Patent Publication Number: US-3879165-A

Title: Vacuum electric furnaces

Description:
United States Patent 11 1 Krieder et al.  
 1451 Apr. 22, 1975 VACUUM ELECTRIC FURNACES [75] Inventors: Benjamin A. Kreider, Richboro;  
 William J. Metalsky, Warminster; Edward N. Cyrway, Jr., Levittown, all of Pa.  
 [73] Assignee: Abar Corporation, Feasterville, Pa.  
 [22] Filed: Apr. 22, 1974 [2]] Appl. No.: 462,961  
 [52] US. Cl. 432/121; 13/31; 432/204 [51] Int. Cl. F27b 9/14 [58] Field of Search 432/121, 203, 205, 204; l3/3l [56] References Cited UNITED STATES PATENTS 1.112.454 10/1914 Joseph .1 432/203 3,072,392 1/1963 Palmer 432/205 3.625.499 12/197] Westercn ..432/205 Primary E.\&#39;an11&#39;ner.lohn J. Camby Attorney, Agent, or Firm-Zachary T. Wobensmith. 2nd; Zachary T. Wobensmith, Ill  
 [57] ABSTRACT A vacuum electric furnace is described having interiorly disposed structure for supporting and advancing work pieces within the furnace including track rails and their supports and carriers supported by and pendant from the track rails with freedom from adverse effects due to thermal expansion and contraction over wide temperature differential, the drive for the carriers and the carriers avoiding undesired stressing attendant upon temperature changes, the rails and the carriers being disposed within the hot zone of the furnace to prevent collection thereon of contaminants.  
 14 Claims, 10 Drawing Figures PATENTED APRZ 2 I975 sum 3 pg 3 VACUUM ELECTRIC FURNACES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to vacuum electric furnaces having a plurality of aligned treating zones and more particularly to apparatus for moving work pieces through the furnace and supporting the work pieces in the furnace during their stay in the respective treating zones.  
 2. Brief Description of the Prior Art Furnaces have heretofore been proposed in which a plurality of treating zones are provided, closed at their outer ends by doors and with movable interior doors for separating and isolating the different zones.  
  The U.S. Pat. to Kugel, No. 802,517 shows a furnace in which the work pieces are carried on wheeled trucks which are advanced within the furnace in any desired manner such as by pushing the trucks.  
  Borner, U.S. Pat. Nos. 3,583,690 and 3,625,496 and Austin, ct al, British Pat. No. 565,104, refer to the use of cars for carrying the work pieces within a furnace. The trucks and their trackways occupy an excessive space within the interior, do not permit of utilizing heating elements over substantially the entire interior, and can be contaminated and coated, particularly if employed in vacuum furnace operation.  
  It has also been proposed as in the U.S. Fat. to Wingate, No. 2,776,134, Sylvester, No. 1,868,856 and Bielefeldt, No. 3,410,547 to employ rollers for supporting the workpieces, directly or in trays. These structurcs have similar shortcomings to those in which trucks, as heretofore referred to. are employed.  
  It has also been proposed to employ endless chains to advance the work pieces as in the U.S. Pat. to Kochendorfer, No( 1,252,813, but this structure is totally unsuited for use in vacuum furnaces.  
  Miskella, in U.S. Pat. No. 2,841,684. shows overhead trackways for movable heating elements but the furnace is at atmospheric pressure and the overhead driving mechanism is at the same pressure. This structure would be totally unsuited for vacuum furnaces.  
  Oetjen. ct al., U.S. Pat. No. 3,192,645, shows a vacuum freeze drying tunnel dryer in which an overhead guide rail is supported for vertical movement. Carriers supported on the guide rail are impelled by an interiorly disposed endless chain with a driving sprocket engaged therewith, the sprocket being driven by an intermittently actuated drive motor which forms part of an electromechanical drive system. If the motor were interiorly disposed it could not successfully function in the high temperature environment of a vacuum electric furnace. The endless chain also would not function satisfactorily in such an environment.  
  Bielefeldt, in U.S. Pat. No. 3,609,295, shows a vacuum electric furnace in which carriers of open ractangular frames are provided for the work pieces. Each carrier is carried on a narrow bar having transverse horizontal axles with small rollers at their ends. Horizontal flanges projecting inwardly from the sides of the vessels provide tracks for the small rollers. The bars are driven by dogs on an endless chain within the vessel, the chain being driven by an exteriorly disposed motor through gearing. The supporting and driving structure is complicated, not adequately leakproof as illustrated either with respect to heat leakage and/or air leakage and would be particularly likely to be affected by the process.  
