US3795985A

US3795985A - Brake for centrifugal extractor

Info

Publication number: US3795985A
Application number: US00181809A
Authority: US
Inventors: H Hasebe; T Mori
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1970-09-21
Filing date: 1971-09-20
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12
Also published as: CA932275A

Abstract

A brake is provided which rapidly retards and stops the rotation of a basket in a centrifugal extractor when its door or cover is opened. A brake shoe is fitted over a brake drum carried by a rotary shaft of the basket and securely held in position by its own elasticity. The brake shoe is provided with a projection with which a brake lever engages when the door or cover is opened, thereby applying the retarding force to the brake drum. In order to ensure the positive engagement of the brake lever with the projection of the brake shoe even when the door or cover is slightly opened and the force causing this engagement is small, means for increasing or amplifying the stroke or displacement of the door or cover being opened is provided in a mechanism coupling the door to the brake lever, and the engaging surfaces of the brake lever and the projection of the brake shoe are inclined at about 15* in the direction of rotation of the brake drum.

Description

Unite States atent [191 Hasebe et all.

[ BRAKE FOR CENTRIFUGAL EXTRACTOR [75] Inventors: Hisaltuni Hasebe; Tosio Mori, both of Hitachi, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Sept. 20, 1971 [21] Appl. No.: 181,809

[ 1 Mar. 12, 1974 Primary Examiner.1ohn J. Camby Assistant Examiner-James C. Yeung Attorney, Agent, or Ft'rm-Craig and Antonelli [5 7] ABSTRACT A brake is provided which rapidly retards and stops the rotation of a basket in a centrifugal extractor when its door or cover is opened. A brake shoe is fitted over a brake drum carried by a rotary shaft of the basket and securely held in position by its own elasticity. The brake shoe is provided with a projection with which a brake lever engages when the door or cover is opened, thereby applying the retarding force to the brake drum. In order to ensure the positive engagement of the brake lever with the projection of the brake shoe even when the door or cover is slightly opened and the force causing this engagement is small, means for increasing or amplifying the stroke or displacement of the door or cover being opened is provided in a mechanism coupling the door to the brake lever, and the engaging surfaces of the brake lever and the projection of the brake shoe are inclined at about 15 in the direction of rotation of the brake drum.

15 Claims, 4 Drawing Figures wiminnmz m4 3.795385 sum 2 or 3 INVENTORS BY o\ mm a N'ML ATTORNEYS PATENIEDm 12 I974 SHEET 3 BF 3 INVENTORS *NSRKvm HRsEBE Nu Tosu: MQR\ QM; r mk ATTORNEYS BRAKE FOR CENTRIFUGAL EXTRACTOR The present invention relates to generally a centrifugal extractor and more particularly a brake therefor.

A brake must be provided in a home centrifugal dehydrator in order to retard and stop the rotation of a basket when a door or cover of the centrifugal extractor is opened so that the safeguarded operation may be ensured. In the prior art centrifugal extractors, the band brakes have been generally used, but they have a common defect that the braking of retarding force produced is in proportion to the force pulling the band so that it naturally follows that the band pulling force must be increased to increase the braking force. Since the band pulling force is generally so designed as to be produced in response to the movement or opening of the cover or door, the latter must be so designed as to produce the greater brake actuating force. In order to increase the efficiency in extracting water from the washed clothes or the like in a basket, the recent trend is toward the higher and higher rotational speed of the basket, for example 3,000 rmp, so that the greater force is required to pull the brake band to retard and stop the rapidly spinning basket within for example seven seconds. Another defect of the band brakes is that a relatively greater displacement or stroke of a lever is required to apply a sufficient tension to the band or belt so that special displacement amplifying means must be provided so that appropriate tension may be produced even when the door is opened by two inches.

In addition to the band brakes there are available other. mechanical and electromagnetic brakes which are more reliable in operation but they are too expensive to be applied in the home centrifugal extractors.

One of the objects of the present invention is therefore to provide a brake for centrifugal extractors which is simple in construction yet highly reliable in operation and inexpensive to manufacture.

