US3869917A

US3869917A - Conduit bender

Info

Publication number: US3869917A
Application number: US393955A
Authority: US
Inventors: Ellsworth W Lapp
Original assignee: KINROTH AND SON Mfg CO
Current assignee: KINROTH AND SON Mfg CO
Priority date: 1973-09-04
Filing date: 1973-09-04
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11

Abstract

An initially straight piece of large diameter, thin-walled conduit is deformed and tightly clamped between a forming die and a holding die and then is drawn into a curved configuration by a pair of drawing shoes which sweep across the end portions of the conduit and draw the latter around the forming die. By virtue of the coaction between the forming die and the holding die, the midportion of the conduit is prevented from collapsing, flattening and wrinkling under the forces exerted on the conduit by the drawing shoes.

Description

[ Mar. 11, 1975 1 CONDUIT BENDER [75] Inventor: Ellsworth W. Lapp, Rockford, Ill.

'[73] Assignee: Kinroth & Son Mfg. Co., Rockford,

Ill.

[22] Filed: Sept. 4, 1973 [21] Appl. No.: 393,955

[52] US. Cl 72/304, 72/369, 72/383 [51] Int. Cl B21d 7/04 [58] Field of Search 72/381, 383, 389, 304, 72/369, 318, 319

[56] References Cited UNITED STATES PATENTS 1,923,272 8/1933 Maroto 72/369 2,285,275 6/1942 Harder 72/369 2,405,931 8/1946 Abramson.... 72/383 2,497,500 2/1950 l-lightower 72/383 3,004,582 10/1961 Key 72/381 3,240,048 3/1966 Calendar 72/369 3,374,532 3/1968 Zenhausern 72/369 3,557,586 1/1971 Zmuda 72/298 FOREIGN PATENTS OR APPLICATIONS 1,431,846 2/1965 France 72/389 46-6345 2/1970 Japan 72/381 45-18772 6/1970 Japan 72/389 Primary Examiner-C. W Lanham Assistant Examiner-M. .1. Keenan Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[57] ABSTRACT An initially straight piece of large diameter, thinwalled conduit is deformed and tightly clamped between a forming die and a holding die and then is drawn into a curved configuration by a pair of drawing shoes which sweep across the end portions of the conduit and draw the latter around the forming die. By virtue of the coaction between the forming die and the holding die, the midportion of the conduit is prevented from collapsing, flattening and wrinkling under the forces exerted on the conduit by the drawing shoes.

10 Claims, 8 Drawing Figures PATENTED MR] 1 5 sum 1 or 5 FMENTEDHARI 1 i95 sum 3 o 5 PATENTEUHARI 1 ms sum u 95 5 CONDUIT BENDER BACKGROUND OF THE INVENTION This invention relates to a device for bending conduit or the like and, more particularly, to a conduit bender of the type which includes a forming die with a generally arcuate groove into which the conduit is bent. Bending of the conduit is effected by a pair of drawing shoes which sweep along the conduit and draw the latter around and into the groove in the forming die. Conduit benders of this general nature are disclosed in Abramson US. Pat. No. 2,405,931 and Holsclaw U.S. Pat. No. 2,892,479.

SUMMARY OF THE INVENTION The general aim of the present invention is to provide a new and improved conduit bender which, when compared with prior benders of the same general type, is capable of bending large diameter, thin-walled conduit more smoothly and uniformly and without collapsing, wrinkling, flattening or otherwise detrimentally distorting the conduit.

A more detailed object is to achieve the foregoing through the provision of a conduit bender having a unique holding die which coacts in a novel manner with the forming die to deform and initially bend an intermediate portion of the conduit, the two dies thereafter tightly clamping and confining the intermediate portion to prevent collapsing and distortion of the intermediate portion as the drawing shoes sweep across the end portions of the conduit.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a new and improved conduit bender embodying the novel features of the present invention and showing the parts as positioned at the completion of the bending operation.

FIG. 2 is an enlarged fragmentary front elevation of the bender illustrated in FIG. 1 and showing the parts as positioned preparatory to the start of the bending operation.

FIG. 3 is a fragmentary side elevation of the bender shown in FIG. 2.

FIG. 4 is a fragmentary cross-section taken substantially along the line 4-4 of FIG. 2.

FIG. 5 is a fragmentary front elevation similar to FIG. 2 but showing the parts as positioned upon completion of the first step of the bending operation.

FIG. 6 is an enlarged view of parts shown in FIG. 5.

