Abstract:
A control switch arrangement for sequentially controlling different operating states in a moving beam reader or an imager employs a force sensing resistor switch requiring a low actuation force, and a control switch with improved tactile feedback and ergonomic efficiency between the switches.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to electro-optical readers for reading indicia, for example, bar code symbols, having parts with different light reflectivities and, in particular, to a control switch arrangement for, and a method of, controlling different operational states in such readers. 
   2. Description of the Related Art 
   Various electro-optical readers have previously been developed for reading bar code symbols appearing on a label, or on a surface of a target. The bar code symbol itself is a coded pattern of indicia. Generally, the readers electro-optically transform graphic indicia of the symbols into electrical signals which are decoded into alphanumeric characters. The resulting characters describe the target and/or some characteristic of the target with which the symbol is associated. Such characters typically comprise input data to a data processing system for applications in point-of-sale processing, inventory control, article tracking and the like. Electro-optical readers of this general type have been disclosed, for example, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470, 4,760,248 and 4,896,026, all of which have been assigned to the assignee of the present invention. 
   As disclosed in some of the above patents, a particularly advantageous embodiment of such a reader resided in emitting a laser light beam from a hand-held, portable laser scanning head which was supported by a user; aiming the head and, more particularly, the laser light beam, at a symbol to be read; repetitively scanning the laser beam in a series of scans across the symbol; detecting the scanned laser light which is reflected off the symbol; and decoding the detected reflected light. Inasmuch as the laser light beam was usually, but not always, generated by a helium-neon gas laser which emitted red laser light at a wavelength of about 6328 Angstrom units, the red laser light was visible to the user and, thus, the user, without difficulty, could properly aim the head and position and maintain the emitted red laser light on and across the symbol during the scanning. 
   However, in the event that the laser light beam was generated by a semiconductor laser diode, as, by way of example, see U.S. Pat. Nos. 4,387,297; 4,409,470 and 4,460,120, then the aiming of the head relative to the symbol was rendered more difficult when the laser diode emitted laser light which was not readily visible to the user. For some laser diodes, the laser light was emitted at a wavelength of about 7800 Angstrom units, which was very close to infrared light and was on the borderline of being visible. Even with the advent of laser diodes whose emitted light was in the visible wavelength range, ambient light tended to mask out the laser diode light. Furthermore, if the laser diode light was moving, for example, by being swept across the symbol, and especially if the laser diode light was being swept at fast rates of speed on the order of a plurality of times per second, for example, at a rate of 40 scans per second, then the laser diode light was not readily visible to the user, even in a darkened room. Hence, due to one or more of such factors as the wavelength of the laser light, the intensity of the laser light, the intensity of the ambient light in the environment in which the laser light was operating, the scanning rate, as well as other factors, the laser diode light was rendered “non-readily visible”. 
   This non-readily visible laser diode light did not enable the user, however, to readily aim the laser diode light at the symbol, at least not without some difficulty and practiced effort because, simply put, the user could not see the laser diode light. The user, therefore, was required to hunt around by trial and error, hope that the scanning laser diode light was eventually properly positioned on and across the symbol, and wait until the scanning system advised him, typically by the lighting of an indicator lamp or by the sounding of an auditory beeper, that the symbol had indeed been successfully decoded and read. This hunting technique was a less-than-efficient and time-consuming procedure for reading symbols, particularly in those applications where a multitude of symbols had to be read every hour and every day. 
   In an attempt to enable the user to readily aim the laser diode light at the symbol, U.S. Pat. No. 4,835,374 proposed an aiming light arrangement to assist the user in visually locating and aiming the head at each symbol when non-readily-visible laser light was employed. The aiming light arrangement utilized a visible light source, e.g., one or more light emitting diodes, which was separate and distinct from the laser light source. A manually-operated trigger was employed to actuate the aiming light arrangement in a first operational state of the trigger for visibly illuminating a region on the symbol. This visible region was used for aiming purposes. Thereupon, in a second operational state of the trigger, the laser light source was actuated, thereby initiating the reading of the symbol. 
   Symbols can also be read by employing imaging devices. For example, an image sensor device may be employed which has a two-dimensional array of cells or photosensors which correspond to image elements or pixels in a field of view of the device. Such an image sensor device may include a two-dimensional or area charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) device and associated circuits for producing electronic signals corresponding to a two-dimensional array of pixel information for a field of view. 
   It is therefore known to use a CCD for capturing a monochrome image of a barcode symbol to be read as, for example, disclosed in U.S. Pat. No. 5,703,349. It is also known to use a CCD with multiple buried channels for capturing a full color image of a target as, for example, disclosed in U.S. Pat. No. 4,613,895. 
