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Publication numberUS2785710 A
Publication typeGrant
Publication dateMar 19, 1957
Filing dateMay 3, 1954
Priority dateMay 3, 1954
Publication numberUS 2785710 A, US 2785710A, US-A-2785710, US2785710 A, US2785710A
InventorsJr Jesse R Mowery
Original AssigneeWalt Inc De
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Automatic brake for power tools
US 2785710 A
Abstract  available in
Images(1)
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Claims  available in
Description  (OCR text may contain errors)

March 19, 1957 J, ow JR 2;785,7l0

AUTOMATIC BRAKE FOR POWER TOOLS Filed may 3. 1954 fawn/vs TOOL ENTOR INV F|G.i JESSE R. MOWERY,JR.

H will.

United States Patent 7 2,785,710 7 AUTOMATIC BRAKE FOR POWER TOOLS Jesse R. Mowery, In, Lancaster, Pa., assignor to De Walt Inc., a corporation of Pennsylvania Application May 3, 1954, Serial No. 427,22i

Claims. (Cl. 143-157) This invention relates to an improved brake for a power saw, particularly a circular power saw.

In many circular power sa-ws, the saw is mounted directly on the motor arbor and operates at a relatively high R. P. M. When the power is turned off, the motor and saw continue to coast, presenting a safety hazard since an operator is apt to be careless when the power is oil". Furthermore, there is a time loss where one must Wait for the blade to stop before making adjustments.

It has accordingly long been recognized that brake means should be provided so that motor and blade may be stopped simultaneously with turning off the power. Accordingly, it is my invention to provide an automatic braking means engaging the circular blade itself.

It is another object of my invention to apply a brake to the blade itself to prevent throw off.

It is a further object of my invention that the brake is always applied when the power is off.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation may be understood by reference to the apparatus embodying my invention and shown in the accompanying drawing in which 1 illustrate a side elevation, partly, in section, of a power driven rotary tool in conjunction with an automatic braking device.

With reference to the drawing, 1 show a motor 1% driving a rotating shaft 12 supporting a woodworking tool such as a saw blade 14 secured thereon. The saw blade guard 16 is secured to the motor by fastening means 18. The guard 16 has the oppositely facing bores 26 formed in its side walls 22. The flange cylinders 24 are secured in bores 20. These cylinders 24 are adapted to hold the spring-loaded pistons 26 which are urged by the compression springs 28 toward the blade or tool 14. A piston shaft 3% protrudes through and slidingly engages a bore 32 formed in the head of each cylinder 24.

There is secured to the bight 4d of guard 16 a doubleacting solenoid or electromagnet 42 having armature plungers 44. When solenoid 42 is activated, the plungers 44 retract longitudinally toward each other into the solenoid. A lever 34 pivotally fulcrumed on lugs 36 secured to guard 16 connects the ends of plungers 44 to the outw wardly extending ends of piston shafts 39.

In operation, the solenoid 42 is connected across the terminals 11 of motor 14 so as to be energized when switch 13, connected in series between power lines and motor 19, is closed so as to cause operating current to pass through the motor windings (Fig. 2). When so energized the armature shaft-s 44 are moved toward each other, rocking the lever 34 to move pistons 26 and brake shoes 27 against the thrust of compression springs 28 and away from the tool 14.

When, on the other hand, the power is turned oif, the solenoid 42 is de-energized and the springs 28 thrust pistons 26 and brake shoes 27 against the sides of tool 14 with braking force. By applying the brake to the blade itself I prevent a possible throw off which might occur where a braking force is applied to the motor 10 or motor shaft 12 itself.

Having described a working embodiment of my invention, I claim:

1. In combination with a power-driven rotary cutting tool having an electric motor and cutting tool mounted on the armature shaft of said motor, a guard mounted on said motor and about a portion of said cutting tool, said guard having a cylinder positioned longitudinally parallel to the armature of said motor, a piston movable to and fro in said cylinder, a brake shoe secured on one end of said piston to engage said rotary cutting tool when said piston is moved to the forward end of said cylinder, resilient means to urge said piston to said forward end of said cylinder and into braking contact with said rotary tool, a solenoid mounted on said guard, a fulcrumed lever connecting said solenoid to said piston, said solenoid and said lever being operatively positioned to move said piston against said resilient member and out of braking position when said solenoid is energized and means connecting said solenoid across the terminals of said electric motor to energize said solenoid when said motor is energized whereby said braking means may be moved by said resilient means into braking position when said motor is de-energized and said braking means may be moved out of braking position when said motor is energized.

