US3453956A - Shock absorber for rotary printing press cylinders - Google Patents

Description

- July 8, 1969 J. R. ELLIS ET AL. 3,453,956

SHOCK ABSORBER FOR ROTARY PRINTING PRESS CYLINDERS Filed Oct. 20, 1965 INVENTORS JARRETT R. ELLIS BY WILLIAM H. WEIDMAN ATTORNEYS United States Patent SHOCK ABSORBER FOR ROTARY PRINTING PRESS CYLINDERS Jarrett R. Ellis, Shaker Heights, and William H. Weidrnan, Maple Heights, Ohio, assignors to Harris-Intertype Corporation, Cleveland, Ohio, a corporation of Delaware Filed Oct. 20, 1965, Ser. No. 498,574 Int. Cl. B41f 7/02, 1/28 US. Cl. 101-217 18 Claims ABSTRACT OF THE DISCLOSURE An improved printing press includes cooperating cylinders which are in a pressure relationship along a line of engagement. The cylinders have axially extending gaps with shock absorbing means adjacent to the gaps for dampening movement of the cylinders in response to a change in pressure as a side of the gap passes the line of engagement.

The present invention relates to rotary machines having cylinders for performing an operation on sheet-like material passing through the machine and more particularly to printing presses and particularly lithographic printing presses.

Offset lithographic printing presses have a plate cylinder, a blanket cylinder, and an impression cylinder with a printing nip being formed between the blanket and rmpression cylinders and the plate cylinder running 1n engagement with the blanket cylinder to form the image to be printed thereon. In offset printing presses, the periphery of the blanket cylinder will have a gap and means in the gap for attaching the blanket to the blanket cylinder. Similarly, the plate cylinder will have a gap which registers with the gap in the blanket cylinder as the cylinders rotate and means in the gap for attaching the plate to the plate cylinder and in sheet fed lithographic printing presses, the impression cylinder also includes a gap in which sheet grippers are located for gripping the leading edge of a sheet to be carried through the printing nip.

In an offset press a printing pressure exists between the blanket cylinder and the impression cylinder when a sheet is being printed at the nip. While the blanket cylinder has a blanket thereon which might be described as relatively soft or yieldable relative to the surface of the impression cylinder, the blanket must be firm enough to maintain this printing pressure to produce quality printing. It will be recognized by those skilled in the art that this printing pressure is relieved and re-established as the leading and trailing edges of the gaps of the blanket cylinder pass the print line in succession.

The abrupt receiving and establishing of pressure as the gaps pass each other may cause shock loads on the cylinders resulting in a bouncing or lateral vibration of the plate cylinder as the pressure is established or relieved and this can result in print disturbances on the printed sheet. Moreover, the shock in certain presses tends to cause backlash movement of the blanket cylinder to slow the cylinder relative to the plate cylinder. At the time pressure is being established or relieved at the printing nip, the periphery of the plate cylinder is in engagement with the blanket and is transferring the image on the plate to the blanket. Any bouncing or movement of the blanket cylinder as the printing pressure is relieved or established may affect the image which is transferred from the plate to the blanket which in turn will be reflected in the final print. Similarly, at the time the leading and trailing edges of the gaps in the blanket and plate cylinders pass each other to alternately relieve and establish an image transferring relationship "ice therebetween, printing will normally be occurring at the printing nip and any bouncing of the blanket cylinder due to relieving or establishing the pressure relationship between the plate cylinder and the blanket cylinder will be reflected in the quality of the printed sheet.

An important object of the present invention is to provide a new and improved printing press in which pressure between cylinders therein including a peripheral gap may be gradually changed as the gap passes the line of engagement of the cylinders to minimize print disturbances.

Another object of the present invention is to provide a new and improved rotary machine having cooperating, rotating cylinders which operate in a pressure relationship, there being a peripheral gap in at least one of the cylinders and the cylinders being so constructed and arranged that the effect of shock between the cylinders as an edge of the gap in the cylinder passes the line of engagement is minimized.