  The structures heretofore available for moving work pieces within a vacuum furnace have various shortcomings, do not make adequate provision to accommodate the growth of both the supporting rails and carrier occasioned by the high temperature differential between operating temperatures and shut down or entrance and exit of work pieces in a vacuum electric furnace, and can be adversely affected by deposition of metal during furnace operation.  
 SUMMARY OF THE INVENTION In accordance with the invention improved apparatus is provided in a vacuum electric furnace for supporting and advancing the work pieces within the furnace including track rails and their supports, and carriers supported by and pendant from the track rails with freedom from adverse effects due to thermal expansion and contraction over wide temperature differential, the drive for the carriers and the carriers avoiding undesired stressing of the carriers attendant on temperature changes, the rails and the carriers being disposed within the hot zone of the furnace to prevent collection thereon of contaminants.  
  It is the principal object of the invention to provide improved structure for supporting and moving work pieces into and along a vacuum electric furnace, with retention as desired for processing.  
  It is a further object of the invention to provide improved structure for processing work pieces within a vacuum electric furnace but which is not limited to such use.  
  It is a further object of the invention to provide supporting and impelling apparatus for work pieces in a vacuum electric furnace which is subjected to a minimum of likelihood of deposit of contaminants.  
  It is a further object of the invention to provide supporting and impelling apparatus which comprises tracks and their supports and carriers supported by and intermittently driven along the tracks which function in the heated zones of the furnace and are particularly suited for operation in that environment.  
  Other objects and advantageous features of the invention will be apparent from the description and claims.  
 BRIEF DESCRIPTION OF THE DRAWINGS The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part hereof, in which:  
  FIGS. 1A and 1B together show a vertical longitudinal sectional view through a vacuum electric furnace in accordance with the invention;  
  FIG. 2 is a transverse sectional view taken approximately on the line 2-2 of FIG. 1;  
  FIG. 3 is an enlarged sectional view taken at the location 3 of FIG. 2;  
  FIG. 4 is a fragmentary longitudinal sectional view taken approximately on the line 44 of FIG. 3;  
 FIG. 5 is a fragmentary plan view of the carrier;  
  FIG. 6 is a fragmentary side elevational view of the carrier shown in FIG. 5;  
  FIG. 7 is a transverse sectional view taken approximately on the line 7-7 of FIG. 6;  
  FIG. 8 is a sectional view, enlarged. taken approximately on the line 8-8 of FIG. and  
  HO. 9 is a sectional view, enlarged, taken approximately on theline 9-9 of FIG. 5.  
  It should, of course, be understood that the description and drawings herein are illustrative merely and that various modifications and changes can be made in the structure disclosed without departing from the spirit of the invention.  
  Like numerals refer to like parts throughout the sev eral views.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings. a vacuum electric furnace is there illustrated which includes a plurality of aligned vessels constituting a preheating section A, a treating section B and a cooling section C. An entrance door is provided supported in any desired manner for movement to an open position for access tothe interior of the section A. The entrance door 15 in closed position seals the interior of the furnace against fluid or vacuum leakage.  
  An isolating valve 16 is interposed between the furnace sections A and B to prevent fluid or vacuum leakage and heat leakage therebetween when in closed position. An isolating gate or valve 17 is interposed between the sections B and C to prevent fluid leakage and heat leakage therebetween when in closed position.  
  An exit door 18 similar to the door 15 is provided at the outlet end of the section C for sealing against fluid or vacuum leakage when in closed position and for access for removal of work pieces and their carriers, as hereinafter explained.  
  The furnace sections A, B and C, preferably each consists of a metallic cylindrical wall 20a, 20b and 20c of vacuum-tight construction.  
  The furnace is provided with suitable provisions for evacuation and for the supply and removal of cooling fluid such as inert gas, but as suitable structure for this purpose is well known a detailed description is not believed to be necessary.  
  Within the interior of the cylindrical walls 20a and 20b of each of the furnace sections A and B a reflective shield 22 is provided to reduce the reflection towards the exterior of radiant heat from the heating elements to be described.  
  The furnace section A, interiorly of the shield 22, is preferably provided with resistance heating elements 23 of any desired type. The heating elements 23 of any desired type. The heating elements 23 can be like those disclosed in the U.S. application of Cyrway, et al., Ser. No. 376,538, filed July 5, 1973, now U.S. Pat. No. 3,812,276, issued May 21, 1974 or those described in Kreider, et al, U.S. Pat. No. 3,737,553 or of any other suitable type.  
