Device to control speed and torque of line return in spring drive device

Abstract

A governing device including a return spring and a spool upon which a line or cord is wound, includes on a fixed housing element a magnetic or a conductive material and on the rotating portion of the spool respectively either a magnet or a layer of conductive material is provided. When the line or cord is retracted by the spring, a hysteresis loop is formed in the conductive material by the magnet causing an eddy current which slows down the rate of retraction of the line to provide safety in the rate of return of the line or cord.

Description

I FIELD OF THE INVENTION

[0001] This invention relates to a power spring driven retractable line or cord device having eddy current governor control of line or cord return for safety.

II BACKGROUND OF THE INVENTION

[0002] In U.S. Pat. 5,920,997 granted Jul. 13, 1999 an automatically retractable chalk line device is disclosed including a power spring 30 which engages a gear 44 which in turn is in driving engagement with a spool 90 which winds a chalk line 100 having a chalk line end portion 106.

[0003] While this chalk line device operates very satisfactorily, a problem has occurred concerning the retraction of the chalk line device. The power spring 30 generates such a large force that the chalk line 100 is in some circumstances retracted so rapidly as to cause danger to the operator during the retraction operation.

[0004] U.S. Pat. No. 4,116,397 discloses a drive arrangement for yarn storage and dispensing units including a winding member 1 rotably mounted on a fixed shaft 3 by a bearing 2. Winding member 1 comprises the rotor of a drive motor, and its inner wall carries a steel spring 13 having permanent magnetic or hysteresis characteristics. This hysteresis ring rotates about a laminar stator core 14 which carries the motor coil 15. In this patent in order to prevent deviations from the ideal characteristic of a hysteresis motor from influencing the length of the yarn coil wound upon the winding member of the yarn storage and dispensing unit, the hysteresis motor used according to the invention for driving the storage and dispensing unit is provided with means for suppressing eddy currents. This eddy currents suppression comprises a hysteresis ring, the axial width of which is restricted to the axial length of the laminated stator core of the motor. This reduces the eddy currents.

[0005] In accordance with the present invention, the eddy current feature is used to control the speed of retraction of a line or cord to maintain the return speed of the line or cord within safe limits. Thus the teachings of the '397 are in opposite to the present invention of utilizing eddy currents to control the rate of retraction of the device.

[0006] U.S. Pat. No. 4,602,360 is directed to sound production devices with magnetic governors for use in toys. The governor mechanism 40 includes rotors 42 and 44 and first and second magnets 46 and 48. The return force of spring 20 urges rotor 42 in a counterclockwise direction as viewed in FIG. 5, at which point elements 42B and 42C are in the dotted positions in radial alignment with the sub-openings 56A and 56C and rotors 42 and 44 then turn in unison causing the magnets 46 and 48 to slide radially outwardly with sub-openings 56A and 58A sliding outward in engagement with elements 42B and 42C until friction pads 50 and 52 come in contact with the inner perifery of housing portion 11B causing a braking action to regulate the speed of the mechanism. However there is no involvement of eddy currents as called for in the present invention to effect the return control mechanism. Thus U.S. Pat. No. 4,602,360 acts on a different principle in effecting its braking action.

[0007] In U.S. Pat. No. 4,779,814 granted Oct. 25, 1988, a backlash prevention device for a fishing reel is provided wherein a spool is connected to a non-magnetic electroconductive member associated with break magnets that generate eddy currents in the non-magnetic electroconductive member to provide a breaking force on the spool. The backlash prevention device includes movable magnets for varying the breaking force to provide a breaking force on the spool. However, this patent is not directed to a spring drive system.

III SUMMARY OF THE INVENTION

[0008] A. Objects

[0009] The terms “line” or “cord” as used herein are to be construed as a string, cord, ribbon, band or similar mechanical element capable of being wound around a spool, drum or similar device.

[0010] One object of the present invention is to provide an arrangement for governing the speed of a spring drive line or cord retraction device.

[0011] Another object of the present invention is to utilize the eddy current principle in governing rotational velocity and torque in a sring drive device.

[0012] Another object of the present invention is to utilize the eddy current principle in governing the speed of retraction in a spring drive device.

