US3858547A

US3858547A - Coating machine having an adjustable rotation system

Info

Publication number: US3858547A
Application number: US424659A
Authority: US
Inventors: Nils H Bergfelt
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-12-14
Filing date: 1973-12-14
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07

Abstract

Coating machine having a vacuum chamber with at least one coating source disposed in the chamber. A plurality of spindle assemblies are mounted in the chamber with each of the spindle assemblies having a rotatable spindle. A substrate holder is carried by each spindle and is adapted to carry a substrate in such a manner that it is adapted to receive coating material from the coating source. Means is provided for rotating the spindle assemblies about the source. Means is also provided for rotating the spindles about their own axes at the same time they are being rotated about the source. Means is provided to permit adjustment of the spacing of the spindle assemblies from the center of rotation about the source. In addition, means is provided to permit adjustment of the angle of the spindle with respect to the coating source to thereby adjust the angle of incidence of the vapor coating stream with respect to the substrates carried by the spindles.

Description

Bergfelt Jan. 7, 1975 COATING MACHINE HAVING AN ADJUSTABLE ROTATION SYSTEM [76] Inventor: Nils H. Bergielt, 2789 Giffen Ave.,

Santa Rosa, Calif. 95403 [22] Filed: Dec. 14, 1973 [21] Appl. No.: 424,659

[52] US. Cl 118/49, 118/53, 269/57 [51] Int. Cl. C23c 13/08 [58] Field 01' Search 118/4949.5, 118/53; 117/1071; 269/57 [56] References Cited UNITED STATES PATENTS 2.351.537 6/1944 Osterberg ct al. 118/49 3,023,727 3/1962 Theodoseau ct al 1 18/49 X 3,128,205 4/1964 lllsley 118/49 3,486,237 12/1969 Sawicki 118/49 3,636,917 l/l972 Baker 118/48 X Primary Examiner-Morris Kaplan Attorney, Agent, or Firm-Flehr, Hohbach, Test, Albritton & Herbert [57] ABSTRACT Coating machine having a vacuum chamber with at least one coating source disposed in the chamber. A plurality of spindle assemblies are mounted in the chamber with each of the spindle assemblies having a rotatable spindle. A substrate holder is carried by each spindle and is adapted to carry a substrate in such a manner that it is adapted to receive coating material from the coating source. Means is provided for rotating the spindle assemblies about the source. Means is also provided for rotating the spindles about their own axes at the same time they are being rotated about the source. Means is provided to permit adjustment of the spacing of the spindle assemblies from the center of rotation about the source. In addition, means is provided to permit adjustment of the angle of the spindle with respect to the coating source to thereby adjust the angle of incidence of the vapor coating stream with respect to the substrates carried by the spindles.

14 Claims, 5 Drawing Figures Patented Jan. 7, 1975 3 Sheets-Sheet 1 Patented Jan. 7, 1975 3 Sheets-Sheet 2 Patented Jan. 7, 1975 3 Sheets-Sheet 5 COATING MACHINE HAVING AN ADJUSTABLE ROTATION SYSTEM BACKGROUND OF THE INVENTION In US. Pat. No. 3,128,205, there is provided a coating machine which has a double rotation system. However, this system utilizes a friction drive in which slippage may occur. In addition, no means is provided for varying the spacing of the substrate holders from the axis of rotation of the substrate holders about the source. For this reason, it is often very difficult to obtain maximum utilization of the space within the vacuum chamber. There is, therefore, a need for a coating machine which has new and improved double rotation system.

SUMMARY OF THE INVENTION AND OBJECTS provided for rotating the spindles of the spindle assem blies about their own axes of rotation during the time that they are being rotated about the source. Means is provided for adjusting the positions of the spindle assemblies radially with respect to the axis of rotation of the spindle assemblies about the source. Means is also provided for adjusting the angles of the spindles with respect to the coating source.

In general, it is an object of the present invention to provide a coating machine with a double rotation system which is adjustable.

Another object of the invention is to provide a coating machine of the above character having spindle assemblies in which the positions of the spindle assemblies can be adjusted along a radius with respect to the axis of rotation of the spindle assemblies about the source.

Another object of the invention is to provide a coating machine of the above character in which the radial adjustments of the spindle assemblies can be readily carried out.

