US2357584A - Grinding machine - Google Patents

Description

Sept. 5,1944. w. F. FRASER I I 2,357,584

GRINDING MACHINE Filed Aug. 29, 1940 5 Sheets-Sheet 1 /f E i I": I :Fni 1* I kg) IE! l i i E DJ 1 grid INVENTOR ATTORNEY P 5, 1944; w. F. FRASER 2,357,584

' GRINDING MACHINE Filed Aug. 29. 1940 s sheets-sheet 2 Sept. 5, 1944. w. F. FRASER GRINDING MACHINE Filed Aug. '29, 1940 5 Sheets-Sheet 5 Sept. 5, 1944. E, F ER 2,357,584

GRINDING MACHINE Filed Aug. 29, 1940 v 5 Sheets-Sheet 4 l 6 ATTORNEY. 2

ENTOR w. F. FRASER GRINDING MACHINE Filed Aug. 29, 1940 5 Sheets-Sheet 5 INVENTOR ATTORNEY: ,i

Patented Sept. 5, 1944 UNITED STATES PATENT OFFICE GRINDING MACHINE. Warren F. Fraser, Westboro, Mass. 3 Application August 29, 1940, Serial No. 354,634

l Claim. (01. 51-50) j This invention relates to surface grinding machines and is more especially concerned with those factors affecting the accuracy of the surface produced by the grinding operation.

A typical machine of this type includes a work support, a wheel head carrying a revolving grinding wheel, and means supporting said head for reciprocating movement to carry said wheel back- Ward and forward across the surface of the work. While machines of this type are old and well known and they have been widely used, they always have a tendency to produce a wavy surface in the work. In some cases, also, there is a discernible difference in the out produced on the forward stroke as compared with that on the return stroke. Of course any such irregularity in the surface is noticeable only uponvery careful inspection, but nevertheless machine manufacturers are quite conscious of this fault. This effect often is referred to as chatter, although no audible chatter is discernible, and it is due to some relative vibration between the work support and the wheel spindle. While it is not customarily troublesome it does become important when extreme accuracy, say down to a fraction of one ten-thousandth of an inch, and fineness of finish are required.

' The present invention is especially concerned with these considerations, andit aims to improve the organization of machines of this type with a iew to minimizing these difficulties.

Y The nature of the invention will be readily understood from the following description when readin connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

' In the drawings,

Figurel is a side elevation of a surface grinder embodying features of this invention; V

Fig. 2'is an elevation of the opposite side of the machine from that shown in Fig. 1;

Fig. 3 isa rear elevation of the machine with parts broken away;

Fig. 4 is a vertical, sectional view through the wheel head and adjacent parts, the sectionbeing taken approximately in the vertical plane of the axis of the wheel spindle; and

Fig. 51s a vertical, sectional View approxito revolve around a vertical axis, together with.

a'wheel head 3, and a grinding wheel 4 mounted in said head. So far as this general organi ation is concerned, the machine is like those commonly used heretofore.

As better shown in Figs. 3 and5, the wheel head 3 is provided with guiding surfaces designed to slide horizontally on ways 5 and 6 which are formed in the upper part of the section 1 of the machine frame or base. In the preferred embodiment of. the invention the wheel head is reciprocated backward and forward in these ways to carry the wheel across the surface of the work by means of an hydraulic mechanism including a cylinder 8. A unique feature of the invention resides in the fact that the axis of this cylinder is located approximately in the same horizontal.

plane with the ways 5 and 6. This relationship is better illustratedin Fig. 5. .Consequently, the thrust exerted on the head to move it in either direction is in the plane of the frictional resistance which this thrust must overcome. Preferably this thrust is exerted approximately midway between the two longitudinal pairs of surfaces between which, this frictional resistance is generated.

It will further be seen from an inspection of Figs. 3 and 4 that the wheel spindle I0 is mounted in axial alignment with the cylinder 8 so. that it also is in approximately. the same horizontal plane with the ways 5 and 6. At its rearward end this spindle isbelt-connected to the driving shaft of an electric motor l2 which is mounted on the wheel head directly above the cylinder and the axis of its shaft preferably is in substantially the vertical plane'passing through the axes of the spindle I0 and cylinder 8.

By making the base section 1 heavy, stiff and rigid and supporting the cylinder, and preferably also the spindle, approximately in the horizontal plane of the ways, any leverage effect of .those forces tending to produce relative vibration between the wheel and the work ,is reduced to a minimum, with a consequent substantial. improvernent inthe operating characteristics of the machine. The fact, also, that this arrangement permits the lowering of the center of gravity of the wheel head to a point close to the horizontal plane of theways, as will be evident from an inspection of Fig. 5, assists in producingthis desirable result.

A further novel feature contributing to this result is the fact that the frame. or base of the machine is made in two sections, as illustrated in each of Figs. 1 to 5, inclusive. The lower section l3, or the main ,part of the base, consists of a heavy, stiff casting designed to rest on the floor and'to support and house certain of the drivin mechanisms, as is customary in machines of this type.

The upper section I also consists of a heavy, stiff casting reinforced both longitudinally and transversely by ribs, such as those shown at l4 and I5 in Figs. 4 and 5. These two sections are secured together at three points only forming the corners of a triangle. Two of these points, I! and 18, Fig. 5, are located at the front of the machine frame near opposite edges thereof, while the third point I9 is at the rear of the frame and is located approximately midway between the vertical planes of the ways 5 and 6.

