Hybrid spring and electric motor tape rule

A tape rule having a housing, a hub, a reel, a tape, a spring, and a motor. The hub and reel are rotatably mounted within the housing. The tape is wound around the reel. The spring is wound around the hub and is attached to at least one of the reel and the tape. The motor is disposed adjacent to the hub and is configured, when activated, to rotate the hub to adjust an amount by which the spring is wound around the hub.

FIELD OF THE INVENTION

The present invention relates to tape rules, and more particularly to tape rules in which the extension of a length of tape from the tape rule housing and/or retraction of the tape into the tape rule housing is facilitated by a combination of an electric motor and a retraction spring, and/or by an electric motor that is selectively activated based on torque or force being exerted on a tape reel.

DESCRIPTION OF THE RELATED ART

As used herein, the term “tape rule” includes, e.g., any mechanism for storing and extending a length of tape or the like, whether or not gradations or other indicia of length are marked on the tape. As used herein, “tape” includes tape, fabric, metal (also referred to as a “blade”), surveyor's tape, line, wire, chain, rope, and any other medium or windable material which may be wrapped or otherwise wound around a spool.

Some tape rules may wrap or otherwise wind a length of tape around an outer spool (also referred to as a “reel”) so that a length of tape is extendable through a tape exit formed in a tape rule housing. The reel may be rotatably disposed in the housing concentrically about a non-rotatable inner spool or spindle (also referred to as “hub”), around which is wrapped several turns of a retraction spring. Examples of such tape rules are shown in U.S. Pat. No. 6,643,947, issued Nov. 11, 2003 to Murray, and in U.S. Pat. No. 8,793,890, issued Aug. 5, 2014 to Delneo et al., the disclosures of which are hereby incorporated herein by reference in their entireties.

SUMMARY

One aspect of the embodiments herein relate to a tape rule having a housing, a hub, a reel, a tape, a spring, and a motor. The hub and reel are rotatably mounted within the housing. The tape is wound around the reel. The spring is wound around the hub and is attached to at least one of the reel and the tape. The motor is disposed adjacent to the hub and is configured, when activated, to rotate the hub to adjust an amount by which the spring is wound around the hub.

In an embodiment, the amount by which the spring is wound around the hub is configured to increase as the tape is extracted from the housing, and the motor is configured, when activated, to rotate the hub in a direction that unwinds the spring relative to the hub to decrease the amount by which the spring is wound around the hub.

In an embodiment, the tape rule is configured, during extraction of the tape from the housing, to determine a parameter value indicative of the amount by which the spring is wound around the hub, to determine whether the parameter value has reached or exceeds a defined threshold, and in response to a determination that the parameter value has reached or exceeds the defined threshold, activate the motor to unwind the spring relative to the hub.

In an embodiment, the parameter value is a value of a force or torque exerted by the spring on the hub, or is a value of a length of the tape that has been extracted from the housing.

In an embodiment, the tape rule further comprises a torque sensor disposed between the motor and the hub, wherein the hub is connected to the motor via the torque sensor, and wherein the tape rule is configured to determine the value of the force or torque based on a measurement from the torque sensor.

In an embodiment, the tape rule comprises a battery, and the motor is configured to draw current from the battery to maintain the hub in a substantially rotationally fixed state relative to the motor as the tape is extracted from the housing. In this embodiment, the tape rule is configured to determine the value of the force or torque by: determining an amount of the current being drawn by the motor from the battery to maintain the hub in the substantially rotationally fixed state as the tape is extracted from the housing, and determining the value of the force or torque based on the amount of the current being drawn by the motor to maintain the hub in the substantially rotationally fixed state.

In an embodiment, the tape rule is further configured, after activating the motor to unwind the spring, to determine whether the parameter value has fallen below the defined threshold by at least a defined buffer amount, and in response to a determination that the parameter value has fallen below the defined threshold by at least the defined buffer amount, to deactivate the motor.

In an embodiment, the defined threshold corresponds to the spring being in a fully wound state in which the spring is substantially non-compressible.

In an embodiment, the defined threshold is reached when less than half of a total length of the tape has been extracted from the housing.

In an embodiment, the amount by which the spring is wound around the hub is configured to decrease as the tape is retracted into the housing, and wherein the motor is configured, when activated, to rotate the hub in a direction that winds the spring relative to the hub to increase the amount by which the spring is wound around the hub.

In an embodiment, the tape rule is further configured, during retraction of the tape into the housing: to determine a parameter value indicative of the amount by which the spring is wound around the hub, to determine whether the parameter value has reached or fallen below a defined threshold, and in response to a determination that the parameter value has reached or fallen below the defined threshold, activate the motor to wind the spring relative to the hub, and in response to a determination that the parameter value has subsequently risen above the defined threshold by at least a defined buffer amount, to deactivate the motor.

In an embodiment, the tape rule is configured to determine a parameter value indicative of the amount by which the spring is wound around the hub, and is configured, after the parameter value has reached or exceeded a first defined threshold, to maintain the parameter value in a range between the first defined threshold and a second defined threshold lower than the first defined threshold by causing the motor to rotate the hub in a first direction to unwind the spring or by causing the motor to rotate the hub in a second direction to wind the spring to adjust the parameter value.

In an embodiment, the tape rule further comprises a clutch disposed between the motor and the hub, wherein the clutch is configured to selectively disengage the motor from the hub based on a value of a force or torque exerted by the hub on the motor.

