GB2096499A - Bar-stock feed finger - Google Patents

Abstract

A feed finger for use in single and multiple spindle lathes and other machine tools comprises a solid body 8 having a thread 2 for screwing into the feed tube of an automatic lathe and containing a bore 9 and lead-in 10 converging into bores 14 of split sleeves 12 the latter being mounted within a bore 11 which is tapered. The bores of split sleeves 12 are closed in to a size slightly smaller than the diameter of the bar material for which they are designed, and the sleeves are retained within the tapered bore 11 by split nut 16 screwed into thread 27 within the body 8. The feed finger is particularly suitable for utilisation with automatic Bar Replacement Magazine mechanisms as new bar can readily be fed through the bore 9, lead-in 10 and the chamfered bores 14 of the split sleeves 12 by a Simple Pusher Head. It is not affected by Centrifugal Force at high spindle speeds and also facilitates manual bar replacement. <IMAGE>

Description

SPECIFICATION Improvements to feed fingers The feed finger shown in Figure 1 is representative of the general type which has been utilised by industry in single spindle and multi spindle lathes and other machines for many years. The finger consists of a tubular barrel 1 Figure 1 having a screw thread at 2 which is threaded into a Feed Tube 3, the latter being reciprocated forwardly and rearwardly by the machine mechanism for feeding bar material through the spring clamping collet fitted within the machine spindle. Such fingers are split by milled slots 4 and sawcuts 5 before being closed in, as shown, particularly, by the approximate elyptical contour of the bore 6.The effect of the closing of the two sections is to provide high frictional contact between the bore 6 and the bar material for which it is designed, so that the full length of bar material can be fed in a short period of time in the machine cycle time without undue slippage. However bar must be fed firstly through the "lead in" section 7 before it can pass through the bore 6, and very considerable force is required to spring the two sections of the finger apart. This is normally accomplished by an operator hammering the outwardly facing end ofthe bar until it forces the two split sections of the finger to open. Because the actual shapes of the various different bar ends are very inconsistent it is virtually impossible to determine the actual effort required to obtain entry of the bar into bore 6.

The foregoing applies to round section bar but still greater difficulty is present when Hexagon or other non circular material is required to be handled. In such cases not only the problems already cited are met with, but also the difficulty of locating the hexagon of the material in line with the hexagon contour of the collapsed elyptical hexagon bore of the feed finger 1. This latter difficulty is accentuated by the fact that the Hexagon angular position of the feed finger bore cannot be seen by the operator as he hammers the bar into the bore. He therefore continues to hammer until the contour of the bar and the feed finger find themselves in alignment. Hexagon feed fingers may be provided with three slots instead of two as illustrated in Figure 1 but the foregoing difficulties remain.

Because of the conditions described it is virtually impossible to utilise the feed fingers as illustrated in Figure 1 in conjunction with an automatic Bar Replacement Magazine because of the problems cited.