Another object of the invention is to provide a machine of the above character in which the spindle assemblies have spindles which are rotated about their own axes and which are adjustable in angle with respect to the source.

Another object of the invention is to provide a coating machine of the above character in which a positive drive without danger of slippage is provided.

Another object of the invention is to provide a coating machine of the above character in which maximum usage is made of the space above the coating source for coating substrates.

Another object of the invention is to provide a coating machine of the above character in which particularly novel driving means is provided for causing the rotation of the system.

Another object of the invention is to provide a coating machine of the above character in which various arrangements of spindle assemblies can be provided.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS I FIG. 1 is a cross-sectional view of a coating machine incorporating the present invention.

FIG. 2 is an enlarged cross-sectional view showing a portion of the double rotation system incorporating the present invention.

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along the line 44 of FIG. 2.

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT The coating machine having an adjustable double rotation system shown in the drawings consists of a large coating chamber or housing 11 which can be of any desired shape as, for example, cylindrical, which is'provided with a cylindrical side wall 12, a planar top wall 13 and a planar bottom wall 14. The top wall 13 and the bottom wall 14 are parallel with respect to each other. A bottom plate 16 is secured to the bottom wall 14 by suitable means such as bolts (not shown). Suitable O-ring sealing means 17 of a conventional type is provided for forming a vacuum-tight seal between the bottom wall 14 and the bottom base plate 16. It can be seen that the chamber or housing 12 provides a large enclosed chamber 19 which is adapted to be evacuated by large vacuum pumps (not shown) to provide the desired degree of vacuum.

Means of a conventional type is provided within the chamber for evaporating coating materials of various types. Thus, there is schematically shown a resistance heated boat 21 and an electron gun 22. By way of example, twelve resistance heated boats 21 can be provided on the bottom plate 16 and two electron guns 22 spaced in a 12 inch circle can be carried by the base plate 16. This makes it possible to utilize a great many different coating materials in the vacuum chamber for depositing very complicated coatings.

A top plate 26 covers a large opening 27 provided in the top wall 13. It is secured to the top wall 13 by suitable means such as bolts (not shown). Suitable O-ring v sealing means 28 is provided for establishing a vacuumtight seal between the top plate 26 and the top wall 13. The coating chamber thus far described is conventional.

The adjustable double rotation system 31 consists of a large centrally disposed stem 32 which extends through a hole 33 provided in the top plate 26. The stem 32 is provided with a radially extending flange 34 at its upper end which is secured to the top plate 26 by suitable means such as bolts 36. O-ring sealing means 37 is mounted between the flange 34 and the top plate 26. A circular transfer plate 39 is secured to the bottom end of the stem 32 by cap screws 41.

A chip changer assembly 42 for monitoring the vapor stream from the source is provided. The assembly 42 is secured to the transfer plate 39 by cap screws 43. The chip changer assembly 42 is conventional and is somewhat similar to the chip changer assembly described in US. Pat. No. 3,387,742. Means is provided for causing operation of the chip changer assembly and consists of a shaft 46 which has its lower extremity secured to the chip changer assembly 42 and which is coaxially disposed within the stem 32. The shaft 46 extends through a vacuum feed-through provided with bearings (not shown). This shaft 46 carries a pulley (not shown) which is driven by a belt (also not shown).

A centrally disposed bearing housing 51 is provided in the chamber 19 and is rotatably mounted upon the stem 32 by upper and lower ball bearing

assemblies

52 and 53. Bearing assembly retaining rings 54 and 56 are provided and are secured to opposite ends of the housing 51 by cap screws 57. Upper and

lower rings

58 and 59 are securedto the housing 51 by cap screws 61. A spoke assembly 62 is secured to the upper and

lower rings

58 and 59 by suitable means such as welding. By way of example, six arms or spokes 63 spaced 60 apart form a part of the spoke assembly 62. A large annular plate or mounting ring 64 is secured to the lower outer extremities of the spokes 63 by bolts 65 extending through horizontal flange portions 63a of the spokes 63.

