SHIELD FOR HEAT TREATING A PLATE WORKPIECE

Abstract

A method of tempering a plate workpiece entails first fitting the plate workpiece with a shield between first and second shield parts each having a respective mask element so as to cover only an edge region of the workpiece while leaving a more central region of the workpiece exposed. The shield and workpiece are then put in an oven with the plate workpiece fitted between the first and second shield parts. The shield also comprises first and second seals on the first and second parts confronting each other and each displaceable on the respective part between a closely juxtaposed working position in which inner portions of the seals are spaced apart by a distance equal generally to a thickness of the plate workpiece and outer portions of the seal bear on each other and a starting position spaced more widely from and out of engagement with each other. The seals engage and clamp the workpiece in the working position.

Claims

1. In a method of tempering a plate workpiece by the steps of: fitting the plate workpiece with a shield between first and second shield parts each having a respective mask element covering only an edge region of the workpiece while leaving a more central region of the workpiece exposed; and heating in an oven the plate workpiece fitted between the first and second shield parts, the improvement wherein the shield also comprises: first and second seals on the first and second parts confronting each other and each displaceable on the respective part between a closely juxtaposed working position in which inner portions of the seals are spaced apart by a distance equal generally to a thickness of the plate workpiece and outer portions of the seal bear on each other and a starting position spaced more widely from and out of engagement with each other, the seals engaging and clamping the workpiece in the working position.

2. The method according to claim 1, wherein the mask elements and the seals thereon are formed congruently with respect to one another and are arranged congruently opposite one another.

3. The method according to claim 1, wherein the first seal in the starting position terminates with an end face at least flush with a first face of the first mask element facing the plate workpiece or is recessed in this first face and the second seal in the starting position terminates with an end face at least flush with a second face of the second mask element facing the plate workpiece or is recessed in this second face, the first and second seals projecting in the working position beyond the respective first and second faces of the mask elements.

4. The method according to claim 1 wherein each of the seals is formed by several parts.

5. The method according to claim 1, wherein each of the first and second shield parts are formed with respective first and second recesses in which the respective seals are movable transversely of a plane of the plate workpiece, the first seal being completely in the first recess in the starting position and terminating at least flush with the first face of the respective mask element facing the plate workpiece or recessed in the respective first face, the second seal being completely recessed in the second recess when in the starting position and terminating at least flush with the second face of the mask element facing the plate workpiece or recessed in the second face, the seals projecting past beyond the first and second faces when in the working position.

6. The method according to claim 5, wherein each of the first and second recesses forms with the respective seal a pressurizable chamber, further comprising: cooling means for supplying the chambers with a pressurized coolant that both cools the respective shields but also shifts the seals into the working positions.

7. The method according to claim 5, further comprising: respective biasing means urging the seals into the working positions.

8. The method according to claim 5, wherein each of the seals is of U-section and has a short inner leg and a long outer leg projecting at a spacing and parallel toward the plate workpiece and of lengths such that in the working position the short legs are closely juxtaposed with the plate workpiece and the long legs engage each other and form a closed chamber around the edge of the workpiece.

9. The method according to claim 1, wherein each of the first and second parts has two of the respective first mask elements and of the respective second mask elements each provided with respective such seals.

10. The method according to claim 1, wherein the parts and the respective mask elements are unitary.

11. The method according to claim 1, wherein the parts and mask elements are formed in multiple parts and are detachably connected to each other.

12. The method according to claim 1, wherein each of the parts is formed in multiple parts.

13. The shield used in the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0034] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

[0035] FIG. 1 is a perspective view of the shield according to the invention;

[0036] FIG. 2 is a top view of the shield; and

[0037] FIG. 3 is a cross section along line of FIG. 2.

SPECIFIC DESCRIPTION OF THE INVENTION

[0038] As seen in FIG. 1, a shield 1 covers at least part of a workpiece plate 2 during tempering of the workpiece 2 in a furnace. The shield 1 is put into a furnace together with a workpiece 2 and then heated approximately to austenitizing temperature for treatment of the plate. The furnace is indicated by a dashed line 28 in the drawing.

[0039] The shield 1 has a first part 3 with an elongated first mask element 4 and an second part 5 opposite this with a second elongated mask element 6. The parts 3 and 5 are each formed as a closed generally rectangular frame and also each have, opposite their first mask elements 4 and 6, elongated second mask elements of which only the first mask element 4′ is shown. The first part 3 is formed integrally with the respective mask elements 4 and 4′ and the second part 5 is similarly formed of one piece with its respective mask elements of which only element 6 is shown. This makes it possible to manufacture the shield 1 at low cost.

[0040] The position of the workpiece 2 between the first mask element 4 and the second mask element 6 is described below. These explanations apply equally to the arrangement of a further part of the printed workpiece 2 between further pairs of mask elements.

[0041] A central region of the plate workpiece 2 is exposed between arranged between the mask elements 4 and 6. To each side the respective edge of the plate workpiece 2 is covered by the first and second mask elements 4 and 6 such that the covered regions of the workpiece 2 are shielded by the shield 1 against further heat application and slowly cools down to a temperature below the austenitizing temperature, in fact close to the martensite start temperature.

[0042] The uncovered central region of the workpiece 2 is thus maintained at austenitizing temperature or heated by the heat application.

[0043] Bar seals 8 and 9 are provided on the mask elements 4 and 6 to improve and more precisely shield the covered region of the workpiece 2 so that no or only very narrow transition areas between hard and soft areas are produced during subsequent shaping and hardening. In addition, the improved shielding makes it possible to cool the subareas to a desired temperature more quickly, so that the dwell time of the workpiece 2 in the furnace can be significantly reduced and considerable energy savings are the result.

