Notice is given that the following patent document contains original material subject to copyright protection. Accordingly, the copyright owner has no objection to the facsimile or digital download reproduction of all or part of the patent document but otherwise reserves all copyrights.
This non-provisional patent application is based on and claims the filing date benefit of U.S. provisional patent application (Application No. 63/088793) filed on Oct. 7, 2020.
The present invention generally relates to tapping heads used with CNC machines. More particularly, tapping heads reduce damage to the tap and damage to the workpiece caused by improper coordination of the axis feed drive and the spindle motor.
The term “synchronizing” in the milling industry refers to synchronizing movement between a CNC machine's axis feed drive and the spindle motor. Typically, the machine programmer tells the CNC machine what feed to use by simply dividing ONE by the number of threads. This number is then multiplied by the spindle's RPM to calculate the actual feed rate, so the tap follows its pitch into the hole.
During operation, CNC machines synchronize the motors used to feed and control the RPMs. Unfortunately, the motor in the CNC machine accelerates, deaccelerates, and reverses direction that can cause undesirable vibration and misalignment of the tapping head that can damage the tap and the threads formed in the workpiece.
What is needed is an improved tapping head that reduces vibration and misalignment and reduces damage to the tap and the workpiece.
A tapping head is configured to hold and drive different taps with a slip joint that introduces a small amount of play between the tap head and the tap to compensate for excessive lead that may damage the tap or the workpiece.
The tapping head includes a base configured to attach to a spindle on a milling machine. Connected to the inside cavity formed in the base is a drive coupler that connects to a driver configured to slide longitudinally inside a drive sleeve. Longitudinally aligned interior splines are formed on the drive sleeve that engages longitudinally aligned exterior splines formed on the upper section of the driver. During assembly, the driver is inserted into the drive sleeve. The two sets of splines radially lock the driver inside the drive sleeve and allow the driver to move inward and outward longitudinally. When assembled, the driver's end is exposed and receives the shaft on a tab. A lock nut attaches to the lower section of the driver to hold a tap securely on the end of the driver.
Located inside the lower cavity of the base and surrounding the upper section of the drive coupler is a clutch pack. The clutch pact includes one center support plate that slides longitudinally into the base and includes lugs that engage slots to hold the support plate in a fixed radial position on the base. Located on opposite sides of the support plate is at least one friction disc. In the embodiment shown herein, two friction discs are positioned on opposite sides of the support disc.
Extending between the bottom surface of the drive coupler and the upper end of the driver is a plurality of axially aligned thrust springs. During operation, the thrush springs force the driver downward from the drive coupler that forces the driver and the tap into the workpiece.
The disposed inside the base and under the lower friction disc is a circular pressure ring. Mounted on the pressure ring is a plurality of clutch springs that force the pressure ring upward and press against the clutch pack. The clutch pack includes two friction discs located on opposite sides of a support disc. When assembled, the two fiction discs press against the inside surface of the base and the lower surface of the pressure ring. When the tapping head is assembled, the clutch pack is disposed around the tipper section of the drive coupler. The two friction discs include lugs that fit into slots formed on the upper section of the drive coupler that couple the two fiction discs to the drive coupler. The support plate includes lugs that couple it to the base.
Located over the top surface of the base is a thrust plate that attaches to the top surface of the drive coupler. Extending downward from the base is a retainer spring assembly that connects the base to the driver. During use, the retainer spring assembly applies a upward biasing force to the driver, which provides an additional pulling force to the driver to quickly pull a tap attached to the driver from the workpiece.
Surrounding the drive coupler, the driver, the pressure ring, and the clutch pack is an outer clutch cover. The clutch cover includes internal threads configured to selectively attach to external threads formed on the base. Extending upward from the clutch cover is a plurality of drive pins that radially lock the clutch cover and the pressure ring. Thus, by tightening the clutch cover on the base, the force exerted by the thrust springs on the pressure ring can be adjusted. Also, by changing the amount of force exerted on the pressure ring, the amount of frictional forces exerted by the clutch pack adjusted.
