US3351752A

US3351752A - Contact printing apparatus

Info

Publication number: US3351752A
Application number: US521860A
Authority: US
Inventors: Hruby Joseph
Original assignee: Multigraphics Inc
Current assignee: AB Dick Co
Priority date: 1966-01-20
Filing date: 1966-01-20
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07
Also published as: DE1572230A1; GB1160878A

Description

J. HRUBY CONTACT PRINTING APPARATUS Nov 7, 1967 3 Sheets-Sheet 1 5V1 Him Filed Jan.

Nov. 7, 1967 J. HRUBY CONTACT PRINTING APPARATUS a sheets-sheet 2 Filed Jan. 20, 1966 m QZ QE at MS $6 fiwenicrr somsak m fig} Nov. 7, 1967 HRUBY CONTACT PRINTING APPARATUS 3 Sheets-Sheet 5 Filed Jan. 20, 1966 1051 016 Wj ar www- United States Patent 3,351,752 CONTACT PRINTING APPARATUS Joseph Hruby, Deerfield, 11]., assignor to Addressograph- Multigraph Corporation, Mount Prospect, Ill., a corporation of Delaware Filed Jan. 20, 1966, Ser. No. 521,860 Claims. (Cl. 240-49) ABSTRACT OF THE DISCLOSURE An exposure apparatus for making contact exposures of a diazo-type copy sheet through a translucent original by sliding the two sheets in superimposed relatlonship directly over the surface of the lamp envelope. A series of spaced apart continuous loop bands are stretched around three cylinders, one of which is a driven roller, with the outside surface of the bands being partially Wrapped in a loop around the outside of the lamp envelope. Guide wheels acting against the surface of the envelope keep it supported inside the loop and against the bands so that the envelope can be rotated about a fixed axis. The lateral ends of the lamp are equipped with single terminals making electrical contact with spaced apart contactors so that electrical contact is made during rotation obviating the need for commutating type devices.

The present invention relates to contact printing apparatus and more particularly to apparatus for exposing a copy sheet in accordance with a superimposed ongmal sheet by means of illumination provided by a rotating light source.

The direct contact or diazo process of producing copies of translucent graphic originals has achieved wide acceptance because of its efficiency, low cost and speed. In carrying out this process, an original sheet and a photosensitive copy sheet, or web, are superimposed and subjected to illumination in order to produce an exposure image on the copy sheet. The completed copy results when the copy sheet is developed by exposure to a developing gas, such as ammonia and water vapor.

A known type of contact printing apparatus for illuminating superimposed copy and original sheets includes a rotating transparent drum enclosing a stationary lamp. Superimposed copy and original sheets are passed around the drum, commonly by a drive belt arrangement, where they are illuminated by light passing through the drum. An advantage of this arrangement is that the lamp is stationary, and no difficulty is encountered in establishing electrical connections to the lamp.

In an attempt to provide a simpler arrangement, and in order to bring the light source closer to the superimposed sheets, it has been proposed that the envelope of the lamp serve itself as the rotating drum. In devices of this type, since the lamp is rotated, problems arise in making the necessary electrical connections to operate the lamp, and known arrangements for making the necessary electrical connections to rotating lamps are quite complex and inconvenient.

Accordingly, it is an object of the present invention to provide improved contact printing apparatus in which the disadvantages of known apparatus are avoided.

Another object is to provide improved apparatus of the type wherein a rotating lamp is used to illuminate a copy sheet in accordance with an original to be copied.

Yet another object of the invention is to provide improved apparatus for establishing electrical connections with a rotating lamp.

Another object of the invention is to provide contact printing apparatus of the type using a rotating vapor ice lamp and including a novel arrangement for establishing an operating potential difference across the lamp.

Still another object of the invention is to provide contact printing apparatus including a novel arrangement for starting a vapor lamp associated with the apparatus either when the lamp is stationary in any angular position, or when the lamp is rotating.

A further object of the invention is to provide an improved arrangement for discontinuing the rotation of the lamp while the lamp is started.

