Patent Description:
<CIT> describes a blade assembly for a hair cutting apparatus including a first blade having teeth extending along a first blade edge, and a second blade having teeth extending along a second blade edge. A distance between the first and second blade edges defines a blade gap. A yoke is coupled to the second blade and configured to convert motion of a drive into reciprocation of the second blade relative to the first blade to cut hair. A spring includes a spring base and at least one spring arm configured to reciprocate with the second blade. A guide assembly includes a guide and a spring retainer, the guide being positioned between the first blade and the second blade, and the spring retainer fixing the spring base relative to the first blade, wherein in response to moving the guide relative to the first blade, the blade gap changes.

<CIT> describes an electric-powered hair trimmer comprising a removable blade assembly that connects to an elongated handle. The removable blade assembly includes an adjustment mechanism to adjust cutting depth. The handle includes two-way facets along its outer surface, and a receptacle defined within its inner surface to receive a removable battery.

According to a first aspect, there is provided a blade assembly according to independent claim <NUM>. Some optional and/or preferable features are provided in the dependent claims.

In one construction, the disclosure provides a blade assembly for a hair cutting apparatus, the blade assembly comprising: a first blade having teeth extending along a first blade edge; a second blade positioned proximate the first blade, the second blade having teeth extending along a second blade edge parallel to the first blade edge and offset from the first blade edge by a blade gap; a yoke coupled to the second blade, the yoke adapted to convert motion of a drive mechanism into reciprocation of the second blade with respect to the first blade to cut hair between the teeth of the first and second blades; a spring having a spring base and at least one spring arm coupled to one of the yoke and second blade, the spring arm reciprocating with the second blade with respect to the first blade; and a spring retainer mounted to the first blade and fixing the spring base with respect to the first blade to prevent relative movement between the spring base and the first blade during reciprocation of the second blade and spring arm with respect to the first blade; wherein the spring arm applies a biasing force on the second blade toward the first blade to maintain the first and second blades in an operational condition when separated from the hair cutting apparatus.

In some constructions the blade assembly further comprises a guide secured to the first blade and sandwiched between the first and second blades, the guide restricting movement of the second blade perpendicular to the first blade edge to maintain a desired blade gap. In some constructions the blade assembly further comprises a slot in the guide; and a fastener secured to the first blade and extending through the slot; wherein the blade gap is adjustable by moving the guide within a range of adjustability defined by the fastener abutting opposite ends of the slot; wherein a desired blade gap is achieved by tightening the fastener to fix the guide to the firs blade with the guide in a position corresponding to the desired blade gap. In some constructions the spring and second blade are movable with the guide, such that the first and second blades are maintained in the operational condition during adjustment of the blade gap. In some constructions the spring retainer includes a portion of the guide, such that the guide serves a first purpose of maintaining the desired blade gap and a second purpose of fixing the spring base with respect to the first blade. In some constructions the guide is T-shaped, having a guide base extending perpendicular to the first blade edge and a cross portion extending parallel to the first blade edge; wherein the guide base includes the spring retainer. In some constructions the spring base is held against the first blade by the spring retainer; and wherein the spring arm includes a fixed end integral with the spring base and a free end coupled to one of the yoke and second blade; wherein the spring arm pivots about the fixed end during reciprocation of the second blade; and wherein neither the spring base nor the spring arm includes a compliance coil to accommodate reciprocation of the second blade.

In another construction, the disclosure provides a blade assembly for a hair cutting apparatus, the blade assembly comprising: a first blade having teeth extending along a first blade edge; a second blade positioned proximate the first blade, the second blade having teeth extending along a second blade edge parallel to the first blade edge and offset from the first blade edge by a blade gap; a yoke coupled to the second blade, the yoke adapted to convert motion of a drive mechanism into reciprocation of the second blade with respect to the first blade to cut hair between the teeth of the first and second blades; a spring biasing the second blade toward the first blade to maintain the first and second blades in an operational condition when separated from the hair cutting apparatus; a fastener secured to the first blade; and a guide having a slot, the fastener extending through the slot; wherein the blade gap is adjustable by moving the guide within a range of adjustability defined by the fastener abutting opposite ends of the slot; wherein a desired blade gap is achieved by tightening the fastener to fix the guide to the first blade with the guide in a position corresponding to the desired blade gap; wherein the blade gap is adjusted with the spring maintaining the first and second blades in the operational condition while separated from the hair cutting apparatus.

In some constructions the spring includes a spring base and at least one spring arm coupled to one of the yoke and second blade, the spring arm reciprocating with the second blade with respect to the first blade; the blade assembly further comprising a spring retainer mounted to the first blade and fixing the spring base with respect to the first blade to prevent relative movement between the spring base and the first blade during reciprocation of the second blade with respect to the first blade. In some constructions a portion of the guide serves as the spring retainer.