According to the present invention there is provided a Feed Finger Figure 2. which consists of a solid tubular section body 8 having a threaded portion 2 for connecting to a Feed Tube as illustrated in Figure 1 at 2, this Body 8 (Figure 2) has a bore 9 converging into a lead-in 10 and is provided with a further bore 11 carrying a series of split tension sleeves 12. These split sleeves 12 have bores 14 slightly smaller than the bar material for which they are designed and also a chamfered lead-in 13 as shown in enlarged section view of this type of sleeve, Figure 6.The bores 14 Figure 2 provide a frictional grip on the bar material such that when the finger is operated rearwardly i.e. to the left, by the machine mechanism of such machines as single or multi spindle lathes there is sufficient friction to trigger the automatic "knock off" device which stops the automatic cycle of such machines with the clamping collet open ready to insert new bar material, this occurring when the feed finger pulls off the short remaining bar end within the spindle. The lead-in 10 and 13 (Figure 6) make it relatively easy for new bar to be fed into a machine spindle by a simple pusher head built into an automatic Bar Replacement Magazine mechanism.The high friction required for feeding of bar material during the machine automatic cycle is generated by the action of the split sleeves being pulled into the taper bore 11 (Figure 2) by the friction between the bar material and the bores of the sleeves 14 as the Feed Finger 8 is operated forwardly i.e. to the right as viewed. For this purpose clearance is arranged at 17 which allows the split sleeves 12 to move to the left as viewed, so in turn causing the bores 14to be reduced in size. The sleeves 12 split on one side by sawcuts 24 are retained in the body 8 by split nut 16 screwed into thread 27 and have angular inside faces 15 which match the angular faces of sleeves 12. The split nut 16 is spung outwardly before assembly so that it is held frictionally within the thread of Body 8 and does not loosen in operation.The reduction of the bores 14 is important particularly for small capacity automatic lathes as the actual time available during automatic cycling for feeding bar for the next workpiece may be as short as 0,2 seconds, so that a high frictional grip is necessary. For machines where feeding of bar is not so critical as regards time available the bore 11 of Body 8 may be parallel not tapered, as sufficient friction may be available between the bores of split sleeves 12 and the bar material, to feed bar without the closing-in effect described. Figure 4 illustrates a Feed Finger of the same type as Figure 2 but designed for smaller size bar material. This smaller capacity finger has a solid Body 20 having a screw thread at 2 for screwing into a Feed Tube 3 as shown in Figure 1.Split Tension Sleeves 21 - Figure 4 are accomodated in a tapered bore 18 and are held against the angular face of Nut 16 by Spring 28 which provides only a light tension, in order to prevent the sleeves 21 from tilting when new bar is being inserted. The Nut 16 is split as already described to prevent loosening, and is screwed into thread 27 within the Body 20. The tension sleeves 21 are split at 24 and are partially reduced on their outside diameters as illustrated at 29 in order to make them more flexible and so more easily closed in by bore 18 due to friction between sleeve bore 19 and the bar material for which they are designed. Clearance 17 permits this closing in effect. The split sleeves 21 have a lead-in 13 Figure 5 and may also have weakening slots 25 to ensure flexibility.Atapered bore 10 in the Body 20 guides newly inserted bar material into the split sleeves 21 (Figure 4). A split sleeve 22 Figure 3 has a Hexagon Bore suitable for this type of bar material and is suitable for use in the Body 20 (Figure 4) but a clearance key, not shown, is necessary to hold the bores of all sleeves in alignment.

Modern single spindle and multi spindle lathes and other machine tools have very high spindle speeds due to the utilisation of Tungsten Carbide and Ceramic tooling. The type of Feed Finger illustrated in Figure 1 which is in general use in industry is adversely affected by the centrifugal force generated by these high speeds. The two or maybe three split sections of such fingers are sprung outwardly by this force, so that much of their grip on bar material is lost and short and unsatisfactory feeding results. In an attempt to overcome this problem higher tension has been built into the Feed Finger split sections but this causes further problems. Bar material is normally fed through the Feed Fingers with the machine spindle stationery (non revolving) so that centrifugal force and therefore the outwardly springing effect on the finger sections is not present.In consequence this higher tension makes insertion of new bar still more difficult, and these Feed Fingers, even more unsuitable for use with an automatic Bar Replacement Magazine mechanism.

Centrifugal force even at these high speeds as described has very little effect on the split sleeves 12 Figure 2 and 21 Figure 4 so that the tension built into them is scarcely affected as neither is the forward feeding effect generated by the pulling back into the taper bore 11 Figure 2 or 18 Figure 4. The Feed Fingers as illustrated in these two Figures 2 and 4 are in consequence suitable for application to automatic Bar Replacement Magazine mechanisms as a simple Pusher Head is able to press new bar material through the leads 10 in the bodies 8 and 20 into the lead-in provided in split sleeves 12 and 21 with only moderate pressure.Additional tension of the split sleeves is generated when the machine spindles are rotating at high speed, by the action of the friction between the bar material and the partially collapsed bores of the sleeves 12 and 21 when actually feeding bar forwardly, as already described.