In an embodiment, the tape rule further comprises a user input element disposed on or in the housing and configured to receive a user input, wherein the tape rule is configured to activate the motor in response to the user input element receiving the user input.

In an embodiment, during retraction of tape into the housing, the spring is configured to exert a force or torque on the reel or on the tape in a second direction, and wherein the tape rule has a mode that, when pre-set or manually activated, causes the tape rule to activate the motor to rotate the hub in a first and opposite direction to reduce the force or torque exerted by the spring on the reel or on the tape during at least part of the retraction of the tape into the housing.

In an embodiment, the mode is an auto slow-down mode that, when pre-set or manually activated, causes the tape rule to determine whether a parameter value indicative of the force or torque being applied by the spring on the reel or tape has reached or exceeds a defined threshold, and wherein the motor is activated to rotate the hub in the first direction during the retraction of the tape in response to a determination that the parameter value has reached or exceeds the defined threshold.

One aspect of the embodiments herein relate to a tape rule that includes a housing, a reel, a tape, and a motor. The reel is rotatably mounted within the housing, and the tape is wound around the reel. The motor is connected to the reel, wherein the tape is configured to exert a force or torque on the reel during extraction of the tape from the housing. The tape rule is configured to determine whether the force or torque exerted by the tape on the reel has reached or exceeds a defined threshold, and in response to a determination that the force or torque exerted by the tape on the reel has reached or exceeds the defined threshold, to activate the motor to output rotation to reduce the force or torque exerted by the tape on the reel.

In an embodiment, the force or torque exerted by the tape on the reel causes or will cause the reel to rotate in a first direction, and wherein the motor, when activated, is also configured to rotate the reel in the first direction.

In an embodiment, the tape rule further comprises a torque sensor disposed adjacent to the reel or to the motor and configured to measure a torque being exerted by the tape on the reel.

In an embodiment, the tape rule is configured to activate the motor in a second and opposite direction to retract the tape into the housing.

DETAILED DESCRIPTION

Embodiments hereof relate to a tape rule that facilitates extraction and/or retraction of tape with a motor (e.g., an electric motor). Some embodiments herein relate to a hybrid spring-and-electric-motor tape rule that combines a retraction spring, which lets out tape from a housing and provides mechanical energy to retract the tape into the housing, and a motor that is able to wind and/or unwind the retraction spring. For instance, the retraction spring may be a spiral spring or coil spring that is wound around a hub, and the motor may be configured to rotate the hub to wind or unwind the spring relative to the hub. In an embodiment, the spring may be any device that is configured to store potential energy during extraction of tape from the housing of the tape rule, and that is configured use the potential energy to retract the tape into the housing. In an embodiment, the motor may be any actuator that is configured to output rotational movement with the input of electrical energy (e.g., electrical current), with or without, e.g., gears, pulleys, clutches, or sprockets. In an embodiment, the motor may be a brushed or brushless motor.

In some cases, when tape is initially being extracted from the housing, the retraction spring may be used to let out the tape, and the motor may be in a deactivated state (e.g., a state in which the motor is not being activated to output rotation). The motor may be activated when a certain condition is satisfied, such as a torque or force being exerted by the retraction spring on the hub reaching or exceeding a defined threshold. The motor may be activated to rotate the hub in a first direction that unwinds the spring relative to the hub. The rotation causes the retraction spring to be wound less tightly around the hub, which may facilitate extraction of more tape from the housing. A more detailed discussion of the activated state and the deactivated state of the motor is provided later in the disclosure.

In some cases, when tape is initially being retracted into the housing, tension from the retraction spring may be used to retract the tape, and the motor may be in a deactivated state. The motor may be activated when another condition is satisfied, such as the torque or force being exerted by the retraction spring on the hub reaching or falling below another defined threshold. The motor may be activated to rotate the hub in a second direction that winds the retraction spring relative to the hub. The rotation causes the retraction spring to be wound more tightly around the hub, which facilitates retraction of more tape into the housing. The use of the motor in the motor-and-retraction-spring combination may reduce an amount of spring needed to let out or retract tape of the tape rule, while the use of the retraction spring may provide a reaction buffer for the motor to activate, allowing the motor to activate or deactivate in a manner that is automatic or otherwise invisible to an end user (though in some embodiments the motor can be manually activated).

Some embodiments herein include a motor that is activated based on a parameter value such as an amount of force or torque being exerted by a tape of a tape rule on a reel of the tape rule. Such embodiments may include a spring to let out and retract the tape, or may omit such a spring. The torque or force may come from a user pulling on one end of the tape, and may be transferred from the tape to the reel. The motor may be activated when, e.g., the force or torque on the reel reaches or exceeds a defined threshold.

FIG. 1Aillustrates an exterior perspective view of a tape rule10according to an embodiment hereof. The tape rule10includes a housing40that is formed by at least housing member41and housing member42. In an embodiment, the housing members41,42may form of two discrete structures (e.g., two clamshell halves) that are secured together by fasteners, snap fitting, adhesive, or any other fastening mechanism. The housing40may house a length of tape103, which may be extracted from the housing40and retracted back into the housing40. In an embodiment, the tape103may be any windable material (e.g., a ribbon, line, cable, or rope) that can be wrapped around a spool. In some instances, the tape103is arranged to carry or display gradations21(e.g., lines) that have been applied to a surface thereof, by any manner. The gradations21may be applied to the surface of the tape by, e.g., paint, etching, stenciling, or a combination thereof. The gradations21may be used with other measuring indicia (e.g., numbers printed on the tape103) for measuring lengths and distances. In an embodiment, the tape103is formed of a ribbon of metal or metal alloy (e.g., steel) or other material.

