SHIM SUPPORTED UPON A PIVOT PIN BETWEEN UPPER AND LOWER RECEIVERS OF AN AR-15/M16/M4 STYLE FIREARM AND FOR REDUCING MISALIGNMENT AND PLAY
An improved shim construction incorporating a thin body exhibiting a profile generally matching a selected mounting ear of a lower assembleable receiver, the shim including an arcuate perimeter with an flat interconnected base surface. The body exhibits an aperture defined therein such that, upon placement between an inner facing surface of the ear and an intermediate positioned cylindrical shaped portion, a subsequent widthwise traversing installation of a pivot pin causes the shim body to be sandwiched between the receivers to occupys an excess tolerance, thereby reducing or eliminating instances of misaligning slop or play exhibited between the receivers. The shim may exhibit a thickness in a range of 0.001″ to 0.010″. A plurality of shims can be provided as a kit and which are applied in scalable fashion to compensate for varying excess tolerance established between the receivers.
The present invention claims the priority of U.S. Ser. No. 61/530,429 filed Sep. 2, 2011.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention teaches an improved shim stock design, improving upon prior art disc shaped shims. The improved shim exhibits a thin arcuate body with a flat bottom which matches the profile of either of the spaced apart ears associated with the lower receiver and between which seats a tubular shaped and downwardly extending protrusion associated with the upper receiver. The shim can be employed either singularly or in a plural/stackable fashion and in order to eliminate the existence of excess tolerance (spacing) exhibiting between the upper and lower receives, such as which is further characterized as “slop” or “play” and which can otherwise result in misalignment between the receivers.
2. Background of the Relevant Art
Firearms such as the M16/M4/AR15 rifle include upper and lower receivers assembleable receivers which, upon assembly, engage at both a rear barrel location of the upper receiver which seats within an upper projecting annular support of the lower receiver which is proximate its stock, as well as at a forward location in which a cross wise apertured and underside extending lug associated with the upper receiver is aligned between outer apertures formed in a pair of spaced apart ears associated with an upper surface of the lower receiver. A pin is laterally displaced through the aligning apertures in order to affix the upper and lower receivers together.
A problem commonly associated with such assembled receivers is the incidence of “slop” or “play” and which is defined as any degree of looseness in the tolerance established between the aligning lugs and ears. Such looseness in the inter-fitting of the parts can be the cause of undesirable rattling or noise.
One solution proposed for addressing looseness between the mounting locations of the upper and lower receivers includes the installation of shims for taking up the excess lateral dimension, such as is depicted by the AR-15/M16 receiver shims produced by Brownells. The Brownells shim depicts a thin walled washer style configuration constructed of a tempered stainless steel for reducing side-to-side play between the receiver halves and the hammer/trigger components.
SUMMARY OF THE PRESENT INVENTIONThe present invention discloses an improved shim stock design insertable between a mounting location established between upper and lower assembleable receivers of a firearm. As described, a first (typically lower) of the receivers exhibits a pair of spaced apart ears, each of which exhibiting an arcuate profile with a level base surface.
A pair of widthwise aligning apertures extend through the ears. The other of the receivers (typically upper) exhibits a generally cylindrical shaped projection aligning between said spaced apart ears, a widthwise extending aperture defined through the cylindrical shaped portion and which communicates with the aligning apertures in the ears.
The improved shim construction incorporates a thin body exhibiting a profile generally matching a selected ear and including an arcuate perimeter with an flat interconnected base surface. The body exhibits an aperture defined therein such that, upon placement between an inner facing surface of a selected ear and the intermediate positioned cylindrical shaped portion and subsequent widthwise traversing installation of a pivot pin, the body is sandwiched between the receivers and occupies an excess tolerance, thereby reducing or eliminating instances of misaligning slop or play exhibited between the receivers.
Additional features include the shim exhibiting a thickness in a range of 0.001″ to 0.010″. A plurality of shims can be provided as a kit and which are applied in scalable fashion to compensate for varying excess tolerance established between the receivers.
Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which:
The present invention teaches an improved shim design which improves upon prior art disc shaped shims. As will be described in reference to the succeeding description, the improved shim exhibits a thin arcuate body with a flat bottom which matches an inner facing profile of either of the spaced apart ears associated with the lower receiver, and between which seats a tubular shaped and downwardly extending protrusion associated with the upper receiver. The shim can be employed either singularly or in a plural/stackable fashion and in order to eliminate the existence of excess tolerance (spacing) exhibiting between the upper and lower receives, such as which is further characterized as “slop” or “play” and which can otherwise result in misalignment between the receivers.
