BURR AND METHOD OF PULPSTONE DRESSING
United States Patent 3608536
A method of dressing a pulpstone by employing a burr having teeth dimensioned to be completely inserted into the peripheral surface of the pulpstone to impart grooves of controlled depth therein and thereby define the land portions between the grooves to accurately control the grinding surface of the pulpstone. A smooth peripheral edge portion on the burr initially contacts the pulpstone to position the burr and bring it up to speed before traversing the pulpstone.
US Patent References:
/1118671.html
Millard - November 1914 - 1118671
/1268624.html
Riley - June 1918 - 1268624
Machine for truing grinding wheels
Smith - April 1930 - 1753448
Apparatus for crush dressing grinding wheels
Wilson - December 1948 - 2456762
Means for forming the surface of grinding wheel
Scrivener - April 1949 - 2468241
/1118671.html
Millard - November 1914 - 1118671
/1268624.html
Riley - June 1918 - 1268624
Machine for truing grinding wheels
Smith - April 1930 - 1753448
Apparatus for crush dressing grinding wheels
Wilson - December 1948 - 2456762
Means for forming the surface of grinding wheel
Scrivener - April 1949 - 2468241
Application Number:
04/812662
Publication Date:
09/28/1971
Filing Date:
04/02/1969
View Patent Images:
Export Citation:
Assignee:
I. W. Roberts Manufacturing Co., Inc. (Lockport, NY)
Primary Class:
International Classes:
B24B53/00; B24B53/14
Field of Search:
125/11,38
Primary Examiner:
Whitehead, Harold D.
Parent Case Data:
CROSS-REFERENCE TO A RELATED APPLICATION
This application is a continuation-in-part of application Ser. No. 751,312 filed Aug. 8, 1968 on a burr and method of pulpstone dressing and now abandoned.
Claims:
What I claim is
1. The method of dressing a pulpstone comprising: providing a burr having spaced teeth and land-defining surfaces therebetween and a smooth peripheral edge portion adjacent one end of said burr with the teeth and land-defining surfaces of the burr extending from the smooth edge portion toward the other end thereof; initially applying the smooth edge portion only of the burr against the surface of the pulpstone; rotating the pulpstone and thereby initiating rotation of the burr prior to engagement of the burr teeth with the stone; and inserting the teeth of the burr completely into the surface of the pulpstone while traversing the burr along the length of the pulpstone having land portions therebetween.
2. The method of dressing a pulpstone as defined in claim 1, including rotating the burr until its peripheral speed reaches that of the pulpstone before traversing the burr along the length of the pulpstone.
3. A burr for dressing a pulpstone to impart grooves of predetermined depth and width in the surface of said pulpstone spaced apart by land portions of predetermined width comprising: a cylindrical element having an outer peripheral surface provided with a plurality of spaced teeth; the height and width of said teeth corresponding to the depth and width of said said teeth being adapted to be completely inserted into the surface of the pulpstone to form grooves of said predetermined depth; said cylindrical element having land-defining surfaces between the root portions of said teeth of a width corresponding to that of said land portions and adapted to fully engage the land portions of said pulpstone, said cylindrical element also having a smooth peripheral edge portion adjacent one end thereof; said teeth extending from said smooth edge portion toward the other end of said cylindrical element.
4. A burr as defined in claim 3, wherein said teeth are parallel.
5. A burr as defined in claim 4, wherein the length of the teeth are disposed at an angle relative to a plane cut along the axis of the cylindrical element.
6. A burr as defined in claim 3 wherein said edge portion of said cylindrical element has a diameter equal to that of a circle circumscribed through the root portions of said teeth and a radius equal to that of said land-defining surfaces.
7. A burr for dressing a pulpstone to impart in the surface of the pulpstone grooves of predetermined depth and width spaced apart by land portions of predetermined width comprising a cylindrical element having an outer peripheral surface provided with a smooth edge portion and a plurality of spaced teeth extending therefrom in a generally axial direction, said teeth being adapted to penetrate the pulpstone surface and to impart grooves of the desired depth and width when inserted therein to a predetermined depth, said edge portion being of a diameter defining said predetermined depth of tooth penetration when engaged against a pulpstone.
