TWI557345B - Output shaft rotary disc group and hobbing cam drive - Google Patents

Description

Output shaft rotary disc set and hobbing cam transmission

This invention relates to a transmission, and more particularly to a hobbing cam transmission.

Referring to Fig. 1, there is a hobbing cam transmission device which is conventionally applied to a CNC (Computer Numerical Control) machine tool automatic tool changer (not shown). The hobbing cam transmission includes a cam 1 and a power output shaft rotary disk set 2 that is coupled to the cam 1. The cam 1 includes a body 11 having an axis L1, and a rib 12 disposed along an axial curve around an outer peripheral surface of the body 11. The rib 12 cooperates with the body 11 to define a groove 13 . The output shaft rotating disk unit 2 includes an output shaft rotating disk 21 having an axis L2 and axially different from the axial direction of the cam 1, and a plurality of shaft holes 22 spaced apart from the outer peripheral surface of the output shaft rotating plate 21, and a plurality of respectively The shaft 23 is disposed on the shaft 23 of the shaft hole 22, and a plurality of rolling bearings 24 respectively pivotally disposed on the shafts 23 and exposing the output shaft rotating disc 21 and accommodating the grooves 13 of the cam 1. The output shaft rotating disk group 2 and the cam 1 are assembled by a rolling bearing 24 partially accommodated in the groove 13. When the cam 1 is driven to rotate, the rib 12 of the cam 1 moves in the axial direction, so that the outer circumferential surface of the rolling bearing 24 located in the groove 13 can rollably abut against the inner wall surface of the rib 12 (see FIG. 2). ), and then moved by the rib 12, The rotating shaft 21 is rotated by the output shaft. In the above process, the rolling bearing 24 rotates with the output shaft to rotate the disk 21, and sequentially enters the groove 13 of the cam 1 in sequence, and is rotated by the rib 12 of the cam 1, whereby the cam 1 can be rotated. The output shaft rotating disk group 2 is continuously driven to rotate until the cam 1 stops rotating.

Referring to FIG. 1 and FIG. 2, since the hobbing cam gear is used for a long period of time, the two phases abut against the inner wall surface of the rib 12 and the outer peripheral surfaces of the rolling bearings 24 to form a belt-shaped wear region 121. In addition, when the machine has a collision or encounters other strong impact accidents, the rolling bearing 24 also impacts the inner wall surface of the rib 12 to form an impact recessed area 122, and the rolling bearings 24 also interlock with the pivoted shaft. The rods 23 push the shaft holes 22 such that the shafts 23 and the shaft holes 22 are deformed by bending and expansion, respectively. Once the deformation of the above components occurs, the transmission precision of the entire hobbing cam transmission is severe. The error is especially affected by the CNC machine that needs high-precision transmission, which makes it impossible to process the finished product that matches the input model. The user only replaces the cam 1, the output shaft rotary disk 21 and the rolling bearings 24 In order to maintain the operation of the machine, it takes a lot of time and cost. Therefore, how to reduce the replacement cost of the hobbing cam transmission of the machine has always been a problem that the industry wants to solve.

Accordingly, a first object of the present invention is to provide an output shaft rotary disk set.

Therefore, the output shaft rotary disk set of the present invention comprises a power output shaft rotation A disk and a first roller set.

The output shaft rotary disk comprises a body and a plurality of shaft holes spaced apart from the outer peripheral surface of the body.

The first roller set includes a plurality of first rollers respectively mounted on the equiaxed holes. Each of the first rollers has a shaft disposed on the shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft. The outer peripheral surface of the rolling bearing of each of the first rollers defines a centrally located contact portion, and two non-contact portions respectively located on opposite sides of the contact portion and having a diameter smaller than the diameter of the contact portion.

Further, a second object of the present invention is to provide a hobbing cam gear which can extend the service life by reducing the replacement cost by simply replacing a part of the parts.

Thus, the hobbing cam transmission of the present invention comprises a cam and a power output shaft rotating disk set as described above.

The cam includes a body and a rib disposed along the axial curve around the outer peripheral surface of the body. The ribs cooperate with the body to define a groove.