By controlling the slop existing between the upper and lower receivers at the front mounting location (the takedown pin defining a second rearward spaced mounting location), the firearm (rifle) can be easily disassembled in a field environment in order to perform any required remedial action (cleaning/clearing obstruction/repair). The shim stock also helps to maintain the normal operation of both the pivot and takedown pins while controlling potential inter-misalignment (again slop) in both rotational and horizontally mounted instances.
The shim stock, see as best shown at 10 in
The shim includes an inner aperture (see inner perimeter wall 16) which matches the corresponding aligned apertures associated with the upper and lower receiver pivot pin mounts. The outer profile of the shim 10 further exhibits angled corner locations 18 and 20, these aligning and seating with corresponding edge profiles of the lower receiver ear surface (see again
Upon installation, the shim 10 removes the existence of any excess tolerance or play between the upper and lower receivers, thereby creating a tighter fit of the two parts. It is further noted that the shim, when installed, will not hinder the operation of the firearm at any time, with the receivers further being broken open for responding to any desired remedial action without changing the process as to how the operator manipulates the firearm, thus allowing the shim to be installed in any firearm or for any operator to use the firearm (rifle) with the shim installed without any additional training.
Having provided a brief description of the structure and manner of installation of the uniquely configured shim, a brief description of the supporting drawings is provided with
Having described my invention, other and additional preferred embodiments will become apparent to those skilled in the art to which it pertains, and without deviating from the scope of the appended claims.
Claims
1. A shim insertable between a mounting location established between upper and lower assembleable receivers of a firearm, a first of the receivers exhibiting a pair of spaced apart ears, each of said ears exhibiting an arcuate profile with a level base surface, a pair of widthwise aligning apertures extending through said ears, the other of the receivers exhibiting a generally cylindrical shaped projection aligning between said spaced apart ears, a widthwise extending aperture defined through said cylindrical shaped portion and which communicates with said aligning apertures in said ears; said shim stock comprising:
- a thin body exhibiting a profile generally matching a selected ear and including an arcuate perimeter with an flat interconnected base surface; and
- said body exhibiting an aperture defined therein such that, upon placement between an inner facing surface of a selected ear and the intermediate positioned cylindrical shaped portion and subsequent widthwise traversing installation of a pivot pin, said body being sandwiched between said receivers and occupying an excess tolerance thereby reducing or eliminating instances of misaligning slop or play exhibited between the receivers.
2. The shim as described in claim 1, said shim exhibiting a thickness in a range of 001″ to 0.010″.
3. The shim as described in claim 1, further comprising a plurality of shims provided as a kit and which are applied in scalable fashion to compensate for varying excess tolerance established between the receivers.
4. The shim as described in claim 3, at least first and second of said shims exhibiting identical cross sectional outlines combined with varying thicknesses ranging between 0.001″ to 0.010″.
5. A shim kit adapted to being insertable between a mounting location established between upper and lower assembleable receivers of a firearm, comprising:
- the lower receiver exhibiting a pair of spaced apart ears, each of which exhibiting an arcuate profile with a level base surface, a pair of widthwise aligning apertures extending through the ears;
- the upper receiver exhibiting a generally cylindrical shaped projection aligning between said spaced apart ears, a widthwise extending aperture defined through said cylindrical shaped portion and communicating with the aligning apertures in the ears;
- said shim kit including a plurality of bodies, each exhibiting a profile generally matching a selected ear and including an arcuate perimeter with an flat interconnected base surface; and
- each of said bodies exhibiting an aperture defined therein such that, upon placement in successively stacked fashion between an inner facing surface of a selected ear and the intermediate positioned cylindrical shaped portion, and subsequent widthwise traversing installation of a pivot pin, said bodies being sandwiched between said receivers and occupying an excess tolerance thereby reducing or eliminating instances of misaligning slop or play exhibited between the receivers.
6. The shim kit as described in claim 5, at least first and second of said shims exhibiting identical cross sectional outlines combined with varying thicknesses.
7. The shim as described in claim 6, said shims exhibiting a thickness in a range of 001″ to 0.010″.
Type: Application
Filed: Sep 4, 2012
Publication Date: Mar 7, 2013
Applicant: ELITE ARMS INC. (Dexter, MI)
Inventor: Scott Eric Watkins (Portage, MI)
Application Number: 13/602,385