US2657046A - Automatic feed mechanism for power presses and like machines - Google Patents

Description

c. E. TALLls 2,657,046

PRESSES AND LIKE MACHINES 6 Sheets-Sheet l Oct. 27, 1953 AUTOMATIC FEED MECHANISM FOR POWER Filed Aug. 20, 1951 C. E. TA LLIS FEE Oct. 27, 1953 AUTOMATIC D MECHANISM FOR POWER PRESSES AND LIKE.' MACHINES 6 Sheets-Sheet 2 Filed Aug. 2o, 1951 CAMLVZJQJZ; fly/MQW N-m A| AI- L c w. n N Q/N NQ wenn 2 m Nm V ...........H- I@ Q Il L. vwr mV I i f3 L, m E. mv S 2 l m /om ////////v7/ Idv Oct. 27, 1953 c. E. TALLls 2,657,046

AUTOMATIC FEED MECHANISM FOR POWER PRESSES AND LIKE MACHINES Filed Aug. 20, 1951 6 Sheets-Sheet 3 I 2 I4 '5 lo I4 9 l2 CM2. MA "ry Sdw-f Oct. 27, 1953 c. E. TALLxs 2,657,046 AUTOMATIC FEED MECHA SMF' POWER n l PRESSES AND LIK AGHI med Aug. 2o, 1951 e sheets-sheet 4 f le 2 3 IG 5 3 2a \32 42/ N k /Nv y Oct. 27, 1953 Q E TALL|5 2,657,046

AUTOMATIC FEED MECHANISM FOR POWER PRESSES AND LIKE MACHINES 6 SheetsSheet 5 Filed Aug. 20, 1951 FIG. IO.

Flats. CAM/4 N444; 47 M #MJ D MECHANISMFOR POWER PRESSES AND LIKE MACHINES 6 Sheets-Sheet 6 Filed Aug. 20, 1951 Patented Oct. 27, 1953 AUTOMATIC FEED MECHANISM FOR POWER PRESSES AND LIKE MACHINES Charles Edward Tallis, Birmingham,

England,

assignor toBirmingham `Tool & Gauge Company Limited, Handsworth, England Application August 20, 1951, Serial No. 242,763 In Great Britain August 29, 1950 6 Claims. 1

This invention comprises improvements 'in or relating to automatic `feed mechanism for power presses and like machines. The object of the present invention is `to provide a hydraulically operated feed mechanism, wherein the pitch of the feed can be readily adjusted whilst the press or like machine is in operation. A further object of this invention is to provide means whereby the extent of intermittent feed movement of the strip or like stockbeing fed can be infinitely varied between limits.

Referring to the drawings,

Figure 1 is a plan view of strip feeding means according to this invention.

Figure 2 is a sectional elevation taken on the line 2 2 of Figure 1 as regards the upper part of the elevation, the lower part corresponding to a section taken on theline 2 2 of Figule.

Figure 3 is a cross sectional view taken on the line 3 3 of Figure 1 or Figure 2.

Figure 4 is a cross sectional view taken on the line 4 4 of Figure 1.

Figures 5, 6 and '7` are detail cross sectional plan views taken on the lines 5, 6 6 and 'I 'I re-` spectively, of Figure `2.

Figures 8 and 9 aredetail cross sectional views taken on the lines 8 8 and 9 9 respectively of Figure 2.

Figure 10 is a cross sectional elevation of the pump or impeller.

Figure 11 is a view taken on the line II II of Figure 10, i. e. an end view of the impeller with the cover removed.

Figure 12 is a viewof the other end of the impeller, and

Figure 13 is a detail sectional view on an enlarged scale of one `of the impeller plungers showing the automaticreplenishing valve mechanism therein.

In herein describing the invention with reference to the accompanying drawings as applied to means for feeding strip metal, a generaloutline of same is rstgiven, the various parts being subsequently described in detail.

