Patent Application
20150296719
Various exemplary embodiments disclosed herein relate generally to power tools and, more particularly but not exclusively, to handheld power tools having removable blades for trimming and cutting vegetation.
Known power tools having interchangeable blades are cumbersome and potentially dangerous to manipulate. For example, U.S. Pat. No. 3,959,878 to Irelan et al., discloses a convertible portable electric tool having interchangeable tool pieces. Each of the interchangeable tool pieces include two parts, a stationary element and a moving element, which are pivoted together at a pin. The stationary element includes a comb of teeth and, likewise, the moving element includes a comb of teeth. The rearward end of the moving element includes an elongated opening for receipt of a drive member. The drive member is rotated by a gear and the resulting circular movement oscillates the moving element about the pivot pin. As a result, the stationary element and the moving element lap one another to cut grass between the teeth upon oscillation of the moving element.
Before attaching a tool piece assembly to the power housing, the user must first rotate the drive member to a predetermined position, such as a top dead center position. Similarly, the user must manually orient the moving element into a predetermined position with respect to the stationary element. After completing these preliminary steps, the drive member can be fitted within the elongated opening of the moving element upon bringing the stationary element into proper registry relative to the power housing. Once the stationary tool element is brought into proper registry and located over guide posts, additional means are provided to maintain the tool piece releasably secured against the housing.
Accordingly, the attachment of tool pieces to a power housing as disclosed by Irelan et al. is a cumbersome process requiring various manual alignment steps to be performed by the user with respect to both the tool piece and the power housing. Generally, known power tools do not provide fool-proof mechanisms to allow easy, safe, and automatic alignment and attachment of cutting elements. Instead, users are required to spend time handling and adjusting cutting blades and other movable parts until precise alignments are achieved before a cutting element can be properly attached. Not only is this time consuming, but the user is also exposed to sharp cutting surfaces and powered moving parts in the process.
A brief summary of various exemplary embodiments is presented below. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, but not to limit the scope of the invention. Detailed descriptions of a preferred exemplary embodiment adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections.
Various embodiments relate to a power tool including: a housing; a selectively actuable motor including a rotary output; a rotary drive element arranged in operative contact with the rotary output of the motor and including a drive pin; a removable blade assembly having a stationary blade and a moving blade in operative contact with the drive pin, wherein movement of the drive pin is translated into movement of the moving blade; a blade holder operable to selectively lock the stationary blade in an aligned position with respect to the housing; and a magnet positioned to contact the stationary blade when the stationary blade occupies the aligned position and hold the stationary blade in the aligned position.
Various embodiments relate to power tool transmission including: a housing; an interface operable to engage a rotary output of a motor; a gearbox operatively connected to the interface to transfer the rotary output to a drive plate including a drive pin; a blade holder operable to selectively lock a stationary blade of a removable blade assembly in an aligned position with respect to the housing; and a magnet positioned to contact the stationary blade when the stationary blade occupies the aligned position.
Various embodiments are described wherein the magnet is movable with respect to the housing such that during attachment of the removable blade assembly to the housing, the magnet is permitted to extend toward the stationary blade under the force of magnetic attraction, away from an initial magnet position occupied by the magnet when the blade holder locks the stationary blade.
Various embodiments are described wherein the magnet is spring biased to return to the initial magnet position.
Various embodiments additionally include a magnet holder including an open frame configured to receive the magnet such that the magnet is exposed on at least one side of the frame.
Various embodiments are described wherein the magnet includes at least one ledge created by an increase in at least one dimension of the magnet, wherein the at least one step is positioned to abut an interior face of the open frame and thereby resist passage of the magnet through the frame.
Various embodiments are described wherein the magnet is at least 0.5 millimeters proud with respect to a blade-facing side of the open frame.
Various embodiments additionally include an alignment feature matching a geometric feature of the removable blade assembly and the magnet at least partially pulls the stationary blade toward alignment with the alignment feature during attachment of the removable blade assembly to the housing.
Various embodiments are described wherein the alignment feature includes at least one edge having a shape that is complementary to a portion of an outer edge of the removable blade assembly.
Various embodiments are described wherein the blade holder is a removable cover and the at least one edge is a portion of a rail arranged to mate with a complementary hook of the removable cover.
Various embodiments are described wherein the alignment feature includes at least one projection having a shape that is received within an interior recess disposed within the removable blade assembly.