Means is provided for rotating the housing 51 carrying the spoke assembly 62 for rotation about the stem 32 and consists of a ring gear 66 secured to the top of the housing by cap screws 67. The ring gear is driven by a spur gear 68 mounted on a shaft 69. The shaft 69 is rotatably mounted in a vacuum feed-through 71 provided in the top plate 26. A pulley 72 is mounted on the upper end of the shaft 69 and is driven by a belt 73. The belt 73 is driven by a pulley 74 mounted on the shaft 76 of an electric 77. The motor 77 is carried by a bracket 78 mounted on theupper wall 13. It can be plate 86 by cap screws 91. Ball bearing assemblies 92 are mounted within the inner and outer bearing blocks 88 and 89. The bearing assembly 92 is retained within the bearing block 88 by a retaining ring 93. The other bearing assembly 92 is retained in the bearing block 89 by retaining ring 94. An elongate shaft 96 is mounted in the bearing assemblies 92 for rotation about the longitudinaly axis of the shaft. The shaft 96, as shown in FIG. 3, is square in cross-section for a purpose hereinafter described.

A planetary bevel gear 97 is secured to the end of the shaft 96 extending through the bearing assembly 92 carried by the bearing block 88. Suitable means such as a key (not shown) is provided so that when the planetary gear 97 is rotated, the shaft 96 is rotated therewith. A retaining ring 98 is mounted on the shaft 96 for retaining the planetary gear 97 on the shaft 96. The planetary bevel gear 97 engages a large stationary sun gear 99 which is secured by cap screws 101 to the transfer plate 39. It can be seen that when the spoke assembly 62 is rotated the bevel gear 97 is forced to rotate by the stationary sun gear 99.

Each of the assemblies 79 include a drive gear 106 which is slidably mounted on the square shaft 96 of the spindle assembly. The drive gear 106 is provided with a large hub 107 upon which there are mounted two closely spaced ball bearing assemblies 108. The drive gear 106 is provided with gear teeth which are formed on two bevels 109 and 111 which are at an exterior angle of approximately 148 with respect to each other. The ball bearing assemblies 108 carrying the hub 107 are mounted in a bearing housing 112 and are retained therein by a retaining ring 113. Since the ball bearing assemblies 108 are locked within the bearing housing 112, the drive gear 106 will always be rotating along the axis of the shaft 96. The two bearing assemblies 108 prevent rocking of the drive gear 106 on the shaft 96. It can be seen that the hub 107 of the drive gear 106 rests against the inner race of the inner ball bearing assembly 108.

A spindle carrier assembly 114 is mounted on each of the housing assemblies 79 and is comprised of a pair of spaced parallel generally L-shaped side plates 116 which are secured to the bearing housing 112 by cap screws 115. Each of the side plates 116 is provided with a cut-out 117 extending vertically through the upper end thereof which accomodates the drive gear 106. A pair of spaced support bars or plates 118 are secured to the side plates 116 by cap screws 121. A can be seen from FIG. 3, the support bars 118 extend over spaced parallel rails or plates 119 forming a part of the housing assembly 79 and are adapted to ride upon the top surfaces thereof for sliding movement longitudinally of the rails. The rails 119 are mounted by cap screws 112 on the bearing blocks 88 and 89.

Each of the rails 119 is provided with two spaced parallel rows of threaded holes 123 which are spaced apart in a direction extending longitudinally of the rails 119 a suitable distance as, for example, 2 inches between holes. Four cap screws 124 are threaded into four of the holes 123 and are adapted'to be threaded into the threaded holesjl25 provided in the side plate 116. Thus, as can be seen by removing the four screws from each of the side plates, it is possible to shift the side plates longitudinally of the rails by 2 inch increments. The drive gear 106 will also slide along the square shaft 96 and will be driven by the square shaft in any position to which the side plates 116 are moved.

A spindle assembly 126 is carried by the side plates 1 16 of each spindle traverse adjustment housing assemblies 79 and consists of a cylindrical housing 126 which has a shaft 128 rotatably mounted therein by a pair of spaced bearing assemblies (not shown). As is well known to those skilled in the art, substrate holders 129 are adapted to be secured to the shaft 128 so they are rotated with the shaft. The substrates are adapted to be secured to the substrate holders. The substrate holders can be of any conventional type as, for example, parabolic, circular and flat.