8. The method of dressing a pulpstone comprising, providing a burr having spaced teeth and a tooth-free peripheral edge portion spaced inwardly from the tip ends of the teeth into the pulpstone, applying the edge portion of the burr against the pulpstone to locate the former relative to the latter, rotating the pulpstone and thereby rotating the burr and traversing the rotating pulpstone with the rotating burr.
9. The method of dressing a pulpstone as defined in claim 1 including pressing the land-defining surfaces of the burr against the land portions of the pulpstone.
1. The method of dressing a pulpstone comprising: providing a burr having spaced teeth and land-defining surfaces therebetween and a smooth peripheral edge portion adjacent one end of said burr with the teeth and land-defining surfaces of the burr extending from the smooth edge portion toward the other end thereof; initially applying the smooth edge portion only of the burr against the surface of the pulpstone; rotating the pulpstone and thereby initiating rotation of the burr prior to engagement of the burr teeth with the stone; and inserting the teeth of the burr completely into the surface of the pulpstone while traversing the burr along the length of the pulpstone having land portions therebetween.
2. The method of dressing a pulpstone as defined in claim 1, including rotating the burr until its peripheral speed reaches that of the pulpstone before traversing the burr along the length of the pulpstone.
3. A burr for dressing a pulpstone to impart grooves of predetermined depth and width in the surface of said pulpstone spaced apart by land portions of predetermined width comprising: a cylindrical element having an outer peripheral surface provided with a plurality of spaced teeth; the height and width of said teeth corresponding to the depth and width of said said teeth being adapted to be completely inserted into the surface of the pulpstone to form grooves of said predetermined depth; said cylindrical element having land-defining surfaces between the root portions of said teeth of a width corresponding to that of said land portions and adapted to fully engage the land portions of said pulpstone, said cylindrical element also having a smooth peripheral edge portion adjacent one end thereof; said teeth extending from said smooth edge portion toward the other end of said cylindrical element.
4. A burr as defined in claim 3, wherein said teeth are parallel.
5. A burr as defined in claim 4, wherein the length of the teeth are disposed at an angle relative to a plane cut along the axis of the cylindrical element.
6. A burr as defined in claim 3 wherein said edge portion of said cylindrical element has a diameter equal to that of a circle circumscribed through the root portions of said teeth and a radius equal to that of said land-defining surfaces.
7. A burr for dressing a pulpstone to impart in the surface of the pulpstone grooves of predetermined depth and width spaced apart by land portions of predetermined width comprising a cylindrical element having an outer peripheral surface provided with a smooth edge portion and a plurality of spaced teeth extending therefrom in a generally axial direction, said teeth being adapted to penetrate the pulpstone surface and to impart grooves of the desired depth and width when inserted therein to a predetermined depth, said edge portion being of a diameter defining said predetermined depth of tooth penetration when engaged against a pulpstone.
8. The method of dressing a pulpstone comprising, providing a burr having spaced teeth and a tooth-free peripheral edge portion spaced inwardly from the tip ends of the teeth into the pulpstone, applying the edge portion of the burr against the pulpstone to locate the former relative to the latter, rotating the pulpstone and thereby rotating the burr and traversing the rotating pulpstone with the rotating burr.
9. The method of dressing a pulpstone as defined in claim 1 including pressing the land-defining surfaces of the burr against the land portions of the pulpstone.
Description:
BACKGROUND OF THE INVENTION
This invention relates to a method for dressing grindstones and, more particularly, to the use of a novel burr for dressing such stones.
In the papermaking industry grinding machines incorporating grindstones, hereinafter referred to as pulpstones, are employed to break up logs or blocks of wood into pulp. The pulpstone is dressed by treating the surface of the pulpstone with a burr which rotates in contact with the pulp stone and roughens its surface to form therein a plurality of grooves the pattern and depth of which determines the characteristics of the pulp fiber produced by the pulpstone. The pulpstone is grooved in order to provide increased pressure per unit area and also to obtain a higher freeness, the term "freeness," as used in the paper-making industry, being the rate of drainage or water release from the pulp.
