FOR A NON-ROTATING TOOL HOLDER

Claim of Priority

[0001] This application claims priority to U.S. application number 16/506,139 filed on July 9, 2019, the entire contents of which are hereby incorporated in their entirety.

Field

[0002] An adjustable damping arrangement for a non-rotating tool holder uses springs to suspend a damper mass in the interior of the ram and damping rubber rings that can be selectively compressed to adjust the dynamic stiffness of the ram.

Background

[0003] Lathe cutting capability is limited by the dynamic stiffness of the machine tool structure. Cutting tools supported by narrow rams at long extensions on vertical lathes provide the reach to cut tall parts, but often lack adequate stiffness. The value of dynamic stiffness varies with frequency and is lowest at specific frequencies related to structural natural frequencies or modes. The minimum stiffness can be 50% or less than the stiffness at the rest of the frequencies, and defines the cutting capacity of the machine. The frequency, stiffness, modal mass, and damping can vary as the machine elements are moved over their operating ranges.

[0004] The critical characteristics of dynamic stiffness are static stiffness, mass, and damping. Static stiffness and mass are often dictated by the machine type and size and can be difficult to alter significantly. Damping which may be defined as the ability to absorb or neutralize vibrating energy can be increased through the addition of machine elements. Greater damping results in higher stiffness.

[0005] Adding a damper to the ram near the cutting tool will increase the cutting capacity of a vertical lathe. A spring-mass-damper may be tuned to a particular frequency for operation of the ram at the greatest extension, the lowest stiffness condition for the ram.

Brief Description of the Drawings

[0006] Figure 1 is a perspective view of a ram with a cutting tool attached. [0007] Figure 2 is a side sectional view of a ram showing a mass damper installed in the interior of the ram.

[0008] Figure 3 is a perspective view of the tie rods and the suspension springs used in a damper assembly.

[0009] Figure 4 is a perspective view of the tie rods connected to the front plate of a damper assembly and mounted on a tool holder.

[0010] Figure 5 is a perspective view of the tie rods, the tension rod, and the suspension springs of a damper assembly.

[0011] Figure 6 is a perspective view of the tie rods, the tension rod, and the suspension springs attached to the front plate of a damper assembly.

[0012] Figure 7 is a perspective view of a damper assembly mounted on a tool holder.

[0013] Figure 8 is a side sectional view of a damper assembly.

[0014] Figure 9 is a bottom view of the damper assembly showing the suspension for the damper mass.

[0015] Figure 10 is a perspective view of the damper assembly.

[0016] Figure 11 is a perspective view of the rear plate of the damper assembly.

[0017] Figure 12 is a side sectional view of another implementation of a ram showing a mass damper installed in the interior of the ram.

Description of the Preferred Embodiment

[0018] Figure 1 is a perspective view of a ram generally designated by the reference numeral 10. The ram 10 may be used on a lathe and comprises a hollow beam 12 having an interior wall 13 best seen in Figure 2. A cutting tool holder 14 may be mounted on the front end 16 of the ram 10 which may support one or more cutting tools 18. Although two tools 18 are shown in the drawing, only one tool at a time is used in a cutting operation. The ram may move vertically or horizontally during operation, but the ram 10 and the tools 18 do not rotate.

[0019] Figure 2 is a side sectional view of a ram 10 showing a damper assembly 21 having a damper mass 20 installed in the interior of the ram 10. The damper mass 20 may be mounted between a front plate 22 and a rear plate 24 in the interior of the hollow beam 12. Upper and lower tie rods 25 and 26, respectively, pass through the front plate 22, the damper mass 20, and the rear plate 24. Ring dampers in the form of stiff rubber rings 30 best seen in Figures 4, 5, and 6 are positioned between the damper mass 20 and the front and rear plates 22 and 24, respectively. As shown on Figures 3 and 8, tie rod nuts 27 may be used on the threaded ends 28 of the tie rods 25 and 26 to fix the distance between the front plate 22 and the rear plate 24.

[0020] As shown on Figures 6, 8, and 10, the ends of the tie rods 25 and 26 pass through a tie rod mounting block 32 that is positioned on an end bracket 23 that is mounted on the front plate 22. A tuning bolt 64 may be threaded into a tuning block 29 and may be mounted on the tie rod mounting block 32 by bolts 54. The end of the tuning bolt 64 abuts a tuning bolt spacer 65. A slotted disk 60 may be positioned between the end bracket 23 and the front plate 22, and the slotted disk 60 may be formed with a hex shaped center aperture 31 which engages a hex head end 41 on a tension rod 40. The slots 61 in the disk 60 may be engaged by a disk locking bolt (not shown) to prevent the disk 60 from rotating as explained more fully below.

[0021] As shown on Figures 3-6 suspension springs 34 may be used to support the damper mass 20 from the upper tie rod 25. The suspension springs 34 may be hung from suspension brackets 35 which rest on the upper tie rod 25. The suspension springs 34 pass through vertical bores 36 in the damper mass 20 (best seen in Figures 2 and 3) and hook onto support pins 37 which engage the bottom surface 38 of the damper mass 20. Eight suspension springs 34 are shown supporting the damper mass 20, four near the front plate 22 and four near the rear plate 24, but a fewer or a greater number of suspension springs may be used.

[0022] As shown in Figure 8, the tension rod 40 passes through the center of the damper mass 20 and is threaded into a plug 42 having a cam surface 43 mounted in a bore in the rear plate 24. The cam surface 43 engages a follower surface 46 on a locking lever 47 as shown on Figures 7, 8 and 11. As shown in Figure 7, the locking lever 47 has two locking feet 48 which are positioned near the outer periphery of the rear plate 24. Movement of the cam surface 43 toward the damper mass 20 causes the locking lever 47 to move radially outward toward periphery of the rear plate 24.

