US3863538A

US3863538A - Rotary cut-off knife and method

Info

Publication number: US3863538A
Application number: US356612A
Authority: US
Inventors: Howard N Behnke
Original assignee: Wyle Laboratories Inc
Current assignee: KBR Wyle Services LLC
Priority date: 1973-05-02
Filing date: 1973-05-02
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04
Also published as: JPS509188A

Abstract

A rotary cut-off knife for use in transversely cutting hose-like tubing wherein the knife comprises a blade body having a pair of opposed end faces and an outer peripheral surface connecting the end faces. The outer peripheral surface is in a continuous curvilinear scalloped configuration and the end faces taper toward each other at margin zones adjacent the outer surface so that it defines a scalloped cutting edge. The taper angle of the end faces toward each other continuously varies circumferentially around the margin zones in order to establish a plurality of alternating cutting and relief zones. The relief zones provide means to eliminate detrimental heat build-up in the cutting edge during actual cutting by the cutting zones. This structure facilitates more efficient cutting operations when the blade is rotated at conventional cutting speeds on tube cutting apparatus.

Description

waited Eehnlte tates atent t191 1451 een. a, 1975 Calif.

[73] Assignee: Wyle Laboratories, El Segundo,

Calif.

[22] Filed: May 2, 1973 [2l] Appl. No.: 356,612

[521 us. ci 83/676, 83/54, :s3/474,A

[51] Int. Cl B23d 35/00, B26d 3/16, B261) 9/02 [58] Field of Search 83/491, 636, 54, 835, 847, 83/663, 676, 651, 431; 30/347, 352, 355;

Primary Examiner-Willie G. Abercrombie Attorney, Agent, or Firm-Fay & Sharpe [57] ABSTRACT A rotary cutoff knife for use in transversely cutting hose-like tubing wherein the knife comprises a blade body having a pair of opposed end faces and an outer peripheral surface connecting the end faces. The outer peripheral surface is in a continuous curvilinear scalloped configuration and the end faces taper toward each other at margin zones adjacent the outer surface so that it defines a scalloped cutting edge. The taper angle of the end faces toward each other continuously varies circumferentially around the margin zones in order to establish a plurality of alternating cutting and relief zones. The relief zones provide means to eliminate detrimental heat build-up in the cutting edge during actual cutting by the cutting zones. This structure facilitates more efficient cutting operations when the blade is rotated at conventional cutting speeds on tube cutting apparatus.

ll Claims, 4 Drawing Figures PATENTEU FEB 4mm ROTARY CUT-OFF KNIFE ANI) METHOD BACKGROUND OF THE INVENTION This invention pertains to the art of cutting tools and more particularly to rotary cutting blades.

The invention is particularly applicable to a rotary cut-off knife of the type employed in cutting hydraulic hose and will be described with particular reference thereto; however, it will be appreciated by those skilled in the art that the present invention has broader applications and may be used in other environments where it is desired to effect cutting operations by use of power driven rotary cut-off knives.

The general type of apparatus which employ knives of the type to which the subject invention is directed may be generally seen in the commonly assigned U.S. Pat. Nos. 3,212,185 for an Apparatus For Preparing Hose and 3,253,333 for a Method Of Preparing Hose. Generally, these machines comprise a motor driven circular blade or knife, means for maintaining a length of hose-like tubing in a desired position with the longitudinal axis thereof disposed generally parallel tothe transverse center axis of rotation of the blade and, means for moving the blade and hose relative to each other in order that the blade will cut and pass generally transversely through the hose during a cutting operation.

Heretofore, conventional cut-off knives have merely comprised thin, circular steel blades having a ground and sharpened outer peripheral edge. Although this type of blade arrangement proved reasonably satisfactory for a conventional hose or light duty hydraulic hose, these blades have proved unsatisfactory for use in cutting heavy duty hydraulic hose. That is, with the recent advent of using multi-layer steel wrap hose, i.e., layers of rubber alternating with layers of steel mesh, it has become increasingly difficult to efficiently cut such hose when using conventional cut-off apparatus having conventional, circular cut-off knives. It has been found that when cutting multi-layer type steel wrap hose by a conventional apparatus and blade, the blade has a tendency to slow down during a cut due to resistance offered by thehose, heat up, lose its cutting edge and become worthless as a cutting tool.

