US3483620A

US3483620A - Coordinate calculator

Info

Publication number: US3483620A
Application number: US625416A
Authority: US
Inventors: Robert R Miller
Original assignee: Precision Metalsmiths Inc
Current assignee: Precision Metalsmiths Inc
Priority date: 1967-03-23
Filing date: 1967-03-23
Publication date: 1969-12-16
Anticipated expiration: 1986-12-16

Description

United States Patent O 3,483,620 CDORDINATE CALCULATOR Robert R. Miller, Cleveland, Ohio, assignor to Precision etalsmiths, lne. Filed Mar. 23, 1967, Ser. No. 625,416 Int. Cl. G0111 3/00, 5/00 U.S. Cl. 33-1 16 Claims ABSTRACT 0F THE DISCLUSURE A calculator for determining the number of castings that can be made with a sprue of a known size and the locations of the casting patterns on the sprue. A pair of pivoted indicator arms associated with a calibrated circular scale indicate the number and locations of patterns around the sprue, and an indicator plate or arm movable along a calibrated linear scale indicates the number and locations of patterns along the length of the sprue.

Background of the invention This invention relates generally to the lost pattern process of investment casting, and more specifically to a calculator for use in making the disposable pattern assemblies or set-ups employed in such a process.

In the lost pattern process of investment casting, a pattern assembly, commonly referred to as a set-up or tree, is prepared by attaching a plurality of patterns to a suitable sprue member. The patterns, which are replicas of the parts to be cast and which include the necessary gates and risers, are made of a disposable material, such as wax, a synthetic resin or a combination of wax and synthetic resin. The set-up or tree is coated or invested with a refractory material in order to form a mold. Thereafter, the patterns are destroyed, such as by heating the mold, to form the mold cavities.

The locations of the several casting patterns on the sprue member are critical. From the standpoint of obtaining the maximum yield of castings from a single mold, it is desirable to use a large number of casting patterns in a set-up. The patterns cannot, however, be so close together as to prevent the mold from being yproperly formed. For example, ceramic shell molds are made by dipping a set-up in a slurry, sanding the slurry-coated set-up with coarse refractory particles and then drying the coating to form a hard refractory layer. These operations of dipping, sanding and drying are repeated until a refractory shell of the desired thickness has been built up around the set-up. When the patterns are too close together on the sprue member, it may be impossible to obtain a satisfactory uniform coating of the slurry around the patterns. Further, a substantial amount of slurry may be retained between closely spaced patterns to form thick wall sections which are diiiicult to dry properly so as to prevent cracking when the mold is subsequently heated, such as during the pattern removal operation or when the mold is iired prior to casting.

The exact locations of the patterns on the sprue member depends on several factors, including the size and complexity of the patterns, the size of the mold and the sprue, the size of the gate required for each pattern, and the metal from which the parts are to be cast. Because of the criticality involved in forming the set-up, the operation has required skilled and experienced personnel. The operation of forming the set-up has also been extremely tedious and time-consuming. These problems have become particularly acute in the light of recent advancements in the lost pattern process which have made it feasible to cast several thousand parts in a single mold.

In order to facilitate proper positioning of the patterns when making a set-up and to provide for eflicient produc- 3,483,520 Patented Dec. 16, i959 tion control in the foundry, there has been a need for an expedient technique of calculating the number of parts that can be cast in a mold and laying out the positions of the patterns on the sprue member before the actual assembly of the set-up. There has also been a need for a means of enabling the person assembling the set-up to locate the patterns in accordance with the predetermined optimum layout without the skill and time which had been required in the past.

Summary of the invention The present invention satisfies the foregoing needs and provides a simple, easy to use calculator which enables a person quickly to determine how many castings can be made with a sprue of a known size and where the casting patterns should be located on the sprue. The use of the calculator to determine the number of castings which can be made with a sprue of a known size contributes to eicient techniques of production control. For example, it is possible to determine the length of the pattern gates which will result in the desired spacing and the highest yield of castings from a mold, the amount of metal required to cast the mold, and the number of set-ups and castings that can be made per man-hour. The use of the calculator to determine the proper locations of the patterns enables relatively unskilled personnel quickly and precisely to attach the patterns to a sprue member when making a set-up.

In the `preferred embodiment of the invention the calculator comprises a calibrated circular scale which is proportioned to the circumference of at least one sprue member or a known diameter. Two movable indicator arms are pivoted at the center of the circular scale. A casting pattern is placed on the scale and the arms are moved against opposite sides of the pattern. The positions of the arms on the calibrated scale indicate the circumferential space required for the pattern on the sprue member and the distance required between two adjacent patterns around the circumference of the sprue member. The total number of patterns that can be placed in a row around the sprue member can be quickly determined by dividing the circumference of the sprue by the sum of the space occupied by each pattern and the distance between adjacent patterns.

