TECHNICAL FIELD

The present invention relates to the field of construction equipment. More specifically, the present invention relates to a hydraulically operated, portable machine for efficient bending of steel reinforcing bar with minimum effort and maximum safety for the user.

BACKGROUND ART In construction, reinforcing steel may be supplied in a variety of different forms. Typically, the reinforcing steel is known as rebar and is available in a variety of diameters and textures. The most common texture is that of a double helical raised spiral surface, which forms a pair of opposite spiral patterns as viewed from one end of the rebar to the other. The raised spiral surfaces enable the bar to engage the concrete and is commonly known as deformed bar or rebar. Rebar is placed into concrete forms to increase the tensile strength of the completed reinforced concrete struc¬ ture. Often, a rebar structure is prebuilt, sometimes on the job site and sometimes away from the job site. This prebuilt rebar assembly is then placed into the form. In many types of construction, whether using rebar preassemblies or placing rebars into the form on site, is often necessary to leave the rebar ends straight where they extend from the concrete structure. In those cases, the extending ends will need to be left straight until after pouring since the level of the

concrete may vary depending on the accuracy of the pour. The shape and amount of the rebar which extends after the concrete is poured is important to the structural integrity of the concrete structure which will be poured later. The placement of rebar bends in the second poured concrete structure is important to strength of the whole structure, and the placement of these bends is related to the finished surface of the first poured concrete structure. Thus, such bends must be made after the first concrete structure is poured. Further, the structural integrity of the exposed rebar itself is critical to the concrete structure which is poured around the extending rebar. Where the rebar is bent without aid, a sharp bend is made at the surface of the concrete. This is especially harmful and can virtually eliminate the usefulness of the exposed rebar. In the best case, the rebar can simply break off. At least a complete failure will form an overt indication that there is no rebar to use. A complete failure may cause the complete repouring of the structure, but at least it will not lead to reliance on the damaged structure and, therefore, result in a later failure and possible loss of lives.

Other rebar bending methods may involve the manual bending of the rebar around an object placed adjacent the rebar where it extends from the concrete. In some cases,, the object will move causing most of the bending to be of small radius at the concrete surface, with only a large radius applied to the remainder of the rebar. In this case, the

construction inspector may be misled into believing that the rebar is properly bent when, in fact, the structural damage done is equivalent to that for a sharp angle bend.

Further, the size of the rebar can cause a different result for different objects over which the rebar is bent.

The radius of the bend needs to be related to the size of the rebar. A one inch diameter rebar should not be bent about a one-half inch radius and, conversely, a one-quarter inch rebar should not be bent about a 10-inch radius. The bends are sometimes used to terminate the rebar. In such cases, the tensile force parallel to the rebar as it extends from the concrete will not wholly be translated into an axial force with respect to the rebar in the concrete. A sharper bend is associated with the creation of force against the bend, whereas a shallow bend enables the rebar to exert more of an axial pulling force in the concrete into which it is placed.

It is for these reasons that a well-placed bend of proper curvature is so important to enable the resulting structure to maximally take advantage of the full strength available in the rebar, as well as the holding force of the rebar, which extends parallel to and along the surface of the concrete from which it extends. One result of the need for proper placement is the need to have an even radiused bend occur at different selected heights above the surface of the concrete. Where an object is used to assist the bending of the rebar, it will usually not have the stability to enable the bend to occur at different selected heights. Where the person bending the rebar

is using force about an object, the object must be of the correct radius and have an adequate height.

Such a bending object would be prohibitive to be placed between extending lengths of rebar, particularly where the spacing is narrow, such as between about six inches and one foot. Further, workers may not be expected to physically transport such a bending object and may require the help of a crane. Even where a structure for rebar bending is employed, the construction worker must still effect the bending. Typically, this is done with mechanical advantage by the use of a pipe placed over the end of the rebar combined with tugging and pulling on the pipe. Even where a properly diameter bending device is present, such haphazard bending is problematic for a number of reasons. First, the bend may still not be proper. Second, the time for physical manipulation is prohibitive. Third, the bending may "trap" the bending device about which the rebar is bent. The time consumed for a single worker to bend each rebar set, which is prohibitive, will be even worse if manual bending results in a trap of the structure. A trapped structure can cause the worker to have to bend the bar back to free the structure. Bending the rebar both ways significantly weakens the rebar.

