WO1991002201A1

WO1991002201A1 - A machine for chamfering the sharp edges of the teeth of annular gears

Info

Publication number: WO1991002201A1
Application number: PCT/EP1990/001238
Authority: WO
Inventors: Bruno Olocco; Gianfranco Pallai
Original assignee: Bocca & Malandrone Di Malandrone & C. S.A.S.
Priority date: 1989-08-01
Filing date: 1990-07-30
Publication date: 1991-02-21
Also published as: IT1233233B; IT8967661A0

Abstract

The machine includes freely-rotatable means (36, 38) for supporting the gear (10) to be worked. A drive gear (48) is arranged to mesh with the gear (10) to be worked and the end edges are chamfered by means of a hob (18) which meshes with the gear (10) to be worked like a worm screw and is arranged so that its cutting edges interfere with the end edges to be chamfered. The drive gear (48) and the hob (18) are interconnected by a positive transmission system (56) driven by a common motor (54) and geared so as to rotate the gear (10) to be worked and the hob (18) in synchronism. Preferably, the machine includes a pair of hobs (18) connected so as to rotate in unison and arranged to engage the end edges to be chamfered on respective opposite faces of the gear (10) to be worked.

Description

A machine for champering the end edges of the teeth of spur gears.

The present invention relates to a machine for chamfering the sharp edges of the teeth of annular gears according to the pre.amble of Claim 1.

In known machines, the gear to be worked is supported by support means, generally in the form of a shaft or mandrel which is rotated in steps, the number of steps being the same as the number of teeth. The chamfering tool is a rotary grinder which is supported by an oscillating element and which, between each step in the rotation of the gear, is brought into engagement with the sharp edge which is situated in correspondence with the grinder for chamfering at that time.

These known machines have the disadvantage of being slow because they work intermittently and chamfer only one sharp edge at a time, at each step in the rotation of the gear.

A more serious problem, however, is the fact that chamfering with a grinder produces an abrasive sludge which not only cannot be recovered for any useful purpose, but is also a pollutant.

The object of the present invention is to provide a machine which does not have these disadvantages.

According to the present invention, this object is achieved by means of a machine as defined in the characterising part of Claim 1 and in the subsequent claims.

By virtue of this concept, the sharp edges are chamfered continuously which achieves operating rates many times faster than those which can be achieved by grinding machines. Moreover, the chamfering takes place by the removal of chips and the steel chippings formed are. a 'valuable material which can be resold to steel-works at quite a high price.

The machine according to the invention has been designed to chamfer the sharp edges of teeth of gears with helical teeth but it can also be applied to spur gears.

The invention "will become clearer from a reading of the following description, with reference to the appended drawings, provided by way of non-limiting example, in which:

Figure 1 is a partial perspective view showing a gear with helical teeth and a hob meshed with the gear for chamfering the edges of the teeth.

Figure 2 is a plan view of a preferred embodiment of the machine according to the invention.

Figure 3 is a side elevation thereof taken on the arrow III of Figure 2,

Figure 4 is a perspective view showing a transmission system which forms part of the machine.

Figure 5 is a detailed perspective view showing a loading device which forms part of the machine, and

Figure 6 is a perspective view showing an unloading device which forms part of the machine. In Figure 1 an annular gear with helical teeth 12 is indicated 10. The gear 10 has a central keying bore 14 which opens into its two opposite faces. The chamfers of the sharp edges corresponding to the intersections of the sides of the teeth 12 with each face of the gear 10 are chamfered as shown at 16.

According to the invention, the chamfers 16 on each face of the gear 10 are produced by means of a chamfering tool constituted by a hob 18. The hob 18 is a mill, similar to a worm screw, with a thread or worm 20 which is cut so that it has cutting edges 22 for forming the chamfers 16 by removing chips.

With reference to Figures 2 to 4, a machine according to the invention comprises a strong bed 24 with a horizontal table 26 on which the main components of the machine are mounted.