Various embodiments are described wherein the blade holder includes a removable cover configured to mate with the housing, wherein when the cover is mated with the housing while the blade in the aligned position, the blade is disposed between the cover and the housing and is prevented from moving out of the aligned position.
In order to better understand various exemplary embodiments, reference is made to the accompanying drawings, wherein:
To facilitate understanding, identical reference numerals have been used to designate elements having substantially the same or similar structure or substantially the same or similar function.
The description and drawings presented herein illustrate various principles. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody these principles and are included within the scope of this disclosure. As used herein, the term, “or,” as used herein, refers to a non-exclusive or (i.e., and/or), unless otherwise indicated (e.g., “or else” or “or in the alternative”). Additionally, the various embodiments described herein are not necessarily mutually exclusive and may be combined to produce additional embodiments that incorporate the principles described herein.
The exemplary transmission 100 includes a housing 110, a bottom cover 120, and a gearcase 130. In the example shown, the housing 110 is formed of a left housing shell 111 and a right housing shell 112 that are attached to each other via three housing screws 310a-c. It will be appreciated that various alternative arrangements may be utilized to form the housing 110 including a unitary shell, additional shells or other parts, and additional or alternative attachment methods.
The bottom cover 120 is shown attached to the bottom of the housing and is removable therefrom. For example, in various embodiments, the housing 110 includes a bottom cover release button 211 attached to a bottom cover hook 813 that engages with a receiving slot (not shown) on the top surface of the bottom cover 120 to hold the cover in place. In some such embodiments, the cover additionally includes four rail hooks (not shown) that engage rails 811a-b, 812a-b on the bottom surface of the housing 110. As such, the bottom cover 120 may be removed from the housing 110 by first sliding the bottom cover release button 211 to disengage that bottom cover hook from the bottom cover 120 and then sliding the bottom cover 120 toward the rear of the transmission 100 to disengage the rail hooks from the housing rails. Various alternative structures for retaining the bottom cover 120 on and releasing the bottom cover 120 from the housing 110 will be apparent.
The housing 110 and bottom cover 120 form a cavity therebetween that is accessible via a blade opening 121 formed by a separation between the housing 110 and the bottom cover 120 at the front of the transmission 100. As shown in
The locating pins 831a-d extend downwardly from the gearcase 130 in four locations positioned to be complementary with the geometric features of the blade assembly 950 such as, for example, being received within interior recesses of the blade assembly 950. As an example,
As another example of an alignment feature, the rear rails 811a-b perform a secondary function. In addition to receiving the rail hooks of the bottom cover 120 for holding the bottom cover 120 in place, the rear rails 811a-b form an edge that is complementary to the rear edge of the blade assembly 950. As such, an operator may easily place the blade in the aligned position by abutting the read edge of the blade assembly 950 against the edge formed by the rear rails 811a-b and then lowering the blade assembly 950 onto the locating pins 831a-d. As shown in
While various alignment features have been described as facilitating placement of the blade assembly 950 in the proper aligned position with respect to the open transmission 800 prior to locking of the blade by the bottom cover 120, the blade may nonetheless move out of the aligned position prior to locking. For example, where the blade assembly 950 is sufficiently long and the open transmission 800 is held upside down for the operator to attach the bottom cover 120, the weight of the blade may cause the blade assembly 950 to pivot at the front edge of the housing and thereby move the back edge of the blade assembly 950 outward away from the transmision and out of engagement with the locating pins 831a-d, rear rails 811a-b, back edges 1011a-b, or other alignment features that may be employed in construction of the transmission. Possible movements out of the aligned position such as this may complicate the manual procedure necessary for the operator in locking the blade assembly in place.
To help counteract such movements out of the aligned position, the housing 110 carries a magnet assembly 840. The magnet assembly 840 carries a magnet that attracts the blade assembly toward the open transmission 800 and into alignment with the various alignment features 811a-b, 831a-d, 1011a-b employed. Thereafter, the magnet resists various forces that would work to move the blade assembly 950 out of the aligned position such as, for example, the force of gravity acting on the unsupported the blade assembly 950 when the open transmission 800 is held upside down. With the blade assembly 950 thus held in the aligned position, the process of reattaching the bottom cover 120 to the open transmission 800 is simplified because the operator need not manually hold the blade assembly 950 in place.