What is needed, therefore, in the construction field is a device and method for enabling the quick, safe, easy and sure bending of rebar. The needed device should have a number of characteristics which give it utilitarian advantages on the

job. The characteristics should include the inability of the device to become "trapped." The bending should be able to be achieved at varying heights above the level of the concrete surface. The bending should always produce an even radius of curvature. The bending should be automatic to eliminate the energy expenditure by the construction worker. The device used for bending should be portable and as lightweight as possible to facilitate its use between closely set rebar and also at elevations significantly above ground level.

SUMMARY OF THE INVENTION

In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to a portable small rebar bending machine which has a frame. First and second spaced anvils are mounted on the frame, and a cylinder is mounted on the frame to pull a bending die between the anvils. A rebar is engaged on one side by the two spaced anvils and on the opposite side by the bending die. Actuation of the cylinder moves the bending die between the anvils to locally bend the rebar. The bending die may be in the form of a cylinder or may be in the form of a rotatable wheel.

It is, thus, a purpose and advantage of this invention to provide a portable small rebar bending machine which can be taken to the job site to locally bend rebar, which may be free or may be partially embedded in a concrete structure.

It is a further purpose and advantage of this invention to utilize hydraulic power in the bending of rebar at the job site, as compared to manual power.

It is a further purpose and advantage of this invention to provide a portable small rebar bending machine which is capable of bending small rebar in confined locations and which is demountable so that it can be readily removed from such confined locations after the rebar is bent.

It is a further purpose and advantage of this invention to provide a rebar bending machine which has a high force-to- weight ratio by virtue of using hydraulic pressure and which is compact so that it can be readily manually placed in constricted locations.

Other purposes and advantages of this invention will become apparent from a study of the following portion of the specification, the claims and the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS FIGURE 1 is an isometric view of the portable small rebar bending machine of this invention. FIGURE 2 is a similar isometric view thereof on reduced scale with some of the parts shown in exploded positions.

FIGURE 3 is a side-elevational view thereof, showing the machine engaged on a small rebar and beginning to make a bend therein. FIGURE 4 is a view similar to FIGURE 3, showing completion of the bend.

FIGURE 5 is an isometric view, similar to FIGURE 1, but on a reduced scale, of a second preferred embodiment of the portable small rebar bending machine of this invention.

FIGURE 6 is an exploded view on enlarged scale of the bending die and yoke of the machine of FIGURE 5.

FIGURE 7 is a side-elevational view of the rebar bending machine of FIGURE 5 showing the second preferred embodiment of the portable small rebar bending machine of this invention engaged on a small rebar and beginning its bend. FIGURE 8 is another embodiment of the yoke similar to that shown in FIGURE 6.

DETAILED DESCRIPTION The portable small rebar bending machine of this invention is generally indicated at 10 in FIGURES 1, 2, 3, 4, 5 and 8. The rebar bending machine 10 illustrated in FIGURES 1, 2, 3 and 4 uses a first preferred bending die which com¬ prises bending hook 12. Rebar bending machine 10 has a frame 14 which integrally carries ears 16 and 17. Two anvil supports are bolted against each ear. Anvil supports 18 and 20 are bolted against opposite sides of ear 16, while anvil supports 22 and 24 are bolted against opposite sides of ear 17. Bolts 26 and 28 extend through aligned bolt holes in anvil support 18, ear 16 and anvil support 20. Nuts are tightened on the bolts to securely clamp those anvil supports to the frame. Similarly, bolts extend through aligned holes in anvil support 22, ear 17 and anvil support 24 to securely attach those anvil

supports to the frame. The outer ends of the anvil supports are spaced in accordance with the parallel faces of the ears, and anvils 30 and 32 are respectively positioned between pairs of anvil supports. The anvils 30 and 32 are preferably each in the form of a grooved wheel. Bolts 34 and 36 extend through corresponding aligned holes in pairs of anvil supports and respectively through anvils 30 and 32. Nuts on the bolts 34 and 36 hold the anvils in place. It is not necessary that the anvils rotate, but the structure can be configured for their rotation by providing shoulder bolts which permit tightening of the nuts without binding of the anvils. The anvils 30 and 32 can be readily removed and replaced by removal of the bolts 34 and 36. This may be necessary to change anvil size or to remove the anvils to aid in placing the rebar bending machine 10 in place or removing it from place after the bend has been achieved.

Actuating cylinder 38 has a threaded nose 40 which screws into the corresponding threaded hole 42 in frame 14. This attaches the cylinder to the frame. The threaded hole 42 extends through the frame, and piston rod 44 extends through the hole (see FIGURE 3) . A set screw in the frame engages upon the threads 40 on the cylinder to retain it in position.. The set screw is seen in FIGURES 1, 2, 3 and 4.