Referring to Figures 1 and 2 the base II of the machine houses a block assembly I containing valve controlled ducts on `which is mounted a support member 2 for two hydraulic rams in the form of two parallel cylinders 3, 4 containing pistons 5, E respectively, arranged to operate in opposite directions (see Figure l) on a suitable table I carried by a saddle 8 which slides, on the cylinders 3, `II so that the latter form` guides for slidably supporting, the table .'I. l

Carried at one end, of the table, 1 a. gripper unit 9, whilst a similar fixed gripper unit I0 ex,- tends across the table and is mounted on the base II. Both these gripper units have hinged covers I2 `acting as a normally xed pressure pad and arranged to open bookwise in the body part of the gripper unit to enable the strip (indicated by the chain dotted line I3) to be placed on pads I4 within each unit, a rubber diaphragm I5 being placed underneath each pad I 4 so that on hydraulic uid such as a suitable oil being fed under the diaphragm I5 the pad I4 is urged towards thecover I2 to grip the strip |13 when the cover is secured in the closed position by the fastening means 56.

The cylinders 3, 4 are connected through the valve block I by means of pipes I6, I' to an impeller (Figure 10) for forcing and withdrawing oil alternately from said cylinders 3, 4. Thus on oil being forced to the forward cylinder 3 the table is moved forward, oil being expelled from the return cylinder 4 and vice versa, the two columns of oil from the cylinders via the block I and pipes IS, Il to the impeller acting after the manner of hydraulic push rods, the oil of each column alternately moving to and fro.

The oil line connected by the pipe Il passes directly through the block I to the forward cylinder 3, but the other oil line is led to the return cylinder 4 through the pipe I5 via a series of valve controlled ducts in the block I whereby the reciprocating motion of the table I is controlled in relationto the opening and closing of the gripper units S, IB which are operated by a separate hydraulic system comprising mainly the operating piston I8 and a small reservoir I9 (see Figure 2).

The arrangement issuch that just prior to the commencement of a forward movement of the table the. gripper unit 9' grips the strip I3, Whilst the unit I0 releases its grip thereon enabling the strip to be fed forward by forward movement of the table "l. Upon the table reaching its extreme forward position it pauses for an instant suncient for the gripping'unit 9 to release its grip on the strip I3, whilst at the same time the gripper unit lil grips the strip and holds it while the table effects a return movement with the released gripper unit 9, it will thus be seen that by repeated reciprocatory cycles of the table l the strip is fed forward intermittently for the purposes of having a stamping, pressing or like operation performed thereon by a machine on which feeding means according to this invention is installed.

The impeller (Figures 10 to 12) is arranged to have an infinitely variable stroke which is adjusted by means of the control knob 25 so that the extent of travel of the table i per cycle can be adjusted within limits to enable a feed of the strip I3 to be readily set in accordance with requirements and so enable the most economical use of the strip to be effected especially in stamping or pressing operations.

For each rotation of the impeller mechanism a complete feeding cycle of the table i is effected so that the impeller may be directly driven from the machine in order to operate the feeding means in correct timed relationship with the pressing, stamping or like operations of the machine.

The connection by means of the pipes it, Il between the irnpeller and the table unit enables feeding means according to this invention to be readily installed on various types of presses and like machines requiring intermittent feed of strip metal or similar stock for which purpose the pipes I6, I'I are preferably of copper or like ductile metal so that they may be readily bent in accord- Y ance with the requirements of a particular installation. l

In cases where the stock to be fed consists of thin strip (i. e. less than .013 thick.) two table units are preferably employed one each side of the press table or the like and operated in unison by a common impeller so that one table unit feeds the strip onto the press tabie whilst the other pulls the scrap strip oif it, thus avoiding strip flexure or buckling which may be further avoided by arranging the table unit pulling the scrap strip to put a slight tension on the strip.

For supporting very thin strip (of the order of 0,05) against` buckling, the movable gripper unitof each table unit may have a rearward extension constantly and slidably engaging a forward extension on the fixed gripper unit.