A bevel gear 131 is mounted on the other end of the shaft 128 and is adapted to engage the drive gear 106. The housing 126 is supported by a clamping body 132 consisting of two

parts

133 and 134 which are fastened together about the housing 126 by screws 136. A pair of spaced parallel legs or arms 137 are secured to the part 133 by suitable means such as welding and extend upwardly at an angle which is substantially parallel to the axis of rotation of the shaft 128. Theupper extremities of the arms 137 are pivotally mounted between the side plates 116 and are secured thereto by dowel pins 138 so as to permit swinging movement of the spindle assembly 126 with axis of swing movement being coincident with the point of contact of the

gears

106 and 131.

Means is provided for locking the spindle assembly 126 in a predetermined angular position and consists of cap screws 141 which are threaded into the part 133. The cap screws 141 extend through arcuate slots 142 provided in the side plates 116. The center of the arc is the axis ofrotation provided by the dowel pins 138. Washers 143 are carried by the cap screws 141 and are adapted to engage the side plates 116. It can be seen that by tightening the cap screws 141, the spindle assemblies 126 can be held in the desired angular position.

In order to facilitate pivotal movement of the spindle assemblies 126, an eye bolt 46 is provided which is seated in a groove 147 provided in the part 133 of the clamping body 132. A roll pin 148 is mounted in a hole 149 provided in the body and extends through the eye bolt 146 to retain the eye bolt within the groove 147. The eye bolt 147 extends through a hole 151 provided in a cross bar 152. The cross bar 152 is secured to the side plates 116 by suitable means such as welding. A washer 153 is provided on the eye bolt and engages the cross bar 152 and is held in place by a nut 154. From the arrangement shown, it can be seen that the eye bolt 146 will carry most of the load of the spindle assembly 126 even when a relatively heavy substrate holder is mounted thereon. When it is desired to change the angle of the spindle assembly 63, it is merely necessary to loosen the nut 154 and the cap screws 141 to permit the spindle assembly to be moved toward the vertical. Conversely, when it is desired to move the spindle assembly further away from the vertical, the nut 154 is tightened on the eye bolt to pull the spindle assembly toward the greater angle from the vertical. As soon as this has been accomplished, the cap screws 141 can be tightened.

Operation of the coating machine having an adjustable double rotation system may now be briefly described as follows. Let it be assumed that the substrate holders 129 have been filled with substrate and that the chamber 19 has been evacuated to the desired degree and that it is desired to begin a coating operation. The double rotation system is placed in operation by energizing the motor 77 which causes rotation of the spur gear 68 and the spur gear 68 causes rotation of the ring gear 66 which, in turn, causes rotation of the stem 32 and the plurality of radially extending spider or spoke assemblies 62 which are carried thereby. The carrying plates 86 rotate with the spoke assemblies and carry the spindle assemblies 126. As this occurs, the planetary bevel gear 97 is caused to rotate by engagement with the stationary sun gear 99. Rotation of the gear 97 causes rotation of the shaft 96. Rotation of the shaft 96 causes rotation of the bevel gear 106. Rotation of the bevel gear 106 causes rotation of the beveled crown gear 131. This causes rotation of the spindle 128 and the substrate holder 129 carried thereby. Thus, it can be seen that a double rotation system is provided in that the substrates carried by the substrate holders 129 are rotated'about an axis which is coincident with the axis of rotation for the stem 32. In addition, they are rotated about an axis which is coincident with the axis of the spindle 128.

An important feature of the present invention is that the distance from the centerline of the axis of rotation for the stem 32 and the spindle assemblies 126 can be adjusted. This can be accomplished by moving the side plates 116 and the bearing housing 112 secured thereto longitudinally of the rails l03 in a direction which is longitudinal of the axis. of the shaft 96. As explained previously, this is accomplished by removing the four cap screws 124 from each of the side plates 116. When this is done, the side plates 116 and the spindle assembly 126 are supported by the side plate 118. This ensures that it will not be necessary for the shaft 96 to support all the weight of the spindle assembly 126 and the substrate holders carried thereby. As soon as the cap screws 124 have been removed, the side plates and the spindle assembly 126 may be moved in increments along the axis of the shaft 96 as determined by the positioning of the holes 103 and then secured in a-desired position by the cap screws 124. It can be seen that it is possible to radially adjust the position of the spindle assembly 126 within the chamber 19 as determined by the length of the shaft 96 and the spacing between the bearing blocks 88 and 89. In all positions of the spindle assembly 126 double rotation of the substrates will still be provided.

