Adjustable steam flow control for an electric steam iron

Abstract: An adjustable steam flow control for an electric steam iron (10) includes a metering rod (36) mounted in threaded engagement with a support bushing (64) and having a lower end (60, 62) that extends into a valve orifice (46) between the water reservoir (20) and the steam generation chamber (32). A pinion gear (54) is secured to the metering rod (36) and engages a spur gear sector (78) on a rotatably mounted steam adjust knob (24). Rotation of the steam adjust knob (24) in one direction or the other by the user causes the metering rod (36) to rotate in its bushing (64) and advance into or retract from the orifice to thus control the steam flow rate. The steam control knob (24) is provided with a spur gear sector (78) so that partial rotation of the steam control knob (24) will rotate the metering rod (36) through its full range of motion.

Description: The present invention relates to an adjustable steam-flow control arrangement for an electric steam iron and, more particularly, to a steam flow control arrangement that provides precise and repeatable control of the steam flow in an electric steam iron. Conventional electric steam irons include a steam generation circuit by which water in a reservoir is supplied to a steam generator with the steam directed to the fabric to be ironed. Most steam generation circuits include a metering valve by which the water flows from the reservoir in a drip-wise manner onto a heated surface, such as the soleplate, and is flashed to steam. The metering valve typically includes a small-diameter orifice between the water reservoir and the steam chamber with the distal end of a metering rod extending into the orifice. The distal end of the metering rod has a variable cross section so that the water flow rate can be controlled by extending the distal end into or withdrawing it from the orifice. Various mechanical arrangements have been employed to control the position of the metering rod relative to the orifice with cam control being the most common. Typically, the electric iron is provided with a steam-flow control knob that is rotatable about an axis and which includes or is connected to a helical cam surface. The cam surface can include detent positions so that the user can select predefined "low", "medium", and "high" steam generation rates and can include an "off" position for dry ironing. The upper end of the metering rod is configured to engage the cam surface so that rotation of the steam control knob by the user in one direction will withdraw the other end of the metering rod from the orifice to increase the water flow to the steam camber and rotation of the control knob in the other direction will extends the other end of the metering rod into the orifice to decrease the water flow to the steam chamber. The control arrangement is such that the metering rod can also seal the orifice to stop the water flow and the generation of steam to allow dry ironing. While cam control systems have enjoyed widespread use in the steam iron art, the cam-control system lacks a certain precision in its operation since dimensional clearances can accumulate so that it is often difficult to provide small increments or decrements in the steam flow. Another type of steam control arrangement, described for example by US-A-2 337 077, having a higher degree of control is the threaded-mount arrangement in which the metering rod is mounted in a threaded bushing in the body of the iron. A user-operable steam control knob is secured to the upper end of the metering rod and is rotatable by the user in one direction to withdraw the other end of the metering rod from the orifice to increase the water flow to the steam chamber and rotatable in the other end direction to insert the other end of the metering rod into the orifice to decrease the water flow to the steam chamber. Since the pitch of the screw threads can be specified at the design stage, precise and repeatable control can be obtained. However, the threaded mount arrangement, in contrast to the cam-control system, requires several rotations of the steam control knob to effect control throughout its full range of operation. Accordingly, it can be difficult to select a desired steam flow rate position. It is an object of the present invention to provide an adjustable steam flow control for an electric steam iron that provides precise and repeatable control of the steam flow. It is another object of the present invention to provide an adjustable steam flow control for an electric steam iron in which precise and repeatable control of the steam flow can be obtained using a steam control knob in which the full steam flow range is obtained in less than one rotation of the steam control knob. It is still another object of the present invention to provide an adjustable steam flow control for an electric steam iron in which small and precise increments or decrements of steam flow can be obtained. The present invention provides an adjustable steam flow control for an electric steam iron which includes an orifice between the water reservoir and the steam generating chamber and a metering rod having a variable cross-section distal end for insertion into and withdrawal from the orifice to control the water flow rate to the steam generating chamber. The metering rod carries an externally threaded portion that is mounted in an internally threaded bushing carried in the support housing. A pinion gear is secured to the metering rod and engages spur gearing on a rotatably mounted steam adjust control. Rotation of the steam adjust control in one direction or the other by the user causes the metering rod to rotate in its bushing and advance into or retract from the orifice thus to control the steam flow rate. In the preferred embodiment, the steam adjust control is provided with a spur gear sector so that partial rotation of the steam adjust control will rotate the metering rod through its full range of motion. The present invention advantageously provides an adjustable steam flow control for an electric steam iron in which steam control can be precisely and smoothly controlled in a positive manner without binding and in which repeatable increments or decrements