Describing now in detail with reference to Figures 1 to 9 the construction and operation of the table unit and gripper units 9, i3 thereon and the oil movement through the block l to the cylinders 3 d it is assumed that the table 'I has just reached its extreme return position in readiness to commence a feeding cycle, in which case the fixed gripper unit Ib is still closed and gripping the strip i3, whilst the movable gripping unit 3 is open.

In order to feed the table forward, oil movement takes place from the impeller (Figure lo) via the pipe I7, and vertical ducts 2l (Figure 4) and 22 in the block I and cylinder support 2 respectively, to the forward cylinder 3. However, before the piston is moved by the oil to in turn move the table "i, the oil movement first takes place along a horizontal duct 23 (Figure 6) communicating the vertical duct 2l to one end of a small piston 24 to move the latter to the right. This causes displacement of oil from the bore of the block` I in which the piston 2A operates into the horizontal duct 25 Via the short duct 43, oil movement in said duct taking place in the direction towards the vertical duct 25 (Figure 2) and from thence to one end of a reduced portion 2i of the piston I8 causing the latter to move to the left and so actuate the separate hydraulic system controlling the gripper units.

When oil is displaced into the horizontal duct 25 it can only move in the direction above mentioned by reason of the fact that movement in the opposite direction i. e. to the left in Figure 6 is checked by the valve member 3S (Figure 2) until a predetermined oil pressure is reached, since the left hand end of the horizontal duct 25 communicates with the vertical duct 3S (Figure 9) which in turn communicates with the annular space 3S around the valve member 39 by means of the short horizontal duct 3i. The valve member 39 is provided with a locally reduced part iii (Figure 2) which allows passage of oil into the horizontal duct il when a predetermined oil pressure is reached sumcient to move the valve member 3S against its spring 5I, the loading of which is set by the screw means 52.

It will also be noted that the vertical duct 33 (Figure 9) communicates with a horizontal duct 50 to enter the annular space 49 around the valve member but thisrvalve cannot be lifted in the manner of the valve member 39, and furthermore, a fiat 43 (Figure 2) on this valve member permits passage of oil to the rear thereof, so that whatever the pressure of the oil supplied to the annular space di] the valve member :i5 is held on its seat by the oil passing to the rear of the valve member by the said iiat 43.

The movement of the piston I8 to the left expels oil from the bore 53 in which it operates via the port 23 (Figure 5) and a flexible pipe 35 to the movable gripper unit S to cause the latter to grip the strip I3 as oil displacement due to movement of the piston i3 causes the space under the diaphragm i5 of the said gripper unit 9 to become filled with oil. At the same time the movement of the piston I8 lcauses oil to be drawn into its bore on the other side of said piston from the fixed gripper unit iii via the duct 29 (Figure 3) in the bracket 33 supporting said gripper unit, the duct the pipe Si and port 32 (Figure 5).

In order to replenish the bore 53 in which the piston i2 (Figures 2 and 5) operates to compensate for any oil loss, the reservoir i9 communicates with the said bore 53 by means of a small vertical duct 5d (Figure 5) to an annular groove 55 in said bore.

It will, therefore, be seen from Figure 2 that the small piston 24% allows lost motion in the oil movement from the pipe ii to the forward cylinder 3 to effect by simultaneous operation of the piston i3, a change of the gripping action of the gripper units on the strip i3 before the table 'I commences to move forward. The table l then moves forward moving with it the strip I3 gripped by the unit 9, which strip is drawn through the open xed gripper unit it.

As the table i' moves forward oil is expelled from the return cylinder i owing to the return of the piston 3 therein, oil movement taking place down the vertical ducts 34 and 23 (Figure 4) in the cylinder support 2 and block I respectively and horizontal duct 25 (Figure 6) after which the oil movement continues up the vertical duct 36 (Figure 9) and via the horizontal duct 3l and is transferred to the annular space 38 around the spring loaded valve member 39. As already described the valve member 39 is provided with a locally reduced part di? (Figure 2) which allows the oil above a predetermined pressure to move past the valve into the horizontal duct di to the vertical duct (i2 which communicates directly with the pipe I6 to the impeller, the suction to the impeller during this phase of the cycle assisting the aforesaid oil movement through the block I from the return cylinder 4, Again as already dcscribed oil movement is not permitted from the duct 35 past the valve member 45.

