US3822512A

US3822512A - Automatic surface grinder

Info

Publication number: US3822512A
Application number: US00268017A
Authority: US
Inventors: N Mercer
Original assignee: Esterline Corp
Current assignee: Esterline Corp
Priority date: 1972-06-30
Filing date: 1972-06-30
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

Automatic grinding to preset depths and spark-out finishing are provided in a surface grinder of the type having a traveling worktable and a grinding-wheel head supported by an elevating screw. The screw is slideable longitudinally in its mount, abutting against a fixed stop in its lower position. A jack is employed to raise the screw by an amount corresponding to the desired stock removal. At the conclusion of each full cycle of operation of the traveling table, the jack is automatically lowered a predetermined distance and the grinding continues with the increments of depth thus selected until the final depth is reached, whereupon the jack actuates a switch, initiating sparkout finishing.

Description

PAIENIEII 9W 3,822,512

SIIEEI 1 BF 3' I DOWNFEED INDICATOR (ZERO AT COMPLETION) SET REFERENCE POSITION --TRAVELING TABLE DOWNFEED INCREMENT SELECTOR? ACTUATE CYLIN DE R I AT END OF EACH FULL TABLE CYCLE PATENIEDJUL 91m 3.822.512

SHEEI 2 [IF-3 1 AUTOMATIC SURFACE GRINDER This invention relates to surface grinders, and more particularly to surface grinders for automatic removal of stock to a precision predetermined depth.

A number of constructions are known for automatic surface grinders which permit an operator to preset the machine for grinding to a predetermined depth without requiring further operations or manipulations between passes of the work for removal! of successive increments of stock and subsequent finishing or spark-out. In general, previously known constructions for such purposes are far more, complex and expensive than manual surface-grinding machines. In addition they are not generally adapted for ordinary manual operation when this type of operation is desired.

In principle, an automatic grinding machine may be constructed by the mere addition to a manual grinding machine of suitable programming switches, along with a motor, to perform the successive adjustments normally performed by an operator as the grinding progresses to the desired limit of stock removal and is thereupon sparked out by further grinding passes at the same depth. However it is found that such a type of automation of a surface grinder constructed for manual operation is either severely limited in precision and convenience of set up, or is prohibitively complex and expensive.

The present invention provides a novel construction for automating the operation of the common type of surface grinder which has a positioning screw extending' in the direction of desired stock removal and threadedly engaging the grinding-tool assembly (or the worktable assembly) for adjustment of the relative po-' sitioning of the tool with respect to the work. In conventional construction, the screw is mounted in fixed longitudinal position in the housing and rotated for all relative positioning of the grinding-tool and the work. In the present construction, provision is made for such rotation but in the performance of the automatic grinding, after a simple type of set-up, the screw itself is longitudinally moved, without rotation, and a mechanism is provided for presetting both the total stock removal and the increments of stock removal with great precision, while at the same time providing for sparking-out or finishing at the ultimate grinding depth.

,Both the broad and narrow aspects of the invention will be most readily-understood by reference to the embodiment illustrated in the drawing, in which:

FIG. 1 is a view in isometric perspective of an automaticsurface grinder embodying the invention, the housing and similar conventional elements being omitted;

FIG. 2 is a rear elevational view, partially in section, of the upper portion of the grinder of FIG. 1 (the grinder head being shown in a different orientation for convenience of illustration);

FIG. 2A is a view generally similar to that of FIG. 2 but showing the lower portion of the machine;

FIG. 3 is a sectional view, partially in elevation, of a portion of the mechanism shown in FIG. 2 and FIG. 2A, but showing the parts in a different position;

FIG. 4 is a transversesectional view along the line 4-4 of FIG. 2; and

FIG. 5 is a transverse sectional view along the line 5-5 of FIG. 2A.

