Patent Publication Number: US-3877148-A

Title: Spring assembly for the lower guard of a circular saw

Description:
United States Patent Huber SPRING ASSEMBLY FOR THE LOWER GUARD OF A CIRCULAR SAW Apr. 15, 1975 Primary ExaminerAl Lawrence Smith Assistant Examiner-J. C. Peters Attorney, Agent, or FirmMarshall J. Breen; Edward L. Bell; Harold Weinstein [57] ABSTRACT A spring assembly for the lower guard of a circular saw having a spring coiled within the housing of the upper guard at the site of the connection of the lower guard prior to assembly thereof. One end of the spring is disposed externally of the fixed housing and is cammed onto the lower guard, by the act of threading the mounting screw into the housing or otherwise. An added safety feature is that the lower guard is notched to received the external end of the coil spring to complete the assembly. The axis of the mounting screw is coincident to the pivotal axis of the lower guard.  
 6 Claims, 6 Drawing Figures SPRING ASSEMBLY FOR THE LOWER GUARD OF A CIRCULAR SAW BACKGROUND OF THE INVENTION Heretofore, the biasing of the lower guards of the prior art&#39; involved mounting the biasing spring along with or to an external housing, or at a location remote from that of the axis about which the lower guard pivoted. The prior art method of assembly was time consuming, and often dangerous in that if the spring slipped it could fly off at a substantial speed and possibly hit either the assembler or an innocent bystander. Even if assembled without accident, the spring biased lower guards of the prior art resulted in added cost.  
 SUMMARY OF THE INVENTION In the present invention, the novel spring assembly for the lower guard of a circular saw is operatively connected at the fixed upper guard of the housing about the pivotal axis of the lower guard. In this configuration, assembly of the spring is both simple and safe.  
  It is therefore an object of the present invention to provide an improved spring assembly for the lower guard of a circular saw which overcomes the prior art disadvantages; which is economical and reliable; which uses a pre-loaded coil spring at the upper guard mounted about the axis of pivoting of the lower guard; which spring has an external end cammed upon the lower guard; which lower guard has a rim having a cam surface that forces the spring thereon by the act of connecting the mounting screw to assemble the fixed upper guard and the lower guard; and which has a notched rim on the upper guard, or lower guard or both to secure the coil spring in position during the assembly or disassembly thereof.  
  Other objects and advantages will be apparent from the following description of one embodiment of the invention, and the novel features will be particularly pointed out hereinafter in the claims.  
 BRIEF DESCRIPTION OF THE DRAWINGS This invention is illustrated in the accompanying drawings in which:  
  FIG. 1 is a front elevational view, from the guard side of a circular saw embodying the present invention.  
  FIG. 2 is an enlarged front elevational view of the coil spring loaded upon the fixed upper guard of the housing; prior to connecting the lower guard.  
  FIG. 3 is an enlarged front elevational view, partly in section, of the spring assembly of the present invention.  
  FIG. 4 is a view taken along line 44 of FIG. 2 showing the coil spring loaded upon the fixed upper guard with one end of the spring externally disposed.  
  FIG. 5 is a side elevational view showing the external end of the spring in dotted line representation after it has been cammed upon the rim of the lower guard, and in solid line representation after it was in final assembled position within the notch.  
  FIG. 6 is a perspective view of the improved spring assembly of the present invention.  
 DESCRIPTION OF THE INVENTION In the illustrated embodiment of the invention, a circular saw 10 is shown in FIG. 1, having a housing 12 in which is mounted a conventional universal motor (not shown). The drive pinion (not shown) of the motor is suitably connected to rotatea saw blade 14 about a fixed axis 16.  
  The housing 12 carries a front handle 18 and a rear handle, 20, as shown in FIG. 1. A trigger actuated switch 22 is mounted adjacent to the rear handle 20 so that when the operator depressed switch 22, the motor, and consequently the saw blade 14, will be activated in the usual manner.  
  An upper stationary or fixed guard 24 illustrated best in FIG. 1, is formed at the blade side of the housing 12 to surround the upper portion of the saw blade 14. Viewing the circular saw 10 in the position shown in FIG. I, the rotation of the saw blade 14 during cutting will be counterclockwise. A sawdust outlet 26 is formed in the upper right-hand corner of the guard 24 to permit ejection of the sawdust, and has a hood 28 to prevent the sawdust from being blown upwardly in the direction of the operator.  