A further object of the present invention is to provide a new and improved lithographic printing press having a blanket cylinder with a gap therein where a part on the periphery of the blanket cylinder adjacent the leading and trailing edges of a gap therein is resiliently deflectable to enable a pressure relationship between the blanket cylinder and a cooperating cylinder to be progressively established and relieved over an appreciable angular movement of the cylinder as the edges of the gap pass the edges of a gap in the other cylinder.

A still further object of the present invention is to provide a new and improved rotary machine having cooperating cylinders which operate in a pressure relationship and in which at least one of the cylinders has a gap therein and a resiliently deflectable surface adjacent at least one edge of the gap to cause the pressure relationship therebetween to vary progressively between minimum and maximum operating values as the edge passes the line of engagement of the cylinders.

Other objects and advantages of the present invention will become apparent from the following detailed description thereof and the accompanying drawings which form a part of the specification and wherein:

FIG. 1 is a diagrammatical illustration of a printing press embodying the present invention; and

FIG. 2 is an enlarged fragmentary elevational view of a portion of the printing press of FIG. 1.

The present invention is susceptible of use in various types of rotary machines wherein at least one of the cooperating rotating cylinders which operate in pressure relationship has a gap in the periphery thereof, but is particularly useful in a printing press, such as an offset lithographic printing press, where the establishment and reestablishment of pressure as a gap passes the print line may cause print disturbances and the like.

Referring to the drawings, FIG. 1 shows an offset lithographic printing press which embodies the present invention. A illustrated therein the lithographic printing press includes a plate cylinder 10, a blanket cylinder 11, and animpression cylinder 12. These cylinders are in engagement as illustrated and the plate cylinder rotates in a counterclockwise direction, the blanket cylinder in a clockwise direction and the impression cylinder in a counterclockwise direction, as viewed in FIG. 1, so that the peripheries of the cylinders move in the same direction at the nip between each of the cylinders. The printing plate 13 with the image to be printed is mounted on the plate cylinder 10 by plate clamps which are located in agap 14 in the periphery of the cylinder. The plate clamps for mounting a plate on the plate cylinder are conventional and therefore have not been shown since the clamps per se are not necessary for an understanding of the present invention. The printing plate has a dampening fluid applied thereto by dampening rolls which form part of a dampening mechanism not shown in detail. Ink is applied to the plate byink rolls 16 which form a part of an inking mechanism also not shown in detail. The dampeners 15 and theinker 16 may be of any suitable, conventional form.

After ink is applied to the plate cylinder 10, the image to be printed is transferred to aconventional blanket 17 mounted on the blanket cylinder 11. Theblanket 17 is held on cylinder 11 byclamps 18 which are mounted in agap 20 in the periphery of the blanket cylinder 11. Thegap 20 is of the same angular extent as thegap 14 in the plate cylinder 10 and registers therewith as .the cylinders are rotated. The image on the blanket cylinder 11 is printed onto a sheet 21 on theimpression cylinder 12 as the blanket cylinder rotates past a printing nip formed by the blanket cylinder 11 and theimpression cylinder 12. The sheet to be printed is carried through the printing nip by grippers 22 on theimpression cylinder 12. The sheet is fed to theimpression cylinder 12 by a conventional feeding mechanism and theimpression cylinder 12 may receive the sheet from afeed cylinder 24, The grippers 22 are disposed in agap 23 in theimpression cylinder 12 with thegap 23 extending for the same angular extent about the impression cylinder as thegaps 14 and 20 extend about the peripheries of the plate cylinder and blanket cylinder, respectively. The grippers 22 carry the sheet to be printed through the printing nip and release the sheet on the outgoing side of the printing nip to another transfer unit for delivery to a subsequent unit or a delivery mechanism. The transfer cylinder and associated mechanisms are not shown in the drawings but may be of any suitable, conventional construction.

The blanket cylinder 11 and theimpression cylinder 12 operate in a pressure relationship when the peripheries of the cylinders are in engagement with each other at the printing line so as to provide the necessary printing pressure for obtaining a quality print. The printing pressure between the cylinder peripheries exists even though no sheet is in the nip and is increased somewhat by the presence of a sheet. It will be appreciated that when the gaps in the blanket cylinder and the impression cylinder rotate so that the leadingedges 25 and 26 of thegaps 20 and 23 pass each other, the pressure between theblanket 17 on the cylinder 11 and the surface of theimpression cylinder 12 is suddenly relieved as thegaps 20 and 23 come into registry with each other. This sudden release of pressure produces a shock which tends to cause a bouncing or lateral vibration or the blanket cylinder 11. A similar bouncing of the blanket cylinder 11 occurs when the pressure relationship between the cylinders is re-established as thetrailing edges 30 and 31 of the gaps pass each other since the operating pressure between the cylinders varies from minimum to maximum as the trailing edges of the gaps meet each other.