FIG. 1Aillustrates the tape103in a fully retracted position. A first longitudinal end103aof the tape103may be attached to a hook member34. A second and opposite longitudinal end of the tape103may be attached to a reel109(illustrated inFIG. 1B) inside the housing40. The tape103may be constructed and arranged to extend generally from a position tangential of the reel109outwardly from a spaced opening22provided in the housing40. The tape103may be movable between a fully retracted position (e.g., in which substantially all of the tape103is in the housing40) and a fully extracted position (e.g., in which substantially all of the tape103has been extracted from the housing40). The extraction of the tape103may cause the reel109to rotate in a first direction, while rotation of the reel109in a second and opposite direction causes the tape103to be retracted into the housing40. In an embodiment, when the tape103is in a partially or fully extracted state, a holding assembly124may be manually actuated to hold the tape103in that state. In an embodiment, the tape103may have a flat cross-section when it is wound around the reel109, and have a concavo-convex cross section when it is extracted from the housing40. The concavo-convex cross section may provide the tape103with additional rigidity that maintains the tape103in a substantially straight shape in a longitudinal direction when the tape103has been extracted from the housing40.

FIGS. 1B-1Dprovide perspective or sectional views that depicts various tape rule components housed in the housing40of the tape rule10. As discussed below in more detail, the components may include a retraction spring and a motor, and may form a hybrid spring-and-electric-motor tape rule. More generally speaking,FIGS. 1B-1Dillustrate the reel109, the tape103, a spring101, a hub105, and a motor107of the tape rule10.

As illustrated inFIGS. 1B and 1D, the reel109may include a protruding portion109a(see, e.g.,FIG. 1D) or a pair of protruding portions used for suspending or otherwise mounting the reel109in the housing40, and a spool portion109bon which the tape103is wound. The spool portion109bmay, for instance, provide a cylindrical structure on which the tape103is wound. In an embodiment, a part of the spool portion109bmay be clipped, pinned, or otherwise connected to the spring101and/or the tape103, such as to a second end of the tape103that is opposite to the first end103a. In another embodiment, the reel109may be directly or indirectly connected to the spring101via an adhesive. In an embodiment, as illustrated inFIG. 1D, the reel109may be rotatably mounted in the housing40via the protruding portion109aand a reel bearing110. The reel bearing110may be, e.g., a plain bearing or ball bearing that fits around the protruding portion109a. In an embodiment, the protruding portion109aand the reel bearing110may be received in a receptacle portion81(e.g., a recess) of the housing member41. The reel bearing110rotatably mounts the reel109within the housing40, and enables the reel109to rotate relative to the housing40. In an embodiment, the reel109may be symmetrical, such that the reel has the protruding portion109aon a first side (e.g., right side) of the spool portion109b, and a second protruding portion on a second and opposite side (e.g., left side) of the spool portion109b. In such an embodiment, the second protruding portion of the reel109may also be surrounded by a respective reel bearing, and the second protruding portion and the respective reel bearing may be received in a receptacle portion of the housing member42. In an embodiment, the reel109may be made of, e.g., molded plastic, metal, or any other material.

Referring again toFIG. 1B, the reel109may be connected to a spring101at a first end thereof. The spring101may be connected to a hub105at a second end thereof, and may be wound around the hub105. In an embodiment, the spring101may be located within the spool portion109bof the reel109, such that the reel109partially or completely encloses the spring101. During extraction of the tape103from the housing40, a first end103aof the tape103may be pulled, such as by a user, from the housing40. The pulling force may be transferred to the reel109, which causes the reel109to rotate. The rotation of the reel109may wind the spring101more tightly around the hub105, as discussed in more detail below. In an embodiment, the spring101may be a spiral torsion spring or coil spring that is wound around the hub105. As the spring101is wound around the hub105in a first direction, the spring101may store potential energy. For instance, as the spring101is wound more tightly around the hub105, the spring101may become more compressed, causing a distance between successive turns (also referred to as successive coils) of the spring101to decrease. The compression of the spring101may store potential energy therein. When the potential energy is released, the spring101may unwind and rotate the reel109in an opposite direction that retracts the tape103into the housing40. In an embodiment, the spring101may be formed from spring steel or any other material.

As stated above, the spring101may in an embodiment be wound around the hub105. As depicted inFIG. 1C, the hub105may have an axial member105athat forms a rotatable axle, a first end105bused for mounting the hub105in the housing40, and a second end105cthat forms a disc portion of the hub105. In an embodiment, the spring101may be connected to and wound around the axial member105a. In an embodiment, the first end105aof the hub105may form a flanged portion that is surrounded by a hub bearing104(e.g., a plain bearing or ball bearing). As depicted inFIG. 1D, the first end105aand the hub bearing104may be received in a receptacle portion80that is formed by a recess in the protruding portion109aof the reel109. The hub bearing104rotatably mounts the hub105within the housing40and within the reel109, and allows the hub105and the reel109to be rotatable relative to each other.