In another construction, the disclosure provides a blade assembly for a hair cutting apparatus, the blade assembly comprising: a first blade having teeth extending along a first blade edge; a second blade positioned proximate the first blade, the second blade having teeth extending along a second blade edge parallel to the first blade edge; a yoke coupled to the second blade, the yoke adapted to convert motion of a drive mechanism into reciprocation of the second blade with respect to the first blade to cut hair between the teeth of the first and second blades; and a spring having a spring base and at least one spring arm extending from the spring base to one of the yoke and second blade, the spring base being fixed with respect to the first blade, the spring arm including a fixed end integral with the spring base and a free end coupled to one of the yoke and second blade, the spring arm pivoting about the fixed end to accommodate reciprocation of the second blade; wherein neither the spring base nor the spring arm includes a compliance coil to accommodate reciprocation of the second blade.

In some constructions the blade assembly further comprises a guide secured to the first blade and sandwiched between the first and second blades, the guide restricting movement of the second blade perpendicular to the first blade edge to maintain a desired blade gap. In some constructions the blade assembly further comprises a slot in the guide; and a fastener secured to the first blade and extending through the slot; wherein the blade gap is adjustable by moving the guide within a range of adjustability defined by the fastener abutting opposite ends of the slot; wherein a desired blade gap is achieved by tightening the fastener to fix the guide to the first blade with the guide in a position corresponding to the desired blade gap. In some constructions the spring and second blade are movable with the guide, such that the first and second blades are maintained in an operational condition during adjustment of the blade gap. In some constructions the blade assembly further comprises a spring retainer incorporated into the guide, the spring retainer fixing the spring base with respect to the first blade.

In another construction, the disclosure provides a blade assembly for a hair cutting apparatus, the blade assembly comprising: a first blade having teeth extending along a first blade edge; a second blade positioned proximate the first blade, the second blade having teeth extending along a second blade edge parallel to the first blade edge and offset from the first blade edge by a blade gap; a yoke coupled to the second blade, the yoke adapted to convert motion of a drive mechanism into reciprocation of the second blade with respect to the first blade to cut hair between the teeth of the first and second blades; a spring having a spring base and at least one spring arm coupled to one of the yoke and second blade, the spring arm reciprocating with the second blade with respect to the first blade, the spring arm applying a biasing force on the second blade toward the first blade; and a guide secured to the first blade and sandwiched between the first and second blades, the guide restricting movement of the second blade perpendicular to the first blade edge to maintain a desired blade gap, the guide being mounted to the first blade and fixing the spring base with respect to the first blade to prevent relative movement between the spring base and the first blade during reciprocation of the second blade with respect to the first blade.

In some constructions the guide traps the spring base against the first blade. In some constructions, the blade assembly further comprises a slot in the guide; and a fastener secured to the first blade and extending through the slot; wherein the blade gap is adjustable by moving the guide within a range of adjustability defined by the fastener abutting opposite ends of the slot; wherein a desired blade gap is achieved by tightening the fastener to fix the guide to the first blade with the guide in a position corresponding to the desired blade gap. In some constructions the spring and second blade are movable with the guide, such that the first and second blades are maintained in an operational condition during adjustment of the blade gap with the blade assembly separated from the hair cutting apparatus.

In another construction, the disclosure provides a method for adjusting a blade gap of a blade assembly for a hair cutting apparatus, the blade assembly including first and second blades having parallel blade edges separated by the blade gap, a spring maintaining the first and second blades in an operational condition, and a spring retainer fixing a portion of the spring to the first blade, the method comprising: removing the blade assembly from the hair cutting apparatus; with the first and second blades in the operational condition, moving the spring retainer and spring perpendicular to the blade edges; and in response to moving the spring retainer and spring, moving the second blade with respect to the first blade to adjust the blade gap while maintaining the first and second blades in the operational condition.

In another construction, the blade assembly for a hair cutting apparatus includes a first blade having teeth extending along a first blade edge, and a second blade having teeth extending along a second blade edge parallel to the first blade edge. A distance between the first and second blade edges defines a blade gap. A yoke is coupled to the second blade and configured to convert motion of a drive into reciprocation of the second blade relative to the first blade to cut hair. A spring includes a spring base and at least one spring arm configured to reciprocate with the second blade. A guide assembly includes a guide and a spring retainer, the guide being positioned between the first blade and the second blade, and the spring retainer fixing the spring base relative to the first blade, wherein in response to moving the guide relative to the first blade, the blade gap changes.

In another construction, the blade assembly for a hair cutting apparatus includes a first blade having teeth extending along a first blade edge, a second blade having teeth extending along a second blade edge, a distance between the first blade edge and the second blade edge defining a blade gap. A biasing member is configured to apply a biasing force on the second blade towards the first blade, and a guide includes a guide base and a cross portion, the cross portion positioned between the first blade and the second blade, the guide configured to move the second blade relative to the first blade to change the blade gap, and the second blade configured to reciprocate relative to the cross portion of the guide.

Additional features and advantages will be set forth in the detailed description which follows, and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplar.

