WO2015025329A1

WO2015025329A1 - Involute helical gear cutter

Info

Publication number: WO2015025329A1
Application number: PCT/IN2013/000776
Authority: WO
Inventors: Apte Rohin
Original assignee: Apte Rohin
Priority date: 2013-08-18
Filing date: 2013-12-17
Publication date: 2015-02-26

Abstract

The Involute Helical Gears have a wide range of application in various products and industriesThe invention is meant for mass production of Involute Helical Gears in a single pass with accuracy, precision, low power consumption and easy machine settings. The machine consists of end milling cutters designed for cutting involute gears. The cutters are placed radially to cut required number of teeth on the workpiece. The workpieces will be moved linearly and radially simultaneously to produce the required involute helical gear.

Description

IN2013/000776

INVOLUTE HELICAL GEAR CUTTER

Description of the Prior Art

The current method of mass production consists of gear hobbing or gear shaping. Gear hobbing machine consists of a bed on which is placed the rotating workpiece holder-chuck and tailstock or collet and tailstock and the gear hob column which can be rotated along its transverse and longitudinal axes. The hob is rotated with the help of hydraulic motor at the said rpm and the gear hob can be rotated along the axis with the said angle. The hob is the gear cutting tool, cylindrical in shape on which cutting teeth are placed helically with specifications required. The workpiece is clamped by chuck and tailstock or collet. The workpiece is rotated to cut gears on it; a jet of lubricating oil is used to lower the temperature of hob and workpiece along with cleaning and lubricating action. The whole process is done by using Computer Numerical Control (CNC) system.

Gear shaving is another process used widely for mass production of gears. The machine consists of a bed on which is placed the workpiece clamping mechanism; chuck and tailstock or collet. The cutting tool consists of a rotating head with plurality of cutting teeth having shape of gear teeth with its said specifications which is supposed to mate with the workpiece. The workpiece rotates at the said rpm; gear shaper cuts gear teeth on workpiece by linear oscillations along with rotation. Thus the gear cutting process takes place in a gear shaping machine. A jet of lubricating oil is used to lower the temperature of hob and workpiece along with cleaning and lubricating action. The whole process is done by using Computer Numerical Control (CNC) system. Drawbacks of the Prior Art:

1. The cycle time of current gear cutting operations is very high compared to the exit rate requirement in an industry.

2. The machine setting time on an average is l/8^th time of a shift. After setting first few workpieces have to be inspected for precision and quality as per the norms specified thus consuming time of production.

3. The cost of spare parts and various accessories is exorbitantly high.

4. The power consumption and the maintenance of these machines is high. A machine has to be dedicated for a single type of gear and at the most to two types in production unit where great variety of gears has to be produced e.g. Automobile industry.

5. Grinding of hob and shaper needs to be done periodically, it requires a grinding machine dedicated only for gear cutting hobs and shaper.

6. Gear hobbing cannot be used to cut shoulder gears of a counter gear shaft (driven gear shaft) of any gear box. The gear shaper performs cutting action only during forward stroke, thus increasing the cycle time and power is wasted in its unproductive return stroke.

7. Guide ways, stroke length and shaper of gear shaping machine has to be changed every time when a different type of gear has to be produced, similarly gear hob has to be changed for different type of gears.

8. Entire cutting tool has to be replaced even if its fewer teeth are damaged or sheared.

9. Concluding from the above said drawbacks the cost price of workpiece is high which affect mass production industries during periodic recessions and low sales period. Description of figures:

I. In Fig.1 is shown the front and side view of assembly of end mill cutters in between the two rings.

1 - End mill cutter

1.1 - Top view of end mill cutter which shows the female Hex to adjust tool using Hex (Allen) key.

2- Taper roller bearing on inner plate

3- Inner ring

4- Adapter

5- Outer ring

6- Taper roller bearing on outer ring

7- The groove made on inner ring to fit circlip

8- inner ring in side view

9- outer ring in side view

II. In Fig.2 is shown the front and side view of driving plates.

10- Front view of driving plate

1 1 - Pulley of the driving plate

12- Driving plate in side view

13- Knurled part of driving plate

III. In Fig.3 is shown the adapter and the end mill cutter used for cutting helical gears.

14- The end mill cutter to cut gear teeth of said specifications it is Al-Tn or Zr-N coated tool, it has very good tool life. The cutter has thread over its surface in order to mate with the adapter. 15- Adapter holds and adjusts the tool; its outer surface is knurled for power transmission and has internal threading.

16- The shoulder on adapter to press fit bearings on it

IV. In Fig.4 is shown the setup of the machine

17- The whole cutting assembly is held by clamping it with the bed

18- Bed on which whole setup is arranged

19- Assembly and transmission of motion using belt and pulley

20- Workpieces are push fitted on the spindle having end portion with threads whose lead is equal to the width of gear

21 - Power is transmitted to driving plates by belt-pulley. The driving plates are rotated in opposite directions

22- Electric motor

23- The clamping of spindle assembly

24- Handle to rotate the spindle

25- Spindle is held in it, it has internal threads mating with workpiece spindle

V. In Fig.5 is shown the tool adjustment setup system.

26- End mill cutter

27- Electric circuit consisting of a LED, D.C. cell and a point contact. This circuit is used for setup of end mill cutters.

28- Disc containing the circuits in plurality for accurate, quick and easy tool setup Description:

1. As shown in Fig. l there is an end mill cutter holding assembly, it has an inner ring 3 and an outer ring 5, both rings have holes equal to the number of teeth on the gear to be cut. The end mill cutters 1 will be placed in between these two rings. Each end mill cutter will be fitted in an adapter 4 which will have internal threads and the cutter will have external threads to mate it with the adapter. The adapter will have its outer surface knurled; two taper bearings 2, 6 are fitted on the ends of adapter to take the axial loads experienced during cutting operation, reduce friction and to hold the cutters in place, the end mill cutter 14 and adapter 15 is shown in Fig.3.both have ISO metric screw threads.