Another object of the present invention is to provide a brake for centrifugal extractors which can positively retard and stop a rapidly spinning basket within a short time in response to a small movement of the door or cover of the dehydrator.

A third object of the present invention is to provide a brake for centrifugal extractors which is almost free from any failure and whose service life is longer.

Briefly stated, the present invention is characterized in that a brake shoe is fitted over a brake drum carried by a shaft of a basket and securely held in position by its own elasticity and provided with a projection; a brake lever is drivingly coupled to a door or cover in such a manner as to engage with the projection when the door or cover is opened and to disengage from the projection when the door or cover is closed; and the en gaging surfaces of the brake lever and the projection of the brake shoe are inclined at an angle in the direction of rotation of the brake drum.

FIG. 1 is a longitudinal side view with some parts shown in section of a centrifugal extractor to which is applied the present invention;

FIG. 2 is a schematic view illustrating a brake actuating system thereof; and

FIGS. 3 and 4 are fragmentary views taken along the line III III of FIG. 1 illustrating the brake applied and released respectively.

Reference is now made to FIG. 1 of the drawing wherein a cylindrical vessel 11 for receiving water is mounted in a housing 10 in a manner well known in the art, and a basket 12 having a large number of perforations 14 formed in the peripheral wall thereof is suported in the vessel 11 by a basket shaft 13. The basket shaft 13 watertightly extends downwardly through the bottom of the vessel 11 and is connected to a shaft 18 of a motor 17 through a coupling 15 made integral with a brake drum 16. The basket shaft 13 is supported by a bearing (not shown) at the bottom of the vessel, the bearing in turn being supported by a bellows (not shown) which in turn is fixed to the vessel 1 1 so that the vibration caused duringthe operation may be prevented from being transmitted to the vessel 11. These bearing and the bellows do not constitute the present invention and are well known in the art so that they are not illustrated in the drawing.

Atthe top of the housing 10, a panel 20 which houses therein control units such as timer extends upwardly from the rear of the housing 10, and a knob 21 of a timer is disposed at the front surface of the panel 20. A door or cover 22 is hinged to the bottom of the panel 20 so that it may swing opened through to change the clothes or the like in the basket 12. A guide cover 23 which defines an opening 24 is fixed to the housing 10 between the door or cover 22 and the vessel 11.

- The motor 17 for spinning the basket 12 is supported by a plurality of springs 25 on a base 26 of a centrifugal extractor to isolate and prevent the vibration. Each of these springs 25 is interposed between the base 26 and an arm or bracket 27 which is welded to the casing of the motor 17 and extends radially outwardly, and conventional spring seats are interposed between the springs 25 and the arms or brackets 27 and between the springs 25 and the base 26. As a consequence even if the motor 17 is inclined during operation, it may be resorted to its normal position under the forces of the springs 25. An annular brake base 28 is securely fixed to the upper surface of the motor 17 with three setscrews 29, and the motor shaft 18 extends through the center of this brake base 28. The brake base 28 carries a wire holder 30, a lever 31 and a brake lever 32 (see FIG. 2). It is seen that the basket shaft 13 and the motor shaft 18 are inteconnected with each other through the coupling 15 with bolts 33 and 34. A brake shoe 35 comprising a steel belt is fitted over the brake drum l6 and is securely held in position by its own elasticity. A cable 36 for applying and releasing brake has the lower end of its core wire 37 connected to the lever 31 and the upper end to a connecting rod 45 to be described hereinafter after the cable 36 is extended upwardly through a space between the housing 10 and the vessel 11. Water extracted from the washed clothes or the like in the basket 12 and received in the vessel 11 is discharged through a hose 38 which is coupled to a discharge port (not shown) in the bottom of the vessel 1 1.

' In FIG. 2 the brake base 28 and its associated parts in FIG. 2. The extension of the hinge 40 beyond the pin 41 terminates into a switch actuating lever 42 which is connected to the upper end of the connecting rod 45.