As illustrated inFIGS. 1C and 1D, a motor107(e.g., a DC motor) may be disposed adjacent to the hub105, at the second end105cthereof, and is combined with the spring101to form a hybrid spring-and-electric-motor tape rule. As illustrated inFIG. 1D, the motor107, hub105, and spring101may be disposed within the spool portion109bof the reel109. In an embodiment, a battery may be disposed adjacent to the motor107. In an embodiment, as depicted inFIG. 1D, a shaft (more generally referred to as a rotor) of the motor107may be directly connected to the hub105. In another embodiment, the shaft of the motor107may be indirectly connected to the hub105via a gearbox (also referred to as a gear train) disposed between the motor107and the hub105. In an embodiment, the motor107may be indirectly connected to the hub105via a torque sensor and/or a clutch, as discussed below in more detail.

In an embodiment, the motor107may be configured, when activated, to rotate the hub105relative to the motor107. In other words, the activated state for the motor may refer to a state in which the motor107draws power (e.g., from a battery) to rotate the hub105relative to the motor107(also referred to as outputting rotation on the hub105). For instance, the motor107may have a stator and a rotor, and when activated may cause the rotor to rotate relative to the stator. The rotor may in some instances be rotationally coupled to the hub105so that they rotate together. In such instances, the hub105may be rotated relative to the stator when the motor107is activated. The motor107may be activated to rotate the hub105in a first direction that unwinds the spring101relative to the hub105, and/or may be activated to rotate the hub105in a second and opposite direction to wind the spring101relative to the hub105. In an embodiment, the hub bearing104that is situated between the hub105and the reel109may allow the motor107to rotate the hub105without rotating the reel109.

In an embodiment, the deactivated state for the motor107may refer to a state in which the hub105is not rotating relative to the motor107, and/or a state in which the motor107is not drawing power from a battery or other power source of the tape rule10. For instance, the deactivated state may include a situation in which the motor107attempts to maintain the hub105in a substantially rotationally fixed state relative to the motor107(e.g., the hub105rotates by less than 0.5°, if at all, relative to the motor107) during extraction or retraction of the tape103. In some cases, if the motor107has a stator and rotor, the motor107may maintain the substantially rotationally fixed state for the hub105by keeping rotor substantially rotationally fixed relative to the stator. To maintain the substantially rotationally fixed state for the hub105, the motor107may need to counteract a force or torque on the hub105that arises from a user pulling on the tape103during extraction of the tape. This pulling force from the user may be transferred to the spring101and cause the spring101to be more wound around the hub105and exert an increased amount of force or torque on the hub105(e.g., a force or torque in a clockwise direction). The motor107may be used to provide an equal amount of counteracting force or torque in an opposite direction (corresponding to, e.g., a counterclockwise direction) to substantially prevent rotation of the hub105relative to the motor107. The amount of counteracting force or torque may depend on how much current the motor107draws from a battery or other power source. In an embodiment, a first current sensor may measure an amount of current that the motor107is drawing from the battery to counteract the force or torque being exerted by the spring101on the hub105. The amount of force or torque exerted by the spring101on the hub105may then be determined based on the amount of current being drawn by the motor107to counteract that force or torque.

As discussed above, the deactivated state may include a situation in which the motor107is not drawing current from the battery, such as when the motor107is electrically disconnected from the battery or other power source. In some instances, the motor107may be braked, such as by electrically shorting a positive and a negative terminal of the motor107. In some instances, a braking mechanism may maintain the hub105in the substantially rotationally fixed state until the motor107is activated. In other instances, the hub105may be allowed to rotate during extraction or retraction of the tape103. For example, when a user is pulling on the tape103during extraction thereof, the pulling force may be transferred to the spring101and cause the hub105to rotate. In this example, rather than counteract the pulling force to prevent rotation of the hub105, the motor107may act as a generator that generates a current from the rotation of the hub105. More specifically, if the motor107has a stator and rotor, the rotation of the hub105may cause the rotor to rotate relative to the stator, and generate a current. In some instances, the motor107may be electrically disconnected from a battery or other power source of the tape rule10while the motor107is acting as a generator. The first current sensor or a different current sensor (e.g., a sensor placed in an electrically shorted path from a positive terminal to a negative terminal of the motor107) may measure an amount of current being generated by the motor107, and determine the amount of force or torque being exerted on the hub105(e.g., by the spring101) based on the amount of current being generated by the motor107.

In an embodiment, the braking mechanism may be provided by the motor107itself, and/or by a separate braking mechanism. The braking mechanism may be provided by the motor107itself by electrically shorting a positive terminal and a negative terminal of the motor107. A separate braking mechanism may be provided by, e.g., a brake pad that engages the hub105when braking is needed, and that disengages the hub105when the motor107is activated.