Upon the table reaching its extreme forward movement the impeller reverses the oil movement and commences to force oil along the pipe I6 and withdraw same along the pipe I1. The return Ablock I and thefvreturncylinder `4 is yas Lfollows:

The oilmoves `up the vertical duct 42 (Figure 2) where it is in contact with the other reduced end 44 of the piston I8 and also is in contact `with Athe end of the-spring loaded valve member 45. However, owing to -the load seton this valve member by the settingV of the screw means 46,

`compressing the springr41 urging said valve member, movement of thelpiston I8rst takes place to displace oil to the fixed gripper unit Illto cause nit to grip the strip I3, whilst ythemovement of the 4piston I8 simultaneously effects withdrawal `of oil from the moving ngripper `unit 9 to cause same to release the strip I3, the movement `of .the piston I8 also causing its reduced end 21 to effect oil movement down the duct 26 to the duct A1'25, where, by means ofthe short duct 48 (Figure 6) it acts upon the other end of the small piston 24 to return same to the position shown in Figure 6. Here again the lost motion afforded tothe oil movement from the pipe I6 to the return cylinder 4 by the pistons I8 and 24, enables the gripping action of the gripper `units to be changed over, whilst the table 1 is stationary before it starts its return movement.

After the piston I8 has thus effected its movement to change over the gripping action, pressure of the oil between the reduced end 44 and the valve member 45 is able to overcome the latter, so that oil movement takes place into the annular space 49 to pass into the horizontal duct 56 and clown the vertical duct 36 (Figure 9) to the horizontal duct 2,5 which communicates with the return cylinder A4 via the vertical ducts 26 and 34 (Figures 2 and 4) to act upon the piston 6 for effecting return movement of the table 1.

Whilst the pressure of the oil moving up the duct 42 (Figure 2) eventually lifts the-valve member 45 to allow oil to pass `to `actually effect return movementof the table 1, whatever the pressure of the oil in the duct 42 it is unable to liit the valve member 39 owing to the fact that a small boreduct 51 (Figure 7) is provided leading 01T the duct 42 to the rear of the valve member `39 so that the pressure of the oil holds the valve member 39 against its seating.

As the table 1 returns the piston 5 enters the forward cylinder `3 (Figure 1) expelling oil therefrom down the ducts 22, 2I (Figure 4) to the pipe I1 which oil `movement is also assisted by the suction of the impeller in the pipe I1.

It will thus be seen that for each cycle of the impeller a complete feeding cycle ris effected so `that the speed of feed is dependant on the speed at which the impeller is driven, whilst the distance the strip I3 is fed perifeeding cycle is dependant on the extent of oil movement to and fro via the pipes I6 and I1 fand block I between the impeller and cylinders 3,44 so that by-varying.v

the extent of oil movement the extent of feeding Amovement of the'table 1 can be varied and so adjusted to suit requirements.

For this purpose the impeller is so arranged and `constructed to enable a variable oil movement to `be obtained. Referring to Figures 10, 11 and 12 the-impeller comprises two pairs of plungers 68, -66 and 6I, 6I operating in1bushes62 in the wall `63 of the impeller housing, `the-pair of plungers 160, 86 which operate together enter a chamber 64 communicating with the pipe I6, whilst in a similar manner the pair of plungers 6I, 6I enter a chamber65 communicating with the pipe I1, the ends of the plungers remote from said lc :harnber are each provided `withnrollers 66 for `pivoted to :support members Aor ,blocks 69, 10.

These pivoted members 161, 68 each :carry l-;uni versally pivoted thereon shoes 1I bearing :against the face of a swash plateor face cam A12 crotatably mounted inthe cover 1-3 of ythe impeller housing and driven in any suitable manner 1in timed relationship with the machine.

