US2068199A - Precision machine tool - Google Patents

Description

Jan. 19, 1937. SELETSKY 2,068,199

PRECISION MACHINE TOOL Filed March 15, 1955 '5 Sheets-Sheet 1 Jan. 19, 1937. v KY -2,068,199

PRECISION MACHINE TOOL Filed March 15, 1935 5 Sheets-Sheet 5 wafiiiiw Patented Jan. 19,1937

UNITED STATES PATENT OFFICE PRECISION MACHINE TOOL land Application March 13, 1935, Serial No. 10,939

7 Claims.

This invention relates to precision machinetools such as locating boring-, milling-, or grinding machines of the type having. a'table which is movable relative to a tool carrier which may be stationary or movable.

The primary object of this invention is the provision of a machine-tool of the above type including the combination of a fluid pressure motor for moving the table with an optically read precision measuring scale for measuring. the movements of the table, whereby the time required for precisely adjusting the table to a fixed point on the scale may be greatly reduced with respect to that required for-exactly adjusting the table by means of the methodsheretofore used in machine-tools of this type.

A further object of the invention is the provision of a machine-tool of the type referred to in which the movable. table carries the measuring scale which is connected to the table by means of a resilient coupling member and constitutes a slide moving along a guideway provided on a fixed part of the machine to form an enclosed space, the graduation of the measuring scale being provided on an internal wall of this space so as to be protected from any wear by rough treatment, or from becoming soiled by lubricating oil or by dust.

With the above and other objects in view, the invention consists in the features of construc tion and operation set forth in the following specification and illustrated in the accompanying drawings in which,

Figure 1 is a perspective view of a boring machine in which the invention is embodied.

Figure 2 is a longitudinal section through the work table and the fluid pressure motor for operating the same.

Figure 3 is a transverse section through the worktable and the bed of the machine, taken along the line 3-3 of Fig. 2.

Figure 4 is a front view, partly drawn in section, of the work table and the bed of the machine.

Figure 5 is a longitudinal section taken on the line 5-5 ofFig. 2.

Figure 6 is a transverse section through the measuring scale.

Figures 7 and 8 show each a modification of a detail concerning the measuring scale.

Fig. 9 is a fragmentary view of a conventional device for illuminating the measuring scale.

The illustrated boring machine comprises a bed I provided with guideways 2 and 3 for the horizontally movable work table 4. A cross rail Germany March 24, 1934 5 is mounted for vertical movement on the two uprights 6 and 1 and supports a tool slide 8. An electric motor 9 is provided to impart movement to the tool spindle l0 and to the cross rail elevating screws ll.

The work table 4 is operated by means of a fluid pressure motor particularly illustrated in Figure 2. A similar mechanism has been described in detail and claimed in the earlier U. S. Patent No, 1,956,110. A motor cylinder I2 is supported on the bed I beneath the table. 4. A piston I3 on a rod 14 can reciprocate within the cylinder. The' pressure fluid destined to actuate the piston is delivered by a pump (not shown) through a pipe IE to a distributor l6 provided with a rotatable valve l! which can direct the fluid either into the pipe it or into the pipe l9, to deliver it to one or the other side of the piston l3, while the fluid which is discharged from the cylinder l2 through the pipes I8 or I9, according to the direction of movement of the piston, returns to the pump by the pipe 20. A third pipe 2| connects the distributor to a locking cylinder 22 to deliver pressure fluid into a space formed between two pistons 23 and 24 carrying each on its outer face conical locking jaws 25 and 26 surrounding the piston rod l4. These jaws coact with the walls of conical recesses 21 and 28 in the cylinder 22, so that when pressure fluid arrives between the pistons 23 and 24 and tends to drive them away from each other, the jaws are strongly pressed against the piston rod l4 and flrmly lock the rod against any movement. The distributor valve H is connected to an operating handle 29 which is visible also in Fig. 1.