The illustrated grinder has a housing of which the upper portion is fragmentarily shown at 10 in FIGS. 1 and 2 and the lower portion 12 is shown in FIG. 2A. A head-support or elevator screw 14 is rotatably mounted in the housing in a manner later to be described, and a sleeve-nut 16 supports a wheel head 18 having a grinding ,wheel 20 and its drive motor 22 as its principal components. A hand wheel 24 provides manual rotation of the elevator screw 14 by means of

bevel gears

26 and 27. The wheel head 18 is guided and confined for sliding vertical motion by conventional vertical tracks or guides (not shown), so that the rotation of the screw 14 adjusts the vertical position of the grinding wheel.

The workpiece 28 (illustrated as a simple bar or plate for simplicity) is suitably mounted on the surface of a traveling table 30 which traverses the work past the grinding wheel in a series of to-and-fro passes with intervening lateral displacement to expose all portions of the work to the grinder.

As thus far described, the illustrated grinding machine is essentially the same as known constructions for manual grinding having the traveling worktable controlled by limit switches and associated components for running the worktable through a. complete cycle each time it is actuated. In manual operation, the hand wheel 24 is adjusted to bring the grinding wheel 20 into contact with the surface of the workpiece and then is advanced by the operator after each cycle of table operation until the desired depth is reached, at which point further table cycles are employed for spark-out or finishing of the surface. The illustrated machine, however, is materially different from known machines in the further features now to be described.

As in prior constructions, the bevel gear 27 is mounted for rotation in the upper part of the housing 10 by a set of thrust bearings 32. In conventional constructions, the head-support or elevating screw 14 is rigidly affixed to the gear 27. In the present construction, the upper portion of the screw 14 extends through a central bore in the gear 27 and is coupled thereto for rotation by keys or splines 34 in suitable keyways. (It will benoted in the drawing that the upper end of the screw 14 is an assembly which is not fabricated integrally with the main body or threaded portion, for convenience of manufacture; such obvious assembly details are not illustrated in the drawing or described herein, being superfluous for understanding and use of the invention.) The upper end of the screw 14 has a cap 36 of enlarged diameter which seats on an internal shoulder 38 in the gear 27,:thus forming a downward limit stop for the vertical motion of the screw permitted by the keyed rotational coupling.

An inverted cup 40 isaffixed to the gear 27 and compresses a coil spring 42 to firmly seat the cap 36. A bracket assembly 44 mounts a dial indicator or gauge 46 with its actuating portion 48 extending down through the axis of the spring 42 to sense the position of the cap 36, a ball 50 being interposed between the cap 36 and the sensor of the gauge to permit free relative rotation. i

The lower end of the screw 14 is formed with a bore or socket 52 which slidingly receives a pintle 54 formed at the upper end of a vertically extending jackscrew rod 56, the base of the pintle 54 being surrounded by a thrust bearing 58 which provides freedom of relative rotation between the two end-to-end members at all times.

The lower portion of the jackscrew rod 56 (again, like the screw 14, assembled from individually fabricated segments for convenience of fabrication, but constituting an integral unit for present purposes) has a threaded drive portion by which it is raised and lowered as hereafter described. Beneath the lower end is a shut-off switch 62 mounted on the housing by a bracket 64. As will be obvious, the illustration of the shut-off switch 62 and its associated support 64 is highly schematic, rather than pictorial, conventional provision for adjustment of position for setting of the switch-actuation point being made.

The jackscrew rod 56 is operated by the action of an upper worm wheel 66 and a lower worm sheel 68 mounted in suitable bearings in the lower portion 12 of the housing. The upper worm wheel 66 is internally threaded and engages the drive portion 60 of the jackscrew. The lower worm wheel 68 is coupled to the jackscrew by keys or splines 70 mating with suitable keyways, so that the lower worm wheel 68 is affixed to the jackscrew for rotational motion only.

i The

respective worm wheels

66 and 68 are driven by an upper worm 72 and a lower worm 74. The shaft 76 of the upper worm 72 is coupled through an overrunning clutch 78 to the shaft 80 of a pinion 82 which engages a rack 84 formed on the surface of an actuator rod 85. A coupling bar 86 drives the actuator rod 85 in response to operation of a hydraulic cylinder assembly 88. As schematically shown in FIG. 1 of the drawing, the hydraulic cylinder assembly 88. is actuated at the end of each full table cycle in response to a suitable signaling switch (not shown). Upon actuation, the hydraulic cylinder 88 moves the actuating rod to drive the pin-.