Similarly, theblanket 17 on the blanket cylinder 11 has a pressure relationship with the plate 13 on the plate cylinder 10 and when thegaps 14 and 20 of these cylinders meet each other at the nip of the two cylinders, this pressure is relieved. As the gaps pass each other and the cylinders are re-engaged and the pressure between them is reestablished. It will be understood by those skilled in the, art that the cylinders in the illustrated machine may have the bearers conventionally used at the outer ends thereof with the bearers on the cooperating cylinders being loaded against each other. The pressure established by the engagement of the peripheral surfaces of the cylinders acts against this loading.

It will be noted that when the pressure is relieved at the print line between the blanket cylinder 11 and theimpression cylinder 12, the plate cylinder is normally in a position when an image is being transferred from the plate to theblanket 17 on the blanket cylinder and any movement of the blanket cylinder relative to the plate cylinder at the line of engagement therebetween may cause a disturbance in the image being transferred which will be refiected in the printed sheet. Similarly when the gap in the blanket cylinder meets and passes the gap in the plate cylinder, the blanket is in the process of transferring an image to a sheet on the impression cylinder and any disturbance caused by the establishment or relieving of the pressure between the plate cylinder and the blanket cylinder may affect the print being made at the print line.

In the illustrated press, each of the cylinders has shock absorbing or shock attenuating means adjacent the edges of the gap to minimize shock disturbances. In the preferred embodiment, the cylinders are all constructed so that the pressure as the edges of the gaps therein pas the line of engagement of a cooperating cylinder is progressively changed over an appreciable angular movement of the cylinder to minimize any tendency of the cylinders to bounce due to shock accompanying the pressure change.

FIG. 2. illustrates the relationship between the blanket clamps, blanket and cylinder when assembled.Blanket 17 extends about the blanket cylinder 11 and is connected at its ends to clamp means 18 located incylinder gap 20.

The ends of theblanket 17 are received by blanket bars and 61 which are connected to the blanket by means of screws and compressively engage the blanket material.Bars 60 and 61 includebeveled side surfaces 62 which cooperate with similarly slanted side surfaces of grooves 63a, 63b in the clamp means 18a, 18b, respectively, to form a dovetail connection between the blanket and the clamp means.

Blanket 17 is longer than the circumferential extent of the blanket cylinder 11 upon which it is assembled. The ends of the blanket are placed in the grooves to form the aforementioned dovetail connection between the blanket and the clamp means so that the blanket is loosely supported on the cylinder. The clamp member or blanket reel 1811 includes arotatable shaft 64 having the groove 63a therein which extends axially therealong and forms the aforementioned dovetail connection withblanket bar 60.Shaft 64 is rotated in a counterclockwise direction to tighten the blanket about the periphery of the cylinder. A ratchet mechanism of conventional design, which is not shown, is connected to the shaft and is operative to prevent a clockwise rotation of the shaft and loosening of the blanket after the blanket has been tightened.Shaft 64 is rotatably supported in the gap by asuitable support member 65 of conventional construction.

Clamp member 18b is connected to the other end of the blanket, and includes a fixedsupport member 66 and amovable support member 67 which is slidably supported on the fixed member.Movable member 67 is connected to the blanket bar by means of a dovetail joint as previously described After the blanket has been tightened by the rotation of theshaft 64 of the clamp member 18w further adjustment in the wrap of the blanket may be made by the clamp member 18b. Themovable support member 67 may be moved with respect to theside 70 of the gap by rotation of adjustment screws 71 in the movable member. It should be understood thatscrews 71 are spaced along clamp member 18b and that the screws and mechanism associated therewith are identical. For this reason only one of the adjustment screws and its associated parts is shown and described herein. Thescrew 71 is adapted to abut one end of arod 72 which is slidable in the movable member. The other end of the rod abuts theside 70 of the gap so that upon clockwise rotation of thescrew 71 the slidable member abuts the side of the gap and forces the movable member away from the side of the gap to further tension a portion of the blanket to eliminate angular misalignment of the blanket on the cylinder. After the blanket has been tensioned to remove any blanket misalignment, astud 74 extending through aslot 73 on the movable member and threaded into the fixedmember 66 is tightened to fix the position of the movable support membe: 67 with respect to the fixedsupport member 66.

