US3020679A - Machine tools - Google Patents

Description

Feb. 13, 1962 LEY MACHINE TOOLS 4 Sheets-Sheet 1 Filed Sept. 4, 1958 ii; 7 li.

INVENTOR JAMES L. HENSLEY ATTORNEYS 1962 J. HENSLEY 3020'679 MACHINE TOOLS Filed Sept. 4, 1958 4 Sheets-Sheet 2 INVENTOR J4MES L. HENSLEY ATTORNEYS Feb. 13, 1962 J. L. HENSLEY MACHINE TOOLS 4 Sheets-Sheet 4 Filed Sept. 4, 1958 m H I I I I I I I I I I I I I I I I I 0 H INVENTOR JAMES L. HE'NSLEY ATTORNEYS 3,020,679 MACHINE TOOLS James L. Hensley, Clinton, Team, assignor to Ty-Sa-Man Machine Company, Knoxville, Tenn., a corporation of Tennessee Filed Sept. 4, 1958, Ser. No. 759,076 8 Claims. (Cl. 51-34) This invention relates to improvements in machine tools, and more particularly to improved means for mounting and driving the end portions of the tool-carrying structures of machine tools such as grinders, saws, and the like.

Although the invention may be utilized advantageously in many difierent types of machines, it will be convenient to refer specifically to the application of the invention in a grinding machine of the type disclosed in Palmer Patent 2,807,123, granted September 24, 1957. The invention is particularly advantageous in such grinding machines, and, having gained an understanding of this embodiment, persons skilled in the art will perceive readily the manner in which the invention may be applied to other types of machines.

The grinding machine disclosed in said Palmer patent includes an elongated bed for supporting steel billets or other large objects to be ground. A rotating grinding wheel is disposed above the bed and is so mounted that it may be moved vertically, transversely with respect to the bed, or longitudinally of the bed. As a result, the wheel may be brought into contact with all or any desired portion of the upper surface of the object being ground. These several movements are independent, in the sense that a separate mechanism is employed for each of them. The rotating Wheel is mounted for vertical movements with respect to an overhead carriage; the carriage is mounted upon a transversely extending bridge or crosshead for movements back and forth across the bed; and the bridge is mounted upon longitudinally extending rails on opposite sides of the bed for movements longitudinally of the bed. The present invention is concerned primarily with the means for driving the bridge back and forth along these rails.

According to the disclosure of the Palmer patent, the bridge carries sets of flanged rollers or wheels which cooperate with the rails in much the same manner as the wheels of a railroad car cooperate with the tracks. The drive for the bridge was in the form of a rack and pinion mechanism. Pinions were fixed to the end portions of a power driven cross shaft extending through the bridge and entirely across the machine. Cooperating with these pinions were long stationary racks fixed in position with respect to the rails. Upon rotation of the cross shaft, the pinions would move along the racks to drive the bridge along the rails.

Another type of drive which has been employed heretofore is of the screw type. In this type of drive, rotatable nuts mounted upon each end of the bridge coact with long screw elements extending along each of the rails. As will be evident, such constructions are very similar in operation to the rack and pinion type disclosed in the Palmer patent.

One of the basic ideas underlying both of these types of drives is that positive control should be exercised over the movements of the end portions of the bridge. If the bridge is initially aligned at right angles to the rails, and it the end portions of the bridge always move together along the rails, the bridge will remain in alignment and binding will be prevented. Although this theory obviously is a sound one, the structures proposed heretofore have made it difficult and expensive to carry out in practice. The physical characteristics of long screws and long racks States Patent Free 3,020,679 Patented Feb. 13, 1962 are such that a number of difficulties are inherent in bridge drives employing such elements.

"Moreover, these prior structures have proved to be rather sensitive to the shock loads resulting from sudden reversals in the direction of longitudinal movement of the bridge along the rails. In a'rack and pinion drive, for example, the entire load often must be borne by a single pair of meshing teeth at each end of the bridge, and shearing of the teeth becomes a problem.

It is an object of this invention to provide improved bridge driving means which will be inexpensive and durable and which will be easy to install and to repair.