In brief, a contact printing machine embodying the features of the present invention may comprise a supporting and easing structure within which is rotatably mounted a fluorescent lamp having a cylindrical envelope over which superimposed copy and original sheets are passed in order to illuminate the sheets. In order fully to support and to rotate the lamp, the machine includes several rollers supporting a plurality of endless belts. The envelope of the lamp is arranged in a loop of the belts included between two adjacent rollers, and one or more of the rollers is driven at a desired speed by means of a drive system in order to move the belts and thereby rotate the lamp.

In accordance with a feature of the invention, the machine includes novel means for establishing the electrical connections for operating the rotating lamp. Within the envelope at each end of the lamp there is disposed an electrode connected between a pair of terminals leading outside of the envelope. Each end of the envelope is provided with a conductive metal end cap electrically connected to a first of the terminals and isolated from the second of the terminals. In order to facilitate the establishment of an operating potential difference between the electrodes, each end of the lamp is provided with a connector frictionally engageable with the pair of terminals and thereby held in place for rotation with the lamp. Each connector includes a contact member disposed substantially along the axis of the lamp, the contact member being electrically connected to the second of the two lamp terminals. The connector includes insulating portions for isolating the first of the two terminals from the contact member.

In order to establish electrical connection to the electrodes, the machine includes a pair of resilient contactors located one near each end of the lamp. The contactors are resiliently biased against the contact members of the connectors, thereby establishing a first electrical connection with the electrodes at each end of the lamp. The machine also includes a conventional power supply for operating the lamp, the power supply being connected to the two resilient contactors, whereby an operating potential difference is established within the lamp between the two electrodes.

In accordance with another feature of the invention, the machine includes a novel arrangement for starting the fluorescent lamp. Thus the metal end caps at each end of the lamp include cylindrical portions overlying the lamp envelope for a distance, the cylindrical portions serving as contact bands. A starting bar is mounted in the machine for movement between an inactive position and a lamp starting position. Conveniently, an Operating handle may be connected to the starting bar to move the bar to the starting position when it is desired to begin a contact printing operation. Supported along the bar are a pair of contactors engageable with the contact band portions of the metal end caps when the starting bar is moved to the lamp starting position, thereby completing an electrical circuit leading from one resilient contactor to the contact portion of one connector and to a first lamp terminal, through one electrode and out a second lamp terminal along the metal cap through the connector to the starting bar, and through the other contact band and electrode to the other resilient contactor. Thus when the Starting bar is in the lamp Starting position, a circuit is provided for a How of starting current through the two electrodes arranged in series circuit relation. When the starting operation is completed, the starting bar is returned to the inoperative position and the lamp is maintained in operation by the potential difference provided by the connection of the two resilient contactors alone.

In accordance with another feature of the invention, and in order to reduce contact arcing and other undesirable phenomena caused by the engagement of the starting bar contactors with the contact bands, there is provided a pair of normally open switch contacts associated with one of the starting bar contactors. These switch contacts are not closed until the starting bar contactors are firmly in engagement with the contact bands. Thus these switch contacts serve to make and break the starting circuit, and any arcing occurs between these switch contacts, rather than between the contactors and the metal end caps of the lamp.

Although with the novel lamp starting arrangement of the present invention the lamp may be started during rotation, it may be desirable to stop the lamp during starting. Accordingly there is provided a novel arrangement for discontinuing the rotation of the lamp during starting. Mounted on the operating handle of the starting bar is a normally closed switch connected to control the energization of the lamp drive motor. As the starting bar is moved from the inactive to the lamp starting position, the switch engages a switch operator and is moved to its open position, thus disconnecting the lamp drive motor and halting the lamp. The arrangement is such that the lamp is completely stopped before the lamp starting circuit is established.

Other objects and advantages and a better understanding of the invention will appear from the following detailed description in conjunction with the drawings, in which:

FIG. 1 is a broken plan view of a direct contact printing machine constructed in accordance with the invention, the top cover being removed more clearly to illustrate the machine;

FIG. 2 is an enlarged sectional view taken along the line 22 of FIG. 1, assuming FIG. 1 to show the complete structure;

FIG. 3 is a broken, enlarged elevational view, partly in section, of a portion of the apparatus of FIG. 1, particularly illustrating the lamp connecting and lamp starting structure;

FIG. 4 is a fragmentary sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is a schematic diagram of a portion of the operating circuit of the machine of FIG. I, particularly illustrating the lamp operating and starting circuitry; and

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 3 illustrating a lamp terminal connector.

