of small magnitude have been fixed such that they are not adjustable relative to each other. These slits are made by piercing or punching a piece of material to make the slit. Other slits have been made which are adjustable; however, these slits are large in physical size and the adjustments cannot be made with accuracy in the micron adjustment region. In the stationary slit type, obviously, the slit is not adjustable and with the prior art adjustable slits, any desired time adjustment cannot be made.
The present invention overcomes the disadvantages of the prior devices by providing a small device capable of making an adjustable slit having a width of about 0.004 inch, adjustable from zero to 0.0005 inch with one revolution of a worm drive means in an adjustable means and maintaining the slit jaws in parallel alignment. The fine adjustment and parallelism are maintained by use of a stationary jaw and a movable or slidable jaw. The movable jaw is driven relative to the stationary jaw by two cams which rotate against the back of a sliding block or element to which one jaw is secured. The two cams are rotated by worm gears which drive the slide element relative to the stationary jaw in order to make slits of different width.
It is therefore an object of the present invention to provide a small sized, simple means of making slits which may be adjusted to obtain desired widths of varying degree.
Another object is to provide a simple, accurate device for maintaining parallelism between surfaces adapted to form a slit.
Other and more specific objects of the invention will become apparent upon a careful consideration ofthe following detailed description when taken together with the accompanying drawing in which:
FIG. 1 is a top-side plan view of the device shown in perspective,
FIG. 2 is a view shown in perspective with portions cut away to more clearly illustrate the operating parts; and
FIG. 3 is a cross sectional view taken along the axis through the length of the device.
The present invention is directed to a very compact, adjustable slit device capable of attaining an extremely minute motion, forward or backward, for the movable jaw of the slit assembly to provide a slit width adjustment of 0.0001 inch or less. This adjustment is accomplished by means of a worm-worm gear drive, with an extremely low rise cam secured to the worm gear. The drive comprises two identical drive means located beside each other in parallelism such that each of the cams on the worm gear contact the back face of a slide member to which one jaw is secured for movement therewith. The cams are held in constant contact with the slide member by means of a tension spring. Thus the tension spring insures that the slide member will contact the cams at all ice times when moving in either direction. In addition to having two driving cams, the slide is guided by a springloaded ball assembly which exerts a downward pressure onto the slide and rides in a centering groove in the top surface of the slide. For the purposes of explanation, the slide with one jaw secured thereto may be referred to as the slidable, movable or adjustable jaw.
Now referring to the drawing, there is shown by illustration a preferred slit assembly which includes a rectangular base 10 having one end 11 thicker than the remainder with the surface of the base from the thick portion to the end being smooth and flat. The thick end 11 is machined from the back side to include a space or hous ing in which a gear drive assembly is assembled. The drive assembly includes a pair of elongated driving worms 12 and a pair of cylindrical driven worm gears 13 each of which are secured in parallel relationship. Each of the worm gears are provided with aslowly rising cam 14 secured to the outer surface thereof and having a greater diameter than the worm gears. The driving worms are smaller at one end 15 than the diameter across the worm at the threaded portion and larger at the opposite end 16 such that the ends of each of the worms serves as a shaft with the smaller end 15 passing through a hole 17 in the base. The upper portion 16 of the driving worms.
have a knurled head 18 secured thereto which serves asthe control knob for rotating the worm. Each driving worm is provided with a groove 21 near the lower end. on the portion extending beyond the base within which a bowed or spring type retaining ring 22 is inserted for positioning the drive worm in the base and for eliminating end play. The driven worm-gears are supported by a shaft 19 such that the driven gears are parallel to each other and in proper position for their threads to engage the driven worm. The shaft 19 is secured in place by a lock screw 20 which screws through the housing to con tact the shaft.
The slit forming jaws are formed on similar steel blocks 23 and 24 which are not as wide as the base member 10. One of the ends of each of the blocks 23 and 24 is formed at an angle with the end sloping from the upper side toward the bottom. The end of each of the blocks has a smooth edged member 25 such as a razor blade secured thereto by a plate 26 and bolts 27 which screw into the upper surface of the plates 23 and 24. One of the blocks is secured to the base by bolts 28 to provide a stationary slit forming surface or jaw. The other block is secured to the base slidable thereon and adjustable relative to the stationary block to form an adjustable slit forming member on the upper side of the block such that when assembled the angle at the end of each block diverges toward the base member. The base member is cut away to form an opening 29 therethrough for the purposes of admitting light to the slit formed by the two jaws. The stationary block is secured to the end of the base removed from the worm-gear drive assembly with the slit torming member facing toward the gear drive assembly.
The slidable block or adjustable slit jaw 24 is provided with an elongated slot or groove 31 along the linear axis and the slidable block is secured on the base between the stationary jaw and the worm-gear arrange ment with the back end of the block in contact with the cams on the worm gears. The adjustable slit jaw is secured to the base by a bridge 32 which includes a retainer housing 33 at its center which extends perpendicular to the base. The retainer housing contains a captivated stainless steel ball 34 which is retained in the housing at the bottom and is backed by a nylon centering washer 35 which centers the bearing and a spring 36 which applies pressure on the steel ball. The spring is held in the retainer housing by a cap 37 secured in the 3 housing. The bridge is secured by bolts 38 such that the steel ball rides in the groove 31.
