US 3107168 A
Description (OCR text may contain errors)
Oct. 15, 1963 Filed March 19, 1959 ig. I
D. J. HOGAN EI'AL TRACK MAINTENANCE APPARATUS LILJHI-l 5 Sheets-Sheet 1 IN VEN TORS. "Q Donald J Hogan y Warren J. Smith Merriam, Larch 8 Smith A7 TOR/VEYS Oct. 15, 1963 D. J. HOGAN EIAL 3,107,168
TRACK MAINTENANCE APPARATUS Filed March 19, 1959 5 Sheets-Sheet 2 um Qk mm t wm t Oct. 15, 1963 I D. J. HOGAN ETAL 3,107,168
TRACK MAINTENANCE APPARATUS Filed March 19, 1959 5 Sheets-Sheet 5 Fig. 5
INV EN TORS Dana/d d Hogan BY Warren J. Smith Merriam, Larch 8 Sin/fl;
ATTORNEYS Oct. 15, 1963 D. J. HOGAN ETAL 3,107,168
TRACK MAINTENANCE APPARATUS Filed March 19, 1959 5 Sheets-Sheet 4 JNVENTORS. Dona/a J. Hogan y Warren J. Smif/r Merriam, Lara/7 8 Smith A TTOR/VEYS United States Patent 3,107,168 TRACK MAINTENANCE APPARATUS Donald J. Hogan, Chicago, and Warren J. Smith, Glen Ellyn, Ill.; said Smith assignor, by mesne assignments,
to Donald J. Hogan, doing business as Donald J. Hogan 8; Company, Chicago, Ill., a sole roprietorship Filed Mar. 19, 1959, Ser. No. 800,600 6 Claims. (Cl. 8814) This invention rel-ates to maintenance equipment for railroad track installations. It is more specifically directed to railroad track aligning apparatus.
Although considerable care is employed in preparing the bed for railroad track installations, the constant impact of high speed rolling equipment on curved and tangent track structure results in a misalignment of the original track profile. Track maintenance equipment is available for laterally adjusting or raising track structures in order to correct any misalignment and provide kink-free and level surface track. The instant invention is concerned with auxiliary apparatus for use in cooperation with track aligning equipment to provide a datum line for the aligning operation.
In the drawings,
FIGURE 1 is a schematic side view showing the relative position of the components of this invention.
FIGURE 2 is a schematic plan view of the illustration in FIGURE 1.
FIGURE 3 is a plan view of a preferred embodiment of the optical sighting component.
FIGURE 4 is a side elevation of a mounting arrangement for the optical sighting component.
FIGURE 5 is a side view of the optical sighting component mount shown in FIGURE 4.
FIGURE 6 is a schematic view of the optical system employed in the sighting component shown in FIGURE 3.
FIGURE 7 shows the prism stool utilized in mounting the coincidence prism in the optical sighting component shown in FIGURE 3.
FIGURE 8 is a side elevation view of one embodiment of the forward target station.
FIGURE 9 is a side view of the embodiment of the forward target station shown in FIGURE 8.
FIGURE 10 is a side elevation view of one embodiment of the rear target station.
FIGURE 11 is a side view of the rear target station shown in FIGURE 10.
FIGURE 12 is an elevation view of one embodiment of the intermediate observation station.
FIGURE 13 is a side view of the intermediate observation station shown in FIGURE 12.
FIGURES 14-17 are schematic illustrations of optical systems which can be utilized in assembling the optical sighting component.
The apparatus of this invention has broad application in track aligning operations; however, to facilitate a description of the invention the following discussion will be directed to its use in track surfacing. This maintenance procedure functions to provide a level tr-ack structure. From a previous inspection of a given stretch of misaligned track the amount that the track structure is to be lifted is predetermined. Generally the raise will be about 1-6 inches. Maintenance operations are then carried out using one of the tracks as the grade track. A preliminary raise is effected by a conventional jack tie tamper which raises the track tothe established reference line and tamps the ballast under the so-called jack tie at the raise to hold the track at the desired elevation. This operation is carried out with the jack tie located at rail joints, centers, and quarters, or other desired track positions depending upon the selected procedure. Immediately following this operation a gang tamper tamps the ballast under every tie to assure a uniform tamping of the ballast for the entire track structure.
