US3650029A

US3650029A - Electric knife blade securing and safety switch device

Info

Publication number: US3650029A
Application number: US34485A
Authority: US
Inventors: William F Trelc
Original assignee: McGraw Edison Co
Current assignee: Toastmaster Inc
Priority date: 1970-05-04
Filing date: 1970-05-04
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21

Abstract

An electric knife having reciprocating carriages supporting adjacent cutting blades, a flexible blade retainer on each carriage cooperating with a blade recess for releasably holding the blade and carriage together, an on-off switch for powering the knife, and a combination blade and safety switch lock device operable in one position to cooperate with the blade retainer only to preclude blade removal while allowing switch operation and operable in a second position to cooperate with the switch only to preclude powering of the knife while allowing removal of the blades.

Description

United States Patent Trelc [151 3,650,029 [451 Mar. 21, 1972 Primary Examiner-Theron E. Condon Assistant Examiner-J. C. Peters [72] Inventor: William F. Trelc, Boonville, Mo. Attorney charles F. Lind [73] Assignee: McGraw-Edison Company, Elgin, lll. [22] Filed: May 4, 1970 [57] An electric knife having reciprocating carriages supporting [21] Appl' 34485 adjacent cutting blades, a flexible blade retainer on each carriage cooperating with a blade recess for releasably holding [52] [1.8. CI the blade and carriage together an 011. 5 switch for powering Cl the knife, and a combination blade and safety switch lock [58] Field of Search ..30/272 R, 272 A device operable in one position to cooperate i the blade retainer only to preclude blade removal while allowing switch [56] References Cited operation and operable in a second position to cooperate with UNITED STATES PATENTS the switch only to preclude powering of the knife while allowmg removal of the blades. 3,322,925 5/1967 Korshak ..30/272 A g 7 3,337,952 8/1967 Rosen ..30/272 A 10 Claims, 5 Drawing Figures to a e4 70 is 59 7.6 =1. 3 56 43 i a, a 61 i I i r 5 e H r:

45 5% n a n==== I an.

PATENTEDHARZI I972 3, 650,029

///I///////////// ,,//'Iflf FIGS ELECTRIC KNIFE BLADE SECURING AND SAFETY SWITCH DEVICE Electric knives commonly have a power unit housing including a motor which reciprocates blade carriage means and the blades secured thereto. Typically, two adjacent blades are reciprocated in opposite directions to effect a sawing action. The blades are removable from the power unit for cleaning, releasable blade retaining means being provided to permit this separable connection with the carriage means. The typical blade retaining device has a locking bar that is confined within a blade recess, and this bar can be released with a manual release element in order to remove the blades from the power unit. Frequently also, electric knives have a safety latch which can be set to preclude the operation of the knife.

This invention relates to and discloses a blade and switch locking device for an electric knife, where the device precludes operation of the unit when the blades can be removed from the unit and/or precludes removal of the blades when the unit can be operated.

A main object of this invention is to provide for use in an electric knife an improved blade retaining and switch operating means which functions automatically and only according to prescribed conditions.

A more specific object of this invention is to provide such an operating means where a control element has a first section that in the blade locked condition cooperates with blade locking means to secure the blades in place and where the same control element has a second section that in the switch locked condition cooperates with the on-off power switch to preclude powering of the unit, the blade locked and switch locked conditions being at different positions of the control element.

These and other objects of this invention will be more fully understood and appreciated after referring to the following specifications, the accompanying drawing forming a part thereof, wherein:

FIG. 1 is a perspective view of an electric knife incorporating the subject invention therein;

FIG. 2 is a elevational sectional view as seen generally from line 2-2 in FIG. 1, except being partly broken away to show the construction details;

F IG. 3 is a top plan view of the construction shown in FIG. 2, again being partly broken away;

FIG. 4 is an elevational sectional view similar to FIG. 2, except showing the blade retaining and switch control device in the switch lock, blade release position; and

FIG. 5 is a perspective view of the blade retaining and switch lock component used in the subject invention.

The electric knife shown includes a housing 12, and a pair of

adjacent blades

14 and 16 projected therefrom that are adapted to reciprocate in directions parallel to lower cutting edges. An on-off control element 18 can be depressed'to close switch contacts 19 (FIG. 2) and complete a power circuit with an electric motor (not shown) to operate the knife, and the subject blade retaining and safety switch control element 20 is located rearwardly adjacent the switch control 18 and operates upon rotation as will be later explained.

