GB2259037A

GB2259037A - Process for the permanent bending of deformable bodies

Info

Publication number: GB2259037A
Application number: GB9217193A
Authority: GB
Inventors: Dietmar Erich Bernhard Lilie
Original assignee: Empresa Brasileira de Compressores SA
Current assignee: Empresa Brasileira de Compressores SA
Priority date: 1991-08-30
Filing date: 1992-08-13
Publication date: 1993-03-03
Anticipated expiration: 2012-08-13
Also published as: IT1255346B; JP2003275821A; GB9217193D0; JP3454480B2; ES2060520B1; FR2680711A1; KR100244593B1; AT404100B; DE4228566A1; ES2060520R; KR930003985A; ITMI921731A1; ES2060520A2; GB2259037B; DE4228566B4; JPH05212448A; CN1037497C; FR2680711B1; ATA172892A; CN1071862A

Abstract

A method of bending metallic blades for use in reed valves of hermetic compressors involves bending through a first angular displacement which corresponds to an expected deformation between 60% and 90% or 110% to 120% of the desired deformation. The actual deformation is then measured to deduce a new displacement to deformation relation. A further displacement is calculated from the new relation, and applied. A number of displacements are determined and applied in succession until the desired deformation is achieved. <IMAGE>

Description

22?J,7 j 1 p 3 PROCESS FOR THE PERMANENT BENDING OF DEFORMABLE BODIES

Field of the Invention

The present invention refers to a process for the 5 automatic bending of different bodies, such as generally metallic rods or blades, in order to achieve a precise plastic or permanent deformation thereof, independently of certain microstructure, molecular composition and/or dimension deviations from respective nominal values which were predetermined for these bodies.

Background of the Invention

The automatic bending of bodies, which are generally in the form of elongated rods or blades, has been achieved through an operation in which the body, which is usually fastened at an end portion of its longitudinal extension, has its free end portion submitted to only one bending through an angular displacement in the direction of the desired plastic deformation to be achieved,. said displacement being carried out in a single plastic deformation operation, by applying a force to the free portion of the body that is going to be bent. Said displacement is calculated so as to guarantee a certain degree of plastic deformation to said body, based on the nominal values of molecular and physical compositions and dimension of the bodies to be bent, considering the values taken from the bending of a plurality of bodies having the same 'constructive and operative characteristics.

In some applications, the prior art automatic bending systems, which impart to the free portion of the body a single angular displacement in a certain direction, are sufficient to cause in the body a deformation within the precision standards required for a desired application of the body to be bent.

2 Nevertheless, in cases where it is fundamental to achieve a bending or plastic deformation within very restricted precision limits, these prior art automatic bending processes do not consider as relevant parameters, during the plastic deformation of each body of a plurality of equal bodies, the deviations that normally occur in terms of dimension, microstructure and molecular composition in said bodies. This problem can be solved by a sequence of bending operations which are carried out in a cumulative manner in relation to each body to be bent, until the final desired precise result is obtained. However, in terms of industrial production as, for example, in the manufacture of reed valves for hermetic compressors used in small refrigeration systems, it is impossible to achieve a precise bending of each reed valve through a practically manual control of the sequential deformation steps applied to each reed valve.

In the presently known automatic bending systems, the angular displacement, which is applied to the free portion of the body to be bent, in order to achieve a final desired plastic deformation, is calculated considering only one body with nominal characteristics. for a plurality of bodies to be bent. Except in rare occasions, the reality is that the bodies from a plurality of bodies to be bent present certain dimensional and microstructural variations- relative to each other. Thus, it is impossible to achieve an automatic homogeneous degree of plastic deformation for all bodies from said plurality of bodies, without deviating f rom the strict precision limits which were previously set up. for said bodies when defined by the reed valves of -55 the already mentioned hermetic compressors. Summary of the Invention

3 Thus, it is a general object of the Present invention to provide a process for the automatic and permanent bending of deformable bodies through high speed automatic operations, in order to guarantee a high precision degree in the plastic deformation of said bodies, despite the deviations that may occur in the nominal microstructure. molecular composition and dimensions of said bodies in relation to a desired nominal value.

The present invention preferably provides 1 an automatic bending process as cited above, which also allows to determine the degree of the angular plastic deformation c) f function of certain dimensional are external variable and the bodies, as a parameters, which to said bodies and which are also related to each body, so that the plastic deformation of a certain body can be achieved as a function of said dimensional parameter that is externai to said body. In this circumstance, the process is directed to cases where the piece to be bent is assembled to a portion of variable dimension belonging to another piece or body, thereby avoiding the selection and grouping procedures for the pairs of dimensionally compatible pieces.