As the pulpstone-grinding surface or the land area between the grooves wears away, production decreases, unit-energy consumption increases and freeness decreases. Accordingly, it is necessary to reshape or redress the peripheral surface or working face of the pulpstone periodically in order to maintain the selected profile on such surface for efficiently producing a uniform quality of pulp.
This is effected by a burr which is mounted on a support having means for moving the burr toward and away from the pulpstone and for traversing the burr along the pulpstone. The burr-tooth pattern is conventionally designed to produce a variety of groove depths in the pulpstone, depending upon the positioning of the burr relative to the surface of the pulpstone. Stating this another way, the teeth of the burr are normally higher than necessary so that it can be used for forming grooves of different depths thereby to obtain a variety of patterns with the same burr. In order to obtain a predetermined pattern on the pulpstone, the operator must precisely position the burr so that the teeth are inserted into the surface of the pulpstone to the desired depth, and no more. As a practical matter, this has proven to be very difficult, resulting in stone patterns in which the grooving is deeper than intended and thereby producing land surfaces between the grooves which are narrower than intended. Such narrower land surfaces not only reduce the overall grinding surface area of the pulpstone, but are weaker and tend to chip and adversely affect the operation of the dressed pulpstone. Moreover, when employing higher pointed teeth than are necessary to produce a groove of a predetermined depth in the pulpstone, there is a tendency for the pulpstone to chip at the edge of its land surface as the tip or crest of the burr tooth leaves the groove. When the groove is shallower than intended, freeness decreases and the flow of fibers through the grooves is seriously impeded.
SUMMARY OF THE INVENTION
The present invention, as hereinafter described, obviates the above-noted disadvantages by employing a simple and novel burr for controlling the depth of the groove desired in the pulpstone without requiring the exercise of skill or judgement on the part of the operator. In accordance with one aspect of my invention, the burr is provided with a tooth height and width precisely dimensioned to the depth and width of groove desired to be imparted to the pulpstone so as to control the land area or grinding-surface area of the pulpstone. The operator then merely bottoms the burr against the pulpstone to produce the intended pattern depth, and the possibility of obtaining a pattern depth which might be shallower or deeper than intended is precluded.
It is sometimes difficult to determine when the burr is precisely bottomed and it has been found advantageous to facilitate bottoming of the burr against the pulpstone. Also, the resistance and drag resulting from initial contact between the static burr teeth and the rotating pulpstone strains and dulls the burr teeth, and preferably is avoided. This also is accomplished with my invention which is characterized in another aspect thereof by the provision of a burr having a smooth, i.e. tooth-free, bottoming peripheral edge portion for initially engaging the pulpstone to locate the burr at the precise tooth depth for the desired pattern and to bring the burr up to rotational speed before engaging the pulpstone with the toothed portion of the burr.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view of a dressing apparatus usable in carrying out the principles of this invention;
FIG. 2 is a side elevational view of the dressing apparatus of FIG. 1;
FIG. 3 is a schematic fragmentary view of a burr of the present invention as it appears in a dressing operation;
FIG. 4 is a corresponding view of a conventional burr as it appears in the same dressing operation; and
FIG. 5 is an enlarged fragmentary front elevational view illustrating the leading edge of the burr in engagement with a pulpstone.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawing, there will be seen a pulpstone dressing apparatus comprising a burr 10 mounted on a carriage 12 for reciprocating movement relative to the carriage toward and away from the surface of a pulpstone 14 which is suitably journaled in a grinding machine indicated at 15 for rotation about its axis. Carriage 12 is slidable on a pair of guide rods 16 and 18 secured at their ends to bracket end members 20 and 22 which in turn are secured to the top of the grinding machine as by means of bolts 24. A fluid-actuated cylinder 26 is connected between bracket end members 20 and 22 and is provided with a piston (not shown) having a piston rod extending beyond bracket end member 22 and connected to a slide block 28. A carriage rod 30 is connected at one end to carriage 12 and at its other end to slide block 28. Supplying fluid pressure to opposite sides of the piston effects reciprocating movement of carriage 12. Thus, the burr 10 is mounted for reciprocating movement with carriage 12 longitudinally of pulpstone 14 for traversing the same.