ion 82 until a cylinder return switch 92 is actuated upon engagement of a stop block 94 on the actuator 85 with a selected

stop pin

96a or 96b or 960 or 96d, etc. These stop pins are distributed about the circumference of a tube 98 at differing points along its length. The tube 98 terminates in a knob 100 calibrated in preselectable downfeed increments. i 4 The lower worm 74 has its shaft 102 connected through bevel gears 104 to a rod 106 which extends through the tube 98 and-has an adjustment knob 108.

Each of the '

worms

72 and 74 locks its

respective worm wheel

66 or 68 against any rotational motion except that imparted by rotation of that worm. Operation of the worm 74 rotates the jackscrew 56 by means of the key-coupling of these elements, and raises or lowers the jackscrew by reason of the engagement of its externally threaded portion 60 with the internal threading of the then-stationary upper worm 66. Operation of the worm'72 is produced by the rack 84 and pinion 82 and is always inthe same direction due to the action of the overrunning clutch 78. Because the jackscrew is then locked against rotation by the lower worm 74, each rack-and-pinion operation produces a lowering of the jackscrew proportional to the length of stroke of the actuator rod 85 preset by the operator by use of knob 100.

The elevated jackscrew 56 and elevator screw 14 are shown in FIG. 3, the cap 36 slightly compressing the spring 42 as the jackscrew 56 urges the elevator screw 14 upward. After each cycle of the traveling worktable, the jackscrew is withdrawn downwardly by the preset increment and the vertical position of the screw 14, and thus of the grinding head, is correspondingly lowered. This continues until the cap 36 abuts against the stop or shoulder which fixes its lowermost position, shown in FIG. 2. The screw 14 now clears the thrust bearing 58 by a very small amount, say of the order of 0.1 mil (illustrated exaggeratedly in FIG. 2). Immediately thereafter, the switch 62 is actuated. The switch initiates a counter (not shown) which then shuts off the operation of the grinder and table after a predetermined number of grinding cycles at the final depth produce sparking out or finishing of the work. Reproducibility of the exact point of actuation of the switch is not critical to operation, affecting only the relatively noncritical performance aspect of determining the exact number of spark-out cycles which are performed.

For any given grinding operation, the hand wheel 24 is used to set a reference position, the total desired downfeed or stock removal is set by manipulation of the knob 108, and the increment of stock removal to be performed in each full table cycle is preset by use of the calibrated knob 100, which is preferably provided with detent stops at each of the marked positions corresponding to the stroke length fixed by the stop-pins 96a, 96b, etc. In an examplary embodiment of the machine illustrated, five values of downfeed increment are provided, from l/ 10 mil to 2 mils. Prior to commencement of operation, the total depth to be removed is shown on the gauge 46, which is used in adjusting the knob 108, and shows the distance by which the cap 36 is raised-from its bottom or zero-reading position. This setting may be made after the reference position has been set by the hand wheel 24, so that the elevator screw remains in the same rotational position throughout the making of the depth-setting and the performance of the grinding. The hand wheel 24 is adjusted, in this mode of use, to produce a grinding wheel elevation corresponding to the completed stock removal, with the table withdrawn to a park position wherein the work is out of contact with the grinding wheel. With the final or finishing position thus set by manipulation of the hand wheel 24, the total desired downfeed or stock removal is set by the use of knob 108 while observing the gauge 46, thus producing a grinding wheel elevation such that starting of the machine (by a Start switch not shown) initiates the first of. the incremental grinding cycles. Alternately, since the total downfeed and reference-position settings are to a large extent independent, the desired removal may be first set by the knob 108 and the grinding-wheel then brought down into contact with the work by the hand wheel 24. For utmost accuracy, the former sequence may be preferred, because rotation of the elevating screw, as can be seen upon study, may change the vertical relations by an amount imperceptible by visual standards, but sufficient to require readjustment to restore the original total-depth setting if accuracy tolerances are small.