Because the location of the clutch pack is affected by the clutch springs, the operator can easily change the feed rate of the tap without fear of damaging the tap. For example, the operator can program a machine's feed rate about 90 to 95% of the mathematically perfect feed rate. The tap then advances the spindle's position a small amount per revolution, tensioning the lighter tension spring without risking tap damage.
When a lower driving force is needed (i.e., taps the 0-80 and 2-56 up to 4-40 sizes), the clutch cover is loosen. When greater driving force is needed for larger taps (i.e., taps 5-40 up to ⅜-16 or ½-13), the clutch cover is tightened on the base to apply more force to the pressure ring, causing it to exert greater force against the clutch pack giving the tapping head more driving power.
If rigid tapping is desired, an optional lockup feature is provided that locks the clutch pack to the drive sleeve. To accomplish this, three dog screws extend inward from the base and press against the sides of the drive sleeve. When the dog screws are tightened, the drive sleeve is locked to the base, which makes the tapping head a solid driving unit with a slip joint.
Disclosed herein is a tapping head 1 configured to hold and drive different size taps 210 that includes a slip joint that introduces a small amount of axial movement or play between the tapping head 1 and the tap 210 to compensate for excessive lead that may damage the tap 210 or a workpiece. The tapping head 1 also includes an adjustable clutch pack. 48 designed to prevent the tap 210 from breaking. Before operating, the clutch pack 48 allows the operator to pre-load the clutch pack 48 to sufficiently drive the tap 210 but allows the clutch pack 48 inside the tapping head 1 to slide if the tap 210 becomes dull. The tapping head 1 also includes an optional lock-up feature that allows the operator to selectively lock and fully engage the clutch pack 48. The driver 125 includes external threads 133 configured to attached to commercially available lock nut 150 that tightens the driver 125 to a tap 210.
As shown more clearly in
Formed on the recessed neck 18 is at least one optional dog screw bore 9 shown more clearly in
As shown in
As shown in
Located inside the recessed cavity 4 in the base 2 is a bearing bushing 20. The bearing bushing 20, shown more clearly in
Located below and aligned coaxially with the bearing bushing 20 is a drive coupler 30 with a cylindrical body 31 and an upward extending perpendicularly aligned neck 34. The drive coupler 30, shown more clearly in
During assembly, the neck 34 on the drive coupler 30 is inserted into the center bore 26 formed in the bearing bushing 20. The top surface of the neck 34 is registered with the top edge of neck 26 and the top surface of the cylindrical body 31 is positioned tinder the base's circular flange 22. Formed on the perimeter edge of the top surface of the neck 34 are three bores 38 that receive the three screws 21 that extend downward from the thrust plate 10. As mentioned above, the screws 21 extend through tje center hole formed in the base 2 and hold the neck 34 of the drive coupler 30 inside the cylindrical body 5.
Also, formed on the neck 34 are three laterally aligned neck bores 36 that are aligned and registered with dog bores 28 formed on the bearing bushing 20.
Formed on the top surface of the cylindrical body 31 of the drive coupler 30 are axially aligned pinholes 32 which are aligned and registered with pinholes 23 formed on the circular flange 22 on the bearing bushing 20. Formed on the sides of the cylindrical body 31 are three dog holes 33 that communicate with the holes 28 on the bearing bushing 20 and with the dome cavity 37 in the drive coupler 30. Extending upward in the sidewall of the cylindrical body 21 and equally spaced apart around the dome cavity 37 are three axially aligned spring slots 39.