of steam flow can be obtained. The invention will now be further described with reference to the accompanying drawings, in which, Figure 1 is a side view, in cross-section, of an electric steam iron incorporating an adjustable steam flow control in accordance with the present invention; Figure 2 is an elevational view of a metering rod; Figure 3 is an enlarged detail of the distal end portion of the metering rod of Figure 2, and its cooperating valve body; Figure 4 is a cross-sectional elevation view of a steam adjust driver member of Figure 1; Figure 5 is a top view, in cross-section, of the driver member of Figure 4 taken along 5-5 of Figure 4; and Figure 6 is a side view, in partial cross-section, of an upper support bearing for the metering rod. An electric steam iron with an adjustable steam flow control in accordance with the present invention is shown in partial cross-section in Figure 1 and is designated generally therein by the reference numeral 10. As shown, the steam iron 10 includes a body portion 12, a handle 14 for manipulating the steam iron 10, a forward or nose portion 16, and an electrically heated soleplate 18. A water-containing reservoir 20 is formed within the body portion 12 of the steam iron 10 and contains a supply of water used for the generation of steam, as explained below. The steam iron 10 includes a fill port (not shown) by which the reservoir 20 is periodically filled by the user, which reservoir 20 may include a transparent or translucent window by which the level of water in the reservoir 20 can be gauged by the user. The steam iron 10 is provided with a user-operable temperature control 22 to control the electric power provided to the soleplate 18 and a steam flow control knob 24 which controls the amount of steam issued from steam apertures (not shown) in the soleplate 18, as is conventional in the art. The temperature control 22 is coupled to a shaft 26, which, in turn, is connected to a thermostat (not shown) that periodically opens and closes an electric circuit to supply power to the soleplate 18 and thus establishes the ironing temperature of the soleplate 18. The soleplate 18 includes an interior surface portion 28 that is closed by a cover plate 30 to define a steam chamber 32 in which water from the reservoir 20 is flashed to steam, as explained more fully below. The steam chamber 32 is connected to passageways (not shown) that lead to the steam apertures formed in the soleplate 18 to provide the steam to the fabric being ironed. While a steam chamber 32 that is integral with the soleplate 18 has been shown in the preferred embodiment, the invention is applicable to those steam irons in which a separate flash-type boiler or flooded boiler is used to generate the steam. The flow of water from the reservoir 20 is controlled by a water metering system which includes a valve body 34 and a metering rod 36. The valve body 34, which may be fabricated from a mouldable plastic, is fitted into a counterbore (unnumbered) in a bottom wall 38 of the reservoir 20 and held in position between the bottom wall 38 and the cover plate 30 by a compression gasket 40. The valve body 34 is formed as a body of revolution and includes an annular flange 42 that is received within the counterbore and bears against the gasket 40 to provide a fluid-tight seal. As shown in the enlarged details of Figure 3, the valve body 34 includes an entryway 44, a through orifice 46, and an exitway 48 for the flow of water from the reservoir 20 into the steam chamber 32. The metering rod 36, as shown in Figure 2 and in the detail of Figure 3, includes shank portion 50, an externally threaded segment 52, and a pinion gear 54 at its upper end. A metering pin 56 extends from the lower, or distal, end of the metering rod 36. As shown in the detail of Figure 3, the metering pin 56 includes first diameter cylindrical portion 58, a second diameter cylindrical portion 60, and an intermediate frusto-conical section 62 that is tapered from the cylindrical portion 58 to the cylindrical portion 60. In the preferred embodiment, the first cylindrical portion 58 has a diameter of 0.76 mm, the second cylindrical portion 60 has a diameter of 0.508 mm, and the intermediate tapered frusto-conical portion 62 has a length of 2.0 mm. The metering rod 36 can be fabricated from a metal or a mouldable plastic or can be formed as a two-piece assembly, as shown in the lower portion of Figure 2, from a shank portion fabricated from a mouldable plastic and a pin portion fabricated from a metal, such as brass. The second cylindrical portion 60 of the metering pin 56 is normally positioned, with an appropriate clearance dimension, within the orifice 46 of the valve body 34. The metering rod 36 is then adjusted to change the cross-sectional through-flow area of the orifice 46 by advancing the frusto-conical portion 62 into and out of the orifice 46 to control the flow of water from the reservoir 20 into the steam chamber 32 and, accordingly, control the steam flow. As shown in Figure 1, the metering rod 36 is carried in an internally threaded bushing 64 that is mounted in or otherwise secured to an appropriate partition within the body portion 12 of the steam iron 10. As can be appreciated, rotation of the metering rod 36 in one direction or the other will cause the metering pin 56 at its lower end to advance into or retract from the orifice 46 to decrease or increase the water flow from the reservoir 20 into the steam chamber 32. In the preferred embodiment, the threads are 6-32 UNC threads (Machinery's Handbook, 20th Edition, Industrial Press Inc 1976, page 1296) to provide an axial displacement of 0.8 mm (0.0313 inches) for each full rotation of the metering rod 36. The upper end of the metering rod 36 is carried in a journal 66, which, as shown in the detail of Figure 6, includes a mounting slot 68 for mounting on an appropriate partition in the handle 14 of the steam iron 10 and a semi-cylindrical bearing surface 70 for constraining the upper end of the metering rod 36. The provision of a semi-cylindrical bearing surface 70 in contrast to a full cylindrical bearing surface allows for a saving in material and simplicity of assembly while providing adequate bearing support for the upper end of the