Referring now to the drawings and initially to FIGS. 1 and 2, there is illustrated a direct contact printing machine generally designated as 10 and embodying the features of the present invention. The machine 10 includes a housing generally designated as 12 within which there is rotatably mounted a fluorescent lamp 14. In order to provide an operating potential across the lamp, the machine includes novel electrical connecting apparatus generally designated as 16 for establishing electrical connection with the two ends of the lamp. In order to start the fluorescent lamp at the beginning of a printing operation, the machine additionally includes novel lamp starting structure generally designated as 18.

Referring now in more detail to the construction of the machine 10, the housing 12 includes a base 20 to which is removably secured a top cover 22 for enclosing the internal structure of the machine and for limiting the escape of light from the machine. Within the machine are mounted a pair of side plates 23a and 2311. At the front of the machine there is provided a paper feed and discharge opening 24 defined in part by a lip member 26 including a feed table portion 26a. When it is desired to make a copy, a transparent or translucent graphic original sheet and a photosensitive copy sheet or web are placed in interfacing or superimposed relation and fed along the feed table 26a into the machine. The superimposed sheets are guided between the sheet table 26a and a guiding assembly 28 to the region of the lamp 14.

In order fully to support and to rotate the lamp 14, the machine includes spaced rollers 30, 32 and 34 extending between

side plates

23a and 23b and around which are arranged a plurality of endless belts 36. A drive motor 38 serves to rotate the roller 30 by means of a drive linkage 40 and drive belt 42. Rotation of the roller 30 causes the belts 36 to travel around a path over the roller 30 and the idler rollers 32 and 34. In order to adjust the tension between the belts 36 and the rollers 30, 32 and 34, there is provided a friction bar 44 over which the belts slide and which is mounted for movement in slots 46 in the

side plates

23a and 23b (FIG. 2) to adjust the tension of the belts 36.

Along the path of the endless belts 36 is an included loop portion 36a disposed between the rollers 30 and 32. The lamp 14 includes an elongated cylindrical envelope 50 formed of glass or other transparent material, the envelope being engaged by the loop portion 36a of the belts 36. To further support the lamp envelope, the machine may include two pairs of friction wheels 51 mounted respectively at the ends of the rollers 30 and 32. The friction wheels 51 serve to space the envelope 50 of the lamp 14 from the rollers 30 and 32 in order to provide elongated entrance and exit regions 52 and 53 at the regions where the belts 36 engage and disengage the lamp 14. Thus, the support and the rotation of the lamp 14 is entirely accomplished by the belts 36, rollers 30, 32 and 34, and friction wheels 51. Accordingly, it is not necessary for the electrical connecting apparatus, described hereinafter, to provide any support for the lamp.

When superimposed copy and original sheets are fed between the feed table 26 and guiding assembly 28 to the entrance region 52, the sheets are held between the belts 36 and lamp envelope 50 and are transported around the lamp 14 to the exit region 53 and then out of the machine. During their travel around the lamp 14, the sheets are exposed to light emanating from the lamp.

The housing 12 includes a control panel 12a (FIG. 1) supporting a power switch 54 and a direction control switch 55 for controlling the direction of rotation of the lamp, whereby the direction may be reversed if desired. At the rear of the housing is an electrical connector 56 for supplying power to the machine and an auxiliary outlet 57 for providing power to a developer or other apparatus. An exposure control 58 is provided for regulating the amount of light to which a copy sheet is exposed during printing by regulating the speed of operation of the drive motor 38. For cooling the machine, a fan is mounted within a fan casing 59 communicating with a ventilation chamber 60 (FIG. 2), and is driven by a fan motor 61.