FIG. 7 is a cross-section taken along the line 7-7 of FIG. 6.

FIG. 8 is a fragmentary front elevation similar to FIGS. 2 and 5 but showing the parts as positioned at the completion of the bending operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes ofillustration, the invention is embodied in a device 10 for bending an initially straight piece of pipe or conduit 11 along a relatively large radius so as to impart a gradual curvature to the conduit. The bender 10 is especially adapted for i use in conjunction with large diameter, thinwalled conduit of the type which is utilized to enshroud electrical wiring. As a specific example, the bender shown in the drawings is designed to bend steel conduit having an outside diameter of 3.50 inches and a wall thickness of 0.070 inch.

The bender 10 comprises a main support formed by fixed upper and lower blocks 13 and 14 (FIGS. 1 and 3) which are spanned by front and rear pairs of upright straps 15, the ends of the straps being connected to the blocks adjacent the corners thereof. As shown in FIGS. 1 and 3, the straps of each pair are spaced horizontally from one another and thus rectangular openings are formed between the straps at the front and rear of the bender and also at the sides thereof.

For the most part, actual bending of the cohduit 11 is effected by a pair of drawing shoes 16 which sweep in opposite directions along the conduit and draw the latter around and into a forming die 17 as shown in FIGS. 1 and 8. Each drawing shoe is defined by a block whose lower surface is formed with a groove 19 (FIG. 3) whose bottom curves concavely and substantially arcuately upon proceeding across the width of the shoe. In accordance with conventional practice, the open bottom side of each groove 19 is of constant width (herein, 3.50 inches) along the entire length of the shoe but the groove gradually tapers upon proceeding from the outboard end of the shoe toward the inboard end thereof as shown in FIGS. 5 and 6. In this particular instance, the outboard end of the groove is curved on a radius equal to the radius of the conduit and thus has a vertical depth of 1.750 inches while the vertical depth of the inboard end of the groove is about 1.650 inches.

The forming die 17 is positioned beneath the drawing shoes 16 and serves to cradle the conduit 11 and to define an anvil for the conduit as the drawing shoes sweep along the conduit. In this instance, the forming die comprises a casting formed with an upwardly opening groove 20 which curves arcuately and convexly upon proceeding from one end of the die toward the other (see FIG. 5). Across the width of the die, the groove curves arcuately and concavely as shown in FIG. 4, the radius of the curvature being substantially equal to the radius of the conduit.

In order to sweep the drawing shoes 16 in opposite directions along the conduit 11 for the purpose of drawing the latter around and into the groove 20 in the forming die 17, the drawing shoes are carried on a parallelogram linkage 21 (FIG. 1) which is adapted to be scissored between collapsed and spread positions so as to move the shoes from their starting positions shown in FIG. 5 to their terminal positions shown in FIGS. 1 and 8. Herein, the linkage 21 comprises two pairs of upper links 23 and two pairs of lower links 24, each pair including one front link and one rear link disposed face-to-face with one another and located on opposite sides of the forming die 17. One drawing shoe 16 is sandwiched between the upper end portions of each pair of lower links 24 and is connected thereto by screws 25 extending through holes in the links and threaded into the shoe. Preferably, the holes in the links are slightly larger than the screws so as to allow limited floating of the drawing shoes on the links. Such floating enables the drawing shoes to better follow and conform to the conduit 11 and prevents binding of the linkage 21 as the shoes press the conduit into the groove 20 in the forming die 17.

As shown in FIGS. 1 and 2, the upper ends of the upper links 23 are connected pivotally at 26 to the upper support block 13 while the lower ends of the upper links are pivoted to the upper ends of the lower links 24 by pivot connections indicated by the reference numeral 27. At their lower ends, the lower links are connected pivotally to a block 29 by pivot pins 30 whose centerlines coincide with the center of curvature of the groove 20 in the forming die 17 when the latter is positioned as shown in FIG. 5. The block 29 is sandwiched Between the frontand rear support straps l and is adapted to be raised and lowered by a thirty ton hydraulic cylinder 31. The latter is located beneath the lower support block 14 and includes an upper nose 33 (FIG. 4) which is threaded into the lower support block. Projecting upwardly from the cylinder and an-- chored rigidly to the movable block 29 is a piston rod 34 which is adapted to be reciprocated upwardly and downwardly as pressure fluid is alternately admitted into and dumped from the lower and upper ends of the cylinder under the control of a valve (not shown).