[0023] As shown in Figure 9, the support pins 37 may be threaded through the ends of the suspension springs 34 to support the bottom surface 38 of the damper mass 20. Thus, the upper and lower tie rods 25 and 26, respectively, do not have to squeeze the stiff rubber rings 30 with enough force to support the weight of the damper mass 20. The suspension springs 34 provide sufficient freedom of movement to the damper mass 20 so that it is able to damp the vibrations in the ram 10. [0024] As shown in Figure 10, the front plate 22 may have two locking pistons 51 positioned near the outer periphery of the front plate 22. The pistons 51 are actuated by bolts 66 which have a cam surface 67. Figure 8 shows the cam surface 67 on one of the bolts 66 that is used to force the locking piston 51 outward as the bolt 66 draws the cam surface 67 against the locking piston 51.

[0025] In order to install the damper into the ram, the following procedure may be used. The damper assembly 21 may be inserted into the interior of the ram 10 and the front plate 22 rests against the interior wall 13. Bolts 66 may then be tightened forcing the cam 69 to move the locking pistons 51 outward to secure the front plate 22 against the interior wall 13 of the ram. Next the tension rod 40 may be tightened (which also rotates the slotted disk 60) to draw the plug 42 into the bore in the rear plate 24 to force the locking lever 47 and the locking feet 48 against the interior wall 13 of the ram. The tension rod 40 is only tightened enough to remove any looseness in the fit of the damper assembly 21 in the bore of the hollow beam 12 and provide light contact pressure against the interior wall 13 of the ram. At this point in the installation, the rear plate 24 will be snug in the ram bore yet will be able to slide axially when the rubber rings 30 are compressed. To prevent the tension rod 40 from vibrating loose, a locking bolt (not shown) may be inserted into one of the slots 61 in the slotted disk 60 and threaded into the front plate 22 to prevent rotation of the disk 60 and loosening of the tension rod 40. The slots 61 in the disk 60 may be spaced differently from the threaded openings in the front plate 22 that receives the locking bolt. This difference operates as a Vernier and allows the disk 60 to be located at increments that are smaller than the spacing between adjacent slots 61.

[0026] The upper and lower tie rods 25 and 26 exert pressure on the stack of parts consisting of the rear plate 24, the rear rubber rings 30, the damper mass 20, the front rubber rings 30, the front plate 22, the end bracket 23 and the tie rod mounting block 32. The tie rod nuts 27 on the upper and lower tie rods 25 and 26 are set to the length of the components with no pressure on the rubber rings 30. In this adjustment, the rubber rings 30 are in their loosest state, and the damper frequency is low.

[0027] The dynamic stiffness of the ram may be adjusted by tuning the damper mass

20 to a particular frequency. The resonant frequency of the damper mass 20 may be adjusted to the resonant frequency of the ram by compressing the rubber rings 30.

[0028] In order to compress the rubber rings 30, the tuning bolt 64 is used. The tuning bolt 64 is threaded into the tuning block 29, and the end of the tuning bolt 64 abuts the tuning bolt spacer 65. Turning the tuning bolt 64 advances it into the tuning block 29 and presses onto the tuning bolt spacer 65, the slotted disc 60, and the front plate 22 to increase the compression on the rubber rings 30.

[0029] In use, the locking feet 48 mechanically couple the rear plate 24 to the interior wall 13 of the ram 10, and the locking pistons 51 couple front plate to the interior wall 13 of the ram 10. The front plate 22 and the rear plate 24 transfer vibration of the ram 10 to the rubber rings 30 which react against the damper mass 20 to absorb vibrational energy of the ram. Because the suspension springs 34 support the weight of the damper mass 20, and the upper and lower tie rods 25 and 26 do not have to squeeze the stiff rubber rings 30 with enough force to support the weight of the damper mass 20, the damper mass 20 has sufficient freedom of movement so that it is able to damp the vibrations in the ram 10.

[0030] Turning to Figure 12, another embodiment of a ram 100 is shown. The ram

100 may be used on a lathe and comprises a hollow beam 12 having an interior wall 13. A cutting tool holder 14 may be mounted on the front end 16 of the ram 100 which may support one or more cutting tools. A damper assembly includes a damper mass 20 installed in the interior of the ram 100. The damper mass 20 may be mounted between a front plate 22’ and a rear plate 24 in the interior of the hollow beam 12. The front plate 22’ is a unitary structure that can extend partially within the ram 100 yet also remain at least partially outside of the internal cavity of the ram 100 and also abut an end 52 of the ram 10 thereby acting as an enclosure of the hollow cavity within the ram 100. Upper and lower tie rods 25 and 26, respectively, pass through the damper mass 20 and the rear plate 24 and are received through bores 54 in the front plate 22’. A backing plate 56 can be fitted onto the front plate 22’ and include bores 58 for receiving the upper and lower tie rods 25 and 26. The threaded ends 28 can extend through both the bores 54 in the end plate 22’ and the bores 58 in the backing plate 56; the ends 28 can be secured with tie rod nuts 27. Ring dampers in the form of stiff rubber rings 30 are positioned between the damper mass 20 and the front and rear plates 22’ and 24, respectively. A tuning bolt 64 may be threaded into a tuning block 29.

[0031] Having thus described the device, various modifications and alterations will occur to those skilled in the art, which modifications and alterations are intended to be within the scope of the device as defined by the appended claims.