The switch actuating lever 42 serves to actuate an actuator 44 which in turn actuates a microswitch 43 in the panel as will be described in more detail hereinafter. The upper end of the cable 36 is fixed to a cable holder 46 with setscrews 47 which in turn is fixed to the housing 10. The wire holder 30 is securely fixed to the brake base 28 with a screw 48 and a pin 49 which is securely held in position by a cotter pin 61, and is provided with a wire holding portion 50 which extends upwardly as shown in FIG. 1. One end of a return spring 51 is connected to the end remote from the wire holding portion 50 of the wire holder 30 while the other end to the lower leg of a U-shaped brake lever 32 to be described in more detail hereinafter. The lever 31 is roughly L- Y shaped and is pivoted with the pin 49 at the bend. The

core wire 37 is connected to the shorter arm 52 of the lever 31, and one end of a spring 54 is connected to the free end of the longer arm 53 while the other end of the spring 54 to the brake lever 32. The upper leg of the U- shaped brake lever 32 which is made of steel is pivoted to the brake base 28 with a pin 55 which is held in position by a cotter pin 60. An engaging portion 56 for engagement with a brake shoe 35 is formed at the free end of the brake lever 32, that is the portion to which is connected the other end of the spring 54. A brake liner 57 made of for example an oil-impregnated asbestos or the like is lined to the inner peripheral surface of the brake shoe 35 whose one end is struck out outwardly to form a projection 58. The engaging surface 59 of the projection 58 which engages with the engaging portion 56 of the brake lever 32 is so formed as to make a predetermined angle relative to the normal constructed at the engaging point as shown in FIG. 3.

Next the mode of operation will be described. The washed clothes or the like are placed into the basket 12, and an appropriate dehydration interval is selected by setting the timer by rotating the knob 21v after the door or cover 22 is closed. Then the motor 17 starts to rotate the basket 12. When the door or cover 22 is closed, the switch actuating lever 42 is in the position indicated by the chain lines in FIG. 2 so that the actuator 44 reminas in the upper position. Therefore the microswitch 43 is closed while the core wire 37 in the cable 36 is pulled upwardly so that the lever 31 is caused to rotate about the pin 49 in the counterclockwise direction. As a consequence the brake lever 32 is caused to rotate in the counterclockwise direction about the pin 55 through the spring 54 against the return spring 51 so that as shown in FIG. 4 the brake lever 32 is disengaged from the projection 58 of the brake shoe. Therefore the brake shoe 35 is permitted to rotate together with the brake drum 16, that is no retarding force is applied to the brake durm.

When the door or cover 22 is opened in the middle of operation of the extractor, the switch actuating lever 42 is displaced to the position indicated by the solid lines in FIG. 2 so that the actuator 44 returns to its normal position thereby opening the micro-switch 43. As a consequence the motor 17 is cut off from the power source because the microswitch 43 is connected in series to the motor 17. However, the rotary parts such as the basket 12 tend to continue their rotations due to their inertias. In this case the displacement of the switch actuating lever 42 permits the downward movement of the connecting rod 45 to loosen the core wire 37. Therefore the brake lever is caused to rotate in the clockwise direction about the pin 55 under the force of the return spring 51 so that the engaging portion 56 of the brake lever 32 engages with the projection 58 of the brake shoe 35 to stop it. Therefore even if there occurs the slippage between the brake liner 57 and the brake drum 16, the retarding force is applied to the-brake drum 16 from the brake shoe 35 which is elastically wrapped around the drum 16, whereby its rotation is stopped. When the brake lever 32 engages with the projection 58 of the brake shoe 35, the great impact would be produced between the engaging surfaces thereof, but the force is applied to the brake shoe 35 in such a direction as to expand itradially so that the force which presses the brake liner 57 against the brake drum 16 is instantaneously reduced. As a consequence the slippage between the brake liner 57 and the brake drum l6is accordingly increased so that no great shock or impact will be exerted on the projection ,58 of the brake shoe 35. If the projection is formed on the other end of the brake shoe 35 in place of the end as shown in drawings, the force exerted from the brake lever 32 to the brake shoe 35 will be applied in such a direction as to cause the latter to contract radially inwardly so that it will be tightly pressed around the brake drum 16. As a consequence the force acting on the engaging surfaces will be remarkably increased so that the strength of the projection 58 must be increased accordingly. Therefore the engaging projection is formed on the end shown in the drawing so that the engagement of the brake lever 32 with the projection 58 may cause the temporary radial outward expansion thereof.

