Abstract:
An improved dough sheeting system and method which allow for improved selection of sheeter gap size and which provide a quick release mechanism to prevent damage to sheeter rollers. Hydraulic actuators, attached to a movable roller, hold the roller in a fixed position relative to an opposing roller. The actuators are engaged with a closing force in excess of the force exerted by the sheeted material against the rollers thereby ensuring that the rollers maintain a gap of fixed width. Thermal expansion blocks mounted to the frame or housing of the opposing roller provide a means for fine adjustments in the sheeter gap.

Description:
BACKGROUND 
   1. Technical Field 
   The present invention relates to an improved apparatus to form a uniform continuous thin sheet of product. More specifically, this invention relates to the use of hydraulic actuators to rigidly fix the position of a movable roller relative to an opposing roller. The invention also relates to the use of thermal expansion blocks to make minute adjustments to the position of the opposing roller thereby precisely adjusting the sheeter gap. 
   2. Description of Related Art 
   In a conventional dough sheeter, opposing rollers are separated by a small gap or nip. Dough or other product material is fed into the nip above the rollers and passes through the rollers to form a sheet. In one configuration, one roller is generally fixed in a frame while an opposing roller is adjustable so that a product thickness can be selected. 
   One adjusting mechanism to manipulate the position of a roller consists of some form of a screw jack driven by a manual crank or electric motor. Alternatively, the adjusting mechanism may consist of other known leveraging mechanisms to implement large-scale and small-scale changes to the size of a sheeter nip. Tapered blocks may be used to fix the position of one roller relative to the other. Another commonly used mechanism to adjust nip size consists of a moveable roller attached to a pivoting frame. 
   A drawback of these and similar designs is that sometimes the combined deflection of the frame, adjusting mechanism, rollers, and bearings exceeds the desired gap setting for high loads and thin products. For example, in potato chip manufacturing, typical sheeter rollers can experience as much as a 0.030 inch (0.762 mm) deflection during operation which can hinder precise sheet thickness control. 
   Extraordinary care is usually required to assure that the rollers do not collide when there is no product in the nip of a sheeter. A sudden loss of dough feed could result in the relief of the elastic strain in the rollers, frame, and adjusting mechanism, resulting in the rollers coming into contact with each other, and being damaged thereby. Damage could also result to rollers with relatively large diameters upon a temperature change; excessive thermal expansion of mechanical parts could cause damage. For example, if the temperature of the rollers is controlled to a temperature below ambient conditions, the loss of coolant could result in both rollers naturally coming to room temperature, and for large diameter rollers, the resulting diameter change in the rollers could exceed the gap between them. 
   One remedy for the possible large mechanical deflection is to clamp the rollers together, and set the gap between the rollers at assembly. In such case, the amount of mechanical strain under a load could be minimized by the elimination of machine elements such as are found in the aforementioned adjusting mechanisms. One drawback to this approach is that gap changes may be made only by changing shims in the machine, a task that would require taking the machine out of production for some period of time. For large diameter rollers, especially those that are temperature controlled, this method does not protect against roller contact resulting from thermal expansion of the rollers beyond the available gap between the rollers. Therefore, damage may still be caused from large temperature changes and thermal expansion of sheeting machinery. 
   Consequently, a need exists for a system and a method for providing safe and effective operation of a dough sheeter having a mechanism for quickly increasing the sheeter gap in order to prevent damage to the rollers. Additionally, a need exists for a system and method to allow for improved accuracy in the adjustment of the sheeter gap, especially while sheeter rollers are in production under a load. Such a system should provide these features and should be capable of high-speed, high-capacity production. Additionally, the resulting system should be mechanically stiff so as to minimize deflections under an operating load. Such a system should provide improved precision in order to produce a thin uniform sheet of product. 