   For many applications, the imaging device is accommodated in a hand-held package which may be pistol-shaped. Moreover, such imaging devices are typically equipped with external lighting to illuminate the symbol to be captured. In addition, such external lighting serves as an aiming source to indicate to the operator just where the symbol is located relative to the cellular array. 
   In another known attempt, U.S. Pat. No. 5,117,098 disclosed a multi-state trigger using dual, double-action switches. However, the known double-action switches are not altogether satisfactory from an ergonomic point of view and typically require a long travel stroke between actuations of the switches, as well as some sort of positive tactile feedback for at least one of the switches, and also require a relatively high actuation force to control the switches. All of these factors, plus the lack of availability of high precision switches capable of very long working lifetimes, have proven disadvantageous in making such readers as ergonomically efficient as possible. 
   SUMMARY OF THE INVENTION 
   OBJECTS OF THE INVENTION 
   One object of this invention is to provide an improved control switch arrangement for and method of controlling different operational states for improving performance of a reader for reading a data-encoded symbol. 
   Another object of this invention is to provide a control switch arrangement which is compact, lightweight, durable and efficient in construction and quiet and reliable in operation, and thus is ideally suited for portable hand-held applications. 
   A further object of this invention is to provide a multi-position, manually-depressible trigger arrangement for controlling aiming and reading. 
   Still another object of this invention is to provide a multi-position trigger arrangement for controlling the reading of symbols located at different distances from the arrangement. 
   FEATURES OF THE INVENTION 
   In keeping with these objects and others which will become apparent hereinafter, one feature of this invention resides, briefly stated, in a control switch arrangement for, and a method of, controlling operational states in an electro-optical reader for reading indicia, such as one-and/or two-dimensional bar code symbols. The reader can be a moving beam reader, or an image capture device. 
   Advantageously, the arrangement includes a force sensing resistor (FSR) switch and a control switch mounted within the reader, preferably on a common circuit board. A trigger assembly is mounted on the reader for transmitting a first force on the FSR switch over a first travel stroke to initiate a first of the operational states, and for transmitting a second force on the control switch over a second travel stroke to initiate a second of the operational states. 
   Using an FSR switch enables a low actuation force to be used, typically from 0.2 to 1.0 Newtons, which is much less than the force required for a conventional tactile switch, typically 1.4 Newtons. Using an FSR switch also enables a minimal travel stroke, typically on the order of less than hundredths of a millimeter. This also means that the second stroke to initiate the control switch can be made longer to better ergonomically distinguish between actuation of the switches. 
   In the preferred embodiment, the trigger assembly includes a plate pivotable in one direction to transmit the first force on the FSR, and a beam pivotable in an opposite direction to transmit the second force on the control switch. A displaceable trigger guard has at least one finger depression, and a pair of projections extending rearwardly to engage the plate and the beam during displacement of the trigger guard. A pair of resilient elements is respectively positioned between the projections and the FSR and control switches. A return spring constantly biases the trigger guard to an undisplaced position. 
   One of the operational states can advantageously be an aiming state, while the other operational state can advantageously be a reading state. In the case of an imaging device, the aiming state employs external lighting to illuminate the symbol, while in the case of a moving beam device, the aiming state may energize an aiming light pattern, either static or dynamic. If aiming is not desired, then one operational state can be for reading close-in symbols, while the other operational state can be used for reading far-out symbols. 
   In accordance with this invention, the FSR switch enables actuation at very low actuation forces and over a very short travel stroke. A greater travel stroke can be designed to actuate the control switch, even with a shorter travel stroke for the control switch, thereby enabling ergonomic efficiency and differentiation between the FSR and the control switches. 

   
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a hand-held reader for reading a bar code symbol in accordance with the prior art; 
       FIG. 2  is an exploded perspective view of a control switch arrangement used in the hand-held reader of  FIG. 1  in accordance with this invention; 
       FIG. 3  is a rear perspective view of some of the components of the control switch arrangement of  FIG. 2 ; 
       FIG. 4  is a side elevational assembled view of the control switch arrangement of  FIG. 2 ; 
       FIG. 5  is a broken-away view of the control switch arrangement in a rest or undisplaced position; and 
       FIGS. 6 and 7  are respective views of the control switch arrangement in different operational states in accordance with this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference numeral  20  in  FIG. 1  generally identifies a hand-held reader for electro-optically reading indicia, such as bar code symbol  24 , located in a range of working distances therefrom. The reader  20  has a pistol grip handle  21  and a manually actuatable trigger  22  which, when depressed, enables a light beam  23  to be directed at the symbol  24 . The reader  20  includes a housing  25  in which a light source  26 , a light detector  27 , signal processing circuitry  28 , and a battery pack  29  are accommodated. A light-transmissive window  30  at a front of the housing enables the light beam  23  to exit the housing, and allows light  31  scattered off the symbol to enter the housing. A keyboard  32  and a display  33  may advantageously be provided on a top wall of the housing for ready access thereto. 