Means are provided for moving burr 10 toward and away from the surface of pulpstone 14, such means comprising a cross-slide 34 having a forked end 36 in which is journaled burr 10 on a shaft 38 extending between the bifurcations of said forked end 36. The cross-slide 34 is provided with a portion 40 having internal threads through a collar 46 on a bracket 48 and is provided with a hand-wheel 50 having a handle 52 thereon. Thus, rotating handwheel 50 will cause screw 40 to be rotated and since axial movement thereof is restrained by collar 46, the nut 40 together with cross-slide 34 will move axially relative to screw 44 to move the burr 10 into and out of engagement with the surface of the pulpstone.
Burr 10 comprises a cylindrical element having an outer peripheral surface provided with a plurality of spaced-apart teeth 60. However, unlike conventional burrs wherein the tooth pattern differs from the pattern desired to be imparted to the stone as shown in FIG. 4, it is a particular feature of this invention that the height and width of the burr teeth 60 correspond exactly to the depth and width of the groove to be imparted, and that the surface 62 of the burr between the root portions of adjacent teeth 60 corresponds exactly to the land surfaces 64 desired on pulpstone 14. As a result, when burr 10 is fully engaged with stone 14 the grooves in the stone are defined by the entire surface area of teeth 60 and the land area or grinding surface of the pulpstone is accurately controlled.
FIG. 4 illustrates a standard prior art burr 10' provided with a plurality of parallel teeth 60' to dress the same pattern in pulpstone 14. As opposed to the burr of the present invention, it will be noted that only a portion of the teeth 60' can be employed to impart grooves of the desired depth in pulpstone 14, the precise degree of penetration being critical and being dependent on the skill of the operator in pressing the burr 10' against the surface of pulpstone 14. Land surfaces 64 are defined only by the degree of penetration of teeth 60', and not by complementary surfaces on the burr, as in the instant invention, and the burr cannot be bottomed without departing from the desired surface pattern.
Another important feature of this invention is the provision of a smooth peripheral edge portion or rim 66 located on the leading edge of burr 10 relative to the direction of traverse of burr 10 relative to pulpstone 14, and extending inwardly from one end 68 thereof. The diameter of edge portion 66 is equal to that of a circle circumscribed through the root portions of teeth 60, the rim 66 and surfaces 62 having a common radius. In other words, rim 66 is spaced inwardly from the outer ends of teeth 60 a radial distance equal to the depth of the groove to be imparted by teeth 60. Teeth 60 extend from the inner end of rim 66 toward the other end 70 of burr 10 and preferably extend in a direction slightly askew or at an angle relative to a plane cut along the axis of the burr as shown in FIGS. 1 and 5.
It should be appreciated that the principles of this invention contemplate the use of other tooth designs such as forming the teeth parallel to the axis of the burr or in the form of a continuous thread extending in a direction slightly askew to a plane normal to the axis of the burr. Also, a "diamond" type design may be utilized whereby the land defining grooves are made at right angles to each other to form teeth lying in parallel horizontal and vertical rows.
When a dressing operation is performed, either prior to initial use of the pulpstone or during a reshaping operation, the operator rotates handwheel 50, advancing the locating rim onto the end peripheral surface of pulpstone 14 until such rim 66 fully engages stone 14 to insure that the burr is completely bottomed on the stone as shown in FIG. 5. Pulpstone 14 is rotated, and burr 10 is rotated by the rotating pulpstone 14, being brought up to the peripheral speed of pulpstone 14 before burr 10 is traversed across the surface of pulpstone 14. Fluid under pressure is admitted to cylinder 26 causing movement of carriage 12 for traversing burr 10 across the surface of pulpstone 14. Thus, before teeth 60 engage pulpstone 14, burr 10 is fully and precisely bottomed and is rotating at the same peripheral speed as pulpstone 14.