The end of the piston rod is provided with a screw threaded portion 30. A rotatable nut 3| is engaged on the screw thread and forms the hub of a gear wheel 32 meshing with a worm gear 33. The wheel 32 is held against longitudinal movement relative to the table 4 by a casing 34 which is secured to an extension 35 of the table. The worm 33 is provided on a shaft 36 carrying a hellcoidal wheel 31 meshing with a helicoidal wheel 38 which is mounted on a shaft 39 for rotation with the shaft and capable of axially sliding along this shaft which is supported with its rear end by the bed of the machine and with its front end by a casing 40 carried by the bed. A bevel wheel 4| on the front end of this shaft meshes with a bevel wheel 42 on a shaft 43, and a second pair of bevel wheels 44 and 45 connects the shaft 43 to a shaft 46 which can be rotated by means of a hand wheel 41 disposed on the same side of the machine as handle so that the operator of the machine can' easily manipulate either the handle 29 or the wheel 41. p

The lower face of the work table 4 carries a longitudinally extending bracket 49 provided with a recess 49 in which is freely engaged a measuring scale 50 having in cross section the general shape of a U or a channel standing on one of its branches. Thus the scale comprises an upper and a lower longitudinal wall 5| and 52, respectively,

and two end walls 53 and 54. Two relatively weak springs 55 act to keep the scale in contact with a surface 55 provided on the machine bed and forming a guideway for the scale which moves together with the table 4. The graduation is formed on the interior face 51 of the scale, and is thereforesituated in the interior of a completely closed space, so as to be fully protectedfrom any rough treatment, aswell as from oil or dust deposit.

In order to connect the scale 50 for movement with the table 4, the bracket 48 carries at both of its ends a plate 58 and 59, respectively. A spring 60 is inserted between the plate 58 and the wall 53 of the scale and maintains a face 5| of the wall 54 of the scale constantly in contact with the 1 plate 59.

It is seen that the'weight of thescale 50 is carried by the bracket 48 which is secured to the table 4. The friction of the scale along the surface 56 of the machine bed is only feeble, since the springs 55 exert only a slight pressure just necessary to maintain the scale in contact with the surface 56. The abutting face SI of the scale is not subjected to any wear as it does not move relatively to the plate 59; for this reason the initial precision of the measuring scale is permanently maintained. 1

The graduation of the scale is observed by means of an optical system, as for example a microscope 62, the objective 53 of which is disposed in an opening 64 provided in the bed of the machine. A diaphragm 65 prevents any lubricating oil from penetrating to the objective. Illumination of the scale may be effected in any conventional manner. Fig. 9 shows a small electric bulb 15 carried by the micrometer casing and lower wall 52 and the bed, and wherefrom such,

oil will be evacuated to the base of the machine. In this manner no oil can arrive on the graduation of the scale.

Figure 7 shows a modified arrangement for carrying the scale. The measuring scale 68 is provided with an inclined face 69 bearing on a correspondingly inclined face of the bracket 10. Owing to its weight the measuring scale will slide downwards on the inclined surface towards the machine bed I, and no springs are required to maintain the scale in contact with the bed; only the arm II of the scale must be made heavy enough so that the scale cannot fall backwards.

In the modification shown in Figure 8, the spring 60 acts upon that end-o1 the scale which is provided with the abutting surface 5|. The

wall 59 .of the bracket is provided with an opening 12 through which penetrates a stud .13 screwed 'into the measuring scale 50. The spring III is disposed between the head of the stud and the plate 59. This arrangement provides the advantage to prevent any stress due to spring pressure from acting upon the measuring scale.