[0044] FIG. 3 shows the first and second mask elements 4 and 6 and the part of the plate workpiece 2 covered between the mask elements 4 and 6 in cross-section. The mask elements 4 and 6 are arranged at a distance from each other and from the plate workpiece 2, so that a gap 7 is formed between the plate workpiece 2 and the first mask element 4 and a further gap 7′ is formed between the plate workpiece 2 and the second mask element 6. The workpiece 2 is arranged between the mask elements without being touched by the mask elements 4 and 6 or the parts 3 and 5. This contact-free shielding enables low-cost and low-wear shielding.

[0045] The seals are fastened to the mask elements, a first seal 8 being fastened to the first mask element 4 and a second seal 9 arranged opposite the first seal 8 being fastened to the second mask element 6. Both seals 8 and 9 are adjusted relative to each other transversely to the plate workpiece plane into a working position. The adjustment direction transverse to the plate workpiece plane is shown in FIG. 3 by a double arrow 27.

[0046] The first part 3 with the first and further mask elements 4 and 4′ formed thereon and the first seal 8 is congruent with the second part 5 with the first mask element 6 formed thereon and the further mask element as well as the second seal 9. In addition, the parts 3 and 5 together with the mask elements 4 and 6 are positioned congruently with each other. The seals 8 and 9 are arranged as a pair of seals opposite each other and congruent with each other so that their end faces lie exactly against each other in the working position. As a result, gaps 7 and 7′ between the mask elements 4 and 6 are optimally closed.

[0047] The further first and second mask elements of which only the element 4′ is shown also have further first and second seals 8 and 9 that are attached to the shield 1 as pairs of seals. These mask elements and seals are correspondingly congruent in design and are positioned congruently with one another.

[0048] The seals 8 and 9, which are arranged in pairs opposite each other, are of U-section. The first seal 8 has a long inner leg 19 and a short outer leg 20. The second seal 9 has a long second leg 21 and a short second leg 22. As shown in FIG. 3, in the working position the seals 8 and 9 are moved toward each other with the short legs 20 and 22 closely juxtaposed with a first strip 10 of the workpiece 2 so that the gaps 7 and 7′ between the mask elements 4 and 6 and the workpiece 2 are almost completely closed and no more heat reaches the covered region of the workpiece 2. This avoids a transition area between the hard and soft areas in the workpiece after the subsequent shaping of the workpiece 2. A small gap remains between the confronting faces of the short legs 20 and 22 and the workpiece 2 in order to shield without contact. This makes shielding particularly cost-effective and low-wear.

[0049] The long legs 19 and 21 of the seals 8 and 9 lie against each other at a location 11 that is offset from the plate workpiece 2. As a result, the area contained between the mask elements 4 and 6 next to the workpiece 2 is completely closed and no heat can reach the edge area of the workpiece 2. Thus the U-shape of the seals 8 and 9 shields an edge of the plate workpiece 2 shielded in a simple manner by a single pair of seals. The area can be cooled to the desired temperature in a short time, since heat no longer reaches the shielded area. The time saved results in significant energy savings.

[0050] As shown in FIG. 3, the seals 8 and 9 are movable and held in respective confronting recesses or grooves 14 and 15 of the shield 1 so as to be displaceable transversely to the plane of the plate workpiece, namely in the direction of the double arrow 27. In a starting position not shown in the figures, the seals 8 and 9 are retracted into the respective recesses 14 and 15 so that the upper first seal 8 terminates with its end face flush with a lower face 12 of the mask element 4 facing the workpiece 2, and the lower second seal 9 ha its end face flush with an upper face 13 of the mask element 6 facing the workpiece 2 in the starting position. Thus, the spacing between the mask elements 4 and 6 is freely accessible and is not limited by parts of the projecting seals 8 and 9. The workpiece 2 can be placed in a simple manner between the mask elements 4 and 6 without touching the seals 8 and 9 or jamming when it is pushed in between the mask elements 4 and 6.

[0051] After shifting the seals 8 and 9 into the working position as shown in FIG. 3, the seals 8 and 9 then project beyond the surfaces 12 and 13 of the mask elements 4 and 6 and into the gap between the mask elements 4 and 6. The gap between the mask elements 4 and 6 and the gaps 7 and 7′ between the mask elements 4 and 6 and the workpiece 2 are at least partially closed by the seals 8 and 9 in the working position.

[0052] The recesses 14 and 15 are grooves extending along a certain length of the corresponding orifice plate 4 and 6. The bar seals 8 and 9 have a length corresponding to the length of the channel and are held and slidably guided piston-style in the respective channel.

[0053] The seals 8 and 9 can be composed of several seals, for example to be able to shield complicated geometries. For this purpose, for example, a large number of seals can be placed next to or against each other, which together form a seal 8 and 9.

[0054] The shield 1 is connected to a cooler 29. The system pressure of the coolant supply is used to move the seals 8 and 9 into the working position. A coolant flows through the shield 1 as soon as it is put into operation in a furnace. The system pressure in the cooler acts hydraulically or pneumatically on the seals 8 and 9 so that these are at least partially pressed like pistons out of the respective recess 14 and 15 and the working position. In this way, a particularly simple and cost-effective actuation is possible. The return of the seals 8 and 9 to the starting position is effected by tension springs 16 and 17 held in the recesses 14,15 and serving to pull the seals 8 and 9 back into the respective recesses 14 and 15 after the pressure in the cooler 29 has dropped.

[0055] The seals 8 and 9 are separate components and are detachably attached to the shield 1. This has the advantage that the seals 8 and 9 can be replaced by seals with other dimensions and that the shield 1 can be used for plate workpieces 2 of different thicknesses.

[0056] The invention is not limited to the embodiments, but is variable in many ways within the scope of the disclosure.

[0057] All individual and combination features disclosed in the description and/or drawing are considered essential to the invention.