[0013] Another object of the present invention is to provide an arrangement for governing the speed of the return of the a line or cord activated by a spring motor after the line or cord has been extended to effect a measurement.

[0014] Another object of the present invention is to utilize the eddy current principle in achieving the control of the rate of retraction of a chalk line device.

[0015] In accordance with the present invention, a governing device including a return spring and a spool upon which a line or cord is wound, includes on a fixed housing a magnetic or a conductive material is provided and on the rotating portion of the spool respectively either a layer of conductive material or a magnet is provided. When the line or cord is retracted by the spring, a hysteresis loop is formed in the conductive material by the magnet causing an eddy current which provides a force opposite to the angular motion which slows down the rate of retraction of the line or cord to provide safety in the rate of return of the line or cord.

IV. THE DRAWINGS

[0016] FIG. 1 is an exploded perspective view of an automatically retractable chalk line device in U.S. Pat. No. 5,920,997.

[0017] FIG. 2 is a schematic perspective view of the external housing of the chalk line device shown in FIG. 1.

[0018] FIG. 3 is a horizontal sectional view looking in the direction of the arrows along line 3-3 in FIG. 2.

[0019] FIG. 4 is a vertical sectional view looking in the direction of the arrows along line 4-4 in FIG. 2.

[0020] FIG. 5A is a partial vertical sectional view illustrating the brake activating mechanism with the brake in the activated position.

[0021] FIG. 5B is a view similar to FIG. 5A with the brake in the deactivated position.

[0022] FIG. 6A is partial horizontal sectional view illustrating the movable plate to allow insertion of chalk into the assembly.

[0023] FIG. 6B is a vertical sectional view looking in the direction of the arrows along the line 68-68 in FIG. 6A illustrating details of the movable plate assembly.

[0024] FIG. 7 is a horizontal sectional view looking in the direction of the arrows along the line 7-7 in FIG. 8.

[0025] FIG. 8 is a vertical sectional view looking in the direction of the arrows along the line 4-4 in FIG. 2, with the chalk line removed.

[0026] FIG. 9 is a horizontal sectional view looking in the direction of the arrows along the line 9-9 in FIG. 11.

[0027] FIG. 10 is a sectional view looking in the direction of the arrows along the line 10-10 in FIG. 9.

[0028] FIG. 11 is a sectional view looking in the direction of the arrows along the line 11-11 in FIG. 12.

[0029] FIG. 12 is a sectional view looking in the direction of the arrows along the line 12-12 in FIG. 11

[0030] FIG. 13A is a sectional view looking in the direction of the arrows along line 13-13 in FIG. 14.

[0031] FIG. 13B is a sectional view looking in the direction of the arrows along the line 13-13 in FIG. 14.

[0032] FIG. 13C is a sectional view looking in the direction of the arrows along the line 13-13 in FIG. 14.

[0033] FIG. 14 is a sectional view looking in the direction of the arrows along line 14-14 in FIGS. 13A and 13B.

V. DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] The automatically retractable chalk line device of U.S. Pat. No. 5,920,997 is indicated in the drawings generally at 1. The assembly includes a housing 2, including a housing body portion 3, having a top surface 4, and a vertical wall 5. The housing includes a spring enclosure portion 6, including an arcuate member 7, a bottom plate 8, including vertical portions 9 and 10 is integral with the arcuate portion 7 by means of fasteners or integral molding.

[0035] The housing includes a top assembly 10, including a top member 11, having downwardly extending sides 12. A spool retainer portion 14, includes an extension of body portion 3 indicated at 16, a bottom plate 18, which supports the spool including shoulder 20. Mechanical fasteners 22 hold the assembly together through openings 23, illustrated in FIG. 3.

[0036] A chalk line discharge portion 24 includes downwardly and inwardly extending walls 26 and 28 terminating in a vertical wall 29, having an opening 29a through which the chalk line exits.

[0037] A power spring 30 includes a plurality of coils 32 and a housing body portion 3 includes a coil retainer 33. The spring includes an inner end 34 which engages a spring shaft, 36 which extends vertically through the spring 30 and engages a first gear assembly indicated generally at 40. A spring support plate 37 a spring cover 38 are located between the spring and the gear assembly 40 (FIG. 1).

