Safety Retracting Mechanism For The Lower Guard Of A Portable Saw

Abstract

A manually operable actuator is connected to the lower guard retracting linkage by a releasable mechanism. Movement of the actuator causes swinging movement of the lower guard to its open position. Continued swinging movement of the lower guard to its open position as a result of being engaged by the work operates the releasable mechanism to disconnect the actuator from the lower guard, whereby spring means will automatically swing the lower guard to its closed position upon removal of the saw from the work irrespective of the position of the actuator. Return movement of the actuator to its closed position resets the releasable mechanism.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the present invention relates to portable saws of the type having a circular blade, which saws are either electrically or pneumatically powered. Portable saws of this type have a fixed upper blade guard, which may form part of the housing of the saw, and a lower blade guard which is mounted for swinging movement back and forth between open and closed positions, thereby to expose the blade when the saw is to be brought into engagement with the work and to enclose the blade at times when the saw is not in engagement with the work. More particularly, the present invention relates to manually operated mechanism for retracting the lower blade guard of a saw of the type under consideration.

2. The Prior Art

It is known in the prior art to provide a manually operable retracting mechanism for the lower guard of a portable saw. In the interest of safety, this handle is located remotely from the lower guard. Actuation of the handle causes the lower guard to be swung to the open position. The guard is closed by positively moving the actuating handle or by simply releasing the latter whereupon spring means act to swing the lower guard to its closed position.

The principal disadvantage of such a retracting mechanism resides in the fact that the lower guard will remain in the open position exposing the cutting blade unless the actuating handle is released or returned to the closed position. This presents a potentially hazardous situation under some circumstances. For example, a workman using such a tool and losing his balance while standing on a ladder might be distracted to an extent that he would not release his grip on the actuating handle or on the trigger controlling the motor. Obviously, serious injury could result in such an eventuality.

Attempts have been made in the prior art to provide mechanism for automatically returning the lower guard to its closed position. In this regard, reference is made to the structure described in Hampton U.S. Pat. No. 1,900,533. This patent shows a portable saw including linkage connecting the lower guard to the trigger which actuates the motor. If the trigger is held in the fully closed position upon removal of the saw from the work, the lower guard will return to the fully closed position. However, the Hampton structure suffers from a major disadvantage in that the lower guard will open only partially and then snap to the closed position unless the saw is brought into engagement with the work upon initial retraction of the lower guard. As is known to those skilled in the art, when it is desired to make top cuts, for example, the usual practice is to retract the guard and then energize the tool motor prior to bringing the saw into engagement with the work. With the Hampton structure, it would be necessary to retract the lower guard only partially and then bring the tool into engagement with the work prior to energizing the motor. Obviously, such use of the power saw would create a potentially hazardous condition because of kick back resulting from placing the circular blade into contact with the work prior to energization of the tool motor.

SUMMARY AND OBJECTS OF THE INVENTION

The present invention may be summarized as the provision of a new and improved retracting mechanism for a portable power saw, which mechanism permits the lower guard to be swung manually to the open position irrespective of whether or not the work is engaged and which mechanism provides for the automatic closing of the lower blade guard upon removal of the tool from the work irrespective of the position of the actuating handle.

A primary object of the present invention is the provision of a new and improved retracting mechanism for a portable saw, which mechanism embodies significant safety features.

Another object of the present invention is the provision of a retracting mechanism for the lower guard of a portable power saw, which mechanism includes an actuator connected with the lower guard linkage by releasable means, the releasable means being operated to disconnect the lower blade guard from the actuator in response to movement of the lower guard as the result of the latter engaging the work.

Still another object of the present invention is the provision of a lower guard retracting mechanism according to the foregoing objects, wherein the releasable means are reset to connect the lower guard linkage with the actuator in response to movement of the latter to its closed position.

Yet another object of the present invention is the provision of a lower guard retracting mechanism according to the foregoing objects, such mechanism providing for the manual retraction of the lower guard irrespective of whether or not the saw is brought into engagement with the work.