  The furnace section A, in the interior thereof, and supported by the furnace wall 20a has a plurality of transversely spaced pairs of brackets 25 secured thereto from which, on each side, supporting arms 26, extending through the shield 22 and between the heating elements 23, depend. Each of the arms 26 has a transverse strip 27 which supports a C-shaped frame 28 with inwardly extending spaced socket plates 29 having spaced sockets 30 through which studs 31 extend. The studs 21 extend through horizontally elongated slots 33 in end track rails 32 and are held against inward displacement by M534 which are not however tightened to the extent to impose {any &#34;restraint on expansion or contraction.  
  Intermediate track rails 35 are also provided mounted and supported in the same manner as the end track rails 32. The rails 32 and 35 are of any suitable metallic material. I  
  The supports thus provided for the rails 32 and, 35 accommodate the growth in length of the track rails 32 and 35 upon increase in temperature attendant upon the heating thereof over the wide range of temperatures which occur within the furnace section A from ambient temperature at shut down to operating temperature for heating, as well as the shrinkage thereof upon cooling.  
  The rails 32 at their terminal ends 36 in the furnace section A, at the entrance and exit of the furnace section A, are preferably relieved to guide the carriers as hereinafter explained.  
  In order to operate the carriers hereinafter to be described a plurality of operating sprockets 40 on shafts 41 are provided preferably with mounting mechanism 42 activated from outside the furnace section A, two being utilized on each side in a specific embodiment of furnace section A.  
  The sprockets 40 can be actuated in any desired manner but a suitable drive is shown and described in the U.S. application of Kreider, et al., filed Dec. 3, I973, Ser. No. 420,796, now U.S. Pat. No. 3,847,539, issued Nov. 12, 1974.  
  The furnace section B is preferably provided in the manner previously described, and on each side, with brackets 25, supporting arms 26, frames 27 with socket plates 29, end track rails 32 and intermediate track rails 35 disposed within the shield 22 and heating elements 23, each of the track rails 32 and 35 having elongated slots 33 through which studs 31 extend to permit longitudinal track rail growth as previously described.  
  The furnace section B is preferably provided with a plurality of driving sprockets 40, three sets being employed on each side in a specific embodiment of furnace section B.  
  The furnace section C may have the reflective shields 22 and heating elements 23 omitted, since its function is for cooling but preferably has brackets 25, supporting arms 26, frames 27 with socket plates 29, end track rails 32 and intermediate track rails 35 with elongated slots 33 as previously described.  
  The furnace section C is preferably provided with a plurality of driving sprockets 40 and their actuating mechanism, two sprockets 40 on each side being employed in a specific embodiment of furnace section C.  
  Referring now more particularly to FIGS. 5 to 9, inclusive, the carrier is there shown at 45.  
  The carrier 45 preferably includes inner elongated parallel frame bars 46 which are subject to longitudinal expansion and contraction upon increase and decreaseof temperature, having a plurality of rollers 47 rotatably carriedthereby at spaced locations on shafts 48, which may be tubes or rods, for engagement of the rollers 47 by the teeth of the sprockets 40 for advancing the carrier 45 as desired. The frame bars 46 can be of any desired length but preferably are such as to be accommodated in single or multiple units within furnace sections.  
  The carriers 45 (see FIGS. 8 and 9) preferably have spacer sleeves 49 outwardly of the frame bars 46 with outer frame bars 50 parallel to the frame bars 46 for substantial portions of their length but interrupted to avoid stress transmission to the bars 46. The outer frame bars 50 also have inturned end portions 53. The shafts 48 at predetermined locations are extended outwardly through the frame bars 50 through fixed and elongated openings 48a and 48b to allow for expansion and contraction and for the reception of trackengaging rollers 54 with outer washers 55. The rollers 54 are supported by the upper edges of the track rails 32 and 35, the washers 55 being disposed outwardly of the track rails 32 and 35.  
  Cotter pins 38 retain the structure carried on the shafts 48 in assembled relation.  
  Stub track rails 56 supported by brackets 57 secured to the interior of the section B can be provided to bridge the gap at this location between the end track rails 32.  
  The frame bars 50 have inturned ends 51 which meet guide bars 52 at the ends of the frame bars 46 to orient the ends of the carriers 45 to aid in alignment of the rollers 54 with the rails 32, 35 and 56 particularly in the transition from one furnace section to the next.  
  The carriers 45, at spaced locations, have spaced carrier brackets 58 secured thereto which support, on pivot pins 59, pendant hanger rods 60. The rods 60 are connected by stabilizer rods 61 and have hooks 62 at their lower ends to engage in openings 63 of work carrier fixtures 64.  
  It will be noted that the carriers 45 are carried on the tops of the track rails 32 and 35, have the sprockets 40 in engagement therewith from below, are held downwardly only by gravity and are movable upwardly if necessary to accommodate dimensional changes with changes of temperature.  
 The mode of operation will now be pointed out.  