Located around the cylindrical body 31 on the drive coupler 30 is the drive sleeve 65. The drive sleeve 65, shown more clearly in
During assembly, the bearing bushing 20 is axially aligned with and fits over the neck 34 on the drive coupler 30. Next, the pinholes 23 on the bearing bushing 20 are aligned with the pinholes 32 formed on the drive coupler 30. Two dog pins 39, shown in
After being assembled, the bearing bushing 20 and the drive coupler 30 are then inserted into the cylindric cavity 7 formed on the base 2. The neck 24 on the bearing bushing 20 fits into the base's neck bore 8 and the dog holes 28 and 38 on the necks 24, 34, respectively, are aligned with the threaded dog holes 9 formed on base 2. The drive screws 17 are then inserted to the threaded screw bores 9 and into dog holes 28 and bore 38 to couple the base 2, the bearing bushing 20 and the drive couple 30 together forming a single locked, three-part structure.
Also, during assembly, the cylindrical body 31 on the drive coupler 30 slides into the upper region 66 on the drive sleeve 65. The cylindrical body 31 is rotated so the dog holes 33 are aligned with the pinholes 71 formed on the drive sleeve 65. A dowel pin 73 is then inserted into each pair of aligned holes 33, 71, to couple the drive coupler 30 to the drive sleeve 65.
The outer diameter of the drive sleeve 65 is less than the inside diameter of the cylindrical lower cavity 7 on the base 2. During assembly, the drive sleeve 65 is inserted into the lower cylindrical cavity 7. A circular space 77 is created between the outer surface of the drive sleeve 65 and the inside surface of the cylindrical lower cavity 7. Inserted into this circular space 77 is a clutch pack 48 that comprises two circular, flat friction discs 50 stacked on opposite sides of a flat support disc 58.
As shown in
The support disc 58, shown more clearly in
As shown in
Also extending between the clutch cover 110 and the base 2 one or more set screws 75 that the operator uses to lock the clutch cover 110 onto the base 2 after the clutch cover 110 has be tightened to its desired location. Each set screw 75 includes an upper tab that fits into one of a plurality of small bores 12 formed on the bottom surface of the base (see
Extending inside the center bore 68 of the drive sleeve 65 is an elongated driver 125 shown in
The drive coupler 30 includes a plurality of spring slots 39 each configured to receive a thrust spring 40. During assembly, one end of a thrust spring 40 is placed inside each spring slot 39 and the opposite end presses against the upper end surface of the driver 125 when the driver 125 is placed inside the drive sleeve 65. Thrust springs 40 exert a downward force on the driver 125 thereby providing a ‘soft engagement’ for the tap 210.
Disposed around the clutch pack 48 and attaching to the base 2 is a clutch cover 110. The clutch cover 110, shown more clearly in
After assembly, the lower ends of clutch springs 56 press against the flange surface 114 to force the clutch pack 48 upward.
Installed inside the center bore 112 and below the flange surface 114 is a bronze bearing 120. Mounted under the bearing 120 is an upper O-ring 121 that fits into a o-ring raceway formed along the upper edge of the drive cover 140. The o-ring 121 creates a water-tight seal between the drive cover 140 and the clutch cover 110.
During assembly, the clutch cover 110 aligned so that its internal threads 113 can mesh with the external threads 6 formed on the base 2. As the clutch cover 110 is rotated and lightened on the base 2, compressing forces are exerted by the clutch springs 56 on the clutch pack 48. By tightening or loosening the clutch cover 110 on the base 2, the operator operatoro can adjust the amount force exerted on the clutch pack and control the amount of slippage of the clutch pack 48. The set screws 75 are then tightened to lock the clutch cover 110 to the base 2.
Disposed between the base 2 and the clutch cover 110 is a retainer ring assembly 89 that prevents the clutch cover 110 from being excessively pulled away from the base 2. The retainer spring assembly 89 includes a retainer spring 90, an upper cap 91, a lower adapter cap 94, and an optional limit wire 98. During assembly, the upper cap 91 includes a wide head that is inserted into an upper recessed cavity formed on the neck 34 of the drive coupler 30 Attached to the head is a shaft that is sufficient in length to extend 30 and into the dome cavity 37 formed inside the drive coupler 30. Formed on the tower end of shaft is a hole.