Another object of the invention is to provide a structure of this character which can be fabricated from parts which are readily available in the variety of sizes required for machines of different lengths, so as to obviate the difliculties encountered heretofore in obtaining long racks or long screws.

Another object of the invention is to provide bridge driving means of a construction such that it may be adjusted easily and quickly to compensate for wear between the relatively movable parts and to assure proper alignment oi'the bridge transversely of the machine.

Still another object of the invention is to improve the resistance of bridge driving structures to the shock loads which result from reversals in the direction of bridge movement.

The foregoing objects may be accomplished, according to one embodiment of the invention, by so constructing a machine of the type having a pair of elongated rails and a bridge movable along such rails that the bridge is driven back and forth along the rails by means of a sprocket and chain mechanism. The drive for the bridge includes a sprocket wheel mounted upon each end portion of a power driven cross shaft which extends from one end of the bridge to the other, and a pair of stationary chains in position to cooperate with the sprocket wheels. Each chain has its end portions fixed with respect to one of the rails by means which will permit adjustment of the longitudinal position of the chain. An intermediate portion of each chain is looped about one of the sprocket wheels and held in firm engagement therewith by idler wheels on the bridge. These idler wheels also may be adjusted to assure proper contact between the chains and the sprocket wheels at all times.

Such a drive may be applied easily to machines of vary ing sizes and types. Chains are widely available on a commercial basis, and the correct length required for a particular installation may be obtained by the simple expedient of adding or removing links. The same expedient may be employed when it becomes necessary to make adjustments to compensate for wear on the parts.

Another outstanding advantage of the system is the ease with which the bridge may be kept in proper alignment transversely of the rails of the machine; If at any time, either during installation or after a period of use, the bridge were to become skewed slightly with respect to the rails,'it could be straightened out very quickly by adjusting the end fittings on the chains so as to produce a slight longitudinal shifting movement of the chains relative to each other. No comparable result'has been attainable as a practical matter in machines having the types of drives used heretofore. i Q

The chain drive also results in a new force distribution pattern which is especially desirable in connection with the large loads caused by sudden reversals in the d rection of bridge movement." Each chain cooperates with a substantial portion of the periphery of the sprocket wheel associated therewith, so that the unit load transmitted to the individual linksiis substantially less than that ordinarily imposed upon the teeth of a rack under like conditions. Moreover, the chain as a Whole is loaded in tension to provide a long ength of material which may undergo elastic deformation if necessary to prevent the development of force concentrations of sufficient magnitude to endanger the structural integrity of the individual links.

A better understanding of the construction of this invention and its many advantages will be gained from a consideration of the following detailed description of the embodiment illustrated in the accompanying drawings in which:

FIG. 1 is a plan view, with certain parts broken away, of a grinding machine embodying the present invention;

FIG. 2 is an end view of the bridge of the grinding machine and shows a portion of one of the rails for supporting the bridge;

FIG. 3 is a transverse cross sectional view taken along the line 3-3 in FIG. 2;

FIG. 4 is a transverse cross sectional view of one end portion of the bridge as viewed along the line 4-4 in FIG. 2;

FIG. 5 is a detail vertical cross sectional view taken along the line 5-5 in FIG. 4;

FIG. 6 is a transverse cross sectional view of one end portion of the bridge and is taken along the line 66 in FIG. 2; and

FIG. 7 is a partial perspective view showing the means employed for anchoring the end portions of the chains of the drive mechanism.

Referring initially to FIG. 1, it will be observed that the illustrated machine is of the same general type as that disclosed in Palmer Patent No. 2,807,123. A carriage structure designated generally by the numeral 10 serves to support a grinding wheel in position for treating the surfaces of objects, such as steel billets, disposed therebeneath. The carriage 16 is mounted for reciprocating movements back and forth across a beam 12 which forms a part of a bridge structure designated generally by the numeral 14. The end portions 16 and 18 of the bridge 14 are mounted upon and driven back and forth along elongated rails 20. in a typical installation, the lengths of the rails may be fifteen feet or longer, so that the total area which can be effectively treated by a grinding wheel supported on the carriage it) is quite substantial.