In addition with the present invention, it is possible to adjust the-angle of the substrates with respect to the sources from which the materials are being evaporated by tilting of the spindle shaft 128. As explained previously, this can be accomplished by loosening the cap screws 141 and then using the nut 154 to position the spindle assembly 128 to the desired angle and then retightening the cap screws 141 to hold the spindle in this predetermined angular position. The crown spur gear 131 and the bevel gear 106 have been designed in such a manner that the spindle 128 will be positively driven through a substantial variation in angle of the axis of the shaft 128. By way of example, an angle ranging from the vertical to 32 from the vertical can be readily accomplished with the mechanism hereinbefore described while still obtaining a positive driving relationship between the bevel gear 106 and the beveled crown gear 131. This is made possible because of the two bevels 109 and 111 provided on the gear 106.

By way of example, in one embodiment of the present invention, 12 inches of travel is permitted for the bevel gear 106 longitudinally of the shaft 96 thus making it possible to change the center distance from the spindle 128 to the center of the sun gear 99 from 20 inches through 32 inches.

From the adjustments hereinbefore described, it can be seen that the radius of rotation can be varied as well as the angle of rotation for the substrates. Varying of the radius of rotation is advantageous because when coating certain types of substrates as, for example, small substrates, it is possible to utilize different radiuses so that it is possible to place a great many more spindle assemblies in the machine to thereby obtain a much greater capacity for the machine. The machine is also advantageous in that it makes it possible to cover substrates which heretofore have been difficult to coat satisfactorily. This can be accomplished by changing the radius and also by tilting of the spindle axis toward or away from the coating source to obtain the coating desired.

By way of example, if it is desired to coat three large substrates, they can be placed apart. In such a case, a substrate as large as 37 inches can be coated in i a coating machine of this type and size. If twelve of the spoke assemblies and spindle assemblies are placed within the coating machine, then it is possible to coat 10 or 11 inch diameter substrates and to almost completely fill the circle with substrates.

Any combination of spoke assemblies and spindle assemblies can be utilized, for example, combinations can be worked out utilizing 1O spokes, five spokes, four spokes or even eight spokes. Substrate holders of various sizes also can be utilized ranging from' 37 inches down to 10 inches or less.

It is apparent from the foregoing that there has been provided a coating machine having an adjustable rotation system which has many advantageous features. It

is constructed in such a way that the angle of the substrate holder with respect to the source can be readily varied. In addition, the radius of rotation about the sources also can be readily adjusted. The system is designed in such a manner that the desired amount of stability is retained. A positive drive is provided so that there is no undesirable slippage. The system is also designed in such a manner that substantially the entire area which is covered by the coating streams from the coating sources will be filled with substrate holders and substrates carried thereby to make possible maximum utilization of the space within the vacuum chamber and also to obtain the desired coating angle or angle of incidence for the vapor stream for the substrates being coated.

I claim:

1. In a coating machine having an adjustable double rotation system, a vacuum chamber, at least one coating source disposed in the vacuum chamber, a plurality of spindle assemblies mounted in the chamber and each having a rotatable spindle, a substrate holder carried by each spindle and adapted to receive at least one substrate which can receive coating material from the coating source, means for orbiting the spindle assemblies about the coating source, means for rotating the spindles about their own axes of rotation during the time that they are being rotated about the source and means for adjusting the spacing of the spindle assemblies substantially along the radial extent toward and away from the axis of rotation of the spindle assemblies about the source, said means for adjusting including a shaft extending radially of the chamber and drive means slidably mounted on said shaft and driving said spindle and means in the chamber for driving said shaft.

2. A machine as in claim 1 together with means for adjusting the angle of the spindle with respect to the position of the coating source.

3. A machine as in claim 1 wherein said means for rotating the spindles of the spindle assemblies about their own axes includes a bevel gear mounted on the spindle 6. A machine as in claim 5 wherein said means within said chamber includes a planetary gear mounted on said shaft and a stationary sun gear having its axis coincident with the axis of rotation for the spindle assemblies about the source and engaging the gear mounted on the shaft.