The actuating cylinder 38 has a conventional cylindrical interior surface in which is engaged a piston. The ends of the cylinder are closed to define head end and rod end sides of the piston. Fluid fittings are provided on the cylinder to

permit the introduction of fluid under pressure to the rod end of the cylinder. This causes retraction of the piston rod from the extended position shown in FIGURES 1, 2 and 3 to the withdrawn position shown in FIGURE 4. The introduction of hydraulic fluid under pressure is controlled from a conventional fluid pressure source, and it is introduced to the rod under the cylinder through hydraulic hose 46. The piston may be extended from the cylinder when hydraulic fluid pressure is removed from hydraulic hose 46 by means of a spring in the head end of the cylinder or by means of another appropriate fluid connection. Hydraulic fluid is preferred because higher pressures can be achieved than can be achieved by compressed air at the usual job site. Furthermore, the cylinder 38 is smaller and lighter for particular tension force in piston rod 44 when high pressure hydraulic fluid is used to actuate the piston, as compared to job site compressed air.

Bending hook 12 is a bending die carrier. It comprises a yoke 48 which is attached to the outer end of piston rod 44. A convenient attachment is by the screw threads seen in FIGURES 2, 3 and 4. A cross pin or set screw prevents unscrewing. The yoke carries hook arms 50 and 52, which are curved to form hooks. The hooks are spaced by means of the yoke. The spacing between the hooks is at least equal to the largest diameter of rebar for which the bending machine 10 is intended.

FIGURES 3 and 4 show the manner in which the small rebar bending .machine 10 is employed. The machine is brought to the

rebar 54 which requires bending. Handle 56 is secured to the cylinder and is convenient for moving and placing the bending machine 10. The machine is positioned so that the rebar 54 lies against the anvils 30 and 32 and between the hook arms 50 and 52 with the hook arms extended. Thereupon, bending die 58 is placed in the hooks of the hook arms. Fluid pressure is supplied in hose 56 moving the piston rod 44 upwardly, as seen in FIGURES 1, 2 and 3, to bring the bending die into engagement with the rebar 54. A shallow bend can be achieved by making a small bend, slightly releasing the bending die, removing the machine along the length of the rebar, and making a small bend. The curvature of the rebar 54 see in FIGURE 3 could be obtained in this way. However, when a sharp bend is required, the piston rod 44 can be retracted further to the position shown in FIGURE 4 making a bend in rebar 54 which is tighter than a right angle. Bends between those illustrated in FIGURES 3 and 4 can be achieved by control of fluid flow. To remove the bending machine from the now bent rebar, the hydraulic pressure is released and bending die 58 is removed from the hook arms. This frees the rebar bending machine 10 to be moved to a new location for further bending.

FIGURES 5 and 7 show the portable small rebar bending machine 10 as having the same frame 14, anvil supports mounted on the frame, anvils 30 and 32, as well as actuating cylinder 38 and its piston rod 44. Yoke 60 is secured to the end of piston rod 44 by means of screw threads and is secured against rotation by a set screw or cross pin, as illustrated. The yoke

60 has two arms which are spaced to receive therebetween the rebar bending die wheel 62. Pivot pin 64 is positioned through appropriate holes in the arms of yoke 60 and through the bending die 62 therebetween. Since it is anticipated that the pivot pin 64 will be regularly removed, instead of having a nut securing it in place, it has a cross cotter pin 66. The bending die wheel has a V-shaped edge like anvils 30 and 32 so that a rebar can be engaged therein.

In the case of the portable small rebar bending machine 10 shown in FIGURES 5, 6 and 7, the piston rod 44 is extended and the die wheel 62 is removed by pulling bend 64. The anvils 30 and 32 are placed against the rebar 68, as shown in FIGURE 7. In this case, the arms of the yoke 60 embrace the rebar 68. In that position, the die wheel 62 is put in place between the arms of the yoke, the pivot pin 64 is replaced and is retained by cotter pin 66. Now, hydraulic fluid under pressure is introduced into the rod end of cylinder 38 to retract the piston rod 44 into the cylinder in the upward direction in FIGURES 5 and 7. This action bends the rebar between the anvils. Upon extension of the piston rod, the rebar bending machine can be moved along the length of the rebar to place other bends therein. The bends may be gentle or sharp, as illustrated in FIGURES 3 and 4. After completion of the necessary bends, the bending machine 10 is removed from the rebar by pulling the pivot pin 64, which allows the bending die 62 to be removed from the yoke for removal of the bending machine.