This application may be more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements in which:.

<FIG> and <FIG> illustrate a hair cutting apparatus <NUM>, such as a trimmer or clipper, having a housing <NUM>, an electric motor <NUM>, a drive mechanism <NUM>, and a blade assembly <NUM>. The housing <NUM> may be a clamshell configuration as illustrated, with top and bottom portions 14a, 14b that surround the motor <NUM> and drive mechanism <NUM>, or can be in any other suitable configuration. The electric motor <NUM> can operate with power from batteries or electricity from an outlet, and includes a rotating motor output shaft <NUM> that rotates about an axis of rotation <NUM>. The drive mechanism <NUM> includes an eccentric drive <NUM> that is offset from the axis of rotation <NUM> of the motor output shaft <NUM>. The blade assembly <NUM> is secured to the hair cutting apparatus housing <NUM> by way of a pair of housing fasteners <NUM>.

<FIG> illustrate the blade assembly <NUM>, which includes a lower blade <NUM>, a spring <NUM>, a guide <NUM>, a washer <NUM>, an upper blade <NUM>, a yoke <NUM>, and a pair of guide fasteners <NUM>. It will be understood that the hair cutting apparatus <NUM> may be moved, turned, positioned, and oriented in many different angles and directions during operation. For the purpose of consistency and clarity, positional terms such as up, above, upward, upper, down, below, beneath, downward, lower, front, forward, rear, rearward are used in this detailed description with respect to the operating position of the hair cutting apparatus <NUM> illustrated in <FIG>.

The lower blade <NUM>, which can also be referred to as a first blade, includes a main body <NUM> and a plurality of lower blade teeth <NUM>. The lower blade teeth <NUM> extend along a nominal lower blade edge <NUM>, which may be defined, for example, by a line connecting the roots of the teeth <NUM>. The lower blade <NUM> also includes a pair of through-holes <NUM> for mounting the blade assembly <NUM> to the housing <NUM> with the housing fasteners <NUM>, and a pair of threaded holes <NUM> for receiving the guide fasteners <NUM>.

The spring <NUM> includes a U-shaped spring base <NUM> and a pair of spring arms <NUM> extending generally parallel to each other from the spring base <NUM>. Each spring arm <NUM> has a fixed end <NUM> integral with the spring base <NUM> and a free end <NUM> coupled to the yoke <NUM> or upper blade <NUM>. The spring base <NUM> sits against the main body <NUM> of the lower blade <NUM> and is held in place by the guide <NUM>. In this regard, the guide <NUM> may also be referred to as a spring retainer. The guide <NUM> fixes the spring base <NUM> with respect to the lower blade <NUM> to prevent relative movement between the spring base <NUM> and the lower blade <NUM> during reciprocation of the spring arms <NUM>, upper blade <NUM>, and yoke <NUM> with respect to the lower blade <NUM>.

The guide <NUM> is a T-shaped piece that is mounted to the lower blade <NUM> and includes a guide base <NUM> and a cross portion <NUM>. The guide base <NUM> includes a pair of arches <NUM> and an arched tunnel <NUM>, all opening toward the lower blade <NUM>, to accommodate and trap the spring base <NUM> against the lower blade <NUM>. The guide base <NUM> therefore incorporates a spring retainer. The guide base <NUM> includes a washer recess <NUM> and a pair of slots <NUM> extending parallel to the major axis of the guide base <NUM> and perpendicular to the major axis of the cross portion <NUM>. The cross portion <NUM> includes a guide edge <NUM> parallel to the lower blade edge <NUM> when the guide <NUM> is installed on the lower blade <NUM>. The guide <NUM> performs two functions: guiding reciprocating movement of the upper blade <NUM> with the guide edge <NUM> and retaining the spring <NUM> against the body <NUM> of the lower blade <NUM> with the guide base <NUM>.

The washer <NUM> sits in the washer recess <NUM> in the guide base <NUM>. The washer <NUM> includes a pair of slots <NUM> that align with the slots <NUM> in the guide base <NUM>. The washer <NUM> also includes an arched portion <NUM> to accommodate the arched tunnel <NUM> in the guide base <NUM>. The guide fasteners <NUM> extend through the slots <NUM>, <NUM> in the washer <NUM> and guide base <NUM>, respectively, and thread into the threaded holes <NUM> in the main body <NUM> of the lower blade <NUM>. With the guide fasteners <NUM> tightened down against the washer <NUM> and guide base <NUM>, the spring base <NUM> is trapped against and fixed with respect to the lower blade <NUM>.