As discussed above, the spring101may be wound around the hub105. As a result, the spring101may exert a force or torque on the hub105. When the tape103is being extracted from the housing40, the spring101may become more tightly wound around the hub105. As a result, the force or torque exerted by the spring101on the hub105may increase.FIG. 1Ddepicts an embodiment in which the motor107may be used to determine a value of the force or torque being exerted by the spring101on the hub105. More specifically, as discussed above, when a user is pulling on the tape103, the pulling force may be transferred by the spring101onto the hub105, in the form of a force or torque on the hub105. The motor107may in some instances provide a counteracting force or torque on the hub105to keep the hub105substantially rotationally fixed during this extraction of the tape103. The amount of counteracting force or torque provided by the motor107may be based on an amount of current being drawn by the motor107from a battery (or other power source). Because this counteracting force or torque is generally equal to the force or torque exerted by the spring101on the hub105, the latter force or torque may be determined based on the amount of current drawn by the motor107from the battery. In another embodiment, the motor107may be electrically disconnected from the battery and may act as a generator. In this embodiment, the force exerted by the user during extraction of the tape103may be transferred to the hub105via the spring101, which may cause both the hub105and a portion of the motor107to be rotated. The motor107may generate a current as a result. The force or torque being exerted by the spring101on the hub105may then be determined based on an amount of current being generated by the motor107in this configuration. Thus, the embodiment ofFIG. 1Dmay use at least one of the implementations discussed above to determine torque or force exerted on the hub105, and may omit the use of a separate torque sensor (i.e., the force or torque may be determined without a separate torque sensor).

FIG. 1Eillustrates another embodiment of a tape rule10A that does include a separate torque sensor106(e.g., a rotary torsion sensor or a reaction torsion sensor) to determine the torque or force being exerted by the spring101on the hub105. The torque sensor106may be disposed between the motor107and the hub105. In this embodiment, the motor107may be indirectly connected to the hub105via the torque sensor106. This embodiment may include a gearbox disposed between the torque sensor106and the motor107, or between the torque sensor106and the hub105, or may omit such a gearbox.

As discussed below, the value of the force or torque on the hub105may be a parameter value indicative of an amount by which the spring101is wound around the hub105, but other parameters may also indicate the amount by which the spring101is wound around the hub. For instance, the amount of tape103(e.g., in units of feet or number of revolutions of the reel109) that has been let out by the spring101may also indicate the amount by which the spring101is wound around the hub. Thus, in an embodiment, the tape rule10A ofFIG. 1Emay combine or replace the torque sensor106with another sensor configured to measure a parameter value indicative of an amount by which the spring101is wound around the hub105, such as a sensor configured to directly measure how much of the tape103has been extracted from the housing40(e.g., by directly measuring how many revolutions the reel109has rotated).

In the embodiment ofFIG. 1E, the tape rule10A may include a clutch108disposed between the hub105and the motor107, and more specifically between the torque sensor106and the hub105. The clutch108may be configured to protect the torque sensor106and the motor107from damage when, for instance, there is a sudden spike in the torque being exerted on the hub105or, more generally speaking, when a rate of increase in the torque being exerted on the hub105reaches or exceeds a defined threshold (e.g., in units of lb-force inches (lbf-in) per second). When there is such a spike in torque, the clutch108may cause the hub105to disengage with the torque sensor106and the motor107, such that the spike in the torque is not transferred to the sensor106and the motor107. When the spike in torque has passed, the clutch108may re-engage the hub105with the torque sensor106and the motor107. In the embodiment illustrated inFIG. 1E, the clutch108may be formed from two discs that engage each other through friction. One of the discs may be in contact with the second end105cof the hub105. The other of the discs may be in contact with the torque sensor106. When there is a spike in the torque being exerted on the hub105, the two discs of the clutch108may slip, thus at least partially disengaging the torque sensor106from the hub105.

As illustrated in the block diagram ofFIG. 1F, the tape rule10may in an embodiment comprise a control circuit102that is configured to selectively activate the motor107to rotate the hub105relative to the motor107. The control circuit102may be, e.g., part of the motor107, part of the torque sensor106, or a separate component. The control circuit102may be implemented with a microprocessor, a programmed logic array (PLA), a field programmable gate array (FPGA), or as any other type of control circuit.

In an embodiment, the control circuit102may activate the motor107, to rotate the hub105relative to the motor107, based on how much of the tape103has been extracted from the housing40, which may be correlated with an amount by which the spring101is wound around (or, more generally speaking, wound relative to) the hub105. For instance, as more of the tape103is extracted from the housing40, the tape103may pull on the reel109and cause the reel109to rotate, which may wind the spring101more tightly around the hub105. The spring101may thus exert more torque or force on the hub105as more of the tape103is extracted from the housing40.

One aspect of the embodiments herein is that the motor107may remain in a deactivated state, in which the hub105is not rotating relative to the motor107, until a certain length of tape103has been extracted from the housing40and the spring101has been correspondingly wound by a sufficient amount around the hub. For instance, the motor107may be in a deactivated state until 10 feet or more of the tape103has been extracted from the housing40. When less than 10 feet of the tape103has been extracted, the amount by which the spring101has been wound around the hub may be too low to trigger the activation of the motor107. In such an embodiment, if the amount of tape103being used is less than 10 feet, the spring101may be used to let out and retract the tape103without activating the motor107. This configuration may reduce usage of the motor107, conserving battery life for the motor107, and reducing wear on the motor107. When the motor107does need to be activated, the spring101may further be used until the motor107accelerates to a fully activated state (e.g., in terms of output torque and/or revolutions per minute), thus providing a reaction buffer for the motor107.

