Patent Application
20180113154
This invention relates, in general, to suspended work platform hoist systems. More specifically, a condition of an electrical power source available on deployed work platforms.
Portable work platforms used for interior or exterior maintenance of a specific structure or a group of similar structures are known. These platforms provide a movable horizontal work surface to support maintenance workers and their tools in the course of performing such tasks as window cleaning, caulking, metal polishing, window re-glazing, sealing and any other general maintenance task that must be performed from heights that range from a few feet above the ground or an interior ground floor to the top floor of a building, which in some circumstances can be several hundred feet above the ground. These portable work platforms are supported by structural cables and respective hoist mechanisms that enable the work platform to be controllably lowered or raised along the side of a building or other vertical structure. Such hoist mechanisms are generally simple machines including an electric induction motor, a gearbox, and a traction mechanism that grips the wire or cable. Generally, a 220 VAC power source is provided to the platform. However, other input line voltages are possible. An independent splitter connects the power source to respective inputs of electric motors in the hoist mechanisms for raising or lowering the platform on the structural cable. Generally, the electric motors are placed at opposing ends of the work platform.
The traditional electric traction hoist has been used for swing stage applications, also known as suspended scaffolding, for nearly 70 years. In the field, voltage sag has been a chronic issue at job sites for decades. With the demand for power increasing in the workplace and the home, aging power grids in many cities have struggled to provide nominal voltage levels during peak power usage hours. Voltage levels at a suspended platform will further decrease as the distance from the power source increases and as workmen on the platform energize tools and the hoist mechanisms to adjust the height of the platform. In addition, as building HVAC systems increase a local electrical load in response to the heat of the afternoon, job site voltages at the platforms can fall to a level that renders the hoists inoperable. Thus, stranding workers on swing stage equipment until an appropriately sized voltage buck/boost transformer is connected at the power source or the source voltage at the platform otherwise returns to an adequate voltage level. When this is the case, a field engineer or support technician has insufficient information as to the voltage level at the platform when under load.
Both analog and digital handheld-multimeters are well known. These electrical measuring devices are typically provided with electrically conductive leads that respectively terminate in corresponding sockets arranged on the multimeter. The leads can be used to contact the individual conductors of a disconnected connector coupled at the end of an electrical input or supply line. Thus, electrical measurements performed at an input or supply connector with a conventional multimeter are measuring an open circuit condition. Furthermore, any modification to the electrical supply circuit elements to permit handheld probe access to supply conductors on a work platform would introduce a significant safety hazard.
To date, there is no known conveniently sized measuring device available to the work platform that is capable of measuring input voltage at the platform while the hoists and possibly other electrical equipment are operating under load.
The present electrical measurement assembly provides a safe, practical, and economical solution that is suitable for use on or in connection with an electrical feed suitable for applying power to work platforms. Furthermore, the present electrical measurement assembly is compact, easy to use, store and transport.
In a first example embodiment, a portable measurement assembly suitable for work platforms includes a housing that forms a first passage arranged to receive a line-in electrical supply and a second passage arranged to provide a line-out to a load. A measurement device is electrically coupled to the line-in electrical supply.
In an alternative embodiment, a similar housing is further arranged with a hinged cover that protects the measurement device.
In another example embodiment, a similar housing is further arranged such that the third passage is aligned with an opening in a protective cover, thereby protecting a display portion of the measurement device.
The portable measurement assembly suitable for work platforms can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the assembly.
To date, there has been no conveniently sized measuring device available to the work platform industry that is capable of measuring line-in voltage at the platform while the hoists and other electrical equipment are operating under load. The present electrical measurement assembly provides a safe, practical, and economical solution that is suitable for use on or in connection with work platforms. Furthermore, the present electrical measurement assembly is compact, easy to use, store and transport.
In use, the present electrical measurement assembly is inserted in line with an available source of electrical power. The assembly can be applied at either end of a supply cable. The assembly provides one or more electrical measures while energizing one or more hoist motors and other electrical equipment on a work platform. When coupled in-line and closer to a building source, the measurement assembly provides information that can confirm nominal operating conditions at that location. When coupled in-line on a work platform, the measurement assembly provides information that can confirm nominal operating conditions or provide an indication that can be communicated to a field engineer or technician as to an appropriate buck/boost transformer that may be required to provide sufficient voltage to a deployed work platform.