According to the invention, the process f or the au toma t i c bendinQ c) f plastically deformable and c-lorigatE?d bodies. in oruder to define in said bodies two portions in dihedral angle joined to each other by means c) f.1 bending line that is at least substantially transversal to the longitudinal axis of the body, comprises the steps of:

a- to set up, experimentally, the relation between the different degrees of angular displacement that is applied, around the bending line, to one of the longitudinal portions of the bodies having the same 1D,ttL-rn, and the resulting plastic deformation., and 4 to determine t h e equation C3 f the 91 displacement v. plastic: deformation-'A standard curve for that pattern of the body to be bent; b- to fasten. from the bending lrne, the other longitudinal portion of each body to a fastening device..

c:- to measure the original position of at leastone point of the free body portion in relation to a fixed point of reference and to register this initial value of relative positioning; d- to impart to the f ree body portion that is being bent a first angular displacement, around the bending line and in the direction of the desired plastic deformation. by an angle corresponding to the achievement of a deformation value situated in one of the intervals between 607 and 907. and between 1107. and 120Z of the desired plastic angular deformation, _ 0 annular considering the Pquation defined in stL=p_"a"; e to Measure the new angular position 'of said point of the free body portion and compare it with the previous pc-sitiort. in order to define the degree of plastic deformatibn which was obtained with the previous angular displacement that was applied to the free body portion:

f- to set up, based on said degree of plastic deformation obtained in step "L-", a new equation for the ItanQular displacement X plastic deformation" curve that i -- specific for that body in respective bending phase and define, mathematically and as a function of the new spL:cific curve, an additional angular displacement to be imparted to the free portion of the body, in order to achieve a desired plastic deformation; g- to apply to the free portion of the body that is being bent another angular displacement around the same bending line, by an angle which corresponds to t h L- only one displacement body within the angle defined in step "f"; h- to submit thE body that is being bent to at least one sequence of the steps #8211. "-f" and "g", in order to achieve the final desired plastic deformation; and i- to release from the fastening device the body presenting the final desired plastic deformation.

The operational sequence described above includes second plastic-deforming angular in order to achieve the bending of the the tolerances required f or the considered application. As defined above, however, the steps CReto. If it And It g " ran be sequentially repeated ti 1 1 tt-ie;-c is achieved the desired precision for the plastic deformation of the body that is being bent.

The bending process mentioned above further allows the automatic definition of the plastic deformation dearee that will be applied to the body, as a function of variable dimensional paramEters of other 2 0 elements to which said body will have to operatively adapt.

Another pc!-=cibil-.;tv nresented by the _process is that it can also USE partial reverse bending techniques (after the únitial bendings), in order to obtain a residual tension relief effect in the bent body when desired and, evc-.!n Go. still keeping the high final precision required in the bending.

Brief Description of the Drawings

The bending process in question will be described W now. with reference to the attached drawings, in which:

Fici.1 shows a block diagram of a possible apparatus to carry out the bending steps mentioned above; Fig.2 shows a nominal standard "angular displacement X plastic deformation" curve c) f a 1 on g i tu d i n a 1 of bodies in the form portion of a certain plurality a:' 1 6 of metallic blades, which are used in the manufacture of reed valves for small hermetic compressors, the fixed point of reference for the original position of the body being spaced away from said original position of the deformation direction to be achieved; and Fig.3 shows a schematic elevational front view of a possible apparatus to e xecute the above mentioned process.

Detniled Description of the Invention

As already mentioned, the process object of this invention is particularly useful for the precise and automatic bending, in industrial production scale, of metallic blades employed in the manufacture of reed valves for hermetic compressors. In a more specif ic way, the present process allows a precise plastic deformation of- the metallic blade that functions as blade impelling means for the suction and discharge valves described in the Brazilian patent application BR 9002967 (corresponding to U.S. application Serial No. 715,818/91) of the same applicant.

As shown in the -attached drawings, the process is used to achieve a precise plastic deformation of a metallic blade or rod 10, through the bending of one of its end portions, around a bending line which is transversal to the longitudinal axis of the blade 10.

In the present case, the blade 10 is represented by a small rod which is used as. elastic impelling means for the reed valves of small hermetic compressors,, as described in the above mentioned prior application.