Proceeding now to a description of the construction, operation and control of the lamp 14, the lamp may comprise a standard type of fluorescent lamp including the envelope 50, the inside of which may be coated with a suitable powdered phosphor material. Supported within the envelope 50 are a pair of electrodes 62 and 63, one near each end of the lamp (FIGS. 3 and 5). A pair of terminals 64 and 65 are connected to the two ends of the electrode 62 and lead out from one end of the envelope 50. Similarly, a pair of terminals 66 and 67 are connected to the electrode 63 at the other end of the lamp. The lamp additionally includes a pair of metallic generally cup-shaped end caps 68 and 70, one overlying each end of the lamp. These caps include generally

cylindrical portions

68a and 70a each extending for a short dislance over the outer wall of the envelope 50. As best appears in FIG. 3, the end caps 68 and 70" are electrically connected respectively to the terminals 64 and 66, but are isolated from the terminals 65 and 67. Thus it can be seen that the electrodes 62 and 63 each have one end electrically communicating with a metallic end cap. The other end of each electrode communicates with the other terminal 65 or 67, and is isolated from the end cap.

In the operation of the lamp 14, and as will readily be understood by those skilled in the art, it is necessary first to preheat the lamp and thereafter to maintain an operating potential difference within the lamp. Preheating, or starting, of the lamp is accomplished by causing current to flow through the lamp electrodes 62 and 63, heating them and causing them to emit electrons. When sufficient electrons are released, the resistance of the gap between the electrodes is low enough to permit striking an arc across the gap. Thereafter, the lamp is maintained in operation by establishing a potential difference between the electrodes 62 and 63.

In accordance with a feature of the invention, the novel electrical connecting apparatus generally designated as 16 is provided. Accordingly, a pair of connectors 72 and 74 are frictionally mounted at the ends of the lamp 14. These connectors are formed of an electrically conductive material such as a suitable metal, and include openings frictionally engageable with the lamp terminals. The connector '74 is provided with an insulating liner 76 surrounding the terminal 66, and with an insulating shield 78 serving to isolate the connector 74 from the end cap 70. Similarly, the connector 72 includes a liner 80 and a shield 82 for isolating the body of the connector 72 from the end cap 68 and from the terminal 64. However, the connectors 72 and 74 are electrically connected respectively to the terminals 67 and 65.

The connectors 72 and 74 include central openings within which are frictionally held

shank portions

84a and 86a of a pair of button

type contact members

84 and 86, the

contacts

84 and 86 being positioned substantially along the axis of the lamp 14. It will be appreciated that the

contacts

84 and 86 are in electrical communication respectively with the electrodes 62 and 63 by means of the connectors 72 and 74 and the terminals 65 and 67, whereas the terminals 64 and 66 and the end caps 68 and 70 are electrically connected to the other ends of the electrodes 6-2 and 63.

In order to establish a potential difference between the

electrodes

58 and 59, there are provided a pair of resilient leaf spring type contactors $8 and 90, one disposed at each end of the lamp 14. The contactors 88 and 90' are secured to the base 20 by means of fasteners 92, but are insulated therefrom by means of insulating material 94. The contactors 88 and 90 are connected respectively to a pair of terminal brackets 96 and 98 to which are secured a pair of conductors 100 and 101 leading to a power supply including first and second conventional ballasts 102 and 103 (FIGS. 1 and As most clearly appears in FIG. 3, the resilient connectors 88 and 90 bear against the

contact members

84 and 86 thereby establishing electrical connections via the connectors 72 and 74 with the spaced electrodes 62 and 63, whereby a lamp operating potential difference is maintained between the spaced lamp electrodes. It will be appreciated that this electrical connection is maintained when the lamp is stationary or rotating, and therefore the lamp is capable of operating during rotation. Furthermore, an extremely simple and compact arrangement is provided in the connectors 72 and 74 and contactors 88 and 90 by which this operating connection may be made.

In accordance with a further feature of the invention, the novel lamp starting structure generally designated as 18 is provided. The structure 18 serves to complete an electrical starting circuit for the lamp 14 thereby allowing a starting current to travel through the electrodes 62 and 63. The starting structure 18 includes a starting bar 104 formed of conductive material and journaled for rotation in the

side plates

23a and 23b by means of insulating bushings 106. The bar is rotatable between an inactive position, as illustrated in the drawings, and a lamp starting position by means of an operating handle 108 which extends from the bar 104 to a convenient position at the front of the machine near the control panel 12a.