The structure for progressively relieving and establishing the pressure relationship between the cylinders is substantially the same in each cylinder and for convenience will be described hereinafter in reference to the blanket cylinder. Thegap 20 of the blanket cylinder 11 has a leadingside 75 and a trailingside 70 which extend inwardly from the periphery of the cylinder for the bot tom of thegap 20. Theside 75 of the gap is cut out to form an undercut 27 which extends in the direction of the circumference of the cylinder to undercut the periphery of the cylinder adjacent the leadingedge 25 of the gap so that theportion 28 of the cylinder periphery adjacent the leading edge of the gap is formed on a resiliently defiectable or cantileveredprojection 29. It will be understood that the undercut 27 preferably extends the full axial length of the cylinder and this resiliently deflectable projection is preferably of uniform cross section for the length of the cylinder. The defiectability of theprojection 29 is such that printing pressure is established immediately after the trailing edge of the gap passes the line of engagement. The trailingside 70 of the gap is also cut out to form an undercut 32 which is similar to and corresponds with the undercut 27 to provide a deflectable cantilevered projection 33 which extends along the trailing edge of the gap.

It will be seen from FIG. 2 that the material of the blanket is relatively thin and as described, is under tension on the blanket cylinder. While the material of the blanket is relatively soft as compared with the material of the cylinder, the material is of uniform thickness at its ends and does not provide a shock absorbing effect. Moreover, the material must offer sufficient rigidity to maintain print pressure. The sides ofgap 20 of the illustrated blanket cylinder have been undercut to provide resiliently defiectable cantilevered projections, as described previously, to eliminate bouncing of the blanket cylinder and its cooperating cylinders as the gaps pass while the cylinders are rotating.

The resiliently deflectable or cantilevered projections described above, extend along the cylinder from the adjacent side of the gap. The deflectability of these projections decreases circumferentially from the sides of the gap in a manner characteristic of cantilevered structures so that the pressure relationship between the cylinders is progressively varied during an appreciable angular movement of the cylinder rather than abruptly at substantially the instant that the edges of the gaps meet at the line of engagement of the cylinders.

It can now be seen that the present invention provides shock absorbing or shock attenuating means along the edges of the gap in a rotating cylinder which prevents or minimizes disturbances as the edge of the gap passes a line of engagement of the cylinder with another cylinder which operates in pressure relationship therewith. In the illustrated embodiment the pressure change associated with the edge passing the line of engagement is caused to occur over an appreciable angular movement of the cylinders by providing a resiliently yieldable surface adjacent the edge of the gap whose stiffness increases proceeding from the gap.

Having described our invention, we claim:

1. In a printing press comprising one cylinder having a hard, crush resistant outer surface for supporting a printing element having leading and trailing end portions during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, a cooperating cylinder operating along a line with said one cylinder, the pressure relationship between said cylinders changing substantially as the leading side of the gap passes the line of engagement of said cylinders, said one cylinder including shock .absorbing means adjacent to the trailing side of said gap radially inwardly of the printing element and providing a leading portion of the hard outer surface, said shock absorbing means terminating within said one cylinder beneath the leading end portion of the printing element for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said trailing side of said gap passes said line during operation of said printing press.

2. In a printing press as set forth in claim 1 wherein said shock absorbing means includes a resiliently yieldable member integrally formed with said cylinder and extending circumferentially along said cylinder from said gap with the yieldability of said member in response to a given load decreasing proceeding from said gap.

3. -In a printing press as set forth in claim 1 wherein said printing element is a blanket which extends at least part way around said one cylinder and said one cylinder includes clamp means located in said gap for clampingly engaging the leading and trailing end. portions of said blanket.