A number of features can be integrated into the novel and inventive electrical measurement assembly suitable for portable work platforms. As will be apparent to those skilled in the art, the separate features can be applied in any desired combination that provides convenient and operator safe access to line-in voltage information under load conditions on portable work platforms. For example, the entire assembly can be appropriately scaled in size to be stored and transported in a tool box. The assembly can be arranged with desired lengths of insulated cable each of which may be terminated in an electrically insulated and weather proof connector.
Alternatively, when a more permanent installation is desired, a platform load side cable may be terminated in an enclosure on the platform rather than a connector. An example enclosure may include a power distribution assembly that receives and distributes a first voltage to hoist mechanisms and that provides a second voltage different from the first voltage for operating one or more tools from the work platform.
Whether the electrical measurement assembly is arranged in a temporary and portable configuration (with two connectors) or a permanent configuration with one or no connectors, the cable conductors and the connectors should be sized appropriately. For example, a 10 gauge conductor is appropriate to safely support a current up to 20 amperes. When such loads are expected, corresponding connectors rated to support 250 volts with a current of 20 amperes should be used. On some work platforms and under some load conditions it may be desirable to use 8 gauge conductors and connectors rated to support 250 volts and a current up to 30 amperes. However sized and selected, such connectors are electrically insulated and weather proof may be arranged with electrically conductive sockets (commonly referred to as a female connector) or tabs (commonly referred to as a male connector) as may be desired. Furthermore, a first or line-in cable length may be different from a second or line-load cable length. Accordingly, the assembly can be arranged in unique configurations to match a layout of specific work platforms if so desired.
In preferred embodiments, the electrical measurement assembly provides an observable display of the AC line-in voltage while providing the line-in voltage to one or more hoist motors, hoist controls, and other electrically powered equipment on the work platform. At present, a measurement element with a digital display is preferred. A first terminal of the measurement element is coupled to an in-line or supply side conductor. A second terminal of the measurement element is coupled to the neutral or return conductor.
In the preferred embodiment, this first terminal is protected by a series-coupled current limiting device such as a time-delay fuse. The current limiting device can be mounted in a fourth opening along a surface of the housing. When the current limiting device is a time-delay fuse, the fuse can be inserted in a cartridge style sub-assembly mounted along a surface of the housing or in a cover of the housing. Such a cartridge-style sub-assembly is generally arranged with an external removable cap to provide replacement access to the time-delay fuse. Alternatively, the current limiting device can be arranged on an insulated mount within the housing.
Whether an analog or a digital display element is deployed, the display portion of the electrical measurement element is mounted in the housing or in a cover of the housing such that the display is observable to operators on the platform or in relative proximity of the electrical measurement assembly when the assembly is coupled in series with a line-in cable from an electrical source.
When an analog or deflection type measurement element is deployed, a graded scale or a color coded scale may be presented along a face of the display as an indicator of a nominal in-line voltage range. On the low-voltage side of the nominal range a set of labels or different colors may be applied over corresponding ranges of the analog scale as an indicator to a field engineer or a technician as to an appropriate buck/boost transformer to use at the building or other power source.
In an example embodiment, the housing may be arranged with a hinged cover that protects the measurement element. Such a hinged cover may further protect and provide access to a removable cap on a cartridge-style fuse holder. The hinged cover may be opaque and made from the same material as the housing. Alternatively, the hinged cover may be translucent and made from plastic or plexiglass. In still other alternatives the hinged cover may be arranged with a suitably sized opening in registration with a display of the measurement device. The opening may remain open or a translucent insert may be fixed in the opening to permit observation of the display of the measurement device while the hinged cover or even a permanent cover is present protecting the measuring device. Such a translucent insert can be plastic, plexiglass, or tempered glass. Alternatively, a wire or plastic screen can be applied over the opening in the cover.
In an example embodiment, the housing may be arranged with at least one mounting tab extending from a surface of the housing. Such a mounting tab or tabs may form a hole or slot that can receive an appendage that is fixed to the work platform for safely securing the electrical measurement assembly when it is on a work platform.
