GB1583568A

GB1583568A - Gear arrangement

Info

Publication number: GB1583568A
Application number: GB3688277A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-09-03
Filing date: 1977-09-03
Publication date: 1981-01-28

Description

(54) GEAR ARRANGEMENT (71) I, FRIEDRICH SCHELL of 23 Metterstrasse, 714 Ludwigsburg-Pflugfelden, Federal Republic of Germany; a German national do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described- in and by the following statement:- The present invention relates to a swashplate epicyclic gear arrangement for coaxial shafts, the driven shaft being mounted in a hollow driving shaft and having a plate which extends in a plane substantially normal to the longitudinal axes of the shafts and supports a gear ring, with which gear ring a swash-plate gear ring is in rolling engagement, the two gear rings, having differing numbers of teeth.

Such gear arrangements are often used as a means of feeding and retracting a crossslide, a tool or a workpiece carrier of, for example, a lathe to and from the machining position as quickly as possible, the relative displacement of the workpiece and the tool during the actual machining operation being at a slower rate, often referred to as the creep speed. To permit such displacement operations to be carried out at varying speeds, feed gears are known which provide a rapid return traverse and a feed motor which employ an epicyclic gear including wormgear.

Such arrangements are, however, costly to produce.

In many cases, hydraulic feed arrangements are preferred. The disadvantage of such arrangements is that- it is not always possible to produce a constant feed rate without heat production and the apparatus vibrating. Accordingly a mechanical drive is preferred.

The present invention seeks to provide a gear arrangement which is mechanically driven, is of simple construction, is simpler to operate than known mechanical drives and is more economical to produce.

The present invention further seeks to provide, in a preferred embodiment, a feed gear, especially one having both arapid: traverse- and a creeping speed drive motor having an overload cut-out switching device.

According to- the present invention there is provided a swash-plate epicyclic gear arrangement for coaxial shafts, in which a driven shaft is mounted in a hollow driving shaft driven by first drive means and includes a- disc portion extending in a plane substantially normal to the longitudinal axes of the shafts, the disc supporting a gear ring with which a swash-plate gear ring is in rolling engagement, the two gear rings having a different number of teeth from one another, wherein the swash-plate gear ring is mounted on an axis inclined with respect to the longitudinal axis of a second driving shaft but being mounted thereon, the second driving shaft and the driven shaft being coaxial with one another, said second driving shaft being rotatable by second drive means, said first drive means is provided with an electromagnetically actuated spring-pressure brake actuated when said first drive means is cut out, the hollow driving shaft having a gearwheel drive incorporating a torque overload cut-out, and wherein said driven shaft is driven, via the two gear rings, by said first drive means and/or said second drive means.

Preferably the connection- between the swash-plåte gear ring and the driven shaft comprises a second pair of swash-plate gearwheels, or is a universal joint.

Advantageously at least one of the drive means is reversible.

Desirably, the gearwheel drive comprises a pinion driven directly by said first drive means, an intermediate gearwheel and an input gearwheel acting upon the first driving shaft, the intermediate guidewheel being mounted on a shaft, the shaft being resiliently supported in a plane perpendicular to the line connecting the centres of the input gearwheel and the pinion, said resilientlysupported shaft, when radially displaced, causing said drive means to be cut out.

This provides a saleguard which not- only protects the gear arrangement and the devices co-operating therewith, but also protects the tool itself. Utilising the arrangement in accordance with the present invention, divergencies of only about 3 % occurred in the critical region, whilst the disconnection utilising known safeguards or brakes had a divergence of from 10% to 20%. For still greater sensitivity, the intermediate gearwheel may also be located between the input gearwheel of the creeping gear drive and the pinion of the creeping gear drive.

Further preferably, the first drive means is a rapid traverse drive motor.

Further advantageously, the resilient support for the intermediate gearwheel shaft comprises a pin having a recess for receiving the intermediate gearwheel, which pin, when subjected to a torque in excess of a predetermined torque, is caused to move from a rest position against the force of a spring, which spring at its other end is supported against a housing.

This safeguard of preventing an excessive torque being transmitted may be used in gear arrangements having one or two directions of rotation. In gear arrangements having one direction of rotation, one end of the pin, corresponding to the given direction of rotation supports an adjustment member which is desirably adjustable by being screwthreaded within the end of the pin. Movement of the pin, sooner or later, causes the adjustment members to act on a limit switch which cuts out the motor in dependence upon the setting of the member.