As can be seen in FIGS. 2 and 3, each of the

blades

14 and 16 is held in a blade carriage 22 which in turn is supported to reciprocate within the housing 12. In this regard, each carriage is received in a front slide bearing 24 and a rear slide bearing 26. The means for reciprocating the carriage is somewhat conventional including a motor output shaft 32 supported within the housing and having a worm configuration 34 driving a pinion 36 keyed to shaft 37 which in turn is rotatably supported in housing bearings 38. Essentrics 40 are keyed to the shaft 37 off center thereof and received in slots 42 of the blade carriages 22 so that shaft rotation reciprocates the carriages Within the housing.

Each carriage is formed of several separate components secured together as by rivots 45, one component 43 being preferably of light weight and self lubricating plastic, and the other component 44 being of metal. The plastic component 43 has an open recess into which the tab end of each blade is received and the metal plate closes the recess to enclose the knife end in a socket fashion. The plastic component 43 further has a U-shaped 46 recess, and a spring element 50 of comparable shape at its rear end is received and held in place in the recess by the resulting boss and metal plate. The forward end of the spring 50 has a tab 52 which is resiliently urged toward the blade socket to the position as seen in FIG. 2 but which can be flexed away from this configuration. The knife end has a corresponding notch 53 into which the spring tab fits which thereby keys the knife to the blade carriage 22.

The switch contacts 19 actually are formed on parallel spring leaf elements 56 and 58 supported on an insulating plastic element 60 that defines part of the front bearing 24, previously mentioned. The element 60 has a lateral extension 62 which in effect rigidly supports one leaf element 56 and which overlies but is spaced from the spring 50 opposite the tab 52. The control element 18 fits through an opening in the housing and has an elongated portion 64 that directly engages the switch leaf 58. Depression of the element 18 moves leaf 58 toward leaf 56 to ultimately contact the same for providing a power connection to drive the knife.

Located rearwardly of the switch element 18 is the switch safety lock and blade retaining control element 20, which is rotatably mounted in an opening of the housing. The control actually is in two pieces, an exposed button piece 70 and an interior piece 74, which are united together by screw 76 threaded into the component 70. A bowed disc type spring 78 is positioned between the housing and exterior component 70 to take up axial slack of the control in the housing as well as retain the control in the rotatably position as set.

The component 74 has two

opposing extensions

80 and 82 which are also located at different axially spaced planes relative to the axis of the rotation. Extension 80 is located closely adjacent the upper face of the plastic carriage component 43 and also can fit under the housing extension 62 when the control is properly rotated (FIG. 2). With the extension in this position, the spring 52 cannot be flexed sufficiently to release the tab 52 from the blade notch 53 since it engages the extension 80 which in turn engages the housing extension 62. Consequently, each blade is securely locked in its blade carriage 22. Extension 82 is located 180 from extension 80 and is out of play in this rotational position of the control 20. Upon rotating the control 20 from the FIG. 2 position to the FIG. 4 position, extension 80 is moved clear of the spring to permit the spring flexture, whereupon the tab 52 releases the blade and the blades can be removed from or inserted into the carriage. In this position, extension 82 is disposed between the switch leaf elements 56 and 58 and also between the sandwiching switch element extension 64 and housing extension 62. Consequently, the switch contacts 19 cannot be closed, and even attempted manual depression of the control element 18 will cause no damage to the switch leaf elements because of the protective plastic extensions 62 and 64.

Each

interferring extension

80 and 82 is semicircular in shape, and blade retaining extension 80 extends across approximately at its high side while switch locking extension 82 extends across approximately l50 at its high side. This provides that either is operative at any and all positions of rotation of the control 20 with a minimum of overlap. The opposite end edges of each extension are beveled and thus fit easily between the respective adjacent elements upon initial movement of the control.

The particular construction is economical since it utilizes some components already required in an electric knife while it yet accommodates the intended functions in an inherently reliable manner. For example, the front carriage slide element 60 is used with its extension 62 as part of the blade retaining and switch contact safety lock device. The control moreover not only positively prevents the switch contacts from being closed, but does so automatically whenever the blades are not locked. The plastic component 74 preferably is injection molded with all extensions and contours built in to minimize machining or additional fabrication.