The manner in which the end portions 16 and 18 of the bridge 14 are supported upon the rails 20 is clearly illustrated in FIGS. 2, 3, 4 and 6 of the drawings. The end portions 16 and 18 include rigid frame units 22 and 24 respectively, which may be of any suitable configurations. The track-engaging components carried by each of the frameworks 22 and 24 are identical, and a description of those associated with the framework 22 will be sufiicient to enable persons skilled in the art to understand the structure.

The inner and outer side walls of the framework 22 have mounted thereon bearings 26 for rotatably sup porting transversely extending shaft members 23 located adjacent each end of the framework 22. Each of the shafts 23, in turn, carries a wheel 30 for engaging the track portion of the rail 20 associated with the end portion 16 of the bridge 14. The rail 20 is made up of a wear plate 32 welded or otherwise rigidly secured to the upper surface of a track 34 in position to be contacted by the wheels 30, and an I-beam 36 for supporting the track member 34. Of course, it will be understood that the I-beam 36 is mounted upon some suitable frame so that it will be located at the proper elevation with respect to the bed of the machine.

The framework 22 also has mounted thereon a pair of rollers 38 and 40 for engaging Wear plates 41 rigidly secured to the sides of the track member 34 to hold the framework 22 securely in position upon the rail 26. In order that the distance between the rollers 38 and 40 may be adjusted so as to compensate for wear between the parts, each of these rollers is adjustably mounted upon the framework 22 by means best illustrated in FIGS. 4 and 5. The inner and outer side walls of the framework 22 have secured thereto sleeves 42 which receive vertical rods 44. Although the fit between each rod 44 and its sleeve 42 should be such as to permit rotation of the rod 44 relative to the sleeve 42, the rod 44 normally will be held stationary in a predetermined angular position by a set screw 46 mounted upon the sleeve 42 and engaging the surface of the rod 44. Vertical movement of each rod 44 in a downward direction is prevented by a collar 48 suitably secured to the upper end portion of the rod 44 in position to bear against the upper end of the sleeve $2. Below the sleeve 42, the rod 44 is provided with eccentric end portion 50 upon which bearings 52 for the rollers 38 and 40 may be mounted.

As will be evident, adjustment of the axes of the rollers 38 and 40 may be accomplished easily by merely loosening the set screws 4-6 and rotating the rods 44 so as to shift the eccentric portions 59 relative to each other. Therefore, the effort required to maintain the proper bearing relationship between the peripheries of the rollers 38 and 40 and the wear plates 41 on the side walls of the track 34 is minimized, and satisfactory guiding of the end portions of the bridge 14 along the rails 20 is assured.

A motor 54- for driving the bridge 14 back and forth along the rails 29 has been illustrated diagrammatically in FIG. l, but has been omitted from the other views in the interest of clarity. The motor 54 is mounted upon the upper end of a conventional gear box 56 carried by the framework 22 of the end portion 16 of the bridge 14, and its output shaft 58 carries a pulley 60 for driving a belt 62. As shown clearly in FIG. 2, the belt 62 passes around a pulley 64 on an input shaft 66 for supplying power to the gear box 56.

The gear box 56 operates in the usual manner and serves as a speed reducing mechanism. Its output shaft 68 has mounted thereon a sprocket wheel 7 0 for driving a roller chain 72 which passes around a sprocket wheel 74 (FIG. 3) fixed to a cross shaft 76. The cross shaft 76 extends entirely across the machine and is mounted for rotation about a horizontal axis by suitable bearings 78 fixed to the frameworks 22 and 24 at the end portions 16 and 18 of the bridge 14. In the illustrated construction, the transverse beam 12 of the bridge 14 is hollow, and the central portion of the cross shaft 76 is disposed within the beam 12. However, the relative locations of the beam 12 and the central portion of the cross shaft 76 may be varied if desired.