The output shaft rotating disk group is coupled to the cam, the output shaft rotating disk and the cam are axially different, and at least one of the first rollers has a groove bearing disposed in the groove of the cam Inside the slot.

Wherein, when the cam rotates, the rib of the cam moves along the axial direction, so that the contact portion of the rolling bearing located in the groove can roll against the inner wall surface of the rib and is further displaced by the rib to Driving the output shaft to rotate the disc, in the process, the rolling bearings follow the output The rotation of the shaft rotary disk sequentially enters the groove of the cam and is rotated by the rib of the cam, whereby the cam continuously drives the output shaft to rotate the disk until the cam stops rotating.

The effect of the present invention is that the inner wall surface of the rib of the cam and the rolling bearing of the first roller are designed by different contours of the outer peripheral surface of the rolling bearing of the first roller group disposed on the outer circumference of the output shaft When the contact portion is in rolling contact, or when an impact is caused to cause a wear depression, the area of the inner wall surface of the rib can be effectively restrained, but only the first roller is removed, and the conventional cylindrical outer circumference is used. The roller of the rolling bearing of the surface is replaced, wherein the outer peripheral surface of the conventional roller is rolled against the region of the inner wall of the rib that is not worn out, so that the hobbing cam transmission can be maintained without affecting the transmission precision. Normal operation, the function of the cam and the output shaft rotary disc can be used for the second time. Therefore, the service life of the output shaft rotating disc and the cam having a high manufacturing cost can be prolonged by merely replacing the roller having a lower manufacturing cost, thereby effectively reducing the replacement cost of the hobbing cam gear.

4‧‧‧ cam

41‧‧‧Ontology

42‧‧‧ ribs

421‧‧‧Band wear zone

422‧‧‧ impact depression

423‧‧‧No impact wear zone

43‧‧‧ trench

5‧‧‧Output shaft rotary disc set

50‧‧‧Power shaft rotary disc

500‧‧‧ ontology

501‧‧‧Axis hole

502‧‧‧ Reserved shaft hole

51‧‧‧First Roller Group

511‧‧‧First Roller

512‧‧‧ shaft

513‧‧‧ rolling bearings

514‧‧‧Contacts

515‧‧‧ Non-contact department

52‧‧‧Second roller group

521‧‧‧Second roller

522‧‧‧ shaft

523‧‧‧ rolling bearings

524‧‧‧Contacts

525‧‧‧ Non-contact department

L4‧‧‧ axis

L5‧‧‧ axis

Other features and advantages of the present invention will be apparent from the detailed description of the preferred embodiments of the accompanying drawings, wherein: FIG. 1 is a perspective view illustrating the hobbing of a conventional automatic tool changer for a CNC machine tool FIG. 2 is a perspective view showing a belt-shaped wear area and an impact recessed area formed by a rolling bearing of a conventional hobbing cam transmission device in the inner wall surface of a rib; Figure 3 is a perspective view showing the connection relationship of the components of a first preferred embodiment of the hobbing cam gear of the present invention, wherein only two of the plurality of second rollers are shown for illustration; A perspective view of a first roller rolling wear of the first preferred embodiment and a belt-shaped wear zone and an impact recessed area formed by the inner wall surface of the rib, FIG. 5 is a perspective view illustrating the first comparison a second roller outer peripheral surface of the preferred embodiment is in contact with the inner wall surface of the rib after being worn by the rib; FIG. 6 is a perspective view showing the first preferred embodiment of the first preferred embodiment The outer surface of the two rollers is rolled against the inner wall surface of the rib after being worn by impact; FIG. 7 is a perspective view showing the first roller rolling wear and impact of the first preferred embodiment A strip-shaped wear region and an impact recessed region are formed in the inner wall surface of the rib. FIG. 8 is a perspective view showing that the outer peripheral surface of the second roller of the first preferred embodiment is another structure. The rib is worn by the inner wall surface after impact; Figure 9 is a perspective view Another embodiment of the first preferred embodiment is illustrated; FIG. 10 is a perspective view showing the connection relationship of the components of a second preferred embodiment of the hobbing cam gear of the present invention, wherein only the drawing is shown. Two of the plurality of second rollers are illustrated; FIG. 11 is a perspective view showing another embodiment of the second preferred embodiment; Figure 12 is a perspective view showing the connection relationship of the components of a third preferred embodiment of the hobbing cam gear of the present invention, wherein only two of the plurality of second rollers are shown for illustration; and Figure 13 It is a perspective view showing another embodiment of the third preferred embodiment.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 3 and FIG. 4, a first preferred embodiment of the hobbing cam transmission of the present invention is applicable to an automatic tool changer (not shown) of a CNC machine tool, and the hobbing cam transmission includes a cam 4. And a power output shaft rotating disk set 5.