The lower adapter cap 94 the lower cavity 130 and presses against the shoulder 131 in the driver 125. The upper end of the lower adapter cap 94 includes an extension lab with a hole. The extension tab is positioned in the upper cavity 129 and the adapter cap 94 is positioned in the lower cavity 130 (see
After inserting the driver 125 into the drive sleeve 65 and attaching the drive cover 140 to the drive sleeve 65, the lower threaded end of the driver 125 extends through the lower opening 142 formed on the drive cover 140. During use, the shaft 212 of a tap 210 is then inserted into the tapered, lower center cavity 132 formed in the driver 125. A lock nut 150, (also called a collet) is then attached to the external threads 133 on the driver 125. When the lock nut 150 is tighten, the tapered sidewalls of the driver 125 are forced inward and press against the tap's shaft 212 to securely hold the tap 210 on the driver 125.
To assemble the taping head 1, the cylindrical body 31 on the drive coupler 30 is inserted into the center bore 68 formed on the upper region 66 of the drive sleeve 65. The cylindrical body 31 is rotated so that the holes 33 are aligned with the pinholes 71 formed on the drive sleeve 65. A dowel pin 73 is (hen inserted into each pair of aligned holes 33, 71, to connect the drive coupler 30 to the drive sleeve 65.
Next, the clutch pack 48 is positioned inside the lower cavity 7 of the base 2 and surrounds the drive coupler 30 and the upper section of the drive sleeve 65. Next, the pressure ring 80 is placed around the drive sleeve 65 and positioned inside the lower cavity 7 of the base 2 and so that the top surface 83 of the pressure ring 80 presses against the lower clutch disc 50.
Next, the thrust springs 40 are placed into the spring slots 39 on the drive coupler 30 and clutch springs 56 are inserted into each clutch spring bore 84 formed on the pressure ring 80.
Next, the retainer spring assembly 89 is attached to the drive coupler 30 and the driver 125.
Next, the center bore 112 on the clutch cover 110 is extended over the driver 125 and the internal threads 113 are attached to the external threads 6 on the base 2. The clutch cove 110 is tightened onto the base 2 so that thrust springs 40 supply resistant force between the pressure ring 80 and the clutch cover 110 to create the desired frictional forces. The driver cover 140 is then attached to the end of the clutch cover 110. A lock nut 150 is then attached to the external threads 133 on the driver 125.
During use, the base 2 is bolted to a spindle 200 attached to a CNC machine. When the spindle 200 is activated and begins to rotate, the base 2 rotates. When the clutch cover 10110 is tightened on the base 2, the clutch pack 48 begins to rotate. Rotation of the clutch pack causes the pressure ring 80 to rotate. When the clutch cover 110 is rotated on the base 2 to adjust the amount of slippage. As stated above, by loosening or tightening the clutch cover 110 on the base 2, the amount of pressure exerted by the thrust springs 40 on the pressure ring 80 is adjusted.
During operation, the spindle 200 causes the base 2 to rotate which causes the drive coupler located inside the base 2. Because the clutch pack 48 is pressed against the drive coupler 30, rotation of the drive coupler 20 causes the drive sleeve 65 and the driver 125 to rotate. When the tap 210 undergoes torque that exceeds the frictional forces exerted by the clutch pack 48, the clutch pack 30 will automatically slip to prevent damage to the tap 210.
Because the drive sleeve 65 can slide axially over the driver 125, damage to the tap 210 is prevented.
As stated above, the operator may tighten the dog screw 17 into the bore 9 located on the base 2 to lock the base 2 to the bearing bushing 20 and drive coupler 30. Fixing the base 2 to the bearing bushing 20 and the drive coupler 30 disengages operation of the clutch pack 48 so that the driver 125 rotates with the drive coupler 30.
In compliance with the statute, the invention described has been described in language more or less specific on structural features. It should be understood however, that the invention is not limited to the features shown, since the means and construction shown, comprises the preferred embodiments for putting the invention into effect. The invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the amended claims, appropriately interpreted under the doctrine of equivalents.
Number | Date | Country | |
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63088793 | Oct 2020 | US |