To initiate the process of the predetermined plastic deformation for a certain plurality of blades 10 having the same pattern, concerning dimensions, molecular composition and microstructure, it is necessary to set up, experimentally, the relation between different degrees of the angular displacement 7 which is applied, around said bending line, to one of the longitudinal portions of the blades 10, and the plastic deformation that is achieved in said one portion.

This setup can be done through any adequate manner that allows the determination of a sampling of said "angular displacement to plastic deformation" relation for the plurality of blades 10 of a same pattern that are noing to be bent.

This experimental procedure allows determination of the equation of the "angular displacement against plastic deformation" standard curve for the pattern of blades to be bent. An example of this type of curve is illustrated in fig.2, in which the axis of the abscis.sas represents the plastic c) r permanent deformation obtained in the pieces, and the axis of the ordinates represents the angular displacement imparted to said pieces in order to achieve such deformation. This curve represents' the desired nominal plastic or permanent deformation that is expected for the pattern of the blade or piece that is being bent.

It should be observed that the curve or plastic def ormation begins after a certain initial displacement of the ordinate axis. This axial displacement results f rom an initial distance D between the non-bent blade and a point of reference which is spaced away thereof in the direction of the bending to. be achieved, and also from an initial elastic deformation EDe of the pil-ce that is being bent.

After finishing the step to determine the "angular displacement against plastic deformation" standard curve for the pattern o f the piece to be bent, the effective bending of the plurality of blades 10 will 'take place.

8 For this purpose, each blade 10 that is bent should have a portion of its going to be longitudinal extension. which is located on either side of the transversal bending line, attached- to a fastening device 20 which, in fig.3, consists of two blocks or pads 21 made of hard metal, one of which being movable and compressible against the other through adequate means which may or may not be automatic. These two blocks 21 of the fastening device 20 must be built so as to. permit a correct and complete immobilizatich of said portion 11 of the blade 10 -.,hich is being hti-ld in -the 'fastening device 20. This fixed portion 11 usually corresponcis to the shortest longitudinal portion of the piece in relation to the bending line.

It should be understood that the positioning of each blade 10 in the fastening device 20 has to be achieved through preferably automatic: devices which can guaantL-L- an equal positioning for the blades 10 of said plurality of blades, as the blades are being supplied to the fastening device 20.

After each blade 10 has been immobilized, it is necessary to register the original position of its free portion 12 that is going to be bent, in order to serve as a parameter for the determination of the final angLI 1 ar displacement that is going to be imparted to the free po-tic)n 12 of the blade 10.

One possible way to register this original position of the blade 10 is to measure the distance along a plane which is parallel to the bending direction of the blade. between a point of reference that is fixed in rplation tn -hr- -fa--,4-pning device 20, and a point of the free portion 12 of the blade.

In figures 1 and 3,there is schematically illustrated 35 a sensina device 30, which is fixed in relation to the fastening device 20 and which includes a probe 31 1 1 1 7 tl 9 that can be displaced from a retracted position, corresponding to the point of reference cited above, until it touches a point of the free portion 12 of the blade 10. This probe 31 moves according to the bending direction of the blade 10, i.e., in 'an orthogonal plane in relation to said free portion 12. When said probe 31 touches the blade 10, it allows the sensing device to detect a new information corresponding to an initial distance Do, between the fixed point of reference and the original position of the blade free portion 12.

After these initial steps, the free portion 12 of the blade 10 can be submitted to an angular displacement around the bending line, which can be defined, transversely or substantially transversely, by the fastening device 20 itself, at the junction of the f ixed portion 11 and the free portion 12 of the blade. The angular displacement of the free portion 12, in the bending direction to be achieved, can be obtained, for example, through a cylindrical rod 40, which is disposed parallel to the bending line and operatively associated to a micrometric table 41 (of, e.g., 0.5mm/turn), which Is driven by a step motor 42 (of, e.g., 500 steps/turn).

The initial angular displacement of the free portion 12 of the blade 10 is achieved by powering the step motor 42, so that the cylindrical rod 40 makes said free portion 12 bend around the bending line and in the direction of the plastic deformation to be obtained, by an angle a corresponding to the achievement of 60% to 90% of the value for the desired plastic angular deformation, taking into account the standard equation,. shown in fig.2, for the plurality of blades. It should be observed that the angle a represented in fig.3 corresponds to the angular displacement imparted to the free portion 12, p in order to have a plastic angular deformation which is lower than the angle a, due to the elastic deformation of said free portion 12, said deformation having already been considered in the setup of the "angular displacement x plastic deformation" standard curve for the plurality of pieces to be bent.