These and other objects and advantages of the present invention will become apparent from the following specification disclosing a preferred embodiment shown in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portable power saw embodying the present invention;

FIG. 2 is an enlarged, partial side elevation and partial section of the saw of FIG. 1, with only the parts constituting the present invention being illustrated;

FIG. 3 is an enlarged section taken along the line 3--3 of FIG. 2;

FIG. 4 is a partial elevation and section similar to FIG. 2, and showing the arrangement of the parts with the lower guard in its partially retracted position;

FIG. 5 is an enlarged section taken along the line 5--5 of FIG. 4;

FIG. 6 is a partial elevation and section similar to FIG. 4, and showing the arrangement of the parts with the lower guard in its fully retracted position as the result of being engaged by the work;

FIG. 7 is an enlarged section taken along the line 7--7 of FIG. 6;

FIG. 8 is a partial elevation and section similar to FIG. 6, and showing the arrangement of the parts after the lower guard has automatically swung to its closed position as the result of the tool being removed from the work;

FIG. 9 is a section taken along the line 9--9 of FIG. 3; and

FIG. 10 is an end view taken along the line 10--10 of FIG. 9.

DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention may be advantageously incorporated in a portable electric saw of the type illustrated in FIG. 1 and generally designated 10. It will be understood that the present invention has equal applicability with saws having other sources of power, such as pneumatic motors, for example.

The power saw 10 includes a housing 11 having a fixed upper guard, generally designated 12. As noted in FIG. 3, the upper guard has an inner wall 14 and an outer wall 15 defining a space 16 therebetween for receiving a circular saw blade 18. This saw blade is mounted on a drive shaft 19 in a manner well known to those skilled in the art.

The saw housing 11 further includes a handle 20, which handle mounts a trigger 21; depression of this trigger causes energization of the electric motor thereby to rotate the circular saw blade 18. The saw 10 also includes an adjustable base or platform 22; this base is preferably of the construction disclosed and claimed in the pending application of Frank A. Kaman et al., Ser. No. 206,639, filed Dec. 10, 1971, and assigned to the assignee of the present application.

A lower blade guard, generally designated 24, is mounted for swinging movement about an annular bearing 25, which bearing is coaxial with the drive shaft 19. A preferred mounting for such a lower blade guard and an associated kerf guide is disclosed and claimed in the pending application of Ronald E. Gronke et al., Ser. No. 58,530, filed July 27, 1970, and assigned to the assignee of the present application. The lower blade guard includes an inner wall 26, an outer, arcuate wall 27, such walls being integral with a wall 28. It will be understood that the lower blade guard 24 is received within the upper blade guard 12 when the former is swung clockwise to its open position.

A coil spring 30 has one end thereof secured to the inner wall 26 of the lower guard at a position adjacent the hub 25. The other end of this spring is suitably secured to a formation (not shown) on the inside of the upper blade guard 12. It will be understood that the spring 30 constantly urges the lower blade guard 24 in a counterclockwise direction toward its closed position.

A first link 31 has one end thereof pivotally connected with the wall 26 of the lower blade guard, as by a pin 33. This end of the link is curved so as to clear the hub 25 and to engage the lower blade guard at a location providing a mechanical advantage for swinging the lower guard to its open position. The other end of the link 31 is pivotally connected to the distal end of another link 34, as by means of a pin 35. The other end of the link 34 is fixed to a shaft 37, which shaft is journaled in aligned bores 38, 39 coaxially formed in the respective walls 14 and 15 of the upper blade guard. It will be understood that the link 34 and the shaft 37 are secured together for movement in unison.

The shaft 37 includes an enlarged portion 40. A collar 42 is mounted on the shaft portion 40 both for rotation and axial movement relative thereto. The collar 42 is received within a recess formed by an annular wall 11a, the latter being part of the housing of the power tool.

A manually operable actuator 44 has a bore 45 formed in one end thereof, which bore rotatably engages the shaft portion 40. The shaft includes a reduced-in-diameter portion 46, which portion mounts a C-type washer 47 for retaining the actuator 44 in place. The actuator 44 includes an annular space 48 receiving an O-ring 49 to prevent the entry of sawdust and other foreign matter into the annular space defined by the outer surface of the housing wall 11a and an annular surface 50 of the actuator.

The portion of the actuator forming the bore 45 includes an annular recess 52 defining a space to receive one end of a coil spring 53. The other end of this spring is received within an annular recess 55 formed in the outer surface of the collar 42. It will be understood that the spring 53 acts to urge the collar 42 axially to the right as viewed in FIGS. 3, 5 and 7. At this time it should be mentioned that suitable means (not shown), such as a spline-type connection, are provided to permit the collar 42 to move axially of the shaft portion 40 relative to the actuator 44 and to cause the collar 42 to rotate in response to swinging movement of the actuator.