The upper blade <NUM>, which may also be referred to as the second blade, sits on top of the lower blade <NUM> and guide <NUM>. The guide <NUM> is sandwiched between the upper and lower blades <NUM>, <NUM>. The upper blade <NUM> includes a main body <NUM> and a plurality of upper blade teeth <NUM>. The upper blade teeth <NUM> extend along a nominal upper blade edge <NUM>, which may be defined, for example, by a line connecting the roots of the teeth <NUM>. The upper blade <NUM> is positioned proximate the lower blade <NUM> with the upper blade edge <NUM> parallel to and offset from the lower blade edge <NUM>. Rearward of the upper blade edge <NUM>, on the bottom side of the upper blade <NUM>, is a depending guide surface <NUM> that is parallel to the upper blade edge <NUM> and that engages the guide edge <NUM>. The guide edge <NUM> restricts movement of the upper blade <NUM> perpendicular to the lower blade edge <NUM>.

The engagement of the guide surface <NUM> against the guide edge <NUM> guides movement of the upper blade <NUM> parallel to the blade edge <NUM> of the lower blade <NUM>. This engagement maintains a consistent blade gap <NUM> (<FIG>) between the parallel upper and lower blade edges <NUM>, <NUM> as the upper blade <NUM> reciprocates with respect to the lower blade <NUM>. The blade gap <NUM> refers to a forward-rearward offset of the blade edges <NUM>, <NUM> and not a vertical separation; the upper blade teeth <NUM> are immediately adjacent or proximate the lower blade teeth <NUM> to perform a shearing function. The guide <NUM> therefore serves the purpose of maintaining a constant blade gap <NUM> in addition to fixing the spring base <NUM> with respect to the lower blade <NUM>.

A pair of feet <NUM> depend from the rear end of the upper blade body <NUM>. The feet <NUM> straddle the guide base <NUM> and sit on the body <NUM> of the lower blade <NUM>. The feet <NUM> create a vertical gap between the rear edges of the upper and lower blades <NUM>, <NUM>, such that the guide base <NUM> can extend rearward through the vertical gap. The distance between the feet <NUM> provides sufficient room for the upper blade <NUM> to reciprocate with respect to the lower blade <NUM> and the guide <NUM>, without the feet <NUM> hitting the guide base <NUM>. The upper blade body <NUM> includes a pair of holes <NUM> for coupling the upper blade <NUM> with the yoke <NUM>.

The yoke <NUM> sits on top of the upper blade <NUM>. A pair of pair of pegs depending from the bottom of the yoke <NUM> are inserted into the holes <NUM> in the main body <NUM> of the upper blade <NUM> so that the yoke <NUM> is coupled to the upper blade <NUM>. The yoke <NUM> includes a receiver <NUM> for receiving the eccentric drive <NUM> of the drive mechanism <NUM>. The yoke <NUM> also includes channels or grooves <NUM> on opposite sides of the receiver <NUM>.

The channels <NUM> receive the free ends <NUM> of the spring arms <NUM>, such that the free ends <NUM> can apply a downward biasing force on the yoke <NUM> and slide forward and rearward within the channels <NUM> as the yoke <NUM> and upper blade <NUM> reciprocate with respect to the lower blade <NUM>. The yoke <NUM> is adapted to convert motion of the drive mechanism <NUM> into reciprocation of the upper blade <NUM> with respect to the lower blade <NUM> to cut hair between the teeth <NUM>, <NUM> of the lower and upper blades <NUM>, <NUM>. In alternative configurations, the spring arms <NUM> may be coupled at their free ends <NUM> to the upper blade <NUM> rather than the yoke <NUM>.

The blade assembly <NUM> is assembled by stacking the spring <NUM>, guide <NUM>, washer <NUM>, upper blade <NUM>, and yoke <NUM> on the lower blade <NUM>, and then extending the guide fasteners <NUM> through the slots <NUM>, <NUM> of the washer <NUM> and guide <NUM> and threading the guide fasteners <NUM> into the threaded holes <NUM> in the lower blade <NUM>. The free ends <NUM> of the spring arms <NUM> are positioned in the channels <NUM> of the yoke <NUM>. The spring <NUM> applies a downward biasing force on the yoke <NUM> and an upward biasing force on the lower blade <NUM> to draw the yoke <NUM> and lower blade <NUM> toward each other. These biasing forces of the spring <NUM> sandwich the upper blade <NUM> between the yoke <NUM> and lower blade <NUM>. The spring <NUM> may be characterized as a tension spring because when the blade assembly <NUM> is assembled, the spring arms <NUM> and spring base <NUM> are separated from each other wider than their at-rest position or relationship, and the spring <NUM> is attempting to draw or pull the spring arms <NUM> and spring base <NUM> back to the at-rest position.