As shown in further detail in
The magnet holder 1142 is formed of plastic or other material as an open frame such that a bottom surface of the magnet 1141 is exposed on the underside of the magnet holder 1142, as is clearly seen in
The magnet holder 1142 may include additional structures. As shown in
In various embodiments, the magnet assembly 840 may be movable with respect to the housing 110. For example, the magnet assembly 840 may be held in a free-floating arrangement with respect to the housing 110. To provide some degree of constraint to the movement allowed of the magnet assembly 840, a rail interface may be formed between the magnet assembly 840 and housing 110. As such, the magnet holder 1142 also includes two magnet holder rails 1144a-b. As can be seen in
In various embodiments, the magnet assembly 840 may be adapted to further assist in pulling the blade assembly 950 into alignment with the alignment features, beyond what is already accomplished by the magnetic attraction. For example, the magnet assembly 840 may be spring biased to return to its initial position in the housing 110 after extending outward to meet the blade assembly 950. In some such embodiments and as can be seen in
Further, various alternative arrangements for mounting a magnet within the housing 110 will be apparent. For example, the magnet assembly 840 or just the magnet 1141 may be fixedly formed within or otherwise attached to the housing 110. In some such embodiments, the magnet 1141 may be configured to be proud below the lower surface of the housing 110 such as, for example, 0.5 mm to 1.0 mm proud.
Turning back to
As shown in
In various embodiments, the power unit 1760 is provided with a safety feature to prevent unintentional or accidental activation of the power tool 1800. Specifically, the power unit 1760 may maintain the power unit trigger 1762 in a locked state until a safety button is pressed 1763. The safety button 1763 is positioned such that it is covered by the transmission 100 when the power tool 1800 is assembled and, as such, the safety button 1763 is not manually accessible. Instead, the transmission 100 is provided with structure for the user to indirectly press the safety button 1763 when operation of the power tool 1800 is desired. Specifically, the transmission 100 includes a left side lock button 170a and a right side lock button 170b, either of which may be slid away from the bottom cover 120 by the operator to press the safety button 1763 and thereby unlock the power unit trigger 1762 for operation of the power tool 1800.
As can be best seen in the example of
The lock arms 1971 a-b both extend underneath a lock plate 1973 having an upwardly extending lock plate finger 1974. The lock plate finger 1974 is received within a t-slot piece channel 1931. The T-slot piece channel 1931 extends entirely through the t-slot piece 531 and is aligned with the safety button 1763 of the power unit 1760 when the power tool 1800 is assembled. The lock plate 1973 is movable up and down with respect to the housing 110 and gearcase 130 along gearcase rails 2013a-b. Specifically, as can be seen in the cross-section across line C-C, the lock plate 1973 includes two lock plate slots 2071a-b that receive the gearcase rails 2031a-b, respectively. The lock plate 1973 is downwardly biased by a lock plate spring 1975 that is disposed between the lock plate 1973 and the t-slot piece 531.
As illustrated in the cross section across line B-B in
As seen in
In various embodiments, the power unit 1760 may be configured to provide an input speed of about 28,000 RPM. In some embodiments, a gear set, such as the dual stage reduction gear set 2431, may have a gear ratio of 20:1 and may therefore provide an output speed of about 1,400 RPM to the drive plate 832 when attached to an 28,000 RPM input. In other embodiments, a gear set, such as the single stage reduction gear set 2331, may have a gear ratio of 10:1 and may therefore provide an output speed of about 2,800 RPM when attached to an 28,000 RPM input. It will be apparent that various alternative arrangements may be utilized to provide such output speeds. For example, the gear ratio of the single stage reduction gear set 2331, the dual stage reduction gear set 2431, or another alternative gear set (not shown) may be tuned to provide an output within the range of 2,000 to 3,200 RPM or within the range of 2,000 to 2,800 RPM.
To enable high speed output, the gear set may connect to a specially balanced drive plate assembly 2531. As shown in
Exemplary blade assemblies 2750, 2850 for use as a blade assembly 950 are detailed in
As another example, in
It will be appreciated that the rear portions of the stationary shrub blade 2751 and stationary shear blade 2851 are provided with similar or identical geometric features such as similarly shaped outer edges and similarly positioned pin holes 1051a-d. As such, the two blade assemblies 2750, 2850 may be interchangeably attached to the transmission 100 as desired by the operator. It will be apparent that enabling attachment of additional blade assembles may be similarly achieved by providing similar or identical geometric features for cooperation with alignment features on the transmission 100.
Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be effected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.
The present application is related to U.S. patent application Ser. No. 11/220,472, filed on Sep. 7, 2005, the entire disclosure of which is hereby incorporated herein for all purposes.