The cam 4 includes a body 41 having an axis L4, and a rib 42 disposed around the outer peripheral surface of the body 41 along an axial curve. The rib 42 cooperates with the body 41 to define a groove 43.

The output shaft rotating disc set 5 is assembled with the cam 4 and includes an output shaft rotating disc 50 having an axis L5 and axially different from the axial direction of the cam 4, and is alternately disposed on the output shaft rotating disc A first roller group 51 and a second roller group 52 of 50 outer circumferences. In the present embodiment, the first roller set 51 is previously disposed on the outer circumference of the output shaft rotary disk 50, however, the second roller set 52 is a substitute for the first roller set 51.

The output shaft rotary disk 50 has a body 500 and a plurality of shaft holes 501 formed at intervals on the outer circumferential surface of the body 500. The first roller group 51 has a plurality of first rollers 511, and the second roller group 52 has a plurality of second rollers Sub521. Each of the first and second rollers 511 and 521 respectively has a shaft 512, 522 axially disposed on the shaft hole 501, and a pivoting shaft 512, 522 respectively and the power shaft rotating disc 50 is exposed. The rolling bearings 513, 523 of the groove 43 can be accommodated. In this embodiment, the first and second rollers 511 and 521 are respectively one of a needle bearing and a roller bearing. The outer circumferential surface of the rolling bearing 513 of each of the first rollers 511 defines a centrally located contact portion 514, and a non-contact portion 515 located on opposite sides of the contact portion 514 and having a diameter smaller than the diameter of the contact portion 514, The outer peripheral surface of the rolling bearing 523 of each of the second rollers 521 is surrounded by a cylindrical shape.

The output shaft rotating disk group 5 and the cam 4 are assembled by a rolling bearing 513, 523 partially accommodated in the groove 43. When the cam 4 rotates, the rib 42 of the cam 4 moves in the axial direction, so that the contact portion 514 of the rolling bearing 513 of the first roller 511 located in the groove 43 or the rolling bearing 523 of the second roller 521 The outer peripheral surface is slidably abutted against the inner wall surface of the rib 42 and is further displaced by the rib 42 to drive the output shaft to rotate the disk 50. In the process, the rolling bearings 513 and 523 rotate with the output shaft. The disk 50 is sequentially rotated into the groove 43 of the cam 4 to be rotated by the rib 42 of the cam 4, whereby the cam 4 can continuously drive the output shaft to rotate the disk group 5 until the cam 4 stops rotating. .

Referring to FIG. 4, the hobbing cam gear is used for a period of time, and the contact portion 514 of the rolling bearing 513 of the first roller 511 previously disposed on the output shaft rotating disk 50 wears the inner wall surface of the rib 42 When a belt-shaped wear zone 421 is formed, or when the machine has a collision or encounters it When the rolling bearing 513 hits the inner wall surface of the rib 42 to form a pair of impact recessed portions 422 corresponding to the contact portion of the rolling bearing 513, the first roller group 51 can be removed from the output. The shaft rotates the disk 50 and is replaced by the second roller set 52. Referring to FIG. 5, when the second roller 521 disposed on the outer circumference of the output shaft rotary disk 50 and the rib 42 of the cam 4 are driven to rotate, the first roller 511 is convex. The belt-shaped wear region 421 formed by the inner wall surface of the rib 42 or the impact depression portion 422 formed by the impact is formed in the region where the outer circumferential surface of the second roller 521 rolls against the inner wall surface of the rib 42, and thus the second The outer peripheral surface of the roller 521 is a non-impact wear area 423 that is rolled against the inner wall surface of the rib 42 and located on opposite sides of the strip-shaped wear area 421 or the impact recessed area 422, respectively.