The instant invention provides a-datum by employing an optical sighting device located at the jack tie tamper which is used to sight along a theoretical datum established by a pair of lineal targets located respectively in front of and behind the jack tie tamper unit. The sighting device is in contact with the track being raised and is so designed to sight along the datum and permit the operator of the jack tamper to determine when the desired raise has been made.
From the drawings, which show a complete specific embodiment of the instant invention, it is seen that the track aligning apparatus of this invention is preferably employed in conjunction with a self-propelled power unit 10 which is generally a so-called jack tie tamper such as the unit marketed under the mark Handyman by the Kalamazoo Mfg. Co. Power unit 10 is fitted with flanged wheels 11 which engage with railroad track structure 12. Rear target station 13 is coupled to power unit 10 by coupling means 14. Forward target station 15 is coupled to power unit 10 in a similar manner by coupling means 16 but is spaced at a greater distance as will hereinafter be explained. Because of the length of coupler required for attaching forward target station 14, wheeled supports can be used at spaced intervals along forward coupler 16 to support the coupler means or other coupling means employed to maintain the desired spacing.
Mounted on each target station is a target board 20. The target board comprises a back board 21 which is traversed by a lineal target 22 approximately wide seen in FIGURES 8 and 9. The area of back board 21 is preferably as large as the area of the field of the telescopic elements of hereinafter described optical sighting device at target distance. In the illustrated embodiment at target area about 5 feet square is used. Back board 21 is attached to the carriages preferably by means of telescoping standards which are vertically adjustable and are held in position by suitable stops. The target board on each target station is positioned astraddle the grade rail and extends equally on each side of the rail. Automatic levelling devices, such as pendulums, can be used in mounting the target boards on the target stations to insure that the lineal target always assumes a horizontal position in track surfacing use.
Forward target station 15 in the embodiment illustrated in FIGURE 8 has a wheel base of about one-half of a standard length of railroad track, i.e. 20 feet. This minimizes deviations in the horizontal positioning of the lineal target 22. Carriage 23 is a light weight I-shaped structural shape preferably made from aluminum and assembled from conveniently handled lengths. Yokes 24 are secured to the lower flange of the beam and serve as wheel mountings for holding the four double flanged wheels 25 upon which carriage 23 rides. A pair of outriggers 26 extend from carriage 23 to provide stability to the station. Socket 27 is mounted on the upper face of the beam and securely braced. Telescoping within socket 27 is adjustable upright 28 to which back board 21 is secured. A plurality of pin and hole fasteners 29 is employed for incrementally adjusting the height of lineal target 22. Adequate bracing is used to insure the rigidity and stability of the target station.
Rear target station 13 shown in FIGURES 10 and 11 employs a rectangular carriage 30 fabricated from C- channels. A pair of axles 31 are underslung on carriage 30 and held in position by suitable journals. Flanged wheels 32 are mounted on axles 31 to provide a mobile unit which can be readily towed. Intermediate transverse frame member 33 supports mounting 34 for the pivotally mounted back board 21. Telescoping stanchion is fastened at one end to mounting 34 and at the other end to a suitable mounting (not shown) on back board 21. Telescoping upright 36 is used to support back board 21 at the desired height. Suitable bracing 37 is also provided. With this arrangement the back board can be swung to either side of carriage 30 in the event that the grade rail is changed by providing duplicate mounting brackets 38 on each side member of the frame.
The intermediate observation station 39 illustrated in FIGURES 12 and 13 employs a rectangular carriage 40 assembled from C-channels having underslung wheels 41 suitably mounted on axles secured to the carriage frame. Outwardly depending from side member 42 of the carriage frame is platform 43 which is positioned vertically above the line track. A stanchion 44 is secured to platform 43 and extends upwardly to the observation station located at a convenient level on power unit 10. Mounted atop stanchion 44 is cradle 45 employed for holding the optical sighting device.