In gear arrangements having two directions of rotation and those in which a rapid traverse and a creeping speed motor are provided, the intermediate gearwheel can also rotate in two opposite directions of rotation, each end of the bolt then being provided with adjustment members which actuate limit switches.

With each movement of the pin from its rest position, in order to attain the required cut-off accuracy and lesser divergence, the pin must be biassed only by one spring at any one time. In dependence upon the prevailing conditions, the springs may also have different spring constants. For these reasons, it is desirable if one or both end sections of the pin are enclosed by the spring and have a smaller diameter than the central section of the pin, a disc member biassed by spring pressure abutting against the transition stage, the intermediate gearwheel in its rest position abutting against a shoulder of the housing and which, during a movement of the intermediate gearwheel in a direction generally towards an end section of the pin, lifts off the shoulder of the housing.

In this manner, it is ensured that, depending upon the direction of rotation, only one of the two springs ensures the monitoring and safeguarding of the arrangement.

To obtain less divergence, it is preferred if the pin moves easily, that is to say, to move the pin it should be necessary to overcome only slight frictional forces. In order to achieve this, it is preferred if the housing part against which the spring is supported includes a ball guide bush which closes the recess in the housing for receiving spring in the manner of a cover, the bush having a cover flange secured to the wall of the housing defining the spring receiving space.

In such a case, it is preferred if a resilient gaiter engaging at one end in a ring groove formed in the cover flange of the ball guide bush and at the other end in a ring groove provided in the end of the pin is provided.

Desirably, means are provided for presetting the brake pressure and for maintaining said pressure. This prevents dust or dirt from entering the guide bush and this contributes to the easy action of the pin. This causes the low divergence during cut-out of the safety device.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a plan view, partially in section, of a swash-plate epicyclic gear having a pair of gearwheels forming a positive connection between a swash-plate gear ring and a driven shaft and incorporating a safety device forming part of the present invention; Fig. 2 is an elevational view, partly in section, looking in the direction of the arrow "A" in Fig. 1; Fig. 3 is a section taken along the line Ill-Ill of Fig. 2.

As shown in Fig. 1, a swash-plate epicyclic gearing 1 comprises a cylindrical housing 2.

Mounted within the housing by means of bearings 3 and 4, is a hollow shaft 5 and, by means of bearings 6 and 7, a driving shaft 8.

The hollow shaft 5 is driven by a rapid traverse motor 12 through a gearwheel drive arrangement 9, 10, 11. The motor 12 is provided with a brake generally referenced 13 which simultaneously acts as a torque overload preventer should the gearing become overloaded.

As shown, the brake 13 is an electromagnetically spring-pressure actuated brake, the electromagnet thereof being coupled to the input of the motor 12 such that, when the motor is cut-off, the electromagnet is not energised. This causes compression springs 27 to act so as to press brake linings 28 against a brake disc 29. The braking force may be varied by screwing a housing cover 31 for the brake into or out of a correspondingly threaded recess 32 of the brake housing. By so doing, the tension of the compression springs 27 is varied. Once the brake has been adjusted, a grub screw 33 is tightened to prevent further accidental adjustment.

The rapid traverse motor 12 is fixedly mounted on the external surface of the housing 2, is continuously regulatable and may be of the reversible type.

The driving shaft 8 terminates in a surface 16 extending obliquely to the longitudinal axis of the shaft, the surface being provided with a collar portion 17 which receives and retains a bearing 18 for a bevel gear 19, the gear 19 also extending obliquely to the longitudinal axis of the driving shaft 8.

An axial bearing 20 is also provided to enable the shaft 8 to absorb forces acting in the general direction of the longitudinal axis of the collar 17.

The bevel gear 19 meshes with a further bevel gear 21 which is coaxially mounted on one end of the hollow shaft 5. The two gears 19 and 21 have similar pitches but have different numbers of teeth, the difference between the numbers of teeth being one or two.

Fixedly mounted on the body of the bevel gear 19 is a smaller bevel gear 22 which meshes with a bevel gear 24 splined onto a driven shaft 23. The gears 22 and 24 have the sme pitch and the same number of teeth.

The driven shaft 23 is mounted in the hollow shaft 5 by means of bearings 25 and 26. An axial bearing 27 is again provided to absorb forces acting longitudinally on the shaft 23. The bevel gears 22 and 24 may be replaced by a ball joint or a similarly acting universal joint.

To save one motor, namely the rapid traverse rotor it may be replaced by a coupling/clutch, for example, as magnetic clutch. The clutch is then used together with a fixed or a variable gearing.