The preferred calculator of the invention also includes a calibrated linear scale, a fixed plate at one end of the scale, and a movable plate which is slidable along the length of the scale. When a casting pattern is placed between the plates, the position of the movable plate on the linear scale indicates the longitudinal space occupied by the pattern on the sprue member and the distance between two adjacent pattern members along the length of the sprue. The total number of patterns which can be positioned in a row extending lengthwise of the sprue member can be quickly determined by dividing the usable length of the sprue by the sum of the space occupied by one pattern and the distance between two adjacent patterns.

The sprue member used in making a set-up may be formed with circumferential and longitudinal grid lines on its outer surface. The spacing of these grid lines corresponds to the calibrations of the circular and linear scales of the calculator. In assembling the set-up, the gate ends of the patterns are attached to the sprue member using the grid lines to locate the patterns around and along the length of the `sprue member. The proper positions of the patterns can be determined in advance by use of the calculator so that it is possible for the person making the set-up precisely to position the patterns on the sprue member by counting the grid lines between each pattern. Thus, the invention makes it possible accurately to make a set-up in a more efficient manner than in the past.

Other objects and a full understanding of the inventlon will be had from the following detailed description taken in conjunction with the accompanying drawing.

Description of the drawing Description of the preferred embodiment Referring now to the drawing, and to FIG. l in particular, there is shown an exemplary pattern set-up of the type which is used to produce a refractory mold. The set-up 10 is comprised of a central sprue member 11 and a plurality of workpiece patterns 12 projecting from the outside wall surface of the sprue member.

In accordance with conventional practice, the patterns 12 and at least the outside wall portion of the sprue member 11 are formed of an expendible material, such as wax, a synthetic resin, or a wax and synthetic resin composition. As shown, the sprue member 11 is in the form of a cylindrical tube, although it may be solid in crosssection if desired. Each of the patterns 12 includes a main portion 12a which defines the shape of the part to be cast in metal and a gate 12b which has its root or stub end attached to the wall of the sprue member 11.

The patterns 12 are positioned in spaced, predetermined locations to form rows that extend around and 'along the length of the sprue member 11. The outside of the sprue member 11 is preferably provided with longitudinal and circumferential grid lines or with other suitable markings which facilitate the attachment of the patterns 12 to the sprue member 11 in the desired locations. The exact distance between the longitudinal and circumferential grid lines shown in FIG. 1 is not critical, but may be on the order of 1/a of an inch so that the lines are easily discernible and can be quickly counted. If desired, certain longitudinal and certain cricumferential lines, for example, every eighth line, maybe heavier or darker than the intermediate lines.

As more fully disclosed in copending application Ser.

No. 530,448 of Claude H. Watts, entitled Investment Casting, filed Feb. 28, 1966 and assigned to a common assignee, the longitudinal and circumferential grid lines may be imposed on the sprue member 11 in several different ways. According to one technique, the sprue member 11 comprises a tube and an internally corrugated cardboard sleeve which surrounds the tube and has a smooth outer surface on which the grid lines are printed. The cardboard sleeve is provided with a thin coating of a low melting point wax. The thickness of the wax coating is sufficient to permit the workpiece patterns to be secured to the sprue member by locally heating the wax coating and embedding the gate ends of the patterns in the softened wax.

Referring nOw to FIG. 2, there is shown the coordinate calculator 15 comprising the invention which is used to determine the number and proper locationsof the patterns 12 on the sprue member 11. The coordinate calculator 15 is comprised of a plate 16 which carries a circular scale y 17 and a linear Scale 18. As more fully described'below,

-the circular scale 17 is used to determine the circumferential positioning of patterns about a sprue member of a given diameter, while the linear scale 18 is used to determine the longitudinal positioning of the patternsv segments A, B and C. The circular scale segments A, B and C are separately -used to determine the layout of patterns around sprue members of three different outside diameters. The inner arc 19 of the segment A is drawn on a radius equal to the outer radius of one particular size sprue member. The inner arc 20 of the segment B is drawn on avradius equal to the outer radius of a sprue member of a different diameter, and the inner arc 21 ot' the segment C is drawn on the radius equal to the outer radius of a sprue member of still a different diameter. lt will be apparent that the circular scale 17 can be divided into a larger number of segments than that shown in order that the scale can be used for a corresponding number of sprue members of different diameters. Alternatively, the scale 17 may be in the form of an annulus having an inner diameter equal to the outside diameter of a single size sprue member to be used vin making a set-up.