Several approaches have thus far been taken in attempting to overcome this problem but none of them have proved reasonably successful. Since blade speed is a function of the cutting machine drive motor horsepower, the apparent solution to the problem was to merely install a larger drive motor. However, following this solution involves considerable undesired extra expense and further, some larger motors require threephase power which is not normally available in small shops or operations of'the type which use these hose cutting apparatus. Likewise, the requirement of three phase power reduced the flexibility of the apparatus for use at remote locations or in the field. Other, suggested minor changes to the conventional type of rotary blades have also proved to be either too costly from a practical standpoint or totally ineffective to properly overcome the present cutting problems for multi-layer steel wrap hose.

The present invention contemplates a new and improved article and method which overcome all of the above referred to problems and others, and provides a new rotary cut-off knife and method of using same which are simple, economical and more versatile in cutting hydraulic hose of the conventional and multilayer steel wrap type.

In accordance with the present invention, there is provided a rotary cut-off knife comprising a generally circular knife body having a pair of opposed end faces, an outer peripheral edge and means for selectively mounting the knife to a cutting machine for high speed rotation thereof about its transverse center axis. The outer peripheral edge has a continuous curvilinear configuration alternating between first portions which are radiused outwardly of the center axis and second portions which are radiused inwardly toward the center axis. The knife end faces converge toward each other at margin zones disposed adjacent the outer peripheral edge to define a continuous curvilinear cutting edge. The angle of convergence ofthese end faces at the first portions is different from the angle of convergence at the second portions such that the :margin zones thus defined are themselves curvilinear circumferentially around the blade.

In accordance with another aspect of the present invention, the angle of convergence of the end faces at each second portion is less than the angle of convergence of the end faces at each first portion.

In accordance with still another aspect of the present invention, Vthe margin zones have curvilinear inner edges defining a plurality of third and fourth portions which follow the same general configuration as the first and second portions respectively. Y

In accordance with still another aspect of the present invention, the radius of curvature of each of the first and second portions is equal and is greater than the radius of curvature of each third and fourth portion.

In accordance with a further aspect of the present invention, there is provided a method of cutting a length `of steel wrap hose into two pieces` which comprises the steps of:

a. providing a thin rotary cutting knife adapted to be mounted for rotation Vabout its transverse center axis and having opposed end faces and a curvilinearly scalloped outer edge, the end faces tapering toward each other at margin zones disposed adjacent the outer peripheral edge in order to define a cutting edge, the angle of taper at each scalloped area being greater than the angle of taper of those areas between each scallop;

b. positioning the length of steel wrap hose adjacent the knife to extend generally parallel to the transverse center axis of the knife;

c. rotating the knife at a speed generally in the range of 2,000 to 4,000 revolutions per minute; and,

d. causing relative movement between the knife and hose so that the knife will engage the hose with the plane of the knife disposed generally normal to the longitudinal axis of the hose whereby the desired cutting will be effected.

The principal object of the present invention is the provision of a new rotary cut-off knife and method of using same which provides a faster cutting operation.

Another object of the present invention is the provision of a new rotary cut-off knife and method of using same which has a longer operative life than conventional rotary cutting knives.

Still another object of the present invention is the provision of a new rotary cut-off knife and method of using same which dissipates heat build-up during a cutting operation.

Yet another object of the present invention is the provision of a new rotary cut-off knife and method of using same which facilitates use in cutting heavier materials in a more efficient manner than possible with conventional rotary cut-off knives.

Yet another object of the present invention is the provision of a new rotary cut-off knife and method of using same which is readily adaptable for use with conventional hose cutting machines and for use in other cut-off environments.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof and wherein:

FIG. 1 is a perspective view of a hosecutting machine ofthe general type with which the knife of the subject invention may be used;

FIG. 2 is a side view of the subject new rotary cut-off knife;

FIG. 3 is a partial cross-sectional view of the knife taken along lines 3 3 in FIG. 2; and,

FIG. 4 is a partial cross-sectional view of the knife taken along lines 4-4 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodi-v ment of the invention only and not for purposes of limiting same, the FIGURES show a rotary cut-off knife A having a cutting area B disposed circumferentially therearound and which knife is adaptable for mounting on and use with hose cutting apparatus C.