To operate the swash-plate epicyclic gearing on, for example, a lathe, it is usually necessary to move a tool or a workpiece holder rapidly towards the machining position. For this purpose, the rapid traverse motor 12 is switched on and a creeping speed motor 14 is inoperative. The bevel gear 21 is driven by the hollow shaft 5 through the gear drive 9, 10, 11. The bevel gear 21 transmits the rotation via the bevel gear 19 and the pair of gearwheels 22, 24 to the driven shaft 23. The tool or workpiece holder is thus rapidly moved to the machining position.

The rapid traverse motor 12 is then switched off and the brake 13 engaged.

Further feed of the tool is effected by operating the creeping speed motor 14.

If the creeping speed motor rotates in the same direction as the rapid traverse motor and both motors are run simultaneously, the rapid drive of the tool is further ac-celerated. If the motors rotate in opposite directions but are both run simultaneously, the drive of the tool is decelerated.

By adjusting the motors, any speed, within certain limits, of drive of the tool can be achieved. By reversing the direction of rotation of the rapid traverse motor the tool carrier may be rapidly returned into its original position after the machining operation has been effected.

When the tool is in the region of the machining position, the creeping traverse motor is, as aforementioned, operated. A slow feed of the tool is with the rapid traverse motor being inoperative. The bevel gear 19 is rotated, in a tumbling manner by the creeping traverse motor 14 through a rubber belt drive 15 and the driving shaft 8. When the number of teeth of a bevel gear with 120 teeth differs by one tooth relative to the associated bevel gear, rotation of the driven shaft 23 through the pair of bevel gears 22 and 24 occurs at a ratio of 120 : 1 relative to the driving shaft 8. By gradual braking of the rapid traverse motor 12, a gradual start may be obtained. The brake may be so arranged that it may be applied by a stop up to a certain torque. Exceeding this torque causes the brake to slip and so acts as a safety clutch for the creeping traverse motor.

By varying the speeds of the creeping and rapid traverse motors, and by varying the directions of rotation thereof, further changes in the transmission ratio may be attained.

The transmission ratio may also be altered by changing the teeth ratio on the bevel gears 19 and 21.

On the cylindrical housing 2, a further housing member 34 is mounted, within which are received gearwheels 9, 10 and 11.

One of these gearwheels is a pinion 11 which is driven by the rapid traverse motor 12 and is flanged to the housing part 34. The pinion 11 meshes with an intermediate gearwheel 10 which, in turn, meshes with an input gearwheel 9 driving the shaft 5.

The intermediate gearwheel 10 is mounted on a shaft 35 in a pin 36, the pin being provided with a recess 30 for receiving the gearwheel 10.

The pin 36 has, moreover, two cylindrical end sections 38 and 39, each of which are surrounded by a helical spring 41 and 42 respectively. The end sections 38 and 39 each have a reduced diameter compared with the diameter of the central portion 37 of the pin 36. A transition portion 43 is formed where each of the end sections 38 and 39 joins the central section 37. A disc 44 is pressed against each transition portion 43 by the spring 41 or 42 respectively when the pin 36 is in its normal, or rest, position.

The disc 44 also in the normal position of the pin, which is that shown in Fig. 2 also abuts against an annular shoulder 45 forming part of the housing 34. The aperture 46 in the shoulder 45 is, however, only wide enough to allow the end section 38 or 39 of the bolt 36 to pass therethrough. The other end of the spring 41 or 42 is supported against the housing 34 through the intermediary of a cylindrical guide bush 47 having an end flange 48 which is fixedly connected by a screw 49 to the wall of the housing 34 defining the space 40 for the spring. To ensure that the pin 36 operates efficiently, the space between the guide bush 47 and the end section 38 of the bolt 36 is filled by balls 51 packed in grease. The balls are prevented from falling out by spring washers 52 snapfitted into the guide bush.

Grooves 54 and 55 are machined into the portion 53 of the bush 47 and into the end sections 38 and 39, into which are snapfitted resilient sealing gaiters 56 and 66.

These gaiters 56 and 66 prevent dirt and dust entering the bush 47.

The free ends of the end portions 38 and 39 of the pin 36 are each provided with a recess carrying an internal screw thread 57, in which adjustment members 58 are screwed.

These adjustment members are so arranged that axial movement of the pin 36 causes one of the members to strike against a pivotally mounted lever 59 which actuates a limit switch 61.