Cradle 45 as shown in FIGURES 4 and 5 comprises a frame 46 having side members 47 and 48 which are joined to lower base 49. Stanchion 4-4 extends through an opening 50 in lower base 49 and connects with a mounting socket 51 secured to the under side of upper base 52 from which cradle 45 is suspended. Upper base 52 fits within side members 47 and 48 and is connected to the cradle assembly solely by leaf hinge 5-; which comprises a strip of thin spring steel 55 attached to the ends of the upper and lower bases 52 and 49 by mounting bars 55 which are traversed by threaded fasteners which engage with the base ends. Transverse saddle elements 56 and 57 are fastened to the frame sides which are also provided with saddle cut-outs conforming to the portion of the sighting device resting therein. Hinged locking straps 58 and 59 and locking screws 60 and 61 cooperate with saddle elements to hold the sighting device in position.
Adjustable blocks 62 and 63, raised and lowered by thumbscrews 64 and 65 which are threaded through brackets 66 and 67 fastened to the frame sides, are employed to pivotally adjust the sighting device. Suitable pins 68 and 69 cooperating with blocks 62 and 63 and brackets 66 and 67 are used to guide the vertical movement of the blocks. The angular displacement of cradle 46 and the sighting device mounted thereon with reference to stationary upper base 52 is controlled by adjusting screw '70. The shank of screw 70 penetrates lower base 49 through a suitable opening and threadably engages with upper base 52. In this position the underside of lower base 49 rests on the shoulder portion of screw 70.
Optical sighting device which is mounted in cradle 46 on the intermediate observation station is a double objective optical system with the respective objectives contrarily facing and cooperating with an intermediate reflecting coincidence means and a suitable viewing objective to permit simultaneous viewing of a pair of lineal targets positioned each to the other at an angle of 180 in coincidence and relative to a reticle. The illustrated viewing device 75 has a lens system schematically shown in FIGURE 6 and assembled as illustrated in FIGURE 3.
Objective 76 is a telephoto lens having a doublet lens 77 positive in power and a single negative lens 78. The spaced components are mounted in tube 79 by conventional expedients. The other objective 80 consists of a pair of spaced positive doublet lens 81 and 82 mounted in tube 83. Objectives 76 and 80 employ lens mountings for adjusting focal length. External threads on tubes 79 and 83 engage with internally threaded openings 84 and 85 provided in prism housing 86 to obtain proper focus. Prism stool 87 which is adjustably mounted in prism housing 86 holds coincidence prism 88 which brings the images produced by objectives 76 and 39 together and in coincidence. Coincidence prism 83 consists of prism 89 providing total internal reflection and prism 90 which reflects the image from objective 80. To effect this a semi-reflecting film 91 is provided at the interface between prisms 89 and 90. As shown in FIG- URE 7, prisms 89 and 90 are held in place on prism stool 87 by hold-down plate 91 which is connected to stool 87 by means of threaded fasteners 92. Resilient cushions 92' are used to prevent cracking of the prisms by plate 91.
With objectives 76 and 8t) and coincidence prism 88 in adjustment the images of lineal targets 22 on the forward and rear target stations are reflected as a coincident image which is viewed through a conventional viewing objective 93. Mounting flange 94 secured to the wall of prism housing 86 holds field lens 95 on which is provided a lineal reticle which permits the relative viewing of the reflected coincident images of both lineal targets 22. Objective 93 is also supported by flange 94. The reticle side of lens 95 is covered by cover plate 96. The lens component is held in place in internally flanged ring 97 by locking ring 98. Viewing objective 93 employs a conventional lens system with an erecting lens system and an adjustable eye piece 98. To improve the appearance of the sighting device, tubular shrouds 99 and 100 are used to cover objectives 76 and 80. Shrouds 99 and 100 are enclosed by windows 101 and 102 and optionally fitted with weather shields 103 and 104. Preferably all optical components are coated with an antirefleetion coating. Eyepiece 98 is also provided with a mask (not shown) to block the vision of the unused eye of the observer.