2. As shown in Fig.2 there are two driving ring plates 10 which have their inner surfaces knurled. The ring plates are placed on the inner ring of the cutter holding assembly. The plates are fitted with roller bearings as shown in Fig 2.the plates are driven by belt - pulley assembly by an electric motor in opposite directions to produce couple moment

3. The diving plates will rotate in opposite directions, thus rotating the end mill cutters due to the couple moment produced. Power transmission is established between the driving ring plates and the end mill cutter through the mating of knurled surfaces. The schematic diagram of power transmission is shown in Fig.4.

4. The workpieces are held on a shaft 20 by push fitting using hydraulic press, shaft ends have threads to obtain radial and linear motion simultaneously. The threads of shaft are designed in such a manner so that when it is rotated Φ degrees (Helix angle of gear) it will travel linearly equal to the width of gear. Thus when one complete rotation (360 ° ) is completed it will travel (3607 < )*w. In one rotation (3607 Φ) number of gears can be cut. The assembly and complete arrangement is shown in FigAthe lead of shaft is equal to the width of the gear. Workpiececs can also be held on a collet and tailstock.

5. The workpiece clamping and feed can be automated using hydraulics and mechatronics.

The method shown in the Fig.4 is suggested taking into consideration all scales (small to large) of manufacturing industries.

6. The tool setup is done by using the setup shown in Fig.5. a disc is mounted with an electric circuit 27 consisting of a LED, D.C. cell and a point contact. The circuit will be closed only when the tool has been adjusted. The disc is fitted on the workpiece spindle and the end mill cutter can be moved linearly with a Hex (Allen) key; point contacts are arranged radially on this disc at a distance equal to the root diameter of the workpiece to be produced. Tool setup can be accurately done as circuit will closed at only one point. Fig5.a shows the position when adjustment is done and the pilot LED is lit. Fig.5.b and Fig.5.c show the two extreme positions were circuit is not closed.

Summary of Invention:

The objective of invention is to overcome the problems experienced with the known art. To increase production rate by reducing cycle time, production cost and delays due to setup changes, machine breakdowns and maintenance. The invention is a single pass involute helical gear cutter in which end mill cutters of said specifications are radially arranged to cut gears. The helical gear can be produced when the workpiece will be rotated at the said helix angle in the said width of gear. Thus the invention is capable to produce N-number of identical gears in one rotation of the workpiece spindle. The machine is meant for mass production of identical involute helical gears of said specifications.

The machine is a single pass gear cutter with end mill cutters of said specifications arranged radially and held by two plates assembly. This assembly of end mill cutter is driven by two plates producing couple moment due rotation in opposite directions.

The machine can take axial as well as thrust loads efficiently, thus minimizing the tool vibrations and chattering. This characteristic of assembly enables it to produce identical parts within given tolerance bands and said accuracy.

N- number of parts can be made in one rotation of workpiece spindle

Where, N = (360 °/ 0)*w

Φ - Helix angle of the gear,

w - Width of gear.

The workpieces will never have defects like ovality or axial run out as they are fit on spindle or collet which will self center the workpieces and hold them axially.

The end mill cutters can be precisely adjusted due to the threading on it and the adapter during the start of operation or even after resharpening is done.

Claims

I claim,

1. A gear cutter comprising of an inner ring and an outer pressure ring holding end mill gear cutters in plurality, arranged radially to cut gear teeth of said specifications. The cutter is meant for mass production of involute helical gears in a single pass.

2. As per claiml, a gear cutter driven by two driving plates meshing with the adapters to rotate them by producing couple moment by rotating in opposite directions. The plates are rotated by belt -pulley assembly at high rpm in opposite directions.

3. As per claiml or 2, a gear cutter which can take axial and thrust loads due the taper roller bearings on the shoulder of the adapter and the whole assembly acts like a thrust roller bearing, thus reducing vibrations and chattering during cutting operations. The accuracy and surface finish of every gear is thus uniformly maintained.

4. As per claim 1,2 or 3, a gear cutter comprising of an inner ring and an outer pressure ring holding end mill gear cutters in plurality, arranged radially to cut gear teeth of said specifications, driven by two. driving plates meshing with the adapters to rotate them by producing couple moment by rotating in opposite directions, producing N- number of gears in one rotation of workpiece spindle

Where, N = (360 °/ 0)*w

Φ - Helix angle of the gear,

w - Width of gear.

5. As per claim 1,2,3 or 4, a gear cutter comprising of an inner ring and an outer pressure ring holding end mill gear cutters in plurality, arranged radially to cut gear teeth of said specifications, , without any ovality or axial run out as the workpieces are push fitted on the spindle thus self-centering is achieved.

6. As per claim 1 ,2,3,4 or 5, a gear cutter comprising of an inner ring and an outer pressure ring holding end mill gear cutters in plurality, arranged radially to cut gear teeth of said specifications, driven by two driving plates meshing with the adapters to rotate them by producing couple moment by rotating in opposite directions, with easy adjustment of end mill cutters due to ISO metric screw thread mating between the adapter and the end mill cutters. The adjustment is made easy and accurate due to the adjustment disc as mentioned in the description.

7. As per claim 1, 2,3,4,5, or 6, a gear cutter comprising of an inner ring and an outer pressure ring holding end mill gear cutters in plurality, arranged radially to cut gear teeth of said specifications, can be used for gear cutting of shoulder gears and driven shafts of gear box of same width and helix angle with variable radii and number of teeth on each gear of the shaft, by arranging multiple gear cutter assemblies linearly.