During the operation of the swash-plate epicyclic gear, the springs 41 and 42, with a pre-set tensioning, are used to safeguard the gearing. The tensioning of the springs is effected by the amount the adjustment members 58 are screwed into the recesses 57.

The further they are screwed into the recesses, the greater amount of axial displacement is necessary to actuate the limit switches 61.

If during an advance of the gearing, a preselected torque is exceeded, the shaft 35 of the intermediate gearwheel 10 is displaced along the axis 62 against the effect of the helical spring 41. The axis 62 extends perpendicularly to the axle 63 forming the connecting line between the axes of rotation 64 and 65 of the pinion 11 and the gearwheel 9 respectively. The disc 44, supported on the transition portion 43 between the central section 37 and the end section 38 of the pin, lifts off the shoulder 45. With sufficient displacement of the pin 36, the limit switch 61 switches off the motor actuated thereby.

The torque overload cut-out of apparatus in accordance with the invention need not be restricted in use to protecting and safeguarding the swash-plate gearings or also other gearings. It may thus be used for monitoring the usefulness of a tool on, for example, a lathe. If, for example, the tool is a drill, the drill may become blunt. It must, therefore, be applied with a greater pressure against a workpiece in order to cutin to the workpiece at all. A greater torque is therefore necessary. If the drill.becomes excessively blunt, an excessive torque is transmitted so as to cause the pin 36 to be displaced axially from its normal position until the limit switch 61 cuts out. A visual or auditory warning device may be provided which simultaneously indicates, to the operator of the machine, that the drill needs changing.

WHAT I CLAIM IS: 1. A swash-plate epicyclic gear arrangement for coaxial shafts, in which a driven shaft is mounted in a hollow driving shaft driven by first drive means and includes a disc portion extending in a plane substantially normal to the longitudinal axes of the shafts, the disc supporting a gear ring with which a swash-plate gear ring is in rolling engagement, the two gear rings having a different number of teeth from one another, wherein the swash-plate gear ring is mounted on an axis inclined with respect to the longitudinal axis of a second driving shaft but being mounted thereon, the second driving shaft and the driven shaft being co-axial with one another, said second driving shaft being rotatable by second drive means, said first drive means is provided with an electromagnetically actuated spring-pressure brake actuated when said first drive means is cut out, the hollow driving shaft having a gearwheel drive incorporating a torque overload cut-out, and wherein said driven shaft is driven, via the two gear rings, by said first drive means and/or by said second drive means.

2. A gear arrangement as claimed in claim 1, in which the connection between the swash-plate gear ring and the driven shaft comprises a second pair of swashplate gearwheels.

3. A gear arrangement as claimed in claim 1 in which the connection between the swash-plate gear ring and the driven shaft comprises a universal joint.

4. A gear arrangement as claimed in claim 1, 2 or 3, in which at least one of the drive means is reversible.

5. An apparatus as claimed in any one of claims 1 to 4 wherein the gearwheel drive comprises a pinion driven directly by said first drive means, an intermediate gearwheel and an input gearwheel acting upon the first driving shaft, the intermediate guidewheel being mounted on a shaft, the shaft being resiliently supported in a plane perpendicular to the line connecting the centres of the input gearwheel and the pinion, said resiliently supported shaft, when radially displaced, causing said drive means to be cut out.