In order to provide a path for current to flow between the end caps 68 and 70, a pair of

contactors

110 and 112 are mounted at spaced positions along the bar 104 for registry respectively with the

cylindrical portions

68a and 70a of the end caps 68 and 70. The

cylindrical portions

68a and 70a serve as contact bands for the

contactors

110 and 112, and when the starting bar 104 is rotated by means of the handle 108 to the lamp starting position, a lamp starting circuit is established. This starting circuit comprises a path including the resilient leaf spring contactor 88, the button contact 84, the connector 72, terminal 65, electrode 62, terminal 64, end cap 68, contactor 110, along the starting 'bar 104 to the contactor 112, the end cap 70, the terminal 66, the electrode 63, the terminal 67, the connector 74, button contact 86, and the other resilient leaf spring contactor 90. In order to start the lamp 14, the starting bar 104 is maintained in the lamp starting position for a short period during which the resistance of the gap between the electrodes 62 and 63 is reduced as discussed above. Thereafter the starting bar 104 is returned to the illustrated inactive position and the lamp is maintained in operation by the above described connecting apparatus 16.

In order to avoid arcing between the

contactors

110 and 112 and the end caps 68 and 70, the lamp starting structure 13 includes a pair of switch contacts 114a and 11422 carried respectively by the contactor 112 and by a switch arm 116 mounted in electrically conducting relation to the starting bar 104 (FIG. 4). Thus as the start ing bar 104 is moved toward the lamp starting position, the

contactors

110 and 112 engage the end caps 68 and 70 while the switch contacts 114a and 11412 remain in their normally open position. As the starting bar 104 is moved the rest of the way to the lamp starting position, the contacts 114a and 114b close, thus completing the lamp starting circuit. Thus any arcing is restricted to the region between the contacts 114a and 11411.

It will be appreciated that due to the simple arrangement of the

contactors

110 and 112 on the starting bar 104 and the use of the end caps 68 and 70 as band type contacts, the starting circuit may be established in any angular position of the lamp 14. Furthermore, if desired, the starting circuit could be established while the lamp is rotating. However, it is desirable to stop the rotation of the lamp 14 while the lamp is being started. Accordingly, and in accordance with a further feature of the invention, there is provided a switch 118 for disconnecting the power to the drive motor and speed control portions of the machine during starting (FIGS. 1, 4 and 5). The switch 118 comprises a normally closed snap acting type switch fastened to the operating handle 108. When the starting bar 104 is rotated to the starting position by means of the handle 108, an actuating lever 120 associated with the switch 118 engages a switch operating bracket 122 fastened to the side plate 23b whereby the switch is moved to the open circuit condition and the drive motor is disconnected, thus stopping the rotation of the lamp 14. After the lamp is started, and the operating handle 108 returned to the inactive position, the switch actuating lever 120 moves away from the bracket 122 and the switch again closes whereupon the drive motor is energized and proceeds to rotate the lamp 14.

Although the present invention has been described with reference to a specific illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the 7 art that will fall within the spirit and the scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In an apparatus for exposing superimposed copy and original sheets by passing said superimposed sheets over the surface of an illuminating source, the combination comprising:

a lamp having a cylindrical envelope,

a pair of spaced apart contactors fixedly mounted to a base support,

terminal means extending axially from the ends of said lamp,

support means acting independently of said contactors for supporting the envelope between said contractors with its axis of rotation lying in a plane substantially parallel to said base member and being in electrical contact therewith,

spacer means for spacing and supporting the envelope with respect to said support means providing entry Way means and exit means at the regions where said support means engage and disengage said envelope, said contactor including conductive biasing elements to accommodate the independent movement of the lamp in said support and spacer means in order to maintain continuous electrical contact of the lamp during rotation.

2. The combination of claim 1 additionally comprising:

an electrode within said envelope connected to said terminal;

an additional terminal at said end of the envelope connected to said electrode, said connector being engageable with said additional terminal; and

means associated with said connector for electrically isolating said additional terminal from said contact portion. 3. The combination of claim 2 additionally comprising: a conductive cap member fixed to said end of said envelope, said cap member being electrically connected to said additional terminal; and

conductive means selectively engageable with said cap member for completing an energizing circuit for said electrode between said conductive means and said contactor.