The described hydraulic power drive is operated in the following manner. First the handle 29 is turned so as to establish communication between the fluid delivery conduit l5 and either' pipe l8 or I9, according to the direction in which the table 4 is desired to be moved. Fluid will then be delivered to one end of the cylinder l2 and discharged from the other end. The piston rod l4 being rigidly connected to the table by the intermediary of the screw threaded portion 39, nut 3| and casing 34, the table 4 will move with the piston l3. The fluid distributor I8, I 1 is constructed in such a manner that while effecting a displacement of the table, a quick acceleration of speed of this latter can be obtained in thebeginning of the movement and then the speed can gradually be decreased to stop the table at the exact or almost the exact desired position. In order to stop the movement, the handle 29 is brought to its median position as represented in Fig. 2. Fluid is then directed into the locking cylinder 22 to cause the clamping jaws 25 and 28 to rigidly lock the piston rod, while both ends of the cylinder I2 are connected with the discharge conduit 20. During the movement of the table 4, the measuring scale 50 will be observed by means of the microscope 62. When after having stopped the table, a fine adjustment of its position is required, the hand wheel 41 will be turned, which wheel, as had been described, is operatively connected to the worm wheel 32 which is rigid with the nut 3|. The nut will thus be rotated and since thepiston rod i4 is locked, the table 4 will move and may be adjusted with great accuracy byobserving the measuring scale through the microscope.

I am aware that the use of a hydraulic power drive for work tables of machine-tools is known in itself, as is also the use of optically read precision scales. But the combination of such driving and measuring devices on a single machinetool is new and results in many advantages as well as in increased efficiency and utility.

. I claim:

1. Ina machine-tool, the combination of a stationary member, a slidable member mounted for movement therealong, a channel-shaped measuring scale carried by the slidable member for measuring the movements thereof, means for urging the scale against a face of the stationary member whereby the walls of the channel-shaped scale and said face of the stationary member form a closed chamber, and a resilient coupling means at one end of the slidable member for connecting the measuring scale to said slidable member to allow for relative linear expansion of the scale and slidable member.

- 2. In a machine-tool, the combination of a abutment on said slidable member, and a spring movement therealong, a measuring. scale mounted for movement with said slidable member for measuring the movements thereof, means for holding the measuring scale in engagement with said frame member during movement of the slidable member, an abutment at one end of said slidable member, and spring means at the opposed end thereof for holding said measuring scale in contact with said abutment during movement of the slidable member and to allow for relative linear expansion of the scale and slidable member.

4. In a machine-tool, the combination of a frame member, a slidable member mounted for movement therealong, said frame member being provided with a surface extending parallel with the direction of movement of said slidable member, a measuring scale mounted for movement with said slidable member for measuring the movements thereof, means for holding the measuring scale in contact with said surface on the frame member during movement of the slidable member, an abutment at one end of said slidable member, andspring means at the opposed end thereof for holding the measuring scale in contact with said abutment during movement of the slidable member and to allow for relative linear expansion of the scale and slidable member.

5. In a machine-tool, the combination of a frame member, a guideway thereon, a slidable member movable alongsaid guideway, said frame member being provided with a surface extending parallel with said guideway, a channel-shaped measuring scale freely carried by said slidable member, spring means for holding the measuring scale in contact with said surface on the frame member whereby the walls of the channel-shaped scale and said surface form a closed chamber, an abutment at one end of said slidable member, and a spring at the opposed end thereof for maintaining the scale in contact with said abutment during movement of the slidable member and to allow for relative linear expansion of the scale and slidable member.

6. In a machine-tool, the combination of a frame member, a slidable member mounted for movement therealong, said frame member being provided with a surface extending parallel with the direction of movement of said slidable member, a measuring scale mounted for movement with said slidable member for measuring the movements thereof, means for holding the measuring scale in contact with said surface on the frame member during movement of the slidable member, anabutment at one end of said slidable member, and spring means at the same end thereof for drawing the measuring scale into contact with said abutment during movement of the slidable member and to allow for relative linear expansion of the scale and slidable member.

7. In a machine-tool, the combination of a frame member, a guideway thereon, a slidable member movable along said guideway, a channelshaped measuring scale freely carried by said slidable member, spring means for holding the measuring scale in .contact with said surface on the frame member whereby the walls of the channel shaped scale and 'said surface form a closed chamber, an abutment at one end of said slidable member, and spring means at the same end thereof for drawing the measuring scale into contact with said abutment during movement of the slidable member and to allow for relative linear expansion of the scale and slidable member.

Leon SELEI'SKY.

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