[0038] The gear assembly 40 includes a large gear, 41 having teeth 42, which engage a small gear 43, having teeth 44 (FIG. 1). Shaft 36 mechanically engages large gear 41 through non-round projection, 39 on the shaft and non-round opening 45 on the large gear. Bottom plate 8 holds the gear assembly in place. The difference in diameter between large gear 41 and small gear 43 provides a substantial mechanical advantage.

[0039] Small gear 43 includes a non-round opening 46 which receives a shaft 50, having a non-round end portion 51. Vertical shaft 50 includes a nonround upper end portion 53, which engages a non-round opening 61, in gear assembly 60. Non-round opening 61 is located within a large gear 63 which has teeth 65 which engages small gear 64 having teeth 67.

[0040] A brake assembly 70 is provided including a brake pad 72 which in engaged position engages the large gear surface 68 and in disengaged position is spaced therefrom as illustrated in FIGS. 1 and 5B. The brake pad 72 is integrally connected to top cover 11 and is nonmoveable. Gear assembly 60 is provided with limited vertical movement on shaft 50 to provide the relative movement between brake pad 72 and gear 63.

[0041] A brake activating assembly 73 includes a horizontally movable plate 74 which is movable over a cam surface 75 located on horizontal housing surface 76. Plate 74 includes an opening 77 for passage of spool shaft 92 to engage small gear 64. A pair of resilient springs 78 held in place with rectangular wall housing 79 resiliently bias a release button 80 into a position wherein button release projection 82 engages an opening 83 in plate 74 to maintain the plate 74 and the gear 63 in the engaged position with disc 72.

[0042] The spool assembly indicated generally at 90 includes a spool shaft 92 extending upwardly from an upper plate 94. A spool core 95 extends between upper plate 94 and bottom plate 96 to hold the chalk line in place. Upper plate 94 and bottom plate 96 are held in place against formed shoulders 97 and 98. The chalk line 100 passes through chalk line retainers 102 and 104 and housing opening 103, and includes a knot 105 an anchor 106 at its end.

[0043] The housing 2 includes an opening 110 as illustrated in FIG. 6A for insertion of chalk.

[0044] A plate 112 is mounted for movement back and forth to open and close this opening. The plate includes a projection 114 for moving the plate back and forth. The plate is also provided with another projection 116 which engages a slot 118 in the housing to maintain the plate in the closed position.

[0045] To open the housing to receive chalk the projection 114 is grasped and sufficient force is provided to overcome the interference fit with the projection 116 and the slot 118 and plate 112 is moved from right to left in FIG. 6A. FIG. 5A shows the brake assembly 70 in the brake engaged position in which the brake pad 72 is an engagement with the surface 68 on the large gear 61. In this position the manual release button 80 is in the position shown with the projection 82 located within the plate slot 83.

[0046] To release the brake, the manual release button 80 is rotated with the grip portion 85 in a clockwise direction against the bias of the spring 78. This forces the plate 74 from right to left so that the slot 77 is located upon the cam 75 and thereby allowing clearance between the brake pad 72 and the large gear surface 68.

[0047] In the operation of the automatic retractable chalk line device, to fill the device with chalk, the plate 112 is moved from right to left in FIG. 6A and the chalk is then poured into the housing through opening 110 so as it will engage the chalk line 100 as the chalk line exits the housing. After filling the housing the plate is moved from left to right in FIG. 6A until the projection 116 engages the slot 118 to hold the plate in the closed position. The anchor 106 is connected to a suitable anchor position in line with the chalk line to be prepared. The operator then moves from right to left in FIGS. 1 to 4 and in so doing the chalk line is rotated about the core 95 to extend the chalk line. In so doing power coil spring 30 is tensioned.

[0048] When the chalk line has been removed sufficiently to draw the line for the distance desired, the line is snapped in a manner similar to engaging a string instrument and the chalk forms the desired line.