More specifically, and with particular reference to FIGS. 2, 3 and 4, rotary cut-off knife. A comprises a thin knife body portion having a pair of oppositely disposed

end faces

12,14 and a continuous curvilinear outer peripheral edge I6. The knife may be manufactured from conventional materials employed for such purposes and, in the preferred embodiment, comprises steel. Likewise, the knife may be hardened or otherwise treated to arrive at the particular physical properties desired as is deemed known in the art. Disposed in the center of body portion l0 is a conventional cutting knife mounting means generally designated which, in the preferred embodiment, comprises a circular mounting hole 22 having a small notch 24 disposed at the circumferential edge thereof for receiving a key or similar member when the knife is mounted to a cutting machine. This arrangement is to prevent undesired relative rotation between the knife and the drive shaft upon which it is mounted during a cutting operation.

Disposed crcumferentially around the cut-off knife adjacent outer preipheral edge 16 are a plurality of radial cutting or first portions 30 and relief or second portions 32. As will be particularly noted from FIG. 1, the first and second portions continuously alternate with one another around the knife. The first portions define scallops which are radiused radially outward of the knife center and the second portions are radiused radially inward toward the center. The outer edge of each first portion has an identical radius of curvature as all the other first portions and each second portion has an identical radius of curvature as all the other second portions. In the preferred embodiment of the invention here under discussion, the radius of all first and

second portions

30,32 are equal to each other.

The areas of extension of the first and second portions along end faces 12,14 from the outer peripheral edge toward the center comprise

margin zones

34,36 respectively. The inner edge of these zones are curvilinear and comprise third and

fourth portions

38,40 which take the same general respective configurations as do first and

second portions

30,32. Here. in the preferred embodiment, each third portion 38 and fourth portion 40 is radiused equal to the other third and fourth portions. Also, the radius of the first and second portions is greater than the radius of the third and fourth portions.

Each cutting or first portion 30 includes a pair of converging

sides

42,44 which begin their convergence from the associated third portion 38 and each second portion includes a pair of converging

sides

46,48 which begin their convergence from the associated fourth portion 40. With particular reference to FIGS, 3 and 4, it will be seen that sides 42,44 are shorter than and coriverge at at taper angle b. The reasons for this particular configuration will be described more fully hereinafter.

Sides

42,44 and 46,48 converge and meet each other to define a cutting edge 50 which extends circumferentially around the rotary cutting knife and, in actuality, acts as outer peripheral edge I6. It will be appreciated from a consideration of each of FIGS. 2, 3 and 4 that not only is cutting edge 50 itself curvilinear in a scalloped type configuration but that

margin areas

34,36 are also scalloped in an undulating fashion between alternating first and

second portions

30,32.

ln use, and because of the particular configuration hereinabove described, as the cut-off knife is rotated at high speeds and contacts a length of hose which is to be cut, those areas of cutting edge 50 extending over first portions 30 actually perform the cutting operation. Because of the fact that taper angle a is greater than taper angle b, second portions 32 merely'act as relief areas so that those portions of cutting edge 50 associated therewith, as well as

sides

46,48, do not actually Contact the hose during cutting. Thus, heat generated by the cutting action of cutting or first portions 30 will be transmitted by conduction to relief or second portions 32 in order to eliminate undesired heat build-up at the actual cutting edge 50 segments of the cutting or first portions. Again problems encountered with previous, conventional rotary cutting knives merely having a circular peripheral edge which itself is merely ground or sharpened have been that in attempting to cut multilayer steel wrap hose, the heat build-up and other deleterious operational effects operate to destroy the cutting edge and render the conventional blades useless for practical application.

In using the type of blade specifically disclosed in FIGS. 2, 3 and 4, attention is now invited to the hose cutting machine C generally shown in FIG. l. It will be appreciated that this machine is merely shown for purposes of describing use of the subject new rotary cutting knife and that other types of rotary cutting machines may be employed without departing from the intent or scope of the present invention. Accordingly, cutting machine C includes a base 70, a base extension or ears 72, a cutting unit 74, a hose carrying table 76, a cut-off arm 78, a skiving unit 80, and a motor 82. The actual operation of the cutting machine at C may be appreciated from a reading and understanding of commonly assigned U.S. Pat. Nos. 3,212,185 and 3,253,333, the disclosures of which are incorporated herein by reference. Briefly, however, use of the knife is made by rotating it about its center transverse axis at high speed and moving the knife and a length of hose 8d relative to each other until the knife contacts the hose and then on through the hose to complete the desired cutting operation. Generally, the high speed comprises rotating rotary eut-off knife A at approximately 2,900 RPM, although it will be appreciated that other speeds may be employed as deemed necessary under particular cutting requirements and environments. Thus, speeds in the range of, for example, from 2,000 to 4,000 RPM could conceivably be employed in certain situations.