In the preferred embodiment, the housing is formed from four walls that extend from a base. Adjacent walls are substantially orthogonal with respect to each other and orthogonal with respect the base. Insulated cables extend from respective openings in the housing. A respective clamp may surround a respective insulated cable and provide strain relief and a weather resistant seal about each opening. In the illustrated embodiment, the insulated cables extend from respective openings in opposed walls of the housing. However, the electrical measurement assembly is not limited to this arrangement. For example, a suitable housing may be round or multifaceted with greater than four walls extending from a base and enclosed with a removable cover. By way of further example, the insulated cables may extend from openings in the same wall, adjacent walls or even the base and a wall as may be desired.
In the preferred embodiment, respective passages for a cartridge-style fuse holder and a digital voltmeter are provided in a removable cover. A respective gasket or seal may surround the respective passages or openings in the removable cover. One or both of the mating or opposed surfaces of the housing and the removable cover may be arranged with a gasket or a corresponding channel to provide a weather resistant barrier to protect the interior of the housing from moisture or contaminants.
In operation, a nominal 220 VAC typically provided at a building electrical supply may sag or drop during peak power usage hours. As the work platform 10 is adjusted vertically along the side of the building further from the building electrical supply, the source voltage available at the platform 10 will also encounter an additional voltage drop due to the electrical resistance of the conductors in the line-in electric supply. This voltage drop further increases when the motors and controllers associated with the hoist mechanisms 16, 18 are enabled. This electrical load may be further increased when an operator is simultaneously energizing one or more electric motors in respective tools on the work platform 10.
As further illustrated in
Although the illustrated embodiment includes two tabs 180, the housing 110 may be supported on the work platform by a single tab 180 or more than two tabs 180. Accordingly, the housing 110 can be modified to include a single tab 180 or more than two tabs 180 as may be desired. While, the illustrated embodiment shows tabs 180 perpendicular to opposed side walls of the housing 110, one or more tabs may be arranged in other orientations with respect to one or more external facing surfaces of the housing 110. While the illustrated embodiment shows each tab 180 arranged to form a single opening 185, one or more additional openings may be added as may be desired to provide multiple options for supporting the portable electrical measurement assembly 100.
In the illustrated arrangement, the housing 110 is arranged with four walls with two opposed walls forming passages into and out from a volume defined by the base 115 and the walls extending from the base 115. Wall 111 forms an opening or passage 112 for an insulated cable 150 to pass into a volume within the housing 110. A threaded cable clamp 172 traverses the wall 111 through the opening 112 and is secured to the opposed surfaces of the wall 111 by a locknut 171 rotationally fastened against the inward facing wall. When so secured, the threaded cable clamp 172 provides a weatherproof seal about the circumference of the insulated cable 150 and the external facing surface of the wall 111. Similarly, wall 113 forms an opening or passage 114 for an insulated cable 152 to pass into the housing 110. The opening 114 supports a threaded cable clamp 174 which is secured to the opposed surfaces of the wall 113 by a locknut 175 rotationally fastened against the inward facing surface of the wall 114. When so secured, the threaded cable clamp 174 provides a weatherproof seal about the circumference of the insulated cable 152 and the external facing surface of the wall 114.
An example housing with a removable cover, sealing gasket, formed flanges, base and cover bonding structures and mounting tabs is commercially available from Hoffman Enclosures, Inc. DBA Pentair Technical Products of Anoka, Minn., U.S.A. An example threaded cable clamp is commercially available from Lapp Group USA of Florham Park, N.J., U.S.A.