Although the Feed Fingers Figures 2 and 4 are particularly suitable for application with Bar Replacement Magazine mechanisms they also provide considerable advantage to an operator when inserting bar into a machine manually.

Background to the invention Feed Fingers for use in single spindle, multiple spindle lathes and other machine tools in general, consist of a tubular body having a thread at one end for screwing into the Feed Tube of the machine and a bore converging into a smaller bore which is of the size of the bar material it is intended to handle. The tubular body is split for the greater part of its length by a sawcut and the 2 sections left by the sawcut are sprung together after heat treatment so that the smaller bar size bore is modified to a generally elyptical shape and in consequence provides a friction grip on bar of the designated size when this is inserted.The action of these Fingers when feeding bar in an automatic lathe is as follows:- With the workspindle collet closed the Feed Finger is retracted by the machine mechanism which drags it over the bar material without moving the material longitudinally. The clamping collet is now opened so that it does not hold the bar and the Feed Finger then by friction feeds the bar forward to the length adjusted forthe next workpiece, the bar meeting a stop to control the exact length fed. The collet then closes and the automatic machining cycle commences. When the length of bar material in the workspindle is completely used up, the Feed Finger pulls off the end of the bar during its retracted stroke.

Now there is no friction between the Finger bore and the bar and the absence of this friction causes a spring within the pull back mechanism to operate this mechanism an additional distance and trigger a "knock off" device which stops the automatic cycle with the clamping collet open ready for insertion of a new bar. In order to insert a new bar the operator has to hammer the outward end of the bar with sufficiently heavy blows to open the closed in split sections already described. Because in practice the bar ends are left rough and even out of square quite considerable blows are necessary to enable the bar to enter the Finger bore and furthermore the shape of the bar ends is not consistent so that the magnitude of the blows is indeterminate.For the foregoing reasons the generally used type of Feed Finger is not practicable or applicable to an automatic Bar Replacement Magazine mechanism. Such a mechanism consists of opening type stock tubes which when opened allow bar from a magazine to drop into the tube which is then closed. The bar end stands out from the tube and it is then necessary for a Pusher Head to press the bar through the Feed Finger and Collet to a predetermined length. A Feed Finger is therefore required which will permit bar to be pusher through its bore without indeterminate heavy blows.

The present invention therefore describes a Feed Finger having a solid body which contains split sleeves lying within a tapered bore of the body, the bores of the split sleeves being slightly smaller than the size of the bar they are designed to accomodate.

When these sleeve are dragged rearwardly over the bar they provide sufficient friction to operate the "knock off" device already referred to when bar is exhausted. When feeding bar forward normally in the machining cycle the friction between the split sleeves and the bar material causes the sleeves to move rearwardly within the tapered bore of the body and so they are closed in more tightly, helped by the weight of the bar. Because the bore of the sleeves is only slightly smaller than the bar size and because lead-in chamfers are provided a simple Pusher Head can readily feed New Barthrough them.

Brief description of the drawings Figure 1 is a sectional view of a representative type of feed finger in general use in automatic lathes.

Figure 2 is a sectional view of a feed finger containing split sleeves in accordance with the invention.

Figure 3 is a sectional view of a split sleeve for hexagon bar material applicable to the feed finger shewn in Figure 4.

Figure 4 is a sectional view of a feed finger of smaller bar capacity than that shewn in Figure 2.

Figure 5 is a sectional view of a split sleeve for use in feed finger shewn in Figure 4.

Figure 6 is a sectional view of a split sleeve for use in feed finger shewn in Figure 2.