One of the requirements which must be fulfilled by the safety device for a centrifugal extractor is that even when the door or cover 22 is opened to such a small extent that a hand may be inserted between the door or cover 22 and the housing 10, the brake is positively applied to stop the basket 12 within a short time interval. Furthermore the perfect braking performance must be maintained as long as the centrifugal extractor is used. In short, the brake must be applied even when the front side edge of the door or cover 22 is opened or lifted by about two inches. In this case the displacement of the leading end of the switch actuating lever 42 is generally about 0.1 inch which is sufficient enough to make the microswitch 43 because the tolerance in displacement of actuator for making and closing the microswitches is generally about 0.1 inch. However, such small displacement in not enough to actuate the prior art band brakes to produce the sufficient braking force. But according to the present invention, the lower end of the core wire 37 is connected to the lever 31 which serves to amplify the displacement of the switch actuating lever 42, and the amplified displacement is further amplified by the brake lever 32 so that the final displacement of the leading end of the brake lever 32 may become the order of one-half inch or more. However the force transmitted to the leading end of the brake lever 32 becomes very small so that the leading end will be pushed away by the rapidly rotating projection 58 even if the brake lever tries to engage with the projection. To overcome this problem, the force of the return spring 51 for the brake lever 32 may be increased to impart the strongforce to the lever 32 to cause it to rotate in the clockwise direction. But this arrangement will inevitably increase the stresses exerted to various component parts so that their mechanical strength must be increased accordingly. Therefore according to the present invention, the engaging surface of the projection 58 of the brake shoe is formed to make a predetermined angle relative to the normal of the brake drum as described hereinbefore. The engaging surface of the brake lever 32 is also inclined at the same angle. Therefore at the instant when the brake lever 32 engages with the projection 58., a force to cause the brake lever to rotate in the clockwise direction is produced between the two engaging surfaces so that the positive engagement between the brake lever and the projection which is further aided by the force of the returning spring 51 may be ensured. As the angle 0 of inclination (see FIG. 3) is increased, the engaging force is increased, but if the angle 6 is increased too much, there is a fear that the brake lever 32 will not disengage from the projection 58 of the brake shoe 35 even when the door or cover 22 is closed. Therefore the optimum engaging angle 0 is between 10 and Another problem of the centrifugal extractor is that the great stress is exerted to the brake system when the door or cover is opened while the basket is spinning and closed again before the rotation of the basket is not completely stopped. That is, when the door or cover 22 is opened, the brake lever 32 engages with the projection 53 of the brake shoe, thus producing the braking force, and is exerted with the component of force which causes the brake lever 32 to engage the projection 58. Therefore even when the door or cover 22 is opened, the brake lever 32 will not be disengaged from the projection immediately as shown in FIG. 4. The force for closing the door or cover 22 is increased in proportion to the ratio of the length from the pin 41 to the front edge of the door or cover to the length from the pin 41 to the leading end of the switch actuating lever 42, and is transmitted to the connecting rod 45. Therefore the core wire 37 is pulled upward with the strong force so that the excess stress is applied to the brake actuating system. To overcome this problem the present invention interposes the spring 54 between the lever 31 and the brake lever 32 so that the spring 54 may extend under a predetermined degree of stress applied to the brake actuating system to thereby prevent the excess stress from exerting to the system. Altematively 'the spring 54 may be interposed between the connecting rod 45 and the core wire 37. It is of course necessary that the spring constant of the spring 54 is made greater than that of the return spring 51 so that the spring 54 may provide a sufficient shock absorbing function for the brake actuating system.

Therefore when the door or cover 22 is opened, the core wire 37 and hence the connecting rod 45 are pulled by the return spring 51. The same is true when the door or cover is closed. Therefore the core wire 37 and the connecting rod 45 smaller in diameter may be employed so that the inertia of the brake actuating system may be decreased. As a consequence even when the door or cover 22 is rapidly opened and closed, the local stress can be minimized. Furthermore because of the spring 54, no excess force is exerted to the pins supporting the levers so that no rattle will be produced even when the dehydrator-is used for a long time.