A distal end of the service cord or insulated cable 150 is terminated in a plug style connector 160 which as indicated by the arrow labelled 12 can be coupled to a building or other line-in electrical supply. Specifically, the separate conductors in the insulated cable 150 are coupled in a one-to-one relationship with the conductive blades or tab(s) 162 that extend beyond the face 161 of the connector. Similarly, a distal end of the service cord or insulated cable 152 is terminated in a female style connector 164 having openings 166 in a face 165 that expose respective sockets 167 that are coupled in a one-to-one relationship with the conductors in the insulated cable 152. The tab(s) 162 in the plug-style connector 160 are labelled and keyed to ensure that a ground tab, line-in tab and a return tab are only coupled to a correspondingly arranged socket opening in a mating female style connector 164. As indicated by the arrow labelled 14 the connector 164 can be coupled to a plug style connector (not shown) coupled to a load on the work platform 10. In a preferred embodiment, after insertion of the plug-style connector 160 into a corresponding female style connector, rotation of the respective connector housings in opposed directions will controllably engage the connectors 160, 164 in a locked state.
As further illustrated in
Alternatively, the display 125 may be an analog style display with a deflection needle that moves linearly from a rest position when no voltage is present on the conductors to a measured voltage corresponding to a present voltage on the conductors within the housing 110. As further indicated in
In the illustrated embodiment, a range is labeled “OK” corresponding to a range of line-in voltages that are expected to provide nominal operating conditions for equipment on the work platform 10. An adjacent range of line-in voltages is represented on the display with the label “III”. This range of voltages may correspond to a buck-boost transformer that can be inserted between the building or other electrical supply and the work platform 10 that is capable of increasing the line-in voltage to the “OK” range from the “III” range. Similarly, additional ranges of line-in voltage levels are depicted by labels “II” and “I”, respectively.
Similarly, an access cap 131 and a small portion of the length of the fuse holder 130 remains on the exterior surface of the removable cover 140 with the remaining or larger portion is confined within the housing 110. When appropriately coupled to the line-in and return conductors of the service cord or insulated cable 150 and the corresponding line-in and return conductors of the service cord or insulated cable 152, both a current limiting device in the fuse holder 130 and the measurement device 120 are coupled in-series with a load on the work platform 10.
The removable cover 140 can be fastened to the housing 110 by fasteners 142. A gasket 145 is arranged between the removable cover 140 and respective surfaces of the walls of the housing 110 such that when the fasteners 142 are tightened in the housing 110 a seal is formed between the walls and the inward facing surface of the removable cover 140. The gasket 145 is made from a non-conductive compressible material. Accordingly, the housing 110 is arranged with a bonding element 219 and the removable cover 140 is arranged with a respective bonding element 242 that separately receive and engage a respective fastener that holds a bonding conductor coupled to the ground conductor from the insulated cable 150 and the insulated cable 152.
As illustrated, the electric circuit 200 includes connectors 160, 164, a digital voltmeter 225 and a time-delay fuse 235. Respective male tabs and female sockets (not shown) provided with the connectors 160, 164 are electrically coupled in a one-to-one relationship via conductors 210, 212, 214. For simplicity of illustration each of the connector terminations are represented symbolically with a solid black rectangle.
In an example embodiment, connector 160 may be a male style or plug style connector that supports three electrically conductive tabs that extend from a face 161 (
The connectors 160, 164 are arranged such that a respective termination at the end of the conductors 210, 212, 214 are separated from one another and protected from moisture and other contaminants. The connectors 160, 164 may be rated for safe operation when coupled to an electrical supply of up to 250 volts (VAC) and a load of up to 30 amperes (A). Example connectors are commercially available from Hubbell Incorporated through distributors in North America and Europe. The conductors 210, 212, 214 may be implemented with 10 American wire gauge (AWG) wire, which defines a desired diameter of a single solid round conductor of non-ferrous metal. Such a wire has a resistance of approximately 1 mOhm/ft. or 3.3 mOhm/m.
The conductors 210, 212, 214 may be arranged in a service cord or insulated cable 150 having a thermoset rubber jacket that surrounds respective oil-resistant and color-coded insulating sleeves. An internal oil-resistant insulating jacket may surround the conductors 210, 212, 214 within the rubber jacket. Such a service cord is commercially available and provides safe operation for operating voltages up to 600 V can be submerged and remains flexible when exposed to temperatures from −40° C. to 90° C. When color-coded, the conductor 210 will be in a white insulating sleeve, the conductor 212 will be in a black insulating sleeve and the conductor 214 will be in a green insulating sleeve. The conductors 210, 212, 214 may be formed with a first desired length of service cord or insulated cable 150 and a second desired length of service cord or insulated cable 152 that are coupled to each other within the housing 110.