It will be observed that all rotation of both the elevating screw and the jackscrew is made at times other than during the grinding operation, so that precision of thread cutting and mating and other fabrication does not limit the precision of stock removal. Likewise, as earlier mentioned, the depth of removal is independent of drift, long-term or short-term, in the point of switchtripping. Such factors are particularly advantageous where repetitious grinding operations are to be performed on successive worktable loads, as in production grinding of successive identical parts, or sets of parts. To grind successive duplicates, the operator merely resets the wheel head position to the same grinding depth, using the highly accurate visual indicator, and reinitiates the operation of the machine, with assurance of complete accuracy of reproduction. For long production runs, no adjustment of the hand wheel 24 is required except occasional compensation for wheel wear. However, when so desired, the machine may be employed for conventional manual (or hydraulic) operation, disregarding the controls provided for the automatic mode of operation.

As will be obvious, the illustrated embodiment is merely exemplary of the principles of the invention.

Many modifications will be observed by those skilled in the art, some obvious and some seen only after study. Accordingly, the scope of the protection to be afforded the invention should not be limited by the particular embodiment described, but should extend toall uses of the invention as defined in the annexed claims, and equivalents thereof.

What is claimed is:

1. In a surface grinder comprising:

a. a housing, a workholder assembly and a grindingtool assembly,

b. guide means mounting one of said assemblies on the housing for inward and outward motion toward and away from the other assembly for advancement and retraction of the grinding-tool with respect to the work,

c. apositioning screw extending in the direction of said motion and threadedly engaged with the movable assembly to adjust the position thereof in response to rotation of the screw, and

d. an adjustment member rotatably mounted on the housing and driving the screw for rotation thereof,

the improvement characterized by:

e. a rotationally fixed but axially sliding coupling between the screw and the rotatable adjustment member,

f. limit-stop means fixing an inward axial limit of sliding of the screw with respect to the rotatable adjustment member and force means urging the screw to the inward limit to maintain a reference axial position of the screw,

g. an auxiliary positioning member reciprocable in the axial direction of the screw and in unidirectional driving engagement with the screw for outward motion thereof from the reference position,

h. means to preset the auxiliary positioning member outward to position the screw outward of the reference position against the urging of the force means,

iand means to withdraw the auxiliary positioning member, and thus produce inward driving of the screw by the force means, as the grinding progresses after initiation, until after the screw again reaches the reference position, so that the grinding reliably proceeds to the preset depth and is thereupon sparked out at that depth.

2. The grinder of claim 1 having a thrust bearing between the screw and the auxiliary positioning member to permit free rotary relative motion therebetween at all times.

3. The grinder of claim 2 further characterized by the adjustment member being centrally apertured to pass the screw and key-coupled thereto and the screw having a head portion abutting against the adjustment member in the reference axial position of the screw and the force means comprising a compression spring having one end abutting against the head portion of the screw and a spring-retainer member secured to the adjustmentmember and engaging the opposite end of the spring. i r

4. The grinder of claim 1 further characterized by having a position-indicator fixedly mounted on the housing and coupled to the outer end of the screw for setting of working depth.

5. The grinder of claim 4 wherein the coupling to the outer end of the screw includes a ball seated on the end of the screw.

6. The machine-tool of claim 1 wherein the means to withdraw the auxiliary positioning member is activated intermittently to change the working depth of the tool in preselected increments.

7. The grinder of claim 1 further characterized by the auxiliary positioning member having an externally threaded segment, an internally threaded rotor surrounding the externally threaded. segment of the positioning member and engaged therewith and mounted for rotation on the housing, and a second rotor surrounding another segment of the positioning member and keyed thereto for rotational motion and mounted for rotation on the housing, so that the auxiliary positioning member may be moved outward by one of the rotors to preset the grinding depth and inward by the other rotor in performance of the grinding.

