Controllable tooling for gear cutting machine

Controllable tooling is mounted in a carrier with parallel spring elements positioned at right angles to an intended path of adjustment for the tooling so that precisely controlled adjustments can be applied to the tooling while it is performing a cutting operation on a workpiece.

BACKGROUND AND BRIEF DESCRIPTION OF INVENTION 
It is known in the art of gear cutting to provide for machines which 
utilize an endless chain for carrying a series of cutting tools into 
engagement with a workpiece to shape the workpiece into a gear form. It is 
also known to arrange a series of cutting tools around a cylindrical body 
for forming gears. 
Although existing gears cutting equipment does a very satisfactory job of 
shaping gear tooth profiles, such as those required for spur and helical 
gears, certain gear applications require a refinement of such equipment to 
provide a lengthwise "crowning" of individual tooth members of whatever 
gear is being manufactured. Crowning is a known feature of certain types 
of bevel gear making machinery (as shown, for example, in U.S. Pat. Nos. 
2,352,689; 2,385,330; and 2,385,331), however, it is not believed to be 
known for other types of gear making machinery which provide for a 
movement of one or more rows of cutting tools in a flat plane through a 
tooth slot. For example, when a series of cutting tools are rigidly 
secured in one or more carriers which are advanced into engagement with a 
workblank, a generally straight cut is formed when viewed in the 
longitudinal (or lengthwise) direction of each tooth slot being shaped 
into the workpiece. In order to crown the side wall portions of such a 
straight cut, it is required that there be a deeper cut at the entry and 
exit ends of the tooth slot as a cutting tool advances into and out of the 
slot. It is a primary purpose of this invention to provide an improved 
mechanical arrangement for controlling positions of selected cutting tools 
as they advance through tooth slots of a workpiece to thereby provide for 
a desired depth of cut to thereby achieve crowning of the individual tooth 
profiles. 
In accordance with a specific embodiment of the present invention, selected 
stock-removing tools of a gear cutting machine are held by a number of 
carriers articulated together to form an endless chain which can be 
advanced into engagement with a workpiece to form tooth slots for a spur 
or helical gear. Mounting means are provided for securing selected tools 
of the series for controlled movements relative to their respective 
carriers to thereby provide for precision cutting and shaping of gear 
tooth profiles as the selected tools are advanced through slots of the 
workpiece. Control means are associated with the carriers for controlling 
the positions of the mounting means relative to the carriers in a way 
which extends or retracts the selected tools during a cutting operation as 
the tools are brought into engagement with the workpiece. Each mounting 
means comprises a mounting block for receiving a stock-removing tool in 
fixed relationship thereto, and the mounting block is suspended in a novel 
way within a bore of an associated carrier with spring elements comprising 
flat ring elements which are fitted around the mounting block and within 
the bore of the carrier. The spring elements are arranged in parallel 
planes at right angles to the desired axis of motion for the tools. The 
use of such spring elements eliminates the need for bearings or bearing 
surfaces and provides for radial rigidity of the tool while permitting 
linear motion of the tool. In addition, this type of suspension of a tool 
provides for a more rapid response with less of a tendency to initially 
stick and then slip to a new position. A displaceable member is fitted 
within the carrier for contacting and moving the mounting means in 
accordance with the degree and type of precision shaping required, and 
each displaceable member is actuated, in turn, by a control bar which 
follows a cam surface provided on a relatively fixed portion of the gear 
machine. In this way controlled movements are dictated to the selected 
tools as the tools move through a work zone of the machine. 
The mechanism of the present invention is very reliable in design and 
provides for a positive and known displacement of the selected cutting 
tools at exactly the right points of travel of each tool relative to a 
tooth slot of the workpiece. The use of spring elements for suspending the 
tools provides for a simple and highly reliable system for positioning and 
moving the tools. Individual components of the mechanism are designed to 
withstand the stresses and workloads associated with production 
manufacture of gears or similar type products. These and other advantages 
and features of the invention will become apparent in the more detailed 
discussion which follows, and in that discussion reference will be made to 
the accompanying drawings as briefly described below.