2. In a cutting mach ne having a motor and a rotary cutting tool, a bracket mounted about the edge of said cutting tool, a pair of oppositely positioned members mounted on said bracket movable to effect equal frictional engagement simultaneously on opposite sides of said cutting tool, resilient means on each of said members operative to move said members into frictional engagement with said cutting tool, a double acting solenoid positioned on said bracket beyond said tool and intermediate said members, and a pair of fulcrumed levers pivoted to said bracket and each engaged at its one end to one end of said double acting solenoid and at its other end to one of said movable members to move said members against said yielding means and out of frictional engagement with said cutting tool.

3. in a cutting machine having a motor and a rotary cutting tool, a bracket mounted about the edge of said cutting tool, a pair of oppositely positioned members mounted on said bracket movable to effect equal frictional engagement simultaneously on opposite sides of said cutting tool, resilient means on each of said members operative to move said members into frictional engagement with said cutting tool, a double acting solenoid positioned on said bracket beyond said tool and intermediate said members, a pair of fulcrumed levers pivoted to said bracket and each engaged at its one end to one end of said double acting solenoid and at its other end to one of said movable members to move said members against said yielding means and out of frictional engagement with said cutting tool, and an electrical conductor operatively connected to said solenoid and to said motor to energize said solenoid when said motor is in operation.

4. in a cutting machine having an electric motor and a rotary cutting tool, a bracket mounted about the edge or" said cutting tool, a pair of oppositely positioned members mounted on said bracket movable to effect equal frictional engagement simultaneously on opposite sides of said cutting tool, resilient means on each of said members operative to move said members into frictional engagement with said cutting tool, a double acting solenoid positioned on said bracket beyond said tool and intermediate said members, a pair of fulcrumed levers pivoted to said bracket and each engaged at its one end to one 5. The combination with a power driven rotary cutting tool having an electric motor and a source of elec:

tnic power, a guardmounted about a portion of said rotary tool, a brake shoe mounted on said guard on each side .of said tool movable from a tool engaging position to a non-engaging position, means to move said brake shoes into tool engaging position, a single electro-magnetic means to move said brake shoes out of tool engaging position, and single switch means operative when plosed to pant es; said, motor and said eleetrotnagnetic means to said source of power whereby said brake shoes are uniformly moved out of engaging position during the operation of said motor and uniformly released into braking position when said switch means is opened to stop said motor.

References Cited the tile of this patent UNITED STATES PATENTS 1,282,483 Steen Oct. 22, 1918 1,811,066 Tannewitz a y a June 23, 193 1 FQREIGN PATENTS 485,143 Germany Nov. 27, 1929