The machine includes a head 28 and a counter-head 30 mounted on respective supports 32, 34 fixed to the table 26. The head 28 and the counter-head 30 carry respective pins 36, 38 which constitute support means for the gear 10 to be worked. The pins 36, 38 are mounted for rotation in their heads 28, 30 and are aligned on a horizontal axis X_*

The two pins 36, 38 have facing ends (not shown in detail) which are adapted to engage like centres the central bore 14 in the gear 10 to be worked. The pin 38 can be moved along its axis X and in the direction of the arrow Fl by means of a hydraulic or pneumatic actuator 40 in order to clamp and centre the gear 10 relative to the pins 36 and 38 and to release it, as will be explained further below. The support 32 carries a slide 42. The slide 42 is movable vertically, as shown by the double arrow F2, by a wheel 44 for the purpose which will be explained below.

A drive shaft 46 with a horizontal axis is rotatable in the slide 42 and is arranged above the axis X of the pins 36 and 38. A replaceable drive gear 48 is keyed to the drive shaft 46. The gear 48 is thus arranged to mesh with the gear 10 to be worked which is carried by the support means or pins 36, 38.

With reference to Figure 2, two slides 50 are mounted on the table in opposing positions relative to the axis X and are movable along a horizontal axis Y which is inclined to the axis X at an angle of the order of 60°. Each slide 50 can be reciprocated along the axis Y by a respective hydraulic or pneumatic actuator 52. The movement of the slides 50 is indicated by the double arrow F3.

Each slide 50 carries a hob 18, like that shown in Figure 1, with its axis vertical.

With reference to Figure 4, means for rotating the drive gear 48 and the hobs 18 in unison are provided under the table 26 of the bed 24. The means include a common electric motor 54. The motor 54 drives a transmission system generally indicated 56. The transmission.^*"-system 56 includes a belt 58 which rotates a pair of "counter-rotating shafts 60, 62. The shafts 60, 62 in turn drive respective telescopic shafts 70, 72 through respective toothed belts 64, 65 and respective universal couplings 66, 68. The shafts 70, 72 in turn, through respective pairs of bevel gears. drive respective vertical shafts 73 which are mounted in the slides 50 and to which the hobs 18 are keyed.

The universal couplings 66, 68 and the telescopic structures of the shafts 70, 72 enable continuous rotary motion to be transmitted correctly from the motor 54 to the hobs 18 carried by the slides 50 regardless of the positions of the slides.

The shaft 60 transmits drive to a conventional gear unit 74 with four interchangeable gears. The gear unit 74 enables the transmission ratio between the shaft 60 and a shaft 76 to be changed according to requirements. The shaft 76 terminates in a worm-screw gear 78 which transmits drive to a telescopic shaft 80 with a vertical axis. The shaft 80 is mounted in the support 32 and in turn transmits drive to the drive shaft 46 of the drive gear 48.

The ratios of the gear transmission system 56 are arranged so as to cause the continuous and synchronised rotation of the hobs 18, on the one hand, and of the gear 10 to be worked, through the drive wheel 48, on the other. When the machine is operating, the hobs 18 can thus work continuously to remove chips from the edges of the teeth 12 (Figure 1) and form the chamfers 16. Typically, two rotations of the gear 10 suffice to form the chamfers 16.

The slides .50 may be advanced slightly during the working to increase the depth of cut.

In the embodiment illustrated, the two slides 50 of the hobs 18 are reciprocable by means of the actuators 52 to bring the hobs into engagement with the gear 10 to be worked and to move them away from the gear. The pin 38 is also movable relative to the pin 36 in order to clamp the gear 10 to be worked and to release it upon completion of the work.

This arrangement enables the use of a loading device, which is generally indicated 82 in Figure 2 and shown in detail in Figure 5, as well as an unloading device shown in Figure 6.