The inner diameter of the brake shoe is made slightly smaller than the outer diameter of the brake drum l6, and the brake liner 57 is lined to the inner surface of the brake shoe 35 so that the braking force maybe maintained almost constant even if the abrasion and wear of the brake liner 57 occur. According to the results of the experiments conducted by the inventors, it was found that the basket 12 can be stopped in about 2 seconds even after the 6,000 repetitive tests.

According to the present invention, the brake lever 32, the lever 31, the wire holder 30, the spring 54 and, the return spring 511 are all mounted upon the single brake base 28 so that the previously preassembled and adjusted brake base assembly may be readily installed in the housing. Thus the centrifugal extractor in accordance with the present invention is best adapted for the conveyor belt line production.

What is claimed is: l. A centrifugal extractor comprising: article receiving basket means, housing means for housing the basket means, an access opening in said housing for providing access to said basket means, door means for opening and closing said access openlng, a basket shaft rotatable with said basket means about an extractor rotational axis, brake drum means carried by said basket shaft, brake shoe means fitted over said brake drum means, projection means having a projection engaging surface on said brake shoe means, said brake shoe means being secured to said' brake drum means such that said brake shoe means rotates with said brake drum means in the absence of retarding forces on said projection means and such that said brake shoe means applies frictional braking forces to said brake drum means in the presence of retarding forces on said projection means, brake lever means having a brake lever engaging surface, brake lever mounting means for mounting said brake lever means for movement between a first nonbraking position with said brake lever engaging surface away from the path of said projection engaging surface and a second braking position with said brake lever engaging surface in the path of said projection engaging surface such that said brake lever engaging surface abuttingly engages said projection engaging surface to apply retarding forces to said projection means, and coupling means for coupling said brake lever means with said door means such that said brake lever means is automatically moved from said first position to said second position in response to opening of said door means, wherein at least one of the brake lever engaging surface and the projection engaging surface extend in a plane parallel to said axis and inclined at an angle with respect to a radius of said brake drum which extends through said engaging surfaces when in the abuttingly engaged position so as to optimize the engagement of said engaging surfaces with one another.

2. An extractor according to claim 1, wherein said engaging surfaces extend parallel to one another at substantially the same angular inclination with respect to said radius.

3. An extractor according to claim 2, wherein said angle between said radius and said engaging surfaces is between 10 and 20 in an angular direction with respect to the rotational direction of said shaft so as to inbetween 10 and 20 in an angular direction with respect to the rotational direction of said shaft so as to increase the locking action of said projection and brake lever means as compared to radially extending engaging surfaces.

6. An extractor according to claim 2, wherein said coupling means includes only mechanical elements.

7. An extractor according to claim 2, wherein said axis extends vertically.

8. An extractor according to claim 6, wherein said brake lever mounting means includes a pivotal connection of the brake lever means at a relatively fixed part of said housing means, and wherein said coupling means includes spring means for automatically pivoting said brake lever means to said second position whenever a cable operably connected with said door means is loosened by opening said door means.

9. An extractor according to claim 5, wherein said coupling means includes only mechanical elements.

10. An extractor according to claim 9, wherein said brake lever mounting means includes a pivotal connection of the brake lever means at a relatively fixed part of said housing means, and wherein said coupling means includes spring means for automatically pivoting said brake lever means to said second position when- I ever a cable operably connected with said door means is loosened by opening said door means.

11. An extractor according to claim 6, wherein means for amplifying the displacement of said door means is inserted in said mechanical coupling means between said brake lever and said door means.

12. In a centrifugal extractor having a clothes receiving basket, housing means for housing the basket including an access opening providing access to said basket, door means to open and close said access opening, means mounting a basket shaft attached to said basket for rotation about a vertical axis, a brake arrangement comprising: a brake drum carried by said shaft; a brake shoe fitted over said brake drum and secured in place by its own elasticity; projection means on said brake shoe; a brake lever having an engaging surface; me chanical coupling means to couple said brake lever with said door means by shifting the engaging surface on said brake lever to engage with an engaging surface of said projection when said door means is opened, wherein both of the engaging surfaces of said brake lever and said projection are inclined at an angle relative to the normal of said brake drum in the direction of rotation of said brake drum.

