US3029595A

US3029595A - Thermally controlled expansible means for imparting motion to mechanism

Info

Publication number: US3029595A
Application number: US51110A
Authority: US
Inventors: John F Sherwood
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-08-22
Filing date: 1960-08-22
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

Aprll 17, 1962 J. F. sHERwooD 3,029,595

THERMALLY CONTROLLEO ExPANsIBLE MEANS FOR IMPARTING MOTION TO MECHANISM Filed Aug. 22, 1960 2 Sheets-Sheet 1 JOHN E SHERWOD m f3 BY ATTORNEY April 17, 1962 J. F. SHERWOOD 3,029,595

THERM CONTROLLED EXPANSIBLE MEAN FOR TO MECHANI ALLY IMPARTING MOTION Filed Aug. 22, 1960 Sheets-Sheet 2 i INVENToR.

JHN F SHE R14/00D @Y ma A fr0/mfr 3 029 595 THERMALLY CONTRLLD EXPANSEBLE MEANS FOR IMPARTING MTION T MECHANKSM John F. Sherwood, P.0. Box 225, Rte. 2, Gaiden, Colo.

p, Filed Aug. 22, 1960, Ser; No. 51,110

6 Claims. (Cl. 60--23) This invention relates to thermally controlled means v for imparting motion to mechanism designed to actuate dampers, valves, shutters, pumps and other devices. The invention embodies certain improvements over the construction shown and described in my U.S..Patent No. 2,815,642, December 10, 1957, for Devices for Utilizing the Thermal Expansion of Wax.

The object of my invention is to produce improved thermally controlled means embodied in `au exceedingly small, compact unit capable of developing greatly increased power, as compared to known devices. The invention comprises improved means for utilizing highly expansible and contractible material in a high pressure cylinder and a novel combination piston and work shaft, with supporting means therefor, operatively connected to mechanism to be actuated by the shaft.

Exceptionally eicient results, in respect to length of shaft travel and pressure exerted by `the shaft, are attained in the unit of my invention by displacement of a very small amount of the expansible material. This is made possible by the use of a reciprocated sha-ftwhich has a very small diameter portion serving as a piston in the high pressure cylinder and a larger diameter portion outside of the cylinder serving as a work shaft connected to the mechanism to be actuated thereby, said shaft being provided with supporting means for mounting the shaft reciprocably in the uni-t housing and for automatically reinforcing the small diameter portion when and to the extent it is moved out of the pressure cylinder.

Another feature of the invention is the provision of a specially shaped and located heating element in the high pressurecylinder. The element is designed and so located relatively to the expansible material and cylinder Walls that the vacuum which is formed when the material cools and the piston is in outward extended position will be in the axial center 'of the cylinder where the heating element cannot come into contact with the vacuum and cause the formation of an uncompressible gas which would retard the return movement of the piston. The presence of the vacuum zone in the axial center of the cylinder, caused by contraction of the expansible material in cooling, yfacilitates the return of the piston due to the absence of resistance in the path of the piston travel.

The shape of the heating element has another advantage in that it is axially hollow and of such diameter that the piston can be received therein, thus permitting usey of la shorter high pressure cylinder than is possible when the heating element is embedded in the expansible Vmaterial in the axial center of the cylinder in Ithe path of movement of the piston.

Another improvement resides in the pre-treatment of the expansibleV material, preferably parain wax, whereby conversion of the material to gaseous form under normal operating temperatures is prevented.

v The aforementioned and other advantages of the invention will be understood by reference to the drawings and following specilication. Y

In the drawings: 1 p

FlG. l is a perspective View of a housing unit containing thermally controlled expansible means embodying my invention for imparting motion -to mechanism.

FlG. 2 is a longitudinal vertical sectional view of same, on a larger scale.

FIGS. 3, 4 and 5 are transverse vertical sectional views inthe planes of the lines 3-3, 4 4 and 5--5, respec-V tively, on FIG.`2, looking in the direction indicated by the arrows.