The loading device 82 includes a feeder 84 situated along one side of the table 26. The feeder 84 comprises a channel 86 in which the gears to be worked, again indicated 10, are deposited side-by-side and face-to face. A pusher 88 is situated in the channel 86 and is moved in the direction of the arrow F4 by a screw-shaft 90 driven by a geared motor 92. A chute 94 is associated with an output end of the channel 86 and extends perpendicular to the channel, downwardly from the output end thereof to an arrival station where a cradle, generally indicated 96, is situated.

Each time a gear 10 to be.workedUs pushed . to the start of the slide 94 it then rolls in the channel 94, in an upright condition, until it is deposited in the cradle 96.

The cradle 96 is carried by a slide 98 associated with a hydraulic or pneumatic actuator 100 which is arranged to cause the cradle 96, holding a gear 10 to be worked, to perform a cycle of movements, indicated by the double arrow F5, so as to bring the gear 10 to a position in which it meshes with the drive gear 48 and is centred on the axis of the pins 36 and 38. Once this position has been reached, the movable pin 38 moves towards the fixed pin 36 to clamp the gear 10 in the working position. At this point, the slide 98 and the cradle 96 are withdrawn by the actuator 100 to the position of Figure 5. This withdrawal is made possible by the fact that the cradle 96 includes a half-cradle or spout 102 which can yield resiliently in the direction of the arrow F6 so that it can be lowered to the position shown in chain line in Figure 5 to release it from the gear 10.

The cradle 96 is pivoted on the slide 98 by means of a pin 104 so that it can yield resiliently in the direction of the arrow F7 if the gear 10 does not mesh with the drive gear 48 due to interference between their respective teeth. A sensor 106, associated with the cradle 96, is mounted in the slide 98 and, in the event of interference, causes the cycle of movements of the cradle 96 to be repeated. Statistically, this repetition of the cycle results in a change in the orientation of the gear 10 in the cradle 96, so that meshing takes place at the end of the second cycle. If this does not occur, the cycle is repeated and continues to be repeated until meshing is achieved.

The same horizontal arrangement of the pins 36, 38, one of which is movable, also allows the unloading device shown in Figure 6 to be used.

As can be seen in Figures 2 and 6, a window 108 is formed in the working zone of the table 26. Under this window is a cradle 110. The cradle 110 is supported, so that it can be inclined, by means of a pin 112 on a bracket 114 which in turn is carried by the rod 115 of a hydraulic or pneumatic actuator (not shown) . The cradle 110 can be raised and lowered by means of this actuator in the directions shown by the double arrow F8.

When the chamfering of a gear 10 is complete, the cradle 110 is raised to the position shown in broken outline in Figure 6 and receives and supports the gear 10. At this point the pin 38 moves away from the pin 36, releasing the gear 10. The cradle 110 is then lowered to the position shown in continuous outline in Figure 6.

A pillar 116 is associated with the cradle 110 and carries a roller 118 at its upper end. When the cradle 110 is lowered, an arm 120 of the cradle engages the roller 118 causing the cradle 110 to be inclined to the position shown in Figure 6.

A chute or sloping channel 122 is also associated with the cradle 110 and the worked gear 10 can be unloaded into this by.rolling from the cradle 110 so as to reach an output .station constituted by a receptacle, a conveyor, etc.

The machine described and illustrated is versatile in that it can chamfer the edges of the teeth of gears of different diameters and pitches. In order to change from one type of gear to be chamfered to another, it suffices, if necessary, to change the drive wheel 48 and possibly the hobs 18 and to modify the ratio of the gear unit 7 . correspondingly. The presence of the vertically-movable slide 42 enables gears 10 and 48 to be meshed throughout a range of interaxial spacings.

According to the invention, a simpler machine could include only ©ne hob such as 18 for chamfering the edges of only one face of an annular gear at a time.