Preparatory to the start of a bending operation, the block 29 is in a lowered position as shown in FIG. 2 and thus the parallelogram linkage 21 is collapsed so as to locate the drawing shoes 16 in their starting positions closely adjacent the vertical centerline of the forming die 17. At this time, the forming die 17 is spaced vertically from the drawing shoes 16 by a sufficient distance to enable endwise insertion of the conduit 11 between the die and the shoes. When the lower end of the cylinder 31 is subsequently pressurized, the block 29 and the pivot pins 30 are forced upwardly and cause the linkage 21 to spread and thereby move the shoes 16 in opposite directions along a path which curves arcuately about the vertically rising pivot pins 30. As explained in more detail below, the forming die 17 is raised in unison with the movable block 29 and thus the path through which the drawing shoes sweep is concentric with the groove 20 in the forming die. As a result of such sweeping, the drawing shoes engage the end portions 35 of the conduit and drawsuch end portions around and into the groove 20 to impart a curved configuration to the conduit.

The bender as described thus far is suitable for use with certain types of conduit, pipes and tubes but has been found to be ineffective to bend large diameter, thin-walled conduit 11 of the type described above and similar conduit in which the ratio of total wall thickness to outside diameter is less than or in the neighborhood of approximately 7 percent. As the end portions 35 of such conduit are drawn into a curved shape, the upper side of the midportion 36 tends to collapse inwardly to a severe degree While the lower side of the midportion tends to wrinkle and flatten upwardly. If severe collapsing, wrinkling and flattening occur, the midportion of the conduit virtually closes upon itself and destroys the usefulness of the conduit.

The present invention is based on my discovery that undesirable distortion of the midportion 36 of the conduit 11 can be avoided by initially deforming the midportion and then confining the midportion very tightly so as to place and keep the midportion under compressive hoop stress and bolster its resistance to collapsing under the forces subsequently exerted as the drawing shoes 16 sweep along the end portions 35 of the conduit. In carrying out the invention, the bender 10 is provided with a holding die 40 which is located above the forming die 17 and between the drawing shoes 16 and which coacts with the forming die to tightly clamp and initially bend the midportion of the conduit before the drawing shoes are swept across the end portions. As the end portions'are then drawn around into the groove 17 by the drawing shoes, the holding and forming dies continue to exert pressure on and confine the midportion and prevent the latter from collapsing, wrinkling and flattening.

More specifically, the holding die 40 is defined by a steel block located directly above and centered relative to the forming die 17 and also centered between the drawing shoes 16. The holding die 40 is supported at the upper ends ofa pair of vertically extending arms 41 (FIGS. 1 and 4) whose lower ends are connected to the movable lower block 29 by the pivot pins 30. As shown in FIG. 4, screws 43 extend through the upper end portions of the arms 41 and are threaded into opposite sides of the holding die to anchor the latter to the arms, there being spacer bushings 44 telescoped over the screws and located between the arms and the holding die. To maintain the arms 41 in vertical positions, the screws 43 also extend through'front and rear plates 45 which are sandwiched between and guided slidably by the front and rear straps 15, respectively. When the lower block 29 is shifted upwardly, the holding die 40, the arms 41 and the plates 45 all move upwardly in unison, the plates sliding upwardly along the straps 15 and preventing the arms from pivoting about the pins 30.

Opening downwardly out of the lower side of the holding die 40 is a downwardly concave groove 46 (FIGS. 4 and 6) which coacts with the groove 20 in the forming die 17 to initially deform and thereafter tightly clamp the midportion 36 of the conduit 11. Between the ends of the holding die 40, the groove 46 curves arcuately about a center coinciding with the centerlines of the pins 30 and thus is concentric with but is curved on a larger radius than the groove 20 in the forming die 17 when the parts are positioned as shown in FIGS. 5 and 8. The groove 46 also curves arcuately across the width of the holding die, has a width of 3.50 inches across its open lower side and has a depth of l.75 inches along the vertical centerline of the die. At the ends of the die, the groove 46 has a depth of about 1.625 inches. The length of the groove preferably is equal to the width of the groove across its open lower side.