DETAILED DESCRIPTION OF INVENTION 
Although the controllable tooling of the present invention may be utilized 
with various kinds of metalworking and gear cutting machines, it was 
specifically developed for the type of machine shown in FIG. 1. This type 
of gear cutting machine is designed to cut spur or helical gears through 
the engagement of a series of stock-removing tools with a workpiece as the 
tools are advanced about the circumference of a relatively large machining 
head. In a machine of this type, a number of stock-removing tools are 
carried on individual link members of an endless chain assembly which 
extends around the entire machining head portion of the machine, and in 
this manner, a great number of stock-removing tools can be brought into 
engagement with a workpiece. 
Considering the specific details of the machine shown in FIG. 1, it can be 
seen that basic machine assemblies are carried on a common base 10, and 
these components include a tool carrying assembly 12 mounted on a housing 
14 together with a work station 16 mounted on its own base 18. The tool 
carrying assembly 12 can be advanced towards and away from a workpiece 20 
through a sliding action of the housing 14 on ways 22. The workpiece 20 is 
mounted on a work spindle 24 for timed rotation or incremental rotation in 
relationship to the advancement of stock-removing tools 26. The 
illustrated stock-removing tools may be of any known design. In a specific 
use of this invention, tools of the type in which the cutting face is not 
resharpened (as shown in U.S. Pat. No. 4,060,881) were used. Transverse 
placement of the workpiece relative to the cutting tools can be achieved 
through a movement of the work station 16 on ways 28 mounted on the base 
18. 
In operation, the type of machine just described provides for an engagement 
of the cutting head portion of the machine with a workblank contained 
within the work station portion of the machine. As the cutting tools 
engage the workpiece, tooth slots are formed in precisely spaced positions 
about the circumference of the workpiece to thereby form a spur or helical 
gear, depending upon the relative tilt of the tool carrying assembly 12 to 
the workpiece. Individual profiles are formed by a generating action 
between the cutting tools and the workpiece as the tools are brought into 
full depth engagement with the workpiece and as the workpiece is precisely 
rotated relative to the cutting tools. After a single tooth slot has been 
formed, the cutting tools of the machine are retracted out of engagement 
with the workpiece, and the workpiece is indexed to a position for forming 
a next adjacent tooth slot to the one just formed. In this manner, tooth 
slots and tooth profiles are formed about the entire circumference of a 
workblank. 
As shown in FIG. 2, the normal action of the machine operation just 
described is to produce tooth slots 30 which have sidewalls 32 having no 
crowning curvature from one face of the gear to an opposite face of the 
gear. This results from the sequential entry of a series of cutting tools 
at one end of the tooth slot, followed by a straight line movement of the 
cutting tools through the tooth slot until the tools leave the slot at an 
opposite side of the gear. 
FIG. 2 also illustrates (with dashed lines) a type of "crowning" curvature 
which is sometimes desirable for tooth profiles of spur or helical gears. 
Although the crowning is greatly exaggerated in the FIG. 2 view (for 
purposed of clarity), it can be appreciated that even a very mild amount 
of lengthwise curvature of the tooth slot requires a repositioning of 
individual cutting tools as they pass through the tooth slot. One way of 
achieving such crowning is shown in FIG. 3 wherein a single cutting tool 
26 is illustrated as engaging a single sidewall 32 of a tooth slot 30. As 
can be seen, the tooth slot is of a type which is formed to full depth by 
separate cutting tools of a series which define a bottom for the slot so 
that the illustrated cutting tool is not required to carry out a dual 
function of shaping the sidewall 32 as well as the bottom of the tooth 
slot. However, it is possible to use tooling which cuts side and bottom 
portions of the tooth slot simultaneously. The dashed line position of the 
wall 32, as shown in FIG. 3, represents the increased depth of cutting 
which can be achieved with the cutting tool 26 if the tool is moved in the 
direction of the arrow. This movement has the effect of removing a greater 
amount of stock from the sidewall portion of the workpiece. Thus, it can 
be seen that such a movement of the cutting tool during the initial part 
of its travel through a tooth slot and again upon leaving the tooth slot 
will produce the type of curved shape shown by the dashed lines in the 
FIG. 2 view. Such movement is very precise and very slight and requires a 
high degree of control of position of the tool as the tool progresses 
through a tooth slot of a workpiece. This control is achieved with the 
mechanisms described in FIGS. 4-7. 
FIG. 4 shows a number of articulated link members 40 making up the endless 
chain of the machine of FIG. 1. The individual link members 40 may be 
considered as carriers for a series of cutting tools 26 which are arranged 
in a single row about the entire circumference of the endless chain. The 
manner in which the links are driven and other details of the operation of 
the machine itself are now known in the art and are disclosed, for 
example, in pending application Ser. No. 929,600, filed on July 31, 1978. 