As best seen in FIG. 9, the shaft portion 40 includes a diametrically disposed, blind bore 57 receiving a coil spring 58 and a pin 59. The spring 58 acts to urge the pin 59 outwardly of the bore 57 for normally maintaining the rounded outer end of the pin 59 received within a recess 60 formed in the inner surface of the collar 42. This recess includes a wall surface 60a shaped such that when the same engages the pin 59 in response to counterclockwise rotation (FIG. 9) of the collar, corresponding rotation will be imparted to the shaft 37. This recess also includes a camming wall 60b for camming the pin 59 inwardly of the bore 57 when the shaft 37 is rotated counterclockwise (FIG. 9) relative to the collar 42.

As noted in FIGS. 9 and 10, the collar 42 rotates an annular surface 61 interrupted by a cam formation, the latter being defined by an included wall 62 and a wall 63. The wall 63 is contained in a plane perpendicular to the logitudinal central axis of the collar. As will be explained hereinbelow, this cam formation is adapted to be engaged by the outer end of a pin 64, which pin is fixedly mounted within a recess 65 formed in the saw housing adjacent the upper blade guard 12.

The actuator 44 includes an integral abutment 67. This abutment is adapted to engage a stop formation 68 to limit swinging movement of the actuator in a counterclockwise direction. The stop 68 may be a formation integral with the inner wall 14 of the upper guard 12.

The operation of the lower guard retracting mechanism of the present invention is as follows:

FIGS. 2 and 3 illustrate the arrangement of the parts when the lower guard 24 is in its fully closed position and when the actuator 44 is in its closed position. With the parts so arranged, the pin 59 will be received within the recess 60.

Assume that the actuator 44 is rotated counterclockwise for retracting the lower guard. Such movement of the actuator causes corresponding rotation of the collar 42. This rotation of the collar will rotate the shaft portion 40 in the same direction as the wall 60a of the recess 60 engages the pin 59 to transfer rotation from the collar 42 to the shaft portion 40. It is apparent that the shaft 37 will be rotated for swinging the lower guard 24 to its open position by the action of the links 31, 34.

FIGS. 4 and 5 illustrate the arrangement of parts when the actuator 44 has been moved to its fully open position. Rotation of the actuator is arrested due to engagement of the abutment 67 with the stop 68.

As the rotating saw blade 18 moves through the work, the lower guard 24 will also come into engagement with the work. Such engagement between the work and the lower blade guard 24 will result in further swinging movement of the former as illustrated in FIG. 6. This additional movement of the lower guard will cause rotation of the shaft portion 40 relative to the collar 42. Such rotation will cause the pin 59 to be brought into engagement with the camming wall 60b, whereupon the pin 59 will be cammed or forced inwardly of the bore 57. As soon as the pin 59 is forced out of the recess 60, the spring 53 will act to shift the collar 42 axially to the right (FIG. 7) whereupon the annular formation 61 of the collar will be brought into abutting engagement with the pin 64. It is apparent that the collar 42 is now disconnected or released from the shaft portion 40. Accordingly, if the saw is removed from the work, the spring 30 will act automatically to swing the lower guard 24 to the fully closed position even if the actuator 44 is held in its fully open position.

Assume that the saw has been removed from the work with the actuator 44 held in the open position. As the operator moves the actuator 44 to the closed position (of course, spring means may be provided to return the actuator upon release of the same), the collar 42 will be rotated thereby bringing the inclined cam surface 62 into engagement with the pin 64. The inclined camming wall 62 acting on the pin 64 will act to shift the collar 42 axially against the force of the spring 53 for aligning the recess 60 axially of the shaft portion 40 for receiving the pin 59. This return movement of the actuator 44 will also result in rotating the collar 42 for receiving the pin 59. Therefore, when the actuator 44 is returned to its closed position, the pin 59 will again be forced into the recess 60 under the influence of the spring 58 thereby repositioning the mechanism to connect the actuator 44 with the lower guard 24.

As mentioned above, spring means may be provided to return the actuator 44 to the closed position upon release of the same. This may be achieved by fashioning the spring 53 in the manner of a torsion spring and securing opposite ends thereof to the actuator 44 and upper guard 12 (or housing portion 11a), respectively.