metering rod 36. The rotary position of the metering rod 36 is controlled by the steam flow control knob 24 and a drive member 72. As shown in Figure 1 and the cross-sectional view of Figure 4, the drive member 72 includes an intermediate portion 74, an upper connection interface 76, and a lower portion that includes a gear sector 78. The drive member 72 is rotatably mounted in an appropriately sized opening in the handle 14 so that the gear sector 78 engages the pinion gear 54 of the metering rod 36. As shown in Figure 5, the gear sector 78 includes gear teeth 80 that occupy an annular sector of approximately 200° and engage the gear teeth 82 of the pinion gear 54. In the preferred embodiment, the gear sector 78 includes eight teeth 82 to provide a 6.25 step-up ratio between the gear sector 78 and the metering rod 36. The axially extending length of the gear teeth on one of the two gears, i.e., the pinion gear 54 in the preferred embodiment, is such that full tooth-to-tooth contact is maintained as the metering rod 36 is advanced or retracted throughout its range of motion. A radially extending tab 84 extends from the lower end of the drive member 72 and engages stop surfaces (not specifically shown) to limit the rotary motion of the drive member 72. The steam flow control knob 24 is connected to the upper end of the drive member 72 through the connection interface 76 which includes resilient latching tabs 86 that engage mating surfaces on the interior of the steam flow control knob 24 to connect the parts together. In normal operation, the steam flow control knob 24 is rotated to a desired setting between a minimum and a maximum value. As a consequence of rotation of the steam flow control knob 24, the gear sector 78 is likewise rotated to rotate the engaged pinion gear 54 and its metering rod 36. As a consequence, the metering pin 56 (Figures 2 and 3) is raised from or inserted into the orifice 46 to increase or decrease the water flow rate from the reservoir 20 into the steam chamber 32. If desired, the metering rod 36 can be advanced to completely block the orifice 46 to interrupt the flow of water to the steam chamber 32 to allow dry ironing. The present invention advantageously provides an adjustable steam flow control for an electric steam iron in which steam control and adjustment is provided by a smooth, positive action when incrementing or decrementing steam flow in which the probability of binding or 'hang-up' is minimal.

Claims: A steam control system for a steam iron, comprising: a housing (12) including a water reservoir (20) and a steam-forming chamber (32); a valving orifice (46) between the reservoir (20) and the steam-forming chamber (32) for admitting water from the reservoir (20) into the steam-forming chamber (32); a longitudinally extending metering member (36) having a portion extending into the valving orifice (46) and movable toward and away therefrom to control the water flow between the reservoir (20) and the steam-forming chamber (32), the metering member (36) mounted in threaded engagement (52, 64) with the housing (12) whereby rotation of the metering member (36) about its longitudinal axis causes a change in the water flow rate between the reservoir (20) and the steam-forming chamber (32); characterised in that the control system comprises a first gear member (54) connected to the metering member (36) for rotation therewith, a second gear member (78) in engagement with the first gear member (54) and rotatable in one direction or the other to rotate the metering member (36) and effect a change in the water flow rate between the reservoir (20) and the steam-forming chamber (32). A steam control system for a steam iron according to claim 1, characterised in that the longitudinally extending metering member (36) comprises a metering rod (36) having an end portion (60, 62) extending into the valving orifice (46), the first gear member (54) comprises a pinion gear member (54) and the second gear member (78) comprises a spur gear member (78). A steam control system according to claim 2, characterised in that it comprises a journal bearing (66) supporting the end of the metering rod (36) opposite the first-mentioned end portion (60, 62) for relative rotation. A steam control system according to claim 3, characterised in that the journal (66) comprises a semi-cylindrical surface supporting the second-mentioned end of the metering rod (36). A steam control system according to any of claims 2 to 4, characterised in that it comprises a rotatably mounted drive member (72), a spur gear (78) being connected to said drive member (72). A steam control system according to claim 5, characterised in that it comprises a user-operable knob (24) connected to the drive member (72). A steam control system according to any of claims 1 to 6, characterised in that a gear ratio, N:M, exists between the second (78) and the first (54) gear members in which N>M, and in which N represents the diameter of the second gear member (78) and M represents the diameter of the first gear member (54). A steam control system according to claim 7, characterised in that the gear ratio between the second (78) and the first gear members (54) is about 6:1. A steam control system according to any of claims 1 to 8, characterised in that the second gear member (78) is constrained for rotation about an axis for a fraction of a full revolution. A steam control system according to claim 9, characterised in that the second gear member (78) is constrained for rotation about an axis in a 200° range. A steam control system according to any of claims 1 to 10, characterised in that the second gear member (78) is an external gear sector. A steam control system according to any of claims 1 to 11, characterised in that the portion of the metering member (36) extending into the valving orifice (46) has a cross-section (58, 60, 62) that varies with length. A steam control system according to any of claims 1 to 12, characterised in that the portion of the metering member (36) extending into the valving orifice (46) is formed as a frusto-conical body (62).

Inventors: CZERNER PETER A, CZERNER, PETER A.
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1990
Main classification: D06F75
IPC codes: D06F75