The operational instruction to the step motor 42 is produced in a central processing unit 50 as, -for example, the microcomputer illustrated in fig. 1, which is accessible-to the operator and instructs the step motor 42 through a digital interface 51 that includes- specific controls for the step motor 42 operation.

Thus, when the angle a for the initial angular displacement of the free portion 12 of the blade 10 is reached, the cylindrical rod 40 is retracted by the table-motor assembly 41, 42, so that said free portion 12 can return to the respective plastic deformation first position P1 illustrated in fig.3.

Then, the central processing unit 50 instructs the probe- 31 of the sensing device 30 to move until it touches again the free portion 12 of the blade 10, so that the sensing device can send to the central processing unit 50, through a probe signal conditioner 52 and interface 51, an, information corresponding to the first plastic deformation D1 obtained. The central processing unit 50 then establishes a new standard curve for the piece that is being bent and defines, mathematically and as a function of the new specific - curve, a second additional angular displacement 0 that is gqing to be imparted to the free portion 12 of the blade 10. A corresponding instruction is then given to the step motor 42, so as to cause the -displacement of the cylindrical rod 40 through the micrometric table 41, in order to impart said second angular displacement 1 h, 11 to the free portion 12 of the blade 10, and then the cylindrical rod 40 is turned to an inoperative condition, so as to allow the free portion 12 to assume a corresponding second pla,r>tic deformation position P2 which, as a function of the first bending approach and with the corresponding correction for the specific curve, is situated within the values required for the specific application.

Afterwards, the blade 10 can be released from the 10 fastening device 20.

It should still be observed that the initial distance D,, between the point of reference and the blade 10 in the original position, is defined by the sensing device 30 and registered in the central processing unit 50, in order to be subtracted from the distance D1 that was measured after the first plastic angular deformation of the blade 10.

As illustrated in fig.1, the central processingunit can be operatively connected, through an analogical interface 60, to another sensing device 70, which is disposed so as to measure, for example, the seat deepness which is specific for each blade that is going to be bent, in order to determine the value for the plastic deformation to be imparted to each blade 10, as a function of a least one dimensional variation in a respective piece or element that is going to be associated to each particular blade.

In another possible embodiment, the determination of which part of the blade is going to be bent is achieved using the information received from both laminar body opposite faces. The measure obtained in the opposite face can be directly achieved by means of a plurality of sensing devices or indirectly, by f reflexion, in the case of optical sensors. The automatic activation of the fastening device for 1 12 the f ixation of the l aminar body that is going to be deformed is carried out by a presence sensing device which reveals the existence of a piece in its surroundings, sending a signal to the central processing unit, which then initiates the bending process. In a possible embodiment, the central processing unit will begin the bending process, sending back to the fastening device an -order to fasten the longitudinal portion c)'f each -lami.nar body opposed to the free po-tiDn of each said body. An alternative embodiment provides a fastening device which automatically fastens the laminar body, once its presence has been detected next to said fastening device. In both cases, the liberation of the already bent pieces is automatically controlled by the central processing unit, which commands the opening of the fastening device after the bending of each impelling means has been concluded.

The actuation c) f the deforming device over the laminar body, which is being submitted to the bending process is related with the motion of the micrometric table which carries, on its loading surface, both the deforming and the sensing devices, which are thus simultaneously forwardly or backwardly moved in relation to the laminar body. In the opposite situation, in which the micrometric table carries the laminar body to be bent, said body will present a forward or a backward movement, in relation to the position sensing device and to the deforming device.

Although there has been described one embodiment of the invention, according to which there is provided only one second plastic-defcirming displacement in the same direction of angular the f irst angular displacement, in order to achieve the final desired plastic deformation, it should be understood that the present bending process can include, besides.

-4 2 13 the first displacement, a plurality of additional angular displacements, which can be as follows:

- all additional displacements having the same direction, which is equal to thaú of the first displacement; all additional displacements having the same direction, which is oppositd to that of the first displacement; Some additional displaceffients having the same direction of the ^first displacement and others having a direction which is opposite to that of the first displacement, wherein the last displacement can be executed in either direction.