Another aspect of the embodiments herein is that the use of the motor107to unwind the spring101and/or to wind the spring101allows a total length of the spring101to be much shorter than a total length of the tape103. More specifically, as discussed above, when the tape103is being extracted from the housing40, the extraction may cause the reel109to rotate in a particular direction, which causes the spring101to be wound more tightly around the hub105. The winding of the spring101around the hub105may cause the spring101to compress or otherwise elastically deform. When a certain length of the tape103has been extracted, the spring101may be compressed to a state in which, e.g., it is not further compressible or, more generally, unable to further elastically deform in the above-mentioned direction. This may occur, for instance, during a “close out” condition in which successive turns of the spring101are compressed to a point at which they come into contact with each other. In this condition, the spring101may be considered to be in a fully wound or fully compressed state. The fully wound or fully compressed spring101may act as a taut, rigid object that prevents the reel109from rotating further in the above-mentioned direction, and thus prevents more tape103from being extracted. Thus, without the motor107, the spring101may need to have a total length that is comparable (e.g., substantially the same as) a total length of the tape103, so that the spring101does not become fully wound until most or all of the tape103has been extracted from the housing40. By combining the spring101with the motor107, however, the spring101may be unwound after it reaches a fully wound state. Once the spring101is unwound, more of the tape103may be extracted. As a result, the spring101may have a total length (e.g., 10 feet) that is substantially shorter than a total length (e.g., 50 feet) of the tape103.

As discussed above, the motor107may be used to adjust an amount by which the spring101is wound around the hub105, by winding and/or unwinding the spring101relative to the hub105. In an embodiment, the motor107may be controlled by the control circuit102of the tape rule10to both rotate the hub105in a first direction when the spring101needs to be unwound during extraction of the tape103, and to rotate the hub105in a second direction when the spring101needs to be wound during retraction of the tape103. In another embodiment, the motor107may be controlled by the control circuit102to rotate the hub105in only one direction. For instance, the motor107may be controlled to rotate the hub105in the first direction when the spring101needs to be unwound during extraction of the tape103. In this instance, a different mechanism (e.g., a ratchet) may be used to retract the tape103, thus making it unnecessary to rotate the motor107in the second direction during retraction of the tape103.

FIG. 1Gillustrates an example method200by which the control circuit102controls the motor107. In an embodiment, the method200includes a step201, in which the control circuit102, during extraction of the tape103from the housing40of the tape rule10/10A, determines a parameter value indicative of an amount by which the spring101is wound around the hub105. As discussed above, the parameter value may be a value of a force or torque (e.g., in lbf-in) exerted by the spring101on the hub105, or a value of a length of tape103(e.g., in feet or number of revolutions of the reel109) that has been extracted from the housing40, or a value of electrical resistance (e.g., in ohms) of the motor107or current drawn or generated (e.g., in amps) by the motor107, or some other parameter value indicative of an amount by which the spring101is wound around the hub105. As discussed above, the control circuit102may determine the parameter value with a torque sensor, if it exists, or may determine the parameter value by determining an amount of current being drawn by the motor107in an embodiment in which the motor107keeps the hub105substantially rotationally fixed, or by determining an amount of current being generated by the motor107in an embodiment in which the motor107acts as a generator.

In step203, the control circuit102may determine whether the parameter value has reached or exceeds a first defined threshold. For instance, the first defined threshold may be a force or torque threshold (e.g., 0.6 lbf-in), a threshold length of tape extracted from the housing40(e.g., 10 feet), or some other threshold value. In an embodiment, the defined threshold may be pre-programmed into the control circuit102.

To illustrate steps201and203,FIGS. 2A and 2Bdepict the tape rule10as the tape103is extracted from the housing40.FIG. 2Aillustrates a situation in which the tape103may be close to a fully retracted state. In this situation, the parameter value determined in step201may be relatively low (e.g., 0.21 lbf-in), and the control unit102may determine in step203that the parameter value has not reached or exceeded the first defined threshold (e.g., 0.6 lbf-in). To extract more of the tape103, a user may exert a pulling force on the first end103aof the tape103. When the spring101is in the state depicted inFIG. 2A, the spring101may absorb some of the pulling force from the hub105. In other words, the pulling force is not directly transferred to the hub105, but is instead used to compress the spring101, and is thus converted into potential energy. The situation depicted inFIG. 2Amay be part of a first stage in which the first defined threshold has not been reached and the motor107remains deactivated. The first stage may rely on the spring101rather than the motor107to let out and retract the tape103. During the first stage, the hub105may be stationary (e.g., non-rotating) relative to the housing40.

In an embodiment, as more of the tape103is extracted (e.g., 10 feet or more), the spring101may be wound to a state depicted inFIG. 2B. In an embodiment, the spring101inFIG. 2Bmay be in a fully wound state in which it is no longer compressible or, more generally speaking, not capable of further elastic deformation. The fully wound state may correspond to a start of a second stage of the tape extraction. In an embodiment, the fully wound state of the spring101may be reached when, e.g., only a fraction (e.g., 25% or 50%) of the total length of the tape103has been extracted. In this fully wound state, the spring101may prevent more tape103from being let out, and may also transfer additional pulling force from the first end103aof the tape103to the hub105(rather than absorbing the additional pulling force). In the situation depicted inFIG. 2B, the parameter value determined in step201may have a relatively higher value (e.g., 0.6 lbf-in), and the control circuit102may determine in step203that the parameter value has reached or exceeds the first defined threshold (e.g., 0.6 lbf-in).