As can be seen from the above description, by the design of the contact portion 514 and the non-contact portion 515 of the outer peripheral surface of the first roller 511, the area of the first roller 511 and the inner wall surface of the rib 42 is limited. And the non-impact wear area 423 of the second roller 521 is in contact with the inner surface of the rib 42 so that the hobbing cam transmission can continue to operate under the influence of the transmission precision. The cam 4 can be used a second time to extend the useful life.

It is to be noted that the outer circumferential contour of the rolling bearing 523 of the second roller 521 is not limited to the above, and may also be the following: Referring to FIG. 6, the outer circumferential surface of the rolling bearing 523 of each second roller 521 Defining a non-contact portion 525 located at the center, and a contact portion on the opposite side of the non-contact portion 525 and having a smaller diameter than the diameter of the non-contact portion 525 524. The relative positions of the contact portion 524 and the non-contact portion 525 of the rolling bearing 523 of the second roller 521 are opposite to the contact portion 514 and the non-contact portion 515 of the rolling bearing 513 of the first roller 511. Therefore, when the second roller 521 disposed on the outer circumference of the output shaft rotary disk 50 and the rib 42 of the cam 4 are driven to rotate, the contact portions 524 of the second roller 521 are respectively rolled. The non-impact wear zone 423 abutting against the inner wall surface of the rib 42 is such that the transmission accuracy of the hobbing cam gear is not affected by the belt wear zone 421 or the impact recess zone 422, and the cam 4 can be achieved. Used twice to extend the lifespan.

In addition, the outer peripheral contours of the rolling bearings 513 and 523 of the first and second rollers 511 and 521 are not limited to the above, and may be the following: Referring to FIG. 7, the outer peripheral surface of each of the first rollers 511 is defined to be formed. A non-contact portion 515 adjacent to the output shaft rotary disk 50, and a contact portion 514 having a diameter larger than the diameter of the non-contact portion 515 away from the output shaft rotary disk 50. Referring to FIG. 8, the outer peripheral surface of the rolling bearing 523 of each of the second rollers 521 defines a contact portion 514 adjacent to the output shaft rotary disk 50 and a diameter away from the output shaft rotary disk 50 and having a smaller diameter than the contact portion 514. Non-contact portion 515. The relative positions of the contact portion 524 and the non-contact portion 525 of the rolling bearing 523 of the second roller 521 are opposite to the contact portion 514 and the non-contact portion 515 of the rolling bearing 513 of the first roller 511. Therefore, when the second roller 521 disposed on the outer circumference of the output shaft rotating disk 50 is driven to rotate with the rib 42 of the cam 4, the contact portion 524 of the second roller 521 is rolled against The inner wall surface of the rib 42 does not hit the wear area 423, so that the transmission precision of the hobbing cam transmission is not affected by the belt grinding The consumption zone 421 or the impact depression zone 422 affects the effect that the cam 4 can be used a second time to extend the service life.

It is worth mentioning that when the machine has a collision or encounters other strong impact accidents and the impact force is more serious, the rolling bearing 513 of the first roller 511 is caused to strike the inner wall surface of the rib 42 to form an impact recessed area 422. In addition, the rolling bearing 513 also pushes the pivoting shaft 512 thereof to push the shaft holes 501, so that the shaft holes 501 are enlarged and deformed, and the shaft 512 shaft of the first roller 511 cannot be supplied. The set position is also unable to continue to be used for the axis setting of the shaft 522 of the second roller 521 that is replaced.

In order to solve the above problem, referring to FIG. 9, the output shaft rotary disk 50 of the output shaft rotary disk group 5 can also be processed to have a plurality of reserved shaft holes 502 formed on the outer peripheral surface and located between each two adjacent axial holes 501, respectively. . The reserved shaft holes 502 are respectively axially slidable by the shafts 522 of the first and second rollers 511 and 521. In this way, the second rollers 521 of the subsequent replacement are respectively disposed on the reserved shaft holes 502, so that the transmission precision of the hobbing cam transmission used for the second time is not affected by the shaft hole 501. The effect of deformation.