The blocks 69, `1I) have a screw .threaded engagement with the threaded portions 14, ,15 ofthe vertical shaft 16 rotatably mounted in the impeller housing and having secured to its lupper end the aforesaid control knob 20. Thethreaded portions 14, 15 of this shaft are of opposite :hand so that on rotation of the shaft the blocks69, 10 are either moved apart or towards one another. Thus by manipulating the knob 20 the shoes `1I are either moved towards the centre ofthe lface `cam 12 to reduce the stroke of the plungers `68.

60 and 6I, 6I so'that the minimum of oil movement takes place along the pipes I6, I1 `or said shoes 1I may be adjusted towards the periphery of the cam 12 to obtain maximum stroke of the plungers and consequent maximum movementof oil along the pipes I6, I1 to operate the table 1 for maximum feeding movement of the strip I3.

The ends of the plngers 60, 6 8, 6I, 64I within the chambers 64, 65 respectively are bored at '1;1 (Figure 13) to receive compression springs 18for abutment therein, the outer `ends of thesprings 18 abutting the wall 63 of the impeller housing in order to maintain the rollers 66 at theother ends of pistons in contact with `the pivoted members 61, 68.

The housing of the pump containing (the swash plate 12 and associated mechanism servesas f a reservoir for oil at atmospheric pressure for gthe purpose of replenishing the two lines of oilunder pressure between the impeller and the cylinders 3, 4 in order to make good any loss. For this purpose communication is eiectel between the housing of the pump and the chambers 6,4, 65 ,bv means of automatic valves contained in --at least one plunger 60 or 6I of each pair.

The automatic valve of one of the plungers 60 is shown in Figure 13 `from which it will be seen that the roller 66 is carried by a forked head 80 having a shank 8I itting in a bore 82 in theother end of the plunger 60, said shank having an axial through bore 83 therein.

Located in the bore 82 for limited sliding movement between the inner end of the shankBI and the annular shoulder 84 in the plunger 60 is 'a valve member 85 the full diameter `portion 860i which is an oil tight sliding iit in the 4bore 82 and when in the-position shown closes the inner end of the bore 83 in the shank 8l from the bore-11 and hence from communication with the charnber 64, the valve member 85 being urged to this position by pressure of oil thereon frornsaid chamber.

However, upon a fall in oil pressure in the chamber 64 and as the pistonri eiTects an outward suction stroke therein the suction on the valve member 85 moves it towards Yand against the annular shoulder 84 enabling oil to be inducted from the impeller housing through the bore 83 in the shank 8| and via the reduced portion 81 of the valve member 85 (which then registers with the annular groove 88 in the plunger) to the bore 11 and from thence into the chamber 64.

Inductance of oil through the above described automatic non-return valve in the'plungert-Evis promoted by virtue `ofthe `fact ftlfiatidue (to. the

7 action of the swash plate 'l2 the'plungers Bil, 50, 6l, 6I are not reciprocated at a constant speed. Thus after a quarter of the way through a feeding cycle when the swash plate has rotated through 90 the plungers 6i advancing into the chamber 65 to impel oil along the pipe Il' to the forward cylinder 3 advances a given distance but the plungers 6U receding from the chamber El! to assist and accommodate return movement of oil from the pipe I6 have a slightly greater extent of movement creating a partial vacuum in the chamber 64 to assist inductance of oil through the plunger 60 that is fitted with the automatic valve.

