US2753668A - Surface grinder - Google Patents

Description

July 10, 1956 J. J. STRNAD 2,753,668

SURFACE GRINDER Filed Aug. 14, 1951 2 Sheets-Sheet 1 Fiji. Fiji 2 I 4 32 39 i flw 1N VEN TO]? JAMES J. STPNAD BY ,0. W

H/S A TTOPNE Y July 10, 1956 J. J. STRNAD 2,753,568

SURFACE GRINDER Filed Aug. 14, 1951 2 Sheets$heet 2 l8 JZO 1N VENTOR JAM E 5 J. \5 TENAD H/J A TTOFNEY SURFACE GRINDER James J. Strnad, Bedford, Ohio, assignor to Lempco Products, Inc., Bedford, Ohio Application August 14, 1951, Serial No. 241,730

3 Claims. (Cl. 51-128) This invention relates to a machine tool and more particularly to a grinding machine which is versatile, fast, and inexpensive to manufacture.

One object of the invention is to provide a machine which is capable of grinding a perfectly flat surface on a given workpiece, such as engine blocks and cylinder heads, where a high degree of accuracy as to the amount of stock to be removed is not required.

Another object of this invention is to provide a machine that requires an absolute minimum of set-up time and provides the ultimate in simplicity and brevity in pregrinding operations.

Another object of this invention is to provide a machine capable of performng grinding operaions with approximately to 12 percent of the horsepower formerly considered necessary for the successful performance of like grinding operations.

Another object of this invention is to construct a machine which is the ultimate in simplicity of construction providing the greatest ease in assembly, repair, and maintenance.

Another object of this invention is to provide a grinding machine which is dustless, gritless, and dirt free, because of a highly eflicient suction means which draws dust and other foreign substances through an inexpensive, efiicient, and readily accessible filtering system of novel and ingenious design.

To the accomplishment of the foregoing and related ends, said invention then consists in the means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and following description setting forth, in detail, certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In the drawings:

Fig. 1 is a persepctive View of the entire machine as seen from the upper right hand side of the machine;

Fig. 2 is an end sectional view of the machine showing the grinding wheel, its suspension, and dust removing means;

Fig. 3 is a perspective view of the air duct;

Fig. 4 is a longitudinal medial sectional view of the entire assembled machine, some parts being shown in elevation for clarity;

Fig. 5 is a top fragmentary view of the grinding wheel spring suspension alone; and

Fig. 6 is a detailed fragmentary view of the water dispensing shield alone.

To the base, shown generally at 1, which is fabricated out of light sheet steel, or other suitable material, a table 2 is attached through the use of a plurality of pairs of screws 3, used in a conventional manner. The base 1 is placed upon a firm and comparatively level foundation or floor, and the table 2 is levelled and locked in position through the use of the set screws 3.

The grinding wheel 4 is next brought level with the table surface 2, by rotating support screws 5, by means States Patent 0 ice of foot wheel 6. This foot wheel is equipped with arms 33, for pedal contact, the arms being in threaded contact, or held by other suitable means to the foot wheel 6. The foot wheel is pressed onto the support screw 5 and held firmly in position by a pin 34, or other suitable means. As the support screw is rotated, it moves upward because it is threadably engaged with a nut 7 fixed to the base. The rounded head of the support screw 5 fits into a hemispherical recess 8, in the motor support 9, which is attached to the base of the motor 10. The motor shaft 11 is fixed to the wheel adapter 14 by a bolt 12 and key 13 (Fig. 5). A grinding wheel base 4 bonded to a grinding wheel 4 by sulphur in the conventional manner is bolted to the wheel adapter 14 as at 15. Thus rotation of the foot wheel 6, through movement of the above described parts, which are held together in fixed relationship in the above described manner, forces the grinding wheel upward into position for the grinding operation which will hereinafter be described.

For the ultimate in operation, the surface of the grinding wheel 4 should, when the machine is not in operation, lie in the same plane as the surface of the table 2. To accomplish this end, the grinding wheel 4 is set in motion and driven by the motor 10, and a wheel dresser of a conventional type, not shown, is moved across the face of the grinding wheel 4, and said wheel is dressed in the conventional manner in preparation for the grinding operation.

The grinding motor 10 is supported by a plurality of leaf springs 16 of light construction which permit vibrations set up by the motor 10, and other external forces, to cause the grinding motor, the grinding wheel 4, and other parts integrally attached thereto, to reciprocate in a vertical path alternately contacting the support screw 5 and the work piece, not shown, as it is reciprocated back and forth across the grinding wheel 4. The contact of the rapidly rotating grinding wheel 4 with the work piece sets up a resistance to the rotation of the grinding wheel 4, and tends to force the grinding wheel 4 and the related parts in a downward direction and tends to increase the degree and rapidity of vertical reciprocations of the grinding wheel 4 and its related parts.