The present invention thus provides a novel and simple expedient for controlling the depth of the groove desired in a pulpstone, and thereby the land area or grinding surface area of the pulpstone, without requiring the exercise of skill or judgment on the part of the operator. Also, error caused by play in the burr-supporting structure is eliminated. This is effected by the provision of a burr having a tooth height precisely dimensioned to the depth of groove to be imparted to the pulpstone with the spaces between the teeth of the burr abutting the land portions of the pulpstone. The provision of a burr having a smooth, peripheral edge portion for initial bottoming engagement with a pulpstone facilitates and insures accurate positioning of the burr relative to the stone, and rotation of the burr is initiated by contact of said bottoming edge portion with the pulpstone whereby the peripheral speed of the burr is caused to equal the peripheral speed of the pulpstone prior to contact of the burr teeth therewith. This avoids the resistance and drag encountered if the burr is static when its teeth initially engage the stone.
It will be appreciated that the locating feature of my invention can be used with burrs which do not include the tooth pattern of my invention. For example, a bottoming rim such as provided at 66 in the burr of FIG. 3 and having a diameter corresponding to the depth of tooth penetration desired for a particular pattern can be provided on the burr of FIG. 4, the burr position determined by pressing rim 66 against the pulpstone being maintained by the burr-supporting apparatus as the pulpstone is traversed by the burr.
A preferred embodiment of this invention having been described and illustrated, it is to be understood that this has been done by way of illustration only and that this invention can be utilized with other burr-supporting arrangements.
This invention relates to a method for dressing grindstones and, more particularly, to the use of a novel burr for dressing such stones.
In the papermaking industry grinding machines incorporating grindstones, hereinafter referred to as pulpstones, are employed to break up logs or blocks of wood into pulp. The pulpstone is dressed by treating the surface of the pulpstone with a burr which rotates in contact with the pulp stone and roughens its surface to form therein a plurality of grooves the pattern and depth of which determines the characteristics of the pulp fiber produced by the pulpstone. The pulpstone is grooved in order to provide increased pressure per unit area and also to obtain a higher freeness, the term "freeness," as used in the paper-making industry, being the rate of drainage or water release from the pulp.
As the pulpstone-grinding surface or the land area between the grooves wears away, production decreases, unit-energy consumption increases and freeness decreases. Accordingly, it is necessary to reshape or redress the peripheral surface or working face of the pulpstone periodically in order to maintain the selected profile on such surface for efficiently producing a uniform quality of pulp.
This is effected by a burr which is mounted on a support having means for moving the burr toward and away from the pulpstone and for traversing the burr along the pulpstone. The burr-tooth pattern is conventionally designed to produce a variety of groove depths in the pulpstone, depending upon the positioning of the burr relative to the surface of the pulpstone. Stating this another way, the teeth of the burr are normally higher than necessary so that it can be used for forming grooves of different depths thereby to obtain a variety of patterns with the same burr. In order to obtain a predetermined pattern on the pulpstone, the operator must precisely position the burr so that the teeth are inserted into the surface of the pulpstone to the desired depth, and no more. As a practical matter, this has proven to be very difficult, resulting in stone patterns in which the grooving is deeper than intended and thereby producing land surfaces between the grooves which are narrower than intended. Such narrower land surfaces not only reduce the overall grinding surface area of the pulpstone, but are weaker and tend to chip and adversely affect the operation of the dressed pulpstone. Moreover, when employing higher pointed teeth than are necessary to produce a groove of a predetermined depth in the pulpstone, there is a tendency for the pulpstone to chip at the edge of its land surface as the tip or crest of the burr tooth leaves the groove. When the groove is shallower than intended, freeness decreases and the flow of fibers through the grooves is seriously impeded.