Claims

1. A machine for chamfering the sharp edges of annular gears (10) each having a central keying bore (14) which opens into two opposite faces of the gear, in which the machine includes support means (36, 38) for the gear which can engage its central bore, means (48) for rotating the gear about its axis (X) and a chamfering tool (18) which can engage the sharp edges to be chamfered, characterised in that the means (36, 38) for supporting the gear (10) are freely rotatable, the means for rotating the gear comprise a drive gear (48) arranged to mesh with the gear (10) to be worked carried by the support means (36, 38), and the chamfering tool is constituted by a hob (18) which is adapted to mesh with the gear to be worked like a worm screw and is arranged so that its cutting edges interfere with the sharp edges to be chamfered, and in that the drive gear (48) and the hob (18) are interconnected by a positive transmission system (56) which is driven continuously by a common motor (54) and is geared so as to rotate the gear (10) to be worked and the hob (18) in synchronism.

2. A machine according to Claim 1, characterised in that it includes a pair of hobs (18) connected by the transmission system (56) so as to rotate in unison and arranged so as to engage the sharp edges to be chamfered on the respective opposite faces of the gear (10) to be worked.

3. A machine according to Claim 1 or Claim 2, characterised in that the or each hob (18) is carried by a slide (50) which is movable towards and away from the gear (10) to"be worked at least to■ adjust .the depth of chamfering cut.

4. A machine according to Claim 3, characterised in that the drive gear (48) is mounted in a replaceable manner on a drive shaft (46) supported by a slide (42) which is movable towards and away from the axis (X) of the gear (10) to be worked to adapt to the diameters and pitches of the pairs of a drive gear (48) and a gear (10) to be worked, the slide (50) of the or each hob (18) also being movable to adapt to the diameters and pitches of the pairs of a hob (18) and a gear (10) to be worked, and the transmission system (56) incorporating a gear unit (74) such as to satisfy the condition of synchronism of gears .and hobs of different diameters and pitches.

5. A machine according to any one of the preceding claims, characterised in that the support means for the gear (10) to be worked comprise a pair of aligned idle pins (36, 38) with facing ends arranged to engage the central bore (14) in the gear to be worked like opposing centres, at least one (38) of the pins being movable along its own axis (X) towards and away from the other pin (36) to clamp the gear (10) between the pins and to release it.

6. A machine according to Claim 5, characterised in that the pins (36, 38) have horizontal axes (X) , the shaft (46) of the drive gear (48) is situated above one of the pins (16) and the or each hob (18) has a vertical axis.

7. A machine according to Claim 6, characterised in that it includes a device for loading the gears (10) to be worked, which is formed essentially by a cradle (96) which is adapted to receive and support a gear (10) to be worked in an upr gήt condition and which can perform a controlled^'movement^"so as to transport the gear from an arrival station to a position in which the gear (10) to be worked is interposed and aligned between the facing ends"-of the ιins (36, 38) which have been moved apart and in^which the gear meshes with the drive gear (48 ) .

8. A machine according to Claim 7, characterised in that the cradle (96) is arranged to perform a controlled cycle of reciprocating movements to bring the gear (10) to be worked into engagement with the drive gear (48) until they mesh with each other, in that the cradle (96) is arranged to yield resiliently should the teeth of the gears (10, 48) interfere, and in that a sensor (106) is associated with the cradle (96) to cause the cycle of movements to be repeated when the teeth interfere.

9. A machine according to Claim 7 or Claim 8, characterised in that it includes a feeder (82) for the gears (20) to be worked, which is formed essentially by a channel (86) in which the gears (10) are deposited side-by-side and face-to-face and which has a pusher (88) vi chπcυes _ei arsto an output end, and by a chute (94) which extends perpendicular to the channel (86) , downwardly from its output end to the cradle (98) , and along which the gears (10) roll one after another.

10. A machine according to Claim 6, characterised in that it includes a device for unloading the worked gears (10) which is formed essentially by a cradle (110) arranged to receive and support the worked gear (10) in an upright condition and which can perform a controlled movement such that it is raised until it receives a gear (10) which is held by the facing ends of the idle pins (36, 38) , is lowered together with the gear (10) released from the pins, and is inclined to enable the gear to roll away.

11. A machine according to Claim 10, characterised in that a chute (118) extends downwardly from the cradle (110) and the gears (10) can leave the machine by rolling down the chute one after another.