Claims (11)

1. A Feed Finger comprising a solid tubular body having a screw head at one end adapted to be threaded into a Feed Tube carried within the spindle of a single spindle or multiple spindle lathe or other machine tool and comprising an open bore at the screw thread end tapering into another bore slightly larger than the diameter of the round bar bar material it is designed to feed, adjacent to which is a further outwardly tapering bore carrying one or a series of split sleeves whose bore is slighly smaller than the size of bar they are designed to feed and whose external diameter has the same angle as the outwardly tapered bore within the body, the split sleeves being capable of sliding a limited distance endwise within the tapered body bore and retained at the end of the body opposite from the thread for engaging the Feed Tube by a hollow nut engaged by a tapped bore in the body, such that bar of the designated size may readily be guided and fed from the rear of the Feed Tube through the bores in the body and into the slightly smaller bore of the split sleeves or sleeve which expand as the bar feeds through, advanced manually or by a mechanically operated Pusher Head, the split sleeves or at least one of them having sufficient frictional grip on the bar material as to make it or them capable of operating the automatic knock-off mechanism provided in most automatic lathes or other machine tools when the bar within the spindle of such machines is practically exhausted and the Feed Finger has pulled off the short bar remnant left within the spindle, but also capable of feeding the maximum length of bar within the machine capacity due to the action of the split sleeve or sleeves which when the clamping collet within the spindle of a machine is opened grip the bar as the Feed Finger is operated forwardly i.e. in the direction towards the hollow nut, as the frictional grip of the split sleeve or sleeves on the bar causes them to slide towards the smaller diameter of tapered bore within the body thus closing their bore or bores more tightly on the bar material, such that even where the time available for feeding the bar material in the smaller capacity machines is extremely short for example 0,2 seconds or slightly less, they operate efficiently.

2. A Feed Finger as claimed in Claim 1 characterised in that the split sleeve or sleeves for gripping the bar material may have circular bores for round material or contoured bores for hexagon or other sectional material, in the latter case a loose key is provided within the body of the finger to maintain the contoured bores of the sleeves in alignment.

3. A Feed Finger as claimed in Claim 1 in which the hollow nut for retaining the split sleeves within the tapered bore of the body is split by a sawcut at one side and then sprung outwardly before assembly so frictionally locking the nut against accidental loosening

4. A Feed Finger as claimed in Claim 1 in which weakening slots running substantially radially part way through their sectional area of the split sleeves may be provided in order to make them more flexible.

5. A Feed Finger as claimed in Claim 1 in which the outside diameter of the split sleeves may be reduced over part of their length in order that they may readily reduce their bores when pulled into the tapered bore of the Feed Finger body.

6. A Feed Finger as claimed in Claim 1 containing a plurality of split sleeves in which one of the sleeves has sufficient tensional grip on the bar material it is designed to feed, such that by itself it is capable of triggering the automatic knock off mechanism as described in Claim 1, whereas the other split sleeves may be of reduced tension and sectional area so that they reduce their internal bores readily when pulled into the tapered bore of the Feed Finger Body.

7. A Feed Finger as claimed in Claim 1 in which a low tensioned spring may be provided at the small end of the tapered section of the split sleeves in order to prevent them from tilting as bar is fed into them.

8. A Feed Finger as claimed in Claim 1 wherein the split sleeves for gripping the bar are readily and cheaply replaceable after removal of the split retaining nut and where one tubular body may be utilised for a range of different bore split sleeves for accomodating different sizes of bar material, entry of the bar material being facilitated by providing a relatively large lead-in chamfer on the first split sleeve to be contacted by the incoming bar.

9. A Feed Finger as claimed in Claim 1 in which the split sleeves for gripping the bar material are all provided with a lead-in or chamfer at their forward ends relative to the incoming bar.

10. A Feed Finger as claimed in Claim 1 in which the bore of the body containing the split sleeves is parallel, not tapered, and the split sleeves likewise have a parallel outside diameter, for use where the additional grip generated by the sliding action of the tapered sleeves is not necessary.

11. A Feed Finger as claimed in Claims 1 to 10 consisting of a solid tubular body containing split sleeves substantially as herein described with reference to the accompanying drawings.