It is seen that the bending die wheel 62 can rotate in the yoke 60. In some cases, it may be desirable that the bending die not rotate, especially in those cases where travel of the rebar bending machine 10 along the rebar is undesirable during the bending process. To achieve this, the yoke 70 shown in FIGURE 8 can be provided. The yoke 70 is the same as the yoke 60 except that it additionally has a locking pin hole 72. The bending die wheel 62 is also used in conjunction with the yoke 70. When it is desired that the bending die wheel not rotate, after it is put in place, locking pin 74 is placed through the locking pin hole 72 and into one of the holes in the die wheel 62 to prevent the die wheel 62 from rotating. In this way, small rebar can be readily bent at the job site with a small, easy-to-use portable small rebar bending machine 10. In use, the rebar bending machine 10 is brought to the job site along with its power supply. Depending on the size of the cylinder 38 and the pressure of the conventionally available air at the job site, air may be used as the fluid under pressure. However, in view of the need for lightness and compactness of the rebar bending machine 10, it is usually configured with a smaller cylinder useful with high pressure hydraulic fluid. Thus, the rebar bending machine 10 is brought to the job site together with its hydraulic power supply. The hydraulic power supply may be electrically powered or com- pressed-air powered. The power supply also has the capability of selectively applying fluid under pressure to the hydraulic hose 46 or connecting the hose to a drain. The cylinder 38 has

a spring therein to extend the piston rod 44 to the position shown in FIGURES 1, 2 and 3 when no fluid pressure is applied.

The rebar bending machine 10 is brought to the rebar 56 which is to be bent. The anvils 30 and 32 are engaged against the rebar, and the rebar is positioned between the arms of the bifurcated hook 12. Bending die 58, of appropriate radius, is placed in the hook. Thereupon, hydraulic fluid under pressure is applied to the hose 46, and the piston rod 44 is retracted. This pulls the die against the rebar 54 and the rebar against the anvils 30 and 32. Continued motion of the piston into the cylinder causes bending. Control of the hydraulic fluid controls the amount of bending. A shallow bend, such as shown in FIGURE 3, can be made. In that case, the rebar bending machine 10 is moved along the rebar making shallow bends to create a long, large radius bend.

In case sharper bends are required, such as illustrated in FIGURE 4, the piston rod is withdrawn into its cylinder to make the sharper bend. In this case, the radius is defined by the radius of the bending die 58. The rebar 54 is held in position by the grooved configuration of the anvil wheels. The groove faces are V-shaped, with a clearance screw at the bottom of the V. The maximum bend is illustrated in FIGURE 4. A lesser bend can be created by controlling the introduction of hydraulic fluid so that the piston stops at the desired position. When bending is complete, the piston is extended by release of hydraulic fluid pressure so that the spring extends the bending hook. When released, the bending die 58 can be

removed from the hook and the rebar bending machine 10 can be taken away from that bending site and taken to the next bending site. If it becomes difficult to remove the machine due to clearances after bending, the bolts holding the anvil supports and/or the anvils can be removed to improve removal clearances.

The rebar bending machine 10 shown in FIGURES 5, 6 and 7 is used in a similar way. However, to begin with the bending die wheel 62 is removed so that the machine can be applied to the rebar, with the rebar against the anvils and with the rebar embraced between the arms of the bifurcated yoke. When in position, the wheel 62 and its pivot pin 64 are replaced. Thereupon, the bending machine is ready for the application of hydraulic fluid under pressure to cause bending. At the completion of the bend, the pivot pin 64 and bending die wheel 62 are removed to permit removal of the machine from the location of that bend.

The use of a bending die wheel instead of the simple bending die 38 permits moving the rebar bending machine more easily along the length of a rebar to permit successive small bends. This makes that configuration of the bending die more convenient for multiple bends along the length of a reinforcing bar. Furthermore, it is more useful in those cases where the rebar starts from a straight end so that the bending machine can be installed over the end of the bar. The use of a bending die wheel provides a machine with fewer loose parts when handling, in case such is permitted. Sometimes, it is

desirable to prevent rotation of the bending die wheel 62. This occurs in cases where the machine wants to move along the length of the rebar during bending, and such would be undesirable. For this reason, the structure of FIGURE 8 permits the locking pin 74 to permit rotation of the wheel 62 to more easily hold the rebar bending machine 10 in the proper place.