7. A machine as in claim 5 together with a stem mounted in said chamber, a housing rotatably mounted on said stem, means carried by said housing for supporting said shafts in a generally horizontal position and means for rotating said housing.

8. In a coating chamber having an adjustable double rotation system, a vacuum chamber, at least one coating source disposed in the vacuum chamber, a stem mounted in the vacuum. chamber, a housing rotatably mounted on the stem, a plurality of radially extending spoke assemblies mounted on said housing, bearing means carried by said spoke assemblies, a generally horizontal shaft mounted in each of the bearing assemblies, a planetary gear carried by the shaft, a stationary sun gear disposed within the chamber and engaging the planetary gear, means for causing rotation of said housing about said stem and to cause rotation of said spoke assemblies and the shafts carried thereby about the axis of said stem so that said shaft is rotated about its axis, a drive member slidably mounted on said shaft, spindle carrier means associated with said drive member and -movable longitudinally of the shaft with said drive member, a spindle assembly, means mounting said spindle assembly on said spindle carrier, said spindle assembly including a spindle rotatably'mounted therein and driven means adapted to engage the drive member and engaging the spindle for causing rotation of the spindle as the drive member is rotated upon rotation of said shaft, said spindle being adapted to carry a substrate holder for carrying'substrates which are to be coated with material emanating from the coating source.

9. A machine as in claim 8 together with means for retaining said spindle carrier means in predetermined positions extending longitudinally of the shaft.

10. A machine as in claim 9 together with means for pivotally mounting said spindle assembly on said spindle carrier means whereby the angle of the spindle with respect to the source can be adjusted.

and bevel gear means for driving the bevel gear on the 11. A machine as in claim 10 wherein the angle can be varied from vertical to 32 from the vertical.

12. A machine as in claim 8 wherein said drive member is in the form ofa bevel gear having teeth with abutting circumferential surfaces inclined at an angle with respect to each other.

13. A machine as in claim 10 wherein said means for adjusting the angle of the spindle assembly includes a member secured to the spindle carrier means to hold the spindle assembly in the desired angular position.

14. A machine as in claim 13 together with additional means for locking said spindle assembly in the desired angular position.

Claims

3. A machine as in claim 1 wherein said means for rotating the spindles of the spindle assemblies about their own axes includes a bevel gear mounted on the spindle and bevel gear means for driving the bevel gear on the spindle.

4. A machine as in claim 3 wherein said bevel gear means includes bevel gears having abutting circumferential surfaces which are inclined at angles with respect to each other.

5. A machine as in claim 1 wherein said drive means includes gearing means.

6. A machine as in claim 5 wherein said means within said chamber includes a planetary gear mounted on said shaft and a stationary sun gear having its axis coincident with the axis of rotation for the spindle assemblies about the source and engaging the gear mounted on the shaft.

8. In a coating chamber having an adjustable double rotation system, a vacuum chamber, at least one coating source disposed in the vacuum chamber, a stem mounted in the vacuum chamber, a housing rotatably mounted on the stem, a plurality of radially extending spoke assemblies mounted on said housing, bearing means carried by said spoke assemblies, a generally horizontal shaft mounted in each of the bearing assemblies, a planetary gear carried by the shaft, a stationary sun gear disposed within the chamber and engaging the planetary gear, means for causing rotation of said housing about said stem and to cause rotation of said spoke assemblies and the shafts carried thereby about the axis of said stem so that said shaft is rotated about its axis, a drive member slidably mounted on said shaft, spindle carrier means associated with said drive member and movable longitudinally of the shaft with said drive member, a spindle assembly, means mounting said spindle assembly on said spindle carrier, said spindle assembly including a spindle rotatably mounted therein and driven means adapted to engage the drive member and engaging the spindle for causing rotation of the spindle as the drive member is rotated upon rotation of said shaft, said spindle being adapted to carry a substrate holder for carrying substrates which are to be coated with material emanating from the coating source.

11. A machine as in claim 10 wherein the angle can be varied from vertical to 32* from the vertical.

12. A machine as in claim 8 wherein said drive member is in the form of a bevel gear having teeth with abutting circumferential surfaces inclined at an angle with respect to each other.