6. A gear arrangement as claimed in claim 5, in which the first drive means is a rapid traverse drive motor.

7. A gear arrangement as claimed in claim 5 or 6, in which the resilient supportfor the intermediate gearwheel shaft comprises a pin having a recess for receiving the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. shoulder 45 is, however, only wide enough to allow the end section 38 or 39 of the bolt 36 to pass therethrough. The other end of the spring 41 or 42 is supported against the housing 34 through the intermediary of a cylindrical guide bush 47 having an end flange 48 which is fixedly connected by a screw 49 to the wall of the housing 34 defining the space 40 for the spring. To ensure that the pin 36 operates efficiently, the space between the guide bush 47 and the end section 38 of the bolt 36 is filled by balls 51 packed in grease. The balls are prevented from falling out by spring washers 52 snapfitted into the guide bush. Grooves 54 and 55 are machined into the portion 53 of the bush 47 and into the end sections 38 and 39, into which are snapfitted resilient sealing gaiters 56 and 66. These gaiters 56 and 66 prevent dirt and dust entering the bush 47. The free ends of the end portions 38 and 39 of the pin 36 are each provided with a recess carrying an internal screw thread 57, in which adjustment members 58 are screwed. These adjustment members are so arranged that axial movement of the pin 36 causes one of the members to strike against a pivotally mounted lever 59 which actuates a limit switch 61. During the operation of the swash-plate epicyclic gear, the springs 41 and 42, with a pre-set tensioning, are used to safeguard the gearing. The tensioning of the springs is effected by the amount the adjustment members 58 are screwed into the recesses 57. The further they are screwed into the recesses, the greater amount of axial displacement is necessary to actuate the limit switches 61. If during an advance of the gearing, a preselected torque is exceeded, the shaft 35 of the intermediate gearwheel 10 is displaced along the axis 62 against the effect of the helical spring 41. The axis 62 extends perpendicularly to the axle 63 forming the connecting line between the axes of rotation 64 and 65 of the pinion 11 and the gearwheel 9 respectively. The disc 44, supported on the transition portion 43 between the central section 37 and the end section 38 of the pin, lifts off the shoulder 45. With sufficient displacement of the pin 36, the limit switch 61 switches off the motor actuated thereby. The torque overload cut-out of apparatus in accordance with the invention need not be restricted in use to protecting and safeguarding the swash-plate gearings or also other gearings. It may thus be used for monitoring the usefulness of a tool on, for example, a lathe. If, for example, the tool is a drill, the drill may become blunt. It must, therefore, be applied with a greater pressure against a workpiece in order to cutin to the workpiece at all. A greater torque is therefore necessary. If the drill.becomes excessively blunt, an excessive torque is transmitted so as to cause the pin 36 to be displaced axially from its normal position until the limit switch 61 cuts out. A visual or auditory warning device may be provided which simultaneously indicates, to the operator of the machine, that the drill needs changing. WHAT I CLAIM IS:

1. A swash-plate epicyclic gear arrangement for coaxial shafts, in which a driven shaft is mounted in a hollow driving shaft driven by first drive means and includes a disc portion extending in a plane substantially normal to the longitudinal axes of the shafts, the disc supporting a gear ring with which a swash-plate gear ring is in rolling engagement, the two gear rings having a different number of teeth from one another, wherein the swash-plate gear ring is mounted on an axis inclined with respect to the longitudinal axis of a second driving shaft but being mounted thereon, the second driving shaft and the driven shaft being co-axial with one another, said second driving shaft being rotatable by second drive means, said first drive means is provided with an electromagnetically actuated spring-pressure brake actuated when said first drive means is cut out, the hollow driving shaft having a gearwheel drive incorporating a torque overload cut-out, and wherein said driven shaft is driven, via the two gear rings, by said first drive means and/or by said second drive means.

intermediate gearwheel, which pin, when subjected to a torque in excess of a predetermined torque, is caused to move from a rest position against the force of a spring, which spring at its other end is supported against a housing.

8. A gear arrangement as claimed in any one of claims 5 to 7, in which at least one end of the pin is formed as an adjustment member, capable of actuating on a limit switch to cut out the drive means.

9. A gear arrangement as claimed in claim 8 wherein the adjustment member is screw-threaded and is adjustable within the end of the pin.

10. A gear arrangement as claimed in claims 8 or 9, in which the pin is capable of being displaced in two opposed directions, each of its two end sections being provided with an adjustment member such that, in use, one adjustment member cuts out the second drive means, which is a creeping traverse motor, in one direction of feed and the other cuts out the creeping traverse motor in the other direction of feed.

11. A gear arrangement as claimed in any one of claims 7 to 10, in which one or both end sections of the pin are enclosed by the spring and have a smaller diameter than the central section of the pin, a disc member biassed by spring pressure abutting against the transition stage, the intermediate gear wheel in its rest position abutting against a shoulder of the housing and which, during a movement of the intermediate gearwheel in a direction generally towards an end section of the pin, lifts off the shoulder of the housing.

12. A gear arrangement as claimed in claim 11, in which the housing part against which the spring is supported includes a ball guide bush which closes the recess in the housing for receiving spring in the manner of a cover, the bush having a cover flange secured to the wall of the housing defining the spring receiving space.

13. A gear arrangement as claimed in claim 12, in which a resilient gaiter engaging at one end in a ring groove formed in the cover flange of the ball guide bush and at the other end in a ring groove provided in the end of the pin is provided.

14. A gear arrangement as claimed in any preceding claim wherein means are provided for pre-setting the brake pressure and for maintaining said pressure.

15. A gear arrangement constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.