Referring back toFIG. 1G, in step205, in response to a determination that the parameter value has reached or exceeds the first defined threshold, the control circuit102may activate the motor107to rotate the hub in a first direction (relative to, e.g., a stator of the motor107) to unwind the spring101relative to the hub105. For instance,FIG. 2Cdepicts the motor107rotating the hub105in a counterclockwise direction to unwind the spring101relative to the hub105. The rotation output by the motor107may reduce the torque or force exerted by the spring101on the hub105, and leave the spring101in a more relaxed state, as illustrated inFIG. 2C. As a result, more of the tape103(e.g., another 6 feet) can be extracted from the housing40. In an embodiment, the motor107may be outputting rotation in the counterclockwise direction while the first end103aof the tape103is continuing to be held by the user. In an embodiment, the hub bearing104may allow the motor107to rotate the hub105without also rotating the reel109. Thus, in this embodiment, the motor107may unwind the spring101relative to the hub105without directly unwinding the tape103relative to the reel109. In an embodiment, steps201through205may be repeated numerous times during extraction of the tape103from the housing40, such as if the length of tape103that is extracted (e.g., 30 feet) is several times more than a total length of the spring101(e.g., 10 feet). In an embodiment, steps203and205may be based on whether the parameter value exceeds the first defined threshold (as opposed to whether the parameter value has reached or exceeds the first defined threshold).

In an embodiment, the motor107may be activated to rotate the hub105in the first (e.g., counterclockwise) direction (relative to a stator of the motor107) for a defined duration or a defined number of revolutions, and then be immediately deactivated. In an embodiment, after the motor107has been activated to rotate the hub in the first direction, the motor may remain activated until the parameter value falls below the defined threshold by at least a defined buffer amount (e.g., 33% of the defined threshold). For instance, the motor107may remain activated until the parameter value falls from 0.6 lbf-in to 0.4 lbf-in, and then may be deactivated. The use of the buffer amount may prevent or reduce hysteresis between the activated state and the deactivated state of the motor107.

As discussed above, the spring101may be used to retract the tape103into the housing40. For instance, when a user relaxes his or her grip on the first end103aof the tape103, or completely lets go of the first end103a, the potential energy stored by the spring101may rotate the reel109in a second (e.g. clockwise) direction that retracts the tape103into the housing40. In an embodiment, the motor107may be activated during the retraction of the tape103only when the parameter value has reached or fallen below a second defined threshold (e.g., 0.2 lbf-in). For instance,FIG. 1Hillustrates an example method300by which the control unit102can activate the motor107to rotate the hub105in the second direction during the retraction of the tape103. The method300may include a step301, in which the control unit102determines the parameter value indicative of the amount by which the spring is wound around the hub. In step303, the control unit102may determine whether the parameter value has reached or fallen below a second defined threshold. For example, the parameter value may be at, e.g., 0.4 lbf-in when retraction begins. As the spring101retracts the tape103, the parameter value decreases. After a certain amount of tape103has been retracted (e.g., 6 feet), the parameter value may decrease to a second defined threshold (e.g., 0.2 lbf-in). An example of this situation is illustrated inFIG. 2D, which illustrates the spring101when the second defined threshold has been reached.

As further illustrated in bothFIGS. 1H and 2D, in response to a determination that the parameter value has reached or fallen below the second defined threshold, the control unit102may in step305activate the motor to output rotation in the second (e.g., clockwise) direction to wind the spring relative to the hub. In an embodiment, the motor107may remain activated to output rotation in the second direction until the parameter value rises above the second defined threshold by a buffer amount (e.g., 100% of the second defined threshold). For instance, the motor107may remain activated until the parameter value reaches 0.4 lbf-in again, and then may be deactivated. As discussed above, the hub bearing104may allow the hub105to rotate without rotating the reel109. That is, the motor107may wind the spring101relative to the hub105without directly rotating the reel109to retract the tape103(the reel109is directly rotated by the spring101). In an embodiment, steps301through305may be repeated many times. In an embodiment, steps303and305may be based on whether the parameter value has fallen below the second defined threshold (as opposed to whether the parameter value has reached or fallen below the second defined threshold).

In an embodiment, the control unit102may automatically activate and deactivate the motor107, and thus provide an invisible user interface. In an embodiment, the determination of whether to activate the motor may be based on only the parameter value that indicates the amount by which the spring101is wound relative to the hub, such that manual activation of the motor107is not available. In another embodiment, the motor107may alternatively or additionally be manually activated. In such an embodiment, the tape rule10may include a mechanical button, touch screen button, or other user input element that, when selected, causes the motor107to rotate the hub105. The user input element may allow a user to select a direction of rotation, or the direction of rotation may be fixed, or may be internally determined by the control unit102.

