US3829985A - Apparatus for drying pulp-insulated wire - Google Patents

Abstract

A plurality of pulp-insulated wires are continuously dried in a heated chamber of a drying oven having a system for continuously changing the drying atmosphere. Preheated air is continuously introduced to an input end of the chamber and moisture-laden gases are continuously exhausted from the chamber at positions spaced along its length. The input air is blown over ducts which carry the hot gases away from the chamber. Input air is thus preheated prior to entering the drying chamber. Use of a preheated air drying system permits an overall reduction in operating temperature of the drying chamber with a result that the pulp-insulation on the wire is provided with improved breaking strength and elongation properties.

Description

United States Patent 1 91 1111 3,829,985

Dunn et al. Aug. 20, 1974 [5 APPARATUS FOR DRYING 3,403,454 /1968 Smith 34/155 PULPJNSULATED WIRE 3,491,457 1/1970 Schreiber et a1... 34/1 3,604,824 9/197] Hardison 34/155 entors: Helmut E. Durr, Chatham; Albert 3,616.459 10/1971 Patton et al. 34/1 H. Haller, Clark, both of NJ. Primar ExaminerCarroll B. Dorit Jr. [73] Ass1gnee: Western Electric Company, y

Incorporated New York, gttfiaerlrlziery, Agent, or F1rm-P. J. Tr1bulsk1, Jr.; W. O.

c [22] Filed: June 23, 1972 21 Appl. No.: 265,920 [57] ABSTRACT A plurality of pulp-insulated wires are continuously dried in a heated chamber of a drying oven having a [22] }J.S.(gl. 34/115246, 3121(5)?) System for continuously Changing the drying atmo b Sphe p e e air is Co sly introduced to an [58] Bed of Search 34/23 3 input end of the chamber and moisture-laden gases .19/1 are continuously exhausted from the chamber at positions spaced along its length. The input air is blown [56] References Cited over ducts which carry the hot gases away from the UNITED STATES PATENTS chamber. Input air is thus preheated prior to entering 1,418,386 6/1922 Maus 34/27 the drying chamber. Use of a preheated air drying sys- 1,432,270 10/1922 Walsh 34/82 tem permits an overall reduction in operating temper- 1945,35l 2/1934 Freeland 34/155 ature of the drying chamber with a result that the gr pulp-insulation on the wire is provided with improved pern e a 2,804,694 9 1957 Clipsham 34/155 breakmg strength and elongano" propemes' 3,041,736 7/1962 Peterson et al. 34/23 1 Claim, 4 Drawing Figures F/G. (PRIOR ART) mEmEm-mn 3.829.985

a or z 26 AWG 22AWG A (AVERAGE (AVERAGE) VALUES VALUES PRIOR BREAKING STRENGTH 3.85 LBS. 7.72 LBS.

ART ELONGATION |.5| v.45

IMPROVED BREAKING STRENGTH 4.53135 QJOLBS DRYER ELONGATION [.86 1.73

APPARATUS FOR DRYING PULP-INSULATED WIRE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in the manufacturing of pulp-insulated wire. More particularly, the invention relates to an improved system for drying pulp-insulated wire on a continuous basis.

2. Description of the Prior Art Pulp-insulated wire is typically produced by a continuous process in which many wires are insulated simultaneously. A plurality of wires, often as many as 60,'are simultaneously coated with a wet pulp layer and are then drawn through a drying oven in order to produce a final dried pulp insulating coating on each of the wires. A thorough description of a pulp-insulating process can be had by referring to Manufacturing Pulp Cable," The Western Electric Engineer, (June-October temperature is usually maintained at approximately 900F. A natural draft vent system is provided at the output end to permit water vapor to escape from the system.

Successful and efficient operation of drying ovens of this sort depends on a delicate balance between the operating temperature and the amount of air flow through the heating chamber. If air flow is decreased too severely by closing the vent, there will develop an excessive build-up of water vapor within the chamber and a consequent loss of efficiency. If the vent is opened too far, an excessively high rate of air flow will cause a reduction in operating temperature which will also result in a loss of efficiency of the oven. These problems become particularly acute on hot and humid days.

In order to strike a balance between these conflicting considerations, the initial heating zones of the chamber are usually operated at a temperature which is undesirably high. When wet pulp-insulation is exposed to a particularly high temperature, the water in the pulp expands very rapidly and as a result, the-elongation properties and breaking strength of the final pulp-insulation are diminished.

In general, a reduction in temperature require either a slower speed of traverse for the wire or a longer oven consuming more valuable manufacturing floor space. Each of these alternatives are economically undesirable. Further, it is desirable that the pulp insulation have improved breaking strength and elongation properties.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved drying oven for pulp-insulated wire which will permit efficient and economical operation at lower temperature than those used on prior-art ovens.

It is also an object of the invention to provide an oven wherein the humidity within a heating chamber can be carefully controlled to permit efficient operation.