The guide fasteners <NUM> and slots <NUM>, <NUM> define a range of adjustability for the guide <NUM> with respect to the lower blade <NUM>, and therefore a range of adjustability for the blade gap <NUM>. The guide <NUM> may be moved perpendicularly toward the lower blade edge <NUM> until one of the guide fasteners <NUM> abuts an end of the slot <NUM> or <NUM> in which it is positioned, at which point the guide <NUM> is prevented by the guide fastener <NUM> from moving any further in that direction with respect to the lower blade <NUM>. The same is true in the opposite direction, perpendicularly away from the lower blade edge <NUM> - the guide <NUM> may be move until one of the guide fasteners <NUM> abuts an end of the slot <NUM> or <NUM> in which it is positioned, at which point the guide <NUM> is prevented from moving any further in such opposite direction with respect to the lower blade <NUM>. The range of adjustability is therefore defined by a guide fastener <NUM> abutting one end or the opposite end of the slot <NUM> or <NUM> in which it resides. It is possible for one fastener <NUM> to define the limit of forward adjustability and the other fastener <NUM> to define the limit of rearward adjustability. The position of the guide <NUM> with respect to the lower blade <NUM> (and therefore the blade gap <NUM>) can be adjusted by loosening the guide fasteners <NUM>, moving the guide <NUM> within the range of adjustability, and tightening the guide fasteners <NUM> when the guide <NUM> is in a desired position and a desired blade gap <NUM> is achieved.

The position of the guide <NUM> corresponds to or defines the width of the blade gap <NUM> because the guide <NUM> is fixed with respect to the lower blade <NUM>, and the upper blade <NUM> reciprocates along the guide edge <NUM>. When the guide <NUM> is adjusted to the forward limit (<FIG>) in the range of adjustability, the blade gap <NUM> is minimized and when the guide <NUM> is adjusted to the rear limit (<FIG>) in the range of adjustability, the blade gap <NUM> is maximized. The blade gap <NUM> determines the length to which the hair cutting apparatus <NUM> will cut hair; the smaller the blade gap <NUM>, the shorter the length to which the hair will be cut.

As illustrated in <FIG>, the blade gap <NUM> can be adjusted with the blade assembly <NUM> fully assembled. This is because the spring <NUM> is carried by the lower blade <NUM> and is held in place with the guide <NUM>, and because the fasteners <NUM> are accessible while the blade assembly <NUM> is assembled. The spring arms <NUM> apply a biasing force on the upper blade <NUM> and yoke <NUM> toward the lower blade <NUM> to maintain the blade assembly <NUM> in the operational condition when attached to the housing <NUM> and when it is detached or separated from the housing <NUM>. When detached from the housing <NUM>, the upper blade <NUM> can be manually reciprocated by one holding the lower blade <NUM> and moving the upper blade <NUM> or yoke <NUM> back and forth parallel to the blade edges <NUM>, <NUM>. When attached to the housing <NUM>, the lower blade <NUM> is fixed with respect to the housing <NUM> and the yoke <NUM> receives the eccentric drive <NUM>, which drives reciprocation of the yoke <NUM> and upper blade <NUM> with respect to the lower blade <NUM>.

Once assembled and adjusted to a desired blade gap <NUM>, the blade assembly <NUM> is attached to the housing <NUM> with the housing fasteners <NUM>. As the blade assembly <NUM> is aligned with the mounting holes on the housing <NUM> so that the housing fasteners <NUM> can be threaded into the housing, the eccentric drive <NUM> aligns with and is received within the receiver <NUM>. When the motor <NUM> is energized, the eccentric drive <NUM> orbits around the motor output shaft axis of rotation <NUM>. The orbital movement of the eccentric drive <NUM> is converted into translational (specifically, reciprocating) movement of the yoke <NUM> and upper blade <NUM> with respect to the lower blade <NUM> (which is held stationary with respect to the housing <NUM> by the housing fasteners <NUM>).

As the yoke <NUM> and upper blade <NUM> reciprocate with respect to the lower blade <NUM>, the spring base <NUM> is fixed with respect to the lower blade <NUM> and the spring arms <NUM> wave back and forth in parallel with each other. More specifically, the fixed ends <NUM> of the spring arms <NUM> remain substantially fixed with respect to the lower blade <NUM>, the spring arms <NUM> pivot about the fixed ends <NUM> during reciprocation of the upper blade <NUM> and yoke <NUM>, and the free ends <NUM> describe arcs. The arcuate movement of the free ends <NUM> is converted into translational movement of the yoke <NUM> and upper blade <NUM> as the free ends <NUM> are free to move forward and rearward in the channels <NUM> with respect to the yoke <NUM>, but are restrained from moving side-to-side within the channels <NUM>. In other words, the channels <NUM> couple the free ends <NUM> and the yoke <NUM> for side-to-side movement, but decouple the free ends <NUM> from the yoke <NUM> for relative forward and rearward movement.

The spring arms <NUM> are of sufficient length (measured from the fixed ends <NUM> to the free ends <NUM>) to accommodate the full range of reciprocating motion of the upper blade <NUM> and yoke <NUM> with respect to the lower blade <NUM>. In known configurations, the spring arms are typically relatively short because of the positioning of the spring base in the blade assembly, and the spring often requires compliance coils in the base or arms to accommodate some of the reciprocating motion. The present disclosure requires no compliance coil in the spring base <NUM> or in the spring arms <NUM> to accommodate reciprocation of the upper blade <NUM> with respect to the lower blade <NUM>.