A base bracket 17 is fastened to the base 1 by a plurality of bolts 20, or other suitable means, at a point where the base is reinforced, as at 18, furnishing means by which the leaf springs 16 are attached to the base 1, the ends of said springs being fastened to the base bracket 17 by socket head cap screws, as at 19, or by other suitable means. The opposite ends of the leaf springs are attached by suitable means, as at 21 (Figs. 2 and 5), to a motor bracket 22, which in turn is attached to the motor 10 by socket head cap screws 23 and brackets 24, or other suitable means. The leaf springs are located in a geometrical pattern, such as a pair of symmetrical trapezoids, to prevent displacement of the motor 10, and its related parts in a horizontal plane. To further prevent horizontal reciprocation, a tongue 25 may be permanently aflixed to the motor bracket 22, as an integral part thereof, and extend into a groove 26, which is created by a pair of blocks 27 which are afiixed to the base 1, as at 28, by socket head set screws or other suitable means. The blocks 27 are equipped with adjustable gibs 29, which are held in place and adjusted through the use of set screws 30, and jam nuts 31, of a conventional type. These blocks serve the further purpose of afiording means whereby it is possible to adjust the grinding wheel 4 and its related parts in a horizontal plane to a centered position with relation to the ends of the machine.

The surface of said grinding wheel must be always in a plane which is parallel to the surface of table 2. This parallelism is maintained, although the said grinding wheel and related parts are in constant reciprocation, by the reaction of the leaf springs 16, serving still a further function other than those functions set out above. The leaf springs at all times maintain the proper parallelism, thus causing all portions of the motor support bracket 22 to remain in proper spaced relationship with respect to the base support bracket 17 and causing the said motor support bracket and it's related parts to remain perpendicular to the surface 32 of table 2. The path thus described by the grinding wheel 4 and its related parts is not actually a linear reciprocation, but might more properly be described as a generally arcuat'e pattern, throughout which the axis of the grinding motor and its related parts remain perpendicular to the surface 32, of table 2. Thus, as the work piece is reciprocated across the said grinding wheel, a flat surface is ground, and the surface of the work piece is intermittently in contact with the grinding wheel 4 across its entire face.

The intermittent contact of the work piece and the grinding wheel 4 serves in two manners to reduce the horsepower necessary for the grinding motor iii to drive said grinding wheel with suflicient force. Firstly, the intermittent contact of the grinding wheel 4 and the workpiece creates a situation wherein external frictional resist ance is applied to said grinding wheel only during the uppermost portion of the reciprocations of the grinding wheel; hence the wheel is free to rotate without encountering the resistance of the workpiece during the greater portion of the time. Secondly, the power needed to drive a grinding wheel during a grinding operation is proportional to the rate of stone breakdown, or the rate of disintegration of the grinding wheel. The rate of stone breakdown in any grinding operation varies with the hardness of the wheel, the coarseness of the grit, the rate of rotation of the wheel, the surface area of the work piece, the physical properties of the work piece, and the force exerted to cause movement of the grinding wheel and the work piece in relation to each other. The rate of stone breakdown is increased in my invention by a factor which is introduced through the novel functioning of the grinding wheel 4 and its related parts which reciprocate in a vertical path, as has previously been described. The impact to which the grinding wheel is subjected each time it comes in contact with the work piece tends to pulverize the surface of said grinding wheel and increase the rate of stone breakdown. The break down of the grinding wheel in the aforesaid manner greatly decreases the requisite capacity of the power furnishing means to the extent that but five to twelve percent of the horsepower formerly considered essential to efficient grinding is necessary in a machine embodying my invention, the previously described variables in grinding stone structure being constant.

Attached to the motor bracket 22, by pins 36, which are notched as at 37, or other suitable means, are one or more coil springs 35 of conventional construction. The opposite end of said coil spring, or springs, is attached firmly to the base, as at 33, by any suitable means. The coil springs thus serve to damp the aforesaid vibrations and reciprocations set up in the motor 14 and its related parts, the vibrations otherwise being too great to be Withstood by the extremely light construction of the entire machine, and being so large as to cause excessive breakdown of the grinding wheel 4.

During the grinding operation, the work piece is manually reciprocated across the face 32 of the table 2, guide means being furnished by guide rail 39, which is fastened to said table through the use of conventional clamp screws, not shown, which are actuated by hand wheels 40.

Some of the dust created by the grinding operation is. drawn by a partial vacuum created by a fan 46 through an annular orifice 41 into an upper opening 44. The rest of the dust is withdrawn through a circular orifice- 42 in the center of the wheel 4 into a plurality of bulba ceous orifices 43 in the adapter 14, thence into the upper opening 44 of the air duct shown generally at 45. Holes 43' are provided in the base 4' of the grinding wheel so that this is possible.

Formerly, it was believed impossible to create a partial vacuum in the center of a grinding wheel or any other rapidly rotating object, such as a propeller, because of the turbulence set up in the central portion of the rapidly rotating object. My invention, as described, accomplishes this end, drawing air towards the center from about onethird of the width of the grinding wheel 4. This is accomplished as a result of the construction of the bulbaceous orifices 43, and the high partial vacuum set up through rotation of an efiicient conventional fan 46, within the air duct 45, which embodies a construction which will be described in more detail subsequently.