8. The grinder of claim 7 wherein the rotors are worm wheels driven by separate worms, so that each rotor is locked against rotation by its worm when the other is operated. 9. The grinder of claim 8 wherein the internally threaded rotor has drive means comprising a rack-andpinion, an overrunning clutch coupling the pinion to the rotor,- and means responsive to completion of grinding at each incremental depth to drive the racka preselected distance, retract the rack, and initiate grinding at the increased depth.

10. The grinder of claim 9 wherein the means to drive the rack includes a manually adjustable selection mem ber having a plurality of end-stop members fixing differing limits of travel of the rack.

11. In a surface grinder comprising a. a housing, a workholder assembly and a grinding tool assembly,

[2. guide means mounting said grinding tool assembly for movement toward and away from said workholder assembly,

c. a' positioning screw on which said grinding tool assembly is mounted for adjustment,

d. an adjustment member on said housing for rotating said screw the improvement characterized by e. non-rotatable coupling means mounted on said screw for sliding movement longitudinally and against turning movement on said screw,

f. limit reference means limiting sliding movement of said screw to a reference position,

g. means biasing said screw to said limit reference means, I

' h. auxiliary positioning means for axially moving and positioning said screw against the force of said biasing means to space said screw a pre-set distance from said reference point, and

'. automatic means for positioning said auxiliary positioning means in successive predetermined increments to a desired depth of grind so that said biasing means moves said screw a corresponding distance whereby said grinding wheel is operative to achieve said desired depth of grind on a workpiece in successive predetermined increments.

12. A surface grinder comprising,

a. A housing, a workholder assembly and a grinding tool assembly,

b. a rotatable positioning screw,

c. means mounting said grinding wheel on said screw for movement toward and away from said workholder,

a. manual adjustment means on said housing including first gear means,

e. second gear means on one end of said screw and meshing with said first gear means for rotating said screw,

f. means mounting said second gear means on said screw for rotation therewith and permitting relative sliding axial movement of said screw and said second gear means,

g. means limiting said sliding movement of said screw to a limit reference position, said screw being biased toward said limit reference position,

h. position means for axially moving and positioning said one end of said screw against said bias a preset distance from said limit reference means, and

. automatic means operative upon each successive pass across said worktable to reposition said positioning means a distance corresponding to a desired depth of grind whereby said one end of said screw and said grinding tool assembly are displaced to said desired depth of grind.

13. The invention as defined in claim 12 wherein said positioning means comprises a jack-screw, gear means slidably and non-rotatably mounted on said jack-screw for urging said feed screw to said pre-set distance from said reference limit positions, a meshing gear and worm means threadably associated with said jack screw for rotating and displacing said jack-screw out of engage-' ment with said feed screw whereby said feed screw is slidably moved and thereby said grinding wheel to a desired depth of grind.

14. The invention as defined in claim 13 wherein said automatic positioning means comprises a rack and pinion connected to said meshing gear and worm means, and means responsive at the completion of a grinding sweep across the worktable to actuate said rack and rotate said meshing gear and worm to displace said jackscrew a pre-set distance corresponding to a desired depth of cut.

Claims

1. In a surface grinder comprising: a. a housing, a workholder assembly and a grinding-tool assembly, b. guide means mounting one of said assemblies on the housing for inward and outward motion toward and away from the other assembly for advancement and retraction of the grinding-tool with respect to the work, c. a positioning screw extending in the direction of said motion and threadedly engaged with the movable assembly to adjust the position thereof in response to rotation of the screw, and d. an adjustment member rotatably mounted on the housing and driving the screw for rotation thereof, the improvement characterized by: e. a rotationally fixed but axially sliding coupling between the screw and the rotatable adjustment member, f. limit-stop means fixing an inward axial limit of sliding of the screw with respect to the rotatable adjustment member and force means urging the screw to the inward limit to maintain a reference axial position of the screw, g. an auxiliary positioning member reciprocable in the axial direction of the screw and in unidirectional driving engagement with the screw for outward motion thereof from the reference position, h. means to preset the auxiliary positioning member outward to position the screw outward of the reference position against the urging of the force means, i. and means to withdraw the auxiliary positioning member, and thus produce inward driving of the screw by the force means, as the grinding progresses after initiation, until after the screw again reaches the reference position, so that the grinding reliably proceeds to the preset depth and is thereupon sparked out at that depth.