4. In a printing press as set forth in claim 1 wherein said printing element is a printing plate which extends at least part way around said one cylinder and said one cylinder includes clamp means located in said gap for clampingly engaging the leading and trailing end portions of said printing plate.

5. In a printing press comprising an impression cylinder having a hard, crush resistant outer surface for at least partially supporting ink receiving material having leading and trailing portions during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, a cooperating print cylinder operating along a line with said impression cylinder, the pressure relationship between said cylinders changing substantially as an edge of the gap passes the line of engagement of said cylinders, said impression cylinder including shock absorbing means adjacent to the trailing side of said gap radially inwardly of the ink receiving material and providing a leading portion of the hard outer surface, said shock absorbing means terminating within said impression cylinder in a circumferential distance from the trailing side of said gap which is no greater than the extent of said leading portion of said ink receiving material for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said trailing side of said gap passes said line during operation of said printing press.

6. In a printing press as set forth in claims 5 wherein said shock absorbing means includes a resiliently yieldable member integrally formed with said impression cylinder and extending circumferentially along said impression cylinder from said gap with the yieldability of said member in response to a given load decreasing proceeding from said gap.

7. In a rotary printing press having cooperating nip forming cylinders, at least one of said cylinders defining an outer support surface for supporting a printing or sheet element during a printing operation, said surface extending circumferentially about the cylinder and having trailing and leading surface portions each lying adjacent to an axial gap in the periphery of said one cylinder and a surface portion intermediate said trailing and leading surface portions, said intermediate surface portion being radially inwardly unyieldable, at least one of said trailing and leading surface portions being defiectable radially inwardly, and means for absorbing shock and maintaining print pressure as said radially inwardly defiectable one of said trailing and leading surface portions passes through the nip comprising yieldable means providing said one surface portion and progressively increasing resistance to the yielding thereof in response to a given load proceeding from the gap adjacent said one of said surface portions toward said intermediate surface portion.

8. In a printing press, a cylinder as defined in claim 7 wherein said yieldable means comprises a yieldable membed extending circumferentially from and connected to said unyieldable portion.

9. In a printing press as defined in claim 8 wherein said member is connected to said rigid portion in a cantilevered manner and is integral therewith.

10. In a printing press as defined in claim 7 wherein said surface has a substantially cylindrical curvature extending the entire length thereof.

11. In a printing press, a pair of cooperating rotating cylinders operating in pressure relationship, at least one of said cylinders defining an outer surface for supporting a printing or sheet element during a printing operation, said one cylinder having an axially extending gap in the periphery thereof which causes the pressure between the peripheries of the cylinders to change as the cylinders rotate, said outer surface of said one cylinder having a surface portion adjacent said gap formed on a circumferentially cantilevered part of said one cylinder and defining an edge thereof which is resiliently deflectable and located radially inwardly of said element for absorbing shock and dampening movement of said cylinders produced in response to the change in pressure.

12. In a printing press including a blanket cylinder and a cooperating cylinder operating in pressure relationship, said blanket cylinder including a gap with axially extending sides therein which causes the pressure between said cylinders to increase and decrease as said gap passes the line of engagement with said cooperating cylinder, said blanket cylinder including a blanket member connected thereto at sides of said gap and extending about said cylinder, and resiliently yieldable shock reducing means at said gap and located radially inwardly of said blanket member, said shock reducing means being yieldable in response to pressure between the cylinders peripherally adjacent said gap, said shock reducing means comprising a portion defining the surface of said blanket cylinder adjacent said gap for supporting said blanket, said portion being undercut to provide a resiliently yieldable support for said blanket.

13. In a printing press comprising a plate cylinder for holding a printing plate during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, a cooperating cylinder operating along a line of engagement with said plate cylinder, the pressure relationship between said cylinders changing substantially as an edge of the gap passes the line of engagement of said cylinders, said plate cylinder including shock absorbing means adjacent to a first side of said gap and located radially inwardly of the printing plate mounted on said plate cylinder for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including a circumferentially extending cantilevered part of said plate cylinder which forms a resiliently yieldable member extending circumferentially along said cylinder from said gap with the yieldability of said member in response to a given load decreasing proceeding from said gap.