FIG. 6 is a view similar to FIG. 2, showing a modification ofthe invention, the left hand end of the structure being broken away.

FiG. 7 is a transverse vertical sectional view in the plane of the line 7-7 of FIG. 6.

l Referring to FiGS. 1-5, elusive, the mechanism of my invention is encased in a housing in which the part 10 is a high pressure cylinder and the part 11iis a cylindrical body in which a reciprocated Vshaft 12 is mounted. The cylindrical body 11 is provided with externally threaded

collars

13, 14. The inner end of the high pressure cylinder 1li is threaded onto the collar 13.

The shaft 12 comprises la small diameter portion 15 integral with or rigidly connected to -a larger diameter portion 16. The portion 15 serves as a piston or plunger which extends from the surface 17 of the shaft portion 16 through a central opening in the collar 13 into the high pressure chamber 1S of the cylinder 10. The larger diameter work shaft 16, broken away at its outer end, in FIG. 2, is designed to have said end operatively connected to mechanism (not shown) to be actuated by the shaft. The inner end of the shaft 16 adjacent the piston portion 15, is provided with a plurality of slots 19 which extend longitudinally from the surface 17 into the shaft and are equally spaced apart circumferentially of the shaft to receive supporting guide plates v20, preferably four in number.

The guide plates 20 support the shaft in the housing l1, and the small diameter piston portion 15 is reinforced by said plates. Each guide plate 2G has flat parallel side surfaces, longitudinally disposed, partially located in a slot 19. The longitudinal edges of the plates 20 are concentric to the shaft 15, as indicated at 21, 22, the width of the plates between said edges being equal to the radial space between the shaft 15 and the inner surface of the cylindrical body ll. The length of each guide plate is such that one end abuts the surface 23 of the inner end of the body 1.1 and the opposite end portion 24 extends into the slot 19 in the shaft portion 16. Each guide plate has an ear or radial projection 25 on its outer edge 22 projecting into an annular groove 26 formed in the inner surface of the body 11 whereby the guide plates are held stationarily inthe housing in reinforcing positions relattively to the piston shaft portion 15.

The high pressure chamber 18 in cylinder l()l is sealed at its inner end by

seals

27, 28, as shown in FlG. 2.

The outer end of the high pressure cylinder 10 contaihs a thermal assembly which includes a resistance Wire holder 30 of porcelain or other suitable material, on which the heating element resistance Wire 31 is wound. The holder 3@ is cup shaped, centrally hollow so that the side walls of the cup and the wire 31 wound thereon are close to the cylinder walls 1t). The resistance element 31 is connectedby wire 32 and screw 33 to the conductor disc 34,

rod 35, and positive electrode 36, which is connected to a source ofelectrical current (not shown). The Wire 31 is `grounded to the casing at 37. The described assembly is held imposition by a cap 38 threaded externally for engaging the internally threaded portion 39 of the cylinder 10. A sealing gasket is indicated at 40.

The high pressure chamber 18 is filled with highly expansible material, preferably parain wax, which is pretreated by heating it to temperatures above the normal operating temperature ofthe unit. This treatment` burns o gases formed by the heated wax Aand removes all material convertible to gaseous form under normal operating temperatures. Thus the expansible material is freed of uncompressible components which interfere with the op-k eration of the piston shaft.

Heating of the element 31k is controlled by thermostatic means (not shown) which may be remotely or otherwise located with respect to the unit. The material in the chamber 18 when heated expands and exerts great pressure against and around the piston shaft portion 15, thereby moving the shaft 12 as a whole to the right, as shown in FIG. Z. For operating dampers, for example, the shaft may be rnade to travel three or four inches by displacement of a very small amount of expansible material, due to the small diameter of the shaft 15,-'which Vmay be 1A@ or 1A; inch in diameter. Such a small diameter shaft, of course, is subject to bending or breaking, under the high pressurekdevelopcd by the expansible material, in that portion which moves yout of the high pressure cylinder into the body 11, but the provision of the supporting guides 20 between the shaft 115 and inner surface ofthe housing 11 automatically reinforces the small diameter piston shaft and obviates bending or breaking thereof.