   SUMMARY OF THE INVENTION 
   An improved dough sheeting system and method are disclosed which allow for improved selection of the size of a sheeter gap or nip, and which provide a quick release mechanism to prevent damage to sheeter rollers. Particularly, the invention includes hydraulic actuators attached to a roller which hold the roller in a fixed position relative to an opposing roller. The actuators are engaged with a closing force in excess of the force exerted by the sheeted material against the rollers thereby ensuring that the rollers maintain a gap of fixed size. Thermal expansion blocks, upon which the frame of an opposing roller is mounted, provide a means for fine adjustments in sheeter gap size. Additional features and advantages of the present invention will become apparent in the following written detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a cross-sectional side drawing of one embodiment of the present invention showing the fixed and moveable roller sections; 
       FIG. 2  is a cross-sectional drawing of a thermal expansion block in accordance with the present invention showing internal fluid passages; 
       FIG. 3  is a perspective view of one embodiment of the present invention showing an external housing and means of rotating sheeting rollers; and, 
       FIG. 4  is an overhead cross-sectional drawing showing a rear fixed roller and a front hydraulic, clamped roller. 
   

   Throughout the drawings, where the same part appears in more than one drawing, the same number is applied thereto. 
   REFERENCE NUMERALS 
     102  mounting block 
     104  thermal expansion block 
     106  bearing housing 
     108  product material 
     110  feeding conveyor 
     112  opposing fixed roller 
     114  adjustable roller 
     116  sheeted product 
     118  exiting conveyor 
     120  connecting member 
     122  mechanical stop 
     124  hydraulic member 
     126  hydraulic actuator 
     128  shims 
     130  fixed stop 
     132  sheeter gap 
     134  internal fluid passages 
     136  moveable section 
     138  fixed section 
     140  external frame 
     302  left side of fixed roller 
     304  right side of fixed roller 
   DETAILED DESCRIPTION 
   While the invention is described below with respect to a preferred embodiment, other embodiments are possible. The concepts disclosed herein apply equally to systems for producing sheeted products. 
   The primary objective of this invention is to provide an apparatus and method which may be used to quickly make adjustments to produce a sheeted product of a desired uniform thickness. The sheeter gap, and hence the thickness of such product, can be precisely controlled by the combination of two mechanisms. The first mechanism is a hydraulic actuator which keeps an adjustable roller fixed in place relative to an opposing roller with less inherent mechanical deflection. The second mechanism is one or more thermal expansion blocks. An opposing roller is mounted to such thermal blocks, and the position of the opposing roller may be finely adjusted by changes in the temperature of such blocks. 
   Under a load of about 2,500 pounds per linear inch (44,650 kilograms per linear meter), as measured along the width of sheeter rollers, a sheeting apparatus with an operating nip size between 0.009 and 0.012 inches (0.23 to 0.24 mm) produces a finished product that is about 0.026 inches (0.65 mm) in thickness. Ordinarily, under such loading, the deflection of the rollers is about 0.030 inches (0.760 mm). In one embodiment of the invention, the deflection is reduced from 0.030 inches (0.760 mm) to about 0.010 inches (0.254 mm) under such a load. According to the embodiment, the equipment is stiffer, thus the amount of deflection is reduced. The stiffer the equipment, and subsequently lower deflection, the less effect variations in dough rheology have on the sheeter nip size and consequently the sheeted product thickness. The largest source of mechanical deflection in a dough sheeting apparatus is found in the interplay between the parts comprising the sheeter nip adjustment mechanism. Some deflection is inherent because of the arrangement of mechanical connections between such parts as the frame, roller housing, roller bearings, and rollers. However, even the reduced deflection is on the same order of magnitude as a typical operating sheeter nip size. 
   With reference to  FIG. 1 , an opposing fixed roller  112  is attached by its bearing housings  106  to one or more thermal expansion blocks  104 , which in turn are connected to mounting blocks  102  attached to an external frame  140 . The thermal blocks can alternatively be attached to the machine frame without intermediate mounting blocks or other similar connectors. The opposing roller  112  is part of a fixed section  138  wherein miniscule physical deflections are minimized as much as possible under operating conditions. 