14. In a printing press comprising a plate cylinder for holding a printing plate during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, a cooperating cylinder operating along a line of engagement with said plate cylinder, the pressure relationship between said cylinders changing substantially as an edge of the gap passes the line of engagement of said cylinders, said plate cylinder including shock absorbing means adjacent to a first side of said gap and located radially inwardly of the printing plate mounted on said plate cylinder for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including an undercut resiliently deflectable projection formed in said printing cylinder adjacent to a radially outer end of said gap and having a radially outer surface which forms a part of the radially outer surface of said plate cylinder and is located immediately adjacent to a radially inner surface of said printing plate.

15. In a printing press comprising an impression cylinder for at least partially supporting ink receiving material during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, a cooperating cylinder operating along a line of engagement with said impression cylinder, the pressure relationship between said cylinders changing substantially as an edge of the gap passes the line of engagement of said cylinders, said impression cylinder including shock absorbing means adjacent to a first side of said gap and located radially inwardly of the ink receiving material which is at least partially supported by said impression cylinder for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including a circumferentially extending cantilevered part of said impression cylinder which forms a resiliently yieldable member extending circumferentially along said cylinder from said gap with the yieldability of said member in response to a given load decreasing proceeding from said gap.

16. In a printing press comprising an impression cylinder for at least partially supporting ink receiving material during operation of said printing press and having an axially extending gap in the periphery thereof having trailing and leading sides, .a cooperating cylinder operating along a line of engagement with said impression cylinder, the pressure relationship between said cylinders changing substantially as an edge of the gap passes the line of engagement of said cylinders, said impression cylinder including shock absorbing means adjacent to a first side of said gap and located radially inwardly of the ink receiving material which is at least partially supported by said impression cylinder for absorbing shock and dampening movement of said cylinders produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including an undercut resiliently deflectable projection formed in said impression cylinder adjacent to a radially outer end of said gap and having a radially outer surface which forms a part of the radially outer surface of said impression cylinder and is located immediately adjacent to a radially inner surface of said ink receiving material.

17. In a printing press comprising plate, impression and blanket cylinders, at least one of said cylinders operating along a line of engagement with a cooperating one of said cylinders and having an axially extending gap in its periphery, clamp means located in said gap for use in positioning material engaging an outer surface of said one cylinder during operation of said printing press, the pressure relationship between said one cylinder and its cooperating cylinder changing substantially as an edge of the gap passes the line of engagement of the cylinders, said one cylinder including shock absorbing means adjacent to a first side of said gap and located radially inwardly of the material engaging said outer surface of said one cylinder for absorbing shock and dampening movement of said one cylinder produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including a circumferentially extending cantilevered part of said one cylinder which forms a resiliently yieldable member extending circumferentially along said one cylinder from said gap with the yieldability of said member in response to a given load decreasing proceeding from said gap.

18. In a printing press comprising plate, impression and blanket cylinders, at least one of said cylinders operating along a line of engagement with a cooperating one of said cylinders and having an axially extending gap in its periphery, clamp means located in said gap for use in positioning material engaging an outer surface of said one cylinder during operation of said printing press, the pressure relationship between said one cylinder and its cooperating cylinder changing substantially as :an edge of the gap passes the line of engagement of the cylinders, said one cylinder including shock absorbing means adjacent to a first side of said gap and located radially in- Wardly of the material engaging said outer surface of said one cylinder for absorbing shock and dampening movement of said one cylinder produced in response to a change in pressure as said first side of said gap passes said line during operation of said printing press, said shock absorbing means including an undercut resiliently defiectable projection formed in said one cylinder adjacent to a radially outer end of said gap and having a radially outer surface which forms a part of the radially outer surface of said one cylinder.

References Cited UNITED STATES PATENTS Ellis 10l-407 Gurin 101-4l5.1 Abelmann 10l-401.2 Stempel 101-217 Norton et al. 101-415.1 XR Fagg 101378 Bryer et al. 101375 Giori 101376 ROBERT E. PULFREY, Primary Examiner. J. R. FISHER, Assistant Examiner.

US. Cl. X.R.

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