  The furnace in operation and with the furnace sections separated by the valves 16 and 17 in closed condition has the first section A heated to preheat the work pieces, the second section B being employed for treating the work pieces, such as by aluminum brazing, and the third section C being utilized for controlled cooling such as with a controlled inert atmosphere.  
  When it is desired to introduce work pieces the door is opened and carriers 45 in supporting relation to work pieces are advanced so as to be supported with the rollers 54 on the upper edges of the track rails 32 and 35. The sprockets 40 can be utilized for advancing movement when the carrier 45 has been advanced to a sufficient extent.  
  Subsequent advancing movement of the carriers 45 into the furnace section B, therefrom into the furnace section C and with delivery from the furnace section C upon opening of the door 18 can also be effected by the engagement of the sprocket 40 with the rollers 47.  
  The valves 16 and 17 are controlled as desired to isolate the carriers 45 and their work pieces in the furnace section B.  
  It will be noted that the carriers 45 with their work pieces are supported on the track rails 32 and 35 and disposed entirely within the heating zone interiorly of the heating elements 23 and the reflective heat insulating shield 22 so that contamination of these parts is avoided.  
 We claim:  
  1. In a vacuum electric furnace having an elongated furnace chamber with an interior heat reflective shield and heating elements disposed within. the reflective shield, the improvement which comprises spaced parallel longitudinal track rails within-the chamber and interior-lyof the heating elements, members for supporting said longitudinal track rails, said connecting members between supporting members and said track rails accommodating longitudinal expansion and contraction of said track rails upon changes of temperature within said chamber, a carrier for work pieces having spaced supporting elements supported by said track rails, said carrier having a pair of spaced elongated longitudinal frame members of predetermined length less than that of the furnace chamber and drive members carried thereon, and driving members extending interiorly of said shield in driving engagement with said drive members on said carrier for advancing said carrier within said furnace chamber. 2. The combination defined in claim 1 in which said connecting members include longitudinally elongated slots. 3. The combination defined in claim 2 in which said slots are in said rails.  
 4. The combination defined in claim 1 in which said supporting members have portions connected to the interior of the furnace chamber at upper portions thereof, and  
 said supporting members have portions extending through said shield.  
 5. The combination defined in claim 1 in which said supporting members have portions connected to the interior of the furnace chamber, and  
 said supporting members have portions extending through said heating elements.  
 6. The combination defined in claim 1 in which said supporting members have pendant portions with C-shaped brackets carried thereby, and  
 said rails are disposed between ends of said brackets.  
 7. The combination defined in claim 1 in which said driving members have sprockets disposed between said rails, and  
 said sprockets engage said carrier from below.  
 8. The combination defined in claim 1 in which said carrier comprises spaced parallel side frame members with transverse connecting members for engagement by said driving members.  
 9. The combination defined in claim 1 in which said carrier comprises spaced parallel side frame members with track engaging rollers mounted to said side frame members for engagement with top portions of said track rails.  
 10. The combination defined in claim 9 in which outer spaced side frame members are provided in spaced relation to said parallel side frame members and outwardly thereof,  
 said track engaging rollers are disposed outwardly of said outer frame members,  
 one set of frame members being continuous and the other set of said frame members being interrupted to avoid stress transfer upon temperature change from one set to the other set.  
 11. The combination defined in claim 1 in which said carrier comprises spaced parallel side rails,  
 said side rails have carrier brackets carried thereon,  
 and  
 work supporting members are carried in pendant relation on said carrier brackets.  
 12. The combination defined in claim 11 in which said worksupporting members are pivotally carried in pendant relation on said carrier brackets.  
 13. The combination defined in claim in which one set of frame members is loosely mounted with respect to the other set to avoid stress transfer upon temperature change from one set to the other set. 14. In a vacuum electric furnace having at least two aligned elongated chamber sections and isolating gate means for interposition between said chamber sections, and atleast one of said chamber sections having an elongated furnace chamber with an interior heat reflective shield and heating elements disposed within the reflective shield. the improvement which comprises spaced parallel longitudinal track rails within each of the chamber sections and interiorly of the heating elements and of a length less than that of chamber section for accommodating said gate means between the ends of the rails of each chamber section,  
 said gate means being movable in the space between the ends of said rails for cutting off communication between adjoining chamber sections,  
 a carrier for work pieces having spaced supporting elements supported by said track rails,  
 said carrier having a pair of spaced longitudinal frame members of predetermined length less than that of the chamber sections and drive members carried thereon, and  
 driving members extending interiorly of said shield in driving engagement with said drive members on said carrier for advancing said carrier within each chamber section,  
 said work carrier in its advancing movement bridging the track rails of adjoining chamber sections.