   In use, an operator holding the handle  21  aims the housing at the symbol and depresses the trigger. The light source  26  emits a light beam which is optically modified and focused by an optical focusing assembly  35  to form a beam spot on the symbol  24 . The beam passes through a beam splitter  34  to a scan mirror  36  which is repetitively oscillated at a scan rate of at least  20  scans a second by a motor drive  38 . The scan mirror  36  reflects the beam incident thereon to the symbol  24  and sweeps the beam spot across the symbol in a scan pattern. The scan pattern can be a line extending lengthwise along the symbol along a scan direction, or a series of lines arranged along mutually orthogonal directions, or an omnidirectional pattern,just to name a few possibilities. 
   The reflected light  31  has a variable intensity over the scan pattern and passes through the window  30  onto the scan mirror  36  where it is reflected onto the splitter  34  and, in turn, reflected to the photodetector  27  for conversion to an analog electrical signal. As known in the art, the signal processing circuitry  28  digitizes and decodes the signal to extract the data encoded in the symbol. 
   In accordance with this invention, the manually actuatable trigger  22  of  FIG. 1  is replaced by a control switch arrangement, as shown in exploded view in  FIG. 2 . The arrangement includes a force sensing resistor (FSR) switch  40  and a control switch  42 , preferably mounted on a common circuit board  44 . 
   A trigger guard  46  is mounted on the reader  20  for pivoting movement about a lower hinge rod  48  (see  FIG. 3 ). The trigger guard  46  preferably has one, or two, finger-receiving depressions  50 ,  52  for receiving respective fingers  54 ,  56  of an operator. As best seen in  FIGS. 3-4 , an upper rear projection  58  and a lower rear projection  60  extend rearwardly from the trigger guard  46 , preferably integrally therewith. 
   An actuating plate  62  is also pivotably mounted on the reader about an upper hinge rod  64 . As best seen in  FIG. 3 , the plate  62  has a cantilever central beam  66  integral therewith, as well as a pair of rear projections  68 ,  70 . The plate  62  also has a pair of front pins  72 ,  74  for insertion into a pair of guide holes  76 ,  78  of a bent return spring  80  having one arm resting against the plate  60  and another arm resting against the trigger guard  46 . 
   The arrangement still further includes an upper resilient element or grommet  82  positioned between the rear projection  70  and the control switch  42 , as well as a lower resilient element or grommet  84  positioned between the rear projection  68  and the FSR switch  40 . As best seen in  FIGS. 5-8 , the grommets  82 ,  84  have different cross-sections and are commonly mounted around their respective peripheries on extensions of the reader. 
   In the rest position of  FIG. 5 , it will be seen that the lower grommet  84  is closely spaced relative to the FSR switch  40 , whereas the upper grommet  82  is more further spaced relative to the control switch  42 . The spring  80  constantly biases the trigger guard  46  to this rest position. 
   Next, if one of the operator&#39;s fingers, for example, finger  54  is pulled back into the depression  50 , as depicted in  FIG. 6 , then the trigger guard  46  is pivoted about lower hinge rod  48  against the force of the spring  80 . The rear projection  60  pivots the plate  62  about the upper hinge rod  64  in one direction and, in turn, transmits a first force from rear projection  68  through the lower grommet  84  to close the FSR switch  40  over the relatively short travel stroke described above. 
   Next, if the same finger, or if two fingers  54 ,  56  are used to pull back on the trigger guard, as depicted in  FIG. 7 , then the trigger guard is further displaced back into the reader against the force of the restoring spring. The rear projection  60  now bends the beam  66  in an opposite direction, and the rear projection  70  transmits a second force through the upper grommet  82  to close the control switch  42  over the relatively longer travel stroke described above. Releasing of finger pressure on the guard allows the spring  80  to return the arrangement to the rest position of  FIG. 5 . 
   Thus, sequential activation of the FSR switch and the control switch is achieved with improved ergonomic efficiency. Very little force is needed to close the FSR switch, and a very little travel stroke needs to be traversed. A little greater travel stroke can be assigned to close the control switch, thereby improving the tactile feedback between these two switches. 
   It will be understood that each of the elements described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in a method of and control switch arrangement for controlling different operational states in an electro-optical reader, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims. 
   What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.