The circular scale 17 further comprises uniformly spaced radial lines or graduations 25 which intersect the inner arcs 19, 20 and 21 of the segments A, B and C, respectively. The spacing between the lines 25 at the points of intersection with the

arcs

19, 20 and 21 is preferably equal to the spacing between the vertical grid lines On the sprue member 11. For example, if the spacing between the vertical grid lines is 1/8 of an inch, 1A inch intervals will be marked olf on each of the

arcs

19, 20 and 21 by the intersection of the lines 25. The spaces be tween the linesk 25 can be sequentially numbered clockwise on each segment A, B and4 C, if desired.

A pair of

arms

26 and 27 are provided at the center of the circular scale 17 and exend radially outwardly over the segments A, B and C. The

arms

26 and 27 are preferably formed of a transparent material, such as Plexiglas or the like. As is most clearly shown in FIG. 3, the arm 26 is comprised of a at strip 28 and an elongated block 29. The block 29 is connected to the upper surface of the strip 28 by pins 30. Referring to FIG. 4, the arm 27 will be seen to be comprised of a at strip 31 and an upstanding, elongated block 32 which is secured to the upper surface of the strip by pins 33. Preferably, the block 32 has a thickness equal to the desired circumferential spacing between the main portions 12a of adjacent patterns on the sprue member 11. This circumferential spacing between adjacent patterns 12 will vary depending upon the size of the pattern, the metal to be cast and other factors, but is. usually on the order of W16 of an inch. The arm 27 can be replaced by arms having blocks of dierent widths when desired. As shown in FIG. 2, the arms` 26 and 2`7 havevertical side faces 2641- and 27a, respectively, which lie in planes extending radially from the pivot mountingftof the arms located at the center of the Scale 17. v Y Y The linear scale 18 of the coordinate calculator 15 is comprised of a plurality of parallel graduations or lines 35. The lines 35 are uniformly spaced aparta distance preferably equal to the spacing between the horizontal grid lines on the sprue member 11, for example 1A; of an inchQThe spaces between the lines 35 may be numbered consecutively fromione end of the scale 18 to the other,l if desired. A pair of7 parallel rods 36 extend lengthwise of the `scale 18 on opposite sides thereof. As shown, the rods 36 are Asecured to he plate 16. A stationary plate 37and a movable plate 38 extend betweenthe rods 36 across the scale 18. TheA stationary plate 37 is positioned so that the vertical `face of the plate which confronts the movable plate V38 is coincident with the first line of the `scale 18. The movable plate 38 is mounted for sliding movement along the rrods 36 by blocks 39 which are secured to the ends of the-plate. The thickness of the plate 38 Ais preferably equal to the desired distance between the .closest portions of* thepatterns inpeach longitudinal row on the spruemernber 11, for example 3/16 of an inch.

Wheny using the calculator 15 to lay out the patterns .i 12 around the sprue member '11, the arm 26 is positioned sov that the vertical side face 26a of the arm is coincident with the first line 25 of the scale segment A, B or C which corresponds to the circumference of the sprue member. As shown in PIG. 2, the vertical side face 26a of the arm 26 is coincident with the rst line 25 of the scale segment A. A casting pattern 12 of the type to be used in making the set-up is placed on the selected scale segment A against the side face 26a of the arm 26 so that the root or stub end of the pattern gate 12b lines on the arc 19. The movable arm 27 is then pivoted against the pattern 12 in the manner shown in FIG. 2 so that the side face 27a abuts the pattern portion 12a.

As explained above, the arm 27 preferably has a thickness equal to the desired spacing between two adjacent patterns in a row around the sprue member 11. Therefore, the position of the right side of the arm 27 on the selected calibrated scale segment A, as viewed in FIG. 2, indicates the space which will be occupied by one pattern 12 circumferentially of the sprue 11 plus the distance between that pattern and the next adjacent pattern. Assuming, for example, that the right side of the arm 27 as shown in FIG. 2 lies on the ninth space of the scale segment A and that thel scale segment A is calibrated in Vs of an inch increments, the position of the arm 27 indicates that the circumferential space which will be occupied by one of the patterns 12 on the sprue member l1 plus the distance between two adjacent patterns around the sprue member will be ll/s inches. The known circumference of the sprue member 11 may then be divided by l1/s inches to determine the total number of patterns which can be placed in a row around the sprue member.