   An adjustable roller  114  is attached by its bearing housing  106  to a connecting member  120 . The connecting member  120  is attached to a mechanical stop  122  and a hydraulic member  124 . Each hydraulic member  124  is engaged by a hydraulic actuator  126 . Such actuator  126  applies a closing force to the hydraulic member  124  such that the closing force is sufficient to keep the entire moveable section  136  fixed in an engaged position by pressing an attached mechanical stop  122  against a fixed stop  130 . A closing force is typically in the range of one-and-a-half to two times the opposing force exerted on the rollers by product material  108  being sheeted. 
   Shims  128  may be inserted between the mechanical stop  122  and the fixed stop  130  in order to perform a coarse adjustment to the sheeter gap  132 . Shims  128  may be placed in other physical locations which ultimately determine the engaged position and the size of the sheeter gap  132 . In a preferred embodiment, the shims  128  are easily accessed and may be readily changed in a relatively short amount of time thereby facilitating the rapid adjustment of the size of the sheeter gap  132 . In another embodiment, a mechanical stop  122  may be adjusted and locked into various positions relative to an opposing fixed roller  112 . 
   Product material  108  is fed to the top of the rollers  112 ,  114  by a feeding conveyor  110 . The product material  108  applies a resisting force against each roller. Such force is less than the force exerted by the hydraulic actuators  126 . Thus, the position of the moveable section  136  remains fixed. The sheeted product  116  leaves the rollers by way of an exiting conveyor  118 . 
   In the operation of one embodiment, at startup, the sheeter gap  132  is 0.40 to 0.50 inches (10.2 to 13 mm) in size as product material  108  is initially fed to the apparatus. This large gap is achieved by actuating one or more hydraulic actuators  126  to an open position. This operating position protects the rollers from colliding due to the lack of dough feed or thermal expansion of the rollers. Next, the hydraulic actuators  126  are actuated to a closed position, thus the sheeter gap  132  is reduced to a preferred operating size of about 0.010 inches (0.254 mm). At the end of operation, the sheeter gap  132  is again returned to a relatively large value by again actuating the hydraulic actuators  126  to an open position before the flow of product material  108  ceases. In this way, the risk of having the sheeter rollers  112 ,  114  inadvertently contact and having them damage each other is reduced. 
   During operation, fine adjustments to the size of the sheeter gap  132  may be made by cooling or heating the thermal expansion blocks  104 . In a preferred embodiment, the blocks  104  are made of stainless steel for providing rapid and effective expansion or contraction. However, other metals, metal alloys, or other materials can be used to obtain a desired thermal expansion in order to achieve a desired range of movement. 
   In one embodiment, with an operating sheeter gap  132  of about 0.010 inches (0.254 mm), an opposing fixed roller  112  can be moved over a range of at least 0.004 inches (0.10 mm) by cooling or heating of at least one attached thermal block  104 . In another embodiment, the range of thermal expansion is 0.007 inches (0.178 mm). Other operating sizes of sheeter gap are possible, and other ranges of thermal expansion are possible. 
   Increasing the temperature of a thermal block  104  causes expansion of the same, resulting in a decrease in the sheeter gap. Similarly, cooling causes contraction of the thermal block  104 , resulting in an increase in the sheeter gap  132 . Physical expansion of the thermal block material is a function of temperature, and such expansion is linearly proportional to changes in temperature. As a thermal block  104  is expanded or contracted, the position of an opposing fixed roller  112  is changed relative to the other roller  114 . 