  A boss 30 shown in FIGS. 2, 4 and 6 is formed on the outer face of the upper guard 24 intermediate the front and rear thereof. The boss 30 has an inner hub 32 which has a central tapped hole 34 defining an axis 36. A groove 37 is formed in the outer circumference of the hub 32 between the hub 32 and the boss 30. The hub 32 is slabbed as at 38 to form a shoulder 40 adjacent thereto. An annular rim 42 is formed on the outer circumference of the boss 30 and has a slightly smaller diameter then the boss 30 to define annular shoulder 44. A slot 46 is formed through the rim 42 with an inner notch 48 formed on the inner side of the slot 46.  
  A coil spring 50 shown best in FIGS. 2 and 6 is disposed in the groove 37 with an inwardly turned end 52 engaging the shoulder 40 and an outwardly turned hook end 54 disposed in the slot 46 to be engaged in the notch 48 in the rim 42 after the coil spring has been wounded from an unwound initial position representative by the dotted end 54 of FIGS. 2 and 6. In the solid line position, the spring 50 has been connected to the fixed upper guard 24 and the blade guard assembly, designated generally 56, is now ready for the next step of the assembly procedure.  
  A lower guard 58 has a boss 60 with an internal hub 62 having a central aperture through which a-shoulder screw 64 will extend to threadably engage the hole 34 and pivotally mount the lower guard 58 to the upper guard 24, where by the lower guard 58 will be telescoped externally of the fixed upper guard 24 as illustrated in FIG. 1 by-the dotted line representation of the lower guard 58 upon introduction of the work, and thus pivot above the axis 36. Arim 66 is formed at the upper end of the lower guard about the hub 62 and defines the outer circumference of the boss 60 whereby the groove 68 is defines between the walls of the rim 66 and the hub 62. In assembly position a hollow chamber 70 will be formed by the corresponding grooves 37 and 68 and into which chamber the coil spring 50 reposes. The lower guard 58 as shown in FIG. 1 substantially encloses the lower portion of the saw blade 14.  
  The rim 66 of the lower guard 58 has a section of reduced width to define a cam surface 72 which terminate in a slotted opening 74. The lower end of the cam surface 72 is notched, as at 76. The hub 62 is annular with a flat upper surface similar to the flat upper surface of the hub 32. Each of the hubs 32 and 62 are of substantial equal diameter so that on assembly of the guards 24 and 58 the hub 62 will be in fixed position to the shoulder 40 to prevent removal of the inner end 52 of the spring from engagement with the shoulder 40. The inner diameter of the rim 66 is sufficiently large to just fit about the outer circumference of the rim 42 and clear of the shoulder 44, is best seen in FIG. 5. Clearance of lower guard 58 and upper guard 24 is determined by shoulder screw 64 and guard surfaces 32 and 62 as shown on FIG. 6.  
  Prior to the assembly of the lower guard 58 the spring 50 is wound within the boss 30 whereby its ends 52 and 54 will be held by the shoulder 40 and the rim 42, respectively. The hook end 54 is disposed in the notch 48 which is adjacent the shoulder 44 as seen in FIGS. 2, 3 and 4.  
  When the lower guard 58 is connected to the upper guard 24 by threading the shoulder screw 64 into the tapped hole 34 the hub 62 will cover the slab 38 of the hub 32 to entrap the straight end 52 upon the shoulder 40 and prevent its accidental removable therefrom. In the assembly position of the lower guard 58 the slots 74 and 46 will be aligned so as to place the cam surface 72 in superposition to the hook end 54 of the coil spring 50, as illustrated in FIG. 3. As the shoulder screw 54 is tightened the boss 60 will be increasingly urged upon the boss 30 so as to force the end 54 of the spring 50 upon the cam surface 72. The cam surface is sufficiently narrow so as to permit the normal spring action to urge the spring upon said cam surface 72. Once the shoulder screw 64 has been completely tightened the lower guard 58 will be completely seated above the rim shoulder 44 as shown in FIG. 5, wherein the initial position of the end 54 of the spring 50 is shown in dotted line representation with the end 54 still in the notch 48. Thereafter the assembly will be complete by the assembler using an implement or screwdriver to shift the end of the spring from the notch 48 of the upper guard 24 to the notch 76 of the lower guard 58. This acts to lock one end of the spring on the lower guard 58 while the other end of the spring is held by the fixed guard 24. Accordingly any movement of the lower guard as it swings open to permit the work-piece to pass in cutting engagement with the saw 10, thus causing the spring 50 to be wound tighter and to bias the lower guard 58 to return to its normally closed position illustrative in FIG. 1 upon removable of the work-piece. The left side 78 of the lower guard 58 as viewed in FIG. 1 has a flat upper surface 80 which acts as a stop by engaging the left side 82 to prevent further counterclockwise movement of the lower guard 58 in the normally closed position represented by the solid line representation thereof. The open position of the lower guard is illustrated in FIG. 1 by the dotted line representation of the lower guard 58 showing the same to be raised almost vertically.  