The shaft 12after having been moved toward the right to lactu-ate-mechanism such as dampers, shutters, and other devices :(not shown), may be returned to initial position by various -means such as springs or hydraulic or other mechanism (not shown). The return stroke of the piston is facilitated bythe fact that the thermally controlled expansible material is allowed to cool at the end of the outward stroke of the shaft and due to the shape and location of the resistance wire holder 30 and wire 31 thereon, a vacuum zone is formed in the axial center of the pressure chamber 1S, as indicated by the dotted lines 41. This arrangement of the heating element not only allows the vacuum to form in the axial center of the chamber in the path of the returning piston shaft, but due to the hollow cup shaped form of the heating element, the shaft can travel to the left to the maximum extent in the pressure cylinder without hindrance by a centrally located ilament such as shown in my aforementioned patent. The reason for the vacuum forming in the axial center of the high pressure cylinder when the piston is in its outward position and the heating element has been made inactive is that the cooling of the expansible material takes place from the outside of the cylinder 10 and contracts the material toward the outer wall, thus producing a vacuum 41 in the axial center of the unit.

4 The location of the cup shaped heating element at the end of the high pressure cylinder opposite the end in which the high pressure seal is located has another advantage. The expansion of the wax near the element imparts fu-ll travel movement to the piston shaft before the wax surrounding the seal becomes liquid, and this lessens the problem of ecient functioning of the seal.

The construction shown in FIGS. 1 5, inclusive, ispartcularly eilicient for imparting travel in excess of one inch to the shaft 12, that is, suflcient travel to expose part of the small diameter piston portion outwardly of the high pressure chamber 18. When the travel of the shaft 12 is one inch or less, the reinforcing and supporting means may be dispensed with, as illustrated in the modification shown in FIGS. 6 and 7.

Referring to said modification shown in FIGS; 6 and 7, the high pressure cylinder 50 and cylindrical housing 51, with

collars

52, 53, resemble the corresponding

parts

10, 11, 13, 14 respectively, shown in FIGS. 1 5, excepting that they are proportioned to accommodate a uniform diameter shaft 54, reciprocably mounted in the housing 51, having a piston end 5,5which projects into the high pressure chamber' 56 inthe cylinder 50. The heating l element, partly broken away, Acomprises the samefresistance wire holder 30 and wire 31 and other parts heretofore described. Seals 27, Z8, such as heretofore described seal the high pressure chamber 56.

The high pressure cylinders 10 and 50 may be provided externally with heat radiating ns as is well known in the art.

Paraflin wax which melts at 70 F. is suitable for use as the highly expansible material of my invention. This can be prepared by mixing paraliins of different melting points, such as Alaska paraffin which melts at minus 10 F. and temperate zone parailin which melts at F. When parain, such for'example as that which melts at 70 F., is heated to cause expansionl thereof in a high pressure cylinder, for example to 200 F., it produces uncompressible gases which interfere with the operation of the piston shaft and with the expansion capacity of the contents of the cylinder. I have overcome this objection by pre-heating the wax before placement in the pressure cylinder,`to temperature above the predetermined operating temperature of the unit. This pre-treatment burns off the components which would otherwise be converted into gas in the cylinder. Thus the wax which I employ is free of gas forming components which would make the expansible material less efficient for its intended purposes.

The specific constructions and arrangements of parts herein illustrated are for exemplary purposes only and it should be understood that the principles of the invention embrace variations and modications thereof which come within the scope of the following claims.

Y I claim: v

1. Thermally controlled means for imparting motion to mechanism', comprising a housingincluding a high pressure cylinder, a shaft reciprocably mounted in the housing having a piston portion in the cylinder, expansible material in the cylinder, and electrical means for heating said material comprising a hollow cylindrical holder mounted in one end of the pressure cylinder, a resistance element on said holder located between the holder and the pressure cylinder side walls, and means for connecting said element to a source of electrical current, cooling of the element and expansible material causing contraction of the material toward the cylinder side walls and formation of a vacuum zone in the axial center of the pressure cylinder and holder in the path of travel of the piston shaft.