Halfway through the cycle the extent of move- Yment of the plungers 63, 69 equals that of the vplungers 6I, and three quarters of the way 'through the cycle a similar accelerated move- :ment of the plungers ti, 6l receding from the Ichamber 65 takes place to create a partial Vacuum in the latter for promoting the desired cil inductance through an automatic valve in one of the plungers 6l identical with that described and shown in one of the plungers The arrangement of the annular groove Se in relation to the reduced portion al of the valve member 85 is such that passage cf oil is only permitted when the valve member is fully against lthe shoulder 84 otherwise too great a quantity of oil would tend to be inducted through the plunger.

claim:

l. Automatic feed mechanism for power presses and like machines comprising in combination a base; a table mounted for reciprocatory movement on said base; hydraulically operated grip- 'ping means adapted to grip stock and mounted on said table for movement therewith; fixed hydraulically operated gripping means adapted to grip stock and mounted on said base so as to extend over the table in alignment with the movable gripping means on the latter; a pair of hydraulic rams mounted on said base and arranged to act in opposite directions on the table for imparting reciprocatory motion to the latter; a hydraulic impeller; a hydraulic system including two hydraulic fluid lines operatively connecting the impeller with the hydraulic rams. for reciprocation of the table; a further hydraulic system comprising a piston arranged for operation by hydraulic fluid from at least one of the two :duid lines of the first mentioned hydraulic system Which piston is adapted to displace fluid to one of the gripping means and withdraw fluid from the other and vice versa -in order to alternately open and close the gripping means in timed relationship with the reciprocation of the table for effecting the automatic intermittent feed of stock to a machine; and a further piston arranged to be also operated on by uid from the two hydraulic fluid lines of the first mentioned hydraulic system and in conjunction with the said piston of the hydraulic system for operating the gripping means, adapted to introduce 'lost-motion into the fluid movement alongthe two hydraulic fluid lines for the purposes of .causing the table to pause at each extreme of its reciprocatory movement in order to enable the gripping action of the gripping means to be changed Whilst the table is stationary.

2. Automatic feed mechanism for power press- -es and like machines comp-rising in combination a base; a table mounted for reciprocatory move- Iment on `said base; hydraulically operated griprping means. adapted to gripl stock and mounted on said table lfor movement therewith; fixed hydraulically operated gripping means adapted to grip stock and mounted on said base so as to extend over the table in alignment with the Ymovable gripping means cn the latter; a pair of hydraulic rams mounted on said base and arranged to act in opposite directions on the table for imparting reciprocatory motion to the latter; a variable stroke hydraulic impeller; a hydraulic system including two hydraulic iluid lines operatively connecting the impeller with the hydraulic Y rams for reciprocation of the table; a block assembly in said base having fluidways therein for connecting said iluid lines to the rams; a further hydraulic system comprising a piston slidable in a bore in said block assembly, said piston being arranged for operation by hydraulic iiuid from one of said fluid lines through said fluidways in order to displace fluid from said bore to one of the gripping means and withdraw fluid from the other and vice versa so as to alternately open and close the gripping means in timed relationship with the reciprocation of the table for effecting the automatic intermittent feed of stock to a machine; and a further piston slidable in a bore in said block assembly and arranged to be also operated on by fluid from said fluid lines of the first mentioned hydraulic system through said fluidways and in conjunction with the said piston of the hydraulic system for operating the gripping means adapted to introduce lost-motion into the huid movement along the two hydraulic fluid lines for the purposes of causing the table to pause at each extreme of its reciprocatory movement in order to enable the gripping action of the gripping means to be changed whilst the table is stationary.

3. Automatic feed mechanism for power presses and like machines comprising in combination a base; a table mounted for reciprocatory movement on said base; hydraulically operated gripping means adapted to grip stock and mounted on said table for movement therewith; fixed hydraulically operated gripping means adapted to grip fixed stock and mounted on said base so as to extend over the table in alignment with the movable gripping means on the latter; a pair of hydraulic rams mounted on said base and arranged to act in opposite directions on the table for imparting reciprocatory motion to the latter, cylinders of said rams forming guides on which the table can slide for reciprocatory movement; a variable stroke hydraulic impeller; a hydraulic system including two hydraulic fluid lines operatively connecting the impeller with the hydraulic rams for reciprocation of the table; a block assembly in said base having uidways therein for connecting said uid lines to the rams; a further hydraulic system comprising a piston slidable in a bore in said block assembly, said piston being arranged for operation by hydraulic fluid from one of said fluid lines through said fluidways in order to displace fluid from said bore to one of the gripping means and withdraw fluid from the other and vice versa so as to alternately open and close the gripping means in timed relationship with the reciprocation of the table for effecting the automatic intermittent feed of stock to a machine; spring loaded valve means in said block assembly for controlling the direction and pressure of fluid movement in the fiuidways for conducting fluid from the said one of said fluid lines to said piston; and a further piston slidable in a bore in said block assembly and arranged to be also operated on by fluid from said fluid lines of the first mentioned hydraulic system through said fluidways and in conjunction with the said piston of the hydraulic system for operating the gripping means adapted to introduce lost-motion into the fluid movement along the two hydraulic uid lines for the purposes of causing the table to pause at each extreme of its reciprocatory movement in order to enable the gripping action of the gripping means to be changed whilst the table is stationary.