In an embodiment, the tape rule10/10A may have a mode, such as an auto slow-down mode, that causes the motor107to be activated to keep the tape103from being retracted too quickly by the spring101. For instance, during retraction of the tape103into the housing40, the spring101may exert a force or torque on the reel109or the tape103in a second direction, such as the direction illustrated on the top ofFIG. 2D. If the force or torque is too high, the tape103may be retracted more quickly than is desirable. Thus, when the tape rule10/10A is in the auto slow-down mode, the control circuit102or other component of the tape rule10/10A may be configured to monitor a parameter value indicative of the force or torque being applied by the spring101on the reel109or tape103. If the parameter value becomes too high, the control circuit102may activate the motor107to rotate the hub105in a first and opposite direction to, e.g., unwind the spring101such that the force or torque exerted by the spring101is reduced. In an embodiment, the force or torque being exerted by the spring101on the reel109or tape103may be related to the force or torque being exerted by the spring101on the hub105, such that the parameter value being monitored may be the force or torque being exerted by the spring101on the hub105. In an embodiment, the control circuit102may activate the motor107during at least part of the retraction of the tape103, so as to keep the parameter value below a defined threshold. In an embodiment, the defined threshold may be a third defined threshold (e.g., 0.3 lbf-in) that is higher than the second defined threshold (e.g., 0.2 lbf-in) at which the spring101is wound during retraction, and lower than first defined threshold (e.g., 0.6 lbf-in) at which the spring101is unwound during extraction, as discussed above. In an embodiment, the use of the third defined threshold may be combined with the use of the second defined threshold and/or first defined threshold, such as to maintain the parameter value in a range between the second defined threshold and the third defined threshold during retraction of the tape103. In an embodiment, the auto slow-down mode may be pre-set, such that the tape rule10/10A is pre-programmed (e.g., during manufacturing) to be in this mode. In an embodiment, this mode may be manually activated, such as via a user input element.

FIG. 3illustrates an embodiment of a tape rule400that includes a motor407, but does not include a retraction spring. In an embodiment, the motor407may be selectively activated based on an amount of torque or force being exerted by a tape403on a reel409. More specifically, the tape rule400may include a housing440, a reel409, tape403, and a motor407. The reel409may be rotatably mounted within the housing440. For instance, a reel bearing410may be fitted around a protruding portion409aof the reel409, and the reel bearing410and the protruding portion409amay be received in a receptacle portion481of the housing440. The reel bearing410may allow the reel409to rotate relative to the housing410. In an embodiment, the tape403may be wound around a spool portion409bof the reel409.

In an embodiment, the motor407may have a shaft407aconnected to the reel409. The shaft407amay be directly connected to the reel409, or may be indirectly connected (e.g., via a gearbox) to the reel409. InFIG. 3, for instance, the shaft407aof the motor407may be directly connected to the reel409via a receptacle portion480of the reel409that receives the shaft407a. During extraction of the tape403from the housing440, the tape403may exert a force or torque on the reel409that causes the reel409to rotate. The shaft407aof the motor407inFIG. 3may rotate with the reel409because it is connected thereto, even if the motor407has not been activated to output rotation at the shaft407a. The rest of the motor407(e.g., a stator407b) may also rotate with the reel409, or may remain stationary relative to the housing440.

In an embodiment, the tape rule400may include a control unit that is configured to determine a force or torque being exerted by the tape403on the reel409. For instance, extracting the tape403may involve a user pulling on the tape403, which may transfer the pulling force, in the form of a force or torque, to the reel409and accelerate the reel409to rotate in a first direction (e.g., counterclockwise). In some cases, the reel409may be accelerated from a stationary state to a rotating state. In an embodiment, the tape rule400may include a torque sensor configured to measure the force or torque being exerted by the tape403on the reel409.

In an embodiment, the control unit may be configured to further determine whether the torque or force exerted by the tape403on the reel409has reached or exceeds a defined threshold. In some instances, it may take more torque to accelerate the reel409from a stationary state to a rotating state to initially extract the tape403, than an amount of torque involved in maintaining the rotation of the reel409to extract more tape403. In such instances, the force or torque exerted by the tape403on the reel409may reach or exceed the defined threshold during the initial extraction of the tape403, when the reel409is starting from a non-rotating or otherwise stationary position.

In an embodiment, in response to a determination that the force or torque exerted by the tape403on the reel409exceeds the defined threshold, the control circuit may be configured to activate the motor407to output rotation at the shaft407ato reduce the force or torque exerted by the tape403on the reel409. For instance, when a user exerts a pulling force on the tape403, the tape403in turn exerts a force or torque on the reel409that causes or will cause the reel409to begin rotating in a first direction. The motor407may assist the user by being activated to rotate the reel409in the first direction, such as by outputting rotation at the shaft407ain the first direction (e.g., relative to the stator407b). The shaft407amay exert a force or torque on the reel409in the first direction, which may reduce the pulling force that a user needs to exert on the tape403, and thus may reduce the amount of force or torque being exerted by the tape403on the reel409. Thus, in an embodiment, the motor407may assist a user in rotating the reel409(e.g., by using energy from a battery attached to the motor407), so that most or all of the rotation of the reel409is driven by the motor407, rather than being manually driven by a user. In an embodiment, the rotation output by the motor407in the first direction may directly force the tape403to extend from the housing440. In an embodiment, the motor407may also be manually activated to extract the tape403.

In an embodiment, after the motor407is activated to rotate the reel409, the torque or force exerted by the tape403on the reel409may decrease. For example, a user may relax his or her grip on the tape403as the motor407takes over in driving the rotation of the reel409. When a control circuit determines that the force or torque being exerted by the tape403on the reel409falls below the defined threshold by any amount, the control circuit may deactivate the motor. Alternatively, the motor407may be deactivated when the force or torque falls below the defined threshold by at least a defined buffer amount.

In an embodiment, the motor407may be activated to output rotation in a second and opposite direction to retract the tape403into the housing440. In an embodiment, the rotation output by the motor407may directly rotate the reel409, and thus directly cause retraction of the tape403into the housing440. In an embodiment, the activation of the motor407in the second direction may be manually triggered (e.g., via a button or other user input element).