  If an alternate procedure is desired for assembling the lower guard 58 to the upper guard 24, then the cam surface 72 may be manually pressed, along with the boss 60, upon boss 30 to cause the hook end 54 of the spring 50 to climb upon the surface 72 and thereafter the assembler will tighten the shoulder screw 64. To complete the assembly the assembler will transfer the end 54 of the spring by use of a screwdriver or the like and push it from the notch 48 to notch 76 of the lower guard 58.  
  Whenever it is desired to remove the lower guard 58 the disassembly maybe made after the hook end 54 is remove from the notch 76 and transfered to the notch 48. Thereafter removing of the shoulder screw 64 will permit removing of the lower guard 58. In this way the coil spring 50 remains loaded upon the boss 30 and ready for reassembly of the lower guard 58 to the circular saw 10.  
  It will be understood that the various changes in the details, materials, arrangement of parts of operating conditions which have been here and describe and illustrative in order to explain the nature of the invention maybe made by those skilled in the art within the principles and scope of the invention.  
  Having thus set forth the nature of the invention, what is claimed herein is:  
 1. A portable electric hand saw comprising:  
 a. a housing,  
 b. a motor mounted in the housing,  
 c. a drive spindle journaled in the housing and operatively connected to be rotated by the motor,  
 d. a circular saw blade mounted on the drive spindle,  
 e. a fixed guard formed on the housing to enclose the top portion of the circular saw blade,  
 f. a boss formed on the fixed guard,  
 g. a hub is formed on the boss,  
 h. a shoulder formed on the hub,  
 i. a rim formed on the boss,  
 j. a slot formed in the rim,  
 k. a spring means carried by the boss in coiled condition, with one end being held on the shoulder and the other end being held in the rim slot,  
 1. a lower guard adapted to be pivotally connected at the boss of the fixed guard to normally enclose the bottom portion of the circular saw blade and on operation of the saw on a workpiece the lower guard to pivot to expose the saw blade,  
 m. a cam surface formed on the lower guard to engage the rim of the boss of the fixed guard at the location of said other end of the spring means, and  
 n. connecting means to pivotally connect the lower guard to the fixed guard and to force the said other end of the spring means upon the cam surface of the lower guard to remove the said other end of the spring means from the rim slot whereby said one end of the spring would be held by the fixed guard and the said other end of the spring will be held by the lower guard so that on pivoting of the lower guard the spring will be increasingly wound to bias the lower guard to return to its normal position whenever the saw is removed from the workpiece.  
 2. The combination claimed in claim 1 wherein:  
 a. a notch formed on the rim at the slot to hold the end of the spring and prevent its accidential removal from the slot prior to lower guard being connected for the end of the spring connected to the shoulder being turned inwardly, and  
 b. the end of the spring disposed in the rim slot being turn outwardly.  
 3. The combination claimed in claim 2 wherein:  
 a. a rim formed on the lower guard at the upper end thereof,  
 b. the cam surface formed on the rim, and  
 c. a chamber means formed between the adjacent rims to house the spring means.  
  4. A blade guard assembly for a portable circular saw having a housing in which a circular saw blade is mounted for rotation on operation of the saw comprismg:  
 a. a fixed guard formed on the housing to enclose the top portion of the circular saw blade,  
  a boss formed on the fixed guard including an internal hub and an external rim,  
 a coil spring disposed in the boss with its inner end held by the hub and its outer end held by the rim, a lower guard having a cam surface and which guard is adapted to be pivotally connected to the fixed guard, and  
  a screw means pivotally connecting the lower guard to the fixed guard whereby forcing of the cam surface to engage the end of the spring held by the rim will cause the end of the spring to seat upon the cam surface out of engagement with the rim so that one end of the spring will be held at the fixed guard and the other end of the spring will be held at the lower guard to permit any movement of the lower guard to tighten the spring and bias the lower guard back to its original position.  
 5. The combination claimed in claim 4 wherein:  
 a. the cam surface is formed on a rim of the lower guard,  
 b. a slot formed on the rim adjacent the cam surface,  
 c. a notch formed at the slot at the lower guard, and  
 d. the end of the spring engaging the rim of the lower guard to be disposed in the notch upon assembly of the lower guard to the fixed guard.  
 6. The combination claimed in claim 5 wherein:  
 a. the rim of the boss having a notch formed therein to receive the end of the spring, and  
 b. the end of the spring being transfered from one notch to the other upon assembly of the lower guard and the fixed guard.