In point of actual construction, the housing 12 is formed of two

separate shells

86 and 88 which meet flush and are held together by screws and the like, one such screw 90 extending through an opening in the housing 86 into a threaded post 92 on the other housing 88. Similar screw connections can be located elsewhere. The components including the switch mount 60, and eccentric drive and blade carriage, and motor (not shown) are securely mounted in the shell 86 while the onoff control 18 and the selective safety and control 20 cooperates with the other shell 88.

I claim:

1. In an electric knife having a housing and blade carriage means supported to reciprocate in the housing, a blade carried by the carriage means and a carriage means tab separably cooperating with the blade for releasably uniting the blade and carriage means together, and a control including cooperating switch elements for powering the knife when the elements are closed, the combination comprising a safety control device including an element supported by the housing and having spaced extensions adjacent the tab and switch elements, where one extension in a first position of the device cooperates with the tab to preclude the removal of the blade from the carriage means and in a second position of the device is clear of the tab to permit the separation of the blade and carriage means, where the other extension in the first position of the device is clear of the switch elements to permit the powering of the knife and in the second position of the device cooperates with the switch elements to preclude the closing thereof and said device being mounted to rotate about an axis and the one and other extensions being defined in separate axially spaced planes along said axis.

2. In a knife combination according to claim 1, further including a portion of the housing spaced from but disposed adjacent the tab, and wherein the one device extension fits between and is thereby restrained by the tab and housing portion in the first position of the device.

3. In a knife combination according to claim 2, wherein a bearing unit generally used to mount the blade carriage means for reciprocation relative to the housing further provides as a part thereof said previously mentioned housing portion.

4. In a knife combination according to claim I, further including a control button extended through an opening in the housing and having within the housing a face portion disposed adjacent one of the switch elements and adapted when depressed to move said one switch element to close the elements, said face portion further being disposed adjacent second device extension when the device is in the second position and operable by cooperation with the second extension to preclude the closing of the switch elements upon attempted depression of the control button.

5. In a knife combination according to claim 1, wherein the other device extension in the second position of the device fits between and mechanically separates the switch elements.

6. In a knife combination according to claim I, wherein said one and other extensions each is of a semi circular shape that together extends over less than 360.

7. In a knife combination according to claim 1, wherein each extension has a generally uniform interior or intermediate land area terminating at tapered end edges.

8. In a knife combination according to claim 1, wherein the tab is part of a flexible spring carried on the carriage means, and said tab normally separably cooperates with shoulders of the blade upon flexture of the spring.

9. In a knife combination according to claim 6, wherein the tab is part of a flexible spring carried on a carriage means, and said tab normally separably cooperating with shoulders of the blade upon flexure of the spring, further including a portion of the housing spaced from but disposed adjacent the tab, and whereinthe one device extension fits between and is thereby restrained by the tab and the housing portion in the first position of the device.

10. In a knife combination according to claim 9, further including a control button extended through an openin in the housing and having within the housing a ace portion isposed adjacent one of the switch elements and adapted when depressed to move said one switch element to close the elements, said face portion further being disposed adjacent second device extension when the device is in the second position and operable by cooperation with the second extension to preclude the closing of the switch elements upon attempted depression of the control button.

Claims

4. In a knife combination according to claim 1, further including a control button extended through an opening in the housing and having within the housing a face portion disposed adjacent one of the switch elements and adapted when depressed to move said one switch elemEnt to close the elements, said face portion further being disposed adjacent second device extension when the device is in the second position and operable by cooperation with the second extension to preclude the closing of the switch elements upon attempted depression of the control button.

6. In a knife combination according to claim 1, wherein said one and other extensions each is of a semi circular shape that together extends over less than 360*.

9. In a knife combination according to claim 6, wherein the tab is part of a flexible spring carried on a carriage means, and said tab normally separably cooperating with shoulders of the blade upon flexure of the spring, further including a portion of the housing spaced from but disposed adjacent the tab, and wherein the one device extension fits between and is thereby restrained by the tab and the housing portion in the first position of the device.

10. In a knife combination according to claim 9, further including a control button extended through an opening in the housing and having within the housing a face portion disposed adjacent one of the switch elements and adapted when depressed to move said one switch element to close the elements, said face portion further being disposed adjacent second device extension when the device is in the second position and operable by cooperation with the second extension to preclude the closing of the switch elements upon attempted depression of the control button.