2. Thermally controlled means for imparting motion to mechanism, comprising a housing including a high pressure cylinder, a shaft reciprocably mounted in the housing having a small diameter piston portion in the cylinder and a slotted larger diameter work shaft portion located outwardly of the cylinder inthe housing, a plurality of supporting guides stationarily located between the-inner surfaces of the housing and the peripheral surface of the piston portion of the shaft and extending into the slotted portion of the work shaft, said supporting guides automatically reinforcing the piston portion of the shaft when and to the extent that it is located outwardly of thev pressure cylinder in its reciprocatory movement, expansible material in the cylinder, and means for heating the material inthe cylinder to expand it and impart motion to the shaft.

3. Thermally controlled means for imparting motion to mechanism, comprising a housing including a high pressure cylinder, a shaft reciprocably mounted in the housing having a small diameter piston portion in the cylinder and a slotted larger diameter work shaft portion located outwardly of the cylinder in the housing, a plurality of supporting guides stationarily located between the inner surfaces of the housing and the peripheral surface of the piston portion of the shaft and extending into the slotted portionof the Work shaft, said supporting guides automatically reinforcing the piston portion of the shaft when and to the extent that it is located outwardly of the pressure cylinder in its reciprocatory movement,'expansible material in the cylinder, and electrical means forheating said material comprising a hollow holder mounted in the cylinder, a resistance element on said holder, and means for connecting said element to a source `of electrical current, the holder having an open end facing the piston end of the shaft and side walls spaced apart from each other to receive the piston end of the shaft between them within the holder.

4. Thermally controlled means for imparting motion to mechanism, comprising a housing including a high pressure cylinder, a shaft reciprocably mounted in the housing having a small diameter piston portion in the cylinder and a slotted larger diameter work shaft portion located outwardly of the cylinder in the housing, a plurality of supporting guides stationarily located between the inner surfaces of the housing and the peripheral surface of the piston portion of the shaft and extending into the slotted portionof the work shaft, an annular groove in the inner surface of the housing, a radially extending ear on the outer edge of each supporting guide projecting into said groove, said supporting guides automatically reinforcing the piston portion of the shaft when and to the extent that it is located outwardly of the pressure cylinder in its reciprocatory movement, expansible material in the cylinder, and means for heating the material in the cylinder to expand it and impart motion to the shaft.

5. Thermally controlled means for imparting motion to mechanism, comprising a housing including a high pressure cylinder, a shaft reciprocably mounted in the housing having a small diameter piston portion in the cylinder and a slotted larger diameter work shaft portion located outwardly of the cylinder in the housing, a plurality ,of supporting guides stationarily located between the inner surfaces of the housing and the peripheral surface of the piston portion of the shaft and extending into the slotted portion of the work shaft, said supporting guides automatically reinforcing the piston portion of the shaft when and to the extent that it is located outwardly of the pressure cylinder in its reciprocatory movement, expansible material in the cylinder, said material having been pre-treated before installation in the pressure cyl- Vinder by removing gas-forming components therefrom,

and means for heating the material in the cylinder to expand it and impart motion to the shaft.

6. Thermally controlled means for imparting motionV to mechanism, comprising a housing including a high pressure cylinder, a shaft reciprocably mounted in the housingV having a piston portion in the cylinder, expansible material in the cylinder, and electrical means for heating said material, the said expansible 4material being parafn wax pre-treated before installation in the pressure cylinder by heating to temperature in excess of the normal operating temperature of the thermally controlled means, Vand the said electiicalmeans for heating the expansible material being located adjacent the cylinder side walls, cooling of the heating means and of the expansible material causing contraction of the material toward the cylinder side walls and formation of a vacuum zone in the axial center of the cylinder in the path of travel of the shaft.

References Cited in the tile of this patent UNITED STATES PATENTS