It will be apparent that the number of patterns which can be placed around the sprue member can be increased by simply lengthening the gates 12b. Thus, the person making the layout can determine the length of the gate which will obtain a maximum yield of castings from the mold. The length of the gate will, of course, vary depending upon the design of the part, the metal to be cast and the feeding requirements.

The person making a set-up may attach one pattern 12 to the sprue member 11 and then count a predetermined number of longitudinal grid lines from the gate of that pattern to determine where the next pattern should be attached. In order to assist the person making the set-up quickly to locate the patterns 12 around the sprue member 11, it is possible to determine from the scale 17 the number of longitudinal grid lines on the sprue between the gates of adjacent patterns when the patterns are properly positioned. This may be accomplished by placing another pattern 12 against the right side of the arm 27, as viewed in FIG. 2, so that the root or stub end of the pattern gate also lies on the arc 19. Assuming that the right hand corner of the gate of the pattern between the

arms

26 and 27 lies on the sixth line of the scale segment A and that the right hand corner of the gate of the other pattern lies on the thirteenth line of the scale segment A, the corresponding portions of the gates of two adjacent patterns in a circumferential row should be separated by 7 lines on the gridded sprue member 11. The person making the set-up 10 would preferably attach a pattern near one end of the sprue member 11 so that the right hand edge of the pattern gate lies on one of the longitudinal grid lines. The next pattern in the circumferential row would be attached so that the right hand edge of the gate is spaced from the corresponding edge of the first pattern gate by the number of lines determined from the scale segment A. Thus, in carrying out the illustrated example of the invention, the location of the right hand edge of each pattern in a circumferential row is determined by counting 7 longitudinal grid lines from the right hand edge of the previously attached pattern sate.

In order to determine the number of patterns which can be placed in each longitudinal row on the sprue member 11, a pattern 12 is vertically positioned against the stationary plate 37 with the root or stub end of the pattern gate abutting the linear scale 18. The plate 38 is then slid against the opposite side of the pattern. Since the thickness of the plate 38 is preferably equal to the desired longitudinal spacing between two adjacent patterns, the position of the left hand surface of the plate 38 on the scale 18, as viewed in FIG. 2, will indicate the longitudinal space occupied by a pattern on the sprue member plus the distance between two adjacent patterns. Assuming, for example, that the left end surface of the plate 38 lies in the fth space of the scale 18, and that the scale 18 is calibrated in eighths of an inch, the longi tudinal space occupied by a pattern 12 on the sprue member 11 plus the longitudinal spacing between two adjacent patterns would be approximately 5/s of an inch. The number of patterns which can be placed in a longitudinal row on the sprue member 11 is determined by dividing the usable length of the sprue member 11 by of an inch.

It will be apparent that the total number of patterns which can be placed on the sprue member 11 can be determined by the product of the number of patterns in a single longitudinal row and the number of patterns in a circumferential row. Assuming that 30 patterns can be placed in a circumferential row and 50 patterns can be placed in a longitudinal row, the total number of patterns that will occupy the sprue member 11 is 1500'.

In order to determine the proper locations of the patterns lengthwise of the sprue member 11, a second pattern 12 can be placed on the linear scale 18 against the left surface of the plate 38, as viewed in FIG. 2. The number of lines 35 between corresponding edges of the two pattern gates indicates the number of circumferential grid lines between the pattern gates when attached to the sprue member 11. Assuming that it is determined from the use of the scale 18 and that there are 4 lines between corresponding edges of longitudinally spaced pattern gates, the person making the set-up 10 will count 4 lines along the length of the sprue member 11 from a previously attached pattern in order to determine the location of the next pattern.

Many modifications and variations of the invention will be apparent to those skilled in the art in view of the foregoing detailed disclosure. Therefore, it is to be understood that the invention can be practiced otherwise than as specifically shown and described.

What is claimed is:

1. A calculator for use in locating the casting patterns on a sprue member comprising a scale divided into a plurality of segments, each of said segments including an arc and a plurality of graduations equally spaced from each other along each are and extending radially outwardly therefrom, each of said arcs being generated on a radius of different length about a common centerpoint corresponding to the outer radius of a sprue member, the spacing of said graduations measured along all of said arcs being equal, and at least one arm mounted at said centerpoint of said scale for pivotal movement, said arm extending radially outwardly from said centerpoint of said scale over said arcs and being movable around said scale.

2. A calculator as claimed in claim 1 wherein said arm has a vertical side face lying in a plane extending radially from the center of said scale.

3. A calculator as claimed in claim 1 including a second arm pivotally mounted at the center of said scale, both of said arms being movable around said segments of said scale.

4. A calcultaor as claimed in claim 1 including a linear scale comprised of a plurality of regularly spaced parallel lines, and a member movable along said linear scale.