As further illustrated in
As further shown in
An example time-delay fuse 235 is safe for operating voltages up to 250 VAC and a meter load current of up to 0.25 A. Such a time-delay fuse 235 and a corresponding panel mounted fuse holder 130 are commercially available from Cooper Bussmann of St. Louis, Mo., U.S.A.
An example panel mounted digital voltmeter 225 is safe for in-line root means square (RMS) measurements of service voltages from about 85 to 264 VAC at frequencies between about 47 to 63 Hz. Such a digital voltmeter 225 is commercially available from Murata Power Solutions of Mansfield, Mass., U.S.A.
As indicated in a top plan view in
As shown in side plan views in
In addition, mounting tabs 680 extend from the lowermost surface of the housing 610. Each of the tabs 680 forms at least one slotted opening 685 for receiving the head of a mounting fastener which may be provided along one of the various structures of a portable work platform (not shown). When the mounting tabs 680 are engaged with corresponding mounting fasteners, the housing 610 is supported by the work platform.
Plug-style connector assembly 660 is electrically coupled at a distal end of the electrical conductors of insulated cable 650 which extends through cable clamp 672 and a left-side wall into the cavity of the housing 610. The cable clamp 672 provides stress relief for the insulated cable 650 by annularly compressing the external insulator of the insulated cable 650. In this way, the cable clamp 672 provides a first seal that prevents the passage of moisture and other contaminants from entering the cavity of the housing 610. The cable clamp 672 is further arranged with an external threaded nut and an internal threaded nut (not shown) that when tightened fixes the cable clamp 672 against the opposed surfaces of the left-side wall of the housing 610. In this way, the cable clamp 672 provides additional stress relief for the insulated cable 650 and provides a second seal that prevents the passage of moisture and other contaminants from entering the cavity of the housing.
Female-style connector assembly 664 is electrically coupled at a distal end of the electrical conductors of insulated cable 652 which extends through cable clamp 674 and a right-side wall into the cavity of the housing 610. When the corresponding internal and external threaded nuts are tightened, the cable clamp 674 provides stress relief for the insulated cable 652 and fixes the cable and connector at the right-side wall of the housing 610 in the same manner as cable clamp 672. In addition, the cable clamp 674 provides corresponding seals at the right-side wall of the housing 610 and with the outer surface of the insulated cable 652. Both seals prevent the passage of moisture and other contaminants from entering the cavity of the housing 610.
As introduced and described, the portable electrical measurement assembly provides a safe, compact, current limited, circuit that provides an inline measure of the electrical load present on a deployed work platform 10. When the portable electrical measurement assembly is coupled between the building supply and the work platform 10 the voltage under load is measured and presented.
The described portable electrical measurement assembly (with two connectors) can be readily modified to be installed permanently on a work platform 10 by coupling the conductors in the insulated cable 152 to a hoist supply circuit on the work platform. The capability to observe the AC voltage reaching the hoist before and during use can now be made permanent with this use of the assembly.
Other contemplated modifications include forming the first and second openings along adjacent walls of the housing or even the same wall as may be desired. Such alternatives may be accompanied by a corresponding change in the length of one or both of the insulated cables as may be required for one or more specific work platforms. In addition, one or both of the openings for a fuse holder and the measurement device may be formed in one or more of the walls of the housing rather than in the removable cover. For example, it might be desirable to mount the fuse holder in one of the side walls where it might be somewhat obscured and protected by the removable cover and a mounting tab or tabs. While the illustrated embodiments show the mounting tabs extending from or connected to a surface of the housing opposed from display portion of the measurement device, the portable measurement assembly is not so limited. For example, it may be desirable to mount the display portion of the measurement device along an adjacent surface from a surface supporting the mounting tabs when a work platform has mounting appendages that would support the measurement assembly at or near a level where it the display is observable to workers on the platform.
One or more illustrative or exemplary embodiments of the electrical measurement assembly have been described above. However, it is to be understood that the assembly is defined by the appended claims and is not limited to the specific embodiments described.