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1168355 *Feb 7, 1910Jan 18, 1916Alvey Ferguson CoElectric bone-saw.
US1282483 *Oct 2, 1916Oct 22, 1918Allis Chalmers Mfg CoCompound band-brake.
US1811066 *Feb 23, 1929Jun 23, 1931Tannewitz Carl ESawing machine
DE485143C *Nov 27, 1929Wilhelm Follender GrossfeldBremsbelagbefestigung
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2801714 *Jun 29, 1956Aug 6, 1957Meadville Res Products CorpHeat insulating friction shoe and piston unit
US2960190 *Feb 24, 1959Nov 15, 1960Molon Motor & Coil CorpMotor brake
US2984268 *Jul 7, 1958May 16, 1961Vuichard George EManually-actuated saw brake
US3103990 *Nov 1, 1960Sep 17, 1963Faye M PiersonHydraulic disc brake
US3124219 *Jan 3, 1961Mar 10, 1964 Disc brake assembly
US3184003 *May 15, 1961May 18, 1965Lambert & Brake CorpBrake structure
US3322240 *Mar 19, 1965May 30, 1967Mallory & Co Inc P RDisc brake for washing machine
US3417843 *Oct 26, 1966Dec 24, 1968Ingersoll Rand CanadaDisc brake for mine hoists
US3703654 *Jun 30, 1971Nov 21, 1972Karubian RalphHand tool with magnetic brake
US4145940 *Jan 26, 1978Mar 27, 1979Woloveke Eugene LBrake apparatus for a motor driven saw blade
US4315371 *Jan 11, 1980Feb 16, 1982Asahi Seimitsu Kabushiki KaishaPreset brake device for line drawing machine, drafting machine or like
US4335514 *Aug 8, 1980Jun 22, 1982Black & Decker Inc.Switch-brake interlock for chain saw
US5253738 *Jul 9, 1991Oct 19, 1993Inventio AgSafety disc brake for lifts
US6092448 *Jan 21, 1999Jul 25, 2000Premark Feg L.L.C.Slicer with staged dynamic braking system
US6813983Jan 16, 2002Nov 9, 2004Sd3, LlcPower saw with improved safety system
US6826988Jan 16, 2002Dec 7, 2004Sd3, LlcMiter saw with improved safety system
US6945148Jan 14, 2002Sep 20, 2005Sd3, LlcMiter saw with improved safety system
US6957601Sep 17, 2001Oct 25, 2005Sd3, LlcTranslation stop for use in power equipment
US6994004Jan 16, 2002Feb 7, 2006Sd3, LlcTable saw with improved safety system
US7000514Jul 25, 2002Feb 21, 2006Sd3, LlcSafety systems for band saws
US7077039Nov 12, 2002Jul 18, 2006Sd3, LlcDetection system for power equipment
US7112018Jan 19, 2005Sep 26, 2006The Boeing CompanyAutomatic position-locking tool carrier apparatus and method
US7197969Sep 13, 2002Apr 3, 2007Sd3, LlcLogic control with test mode for fast-acting safety system
US7231856Jun 13, 2002Jun 19, 2007Sd3, LlcApparatus and method for detecting dangerous conditions in power equipment
US7290472 *Sep 1, 2004Nov 6, 2007Sd3, LlcMiter saw with improved safety system
US7350444 *Aug 13, 2001Apr 1, 2008Sd3, LlcTable saw with improved safety system
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US7481140Apr 15, 2005Jan 27, 2009Sd3, LlcDetection systems for power equipment
US7610836Aug 13, 2001Nov 3, 2009Sd3, LlcReplaceable brake mechanism for power equipment
US7640837Mar 27, 2008Jan 5, 2010Sd3, LlcTable saw with improved safety system
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US7661343Apr 17, 2007Feb 16, 2010Sd3, LlcBrake mechanism for power equipment
US7712403 *Jul 2, 2002May 11, 2010Sd3, LlcActuators for use in fast-acting safety systems
US7908950Jan 4, 2010Mar 22, 2011Sd3Table saw with improved safety system
US7958806Nov 2, 2009Jun 14, 2011Sd3, LlcReplaceable brake mechanism for power equipment
US8011279Dec 17, 2007Sep 6, 2011Sd3, LlcPower equipment with systems to mitigate or prevent injury
US8061246 *Mar 26, 2010Nov 22, 2011Sd3, LlcMiter saw with improved safety system
US8430005 *Nov 21, 2011Apr 30, 2013Sd3, LlcMiter saw with improved safety system
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US20120137848 *Nov 21, 2011Jun 7, 2012Gass Stephen FMiter saw with improved safety system
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DE19750819A1 *Nov 17, 1997May 20, 1999Kocks TechnikTube and long stock cutting machine using powered disc tool
EP0042918A1 *Apr 8, 1981Jan 6, 1982Robert Bosch GmbhHand tool operated by an electric motor
EP0465831A1 *Jun 6, 1991Jan 15, 1992Inventio AgSafety disc brake for elevators
Classifications
U.S. Classification83/68, 188/72.1, 188/59, 83/70, 188/110, 188/171
International ClassificationF16D55/224, B27B5/38, F16D59/02, F16D65/14
Cooperative ClassificationF16D59/02, F16D55/2245, F16D2121/22, B27B5/38
European ClassificationF16D59/02, B27B5/38, F16D55/224B