The air and grinding dust is drawn into the upper opening 44, as described, thence is set in a rotational motion due to the action of fan 4.6, and is thus forced outwardly and downward in a swirling manner through a helical passage 47. The air passes from the helical passage into a transport duct 48, which is. preferably rectangular in construction. A flexible duct 49, of a synthetic rubber, such as Neoprene, or other suitable material, is affixed to the transport duct 48 to serve a bifunctional purpose. This duct forms an airtight passage between the transport duct and. a filter duct 50, permitting relative movement of the transport duct with respect to the filter duct, and the flexible duct also permits a filter duct 50 of the preferred round form to be used in conjunction with a transport duct 48 in its preferred rectangular form.

The air and grinding dust passes from the filter duct into a filter shown generally at 51, which is of novel construction. The dust laden exhaust air impinges against impinger plates 52 and 53 which are firmly afiixed in angular relationship to cause a turbulent condition to be set up in the entrance region 54. A part of said exhaust air strikes upper impinger plate 52 and is thence deflected against lower plate 53 and then deflected back towards the filter duct 56. Another portion of the exhaust air strikes the lower plate 53, is thence deflected upward against the upper plate 52 and is then deflected back towards the filter duct 50. In this manner turbulence is set up at 5 and much of the grinding dust settles out at 55. The dust collected at 55 may be removed through a cleaning port 56 in the rear of the filter cabinet.

The exhaust air passes from turbulent area 54 downward and outward through a filter 57 of a type commonly used in hot air furnaces. From this filter the exhaust air passes through a wet filter shown generally at 58. The wet filter consists of a small pump 59 of any preferred type, a conduit 64), a dispensing shield 61, which consists of a piece of sheet metal or other suitable material perforated with a series of orifices as at 62. (Fig. 6), and a piece of ordinary copper screen 63. Water is pumped from. a reservoir 64, by the pump 59, transported through the conduit 60, which may be a piece of rubber hose, and thence to the dispensing shield 61. The water flows across the dispensing shield and through the orifices 62, over the screen 63, forming a uniform and thin film over the entire surface of said screen. The water then flows downward over the screen to the reservoir 64. Dust entrapped in this water is collected at the bottom of the reservoir and may be removed through the top after moving the removable top 67.

The exhaust air, which is now cleaned, flows through opening 65, which is enclosed by a perforated protective means, such as screen or perforated sheet metal 66.

Exhaustive tests have demonstrated that this combination wet and dry filter and exhaust system is far more etficient than any similar device previously used in the art, to such an extent that the operator may operate my grinding machine without the use of protective goggles, and without the use of a dust mask.

It will be understood that the foregoing description of embodiments of the invention is by way of example only, and that many modifications, omissions, and additions are possible without departing from the spirit of the invention.

I claim:

1. A grinding machine comprising a base, a work table mounted on said base, spring means mounted on said base, a motor mounted on said spring means, slide means engaged between said motor and said base to prevent movement of said motor in one direction, said spring means being arranged to hold said motor so that the axis thereof is vertical, and a grinding wheel fixed to said motor adapted to be rotated thereby, said motor and grinding wheel thereby being free to vibrate perpendicular to said work table, and auxiliary springs engaged between said motor and said base to shorten the period of vibration of the motor and grinding wheel.

2. A grinding machine comprising a base, a work table mounted on said base, spring means mounted on said base, a motor mounted on said spring means, slide means engaged between said motor and said base to prevent movement of said motor in one direction, said spring means being arranged to hold said motor so that the axis thereof is vertical, and a grinding wheel fixed to said motor adapted to be rotated thereby, said motor and grinding wheel thereby being free to vibrate perpendicular to said work table, adjustable stop means engaging the end of said motor opposite said grinding wheel and foot-engageable adjustment means connected to said stop means whereby said stop means may be adjusted.

3. A grinding machine comprising a base, a work table mounted on said base, a motor resiliently mounted on said base for vibration perpendicularly to said Work table, a tongue on said motor, adjustable guide means mounted on said base on each side of said tongue whereby said motor may be adjusted slightly in a direction longitudinally of said Work table, said tongue being in sliding engagement with said adjustable guide means, and a grinding wheel driven by said motor, said motor and wheel being free to vibrate towards and away from the work piece on said work table.

References Cited in the file of this patent UNITED STATES PATENTS 926,101 Connet June 29, 1909 1,051,695 Cramer Jan. 28, 1913 1,244,584 Carter Oct. 30, 1917 1,272,489 Marascio July 16, 1918 1,419,140 Hutchinson June 13, 1922 1,701,815 Maddox Feb. 12, 1929 1,770,074 Goodhue July 8, 1930 2,270,151 Terry et a1. Jan. 13, 1942 2,291,550 Heinichen July 28, 1942 2,378,512 Talboys et a1 June 19, 1945 2,409,416 Broberg Oct. 15, 1946 2,477,484 Hunt July 26, 1949 2,486,850 Ives Nov. 1, 1949 2,522,942 Gillen Sept. 19, 1950 2,645,886 Peterson July 21, 1953 FOREIGN PATENTS 519,364 Germany Feb. 26, 1931

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