ln order that the benefits derived from the subject rotary cut-off knife may be more fully appreciated, TABLE I set forth hereinbelow shows comparative tests conducted on a conventional hose cut-off machine between a conventional rotary cut-off knife and the subject knife using three different types of multilayer steel wrapped hose. The comparative tests were conducted under conditions where the blades would effect the cuts in the shortest period of time without causing permanent blade damage. As will be seen from the TABLE, the subject new knife requires far less time to effect each cut and requires a substantially lower amperage draw during the cuts. Although test results for five test cuts are shown in TABLE I, it will be seen that there are two test cuts for hose having a fine wire braid and for hose having a standard wire braid. The amperage readings shown in the TABLE were each taken as the blade broke through the hose during the eut.

TABLE l Cut-oft' Machine Running No Load at [2.5 amps Blade RPM 290() Conventional Circular New Rotary Cut-Off Knife Rotary Cut-Off Knife The increased amperage draw required when using the conventional knife, along with the attendant fluctuations, are very hard on the cut-off machine and circuitry from the standpoint of reducing the useful life of the machine and requiring more frequent maintenance and replacement of parts. Such a situation adds both cost and downtime to any operation where constant use of the machine is required. Likewise, because of the longer cutting time required, valuable production or work time can be lost and if it is attempted to cut the hose in a shorter period of time, there is substantial probability that the cutting edge ofthe knife will be ruined. This too adds further undesired operational cost. However, these problems are all overcome by using the subject new cut-off knife as shown in the comparative test results of TABLE l.

By way of further information and merely for purposes of describing the preferred embodiment of the invention only inorder that it may be more clearly understood by those skilled in the art, specific dimen sional characteristics will hereinafter be given for a 7 inch diameter rotary knife which includes the concepts of the subject invention. lt has been found particularly advantageous to have 20 first and 20 second portions spaced around the outer peripheral edge of knife body l0. ln other words, and as measured from center to center, the first and second portions are each spaced 18 from their associated adjacent first or second portion. A knife body thickness of three thirty-seconds inch has been found to be particularly desirable for normal knife usage with

sides

42,44! each extending inwardly seven thirty-seconds inch as measured along the knife centerline from the outermost portion of edge 50 and

sides

46,48 each extending inwardly three-eighths inch as measured along the centerline at the innermost portion of edge 50. Also, and for the same 7 inch diameter blade, a radius of l inch for first and

second portions

30,32 and a radius of eleven thirty-seconds inch for third and

fourth portions

38,40 have been found particularly advantageous for normal knife usage. It will be appreciated by those skilled in the art, however, that variations to these dimensions may be made without departing from the intent and scope of the subject invention and that larger or smaller diameter blades may require other dimensional configurations in order to arrive at the desired operational results.

The invention has been described with reference to the preferred embodiment. Obviously, modifications and alternations will occur to others upon the reading and understanding of the specification. It is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Having thus descibed my inention. l now claim:

l. A rotary cutting knife comprising:

a generally circular knife body including a pair of opposed end faces and an outer peripheral edge, said peripheral edge comprising a continuous curvilinear configuration alternating between a plurality of radially disposed first portions radiused outwardly of the center transverse axis of said knife body and second portions radiused inwardly toward said cen ter axis, said end faces converging toward each other adjacent said outer peripheral edge to define a continuous curvilinear cutting edge at said outer peripheral surface, the angle of convergence of said end faes at said first portions being different from the angle of convergence of said second por tions; and, means for selectively mounting said knife to apparatus for rotating said knife about its transverse center axis.

2. The rotary cutting knife as defined in claim 1 wherein the angle of convergence of each said second portion is less than the angle of convergence of each said first portion.

3. The rotary cutting knife as defined in claim 2 wherein said tapered portions of said end faces define a curvilinear margin zone on each end face, said margin zones each having an inner edge spaced inwardly along the associated end face from said outer peripheral edge, said inner edge comprising a plurality of third and fourth portions following the same general configuration as said cutting edge at said plurality of first and second portions respectively.