4. A step by step feeding device for feeding sheet material with a step by step motion, said device comprising a stationary material support, a reciprocable material support, a primary pressure uid instrumentality including a pressure uid pump for reciprocating said reciprocable support, and a pressure fluid actuated clamp mounted on each support, one of said clamps being reciprocable with said reciprocable support, in combination with a secondary self-contained sealed unit pressure iiuid instrumentality including a free action type reciprocating piston, a cylinder in which said piston reciprocates, conduit means connecting said clamps with said cylinder on opposite sides of said piston, and an axial rod medially of which said piston is rigidly mounted, the respective ends of said rod being of reduced diameter with respect to the corresponding operative face of said piston and being successively subjected to the pressure of the uid of said primary pressure liuid instrumentality to alternately move said piston in opposite directions to alternately supply uid under pressure to, and Withdraw fluid from, said clamps at the end of each step by step movement of said reciprocable support and before the initiation of the succeeding step by step movement thereof, whereby the reciprocable support will remain at a standstill while the fluid is being forced to one clamp and being withdrawn from the other clamp and until the space occupied by the displaced portion of the piston rod has been filled with oil when the initiation of the next step by step movement will take place.

5. A step by step feeding device for feeding sheet material with a step by step motion, said device comprising a stationary material support, a reciprocable material support, a primary pressure fluid instrumentality for reciprocating said reciprocable support, and a pressure fluid actuated clamp mounted on each support, one of said clamps being reciprocable with said reciprocable support, in combination with a secondary selfcontained sealed unit pressure uid instrumentality including a reciprocating piston, a cylinder in which said piston reciprocates, conduit means connecting said clamps with said cylinder on opposite sides of said piston, and an axial rod media-ily of which said piston is rigidly mounted, the respective ends of said rod being of reduced diameter with relation to the corresponding operative faces of said piston and being successively subjected to the pressure of the fluid of the primary pressure iluid instrumentality to alternately move said piston in opposite directions to alternately supply uid under pressure to, and withdraw fluid from, said clamps.

6. A step by .step feeding device for feeding sheet material with a step by step motion, said device comprising a stationary material support, a reciprocable material support, a primary pressure iluid instrumentality for reciprocating said reciprocable support, and a pressure fluid actuated clarnp mounted on each support, one of said clamps being reciprocable with said reciprocable support, in combination with a secondary pressure fluid instrumentality including a double acting secondary system pump and conduit means connecting said clamps With said pump, said pump having portions successively subjected to the pressure of the fluid of said primary pressure duid instrumentality to operate said pump to alternately supply fluid under pressure to, and withdraw fluid from, said clamps at the end of each step by step movement of said reciprocable support and before the initiation of the succeeding step by step movement thereof, whereby the reciprocable support will remain at a standstill while the fluid is being forced to one clamp and simultaneously is being withdrawn from the other clamp.

CHARLES EDWARD TALLIS.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,257,507 Malocsay Feb. 26, 1918 1,297,341 Gail Mar. 18, 1919 2,228,245 Barker et al Jan. 14, 1941 2,344,565 Scott et al Mar. 21, 1944 2,467,740 Haller Apr. 19, 1949

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