13. A brake as set forth in claim 12 wherein said angle between said engaging surfaces of said brake lever and said projection and said normal is 10 to 20.

14. A brake as set forth in claim 12 wherein a spring is interposed in said mechanical coupling means between said brake lever and said door means to relax the excess local stress applied to said mechanical coupling means.

15. A brake as set forth in claim 12 wherein means for amplifying the displacement of said door or cover is inserted in said mechanical coupling means between said brake lever and said door means.

Claims

1. A centrifugal extractor comprising: article receiving basket means, housing means for housing the basket means, an access opening in said housing for providing access to said basket means, door means for opening and closing said access opening, a basket shaft rotatable with said basket means about an extractor rotational axis, brake drum means carried by said basket shaft, brake shoe means fitted over said brake drum means, projection means having a projection engaging surface on said brake shoe means, said brake shoe means being secured to said brake drum means such that said brake shoe means rotates with said brake drum means in the absence of retarding forces on said projection means and such that said brake shoe means applies frictional braking forces to said brake drum means in the presence of retarding forces on said projection means, brake lever means having a brake lever engaging surface, brake lever mounting means for mounting said brake lever means for movement between a first non-braking position with said brake lever engaging surface away from the path of said projection engaging surface and a second braking position with said brake lever engaging surface in the path of said projection engaging surface such that said brake lever engaging surface abuttingly engages said projection engaging surface to apply retarding forces to said projection means, and coupling means for coupling said brake lever means with said door means such that said brake lever means is automatically moved from said first position to said second position in response to opening of said door means, wherein at least one of the brake lever engaging surface and the projection engaging surface extend in a plane parallel to said axis and inclined at an angle with respect to a radius of said brake drum which extends through said engaging surfaces when in the abuttingly engaged position so as to optimize the engagement of said engaging surfaces with one another.

3. An extractor according to claim 2, wherein said angle between said radius and said engaging surfaces is between 10* and 20* in an angular direction with respect to the rotational direction of said shaft so as to increase the locking action of said projection and brake lever means as compared to radially extending engaging surfaces.

4. An extractor according to claim 2, wherein said brake lever is engageable with said brake shoe means only at said projection engaging surface, and wherein said projection engaging surface extends only from a fixed circumferential position on said brake shoe means outwardly from said axis at said angular inclination with respect to said radius.

5. An extractor according to claim 4, wherein said angle between said radius and said engaging surfaces is between 10* and 20* in an angular direction with respect to the rotational direction of said shaft so as to increase the locking action of said projection and brake lever means as compared to radially extending engaging surfaces.

7. An extractor according to claim 2, wherein said axis extends vertically.

10. An extractor according to claim 9, wherein said brake lever mounting means includes a pivotal connection of the brake lever means at a relatively fixed part of said housing means, and wherein said coupling means includes spring means for automatically pivoting said brake lever means to said second position whenever a cable operably connected with said door means is loosened by opening said door means.

12. In a centrifugal extractor having a clothes receiving basket, housing means for housing the basket including an access opening providing access to said basket, door means to open and close said access opening, means mounting a basket shaft attached to said basket for rotation about a vertical axis, a brake arrangement comprising: a brake drum carried by said shaft; a brake shoe fitted over said brake drum and secured in place by its own elasticity; projection means on said brake shoe; a brake lever having an engaging surface; mechanical coupling means to couple said brake lever with said door means by shifting the engaging surface on said brake lever to engage with an engaging surface of said projection when said door means is opened, wherein both of the engaging surfaces of said brake lever and said projection are inclined at an angle relative to the normal of said brake drum in the direction of rotation of said brake drum.

13. A brake as set forth in claim 12 wherein said angle between said engaging surfaces of said brake lever and said projection and said normal is 10* to 20*.