The blade gap <NUM> is adjusted by removing the housing fasteners <NUM>, adjusting the blade gap <NUM>, and reattaching the blade assembly <NUM> to the housing <NUM> with the housing fasteners <NUM>. The upper blade <NUM> and yoke <NUM> move with respect to the lower blade <NUM> in response to movement of the spring <NUM> and guide <NUM> with respect to the lower blade <NUM>. Because the spring <NUM>, upper blade <NUM>, and yoke <NUM> are movable with the guide <NUM>, while the blade assembly <NUM> is maintained in the operational condition, the operator can see the actual blade gap <NUM> during the adjustment. This is distinguished from known configurations in which the upper blade is not maintained on the lower blade when the lower blade is removed from the housing, and in which the operator must therefore guess at the actual blade gap <NUM> setting when adjusting the guide on the lower blade. The operator using such known configurations is not certain of what the actual blade gap <NUM> will look like until the blade assembly is actually reassembled (often by reattaching the lower blade to the rest of the blade assembly that is still connected to the housing).

Thus, the disclosure provides, among other things, a blade assembly having an entrapped spring to hold the upper and lower blades in an operational condition and an adjustable guide member for adjusting the blade gap while the upper and lower blades are held in the operational condition. Various features and advantages of the disclosure are set forth in the following claims.

Referring now to <FIG>, illustrated therein is another embodiment of hair cutting apparatus <NUM>. <FIG> and <FIG> illustrate a hair cutting apparatus <NUM>, such as a trimmer or clipper, comprising housing <NUM>, electric motor <NUM>, drive mechanism <NUM>, and blade assembly <NUM>. In one embodiment, housing <NUM> comprises a clamshell configuration with top and bottom housings <NUM>, <NUM> that surround motor <NUM> and drive mechanism <NUM>, although other configurations for housing <NUM> could be practiced and still utilize the features described in this disclosure. In one embodiment electric motor <NUM> operates with power from batteries or electricity from an outlet, and includes rotating motor output shaft <NUM> that rotates about axis of rotation <NUM>. Drive mechanism <NUM> comprises eccentric drive <NUM> that is offset from axis of rotation <NUM> of motor output shaft <NUM>. Blade assembly <NUM> is coupled secured to housing <NUM> by housing fasteners.

<FIG> illustrate blade assembly <NUM>, which comprises lower blade <NUM>, spring <NUM>, washer <NUM>, upper blade <NUM>, yoke <NUM>, guide fasteners <NUM>, and guide <NUM>. Lower blade <NUM>, which can also be referred to as a first blade, comprises main body <NUM> and a plurality of lower blade teeth <NUM>. Lower blade teeth <NUM> extend along a nominal lower blade edge <NUM>, which may be defined, for example, by a line <NUM> connecting the roots of teeth <NUM>. Lower blade <NUM> also includes a pair of through-holes <NUM> through which guide fasteners <NUM> insert to couple guide <NUM> to lower blade <NUM>, and a pair of threaded holes <NUM> for receiving guide fasteners <NUM> to mount blade assembly <NUM> to housing <NUM>.

In one embodiment spring <NUM> comprises U-shaped spring base <NUM>, a pair of securing arms <NUM> extend generally parallel to each other from the spring base <NUM>, and a pair of arcuate-shaped fixed ends <NUM> opposite a pair of free ends <NUM> along each arm <NUM>. Free ends <NUM> of spring <NUM> interface against channels <NUM> in yoke <NUM> to bias yoke <NUM> against upper blade <NUM>.

Guide <NUM> is a T-shaped piece mounted to lower blade <NUM>. Guide <NUM> comprises guide base <NUM> and cross portion <NUM>. Guide base <NUM> comprises slots <NUM> extending parallel to the major axis of the guide base <NUM> and perpendicular to the major axis of the cross portion <NUM>. Cross portion <NUM> comprises guide edge <NUM> parallel to lower blade edge <NUM> when guide <NUM> is disposed above lower blade <NUM> (as shown in <FIG>). Guide <NUM> performs at least two functions: guiding reciprocating movement of upper blade <NUM> with guide edge <NUM> and retaining spring <NUM> against body <NUM> of lower blade <NUM> with tongue <NUM> of guide base <NUM>.

Washer <NUM> interfaces against guide base <NUM>. Washer <NUM> comprises slots <NUM> that align with slots <NUM> in guide base <NUM>. Guide fasteners <NUM> extend through slots <NUM>, <NUM> in washer <NUM> and guide base <NUM>, respectively, and thread into threaded holes <NUM> in main body <NUM> of lower blade <NUM>.