5. A calculator as claimed in claim 4 wherein said member comprises a plate extending across said linear scale, and means mounting said plate for sliding movement.

6. A calculator as claimed in claim 5 including another plate extending across said linear scale.

7. A calculator for use in locating the casting patterns on a sprue member comprising a scale divided into a plurality of segments, each of said segments including an arc and a plurality of graduations equally spaced from each other along each arc and extending radially outwardly therefrom, each of said arcs being generated on a radius of different length about a common centerpoint and corresponding to the outer radius of a sprue member, the spacing of said graduations measured along all of said arcs being equal, and a pair of arms pivotally mounted at said common centerpoint of said scale, each of said arms having a vertical side face which lies in a plane extending from said centerpoint and which extends radially beyond said arcs.

8. A calculator as claimed in claim 7 including a lineal scale comprising a plurality of equally spaced, parallel lines; a rst member extending across said scale, said first member having a face lying in a plane normal to said scale and containing one of said parallel lines; and a movable second member extending across said linear scale, said second member being movable along the length of said linear scale toward and away from said face of said rst member.

9. In a process of making a set-up by attaching the ends of casting patterns to a cylindrical sprue member. a method of determining the number of patterns which can be attached to the sprue member comprising the steps of:

(a) providing on a flat surface a radially outwardly extending calibrated scale along an arc scribed on a radius equal to the outer radius of said sprue member, and

(b) positioning a casting pattern on said surface so that:

(i) the end of the pattern to be attached to said sprue member lies on said arc,

(ii) the pattern extends radially beyond said arc,

(iii) one Side of the pattern is coincident with a calibration of said scale, whereby the circumferential space on said sprue member to be occupied by the pattern can be determined by the location on said scale of the side of the pattern opposite to said one side.

10. The method as claimed in claim 9 including the step of:

(c) placing against said opposite side of the pattern a member that extends toward the center point about which said arc is scribed, said member having a thickness equal to the desired circumferential spacing between the closest portions of adjacent patterns on said sprue member. 11. The method as claimed in claim 9 including the step of:

(c) placing the end of a pattern to be attached to said sprue member on a calibrated linear scale so that one face of the pattern lies in a plane containing a calibration of said linear scale, whereby the longitudinal space to be occupied by the pattern on said sprue member can be determined by the location on said linear scale of the face of the pattern opposite to said one face. 12. The method as claimed in claim 11 including the step of:

(d) placing against said opposite face of the pattern a member having a thickness equal to the desired longitudinal spacing between the closest portions of two adjacent patterns on said sprue member.

13. A method as claimed in claim 9 wherein said calibrated scale corresponds to a scale on said sprue member.

14. In a process of making a set-up by attaching the ends of casting patterns to a cylindrical sprue member, a method of determining the number of patterns which can be attached to the sprue member comprising the steps of t (a) providing on a at surface a scale having circularly spaced radial calibrations which extend toward a common center point,

(b) positioning a casting pattern on said surface over said scale so that:

(i) the end of the pattern to be attached to the sprue member is spaced from said center point a distance equal to the outer radius of the sprue member,

(ii) one side of the pattern lies in a plane normal to said surface and including one of said calibrations and said center point,

(c) and placing against the side of said pattern opposite to said one side a member which extends across said scale radially toward said center point, said member having a thickness equal to the desired circumferential spacing between the closest portions of adjacent patterns on said sprue member.

15'. A method as claimed in claim 14 wherein said scale includes an arc scribed on a radius equal to the outer radius of the sprue member, said calibrations being spaced along said arc.

16. In a process of making a set-up by attaching the ends of casting patterns to a cylindrical sprue member, a method of determining the number of patterns which can be attached to the sprue member comprising the steps of:

(a) providing on a flat surface a scale having circularly spaced, radial calibrations extending toward a center point,

(b) placing a casting pattern on said surface over said scale so that one side portion of the pattern abuts a side face of a first arm, said side face of said rst arm lying in a plane extending radially from said center point and containing one of said calibrations.

(c) positioning said pattern on said scale so that the end of the pattern to be attached to said sprue member is spaced from said center point a distance equal to the outer radius of the sprue member,

(d) and placing the side face of a second arm against the side of the pattern opposite said one side, said side face of said second arm lying inra plane extending radially from said center point. y y

References Cited UNITED STATES PATENTS 639,671 12/1899 De Smith.

878,819 2/1908 Mooney 33-75 1,226,141 5/1917 Sterling et al. 33-75 1,555,792 9/ 1925 Souder.

SAMUEL S, MATTHEWS, Primary Examiner