SUMMARY OF THE INVENTION
The present invention, as hereinafter described, obviates the above-noted disadvantages by employing a simple and novel burr for controlling the depth of the groove desired in the pulpstone without requiring the exercise of skill or judgement on the part of the operator. In accordance with one aspect of my invention, the burr is provided with a tooth height and width precisely dimensioned to the depth and width of groove desired to be imparted to the pulpstone so as to control the land area or grinding-surface area of the pulpstone. The operator then merely bottoms the burr against the pulpstone to produce the intended pattern depth, and the possibility of obtaining a pattern depth which might be shallower or deeper than intended is precluded.
It is sometimes difficult to determine when the burr is precisely bottomed and it has been found advantageous to facilitate bottoming of the burr against the pulpstone. Also, the resistance and drag resulting from initial contact between the static burr teeth and the rotating pulpstone strains and dulls the burr teeth, and preferably is avoided. This also is accomplished with my invention which is characterized in another aspect thereof by the provision of a burr having a smooth, i.e. tooth-free, bottoming peripheral edge portion for initially engaging the pulpstone to locate the burr at the precise tooth depth for the desired pattern and to bring the burr up to rotational speed before engaging the pulpstone with the toothed portion of the burr.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view of a dressing apparatus usable in carrying out the principles of this invention;
FIG. 2 is a side elevational view of the dressing apparatus of FIG. 1;
FIG. 3 is a schematic fragmentary view of a burr of the present invention as it appears in a dressing operation;
FIG. 4 is a corresponding view of a conventional burr as it appears in the same dressing operation; and
FIG. 5 is an enlarged fragmentary front elevational view illustrating the leading edge of the burr in engagement with a pulpstone.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawing, there will be seen a pulpstone dressing apparatus comprising a burr 10 mounted on a carriage 12 for reciprocating movement relative to the carriage toward and away from the surface of a pulpstone 14 which is suitably journaled in a grinding machine indicated at 15 for rotation about its axis. Carriage 12 is slidable on a pair of guide rods 16 and 18 secured at their ends to bracket end members 20 and 22 which in turn are secured to the top of the grinding machine as by means of bolts 24. A fluid-actuated cylinder 26 is connected between bracket end members 20 and 22 and is provided with a piston (not shown) having a piston rod extending beyond bracket end member 22 and connected to a slide block 28. A carriage rod 30 is connected at one end to carriage 12 and at its other end to slide block 28. Supplying fluid pressure to opposite sides of the piston effects reciprocating movement of carriage 12. Thus, the burr 10 is mounted for reciprocating movement with carriage 12 longitudinally of pulpstone 14 for traversing the same.
Means are provided for moving burr 10 toward and away from the surface of pulpstone 14, such means comprising a cross-slide 34 having a forked end 36 in which is journaled burr 10 on a shaft 38 extending between the bifurcations of said forked end 36. The cross-slide 34 is provided with a portion 40 having internal threads through a collar 46 on a bracket 48 and is provided with a hand-wheel 50 having a handle 52 thereon. Thus, rotating handwheel 50 will cause screw 40 to be rotated and since axial movement thereof is restrained by collar 46, the nut 40 together with cross-slide 34 will move axially relative to screw 44 to move the burr 10 into and out of engagement with the surface of the pulpstone.
Burr 10 comprises a cylindrical element having an outer peripheral surface provided with a plurality of spaced-apart teeth 60. However, unlike conventional burrs wherein the tooth pattern differs from the pattern desired to be imparted to the stone as shown in FIG. 4, it is a particular feature of this invention that the height and width of the burr teeth 60 correspond exactly to the depth and width of the groove to be imparted, and that the surface 62 of the burr between the root portions of adjacent teeth 60 corresponds exactly to the land surfaces 64 desired on pulpstone 14. As a result, when burr 10 is fully engaged with stone 14 the grooves in the stone are defined by the entire surface area of teeth 60 and the land area or grinding surface of the pulpstone is accurately controlled.