Upper blade <NUM>, which may also be referred to as the second blade, sits on top of lower blade <NUM> and guide <NUM> (from the perspective of <FIG>). Guide <NUM> is disposed between upper and lower blades <NUM>, <NUM>. Upper blade <NUM> comprises main body <NUM> and a plurality of upper blade teeth <NUM>. Upper blade teeth <NUM> extend along nominal upper blade edge <NUM>, which in one embodiment is defined by a line <NUM> connecting the roots of teeth <NUM>. Upper blade <NUM> is positioned proximate lower blade <NUM> with upper blade edge <NUM> parallel to and offset from lower blade edge <NUM>. Depending guide surface <NUM> is on a bottom of the upper blade <NUM> (from the perspective of <FIG>) and is parallel to upper blade edge <NUM>. Depending guide surface <NUM> engages guide edge <NUM>. Guide edge <NUM> restricts movement of upper blade <NUM> perpendicular to lower blade edge <NUM>.

The engagement of guide surface <NUM> against guide edge <NUM> guides movement of upper blade <NUM> parallel to blade edge <NUM> of lower blade <NUM>. This engagement maintains a consistent blade gap <NUM> between parallel upper and lower blade edges <NUM>, <NUM> as upper blade <NUM> reciprocates with respect to lower blade <NUM>. Blade gap <NUM> refers to a forward-rearward offset of the blade edges <NUM>, <NUM>, and not a vertical separation. Upper blade teeth <NUM> are immediately adjacent or proximate lower blade teeth <NUM> to perform a shearing function. Guide <NUM> serves at least the purposes of maintaining a constant blade gap <NUM>, and tongue <NUM> fixes spring base <NUM> with respect to lower blade <NUM>.

Feet <NUM> protrude from upper blade main body <NUM>. Feet <NUM> straddle guide base <NUM> and are disposed on body <NUM> of lower blade <NUM> when blade assembly <NUM> is fully assembled. Feet <NUM> create a vertical gap between upper and lower blades <NUM>, <NUM>. The distance between feet <NUM> provides sufficient room for upper blade <NUM> to reciprocate with respect to lower blade <NUM> and guide <NUM> without feet <NUM> hitting guide base <NUM>. Upper blade body <NUM> comprises a pair of holes <NUM> for coupling upper blade <NUM> with yoke <NUM>.

Yoke <NUM> is disposed above upper blade <NUM> (from the perspective of <FIG>). Pegs <NUM> protrude from lower surface <NUM> of yoke <NUM> and are inserted into holes <NUM> in main body <NUM> of upper blade <NUM> to couple yoke <NUM> to upper blade <NUM>. Yoke <NUM> comprises receiver <NUM> that couples with eccentric drive <NUM> of drive mechanism <NUM>. Yoke <NUM> also comprises channels or grooves <NUM> on opposite sides of the receiver <NUM>.

Channels <NUM> comprise hole <NUM> through which free ends <NUM> of spring arms <NUM> extend. Free ends <NUM> apply a downward (from the perspective of <FIG>) biasing force on upper blade <NUM>.

Yoke <NUM> converts motion of drive mechanism <NUM> into reciprocation of upper blade <NUM> with respect to lower blade <NUM>. This reciprocation cuts hair between teeth <NUM>, <NUM> of lower and upper blades <NUM>, <NUM>. In one or more alternate embodiments, free ends <NUM> are coupled to upper blade <NUM> rather than the yoke <NUM>.

Turning to <FIG>, fixed ends <NUM> are disposed within respective channels <NUM> of guide <NUM>. Channels <NUM> comprise channel arcs <NUM>, around which fixed ends <NUM> are disposed, upper channel <NUM>, against which spring arms <NUM> are disposed, lower channel <NUM>, against which securing arms <NUM> of spring <NUM> are disposed, and channel sidewalls <NUM>, which secure spring <NUM> laterally within channel <NUM>. Spring base <NUM> is biased against tongue <NUM>, both securing spring <NUM> against guide <NUM> and biasing free ends <NUM> of spring <NUM> against upper surface <NUM> of upper blade <NUM>.

Guide <NUM> comprises center body member <NUM> between a pair of side members <NUM>. Guide <NUM> is coupled to lower blade <NUM> via fasteners extending through holes <NUM>. Guide <NUM> is coupled to lower housing <NUM> with a screw (not shown) that passes through lower housing <NUM> and hole <NUM>, the screw having threads that engage the inner surface of hole <NUM>. Tongue <NUM> protrudes from guide <NUM> towards yoke <NUM> when blade assembly <NUM> is fully assembled.

In one embodiment, blade assembly <NUM> is assembled by stacking spring <NUM>, guide <NUM>, washer <NUM>, upper blade <NUM>, guide <NUM> and yoke <NUM> on lower blade <NUM>, and extending guide fasteners <NUM> through slots <NUM>, <NUM> of washer <NUM> and guide <NUM> and threading guide fasteners <NUM> into threaded holes <NUM> in lower blade <NUM>. Spring <NUM> applies a downward biasing force (from the perspective of <FIG>) on upper blade <NUM>. This biasing force of spring <NUM> sandwiches guide <NUM> between upper blade <NUM> and lower blade <NUM>. Spring <NUM> functions as a tension spring because free ends <NUM> exert the tension of arms <NUM> against upper blade <NUM>.