It will be noted that each objective 76 and S0 cooperates with the viewing objective to form a telescope. The magnifying capacities of the telescope including objective 76 and the telescope including objective 8% are determined by the relative position of the intermediate observation station from the forward and rear target stations, the ratio of the magnifying powers being equal to the ratio of the target station distances. For example, with the intermediate observation station positioned 25 feet from the rear target station and 100 feet from the forward target station the ratio of the magnifying power of the rear objective to the magnifying power of the forward objective equals 1:4. In the illustrative embodiment viewing objective and the rear objective is 3X power telescope and viewing objective and the forward objective provides a 12X power telescope. Other magnifying powers can be used to provide the desired ratio. By using the magnifying power ratio system the images of the targets of equal length also have the same length.
In employing the subject invention as an aid in resurfacing track structures by raising the track, viewing device 75 is mounted on intermediate observation station 39 which is coupled to jack tie tamper on power unit 10. At the field location where a predetermined raise in the track structure is to be made, forward and rear target stations 13 and 15 are coupled to power unit 10 and the assembly moved onto level track. To minimize irregularities in track structure the observation station is preferably located closer to the rear target station. For example, in the illustrative embodiment the observation station is placed 25 feet from the rear target station and 100 feet from the forward target station. It is preferred that the spacing of the forward and rear target stations be located about 75200 feet apart and the intermediate observation station be located closer to the rear target station at about /a%; the total distance. Other locations and spacings, however, can be used as desired. Suitable coupling devices are employed to maintain the proper distances.
Lineal targets 22 on target stations 13 and 15 are initially placed at the same height above the level rail structure, the height being determined by the height of the optical plane of the viewing device 75. The targets are brought into horizontal adjustment and viewing de- 5. vice 75 adjusted until the target images are coincident and in alignment with the reticle. :In this condition the theoretical datum plane formed by the opposed targets is parallel and coincident with the optical plane of the viewing device. The forward lineal target is then raised an additional distance equal to the predetermined amount that the rail structure is to be raised. This will vary in raising the track structure to raise the gradual run-oil section of track but will be constant during the remainder of the track surfacing operation. The assembly is moved onto the track to be resurfaced. It may be necessary at this time to readjust the optical plane to maintain its proper alignment with the datum plane. The operator locates the jack tie tamper over the selected jack tie. In looking through the eyepiece of the sighting device it will be observed that the coincident target images and the lineal reticle are displaced as is shown in FIGURE 6A. The apparent distance between the image and the reticle line will be indicative of the amount the track level will be raised. The operator, by observing the targets through the eyepiece, manipulates the jack tie tamper controls to raise the track to the desired level. The track in being raised also raises the intermediate observation station and at the desired level the coincident images and the reticle will be aligned ino the viewing scope as shown in FIG- URE 6B. The machine then tamps the ballast around the jack tie to hold the raise. Raising continues with no further adjustments in the sighting apparatus.
The raise can be made by simultaneously elevating both tracks or by sequentially raising the grade track and then raising the other track. Cross level of the track can be observed in the sighting device by noting the position of the reflected target images. If the tracks are not cross-leveled the optical plane will be askew and the images will cross as seen in FIGURE 6C rather than coinciding. If crossing of the images occurs the level of the other track must be adjusted to bring the images into coincidence. In cross levelling it may also be desirable to use a spirit level, inclinometer, or the like.