Each end portion of the cross shaft 76 has fixed thereto a drive sprocket 30 for moving the bridge 14 back and forth along the rails 20 upon rotation of the cross shaft 76. In order to accomplish this result, each sprocket 80 engages an intermediate portion of a long roller chain 82, the ends of which are held stationary with respect to the rails 20 by means which will be described in greater detail below.

Each of the chains 82 is guided around a substantial portion of its sprocket wheel 80 by means of a pair of chain idler wheels 84 having smooth peripherial surfaces 86 for contacting the chain 82. The absence of sprocket teeth on the chain idler wheels 84 permits adjustment of the wheels 84 with respect to the chains 32 without regard to the spacing of the transverse roller members in the chains 82.

Each pair of the chain idler wheels 84 is supported by a bracket member 88 secured by bolts 90 or other suitable means to an angle member 22 welded to the outer side wall of one of the framework units 22 and 24. Referring to the lower left portion of FIG. 3, it will be observed that each chain idler Wheel 84 is mounted upon bearings 94 held in place on an eccentric portion 96 of a stud member 98 carried by the bracket 88. A cover plate receives the outer end portions of the stud elements 98 for each pair of idler wheels 84 and is clamped in position by nuts 102 threadedly engaging the stud elements 98. In order to adjust the position of a chain idler wheel, it is necessary to turn the nut 102 on its mounting stud 98 slightly so as to free the cover plate 100 from clamping engagement with the eccentric portion 96 of the stud element 98. Then the stud element 98 may be rotated slightly about its axis to change the position of its eccentric portion 96. The parts then may be secured in their adjusted positions by tightening the nut 102.

As each chain 82 passes outwardly around the idler wheels 84, it comes into contact with a supporting member fixed to brackets 106 mounted upon the I-beam member 36 of the longitudinal rail 20. These guide members 104 preferably extend along substantially the full lengths of the rails 20 to support the chains 82 so as to prevent any tendency for the chains 82 to sag under their own weight. As a result, tightening of the chains 82 to obviate the existence of slack is materially simplified.

FIG. 7 illustrates the manner in which the extreme end portions of the chains 82 are connected to the rails 20. The end of each rail 20 has fixed thereto a laterally extending member 108 which extends into alignment with the axis of the adjacent chain 82. The endmost link 110 of the chain 82 is pivotally connected to an end of a bolt 112, which passes through an opening in the bracket member 108 and is adjustably secured thereto by nuts 114 engaging opposite faces of the member 108. When it is desired to adjust the chain 82, the nuts 114 are manipulated so as to move the endmost link 110 of the chain 82 toward or away from the end member 108, as desired.

During initial assembly of the apparatus, the chains 82 are brought into operative position with respect to their drive sprockets 80 before the ends of the chains 82 are fixed to therails 20. In this connection, it will be observed that When a chain 82 is brought into contact with a sprocket wheel 80, the chain 82 will be fixed relative to the bridge 14 so long as the cross shaft 76 is held against rotation. Therefore, bodily movements of the chains 82 along the rails 20 will result in movements of the end portions of the bridge 14. These bodily movements of the chains 82 may be controlled closely by the bolts 112 which serve to connect the ends of the chains 82 to the rails 20. If the bridge 14 should be skewed slightly with respect to the rails 20, it may be brought into proper alignment by adjustment of one chain 82 relative to the other chain 82 so as to swing the ends of the bridge 14 into the required positions.

After a machine has been in operation for some time, it frequently will be found that further adjustments in the alignment of the bridge are desirable. These also may be accommodated in the manner described above. It is such a simple matter to adjust the alignment of the bridge 14 by manipulating the appropriate bolts 112 that the operators of the machines will have no hesitancy about undertaking such adjustments whenever necessary. Moreover, it will be observed that the time required for an adjustment of this character is exceedingly short so that production operations need not be suspended for prolonged periods of time.

Maintenance is further simplified by the facility with which compensations for wear between the teeth of the sprocket wheels 80 and the links of the chains 82 may be effected. The adjustable idler wheels 84 and the bolts 112 may be moved sufficiently to take care of much of the wear. Then, when the centrally located links of the chains 82 wear out, it is not difficult to replace these links so as to restore the chains 82 to their original condition.