[0049] To retract the line, the manual release button 80 is pivoted in a clockwise direction by the operator engaging the grip portion 85 and the plate 74 moves from right to left in FIGS. 5A and 5B whereby the cam surface 75 is located within the slot 77 of the plate, providing clearance between the brake pad 72 and the large gear 61. The power coil spring 30 is then free to unwind within the housing. This results in shaft 36 driving large gear 41 and small gear 44. Small gear 44 in turn drives shaft 53 and large gear 61. Large gear 61 drives small gear 64. Small gear 64 in-turn drives the spool shaft 94, which causes the chalk line 100 to be rotated back into the loaded position.

[0050] As an example, the power coil spring has a diameter of 3 inches, and is {fraction (1/64)}th inch in thickness. Large gears 41 and 61 conveniently have a diameter of 2 and {fraction (9/16)} inches and small gears 44 and 64 conveniently have a diameter of {fraction (15/16)} inch.

[0051] In accordance with the present invention, as shown in FIGS. 10-12, the rate of retraction of a line or cord is reduced by the eddy currect speed governor 200. The governor includes a housing 210 enclosing a power spring 230 and an arbor 232 extending into upper and lower housing portions 212 and 214. The spool assembly 240 has a cylindrical body portion 242 and upper and lower flanges 244 and 246 which retain line 250 in place. The line passes through a retainer 280 during winding and unwinding. At least one mechanical fastener 290 holds the housing in the assembled position.

[0052] A magnet assembly 260 includes north and south portions 262 and 264 which generate magnetic field lines 266 as shown in FIG. 10. A conductive disc 270 made of conductive material including but not limited to copper, aluminium, silver, gold, steel, platinum is bonded or attached to rotatable flange 246. As the spool rotates the magnetic field lines generate eddy currents in conductive disc 270 which act in a direction to oppose the winding power of spring 230, and the motion of the spool.

[0053] In FIGS. 13A and 13B the gear assembly 40 described hereinabove is provided.

[0054] In FIG. 13A the spool assembly 240″ includes upper and lower magnet assemblies 260a, 260b which generate magnetic fields respectively in upper and lower conductive plates 270a and 270b to oppose rotation and slow down the rate of retraction.

[0055] In FIG. 13B the spool assembly 240″ includes only lower magnet assembly 260c which generates magnetic fields in lower conductive plate 270c to oppose rotation and slow down the rate of retraction.

[0056] In FIG. 13C the spool assembly 240′″ includes two independent lower magnet assemblies, 260d and 260e with conductive plate 270d located between. Conductive plate 270d, having non-round opening, 271 mechanically engages non-round projection, 290 of spool assembly 240′″. Magnet 260d is bonded or attached to bottom plate 18a. Magnet 260e is bonded or attached to circular cap 280. Circular cap 280, having retainer groove, 282 snaps into retainer lip 300 of bottom plate 18a, allowing said circular cap 280 to rotate frictionally in relation to bottom plate 18a. Thumb tabs 281, outside knurl or other method is provide for a means of manually rotating circular cap 280.

[0057] Manual rotation of circular cap 280, containing magnet 260e, in relation to magnet 260d, causes the magnetic poles 262 and 264, in FIG. 10, of the opposing magnets, to align or misalign in relation with each other. This alignment varies the strength of magnetic fields acting upon the conductive plate 270d, therefore varying the opposing force of rotation and allowing for a manually adjustable slow down rate of retraction.

[0058] The advantage of the present invention is apparent. The line or cord is fully retractable through the action of the power coil spring and the retraction is much safer because the rate of retraction is slowed down to a safe speed by the eddy current producing assemblies 240, 240′, 240″ and 240′″.

[0059] It will be apparent to those skilled in the art that these eddy current producing assemblies may be used to control and govern the rate of retraction of any line or cord which is to be wound upon a spool assembly powered by a power spring.

Claims

1. A retractable line or cord device comprising: a rotatable spool having means for retaining a flexible line or cord; a power spring mounted in driving relationship to rotate said spool; at least a portion of said spool comprising a conductive portion or a portion of magnetic material capable of generating magnetic field lines; and a fixed member located adjacent said spool; said fixed member comprising at least a portion of magnetic material capable of generating magnetic field lines if the spool comprises said conductive portion and produce eddy currents in said spool conductive portion; and if said spool comprises a portion of magnetic material capable of generating magnetic field lines, said fixed member comprises a conductive portion.