The placement of guide fasteners <NUM> in slots <NUM>, <NUM> defines a range of positions of guide <NUM> with respect to lower blade <NUM>, and therefore a range of widths for blade gap <NUM>. Guide <NUM> may be moved toward lower blade edge <NUM> until one of guide fasteners <NUM> is disposed against an end of slot <NUM> or <NUM> in which it is positioned, at which point guide <NUM> is prevented by guide fastener <NUM> from moving further. It is possible for one fastener <NUM> to define the limit of forward adjustability and the other fastener <NUM> to define the limit of rearward adjustability. The position of guide <NUM> with respect to lower blade <NUM> (and therefore blade gap <NUM>) can be adjusted by loosening guide fasteners <NUM>, moving guide <NUM> within the range of positions, and tightening guide fasteners <NUM> when guide <NUM> is in a desired position and a desired blade gap <NUM> is achieved.

The position of guide <NUM> corresponds to or defines the width of blade gap <NUM> because guide <NUM> is fixed with respect to lower blade <NUM>, and upper blade <NUM> reciprocates along guide edge <NUM>. When guide <NUM> is adjusted to the forward limit in the range of positions, blade gap <NUM> is minimized and when guide <NUM> is adjusted to the rear limit in the range of positions, blade gap <NUM> is maximized. Blade gap <NUM> determines the length to which the hair cutting apparatus <NUM> will cut hair; the smaller blade gap <NUM> is, the shorter the length to which the hair will be cut.

When assembled and adjusted to a desired blade gap <NUM>, blade assembly <NUM> is attached to housing <NUM> via housing fasteners. When blade assembly <NUM> is aligned with the mounting holes on housing <NUM> so that housing fasteners can be threaded into housing <NUM>, eccentric drive <NUM> protrudes within receiver <NUM>. When motor <NUM> is engaged, eccentric drive <NUM> rotates around axis of rotation <NUM>. Orbital movement of eccentric drive <NUM> is converted into reciprocating movement of yoke <NUM> and upper blade <NUM> with respect to lower blade <NUM>, which is held stationary with respect to housing <NUM> by fasteners threaded through holes <NUM> that couple lower blade to housing <NUM>.

When yoke <NUM> and upper blade <NUM> reciprocate with respect to lower blade <NUM>, spring base <NUM> is fixed with respect to lower blade <NUM>. Fixed ends <NUM> of spring arms <NUM> remain substantially fixed with respect to lower blade <NUM> by virtue of being coupled to guide <NUM>.

Spring arms <NUM> are of sufficient length to accommodate a range of reciprocating motion of upper blade <NUM> and yoke <NUM> with respect to lower blade <NUM>. In various other embodiments, spring <NUM> requires compliance coils in the base or arms to accommodate some of the reciprocating motion. According to various embodiments consistent with the present disclosure, on the other hand, no compliance coils in spring base <NUM> or in spring arms <NUM> are required to accommodate reciprocation of upper blade <NUM> with respect to lower blade <NUM>.

Claim 1:
A blade assembly (<NUM>) for a hair cutting apparatus (<NUM>) comprising:
a first blade (<NUM>) having teeth extending (<NUM>) along a first blade edge (<NUM>) defined by a line connecting the roots of the teeth (<NUM>);
a second blade (<NUM>) having teeth (<NUM>) extending along a second blade edge (<NUM>) defined by a line connecting the roots of the teeth (<NUM>), the second blade edge (<NUM>) parallel to the first blade edge (<NUM>), a distance between the first blade edge (<NUM>) and the second blade edge (<NUM>) defining a blade gap (<NUM>);
a yoke (<NUM>) coupled to the second blade (<NUM>), the yoke (<NUM>) reciprocates the second blade (<NUM>) relative to the first blade (<NUM>);
a spring (<NUM>) comprising:
a pair of spring arms (<NUM>);
a pair of arcuate-shaped fixed ends (<NUM>) opposite a pair of free ends (<NUM>) along each spring arm (<NUM>), the free ends (<NUM>) interface against the yoke (<NUM>) to bias the yoke (<NUM>); and
a U-shaped spring base (<NUM>) that extends between a pair of securing arms (<NUM>) that extend generally parallel to each other from the U-shaped spring base (<NUM>);
characterised by
a guide (<NUM>) comprising:
a tongue (<NUM>) that interfaces against the spring base (<NUM>), the tongue (<NUM>) protruding from the guide (<NUM>) towards the yoke (<NUM>); and
channels (<NUM>) including channel arcs (<NUM>) around which the pair of arcuate-shaped fixed ends (<NUM>) are disposed, upper channels (<NUM>) against which the pair of spring arms (<NUM>) are disposed, lower channels (<NUM>) against with the securing arms (<NUM>) are disposed, and channel sidewalls (<NUM>) which secure the spring (<NUM>) laterally within the channels (<NUM>).