   With reference to  FIG. 1  and  FIG. 2 , in one embodiment, even though an opposing roller  112  is attached to a fixed section  138  of a sheeting apparatus, the position of the opposing roller  112  relative to an adjustable roller  114  can be manipulated by changing the temperature of at least one thermal block  104 . The sheeter gap  132  can thus be adjusted even while the adjustable roller  114  is fixed in place by a hydraulic force. In one embodiment, a thermal block  104  contains at least one internal fluid passage  134 , which facilitates the uniform cooling and/or heating of said thermal block  104  by passing a fluid of a different temperature through the fluid passage  134 . A fluid may be composed of one or more compounds known in the industry used for such heat exchanging purposes including, but not limited to, water, oil, glycol, and ethanol. The fluid may also be a gas. Heating or cooling of a thermal block  104  may be accomplished by other means including electric heaters, contact with a refrigeration element, or passing a fluid around the exterior of the block. A thermal block  104  may also be composed of several elements or mechanical pieces that in combination expand or contract to perform an expanding or contracting function. Other similar embodiments are possible. 
   With reference to  FIGS. 3 and 4 , temperature adjustment to one or more thermal expansion blocks  104  may be made independently on a left side  302  and a right side  304  of a fixed roller  112 . Such independent adjustment allows fine tuning to the corresponding sheeter gap  132  and resulting sheeted product  116 . In one embodiment, such independent adjustment ensures uniform thickness of a sheeted product  116  across the width of a sheeter gap  132 . Such independent adjustment compensates for differing amounts of deflection in left and right sides. In another embodiment, it is desirable to have a sheeted product  116  of non-uniform thickness across the width of a sheeter gap  132 , different thicknesses on right and left sides. 
   With reference to  FIG. 1 , the hydraulic actuators  126  may be rapidly actuated thereby releasing the force pressing the adjustable roller  114  into position against a fixed stop  130  in response to a change in one or more process conditions. According to the present invention, if there is a sudden loss of product material  108  between the rollers  112 ,  114 , the quick release mechanism prevents the adjustable roller  114  from forcefully contacting the fixed roller  112 . The release mechanism also applies to a loss of thermal control of one or more thermal blocks  104 , loss of roller cooling, or loss of communication with the process equipment, during operation. 
   One embodiment uses water in the internal fluid passages  134  of the thermal blocks  104  to control thermal block temperature. The sheeter gap  132  is adjusted over a size range by controlling the amount of thermal expansion of the thermal block  104 . The amount of thermal expansion is controlled by using a water temperature between an ambient water supply temperature (about 75 degrees F. in the summer) and 180 degrees F., a range sufficiently below the boiling point of water so as to not produce steam. In one embodiment, cooling of the thermal block  104  is accomplished by ambient air cooling. In another embodiment, cooling is accomplished with water cooled by a separate refrigeration device to approximately 35 degrees F., thereby increasing the sheeter gap adjustment range, and allowing for more rapid changes from one temperature set point to another. In still another embodiment, alternate heat transfer fluids such as oil, glycol, or others could be used in conjunction with external heating and cooling systems to provide for a temperature range greater than that range between water&#39;s freezing and boiling points. 
   One aspect of the present embodiment is that the hydraulically actuated roller position can be easily adjusted using shims, which reduces the need for a large adjustment range for thermal blocks, and thus permits the use of simple and low cost ancillary heating equipment. One shim arrangement provides for a sheeter gap range suitable for a single product. An alternate shim size can then be used for an alternate product of a different thickness. 
   Returning to  FIG. 3 , which is a perspective view of the apparatus shown in  FIG. 4 , a means of rotating the sheeting rollers—typically gears attached to axle ends—are positioned and accessible on the outside of their housings  106 ,  120 . For example, the supporting/driving axles for the fixed  112  roller and the adjustable roller  114  pass through the housings  106 ,  120  and are collared by gears, wheels, or flanges outside of the housings  106 ,  120 . In the embodiment shown in  FIG. 3 , the rollers  112 ,  114  and roller housings  106 ,  120  are moveable within an external frame. If desired, however, the housings  106 ,  120  alternatively can be designed to have adequate space through which the adjustable roller&#39;s  114  axle can move when the hydraulic actuators engage and disengage. 
   While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.