4. The rotary cuting knife as defined in claim 3 wherein the radius of curvature of each said first and second portion is greater than the radius of curvature of each said third and fourth portion.

5. The rotary cutting knife as defined in claim 4 wherein the radius of curvature of each said first and second portion is equal to the other of said first and second portions.

6. The rotary cutting knife as defined in claim 5 wherein the radius of curvature of each said third and fourth portions is equal to the radius of curvature of the other of said third and fourth portions.

7. The rotary cutting knife as defined in claim 3 wherein the plurality of first and second portions comprise twenty of each said portion equally spaced alternately around said knife body.

8. A rotary cutting knife for particular use in cutting lengths of multi-layer steel wrap hose, said blade comprising:

a thin, generally circular knife body having a pair of opposed, generally flat end faces and an outer peripheral edge extending between said end faces;

means for selectively mounting said knife to apparatus for rotating of said knife at high speed about its transverse center axis;

said outer peripheral edge being scalloped and having a continuous curvilinear configuration alternating between a plurality of radial first portions radiused outwardly of said center axis, the radius of said first and second portions being substantially equal to each other;

said end faces converging toward each other from an area thereon adjacent said outer peripheral edge to define a scalloped cutting edge at said outer peripheral surface, the angle of convergence of said end faces at said first portions being different from the angle of convergence at said second portions; and,

the converging areas of said end faces each defining a margin area having an inner edge spaced inwardly along the associated end face from said outer peripheral edge` said inner edge comprising a plurality of third and fourth portions following the same general scalloped configuration as said first and second portions respectively.

9. The rotary cutting knife as defined vin claim 8 wherein the angle of convergence of said end faces at said second portions is less than the angle of convergence at said first portions whereby said margin areas have a continuous circumferential curvilinear surface.

l0. The rotary cutting knife as defined in claim 9 wherein the radius of curvature of each said third and fourth portions is equal and is less than the radius of curvature of each said first and second portions.

11. The rotary cutting knife as defined in claim l0 wherein said plurality of said first and second portions comprise twenty of each of said portions equally spaced alternately around said knife body.

* k #i l 4(

Claims

1. A rotary cutting knife comprising: a generally circular knife body including a pair of opposed end faces and an outer peripheral edge, said peripheral edge comprising a continuous curvilinear configuration alternating between a plurality of radially disposed first portions radiused outwardly of the center transverse axis of said knife body and second portions radiused inwardly toward said center axis, said end faces converging toward each other adjacent said outer peripheral edge to define a continuous curvilinear cutting edge at said outer peripheral surface, the angle of convergence of said end faes at said first portions being different from the angle of convergence of said second portions; and, means for selectively mounting said knife to apparatus for rotating said knife about its transverse center axis.

8. A rotary cutting knife for particular use in cutting lengths of multi-layer steel wrap hose, said blade comprising: a thin, generally circular knife body having a pair of opposed, generally flat end faces and an outer peripheral edge extending between said end faces; means for selectively mounting said knife to apparatus for rotating of said knife at high speed about its transverse center axis; said outer peripheral edge being scalloped and having a continuous curvilinear configuration alternating between a plurality of radial first portions radiused outwardly of said center axis, the radius of said first and second portions being substantially equal to each other; said end faces converging toward each other from an area thereon adjacent said outer peripheral edge to define a scalloped cutting edge at said outer peripheral surface, the angle of convergence of said end faces at said first portions being different from the angle of convergence at said second portions; and, the converging areas of said end faces each defining a margin area having an inner edge spaced inwardly along the associated end face from said outer peripheral edge, said inner edge comprising a plurality of third and fourth portions following the same general scalloped cOnfiguration as said first and second portions respectively.

9. The rotary cutting knife as defined in claim 8 wherein the angle of convergence of said end faces at said second portions is less than the angle of convergence at said first portions whereby said margin areas have a continuous circumferential curvilinear surface.

10. The rotary cutting knife as defined in claim 9 wherein the radius of curvature of each said third and fourth portions is equal and is less than the radius of curvature of each said first and second portions.

11. The rotary cutting knife as defined in claim 10 wherein said plurality of said first and second portions comprise twenty of each of said portions equally spaced alternately around said knife body.