Although in the foregoing description the use of the instant invention in track surfacing was discussed in re lation to the raising of tangent track, it is to be understood that this invention has application in raising curved track as well as the aligning of tangent and curved track. It is also apparent that various modifications can be made in the illustrative embodiments without departing from the scope of the instant invention. The sighting device can be constructed employing other objective systems and by using alternative reflecting coincidence means such as mirrors, semi-reflecting pellicles, and alternative prism-s for bringing the target images together and into coincidence. For example in FIGURES 14-17 several schematic optical arrangements are illustrated which permit the simultaneous viewing of a pair of opposed targets, positioned each to the other at an angle of 180 in coincidence and relative to a reticle, through an orthogonal viewing objective. In FIGURE 14 no objective is used in combination with viewing objective 110 which comprises spaced positive lens 111 and 112 with reticle 113 positioned intermediate thereto. Reflecting coincidence prism -114 employing the same prism system as used in the above described complete specific embodiment comprises a large 45 -9045 prism 115 having its hypotenuse face normal to the line of sight or optical axis directed toward the rear target 22B. The light from target 22B is reflected from a leg face of prism 115 along an axis parallel to the hypotenuse face. The light from the forward target 22A is directed along an axis normal to the leg face of small 45 9045 prism 116, refiectedfrom the interface formed at the abutment of the hypotenuse face of small prism 116 and the leg face of large prism 115 and brought into coincidence with the reflected light from the rear target 2213. The coincident images formed are viewed along the axis of viewing objective 110 relative to reticle 113. Sighting objective 117 is a Galilean type telescope having an afocal lens system comprising negative lens 118 and positive lens 119. In this arrangement the viewing objective is used without an accompanying lens system to view the rear target image and its magnifying power is unchanged. The afocal sighting lens system 117 has a magnifying power which cooperates with the viewing lens system to provide a telescope of appropriate magnifying power. A typical arrangement of this type for use in a spacing of the observation station 25 feet from the rear target and feet from the forward target would employ a 3 X power viewing system in combination with a 4X power sighting lens system 117. For this same spacing arrangement using the dual afocal sighting lens systems shown in FIG- URE 15 the sighting lens system "120 which is directed toward the rearward target 2213 could have a /2 X magnifying power and the sighting lens system directed to ward the forward target could have a 2X magnifying power. These lens systems in combination with a 6X magnifying power viewing lens system 122 would provide properly ratioed telescopic systems for simultaneously viewing the opposed target together and in coincidence. FIGURES 16 and 17 illustrate arrangements in which the optics of the sighting lens systems are based on the relationships of the focal length of each sighting system to the distances of the observation station from each target station. In FIGURE 16 an alternative reflecting coincidence prism 125 is used. The sighting lens systems 126 and 127 are both positioned on the same side of prism 125 and the image of the rear target 22B reflected into the coincidence prism 125 by means of a system of mirrors 128 and 128 The reflected coincident images are viewed through a conventional viewing system 129 with an erecting eyepiece in relation to reticle 130. For use in the above exemplary target spacing, tar-get sighting lens 126 would have a focal length of s and target sighting lens 127 would have a focal length of Ks where The magnifying power of the viewing lens would be selected to permit the targets to be viewed with facility. FIGURE 17 illustrates another arrangement utilizing the sighting lens systems 131 and 132 positioned on the same side of coincidence prism 133. In this instance, each of the target images 22A and 22B are reflected through the viewing lens 131 having a focal length of Kr and 132 having a focal length of s by means of mirrors 134 and 135 respectively. The reflected images are brought together and coincided by prism 133 and the reflected coincident images viewed in relation to reticle 136 by viewing lens system 137. In both the embodiments shown in FIGURES 16 and 17 the optic systems formed by the viewing lens system and the forward target sighting lens system and the rear target sighting lens system, respectively, have a ratio of magnifying powers which is equal to the ratio of the forward and rear target distances, respectively, from the observation station. Other optical systems can also be used wherein the magnifying powers are not ratioed. These systems are not preferred because they employ less sensitive expedients for determining the various alignments involved in using the instant invention due to each of target image coincidence where the optical and datum planes are parallel but not aligned. Although the axes of the illustrative optical system are coplanar and lie in the optical plane of the sighting device, prism and lens arrangments can be used to provide non-planar arrangements as well as viewing systems having axes which are not perpendicular to the axes of the sighting systems. In all instances, however, the optical plane of the instrument will be the plane in which the conjugate images formed of the reticle in the viewing system by the first and second sighting systems positioned respectively between said reticle and the opposed targets lie. Generally this plane is substantially parallel to the datum plane formed by said opposed targets. Various arrangements can also be utilized in constructing the target stations and observation station for use with and for coupling to different types of jack tie tampers. In this regard it may be desirable to provide self-propelled target stations or use mechanical arrangements controllable at the power unit for raising, lowering, or otherwise adjusting the target levels or the like. Vertical incremental mensuration indicia to provide a means for effecting raises of different heights and for use in making run-offs after the last ful raise is made can also be provided on the target back board. Illuminated targets can also be used for night operations. Target back boards can be made in various forms to minimize wind loads. Reticle design can include illuminated reticles for night operations.