These and other objects are achieved by providing a drying oven wherein the atmosphere within a heating chamber is positively and continuously replaced with preheated air. This results in an overall reduction in the operating temperature of the chamber and improved tensile and elongation properties in the final pulp insulation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a sectional view taken along the lines 3-3 of the drying oven of FIG. 2; and

FIG. 4 is a chart showing numerical values of improved properties associated with use of the inventive drying-oven, atmosphere-control system of FIG. 2.

DETAILED DESCRIPTION A drying oven, designated generally by the numeral 20 and shown in FIG. 2, is basically a modification of a prior art drying oven, designated generally by the numeral 22 and shown in FIG. 1. Comparing FIGS. 1 and 2, it can be seen that a natural draft vent arrangement 24 has been removed from the oven 22 and has been replaced with a forced draft venting system.

The venting system of oven 20 includes a plurality of vent stacks 26 which form a connection from a heating chamber 28 to an exhaust manifold 30. A fan 32 draws air .from the exhaust manifold 30 and drives it to an exhaust vent 34. Wires 36, having wet pulp applied on their surfaces enter the oven 20 at an input side 38 which is on the right side of the oven. The wires 36 pass through the heating chamber 28 which is surrounded by electric heating coils 40. The heating coils 40 are controlled thermostatically to provide three separate zones of heat, designated in FIGS. 1 and 2 as zones A, B and C.

It has been found that zones A and B can be operated at a temperature of approximately ll5014 l200F. Zone C can be operated at a temperature of approximately 900F.

Gases from the heating chamber 28 are drawn upwardly through the vent stacks 26 and are discharged through the exhaust vent 34. Make-up air is provided from the ambient atmosphere through a fan 42 and an input air duct 44. The duct 44 surrounds the vent stacks 26. This arrangement permits the relatively cool input air to be preliminarily heated by passing over the relatively hot vent stacks 26. The input air duct 44 is also provided with an auxiliary electric heater 46 which is used to assure that the input air entering the heating chamber 28 is raised to a temperature of at least 900F.

The fans 32 and 42 are controlled to provide a flow speed of air of approximately 6-7 feet per second through the heating chamber 28. Additional control of air flow is achieved by varying the opening of a draftcontrol port 48. Typically, the chamber 28 has a length of about 27 feet. This means that the atmosphere within the chamber is completely exchanged at a frequency of at least 12 times per minute.

The exchange of atmosphere within the chamber 28 can take place with great rapidity, because the makeup air being introduced with the input side 38 of the chamber is preheated. Thus, the drying oven can be operated efficiently with relatively low temperatures in zones A and B and with the consequent result that the breaking strength and elongation properties of the final insulated wire 36 are improved. By referring to FIG. 4 one can see the tabulated results of the improved properties. The values shown in association with the term Prior Art are obtained through use of an oven of the type which is shown in FIG. 1. The values associated with the term, Improved Drying are obtained through use of the oven 20, shown in FIG. 2.

Although certain embodiments of the invention have been shown in the drawings and described in the specification, it is to be understood that the invention is not limited thereto, is capable of modification and can be arranged without departing from the spirit and scope of the invention.

What is claimed is:

1. In a drying oven for continuously drying pulpinsulated wire, the oven having an open-ended heating chamber divided into at least two zones, heating elements located in each of the zones, means for moving wire into an input side of the chamber and in sequence through each of the zones and past the heating elements, and means for separately controlling the heat output of the heating element in each of the zones to establish a separate, predetermined temperature in each of the Zones, the improvement which comprises:

L566-PT UNITED STATES :PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.829.985 I Dated Aflgnqi' 9n; 107A lnventbr(s) n mug mrgvagd Albgg; H,- Ha11er 7 It is certifiedfghat error appears inrhe above-identified patent and that said Letters Patent are herebyfcbrrected as shown below:

Column 2; line 47, "115o14 12o0F" should be --1-15"0-120 0F--.

Signed arid sealed this 19th day pf November 1974.

(SEAL) Attest:

c. MARSHAILLJDANN Commissioner of Patents MCCOY M. GI SON JR. Attesting Officer

Claims (1)

1. In a drying oven for continuously drying pulp-insulated wire, the oven having an open-ended heating chamber divided into at least two zones, heating elements located in each of the zones, means for moving wire into an input side of the chamber and in sequence through each of the zones and past the heating elements, and means for separately controlling the heat output of the heating element in each of the zones to establish a separate, predetermined temperature in each of the zones, the improvement which comprises: means for replacing water vapor within the chamber with air, including a duct for supplying air to the input side of the heating chamber, a series of vent stacks distributed along the length of the chamber, and means for drawing gases through the vent stacks from the heating chamber; and means for preheating the air, including portions of the vent stacks, located within the duct to transfer heat from the gases drawn from the chamber to the air in the duct, and including an auxiliary heater to further heat the air prior to its introduction into the chamber.

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