Failsafe system for electrostatic copying apparatus

Claim 2

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advancing means to produce first signals in response to detection of sheets in said portion of said path; and timer means actuatable by said means for producing said latent images to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means.

Claim 3

A combination as defined in claim 1, further comprising drive means for continuously moving said surface at a predetermined speed, said feeding means being arranged to convey said sheets into said path at said predetermined speed and said advancing means comprising a pair of rotary members located at the opposite sides of said path and means for rotating at least one of said rotary members.

Claim 4

A combination as defined in claim 1, further comprising drive means for continuously moving said surface at a predetermined speed, said feeding means being arranged to convey said sheets into said path at said predetermined speed and said means for producing said latent images comprising a carriage arranged to move originals with reference to said surface and means for imaging successive portions of the thus moved original onto successive portions of said surface, said carriage comprising means for actuating said timer means.

Claim 5

A combination as defined in claim 3, wherein said timer means comprises electric switch means and said means for actuating said switch means includes a projection provided on said carriage.

Claim 6

A combination as defined in claim 1, further comprising means for terminating the operation of said apparatus in response to simultaneous generation of first and second signals by said detector means and said timer means.

Claim 7

A combination as defined in claim 5, wherein said operation terminating means comprises means for terminating the movement of said surface and for deactivating said fusing means and said feeding means.

Claim 8

A combination as defined in claim 1, further comprising second timer means for generating third signals at such intervals that, during the generation of third signals, said detector means produces first signals in response to detection of successive sheets in said predetermined portion of said path in the normal course of transport of sheets along said path, and means for terminating the operation of said apparatus in response to the absence of simultaneous generation of first and third signals by said detector means and said second timer means.

Claim 9

A combination as defined in claim 7, wherein the means for terminating the operation of said apparatus in response to the absence of simultaneous generation of first and third signals by said detector means and said second timer means comprising an electric circuit.

Claim 10

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets, said fusing means comprising heat generating means; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advancing means to produce first signals in response to detection of sheets in said portion of said path; timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means; means for terminating the operation of said apparatus in response to simultaneous generation of first and second signals by said detector means and said timer means, said operation terminating means comprising means for terminating the movement of said surface and for deactivaTing said fusing means and said feeding means; and cooling means arranged to cool said fusing means irrespective of the simultaneous generation of first and second signals by said detector means and said timer means.

Claim 11

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets, said fusing means comprising heat generating means; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advancing means to produce first signals in response to detection of sheets in said portion of said path; timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means; means for terminating the operation of said apparatus in response to simultaneous generation of first and second signals by said detector means and said timer means, said operation terminating means comprising means for terminating the movement of said surface and for deactivaTing said fusing means and said feeding means; and cooling means arranged to cool said fusing means irrespective of the simultaneous generation of first and second signals by said detector means and said timer means.

Claim 12

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advancing means to produce first signals in response to detection of sheets in said portion of said path; said detector means comprising a signal emitting element; timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means, said timer means comprising switch means which is actuated periodically by said means for producing said latent images; amplifier means for amplifying the first signals from said element; a logical circuit having a first input connected with said amplifier means, a second input arranged to receive second signals on closing of said switch means, and an output arranged to emit signals in response to simultaneous reception of first and second signals at said first and second inputs; and means for terminating the operation of said apparatus in response to signals from the output of said logical circuit.

Claim 13

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advancing means to produce first signals in response to detection of sheets in said portion of said path; said detector means comprising a signal emitting element; timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means, said timer means comprising switch means which is actuated periodically by said means for producing said latent images; amplifier means for amplifying the first signals from said element; a logical circuit having a first input connected with said amplifier means, a second input arranged to receive second signals on closing of said switch means, and an output arranged to emit signals in response to simultaneous reception of first and second signals at said first and second inputs; and means for terminating the operation of said apparatus in response to signals from the output of said logical circuit.

Claim 14

A combination as defined in claim 10, wherein said means for terminating the operation of said apparatus comprises relay means arranged to change its condition of energization in response to signals from the output of said logical circuit and to thus immediately terminate the operation of said apparatus.

Claim 15

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advanciNg means to produce first signals in response to detection of sheets in said portion of said path, said detector means comprising a signal emitting element; first timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means; second timer means actuatable by said means for producing said latent images at such intervals that said predetermined portion of said path contains successive sheets during successive actuations of said second timer means in the course of normal transport of sheets along said path, said second timer means comprising electric switch means which is actuated periodically by said means for producing said latent images to produce third signals in response to actuation thereof; amplifier means arranged to amplify the first signals emitted by said element; a logical circuit having a first input connected with said amplifier means, a second input connected with said switch means and an output arranged to transmit signals in response to simultaneous reception of first and third signals at said first and second inputs thereof; and means for terminating the operation of said apparatus in response to signals from the output of said logical circuit.

Claim 16

In an electrostatic copying apparatus, a combination comprising a driven xerographic surface; means for producing on said surface a series of electrostatic latent images by imaging successive portions of at least one original onto successive portions of said surface; means for converting said latent images into powder images; feeding means for transferring successive powder images onto successive sheets of transfer material - which are normally separated from each other by gaps each extending between the trailing edge of a preceding sheet and the leading edge of the next-following sheet - by conveying such sheets into a predetermined path wherein the leading edge of each sheet contacts said surface at a first point and the trailing edge of each sheet moves away from contact with said surface at a second point; fusing means adjacent to said path downstream of said second point and arranged to fix the powder images to the respective sheets; sheet advancing means adjacent to said path downstream of said fusing means; photoelectric detector means adjacent to a predetermined portion of said path intermediate said second point and said advanciNg means to produce first signals in response to detection of sheets in said portion of said path, said detector means comprising a signal emitting element; first timer means actuatable to produce second signals at such intervals that, while said timer means is being actuated, one of said gaps is located in said predetermined portion of said path in the normal course of transport of sheets into the range of said advancing means so that the generation of first signals by said detector means normally does not coincide with the generation of second signals by said timer means; second timer means actuatable by said means for producing said latent images at such intervals that said predetermined portion of said path contains successive sheets during successive actuations of said second timer means in the course of normal transport of sheets along said path, said second timer means comprising electric switch means which is actuated periodically by said means for producing said latent images to produce third signals in response to actuation thereof; amplifier means arranged to amplify the first signals emitted by said element; a logical circuit having a first input connected with said amplifier means, a second input connected with said switch means and an output arranged to transmit signals in response to simultaneous reception of first and third signals at said first and second inputs thereof; and means for terminating the operation of said apparatus in response to signals from the output of said logical circuit.