Although a single embodiment of the invention has been illustrated and described in detail, various changes and modifications will be apparent to persons skilled in the art. It is intended, therefore, that the foregoing description be considered as exemplary only, and that the scope of the invention be ascertained from the following claims.

I claim:

1. In apparatus of the type having frame means including a pair of spaced apart parallel rails and a structure extending across the space between said rails and being mounted on said rails for movement along said rails, the improvement which comprises a first drive assembly disposed adjacent to one of said rails; said drive assembly including a sprocket wheel mounted on said structure for rotation about an axis extending transversely of said rails, a chain disposed in the plane of said sprocket wheel and being looped about a portion of the periphery of said sprocket wheel, means fixing the end portions of said chain to said frame means at points located upon a line in said plane, a pair of guide wheels having smooth peripheries for contacting said chain as it passes from said line to the periphery of said sprocket wheel, and adjustable means mounting said guide wheels on said structure for free rotation in the plane of said sprocket wheel about axes which may be shifted relative to the. axis of said sprocket wheel to adjust the position of said chain; a second drive assembly like said first drive assembly disposed adjacent to the other of said rails; and means for rotating the sprocket wheels of said assemblies simultaneously to move said sprocket wheels along said chains and thereby cause said structure to move along said rails.

2. In apparatus of the type having frame means including a pair of spaced apart parallel rails and a structure extending across the spaces between said rails and being mounted on 'said rails for movement along said rails, the improvement which comprises a first drive assembly disposed adjacent to one of said rails; said drive assembly including a sprocket wheel mounted on said structure for rotation about an axis extending transversely of said rails, a chain disposed in the plane of said sprocket wheel and being looped about a portion of the periphery of said sprocket wheel, adjustable means fixing the end portions of said chain to said frame means'at points located upon a line in said plane and permitting lengthwise adjustment of said end portions, a pair of guide wheels having smooth peripheries for contacting said chain as it passes from said line to the periphery of said sprocket wheel, and adjustable means mounting each of said guide Wheels on said structure, each of said last-mentioned adjustable means including a shaft carried by said structure for rotational adjustment thereon and having an eccentric portion and bearing means mounting a guide wheel on the eccentric portion for free rotation, whereby the axes of said guide wheels may be shifted relative to the axis of said sprocket wheel to adjust the position of said chain; a second drive assembly like said first drive assembly disposed adjacent to the other of said rails; and means for rotating the sprocket wheels of said assemblies simultaneously to move said sprocket wheels along said chains and thereby cause said structure to move along said rails.

3. In apparatus of the type having frame means including a pair of spaced apart, horizontally extending parallel rails, and a structure extending across the space between said rails and being mounted on said rails for movement along said rails, the improvement which comprises a first drive assembly disposed adjacent to one of said rails; said drive assembly including a sprocket wheel mounted on said structure for rotation about an axis extending transversely of said rails, a chain disposed in the plane of said sprocket wheel and being looped about a portion of the periphery of said sprocket wheel, means fixing the end portions of said chain to said frame means at points located upon a horizontal line in said plane below said sprocket wheel, a pair of chain guide wheels having smooth peripheries for guiding portions of said chain between said line and said sprocket wheel, and adjustable means mounting said guide wheels on said structure adjacent said line for free rotation in the plane of said sprocket wheel about axes which may be shifted relative to said line to adjust said chain, and an elongated support fixed to said frame means and having an upper face positioned immediately below-said line for supporting the portion of said chain extending along said line; a second drive assembly like said first drive assembly disposed adjacent to the other of said rails; and means for rotating the sprocket wheels of said assemblies simultaneously to move said wheels along said chains and thereby cause said structure to move along said rails.