FIG. 4 illustrates a standard prior art burr 10' provided with a plurality of parallel teeth 60' to dress the same pattern in pulpstone 14. As opposed to the burr of the present invention, it will be noted that only a portion of the teeth 60' can be employed to impart grooves of the desired depth in pulpstone 14, the precise degree of penetration being critical and being dependent on the skill of the operator in pressing the burr 10' against the surface of pulpstone 14. Land surfaces 64 are defined only by the degree of penetration of teeth 60', and not by complementary surfaces on the burr, as in the instant invention, and the burr cannot be bottomed without departing from the desired surface pattern.
Another important feature of this invention is the provision of a smooth peripheral edge portion or rim 66 located on the leading edge of burr 10 relative to the direction of traverse of burr 10 relative to pulpstone 14, and extending inwardly from one end 68 thereof. The diameter of edge portion 66 is equal to that of a circle circumscribed through the root portions of teeth 60, the rim 66 and surfaces 62 having a common radius. In other words, rim 66 is spaced inwardly from the outer ends of teeth 60 a radial distance equal to the depth of the groove to be imparted by teeth 60. Teeth 60 extend from the inner end of rim 66 toward the other end 70 of burr 10 and preferably extend in a direction slightly askew or at an angle relative to a plane cut along the axis of the burr as shown in FIGS. 1 and 5.
It should be appreciated that the principles of this invention contemplate the use of other tooth designs such as forming the teeth parallel to the axis of the burr or in the form of a continuous thread extending in a direction slightly askew to a plane normal to the axis of the burr. Also, a "diamond" type design may be utilized whereby the land defining grooves are made at right angles to each other to form teeth lying in parallel horizontal and vertical rows.
When a dressing operation is performed, either prior to initial use of the pulpstone or during a reshaping operation, the operator rotates handwheel 50, advancing the locating rim onto the end peripheral surface of pulpstone 14 until such rim 66 fully engages stone 14 to insure that the burr is completely bottomed on the stone as shown in FIG. 5. Pulpstone 14 is rotated, and burr 10 is rotated by the rotating pulpstone 14, being brought up to the peripheral speed of pulpstone 14 before burr 10 is traversed across the surface of pulpstone 14. Fluid under pressure is admitted to cylinder 26 causing movement of carriage 12 for traversing burr 10 across the surface of pulpstone 14. Thus, before teeth 60 engage pulpstone 14, burr 10 is fully and precisely bottomed and is rotating at the same peripheral speed as pulpstone 14.
The present invention thus provides a novel and simple expedient for controlling the depth of the groove desired in a pulpstone, and thereby the land area or grinding surface area of the pulpstone, without requiring the exercise of skill or judgment on the part of the operator. Also, error caused by play in the burr-supporting structure is eliminated. This is effected by the provision of a burr having a tooth height precisely dimensioned to the depth of groove to be imparted to the pulpstone with the spaces between the teeth of the burr abutting the land portions of the pulpstone. The provision of a burr having a smooth, peripheral edge portion for initial bottoming engagement with a pulpstone facilitates and insures accurate positioning of the burr relative to the stone, and rotation of the burr is initiated by contact of said bottoming edge portion with the pulpstone whereby the peripheral speed of the burr is caused to equal the peripheral speed of the pulpstone prior to contact of the burr teeth therewith. This avoids the resistance and drag encountered if the burr is static when its teeth initially engage the stone.
It will be appreciated that the locating feature of my invention can be used with burrs which do not include the tooth pattern of my invention. For example, a bottoming rim such as provided at 66 in the burr of FIG. 3 and having a diameter corresponding to the depth of tooth penetration desired for a particular pattern can be provided on the burr of FIG. 4, the burr position determined by pressing rim 66 against the pulpstone being maintained by the burr-supporting apparatus as the pulpstone is traversed by the burr.
A preferred embodiment of this invention having been described and illustrated, it is to be understood that this has been done by way of illustration only and that this invention can be utilized with other burr-supporting arrangements.