The forming die 17 is adapted to close upwardly upon the holding die 40 to deform the midportion 36 of the conduit 11 between the

grooves

20 and 46. In order to close the dies, a second thirty ton hydraulic cylinder 50 is anchored rigidly to the upper side of the lower movable block 29 and includes a reciprocable rod 51 (FIG. 4) which shifts the forming die 17 upwardly when pressurefluid is admitted into the lower end of the cylinder. As shown in FIG. 4, the rod 51 carries an adapter 53 which, in turn, is pinned to the forming die 17 as indicated generally at 54 so as to reciprocate the die when the rod is reciprocated while allowing the die to turn about the axis of the rod. Being turnable on the rod, the forming die 17 is free to seek alinement with the loosely mounted drawing shoes 16 when the conduit is located between the die and the shoes.

Preparatory to bending the conduit 11, the

rods

34 and 51 of the

cylinders

31 and 50 are both retracted so as to locate the drawing shoes 16 in their starting positions directly adjacent opposite sides of the holding die 40 and to retract the forming die 17 downwardly away from the drawing shoes and the holding die (see FIG. 2). With the parts thus positioned, there is ample clearance to permit endwise insertion of the conduit between the forming die on the one hand and the drawing shoes and the holding die on the other hand.

After the conduit 11 has been positioned as shown in FIG. 2, the lower end of the cylinder 50 is pressurized to extend the rod 51 upwardly and thereby close the forming die 17 upon the holding die 40. As the forming die moves upwardly, the conduit is lifted until the upper side of the intermediate portion 36 engages the extreme ends 55 (FIG. 6) of the arcuate groove 46 in the holding die 40. With continued upward movement of the forming die 17, the intermediate portion 36 of the conduit is deformed between the two dies with the upper side of the intermediate portion being forced upwardly to completely fill the arcuate groove 46 in the holding die and with the lower side of the intermediate portion being curved downwardly around the bottom of the concentric groove 20 in the forming die (see FIG. 6). Accordingly, the intermediate portion is initially deformed between the two dies to facilitate smooth bending of the conduit when the drawing shoes 16 subsequently sweep across the end portions 35.

Upward movement of the forming die 17 is terminated when flat lands 60 (FIG. 4) on the upper side of the forming die engage and stop against opposing lands 61 on the lower sideof the holding die 40. With the dies thus closed, the vertical clearance a (FIG. 6) between the bottoms of the

grooves

20 and 46 along the vertical centerline of the bender 10 is approximately 3.25 inches or about 0.25 inches less than the original outside diameter of the conduit 11. Accordingly, in addition to being bent by the dies, the intermediate portion 36 of the conduit is actually reduced in diameter in the vertical direction while still being tightly confined in a horizontal direction by the side walls of the grooves and 46. I believe, although without complete certainty, that the reduction in diameter is accommodated within the grooves by virtue of the upper and lower sides of the intermediate portion 36 stretching or elongating in a direction lengthwise of the conduit and also because the wall thickness of certain portions of the intermediate portion actually increases or grows. For example, I have found that the wall thickness at the points b (FIG. 7) increases to about 0.075 inch, the wall thickness at the points 0 increases to approximately 0.0725 inch while the wall thickness at the point d remains at or near its original dimension of 0.070 inch.

When the dies 17 and 40 are fully closed, a force of approximately 1560 psi. is exerted by the dies on the intermediate portion 36 of the conduit 11. Thus, in addition to being initially deformed as shown in FIG. 6, the intermediate portion is confined and clamped very tightly by the dies. It is believed that such tight clamping induces compressive hoop stress into the intermediate portion 36 and thereby increases the resistance of the intermediate portion to collapsing, wrinkling and flattening when the drawing shoes 16 draw the end portions 35 of the conduit around into the groove 20 in the forming die 17.

After the intermediate portion 36 of the conduit 11 has been initially deformed and tightly clamped between the closed dies 17 and 40, the lower end of the cylinder 31 is pressurized to extend the rod 34 and lift the lower movable block 29. As an incident to such lifting, the forming die 17, the clamped conduit 11, and the holding die 40 are all raised upwardly in unison and, at the same time, the parallelogram linkage 21 spreads to cause the drawing shoes 16 to sweep along opposite end portions 35 of the conduit and draw the latter around the forming die, the drawing shoes moving from the positions shown in FIG. 5 to the positions shown in FIGS. 1 and 8. The

rods

34 and 51 of the

cylinders

31 and 50 then may be retracted to permit removal of the conduit from the bender 10.