4. In apparatus of the type having frame means including a pair of spaced apart parallel rails and a structure extending across the space between said rails and being mounted on said rails for movement along said rails, the improvement which comprises a first drive assembly disposed adjacent to one of said rails; said drive assembly including a sprocket wheel mounted on said structure for rotation about an axis extending transversely of said rails, a chain disposed in the plane of said sprocket wheel and being looped about a portion of the periphery of said sprocket wheel, means fixing the end portions of said chain to said frame means at points located upon a line in said plane, a pair of guide wheels having smooth peripheries for contacting said chain as it passes from said line to the periphery of said sprocket wheel, and means mounting said guide wheels on said structure for free rotation in the plane of said sprocket wheel; a second drive assembly like said first drive assembly disposed adjacent to the other of said rails; and means for rotating the sprocket wheels of said assemblies simultaneously to move said sprocket wheels along said chains and thereby cause said structure to move along said rails.

5. In apparatus of the type having frame means including a pair of spaced apart parallel rails and a structure extending across the spaces between said rails and being mounted on said rails for movement along said rails, the improvement which comprises a first drive assembly disposed adjacent to one of said rails; said drive assembly including a sprocket wheel mounted on said structure for rotation about an axis extending transversely of said rails, a chain disposed in the plane of said sprocket wheel and being looped about a portion of the periphery of said sprocket wheel, means fixing the end portions of said chain to said frame means at points located upon a line in said plane, a pair of guide wheels having smooth peripheries for contacting said chain as it passes from said line to the periphery of said sprocket wheel, and means mounting each of said guide wheels on said structure, each of said last-mentioned means including a shaft carried by said structure for rotational adjustment thereon and having an eccentric portion and bearing means mounting a guide wheel on the eccentric portion for free rotation, whereby the axes of said guide wheels may be shifted relative to the axis of said sprocket wheel to adjust the position of said chain, a second drive assembly like said first drive assembly disposed adjacent to the other of said rails; and means for rotating the sprocket wheels of said assemblies simultaneously to move said sprocket wheels along said chains and thereby cause said structure to move along said rails.

6. In a machine tool having a pair of spaced part parallel rails and a structure extending across the space between the rails and being mounted on the rails for movement therealong, the combination therewith, of drive means for moving the structure along the rails, said drive means comprising a sprocket wheel mounted on the structure for rotation about an axis extending transversely of said rails, a chain extending lengthwise of one of the rails and having opposite end portions fixed relative to said rail, said chain having a looped portion thereof intermediate said ends extending over the sprocket, and a pair of guide wheels having smooth peripheries in guiding relation to the chain on opposite sides of the looped portion.

7. In a machine tool having a pair of spaced apart parallel rails and a structure extending across the space between the rails and being mounted on the rails for movement therealong, the combination therewith, of drive means for moving the structure along the rails, said drive means comprising a sprocket wheel mounted on the structure for rotation about an axis extending transversely of said rails, a chain extending lengthwise of one of the rails and having opposite end portions fixed relative to said rail, said chain having a looped portion thereof intermediate said ends extending over the sprocket, and a pair of guide wheels in guiding relation with the chain on opposite sides of the looped portion and with the sides of the looped portion tangent to the guide wheels spaced apart a distance no greater than the diameter of the sprocket wheel.

8. In a machine tool having a pair of spaced apart parallel rails and a structure extending across the space between the rails and being mounted on the rails for movement therealong, the combination therewith, of drive means for moving the structure along the rails, said drive means comprising a sprocket wheel mounted on the structure for rotation about an axis extending transversely of said rails, a chain extending lengthwise of one of the rails and having opposite end portions fixed relative to said rail, said chain having a looped portion thereof intermediate said ends extending over the sprocket, and a pair of guide wheels in guiding relation with the chain on opposite sides of the looped portion, said guide wheels having their peripheries closer to the periphery of the sprocket wheel than the diameter of the wheels.

References Cited in the file of this patent UNITED STATES PATENTS 1,655,578 Stebbins Jan. 10, 1928 2,128,023 Specht et a1 Aug. 23, 1938 2,427,135 Guier Sept. 9, 1947 2,807,123 Palmer Sept. 24, 1957 FOREIGN PATENTS 9,512 Germany Nov. 26, 1879

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