A tension spring 41 is secured to the slidable jaw along the axis thereof by a pin 42 and to the center of the raised portion of the base or housing which houses the gears by a screw 43. The tension spring serves to maintain the back face of slidable jaw in contact with the two cams secured to the worm gear. The stainless steel ball bearing against the top of the slidable jaw maintains proper pressure contact between the base and the slidable jaw thereby eliminating excessive friction during adjustment of the slidable jaw. Rotation of the knurled head on the worm rotates the Worm gear which in turn rotates the cams against the back face of the slidable jaw. The knurled head is provided with a small hole 5'1 within which a small pin 52 may be inserted to aid in turning the drive for minute adjustments. The spring will maintain the slidable jaw in contact with the cam such that the slidable jaw will move in either direction depending on the rotation of the cam.
The particular slit device illustrated is constructed on a stainless steel base 95 inch wide, 3% inches in length and has a height varying from ,4 inch to a minimum of inch at the slit. The slit is inch in length and adjustable for a width of 0.004 inch with a fine adjustment from zero to 0.0001 inch. The gear ratio between the worm and worm gear of 32:1 and a cam rise of 0.004 inch in 90 degrees moves the cam 11% degrees with one revolution of the driving worm. Thus the cam will move the adjustable jaw 0.0005 inch with one revolution of the driving worm. With only a very small rotational movement of the cam, the slit width can be adjusted for very small changes between zero and 0.0005 inch within the movement resulting during one revolution of the driving worm.
It is important that the elements forming the slit be very smooth along their slit surfaces therefore it is important that the two surfaces be ground and honed or made with perfectly smooth surfaces. Otherwise the slit face surfaces may have a wavey face which would not permit the fine narrow slit width over the entire length. Any roughness of the surface would have a deleterious effect on any spectrum or photo taken through the slit.
In operation, the relative parts are assembled onto the base and the slit width is adjusted for the correct opening by rotation of the drive worms. Since the device comprises two worm drives each of the drives must be rotated simultaneously to slide the slidable jaw relative to the stationary jaw in order to more accurately position the slidable jaw in parallelism with the stationary jaw. The steel ball retained in the bridge rides in the groove in the upper surface of the slidable jaw to allow for a pivotal and slidable movement of the slidable jaw. If the slidable jaw were secured for strictly a forward and backward motion, there is a possibility that the two jaws of the slit would not be parallel. Likewise, this is true, if there is only one drive means for moving the slidable jaw. The use of two drive means and the steel ball which permits a pivotal as well as a slidable movement provides a device in which the slidable jaw can be accurately aligned for parallelism with the stationary jaw. Since the cams on each of the drive means and the radio of the drive worm to the driven worm gear are the same for each of the drive means, the same rotational movement for each drive worm would result in a parallel movement of the slidable jaw provided the jaws are parallel at the beginning of the adjustment.
The small size of the adjustable slit device makes it useful with a vacuum spectrograph wherein the slit can be adjusted and then enclosed in the vacuum system in the light path without the use of any bulky slit holders. Obviously, the device could be used for other purposes and also the size of the device could be enlarged Without departing from the invention.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. An adjustable slit device which comprises an elongated base, a stationary jaw secured at one end on the upper surface of said base, an axially aligned linear slidable jaw slidably and pivotally mounted on the upper surface of said base relative to said stationary jaw, a groove in the upper surface of said slidable jaw, a bridge means secured to said base and across said slidable jaw for securing said slidable jaw on said base for pivotal and slidable motion relative to said stationary jaw, said means including a steel ball under pressure in a direction toward said base which rides in said groove in said slidable jaw, and a drive means secured to said base to impart slidable motion to said slidable jaw as said drive means is operated.
2. An adjustable slit device as claimed in claim 1, wherein said drive means includes parallel worm-worm gears and a cam secured to each of said worm gears rotatable therewith and positioned in contact with said slidable jaw to impart slidable motion thereto.
3. An adjustable slit device which comprises an elongated base, a stationary jaw secured at one end on the upper surface of said base, a slidable jaw slidably and pivotably mounted on the upper surface of said base relative to said stationary jaw, an axially extending groove in the upper surface of said slidable jaw, a bridge secured to said base across said slidable jaw, said bridge comprising a centrally located retainer housing perpendicular to said base, a spring pressed steel ball secured under pressure in said retainer housing, said steel ball adapted to ride in said groove in said slidable jaw to secure said slidable jaw for pivotal and slidable motion on said base relative to said stationary jaw, drive means for imparting slidable motion to said slidable jaw, said drive means including parallel drive worms and parallel driven worm gears adapted to be driven by said drive worms, a cam secured to the surface of each of said driven worm gears and adapted to contact said slidable jaw to impart a slidable mot-ion thereto, and a spring means secured to said slidable jaw and to the base at said drive means to maintain said slidable jaw in contact with said cam in either direction of motion.
References Cited in the file of this patent UNITED STATES PATENTS 811,164 Murray Jan. 30, 1906 1,211,733 McQueen Jan. 9, 1917 2,168,215 Keitel Aug. 1, 1939 2,255,933 Land Sept. 16, 1941 2,467,600 Shipley Apr. 19, 1949 2,548,755 Vossberg et a1. Apr. 10, 1951 2,755,707 Meltzer July 24, 1956 FOREIGN PATENTS 813,245 Great Britain May 13, 1959 821,393 Great Britain Oct. 7, 1959 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, 2, 998 73O September 5 1961 Nicholas M. Raskhodoff et e1.
It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 3, line 63, for "radio" read ratio Signed and sealed this 17th day of April 1962.,
( SEAL) Attest:
ESTON. G. JOHNSON DAVID L.., LADD Commissioner of Patents Attesting Officer