In addition, endless chain type machines are shown in the U.S. Pat. Nos. 
1,468,393 and 1,469,602. In the arrangement shown in FIG. 4, every other 
cutting tool 26 of the series is arranged to be axially controlled in its 
position relative to the carrier 40 with which it is associated. Tools 
which are not so controlled are fixed in their relationship to the carrier 
and serve, for example, to rough out a tooth slot or to define the full 
depth bottom portion of the slot, leaving it to the remaining controllable 
tools to shape the sidewall portions thereof. 
Referring to FIGS. 5 and 6, it can be seen that each of the controllable 
tools is secured within a mounting means 50 which comprises a mounting 
block having an exterior profile made up of cylindrical surfaces for being 
fitted within a bore 52 formed in the carrier. The mounting block 50 is 
suspended within the bore with a pair of spring elements 54 which comprise 
metallic, flat, ring elements fitted around opposite ends of the mounting 
block and within the bore of the carrier to provide for a secure 
suspension of the mounting block within the bore. These springs serve to 
constrain the tool radially while, at the same time, permitting limited 
(on the order of 0.001 to 0.005 inches) axial movement of the tool. This 
arrangement is simple and reliable and eliminates the need for fitting the 
tool within bearing surfaces since there is no functional engagement of 
the tool with the mounting block or with the carrier. The spring elements 
54 are placed at right angles to the intended line of travel of the tool, 
thus assuring accurate linear movement of the tool with no deviation from 
its intended path of travel. As the mounting block is moved (in axial 
directions along the axis of the cutting tool 26), the spring elements 54 
are flexed away from their normal positions shown in FIG. 5, and there is 
a tendency for the mounting block to be returned to its normal position as 
soon as it is released from a displaced position. The mounting block 50 is 
contacted and moved by a separate displaceable member 55. The displaceable 
member 55 is of a generally cylindrical form and is fitted within a 
separate portion of the link member 40 so that it does not have to be 
removed from the link when the tool holder portion 42 is removed for 
changing or adjusting tools. The displaceable member 55 is mounted within 
a pair of sleeves having roller bearings 56 therebetween, and a hardened 
end portion 58 is provided for making actual contact with a similarly 
hardened end portion 60 of the mounting block 50. Thus, as the 
displaceable member 55 is moved toward and away from the mounting block 
50, the mounting block 50 is, in turn, advanced and retracted relative to 
a workpiece. 
Control of the displaceable member 55 is achieved through the use of a 
control bar 62 (see also FIG. 6) having an inclined surface 64 for 
contacting a portion of the displaceable member 55. As can be seen from 
the views of FIGS. 6 and 7, transverse movements of the control bar 62, as 
determined by a cam 66 and a follower 68 carried at the end of the control 
bar dictate movement of the displaceable member 55 and the mounting block 
50 with its contained cutting blade 26. It can be seen that the control 
bar 62 is fitted transversely through a portion of the carrier 40 with its 
follower being carried externally thereof for contacting a cam surface 66 
arranged along the side of the machine housing in which the endless chain 
is mounted for movement. The shape of the profile of the cam surface 66 
determines the precise point at which shaping begins and ends in any tooth 
slot of a workpiece being formed by the cutting tools being carried by the 
endless chain. The working end of the control bar 62, including the 
inclined surface 64 formed thereon, is mounted on bearings for ease of 
operation. The control bar 62 is loaded against a spring 69 which is 
arranged to maintain the follower 68 of the control bar in contact with 
the cam surface 66. 
FIG. 6 also shows details for the securement of individual cutting blades 
26 into respective mounting blocks 50 with screw fasteners 70. In addition 
there is shown a key element 72 which serves to engage a slot formed in a 
cylindrical portion of the mounting block 50 to prevent rotation of the 
mounting block (and its contained cutting tool) within the carrier in 
which it is mounted. 
Having described structural features and detail of a specific and preferred 
embodiment of the present invention, it can be appreciated that similar 
arrangements can be provided on fully equivalent machinery to that which 
has been disclosed herein. For example, the cutting tools which are shown 
could just as well be grinding elements, and the novel spring mounting of 
the tools can be applied to other forms of machinery and to other tool 
holding requirements. Equivalent substitutions of structural detail and 
equivalent uses are intended to be included within the scope of protection 
defined in the claims below.