Accordingly, it is intended that the instant invention be limited only as set forth in the appended claims.
What is claimed is:
l. A system for facilitating the realignment of a railroad track installation which comprises a forward target station and a rear target station adapted to be positioned on said track installation in spaced relation, each of said target stations having a lineal target normal to said track installation, the lineal targets cooperating to provide a datum plane substantially parallel to an aligned grade rail; an observation station intermediate said target stations and closer to said rear target station and means for coupling said forward target station, observation station and rear target station a fixed distance apart to each other, said observation station including a telescopic sighting device comprising a first optical system sighting along an axis on said forward target, a second optical system sighting along an axis on said rear target, the sighting axes of said optical systems being substantially 180 apart in substantial alignment and lying in an optical plane, a reflecting coincidence means cooperating with said optical systems to bring the images of said lineal targets together and coincident to provide a target image, and an optical viewing system having a lineal reticle positioned therein in alignment with said optical plane, said optical plane being the plane in which the conjugate images formed of said reticle by the first and second optical systems positioned respectively between said reticle and said targets lie, a means adapted to directly interconnect said sighting device and said track installation, and a cradle installed on said means and holding said sighting device, said cradle having adjustable means cooperating therewith for bringing said optical plane into parallel alignment with said datum plane, said optical viewing system cooperating respectively with said first and second sighting systems to provide a first telescope and a second telescope, the ratio of the magnifying power of said first telescope to the magnifying power of said second telescope being substantially equal to the ratio of the distances of said sighting device from the forward and rear target stations respectively.
2. A system in accordance with claim 1 in which said coincidence means comprises a large and a small prism component having 459045 isosceles triangular ends, the axis of said first objective being normal to the hypotenuse face of said large prism, said large prism reflecting from a leg face and providing total internal reflection parallel to the hypotenuse face thereof to the interface formed between a leg face of said large prism and the hypotenuse face of said small prism, said interface having a multiple layer coating such that the reflection of light from said interface and the transmission of light through said interface is substantially equal, the 'axis of said second objective being normal to a leg face of said smaller prism, light from said second objective being reflected from said interface and combining with light reflected from said first objective wherein the axis of the viewing system is orthogonal to the sighting axes.
3. A system in accordance with claim 1 in which said means adapted to directly interconnect said sighting device and said track installation includes a frame having mounted thereon track engaging wheels, an upright stanchion mounted on said frame superposed in relationship to said aligned grade rail, said cradle being installed on said stanchion holding said sighting device.