3. The grinder of claim 2 further characterized by the adjustment member being centrally apertured to pass the screw and key-coupled thereto and the screw having a head portion abutting against the adjustment member in the reference axial position of the screw and the force means comprising a compression spring having one end abutting against the head portion of the screw and a spring-retainer member secured to the adjustment member and engaging the opposite end of the spring.

7. The grinder of claim 1 further characterized by the auxiliary positioning member having an externally threaded segment, an internally threaded rotor surrounding the externally threaded segment of the positioning member and engaged therewith and mounted for rotation on the housing, and a second rotor surrounding another segment of the positioning member and keyed thereto for rotational motion and mounted for rotation on the housing, so that the auxiliary positioning member may be moved outward by one of the rotors to preset the grinding depth and inward by the other rotor in performance of the grinding.

8. The grinder of claim 7 wherein the rotors are worm wheels driven by separate worms, so that each rotor is locked against rotation by its worm when the other is operated.

9. The grinder of claim 8 wherein the internally threaded rotor has drive means comprising a rack-and-pinion, an overrunning clutch coupling the pinion to the rotor, and means responsive to completion of grinding at each incremental depth to drive the rack a preselected distance, retract the rack, and initiate grinding at the increased depth.

10. The grinder of claim 9 wherein the means to drive the rack includes a manually adjustable selection member having a plurality of end-stop members fixing differing limits of travel of the rack.

11. In a surface grinder comprising a. a housing, a workholder assembly and a grinding tool assembly, b. guide means mounting said grinding tool assembly for movement toward and away from said workholder assembly, c. a positioning screw on which said grinding tool assembly is mounted for adjustment, d. an adjustment member on said housing for rotating said screw the improvement characterized by e. non-rotatable coupling means mounted on said screw for sliding movement longitudinally and against turning movement on said screw, f. limit reference means limiting sliding movement of said screw to a reference position, g. means biasing said screw to said limit reference means, h. auxiliary positioning means for axially moving and positioning said screw against the force of said biasing means to space said screw a pre-set distance from said reference point, and i. automatic means for positioning said auxiliary positioning means in successive predetermined increments to a desired depth of grind so that said biasing means moves said screw a corresponding distance whereby said grinding wheel is operative to achieve said desired depth of grind on a workpiece in successive predetermined increments.

12. A surface grinder comprising, a. A housing, a workholder assembly and a grinding tool assembly, b. a rotatable positioning screw, c. means mounting said grinding wheel on said screw for movement toward and away from said workholder, d. manual adjustment means on said housing including first gear means, e. second gear means on one end of said screw and meshing with said first gear means for rotating said screw, f. means mounting said second gear means on said screw for rotation therewith and permitting relative sliding axial movement of said screw and said second gear means, g. means limiting said sliding movement of said screw to a limit reference position, said screw being biased toward said limit reference position, h. position means for axially moving and positioning said one end of said screw against said bias a pre-set distance from said limit reference means, and i. automatic means operative upon each successive pass across said worktable to reposition said positioning means a distance corresponding to a desired depth of grind whereby said one end of said screw and said grinding tool assembly are displaced to said desired depth of grind.

13. The invention as defined in claim 12 wherein said positioning means comprises a jack-screw, gear means slidably and non-rotatably mounted on said jack-screw for urging said feed screw to said pre-set distance from said reference limit positions, a meshing gear and worm means threadably associated with said jack screw for rotating and displacing said jack-screw out of engagement with said feed screw whereby said feed screw is slidably moved and thereby said grinding wheel to a desired depth of grind.

14. The invention as defined in claim 13 wherein said automatic positioning means comprises a rack and pinion connected to said meshing gear and worm means, and means responsive at the completion of a grinding sweep across the worktable to actuate said rack and rotate said meshing gear and worm to displace said jack-screw a pre-set distance corresponding to a desired depth of cut.