From the foregoing, it will be apparent that the present invention brings to the art a new and improved conduit bender 10 which is effective to bend large diameter, thin-walled conduit 11 without causing the same to wrinkle, flatten or collapse, the improved results thus obtained being primarily attributable to the novel coaction between the forming die 17 and the holding die 40. It will be appreciated that the specific dimensions given herein are merely exemplary and may be varied as necessary to obtain the best results. When bending conduits of different sizes, the drawing shoes 16, the forming die 17 and the holding die 40 are replaced with appropriately sized counterparts, and suitable adjustments are made to the linkage 21 in order to effect op timum bending. Also, it should be understood that the linkage 21 is merely illustrative of one manner of actuating the drawing shoes 16 and that different linkages or actuating arrangements may be employed and particularly when it is desired to bend the conduit through a full angle.

I claim as my invention:

1. In a device for bending conduit, the combination of, a support, opposed forming and holding dies on said support, means for closing said dies upon a length of conduit disposed between the dies, said dies being sized to deform and clamp an intervening intermediate portion of the conduit as an incident to closing of said dies, a pair of drawing shoes disposed on opposite sides of said holding die in opposing relation with said forming die, and means for moving said shoes away from said holding die and along said forming die to cause the shoes to sweep along the end portions of the conduit and draw such end portions around said forming die while said intermediate portion is clamped between said forming and holding dies.

2. In a device for bending conduit, the combination of, a support, a forming die on said support and having a generally arcuate groove opening out of one side thereof, a pair of drawing shoes on said support and facing said groove, means mounting said drawing shoes on said support for arcuate movement about the center of curvature of said groove and in opposite directions from starting positions in which said shoes are spaced apart angularly by a predetermined distance and terminal positions in which the shoes are spaced apart angularly by a greater distance, a holding die on said support and having a generally arcuate groove opening out of one side thereof and facing the groove in said forming die, the groove in said holding die being substantially shorter in arcuate length than the groove in said forming die and being located between said drawing shoes, means for producing relative movement between said dies to close the dies upon a piece of conduit inserted therebetween, the grooves in said dies being sized to deform and tightly clamp the intervening portion of the conduit as an incident to closing of said dies, and mechanism for moving said drawing shoes from said starting positions to said terminal positions while said intervening portion is clamped between said dies whereby said drawing shoes sweep across the end portions of the conduit and draw such end portions around into the groove in said forming die.

3. A device as defined in claim 2 in which the maximum clearance between the bottoms of the grooves in said dies is less than the original outside diameter of said conduit when said dies are closed.

4. A device as defined in claim 3 in which said grooves are substantially concentric when said dies are closed.

5. A device as defined in claim 4 in which the length of the groove in said holding dieis approximately equal to the original outside diameter of said conduit.

6. A device as defined in claim 3 in which said lastmentioned means move said forming die physically toward said holding die in order to close said dies.

7. A device as defined in claim 6 in which said lastmentioned means comprise a hydraulic cylinder operably connected to close said forming die upon said holding'die, said mechanism comprising a second hydraulic cylinder, a block connected to said second cylinder and movable in response to pressurization of the latter, a

linkage connected between said block and said drawing shoes and operable to sweep the drawing shoes along the conduit as an incident to movement of said block,

said first cylinder and said holding die being connected to said block whereby the forming and holding dies are moved in unison when said block is moved.

8. A device as defined in claim 2 further including means mounting said forming die for turning on said support about an axis extending in the direction of closing of said dies.

9. A device as defined in claim 2 further including means mounting said drawing shoes 'for limited floating toward and away from said conduit.

10. A method of bending conduit comprising the steps of, placing an initially straight length of conduit between a forming die and a holding die, closing the dies upon an intermediate portion of the conduit and deforming such portion with said dies to place the intermediate portion under compressive hoop stress, and maintaining the stress on said intermediate portion while moving a pair of drawing shoes in opposite directions away from said intermediate portion and along the end portions of the conduit to draw such end portions around and into said forming die.

Claims

5. A device as defined in claim 4 in which the length of the groove in said holding die is approximately equal to the original outside diameter of said conduit.

7. A device as defined in claim 6 in which said lastmentioned means comprise a hydraulic cylinder operably connected to close said forming die upon said holding die, said mechanism comprising a second hydraulic cylinder, a block connected to said second cylinder and movable in response to pressurization of the latter, a linkage connected between said block and said drawing shoes and operable to sweep the drawing shoes along the conduit as an incident to movement of said block, said first cylinder and said holding die being connected to said block whereby the forming and holding dies are moved in unison when said block is moved.

9. A device as defined in claim 2 further including means mounting said drawing shoes for limited floating toward and away from said conduit.