9 it is also possible to carry out the present process through two angular displacements in opposite directions, the first one being inade so as to produce an angular deformation value ranging from 110% to 120% of the final desired plastic deformation Value. In this case, as well as in all other cases in which there is carried out at least one additional angu 1 ar displacement, in an opposite direction relative to the anterior displacement, which can be the first or an additional one, said angular displacement in an opposite direction allows a relief in the residual tensions of the prior dis?lacements.

r 14

Claims

I- Process for the permanent bending of deformable bodies, in order to define in said elc)rfgatL-d bodies two portions in dihedral angle and united to each other through a bending line which -is at least substantially transversal to the ' longitudinal axis of the body, characterized in that it comprises the steps of:

f a- to Set up', ex-perimentally, the relation between the different degrees of angular- displacement that is applied, 'around the' bending line, to one of the longitudinal portions of the bodies having the same pattern, and the resulting plastic deformation; and to deter-mine the equation of the $$angular displacement x plastic deformation" standard curve for that pattern of the body to be bent; b- to fasten, from the bending line, the other longitudinal portion of each body to a fastening device; c- to measure the original position of at least one paint of the free body portion in relation to a fixed point of reference and to register this initial value of relative positioning; d- to impart to the free portion of the 1 body that is being bent a first angular. displacement, around the bending line and in the direction of the desired plastic deformation, by an angle corresponding to the achievement of a deformation value situated in one of the intervals between 60% and 90% and between110% and 120% of the desired plastic angular deformation, considering the equation defined in step- #Calf e- to measure the new angular pa;ition of said point of the free body portion and compare it with the previous position, in order to define the degree of plastic deformation which was obtained with the previous angular displacement that was applied to the free body portion; f- to set up, based on said degree of plastic deformation obtained in step "L-", a new equation for the Atangular displacement X plastic deformation" curve, that is specific for that body in the respective bending phase and define, mathematically and as a function of the new specific curve, an additional angular displacement to be imparted to the free portion of. the body, in order to achieve a desired plastic deformation; g- to apply to the free portion of the body that is being bent another angular displacement around the same bending line, by an angle which corresponds to the angle defined in step V'; h- to submit the body that is being bent to at least one sequence of the steps "L-", "f" and "g", in order to achieve the final desired plastic deformation; and i- to release from the fastening device the body 20 presenting the final desired plastic deformation.
2- Process, as in claim 1, wherein at least one additional angular displacement is in the direction of the final desired plastic deformation, said displacement causing a respective plastic deformation which is closest to the final desired one, in relation to the previous plastic deformation.
3- Process, as in claim 2, wherein there is provided a plurality_ of additional angular displacements in the direction c) f the final desired plastic deformation, said displacements causing the respective plastic deformations which are progressively closest ti the final desired one.
4- Process, as in claim 3, wherein said additional angular displacements are sequential.
5- Process, as in claim 4, wherein said additional an gular displacements have all the same direction.
1 1 16 6- Process, as in claim 5, wherein said additional angular displacements have all the same direction of the final desired plastic deformation.
7- Process, as in claim 6, wherein at least the last angular displacement occurs in the opposite direction in relation to the previous displacement.
8- Process, as in claim 7, wherein at least the last angular displacement occurs in the opposite direction in relation to the first angular displacement.
9- Process, as in claim 1, wherein at least one angular displacement in the direction of the final plastic deformation corresponds, sequentially, to at least one adjustment angular displacement in the opposite direction.
10- Process, as in claim 1, wherein at least one angular displacement occurs in the opposite direction relative to the final desired plastic deformation.
11- Process, as in claim 1, wherein it includes the additional step of: to measure, before the body liberation, the new angular position cif said free portion paint of the elongated body and compare it -with the position that- said point should present in the. desired plastic deformation condi - tion, inorder to define the piece acceptability.

1 1 I.

1 W
12. A method of bending a first portion of a body relative to a second portion of the body, to a desired plastic deformation, the method comprising the steps of (i) determining a first angular displacement to be applied corresponding to an expected plastic deformation calculated from a predetermined displacement to deformation relation, the expected plastic deformation being between 60% and 90% or between 110% and 120% of the desired plastic deformation, (ii) imparting the first angular displacement to the first portion, (iii) measuring the plastic deformation obtained, (iv) determining from the measured plastic deformation a new relation between further angular displacement and plastic deformation, and hence determining a second angular displacement to be applied to approach or achieve the desired plastic deformation, and (iv) imparting the second angular displacement to-the first position of the body.
13. A method of bending a metallic blade according to claim 12, the blade being of a type adapted for use in reed valves of hermetic compressors.
14. A method substantially as hereinbefore described with reference to the accompanying drawings.