These connections of the upper frame section to the lower section may conveniently consist simply of bolts passing loosely through the lowermost web or plate of the upper section and threaded into the metal of the lower section. Each of these bolts extends through a bearing area, preferably consisting of a series. of spacing sh r r s s- .Su h .a three-point support for the upper frame section reduces the distorting effects of expansion and contraction .of the base on the upper frame section and the ways which are a part of it, This construction also permits the designing of the upper frame section so thatit is of a more nearly uniform thickn ss, is less liable to warp, and its tendency to change dimensions in ways that will affect the operation of the wheel on the work are reduced. This result is further aided by the fact that the motor is located overhead and moves with the wheel head so that no slots are made through the main plates of either base section, as is customarily required for the passage of the driving belt.

The arrangement for reciprocating the Wheel head further is unique in that the cylinder 8 is fastened securely to the wheel head and moves therewith, the piston being stationary. As best shown in Figs. 1, 4 and ,5, the cylinder fits snugly into a bore formed for it in the frame portion of the wheel head, and a circumferential flange 2|, integral with the cylinder, is secured to the adjacent portion of the wheel head frame by bolts or screws, such as those shown at 22, F g. 5.

The 'oil or other fluid used in this mechanism is I conducted to and from the cylinder through pas.- sages or ducts a and b, 5,,extending longitudinally through the piston rod 23 and one of them also passing through the piston. Pipes or tubes,

one of which is shown in Fig. 1 at 2,4, connect the pistonrod with a valve mechanism 25 and a suitable source of oil supply by means of which the flow of oil to and from the cylinder 4 is produced in properly timed relationship to the cycles of operations of the machine. So far as this supply and the valve mechanism are concerned, they may be like those heretofore used in hydraulically operated surface grinders, as for example, that shown in my earlier Patent No. 2,018,847 dated October 29, 1935.

It is desirable to maintain a definite relationship between the traversing speed of the grinding wheel and the rotary speed .of the work. In addition, it is desirable to be able to change these speeds when desired. A novel feature of this in,- vention resides in a mechanism with which this result can be produced.

Referring again to Fig. 2, it will be seen that the 'oil or other liquid used in the hydraulicrnechanism for reciprocating the wheel head includes a rotary pump 28 drawing oil through the pipe 21 from the supply tank .30 and forcing it through the pipe 28 into the valve mechanism 25 and thence in the c linde :8 wh n a lowed to do o by the valve mechanism. The exhaust oil is returned from the valve mechanism to the tank through the pipe 3|.

For the purpose of driving both this pump and also the rotary chuck 2, an electric motor 32, Fig. 3, is mounted on the machine frame at the rearward end thereof where it drives a variable speed mechanism mounted in the housing 33. As better shown in Fig. 1, the particular variable speed mechanism used in this machine is of the Reeves type including two pulleys, each pulley including two reversely positioned cones which are adjustable toward and from each other. The pulleys are connected by a belt of frusto-conical form in cross-section so that the operating ratio may be varied through a wide range by the adjustment of these conical pulley sections toward and from each other. In Fig. 1, this variable speed mechanism is indicated at 34. The adjusting shaft for the mechanism is shown at 35, and the power output shaft is shown in Figs. 2 and 3 at 3.6. A long belt 31, Fig. 2, connects the pulley 38 on the shaft .36- with a driven pulley 40 on .a jack shaft 4|, mounted in the chuck bracket 42, and this belt not only drives that pulley but also the pulley 43 of the pump 26, an idler 44 resting on the belt between the pulleys 43 and 3,8 .to keep it taut. At the front .of the machine the pulley 40 is belted to another pulley 45 on the driying shaft46 for the chuck 2, this chuck drive, for ex? ample, being like that shown in my patent above referred to. In order to provide for the convenient adjustment of the variable speed driving mechanism 34, the screw shaft or adjusting shaft 35 of this mechanism is connected by means of a sprocket and chain drive with a hand wheel 4], Fig. I mounted on the side of the frame, so that by turning this wheel the driving speed of both the chuck 2 and the pump 43 can be increased or reduced, as desired. An indicating disk .48 preferably is geared to the hand wheel 41 and is graduated in any .convenient manner as, for example, to indicate chuck speeds.

With this arrangement the speeds of both the Wheel head and the chuck can be varied through a wide range. In addition, it also avoids the necessity for operating the pump continuously at the maximum output which it must be expected to deliver under some conditions. The normal relationship between the pump speed and the chuck speed is such that the wheel head is traversed at the maximum speed required for that particular work speed. When it is desired to reduce the speed of traverse of the wheel, that result is accomplished by adjustment of a throttle valve which is actuated by turning the knob 50 attached to a shaft 5| extending through the machine and having on the back thereof a lever 52 connected through a link 53 to a similar lever 54 on an extension of the throttle 55.

The long horizontal belt 31, Fig. 2, accommoe dates the vertical adjustment of the chuck 2 without affecting the driving connections be,- tween the chuck and the Variable speed mechanism.

While I have herein shown and described preferred embodiments of the features of my invene tion, it will be evident that the invention may be embodied in other forms without departing from the spirit or scope thereof, and that said features may be used independently of ,each other when desired for any reason.

The feature of making the supporting frame in upper and lower sections and supporting one on the other through a threeepoint bearing is not here claimed but is claimed in a divisional application Ser. No. 436,130, filed March 25, 1942. Having thus described my invention, what I desire to claim as new is: t

In a grinding machine, the combination of a grinding wheel, a wheel head including a horizontal spindle on the forward end of which said wheel is mounted, a work support, a machine frame provided with horizontal ways supporting said wheel head for reciprocating movement thereon toward and from said work support, mechanism for producing said movement, said mechanism including an hydraulic cylinder mounted rigidly in said frame behind said spindle and in axial alignment therewith, a piston working in said cylinder, both the spindle and the cylinder being supported midway between said ways with their common axis in the same horizontal plane with the ways, a motor mounted on said wheel head above said axis to reciprocate with said head, and means connecting said motor with the rearward end of said spindle to drive the latter.

WARREN F. FRASER.

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