4. A system in accordance with claim 1 in which said observation station is provided with an automotive power unit.
5. A system for facilitating the realignment of a railroad track installation which comprises a forward target station and a rear target station adapted to be positioned on said track installation in spaced relation, each of said target stations having a lineal target normal to said track installation, the lineal targets cooperating to provide a datum plane substantially parallel to an aligned grade rail; an observation station intermediate said target stations and closer to said rear target station and means for coupling said forward target station, observation station and rear target station a fixed distance apart to each other, said observation station including a telescopic sighting device comprising a first objective directed toward said forward target station, an opposed, contrarily directed second objective directed toward said rear target station, the sighting axes of said objectives being substantially apart in substantial alignment and lying in an optical plane, a reflecting coincidence means positioned intermediate said objectives and aligned with the optical axes thereof to bring the images of said lineal targets together and coincident to provide a target image, said coincidence means comprising a large and a small prism component, having 459045 isosceles triangular ends, the axis of said first objective being normal to the hypotenuse face of said large prism, said large prism reflecting from a leg face and providing total internal reflection parallel to the hypotenuse face thereof to the interface formed between a leg face of said large prism and the hypotenuse face of said small prism, said interface having a multiple layer coating such that the reflection of light from said interface and the transmission of light through said interface is substantially equal, the axis of said second objective being normal to a leg face of said smaller prism, light from said second objective being reflected from said interface and combining with light reflected from said first objective, and an orthogonal viewing objective having a lineal reticle positioned therein in alignment with said optical plane, said optical plane being the plane in which the conjugate images formed of said reticle by the first and second objectives positioned respectively between said reticle and said target lie, and an upright stanchion adapted to directly interconnect said sighting device and said track installation, a cradle installed on said stanchion and holding said sighting device, said cradle having adjustable means cooperating therewith for bringing said optical plane into parallel alignment with said datum plane, and an automotive power unit for said observation station, said target stations being coupled to said power unit, said viewing objective cooperating respectively with said first and second objectives to provide a first telescope and a second telescope, the ratio of the magnifying power of said first teelscope to the magnifying power of the said second telescope being equal to the ratio of the distances of said sighting device from the forward and rear target stations respectively.
6. For use in a track maintenance system for facilitating the realignment of a railroad track installation comprising a forward target station, a rear target station adapted to be positioned on a track installation in spaced relation, each of said target stations having a lineal target normal to said track installation and an observation station intermediate said target stations and closer to said rear target station, said forward target station, observation station and rear target station being adapted to be coupled together a fixed distance apart each to the other, an optical viewing system adapted to be mounted on said observation station, comprising a first objective adapted to sight along an axis on one target comprising a positive lens and a negative lens spaced apart, a contrarily directed second objective adapted to sight along an axis on the other target comprising a pair of spaced positive lens, a reflecting coincidence means comprising a large and a small prism component, having 45 9045 isosceles triangular ends, the axis of said first objective being normal to the hypotenuse face of said large prism, said large prism reflecting from a leg face and providing total internal reflection parallel to the hypotenuse face thereof to the interface formed between a leg face of said large prism and the hypotenuse face of said small prism, said interface having a multiple layer coating such that the reflection of light from said interface and the transmission of light through said interface is substantially equal, the axis of said second objective being normal to a leg face of said smaller prism, light from said second objective being reflected from said interface and combining with light reflected from said first objective, said coincidence means positioned intermediate said objectives and aligned with the optical axes thereof to bring the images of the targets viewed by each of said objectives together and in coincidence, and an orthogonal viewing scope having an optical axis normal to the axes of said objectives, the axes of said objectives and said viewing scope being coplanar and being in an optical plane, said viewing scope being provided with a lineal reticle, said optical plane being the plane in which the conjugate images formed of said reticle by the first and second objectives positioned respectively between said reticle and said target lie, said viewing objective cooperating respectively with said first and second sighting objectives to provide a first and a second telescope, the ratio of the magnifying powers of the first and second telescope-s being substantially equal to the ratio of the distances from said observer to the opposed lineal targets.
References Cited in the file of this patent UNITED STATES PATENTS 897,045 Young Aug. 25, 1908 2,763,932 McMillan Sept. 25, 1956 2,945,416 Fuketa et al July 19, 1960 2,974,607 Talboys Mar. 14, 1961 FOREIGN PATENTS 416,182 France Dec. 2, 1909 612,775 Germany May 9, 1935 580,043 Great Britain Aug. 26, 1946 269,544 Italy Nov. 22, 1929 OTHER REFERENCES Jenkins and White, Fundamentals of Optics, published in 1950 by McGraw-Hill, page 168.