4. In apparatus for exposing superimposed original and copy sheets to light from a vapor lamp having a cylindrical envelope, the combination comprising:

means engageable with the envelope of the lamp for supporting the lamp;

means for rotating the lamp;

first and second cylindrical contact bands surrounding the envelope, one near each end of the lamp;

first and second additional contacts, one associated with each end of the lamp and located substantially along the axis of the lamp;

first and second electrodes within the lamp envelope;

means for connecting each electrode between one of said cylindrical contact bands and one of said additional contacts;

first and second contactor means disposed near the ends of the lamp and engageable with said additional contacts for establishing a difference in potential between said electrodes to operate the lamp; and

means for starting the lamp including third and fourth contactors selectively engageable with said first and second contact bands for completing a circuit allowing current to flow through said electrodes.

5. The combination of claim 4 wherein said starting means comprises: a conductive member mounted for movement between an inactive position and a lamp starting position, said third and fourth contactors being mounted on said member for engagement with said contact bands in the lamp starting position of the member for connecting said electrodes in a series circuit relation with one another.

6. The combination of claim 5 additionally comprising: switch contacts associated with said starting means movable from an open condition to a closed condition when said member reaches the lamp starting position to interconnect the third and fourth connectors after the third and fourth connectors engage the contact bands.

7. The combination of claim 4 wherein said connecting means comprises:

a pair of terminals at each end of the lamp, each pair being connected to one of said electrodes and a first terminal of each pair being connected to one of said contact bands;

first and second connectors mounted respectively on the pair of terminals at each end of the lamp, each connector supporting one of said additional contacts and including means for electrically interconnecting the additional contact and the second of the pair of terminals; and

insulating means associated with each connector for isolating the additional contact from the first terminal of the pair.

8. The combination of claim 7 additionally comprising: a metal end cap at each end of the envelope, said contact bands comprising integral portions of said end caps.

9. The combination of claim 5 additionally comprising means for preventing rotation of the lamp when said conductive member is moved to said lamp starting position.

10. The combination of claim 9 wherein said rotation preventing means comprises a switch connected to control said lamp rotating means and operable to deenergize said lamp rotating means in response to movement of said conductive member to said lamp starting position.

References Cited UNITED STATES PATENTS 9/1949 Young 2405l.11 3/ 9 Ellis 240-49 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,351,752 November 7, 1967 Joseph Hruby It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 35, for "67 and 65" read 65 and 67 11ne 47, for "58 and 59" read 62 and 63 column 7, lines 15 and 16, for "contractors" read contactors Signed and sealed this 12th day of November 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. IN AN APPARATUS FOR EXPOSING SUPERIMPOSED COPY AND ORIGINAL SHEETS BY PASSING SAID SUPERIMPOSED SHEETS OVER THE SURFACE OF AN ILLUMINATING SOURCE, THE COMBINATION COMPRISING: A LAMP HAVING A CYLINDRICAL ENVELOPE, A PAIR OF SPACED APART CONTACTORS FIXEDLY MOUNTED TO A BASE SUPPORT, TERMINAL MEANS EXTENDING AXIALLY FROM THE ENDS OF SAID LAMP, SUPPORT MEANS ACTING INDEPENDENTLY OF SAID CONTACTORS FOR SUPPORTING THE ENVELOPE BETWEEN SAID CONTRACTORS WITH ITS AXIS OF ROTATION LYING IN A PLANE SUBSTANTIALLY PARALLEL TO SAID BASE MEMBER AND BEING IN ELECTRICAL CONTACT THEREWITH, SPACER MEANS FOR SPACING AND SUPPORTING THE ENVELOPE WITH RESPECT TO SAID SUPPORT MEANS PROVIDING ENTRY WAY MEANS AND EXIT MEANS AT THE REGIONS WHERE SAID SUPPORT MEANS ENGAGE AND DISENGAGE SAID ENVELOPE, SAID CONTRACTOR INCLUDING CONDUCTIVE BIASING ELEMENTS TO ACCOMMODATE THE INDEPENDENT MOVEMENT OF THE LAMP IN SAID SUPPORT AND SPACER MEANS IN ORDER TO MAINTAIN CONTINUOUS ELECTRICAL CONTACT OF THE LAMP DURING ROTATION.