As can be seen from the above description, the first preferred embodiment of the hobbing cam transmission of the present invention has rolling bearings 513, 523 of the first and second roller sets 51, 52 which are alternately disposed on the outer circumference of the output shaft rotary disk 50. The different concave-convex changes of the outer peripheral surface or the oppositely symmetrical contour design, when the inner wall surface of the rib 42 of the cam 4 is in rolling contact with the rolling bearing 513 of the first roller 51, or when an impact is caused to cause a wear depression, Whole set of hobbing The cam gear is removed and replaced, and the first roller 511 is removed and replaced by the second roller 521, respectively, so that the normal operation of the hobbing cam gear can be maintained without affecting the transmission accuracy. . Therefore, the service life of the output shaft rotary disk 50 and the cam 4 having a high manufacturing cost is prolonged by replacing only the first and second rollers 511 and 521 having a low manufacturing cost, thereby effectively reducing the hobbing. The cost of replacing the cam gear. More preferably, the present invention cooperates with the formation of the reserved shaft holes 502 on the output shaft rotary disk 50 to further assist in achieving the above-mentioned effects.

Referring to FIG. 10, a second preferred embodiment of the hobbing cam transmission of the present invention is applicable to a CNC indexing plate (not shown). The assembly of the second preferred embodiment is substantially identical to the first comparison. In a preferred embodiment, there is a cam 1 and an output shaft rotating disc set 2, respectively, the difference is only in the shape and size of the cam 1 and the output shaft rotating disc group 2 of the two, so as to be applicable to different Within the device to achieve the same effect of the rotary drive.

Referring to Fig. 11, more preferably, the output shaft rotary disk 50 of the output shaft rotary disk unit 5 can be machined to have a plurality of reserved shaft holes 502 formed on the outer peripheral surface and located between each two adjacent axial holes 501, respectively. Thereby, the second rollers 521 on the subsequent replacement are respectively disposed on the reserved shaft holes 502, and the power shaft rotation disk 50 can be used for a second time to extend the service life.

As can be seen from the above description, the second preferred embodiment also has the same effects as the first preferred embodiment.

Referring to Figure 12, a third of the hobbing cam drive of the present invention The preferred embodiment is applicable to a CNC automatic feeding indexing plate (not shown). The assembly of the third preferred embodiment is substantially the same as the first preferred embodiment, and has a cam 1 and an output shaft respectively. Returning to the turntable group 2, the difference lies only in the difference in the shape of the components of the cam 1 and the output shaft rotary disk group 2, so as to be applicable to different devices, thereby achieving the same effect of the rotary transmission.

Preferably, referring to Fig. 13, the power output shaft rotary disk unit 5 of the present embodiment further includes a power output shaft rotary disk 50 having a plurality of reserved shaft holes 502 formed at intervals on the outer circumferential surface. The output shaft rotary discs 50 are coaxially connected side by side. Thereby, the second rollers 521 on the subsequent replacement are respectively disposed on the reserved shaft holes 502, and the power shaft rotation disk 50 can be used for a second time to extend the service life. It is worth mentioning that the output shaft rotating discs 50 can also be integrally formed.

As apparent from the above description, the third preferred embodiment also has the same effects as the first preferred embodiment.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

4‧‧‧ cam

41‧‧‧Ontology

42‧‧‧ ribs

43‧‧‧ trench

5‧‧‧Output shaft rotary disc set

50‧‧‧Power shaft rotary disc

500‧‧‧ ontology

501‧‧‧Axis hole

51‧‧‧First Roller Group

511‧‧‧First Roller

512‧‧‧ shaft

513‧‧‧ rolling bearings

514‧‧‧Contacts

515‧‧‧ Non-contact department

52‧‧‧Second roller group

521‧‧‧Second roller

522‧‧‧ shaft

523‧‧‧ rolling bearings

L4‧‧‧ axis

L5‧‧‧ axis

Claims (10)