It should be apparent that the present invention provides a new and improved lower guard retracting mechanism having important safety features. The releasable mechanism between the actuator 44 and the lower blade guard 24 is actuated in response to engagement between the lower guard and the work. Should the saw be removed from the work at any time thereafter, the lower guard 24 will automatically swing to its closed position irrespective of the position of the actuator 44.

Claims

We claim:

1. A guard retracting mechanism for a portable saw of the type having a circular blade, a fixed upper guard and a lower guard mounted for swinging movement back and forth between open and closed positions, said mechanism comprising:

a. an actuator movable back and forth between closed and open positions;

b. a force transmitting assembly connected to said lower guard;

c. spring means for urging said lower guard to its closed position;

d. releasable means connecting said actuator with said force transmitting assembly, which releasable means include force transmitting elements normally interengaged whereby movement of said actuator to its open position causes swinging movement of said lower guard to its open position;

e. said releasable means including cam means for disengaging said elements in response to movement of said lower guard toward its open position independently of said actuator, whereby said spring means is permitted to swing said lower guard to its closed position irrespective of the position of said actuator; and

f. other cam means operable in response to movement of said actuator toward its closed position for engaging said elements.

2. The mechanism according to claim 1 further defined by:

a. said releasable means including a shaft and a collar mounted thereon for both rotation and axial movement relative to the shaft, which shaft has a diametrically disposed bore therein;

b. said actuator being connected with said collar and said shaft being connected with said force transmitting assembly;

c. said collar including a recess having a first wall and a camming wall, the latter forming part of said camming means;

d. a pin received in said bore;

e. second spring means in said bore engaged with said pin normally urging the latter outwardly with one end of the pin received in said recess and engaged with said first wall, which first wall and the engaged surface of said pin constitute said force transmitting elements;

f. third spring means urging said collar in one axial direction and being adapted to shift said collar in said one direction when said pin is forced from said recess by the action of said camming wall resulting from rotation of said shaft relative to said collar; and

g. second camming means for shifting said collar in its other direction in response to movement of said actuator toward its closed position.

3. The mechanism according to claim 2 wherein said force transmitting assembly includes linkage connecting said shaft with said lower guard.

4. A guard retracting mechanism for a portable saw of the type having a circular blade, a fixed upper guard and a lower guard mounted for swinging movement back and forth between open and closed positions, said mechanism comprising:

a. an actuator mounted on the saw housing for movement back and forth between open and closed positions;

b. spring means urging the lower guard to its closed position;

c. force transmitting means connecting said actuator with said lower guard such that movement of the former toward its open position causes corresponding movement of the lower guard;

d. said force transmitting means including releasable means operable to disconnect said actuator from said lower guard in response to movement of the latter toward its open position independently of the former, whereupon said spring means is permitted to swing said lower guard to its closed position irrespective of the position of said actuator; and

e. reset means operable in response to movement of said actuator toward its closed position for re-establishing the connection between said actuator and said lower guard.

5. A guard retracting mechanism for a portable saw of the type having a circular blade, a fixed upper guard and a lower guard mounted for swinging movement back and forth between open and closed positions, said mechanism comprising:

a. spring means connected with said lower guard for urging the same to its closed position;

b. a shaft;

c. linkage connecting said shaft with said lower guard such that rotation of the former causes swinging movement of the latter;

d. an actuator including a collar mounted on said shaft for rotation and for axial movement relative thereto, which actuator is mounted for swinging movement back and forth between open and closed positions and thereby imparts corresponding rotation to said collar;

e. releasable means connecting said collar with said shaft for rotation in unison such that swinging movement of said actuator to its open position causes corresponding movement of said lower guard;

f. said releasable means including first cam means for disconnecting said collar from said shaft in response to rotation of the latter relative to the former; and

g. second cam means for re-establishing the connection between said collar and said shaft in response to rotation of the former relative to the latter.

6. The mechanism according to claim 5 further defined by:

a. said releasable means being defined by a pin yieldably mounted in a bore formed in said shaft and by a recess formed in said collar, one end of the pin being normally received in said recess;

b. said first cam means including a camming wall forming part of said recess, said camming wall being adapted to force said pin out of said recess in response to movement of the shaft relative to the collar;

c. said releasable means also including other spring means for shifting the collar axially in one direction upon disengagement of said pin from said recess; and

d. said second cam means including a cam and cam follower for shifting said collar axially in the other direction.

7. The mechanism according to claim 6 wherein said collar is mounted for said axial movement relative to said actuator, said other spring means being interposed between said actuator and said collar.