2. A retractable line or cord device according to claim 1 wherein said portion of magnetic material capable of generating magnetic field lines comprises a magnet assembly including a plurality of north and south pole portions.

3. A retractable line or cord device according to claim 2 wherein said conductive material comprises at least one material selected from copper, aluminium, silver, gold, steel and platinum.

4. A retractable line or cord device according to claim 3 wherein said conductive material comprises a disc made of said conductive material

5. A retractable line or cord device according to claim 2 wherein said spool includes a spool assembly comprising upper and lower magnet assemblies which generate magnetic fields respectively in upper and lower conductive plates located in said fixed member to oppose rotation and slow down the rate of retraction.

6. A retractable line or cord device according to claim 2 wherein said spool includes a spool assembly comprising a lower magnet assembly which generates magnetic fields in said lower conductive plate located in said fixed member to oppose rotation and slow down the rate of retraction.

7. A retractable line or cord device according to claim 2 wherein said spool includes a spool assembly comprising of two lower magnet assemblies, which generate a magnetic field in said lower rotating conductive disc, located between said magnet assemblies; and a manually adjustable rotational member, containing one of said magnets which allow radial alignment of said magnets, in relation to each other, that allow the generating of variable strength magnetic fields in said lower rotating conductive disc to oppose rotation and variably slow down the rate of retraction.

8. A retractable line or cord device according to claim 2 wherein a gear assembly is in driving engagement with said coil spring, and said coil spring includes a first shaft vertically extending within said coil spring and engaging said gear assembly.

9. A retractable line or cord device according to claim 8 wherein said gear assembly includes a first large gear; said large gear being in driving engagement with a small gear.

10. A retractable line or cord device according to claim 9 wherein said small gear being in driving engagement with a second vertically extending shaft; said second shaft being in driving engagement with a second large gear; said second large gear being in driving engagement with a small gear, laterally spaced therefrom; said second small gear being in driving engagement with a vertically extending spool shaft; said spool shaft being integral with said spool; said spool having a line or cord wound about a spool core.

11. A retractable line or cord device according to claim 10 wherein said line or cord extends outwardly from said spool and anchoring means are provided for anchoring said line or cord located outside said retraction device housing.

12. A retractable line or cord device according to claim 10 wherein brake means are provided for maintaining said power spring in tension position; and means for releasing said brake means are provided to allow said power spring to drive said first gear, said second gear, said third gear, said fourth gear, and said spool to retract said line or cord.

13. A retractable line or cord device comprising: a rotatable spool having means for retaining a flexible line or cord; a power spring mounted in driving relationship to rotate said spool; at least a portion of said spool comprising a conductive portion and a fixed member located adjacent said spool; said fixed member comprising at least a portion of magnetic material capable of generating magnetic field lines in said spool conductive portion and produce eddy currents in said spool conductive portion.

14. A retractable line or cord device according to claim 13 wherein said portion of magnetic material capable of generating magnetic field lines comprises a magnet assembly including a plurality of north and south pole portions.

15. A retractable line or cord device according to claim 14 wherein said conductive material comprises a disc.

16. A retractable line or cord device according to claim 14 wherein said conductive material at least one material selected from copper, aluminium, silver, gold, steel and platinum.

17. A retractable line or cord device comprising: a rotatable spool having means for retaining a flexible line or cord; a power spring mounted in driving relationship to rotate said spool; at least a portion of said spool comprising a portion of magnetic material capable of generating magnetic field lines in an adjacent conductive portion; and a fixed member located adjacent said spool; said fixed member comprising a conductive portion which during rotation of said spool receives magnetic field lines from said magnetic material in said spool, and generates eddy currents in said conductive material.

18. A retractable line or cord device according to claim 17 wherein said portion of magnetic material capable of generating magnetic field lines comprises a magnet assembly including a plurality of north and south pole portions.

19. A retractable line or cord device according to claim 17 wherein said conductive material comprises at least one material selected from copper, aluminium, silver, gold, steel and platinum.

20. A retractable line or cord device according to claim 19 wherein said conductive material comprises a disc made of said conductive material.