The utility model relates to a power output shaft rotary disk set, comprising: a power output shaft rotary disk, comprising: a body and a plurality of axial holes formed at intervals on the outer peripheral surface of the body; and a first roller set including a plurality of respectively mounted on the axial holes a first roller, each of the first rollers has a shaft disposed on the shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft, and the outer peripheral surface of the rolling bearing of each first roller is defined a contact portion located at the center, and two non-contact portions respectively located on opposite sides of the contact portion and having a diameter smaller than the diameter of the contact portion. The output shaft rotary disk set according to claim 1, wherein the output shaft rotary disk further comprises a plurality of reserved shaft holes formed on the outer peripheral surface of the body and located between each adjacent axial hole respectively. And can be respectively provided for the shaft shafts of the first rollers. The power shaft rotary disk set according to claim 1, wherein the power output shaft rotary disk further comprises a plurality of reserved shaft holes formed on the outer peripheral surface of the body and rotating the axis of the disk along the output shaft The shafts are respectively arranged side by side with the shaft holes, and can be respectively provided for the shafts of the first rollers. The power shaft rotating disk group according to claim 1, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of second plurality of roller holes Roller, each of the second rollers has a shaft axially disposed on the shaft hole, and a rolling bearing pivoted on the shaft and exposed outside the rotating shaft of the output shaft, and the outer circumference of the rolling bearing of each second roller The face is surrounded by a cylindrical shape. The power shaft pivoting disk set according to claim 2, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of mounting shaft holes a second roller, each of the second rollers has a shaft axially disposed on the reserved shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft, and the rolling bearing of each second roller The outer peripheral surface is surrounded by a cylindrical shape. The power shaft rotating disk group according to claim 3, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of the plurality of roller holes that can be installed in the reserved shaft holes a second roller, each of the second rollers has a shaft axially disposed on the reserved shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft, and the rolling bearing of each second roller The outer peripheral surface is surrounded by a cylindrical shape. The power shaft rotating disk group according to claim 1, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of second plurality of roller holes Roller, each of the second rollers has a shaft axially disposed on the shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft, and the outer peripheral surface of the rolling bearing of each second roller is defined A non-contact portion located at the center, and two contact portions respectively located on opposite sides of the non-contact portion and having a diameter larger than the diameter of the non-contact portion. The power shaft pivoting disk set according to claim 2, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of mounting shaft holes a second roller, each of the second rollers has a shaft axially disposed on the reserved shaft hole, and a shaft is pivoted outside the shaft Rolling bearing outside the output shaft rotating disc, the outer peripheral surface of the rolling bearing of each second roller defines a non-contact portion at the center, and two are respectively located on opposite sides of the non-contact portion and have a diameter larger than the diameter of the non-contact portion Contact. The power shaft rotating disk group according to claim 3, further comprising a second roller group that can replace the first roller group, the second roller group having a plurality of the plurality of roller holes that can be installed in the reserved shaft holes a second roller, each of the second rollers has a shaft axially disposed on the reserved shaft hole, and a rolling bearing pivoted on the shaft and exposing the outer shaft of the output shaft, and the rolling bearing of each second roller The outer peripheral surface defines a non-contact portion at the center, and two contact portions respectively located on opposite sides of the non-contact portion and having a diameter larger than the diameter of the non-contact portion. A hobbing cam transmission device comprising: a cam, comprising a body, and a rib disposed along the axial curve around the outer peripheral surface of the body, the rib cooperating with the body to define a groove; and a The output shaft rotary disk set according to any one of claims 1 to 9, wherein the output shaft rotary disk group is coupled to the cam, and the output shaft rotary disk and the cam have axial directions different from each other, and a rolling bearing of at least one of the first rollers is received in the groove of the cam; wherein, when the cam rotates, the rib of the cam moves along the axial direction so as to be received in the groove The contact portion of the rolling bearing can roll against the inner wall surface of the rib and be pushed by the rib Shifting to drive the output shaft to rotate the disk. In the process, the rolling bearings are sequentially rotated into the groove of the cam as the output shaft rotates, and are rotated by the rib of the cam, thereby The cam continuously drives the output shaft to rotate the disk group until the cam stops rotating.